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we propose a simple but effective modular approach mopa ( modular objectnav with pointgoal agents ) to systematically investigate the inherent modularity of the object navigation task in embodied ai. mopa consists of four modules : ( a ) an object detection module trained to identify objects from rgb images, ( b ) a map building module to build a semantic map of the observed objects, ( c ) an exploration module enabling the agent to explore the environment, and ( d ) a navigation module to move to identified target objects. we show that we can effectively reuse a pretrained pointgoal agent as the navigation model instead of learning to navigate from scratch, thus saving time and compute. we also compare various exploration strategies for mopa and find that a simple uniform strategy significantly outperforms more advanced exploration methods.
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arxiv:2304.03696
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this work presents an analysis of the functional derivative of the superconducting transition temperature t $ _ c $ with respect to the electron - phonon coupling function $ \ alpha ^ 2f ( \ omega ) $ [ $ \ delta t _ c / \ delta \ alpha ^ 2 $ f ( $ \ omega $ ) ] and $ \ alpha ^ 2f ( \ omega ) $ spectrum of h $ _ 3 $ s ( $ im \ bar3m $ ), in the pressure range where the high - t $ _ c $ was measured ( 155 - 225 gpa ). the calculations are done in the framework of the migdal - eliashberg theory. we find for this electron - phonon superconductor, a correlation between the maximums of $ \ delta t _ c / \ delta \ alpha ^ 2 $ f ( $ \ omega $ ) and $ \ alpha ^ 2f ( \ omega ) $ with its higher t $ _ c $. we corroborate this behavior in other electron - phonon superconductors by analyzing data available in the literature, which suggests its validity in this type of superconductors. the correlation observed could be considered as a theoretical tool that in an electron - phonon superconductor, allows describing qualitatively the proximity to its highest t $ _ c $, and determining the optimal physical conditions ( pressure, alloying or doping concentration ) that lead to the superconductor reaching its highest t $ _ c $ possible.
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arxiv:2006.15248
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a frame is a generalization of a basis of a vector space to a redundant overspanning set whose vectors are linearly dependent. frames find applications in signal processing and quantum information theory. we present a genetic algorithm that can generate maximally orthogonal frames of arbitrary size $ n $ in $ d $ - dimensional complex space. first, we formalize the concept of maximally orthogonal frame and demonstrate that it depends on the choice of an energy function to weigh the different pairwise overlaps between vectors. then, we discuss the relation between different energy functions and well - known frame varieties such as tight and grassmannian frames and complex projective $ p $ - designs. obtaining maximally orthogonal frames poses a global non - convex minimization problem. we discuss the relation with established numerical problems such as the thomson problem and the problem of finding optimal packings in complex projective space. to tackle the minimization, we design a hybrid genetic algorithm that features local optimization of the parents. to assess the performance of the algorithm, we propose two visualization techniques that allow us to analyze the coherence and uniformity of high - dimensional frames. the genetic algorithm is able to produce highly - symmetric universal frames, such as equiangular tight frames, symmetric, informationally complete, positive operator - valued measurements ( sic - povms ) and maximal sets of mutually unbiased bases, for configurations of up to $ d = 6 $ and $ n = 36 $, with runtimes of the order of several minutes on a regular desktop computer for the largest configurations.
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arxiv:2504.21084
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this paper proposes a novel approach to image deblurring and digital zooming using sparse local models of image appearance. these models, where small image patches are represented as linear combinations of a few elements drawn from some large set ( dictionary ) of candidates, have proven well adapted to several image restoration tasks. a key to their success has been to learn dictionaries adapted to the reconstruction of small image patches. in contrast, recent works have proposed instead to learn dictionaries which are not only adapted to data reconstruction, but also tuned for a specific task. we introduce here such an approach to deblurring and digital zoom, using pairs of blurry / sharp ( or low - / high - resolution ) images for training, as well as an effective stochastic gradient algorithm for solving the corresponding optimization task. although this learning problem is not convex, once the dictionaries have been learned, the sharp / high - resolution image can be recovered via convex optimization at test time. experiments with synthetic and real data demonstrate the effectiveness of the proposed approach, leading to state - of - the - art performance for non - blind image deblurring and digital zoom.
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arxiv:1110.0957
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some invariant sets may attract a nearby set of initial conditions but nonetheless repel a complementary nearby set of initial conditions. for a given invariant set $ x \ subset \ r ^ n $ with a basin of attraction $ n $, we define a stability index $ \ sigma ( x ) $ of a point $ x \ in x $ that characterizes the local extent of the basin. let $ b _ { \ epsilon } $ denote a ball of radius $ \ epsilon $ about $ x $. if $ \ sigma ( x ) > 0 $, then the measure of $ b _ { \ epsilon } \ setminus n $ relative the measure of the ball is $ o ( \ epsilon ^ { | \ sigma ( x ) | } ) $, while if $ \ sigma ( x ) < 0 $, then the measure of $ b _ { \ epsilon } \ cap n $ relative the measure of the ball is of the same order. we show that this index is constant along trajectories, and relate this orbit invariant to other notions of stability such as milnor attraction, essential asymptotic stability and asymptotic stability relative to a positive measure set. we adapt the definition to local basins of attraction ( i. e. where $ n $ is defined as the set of initial conditions that are in the basin and whose trajectories remain local to $ x $ ). this stability index is particularly useful for discussing the stability of robust heteroclinic cycles, where several authors have studied the appearance of cusps of instability near cycles that are milnor attractors. we study simple ( robust heteroclinic ) cycles in $ \ r ^ 4 $ and show that the local stability indices ( and hence local stability properties ) can be calculated in terms of the eigenvalues of the linearization of the vector field at steady states on the cycle. in doing this, we extend previous results of krupa and melbourne ( 1995, 2004 ) and give criteria for simple heteroclinic cycles in $ \ r ^ 4 $ to be milnor attractors.
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arxiv:1008.3063
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in the proposed sehybridsn model, a dense block was used to reuse shallow feature and aimed at better exploiting hierarchical spatial spectral feature. subsequent depth separable convolutional layers were used to discriminate the spatial information. further refinement of spatial spectral features was realized by the channel attention method, which were performed behind every 3d convolutional layer and every 2d convolutional layer. experiment results indicate that our proposed model learn more discriminative spatial spectral features using very few training data. sehybridsn using only 0. 05 and 0. 01 labeled data for training, a very satisfactory performance is obtained.
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arxiv:2111.10293
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in this paper, we study power management ( pm ) policies for an energy harvesting additive white gaussian noise ( eh - awgn ) channel. the arrival rate of the harvested energy is assumed to remain unchanged during each data frame ( block code ) and to change independently across block codes. the harvested energy sequence is known causally ( online ) at the transmitter. the transmitter is equipped with a rechargeable battery with infinite energy storage capacity. the transmitter is able to adapt the allocated energy and the corresponding transmission rate of each block according to a pm policy. three novel online pm policies are established. the policies are universal, in the sense of the distribution of the harvested energy, and simple, in the sense of complexity, and asymptotically optimal, in the sense of maximum achievable average rates ( throughput ) taken over a long - term horizon of blocks.
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arxiv:1808.00450
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the combination of data from long - baseline and reactor oscillation experiments leads to a preference of the leptonic cp phase $ \ delta _ { \ rm cp } $ in the range between $ \ pi $ and $ 2 \ pi $. we study the statistical significance of this hint by performing a monte carlo simulation of the relevant data. we find that the distribution of the standard test statistic used to derive confidence intervals for $ \ delta _ { \ rm cp } $ is highly non - gaussian and depends on the unknown true values of $ \ theta _ { 23 } $ and the neutrino mass ordering. values of $ \ delta _ { \ rm cp } $ around $ \ pi / 2 $ are disfavored at between $ 2 \ sigma $ and $ 3 \ sigma $, depending on the unknown true values of $ \ theta _ { 23 } $ and the mass ordering. typically the standard $ \ chi ^ 2 $ approximation leads to over - coverage of the confidence intervals for $ \ delta _ { \ rm cp } $. for the 2 - dimensional confidence region in the ( $ \ delta _ { \ rm cp }, \ theta _ { 23 } $ ) plane the usual $ \ chi ^ 2 $ approximation is better justified. the 2 - dimensional region does not include the value $ \ delta _ { \ rm cp } = \ pi / 2 $ up to the 86. 3 \ % ( 89. 2 \ % ) ~ cl assuming a true normal ( inverted ) mass ordering. furthermore, we study the sensitivity to $ \ delta _ { \ rm cp } $ and $ \ theta _ { 23 } $ of an increased exposure of the t2k experiment, roughly a factor 12 larger than the current exposure and including also anti - neutrino data. also in this case deviations from gaussianity may be significant, especially if the mass ordering is unknown.
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arxiv:1506.07685
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we measure the shot noise of a quantum point - contact using a capacitively coupled inas double quantum dot as an on - chip sensor. our measurement signals are the ( bidirectional ) interdot electronic tunneling rates which are determined by means of time - resolved charge sensing. the detector frequency is set by the relative detuning of the energy levels in the two dots. for nonzero detuning, the noise in the quantum point contact generates inelastic tunneling in the double dot and thus causes an increase in the interdot tunneling rate. conservation of spectral weight in the dots implies that this increase must be compensated by a decrease in the rate close to zero detuning, which is quantitatively confirmed in our experiment.
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arxiv:0904.3656
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to explain the observed muon anomaly and simultaneously evade bounds from lepton flavor violation in the same model parameter space is a long cherished dream. in view of a generalized two higgs doublet model, with a yukawa structure as a perturbation of type - x, we are able to get substantial parameter space satisfying this criteria. we are focusing on a region with " { \ bf wrong - sign } " lepton - yukawa coupling which gives rise to an interesting phenomenological consequences. we found that in the " wrong - sign " region, it is possible to probe the low - mass pseudoscalar in flavor - violating decay mode with considerably better significance compared to the " right - sign " region. performing a simple cut - based analysis we show that at 14 tev run of the lhc with $ 300 fb ^ { - 1 } $ integrated luminosity, part of the model parameter space can be probed with significance $ \ geq 5 \ sigma $ which further improves with artificial neural network analysis.
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arxiv:2103.10632
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we study the dynamics of nuclear star clusters, the dense stellar environments surrounding massive black holes in the centers of galaxies. we consider angular momentum diffusion due to two - body scatterings among stellar objects and energy advection due to gravitational wave emission upon interaction with the central massive black hole. such dynamics is described by a two - dimensional fokker - planck equation in energy - angular momentum space. focusing on the transition between the diffusion - dominated region and the advection - dominated one, we utilize self - similarity to obtain a full solution for the fokker - planck equation. this solution provides the density and flux of the stellar objects in nuclear star clusters. this improves the rate estimates for extreme mass - ratio inspirals, and has interesting implications for a new class of galactic center transients called quasi - periodic eruptions.
