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the development of natural language processing ( nlp ) in general and machine reading comprehension in particular has attracted the great attention of the research community. in recent years, there are a few datasets for machine reading comprehension tasks in vietnamese with large sizes, such as uit - viquad and uit - vinewsqa. however, the datasets are not diverse in answers to serve the research. in this paper, we introduce uit - viwikiqa, the first dataset for evaluating sentence extraction - based machine reading comprehension in the vietnamese language. the uit - viwikiqa dataset is converted from the uit - viquad dataset, consisting of comprises 23. 074 question - answers based on 5. 109 passages of 174 wikipedia vietnamese articles. we propose a conversion algorithm to create the dataset for sentence extraction - based machine reading comprehension and three types of approaches for sentence extraction - based machine reading comprehension in vietnamese. our experiments show that the best machine model is xlm - r _ large, which achieves an exact match ( em ) of 85. 97 % and an f1 - score of 88. 77 % on our dataset. besides, we analyze experimental results in terms of the question type in vietnamese and the effect of context on the performance of the mrc models, thereby showing the challenges from the uit - viwikiqa dataset that we propose to the language processing community.
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arxiv:2105.09043
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the epoch of reionization ( eor ) sets a fundamental benchmark in cosmic structure formation, corresponding to the formation of the first luminous objects that act to ionize the neutral intergalactic medium ( igm ). recent observations at near - ir and radio wavelengths imply that we are finally probing into this key epoch of galaxy formation at $ z \ ge 6 $. the square kilometer array ( ska ) will provide critical insight into the eor in a number of ways. first, the ability of the ska to image the neutral igm in 21cm emission is a truly unique probe of the process of reionization, and is recognized as the next necessary and fundamental step in our study of the evolution of large scale structure and cosmic reionization. second, study of hi 21cm absorption toward the first radio loud objects probes small to intermediate scale structure in the neutral ' cosmic web ', as well as hi in the first collapsed structures ( proto - disks and mini - halos ). and third, the incomparable sensitivity of the ska allows for the study of the molecular gas, dust, and star formation activity in the first galaxies, as well as the radio continuum emission from the first accreting massive black holes. such objects will be obscured at optical wavelengths due to absorption by the neutral igm.
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arxiv:astro-ph/0409312
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both the current upgrades to accelerator - based hep detectors ( e. g. atlas, cms ) and also future projects ( e. g. cepc, fcc ) feature large - area silicon - based tracking detectors. we are investigating the feasibility of using cmos foundries to fabricate silicon radiation detectors, both for pixels and for large - area strip sensors. a successful proof of concept would open the market potential of cmos foundries to the hep community, which would be most beneficial in terms of availability, throughput and cost. in addition, the availability of multi - layer routing of signals will provide the freedom to optimize the sensor geometry and the performance, with biasing structures implemented in poly - silicon layers and mim - capacitors allowing for ac coupling. a prototyping production of strip test structures and rd53a compatible pixel sensors was recently completed at lfoundry in a 150nm cmos process. this presentation will focus on the characterization of pixel modules, studying the performance in terms of charge collection, position resolution and hit efficiency with measurements performed in the laboratory and with beam tests. we will report on the investigation of rd53a modules with 25x100 mu ^ 2 cell geometry.
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arxiv:2111.07797
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in this letter we consider the problem of certification of quantum measurements with an arbitrary number of outcomes. we propose a simple scheme for certifying any set of $ d $ - outcome projective measurements which do not share any common invariant proper subspace, termed here genuinely incompatible, and the maximally entangled state of two qudits. for our purpose, we focus on a simpler scenario, termed as one - sided device - independent scenario where the resource employed for certification is quantum steering. we also study robustness of our self - testing statements for a certain class of genuinely incompatible measurements including mutually unbiased bases which are essential for several quantum information - theoretic tasks such as quantum cryptography.
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arxiv:2107.02937
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cognitive acoustic cues have an important role in shaping the phonological structure of language as a means to optimal communication. in this paper we introduced p - trac procedure in order to track dispersion of contrasts in different contexts in lexicon. the results of applying p - trac procedure to the case of dispersion of contrasts in pre - consonantal contexts and in consonantal positions of cvcc sequences in persian provide evidence in favor of phonetic basis of dispersion argued by licensing by cue hypothesis and the dispersion theory of contrast. the p - trac procedure is proved to be very effective in revealing the dispersion of contrasts in lexicon especially when comparing the dispersion of contrasts in different contexts.
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arxiv:1510.00760
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an r - parity violating susy model with lepton - number violating couplings $ \ lambda ' _ { i33 } $, i = 2, 3 can generate a neutrino mass spectrum that explains the recent results from neutrino oscillation experiments. these r - parity violating couplings lead to a clean signal with at least one isolated lepton and at least three tagged $ b $ jets that is accessible in chargino and neutralino production at the tevatron collider. this signature can be probed at $ 3 \ sigma $ up to $ m _ { 1 / 2 } = 230 $ gev ( 320 gev ) with an integrated luminosity of $ 2 fb ^ { - 1 } $ ( $ 30 fb ^ { - 1 } $ ).
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arxiv:hep-ph/0108261
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in existing image classification systems that use deep neural networks, the knowledge needed for image classification is implicitly stored in model parameters. if users want to update this knowledge, then they need to fine - tune the model parameters. moreover, users cannot verify the validity of inference results or evaluate the contribution of knowledge to the results. in this paper, we investigate a system that stores knowledge for image classification, such as image feature maps, labels, and original images, not in model parameters but in external high - capacity storage. our system refers to the storage like a database when classifying input images. to increase knowledge, our system updates the database instead of fine - tuning model parameters, which avoids catastrophic forgetting in incremental learning scenarios. we revisit a knn ( k - nearest neighbor ) classifier and employ it in our system. by analyzing the neighborhood samples referred by the knn algorithm, we can interpret how knowledge learned in the past is used for inference results. our system achieves 79. 8 % top - 1 accuracy on the imagenet dataset without fine - tuning model parameters after pretraining, and 90. 8 % accuracy on the split cifar - 100 dataset in the task incremental learning setting.
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arxiv:2204.01186
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explosion ", where a neutron star is formed with relatively low mass and energy ejection. however, the current upper limit on r does not allow one to rule out $ m _ c \ sim1m _ \ odot $.
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arxiv:1703.06723
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in cosmological models favored by current observations, the first astrophysical objects formed in dark matter halos at redshifts starting at z > 20, and their properties were determined by primordial h _ 2 molecular chemistry. these protogalaxies were very abundant, but substantially less massive than typical galaxies in the local universe. extreme metal - poor stars, and massive black holes in their nuclei reionized the bulk of the hydrogen in the intergalactic medium. reionization may have taken place over an extended redshift interval, ending around z = 7. observational probes of the process of reionization are afforded by studying the polarization of the cosmic microwave background anisotropies, as well as by studying the spectra and abundance of distant lyman alpha - emitting galaxies. here we review theoretical expectations on how and when the first galaxies formed, and summarize future observational prospects of probing hydrogen reionization.
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arxiv:astro-ph/0304131
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in this report, we investigate the effect of low coefficient of thermal expansion ( cte ) metals on the operating speed of hafnium - based oxide capacitance. we found that the cooling process of low cte metals during rapid thermal annealing ( rta ) generates in - plane tensile stresses in the film, this facilitates an increase in the volume fraction of the o - phase and significantly improves the domain switching speed. however, no significant benefit was observed at electric fields less than 1 mv / cm. this is because at low voltage operation, the defective resistance ( dead layer ) within the interface prevents electron migration and the increased rc delay. minimizing interface defects will be an important key to extending endurance and retention.
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arxiv:2307.04404
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since the extreme value index ( evi ) controls the tail behaviour of the distribution function, the estimation of evi is a very important topic in extreme value theory. recent developments in the estimation of evi along with covariates have been in the context of nonparametric regression. however, for the large dimension of covariates, the fully nonparametric estimator faces the problem of the curse of dimensionality. to avoid this, we apply the single index model to evi regression under pareto - type tailed distribution. we study the penalized maximum likelihood estimation of the single index model. the asymptotic properties of the estimator are also developed. numerical studies are presented to show the efficiency of the proposed model.
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arxiv:2203.05758
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we give explicit representation formulas for marginally trapped submanifolds of co - dimension two in pseudo - riemannian spaces with arbitrary signature and constant sectional curvature. this paper is dedicated to the memory of franki dillen, 1963 - 2013.
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arxiv:1309.3875
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deep learning ( dl ) has achieved remarkable progress over the past decade and been widely applied to many safety - critical applications. however, the robustness of dl systems recently receives great concerns, such as adversarial examples against computer vision systems, which could potentially result in severe consequences. adopting testing techniques could help to evaluate the robustness of a dl system and therefore detect vulnerabilities at an early stage. the main challenge of testing such systems is that its runtime state space is too large : if we view each neuron as a runtime state for dl, then a dl system often contains massive states, rendering testing each state almost impossible. for traditional software, combinatorial testing ( ct ) is an effective testing technique to reduce the testing space while obtaining relatively high defect detection abilities. in this paper, we perform an exploratory study of ct on dl systems. we adapt the concept in ct and propose a set of coverage criteria for dl systems, as well as a ct coverage guided test generation technique. our evaluation demonstrates that ct provides a promising avenue for testing dl systems. we further pose several open questions and interesting directions for combinatorial testing of dl systems.
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arxiv:1806.07723
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the development of prototype metropolitan - scale quantum networks is underway and entails transmitting quantum information via single photons through deployed optical fibers spanning several tens of kilometers. the major challenges in building metropolitan - scale quantum networks are compensation of polarization mode dispersion, high - precision clock synchronization, and compensation for cumulative transmission time fluctuations. one approach addressing these challenges is to co - propagate classical probe signals in the same fiber as the quantum signal. thus, both signals experience the same conditions, and the changes of the fiber can therefore be monitored and compensated. here, we demonstrate the distribution of polarization entangled quantum signals co - propagating with the white rabbit precision time protocol ( wr - ptp ) classical signals in the same single - core fiber strand at metropolitan - scale distances. our results demonstrate the feasibility of this quantum - classical coexistence by achieving high - fidelity entanglement distribution between nodes separated by 100 km of optical fiber. this advancement is a significant step towards the practical implementation of robust and efficient metropolitan - scale quantum networks.
