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deterministic generation of single photons is essential for many quantum information technologies. a bulk optical nonlinearity emitting a photon pair, where the measurement of one of the photons heralds the presence of the other, is commonly used with the caveat that the single - photon emission rate is constrained due to a trade - off between multiphoton events and pair emission rate. using an efficient and low noise photon - number - resolving superconducting nanowire detector we herald, in real time, a single photon at telecommunication wavelength. we perform a second - order photon correlation $ g ^ { 2 } ( 0 ) $ measurement of the signal mode conditioned on the measured photon number of the idler mode for various pump powers and demonstrate an improvement of a heralded single - photon source. we develop an analytical model using a phase - space formalism that encompasses all multiphoton effects and relevant imperfections, such as loss and multiple schmidt modes. we perform a maximum - likelihood fit to test the agreement of the model to the data and extract the best - fit mean photon number $ \ mu $ of the pair source for each pump power. a maximum reduction of $ 0. 118 \ pm 0. 012 $ in the photon $ g ^ { 2 } ( 0 ) $ correlation function at $ \ mu = 0. 327 \ pm 0. 007 $ is obtained, indicating a strong suppression of multiphoton emissions. for a fixed $ g ^ { 2 } ( 0 ) = 7e - 3 $, we increase the single pair generation probability by 25 %. our experiment, built using fiber - coupled and off - the - shelf components, delineates a path to engineering ideal sources of single photons. | arxiv:2112.11430 |
in artificial neural networks, neurons are usually implemented with highly dissipative cmos - based operational amplifiers. a more energy - efficient implementation is a ' spin - neuron ' realized with a magneto - tunneling junction ( mtj ) that is switched with a spin - polarized current ( representing weighted sum of input currents ) that either delivers a spin transfer torque or induces domain wall motion in the soft layer of the mtj. here, we propose and analyze a different type of spin - neuron in which the soft layer of the mtj is switched with mechanical strain generated by a voltage ( representing weighted sum of input voltages ) and term it straintronic spin - neuron. it dissipates orders of magnitude less energy in threshold operations than the traditional current - driven spin neuron at 0 k temperature and may even be faster. we have also studied the room - temperature firing behaviors of both types of spin neurons and find that thermal noise degrades the performance of both types, but the current - driven type is degraded much more than the straintronic type if both are optimized for maximum energy - efficiency. on the other hand, if both are designed to have the same level of thermal degradation, then the current - driven version will dissipate orders of magnitude more energy than the straintronic version. thus, the straintronic spin neuron is superior to current - driven spin neurons. | arxiv:1504.00940 |
in this paper we consider second order optimality conditions for a bilinear optimal control problem governed by a strongly continuous semigroup operator, the control entering linearly in the cost function. we derive first and second order optimality conditions, taking advantage of the goh transform. we then apply the results to the heat and wave equations. | arxiv:1602.06469 |
based on propostion 6 of his principia, newton ' s geometrical derivation in propositions 10 and 11 for the radial dependence of the two central forces that lead to elliptical orbits is notoriously difficult. an alternate and more transparent derivation is obtained by applying the affine transformation of a circle into an ellipse. | arxiv:1805.08872 |
we study the hydrodynamics of a gas of noninteracting weyl fermions coupled to the electromagnetic field in $ ( 2n + 1 ) + 1 $ spacetime dimensions using the chiral kinetic theory, which encodes the gauge anomaly in the chern character of the nonabelian berry connection over the fermi surface. we derive the anomalous contributions to the relativistic hydrodynamic currents in equilibrium and at a finite temperature, which agree with and provides an approach complementary to the results derived previously using thermodynamic constraints. | arxiv:1606.04945 |
the shannon game has long been used as a thought experiment in linguistics and nlp, asking participants to guess the next letter in a sentence based on its preceding context. we extend the game by introducing an optional extra modality in the form of image information. to investigate the impact of multimodal information in this game, we use human participants and a language model ( lm, gpt - 2 ). we show that the addition of image information improves both self - reported confidence and accuracy for both humans and lm. certain word classes, such as nouns and determiners, benefit more from the additional modality information. the priming effect in both humans and the lm becomes more apparent as the context size ( extra modality information + sentence context ) increases. these findings highlight the potential of multimodal information in improving language understanding and modeling. | arxiv:2303.11192 |
the concept of proxy re - encryption ( pre ) dates back to the work of blaze, bleumer, and strauss in 1998. pre offers delegation of decryption rights, i. e., it securely enables the re - encryption of ciphertexts from one key to another, without relying on trusted parties. pre allows a semi - trusted third party termed as a ` ` proxy " to securely divert encrypted files of user a ( delegator ) to user b ( delegatee ) without revealing any information about the underlying files to the proxy. to eliminate the necessity of having a costly certificate verification process, green and ateniese introduced an identity - based pre ( ib - pre ). the potential applicability of ib - pre sprung up a long line of intensive research from its first instantiation. unfortunately, till today, there is no collusion - resistant unidirectional ib - pre secure in the standard model, which can withstand quantum attack. in this paper, we present the first concrete constructions of collusion - resistant unidirectional ib - pre, for both selective and adaptive identity, which are secure in standard model based on the hardness of learning with error problem. | arxiv:2011.08456 |
a perturbation approach is used for analysis of a near - cloak in shielding a finite scatterer from an incident flexural wave. the effect of the boundary conditions on the interior surface of the cloaking layer is analysed in detail, based on the explicit analytical solutions of a wave propagation problem for a membrane as well as a kirchhoff flexural plate. it is shown that the dirichlet boundary condition on the interior contour of the cloak significantly reduces the cloaking action in the membrane case, and it also makes cloaking impossible for flexural waves in a kirchhoff plate. | arxiv:1501.06853 |
clustering is an essential data mining tool for analyzing and grouping similar objects. in big data applications, however, many clustering algorithms are infeasible due to their high memory requirements and / or unfavorable runtime complexity. in contrast, contraction clustering ( raster ) is a single - pass algorithm for identifying density - based clusters with linear time complexity. due to its favorable runtime and the fact that its memory requirements are constant, this algorithm is highly suitable for big data applications where the amount of data to be processed is huge. it consists of two steps : ( 1 ) a contraction step which projects objects onto tiles and ( 2 ) an agglomeration step which groups tiles into clusters. this algorithm is extremely fast in both sequential and parallel execution. our quantitative evaluation shows that a sequential implementation of raster performs significantly better than various standard clustering algorithms. furthermore, the parallel speedup is significant : on a contemporary workstation, an implementation in rust processes a batch of 500 million points with 1 million clusters in less than 50 seconds on one core. with 8 cores, the algorithm is about four times faster. | arxiv:1907.03620 |
the system level synthesis ( sls ) approach facilitates distributed control of large cyberphysical networks in an easy - to - understand, computationally scalable way. we present an overview of the sls approach and its associated extensions in nonlinear control, mpc, adaptive control, and learning for control. to illustrate the effectiveness of sls - based methods, we present a case study motivated by the power grid, with communication constraints, actuator saturation, disturbances, and changing setpoints. this simple but challenging case study necessitates the use of model predictive control ( mpc ) ; however, standard mpc techniques often scales poorly to large systems and incurs heavy computational burden. to address this challenge, we combine two sls - based controllers to form a layered mpc - like controller. our controller has constant computational complexity with respect to the system size, gives a 20 - fold reduction in online computation requirements, and still achieves performance that is within 3 % of the centralized mpc controller. | arxiv:2010.01292 |
the theoretical models providing mathematical abstractions for several significant optimization problems in machine learning, combinatorial optimization, computer vision and statistical physics have intrinsic similarities. we propose a unified framework to model these computation tasks where the structures of these optimization problems are encoded by functions attached on the vertices and edges of a graph. we show that computing max 2 - csp admits polynomial - time approximation scheme ( ptas ) on planar graphs, graphs with bounded local treewidth, $ h $ - minor - free graphs, geometric graphs with bounded density and graphs embeddable with bounded number of crossings per edge. this implies computing max - cut, max - dicut and max $ k $ - cut admits ptass on all these classes of graphs. our method also gives the first ptas for computing the ground state of ferromagnetic edwards - anderson model without external magnetic field on $ d $ - dimensional lattice graphs. these results are widely applicable in vision, graphics and machine learning. | arxiv:1412.0340 |
aim of this article is to prove the inequality $ n \ sum _ { i = 1 } ^ { n } a _ ib _ i \ leq \ sum _ { i = 1 } ^ { n } a _ i \ sum _ { i = 1 } ^ n b _ i $ when $ a _ i $ are $ n $ increasing positive real numbers and $ b _ i $ are $ n $ decreasing real numbers. we also prove generalizations of this result. | arxiv:2209.05560 |
in view of the advantages of simplicity and effectiveness of the kaczmarz method, which was originally employed to solve the large - scale system of linear equations $ ax = b $, we study the greedy randomized block kaczmarz method ( me - grbk ) and its relaxation and deterministic versions to solve the matrix equation $ axb = c $, which is commonly encountered in the applications of engineering sciences. it is demonstrated that our algorithms converge to the unique least - norm solution of the matrix equation when it is consistent and their convergence rate is faster than that of the randomized block kaczmarz method ( me - rbk ). moreover, the block kaczmarz method ( me - bk ) for solving the matrix equation $ axb = c $ is investigated and it is found that the me - bk method converges to the solution $ a ^ { + } cb ^ { + } + x ^ { 0 } - a ^ { + } ax ^ { 0 } bb ^ { + } $ when it is consistent. the numerical tests verify the theoretical results and the methods presented in this paper are applied to the color image restoration problem to obtain satisfactory restored images. | arxiv:2408.05444 |
in this paper we describe our machine learning solution for the recsys challenge, 2015. we have proposed a time efficient two - stage cascaded classifier for the prediction of buy sessions and purchased items within such sessions. based on the model, several interesting features found, and formation of our own test bed, we have achieved a reasonable score. usage of random forests helps us to cope with the effect of the multiplicity of good models depending on varying subsets of features in the purchased items prediction and, in its turn, boosting is used as a suitable technique to overcome severe class imbalance of the buy - session prediction. | arxiv:1508.03856 |