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arxiv:2406.07627
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generative retrieval is a promising new paradigm in text retrieval that generates identifier strings of relevant passages as the retrieval target. this paradigm leverages powerful generative language models, distinct from traditional sparse or dense retrieval methods. in this work, we identify a viable direction to further enhance generative retrieval via distillation and propose a feasible framework, named dgr. dgr utilizes sophisticated ranking models, such as the cross - encoder, in a teacher role to supply a passage rank list, which captures the varying relevance degrees of passages instead of binary hard labels ; subsequently, dgr employs a specially designed distilled ranknet loss to optimize the generative retrieval model, considering the passage rank order provided by the teacher model as labels. this framework only requires an additional distillation step to enhance current generative retrieval systems and does not add any burden to the inference stage. we conduct experiments on four public datasets, and the results indicate that dgr achieves state - of - the - art performance among the generative retrieval methods. additionally, dgr demonstrates exceptional robustness and generalizability with various teacher models and distillation losses.
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arxiv:2402.10769
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we show that even small nonlinearities significantly affect particle production in the dynamical casimir effect at large evolution times. to that end, we derive the effective hamiltonian and resum leading loop corrections to the particle flux in a massless scalar field theory with time - dependent dirichlet boundary conditions and quartic self - interaction. to perform the resummation, we assume small deviations from the equilibrium and employ a kind of rotating wave approximation. besides that, we consider a quantum circuit analog of the dynamical casimir effect, which is also essentially nonlinear. in both cases, loop contributions to the number of created particles are comparable to the tree - level values.
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arxiv:2108.07747
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magnetic particle imaging ( mpi ) is an in - vivo imaging method to detect magnetic nanoparticles for blood vessel imaging and molecular target imaging. compared with conventional molecular imaging devices ( such as nuclear medicine imaging pet and spect ), magnetic nanoparticles have longer storage periods than radionuclides without ionizing radiation. mpi has higher detection sensitivity compared with mri. to accurately locate molecular probes in living organisms, high - resolution images are needed to meet the requirements of precision medicine. the spatial resolution of the latest domestic and international mpi equipment is 1 - 6 mm and has not yet met the requirements of medical imaging detection. we previously studied the spatial encoding technology based on pulsed square wave stimulation, which significantly improved the image resolution along the field free line ( ffl ) direction. this study proposes an innovative idea of high - resolution mpi based on stimulated emission depletion ( sted ) of magnetic nanoparticle signals. the stimulated emission was implemented by using cosine stimulation on ffl - based mpi scanner systems. the sted signal was generated by adding an offset magnetic field parallel to the ffl, which may form a donut - shaped focal spot or a regular gaussian focal spot depending on the offset field strength. focal spot modulation techniques and deconvolution algorithms were developed to improve image resolution.
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arxiv:2404.16596
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the rho - meson eletromagnetic form factors are calculated, both in covariant and light - front framework with constituintes quarks. the effect of the breakdown rotational symmetry for the one - body current operador in the null - plane is investigate by comparing calculations within ligth - front and covariant approaches.
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arxiv:nucl-th/9706032
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we address the problem of compressed sensing ( cs ) with prior information : reconstruct a target cs signal with the aid of a similar signal that is known beforehand, our prior information. we integrate the additional knowledge of the similar signal into cs via l1 - l1 and l1 - l2 minimization. we then establish bounds on the number of measurements required by these problems to successfully reconstruct the original signal. our bounds and geometrical interpretations reveal that if the prior information has good enough quality, l1 - l1 minimization improves the performance of cs dramatically. in contrast, l1 - l2 minimization has a performance very similar to classical cs and brings no significant benefits. all our findings are illustrated with experimental results.
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arxiv:1408.5250
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in signal processing the rudin - shapiro polynomials have good autocorrelation properties and their values on the unit circle are small. binary sequences with low autocorrelation coefficients are of interest in radar, sonar, and communication systems. in this paper we show that the mahler measure of the rudin - shapiro polynomials of degree $ n = 2 ^ k - 1 $ is asymptotically $ ( 2n / e ) ^ { 1 / 2 } $, as it was conjectured by b. saffari in 1985. our approach is based heavily on the saffari and montgomery conjectures proved recently by b. rodgers.
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arxiv:1708.01189
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it is well known that textual data on the internet and other digital platforms contain significant levels of bias and stereotypes. although many such texts contain stereotypes and biases that inherently exist in natural language for reasons that are not necessarily malicious, there are crucial reasons to mitigate these biases. for one, these texts are being used as training corpus to train language models for salient applications like cv - screening, search engines, and chatbots ; such applications are turning out to produce discriminatory results. also, several research findings have concluded that biased texts have significant effects on the target demographic groups. for instance, masculine - worded job advertisements tend to be less appealing to female applicants. in this paper, we present a text style transfer model that can be used to automatically debias textual data. our style transfer model improves on the limitations of many existing style transfer techniques such as loss of content information. our model solves such issues by combining latent content encoding with explicit keyword replacement. we will show that this technique produces better content preservation whilst maintaining good style transfer accuracy.
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arxiv:2201.08643
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here we report the results of searching millisecond pulsar ( msp ) candidates from the fermi lat second source catalog ( 2fgl ). seven unassociated $ \ gamma - $ ray sources in this catalog are identified as promising msp candidates based on their $ \ gamma $ - ray properties. through the x - ray analysis, we have detected possible x - ray counterparts, localized to an arcsecond accuracy. we have systematically estimated their x - ray fluxes and compared with the corresponding $ \ gamma $ - ray fluxes. the x - ray to $ \ gamma $ - ray flux ratios for 2fgl j1653. 6 - 0159 and 2fgl j1946. 4 - 5402 are comparable with the typical value for pulsars. for 2fgl j1625. 2 - 0020, 2fgl j1653. 6 - 0159 and 2fgl j1946. 4 - 5402, their candidate x - ray counterparts are bright enough for performing a detailed spectral and temporal analysis to discriminate their thermal / non thermal nature and search for the periodic signal. we have also searched for possible optical / ir counterparts at the x - ray positions. for the optical / ir source coincident with the brightest x - ray object that associated with 2fgl j1120. 0 - 2204, its spectral energy distribution is comparable with a late - type star. evidence for the variability has also been found by examining its optical light curve. all the aforementioned 2fgl sources resemble a pulsar in one or more aspects, which make them as the promising targets for follow - up investigations.
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arxiv:1507.02604
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we prove that if for the curved $ n $ - body problem the masses are given, the minimum distance between the point masses of a specific type of relative equilibrium solution to that problem has a universal lower bound that is not equal to zero. we furthermore prove that the set of all such relative equilibria is compact. this class of relative equilibria includes all relative equilibria of the curved $ n $ - body problem in $ \ mathbb { s } ^ { 2 } $, $ \ mathbb { h } ^ { 2 } $ and a significant subset of the relative equilibria for $ \ mathbb { s } ^ { 3 } $ and $ \ mathbb { h } ^ { 3 } $.
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arxiv:1401.3058
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this paper generalizes the existing minimal model of the hypothalamic - pituitary - adrenal ( hpa ) axis in a realistic way, by including memory terms : distributed time delays, on one hand and fractional - order derivatives, on the other hand. the existence of a unique equilibrium point of the mathematical models is proved and a local stability analysis is undertaken for the system with general distributed delays. a thorough bifurcation analysis for the distributed delay model with several types of delay kernels is provided. numerical simulations are carried out for the distributed delays models and for the fractional - order model with discrete delays, which substantiate the theoretical findings. it is shown that these models are able to capture the vital mechanisms of the hpa system.
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arxiv:1611.08100
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the paper explores the prospects of observing the phenomenon of dynamical anderson localisation via non - resonant raman - type rotational excitation of molecules by periodic trains of short laser pulses. we define conditions for such an experiment, and show that current femtosecond technology used for non - adiabatic laser alignment of linear molecules is sufficient for this task. several observables which can serve as indicator for anderson localisation are suggested for measurement, and the influence of experimental limitations imposed by laser intensity noise, finite pulse duration, limited number of pulses in a train, and thermal effects is analysed.
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arxiv:1305.5995
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the non - additive kinetic potential $ v ^ { \ text { nad } } $ is a key quantity in density - functional theory ( dft ) embedding methods, such as frozen density embedding theory and partition dft. $ v ^ { \ text { nad } } $ is a bi - functional of electron densities $ \ rho _ { \ rm b } $ and $ \ rho _ { \ rm tot } = \ rho _ { \ rm a } + \ rho _ { \ rm b } $. it can be evaluated using approximate kinetic - energy functionals, but accurate approximations are challenging. the behavior of $ v ^ { \ text { nad } } $ in the vicinity of the nuclei has long been questioned, and singularities were seen in some approximate calculations. in this article, the existence of singularities in $ v ^ { \ text { nad } } $ is analyzed analytically for various choices of $ \ rho _ { \ rm b } $ and $ \ rho _ { \ rm tot } $, using the nuclear cusp conditions for the density and kohn - sham potential. it is shown that no singularities arise from smoothly partitioned ground - state kohn - sham densities. we confirm this result by numerical calculations on diatomic test systems hehe, heli $ ^ + $, and h $ _ 2 $, using analytical inversion to obtain a numerically exact $ v ^ { \ rm nad } $ for the local density approximation. we examine features of $ v ^ { \ rm nad } $ which can be used for development and testing of approximations to $ v ^ { \ rm nad } [ \ rho _ { \ rm b }, \ rho _ { \ rm tot } ] $ and kinetic - energy functionals.
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arxiv:2207.04160
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recent methods for embodied instruction following are typically trained end - to - end using imitation learning. this often requires the use of expert trajectories and low - level language instructions. such approaches assume that neural states will integrate multimodal semantics to perform state tracking, building spatial memory, exploration, and long - term planning. in contrast, we propose a modular method with structured representations that ( 1 ) builds a semantic map of the scene and ( 2 ) performs exploration with a semantic search policy, to achieve the natural language goal. our modular method achieves sota performance ( 24. 46 % ) with a substantial ( 8. 17 % absolute ) gap from previous work while using less data by eschewing both expert trajectories and low - level instructions. leveraging low - level language, however, can further increase our performance ( 26. 49 % ). our findings suggest that an explicit spatial memory and a semantic search policy can provide a stronger and more general representation for state - tracking and guidance, even in the absence of expert trajectories or low - level instructions.
