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results are reported from a search for physics beyond the standard model in proton - proton collision events with a charged lepton ( electron or muon ), two jets identified as originating from a bottom quark decay, and significant imbalance in the transverse momentum. the search was performed using a data sample corresponding to 35. 9 inverse femtobarns, collected by the cms experiment in 2016 at sqrt ( s ) = 13 tev. events with this signature can arise, for example, from the electroweak production of gauginos, which are predicted in models based on supersymmetry. the event yields observed in data are consistent with the estimated standard model backgrounds. limits are obtained on the cross sections for chargino - neutralino production in a simplified model of supersymmetry with the decays chargino to w + / - lsp and neutralino to h lsp. values of m [ chargino ] between 220 and 490 gev are excluded at 95 % confidence level by this search when the lsp is massless, and values of m [ lsp ] are excluded up to 110 gev for m [ chargino ] about 450 gev.
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arxiv:1706.09933
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unconditional security of the bb84 quantum key distribution protocol has been proved by exploiting the fundamental laws of quantum mechanics, but the practical quantum key distribution system maybe hacked by considering the imperfect state preparation and measurement respectively. until now, different attacking schemes have been proposed by utilizing imperfect devices, but the general security analysis model against all of the practical attacking schemes has not been proposed. here, we demonstrate that the general practical attacking schemes can be divided into the trojan horse attack, strong randomness attack and weak randomness attack respectively. we prove security of bb84 protocol under randomness attacking models, and these results can be applied to guarantee the security of the practical quantum key distribution system.
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arxiv:1508.06396
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this study proposes a novel coupled - mode theory for two - dimensional exterior helmholtz problems. the proposed approach is based on the separation of the entire space r2 into a fictitious disk and its exterior. the disk is allocated in such a way that it comprises all the inhomogeneity ; therefore, the exterior supports cylindrical waves with a continuous spectrum. for the interior, we expand an unknown wave field using normal modes that satisfy some auxiliary boundary conditions on the surface of the disk. for the interior expansion, we propose combining the neumann and dirichlet normal modes. we show that the proposed expansion sacrifices l2 orthogonality but significantly improve the convergence. finally, we present some numerical verifications of the proposed coupled - mode theory.
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arxiv:2201.09502
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recently, superconductivity at high temperatures has been observed in bulk la $ _ 3 $ ni $ _ 2 $ o $ _ { 7 - { \ delta } } $ under high pressure. however, the attainment of high - purity la $ _ 3 $ ni $ _ 2 $ o $ _ { 7 - { \ delta } } $ single crystals, exhibiting controlled and homogeneous stoichiometry through the post - annealing process in an oxygen - rich floating zone furnace, remains a formidable challenge. here, we report the crystal structure and physical properties of single crystals of sr - doped la $ _ 3 $ ni $ _ 2 $ o $ _ 7 $ synthesized at high pressure ( 20 gpa ) and high temperature ( 1400 { \ deg } c ). through single crystal x - ray diffraction, we showed that high - pressure - synthesized paramagnetic sr - doped la $ _ 3 $ ni $ _ 2 $ o $ _ 7 $ crystallizes in an orthorhombic structure with ni - o - ni bond angles of 173. 4 ( 2 ) { \ deg } out - of - plane and 175. 0 ( 2 ) { \ deg } and 176. 7 ( 2 ) { \ deg } in plane. the substitution of sr alters in band filling and the ratio of ni $ ^ { 2 + } $ / ni $ ^ { 3 + } $ in sr - doped la $ _ 3 $ ni $ _ 2 $ o $ _ 7 $, aligning them with those of " la $ _ 3 $ ni $ _ 2 $ o $ _ { 7. 05 } $ ", thereby leading to significant modifications in properties under high pressure relative to the unsubstituted parent phase. at ambient pressure, sr - doped la $ _ 3 $ ni $ _ 2 $ o $ _ 7 $ exhibits insulating properties, and the conductivity increases as pressure goes up to 10 gpa. however, upon further increasing pressure beyond 10. 7 gpa, sr - doped la $ _ 3 $ ni $ _ 2 $ o $ _ 7 $ transits back from a metal - like behavior to an insulator. the insulator - metal - insulator trend under high pressure dramatically differs from the behavior of the parent compound la $ _ 3 $ ni $ _ 2 $ o $ _ { 7 - { \ delta } } $, despite their similar behavior in the low - pressure regime. these experimental results underscore the
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arxiv:2312.14251
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we introduce ( n + 1 ) - preprojective algebras of algebras of global dimension n. we show that if an algebra is n - representation - finite then its ( n + 1 ) - preprojective algebra is self - injective. in this situation, we show that the stable module category of the ( n + 1 ) - preprojective algebra is ( n + 1 ) - calabi - yau, and, more precisely, it is the ( n + 1 ) - amiot cluster category of the stable n - auslander algebra of the original algebra. in particular this stable category contains an ( n + 1 ) - cluster tilting object. we show that even if the ( n + 1 ) - preprojective algebra is not self - injective, under certain assumptions ( which are always satisfied for n \ in { 1, 2 } ) the results above still hold for the stable category of cohen - macaulay modules.
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arxiv:0912.3412
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the flux of low energy atmospheric neutrinos ( e _ nu ~ 4 gev ) has been studied with the macro detector at gran sasso by detecting nu _ mu interactions inside the apparatus, and by upward - going stopping muons. the updated analysis of the data collected until now with the complete apparatus will be presented. the results show a deficit of the measured number of events in an uniform way over the whole zenith angle with respect to monte carlo predictions. the deficit and the angular distributions, when interpreted in terms of neutrino oscillations, are consistent with the macro results on the much higher energy upward throughgoing muons ( e _ nu ~ 100 gev ).
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arxiv:hep-ex/9905028
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vision language models excel in handling a wide range of complex tasks, including optical character recognition ( ocr ), visual question answering ( vqa ), and advanced geometric reasoning. however, these models fail to perform well on low - level basic visual tasks which are especially easy for humans. our goal in this work was to determine if these models are truly " blind " to geometric reasoning or if there are ways to enhance their capabilities in this area. our work presents a novel automatic pipeline designed to extract key information from images in response to specific questions. instead of just relying on direct vqa, we use question - derived keywords to create a caption that highlights important details in the image related to the question. this caption is then used by a language model to provide a precise answer to the question without requiring external fine - tuning.
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arxiv:2410.22029
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cross sections are calculated for neutrino scattering off heavy nuclei at energies below 50 mev. the theory of fermi liquid is applied to estimate the rate of neutrino - nucleon elastic and inelastic scattering in a nuclear medium in terms of dynamic form factors. the cross sections, obtained here in a rather simple way, are in agreement with the results of the other much more sophisticated nuclear models. a background rate from the solar neutrino interactions within a large ge detector is estimated in the above - mentioned approach. the knowledge of the rate is in particular rather important for new - generation large - scale neutrino experiments.
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arxiv:nucl-th/0703036
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we report measurements and searches for resonant $ b ^ { \ pm } \ to k ^ { \ pm } h \ to k ^ { \ pm } \ gamma \ gamma $ decays where $ h $ is a $ \ eta, \ eta ^ { \ prime }, \ eta _ { c }, \ eta _ { c } ( 2s ), \ chi _ { c0 }, \ chi _ { c2 }, j / \ psi $ meson or the x ( 3872 ) particle.
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arxiv:hep-ex/0608037
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we measure ejecta mass as a function of azimuthal and impact angle for 104 m / s oblique impacts into sand. we find that the ejecta mass distribution is strongly sensitive to azimuthal angle with as high as 8 times more mass in ejecta on the downrange side compared to the uprange side. crater radii, measured from the impact point, are measured at different impact and azimuthal angles. crater ejecta scaling laws are modified to depend on azimuthal and impact angle. we find that crater radii are sensitive to both impact and azimuthal angle but the ejecta mass as a function of both angles can be estimated from the cube of the crater radius without an additional angular dependent function. the ejecta distributions are relevant for processes that depend upon the integrated properties of approximately 100 m / s impacts occurring in the outer solar system and possibly during planetesimal formation.
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arxiv:2404.16677
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this paper considers the task of estimating the $ l _ 2 $ norm of a $ n $ - dimensional random gaussian vector from noisy measurements taken after many of the entries of the vector are \ emph { missed } and only $ k \ ( 0 \ le k \ le n ) $ entries are retained and others are set to $ 0 $. specifically, we evaluate the minimum mean square error ( mmse ) estimator of the $ l _ 2 $ norm of the unknown gaussian vector performing measurements under additive white gaussian noise ( awgn ) on the vector after the data missing and derive expressions for the corresponding mean square error ( mse ). we find that the corresponding mse normalized by $ n $ tends to $ 0 $ as $ n \ to \ infty $ when $ k / n $ is kept constant. furthermore, expressions for the mse is derived when the variance of the awgn noise tends to either $ 0 $ or $ \ infty $. these results generalize the results of dytso et al. \ cite { dytso2019estimating } where the case $ k = n $ is considered, i. e. the mmse estimator of norm of random gaussian vector is derived from measurements under awgn noise without considering the data missing phenomenon.
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arxiv:2010.08299
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in this paper, we discuss the boundary behavior of bounded pluriharmonic functions on the teichm \ " uller space. we will show a version of the fatou theorem that every bounded pluriharmonic function admits the radial limits along the teichm \ " uller geodesic rays, and a version of the f. and m. riesz theorem that the radial limit of a non - constant bounded holomorphic function is not constant on any non - null measurable set on the bers boundary in terms of the pluriharmonic measure. as a corollary, we obtain the non - ergodicity of the action of the torelli group for a closed surface of genus $ g \ ge 2 $ on the space of projective measured foliations.
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arxiv:2312.13535
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the gamma component of air radiation dose rates is a function of the amount and spread of radioactive nuclides in the environment. these radionuclides can be natural or anthropogenic in origin. the field of view describes the area of radionuclides on, or below, the ground that is responsible for determining the air dose rate, and hence correspondingly the external radiation exposure. this work describes monte carlo radiation transport calculations for the field of view under a variety of situations. presented first are results for natural 40k and thorium and uranium series radionuclides distributed homogeneously within the ground. results are then described for atmospheric radioactive caesium fallout, such as from the fukushima daiichi nuclear power plant accident. various stages of fallout evolution are considered through the depth distribution of 134cs and 137cs in soil. the fields of view for the natural radionuclides and radiocaesium are different. this can affect the responses of radiation monitors to these nuclides if the detector is partially shielded from the ground within its field of view. the field of view also sets the maximum reduction in air dose rates that can be achieved through local decontamination or remediation measures. this maximum efficiency can be determined quickly from the data presented here for the air dose rate versus the spatial extent of radioactive source on the ground.
