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we present an integration of a safe c dialect, checked c, for the internet of things operating system riot. we utilize this integration to convert parts of the riot network stack to checked c, thereby achieving spatial memory safety in these code parts. similar to prior research done on iot operating systems and safe c dialects, our integration of checked c remains entirely optional, i. e. compilation with a standard c compiler not supporting the checked c language extension is still possible. we believe this to be the first proposed integration of a safe c dialect for the riot operating system. we present an incremental process for converting riot modules to checked c, evaluate the overhead introduced by the conversions, and discuss our general experience with utilizing checked c in the internet of things domain. | arxiv:2005.09516 |
the covid - 19 pandemic has forced policy makers to decree urgent confinements to stop a rapid and massive contagion. however, after that stage, societies are being forced to find an equilibrium between the need to reduce contagion rates and the need to reopen their economies. the experience hitherto lived has provided data on the evolution of the pandemic, in particular the population dynamics as a result of the public health measures enacted. this allows the formulation of forecasting mathematical models to anticipate the consequences of political decisions. here we propose a model to do so and apply it to the case of portugal. with a mathematical deterministic model, described by a system of ordinary differential equations, we fit the real evolution of covid - 19 in this country. after identification of the population readiness to follow social restrictions, by analyzing the social media, we incorporate this effect in a version of the model that allow us to check different scenarios. this is realized by considering a monte carlo discrete version of the previous model coupled via a complex network. then, we apply optimal control theory to maximize the number of people returning to " normal life " and minimizing the number of active infected individuals with minimal economical costs while warranting a low level of hospitalizations. this work allows testing various scenarios of pandemic management ( closure of sectors of the economy, partial / total compliance with protection measures by citizens, number of beds in intensive care units, etc. ), ensuring the responsiveness of the health system, thus being a public health decision support tool. | arxiv:2009.00660 |
we study the vacuum interaction of a scalar field and two concentric spheres defined by a singular potential on their surfaces. the potential is a linear combination of the dirac - $ \ delta $ and its derivative. the presence of the delta prime term in the potential causes that it behaves differently when it is seen from the inside or from the outside of the sphere. we study different cases for positive and negative values of the delta prime coupling, keeping positive the coupling of the delta. as a consequence, we find regions in the space of couplings, where the energy is positive, negative or zero. moreover, the sign of the $ \ delta ' $ couplings cause different behavior on the value of the casimir energy for different values of the radii. this potential gives rise to general boundary conditions with limiting cases defining dirichlet and robin boundary conditions what allows us to simulate purely electric o purely magnetic spheres. | arxiv:2009.03785 |
( abridged ) we present new spitzer, ukirt and mmt observations of the blue compact dwarf galaxy ( bcd ) mrk 996, with an oxygen abundance of 12 + log ( o / h ) = 8. 0. this galaxy has the peculiarity of possessing an extraordinarily dense nuclear star - forming region, with a central density of ~ 10 ^ 6 cm ^ { - 3 }. the nuclear region of mrk 996 is characterized by several unusual properties : a very red color j - k = 1. 8, broad and narrow emission - line components, and ionizing radiation as hard as 54. 9 ev, as implied by the presence of the oiv 25. 89 micron line. the nucleus is located within an exponential disk with colors consistent with a single stellar population of age > 1 gyr. the infrared morphology of mrk 996 changes with wavelength. the irs spectrum shows strong narrow polycyclic aromatic hydrocarbon ( pah ) emission, with narrow line widths and equivalent widths that are high for the metallicity of mrk 996. gaseous nebular fine - structure lines are also seen. a cloudy model requires that they originate in two distinct hii regions : a very dense hii region of radius ~ 580 pc with densities declining from ~ 10 ^ 6 at the center to a few hundreds cm ^ { - 3 } at the outer radius, where most of the optical lines arise ; and a hii region with a density of ~ 300 cm ^ { - 3 } that is hidden in the optical but seen in the mir. we suggest that the infrared lines arise mainly in the optically obscured hii region while they are strongly suppressed by collisional deexcitation in the optically visible one. the hard ionizing radiation needed to account for the oiv 25. 89 micron line is most likely due to fast radiative shocks propagating in an interstellar medium. a hidden population of wolf - rayet stars of type wne - w or a hidden agn as sources of hard ionizing radiation are less likely possibilities. | arxiv:0809.3082 |
to elucidate the atomistic origin of volume relaxation in soda - lime silicate glass annealed below the glass transition temperature ( tg ), the experimental and calculated raman spectra were compared. by decomposing the calculated raman spectra into a specific group of atoms, we found that the raman peak at 1050 cm - 1 corresponds to bridging oxygen with a small si - o - si bond angle. the experimental raman spectra indicated that, during annealing below tg, a homogenization reaction q2 + q4 - > 2q3 proceeds in the early stage of structural relaxation. then, the si - o - si units with relatively small angles decrease even in the later stages, which is first evidence of ring deformation causing volume relaxation of soda - lime silicate glass because decreasing small si - o - si angles corresponds to the reduce of acute o - o - o angle in a ring and can expand the space inside the rings, and na can be inserted into the ring center. in conclusion the ring deformation and na displacement is the origin of the volume relaxation of soda - lime silicate glass below tg. | arxiv:2309.15591 |
sets of solutions to finite systems of equations in a free group, are equivalent to sets of homomorphisms from a fixed f. p. group into a free group. the latter can be encoded in a diagram, the construction of which is valid also for f. g. groups. the diagram is known to be canonical for a fixed f. g. group with a fixed generating set. in this paper we prove that the construction depends on the chosen generating set of the given f. g. group. | arxiv:1802.02431 |
in this review i will describe progress that has been made in determining masses of galaxy clusters using ` weak lensing ' and how this technique my be applied in the future to determine the dark matter distribution both on supercluster scales and on the scale of galaxy haloes. | arxiv:astro-ph/9509019 |
localized static solutions of the 2d - o ( 3 ) model are investigated in a representation with the 3 - vector field $ \ vec phi $ split into the unit vector $ \ hat phi $ and the modulus $ \ phi $. as in the nonlinear version of the model this allows for the definition of a topological winding number $ b $, and for the separation of the complete configuration space into distinct $ b $ - sectors. for small values of the $ \ phi ^ 4 $ - coupling strength the stable energy minima in these sectors are characterized by bag formation in the modulus field which in the standard cartesian representation of the linear o ( 3 ) model would be unstable towards decay into the trivial b = 0 vacuum. stabilized by $ b $ - conservation they exhibit a surprising variety of very appealing features for multiply charged systems. with the total charge bound into one common deep bag opposite ways of distributing the topological charge density inside the bag can be realized : pointlike structures which retain the individuality of single constituents ( or doubly charged pairs ), or a deconfined charge density spread uniformly throughout the interior of the bag. it is suggested that this extension supplies a crucial link to overcome the unsatisfactory existing mismatch between multiskyrmion configurations and nuclear structure. | arxiv:hep-ph/9905473 |