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arxiv:2402.00617
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motivated by the study of an hecke action on iterated shimura integrals undertaken in [ h ], in this appendix to [ h ] we prove that, for any prime $ p \ geq 5 $ and for any integer $ n \ geq 1 $, every complex irreducible representation of $ g = \ mathrm { sl } _ 2 ( \ mathbb { z } / p ^ n \ mathbb { z } ) $ that are trivial on $ \ mathbf { z } ( g ) $ appears as an irreducible constituent of the conjugation representation of $ g $.
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arxiv:2303.02807
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semantic communication ( semcom ), regarded as the evolution of the traditional shannon ' s communication model, stresses the transmission of semantic information instead of the data itself. federated learning ( fl ), owing to its distributed learning and privacy - preserving properties, has received attention from both academia and industry. in this paper, we introduce a system that integrates fl and semcom, which is called fedsem. we have also proposed an optimization problem related to resource allocation for this system. the objective of this problem is to minimize the energy consumption and delay of fl, as well as the transmission energy of semcom, while maximizing the accuracy of the model trained through fl. the channel access scheme is orthogonal frequency - division multiple access ( ofdma ). the optimization variables include the binary ( 0 - 1 ) subcarrier allocation indicator, the transmission power of each device on specific subcarriers, the computational frequency of each participating device, and the compression rate for semcom. to tackle this complex problem, we propose a resource allocation algorithm that decomposes the original problem into more tractable subproblems. by employing convex optimization techniques, we transform the non - convex problem into convex forms, ensuring tractability and solution effectiveness. our approach includes a detailed analysis of time complexity and convergence, proving the practicality of the algorithm. numerical experiments validate the effectiveness of our approach, showing superior performance of our algorithm in various scenarios compared to baseline methods. hence, our solution is useful for enhancing the operational efficiency of fedsem systems, offering significant potential for real - world applications.
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arxiv:2503.06058
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we define united k - theory for real c * - algebras, generalizing bousfield ' s topological united k - theory. united k - theory incorporates three functors - - real k - theory, complex k - theory, and self - conjugate k - theory - - and the natural transformations among them. the advantage of united k - theory over ordinary k - theory lies in its homological algebraic properties, which allow us to construct a kunneth - type, non - splitting, short exact sequence whose middle term is the united k - theory of the tensor product of two real c * - algebras a and b which holds as long as the complexification of a is in the bootstrap category. since united k - theory contains ordinary k - theory, our sequence provides a way to compute the k - theory of the tensor product of two real c * - algebras. as an application, we compute the united k - theory of the tensor product of two real cuntz algebras. unlike in the complex case, it turns out that the isomorphism class of the tensor product o _ { k + 1 } otimes o _ { l + 1 } is not determined solely by the greatest common divisor of k and l. hence we have examples of non - isomorphic, simple, purely infinite, real c * - algebras whose complexifications are isomorphic.
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arxiv:math/0208068
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segregation of garbage is a primary concern in many nations across the world. even though we are in the modern era, many people still do not know how to distinguish between organic and recyclable waste. it is because of this that the world is facing a major crisis of waste disposal. in this paper, we try to use deep learning algorithms to help solve this problem of waste classification. the waste is classified into two categories like organic and recyclable. our proposed model achieves an accuracy of 94. 9 %. although the other two models also show promising results, the proposed model stands out with the greatest accuracy. with the help of deep learning, one of the greatest obstacles to efficient waste management can finally be removed.
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arxiv:2202.12258
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this two - part paper presents a feedback - based cross - layer framework for distributed sensing and estimation of a dynamic process by a wireless sensor network ( wsn ). sensor nodes wirelessly communicate measurements to the fusion center ( fc ). cross - layer factors such as packet collisions and the sensing - transmission costs are considered. each sn adapts its sensing - transmission action based on its own local observation quality and the estimation quality feedback from the fc under cost constraints for each sn. in this first part, the optimization complexity is reduced by exploiting the statistical symmetry and large network approximation of the wsn. structural properties of the optimal policy are derived for a coordinated and a decentralized scheme. it is proved that a dense wsn provides sensing diversity, so that only a few sns with the best local observation quality need to be activated, despite the fluctuations of the wsn. the optimal policy dictates that, when the estimation quality is poor, only the best sns activate, otherwise all sns remain idle to preserve energy. the costs of coordination and feedback are evaluated, revealing the scalability of the decentralized scheme to large wsns, at the cost of performance degradation. simulation results demonstrate cost savings from 30 % to 70 % over a non - adaptive scheme, and significant gains over a previously proposed estimator which does not consider these cross - layer factors.
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arxiv:1410.0431
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parameters of recent neural networks require a huge amount of memory. these parameters are used by neural networks to perform machine learning tasks when processing inputs. to speed up inference, we develop partition pruning, an innovative scheme to reduce the parameters used while taking into consideration parallelization. we evaluated the performance and energy consumption of parallel inference of partitioned models, which showed a 7. 72x speed up of performance and a 2. 73x reduction in the energy used for computing pruned layers of tinyvgg16 in comparison to running the unpruned model on a single accelerator. in addition, our method showed a limited reduction some numbers in accuracy while partitioning fully connected layers.
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arxiv:1901.11391
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this paper presents an efficient multi - scale vision transformer, called rest, that capably served as a general - purpose backbone for image recognition. unlike existing transformer methods, which employ standard transformer blocks to tackle raw images with a fixed resolution, our rest have several advantages : ( 1 ) a memory - efficient multi - head self - attention is built, which compresses the memory by a simple depth - wise convolution, and projects the interaction across the attention - heads dimension while keeping the diversity ability of multi - heads ; ( 2 ) position encoding is constructed as spatial attention, which is more flexible and can tackle with input images of arbitrary size without interpolation or fine - tune ; ( 3 ) instead of the straightforward tokenization at the beginning of each stage, we design the patch embedding as a stack of overlapping convolution operation with stride on the 2d - reshaped token map. we comprehensively validate rest on image classification and downstream tasks. experimental results show that the proposed rest can outperform the recently state - of - the - art backbones by a large margin, demonstrating the potential of rest as strong backbones. the code and models will be made publicly available at https : / / github. com / wofmanaf / rest.
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arxiv:2105.13677
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this research investigates flight delay trends by examining factors such as departure time, airline, and airport. it employs regression machine learning methods to predict the contributions of various sources to delays. time - series models, including lstm, hybrid lstm, and bi - lstm, are compared with baseline regression models such as multiple regression, decision tree regression, random forest regression, and neural network. despite considerable errors in the baseline models, the study aims to identify influential features in delay prediction, potentially informing flight planning strategies. unlike previous work, this research focuses on regression tasks and explores the use of time - series models for predicting flight delays. it offers insights into aviation operations by independently analyzing each delay component ( e. g., security, weather ).
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arxiv:2408.02802
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why has the problematic of complexity appeared so late? and why would it be justified?
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arxiv:cs/0610049
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we present observable upper bounds of squared concurrence, which are the dual inequalities of the observable lower bounds introduced in [ f. mintert and a. buchleitner, phys. rev. lett. 98, 140505 ( 2007 ) ] and [ l. aolita, a. buchleitner and f. mintert, phys. rev. a 78, 022308 ( 2008 ) ]. these bounds can be used to estimate entanglement for arbitrary experimental unknown finite - dimensional states by few experimental measurements on a twofold copy $ \ rho \ otimes \ rho $ of the mixed states. furthermore, the degree of mixing for a mixed state and some properties of the linear entropy also have certain relations with its upper and lower bounds of squared concurrence.
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arxiv:0806.2598
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in the study of weakly turbulent wave systems possessing incomplete self - similarity it is possible to use dimensional arguments to derive the scaling exponents of the kolmogorov - zakharov spectra, provided the order of the resonant wave interactions responsible for nonlinear energy transfer is known. furthermore one can easily derive conditions for the breakdown of the weak turbulence approximation. it is found that for incompletely self - similar systems dominated by three wave interactions, the weak turbulence approximation usually cannot break down at small scales. it follows that such systems cannot exhibit small scale intermittency. for systems dominated by four wave interactions, the incomplete self - similarity property implies that the scaling of the interaction coefficient depends only on the physical dimension of the system. these results are used to build a complete picture of the scaling properties of the surface wave problem where both gravity and surface tension play a role. we argue that, for large values of the energy flux, there should be two weakly turbulent scaling regions matched together via a region of strongly nonlinear turbulence.
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arxiv:physics/0304077
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we propose a general argument to show that if a physical system can mediate locally the generation of entanglement between two quantum systems, then it itself must be non - classical. remarkably, we do not assume any classical or quantum formalism to describe the mediating physical system : our result follows from general information - theoretic principles, drawn from the recently proposed constructor theory of information. this argument provides the indispensable theoretical basis for recently proposed tests of non - classicality in gravity, based on witnessing gravitationally - induced entanglement in quantum probes.
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arxiv:2003.07974
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we study $ p $ - - harmonic maps with dirichlet boundary conditions from a planar domain into a general compact riemannian manifold. we show that as $ p $ approaches $ 2 $ from below, they converge up to a subsequence to a minimizing singular renormalizable harmonic map. the singularities are imposed by topological obstructions to the existence of harmonic mappings ; the location of the singularities being governed by a renormalized energy. our analysis is based on lower bounds on growing balls and also yields some uniform weak - $ l ^ p $ bounds ( also known as marcinkiewicz or lorentz $ l ^ { p, \ infty } $ ).
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arxiv:2301.06955
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sentence - level relation extraction ( re ) aims at identifying the relationship between two entities in a sentence. many efforts have been devoted to this problem, while the best performing methods are still far from perfect. in this paper, we revisit two problems that affect the performance of existing re models, namely entity representation and noisy or ill - defined labels. our improved re baseline, incorporated with entity representations with typed markers, achieves an f1 of 74. 6 % on tacred, significantly outperforms previous sota methods. furthermore, the presented new baseline achieves an f1 of 91. 1 % on the refined re - tacred dataset, demonstrating that the pretrained language models ( plms ) achieve high performance on this task. we release our code to the community for future research.
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arxiv:2102.01373
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motivated by string / m - theory predictions that scalar field couplings with the gauss - bonnet invariant, g, are essential in the appearance of non - singular early time cosmologies, we discuss the viability of an interesting alternative gravitational theory, namely, modified gauss - bonnet gravity, and present the viability bounds arising from the energy conditions. in particular, we consider a specific realistic form of f ( g ) analyzed in the literature that accounts for the late - time cosmic acceleration and that has been found to cure the finite - time future singularities present in the dark energy models, and further examine the respective viability of the specific f ( g ) model imposed by the weak energy condition.