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arxiv:1509.09125
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this paper introduces a computationally efficient technique for estimating high - resolution doppler blood flow from an ultrafast ultrasound image sequence. more precisely, it consists in a new fast alternating minimization algorithm that implements a blind deconvolution method based on robust principal component analysis. numerical investigation carried out on \ textit { in vivo } data shows the efficiency of the proposed approach in comparison with state - of - the - art methods.
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arxiv:2011.01811
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with the rapid development of multimedia, the shift from unimodal textual sentiment analysis to multimodal image - text sentiment analysis has obtained academic and industrial attention in recent years. however, multimodal sentiment analysis is affected by unimodal data bias, e. g., text sentiment is misleading due to explicit sentiment semantic, leading to low accuracy in the final sentiment classification. in this paper, we propose a novel counterfactual multimodal sentiment analysis framework ( cf - msa ) using causal counterfactual inference to construct multimodal sentiment causal inference. cf - msa mitigates the direct effect from unimodal bias and ensures heterogeneity across modalities by differentiating the treatment variables between modalities. in addition, considering the information complementarity and bias differences between modalities, we propose a new optimisation objective to effectively integrate different modalities and reduce the inherent bias from each modality. experimental results on two public datasets, mvsa - single and mvsa - multiple, demonstrate that the proposed cf - msa has superior debiasing capability and achieves new state - of - the - art performances. we will release the code and datasets to facilitate future research.
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arxiv:2412.07292
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the notion of a real - valued function is central to mathematics, computer science, and many other scientific fields. despite this importance, there are hardly any positive results on decision procedures for predicate logical theories that reason about real - valued functions. this paper defines a first - order predicate language for reasoning about multi - dimensional smooth real - valued functions and their derivatives, and demonstrates that - despite the obvious undecidability barriers - certain positive decidability results for such a language are indeed possible.
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arxiv:2306.16505
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argentina has a large yet little - known indigenous linguistic diversity, encompassing at least 40 different languages. the majority of these languages are at risk of disappearing, resulting in a significant loss of world heritage and cultural knowledge. currently, unified information on speakers and computational tools is lacking for these languages. in this work, we present a systematization of the indigenous languages spoken in argentina, classifying them into seven language families : mapuche, tup \ ' i - guaran \ ' i, guaycur \ ' u, quechua, mataco - mataguaya, aymara, and chon. for each one, we present an estimation of the national indigenous population size, based on the most recent argentinian census. we discuss potential reasons why the census questionnaire design may underestimate the actual number of speakers. we also provide a concise survey of computational resources available for these languages, whether or not they were specifically developed for argentinian varieties.
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arxiv:2501.09943
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the thick gas electron multiplier ( thgem ) is a robust high - gain gas - avalanche electron multiplier - a building block of a variety of radiation detectors. it can be manufactured economically by standard printed - circuit drilling and etching technology. we present a detailed review of the thgem and its derivatives. we focus on the physics phenomena that govern their operation and performances under different operation conditions. technological aspects associated with the production of these detectors and their current and potential applications are discussed.
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arxiv:2303.01083
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atomically thin mos2 / graphene heterostructures are promising candidates for nanoelectronic and optoelectronic technologies. among different graphene substrates, epitaxial graphene ( eg ) on sic provides several potential advantages for such heterostructures including high electronic quality, tunable substrate coupling, wafer - scale processability, and crystalline ordering that can template commensurate growth. exploiting these attributes, we demonstrate here the thickness - controlled van der waals epitaxial growth of mos2 on eg via chemical vapor deposition, giving rise to transfer - free synthesis of a two - dimensional heterostructure with registry between its constituent materials. the rotational commensurability observed between the mos2 and eg is driven by the energetically favorable alignment of their respective lattices and results in nearly strain - free mos2, as evidenced by synchrotron x - ray scattering and atomic - resolution scanning tunneling microscopy ( stm ). the electronic nature of the mos2 / eg heterostructure is elucidated with stm and scanning tunneling spectroscopy, which reveals bias - dependent apparent thickness, band bending, and a reduced bandgap of ~ 0. 4 ev at the monolayer mos2 edges.
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arxiv:1604.00677
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galaxy clusters are expected to form hierarchically in a lcdm universe, growing primarily through mergers with lower mass clusters and the continual accretion of group - mass halos. galaxy clusters assemble late, doubling their masses since z ~ 0. 5, and so the outer regions of clusters should be replete with infalling group - mass systems. we present an xmm - newton survey to search for x - ray groups in the infall regions of 23 massive galaxy clusters at z ~ 0. 2, identifying 39 x - ray groups that have been spectroscopically confirmed to lie at the cluster redshift. these groups have mass estimates in the range 2x10 ^ 13 - 7x10 ^ 14msun, and group - to - cluster mass ratios as low as 0. 02. the comoving number density of x - ray groups in the infall regions is ~ 25x higher than that seen for isolated x - ray groups from the xxl survey. the average mass per cluster contained within these x - ray groups is 2. 2x10 ^ 14msun, or 19 % of the mass within the primary cluster itself. we estimate that ~ 10 ^ 15msun clusters increase their masses by 16 % between z = 0. 223 and the present day due to the accretion of groups with m200 > 10 ^ 13. 2msun. this represents about half of the expected mass growth rate of clusters at these late epochs. the other half is likely to come from smooth accretion of matter not bound in halos. the mass function of the infalling x - ray groups appears significantly top - heavy with respect to that of field x - ray systems, consistent with expectations from numerical simulations, and the basic consequences of collapsed massive dark matter halos being biased tracers of the underlying large - scale density distribution.
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arxiv:1709.04945
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in this work we extend the fourier - stieltjes transform of a vector measure and a continuous function defined on compact groups to locally compact groups. to do so, we consider a representation l of a normal compact subgroup k of a locally compact group g, and we use a representation of g induced by that of l. then, we define the fourier - stieltjes transform of a vector measure and that of a continuous function with compact support defined on g from the representation of g. then, we extend the shur orthogonality relation established for compact groups to locally compact groups by using the representations of g induced by the unitary representations of one of its normal compact subgroups. this extension enables us to develop a fourier - stieltjes transform in series form that is linear, continuous, and invertible.
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arxiv:2202.07055
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when answering a question, people often draw upon their rich world knowledge in addition to the particular context. while recent works retrieve supporting facts / evidence from commonsense knowledge bases to supply additional information to each question, there is still ample opportunity to advance it on the quality of the evidence. it is crucial since the quality of the evidence is the key to answering commonsense questions, and even determines the upper bound on the qa systems performance. in this paper, we propose a recursive erasure memory network ( rem - net ) to cope with the quality improvement of evidence. to address this, rem - net is equipped with a module to refine the evidence by recursively erasing the low - quality evidence that does not explain the question answering. besides, instead of retrieving evidence from existing knowledge bases, rem - net leverages a pre - trained generative model to generate candidate evidence customized for the question. we conduct experiments on two commonsense question answering datasets, wiqa and cosmosqa. the results demonstrate the performance of rem - net and show that the refined evidence is explainable.
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arxiv:2012.13185
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this paper proves continuity of value functions in discounted periodic - review single - commodity total - cost inventory control problems with \ revision { continuous inventory levels, } fixed ordering costs, possibly bounded inventory storage capacity, and possibly bounded order sizes for finite and infinite horizons. in each of these constrained models, the finite and infinite - horizon value functions are continuous, there exist deterministic markov optimal finite - horizon policies, and there exist stationary deterministic markov optimal infinite - horizon policies. for models with bounded inventory storage and unbounded order sizes, this paper also characterizes the conditions under which $ ( s _ t, s _ t ) $ policies are optimal in the finite horizon and an $ ( s, s ) $ policy is optimal in the infinite horizon.
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arxiv:2112.14898
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recently, the intrinsic magnetic topological insulator mnbi $ _ 2 $ te $ _ 4 $ has attracted great attention. it has an out - of - plane antiferromagnetic order, which is believed to open a sizable energy gap in the surface states. this gap, however, was not always observable in the latest angle - resolved photoemission spectroscopy ( arpes ) experiments. to address this issue, we analytically derive an effective model for the two - dimensional ( 2d ) surface states by starting from a three - dimensional ( 3d ) hamiltonian for bulk mnbi $ _ 2 $ te $ _ 4 $ and taking into account the spatial profile of the bulk magnetization. our calculations suggest that the diminished surface gap may be caused by a much smaller and more localized intralayer ferromagnetic order. in addition, we calculate the spatial distribution and penetration depth of the surface states, which indicates that the surface states are mainly embedded in the first two septuple layers from the terminating surface. from our analytical results, the influence of the bulk parameters on the surface states can be found explicitly. furthermore, we derive a $ \ bf { k } \ cdot \ bf { p } $ model for mnbi $ _ 2 $ te $ _ 4 $ thin films and show the oscillation of the chern number between odd and even septuple layers. our results will be helpful for the ongoing explorations of the mnbi $ _ x $ te $ _ y $ family.
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arxiv:2009.11026
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presburger arithmetic $ \ mathop { \ mathbf { pra } } \ nolimits $ is the true theory of natural numbers with addition. we consider linear orderings interpretable in presburger arithmetic and establish various necessary and sufficient conditions for interpretability depending on dimension $ n $ of interpretation. we note this problem is relevant to the interpretations of presburger arithmetic in itself, as well as the characterization of automatic orderings. for $ n = 2 $ we obtain the complete criterion of interpretability.