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arxiv:2110.07342
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in this paper, we prove that there exists an equivalence between 2 - category of smooth deligne - mumford stacks with torus - embeddings and actions, and the 1 - category of stacky fans. for this purpose, we obtain two main results. the first is to investigate a combinatorial aspect of the 2 - category of toric algebraic stacks defined in \ cite { i2 }. we establish an equivalence between the 2 - category of toric algebraic stacks and the 1 - category of stacky fans. the second is to give a geometric characterization theorem for toric algebraic stacks.
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arxiv:math/0610548
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multiple sequence alignment ( msa ) plays a pivotal role in unveiling the evolutionary trajectories of protein families. the accuracy of protein structure predictions is often compromised for protein sequences that lack sufficient homologous information to construct high quality msa. although various methods have been proposed to generate virtual msa under these conditions, they fall short in comprehensively capturing the intricate coevolutionary patterns within msa or require guidance from external oracle models. here we introduce msagpt, a novel approach to prompt protein structure predictions via msa generative pretraining in the low msa regime. msagpt employs a simple yet effective 2d evolutionary positional encoding scheme to model complex evolutionary patterns. endowed by this, its flexible 1d msa decoding framework facilitates zero or few shot learning. moreover, we demonstrate that leveraging the feedback from alphafold2 can further enhance the model capacity via rejective fine tuning ( rft ) and reinforcement learning from af2 feedback ( rlaf ). extensive experiments confirm the efficacy of msagpt in generating faithful virtual msa to enhance the structure prediction accuracy. the transfer learning capabilities also highlight its great potential for facilitating other protein tasks.
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arxiv:2406.05347
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we analyze null - and spacelike radial geodesics in schwarzschild - de sitter spacetime connecting two conjugate static sphere observers, i. e. free - falling observers at a fixed radius in between the two horizons. we explicitly determine the changes in the causal structure with respect to these natural observers as a result of the inward bending of the black hole singularity, as well as the outward bending of asymptotic infinity. notably, the inward and outward bending changes as a function of the black hole mass, first increasing towards a maximum and then decreasing to vanish in the extreme nariai limit. for a generic mass of the black hole this implies the existence of finite size ( temporal ) windows for the presence of symmetric radial geodesics between the static sphere observers probing the interior region of the black hole, as well as the exterior de sitter region. we determine the size of the interior ( black hole ) and exterior ( de sitter ) temporal windows in $ 4 $, $ 5 $ and $ 6 $ spacetime dimensions, finding that they are equal in $ d = 5 $, and compute the proper lengths of the symmetric radial geodesics. we comment on the implications for information exchange and the potential role of the symmetric radial geodesics in a geodesic approximation of static sphere correlators in schwarzschild - de sitter spacetime.
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arxiv:2312.06878
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object recognition and detection are well - studied problems with a developed set of almost standard solutions. identity documents recognition, classification, detection, and localization are the tasks required in a number of applications, particularly, in physical access control security systems at critical infrastructure premises. in this paper, we propose the new original architecture of a model based on an artificial convolutional neural network and semantic segmentation approach for the recognition and detection of identity documents in images. the challenge with the processing of such images is the limited computational performance and the limited amount of memory when such an application is running on industrial oneboard microcomputer hardware. the aim of this research is to prove the feasibility of the proposed technique and to obtain quality metrics. the methodology of the research is to evaluate the deep learning detection model trained on the mobile identity document video dataset. the dataset contains five hundred video clips for fifty different identity document types. the numerical results from simulations are used to evaluate the quality metrics. we present the results as accuracy versus threshold of the intersection over union value. the paper reports an accuracy above 0. 75 for the intersection over union ( iou ) threshold value of 0. 8. besides, we assessed the size of the model and proved the feasibility of running the model on an industrial one - board microcomputer or smartphone hardware.
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arxiv:2503.01085
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silicene, a hexagonal buckled 2 - d allotrope of silicon, shows potential as a platform for numerous new applications, and may allow for easier integration with existing silicon - based microelectronics than graphene. here, we show that silicene could function as an ultrafast electrical dna sequencing device. we investigated the stability of this novel nano - bio system, its electronic properties and the pronounced effects on the transverse electronic transport, i. e., changes in the transmission and the conductance caused by adsorption of each nucleobase, explored by us through the non - equilibrium green ' s function method. intriguingly, despite the relatively weak interaction between nucleobases and silicene, significant changes in the transmittance at zero bias are predicted by us, in particular for the two nucleobases cytosine and guanine. our findings suggest that silicene could be utilized as an integrated - circuit biosensor as part of a lab - on - a - chip device for dna sequencing.
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arxiv:1404.2706
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we analyze the problem of extracting the correlation length from infinite matrix product states ( mps ) and corner transfer matrix ( ctm ) simulations. when the correlation length is calculated directly from the transfer matrix, it is typically significantly underestimated for finite bond dimensions used in numerical simulation. this is true even when one considers ground states at a distance from the critical point. we introduce extrapolation procedure to overcome this problem. to that end we quantify how much the dominant part of the mps / ctm transfer matrix spectrum deviates from being continuous. the latter is necessary to capture the exact asymptotics of the correlation function where the exponential decay is typically modified by an additional algebraic term. by extrapolating such a refinement parameter to zero, we show that we are able to recover the exact value of the correlation length with high accuracy. in a generic setting, our method reduces the error by a factor of $ \ sim 100 $ as compared to the results without extrapolation and a factor of $ \ sim 10 $ as compared to simple extrapolation schemes using bond dimension. we test our approach in a number of solvable models both in 1d and 2d. subsequently, we apply it to 1d xxz spin - $ \ frac32 $ and the bose - hubbard models in a massive regime in the vicinity of bkt critical point. we then fit the scaling form of the correlation length and extract the position of the critical point and obtain results comparable or better than those of other state - of - the - art numerical methods. finally, we show how the algebraic part of the correlation function asymptotics can be directly recovered from the scaling of the dominant form factor within our approach. our method provides the means for detailed studies of phase diagrams of quantum models in 1d and, through the finite correlation length scaling of projected entangled pair states, also in 2d.
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arxiv:1801.08554
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we characterize exotic c * - algebras of twisted, principal \ ' etale groupoids, together with the abelian subalgebra associated to the unit space, as precisely being the inclusions " $ a \ subseteq b $ " of c * - algebras in which $ a $ is abelian, regular, and satisfies the extension property ( pure states extend uniquely to $ b $ ). when $ b $ is moreover nuclear, we deduce that the corresponding opaque ideal is trivial. as an application, we give a streamlined characterization of kumjian ' s c * - diagonals as the regular abelian subalgebras satisfying the extension property with vanishing opaque ideal.
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arxiv:2110.09445
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we demonstrate that the differential ac - stark shift of a ground - state hyperfine transition in an optical trap can be eliminated by using properly polarized trapping light. we use the vector polarizability of an alkali - metal atom to produce a polarization - dependent ac - stark shift that resembles a zeeman shift. we study a transition from the | 2s1 / 2, f = 2, mf = - 2 > to the | 2s1 / 2, f = 1, mf = - 1 > state of 7li to observe 0. 59 + - 0. 02 hz linewidth with interrogation time of 2 s and 0. 82 + - 0. 06 s coherence time of a superposition state. implications of the narrow linewidth and the long coherence time for precision spectroscopy and quantum information processing using atoms in an optical lattice are discussed.
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arxiv:1311.1290
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stress fibers are contractile actomyosin bundles commonly observed in the cytoskeleton of metazoan cells. the spatial profile of the polarity of actin filaments inside contractile actomyosin bundles is either monotonic ( graded ) or periodic ( alternating ). in the framework of linear irreversible thermodynamics, we write the constitutive equations for a polar, active, elastic one - dimensional medium. an analysis of the resulting equations for the dynamics of polarity shows that the transition from graded to alternating polarity patterns is a nonequilibrium lifshitz point. active contractility is a necessary condition for the emergence of sarcomeric, alternating polarity patterns.
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arxiv:1011.6062
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we present the x - ray analysis of the most luminous obscured active galactic nuclei ( agn ) inside local ultraluminous infrared galaxies ( ulirgs ). our sample consists of ten sources, harbouring agn components with estimated luminosity in excess of ~ 10 ^ 12 l _ sun and yet unidentified at optical wavelengths because of their large obscuration. according to the chandra and xmm - newton spectra, only in two cases out of ten clear agn signatures are detected at 2 - 10 kev in the shape of reflected emission. the x - ray flux from the starburst ( sb ) components, instead, is always broadly consistent with the expectations based on their ir emission. the most convincing explanation for the missing agn detections is therefore the compton - thickness of the x - ray absorber. in general, the combination of our mid - ir and x - ray spectral analysis suggests that the environment surrounding the agn component in ulirgs is much richer in gas and dust than in ordinary active galaxies, and the degree of agn absorption can be tentatively related to the sb intensity, indicating a strong interaction between the two processes and supporting the ulirg / quasar evolutionary scheme.
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arxiv:1103.3212
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we study lifelong learning in linear bandits, where a learner interacts with a sequence of linear bandit tasks whose parameters lie in an $ m $ - dimensional subspace of $ \ mathbb { r } ^ d $, thereby sharing a low - rank representation. current literature typically assumes that the tasks are diverse, i. e., their parameters uniformly span the $ m $ - dimensional subspace. this assumption allows the low - rank representation to be learned before all tasks are revealed, which can be unrealistic in real - world applications. in this work, we present the first nontrivial result for sequential multi - task linear bandits without the task diversity assumption. we develop an algorithm that efficiently learns and transfers low - rank representations. when facing $ n $ tasks, each played over $ \ tau $ rounds, our algorithm achieves a regret guarantee of $ \ tilde { o } \ big ( nm \ sqrt { \ tau } + n ^ { \ frac { 2 } { 3 } } \ tau ^ { \ frac { 2 } { 3 } } d m ^ { \ frac13 } + nd ^ 2 + \ tau m d \ big ) $ under the ellipsoid action set assumption. this result can significantly improve upon the baseline of $ \ tilde { o } \ left ( nd \ sqrt { \ tau } \ right ) $ that does not leverage the low - rank structure when the number of tasks $ n $ is sufficiently large and $ m \ ll d $. we also demonstrate empirically on synthetic data that our algorithm outperforms baseline algorithms, which rely on the task diversity assumption.