a change in the mass of the galaxy with time will leave its imprint on the motions of the stars, with stars having radially outward ( mass loss ) or inward ( mass accretion ) bulk motions. here we test the feasibility of using the mean radial motion of stars in the stellar halo to constrain the rate of change of mass in the galaxy, for example, due to decay of dark matter into invisible dark sector particles or more conservatively from the settling of baryons. in the current $ \ lambda $ cdm paradigm of structure formation, the stellar halo is formed by accretion of satellites onto the host galaxy. over time, as the satellites disrupt and phase mix, the mean radial motion $ \ langle v _ { r } \ rangle $ of the stellar halo is eventually expected to be close to zero. but most halos have substructures due to incomplete mixing of specific accretion events and this can lead to nonzero $ \ langle v _ { r } \ rangle $ in them. using simulations, we measure the mean radial motion, $ \ langle v _ { r } \ rangle $, of stars in 13 $ \ lambda $ cdm stellar halos lying in a spherical shell of radius 30 kpc. we find that for most halos, the shell motion is quite small, with 75 \ % of halos having $ \ langle v _ { r } \ rangle \ lesssim 1. 2 \ { \ rm km } s ^ { - 1 } $. when substructures are removed by using a clustering algorithm, $ \ langle v _ { r } \ rangle $ is reduced even further, with 75 \ % of halos having $ \ langle v _ { r } \ rangle \ lesssim 0. 6 \ { \ rm km } s ^ { - 1 } $. a value of $ \ langle v _ { r } \ rangle \ approx 0. 6 \ { \ rm km } s ^ { - 1 } $ can be attained corresponding to a galactic mass loss rate of 2 \ % per gyr. we show that this can place constraints on dark matter decay parameters such as the decay lifetime and the kick velocity that is imparted to the daughter particle. the advent of all - sky stellar surveys involving millions to billions of stars is encouraging for detecting signatures of dark matter decay. | arxiv:2207.11739 |
neural architecture search ( nas ), i. e., the automation of neural network design, has gained much popularity in recent years with increasingly complex search algorithms being proposed. yet, solid comparisons with simple baselines are often missing. at the same time, recent retrospective studies have found many new algorithms to be no better than random search ( rs ). in this work we consider, for the first time, a simple local search ( ls ) algorithm for nas. we particularly consider a multi - objective nas formulation, with network accuracy and network complexity as two objectives, as understanding the trade - off between these two objectives is arguably the most interesting aspect of nas. the proposed ls algorithm is compared with rs and two evolutionary algorithms ( eas ), as these are often heralded as being ideal for multi - objective optimization. to promote reproducibility, we create and release two benchmark datasets, named macronas - c10 and macronas - c100, containing 200k saved network evaluations for two established image classification tasks, cifar - 10 and cifar - 100. our benchmarks are designed to be complementary to existing benchmarks, especially in that they are better suited for multi - objective search. we additionally consider a version of the problem with a much larger architecture space. while we find and show that the considered algorithms explore the search space in fundamentally different ways, we also find that ls substantially outperforms rs and even performs nearly as good as state - of - the - art eas. we believe that this provides strong evidence that ls is truly a competitive baseline for nas against which new nas algorithms should be benchmarked. | arxiv:2004.08996 |
there has been a growing interest within the astrophysics community in highly magnetized and fast - spinning white dwarfs ( wds ), commonly referred to as hmwds. wds with these characteristics are quite uncommon and possess magnetic fields $ \ geqslant 10 ^ 6 $ g, along with short rotation periods ranging from seconds to just a few minutes. based on our previous work, we analyze the emission of gravitational waves ( gws ) in hmwds through two mechanisms : matter accretion and magnetic deformation, which arise due to the asymmetry surrounding the star ' s rotational axis. here, we perform a thorough self - consistent analysis, accounting for rotation and employing a realistic equation of state to investigate the stability of stars. our investigation focuses on the emission of gravitational radiation from six rapidly spinning wds : five of them are situated within binary systems, while one is an axp, proposed as a magnetic accreting wd. furthermore, we apply the matter accretion mechanism alongside the magnetic deformation mechanism to assess the influence of one process on the other. our discoveries indicate that these wds could potentially act as gw sources for bbo and decigo, depending on specific parameters, such as their mass, the angle ( $ \ alpha $ ) between the magnetic and rotational axes, and the accumulated mass ( $ \ delta m $ ) at their magnetic poles, which is influenced by the effect of matter accretion. however, detecting this particular class of stars using the lisa and tianqin space detectors seems unlikely due to the challenging combination of parameters such as a large $ \ delta m $, a large $ \ alpha $ angle and a small wd mass value. | arxiv:2405.02507 |
phase sensitive amplifiers ( psa ), contrary to usual phase insensitive amplifiers ( pia ), are in principle capable to achieve noiseless amplification, i. e. exhibit a quantum - limited noise figure ( nf ) of 0 db. when implemented using four - wave mixing ( fwm ) in a nonlinear fiber, extra waves can be generated by undesired fwm processes, which may introduce extra input ports for vacuum fluctuations, thus potentially degrading the nf. in this situation, we give here a general analytical quantum derivation of the psa nf, valid for an arbitrary number of nonlinearly coupled modes. this expression is usable as soon as a linear input - output relation can be found for the annihilation and creation operators of the involved modes. it predicts that the noise level depends on the number of interacting waves. we illustrate the usefulness of this expression in the case of six waves, corresponding to four interacting quantum modes. in this example the signal nf is degraded by 0. 4 db, compared to 10 db obtained for pia operation of the same scheme. | arxiv:2012.09031 |
photoevaporation driven by the central star is expected to be a ubiquitous and important mechanism to disperse the circumstellar dust and gas from which planets form. here, we present a detailed study of the circumstellar disk surrounding the nearby star tw hya and provide observational constraints to its photoevaporative wind. our new high - resolution ( r ~ 30, 000 ) mid - infrared spectroscopy in the [ ne ii ] 12. 81 { \ mu } m line confirms that this gas diagnostic traces the unbound wind component within 10au from the star. from the blueshift and asymmetry in the line profile, we estimate that most ( > 80 % ) of the [ ne ii ] emission arises from disk radii where the midplane is optically thick to the redshifted outflowing gas, meaning beyond the 1 or 4au dust rim inferred from other observations. we re - analyze high - resolution ( r ~ 48, 000 ) archival optical spectra searching for additional transitions that may trace the photoevaporative flow. unlike the [ ne ii ] line, optical forbidden lines from oi, sii, and mgi are centered at the stellar velocity and have symmetric profiles. the only way these lines could trace the photoevaporative flow is if they arise from a disk region physically distinct from that traced by the [ ne ii ] line, specifically from within the optically thin dust gap. however, the small ( ~ 10 km / s ) fwhm of these lines suggest that most of the emitting gas traced at optical wavelengths is bound to the system rather than unbound. we discuss the implications of our results for a planet - induced versus a photoevaporation - induced gap. | arxiv:1105.0045 |
we present a robust bayesian method to analyze forestry data when samples are selected with probability proportional to length from a finite population of unknown size. specifically, we use bayesian predictive inference to estimate the finite population mean of shrub widths in a limestone quarry dominated by re - growth of mountain mahogany. the data on shrub widths are collected using transect sampling and it is assumed that the probability that a shrub is selected is proportional to its width ; this is length - biased sampling. in this type of sampling, the population size is also unknown and this creates an additional challenge. the quantity of interest is average finite population shrub width and the total shrub area of the quarry can be estimated. our method is assisted by using the three - parameter generalized gamma distribution, thereby robustifying our procedure against a possible model failure. using conditional predictive ordinates, we show that the model, which accommodates length bias, performs better than the model that does not. in the bayesian computation, we overcome a technical problem associated with gibbs sampling by using a random sampler. | arxiv:1902.04242 |
we introduce a new geometric - analytic functional that we analyse in the context of free discontinuity problems. its main feature is that the geometric term ( the length of the jump set ) appears with negative sign. this is motivated by searching quantitative inequalities for best constants of sobolev - poincar \ ' e inequalities with trace terms in $ \ mathbb { r } ^ n $ which correspond to fundamental eigenvalues associated to semilinear problems for the laplace operator with robin boundary conditions. our method is based on the study of this new, degenerate, functional which involves an obstacle problem in interaction with the jump set. ultimately, this becomes a mixed free discontinuity / free boundary problem occuring above / at the level of the obstacle, respectively. | arxiv:2010.05883 |
traffic matrix estimation has always caught attention from researchers for better network management and future planning. with the advent of high traffic loads due to cloud computing platforms and software defined networking based tunable routing and traffic management algorithms on the internet, it is more necessary as ever to be able to predict current and future traffic volumes on the network. for large networks such origin - destination traffic prediction problem takes the form of a large under - constrained and under - determined system of equations with a dynamic measurement matrix. in this work, we present our compressed sensing with dynamic model estimation ( cs - dme ) architecture suitable for modern software defined networks. our main contributions are : ( 1 ) we formulate an approach in which measurement matrix in the compressed sensing scheme can be accurately and dynamically estimated through a reformulation of the problem based on traffic demands. ( 2 ) we show that the problem formulation using a dynamic measurement matrix based on instantaneous traffic demands may be used instead of a stationary binary routing matrix which is more suitable to modern software defined networks that are constantly evolving in terms of routing by inspection of its eigen spectrum using two real world datasets. ( 3 ) we also show that linking this compressed measurement matrix dynamically with the measured parameters can lead to acceptable estimation of origin destination ( od ) traffic flows with marginally poor results with other state - of - art schemes relying on fixed measurement matrices. ( 4 ) furthermore, using this compressed reformulated problem, a new strategy for selection of vantage points for most efficient traffic matrix estimation is also presented through a secondary compression technique based on subset of link measurements. | arxiv:1811.02165 |
recently a novel real - space rg algorithm was introduced, identifying the relevant degrees of freedom of a system by maximizing an information - theoretic quantity, the real - space mutual information ( rsmi ), with machine learning methods. motivated by this, we investigate the information theoretic properties of coarse - graining procedures, for both translationally invariant and disordered systems. we prove that a perfect rsmi coarse - graining does not increase the range of interactions in the renormalized hamiltonian, and, for disordered systems, suppresses generation of correlations in the renormalized disorder distribution, being in this sense optimal. we empirically verify decay of those measures of complexity, as a function of information retained by the rg, on the examples of arbitrary coarse - grainings of the clean and random ising chain. the results establish a direct and quantifiable connection between properties of rg viewed as a compression scheme, and those of physical objects i. e. hamiltonians and disorder distributions. we also study the effect of constraints on the number and type of coarse - grained degrees of freedom on a generic rg procedure. | arxiv:1809.09632 |