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arxiv:1911.07182
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the bosonic content of string theory in curved background of multidimensional structure with p - branes has a systematic geometrical description as an effective sigma - model of gravity in lower dimension ( say 3 + 1 ) with additional interacting dilatonic and p - brane fields. if the target - space is locally symmetric, solutions with intersecting p - branes can be found. some static solutions are p - brane generalizations of black holes ( including the standard reissner - nordstr " om class ), which allow the prediction of detectable features of the higher - dimensional p - brane geometry via scaling properties of black hole thermal properties. e. g. the hawking temperature t _ h depends critically on the p - brane intersection topology.
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arxiv:gr-qc/9912012
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in 2001, zhongmin shen asked if it is possible for two projectively related finsler metrics to have the same riemann curvature tensor, [ 14, page 184 ]. in this paper, we provide an answer to this question, within the class of finsler metrics of scalar flag curvature. in theorem 3. 1, we show that the answer is negative, for non - vanishing scalar flag curvature. the answer is known to be positive when the scalar flag curvature vanishes, [ 12, 14 ] and this positive answer is related to the existence of many solutions to hilbert ' s fourth problem. as a generalisation of this problem, we can ask if it is possible for a given spray, with non - vanishing scalar flag curvature, to represent, after reparametrisation, the geodesic spray of a finsler metric. in proposition 3. 3, we show how to construct sprays whose projective class does not contain any finsler metrizable spray with the same riemann curvature tensor.
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arxiv:1412.5282
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the rapid expansion in the usage of social media networking sites leads to a huge amount of unprocessed user generated data which can be used for text mining. author profiling is the problem of automatically determining profiling aspects like the author ' s gender and age group through a text is gaining much popularity in computational linguistics. most of the past research in author profiling is concentrated on english texts \ cite { 1, 2 }. however many users often change the language while posting on social media which is called code - mixing, and it develops some challenges in the field of text classification and author profiling like variations in spelling, non - grammatical structure and transliteration \ cite { 3 }. there are very few english - hindi code - mixed annotated datasets of social media content present online \ cite { 4 }. in this paper, we analyze the task of author ' s gender prediction in code - mixed content and present a corpus of english - hindi texts collected from twitter which is annotated with author ' s gender. we also explore language identification of every word in this corpus. we present a supervised classification baseline system which uses various machine learning algorithms to identify the gender of an author using a text, based on character and word level features.
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arxiv:1806.05600
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it is known that, if a locally perturbed periodic self - adjoint operator on a combinatorial or quantum graph admits an eigenvalue embedded in the continuous spectrum, then the associated eigenfunction is compactly supported - - that is, if the fermi surface is irreducible, which occurs generically in dimension two or higher. this article constructs a class of operators whose fermi surface is reducible for all energies by coupling several periodic systems. the components of the fermi surface correspond to decoupled spaces of hybrid states, and in certain frequency bands, some components contribute oscillatory hybrid states ( corresponding to spectrum ) and other components contribute only exponential ones. this separation allows a localized defect to suppress the oscillatory ( radiation ) modes and retain the evanescent ones, thereby leading to embedded eigenvalues whose associated eigenfunctions decay exponentially but are not compactly supported.
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arxiv:1307.6838
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in this work we outline a simple and numerically inexpensive approach to describe the spectral features of the single - impurity anderson model. the method combines aspects of the density matrix embedding theory ( dmet ) approach with a spectral broadening approach inspired by those used in numerical renormalization group ( nrg ) methods. at zero temperature for a wide range of u, the spectral function produced by this approach is found to be in good agreement with general expectations as well as more advanced and complex numerical methods such as dmrg - based schemes. the theory developed here is simply transferable to more complex impurity problems.
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arxiv:1611.04521
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an important and widely neglected aspect of the interaction between an accretion disc and a massive companion with a coplanar orbit is the vertical component of the tidal force. as shown by lubow, the response of the disc to vertical forcing is resonant at certain radii, at which a localized torque is exerted, and from which a compressive wave ( p mode ) may be emitted. although these vertical resonances are weaker than the corresponding lindblad resonances, the m = 2 inner vertical resonance in a binary star is typically located within the tidal truncation radius of a circumstellar disc. in this paper i develop a general theory of vertical resonances, allowing for non - linearity of the response, and dissipation by radiative damping and turbulent viscosity. the problem is reduced to a universal, non - linear ordinary differential equation with two real parameters. solutions of the complex non - linear airy equation are presented to illustrate the non - linear saturation of the resonance and the effects of dissipation. it is argued that the m = 2 inner vertical resonance is unlikely to truncate the disc in cataclysmic variable stars, but contributes to angular momentum transport and produces a potentially observable non - axisymmetric structure.
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arxiv:astro-ph/0112443
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##tated the infinitesimal approach to calculus, which had fallen into disrepute in favour of the theory of limits, by extending the field of real numbers to the hyperreal numbers which include infinitesimal and infinite quantities. an even larger number system, the surreal numbers were discovered by john horton conway in connection with combinatorial games. the development and continual improvement of computers, at first mechanical analog machines and then digital electronic machines, allowed industry to deal with larger and larger amounts of data to facilitate mass production and distribution and communication, and new areas of mathematics were developed to deal with this : alan turing ' s computability theory ; complexity theory ; derrick henry lehmer ' s use of eniac to further number theory and the lucas – lehmer primality test ; rozsa peter ' s recursive function theory ; claude shannon ' s information theory ; signal processing ; data analysis ; optimization and other areas of operations research. in the preceding centuries much mathematical focus was on calculus and continuous functions, but the rise of computing and communication networks led to an increasing importance of discrete concepts and the expansion of combinatorics including graph theory. the speed and data processing abilities of computers also enabled the handling of mathematical problems that were too time - consuming to deal with by pencil and paper calculations, leading to areas such as numerical analysis and symbolic computation. some of the most important methods and algorithms of the 20th century are : the simplex algorithm, the fast fourier transform, error - correcting codes, the kalman filter from control theory and the rsa algorithm of public - key cryptography. at the same time, deep insights were made about the limitations to mathematics. in 1929 and 1930, it was proved the truth or falsity of all statements formulated about the natural numbers plus either addition or multiplication ( but not both ), was decidable, i. e. could be determined by some algorithm. in 1931, kurt godel found that this was not the case for the natural numbers plus both addition and multiplication ; this system, known as peano arithmetic, was in fact incomplete. ( peano arithmetic is adequate for a good deal of number theory, including the notion of prime number. ) a consequence of godel ' s two incompleteness theorems is that in any mathematical system that includes peano arithmetic ( including all of analysis and geometry ), truth necessarily outruns proof, i. e. there are true statements that cannot be proved within the system. hence mathematics cannot be reduced to mathematical logic, and david hilbert
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https://en.wikipedia.org/wiki/History_of_mathematics
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we construct a gr \ " obner - shirshov basis of the temperley - lieb algebra $ \ mathfrak { t } ( d, n ) $ of the complex reflection group $ g ( d, 1, n ) $, inducing the standard monomials expressed by the generators $ \ { e _ i \ } $ of $ \ mathfrak { t } ( d, n ) $. this result generalizes the one for the coxeter group of type $ b _ n $ in \ cite { kimssleedi }. we also give a combinatorial interpretation of the standard monomials of $ \ mathfrak { t } ( d, n ) $, relating to the fully commutative elements of the complex reflection group $ g ( d, 1, n ) $. in this way, we obtain the dimension formula of $ \ mathfrak { t } ( d, n ) $.
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arxiv:1808.06523
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, no patient, no matter, no illness, no one to heal, no substance, no person, no thing and no place that needs to be influenced. this is what the practitioner must first be clear about. christian scientists avoid almost all medical treatment, relying instead on christian science prayer. this consists of silently arguing with oneself ; there are no appeals to a personal god, and no set words. caroline fraser wrote in 1999 that the practitioner might repeat : " the allness of god using eddy ' s seven synonyms — life, truth, love, spirit, soul, principle and mind, " then that " spirit, substance, is the only mind, and man is its image and likeness ; that mind is intelligence ; that spirit is substance ; that love is wholeness ; that life, truth, and love are the only reality. " she might deny other religions, the existence of evil, mesmerism, astrology, numerology, and the symptoms of whatever the illness is. she concludes, fraser writes, by asserting that disease is a lie, that this is the word of god, and that it has the power to heal. christian science practitioners are certified by the church of christ, scientist, to charge a fee for christian science prayer. there were 1, 249 practitioners worldwide in 2015 ; in the united states in 2010 they charged $ 25 – $ 50 for an e - mail, telephone or face - to - face consultation. their training is a two - week, 12 - lesson course called " primary class ", based on the recapitulation chapter of science and health. practitioners wanting to teach primary class take a six - day " normal class ", held in boston once every three years, and become christian science teachers. there are also christian science nursing homes. they offer no medical services ; the nurses are christian scientists who have completed a course of religious study and training in basic skills, such as feeding and bathing. the christian science journal and christian science sentinel publish anecdotal healing testimonials ( they published 53, 900 between 1900 and april 1989 ), which must be accompanied by statements from three verifiers : " people who know [ the testifier ] well and have either witnessed the healing or can vouch for [ the testifier ' s ] integrity in sharing it ". philosopher margaret p. battin wrote in 1999 that the seriousness with which these testimonials are treated by christian scientists ignores factors such as false positives caused by self - limiting conditions. because no negative accounts
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https://en.wikipedia.org/wiki/Christian_Science
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given a hilbert space $ h $, the set $ p ( h ) $ of one - dimensional subspaces of $ h $ becomes an orthoset when equipped with the orthogonality relation $ \ perp $ induced by the inner product on $ h $. here, an \ emph { orthoset } is a pair $ ( x, \ perp ) $ of a set $ x $ and a symmetric, irreflexive binary relation $ \ perp $ on $ x $. in this contribution, we investigate what conditions on an orthoset $ ( x, \ perp ) $ are sufficient to conclude that the orthoset is isomorphic to $ ( p ( h ), \ perp ) $ for some orthomodular space $ h $, where \ emph { orthomodular spaces } are linear spaces that generalize hilbert spaces. in order to achieve this goal, we introduce \ emph { sasaki maps } on orthosets, which are strongly related to sasaki projections on orthomodular lattices. we show that any orthoset $ ( x, \ perp ) $ with sufficiently many sasaki maps is isomorphic to $ ( p ( h ), \ perp ) $ for some orthomodular space, and we give more conditions on $ ( x, \ perp ) $ to assure that $ h $ is actually a hilbert space over $ \ mathbb r $, $ \ mathbb c $ or $ \ mathbb h $.