the outbursts of low mass x - ray binaries are prolonged relative to those of dwarf nova cataclysmic variables as a consequence of x - ray irradiation of the disc. we show that the time - scale of the decay light curve and its luminosity at a characteristic time are linked to the radius of the accretion disc. hence a good x - ray light curve permits two independent estimates of the disc radius. in the case of the milli - second pulsars sax j1808. 4 - 3658 and xte j0929 - 314 the agreement between these estimates is very strong. our analysis allows new determinations of distances and accretion disc radii. our analysis will allow determination of accretion disc radii for sources in external galaxies, and hence constrain system parameters where other observational techniques are not possible. we also use the x - ray light curves to estimate the mass transfer rate. the broken exponential decay observed in the 2002 outburst of sax j1808. 4 - 3658 may be caused by the changing self - shadowing of the disc. | arxiv:astro-ph/0610108 |
we use the canonical coset parameterization and provide a formula with the unitary part of the bures measure for non - degenerate systems in terms of the product of even euclidean balls. this formula is shown to be consistent with the sampling of random states through the generation of random unitary matrices. | arxiv:0910.2910 |
matrix profile has been recently proposed as a promising technique to the problem of all - pairs - similarity search on time series. efficient algorithms have been proposed for computing it, e. g., stamp, stomp and scrimp + +. all these algorithms use the z - normalized euclidean distance to measure the distance between subsequences. however, as we observed, for some datasets other euclidean measurements are more useful for knowledge discovery from time series. in this paper, we propose efficient algorithms for computing matrix profile for a general class of euclidean distances. we first propose a simple but efficient algorithm called aamp for computing matrix profile with the " pure " ( non - normalized ) euclidean distance. then, we extend our algorithm for the p - norm distance. we also propose an algorithm, called acamp, that uses the same principle as aamp, but for the case of z - normalized euclidean distance. we implemented our algorithms, and evaluated their performance through experimentation. the experiments show excellent performance results. for example, they show that aamp is very efficient for computing matrix profile for non - normalized euclidean distances. the results also show that the acamp algorithm is significantly faster than scrimp + + ( the state of the art matrix profile algorithm ) for the case of z - normalized euclidean distance. | arxiv:1901.05708 |
we have statistically analyzed a set of 115 low frequency ( deca - hectometer wavelengths range ) type ii and type iii bursts associated with major solar energetic particle ( sep : ep > 10 mev ) events and their solar causes such as solar flares and coronal mass ejections ( cmes ) observed from 1997 to 2014. we classified them into two sets of events based on the duration of the associated solar flares : 75 impulsive flares ( duration < 60 min ) and 40 gradual flares ( duration > 60 min ). the impulsive flare - associated sep events ( rt = 989. 23 min : 2. 86 days ) are short lived and they quickly reach their peak intensity ( shorter rise time ) when compared with gradual flares associated events ( rt = 1275. 45 min : 3. 34 days ). we found a good correlation between the logarithmic peak intensity of all seps and properties of cmes ( space speed : cc = 0. 52, secc = 0. 083 ), and solar flares ( log integrated flux : cc = 0. 44, secc = 0. 083 ). this particular result gives no clear cut distinction between flare - related and cme - related sep events for this set of major sep events. we derived the peak intensity, integrated intensity, duration and slope of these bursts from the radio dynamic spectra observed by wind / waves. most of the properties ( peak intensity, integrated intensity and starting frequency ) of dh type ii bursts associated with impulsive and gradual flare events are found to be similar in magnitudes. in addition, we also found a significant correlation between the properties of seps and key parameters of dh type iii bursts. this result shows a closer association of peak intensity of the seps with the properties of dh type iii radio bursts than with the properties dh type ii radio bursts, at least for this set of 115 major sep events. | arxiv:2007.05726 |
future wireless networks will need to improve adaptive resource allocation and decision - making to handle the increasing number of intelligent devices. unmanned aerial vehicles ( uavs ) are being explored for their potential in real - time decision - making. moreover, cognitive non - orthogonal multiple access ( cognitive - noma ) is envisioned as a remedy to address spectrum scarcity and enable massive connectivity. this paper investigates the design of joint subchannel and power allocation in an uplink uav - based cognitive noma network. we aim to maximize the cumulative sum rate by jointly optimizing the subchannel and power allocation based on the uav ' s mobility at each time step. this is often formulated as an optimization problem with random variables. however, conventional optimization algorithms normally introduce significant complexity, and machine learning methods often rely on large but partially representative datasets to build solution models, assuming stationary testing data. consequently, inference strategies for non stationary events are often overlooked. in this study, we introduce a novel active inference - based learning approach, rooted in cognitive neuroscience, to solve this complex problem. the framework involves creating a training dataset using random or iterative methods to find suboptimal resource allocations. this dataset trains a mobile uav offline, enabling it to learn a generative model of discrete subchannels and continuous power allocation. the uav then uses this model for online inference. the method incrementally derives new generative models from training data by identifying dynamic equilibrium conditions between required actions and variables, represented within a unique dynamic bayesian network. the proposed approach is validated through numerical simulations, showing efficient performance compared to suboptimal baseline schemes. | arxiv:2310.11070 |
it has recently been conjectured that neural network solution sets reachable via stochastic gradient descent ( sgd ) are convex, considering permutation invariances ( entezari et al., 2022 ). this means that a linear path can connect two independent solutions with low loss, given the weights of one of the models are appropriately permuted. however, current methods to test this theory often require very wide networks to succeed. in this work, we conjecture that more generally, the sgd solution set is a " star domain " that contains a " star model " that is linearly connected to all the other solutions via paths with low loss values, modulo permutations. we propose the starlight algorithm that finds a star model of a given learning task. we validate our claim by showing that this star model is linearly connected with other independently found solutions. as an additional benefit of our study, we demonstrate better uncertainty estimates on the bayesian model averaging over the obtained star domain. further, we demonstrate star models as potential substitutes for model ensembles. our code is available at https : / / github. com / aktsonthalia / starlight. | arxiv:2403.07968 |
we analyze the asymptotic behavior of solutions to wave equations with strong damping terms. if the initial data belong to suitable weighted $ l ^ 1 $ spaces, lower bounds for the difference between the solutions and the leading terms in the fourier space are obtained, which implies the optimality of expanding methods and some estimates proposed in this paper. | arxiv:1810.09114 |