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arxiv:1012.0953
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supply chain management ( scm ) plays a vital role in the global economy, as evidenced by recent covid - 19 supply chain challenges. traditional scm faces security and efficiency issues, but they can be addressed by leveraging digital twins ( dts ) and blockchain technology. t he combination of blockchain and dts can refine the concepts of both technologies and reform scm to advance into industry 4. 0. in this paper, we provide a comprehensive literature review of the blockchain - based digital twin ( dt ) solutions to optimise the processes of data management, data storage, and data sharing in scm. we also investigate the key benefits of the integration of blockchain and dts and examine their potential implementation in various scm areas, including smart manufacturing, intelligent maintenance, and blockchain - based dt shop floor, warehouse, and logistics. finally, we put forward recommendations for future research directions.
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arxiv:2202.03966
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it is well - understood that the robustness of mechanical and robotic control systems depends critically on minimizing sensitivity to arbitrary application - specific details whenever possible. for example, if a system is defined and performs well in one particular euclidean coordinate frame then it should be expected to perform identically if that coordinate frame is arbitrarily rotated or scaled. similarly, the performance of the system should not be affected if its key parameters are all consistently defined in metric units or in imperial units. in this paper we show that a recently introduced generalized matrix inverse permits performance consistency to be rigorously guaranteed in control systems that require solutions to underdetermined and / or overdetermined systems of equations.
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arxiv:1806.01776
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quantum optimal control problems are typically solved by gradient - based algorithms such as grape, which suffer from exponential growth in storage with increasing number of qubits and linear growth in memory requirements with increasing number of time steps. these memory requirements are a barrier for simulating large models or long time spans. we have created a nonstandard automatic differentiation technique that can compute gradients needed by grape by exploiting the fact that the inverse of a unitary matrix is its conjugate transpose. our approach significantly reduces the memory requirements for grape, at the cost of a reasonable amount of recomputation. we present benchmark results based on an implementation in jax.
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arxiv:2203.12717
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circumbinary disks are considered to exist in a wide variety of astrophysical objects, e. g., young binary stars, protoplanetary systems, and massive binary black hole systems in active galactic nuclei ( agns ). however, there is no definite evidence for the circumbinary disk except for some in a few young binary star systems. in this letter, we study possible oscillation modes in circumbinary disks around eccentric and circular binaries. we find that progarde, nonaxisymmetric waves are induced in the inner part of the circumbinary disk by the tidal potential of the binary. such waves would cause variabilities in emission line profiles from circumbinary disks. because of prograde precession of the waves, the distance between each component of the binary and the inner edge of the circumbinary disk varies with the beat period between the precession period of the wave and the binary orbital period. as a result, light curves from the circumbinary disks are also expected to vary with the same period. the current study thus provides a new method to detect circumbinary disks in various astrophysical systems.
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arxiv:0809.0836
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this review describes the field of bose polarons, arising when mobile impurities are immersed into a bosonic quantum gas. the latter can be realized by a bose - einstein condensate ( bec ) of ultracold atoms, or of exciton polaritons in a semiconductor, which has led to a series of experimental observations of bose polarons near inter - species feshbach resonances that we survey. following an introduction to the topic, with references to its historic roots and a presentation of the bose polaron hamiltonian, we summarize state - of - the - art experiments. next we provide a detailed discussion of polaron models, starting from the ubiquitous fr \ " ohlich hamiltonian that applies at weak couplings. we proceed by a survey of concurrent theoretical methods used for solving strongly interacting bose polaron problems. the subsequent sections are devoted to the large bodies of work investigating strong coupling bose polarons, including detailed comparisons with radio - frequency ( rf ) spectra obtained in ultracold atom experiments ; to investigations of universal few - body and efimov states associated with a feshbach resonance in atomic mixtures ; to studies of quantum dynamics and polarons out of equilibrium ; bose polarons in low - dimensional ; induced interactions among polarons and bipolaron formation ; and to bose polarons at non - zero temperatures. we end our review by detailed discussions of closely related experimental setups and systems, including ionic impurities, systems with strong light - matter interactions, and variations and extensions of the bose polaron concepts e. g. to baths with topological order or strong interactions relevant for correlated electrons. finally, an outlook is presented, highlighting possible future research directions and open questions in the field as a whole.
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arxiv:2410.09413
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nested sampling is a bayesian sampling technique developed to explore probability distributions lo - calised in an exponentially small area of the parameter space. the algorithm provides both posterior samples and an estimate of the evidence ( marginal likelihood ) of the model. the nested sampling algo - rithm also provides an efficient way to calculate free energies and the expectation value of thermodynamic observables at any temperature, through a simple post - processing of the output. previous applications of the algorithm have yielded large efficiency gains over other sampling techniques, including parallel tempering ( replica exchange ). in this paper we describe a parallel implementation of the nested sampling algorithm and its application to the problem of protein folding in a go - type force field of empirical potentials that were designed to stabilize secondary structure elements in room - temperature simulations. we demonstrate the method by conducting folding simulations on a number of small proteins which are commonly used for testing protein folding procedures : protein g, the sh3 domain of src tyrosine kinase and chymotrypsin inhibitor 2. a topological analysis of the posterior samples is performed to produce energy landscape charts, which give a high level description of the potential energy surface for the protein folding simulations. these charts provide qualitative insights into both the folding process and the nature of the model and force field used.
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arxiv:1010.4735
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this paper introduces a new conceptual framework that recasts surface roughness effects as a " ray deflection function " ( rdf ) which can be statistically represented through a modified zernike - fourier hybrid approach that directly connects the psd with statistical aberration coefficients through spectral overlap integration. by establishing a direct mathematical relationship between the power spectral density ( psd ) of surface imperfections and the statistical distribution of aberration coefficients, we develop a formalism that bridges known probabilistic scattering theory with deterministic aberration analysis. this transformation allows surface roughness to be seamlessly integrated with other optical aberrations by expressing its effects through equivalent modifications to the ideal mirror shape. this framework provides computational advantages for ray - tracing simulations while maintaining statistical fidelity to established scattering models, particularly for predicting the three - dimensional structure of imperfect focal bodies in optical systems.
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arxiv:2505.01019
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a spatially one dimensional coupled map lattice possessing the same symmetries as the miller huse model is introduced. our model is studied analytically by means of a formal perturbation expansion which uses weak coupling and the vicinity to a symmetry breaking bifurcation point. in parameter space four phases with different ergodic behaviour are observed. although the coupling in the map lattice is diffusive, antiferromagnetic ordering is predominant. via coarse graining the deterministic model is mapped to a master equation which establishes an equivalence between our system and a kinetic ising model. such an approach sheds some light on the dependence of the transient behaviour on the system size and the nature of the phase transitions.
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arxiv:nlin/0002035
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a long - standing conjecture of kelly states that every regular tournament on n vertices can be decomposed into ( n - 1 ) / 2 edge - disjoint hamilton cycles. we prove this conjecture for large n. in fact, we prove a far more general result, based on our recent concept of robust expansion and a new method for decomposing graphs. we show that every sufficiently large regular digraph g on n vertices whose degree is linear in n and which is a robust outexpander has a decomposition into edge - disjoint hamilton cycles. this enables us to obtain numerous further results, e. g. as a special case we confirm a conjecture of erdos on packing hamilton cycles in random tournaments. as corollaries to the main result, we also obtain several results on packing hamilton cycles in undirected graphs, giving e. g. the best known result on a conjecture of nash - williams. we also apply our result to solve a problem on the domination ratio of the asymmetric travelling salesman problem, which was raised e. g. by glover and punnen as well as alon, gutin and krivelevich.
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arxiv:1202.6219
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in usual quantum theory, the information available about a quantum system is defined in terms of the density matrix describing it on a spacelike surface. this definition must be generalized for extensions of quantum theory which do not have a notion of state on a spacelike surface. it must be generalized for the generalized quantum theories appropriate when spacetime geometry fluctuates quantum mechanically or when geometry is fixed but not foliable by spacelike surfaces. this paper introduces a four - dimensional notion of the information available about a quantum system ' s boundary conditions in the various sets of decohering histories it may display. the idea of spacetime information is applied in several contexts : when spacetime geometry is fixed the information available through alternatives restricted to a spacetime region is defined. the information available through histories of alternatives of general operators is compared to that obtained from the more limited coarse - grainings of sum - over - histories quantum mechanics. the definition of information is considered in generalized quantum theories. we consider as specific examples time - neutral quantum mechanics with initial and final conditions, quantum theories with non - unitary evolution, and the generalized quantum frameworks appropriate for quantum spacetime. in such theories complete information about a quantum system is not necessarily available on any spacelike surface but must be searched for throughout spacetime. the information loss commonly associated with the ` ` evolution of pure states into mixed states ' ' in black hole evaporation is thus not in conflict with the principles of generalized quantum mechanics.
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arxiv:gr-qc/9409005
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we review the recent approach of correlation based networks of financial equities. we investigate portfolio of stocks at different time horizons, financial indices and volatility time series and we show that meaningful economic information can be extracted from noise dressed correlation matrices. we show that the method can be used to falsify widespread market models by directly comparing the topological properties of networks of real and artificial markets.
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arxiv:cond-mat/0401300
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we place a 2. 5 % limit on the anthropogenic contribution to the modern abundance of 81kr / kr in the atmosphere at the 90 % confidence level. due to its simple production and transport in the terrestrial environment, 81kr ( halflife = 230, 000 yr ) is an ideal tracer for old water and ice with mean residence times in the range of 10 ^ 5 - 10 ^ 6 years. in recent years, 81kr - dating has been made available to the earth science community thanks to the development of atom trap trace analysis ( atta ), a laser - based atom counting technique. further upgrades and improvements to the atta technique now allow us to demonstrate 81kr / kr measurements with relative uncertainties of 1 % and place this new limit on anthropogenic 81kr. as a result of this limit, we have removed a potential systematic constraint for 81kr - dating.
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arxiv:1702.01652
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the emergence of synchronization in a network of coupled oscillators is a pervasive topic in various scientific disciplines ranging from biology, physics, and chemistry to social networks and engineering applications. a coupled oscillator network is characterized by a population of heterogeneous oscillators and a graph describing the interaction among the oscillators. these two ingredients give rise to a rich dynamic behavior that keeps on fascinating the scientific community. in this article, we present a tutorial introduction to coupled oscillator networks, we review the vast literature on theory and applications, and we present a collection of different synchronization notions, conditions, and analysis approaches. we focus on the canonical phase oscillator models occurring in countless real - world synchronization phenomena, and present their rich phenomenology. we review a set of applications relevant to control scientists. we explore different approaches to phase and frequency synchronization, and we present a collection of synchronization conditions and performance estimates. for all results we present self - contained proofs that illustrate a sample of different analysis methods in a tutorial style.