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arxiv:2207.09148
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in this study, we conclude the vertical, complete and horizontal lifts of frenet formulas given by ( 1 ) and defined on space r3 to its tangent space tr3 = r6.
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arxiv:0902.3567
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we demonstrate a universal mechanism for terminating spiral waves in excitable media using an established topological framework. this mechanism dictates whether high - or low - energy defibrillation shocks succeed or fail. furthermore, this mechanism allows for the design of a single minimal stimulus capable of defibrillating, at any time, turbulent states driven by multiple spiral waves. we demonstrate this method in a variety of computational models of cardiac tissue ranging from simple to detailed human models. the theory described here shows how this mechanism underlies all successful defibrillation and can be used to further develop existing and future low - energy defibrillation strategies.
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arxiv:2109.10850
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the biham - middleton - levine ( bml ) traffic model is a simple two - dimensional, discrete cellular automaton ( ca ) that has been used to study self - organization and phase transitions arising in traffic flows. from the computational point of view, the bml model exhibits the usual features of discrete ca, where the state of the automaton are updated according to simple rules that depend on the state of each cell and its neighbors. in this paper we study the impact of various optimizations for speeding up ca computations by using the bml model as a case study. in particular, we describe and analyze the impact of several parallel implementations that rely on cpu features, such as multiple cores or simd instructions, and on gpus. experimental evaluation provides quantitative measures of the payoff of each technique in terms of speedup with respect to a plain serial implementation. our findings show that the performance gap between cpu and gpu implementations of the bml traffic model can be reduced by clever exploitation of all cpu features.
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arxiv:1804.07981
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we establish the existence of a positive solution to the problem $ $ - \ delta u + v ( x ) u = f ( u ), \ qquad u \ in d ^ { 1, 2 } ( \ mathbb { r } ^ { n } ), $ $ for $ n \ geq3 $, when the nonlinearity $ f $ is subcritical at infinity and supercritical near the origin, and the potential $ v $ vanishes at infinity. our result includes situations in which the problem does not have a ground state. then, under a suitable decay assumption on the potential, we show that the problem has a positive bound state.
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arxiv:1711.04745
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this contains part i of the book : congruence lattices of finite lattices, which covers about 80 years of research and more than 250 papers.
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arxiv:2104.06539
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we consider a spherically symmetric line element which admits either a black hole geometry or a wormhole geometry and show that in both cases the apparent horizon or the wormhole throat is partially characterized by the zero - set of a single curvature invariant. the detection of the apparent horizon by this invariant is consistent with the geometric horizon detection conjectures and implies that it is a geometric horizon of the black hole, while the detection of the wormhole throat presents a conceptual problem for the conjectures. to distinguish between these surfaces, we determine a set of curvature invariants that fully characterize the apparent horizon and wormhole throat. motivated by this result, we introduce the concept of a geometric surface as a generalization of a geometric horizon and extend the geometric horizon detection conjectures to geometric surfaces. as an application, we employ curvature invariants to characterize three important surfaces of the line element introduced by simpson, martin - moruno and visser which describes transitions between regular vaidya black holes, traversable wormholes, and black bounces.
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arxiv:2104.08935
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the main ingredient for local superconformal methods is the multiplet of gauge fields : the weyl multiplet. we construct the transformations of this multiplet for $ \ mathcal { n } = 3 $, $ d = 4 $. the construction is based on a supersymmetry truncation from the $ \ mathcal { n } = 4 $ weyl multiplet, on coupling with a current multiplet, and on the implementation of a soft algebra at the nonlinear level, extending su $ ( 2, 2 | 3 ) $. this is the first step towards a superconformal calculus for $ \ mathcal { n } = 3 $, $ d = 4 $.
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arxiv:1702.06442
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measurements of di - jet production at hera provide an important test of nlo qcd calculations. it is also a source of information about partonic content of the photon, complementary to the measurements in e + e - experiments. in this article we review the status of the photon structutre studies with particular emphasis on hera measurements.
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arxiv:hep-ex/0102019
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we observe that the rector invariants classifying the genus of bs ^ 3 show up in ( orthogonal and unitary ) k - theory. we then use this knowledge to show purely algebraically how the k - theory of the spaces in the genus of bs ^ 3 differ. this provides new insights into a result of notbohm in the case of bs ^ 3.
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arxiv:math/0501513
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= = = founding = = = science saru was founded on february 4, 2013 by masaaki yuasa and eunyoung choi. yuasa and choi had previously worked together on numerous projects, and choi had prior experience leading ankama japan, a studio which utilized similar digital animation production techniques and employed a multinational staff. the creation of the studio was proposed by choi during the making of the short film kick - heart ( 2013 ), which was the first large - scale japanese animated project to be successfully crowdfunded on kickstarter. the studio ' s first official production under the science saru name was an episode of the american adventure time animated series entitled food chain ( 2014 ), on which yuasa worked as director, writer, and storyboard artist ; choi served as co - director. by july 2014, the studio was also recognized for creating the digital animation for yuasa ' s animated series ping pong the animation ( 2014 ). science saru ' s first production location was a small suburban house converted into an impromptu animation studio. by the end of 2013, the company had expanded to a staff of five, including yuasa, choi, and abel gongora, a former member of ankama japan ; the studio ' s first productions began with this small crew. = = = early work as a subcontractor ( 2014 – 2015 ) = = = science saru began its corporate activities by taking on subcontracting work, as well as by collaborating with other studios on projects. the studio ' s first project was the adventure time episode food chain ( 2014 ). the episode was produced entirely in - house, and yuasa and choi were given free rein by series creator pendleton ward to develop the episode as they saw fit. food chain received critical acclaim as one of the best episodes of the series, was an official competition selection at annecy, and was nominated for the annie award for outstanding television direction. another early highlight was yuasa ' s television series ping pong the animation ( 2014 ) ; science saru provided ' digitally assisted ' animation production services, while tatsunoko production served as the primary studio. the series was awarded a jury selection prize at the japan media arts festival, and won the grand prize for television animation at the tokyo anime awards festival ; additionally, character designer and longtime collaborator nobutake ito won the best animator award for individual achievement. ping pong the animation was subsequently highlighted as one of the best japanese animated series of the decade. science saru also provided production assistance
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https://en.wikipedia.org/wiki/Science_Saru
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the search of high - order periodic orbits has been typically restricted to problems with symmetries that help to reduce the dimension of the search space. well - known examples include reversible maps with symmetry lines. the present work proposes a new method to compute high - order periodic orbits in twist maps without the use of symmetries. the method is a combination of the parameterization method in fourier space and a newton - gauss multiple shooting scheme. the parameterization method has been successfully used in the past to compute quasi - periodic invariant circles. however, this is the first time that this method is used in the context of periodic orbits. numerical examples are presented showing the accuracy and efficiency of the proposed method. the method is also applied to verify the renormalization prediction of the residues ' convergence at criticality ( extensively studied in reversible maps ) in the relatively unexplored case of maps without symmetries.
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arxiv:2003.02788
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the quasi - integrable kdv equation has been obtained from the corresponding deformation of the hamiltonian for the usual kdv system. following suitable gauge - fixing, it has been found that the quasi - conservation condition is satisfied and an infinite number of anomalous conservation laws are obtained, with some containing possible conserved charges. judicious choice of deformation of the hamiltonian clearly leads to a conserved charge, manifesting quasi - integrability, but also creates a hierarchy of higher - derivative equations with at least one conserved charge. a particular quasi - deformation parameterization of the hamiltonian is found to complement the same of the nls system, following an approximate equivalence of the two systems obtained earlier, in the weak coupling limit. single - soliton solutions for all these cases are obtained, with manifest scaling due to the quasi - integrable deformation. finally, quasi - conservation formulation for the complex coupled generalized kdv system is obtained.
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arxiv:1612.07499
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we predict that triangle singularities of hadron spectroscopy can be strongly affected in heavy ion collisions. to do it we examine various effects on the singularity - inducing triangle loop of finite temperature in the terminal hadron phase. it appears that peaks seen in central heavy ion collisions are more likely to be hadrons than rescattering effects under two conditions. first, the flight - time of the intermediate hadron state must be comparable to the lifetime of the equilibrated fireball ( else, the reaction mostly happens in vacuo after freeze out ). second, the medium effect over the triangle - loop particle mass or width must be sizeable. when these ( easily checked ) conditions are met, the medium quickly reduces the singularity : at t about 150 mev, even by two orders of magnitude, acting then as a spectroscopic filter.
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arxiv:2008.12031
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this paper aims to improve the accuracy of texture classification based on extracting texture features using five different texture methods and classifying the patterns using a naive bayesian classifier. three statistical - based and two model - based methods are used to extract texture features from eight different texture images, then their accuracy is ranked after using each method individually and in pairs. the accuracy improved up to 97. 01 % when model based - gaussian markov random field ( gmrf ) and fractional brownian motion ( fbm ) - were used together for classification as compared to the highest achieved using each of the five different methods alone ; and proved to be better in classifying as compared to statistical methods. also, using gmrf with statistical based methods, such as gray level co - occurrence ( glcm ) and run - length ( rlm ) matrices, improved the overall accuracy to 96. 94 % and 96. 55 % ; respectively.
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arxiv:1512.08814
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the $ \ lambda $ separation energy for $ \ lambda $ - hypernuclei, denoted $ b _ \ lambda $, measured in 1967, 1968, and 1973 are recalibrated using the current best mass estimates for particles and nuclei. the recalibrated $ b _ \ lambda $ are systematically larger ( except in the case of $ ^ 6 _ \ lambda $ he ) than the original published values by about 100 kev. the effect of this level of recalibration is very important for light hypernuclei, especially for the hypertriton. the early $ b _ \ lambda $ values measured in 1967, 1968, and 1973 are widely used in theoretical research, and the new results provide better constraints on the conclusions from such studies.