ensemble clustering is a fundamental problem in the machine learning field, combining multiple base clusterings into a better clustering result. however, most of the existing methods are unsuitable for large - scale ensemble clustering tasks due to the efficiency bottleneck. in this paper, we propose a large - scale spectral ensemble clustering ( lsec ) method to strike a good balance between efficiency and effectiveness. in lsec, a large - scale spectral clustering based efficient ensemble generation framework is designed to generate various base clusterings within a low computational complexity. then all based clustering are combined through a bipartite graph partition based consensus function into a better consensus clustering result. the lsec method achieves a lower computational complexity than most existing ensemble clustering methods. experiments conducted on ten large - scale datasets show the efficiency and effectiveness of the lsec method. the matlab code of the proposed method and experimental datasets are available at https : / / github. com / li - hongmin / mypaperwithcode. | arxiv:2106.09852 |
we search for persistent and quasi - periodic release events of streamer blobs during 2007 with the large angle spectrometric coronagraph on the \ textit { solar and heliospheric observatory } and assess the velocity of the slow solar wind along the plasma sheet above the corresponding streamer by measuring the dynamic parameters of blobs. we find 10 quasi - periodic release events of streamer blobs lasting for three to four days. in each day of these events, we observe three - five blobs. the results are in line with previous studies using data observed near the last solar minimum. using the measured blob velocity as a proxy for that of the mean flow, we suggest that the velocity of the background slow solar wind near the sun can vary significantly within a few hours. this provides an observational manifestation of the large velocity variability of the slow solar wind near the sun. | arxiv:0907.0819 |
recently, more and more research has focused on using graph neural networks ( gnn ) to solve the graph similarity computation problem ( gsc ), i. e., computing the graph edit distance ( ged ) between two graphs. these methods treat gsc as an end - to - end learnable task, and the core of their architecture is the feature fusion modules to interact with the features of two graphs. existing methods consider that graph - level embedding is difficult to capture the differences in local small structures between two graphs, and thus perform fine - grained feature fusion on node - level embedding can improve the accuracy, but leads to greater time and memory consumption in the training and inference phases. however, this paper proposes a novel graph - level fusion module different attention ( diffatt ), and demonstrates that graph - level fusion embeddings can substantially outperform these complex node - level fusion embeddings. we posit that the relative difference structure of the two graphs plays an important role in calculating their ged values. to this end, diffatt uses the difference between two graph - level embeddings as an attentional mechanism to capture the graph structural difference of the two graphs. based on diffatt, a new gsc method, named graph edit distance learning via different attention ( redraft ), is proposed, and experimental results demonstrate that redraft achieves state - of - the - art performance in 23 out of 25 metrics in five benchmark datasets. especially on mse, it respectively outperforms the second best by 19. 9 %, 48. 8 %, 29. 1 %, 31. 6 %, and 2. 2 %. moreover, we propose a quantitative test remaining subgraph alignment test ( resat ) to verify that among all graph - level fusion modules, the fusion embedding generated by diffatt can best capture the structural differences between two graphs. | arxiv:2308.13871 |
we propose a bayesian framework for the received - signal - strength - based cooperative localization problem with unknown path loss exponent. our purpose is to infer the marginal posterior of each unknown parameter : the position or the path loss exponent. this probabilistic inference problem is solved using message passing algorithms that update messages and beliefs iteratively. to enable the numerical tractability, we combine the variable discretization and monte - carlo - based numerical approximation schemes. to further improve computational efficiency, we develop an auxiliary importance sampler that updates the beliefs with the help of an auxiliary variable. to sample from a normalized likelihood function, which is an important ingredient of the proposed auxiliary importance sampler, we develop a stochastic sampling strategy that mathematically interprets and corrects an existing heuristic strategy. the proposed message passing algorithms are analyzed systematically in terms of computational complexity, demonstrating the computational efficiency of the proposed auxiliary importance sampler. various simulations are conducted to validate the overall good performance of the proposed algorithms. | arxiv:1904.00715 |
we measured the transport properties and susceptibility of single crystals ca $ _ { 1 - x } $ la $ _ x $ fe $ _ 2 $ as $ _ 2 $ ( x = 0, 0. 05, 0. 1, 0. 15, 0. 19 and 0. 25 ). large in - plane resistivity anisotropy similar to that in co - doped 122 iron - pnictides is observed although no transition metals were introduced in the feas - plane. the in - plane resistivity anisotropy gradually increases with la doping below t $ _ { sdw } $, being different from the hole - doped 122 superconductors. the susceptibilities of the samples show that la doping leads to suppression of sdw and induces a curie - weiss - like behavior at low temperature, which is much stronger than the other 122 iron - based superconductors. | arxiv:1202.3589 |
objective : a novel ecg classification algorithm is proposed for continuous cardiac monitoring on wearable devices with limited processing capacity. methods : the proposed solution employs a novel architecture consisting of wavelet transform and multiple lstm recurrent neural networks. results : experimental evaluations show superior ecg classification performance compared to previous works. measurements on different hardware platforms show the proposed algorithm meets timing requirements for continuous and real - time execution on wearable devices. conclusion : in contrast to many compute - intensive deep - learning based approaches, the proposed algorithm is lightweight, and therefore, brings continuous monitoring with accurate lstm - based ecg classification to wearable devices. significance : the proposed algorithm is both accurate and lightweight. the source code is available online [ 1 ]. | arxiv:1812.04818 |
in the unit - cost comparison model, a black box takes an input two items and outputs the result of the comparison. problems like sorting and searching have been studied in this model, and it has been generalized to include the concept of priced information, where different pairs of items ( say database records ) have different comparison costs. these comparison costs can be arbitrary ( in which case no algorithm can be close to optimal ( charikar et al. stoc 2000 ) ), structured ( for example, the comparison cost may depend on the length of the databases ( gupta et al. focs 2001 ) ), or stochastic ( angelov et al. latin 2008 ). motivated by the database setting where the cost depends on the sizes of the items, we consider the problems of sorting and batched predecessor where two non - uniform sets of items $ a $ and $ b $ are given as input. ( 1 ) in the ram setting, we consider the scenario where both sets have $ n $ keys each. the cost to compare two items in $ a $ is $ a $, to compare an item of $ a $ to an item of $ b $ is $ b $, and to compare two items in $ b $ is $ c $. we give upper and lower bounds for the case $ a \ le b \ le c $. notice that the case $ b = 1, a = c = \ infty $ is the famous ` ` nuts and bolts ' ' problem. ( 2 ) in the disk - access model ( dam ), where transferring elements between disk and internal memory is the main bottleneck, we consider the scenario where elements in $ b $ are larger than elements in $ a $. the larger items take more i / os to be brought into memory, consume more space in internal memory, and are required in their entirety for comparisons. we first give output - sensitive lower and upper bounds on the batched predecessor problem, and use these to derive bounds on the complexity of sorting in the two models. our bounds are tight in most cases, and require novel generalizations of the classical lower bound techniques in external memory to accommodate the non - uniformity of keys. | arxiv:2004.13197 |