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arxiv:2501.13390
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mathematical modeling offers the opportunity to test hypothesis concerning myeloproliferative emergence and development. we tested different mathematical models based on a training cohort ( n = 264 patients ) ( registre de la c \ ^ ote d ' or ) to determine the emergence and evolution times before jak2v617f classical myeloproliferative disorders ( respectively polycythemia vera and essential thrombocytemia ) are diagnosed. we dissected the time before diagnosis as two main periods : the time from embryonic development for the jak2v617f mutation to occur, not disappear and enter in proliferation, and a second time corresponding to the expansion of the clonal population until diagnosis. we demonstrate using progressively complexified models that the rate of active mutation occurrence is not constant and doesn ' t just rely on individual variability, but rather increases with age and takes a median time of 63. 1 + / - 13 years. a contrario, the expansion time can be considered as constant : 8. 8 years once the mutation has emerged. results were validated in an external cohort ( national fimbank cohort, n = 1248 patients ). analyzing jak2v617f essential thrombocytema versus polycythemia vera, we noticed that the first period of time ( rate of active homozygous mutation occurrence ) for pv takes approximatively 1. 5 years more than for et to develop when the expansion time was quasi - similar. in conclusion, our multi - step approach and the ultimate time - dependent model of mpn emergence and development demonstrates that the emergence of a jak2v617f mutation should be linked to an aging mechanism, and indicates a 8 - 9 years period of time to develop a full mpn.
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arxiv:2406.06765
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in modern - era video streaming systems, videos are streamed and displayed on a wide range of devices. such devices vary from large - screen uhd and hdtvs to medium - screen desktop pcs and laptops to smaller - screen devices such as mobile phones and tablets. it is well known that a video is perceived differently when displayed on different devices. the viewing experience for a particular video on smaller screen devices such as smartphones and tablets, which have high pixel density, will be different with respect to the case where the same video is played on a large screen device such as a tv or pc monitor. being able to model such relative differences in perception effectively can help in the design of better quality metrics and in the design of more efficient and optimized encoding profiles, leading to lower storage, encoding, and transmission costs. this paper presents a new, open - source dataset consisting of subjective ratings for various encoded video sequences of different resolutions and bitrates ( quality ) when viewed on three devices of varying screen sizes : tv, tablet, and mobile. along with the subjective scores, an evaluation of some of the most famous and commonly used open - source objective quality metrics is also presented. it is observed that the performance of the metrics varies a lot across different device types, with the recently standardized itu - t p. 1204. 3 model, on average, outperforming their full - reference counterparts. the dataset consisting of the videos, along with their subjective and objective scores, is available freely on github at https : / / github. com / nabajeetbarman / multiscreen - dataset.
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arxiv:2305.03138
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this paper has been withdrawn by the author due to that the main results and approaches are closedly parallel to the ones in lie algebra case.
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arxiv:0911.3467
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though appropriate for core internet infrastructure, the internet protocol is unsuited to routing within and between emerging ad - hoc edge networks due to its dependence on hierarchical, administratively assigned addresses. existing ad - hoc routing protocols address the management problem but do not scale to internet - wide networks. the promise of ubiquitous network computing cannot be fulfilled until we develop an unmanaged internet protocol ( uip ), a scalable routing protocol that manages itself automatically. uip must route within and between constantly changing edge networks potentially containing millions or billions of nodes, and must still function within edge networks disconnected from the main internet, all without imposing the administrative burden of hierarchical address assignment. such a protocol appears challenging but feasible. we propose an architecture based on self - certifying, cryptographic node identities and a routing algorithm adapted from distributed hash tables.
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arxiv:cs/0603075
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in neuroimaging studies, it becomes increasingly important to study associations between different imaging modalities using image - on - image regression ( iir ), which faces challenges in interpretation, statistical inference, and prediction. our motivating problem is how to predict task - evoked fmri activity using resting - state fmri data in the human connectome project ( hcp ). the main difficulty lies in effectively combining different types of imaging predictors with varying resolutions and spatial domains in iir. to address these issues, we develop bayesian image - on - image regression via deep kernel learning gaussian processes ( bird - gp ) and develop efficient posterior computation methods through stein variational gradient descent. we demonstrate the advantages of bird - gp over state - of - the - art iir methods using simulations. for hcp data analysis using bird - gp, we combine the voxel - wise falff maps and region - wise connectivity matrices to predict fmri contrast maps for language and social recognition tasks. we show that falff is less predictive than the connectivity matrix for both tasks, but combining both yields improved results. angular gyrus right emerges as the most predictable region for the language task ( 75. 9 % predictable voxels ), while superior parietal gyrus right tops for the social recognition task ( 48. 9 % predictable voxels ). additionally, we identify features from the resting - state fmri data that are important for task fmri prediction.
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arxiv:2311.05649
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black holes and wormholes in the gravitational path integral can be used to calculate the statistics of heavy operators. an explicit example in higher dimensions is provided by thin shells of matter. we study these solutions in 3d gravity, and reproduce the behavior of black holes and wormholes from the dual cft using the large - $ c $ conformal bootstrap. the cft operator that creates a thin shell black hole is a line defect, so we begin by using the bootstrap to study the statistics of line defects, both at finite $ c $ and in the holographic large - $ c $ limit. the crossing equation leads to a universal formula for the average high - energy matrix elements of the line defect in any compact, unitary 2d cft with $ c > 1 $. the asymptotics are controlled by a line defect in liouville cft at the same value of the central charge. at large $ c $, three distinct quantities are related : the statistics of line defects in holographic cfts, the individual matrix elements of a line defect in liouville cft, and the on - shell action of black holes and wormholes in 3d gravity. the three calculations match for black holes, and if the statistics of the line defects are assumed to be approximately gaussian, then a class of wormholes is also reproduced by the dual cft.
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arxiv:2404.15183
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over the last decade, a large variety of clustering algorithms have been developed to detect coregulatory relationships among genes from microarray gene expression data. model based clustering approaches have emerged as statistically well grounded methods, but the properties of these algorithms when applied to large - scale data sets are not always well understood. an in - depth analysis can reveal important insights about the performance of the algorithm, the expected quality of the output clusters, and the possibilities for extracting more relevant information out of a particular data set. we have extended an existing algorithm for model based clustering of genes to simultaneously cluster genes and conditions, and used three large compendia of gene expression data for s. cerevisiae to analyze its properties. the algorithm uses a bayesian approach and a gibbs sampling procedure to iteratively update the cluster assignment of each gene and condition. for large - scale data sets, the posterior distribution is strongly peaked on a limited number of equiprobable clusterings. a go annotation analysis shows that these local maxima are all biologically equally significant, and that simultaneously clustering genes and conditions performs better than only clustering genes and assuming independent conditions. a collection of distinct equivalent clusterings can be summarized as a weighted graph on the set of genes, from which we extract fuzzy, overlapping clusters using a graph spectral method. the cores of these fuzzy clusters contain tight sets of strongly coexpressed genes, while the overlaps exhibit relations between genes showing only partial coexpression.
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arxiv:0801.2033
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we provide a characterization of the clifford torus in s3 via moving frames and contact structure equations. more precisely, we prove that minimal surfaces in s3 with constant contact angle must be the clifford torus. some applications of this result are then given, and some examples are discussed.
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arxiv:0705.3089
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the dynamics and decoherence of an electronic spin - 1 / 2 qubit coupled to a bath of nuclear spins via hyperfine interactions in a quantum dot is studied. we show how exact results from the integrable solution can be used to understand the dynamic behavior of the qubit. it is possible to predict the main frequency contributions and their broadening for relatively general initial states analytically, leading to an estimate of the corresponding decay times. furthermore, for a small bath polarization, a new low - frequency time scale is observed.
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arxiv:1005.0001
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various authors have invoked discretized fractional brownian ( fbm ) motion as a model for chain polymers with long range interaction of monomers along the chain. we show that for these, in contrast to the brownian case, linear forces are acting between all pairs of constituents, attractive for small hurst index h and mostly repulsive when h is larger than 1 / 2. in the second part of this paper we extend this study to periodic fbm and related models with a view to ring polymers with long range interactions.
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arxiv:1907.09850
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in logarithmic conformal field theory, primary fields come together with logarithmic partner fields on which the stress - energy tensor acts non - diagonally. exploiting this fact and global conformal invariance of two - and three - point functions, operator product expansions of logarithmic operators in arbitrary rank logarithmic conformal field theory are investigated. since the precise relationship between logarithmic operators and their primary partners is not yet sufficiently understood in all cases, the derivation of operator product expansion formulae is only possible under certain assumptions. the easiest cases are studied in this paper : firstly, where operator product expansions of two primaries only contain primary fields, secondly, where the primary fields are pre - logarithmic operators. some comments on generalization towards more relaxed assumptions are made, in particular towards the case where logarithmic fields are not quasi - primary. we identify an algebraic structure generated by the zero modes of the fields, which proves useful in determining settings in which our approach can be successfully applied.
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arxiv:hep-th/0107242
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we investigate the two - dimensional lattice gross - neveu model, using the domain - wall fermion formulation, as a toy model of lattice qcd. we study features of the phase diagram related to the mechanism of chiral symmetry restoration, and find that the parity - broken phase ( aoki phase ) exists for finite extent in the extra dimension ( $ n _ s $ ). we also find that o ( a ) scaling violation terms vanishes in the limit of $ n _ s \ to \ infty $.
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arxiv:hep-lat/9909153
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it has been almost 40 years since the proposal of the idea that hawking radiation of black holes does not lead to a complete evaporation but rather a " remnant " state. though traditionally viewed with great criticisms especially from the high energy physics community, in recent years, various approaches have demonstrated that black hole remnants remain a viable possibility. in this review, which is primarily aimed as an introduction to the subject, we will discuss some possible routes to forming remnants and their respective properties and challenges.
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arxiv:2412.00322
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we use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the cfhtlens dataset. this dataset is derived from the cfhtls - wide survey, and encompasses 154 sq. deg of high - quality shape data. using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10 ^ 9 msun to 10 ^ 10. 5 msun into those likely to lie in high - density environments ( hde ) and those likely to lie in low - density environments ( lde ). through comparison with galaxy catalogues extracted from the millennium simulation, we show that the sample of hde galaxies should primarily ( ~ 61 % ) consist of satellite galaxies in groups, while the sample of lde galaxies should consist of mostly ( ~ 87 % ) non - satellite ( field and central ) galaxies. comparing the lensing signals around samples of hde and lde galaxies matched in stellar mass, the lensing signal around hde galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~ 500 - - 1000 kpc, the typical separation between satellites and group centres. more importantly, the subhalos of hde galaxies are less massive than those around lde galaxies by a factor 0. 65 + / - 0. 12, significant at the 2. 9 sigma level. a natural explanation is that the halos of satellite galaxies are stripped through tidal effects in the group environment. our results are consistent with a typical tidal truncation radius of ~ 40 kpc.