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arxiv:1908.03134
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standards of wired ethernet. wi - fi has become the de facto standard for access in private homes, within offices, and at public hotspots. some businesses charge customers a monthly fee for service, while others have begun offering it free in an effort to increase the sales of their goods. cellular data service offers coverage within a range of 10 - 15 miles from the nearest cell site. speeds have increased as technologies have evolved, from earlier technologies such as gsm, cdma and gprs, through 3g, to 4g networks such as w - cdma, edge or cdma2000. as of 2018, the proposed next generation is 5g. low - power wide - area networks ( lpwan ) bridge the gap between wi - fi and cellular for low - bitrate internet of things ( iot ) applications. mobile - satellite communications may be used where other wireless connections are unavailable, such as in largely rural areas or remote locations. satellite communications are especially important for transportation, aviation, maritime and military use. wireless sensor networks are responsible for sensing noise, interference, and activity in data collection networks. this allows us to detect relevant quantities, monitor and collect data, formulate clear user displays, and to perform decision - making functions wireless data communications are used to span a distance beyond the capabilities of typical cabling in point - to - point communication and point - to - multipoint communication, to provide a backup communications link in case of normal network failure, to link portable or temporary workstations, to overcome situations where normal cabling is difficult or financially impractical, or to remotely connect mobile users or networks. = = = = peripherals = = = = peripheral devices in computing can also be connected wirelessly, as part of a wi - fi network or directly via an optical or radio - frequency ( rf ) peripheral interface. originally these units used bulky, highly local transceivers to mediate between a computer and a keyboard and mouse ; however, more recent generations have used smaller, higher - performance devices. radio - frequency interfaces, such as bluetooth or wireless usb, provide greater ranges of efficient use, usually up to 10 feet, but distance, physical obstacles, competing signals, and even human bodies can all degrade the signal quality. concerns about the security of wireless keyboards arose at the end of 2007 when it was revealed that microsoft ' s implementation of encryption in some of its 27 mhz models were highly insecure. = = = energy transfer = = = wireless energy transfer is a process whereby electrical energy is transmitted
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https://en.wikipedia.org/wiki/Wireless
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we report the highest - fidelity observations of the spiral galaxy m51 in co emission, revealing the evolution of giant molecular clouds ( gmcs ) vis - a - vis the large - scale galactic structure and dynamics. the most massive gmcs ( so - called gmas ) are first assembled and then broken up as the gas flow through the spiral arms. the gmas and their h2 molecules are not fully dissociated into atomic gas as predicted in stellar feedback scenarios, but are fragmented into smaller gmcs upon leaving the spiral arms. the remnants of gmas are detected as the chains of gmcs that emerge from the spiral arms into interarm regions. the kinematic shear within the spiral arms is sufficient to unbind the gmas against self - gravity. we conclude that the evolution of gmcs is driven by large - scale galactic dynamics - - their coagulation into gmas is due to spiral arm streaming motions upon entering the arms, followed by fragmentation due to shear as they leave the arms on the downstream side. in m51, the majority of the gas remains molecular from arm entry through the inter - arm region and into the next spiral arm passage.
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arxiv:0907.1656
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we classify two - qubit commuting hamiltonians in terms of their computational complexity. suppose one has a two - qubit commuting hamiltonian h which one can apply to any pair of qubits, starting in a computational basis state. we prove a dichotomy theorem : either this model is efficiently classically simulable or it allows one to sample from probability distributions which cannot be sampled from classically unless the polynomial hierarchy collapses. furthermore, the only simulable hamiltonians are those which fail to generate entanglement. this shows that generic two - qubit commuting hamiltonians can be used to perform computational tasks which are intractable for classical computers under plausible assumptions. our proof makes use of new postselection gadgets and lie theory.
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arxiv:1602.04145
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in isolated nonlinear optical waveguide arrays with bounded energy spectrum, simultaneous conservation of energy and power of the optical modes enables study of coupled thermal and particle transport in the negative temperature regime. here, based on exact numerical simulation and rationale from landauer formalism, we predict generic violation of the wiedemann - franz law in such systems. this is rooted in the spectral decoupling of thermal and power current of optical modes, and their different temperature dependence. our work extends the study of coupled thermal and particle transport into unprecedented regimes, not reachable in natural condensed matter and atomic gas systems.
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arxiv:2307.16529
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we study nonlinear serial dependence tests for non - gaussian time series and residuals of dynamic models based on portmanteau statistics involving nonlinear autocovariances. a new test with an asymptotic $ \ chi ^ 2 $ distribution is introduced for testing nonlinear serial dependence ( nlsd ) in time series. this test is inspired by the generalized covariance ( gcov ) residual - based specification test, recently proposed as a diagnostic tool for semi - parametric dynamic models with i. i. d. non - gaussian errors. it has a $ \ chi ^ 2 $ distribution when the model is correctly specified and estimated by the gcov estimator. we derive new asymptotic results under local alternatives for testing hypotheses on the parameters of a semi - parametric model. we extend it by introducing a gcov bootstrap test for residual diagnostics, \ color { black } which is also available for models estimated by a different method, such as the maximum likelihood estimator under a parametric assumption on the error distribution. \ color { black } a simulation study shows that the tests perform well in applications to mixed causal - noncausal autoregressive models. the gcov specification test is used to assess the fit of a mixed causal - noncausal model of aluminum prices with locally explosive patterns, i. e. bubbles and spikes between 2005 and 2024.
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arxiv:2312.05373
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in high - temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. how this stripe order evolves across optimal doping remains a controversial question. here we present a systematic resonant inelastic x - ray scattering ( rixs ) study of weak charge correlations in la2 - xsrxcuo4 ( lsco ) and la1. 8 - xeu0. 2srxcuo4 ( lesco ). ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. upon increasing doping x, the long - range temperature dependent stripe order is found to be replaced by short - range temperature independent correlations at a critical point xc = 0. 15 distinct from the pseudogap critical doping. we argue that the doping and temperature independent short - range correlations originate from unresolved electron - phonon coupling that broadly peaks at the stripe ordering vector. in lsco, long - range static stripe order vanishes in a quantum critical point around optimal doping.
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arxiv:2206.06695
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the solar system includes two planets - - - mercury and mars - - - significantly less massive than earth, and all evidence indicates that planets of similar size orbit many stars. in fact, one of the first exoplanets to be discovered is a lunar - mass planet around a millisecond pulsar. novel classes of exoplanets have inspired new ideas about planet formation and evolution, and these " sub - earths " should be no exception : they include planets with masses between mars and venus for which there are no solar system analogs. advances in astronomical instrumentation and recent space missions have opened the sub - earth frontier for exploration : the kepler mission has discovered dozens of confirmed or candidate sub - earths transiting their host stars. it can detect mars - size planets around its smallest stellar targets, as well as exomoons of comparable size. although the application of the doppler method is currently limited by instrument stability, future spectrographs may detect equivalent planets orbiting close to nearby bright stars. future space - based microlensing missions should be able to probe the sub - earth population on much wider orbits. a census of sub - earths will complete the reconnaissance of the exoplanet mass spectrum and test predictions of planet formation models, including whether low - mass m dwarf stars preferentially host the smallest planets. the properties of sub - earths may reflect their low gravity, diverse origins, and environment, but they will be elusive : observations of eclipsing systems by the james webb space telescope may give us our first clues to the properties of these small worlds.
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arxiv:1308.6308
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we present a simple mechanism by which supersymmetry can be dynamically broken in intersecting brane models, naturally generating an exponentially small scale. rather than utilize either non - abelian gauge dynamics or d - instantons, our mechanism uses worldsheet instantons to generate the small scale in a hidden sector.
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arxiv:0708.4116
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dropout and other feature noising schemes control overfitting by artificially corrupting the training data. for generalized linear models, dropout performs a form of adaptive regularization. using this viewpoint, we show that the dropout regularizer is first - order equivalent to an l2 regularizer applied after scaling the features by an estimate of the inverse diagonal fisher information matrix. we also establish a connection to adagrad, an online learning algorithm, and find that a close relative of adagrad operates by repeatedly solving linear dropout - regularized problems. by casting dropout as regularization, we develop a natural semi - supervised algorithm that uses unlabeled data to create a better adaptive regularizer. we apply this idea to document classification tasks, and show that it consistently boosts the performance of dropout training, improving on state - of - the - art results on the imdb reviews dataset.
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arxiv:1307.1493
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understanding the collective behavior of a quantum many - body system, a system composed of a large number of interacting microscopic degrees of freedom, is a key aspect in many areas of contemporary physics. however, as a direct consequence of the difficultly of the so - called many - body problem, many exotic quantum phenomena involving extended systems, such as high temperature superconductivity, remain not well understood on a theoretical level. entanglement renormalization is a recently proposed numerical method for the simulation of many - body systems which draws together ideas from the renormalization group and from the field of quantum information. by taking due care of the quantum entanglement of a system, entanglement renormalization has the potential to go beyond the limitations of previous numerical methods and to provide new insight to quantum collective phenomena. this thesis comprises a significant portion of the research development of er following its initial proposal. this includes exploratory studies with er in simple systems of free particles, the development of the optimisation algorithms associated to er, and the early applications of er in the study of quantum critical phenomena and frustrated spin systems.
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arxiv:1109.5424
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the crystal structure of bulk srtio $ _ 3 $ ( sto ) transitions from cubic to tetragonal at around 105k. recent local scanning probe measurements of laalo $ _ 3 $ / srtio $ _ 3 $ ( lao / sto ) interfaces indicated the existence of spatially inhomogeneous electrical current paths and electrostatic potential associated with the structural domain formation in the tetragonal phase of sto. however, how these effects impact the electron conduction in lao / sto devices has not been fully studied. here we report a study of temperature dependent electronic transport in combination with the polarized light microscopy of structural domains in mesoscopic scale lao / sto devices. by reducing the spatial size of the conductive interface to be comparable to the size of a single tetragonal domain of sto, the anisotropy of interfacial electron conduction in relationship to the domain wall and its direction was characterized in the temperature range $ t $ = 10 - 300k. it was found that the four - point resistance measured with current parallel to the domain wall in device is larger than the resistance measured perpendicular to the domain wall. this observation is qualitatively consistent with the current diverting effect from a more conductive domain wall within the sample. among all the samples studied, the maximum resistance ratio found is at least 10 and could be as large as 10 $ ^ 5 $ at $ t $ = 10k. this electronic anisotropy may have implications on other oxide hetero - interfaces and the further understanding of electronic / magnetic phenomena found in lao / sto.