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arxiv:1209.1335
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we present a construction of 1 - perfect binary codes, which gives a new lower bound on the number of such codes. we conjecture that this lower bound is asymptotically tight.
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arxiv:math/0608278
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there has been some interest on how the average character degree affects the structure of a finite group. we define, and denote by $ \ mathrm { anz } ( g ) $, the average number of zeros of characters of a finite group $ g $ as the number of zeros in the character table of $ g $ divided by the number of irreducible characters of $ g $. we show that if $ \ mathrm { anz } ( g ) < 1 $, then the group $ g $ is solvable and also that if $ \ mathrm { anz } ( g ) < \ frac { 1 } { 2 } $, then $ g $ is supersolvable. we characterise abelian groups by showing that $ \ mathrm { anz } ( g ) < \ frac { 1 } { 3 } $ if and only if $ g $ is abelian.
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arxiv:2011.12374
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two novel ( and proprietary ) strategies for the structural identification of a nanocrystal from either a single high - resolution ( hr ) transmission electron microscopy ( tem ) image or a single precession electron diffraction pattern are proposed and their advantages discussed in comparison to structural fingerprinting from powder x - ray diffraction patterns. simulations for cubic magnetite and maghemite nanocrystals are used as examples. this is an expanded and updated version of a conference paper that has been published in suppl. proc. of tms 2008, 137th annual meeting & exhibition, volume 1, materials processing and properties, pp. 25 - 32.
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arxiv:0804.0063
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$ \ alpha $ - rucl $ _ 3 $, a well - known candidate material for kitaev quantum spin liquid, is prone to stacking disorder due to the weak van der waals bonding between the honeycomb layers. after a decade of intensive experimental and theoretical studies, the detailed correlation between stacking degree of freedom, structure transition, magnetic and thermal transport properties remains unresolved. in this work, we reveal the effects of a small amount of stacking disorder inherent even in high quality $ \ alpha $ - rucl $ _ 3 $ crystals. this small amount of stacking disorder results in the variation of the magnetic ordering temperature, suppresses the structure transition and thermal conductivity. crystals with minimal amount of stacking disorder have a t $ _ n > $ 7. 4 \, k and exhibit a well - defined structure transition around 140 \, k upon cooling. for those with more stacking faults and a t $ _ n $ below 7 \, k, the structure transition occurs well below 140 \, k upon cooling and is incomplete, manifested by the diffuse streaks and the coexistence of both high temperature and low temperature phases down to the lowest measurement temperature. both types of crystals exhibit oscillatory field dependent thermal conductivity and a plateau - like feature in thermal hall resistivity in the field - induced quantum spin liquid state. however, $ \ alpha $ - rucl $ _ 3 $ crystals with minimal amount of stacking disorder have a higher thermal conductivity that pushes the thermal hall conductivity to be closer to the half - integer quantized value. these findings demonstrate a strong correlation between layer stacking, structure transition, magnetic and thermal transport properties, underscoring the importance of interlayer coupling in $ \ alpha $ - rucl $ _ 3 $ despite the weak van der waals bonding.
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arxiv:2303.03682
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we present perin, a novel permutation - invariant approach to sentence - to - graph semantic parsing. perin is a versatile, cross - framework and language independent architecture for universal modeling of semantic structures. our system participated in the conll 2020 shared task, cross - framework meaning representation parsing ( mrp 2020 ), where it was evaluated on five different frameworks ( amr, drg, eds, ptg and ucca ) across four languages. perin was one of the winners of the shared task. the source code and pretrained models are available at https : / / github. com / ufal / perin.
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arxiv:2011.00758
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this study explores the dynamics of finite - size fibers suspended freely in a viscoelastic turbulent flow. for a fiber suspended in newtonian flows, two different flapping regimes were identified previously by rosti et al ( 2018 ). here we explore, how the fiber dynamics is modified by the elasticity of the carrier fluid by performing direct numerical simulations of a two - way coupled fiber - fluid system in a parametric space spanning different deborah numbers, fiber bending stiffness and the linear density difference between fiber and fluid. we examine how these parameters influence various fiber characteristics such as the frequency of flapping, curvature, and alignment with the fluid strain and polymer stretching directions. results reveal that the neutrally - bouyant fibers, depending on their flexibility, oscillate with large and small time scales transpiring from the flow, but the smaller time - scales are suppressed as the polymer elasticity increases. polymer stretching is uncommunicative to denser - than - fluid fibers, which flap with large time scales from the flow when flexible and with their natural frequency when rigid. thus, the characteristic elastic time scale has a subdominant effect when the fibers are neutrally - bouyant, while its effect is absent when the fibers become more inertial. additionally, we see that the inertial fibers have larger curvatures and are less responsive to the polymer presence, whereas the neutrally - bouyant fibers show quantitative changes. also, the neutrally - bouyant fibers show a higher alignment with the polymer stretching directions compared to the denser ones. in a nutshell, the polymers exert a larger influence on neutrally - bouyant fibers compared to the denser ones. the study comprehensively addresses the interplay between polymer elasticity and the fiber structural properties in determining its response behaviour in an elasto - inertial turbulent flow.
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arxiv:2403.04305
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in the present paper we study local and 2 - local derivations of locally finite split simple lie algebras. namely, we show that every local and 2 - local derivation on such lie algebra is a derivation.
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arxiv:2002.00678
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we consider data in the form of pairwise comparisons of n items, with the goal of precisely identifying the top k items for some value of k < n, or alternatively, recovering a ranking of all the items. we analyze the copeland counting algorithm that ranks the items in order of the number of pairwise comparisons won, and show it has three attractive features : ( a ) its computational efficiency leads to speed - ups of several orders of magnitude in computation time as compared to prior work ; ( b ) it is robust in that theoretical guarantees impose no conditions on the underlying matrix of pairwise - comparison probabilities, in contrast to some prior work that applies only to the btl parametric model ; and ( c ) it is an optimal method up to constant factors, meaning that it achieves the information - theoretic limits for recovering the top k - subset. we extend our results to obtain sharp guarantees for approximate recovery under the hamming distortion metric, and more generally, to any arbitrary error requirement that satisfies a simple and natural monotonicity condition.
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arxiv:1512.08949
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we investigate the impact of using multipoint p - t profiles of varying complexity on the retrieval of synthetically generated hot jupiter transmission spectra modelled after state - of - the - art observations of the hot jupiter wasp - 39 ~ b with jwst. we perform homogenised atmospheric retrievals with the taurex retrieval framework on a sample of synthetically generated transmission spectra, accounting for varying cases of underlying p - t profiles, cloud - top pressures, and expected noise levels. these retrievals are performed using a fixed - pressure multipoint p - t prescription with increasing complexity, ranging from isothermal to an eleven - point profile. we evaluate the performance of the retrievals based on the bayesian model evidence, and the accuracy of the retrievals compared to the known input parameters. we find that performing atmospheric retrievals using an isothermal prescription for the pressure - temperature profile consistently results in wrongly retrieved atmospheric parameters when compared to the known input parameters. for an underlying p - t profile with a fully positive lapse rate, we find that a two - point profile is sufficient to retrieve the known atmospheric parameters, while under the presence of an atmospheric temperature inversion, we find that a more complex profile is necessary. our investigation shows that, for a data quality scenario mirroring state - of - the - art observations of a hot jupiter with jwst, an isothermal p - t prescription is insufficient to correctly retrieve the known atmospheric parameters. we find a model complexity preference dependent on the underlying pressure - temperature structure, but argue that a p - t prescription on the complexity level of a four - point profile should be preferred. this represents the overlap between the lowest number of free parameters and highest model preference in the cases investigated in this work.
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arxiv:2409.09127
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objective : this paper investigates the potential of ensemble learning for variants of adjustment methods used in analogy - based effort estimation. the number k of analogies to be used is also investigated. method we perform a large scale comparison study where many ensembles constructed from n out of 40 possible valid variants of adjustment methods are applied to eight datasets. the performance of each method was evaluated based on standardized accuracy and effect size. results : the results have been subjected to statistical significance testing, and show reasonable significant improvements on the predictive performance where ensemble methods are applied. conclusion : our conclusions suggest that ensembles of adjustment methods can work well and achieve good performance, even though they are not always superior to single methods. we also recommend constructing ensembles from only linear adjustment methods, as they have shown better performance and were frequently ranked higher.
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arxiv:1703.04568
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recently developed survival analysis methods improve upon existing approaches by predicting the probability of event occurrence in each of a number pre - specified ( discrete ) time intervals. by avoiding placing strong parametric assumptions on the event density, this approach tends to improve prediction performance, particularly when data are plentiful. however, in clinical settings with limited available data, it is often preferable to judiciously partition the event time space into a limited number of intervals well suited to the prediction task at hand. in this work, we develop a method to learn from data a set of cut points defining such a partition. we show that in two simulated datasets, we are able to recover intervals that match the underlying generative model. we then demonstrate improved prediction performance on three real - world observational datasets, including a large, newly harmonized stroke risk prediction dataset. finally, we argue that our approach facilitates clinical decision - making by suggesting time intervals that are most appropriate for each task, in the sense that they facilitate more accurate risk prediction.
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arxiv:2310.15853
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the capability to learn latent representations plays a key role in the effectiveness of recent machine learning methods. an active frontier in representation learning is understanding representations for combinatorial structures which may not admit well - behaved local neighborhoods or distance functions. for example, for polygons, slightly perturbing vertex locations might lead to significant changes in their combinatorial structure and may even lead to invalid polygons. in this paper, we investigate representations to capture the underlying combinatorial structures of polygons. specifically, we study the open problem of visibility reconstruction : given a visibility graph g, construct a polygon p whose visibility graph is g. we introduce visdiff, a novel diffusion - based approach to reconstruct a polygon from its given visibility graph g. our method first estimates the signed distance function ( sdf ) of p from g. afterwards, it extracts ordered vertex locations that have the pairwise visibility relationship given by the edges of g. our main insight is that going through the sdf significantly improves learning for reconstruction. in order to train visdiff, we make two main contributions : ( 1 ) we design novel loss components for computing the visibility in a differentiable manner and ( 2 ) create a carefully curated dataset. we use this dataset to benchmark our method and achieve 21 % improvement in f1 - score over standard methods. we also demonstrate effective generalization to out - of - distribution polygon types and show that learning a generative model allows us to sample the set of polygons with a given visibility graph. finally, we extend our method to the related combinatorial problem of reconstruction from a triangulation. we achieve 95 % classification accuracy of triangulation edges and a 4 % improvement in chamfer distance compared to current architectures.