the task of open - vocabulary object - centric image retrieval involves the retrieval of images containing a specified object of interest, delineated by an open - set text query. as working on large image datasets becomes standard, solving this task efficiently has gained significant practical importance. applications include targeted performance analysis of retrieved images using ad - hoc queries and hard example mining during training. recent advancements in contrastive - based open vocabulary systems have yielded remarkable breakthroughs, facilitating large - scale open vocabulary image retrieval. however, these approaches use a single global embedding per image, thereby constraining the system ' s ability to retrieve images containing relatively small object instances. alternatively, incorporating local embeddings from detection pipelines faces scalability challenges, making it unsuitable for retrieval from large databases. in this work, we present a simple yet effective approach to object - centric open - vocabulary image retrieval. our approach aggregates dense embeddings extracted from clip into a compact representation, essentially combining the scalability of image retrieval pipelines with the object identification capabilities of dense detection methods. we show the effectiveness of our scheme to the task by achieving significantly better results than global feature approaches on three datasets, increasing accuracy by up to 15 map points. we further integrate our scheme into a large scale retrieval framework and demonstrate our method ' s advantages in terms of scalability and interpretability. | arxiv:2309.14999 |
an experimental study is presented, about transitions between non - equilibrium steady states ( ness ) in a dissipative medium. the core device is a small rotating blade that imposes cycles of increasing and decreasing forcings to a granular gas, shaken independently. the velocity of this blade is measured, subject to the transitions imposed by the periodic torque variation. the hatano - sasa equality, that generalises the second principle of thermodynamics to ness, is verified with a high accuracy ( a few $ 10 ^ { - 3 } $ ), at different variation rates. besides, it is observed that the fluctuating velocity at fixed forcing follows a generalised gumbel distribution. a rough evaluation of the mean free path in the granular gas suggests that it might be a correlated system, at least partially. | arxiv:1208.4039 |
the weak decay of the kaon to two pions is studied within the njl model. using the standard effective weak hamiltonian, both the decay amplitude arising from an intermediate state \ sigma - meson and the direct decay amplitude are calculated. the effect of final state interactions is also included. when the matching scale is chosen such that the decay amplitude with isospin i = 2 is close to its experimental value, the \ sigma - meson contributes more than 85 % of the total i = 0 amplitude. this supports recent suggestions that the \ sigma - meson should play a vital role in explaining the \ delta i = 1 / 2 rule in this system. | arxiv:1409.2639 |
in a previous work [ j. chem. phys. 155, 244111 ( 2021 ) ], we found counterexamples to the fundamental hohenberg - kohn theorem from density - functional theory in finite - lattice systems represented by graphs. here, we demonstrate that this only occurs at very peculiar and rare densities, those where density sets arising from degenerate ground states, called degeneracy regions, touch each other or the boundary of the whole density domain. degeneracy regions are shown to generally be in the shape of the convex hull of an algebraic variety, even in the continuum setting. the geometry arising between density regions and the potentials that create them is analyzed and explained with examples that, among other shapes, feature the roman surface. | arxiv:2206.12366 |
skew polynomials are a class of non - commutative polynomials that have several applications in computer science, coding theory and cryptography. in particular, skew polynomials can be used to construct and decode evaluation codes in several metrics, like e. g. the hamming, rank, sum - rank and skew metric. we propose a fast divide - and - conquer variant of k \ " otter - nielsen - h { \ o } holdt ( knh ) interpolation algorithm : it inputs a list of linear functionals on skew polynomial vectors, and outputs a reduced gr \ " obner basis of their kernel intersection. we show, that the proposed knh interpolation can be used to solve the interpolation step of interpolation - based decoding of interleaved gabidulin codes in the rank - metric, linearized reed - solomon codes in the sum - rank metric and skew reed - solomon codes in the skew metric requiring at most $ \ tilde { o } ( s ^ { \ omega } m ( n ) ) $ operations in $ \ mathbb { f } _ { q ^ m } $, where $ n $ is the length of the code, $ s $ the interleaving order, $ m ( n ) $ the complexity for multiplying two skew polynomials of degree at most $ n $, $ { \ omega } $ the matrix multiplication exponent and $ \ tilde { o } ( \ cdot ) $ the soft - o notation which neglects log factors. this matches the previous best speeds for these tasks, which were obtained by top - down minimal approximant bases techniques, and complements the theory of efficient interpolation over free skew polynomial modules by the bottom - up knh approach. in contrast to the top - down approach the bottom - up knh algorithm has no requirements on the interpolation points and thus does not require any pre - processing. | arxiv:2207.01319 |
the renormalization paradigm for low - dimensional dynamical systems is that of hyperbolic horseshoe dynamics. does this paradigm survive a transition to more physically relevant systems in higher dimensions? this article addresses this question in the context of lorenz dynamics which originates in homoclinic bifurcations of flows in three dimensions and higher. a conjecture classifying the dynamics of the lorenz renormalization operator is stated and supported with numerical evidence. | arxiv:1805.01226 |
we characterize the vertices belonging to all minimum dominating sets, to some minimum dominating sets but not all, and to no minimum dominating set. we refine this characterization for some well studied sub - classes of graphs : chordal, claw - free, triangle - free. also we exhibit some graphs answering to some open questions of the literature on minimum dominating sets. | arxiv:1909.02843 |
functional relations are proposed for transfer matrices of solvable vertex models associated with the twisted quantum affine algebras $ u _ q ( x ^ { ( \ kappa ) } _ n ) $ where $ x ^ { ( \ kappa ) } _ n = a ^ { ( 2 ) } _ n, d ^ { ( 2 ) } _ n, e ^ { ( 2 ) } _ 6 $ and $ d ^ { ( 3 ) } _ 4 $. their solutions are obtained for $ a ^ { ( 2 ) } _ n $ and conjectured for $ d ^ { ( 3 ) } _ 4 $ in the dressed vacuum form in the analytic bethe ansatz. | arxiv:hep-th/9408135 |
for source sequences of length l symbols we proposed to use a more realistic value to the usual benchmark of number of code letters by source letters. our idea is based on a quantifier of information fluctuation of a source, f ( u ), which corresponds to the second central moment of the random variable that measures the information content of a source symbol. an alternative interpretation of typical sequences is additionally provided through this approach. | arxiv:1807.02603 |
we study the propagation of light in a three - dimensional double - periodic ag / tio2 multilayer metamaterial composed of coupled plasmonic waveguides operating in the visible and uv spectral range. for these frequencies, light propagation in the plane of the waveguides is described by a negative phase velocity, while for the orthogonal direction light propagation is described by a bloch wave composed of a large number of harmonics. as a result, the material cannot generally be described by a single phase index : decomposing the bloch wave into different harmonics we show that for the wavelength range of interest the positive index m = 1 harmonic dominates the propagation of light in the orthogonal direction. these results are corroborated by numerical simulations and optical refraction experiments on a double - periodic ag / tio2 multilayer metamaterial prism in the 380 - 600 nm spectral range, which show that positive refraction associated with right - handed harmonics dominates. studying the isofrequency contours we find that despite the occurrence of multiple harmonics the double - periodic structure can act as a flat lens : for a slab consisting of an integer number of unit cells all harmonics are degenerate and constructively interfere at the image plane. this work identifies important considerations relevant to the design of many three dimensional periodic metamaterials. | arxiv:1404.4707 |