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arxiv:1703.07229
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a large distance propagation in turbulent atmosphere results in disintegration of laser beam into speckles. we find that the most intense speckle approximately preserves both the gaussian shape and the diameter of the initial collimated beam while loosing energy during propagation. one per 1000 of atmospheric realizations produces at 7km distance an intense speckle above 20 \ % of the initial power. such optimal realizations create effective extended lenses focusing the intense speckle beyond the diffraction limit of vacuum propagation. atmospheric realizations change every several milliseconds. we propose to use intense speckles to greatly increase the time - averaged power delivery to the target plane by triggering the pulsed laser operations only at times of optimal realizations. resulting power delivery and laser irradiance at the intense speckles well exceeds both intensity of diffraction - limited beam and intensity averaged over typical realizations.
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arxiv:1711.02841
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which matrices can be written as sums or products of square - zero matrices? this question is the central premise of this dissertation. over the past 25 years a significant body of research on products and linear combinations of square - zero matrices has developed, and it is the aim of this study to present this body of research in a consolidated, holistic format, that could serve as a theoretical introduction to the subject. the content of the research is presented in three parts : first results within the broader context of sums and products of nilpotent matrices are discussed, then products of square - zero matrices, and finally sums of square - zero matrices.
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arxiv:1804.02140
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we study the riemannian geometry of 3d axisymmetric ideal fluids. we prove that the $ l ^ 2 $ exponential map on the group of volume - preserving diffeomorphisms of a $ 3 $ - manifold is fredholm along axisymmetric flows with sufficiently small swirl. along the way, we define the notions of axisymmetric and swirl - free diffeomorphisms of any manifold with suitable symmetries and show that such diffeomorphisms form a totally geodesic submanifold of infinite $ l ^ 2 $ diameter inside the space of volume - preserving diffeomorphisms whose diameter is known to be finite. as examples we derive the axisymmetric euler equations on $ 3 $ - manifolds equipped with each of thurston ' s eight model geometries.
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arxiv:1911.10302
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the recently introduced intelligent trial - and - error ( it & e ) algorithm showed that robots can adapt to damage in a matter of a few trials. the success of this algorithm relies on two components : prior knowledge acquired through simulation with an intact robot, and bayesian optimization ( bo ) that operates on - line, on the damaged robot. while it & e leads to fast damage recovery, it does not incorporate any safety constraints that prevent the robot from attempting harmful behaviors. in this work, we address this limitation by replacing the bo component with a constrained bo procedure. we evaluate our approach on a simulated damaged humanoid robot that needs to crawl as fast as possible, while performing as few unsafe trials as possible. we compare our new " safety - aware it & e " algorithm to it & e and a multi - objective version of it & e in which the safety constraints are dealt as separate objectives. our results show that our algorithm outperforms the other approaches, both in crawling speed within the safe regions and number of unsafe trials.
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arxiv:1611.09419
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of information such as geographic data, property valuation and real estate advice being moved online. this has been successful, with companies like zillow ( us ), rightmove ( uk ), pricehubble ( ch ) and aurum proptech ( india ) being in the top listed companies in their respective markets. the rise of digital technology during the 21st century has led to the development of a sharing economy, where applications such as ridesharing platforms became common. this also extended to real estate, as websites such as airbnb and wework made it possible for property owners to rent out their property for part of the year. the covid - 19 accelerated the adoption of information technology in the real estate industry. the pandemic helped to drive e - commerce and resulted in the closure of many traditional retail stores, which has impacted the commercial real estate industry. blockchain technology has also been used to track property for the purposes of land registration and resolve potential ownership disputes. post pandemic, proptech is increasingly influenced by wider societal concerns, such as town planning, and public sector applications. an example of this can be seen in the uk, where the government started a ' proptech innovation fund '. under the banner of ' proptech ' this saw initially investment in citizen involvement solutions. more recent developments see applications in land assessment. = = investment in real estate technology = = during the 2010s, numerous property technology startups were created, dealing with aspects of real estate such as design and construction, listings, and transactions. these startups have been supported by seed funding and investment from a range of sources, particularly venture capital funds. in 2015, investment into property technology grew, with more than $ 1. 7 billion in funding being invested across over 190 deals. this represented a 50 % increase year - over - year and a 821 % increase in funding compared to 2011. deal activity also increased, growing 378 % with respect to 2011 ' s total, and 12 % year - over - year. this investment appeared to increase further in 2017 to £8. 5 billion. in the first six months of 2019, $ 12. 9 billion of venture capital funding was invested into real - estate technology startups, which surpassed the $ 12. 7 billion of investments in 2017. = = references = =
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https://en.wikipedia.org/wiki/Property_technology
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recent measurements showed that the period derivative of the ' high - b ' radio pulsar psr j1734 - 3333 is increasing with time. for neutron stars evolving with fallback disks, this rotational behavior is expected in certain phases of the long - term evolution. using the same model as employed earlier to explain the evolution of anomalous x - ray pulsars and soft gamma - ray repeaters, we show that the period, the first and second period derivatives and the x - ray luminosity of this source can simultaneously acquire the observed values for a neutron star evolving with a fallback disk. we find that the required strength of the dipole field that can produce the source properties is in the range of 10 ^ { 12 } - 10 ^ { 13 } g on the pole of the neutron star. when the model source reaches the current state properties of psr j1734 - 3333, accretion onto the star has not started yet, allowing the source to operate as a regular radio pulsar. our results imply that psr j1734 - 3333 is at an age of ~ 3 x 10 ^ 4 - 2 x 10 ^ 5 years. such sources will have properties like the x - ray dim isolated neutron stars or transient axps at a later epoch of weak accretion from the diminished fallback disk.
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arxiv:1211.4689
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in many real - world openflow - based sdn deployments, the ability to program heterogeneous forwarding elements built with different forwarding architectures is a desirable capability. in this paper, we discuss a data plane programming framework suitable for a flexible and protocol - oblivious data plane and show how openflow can evolve to provide a generic interface for platform - independent programming and platform - specific compiling. we also show how an abstract instruction set can play a pivotal role to support different programming styles mapping to different forwarding chip architectures. as an example, we compare the compiler - mode and interpreter - mode implementations for an npu - based forwarding element and conclude that the compiler - mode implementation can achieve a performance similar to that of a conventional non - sdn implementation. built upon our protocol - oblivious forwarding ( pof ) vision, this work presents our continuous efforts to complete the ecosystem and pave the sdn evolving path. the programming framework could be considered as a proposal for the openflow 2. 0 standard.
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arxiv:1405.0060
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the determination of the optical spectrum of single - wall carbon nanotubes ( swcnts ) is essential for the development of opto - electronic components and sensors with application in many fields. real swcnts are finite, but almost all the studies performed so far use infinite swcnts. however, the spectra of finite and infinite systems are different. in this work the optical spectrum of finite ( 3, 3 ) and ( 5, 5 ) swcnts is calculated as a function of nanotube length. for the ( 3, 3 ) swcnts, the calculated absorption spectra for light polarised both parallel and perpendicularly to the nanotube axis are in good agreement with experimental results. however, our results indicate that the lowest energy peak present in the experimental results for light polarised parallel to the nanotube axis can be attributed to a surface - plasmon resonance that is a consequence of the finite nature of the swcnts and not to the presence of swcnts with other chiralities, as claimed by the previous theoretical works. the surface - plasmon resonance is also studied using the aharonov - bohm effect. finally, this work demonstrates that the surface - plasmon resonance in finite swcnt can be described using a 1d infinite well.
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arxiv:1712.04870
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we make a spectral analysis of discrete schroedinger operators on the half - line, subject to complex robin - type boundary couplings and complex - valued potentials. first, optimal spectral enclosures are obtained for summable potentials. second, general smallness conditions on the potentials guaranteeing a spectral stability are established. third, a general identity which allows to generate optimal discrete hardy inequalities for the discrete dirichlet laplacian on the half - line is proved.
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arxiv:2111.08265
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by using the exact solutions of the weyl equation in a constant magnetic field, the equal - time wigner function for magnetized chiral plasma is derived. it is found that the dependence of the wigner function on the component of momentum along the magnetic field is asymmetric and is correlated with the fermion chirality. such a dependence is principal for reproducing the correct chiral magnetic and chiral separation effects. in the lowest landau level approximation, the equation for the equal - time wigner function in a strong magnetic field is derived. by making use of this equation, it is found that the longitudinal collective modes in a strong magnetic field are gapped plasmons whose gap is determined by the magnetic field. unlike the ordinary magnetic field, an axial one allows for the dispersion law of the collective excitations asymmetric in the wave vector. the thermoelectric phenomena for chiral fermions in strong magnetic and axial magnetic fields are studied and the corresponding transport coefficients are calculated.
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arxiv:1707.01105
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model atmospheres have been computed for m dwarfs that are strongly irradiated by nearby hot companions. a variety of primary and secondary spectral types are explored in addition to models specific to four known systems : gd 245, nn ser, aa dor, and uu sge. this work demonstrates that a dramatic temperature inversion is possible on at least one hemisphere of an irradiated m dwarf and the emergent spectrum will be significantly different from an isolated m dwarf or a black body flux distribution. for the first time, synthetic spectra suitable for direct comparison to high - resolution observations of irradiated m dwarfs in non - mass transferring post - common envelope binaries are presented. the effects of departures from local thermodynamic equilibrium on the balmer line profiles are also discussed.
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arxiv:astro-ph/0406599
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we present predictions and projections for hadron - in - jet measurements and electron - jet azimuthal correlations at the future electron - ion collider ( eic ). these observables directly probe the three - dimensional ( 3d ) structure of hadrons, in particular, the quark transversity and sivers parton distributions and the collins fragmentation functions. we explore the feasibility of these experimental measurements by detector simulations and discuss detector requirements. we conclude that jet observables have the potential to enhance the 3d imaging eic program.