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arxiv:2410.05530
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we investigate radial oscillations of proto - neutron stars, employing equations of state described by the brueckner - hartree - fock theory or the relativistic mean field model, and assuming isentropy and fixed lepton fractions for the internal structure. we calculate the eigenfrequencies and corresponding oscillation functions, which show different characteristics in different mass regions. in the low - mass region around 1. 4 solar mass, the radial oscillation frequencies are lowered by large entropy and neutrino trapping, along with a reduction of the average adiabatic index. in the region close to the maximum mass, the fundamental oscillation frequency drops rapidly and vanishes at the maximum mass, in accordance with the critical stability criterion $ \ partial m / \ partial \ rho _ c = 0 $, as for cold neutron stars.
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arxiv:2408.06599
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the advanced complex electronic systems increasingly demand safer and more secure hardware parts. correspondingly, fault injection became a major verification milestone for both safety - and security - critical applications. however, fault injection campaigns for gate - level designs suffer from huge execution times. therefore, designers need to apply early design evaluation techniques to reduce the execution time of fault injection campaigns. in this work, we propose a method to represent gate - level single - event transient ( set ) faults by multiple single - event upset ( seu ) faults at the register - transfer level. introduced approach is to identify true and false logic paths for each set in the flip - flops fan - in logic cones to obtain more accurate sets of flip - flops for multiple seus injections at rtl. experimental results demonstrate the feasibility of the proposed method to successfully reduce the fault space and also its advantage with respect to state of the art. it was shown that the approach is able to reduce the fault space, and therefore the fault - injection effort, by up to tens to hundreds of times.
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arxiv:2103.05106
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astrod - gw ( astrod [ astrodynamical space test of relativity using optical devices ] optimized for gravitational wave detection ) is a gravitational - wave mission with the aim of detecting gravitational waves from massive black holes, extreme mass ratio inspirals ( emris ) and galactic compact binaries, together with testing relativistic gravity and probing dark energy and cosmology. mission orbits of the 3 spacecrafts forming a nearly equilateral triangular array are chosen to be near the sun - earth lagrange points l3, l4 and l5. the 3 spacecrafts range interferometrically with one another with arm length about 260 million kilometers. for 260 times longer arm length, the detection sensitivity of astrod - gw is 260 fold better than that of elisa / ngo in the lower frequency region by assuming the same acceleration noise. therefore, astrod - gw will be a better cosmological probe. in previous papers, we have worked out the time delay interferometry ( tdi ) for the ecliptic formation. to resolve the reflection ambiguity about the ecliptic plane in source position determination, we have changed the basic formation into slightly inclined formation with half - year precession - period. in this paper, we optimize a set of 10 - year inclined astrod - gw mission orbits numerically using ephemeris framework starting at june 21, 2035, including cases of inclination angle is 0 { \ deg } ( no inclination ), 0. 5 { \ deg }, 1. 0 { \ deg }, 1. 5 { \ deg }, 2. 0 { \ deg }, 2. 5 { \ deg } and 3. 0 { \ deg }. we simulate the time delays of the first and second generation tdi configurations for the different inclinations, and compare / analyse the numerical results to attain the requisite sensitivity of astrod - gw by suppressing laser frequency noise below the secondary noises. to explicate our calculation process for different inclination cases, we take the 1. 0 { \ deg } as example to show the orbit optimization and tdi simulation.
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arxiv:1409.4162
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standard treatments of general relativity accept the gravitational slowing of clocks as a primary phenomenon, requiring no further analysis as to cause. rejecting this attitude, i argue that one or more of the fundamental " constants " governing the quantum mechanics of atoms must depend upon position in a gravitational field. a simple relationship governing the possible dependencies of e, h, c and m is deduced, and arguments in favor of the choice of the electron rest mass, m, are presented. the reduction of rest mass is thus taken to be the sole cause of clock slowing. importantly, this dependency implies another effect, heretofore unsuspected, namely, the gravitational elongation of measuring rods. an alternate ( " telemetric " ) system of measurement is introduced, leading to a metric that is conformally related to the usual proper metric. in terms of the new system, many otherwise puzzling phenomena may be simply understood. in particular, the geometry of the schwarzschild space as described by the telemetric system differs profoundly from that described by proper measurments, leading to a very different understanding of the structure of black holes. the theory is extended to cosmology, leading to a remarkable alternate view of the structure and history of the universe.
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arxiv:gr-qc/0001036
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with gaussian expansion method ( gem ), realistic wave functions are used to calculate coupled - channel effects for the bottomonium under the framework of $ { } ^ 3p _ 0 $ model. the simplicity and accuracy of gem are explained. we calculate the mass shifts, probabilities of the $ b $ meson continuum, $ s - d $ mixing angles, strong and dielectric decay widths. our calculation shows that both $ s - d $ mixing and the $ b $ meson continuum can contribute to the suppression of the vector meson ' s dielectric decay width. we suggest more precise measurements on the radiative decays of $ \ upsilon ( 10580 ) $ and $ \ upsilon ( 11020 ) $ to distinguish these two effects. the above quantities are also calculated with simple harmonic oscillator ( sho ) wave function approximation for comparison. the deviation between gem and sho indicates that it is essential to treat the wave functions accurately for near threshold states.
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arxiv:1606.06927
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low rank representation ( lrr ) has recently attracted great interest due to its pleasing efficacy in exploring low - dimensional subspace structures embedded in data. one of its successful applications is subspace clustering which means data are clustered according to the subspaces they belong to. in this paper, at a higher level, we intend to cluster subspaces into classes of subspaces. this is naturally described as a clustering problem on grassmann manifold. the novelty of this paper is to generalize lrr on euclidean space onto an lrr model on grassmann manifold in a uniform kernelized framework. the new methods have many applications in computer vision tasks. several clustering experiments are conducted on handwritten digit images, dynamic textures, human face clips and traffic scene sequences. the experimental results show that the proposed methods outperform a number of state - of - the - art subspace clustering methods.
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arxiv:1504.01806
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we theoretically characterize gradient descent dynamics in deep linear networks trained at large width from random initialization and on large quantities of random data. our theory captures the ` ` wider is better " effect of mean - field / maximum - update parameterized networks as well as hyperparameter transfer effects, which can be contrasted with the neural - tangent parameterization where optimal learning rates shift with model width. we provide asymptotic descriptions of both non - residual and residual neural networks, the latter of which enables an infinite depth limit when branches are scaled as $ 1 / \ sqrt { \ text { depth } } $. we also compare training with one - pass stochastic gradient descent to the dynamics when training data are repeated at each iteration. lastly, we show that this model recovers the accelerated power law training dynamics for power law structured data in the rich regime observed in recent works.
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arxiv:2502.02531
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the authors report on the crystallographic orientation dependence of the schottky properties for heterojunctions between a half - metallic ferromagnet la $ _ 0. 6 $ sr $ _ 0. 4 $ mno $ _ 3 $ ( lsmo ) and nb - doped srtio3 semiconductor. the schottky barrier height determined by in situ photoemission measurements is independent for the substrate orientations ( 001 ) and ( 110 ), while the magnetic properties of lsmo ( 110 ) films are more enhanced than for ( 001 ) films. these results suggest that the performance of magnetic devices based on ferromagnetic manganite is improved by using ( 110 ) - oriented substrates.
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arxiv:0905.2018
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in this paper, we continue the study of bos et al. ( 2018 ) regarding statistical and numerical considerations of the backus ( 1962 ) product approximation. while the approximation is typically quite good for seismological scenarios, bos et al. ( 2018 ) demonstrate a physical scenario that could, in spite of the stability conditions for isotropic media, lead to an issue within the backus average. using the preliminary reference earth model of dziewo \ ' nski and anderson ( 1981 ) and a case study in the upper oceanic crust, we investigate whether this issue is likely to occur in the context of seismology.
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arxiv:1804.01917
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collective effects in particle accelerators are one of the key constituents for determining the ultimate particle accelerator performance. their role is becoming increasingly important as particle accelerators are being pushed ever closer towards the intensity and beam brightness frontiers. they are slightly peculiar in their nature as their impact and significance depend not only on external fields but also on the beam properties themselves. this results in a highly coupled and convoluted system. in these lectures we will give a brief overview over collective effects in particle accelerators in general. we will cover the topics in a highly conceptual and illustrative manner. the goal will be for the students to get an intuitive impression on the nature and the aftermath of collective effects. the lectures will cover different types of collective effects along with their manifestation in accelerators and briefly outline the limitations they impose along with a few means for potential mitigation techniques.
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arxiv:2107.06109
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we point out that the geometry of connected totally geodesic compact null hypersurfaces in lorentzian manifolds is only slightly more specialized than that of riemannian flows over compact manifolds, the latter mathematical theory having been much studied in the context of foliation theory since the work by reinhart ( ann math 69 : 119, 1959 ). we are then able to import results on riemannian flows to the horizon case, so obtaining theorems on the dynamical structure of compact horizons that do not rely on ( non - ) degeneracy assumptions. furthermore, we clarify the relation between isometric / geodesible riemannian flows and non - degeneracy conditions. this work also contains some positive results on the possibility of finding, in the degenerate case, lightlike fields tangent to the horizon that have zero surface gravity.
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arxiv:2410.07231
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skiroc2 is an asic to readout the silicon pad detectors for the electromagnetic calorimeter in the international linear collider. characteristics of skiroc2 and the new version of skiroc2a, packaged with bga, are measured with testboards and charge injection. the results on the signal - to - noise ratio of both trigger and adc output, threshold tuning capability and timing resolution are presented.
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arxiv:1703.08105
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this paper aims to explain how a deep neural network ( dnn ) gradually extracts new knowledge and forgets noisy features through layers in forward propagation. up to now, although the definition of knowledge encoded by the dnn has not reached a consensus, previous studies have derived a series of mathematical evidence to take interactions as symbolic primitive inference patterns encoded by a dnn. we extend the definition of interactions and, for the first time, extract interactions encoded by intermediate layers. we quantify and track the newly emerged interactions and the forgotten interactions in each layer during the forward propagation, which shed new light on the learning behavior of dnns. the layer - wise change of interactions also reveals the change of the generalization capacity and instability of feature representations of a dnn.
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arxiv:2409.08712
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we have considered optical beams with phase singularity and experimentally verified that these beams, although being classical, have properties of two mode entanglement in quantum states. we have observed the violation of bell ' s inequality for continuous variables using the wigner distribution function ( wdf ) proposed by chowdhury et al. [ phys. rev. a \ textbf { 88 }, 013830 ( 2013 ) ]. our experiment establishes a new form of bell ' s inequality in terms of the wdf which can be used for classical as well as quantum systems.