in this paper we consider the influence of collisional fluctuations on the mollow spectra of resonance fluorescence ( rf ). the fluctuations are taken into account by a simple shift of the constant detuning, involved in a set of optical bloch equations by collision frequency noise which is modelled by a two - step random telegraph signal ( rts ). we consider in detail the mollow spectra for rf in the case of an arbitrary detuning of the laser frequency, where the emitter is a member of a statistical ensemble in thermodynamic equilibrium with the buffer gas at temperature $ t $ which is treated as a colored environment, and velocity $ v $ is distributed with the maxwell - boltzmann density. | arxiv:1312.0112 |
satellite imagery is widely used in many application sectors, including agriculture, navigation, and urban planning. frequently, satellite imagery involves both large numbers of images as well as high pixel counts, making satellite datasets computationally expensive to analyze. recent approaches to satellite image analysis have largely emphasized deep learning methods. though extremely powerful, deep learning has some drawbacks, including the requirement of specialized computing hardware and a high reliance on training data. when dealing with large satellite datasets, the cost of both computational resources and training data annotation may be prohibitive. | arxiv:2105.12633 |
this article discusses two versions of elliptic equations obtained from a system of equations describing a rational cuboid. analysis of elliptic equations shows that they are equivalent, and that there are rational points on the elliptic curves, but they do not belong to any right triangle with rational sides. | arxiv:2311.11949 |
human motion synthesis and editing are essential to many applications like film post - production. however, they often introduce artefacts in motions, which can be detrimental to the perceived realism. in particular, footskating is a frequent and disturbing artefact requiring foot contacts knowledge to be cleaned up. current approaches to obtain foot contact labels rely either on unreliable threshold - based heuristics or on tedious manual annotation. in this article, we address foot contact label detection from motion with a deep learning. to this end, we first publicly release underpressure, a novel motion capture database labelled with pressure insoles data serving as reliable knowledge of foot contact with the ground. then, we design and train a deep neural network to estimate ground reaction forces exerted on the feet from motion data and then derive accurate foot contact labels. the evaluation of our model shows that we significantly outperform heuristic approaches based on height and velocity thresholds and that our approach is much more robust on motion sequences suffering from perturbations like noise or footskate. we further propose a fully automatic workflow for footskate cleanup : foot contact labels are first derived from estimated ground reaction forces. then, footskate is removed by solving foot constraints through an optimisation - based inverse kinematics ( ik ) approach that ensures consistency with the estimated ground reaction forces. beyond footskate cleanup, both the database and the method we propose could help to improve many approaches based on foot contact labels or ground reaction forces, including inverse dynamics problems like motion reconstruction and learning of deep motion models in motion synthesis or character animation. our implementation, pre - trained model as well as links to database can be found at https : / / github. com / interdigitalinc / underpressure. | arxiv:2208.04598 |
noise contrastive estimation ( nce ) is a powerful parameter estimation method for log - linear models, which avoids calculation of the partition function or its derivatives at each training step, a computationally demanding step in many cases. it is closely related to negative sampling methods, now widely used in nlp. this paper considers nce - based estimation of conditional models. conditional models are frequently encountered in practice ; however there has not been a rigorous theoretical analysis of nce in this setting, and we will argue there are subtle but important questions when generalizing nce to the conditional case. in particular, we analyze two variants of nce for conditional models : one based on a classification objective, the other based on a ranking objective. we show that the ranking - based variant of nce gives consistent parameter estimates under weaker assumptions than the classification - based method ; we analyze the statistical efficiency of the ranking - based and classification - based variants of nce ; finally we describe experiments on synthetic data and language modeling showing the effectiveness and trade - offs of both methods. | arxiv:1809.01812 |
a wireless vapor sensor based upon the quantum capacitance effect in graphene is demonstrated. the sensor consists of a metal - oxide - graphene variable capacitor ( varactor ) coupled to an inductor, creating a resonant oscillator circuit. the resonant frequency is found to shift in proportion to water vapor concentration for relative humidity ( rh ) values ranging from 1 % to 97 % with a linear frequency shift of 5. 7 + - 0. 3 khz / rh %. the capacitance values extracted from the wireless measurements agree with those determined from capacitance - voltage measurements, providing strong evidence that the sensing arises from the variable quantum capacitance in graphene. these results represent a new sensor transduction mechanism and pave the way for graphene quantum capacitance sensors to be studied for a wide range of chemical and biological sensing applications. | arxiv:1306.6940 |
strong light - matter interactions as realized in an optical cavity provide a tantalizing opportunity to control the properties of condensed matter systems. inspired by experimental advances in cavity quantum electrodynamics and the fabrication and control of two - dimensional magnets, we investigate the fate of a quantum critical antiferromagnet coupled to an optical cavity field. using unbiased quantum monte carlo simulations, we compute the scaling behavior of the magnetic structure factor and other observables. while the position and universality class are not changed by a single cavity mode, the critical fluctuations themselves obtain a sizable enhancement, scaling with a fractional exponent that defies expectations based on simple perturbation theory. the scaling exponent can be understood using a generic scaling argument, based on which we predict that the effect may be even stronger in other universality classes. our microscopic model is based on realistic parameters for two - dimensional magnetic quantum materials and the effect may be within the range of experimental detection. | arxiv:2302.08528 |
we present the derivation of the hydrodynamic limit under eulerian scaling for a general class of one - dimensional interacting particle systems with two or more conservation laws. following yau ' s relative entropy method it turns out that in case of more than one conservation laws, in order that the system exhibit hydrodynamic behaviour, some particular identities reminiscent of onsager ' s reciprocity relations must hold. we check validity of these identities for a wide class of models. it also follows that, as a general rule, the equilibrium thermodynamic entropy ( as function of the densities of the conserved variables ) is a globally convex lax entropy of the hyperbolic systems of conservation laws arising as hydrodynamic limit. the onsager relations arising in this context and its consequences seem to be novel. as concrete examples we also present a number of models modeling deposition ( or domain growth ) phenomena. | arxiv:math/0210426 |