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arxiv:1301.7421
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astrometry and spectroscopy of the s - stars in the galactic center provide a unique way to probe the properties of the central supermassive black hole, as well as the post - newtonian effects caused by its gravity, e. g. gravitational redshift and general relativistic precession. it has also been suggested that the photometry of s - stars can be used for studying the properties of gaseous environment of sgr a $ ^ * $. due to the high velocities of the s - stars, sometimes approaching $ ~ 0. 1c $, their photometric signal should be considerably affected by the doppler boosting. we calculate this relativistic effect for several s - stars closely approaching the central black hole ( most of them recently announced ) and show that the amplitude of the photometric variability due to the doppler boosting for some of them ( s62 and s4714 ) exceeds $ 6 \ % $ ; for the well studied star s2 it is about $ 2 \ % $. measurement of the doppler boosting can confirm the existence and help refine orbital parameters of the s - stars with noisy spectroscopy and astrometry. this effect should be explicitly accounted for when the photometry of s - stars is used for probing the medium around the sgr a $ ^ * $. we discuss the observability of the doppler boosting given the complications typical for the galactic center and conclude, in particular, that the purely photometric detection of the higher order relativistic corrections to the doppler boosting signal ( due to the gravitational redshift and transverse doppler shift, which we also calculate ) is hardly possible for the s - stars.
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arxiv:2010.11435
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searches for pseudo - magnetic spin couplings require implementation of techniques capable of sensitive detection of such interactions. while spin - exchange relaxation free ( serf ) magnetometry is one of the most powerful approaches enabling the searches, it suffers from a strong magnetic coupling, deteriorating the pseudo - magnetic coupling sensitivity. to address this problem, here, we compare, via numerical simulations, the performance of serf magnetometer and noble - gas - alkali - metal co - magnetometer, operating in a so - called self - compensating regime. we demonstrate that the co - magnetometer allows reduction of the sensitivity to low - frequency magnetic fields without loss of the sensitivity to nonmagnetic couplings. based on that we investigate the responses of both systems to the oscillating and transient spin perturbations. our simulations reveal about five orders of magnitude stronger response to the neutron pseudo - magnetic coupling and about three orders of magnitude stronger response to the proton pseudo - magnetic coupling of the co - magnetometer than those of the serf magnetometer. different frequency responses of the co - magnetometer to magnetic and nonmagnetic perturbations enables differentiation between these two types of interactions. this outlines the ability to implement the co - magnetometer as an advanced sensor for the global network of optical magnetometer for exotic physics searches ( gnome ), aiming at detection of ultra - light bosons ( e. g., axion - like particles ).
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arxiv:2107.05501
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we compute the two - loop massless qcd corrections to the helicity amplitudes for the production of two massive vector bosons in quark - antiquark annihilation, allowing for an arbitrary virtuality of the vector bosons : $ q \ bar q ' \ to v _ 1v _ 2 $. combining with the leptonic decay currents, we obtain the full two - loop qcd description of the corresponding electroweak four - lepton production processes. the calculation is performed by projecting the two - loop diagrams onto an appropriate basis of lorentz structures. all two - loop feynman integrals are reduced to a basis of master integrals, which are then computed using the differential equations method and optimised for numerical performance. we provide a public c + + code which allows for fast and precise numerical evaluations of the amplitudes.
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arxiv:1503.04812
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we discuss the relation between the two nucleon bethe - salpeter amplitude and the light front wave functions. both approaches provide a covariant description for the deuteron bound state and the two nucleon scattering state. a comparison is done for the spin - orbit functions as well explicit integrals are given on the basis of the nakanishi integral representation method.
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arxiv:nucl-th/9811022
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in this paper, we present a novel approach to developing an english automatic speech recognition ( asr ) system that can effectively handle hindi queries, without compromising its performance on english. we propose a novel acoustic model ( am ), referred to as splithead with attention ( sha ) model, features shared hidden layers across languages and language - specific projection layers combined via a self - attention mechanism. this mechanism estimates the weight for each language based on input data and weighs the corresponding language - specific projection layers accordingly. additionally, we propose a language modeling approach that interpolates n - gram models from both english and transliterated hindi text corpora. our results demonstrate the effectiveness of our approach, with a 69. 3 % and 5. 7 % relative reduction in word error rate on hindi and english test sets respectively when compared to a monolingual english model.
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arxiv:2503.07522
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we obtain a formula for the m \ " obius number of the socle of any group. specifically, the m \ " obius number of a direct product of simple groups is computed in terms of the m \ " obius numbers of the simple groups which make up the product.
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arxiv:1002.3503
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we present multi - frequency polarization observations of the diffuse radio synchrotron background modulated by faraday rotation. no total intensity is observed, indicating that total intensity does not vary on scales below approximately a degree. however, polarized intensity and polarization angle show abundant small - scale structure due to faraday rotation in the warm ionized disk on small scales. the distribution of rotation measures enables us to estimate structure in magnetic field, weighted with electron density, in the warm ionized disk.
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arxiv:astro-ph/0109312
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in this paper we make a systematic study of certain motivic cohomology classes ( " rankin - eisenstein classes " ) attached to the rankin - - selberg convolution of two modular forms of weight $ \ ge 2 $. the main result is the computation of the $ p $ - adic syntomic regulators of these classes. as a consequence we prove many cases of the perrin - riou conjecture for rankin - - selberg convolutions of cusp forms.
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arxiv:1501.03289
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we study the tidal interaction of galaxies in the eridanus supergroup, using hi data from the pre - pilot survey of wallaby ( widefield askap l - band legacy all - sky blind survey ). we obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter $ s _ { sum } $. for low - mass galaxies of $ m _ * \ lesssim 10 ^ 9 m _ \ odot $, we find a dependence of decreasing hi - to - optical disk size ratio with increasing $ s _ { sum } $, but no dependence of hi spectral line asymmetry with $ s _ { sum } $. this is consistent with the behavior expected under tidal stripping. we confirm that the color profile shape and color gradient depend on the stellar mass, but there is additional correlation of low - mass galaxies having their color gradients within $ 2r _ { 50 } $ increasing with higher $ s _ { sum } $. for these low - mass galaxies, the dependence of color gradients on $ s _ { sum } $ is driven by color becoming progressively redder in the inner disk when tidal perturbations are stronger. for high - mass galaxies, there is no dependence of color gradients on $ s _ { sum } $, and we find a marginal reddening throughout the disks with increasing $ s _ { sum } $. our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.
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arxiv:2112.06564
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foundational vision models, such as the segment anything model ( sam ), have achieved significant breakthroughs through extensive pre - training on large - scale visual datasets. despite their general success, these models may fall short in specialized tasks with limited data, and fine - tuning such large - scale models is often not feasible. current strategies involve incorporating adaptors into the pre - trained sam to facilitate downstream task performance with minimal model adjustment. however, these strategies can be hampered by suboptimal learning approaches for the adaptors. in this paper, we introduce a novel multi - scale contrastive adaptor learning method named mca - sam, which enhances adaptor performance through a meticulously designed contrastive learning framework at both token and sample levels. our token - level contrastive adaptor ( tc - adaptor ) focuses on refining local representations by improving the discriminability of patch tokens, while the sample - level contrastive adaptor ( sc - adaptor ) amplifies global understanding across different samples. together, these adaptors synergistically enhance feature comparison within and across samples, bolstering the model ' s representational strength and its ability to adapt to new tasks. empirical results demonstrate that mca - sam sets new benchmarks, outperforming existing methods in three challenging domains : camouflage object detection, shadow segmentation, and polyp segmentation. specifically, mca - sam exhibits substantial relative performance enhancements, achieving a 20. 0 % improvement in mae on the cod10k dataset, a 6. 0 % improvement in mae on the camo dataset, a 15. 4 % improvement in ber on the istd dataset, and a 7. 9 % improvement in mdice on the kvasir - seg dataset.
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arxiv:2408.05936
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we consider the models of relaxational dynamics within the framework of berendsen ' s and nose - hoover ' s thermostats. on studying the crucial case of ideal gas we come to the conclusion that both models mentioned above do not allow for describing the true thermodynamical equilibrium.
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arxiv:cond-mat/0112477
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we study exact effective superpotentials of four - dimensional { \ cal n } = 2 supersymmetric gauge theories with gauge group u ( n ) and various amounts of fundamental matter on r ^ 3 x s ^ 1, broken to { \ cal n } = 1 by turning on a classical superpotential for the adjoint scalar. on general grounds these superpotentials can easily be constructed once we identify a suitable set of coordinates on the moduli space of the gauge theory. these coordinates have been conjectured to be the phase space variables of the classical integrable system which underlies the { \ cal n } = 2 gauge theory. for the gauge theory under study these integrable systems are degenerations of the classical, inhomogeneous, periodic sl ( 2, c ) spin chain. ambiguities in the degeneration provide multiple coordinate patches on the gauge theory moduli space. by studying the vacua of the superpotentials in several examples we find that the spin chain provides coordinate patches that parametrize holomorphically the part of the gauge theory moduli space which is connected to the electric ( as opposed to magnetic or baryonic ) higgs and coulomb branch vacua. the baryonic branch root is on the edge of some coordinate patches. as a product of our analysis all maximally confining ( non - baryonic ) seiberg - witten curve factorizations for n _ f \ leq n _ c are obtained, explicit up to one constraint for equal mass flavors and up to two constraints for unequal mass flavors. gauge theory addition and multiplication maps are shown to have a natural counterpart in this construction. furthermore it is shown how to integrate in the meson fields in this formulation in order to obtain three and four dimensional affleck - dine - seiberg - like superpotentials.
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arxiv:hep-th/0411110
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separation of competing speech is a key challenge in signal processing and a feat routinely performed by the human auditory brain. a long standing benchmark of the spectrogram approach to source separation is known as the ideal binary mask. here, we train a convolutional deep neural network, on a two - speaker cocktail party problem, to make probabilistic predictions about binary masks. our results approach ideal binary mask performance, illustrating that relatively simple deep neural networks are capable of robust binary mask prediction. we also illustrate the trade - off between prediction statistics and separation quality.