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arxiv:2007.07281
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error distribution analysis is an important assistant technology for the research of sins ( strapdown inertial navigation system ). error distribution result can provide the contribution of different errors to final navigation error, which is helpful for modifying and optimizing sins. to realize decomposing the navigation error into parts that caused by each error source, the sins error state space model is established and covariance matrix is decomposed according to error sources. the proposed error distribution analysis method based on 34 - dimension sins error model can quantitatively analyze the contribution to the end navigation error of initial errors, imu ( inertial measurement unit ) bias, imu scale factor errors, mounting errors of gyroscopes and accelerometers, and imu stochastic errors. the simulations in static condition and single axis rotation condition indict that the distribution result of proposed analysis method accords with the law of error propagation. after trajectory determined, the corresponding error distribution result will be calculated with the proposed method. compared with the monte - carlo method and other method based on covariance matrix, the proposed method uses more complete error model, considers the interaction effect of error sources and can be easily realized with less computation.
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arxiv:2203.11810
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we use twisted fourier - mukai transforms to study the relation between an abelian fibration on a holomorphic symplectic manifold and its dual fibration. our reasoning leads to an equivalence between the derived category of coherent sheaves on one space and the derived category of twisted sheaves on the other space.
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arxiv:math/0404365
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in this paper, we investigate the relations between the pitch, the angle of pitch and drall of parallel ruled surface of a closed curve in dual lorentzian space.
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arxiv:1009.2625
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genomic imprinting and maternal effects are two epigenetic factors that have been increasingly explored for their roles in the etiology of complex diseases. this is part of a concerted effort to find the " missing heritability. " accordingly, statistical methods have been proposed to detect imprinting and maternal effects simultaneously based on either a case - parent triads design or a case - mother / control - mother pairs design. however, existing methods are full - likelihood based and have to make strong assumptions concerning mating type probabilities ( nuisance parameters ) to avoid overparametrization. in this paper we propose to augment the two popular study designs by combining them and including control - parent triads, so that our sample may contain a mixture of case - parent / control - parent triads and case - mother / control - mother pairs. by matching the case families with control families of the same structure and stratifying according to the familial genotypes, we are able to derive a partial likelihood that is free of the nuisance parameters. this renders unnecessary any unrealistic assumptions and leads to a robust procedure without sacrificing power. our simulation study demonstrates that our partial likelihood method has correct type i error rate, little bias and reasonable power under a variety of settings.
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arxiv:1304.4799
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we introduce a mean field game for a family of filtering problems related to the classic sequential testing of the drift of a brownian motion. to the best of our knowledge this work presents the first treatment of mean field filtering games with stopping and an unobserved common noise in the literature. we show that the game is well - posed, characterize the solution, and establish the existence of an equilibrium under certain assumptions. we also perform numerical studies for several examples of interest.
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arxiv:2403.18297
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we provide single - model estimates of aleatoric and epistemic uncertainty for deep neural networks. to estimate aleatoric uncertainty, we propose simultaneous quantile regression ( sqr ), a loss function to learn all the conditional quantiles of a given target variable. these quantiles can be used to compute well - calibrated prediction intervals. to estimate epistemic uncertainty, we propose orthonormal certificates ( ocs ), a collection of diverse non - constant functions that map all training samples to zero. these certificates map out - of - distribution examples to non - zero values, signaling epistemic uncertainty. our uncertainty estimators are computationally attractive, as they do not require ensembling or retraining deep models, and achieve competitive performance.
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arxiv:1811.00908
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results are presented from a one - neutron knockout reaction at relativistic energies on 56ti using the gsi frs as a two - stage magnetic spectrometer and the miniball array for gamma - ray detection. inclusive and exclusive longitudinal momentum distributions and cross - sections were measured enabling the determination of the orbital angular momentum of the populated states. first - time observation of the 955 ( 6 ) kev nu p3 / 2 - hole state in 55ti is reported. the measured data for the first time proves that the ground state of 55ti is a 1 / 2 - state, in agreement with shell - model calculations using the gxpf1a interaction that predict a sizable n = 34 gap in 54ca.
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arxiv:0810.3157
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machine translation models have discrete vocabularies and commonly use subword segmentation techniques to achieve an ' open vocabulary. ' this approach relies on consistent and correct underlying unicode sequences, and makes models susceptible to degradation from common types of noise and variation. motivated by the robustness of human language processing, we propose the use of visual text representations, which dispense with a finite set of text embeddings in favor of continuous vocabularies created by processing visually rendered text with sliding windows. we show that models using visual text representations approach or match performance of traditional text models on small and larger datasets. more importantly, models with visual embeddings demonstrate significant robustness to varied types of noise, achieving e. g., 25. 9 bleu on a character permuted german - english task where subword models degrade to 1. 9.
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arxiv:2104.08211
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surface critical phenomena and the related onset of goldstone modes probe the fundamental properties of the confining flux in quantum chromodynamics. new ideas on surface roughening and their implications for lattice studies of quark confinement are presented. problems with the oversimplified string description of the wilson flux sheet are discussed.
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arxiv:hep-lat/9911007
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the magnitude of binding energy used in the conventional nuclear theory to explain the emc experimental data, seems to be larger than the one expected. in this paper to get sufficient depletion in the binding energy, different oscillator - model parameters $ \ textit { $ h \ omega $ } $ for different shells and the proton ( neutron ) structure function that have good agrement with experimental data are used. the extracted results for $ ^ 4he, ^ { 12 } c, ^ { 40 } ca $ and $ ^ { 56 } fe $ nuclei show that one can get improved results in medium x ranges by less binding energy.
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arxiv:0802.1623
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malaria is the one of the leading causes of morbidity and mortality in many developing countries. the development of a highly effective and readily deployable vaccine represents a major goal for world health. there has been recent progress in developing a clinically effective vaccine manufactured using plasmodium falciparum sporozoites ( pfspz ) extracted from the salivary glands of anopheles sp. mosquitoes. the harvesting of pfspz requires dissection of the mosquito and manual removal of the salivary glands from each mosquito by trained technicians. while pfspz - based vaccines have shown highly promising results, the process of dissection of salivary glands is tedious and labor intensive. we propose a mechanical device that will greatly increase the rate of mosquito dissection and deskill the process to make malaria vaccines more affordable and more readily available. this device consists of several components : a sorting stage in which the mosquitoes are sorted into slots, a cutting stage in which the heads are removed, and a squeezing stage in which the salivary glands are extracted and collected. this method allows mosquitoes to be dissected twenty at a time instead of one by one as previously done and significantly reduces the dissection time per mosquito.
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arxiv:1903.02532
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bound states are stationary in time and interact continuously. even a first approximation of atomic wave functions in qed requires contributions of all orders in \ alpha. bound state perturbation theory depends on the choice of this first approximation, just as the taylor expansion of an ordinary function depends on the expansion point. considering the expansion to be not in $ \ alpha $ but in $ \ hbar $, i. e., in the number of loops, defines the perturbative expansion uniquely also for bound states. i show how the schr \ " odinger equation for positronium with the classical potential $ v ( r ) = - \ alpha / r $ corresponds to the born, $ o ( \ hbar ^ 0 ) $ bound state approximation in qed. standard perturbation theory is based on an expansion around $ o ( \ alpha ^ 0 ) $ free states that have no overlap with bound states. perturbing around bound states requires using interacting $ in $ and $ out $ states. for born states the binding potential arises from a classical gauge field. in the absence of loops the qcd scale $ \ lambda _ { qcd } $ can originate from a boundary condition imposed on the solution of the classical gluon field equations. a perturbative expansion may be relevant even for hadrons, if their non - perturbative features such as confinement and chiral symmetry breaking are present already in the born term.
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arxiv:1711.10851
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we study uniform $ \ epsilon - $ bpb approximations of bounded linear operators between banach spaces from a geometric perspective. we show that for sufficiently small positive values of $ \ epsilon, $ many geometric properties like smoothness, norm attainment and extremality of operators are preserved under such approximations. we present examples of pairs of banach spaces satisfying non - trivial norm preserving uniform $ \ epsilon - $ bpb approximation property in the global sense. we also study these concepts in case of bounded linear operators between hilbert spaces. our approach in the present article leads to the improvement and generalization of some earlier results in this context.
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arxiv:2407.07490
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we study the $ sig $ dimension of trees under $ l _ { \ infty } $ metric and answer an open problem posed by michael and quint ( discrete applied mathematics : 127, pages 447 - 460, 2003 ). let $ t $ be a tree with atleast two vertices. for each $ v \ in v ( t ) $, let leaf - degree $ ( v ) $ denote the number of neighbours of $ v $ that are leaves. we define the maximum leaf - degree as $ \ alpha ( t ) = \ max _ { x \ in v ( t ) } $ leaf - degree $ ( x ) $. let $ s = \ { v \ in v ( t ) | $ leaf - degree $ ( v ) = \ alpha \ } $. if $ | s | = 1 $, we define $ \ beta ( t ) = \ alpha ( t ) - 1 $. otherwise define $ \ beta ( t ) = \ alpha ( t ) $. we show that for a tree $ t $, $ sig _ \ infty ( t ) = \ lceil \ log _ 2 ( \ beta + 2 ) \ rceil $ where $ \ beta = \ beta ( t ) $, provided $ \ beta $ is not of the form $ 2 ^ k - 1 $, for some positive integer $ k \ geq 1 $. if $ \ beta = 2 ^ k - 1 $, then $ sig _ \ infty ( t ) \ in \ { k, k + 1 \ } $. we show that both values are possible.
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arxiv:0910.5380
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these lectures cover aspects of primordial cosmology with a focus on observational tests of physics beyond the standard model. the presentation is divided into two parts : in part i, we study the production of new light particles in the hot big bang and describe their effects on the anisotropies of the cosmic microwave background. in part ii, we investigate the possibility of very massive particles being created during inflation and determine their imprints in higher - order cosmological correlations.
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arxiv:1807.03098
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it is argued that important information on the emergence of space is hidden at the quark / hadron level. the arguments follow from the acceptance of the conception that space is an attribute of matter. they involve in particular the discussion of possibly relevant mass and distance scales, the generalization of the concept of mass as suggested by the phase - space - based explanation of the rishon model, and the phenomenological conclusions on the structure of excited baryons that are implied by baryon spectroscopy. a counterpart of the eddington - weinberg relation concerning regge towers of hadronic resonances is noted.