spatio - temporal feature learning is of central importance for action recognition in videos. existing deep neural network models either learn spatial and temporal features independently ( c2d ) or jointly with unconstrained parameters ( c3d ). in this paper, we propose a novel neural operation which encodes spatio - temporal features collaboratively by imposing a weight - sharing constraint on the learnable parameters. in particular, we perform 2d convolution along three orthogonal views of volumetric video data, which learns spatial appearance and temporal motion cues respectively. by sharing the convolution kernels of different views, spatial and temporal features are collaboratively learned and thus benefit from each other. the complementary features are subsequently fused by a weighted summation whose coefficients are learned end - to - end. our approach achieves state - of - the - art performance on large - scale benchmarks and won the 1st place in the moments in time challenge 2018. moreover, based on the learned coefficients of different views, we are able to quantify the contributions of spatial and temporal features. this analysis sheds light on interpretability of the model and may also guide the future design of algorithm for video recognition. | arxiv:1903.01197 |
molecular beam epitaxy of ge ( 111 ) thin films on epitaxial - gd2o3 / si ( 111 ) substrates is reported, along with a systematic investigation of the evolution of ge growth, and structural defects in the grown epilayer. while ge growth begins in the volmer - weber growth mode, the resultant islands coalesce within the first 10 nm of growth, beyond which a smooth two - dimensional surface evolves. coalescence of the initially formed islands results in formation of rotation and reflection microtwins, which constitute a volume fraction of less than 1 %. it is also observed that while the stacking sequence of the ( 111 ) planes in the ge epilayer is similar to that of the si substrate, the ( 111 ) planes of the gd2o3 epilayer are rotated by 180 degree about the [ 111 ] direction. in metal - semiconductor - metal schottky photodiodes fabricated with these all - epitaxial ge - on - insulator ( geoi ) samples, significant suppression of dark current is observed due to the presence of the gd2o3 epilayer. these results are promising for application of these geoi structures as virtual substrates, or for realization of high - speed group - iv photonic components. | arxiv:1801.02462 |
we determine the automorphism groups of koras - russell threefolds of the second kind. in particular we show that these groups are semi - direct products of two subgroups, one given by the multiplicative group and the other isomorphic to a polynomial ring in two variables with the addition law. we also show that these groups are generated by algebraic subgroups isomorphic to gm and ga. | arxiv:1507.06087 |
this article presents counter examples for three articles claiming that p = np. articles for which it applies are : moustapha diaby " p = np : linear programming formulation of the traveling salesman problem " and " equality of complexity classes p and np : linear programming formulation of the quadratic assignment problem ", and also sergey gubin " a polynomial time algorithm for the traveling salesman problem " | arxiv:cs/0610125 |
##s cut. rojas accused a neighbour, but despite brutal interrogation, this neighbour would not confess to the crimes. inspector alvarez, a colleague of vucetich, went to the scene and found a bloody thumb mark on a door. when it was compared with rojas ' prints, it was found to be identical with her right thumb. she then confessed to the murder of her sons. a fingerprint bureau was established in calcutta ( kolkata ), india, in 1897, after the council of the governor general approved a committee report that fingerprints should be used for the classification of criminal records. working in the calcutta anthropometric bureau, before it became the fingerprint bureau, were azizul haque and hem chandra bose. haque and bose were indian fingerprint experts who have been credited with the primary development of a fingerprint classification system eventually named after their supervisor, sir edward richard henry. the henry classification system, co - devised by haque and bose, was accepted in england and wales when the first united kingdom fingerprint bureau was founded in scotland yard, the metropolitan police headquarters, london, in 1901. sir edward richard henry subsequently achieved improvements in dactyloscopy. in the united states, henry p. deforrest used fingerprinting in the new york civil service in 1902, and by december 1905, new york city police department deputy commissioner joseph a. faurot, an expert in the bertillon system and a fingerprint advocate at police headquarters, introduced the fingerprinting of criminals to the united states. = = = uhlenhuth test = = = the uhlenhuth test, or the antigen – antibody precipitin test for species, was invented by paul uhlenhuth in 1901 and could distinguish human blood from animal blood, based on the discovery that the blood of different species had one or more characteristic proteins. the test represented a major breakthrough and came to have tremendous importance in forensic science. the test was further refined for forensic use by the swiss chemist maurice muller in the year 1960s. = = = dna = = = forensic dna analysis was first used in 1984. it was developed by sir alec jeffreys, who realized that variation in the genetic sequence could be used to identify individuals and to tell individuals apart from one another. the first application of dna profiles was used by jeffreys in a double murder mystery in the small english town of narborough, leicestershire, in 1985. a 15 - year - old school girl by the name of lynda mann was raped and murdered | https://en.wikipedia.org/wiki/Forensic_science |
we present local structural evidence for the existence of charge inhomogeneities at low temperature in underdoped and optimally doped la _ 2 - xsr _ xcuo _ 4. the inhomogeneities disappear for x > 0. 2. the evidence for the charge inhomogeneities comes from an anomalous increase in the in - plane cu - o bond length distribution in the underdoped samples as well as evidence for cuo _ 6 octahedral tilt inhomogeneities in the intermediate range structure. preliminary analysis of the temperature dependence of this phenomenon indicates that the inhomogeneities set in at temperatures in the range 60 k < tco < 130 k which depends on doping. | arxiv:cond-mat/0005032 |
the 50 \, kton \, ino - ical is a proposed underground high energy physics experiment at theni, india ( $ 9 ^ { \ circ } 57 ' n $, $ 77 ^ { \ circ } 16 ' e $ ) to study the neutrino oscillation parameters using atmospheric neutrinos. the resistive plate chamber ( rpc ) has been chosen as the active detector element for the ical detector. an experimental setup consisting of 12 layers of glass rpcs of size 2 \, m \, $ \ times $ \, 2 \, m has been built at iichep, madurai to study the long term stability and performance of rpcs which are produced on a large scale in indian industry. in this paper, the studies on the performance of rpcs are presented along with the angular distribution of muons at madurai ( $ 9 ^ { \ circ } 56 ' n, 78 ^ { \ circ } 00 ' e $ and altitude $ \ approx $ \, 160 \, m from sea level ). | arxiv:1706.00901 |
liquid drops adhere to solid surfaces due to surface tension but can depin and run back along the surface due to wind or gravity forcing. this work develops a simple mechanistic model for depinning by combined gravity and high - reynolds - number wind forcing and tests that model using water drops on a roughened aluminum surface. on non - inclined surfaces, drops depin at a constant critical weber number, $ w \! e _ { \ mathrm { crit } } = 7. 9 $, for the present wettability conditions. on inclined surfaces, $ w \! e _ { \ mathrm { crit } } $ decreases linearly with the product of the bond number and the width - to - height aspect ratio of the unforced drop. the linear slope is different in distinct wind - and gravity - dominated forcing regimes above and below $ w \! e _ { \ mathrm { crit } } = 4 $. contact line shapes and drop profile shapes are measured at depinning conditions but do not adequately explain the differences between the two forcing regimes. | arxiv:2009.04059 |