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arxiv:1503.06962
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we present new bounds on the existence of general quantum maximum distance separable codes ( qmds ) : the length $ n $ of all qmds codes with local dimension $ d $ and distance $ d \ geq 3 $ is bounded by $ n \ leq d ^ 2 + d - 2 $. we obtain their weight distribution and present additional bounds that arise from rains ' shadow inequalities. our main result can be seen as a generalization of bounds that are known for the two special cases of stabilizer qmds codes and absolutely maximally entangled states, and confirms the quantum mds conjecture in the special case of distance - three codes. as the existence of qmds codes is linked to that of highly entangled subspaces ( in which every vector has uniform $ r $ - body marginals ) of maximal dimension, our methods directly carry over to address questions in multipartite entanglement.
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arxiv:1907.07733
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mixed dark matter models with one low - mass ( e. g. 2. 4ev ) neutrino flavor are shown to be in good agreement with observations if the neutrinos have non - zero chemical potentials. this agreement holds ( except for the problem with a low - age universe ) even for high values of the hubble - parameter. massless neutrinos with non - zero chemical potentials may reconcile cold dark matter with observations. some fine - tuning is required to avoid problems with big bang nucleosynthesis.
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arxiv:astro-ph/9502052
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given a max - plus linear system and a semimodule, the problem of computing the maximal controlled invariant subsemimodule is still open to this day. in this paper, we consider this problem for the specific class of fully actuated systems and constraints in the form of precedence semimodules. the assumption of full actuation corresponds to the existence of an input for each component of the system state. a precedence semimodule is the set of solutions of inequalities typically used to represent time - window constraints. we prove that, in this setting, it is possible to ( i ) compute the maximal controlled invariant subsemimodule and ( ii ) decide the convergence of a fixed - point algorithm introduced by r. d. katz in strongly polynomial time.
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arxiv:2503.03357
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emerging technologies are technologies whose development, practical applications, or both are still largely unrealized. these technologies are generally new but also include old technologies finding new applications. emerging technologies are often perceived as capable of changing the status quo. emerging technologies are characterized by radical novelty ( in application even if not in origins ), relatively fast growth, coherence, prominent impact, and uncertainty and ambiguity. in other words, an emerging technology can be defined as " a radically novel and relatively fast growing technology characterised by a certain degree of coherence persisting over time and with the potential to exert a considerable impact on the socio - economic domain ( s ) which is observed in terms of the composition of actors, institutions and patterns of interactions among those, along with the associated knowledge production processes. its most prominent impact, however, lies in the future and so in the emergence phase is still somewhat uncertain and ambiguous. " emerging technologies include a variety of technologies such as educational technology, information technology, nanotechnology, biotechnology, robotics, and artificial intelligence. new technological fields may result from the technological convergence of different systems evolving towards similar goals. convergence brings previously separate technologies such as voice ( and telephony features ), data ( and productivity applications ) and video together so that they share resources and interact with each other, creating new efficiencies. emerging technologies are those technical innovations which represent progressive developments within a field for competitive advantage ; converging technologies represent previously distinct fields which are in some way moving towards stronger inter - connection and similar goals. however, the opinion on the degree of the impact, status and economic viability of several emerging and converging technologies varies. = = history of emerging technologies = = in the history of technology, emerging technologies are contemporary advances and innovation in various fields of technology. over centuries innovative methods and new technologies have been developed and opened up. some of these technologies are due to theoretical research, and others from commercial research and development. technological growth includes incremental developments and disruptive technologies. an example of the former was the gradual roll - out of dvd ( digital video disc ) as a development intended to follow on from the previous optical technology compact disc. by contrast, disruptive technologies are those where a new method replaces the previous technology and makes it redundant, for example, the replacement of horse - drawn carriages by automobiles and other vehicles. = = emerging technology debates = = many writers, including computer scientist bill joy, have identified clusters of technologies that they consider critical to humanity ' s future. joy warns that the
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https://en.wikipedia.org/wiki/Emerging_technologies
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this article addresses a fundamental problem faced by the ab initio community : the lack of an effective formalism for the rapid exploration and exchange of new methods. to rectify this, we introduce a novel, basis - set independent, matrix - based formulation of generalized density functional theories which reduces the development, implementation, and dissemination of new ab initio techniques to the derivation and transcription of a few lines of algebra. this new framework enables us to concisely demystify the inner workings of fully functional, highly efficient modern ab initio codes and to give complete instructions for the construction of such for calculations employing arbitrary basis sets. within this framework, we also discuss in full detail a variety of leading - edge ab initio techniques, minimization algorithms, and highly efficient computational kernels for use with scalar as well as shared and distributed - memory supercomputer architectures.
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arxiv:cond-mat/9909130
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over half a century from the discovery of gamma - ray bursts ( grbs ), the dominant radiation mechanism responsible for their bright and highly variable prompt emission remains poorly understood. spectral information alone has proven insufficient for understanding the composition and main energy dissipation mechanism in grb jets. high - sensitivity polarimetric observations from upcoming instruments in this decade may help answer such key questions in grb physics. this article reviews the current status of prompt grb polarization measurements and provides comprehensive predictions from theoretical models. a concise overview of the fundamental questions in prompt grb physics is provided. important developments in gamma - ray polarimetry including a critical overview of different past instruments are presented. theoretical predictions for different radiation mechanisms and jet structures are confronted with time - integrated and time - resolved measurements. the current status and capabilities of upcoming instruments regarding the prompt emission are presented. the very complimentary information that can be obtained from polarimetry of x - ray flares as well as reverse - shock and early to late forward - shock ( afterglow ) emission is highlighted. finally, promising directions for overcoming the inherent difficulties in obtaining statistically significant prompt - grb polarization measurements are discussed, along with prospects for improvements in the theoretical modeling, which may lead to significant advances in the field.
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arxiv:2109.03286
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does galaxy evolution proceed through the green valley via multiple pathways or as a single population? motivated by recent results highlighting radically different evolutionary pathways between early - and late - type galaxies, we present results from a simple bayesian approach to this problem wherein we model the star formation history ( sfh ) of a galaxy with two parameters, [ t, \ tau ] and compare the predicted and observed optical and near - ultraviolet colours. we use a novel method to investigate the morphological differences between the most probable sfhs for both disc - like and smooth - like populations of galaxies, by using a sample of 126, 316 galaxies ( 0. 01 < z < 0. 25 ) with probabilistic estimates of morphology from galaxy zoo. we find a clear difference between the quenching timescales preferred by smooth - and disc - like galaxies, with three possible routes through the green valley dominated by smooth - ( rapid timescales, attributed to major mergers ), intermediate - ( intermediate timescales, attributed to minor mergers and galaxy interactions ) and disc - like ( slow timescales, attributed to secular evolution ) galaxies. we hypothesise that morphological changes occur in systems which have undergone quenching with an exponential timescale \ tau < 1. 5 gyr, in order for the evolution of galaxies in the green valley to match the ratio of smooth to disc galaxies observed in the red sequence. these rapid timescales are instrumental in the formation of the red sequence at earlier times ; however we find that galaxies currently passing through the green valley typically do so at intermediate timescales.
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arxiv:1501.05955
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within the thermal wave model framework a comparison among wigner function, husimi function, and the phase - space distribution given by a particle tracking code is made for a particle beam travelling through a linear lens with small aberrations. the results show that the quantum - like approach seems to be very promising.
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arxiv:acc-phys/9510003
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we study fluctuation properties of a one - dimensional anisotropic heisenberg model out of equilibrium, focusing in particular on the gapped regime. within the open - system setting we study large - deviation properties of the spin current. numerically evaluating the first four current cumulants in a nonequilibrium stationary state at high energies, we find that the first two cumulants scale with the system size in a diffusive way, while the 3rd and the 4th cumulants do not. this means that the model is not an ordinary diffusive spin conductor.
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arxiv:1405.5541
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a challenge that machine learning practitioners in the industry face is the task of selecting the best model to deploy in production. as a model is often an intermediate component of a production system, online controlled experiments such as a / b tests yield the most reliable estimation of the effectiveness of the whole system, but can only compare two or a few models due to budget constraints. we propose an automated online experimentation mechanism that can efficiently perform model selection from a large pool of models with a small number of online experiments. we derive the probability distribution of the metric of interest that contains the model uncertainty from our bayesian surrogate model trained using historical logs. our method efficiently identifies the best model by sequentially selecting and deploying a list of models from the candidate set that balance exploration - exploitation. using simulations based on real data, we demonstrate the effectiveness of our method on two different tasks.
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arxiv:2105.13420
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clouds play a crucial role in the earth ' s water and energy cycles, underscoring the importance of high spatiotemporal resolution data on cloud phase and properties for accurate numerical modeling and weather prediction. currently, moderate resolution imaging spectroradiometer ( modis ) provides cloud products with a spatial resolution of 1 km. however, these products suffer from a lengthy revisit cycle. this study develops a generative diffusion model ( donated as clouddiff ) for super - resolution retrieval of high spatiotemporal cloud phase and properties, applicable both day and night. leveraging 2 km spatial resolution himawari - 8 advanced himawari imager ( ahi ) thermal infrared ( tir ) radiances and viewing geometry as condition, alongside daytime modis products as targets, the model can generate cloud phase ( clp ), cloud top height ( cth ), cloud optical thickness ( cot ), and cloud effective radius ( cer ) at 1 km spatial resolution and 10 - minute temporal resolution. the conditional diffusion model can generate sharper images and capture finer local features than deterministic super - resolution approaches. it draws multiple samples based on the underlying probability distribution, enabling retrieval uncertainty assessment. evaluations show agreement between cloud phase and properties derived from the clouddiff and modis cloud products. the ensemble mean is found to enhance retrieval accuracy and credibility, outperforming the deterministic model.
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arxiv:2405.04483
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in this letter, we propose a quantized topological response in trapped 1d quantum gases. the experimental protocol for the response requires the application of an instant optical pulse to a half - infinite region in an asymptotically harmonic trap and measuring the density distribution. we show that the corresponding linear response is described by a universal quantized formula in the thermal dynamical limit, which is invariant under local continuous deformations of the trapping potential $ v $, atom distribution $ f _ \ lambda $, the spatial envelope of the optical pulse $ \ theta _ p $, and the measurement region $ \ theta _ m $. we test the statement by various numerical analysis, the result of which is consistent with the analytical prediction to high accuracy. we further show that a short but finite optical pulse duration only results in a violation of the quantization near the transition time, which suggests that quantized response could be observed in realistic experiments. we also generalize our results to non - linear quantized topological responses for atoms in higher dimensional harmonic traps.