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arxiv:1406.6239
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as the demands for electric vehicles, electric aircrafts, unmanned aircraft systems, and other motor - driven systems increase, high - performance motor drives employing variable frequency control with higher efficiency and reliability are becoming increasingly important parts of the ever - changing technological landscape. this study proposes a field programmable gate array ( fpga ) - based variable frequency soft - starting motor drive for a three - phase induction motor. the inverter output voltage and the load currents are analyzed for the harmonic contents using matlab. in the experimental realization, a four - pole squirrel cage delta - connected induction motor is utilized with a switching frequency of 4 khz. the current and voltage characteristics of the induction motor are studied under different operating conditions to study harmonic contents and the effect of changing soft - start duration. the findings demonstrate a low - cost, flexible control of the induction motor with improved harmonic performance.
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arxiv:2311.00720
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we study quantum information scrambling in a random unitary circuit that exchanges qubits with an environment at a rate $ p $. as a result, initially localized quantum information not only spreads within the system, but also spills into the environment. using the out - of - time - order correlator ( otoc ) to characterize scrambling, we find a nonequilibrium phase transition in the directed percolation universality class at a critical swap rate $ p _ c $ : for $ p < p _ c $ the ensemble - averaged otoc exhibits ballistic growth with a tunable light cone velocity, while for $ p > p _ c $ the otoc fails to percolate within the system and vanishes uniformly within a finite timescale, indicating that all local operators are rapidly swapped into the environment. to elucidate its information - theoretic consequences, we demonstrate that the transition in operator spreading coincides with a transition in an observer ' s ability to decode the system ' s initial quantum information from the swapped - out, or " radiated, " qubits. we present a simple decoding scheme which recovers the system ' s initial information with perfect fidelity in the nonpercolating phase, and with continuously decreasing fidelity with decreasing swap rate in the percolating phase. depending on the initial state of the swapped - in qubits, we further observe a corresponding entanglement transition in the coherent information from the system into the radiated qubits.
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arxiv:2210.14242
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the rapid advancement of extended reality ( xr, encompassing ar, mr, and vr ) and spatial computing technologies forms a foundational layer for the emerging metaverse, enabling innovative applications across healthcare, education, manufacturing, and entertainment. however, research in this area is often limited by the lack of large, representative, and highquality application datasets that can support empirical studies and the development of new approaches benefiting xr software processes. in this paper, we introduce xrzoo, a comprehensive and curated dataset of xr applications designed to bridge this gap. xrzoo contains 12, 528 free xr applications, spanning nine app stores, across all xr techniques ( i. e., ar, mr, and vr ) and use cases, with detailed metadata on key aspects such as application descriptions, application categories, release dates, user review numbers, and hardware specifications, etc. by making xrzoo publicly available, we aim to foster reproducible xr software engineering and security research, enable cross - disciplinary investigations, and also support the development of advanced xr systems by providing examples to developers. our dataset serves as a valuable resource for researchers and practitioners interested in improving the scalability, usability, and effectiveness of xr applications. xrzoo will be released and actively maintained.
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arxiv:2412.06759
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we propose high - velocity collisions of protogalaxies as a new pathway to form supermassive stars ( smss ) with masses of ~ 10 ^ 5 msun at high redshift ( z > 10 ). when protogalaxies hosted by dark matter halos with a virial temperature of ~ 10 ^ 4 k collide with a relative velocity > 200 km / s, the gas is shock - heated to ~ 10 ^ 6 k and subsequently cools isobarically via free - free emission and he ^ +, he, and h line emission. since the gas density ( > 10 ^ 4 cm ^ { - 3 } ) is high enough to destroy h _ 2 molecules by collisional dissociation, the shocked gas never cools below ~ 10 ^ 4 k. once a gas cloud of ~ 10 ^ 5 msun reaches this temperature, it becomes gravitationally unstable and forms a sms which will rapidly collapse into a super massive black hole ( smbh ) via general relativistic instability. we perform a simple analytic estimate of the number density of direct - collapse black holes ( dcbhs ) formed through this scenario ( calibrated with cosmological n - body simulations ) and find n _ { dcbh } ~ 10 ^ { - 9 } mpc ^ { - 3 } ( comoving ) by z = 10. this could potentially explain the abundance of bright high - z quasars.
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arxiv:1504.00676
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we report the first constraints on the properties of weakly interacting low - mass dark matter ( dm ) particles using asteroseismology. the additional energy transport mechanism due to accumulated asymmetric dm particles modifies the central temperature and density of low - mass stars and suppresses the convective core expected in 1. 1 - 1. 3 ms stars even for an environmental dm density as low as the expected in the solar neighborhood. an asteroseismic modeling of the stars kic 8006161, hd 52265 and alpha cen b revealed small frequency separations significantly deviated from the observations, leading to the exclusion of a region of the dm parameter space mass versus spin - dependent dm - proton scattering cross section comparable with present experimental constraints.
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arxiv:1212.2985
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this work presents an extension of discretely entropy stable discontinuous galerkin ( dg ) methods to the resistive magnetohydrodynamics ( mhd ) equations. although similar to the compressible navier - stokes equations at first sight, there are some important differences concerning the resistive mhd equations that need special focus. the continuous entropy analysis of the ideal mhd equations, which are the advective parts of the resistive mhd equations, shows that the divergence - free constraint on the magnetic field components must be incorporated as a non - conservative term in a form either proposed by powell or janhunen. consequently, this non - conservative term needs to be discretized, such that the approximation is consistent with the entropy. as an extension of the ideal mhd system, we address in this work the continuous analysis of the resistive mhd equations and show that the entropy inequality holds. thus, our first contribution is the proof that the resistive terms are symmetric and positive semi - definite when formulated in entropy space as gradients of the entropy variables. moreover, this enables the construction of an entropy stable dg discretization for the resistive mhd equations. however, the resulting method suffers from large errors in the divergence - free constraint, since no particular treatment of divergence errors is included in the standard resistive mhd model. hence, our second contribution is the extension of the resistive mhd equations with proper divergence cleaning based on a generalized lagrange multiplier ( glm ) strategy. we construct and analyze a dg method that is entropy stable for the resistive mhd equations and has a built - in glm divergence cleaning mechanism. the theoretical derivations and proofs are then verified by several numerical examples...
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arxiv:1711.05576
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motion of the vehicle is used to simulate a large antenna, giving the radar a higher resolution. ground - penetrating radar – a specialized radar instrument that is rolled along the ground surface in a cart and transmits a beam of radio waves into the ground, producing an image of subsurface objects. frequencies from 100 mhz to a few ghz are used. since radio waves cannot penetrate very far into earth, the depth of gpr is limited to about 50 feet. collision avoidance system – a short range radar or lidar system on an automobile or vehicle that detects if the vehicle is about to collide with an object and applies the brakes to prevent the collision. radar fuze – a detonator for an aerial bomb which uses a radar altimeter to measure the height of the bomb above the ground as it falls and detonates it at a certain altitude. = = = = radiolocation = = = = radiolocation is a generic term covering a variety of techniques that use radio waves to find the location of objects, or for navigation. global navigation satellite system ( gnss ) or satnav system – a system of satellites which allows geographical location on earth ( latitude, longitude, and altitude / elevation ) to be determined to high precision ( within a few metres ) by small portable navigation instruments, by timing the arrival of radio signals from the satellites. these are the most widely used navigation systems today. the main satellite navigation systems are the us global positioning system ( gps ), russia ' s glonass, china ' s beidou navigation satellite system ( bds ) and the european union ' s galileo. global positioning system ( gps ) – the most widely used satellite navigation system, maintained by the us air force, which uses a constellation of 31 satellites in low earth orbit. the orbits of the satellites are distributed so at any time at least four satellites are above the horizon over each point on earth. each satellite has an onboard atomic clock and transmits a continuous radio signal containing a precise time signal as well as its current position. two frequencies are used, 1. 2276 and 1. 57542 ghz. since the velocity of radio waves is virtually constant, the delay of the radio signal from a satellite is proportional to the distance of the receiver from the satellite. by receiving the signals from at least four satellites a gps receiver can calculate its position on earth by comparing the arrival time of the radio signals. since each satellite ' s position is known precisely at any given time, from the delay the position of the receiver can be
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https://en.wikipedia.org/wiki/Radio
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we have optically identified a recently discovered integral source, igr j08390 - - 4833, with a cataclysmic variable, i. e. an accreting white dwarf in a binary system. the spectrum exhibits a rising blue continuum together with balmer and heii emission lines. analysis of the light curve of the source shows clear presence of intrinsic variability on a time scale of the order of an hour, although we do not claim that this variability is periodic. therefore we are not yet able to classify the object into a specific cv subclass.
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arxiv:0810.1434
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the thz atmospheric windows centered at roughly 1. 3 and 1. 5 ~ thz, contain numerous spectral lines of astronomical importance, including three high - j co lines, the n + line at 205 microns, and the ground transition of para - h2d +. the co lines are tracers of hot ( several 100k ), dense gas ; n + is a cooling line of diffuse, ionized gas ; the h2d + line is a non - depleting tracer of cold ( ~ 20k ), dense gas. as the thz lines benefit the study of diverse phenomena ( from high - mass star - forming regions to the wim to cold prestellar cores ), we have built the co n + deuterium observations receiver ( condor ) to further explore the thz windows by ground - based observations. condor was designed to be used at the atacama pathfinder experiment ( apex ) and stratospheric observatory for infrared astronomy ( sofia ). condor was installed at the apex telescope and test observations were made to characterize the instrument. the combination of condor on apex successfully detected thz radiation from astronomical sources. condor operated with typical trec = 1600k and spectral allan variance times of 30s. condor ' s first light observations of co 13 - 12 emission from the hot core orion fir4 ( = omc1 south ) revealed a narrow line with t ( mb ) = 210k and delta ( v ) = 5. 4km / s. a search for n + emission from the ionization front of the orion bar resulted in a non - detection. the successful deployment of condor at apex demonstrates the potential for making observations at thz frequencies from ground - based facilities.
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arxiv:astro-ph/0606560
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we underline and comment some features of the data obtained in the beautiful experiment by g. s. boebinger, y. ando, a. passner, t. kimura, m. okuya, j. shimoyama, k. kishio, k. tamasaku, n. ichikawa, and s. uchida, phys. rev. lett. 77, 5417 ( 1996 ). while in our general interpretation we agree with the authors that ` ` it is possible that charge ordering could underlie the unusual insulating behavior ' ' observed ` ` in all underdoped lsco samples ' ', we further notice that some specific features of the data are most naturally interpreted in the light of our proposal for an incommensurate charge - density - wave quantum - critical - point scenario.