the root - cause diagnostics of product quality defects in multistage manufacturing processes often requires a joint identification of crucial stages and process variables. to meet this requirement, this paper proposes a novel penalized matrix regression methodology for two - dimensional variable selection. the method regresses a scalar response variable against a matrix - based predictor using a generalized linear model. the unknown regression coefficient matrix is decomposed as a product of two factor matrices. the rows of the first factor matrix and the columns of the second factor matrix are simultaneously penalized to inspire sparsity. to estimate the parameters, we develop a block coordinate proximal descent ( bcpd ) optimization algorithm, which cyclically solves two convex sub - optimization problems. we have proved that the bcpd algorithm always converges to a critical point with any initialization. in addition, we have also proved that each of the sub - optimization problems has a closed - form solution if the response variable follows a distribution whose ( negative ) log - likelihood function has a lipschitz continuous gradient. a simulation study and a dataset from a real - world application are used to validate the effectiveness of the proposed method. | arxiv:1912.00326 |
in this series of papers, we present a set of methods to revive quantum geometrodynamics which encountered numerous mathematical and conceptual challenges in its original form promoted by wheeler and de witt. in this paper, we introduce the regularization scheme on which we base the subsequent quantization and continuum limit of the theory. specifically, we employ the set of piecewise constant fields as the phase space of classical geometrodynamics, resulting in a theory with finitely many degrees of freedom of the spatial metric field. as this representation effectively corresponds to a lattice theory, we can utilize well - known techniques to depict the constraints and their algebra on the lattice. we are able to compute the lattice corrections to the constraint algebra. this model can now be quantized using the usual methods of finite - - dimensional quantum mechanics, as we demonstrate in the following paper. the application of the continuum limit is the subject of a future publication. | arxiv:2305.10097 |
continual learning is considered a key step toward next - generation artificial intelligence. among various methods, replay - based approaches that maintain and replay a small episodic memory of previous samples are one of the most successful strategies against catastrophic forgetting. however, since forgetting is inevitable given bounded memory and unbounded tasks, how to forget is a problem continual learning must address. therefore, beyond simply avoiding catastrophic forgetting, an under - explored issue is how to reasonably forget while ensuring the merits of human memory, including 1. storage efficiency, 2. generalizability, and 3. some interpretability. to achieve these simultaneously, our paper proposes a new saliency - augmented memory completion framework for continual learning, inspired by recent discoveries in memory completion separation in cognitive neuroscience. specifically, we innovatively propose to store the part of the image most important to the tasks in episodic memory by saliency map extraction and memory encoding. when learning new tasks, previous data from memory are inpainted by an adaptive data generation module, which is inspired by how humans complete episodic memory. the module ' s parameters are shared across all tasks and it can be jointly trained with a continual learning classifier as bilevel optimization. extensive experiments on several continual learning and image classification benchmarks demonstrate the proposed method ' s effectiveness and efficiency. | arxiv:2212.13242 |
i discuss a model for quantized gravitation based on the simplicial lattice discretization. it has been studied in some detail using a comprehensive finite size scaling analysis combined with renormalization group methods. the results are consistent with a value for the universal critical exponent for gravitation $ \ nu = 1 / 3 $, and suggest a simple relationship between newton ' s constant, the gravitational correlation length and the observable average space - time curvature. some perhaps testable phenomenological implications are discussed, such as the scale dependence of newton ' s constant and properties of quantum curvature fluctuations. | arxiv:hep-th/0101175 |
in this study, we employ molecular simulations to investigate the enhancement in thermal conductance at the solid / liquid interface in the presence of a meniscus reported previously ( klochko et al., phys. chem. chem. phys. 25 ( 4 ) : 3298 - 3308, 2023 ). we vary the solid / liquid interaction strength at lennard - jones interfaces for both confined liquid and meniscus systems, finding that the presence of a meniscus yields an enhancement in the interfacial thermal conductance across all wettabilities. however, the magnitude of the enhancement is found to depend on the surface wettability, initially rising monotonously for low to moderate wettabilities, followed by a sharp rise between moderate and high wettabilities. the spectral decomposition of heat flux formalism was applied to understand the nature of this phenomenon further. by computing the in - plane and out - of - plane components of the heat fluxes within both the interfacial solid and liquid, we show that the initial monotonous rise in conductance enhancement predominantly stems from a rise in the coupling of out - of - plane vibrations within both the solid and the liquid. in contrast, the subsequent sharp rise at more wetting interfaces is linked to sharp increases in the utilization of the in - plane modes of the solid and liquid. these observations result from the interplay between the solid / liquid adhesive forces and the liquid / vapor interfacial tension. our results can aid engineers in optimizing thermal transport at realistic interfaces, which is critical to designing effective cooling solutions for electronics, among other applications. | arxiv:2408.12485 |
in recent years, the traditional feature engineering process for training machine learning models is being automated by the feature extraction layers integrated in deep learning architectures. in wireless networks, many studies were conducted in automatic learning of feature representations for domain - related challenges. however, most of the existing works assume some supervision along the learning process by using labels to optimize the model. in this paper, we investigate an approach to learning feature representations for wireless transmission clustering in a completely unsupervised manner, i. e. requiring no labels in the process. we propose a model based on convolutional neural networks that automatically learns a reduced dimensionality representation of the input data with 99. 3 % less components compared to a baseline principal component analysis ( pca ). we show that the automatic representation learning is able to extract fine - grained clusters containing the shapes of the wireless transmission bursts, while the baseline enables only general separability of the data based on the background noise. | arxiv:2308.03530 |
we propose the conjecture that every tree with order $ n $ at least $ 2 $ and total domination number $ \ gamma _ t $ has at most $ \ left ( \ frac { n - \ frac { \ gamma _ t } { 2 } } { \ frac { \ gamma _ t } { 2 } } \ right ) ^ { \ frac { \ gamma _ t } { 2 } } $ minimum total dominating sets. as a relaxation of this conjecture, we show that every forest $ f $ with order $ n $, no isolated vertex, and total domination number $ \ gamma _ t $ has at most $ \ min \ left \ { \ left ( 8 \ sqrt { e } \, \ right ) ^ { \ gamma _ t } \ left ( \ frac { n - \ frac { \ gamma _ t } { 2 } } { \ frac { \ gamma _ t } { 2 } } \ right ) ^ { \ frac { \ gamma _ t } { 2 } }, ( 1 + \ sqrt { 2 } ) ^ { n - \ gamma _ t }, 1. 4865 ^ n \ right \ } $ minimum total dominating sets. | arxiv:1804.10476 |
the anomalous hall coefficient rs has been studied for the reentrant spin glass system fe0. 7al0. 3 by measuring the magnetization m and the hall resistivity r _ h. we have found that r _ s exhibits anomalous temperature dependence at the spin - glass transition temperature t _ g, indicating that an additional term appears along with the beginning of the spin glass phase. the result is discussed in relation to the recent proposal of the chirality mechanism of the hall effect in the spin glass phase. | arxiv:cond-mat/0211368 |
it was pointed out by y. eliashberg in his icm 2006 plenary talk that the rich algebraic formalism of symplectic field theory leads to a natural appearance of quantum and classical integrable systems, at least in the case when the contact manifold is the prequantization space of a symplectic manifold. in this paper we generalize the definition of gravitational descendants in sft from circle bundles in the morse - bott case to general contact manifolds. after we have shown that for the basic examples of holomorphic curves in sft, that is, branched covers of cylinders over closed reeb orbits, the gravitational descendants have a geometric interpretation in terms of branching conditions, we compute the corresponding sequences of poisson - commuting functions when the contact manifold is the unit cotangent bundle of a riemannian manifold. | arxiv:0907.0789 |
the drosophila larva, a soft - body animal, can bend its body and roll efficiently to escape danger. however, contrary to common belief, this rolling motion is not driven by the imbalance of gravity and ground reaction forces. through functional imaging and ablation experiments, we demonstrate that the sequential actuation of axial muscles within an appropriate range of angles is critical for generating rolling. we model the interplay between muscle contraction, hydrostatic skeleton deformation, and body - environment interactions, and systematically explain how sequential muscle actuation generates the rolling motion. additionally, we constructed a pneumatic soft robot to mimic the larval rolling strategy, successfully validating our model. this mechanics model of soft - body rolling motion not only advances the study of related neural circuits, but also holds potential for applications in soft robotics. | arxiv:2410.07644 |
in a previous work we showed that, in a suitable setting, one can use diffeomorphism invariance in order to derive gravitational field equations from boundary terms of the gravitational action. standing by our results we reply here to a recent comment questioning their validity. | arxiv:gr-qc/0703080 |
middleboxes are increasingly deployed across geographically distributed data centers. in these scenarios, the wan latency between different sites can significantly impact the performance of stateful middleboxes. the deployment of middleboxes across such infrastructures can even become impractical due to the high cost of remote state accesses. we introduce constellation, a framework for the geo distributed deployment of middleboxes. constellation uses asynchronous replication of specialized state objects to achieve high performance and scalability. the evaluation of our implementation shows that, compared with the state - of - the - art [ 80 ], constellation improves the throughput by a factor of 96 in wide area networks. | arxiv:2003.05111 |
a variable - range interacting ising model with spin - 1 / 2 particles exhibits distinct behavior depending on the fall - off rates in the range of interactions, notably non - local ( nl ), quasi - local ( ql ), and local. it is unknown if such a transition occurs in this model with an arbitrary spin quantum number. we establish its existence by analyzing the profiles of entanglement entropy, mutual information, and genuine multipartite entanglement ( gme ) of the weighted graph state ( wgs ), which is prepared when the multi - level maximally coherent state at each site evolves according to the spin - s ising hamiltonian. specifically, we demonstrate that the scaling of time - averaged mutual information and the divergence in the first derivative of gme with respect to the fall - off rate in the wgs can indicate the transition point from nl to ql, which scales logarithmically with individual spin dimension. additionally, we suggest that the existence of a saturation value of a finite number of qudits capable of mimicking the gme pattern of an arbitrarily large system - size can reveal the second transition point between quasi - local and local regions. | arxiv:2311.08232 |