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arxiv:2207.02382
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a combined variable theory of gravity and scalar field is developed under adm formulation by redefining new canonical conjugate variables ( { \ phi }, { \ pi } ). it is a dynamical theory of the space - matter with implicit time dependence. quantizing this new field theory results in quantization of geometry and scalar field combined.
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arxiv:1704.04004
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a large electric field is typically present in anodic or passive oxide films. stresses induced by such a large electric field are critical in understanding the breakdown mechanism of thin oxide films and improving their corrosion resistance. in this work, we consider electromechanical coupling through the electrostrictive effect. a continuum model incorporating lattice misfit and electric field - induced stresses is developed. we perform a linear stability analysis of the full coupled model and show that, for typical oxides, neglecting electrostriction underestimates the film ' s instability, especially in systems with a large electric field. moreover, a region where electrostriction can potentially provide a stabilizing effect is identified, allowing electrostriction to enhance corrosion resistance. we identified an equilibrium electric field intrinsic to the system and the corresponding equilibrium film thickness. the film ' s stability is very sensitive to the electric field : a 40 percent deviation from the equilibrium electric field can change the maximum growth rate by nearly an order of magnitude. moreover, our model reduces to classical morphological instability models in the limit of misfit - only, electrostatic - only, and no - electrostriction cases. finally, the effect of various parameters on the film ' s stability is studied.
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arxiv:2404.05093
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grasp planning and most specifically the grasp space exploration is still an open issue in robotics. this article presents a data - driven oriented methodology to model the grasp space of a multi - fingered adaptive gripper for known objects. this method relies on a limited dataset of manually specified expert grasps, and uses variational autoencoder to learn grasp intrinsic features in a compact way from a computational point of view. the learnt model can then be used to generate new non - learnt gripper configurations to explore the grasp space.
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arxiv:2109.08504
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an experimental photochemistry study involving gas - and solid - phase amino acids ( glycine, dl - valine, dl - proline ) and nucleobases ( adenine and uracil ) under soft x - rays was performed. the aim was to test the molecular stabilities of essential biomolecules against ionizing photon fields inside dense molecular clouds and protostellar disks analogs. in these environments, the main energy sources are the cosmic rays and soft x - rays. the measurements were taken at the brazilian synchrotron light laboratory ( lnls ), employing 150 ev photons. in - situ sample analysis was performed by time - of - flight mass spectrometer ( tof - ms ) and fourier transform infrared ( ftir ) spectrometer, for gas - and solid - phase analysis, respectively. the half - life of solid phase amino acids, assumed to be present at grain mantles, is at least 3e5 years and 3e8 years inside dense molecular clouds and protoplanetary disks, respectively. we estimate that for gas - phase compounds these values increase one order of magnitude since the dissociation cross section of glycine is lower at gas - phase than at solid phase for the same photon energy. the half - life of solid phase nucleobases is about 2 - 3 orders of magnitude higher than found for amino acids. the results indicate that nucleobases are much more resistant to ionizing radiation than amino acids. we consider these implications for the survival and transfer of biomolecules in space environments.
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arxiv:1010.1771
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in recent years, more and more gamma - ray bursts with late rebrightenings in multi - band afterglows unveil the late - time activities of the central engines. grb 100814a is a special one among the well - sampled events, with complex temporal and spectral evolution. the single power - law shallow decay index of the optical light curve observed by grond between 640 s and 10 ks is $ \ alpha _ { \ rm opt } = 0. 57 \ pm 0. 02 $, which apparently conflicts with the simple external shock model expectation. especially, there is a remarkable rebrightening in the optical to near infrared bands at late time, challenging the external shock model with synchrotron emission coming from the interaction of the blast wave with the surrounding interstellar medium. in this paper, we invoke a magnetar with spin evolution to explain the complex multi - band afterglow emission of grb 100814a. the initial shallow decay phase in optical bands and the plateau in x - ray can be explained as due to energy injection from a spin - down magnetar. at late time, with the falling of materials from the fall - back disk onto the central object of the burster, angular momentum of the accreted materials is transferred to the magnetar, which leads to a spin - up process. as a result, the magnetic dipole radiation luminosity will increase, resulting in the significant rebrightening of the optical afterglow. it is shown that the observed multi - band afterglow emission can be well reproduced by the model.
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arxiv:1504.01824
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an increasing number of applications is concerned with recovering a sparse matrix from noisy observations. in this paper, we consider the setting where each row of the unknown matrix is sparse. we establish minimax optimal rates of convergence for estimating matrices with row sparsity. a major focus in the present paper is on the derivation of lower bounds.
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arxiv:1509.00319
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layered models like neural networks appear to extract key features from data through empirical risk minimization, yet the theoretical understanding for this process remains unclear. motivated by these observations, we study a two - layer nonparametric regression model where the input undergoes a linear transformation followed by a nonlinear mapping to predict the output, mirroring the structure of two - layer neural networks. in our model, both layers are optimized jointly through empirical risk minimization, with the nonlinear layer modeled by a reproducing kernel hilbert space induced by a rotation and translation invariant kernel, regularized by a ridge penalty. our main result shows that the two - layer model can " automatically " induce regularization and facilitate feature learning. specifically, the two - layer model promotes dimensionality reduction in the linear layer and identifies a parsimonious subspace of relevant features - - even without applying any norm penalty on the linear layer. notably, this regularization effect arises directly from the model ' s layered structure, independent of optimization dynamics. more precisely, assuming the covariates have nonzero explanatory power for the response only through a low dimensional subspace ( central mean subspace ), the linear layer consistently estimates both the subspace and its dimension. this demonstrates that layered models can inherently discover low - complexity solutions relevant for prediction, without relying on conventional regularization methods. real - world data experiments further demonstrate the persistence of this phenomenon in practice.
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arxiv:2310.11736
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the brain is immensely complex, with diverse components and dynamic interactions building upon one another to orchestrate a wide range of functions and behaviors. understanding patterns of these complex interactions and how they are coordinated to support collective neural activity and function is critical for parsing human and animal behavior, treating mental illness, and developing artificial intelligence. rapid experimental advances in imaging, recording, and perturbing neural systems across various species now provide opportunities and challenges to distill underlying principles of brain organization and function. here, we take stock of recent progresses and review methods used in the statistical analysis of brain networks, drawing from fields of statistical physics, network theory and information theory. our discussion is organized by scale, starting with models of individual neurons and extending to large - scale networks mapped across brain regions. we then examine the organizing principles and constraints that shape the biological structure and function of neural circuits. finally, we describe current opportunities aimed at improving models in light of recent developments and at bridging across scales to contribute to a better understanding of brain networks.
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arxiv:2408.02640
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fiber - reinforced polymer composite ( frpc ) materials are used extensively in various industries, such as aerospace, automobiles, and electronics packaging, due to their remarkable specific strength and desirable properties, such as enhanced durability and corrosion resistance. the evolution of thermal properties in frpcs is crucial for advancing thermal management systems, optimizing material performance, and enhancing energy efficiency across these diverse sectors. despite significant research efforts to develop new materials with improved thermal properties and reduced thermal degradation, there is a lack of understanding of the thermal transport phenomena considering the influence of microscale reinforcement morphology in these composites. in the current study, we performed experimental investigations complemented by computations to determine the thermal transport properties and associated phenomena in epoxy and carbon fiber - reinforced epoxy composites. the experimental findings were utilized as input data for numerical analysis to examine the impact of fiber morphology and volume fraction in thermal transport phenomena. our results revealed that composites incorporating non - circular fibers manifested higher thermal conductivity than traditional circular fibers in the transverse direction. this can be attributed to increased interconnected heat flow pathways facilitated by the increased surface area of non - circular fibers with the same cross - sectional areas, resulting in efficient heat transfer.
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arxiv:2403.17650
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we study the quantum walk in momentum space using a coin arranged in quasi - periodic sequences following a fibonacci prescription. we build for this system a classical map based on the trace of the evolution operator. the sub - ballistic behavior of this quantum walk is connected with the power - law decay of the time correlations of the trace map.
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arxiv:0802.2289
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since diarization and source separation of meeting data are closely related tasks, we here propose an approach to perform the two objectives jointly. it builds upon the target - speaker voice activity detection ( ts - vad ) diarization approach, which assumes that initial speaker embeddings are available. we replace the final combined speaker activity estimation network of ts - vad with a network that produces speaker activity estimates at a time - frequency resolution. those act as masks for source extraction, either via masking or via beamforming. the technique can be applied both for single - channel and multi - channel input and, in both cases, achieves a new state - of - the - art word error rate ( wer ) on the libricss meeting data recognition task. we further compute speaker - aware and speaker - agnostic wers to isolate the contribution of diarization errors to the overall wer performance.
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arxiv:2303.03849
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we continue our account of relativistic recoil effects in muonic atoms and present explicitly analytic results at first order in electron - vacuum - polarization effects. the results are obtained within a grotch - type approach based on an effective dirac equation. some expressions are cumbersome and we investigate their asymptotic behavior. previously relativistic two - body effects due to the one - loop electron vacuum polarization were studied by several groups. our results found here are consistent with the previous result derived within a breit - type approach ( including ours ) and disagree with a recent attempt to apply a grotch - type approach.
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arxiv:1311.5790
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due to a printing error the above mentioned article [ annals of applied probability 10 ( 2000 ) 75 - - 103, doi : 10. 1214 / aoap / 1019737665 ] had numerous equations appearing incorrectly in the print version of this paper. the entire article follows as it should have appeared. ims apologizes to the author and the readers for this error. a recent paper by harrison and van mieghem explained in general mathematical terms how one forms an ` ` equivalent workload formulation ' ' of a brownian network model. denoting by $ z ( t ) $ the state vector of the original brownian network, one has a lower dimensional state descriptor $ w ( t ) = mz ( t ) $ in the equivalent workload formulation, where $ m $ can be chosen as any basis matrix for a particular linear space. this paper considers brownian models for a very general class of open processing networks, and in that context develops a more extensive interpretation of the equivalent workload formulation, thus extending earlier work by laws on alternate routing problems. a linear program called the static planning problem is introduced to articulate the notion of ` ` heavy traffic ' ' for a general open network, and the dual of that linear program is used to define a canonical choice of the basis matrix $ m $. to be specific, rows of the canonical $ m $ are alternative basic optimal solutions of the dual linear program. if the network data satisfy a natural monotonicity condition, the canonical matrix $ m $ is shown to be nonnegative, and another natural condition is identified which ensures that $ m $ admits a factorization related to the notion of resource pooling.