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arxiv:cond-mat/9709278
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most existing trackers based on deep learning perform tracking in a holistic strategy, which aims to learn deep representations of the whole target for localizing the target. it is arduous for such methods to track targets with various appearance variations. to address this limitation, another type of methods adopts a part - based tracking strategy which divides the target into equal patches and tracks all these patches in parallel. the target state is inferred by summarizing the tracking results of these patches. a potential limitation of such trackers is that not all patches are equally informative for tracking. some patches that are not discriminative may have adverse effects. in this paper, we propose to track the salient local parts of the target that are discriminative for tracking. in particular, we propose a fine - grained saliency mining module to capture the local saliencies. further, we design a saliency - association modeling module to associate the captured saliencies together to learn effective correlation representations between the exemplar and the search image for state estimation. extensive experiments on five diverse datasets demonstrate that the proposed method performs favorably against state - of - the - art trackers.
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arxiv:2108.03637
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the elliptic flow $ v _ 2 $ and the ratio of the shear viscosity over the entropy density, $ \ eta / s $, of gluon matter are calculated from the perturbative qcd ( pqcd ) based parton cascade boltzmann approach of multiparton scatterings. for au + au collisions at $ \ sqrt { s } = 200 $ a gev the gluon plasma generates large $ v _ 2 $ values measured at the bnl relativistic heavy ion collider. standard pqcd yields $ \ eta / s \ approx 0. 08 - 0. 15 $ as small as the lower bound found from the anti - de sitter / conformal field theory conjecture.
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arxiv:0711.0961
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with the advent of smartphone technology, it has become possible to conceive of entirely new classes of applications. social swarming, in which users armed with smartphones are directed by a central director to report on events in the physical world, has several real - world applications : search and rescue, coordinated fire - fighting, and the darpa balloon hunt challenge. in this paper, we focus on the following problem : how does the director optimize the selection of reporters to deliver credible corroborating information about an event. we first propose a model, based on common intuitions of believability, about the credibility of information. we then cast the problem posed above as a discrete optimization problem, and introduce optimal centralized solutions and an approximate solution amenable to decentralized implementation whose performance is about 20 % off on average from the optimal ( on real - world datasets derived from google news ) while being 3 orders of magnitude more computationally efficient. more interesting, a time - averaged version of the problem is amenable to a novel stochastic utility optimization formulation, and can be solved optimally, while in some cases yielding decentralized solutions. to our knowledge, we are the first to propose and explore the problem of extracting credible information from a network of smartphones.
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arxiv:1009.6006
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the correct modeling of $ e ^ + e ^ - $ collision events at the international linear collider ( ilc ), as well as the response of a collider detector like the silicon detector ( sid ), is crucial to evaluating the expected sensitivity to key properties of the higgs boson. in this document we describe the event generation and detector simulation in use for the sid letters of interest submitted for the 2021 snowmass community planning exercise.
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arxiv:2106.00819
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we develop an easy java simulation ( ejs ) model for students to experience the physics of idealized one - dimensional collision carts. the physics model is described and simulated by both continuous dynamics and discrete transition during collision. in the field of designing computer simulations, we discuss briefly three pedagogical considerations such as 1 ) consistent simulation world view with pen paper representation, 2 ) data table, scientific graphs and symbolic mathematical representations for ease of data collection and multiple representational visualizations and 3 ) game for simple concept testing that can further support learning. we also suggest using physical world setup to be augmented complimentary with simulation while highlighting three advantages of real collision carts equipment like tacit 3d experience, random errors in measurement and conceptual significance of conservation of momentum applied to just before and after collision. general feedback from the students has been relatively positive, and we hope teachers will find the simulation useful in their own classes. 2015 resources added : http : / / iwant2study. org / ospsg / index. php / interactive - resources / physics / 02 - newtonian - mechanics / 02 - dynamics / 46 - one - dimension - collision - js - model http : / / iwant2study. org / ospsg / index. php / interactive - resources / physics / 02 - newtonian - mechanics / 02 - dynamics / 195 - elastic - collision
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arxiv:1204.4964
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existing methods for stereo work on narrow baseline image pairs giving limited performance between wide baseline views. this paper proposes a framework to learn and estimate dense stereo for people from wide baseline image pairs. a synthetic people stereo patch dataset ( s2p2 ) is introduced to learn wide baseline dense stereo matching for people. the proposed framework not only learns human specific features from synthetic data but also exploits pooling layer and data augmentation to adapt to real data. the network learns from the human specific stereo patches from the proposed dataset for wide - baseline stereo estimation. in addition to patch match learning, a stereo constraint is introduced in the framework to solve wide baseline stereo reconstruction of humans. quantitative and qualitative performance evaluation against state - of - the - art methods of proposed method demonstrates improved wide baseline stereo reconstruction on challenging datasets. we show that it is possible to learn stereo matching from synthetic people dataset and improve performance on real datasets for stereo reconstruction of people from narrow and wide baseline stereo data.
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arxiv:1910.01241
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during communication, the interpretation of utterances is sensitive to a listener ' s probabilistic prior beliefs, something which is captured by one currently influential model of pragmatics, the rational speech act ( rsa ) framework. in this paper we focus on cases when this sensitivity to priors leads to counterintuitive predictions of the framework. our domain of interest is exhaustivity effects, whereby a sentence such as " mary came " is understood to mean that only mary came. we show that in the baseline rsa model, under certain conditions, anti - exhaustive readings are predicted ( e. g., " mary came " would be used to convey that both mary and peter came ). the specific question we ask is the following : should exhaustive interpretations be derived as purely pragmatic inferences ( as in the classical gricean view, endorsed in the baseline rsa model ), or should they rather be generated by an encapsulated semantic mechanism ( as argued in some of the recent formal literature )? to answer this question, we provide a detailed theoretical analysis of different rsa models and evaluate them against data obtained in a new study which tested the effects of prior beliefs on both production and comprehension, improving on previous empirical work. we found no anti - exhaustivity effects, but observed that message choice is sensitive to priors, as predicted by the rsa framework overall. the best models turn out to be those which include an encapsulated exhaustivity mechanism ( as other studies concluded on the basis of very different data ). we conclude that, on the one hand, in the division of labor between semantics and pragmatics, semantics plays a larger role than is often thought, but, on the other hand, the tradeoff between informativity and cost which characterizes all rsa models does play a central role for genuine pragmatic effects.
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arxiv:2202.07023
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we present monitoring observations of the active t tauri star rw aur, from 2010 october to 2015 january, using optical high - resolution ( r > 10000 ) spectroscopy with cfht - espadons. optical photometry in the literature shows bright, stable fluxes over most of this period, with lower fluxes ( by 2 - 3 mag. ) in 2010 and 2014. in the bright period our spectra show clear photospheric absorption, complicated variation in the ca ii 8542 a emission } profile shapes, and a large variation in redshifted absorption in the o i 7772 and 8446 a and he i 5876 a lines, suggesting unstable mass accretion during this period. in contrast, these line profiles are relatively uniform during the faint periods, suggesting stable mass accretion. during the faint periods the photospheric absorption lines are absent or marginal, and the averaged li i profile shows redshifted absorption due to an inflow. we discuss ( 1 ) occultation by circumstellar material or a companion and ( 2 ) changes in the activity of mass accretion to explain the above results, together with near - infrared and x - ray observations from 2011 - 2015. neither scenario can simply explain all the observed trends, and more theoretical work is needed to further investigate their feasibilities.
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arxiv:1602.07372
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we exploit the ward - slavnov - taylor identity relating the 3 - gluons to the ghost - gluon vertices to conclude either that the ghost dressing function is finite and non vanishing at zero momentum while the gluon propagator diverges ( although it may do so weakly enough not to be in contradiction with current lattice data ) or that the 3 - gluons vertex is non - regular when one momentum goes to zero. we stress that those results should be kept in mind when one studies the infrared properties of the ghost and gluon propagators, for example by means of dyson - schwinger equations.
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arxiv:hep-ph/0702092
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the ( 2, 0 ) ( 3, 0 ) and ( 4, 0 ) bands of the a $ ^ 1 \ pi - $ x $ ^ 1 \ sigma ^ + $ system of $ ^ { 12 } $ c $ ^ { 16 } $ o have been re - investigated by high - resolution vacuum ultraviolet absorption spectroscopy. a vuv fourier - transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet - cooled spectrum, a room temperature static gas spectrum and a high temperature ( 900 k ) quasi - static gas spectrum, resulting in absolute accuracies of 0. 01 $ - $ 0. 02 cm $ ^ { - 1 } $ for the rotational line frequencies. precise laser - based data were included in the analysis allowing for a highly accurate determination of band origins. rotational levels up to $ j = 52 $ were observed. the data were used to perform an improved analysis of the perturbations in the a $ ^ 1 \ pi $, $ v = 2 $, $ v = 3 $, and $ v = 4 $ levels by vibrational levels of the d $ ^ 1 \ delta $, i $ ^ 1 \ sigma ^ - $, e $ ^ 3 \ sigma ^ - $, d $ ^ 3 \ delta $, and a $ ' ^ 3 \ sigma ^ + $ states.
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arxiv:1510.02509
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it was recently discovered that friction between surfaces bearing phosphatidylcholine ( pc ) lipid bilayers can be increased by two orders of magnitude or more via an externally - applied electric field, and that this increase is fully reversible when the field is switched off. while this striking effect holds promising application potential, its molecular origin remains unknown due to difficulty in experimentally probing confined membrane structure at a molecular level. our earlier molecular dynamics simulations revealed the equilibrium electroporated structure of such confined lipid membranes under an electric field ; here we extend this approach to study the associated sliding friction between two solid surfaces across such pc bilayers. we identify the enhanced friction in the field as arising from membrane undulations due to the electroporation ; this leads to some dehydration at the lipid - water interfaces, leading to closer contact and thus increased attraction between the zwitterionic headgroups, which results in increased frictional dissipation between the bilayers as they slide past each other. additionally, the electric field facilitates formation of lipid bridges spanning the intersurface gap ; at the sliding velocities of the experiments, these bridges increase the friction by topologically - forcing the slip - plane to pass through the acyl tail - tail interface, associated with higher dissipation during sliding. our results account quantitatively for the experimentally - observed electro - modulated friction with boundary lipid bilayers, and indicate more generally how they may affect interactions between contacting surfaces, where high local transverse fields may be ubiquitous.