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arxiv:1809.05402
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the coexistence of infinitely many attractors is called extreme multistability in dynamical systems. in coupled systems, this phenomenon is closely related to partial synchrony and characterized by the emergence of a conserved quantity. we propose a general design of coupling that leads to partial synchronization, which may be a partial complete synchronization or partial antisynchronization and even a mixed state of complete synchronization and antisynchronization in two coupled systems and, thereby reveal the emergence of extreme multistability. the proposed design of coupling has wider options and allows amplification or attenuation of the amplitude of the attractors whenever it is necessary. we demonstrate that this phenomenon is robust to parameter mismatch of the coupled oscillators.
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arxiv:1505.02094
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in causal inference, sensitivity analysis is important to assess the robustness of study conclusions to key assumptions. we perform sensitivity analysis of the assumption that missing outcomes are missing completely at random. we follow a bayesian approach, which is nonparametric for the outcome distribution and can be combined with an informative prior on the sensitivity parameter. we give insight in the posterior and provide theoretical guarantees in the form of bernstein - von mises theorems for estimating the mean outcome. we study different parametrisations of the model involving dirichlet process priors on the distribution of the outcome and on the distribution of the outcome conditional on the subject being treated. we show that these parametrisations incorporate a prior on the sensitivity parameter in different ways and discuss the relative merits. we also present a simulation study, showing the performance of the methods in finite sample scenarios.
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arxiv:2305.06816
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multiphase ranking functions ( $ \ mathit { m { \ phi } rfs } $ ) were proposed as a means to prove the termination of a loop in which the computation progresses through a number of " phases ", and the progress of each phase is described by a different linear ranking function. our work provides new insights regarding such functions for loops described by a conjunction of linear constraints ( single - path loops ). we provide a complete polynomial - time solution to the problem of existence and of synthesis of $ \ mathit { m { \ phi } rf } $ of bounded depth ( number of phases ), when variables range over rational or real numbers ; a complete solution for the ( harder ) case that variables are integer, with a matching lower - bound proof, showing that the problem is conp - complete ; and a new theorem which bounds the number of iterations for loops with $ \ mathit { m { \ phi } rfs } $. surprisingly, the bound is linear, even when the variables involved change in non - linear way. we also consider a type of lexicographic ranking functions, $ \ mathit { llrfs } $, more expressive than types of lexicographic functions for which complete solutions have been given so far. we prove that for the above type of loops, lexicographic functions can be reduced to $ \ mathit { m { \ phi } rfs } $, and thus the questions of complexity of detection and synthesis, and of resulting iteration bounds, are also answered for this class.
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arxiv:1703.07547
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deep learning has proven to be effective in a wide variety of loss minimization problems. however, many applications of interest, like minimizing projected bellman error and min - max optimization, cannot be modelled as minimizing a scalar loss function but instead correspond to solving a variational inequality ( vi ) problem. this difference in setting has caused many practical challenges as naive gradient - based approaches from supervised learning tend to diverge and cycle in the vi case. in this work, we propose a principled surrogate - based approach compatible with deep learning to solve vis. we show that our surrogate - based approach has three main benefits : ( 1 ) under assumptions that are realistic in practice ( when hidden monotone structure is present, interpolation, and sufficient optimization of the surrogates ), it guarantees convergence, ( 2 ) it provides a unifying perspective of existing methods, and ( 3 ) is amenable to existing deep learning optimizers like adam. experimentally, we demonstrate our surrogate - based approach is effective in min - max optimization and minimizing projected bellman error. furthermore, in the deep reinforcement learning case, we propose a novel variant of td ( 0 ) which is more compute and sample efficient.
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arxiv:2411.05228
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message passing is a fundamental procedure for graph neural networks in the field of graph representation learning. based on the homophily assumption, the current message passing always aggregates features of connected nodes, such as the graph laplacian smoothing process. however, real - world graphs tend to be noisy and / or non - smooth. the homophily assumption does not always hold, leading to sub - optimal results. a revised message passing method needs to maintain each node ' s discriminative ability when aggregating the message from neighbors. to this end, we propose a memory - based message passing ( mmp ) method to decouple the message of each node into a self - embedding part for discrimination and a memory part for propagation. furthermore, we develop a control mechanism and a decoupling regularization to control the ratio of absorbing and excluding the message in the memory for each node. more importantly, our mmp is a general skill that can work as an additional layer to help improve traditional gnns performance. extensive experiments on various datasets with different homophily ratios demonstrate the effectiveness and robustness of the proposed method.
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arxiv:2202.00423
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clustering is one of the main tasks in exploratory data analysis and descriptive statistics where the main objective is partitioning observations in groups. clustering has a broad range of application in varied domains like climate, business, information retrieval, biology, psychology, to name a few. a variety of methods and algorithms have been developed for clustering tasks in the last few decades. we observe that most of these algorithms define a cluster in terms of value of the attributes, density, distance etc. however these definitions fail to attach a clear meaning / semantics to the generated clusters. we argue that clusters having understandable and distinct semantics defined in terms of quartiles / halves are more appealing to business analysts than the clusters defined by data boundaries or prototypes. on the samepremise, we propose our new algorithm named as quartile clustering technique. through a series of experiments we establish efficacy of this algorithm. we demonstrate that the quartile clustering technique adds clear meaning to each of the clusters compared to k - means. we use db index to measure goodness of the clusters and show our method is comparable to em ( expectation maximization ), pam ( partition around medoid ) and k means. we have explored its capability in detecting outlier and the benefit of added semantics. we discuss some of the limitations in its present form and also provide a rough direction in addressing the issue of merging the generated clusters.
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arxiv:1203.4157
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this work provides a concrete implementation of e. fermi ' s model of particle acceleration in magnetohydrodynamic ( mhd ) turbulence, connecting the rate of energization to the gradients of the velocity of magnetic field lines, which it characterizes within a multifractal picture of turbulence intermittency. it then derives a transport equation in momentum space for the distribution function. this description is shown to be substantiated by a large - scale numerical simulation of strong mhd turbulence. the present, general framework can be used to model particle acceleration in a variety of environments.
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arxiv:2210.01038
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experimental studies of fission induced in relativistic nuclear collisions show a systematic enhancement of the excitation energy of the primary fragments by a factor of ~ 2, before their decay by fission and other secondary fragments. although it is widely accepted that by doubling the energies of the single - particle states may yield a better agreement with fission data, it does not prove fully successful, since it is not able to explain yields for light and intermediate mass fragments. state - of - the - art calculations are successful to describe the overall shape of the mass distribution of fragments, but fail within a factor of 2 - 10 for a large number of individual yields. here, we present a novel approach that provides an account of the additional excitation of primary fragments due to final state interaction with the target. our method is applied to the 238u + 208pb reaction at 1 gev / nucleon ( and is applicable to other energies ), an archetype case of fission studies with relativistic heavy ions, where we find that the large probability of energy absorption through final state excitation of giant resonances in the fragments can substantially modify the isotopic distribution of final fragments in a better agreement with data. finally, we demonstrate that large angular momentum transfers to the projectile and to the primary fragments via the same mechanism imply the need of more elaborate theoretical methods than the presently existing ones.
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arxiv:1912.05468
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multi - wavelength ( mw ) observations of fast radio bursts ( frbs ) is a key avenue to uncover the yet - unknown origin ( s ) of these extragalactic signals. in this proceeding, we discuss the need for precise localization to conduct mw studies. we present a number of theoretical predictions of mw counterparts and mention a few examples of on - going mw campaigns.
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arxiv:2311.02360
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we report on a detailed spatial and spectral analysis of the large - scale x - ray emission from the merging cluster cygnus a. we use 2. 2 ms chandra and 40 ks xmm - newton archival datasets to determine the thermodynamic properties of the intracluster gas in the merger region between the two sub - clusters in the system. these profiles exhibit temperature enhancements that imply significant heating along the merger axis. possible sources for this heating include the shock from the ongoing merger, past activity of the powerful agn in the core, or a combination of both. to distinguish between these scenarios, we compare the observed x - ray properties of cygnus a with simple, spherical cluster models. these models are constructed using azimuthally averaged density and temperature profiles determined from the undisturbed regions of the cluster and folded through marx to produce simulated chandra observations. the thermodynamic properties in the merger region from these simulated x - ray observations were used as a baseline for comparison with the actual observations. we identify two distinct components in the temperature structure along the merger axis, a smooth, large - scale temperature excess we attribute to the ongoing merger, and a series of peaks where the temperatures are enhanced by 0. 5 - 2. 5 kev. if these peaks are attributable to the central agn, the location and strength of these features imply that cygnus a has been active for the past 300 myr injecting a total of $ \ sim $ 10 $ ^ { 62 } $ erg into the merger region. this corresponds to $ \ sim $ 10 % of the energy deposited by the merger shock.
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arxiv:2401.02912
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context. inferring spectral parameters from x - ray data is one of the cornerstones of high - energy astrophysics, and is achieved using software stacks that have been developed over the last twenty years and more. however, as models get more complex and spectra reach higher resolutions, these established software solutions become more feature - heavy, difficult to maintain and less efficient. aims. we present jaxspec, a python package for performing this task quickly and robustly in a fully bayesian framework. based on the jax ecosystem, jaxspec allows the generation of differentiable likelihood functions compilable on core or graphical process units ( resp. cpu and gpu ), enabling the use of robust algorithms for bayesian inference. methods. we demonstrate the effectiveness of jaxspec samplers, in particular the no u - turn sampler, using a composite model and comparing what we obtain with the existing frameworks. we also demonstrate its ability to process high - resolution spectroscopy data and using original methods, by reproducing the results of the hitomi collaboration on the perseus cluster, while solving the inference problem using variational inference on a gpu. results. we obtain identical results when compared to other softwares and approaches, meaning that jaxspec provides reliable results while being $ \ sim 10 $ times faster than existing alternatives. in addition, we show that variational inference can produce convincing results even on high - resolution data in less than 10 minutes on a gpu. conclusions. with this package, we aim to pursue the goal of opening up x - ray spectroscopy to the existing ecosystem of machine learning and bayesian inference, enabling researchers to apply new methods to solve increasingly complex problems in the best possible way. our long - term ambition is the scientific exploitation of the data from the newathena x - ray integral field unit ( x - ifu ).
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arxiv:2409.05757
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