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arxiv:math/0610352
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kernel methods are powerful and flexible approach to solve many problems in machine learning. due to the pairwise evaluations in kernel methods, the complexity of kernel computation grows as the data size increases ; thus the applicability of kernel methods is limited for large scale datasets. random fourier features ( rff ) has been proposed to scale the kernel method for solving large scale datasets by approximating kernel function using randomized fourier features. while this method proved very popular, still it exists shortcomings to be effectively used. as rff samples the randomized features from a distribution independent of training data, it requires sufficient large number of feature expansions to have similar performances to kernelized classifiers, and this is proportional to the number samples in the dataset. thus, reducing the number of feature dimensions is necessary to effectively scale to large datasets. in this paper, we propose a kernel approximation method in a data dependent way, coined as pseudo random fourier features ( prff ) for reducing the number of feature dimensions and also to improve the prediction performance. the proposed approach is evaluated on classification and regression problems and compared with the rff, orthogonal random features and nystr { \ " o } m approach
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arxiv:1711.09783
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the structure of transition amplitudes in field theory in a three - dimensional space whose spatial coordinates are noncommutative and satisfy the su ( 2 ) lie algebra commutation relations is examined. in particular, the basic notions for constructing the observables of the theory as well as subtleties related to the proper treatment of $ \ delta $ distributions ( corresponding to conservation laws ) are introduced. explicit examples are given for scalar field theory amplitudes in the lowest order of perturbation.
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arxiv:0712.1670
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primordial magnetic fields ( pmfs ) may explain observations of magnetic fields on extragalactic scales. they are most cleanly constrained by measurements of cosmic microwave background radiation ( cmb ) anisotropies. their effects on cosmic recombination may even be at the heart of the resolution of the hubble tension. we present the most detailed analysis of the effects of pmfs on cosmic recombination to date. to this end we extend the public magneto - hydrodynamic code { \ sl enzo } with a new cosmic recombination routine, monte - carlo simulations of lyman - $ \ alpha $ photon transport, and a compton drag term in the baryon momentum equation. the resulting code allows us, for the first time, to realistically predict the impact of pmfs on the cosmic ionization history and the clumping of baryons during cosmic recombination. our results identify the importance of mixing of lyman - $ \ alpha $ photons between overdense - and underdense - regions for small pmf strength. this mixing speeds up recombination beyond the speed - up due to clumping. we also investigate the effects of pecuilar flows on the recombination rate and find it to be small for small pmf strengths. for non - helical pmfs with a batchelor spectrum we find a surprising dependency of results on ultra - violet magnetic modes. we further show that the increase in the ionization fraction at low redshift by hydrodynamic baryon heating due to pmf dissipation is completely compensated by the faster recombination from baryon clumping. the present study shall serve as a theoretical foundation for a future precise comparison of recombination with pmfs to cmb data.
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arxiv:2312.11448
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we present and compare two families of ensembles of random density matrices. the first, static ensemble, is obtained foliating an unbiased ensemble of density matrices. as criterion we use fixed purity as the simplest example of a useful convex function. the second, dynamic ensemble, is inspired in random matrix models for decoherence where one evolves a separable pure state with a random hamiltonian until a given value of purity in the central system is achieved. several families of hamiltonians, adequate for different physical situations, are studied. we focus on a two qubit central system, and obtain exact expressions for the static case. the ensemble displays a peak around werner - like states, modulated by nodes on the degeneracies of the density matrices. for moderate and strong interactions good agreement between the static and the dynamic ensembles is found. even in a model where one qubit does not interact with the environment excellent agreement is found, but only if there is maximal entanglement with the interacting one. the discussion is started recalling similar considerations for scattering theory. at the end, we comment on the reach of the results for other convex functions of the density matrix, and exemplify the situation with the von neumann entropy.
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arxiv:1407.7052
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the galactic superluminal transient x - ray source grs 1915 + 105 was observed with the pointed proportional counters ( ppcs ) onboard the indian satellite irs - p3 during 1996 july 23 - 27. we report here details of the behavior of this source during the relatively quiet and low luminosity state. large intensity variations by a factor of 2 to 3, generally seen in black - hole candidates, are observed at a time scale of 100 ms to few seconds. no significant variation is detected over larger time scale of minute or more. the intensity variations are described as sum of shots in the light curve, and the number distribution of the shots are found to be exponential function of the fluence and duration of the shots. the cross correlation spectrum between 6 - 18 kev and 2 - 6 kev x - rays is found to have asymmetry signifying a delay of the hard x - rays by about 0. 2 to 0. 4 sec. this supports the idea of hard x - rays being generated by compton up - scattering from high energy clouds near the source of soft x - rays. very strong and narrow quasi periodic oscillations in the frequency range 0. 62 to 0. 82 hz are observed. we discuss about a model which explains a gradual change in the qpo frequencies with corresponding changes in the mass accretion rate of the disk.
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arxiv:astro-ph/9710283
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we investigate new shapes of local primordial non - gaussianities in the cmb. allowing for a primordial isocurvature mode along with the main adiabatic one, the angular bispectrum is in general a superposition of six distinct shapes : the usual adiabatic term, a purely isocurvature component and four additional components that arise from correlations between the adiabatic and isocurvature modes. we present a class of early universe models in which various hierarchies between these six components can be obtained, while satisfying the present upper bound on the isocurvature fraction in the power spectrum. remarkably, even with this constraint, detectable non - gaussianity could be produced by isocurvature modes. we finally discuss the prospects of detecting these new shapes with the planck satellite.
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arxiv:1104.2567
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elastic ed scattering, with deuteron polarization, up to high momentum transfer provides detailed information on the deuteron wave function. this determines the range dependence of the orbital and spin components of the one - and two - body currents, restricting contributions of isobar and meson - exchange currents and of quark / gluon degrees of freedom, as well as the nucleon component. the r - matrix boundary condition model combines all these effects, predicting nucleon - nucleon reactions and the deuteron form - factors simultaneously. a brief description of the model is followed by a comparison of its results with data, emphasizing the restrictions placed on the model by ed elastic form - factors.
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arxiv:nucl-th/0002026
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the schrodinger equation is considered with the first order time derivative changed to a caputo fractional derivative, the time fractional schrodinger equation. the resulting hamiltonian is found to be non - hermitian and non - local in time. the resulting wave functions are thus not invariant under time reversal. the time fractional schrodinger equation is solved for a free particle and for a potential well. probability and the resulting energy levels are found to increase over time to a limiting value depending on the order of the time derivative. new identities for the mittag - leffler function are also found and presented in an appendix.
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arxiv:math-ph/0410028
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mammalian offspring require parental care, at least in the form of suckling during their early development. while mothers need to invest considerable time and energy in ensuring the survival of their current offspring, they also need to optimize their investment in one batch of offspring in order to ensure future reproduction and hence lifetime reproductive success. free - ranging dogs live in small social groups, mate promiscuously, and lack the cooperative breeding biology of other group living canids. they face high early life mortality, which in turn reduces fitness benefits of the mother from a batch of pups. we carried out a field based study on free - ranging dogs in india to understand the nature of parental care provided by mothers at different stages of pup development. using behavioural patterns of mother - pup interactions, we draw up a timeline of pup ontogeny. our analysis reveals that mothers cleverly reduce investment in energy intensive active care and increase passive care as the pups grow older, thereby keeping overall levels of parental care more or less constant over pup age.
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arxiv:1607.01135
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modern observations based on general relativity indicate that the spatial geometry of the expanding, large - scale universe is very nearly euclidean. this basic empirical fact is at the core of the so - called " flatness problem ", which is widely perceived to be a major outstanding problem of modern cosmology and as such forms one of the prime motivations behind inflationary models. an inspection of the literature and some further critical reflection however quickly reveals that the typical formulation of this putative problem is fraught with questionable arguments and misconceptions and that it is moreover imperative to distinguish between different varieties of problem. it is shown that the observational fact that the large - scale universe is so nearly flat is ultimately no more puzzling than similar " anthropic coincidences ", such as the specific ( orders of magnitude of the ) values of the gravitational and electromagnetic coupling constants. in particular, there is no fine - tuning problem in connection to flatness of the kind usually argued for. the arguments regarding flatness and particle horizons typically found in cosmological discourses in fact address a mere $ single $ issue underlying the standard flrw cosmologies, namely the $ extreme $ improbability of these models with respect to any " reasonable measure " on the " space of all spacetimes ". this issue may be expressed in different ways and a phase space formulation, due to penrose, is presented here. a horizon problem only arises when additional assumptions - which are usually kept implicit and at any rate seem rather speculative - are made.
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arxiv:1803.05148
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in this paper we find chromatic numbers of distance graphs $ g ( n, 3, 2 ) $ for infinitely many n. also we improve upper bound for $ \ chi ( g ( n, r, s ) ) $ in large part of cases.
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arxiv:1608.01873
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evidence networks can enable bayesian model comparison when state - of - the - art methods ( e. g. nested sampling ) fail and even when likelihoods or priors are intractable or unknown. bayesian model comparison, i. e. the computation of bayes factors or evidence ratios, can be cast as an optimization problem. though the bayesian interpretation of optimal classification is well - known, here we change perspective and present classes of loss functions that result in fast, amortized neural estimators that directly estimate convenient functions of the bayes factor. this mitigates numerical inaccuracies associated with estimating individual model probabilities. we introduce the leaky parity - odd power ( l - pop ) transform, leading to the novel ` ` l - pop - exponential ' ' loss function. we explore neural density estimation for data probability in different models, showing it to be less accurate and scalable than evidence networks. multiple real - world and synthetic examples illustrate that evidence networks are explicitly independent of dimensionality of the parameter space and scale mildly with the complexity of the posterior probability density function. this simple yet powerful approach has broad implications for model inference tasks. as an application of evidence networks to real - world data we compute the bayes factor for two models with gravitational lensing data of the dark energy survey. we briefly discuss applications of our methods to other, related problems of model comparison and evaluation in implicit inference settings.
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arxiv:2305.11241
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in this paper, we investigate a decentralized control problem with nested subsystems, which is a general model for one - directional communication amongst many subsystems. the noises in our dynamics are modelled as uncertain variables which take values in finite sets. the objective is to minimize a worst - case shared cost. we demonstrate how the prescription approach can simplify the information structure and derive a structural form for optimal control strategies. the structural form allows us to restrict attention to control strategies whose domains do not grow in size with time, and thus, this form can be utilized in systems with long time horizons. finally, we present a dynamic program to derive the optimal control strategies and validate our results with a numerical example.
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arxiv:2109.06328
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