azimuthal flow is driven in the edge of the large plasma device ( lapd ) [ w. gekelman, { \ itshape et. al }, rev. sci. instr. { \ bfseries 62 }, 2875 ( 1991 ) ] through biasing a section of the vacuum vessel relative to the plasma source cathode. as the applied bias exceeds a threshold, a transition in radial particle confinement is observed, evidenced by a dramatic steepening in the density profile, similar to the l - to h - mode transition in toroidal confinement devices. the threshold behavior and dynamic behavior of radial transport is related to flow penetration and the degree of spatial overlap between the flow shear and density gradient profiles. an investigation of the changes in turbulence and turbulent particle transport associated with the confinement transition is presented. two - dimensional cross - correlation measurements show that the spatial coherence of edge turbulence in lapd changes significantly with biasing. the azimuthal correlation in the turbulence increases dramatically, while the radial correlation length is little altered. turbulent amplitude is reduced at the transition, particularly in electric field fluctuations, but the dominant change observed is in the cross - phase between density and electric field fluctuations. the changes in cross - phase lead to a suppression and then apparent reversal of turbulent particle flux as the threshold is exceeded. | arxiv:0807.3504 |
this paper presents a systematic literature review ( slr ) on the explainability and interpretability of machine learning ( ml ) models within the context of predictive process mining, using the prisma framework. given the rapid advancement of artificial intelligence ( ai ) and ml systems, understanding the " black - box " nature of these technologies has become increasingly critical. focusing specifically on the domain of process mining, this paper delves into the challenges of interpreting ml models trained with complex business process data. we differentiate between intrinsically interpretable models and those that require post - hoc explanation techniques, providing a comprehensive overview of the current methodologies and their applications across various application domains. through a rigorous bibliographic analysis, this research offers a detailed synthesis of the state of explainability and interpretability in predictive process mining, identifying key trends, challenges, and future directions. our findings aim to equip researchers and practitioners with a deeper understanding of how to develop and implement more trustworthy, transparent, and effective intelligent systems for predictive process analytics. | arxiv:2312.17584 |
surfactant distribution heterogeneities at a fluid / fluid interface trigger the marangoni effect, i. e. a bulk flow due to a surface tension gradient. the influence of surfactant solubility in the bulk on these flows remains incompletely characterized. here we study marangoni flows sustained by injection of hydrosoluble surfactants at the air / water interface. we show that the flow extent increases with a decrease of the critical micelle concentration, i. e. the concentration at which these surfactants self - assemble in water. we document the universality of the surface velocity field and predict scaling laws based on hydrodynamics and surfactant physicochemistry that capture the flow features. | arxiv:1312.3964 |
we consider spectroscopies of strongly interacting atomic gases, and we propose a model for describing the coupling between quasiparticles and gapless phonon - like modes. our model explains features in a wide range of different experiments in both fermionic and bosonic atom gases in various spectroscopic methods. | arxiv:0910.4447 |
frieze patterns have attracted significant attention recently, motivated by their relationship with cluster algebras. a longstanding open problem has been to provide a combinatorial model for frieze patterns over the ring of integers modulo $ n $ akin to conway and coxeter ' s celebrated model for positive integer frieze patterns. here we solve this problem using the farey complex of the ring of integers modulo $ n $ ; in fact, using more general farey complexes we provide combinatorial models for frieze patterns over any rings whatsoever. our strategy generalises that of the first author and of morier - genoud et al. for integers and that of felikson et al. for eisenstein integers. we also generalise results of singerman and strudwick on diameters of farey graphs, we recover a theorem of morier - genoud on enumerating friezes over finite fields, and we classify those frieze patterns modulo $ n $ that lift to frieze patterns over the integers in terms of the topology of the corresponding farey complexes. | arxiv:2312.12953 |
sensors for particle tracking detectors are required to provide a maximum active area in addition to fulfilling performance criteria concerning radiation hardness, charge collection and operating conditions ( e. g. leakage current, depletion voltage and breakdown voltage ). while the requirement for optimised coverage within the tracking detector necessitates a slim sensor edge between active region and physical sensor edge, wider edge regions were found to be beneficial for the sensor performance during an early prototyping phase. in order to study the impact of differently sized edge regions, test structures were used to compare their individual active regions. measurements of each diode were performed using a micro - focused x - ray beam to map its respective active area. this paper presents measurements of these test structures using area - x showing that the active area of a silicon particle tracking sensor does not only depend on the size of its bias ring, but also the size and configuration of its edge structure. | arxiv:2505.10107 |
this study documents the impact of a summer camp series that introduces high school students to coding, data science, and deep learning. hosted on - campus, the camps provide an immersive university experience, fostering technical skills, collaboration, and inspiration through interactions with mentors and faculty. campers ' experiences are documented through interviews and pre - and post - camp surveys. key lessons include the importance of personalized feedback, diverse mentorship, and structured collaboration. survey data reveals increased confidence in coding, with 68. 6 \ % expressing interest in ai and data science careers. the camps also play a crucial role in addressing disparities in stem education for underrepresented minorities. these findings underscore the value of such initiatives in shaping future technology education and promoting diversity in stem fields. | arxiv:2410.02782 |
assessing network security is a complex and difficult task. attack graphs have been proposed as a tool to help network administrators understand the potential weaknesses of their network. however, a problem has not yet been addressed by previous work on this subject ; namely, how to actually execute and validate the attack paths resulting from the analysis of the attack graph. in this paper we present a complete pddl representation of an attack model, and an implementation that integrates a planner into a penetration testing tool. this allows to automatically generate attack paths for penetration testing scenarios, and to validate these attacks by executing the corresponding actions - including exploits - against the real target network. we present an algorithm for transforming the information present in the penetration testing tool to the planning domain, and show how the scalability issues of attack graphs can be solved using current planners. we include an analysis of the performance of our solution, showing how our model scales to medium - sized networks and the number of actions available in current penetration testing tools. | arxiv:1306.4044 |
ultra - intense lasers produce and manipulate plasmas, allowing to locally generate extremely high static and electromagnetic fields. this letter presents a concept of an ultra - intense optical tweezer, where two counter - propagating circularly polarized intense lasers of different frequencies collide on a nano - foil. interfering inside the foil, lasers produce a beat wave, which traps and moves plasma electrons as a thin sheet with an optically controlled velocity. the electron displacement creates a plasma micro - capacitor with an extremely strong electrostatic field, that efficiently generates narrow - energy - spread ion beams from the multi - species targets, e. g. protons from the hydrocarbon foils. the proposed ion accelerator concept is explored theoretically and demonstrated numerically with the multi - dimensional particle - in - cell simulations. | arxiv:1707.07290 |
the mapping of steady - state nonequilibrium dynamical mean - field theory from the lattice to the impurity is described in detail. our focus is on the case with current flow under a constant dc electric field of arbitrary magnitude. in addition to formulating the problem via path integrals and functional derivatives, we also describe the distribution function dependence of the retarded and advanced green ' s functions. our formal developments are exact for the falicov - kimball model. we also show how these formal developments are modified for more complicated models ( like the hubbard model ). | arxiv:0902.4055 |
we classify the morita equivalence classes of blocks with elementary abelian defect groups of order $ 16 $ with respect to a complete discrete valuation ring with algebraically closed residue field of characteristic two. as a consequence, blocks with this defect group are derived equivalent to their brauer correspondent in the normalizer of a defect group and so satisfy brou \ ' e ' s conjecture. | arxiv:1612.03485 |
spins of donor electrons and nuclei in silicon are promising quantum bit ( qubit ) candidates which combine long coherence times with the fabrication finesse of the silicon nanotechnology industry. we outline a potentially scalable spin qubit architecture where donor nuclear and electron spins are coupled to spins of electrons in quantum dots and discuss requirements for donor placement aligned to quantum dots by single ion implantation. | arxiv:1110.2228 |
we study the three - dimensional dirac and klein - gordon equations with scalar and vector potentials of equal magnitudes as an attempt to give a proper physical interpretation of this class of problems which has recently been accumulating interest. we consider a large class of these problems in which the potentials are noncentral ( angular - dependent ) such that the equations separate completely in spherical coordinates. the relativistic energy spectra are obtained and shown to differ from those of well - known problems that have the same nonrelativistic limit. consequently, such problems should not be misinterpreted as the relativistic extension of the given potentials despite the fact that the nonrelativistic limit is the same. the coulomb, oscillator and hartmann potentials are considered. this shows that although the nonrelativistic limit is well - defined and unique, the relativistic extension is not. additionally, we investigate the klein - gordon equation with uneven mix of potentials leading to the correct relativistic extension. we consider the case of spherically symmetric exponential - type potentials resulting in the s - wave klein - gordon - morse problem. | arxiv:hep-th/0503208 |
semiconductor microelectronics are emerging as a powerful tool for building smart, autonomous robots too small to see with the naked eye. yet a number of existing microrobot platforms, despite significant advantages in speed, robustness, power consumption, or ease of fabrication, have no clear path towards electronics integration, limiting their intelligence and sophistication when compared to electronic cousins. here, we show how to upgrade a self - propelled particle into an an electronically integrated microrobot, reaping the best of both in a single design. inspired by electrokinetic micromotors, these robots generate electric fields in a surrounding fluid, and by extension propulsive electrokinetic flows. the underlying physics is captured by a model in which robot speed is proportional to applied current, making design and control straightforward. as proof, we build basic robots that use on - board circuits and a closed - loop optical control scheme to navigate waypoints and move in coordinated swarms at speeds of up to one body length per second. broadly, the unification of micromotor propulsion with on - robot electronics clears the way for robust, fast, easy to manufacture, electronically programmable microrobots that operate reliably over months to years. | arxiv:2409.07293 |