( abridged ) we present an analysis of a 10 - day continuous asca observation of the narrow - line seyfert 1 galaxy iras 13224 - 3809. the soft ( 0. 7 - 1. 3 kev ) and hard ( 1. 3 - 10 kev ) x - ray band light curves binned to 5000s reveal trough - to - peak variations by a factor > 25 and 20, respectively. the light curves in the soft and hard bands are strongly correlated without any significant delay. however, this correlation is not entirely due to changes in the power - law flux alone but also due to changes in the soft x - ray hump emission above the power law. the presence of a soft x - ray hump below 2 kev, previously detected in rosat and asca data, is confirmed. time resolved spectroscopy using daily sampling reveals changes in the power - law slope, with gamma in the range 1. 74 - 2. 47, however, day - to - day variations in gamma are not significant. the soft hump emission is found to dominate the observed variability on a timescale of a week, but on shorter timescales ( 20000s ) the power - law component appears to dominate the observed variability. flux resolved spectroscopy reveals that at high flux levels the power law becomes steeper and the soft hump more pronounced. the steepening of the photon index with the fluxes in the soft and hard bands can be understood in the framework of disk / corona models in which accretion disk is heated by viscous dissipation as well as by reprocessing of hard x - rays following an x - ray flare resulting from coronal dissipation through magnetic reconnection events. | arxiv:astro-ph/0205114 |
a set of coupled time - dependent ginzburg - landau equations ( tdgl ) for superconductors of mixed d - and s - wave symmetry are derived microscopically from the gor ' kov equations by using the analytical continuation technique. the scattering effects due to impurities with both nonmagnetic and magnetic interactions are considered. we find that the d - and s - wave components of the order parameter can have very different relaxation times in the presence of nonmagnetic impurities. this result is contrary to a set of phenomenologically proposed tdgl equations and thus may lead to new physics in the dynamics of flux motion. | arxiv:cond-mat/9810206 |
in this article we explicitely construct transformation bewteen separable and flat coordinates for flat st \ " ackel systems and exploit the structre of these systems in flat coordinates. in the elliptic case these coordinates become well known generalized elliptical coordinates of jacobi. | arxiv:1406.2117 |
the rapid expansion of connected and autonomous vehicles ( cavs ) and the shift towards millimiter - wave ( mmwave ) frequencies offer unprecedented opportunities to enhance road safety and traffic efficiency. sidelink communication, enabling direct vehicle - to - vehicle ( v2v ) communications, play a pivotal role in this transformation. as communication technologies transit to higher frequencies, the associated increase in bandwidth comes at the cost of a severe path and penetration loss. in response to these challenges, we investigate a network configuration that deploys beamforming - capable unmanned aerial vehicles ( uavs ) as relay nodes. in this work, we present a comprehensive analytical framework with a groundbreaking performance metric, i. e. average access probability, that quantifies user satisfaction, considering factors across different protocol stack layers. additionally, we introduce two radio resources assignment ( rra ) methods tailored for uavs. these methods consider parameters such as resource availability, vehicle distribution, and latency requirements. through our analytical approach, we optimize the average access probability by controlling uav altitude based on traffic density. our numerical findings validate the proposed model and strategy, which ensures that quality of service ( qos ) standards are met in the domain of vehicle - to - anything ( v2x ) sidelink communications. | arxiv:2403.12059 |
the skew mean curvature flow ( smcf ) is a schr \ " odinger - type geometric flow canonically defined on a co - dimension two submanifold, which generalizes the famous vortex filament equation in fluid dynamics. in this paper, we prove the local existence and uniqueness of general dimensional smcf in euclidean spaces. | arxiv:1904.03822 |
recent advances in machine learning ( ml ) have expedited materials discovery and design. one significant challenge faced in ml for materials is the expansive combinatorial space of potential materials formed by diverse constituents and their flexible configurations. this complexity is particularly evident in molecular mixtures, a frequently explored space for materials such as battery electrolytes. owing to the complex structures of molecules and the sequence - independent nature of mixtures, conventional ml methods have difficulties in modeling such systems. here we present molsets, a specialized ml model for molecular mixtures. representing individual molecules as graphs and their mixture as a set, molsets leverages a graph neural network and the deep sets architecture to extract information at the molecule level and aggregate it at the mixture level, thus addressing local complexity while retaining global flexibility. we demonstrate the efficacy of molsets in predicting the conductivity of lithium battery electrolytes and highlight its benefits in virtual screening of the combinatorial chemical space. | arxiv:2312.16473 |
imaging the structure of major fault zones is essential for our understanding of crustal deformations and their implications on seismic hazards. investigating such complex regions presents several issues, including the variation of seismic velocity due to the diversity of geological units and the cumulative damage caused by earthquakes. conventional migration techniques are in general strongly sensitive to the available velocity model. here we apply a passive matrix imaging approach which is robust to the mismatch between this model and the real seismic velocity distribution. this method relies on the cross - correlation of ambient noise recorded by a geophone array. the resulting set of impulse responses form a reflection matrix that contains all the information about the subsurface. in particular, the reflected body waves can be leveraged to : ( i ) determine the transmission matrix between the earth ' s surface and any point in the subsurface ; ( ii ) build a confocal image of the subsurface reflectivity with a transverse resolution only limited by diffraction. as a study case, we consider seismic noise ( 0. 1 - 0. 5 hz ) recorded by the dense array for northern anatolia ( dana ) that consists of 73 stations deployed for 18 months in the region of the 1999 izmit earthquake. passive matrix imaging reveals the scattering structure of the crust and upper mantle around the nafz over a depth range of 60 km. the results show that most of the scattering is associated with the northern branch that passes throughout the crust and penetrates into the upper mantle. | arxiv:2303.06123 |
the variational autoencoder ( vae ) is a powerful generative model that can estimate the probability of a data point by using latent variables. in the vae, the posterior of the latent variable given the data point is regularized by the prior of the latent variable using kullback leibler ( kl ) divergence. although the standard gaussian distribution is usually used for the prior, this simple prior incurs over - regularization. as a sophisticated prior, the aggregated posterior has been introduced, which is the expectation of the posterior over the data distribution. this prior is optimal for the vae in terms of maximizing the training objective function. however, kl divergence with the aggregated posterior cannot be calculated in a closed form, which prevents us from using this optimal prior. with the proposed method, we introduce the density ratio trick to estimate this kl divergence without modeling the aggregated posterior explicitly. since the density ratio trick does not work well in high dimensions, we rewrite this kl divergence that contains the high - dimensional density ratio into the sum of the analytically calculable term and the low - dimensional density ratio term, to which the density ratio trick is applied. experiments on various datasets show that the vae with this implicit optimal prior achieves high density estimation performance. | arxiv:1809.05284 |
economic model predictive control ( mpc ) dissipativity theory is central to discussing the stability of policies resulting from minimizing economic stage costs. in its current form, the dissipativity theory for economic mpc applies to problems based on deterministic dynamics or to very specific classes of stochastic problems, and does not readily extend to generic markov decision processes. in this paper, we clarify the core reason for this difficulty, and propose a generalization of the economic mpc dissipativity theory that circumvents it. this generalization focuses on undiscounted infinite - horizon problems and is based on nonlinear stage cost functionals, allowing one to discuss the lyapunov asymptotic stability of policies for markov decision processes in terms of the probability measures underlying their stochastic dynamics. this theory is illustrated for the stochastic linear quadratic regulator with gaussian process noise, for which a storage functional can be provided explicitly. for the sake of brevity, we limit our discussion to undiscounted markov decision processes. | arxiv:2104.10997 |