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arxiv:2303.08555
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close binaries of double white dwarfs ( dwds ) inspiral and merge by emitting gravitational wave ( gw ). orbital motion of some of these binaries are expected to be observed at low frequency band by space - borne laser interferometric detectors of gw. the merger remnant may suffer thermonuclear runaway and explode as type ia supernova if they are massive enough. as gw sources the remnants have so far been scarcely studied. here we propose a new mechanism of gw emission from dwd merger remnants which may be observed by planned gw detectors in decihertz frequency band. a remnant is temporarily expected to have a high degree of differential rotation as a consequence of merger process. it is then unstable to oscillation modes whose azimuthal pattern speed coincides with the stellar rotation. we solve eigenvalue problem of differentially rotating remnants and identify unstable eigenmodes which may be categorized to inertial modes. the estimate of characteristic strain of gw shows that they may be detectable within the distance of the virgo cluster by planned gravitational wave observatories targeting the decihertz band.
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arxiv:2009.13017
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we give new estimates for the eigenvalues of the hypersurface dirac operator in terms of the intrinsic energy - momentum tensor, the mean curvature and the scalar curvature. we also discuss their limiting cases as well as the limiting cases of the estimates obtained by x. zhang and o. hijazi in [ 13 ] and [ 10 ]. we compare these limiting cases with those corresponding to the friedrich and hijazi inequalities. we conclude by comparing these results to intrinsic estimates for the dirac - schr \ " odinger operator d _ f = d - f / 2.
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arxiv:math/0101111
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explicit expressions are presented that describe the input - output behaviour of a nonlinear system in both the frequency and the time domain. the expressions are based on a set of coefficients that do not depend on the input to the system and are universal for a given system. the anharmonic oscillator is chosen as an example and is discussed for different choices of its physical parameters. it is shown that the typical approach for the determination of the volterra series representation is not valid for the important case when the nonlinear system exhibits oscillatory behaviour and the input has a pole at the origin ( in the frequency domain ), e. g. the unit - step function. for this case, resonant effects arise and the analysis requires additional care.
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arxiv:math/0612319
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the earth ' s revolution is modified by changes in inclination of its rotation axis. despite the fact that the gravity field is central, the earth ' s trajectory is not closed and the equinoxes drift. milankovic ( 1920 ) argued that the shortest precession period of solstices is 20, 7kyr : the summer solstice in one hemisphere takes place alternately every 11kyr at perihelion and at aphelion. we have submitted the time series for the earth ' s pole of rotation, global mean surface temperature and ephemeris to iterative singular spectrum analysis. issa extracts from each a trend, a 1yr and a 60yr component. both the apparent drift of solstices of earth around the sun and the global mean temperature exhibit a strong 60yr oscillation. the " fixed dates " of solstices actually drift. comparing the time evolution of the winter and summer solstices positions of the rotation pole and the first issa component ( trend ) of the temperature allows one to recognize some common features. a basic equation from milankovic links the derivative of heat received at a given location on earth to solar insolation, known functions of the location coordinates, solar declination and hour angle, with an inverse square dependence on the sun - earth distance. we have translated the drift of solstices as a function of distance to the sun into the geometrical insolation theory of milankovic. shifting the inverse square of the 60yr issa drift of solstices by 15 years with respect to the first derivative of the 60yr issa trend of temperature, that is exactly a quadrature in time, puts the two curves in quasi - exact superimposition. the probability of a chance coincidence appears very low. correlation does not imply causality when there is no accompanying model. here milankovic ' s equation can be considered as a model that is widely accepted. this paper identifies a case of agreement between observations and a mathematical formulation.
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arxiv:2207.09269
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understanding how renormalized quasiparticles emerge in strongly correlated electron materials provides a challenge for both experiment and theory. it has been predicted that distinctive spin and orbital screening mechanisms drive this process in multiorbital materials with strong coulomb and hund ' s interactions. here, we provide the experimental evidence of both mechanisms from angle - resolved photoemission spectroscopy on rbfe $ _ 2 $ as $ _ 2 $. we observe that the emergence of low - energy fe 3 $ d _ { xy } $ quasiparticles below 90k is tied to spin screening. a second process changes the spectral weight at high energies up to room temperature. supported by theoretical calculations we attribute it to orbital screening of fe 3d atomic excitations. these two cascading screening processes drive the temperature evolution from a bad metal to a correlated fermi liquid.
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arxiv:2503.06314
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low - density, highly porous graphene / graphene oxide ( go ) based - foams have shown high performance in energy absorption applications, even under high compressive deformations. in general, foams are very effective as energy dissipative materials and have been widely used in many areas such as automotive, aerospace and biomedical industries. in the case of graphene - based foams, the good mechanical properties are mainly attributed to the intrinsic graphene and / or go electronic and mechanical properties. despite the attractive physical properties of graphene / go based - foams, their structural and thermal stabilities are still a problem for some applications. for instance, they are easily degraded when placed in flowing solutions, either by the collapsing of their layers or just by structural disintegration into small pieces. recently, a new and scalable synthetic approach to produce low - density 3d macroscopic go structure interconnected with polydimethylsiloxane ( pdms ) polymeric chains ( pgo ) was proposed. a controlled amount of pdms is infused into the freeze - dried foam resulting into a very rigid structure with improved mechanical properties, such as tensile plasticity and toughness. the pdms wets the graphene oxide sheets and acts like a glue bonding pdms and go sheets. in order to obtain further insights on mechanisms behind the enhanced mechanical pgo response we carried out fully atomistic molecular dynamics ( md ) simulations. based on md results, we build up a structural model that can explain the experimentally observed mechanical behavior.
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arxiv:1801.06257
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in terms of this of the spalf $ \ mathbf { x } $. in particular, the laplace exponent of $ ( \ mathbf { t } _ { \ rm r }, \ mathbb { x } _ { \ mathbf { t } _ { \ rm r } } ) $ solves a functional equation leaded by the laplace exponent of $ \ mathbf { x } $. this equation extends in higher dimension a classical fluctuation identity satisfied by the laplace exponents of the ladder processes. then we give an expression of the distribution of $ \ { ( \ mathbf { t } _ { \ rm r }, \ mathbb { x } _ { \ mathbf { t } _ { \ rm r } } ), { \ rm r } \ in \ mathbb { r } _ + ^ d \ } $ in terms of the distribution of $ \ { \ mathbb { x } _ { \ rm t }, { \ rm t } \ in \ mathbb { r } _ + ^ d \ } $ by the means of a kemperman - type formula, well - known for spectrally positive l \ ' evy processes.
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arxiv:1912.10474
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we study the spectra of general $ n \ times n $ toeplitz matrices given by symbols in the wiener algebra perturbed by small complex gaussian random matrices, in the regime $ n \ gg 1 $. we prove an asymptotic formula for the number of eigenvalues of the perturbed matrix in smooth domains. we show that these eigenvalues follow a weyl law with probability sub - exponentially close to $ 1 $, as $ n \ gg1 $, in particular that most eigenvalues of the perturbed toeplitz matrix are close to the curve in the complex plane given by the symbol of the unperturbed toeplitz matrix.
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arxiv:1905.10265
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in this paper, we explore the use of the virtual element method concepts to solve scalar and system hyperbolic problems on general polygonal grids. the new schemes stem from the active flux approach \ cite { af1 }, which combines the usage of point values at the element boundaries with an additional degree of freedom representing the average of the solution within each control volume. along the lines of the family of residual distribution schemes introduced in \ cite { abgrall _ af, abgrall2023activefluxtriangularmeshes } \ red { that integrate the active flux technique }, we devise novel third order accurate methods that rely on the vem technology to discretize gradients of the numerical solution by means of a polynomial - free approximation, \ red { by } adopting a virtual basis that is locally defined for each element. the obtained discretization is globally continuous, and for nonlinear problems it needs a stabilization which is provided by \ new { a monolithic convex limiting strategy extended from \ cite { abgrall _ bp _ pampa } }. this is applied to both point and average values of the discrete solution. we show applications to scalar problems, as well as to the acoustics and euler equations in two dimension. the accuracy and the robustness of the proposed schemes are assessed against a suite of benchmarks involving smooth solutions, shock waves and other discontinuities.
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arxiv:2412.01341
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electron correlation and long - range magnetic ordering have a significant impact on the electronic structure and physical properties of solids. here, we investigate the electronic structure of ilmenite mntio $ _ { 3 } $ using room temperature photoemission spectroscopy and theoretical approaches within density functional theory ( dft ), dft + $ u $ and dft + dynamical mean field theory ( dmft ). mn 2 $ p $ ( ti 2 $ p $ ) core level photoemission spectra, confirming mn $ ^ { 2 + } $ ( ti $ ^ { 4 + } $ ) oxidation state, exhibit multiple satellites which are very similar to that of mno ( tio $ _ { 2 } $ ), suggesting similar strength of various interactions in this system. valence band spectra collected at different photon energies suggest dominant mn 3 $ d $ character in the highest occupied band with a wide insulating gap. dft ( + $ u $ ) correctly predicts the experimentally observed anti - ferromagnetic ( afm ) insulating ground state for mntio $ _ 3 $ where the requirement of a large $ u $ to reproduce the experimental values of magnetic moment and band gap signifies the importance of electron correlation. magnetically disordered paramagnetic ( pm ) phase could be well captured within dft + dmft, which provides an excellent agreement for the experimental band gap, paramagnetic moment, valence band spectra as well as dominant mn 3 $ d $ character in the highest occupied band. the calculated spectral function remains largely unaffected and exhibits sharper features in the magnetically ordered afm phase. we show that the electronic structure of mntio $ _ { 3 } $ in both the pm and afm phases can be accurately described within dft + dmft.
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arxiv:2408.16301
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high - energy neutrinos are expected to be produced by the interaction of accelerated particles near the acceleration sites. for this reason, it is interesting to search for correlation in the arrival directions of ultra - high energy cosmic rays ( uhecrs ) and he neutrinos. we present here the results of a search for correlations between uhecr events measured by the pierre auger observatory and telescope array and high - energy neutrino candidate events from icecube and antares. we perform a cross - correlation analysis, where the angular separation between the arrival directions of uhecrs and neutrinos is scanned. when comparing the results with the expectations from a null hypothesis contemplating an isotropic distribution of neutrinos or of uhecr we obtain post - trial p - values of the order of $ \ sim 10 ^ { - 2 } $.
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arxiv:1905.03997
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