we study dynamics of opinion formation in a network of coupled agents. as the network evolves to a steady state, opinions of agents within the same community converge faster than those of other agents. this framework allows us to study how network topology and network flow, which mediates the transfer of opinions between agents, both affect the formation of communities. in traditional models of opinion dynamics, agents are coupled via conservative flows, which result in one - to - one opinion transfer. however, social interactions are often non - conservative, resulting in one - to - many transfer of opinions. we study opinion formation in networks using one - to - one and one - to - many interactions and show that they lead to different community structure within the same network. | arxiv:1407.2587 |
needle - in - a - haystack problems exist across a wide range of applications including rare disease prediction, ecological resource management, fraud detection, and material property optimization. a needle - in - a - haystack problem arises when there is an extreme imbalance of optimum conditions relative to the size of the dataset. for example, only $ 0. 82 \ % $ out of $ 146 $ k total materials in the open - access materials project database have a negative poisson ' s ratio. however, current state - of - the - art optimization algorithms are not designed with the capabilities to find solutions to these challenging multidimensional needle - in - a - haystack problems, resulting in slow convergence to a global optimum or pigeonholing into a local minimum. in this paper, we present a zooming memory - based initialization algorithm, entitled zombi. zombi actively extracts knowledge from the previously best - performing evaluated experiments to iteratively zoom in the sampling search bounds towards the global optimum " needle " and then prunes the memory of low - performing historical experiments to accelerate compute times by reducing the algorithm time complexity from $ o ( n ^ 3 ) $ to $ o ( \ phi ^ 3 ) $ for $ \ phi $ forward experiments per activation, which trends to a constant $ o ( 1 ) $ over several activations. additionally, zombi implements two custom adaptive acquisition functions to further guide the sampling of new experiments toward the global optimum. we validate the algorithm ' s optimization performance on three real - world datasets exhibiting needle - in - a - haystack and further stress - test the algorithm ' s performance on an additional 174 analytical datasets. the zombi algorithm demonstrates compute time speed - ups of 400x compared to traditional bayesian optimization as well as efficiently discovering optima in under 100 experiments that are up to 3x more highly optimized than those discovered by similar methods mip - ego, turbo, and hebo. | arxiv:2208.13771 |
research has a long history of discussing what is superior in predicting certain outcomes : statistical methods or the human brain. this debate has repeatedly been sparked off by the remarkable technological advances in the field of artificial intelligence ( ai ), such as solving tasks like object and speech recognition, achieving significant improvements in accuracy through deep - learning algorithms ( goodfellow et al. 2016 ), or combining various methods of computational intelligence, such as fuzzy logic, genetic algorithms, and case - based reasoning ( medsker 2012 ). one of the implicit promises that underlie these advancements is that machines will 1 day be capable of performing complex tasks or may even supersede humans in performing these tasks. this triggers new heated debates of when machines will ultimately replace humans ( mcafee and brynjolfsson 2017 ). while previous research has proved that ai performs well in some clearly defined tasks such as playing chess, playing go or identifying objects on images, it is doubted that the development of an artificial general intelligence ( agi ) which is able to solve multiple tasks at the same time can be achieved in the near future ( e. g., russell and norvig 2016 ). moreover, the use of ai to solve complex business problems in organizational contexts occurs scarcely, and applications for ai that solve complex problems remain mainly in laboratory settings instead of being implemented in practice. since the road to agi is still a long one, we argue that the most likely paradigm for the division of labor between humans and machines in the next decades is hybrid intelligence. this concept aims at using the complementary strengths of human intelligence and ai, so that they can perform better than each of the two could separately ( e. g., kamar 2016 ). | arxiv:2105.00691 |
qcd spectral functions of hadrons in the pseudo - scalar and vector channels are extracted from lattice monte carlo data of the imaginary time green ' s functions. the maximum entropy method works well for this purpose, and the resonance and continuum structures in the spectra are obtained in addition to the ground state peaks. | arxiv:hep-lat/9905034 |
we consider the critical branching processes in correlated random environment which is positively associated and study the probability of survival up to the n - th generation. moreover, when the environment is given by fractional brownian motion, we estimate also the tail of progeny as well as the tail of width. | arxiv:1903.11338 |
x 2 ) = f ( x 1 ) f ( x 2 ) { \ displaystyle f ( x _ { 1 } x _ { 2 } ) = f ( x _ { 1 } ) f ( x _ { 2 } ) } an anti - involution does not obey the last axiom but instead f ( x 1 x 2 ) = f ( x 2 ) f ( x 1 ) { \ displaystyle f ( x _ { 1 } x _ { 2 } ) = f ( x _ { 2 } ) f ( x _ { 1 } ) } this former law is sometimes called antidistributive. it also appears in groups as ( xy ) −1 = ( y ) −1 ( x ) −1. taken as an axiom, it leads to the notion of semigroup with involution, of which there are natural examples that are not groups, for example square matrix multiplication ( i. e. the full linear monoid ) with transpose as the involution. = = = ring theory = = = in ring theory, the word involution is customarily taken to mean an antihomomorphism that is its own inverse function. examples of involutions in common rings : complex conjugation on the complex plane, and its equivalent in the split - complex numbers taking the transpose in a matrix ring. = = = group theory = = = in group theory, an element of a group is an involution if it has order 2 ; that is, an involution is an element a such that a = e and a2 = e, where e is the identity element. originally, this definition agreed with the first definition above, since members of groups were always bijections from a set into itself ; that is, group was taken to mean permutation group. by the end of the 19th century, group was defined more broadly, and accordingly so was involution. a permutation is an involution if and only if it can be written as a finite product of disjoint transpositions. the involutions of a group have a large impact on the group ' s structure. the study of involutions was instrumental in the classification of finite simple groups. an element x of a group g is called strongly real if there is an involution t with xt = x−1 ( where xt = x−1 = t−1 ⋅ x ⋅ | https://en.wikipedia.org/wiki/Involution_(mathematics) |
we study a dark energy model composed of a bare negative cosmological constant and a single ultra - light axion, motivated by the string axiverse. assuming that intelligent observers can exist and observe an accelerating universe, we derive nontrivial constraints on both the axion mass and the bare cosmological constant. the axion mass is bounded from above to avoid fine - tuning of the initial misalignment angle near the hilltop, and from below because extremely light axions would require the bare cosmological constant to be unnaturally close to zero to achieve accelerated expansion. as a result, the anthropically allowed axion mass range typically lies around $ m = \ mathcal { o } ( 10 ) \, h _ 0 $ for a decay constant close to the planck scale, where $ h _ 0 $ is the observed value of the hubble constant. in this framework, the dark energy equation of state parameter $ w _ 0 $ generically deviates from $ - 1 $ by $ \ mathcal { o } ( 0. 1 ) $, providing a natural explanation for why $ w \ ne - 1 $ may be expected. this outcome is intriguingly consistent with recent desi hints of time - varying dark energy, and offers a compelling anthropic explanation within the $ \ lambda $ + axion framework. | arxiv:2504.12852 |
we describe an end - to - end speech synthesis system that uses generative adversarial training. we train our vocoder for raw phoneme - to - audio conversion, using explicit phonetic, pitch and duration modeling. we experiment with several pre - trained models for contextualized and decontextualized word embeddings and we introduce a new method for highly expressive character voice matching, based on discreet style tokens. | arxiv:2310.09636 |
recently discovered valley photonic crystals ( vpcs ) mimic many of the unusual properties of two - dimensional gapped valleytronic materials such as bilayer graphene or mos2. of the utmost interest to optical communications is their ability to support topologically protected chiral edge ( kink ) states at the internal domain wall between two vpcs with spectrally overlapping bandgap zones and opposite half - integer valley - chern indices. we experimentally demonstrate the robustness of the kink states in vpcs that support degenerate transverse - electric - like ( te ) and transverse - magnetic - like ( tm ) topological phases, thus enabling polarization multiplexing in a single topological waveguide. the propagation direction of the kink states is locked to the valleys of the reverse brave lattice and, therefore, cannot be reversed in the absence of inter - valley scattering. at the intersection between the internal domain wall and the external edge separating the vpcs from free space, the kink states are shown to exhibit > 97 % out - coupling efficiency into directional free - space beams. this constitutes the first experimental demonstration of meron - like valley - projected topological phases with half - integer valley - chern indices. | arxiv:1706.04731 |
researchers are often interested in predicting outcomes, conducting clustering analysis to detect distinct subgroups of their data, or computing causal treatment effects. pathological data distributions that exhibit skewness and zero - inflation complicate these tasks - requiring highly flexible, data - adaptive modeling. in this paper, we present a fully nonparametric bayesian generative model for continuous, zero - inflated outcomes that simultaneously predicts structural zeros, captures skewness, and clusters patients with similar joint data distributions. the flexibility of our approach yields predictions that capture the joint data distribution better than commonly used zero - inflated methods. moreover, we demonstrate that our model can be coherently incorporated into a standardization procedure for computing causal effect estimates that are robust to such data pathologies. uncertainty at all levels of this model flow through to the causal effect estimates of interest - allowing easy point estimation, interval estimation, and posterior predictive checks verifying positivity, a required causal identification assumption. our simulation results show point estimates to have low bias and interval estimates to have close to nominal coverage under complicated data settings. under simpler settings, these results hold while incurring lower efficiency loss than comparator methods. lastly, we use our proposed method to analyze zero - inflated inpatient medical costs among endometrial cancer patients receiving either chemotherapy and radiation therapy in the seer medicare database. | arxiv:1810.09494 |
this paper presents a novel approach to auv localization, based on a semantic - aided particle filter. particle filters have been used successfully for robotics localization since many years. most of the approaches are however based on geometric measurements and geometric information and simulations. in the past years more and more efforts from research goes towards cognitive robotics and the marine domain is not exception. moving from signal to symbol becomes therefore paramount for more complex applications. this paper presents a contribution in the well - known area of underwater localization, incorporating semantic information. an extension to the standard particle filter approach is presented, based on semantic information of the environment. a comparison with the geometric approach shows the advantages of a semantic layer to successfully perform self - localization. | arxiv:1905.07470 |
the secondary emission yield ( sey ) properties of colaminated cu samples for lhc beam screens are correlated to the surface chemical composition determined by x - ray photoelectron spectroscopy. the surface of the " as received " samples is characterized by the presence of significant quantities of contaminating adsorbates and by the maximum of the sey curve ( dmax ) being as high as 2. 2. after extended electron scrubbing at kinetic energy of 10 and 500 ev, the dmax value drops to the ultimate values of 1. 35 and 1. 1, respectively. in both cases the surface oxidized phases are significantly reduced, whereas only in the sample scrubbed at 500 ev the formation of a graphitic - like c layer is observed. we find that the electron scrubbing of technical cu surfaces can be described as occurring in two steps, where the first step consists in the electron induced desorption of weakly bound contaminants that occurs indifferently at 10 and at 500 ev and corresponds to a partial decrease of dmax, and the second step, activated by more energetic electrons and becoming evident at high doses, which increases the number of graphitic - like c - c bonds via the dissociation of adsorbates already contaminating the " as received " surface or accumulating on this surface during irradiation. our results demonstrate how the kinetic energy of impinging electrons is a crucial parameter when conditioning technical surfaces of cu and other metals by means of electron induced chemical processing. | arxiv:1308.1290 |
the effect of disorder on magnonic transport in low - dimensional magnetic materials is studied in the framework of a classical spin model. numerical investigations give insight into scattering properties of the systems and show the existence of anderson localization in 1d and weak localization in 2d, potentially affecting the functionality of magnonic devices. | arxiv:1506.09045 |
we have performed abundance analysis of two slowly rotating, late a - type stars, hd 32115 ( hr 1613 ) and hd 37594 ( hr 1940 ), based on obtained echelle spectra covering the spectral range 4000 - 9850 aangstrom. these spectra allowed us to identify an extensive line list for 31 chemical elements, the most complete to date for a - type stars. two approaches to abundance analysis were used, namely a ` ` manual ' ' ( interactive ) and a semi - automatic procedure for comparison of synthetic and observed spectra and equivalent widths. for some elements non - lte ( nlte ) calculations were carried out and the corresponding corrections have been applied. the abundance pattern of hd 32115 was found to be very close to the solar abundance pattern, and thus may be used as an abundance standard for chemical composition studies in middle and late a stars. further, its h - alpha line profile shows no core - to - wing anomaly like that found for cool ap stars and therefore also may be used as a standard in comparative studies of the atmospheric structures of cool, slowly rotating ap stars. hd 37594 shows a metal deficiency at the level of - 0. 3 dex for most elements and triangle - like cores of spectral lines. this star most probably belongs to the delta scuti group. | arxiv:astro-ph/0206143 |
we introduce a variant of the multi - grid monte carlo ( mgmc ) method, based on the embedding of an $ xy $ model into the target model, and we study its mathematical properties for a variety of nonlinear $ \ sigma $ - models. we then apply the method to the two - dimensional $ o ( n ) $ - symmetric nonlinear $ \ sigma $ - models ( also called $ n $ - vector models ) with $ n = 3, 4, 8 $ and study its dynamic critical behavior. using lattices up to $ 256 \ times 256 $, we find dynamic critical exponents $ z _ { int, { \ cal m } ^ 2 } \ approx 0. 70 \ pm 0. 08 $, $ 0. 60 \ pm 0. 07 $, $ 0. 52 \ pm 0. 10 $ for $ n = 3, 4, 8 $, respectively ( subjective 68 \ % confidence intervals ). thus, for these asymptotically free models, critical slowing - down is greatly reduced compared to local algorithms, but not completely eliminated ; and the dynamic critical exponent does apparently vary with $ n $. we also analyze the static data for $ n = 8 $ using a finite - size - scaling extrapolation method. the correlation length $ \ xi $ agrees with the four - loop asymptotic - freedom prediction to within $ \ approx 1 \ % $ over the interval $ 12 < \ xi < 650 $. | arxiv:hep-lat/9604015 |
we explore the evolution of supermassive black holes ( smbh ) centered in a circumnuclear disk ( cnd ) as a function of the mass supply from the host galaxy and considering different star formation laws, which may give rise to a self - regulation via the injection of supernova - driven turbulence. a system of equations describing star formation, black hole accretion and angular momentum transport was solved for an axisymmetric disk in which the gravitational potential includes contributions from the black hole, the disk and the hosting galaxy. our model extends the framework provided by kawakatu et al. ( 2008 ) by separately considering the inner and outer part of the disk, and by introducing a potentially non - linear dependence of the star formation rate on the gas surface density and the turbulent velocity. the star formation recipes are calibrated using observational data for ngc 1097, while the accretion model is based on turbulent viscosity as a source of angular momentum transport in a thin viscous accretion disk. we find that current data provide no strong constraint on the star formation recipe, and can in particular not distinguish between models entirely regulated by the surface density, and models including a dependence on the turbulent velocity. the evolution of the black hole mass, on the other hand, strongly depends on the applied star formation law, as well as the mass supply from the host galaxy. we suggest to explore the star formation process in local agn with high - resolution alma observations to break the degeneracy between different star formation models. | arxiv:1309.4909 |
a report to the fermilab director from the study group on future neutrino experiments at fermilab | arxiv:hep-ex/0304017 |
the hamiltonian equation of motion is studied for a vortex occuring in 2 - dimensional heisenberg ferromagnet of anisotropic type by starting with the effective action for the spin field formulated by the bloch ( or spin ) coherent state. the resultant equation shows the existence of a geometric force that is analogous to the so - called magnus force in superfluid. this specific force plays a significant role for a quantum dynamics for a single vortex, e. g, the determination of the bound state of the vortex trapped by a pinning force arising from the interaction of the vortex with an impurity. | arxiv:cond-mat/9512175 |
memoir on the sigma invariants and their applications, version 2 | arxiv:1204.0214 |
we discuss gluing of objects and gluing of morphisms in tensor triangulated categories. we illustrate the results by producing, among other things, a mayer - vietoris exact sequence involving picard groups. | arxiv:math/0605094 |
3 - dimensional multiple - input multiple - output ( 3d mimo ) systems have received great interest recently because of the spatial diversity advantage and capability for full - dimensional beamforming, making them promising candidates for practical realization of massive mimo. in this paper, we present a low - cost test equipment ( channel sounder ) and post - processing algorithms suitable for investigating 3d mimo channels, as well as the results from a measurement campaign for obtaining elevation and azimuth characteristics in an outdoor - to - indoor ( o2i ) environment. due to limitations in available antenna switches, our channel sounder consists of a hybrid switched / virtual cylindrical array with effectively 480 antenna elements at the base station ( bs ). the virtual setup increased the overall mimo measurement duration, thereby introducing phase drift errors in the measurements. using a reference antenna measurements, we estimate and correct for the phase errors during post - processing. we provide the elevation and azimuth angular spreads, for the measurements done in an urban macro - cellular ( uma ) and urban micro - cellular ( umi ) environments, and study their dependence on the ue height. based on the measurements done with ue placed on different floors, we study the feasibility of separating users in the elevation domain. the measured channel impulse responses are also used to study the channel hardening aspects of massive mimo and the optimality of maximum ratio combining ( mrc ) receiver. | arxiv:1703.10607 |
a spartan random process ( srp ) is used to estimate the correlation structure of time series and to predict ( extrapolate ) the data values. srp ' s are motivated from statistical physics, and they can be viewed as ginzburg - landau models. the temporal correlations of the srp are modeled in terms of ` interactions ' between the field values. model parameter inference employs the computationally fast modified method of moments, which is based on matching sample energy moments with the respective stochastic constraints. the parameters thus inferred are then compared with those obtained by means of the maximum likelihood method. the performance of the spartan predictor ( sp ) is investigated using real time series of the quarterly s & p 500 index. sp prediction errors are compared with those of the kolmogorov - wiener predictor. two predictors, one of which explicit, are derived and used for extrapolation. the performance of the predictors is similarly evaluated. | arxiv:0709.3418 |
generalizing the work of kobayashi and the second author for elliptic curves with supersingular reduction at the prime $ p $, b \ " uy \ " ukboduk and lei constructed multi - signed selmer groups over the cyclotomic $ \ mathbb { z } _ p $ - extension of a number field $ f $ for more general non - ordinary motives. in particular, their construction applies to abelian varieties over $ f $ with good supersingular reduction at all the primes of $ f $ above $ p $. in this article, we scrutinize the case in which $ f $ is imaginary quadratic, and prove a control theorem ( that generalizes kim ' s control theorem for elliptic curves ) of multi - signed selmer groups of non - ordinary motives over the maximal abelian pro - $ p $ extension of $ f $ that is unramified outside $ p $, which is the $ \ mathbb { z } _ p ^ 2 $ - extension of $ f $. we apply it to derive a sufficient condition when these multi - signed selmer groups are cotorsion over the corresponding two - variable iwasawa algebra. furthermore, we compare the iwasawa $ \ mu $ - invariants of multi - signed selmer groups over the $ \ mathbb { z } _ p ^ 2 $ - extension for two such representations which are congruent modulo $ p $. | arxiv:2309.02016 |
this paper presents an approach to introduce physics students to the basic concepts of large language models ( llms ) using python - based activities in google colab. the teaching strategy integrates active learning strategies and combines theoretical ideas with practical, physics - related examples. students engage with key technical concepts, such as word embeddings, through hands - on exploration of the word2vec neural network and gpt - 2 - an llm that gained a lot of attention in 2019 for its ability to generate coherent and plausible text from simple prompts. the activities highlight how words acquire meaning and how llms predict subsequent tokens by simulating simplified scenarios related to physics. by focusing on word2vec and gpt - 2, the exercises illustrate fundamental principles underlying modern llms, such as semantic representation and contextual prediction. through interactive experimenting in google colab, students observe the relationship between model parameters ( such as temperature ) in gpt - 2 and output behaviour, understand scaling laws relating data quantity to model performance, and gain practical insights into the predictive capabilities of llms. this approach allows students to begin to understand how these systems work by linking them to physics concepts - systems that will shape their academic studies, professional careers and roles in society. | arxiv:2501.05577 |
the use of uncontrolled financial spreadsheets can expose organizations to unacceptable business and compliance risks, including errors in the financial reporting process, spreadsheet misuse and fraud, or even significant operational errors. these risks have been well documented and thoroughly researched. with the advent of regulatory mandates such as sox 404 and fdicia in the u. s., and mifid, basel ii and combined code in the uk and europe, leading tax and audit firms are now recommending that organizations automate their internal controls over critical spreadsheets and other end - user computing applications, including microsoft access databases. at a minimum, auditors mandate version control, change control and access control for operational spreadsheets, with more advanced controls for critical financial spreadsheets. this paper summarises the key issues regarding the establishment and maintenance of control of business critical spreadsheets. | arxiv:0805.4211 |
applications of satellite data in areas such as weather tracking and modeling, ecosystem monitoring, wildfire detection, and land - cover change are heavily dependent on the trade - offs to spatial, spectral and temporal resolutions of observations. in weather tracking, high - frequency temporal observations are critical and used to improve forecasts, study severe events, and extract atmospheric motion, among others. however, while the current generation of geostationary satellites have hemispheric coverage at 10 - 15 minute intervals, higher temporal frequency observations are ideal for studying mesoscale severe weather events. in this work, we apply a task specific optical flow approach to temporal up - sampling using deep convolutional neural networks. we apply this technique to 16 - bands of goes - r / advanced baseline imager mesoscale dataset to temporally enhance full disk hemispheric snapshots of different spatial resolutions from 15 minutes to 1 minute. experiments show the effectiveness of task specific optical flow and multi - scale blocks for interpolating high - frequency severe weather events relative to bilinear and global optical flow baselines. lastly, we demonstrate strong performance in capturing variability during a convective precipitation events. | arxiv:1907.12013 |
on top of the mean - field analysis of a bose - einstein condensate, one typically applies the bogoliubov theory to analyze quantum fluctuations of the excited modes. therefore, one has to diagonalize the bogoliubov hamiltonian in a symplectic manner. in our article we investigate the topology of these bogoliubov excitations in inversion - invariant systems of interacting bosons. we analyze how the condensate influences the topology of the bogoliubov excitations. analogously to the fermionic case, here we establish a symplectic extension of the polarization characterizing the topology of the bogoliubov excitations and link it to the eigenvalues of the inversion operator at the inversion - invariant momenta. we also demonstrate an instructive but experimentally feasible example that this quantity is also related to edge states in the excitation spectrum. | arxiv:1503.02503 |
modern internet services, such as those at google, yahoo!, and amazon, handle billions of requests per day on clusters of thousands of computers. because these services operate under strict performance requirements, a statistical understanding of their performance is of great practical interest. such services are modeled by networks of queues, where each queue models one of the computers in the system. a key challenge is that the data are incomplete, because recording detailed information about every request to a heavily used system can require unacceptable overhead. in this paper we develop a bayesian perspective on queueing models in which the arrival and departure times that are not observed are treated as latent variables. underlying this viewpoint is the observation that a queueing model defines a deterministic transformation between the data and a set of independent variables called the service times. with this viewpoint in hand, we sample from the posterior distribution over missing data and model parameters using markov chain monte carlo. we evaluate our framework on data from a benchmark web application. we also present a simple technique for selection among nested queueing models. we are unaware of any previous work that considers inference in networks of queues in the presence of missing data. | arxiv:1001.3355 |
quantum kerr - nonlinear oscillator is a paradigmatic model in cavity and circuit quantum electrodynamics, and quantum optomechanics. we theoretically study the echo phenomenon in a single impulsively excited ( " kicked " ) kerr - nonlinear oscillator. we reveal two types of echoes, " quantum " and " classical " ones, emerging on the long and short time - scales, respectively. the mechanisms of the echoes are discussed, and their sensitivity to dissipation is considered. these echoes may be useful for studying decoherence processes in a number of systems related to quantum information processing. | arxiv:2009.01603 |
space r n { \ displaystyle \ mathbb { r } ^ { n } }, the formula for the reflection in the hyperplane through the origin, orthogonal to a { \ displaystyle a }, is given by ref a ( v ) = v − 2 v ⋅ a a ⋅ a a, { \ displaystyle \ operatorname { ref } _ { a } ( v ) = v - 2 { \ frac { v \ cdot a } { a \ cdot a } } a, } where v ⋅ a { \ displaystyle v \ cdot a } denotes the dot product of v { \ displaystyle v } with a { \ displaystyle a }. note that the second term in the above equation is just twice the vector projection of v { \ displaystyle v } onto a { \ displaystyle a }. one can easily check that refa ( v ) = −v, if v { \ displaystyle v } is parallel to a { \ displaystyle a }, and refa ( v ) = v, if v { \ displaystyle v } is perpendicular to a. using the geometric product, the formula is ref a ( v ) = − a v a a 2. { \ displaystyle \ operatorname { ref } _ { a } ( v ) = - { \ frac { ava } { a ^ { 2 } } }. } since these reflections are isometries of euclidean space fixing the origin they may be represented by orthogonal matrices. the orthogonal matrix corresponding to the above reflection is the matrix r = i − 2 a a t a t a, { \ displaystyle r = i - 2 { \ frac { aa ^ { t } } { a ^ { t } a } }, } where i { \ displaystyle i } denotes the n × n { \ displaystyle n \ times n } identity matrix and a t { \ displaystyle a ^ { t } } is the transpose of a. its entries are r i j = δ i j − 2 a i a j ‖ a ‖ 2, { \ displaystyle r _ { ij } = \ delta _ { ij } - 2 { \ frac { a _ { i } a _ { j } } { \ left \ | a \ right \ | ^ { 2 } } }, } where δij is the kronecker delta. the formula for the reflection in the affine hyperplane v ⋅ a = c { \ displaystyle v \ cdot | https://en.wikipedia.org/wiki/Reflection_(mathematics) |
the possibility of achieving a gauge coupling grand unification by increasing the qcd degrees of freedom at higher energies is investigated. when confronted with precision low - energy data, the generic weak - mixing angle relation sin ^ 2 ( theta _ w ) = n / 2 ( n + 1 ) requires n = 7 colors at the gut scale m _ u ~ 10 ^ 17 gev. with the exclusive addition of light higgs doublets to the standard model particle content, such a unification may also occur if n = 5 at m _ u ~ 10 ^ 16 gev. | arxiv:hep-ph/0305092 |
chaos as typical property of non - linear systems has revealed its crucial role in various problems of astrophysics and cosmology. the problems discussed at these lectures include planetary dynamics, galactic dynamics, reconstruction of the substructure of clusters of galaxies, instability in wheeler - dewitt superspace. the choice of the problems aimed to show also the diversity of approaches and mathematical tools, which include the geometric criterion ( ricci ) of relative instability in many dimensional systems, the estimation of kolmogorov - sinai entropy, the hyperbolicity in pseudo - riemannian spaces, etc. | arxiv:astro-ph/0410258 |
we show at one - loop and first order in the noncommutativity parameters that in any noncommutative gut inspired theory the total contribution to the fermionic four point functions coming only from the interaction between fermions and gauge bosons, though not uv finite by power counting, is uv finite at the end of the day. we also show that this is at odds with the general case for noncommutative gauge theories - - chiral or otherwise - - defined by means of seiberg - witten maps that are the same - - barring the gauge group representation - - for left - handed spinors as for right - handed spinors. we believe that the results presented in this paper tilt the scales to the side of noncommutative guts and noncommutative gut inspired versions of the standard model. | arxiv:0907.2464 |
using data samples collected at center of mass energies of $ \ sqrt { s } $ = 4. 009, 4. 226, 4. 257, 4. 358, 4. 416 and 4. 599 gev with the besiii detector operating at the bepcii storage ring, we search for the isospin violating decay $ y ( 4260 ) \ rightarrow j / \ psi \ eta \ pi ^ { 0 } $. no signal is observed, and upper limits on the cross section $ \ sigma ( e ^ { + } e ^ { - } \ rightarrow j / \ psi \ eta \ pi ^ { 0 } ) $ at the 90 \ % confidence level are determined to be 3. 6, 1. 7, 2. 4, 1. 4, 0. 9 and 1. 9 pb, respectively. | arxiv:1505.00539 |
ngc 6822 is an irregular dwarf galaxy and part of the local group. its close proximity and apparent isolation provide a unique opportunity to study galactic evolution without any obvious strong external influences. this paper aims to study the spatial distribution of the asymptotic giant branch ( agb ) population and metallicity in ngc 6822. using deep, high quality jhk photometry, taken with wfcam on ukirt, carbon - and oxygen - rich agb stars have been isolated. the ratio between their number, the c / m ratio, has then been used to derive the [ fe / h ] abundance across the galaxy. the tip of the red giant branch is located at k0 = 17. 41 \ pm 0. 11 mag and the colour separation between carbon - and oxygen - rich agb stars is at ( j - k ) 0 = 1. 20 \ pm 0. 03 mag ( i. e. ( j - k ) 2mas s { \ guillemotright } 1. 28 mag ). a c / m ratio of 0. 62 \ pm 0. 03 has been derived in the inner 4 kpc of the galaxy, which translates into an iron abundance of [ fe / h ] = - 1. 29 \ pm0. 07 dex. variations of these parameters were investigated as a function of distance from the galaxy centre and azimuthal angle. the agb population of ngc 6822 has been detected out to a radius of 4 kpc giving a diameter of 56 arcmin. it is metal - poor, but there is no obvious gradient in metallicity with either radial distance from the centre or azimuthal angle. the detected spread in the trgb magnitude is consistent with that of a galaxy surrounded by a halo of old stars. the c / m ratio has the potential to be a very useful tool for the determination of metallicity in resolved galaxies but a better calibration of the c / m vs. [ fe / h ] relation and a better understanding of the sensitivities of the c / m ratio to stellar selection criteria is first required. | arxiv:1202.3285 |
we present a revised and complete optical afterglow light curve of the binary neutron star merger gw170817, enabled by deep hubble space telescope ( hst ) f606w observations at $ \ approx \! 584 $ days post - merger, which provide a robust optical template. the light curve spans $ \ approx 110 - 362 $ days, and is fully consistent with emission from a relativistic structured jet viewed off - axis, as previously indicated by radio and x - ray data. combined with contemporaneous radio and x - ray observations, we find no spectral evolution, with a weighted average spectral index of $ \ langle \ beta \ rangle = - 0. 583 \ pm 0. 013 $, demonstrating that no synchrotron break frequencies evolve between the radio and x - ray bands over these timescales. we find that an extrapolation of the post - peak temporal slope of gw170817 to the luminosities of cosmological short grbs matches their observed jet break times, suggesting that their explosion properties are similar, and that the primary difference in gw170817 is viewing angle. additionally, we place a deep limit on the luminosity and mass of an underlying globular cluster of $ l \ lesssim 6. 7 \ times 10 ^ { 3 } \, l _ { \ odot } $, or $ m \ lesssim 1. 3 \ times 10 ^ { 4 } \, m _ { \ odot } $, at least 4 standard deviations below the peak of the globular cluster mass function of the host galaxy, ngc4993. this limit provides a direct and strong constraint that gw170817 did not form and merge in a globular cluster. as highlighted here, hst ( and soon jwst ) enables critical observations of the optical emission from neutron star merger jets and outflows. | arxiv:1908.08046 |
we construct two - band topological semimetals in four dimensions using the unstable homotopy of maps from the three - torus $ t ^ 3 $ ( brillouin zone of a 3d crystal ) to the two - sphere $ s ^ 2 $. dubbed ` ` hopf semimetals ' ', these gapless phases generically host nodal lines, with a surface enclosing such a nodal line in the four - dimensional brillouin zone carrying a hopf flux. these semimetals show a unique class of surface states : while some three - dimensional surfaces host gapless fermi - arc states { \ em and } drumhead states, other surfaces have gapless fermi surfaces. gapless two - dimensional corner states are also present at the intersection of three - dimensional surfaces. | arxiv:2309.14119 |
it is shown that if a metric space exhibits certain finiteness and tree - like properties, then elements of its group of bounded displacement which are infinitely divisible are also torsion. this extends a result of n. m. suchkov, a. a. shlepkin, and d. a. taysnyov. | arxiv:2504.21496 |
we give a definition of the gray tensor product in the setting of scaled simplicial sets which is associative and forms a left quillen bifunctor with respect to the bicategorical model category of lurie. we then introduce a notion of oplax functor in this setting, and use it in order to characterize the gray tensor product by means of a universal property. a similar characterization was used by gaitsgory and rozenblyum in their definition of the gray product, thus giving a promising lead for comparing the two settings. | arxiv:2006.14495 |
we show that the whole range of rhic data for hadron production in d - au collisions is compatible with geometric scaling. to establish the scaling violations expected from small - x evolution a larger kinematic range in transverse momentum and rapidity would be needed. we point out that the fall - off of the p _ t distribution of produced hadrons at large p _ t is a sensitive probe of small - x evolution especially at the lhc. | arxiv:0806.4126 |
time - series of persistence diagrams, known as vineyards, have shown to be useful in diverse applications. a natural algebraic version of vineyards is a time series of persistence modules equipped with interleaving maps between the persistence modules at different time values. we call this a vineyard module. in this paper we will set up the framework for representing vineyards modules via families of matrices and outline an algorithmic way to change the bases of the persistence modules at each time step within the vineyard module to make the matrices in this representation as simple as possible. with some reasonable assumptions on the vineyard modules, this simplified representation of the vineyard module can be completely described ( up to isomorphism ) by the underlying vineyard and a vector of finite length. we first must set up a lot of preliminary results about changes of bases for persistence modules where we are given $ \ epsilon $ - interleaving maps for sufficiently close $ \ epsilon $. while this vector representation is not in general guaranteed to be unique we can prove that it will be always zero when the vineyard module is isomorphic to the direct sum of vine modules. this new perspective on vineyards provides an interesting and yet tractable case study within multi - parameter persistence. | arxiv:2307.06020 |
recent measurements of jet cross sections at hera, the tevatron and the lhc that provide constraints on parton distribution functions and allow for determinations of the strong coupling constant are presented. | arxiv:1302.4652 |
using the framework of infinite matrix product states, the existence of an \ textit { anomalous } dynamical phase for the transverse - field ising chain with sufficiently long - range interactions was first reported in [ j. ~ c. ~ halimeh and v. ~ zauner - stauber, arxiv : 1610 : 02019 ], where it was shown that \ textit { anomalous } cusps arise in the loschmidt - echo return rate for sufficiently small quenches within the ferromagnetic phase. in this work we further probe the nature of the anomalous phase through calculating the corresponding fisher - zero lines in the complex time plane. we find that these fisher - zero lines exhibit a qualitative difference in their behavior, where, unlike in the case of the regular phase, some of them terminate before intersecting the imaginary axis, indicating the existence of smooth peaks in the return rate preceding the cusps. additionally, we discuss in detail the infinite matrix product state time - evolution method used to calculate fisher zeros and the loschmidt - echo return rate using the matrix product state transfer matrix. our work sheds further light on the nature of the anomalous phase in the long - range transverse - field ising chain, while the numerical treatment presented can be applied to more general quantum spin chains. | arxiv:1709.06050 |
the infinitesimal generators of l \ ' evy processes in euclidean space are pseudo - differential operators with symbols given by the l \ ' evy - khintchine formula. this classical analysis relies heavily on fourier analysis which in the case when the state space is a lie group becomes much more subtle. still the notion of pseudo - differential operators can be extended to connected, simply connected nilpotent lie groups by employing the weyl functional calculus. with respect to this definition, the generators of l \ ' evy processes in the simplest step 3 nilpotent lie group $ g $ are pseudo - differential operators which admit $ c _ c ( g ) $ as its core. | arxiv:1207.0304 |
the fact that internet companies may record our personal data and track our online behavior for commercial or political purpose has emphasized aspects related to online privacy. this has also led to the development of search engines that promise no tracking and privacy. search engines also have a major role in spreading low - quality health information such as that of anti - vaccine websites. this study investigates the relationship between search engines ' approach to privacy and the scientific quality of the information they return. we analyzed the first 30 webpages returned searching ' vaccines autism ' in english, spanish, italian and french. the results show that alternative search engines ( duckduckgo, ecosia, qwant, swisscows and mojeek ) may return more anti - vaccine pages ( 10 to 53 percent ) than google. com ( zero ). some localized versions of google, however, returned more anti - vaccine webpages ( up to 10 percent ) than google. com. our study suggests that designing a search engine that is privacy savvy and avoids issues with filter bubbles that can result from user tracking is necessary but insufficient ; instead, mechanisms should be developed to test search engines from the perspective of information quality ( particularly for health - related webpages ), before they can be deemed trustworthy providers of public health information. | arxiv:1912.00898 |
in this paper we study the existence of solutions to the following generalized nonlinear two - parameter problem \ begin { equation * } a ( u, v ) \ ; = \ ; \ lambda \, b ( u, m ) + \ mu \, m ( u, v ) + \ varepsilon \, f ( u, v ), \ end { equation * } for a triple $ ( a, b, m ) $ of continuous, symmetric bilinear forms on a real separable hilbert space $ v $ and nonlinear form $ f $. this problem is a natural abstraction of nonlinear problems that occur for a large class of differential operators, various elliptic pde ' s with nonlinearities in either the differential equation and / or the boundary conditions being a special subclass. first, a fredholm alternative for the associated linear two - parameter eigenvalue problem is developed, and then this is used to construct a nonlinear version of the fredholm alternative. lastly, the steklov - robin fredholm equation is used to exemplify the abstract results. | arxiv:2209.01254 |
for two relatively prime square - free positive integers $ a $ and $ b $, we study integers of the form $ a p + b p _ { 2 } $ and give a new lower bound for it, where $ a p $ and $ b p _ { 2 } $ are both square - free, $ p $ denotes a prime, and $ p _ { 2 } $ has at most two prime factors. we also consider some special cases where $ p $ is small, $ p $ and $ p _ 2 $ are within short intervals, $ p $ and $ p _ 2 $ are within arithmetical progressions and a goldbach - type upper bound result. our new results generalize and improve the previous results. | arxiv:2309.03218 |
infrastructure inspection is a very costly task, requiring technicians to access remote or hard - to - reach places. this is the case for power transmission towers, which are sparsely located and require trained workers to climb them to search for damages. recently, the use of drones or helicopters for remote recording is increasing in the industry, sparing the technicians this perilous task. this, however, leaves the problem of analyzing big amounts of images, which has great potential for automation. this is a challenging task for several reasons. first, the lack of freely available training data and the difficulty to collect it complicate this problem. additionally, the boundaries of what constitutes a damage are fuzzy, introducing a degree of subjectivity in the labelling of the data. the unbalanced class distribution in the images also plays a role in increasing the difficulty of the task. this paper tackles the problem of structural damage detection in transmission towers, addressing these issues. our main contributions are the development of a system for damage detection on remotely acquired drone images, applying techniques to overcome the issue of data scarcity and ambiguity, as well as the evaluation of the viability of such an approach to solve this particular problem. | arxiv:2111.15581 |
y - rita developed a vision substitution system using a 20x20 array of metal rods that could be raised and lowered, producing tactile " dots " analogous to the pixels of a screen. people sitting in a chair equipped with this device could identify pictures from the pattern of dots poked into their backs. the first us patent for a tactile telephone was granted to thomas d. shannon in 1973. an early tactile man - machine communication system was constructed by a. michael noll at bell telephone laboratories, inc. in the early 1970s and a patent was issued for his invention in 1975. in 1994, the aura interactor vest was developed. the vest is a wearable force - feedback device that monitors an audio signal and uses electromagnetic actuator technology to convert bass sound waves into vibrations that can represent such actions as a punch or kick. the vest plugs into the audio output of a stereo, tv, or vcr and the audio signal is reproduced through a speaker embedded in the vest. in 1995, thomas massie developed the phantom ( personal haptic interface mechanism ) system. it used thimble - like receptacles at the end of computerized arms into which a person ' s fingers could be inserted, allowing them to " feel " an object on a computer screen. in 1995, norwegian geir jensen described a wristwatch haptic device with a skin tap mechanism, termed tap - in. the wristwatch would connect to a mobile phone via bluetooth, and tapping - frequency patterns would enable the wearer to respond to callers with selected short messages. in 2015, the apple watch was launched. it uses skin tap sensing to deliver notifications and alerts from the mobile phone of the watch wearer. = = types of mechanical touch sensing = = human sensing of mechanical loading in the skin is managed by mechanoreceptors. there are a number of types of mechanoreceptors but those present in the finger pad are typically placed into two categories. fast acting ( fa ) and slow acting ( sa ). sa mechanoreceptors are sensitive to relatively large stresses and at low frequencies while fa mechanoreceptors are sensitive to smaller stresses at higher frequencies. the result of this is that generally sa sensors can detect textures with amplitudes greater than 200 micrometers and fa sensors can detect textures with amplitudes less than 200 micrometers down to about 1 micrometer, though some research suggests that fa can only detect textures smaller than the fingerprint wavelength. | https://en.wikipedia.org/wiki/Haptic_technology |
mathematical modeling of gravitating configurations of physical fields is one of the priority directions of the modern theory of gravity. most of the exact solutions constructed within the framework of the general relativity are static or stationary configurations. this is due to the objective complexity of solving the einstein equations under the assumption of nonstationarity. we present an approach to constructing nonstationary configurations of a spherically symmetric nonlinear real scalar field and the electromagnetic field, which areassumed both to be minimally coupled to gravity. it is based on the isolation of one invariant equation written in terms of the characteristic function and scalar field potential. using the proposed method, an exact nonstationary solution with a nontrivial topology of space - time will be constructed. | arxiv:1912.00357 |
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