in this paper we present a novel broadband approach for the extraction of dispersion curves of multiple time frequency overlapped dispersive modes such as in borehole acoustic data. the new approach works jointly in the fourier and space time domains and, in contrast to existing space time approaches that mainly work for time frequency separated signals, efficiently handles multiple signals with significant time frequency overlap. the proposed method begins by exploiting the slowness ( phase and group ) and time location estimates based on frequency - wavenumber ( f - k ) domain sparsity penalized broadband dispersion extraction method as presented in \ cite { aerontsp2011 }. in this context we first present a cramer rao bound ( crb ) analysis for slowness estimation in the ( f - k ) domain and show that for the f - k domain broadband processing, group slowness estimates have more variance than the phase slowness estimates and time location estimates. in order to improve the group slowness estimates we exploit the time compactness property of the modes to effectively represent the data as a linear superposition of time compact space time propagators parameterized by the phase and group slowness. a linear least squares estimation algorithm in the space time domain is then used to obtain improved group slowness estimates. the performance of the method is demonstrated on real borehole acoustic data sets. | arxiv:1312.3981 |
synthetic samples from diffusion models are promising for leveraging in training discriminative models as replications of real training datasets. however, we found that the synthetic datasets degrade classification performance over real datasets even when using state - of - the - art diffusion models. this means that modern diffusion models do not perfectly represent the data distribution for the purpose of replicating datasets for training discriminative tasks. this paper investigates the gap between synthetic and real samples by analyzing the synthetic samples reconstructed from real samples through the diffusion and reverse process. by varying the time steps starting the reverse process in the reconstruction, we can control the trade - off between the information in the original real data and the information added by diffusion models. through assessing the reconstructed samples and trained models, we found that the synthetic data are concentrated in modes of the training data distribution as the reverse step increases, and thus, they are difficult to cover the outer edges of the distribution. our findings imply that modern diffusion models are insufficient to replicate training data distribution perfectly, and there is room for the improvement of generative modeling in the replication of training datasets. | arxiv:2311.13090 |
the phase space of quantum mechanics can be viewed as the complex projective space endowed with a kaehlerian structure given by the fubini - study metric and an associated symplectic form. we can then interpret the schrodinger equation as generating a hamiltonian dynamics. based upon the geometric structure of the quantum phase space we introduce the corresponding natural microcanonical and canonical ensembles. the resulting density matrix for the canonical ensemble differs from density matrix of the conventional approach. as an illustration, the results are applied to the case of a spin one - half particle in a heat bath with an applied magnetic field. | arxiv:quant-ph/9709048 |
one of the fundamental questions about quasars is related to their central supermassive black holes. the reason for the existence of these black holes with such a huge mass is still unclear and various models have been proposed to explain them. however, there is still no comprehensive explanation that is accepted by the community. the only thing we are sure of is that these black holes were not created by the collapse of giant stars, nor by the accretion of matter around them. moreover, another important question is the mass distribution of these black holes over time. observations have shown that if we go back through redshift, we see black holes with more masses, and after passing the peak of star formation redshift, this procedure decreases. nevertheless, the exact redshift of this peak is still controversial. in this paper, with the help of deep learning and the lstm algorithm, we tried to find a suitable model for the mass of central black holes of quasars over time by considering quasarnet data. our model was built with these data reported from redshift 3 to 7 and for two redshift intervals 0 to 3 and 7 to 10, it predicted the mass of the quasar ' s central supermassive black holes. we have also tested our model for the specified intervals with observed data from central black holes and discussed the results. | arxiv:2301.01459 |
sensing and manipulating targets hidden under scattering media are universal problems that take place in applications ranging from deep - tissue optical imaging to laser surgery. a major issue in these applications is the shallow light penetration caused by multiple scattering that reflects most of incident light. although advances have been made to eliminate image distortion by a scattering medium, dealing with the light reflection has remained unchallenged. here we present a method to minimize reflected intensity by finding and coupling light into the anti - reflection modes of a scattering medium. in doing so, we achieved more than a factor of 3 increase in light penetration. our method of controlling reflected waves makes it readily applicable to in vivo applications in which detector sensors can only be positioned at the same side of illumination and will therefore lay the foundation of advancing the working depth of many existing optical imaging and treatment technologies. | arxiv:1308.6553 |
we report the analysis of time - series of infrared $ jhk _ s $ photometry of the dwarf nova v2051 oph in quiescence. we modelled the ellipsoidal variations caused by the distorted mass - donor star to infer its $ jhk _ s $ fluxes. from its infrared colors we estimate a spectral type of $ m ( 8. 0 \ pm 1. 5 ) $ and an equivalent blackbody temperature of $ t _ \ mathrm { bb } = ( 2700 \ pm270 ) \, k $. we used the barnes & evans relation to infer a photometric parallax distance of $ d _ \ mathrm { be } = ( 102 \ pm16 ) $ pc to the binary. at this short distance, the corresponding accretion disc temperatures in outburst are too low to be explained by the disc - instability model for dwarf nova outbursts, underscoring a previous suggestion that the outbursts of this binary are powered by mass - transfer bursts. | arxiv:1801.01478 |
chemistry in titan ' s n2 - ch4 atmosphere produces complex organic aerosols. the chemical processes and the resulting organic compounds are still far from understood, although extensive observations, laboratory, and theoretical simulations have greatly improved physical and chemical constraints on titan ' s atmosphere. here, we conduct a series of titan atmosphere simulation experiments with n2 - ch4 gas mixtures and investigate the effect of initial ch4 ratio, pressure, and flow rate on the production rates and composition of the gas and solid products at a titan relevant temperature ( 100 k ) for the first time. we find that the production rate of the gas and solid products increases with increasing ch4 ratio. the nitrogen - containing species have much higher yield than hydrocarbons in the gas products, and the n - to - c ratio of the solid products appears to be the highest compared to previous plasma simulations with the same ch4 ratio. the greater degree of nitrogen incorporation in the low temperature simulation experiments suggests temperature may play an important role in nitrogen incorporation in titan ' s cold atmosphere. we also find that h2 is the dominant gas product and serves as an indicator of the production rate of new organic molecules in the experiment, and that ch2nh may greatly contribute to the incorporation of both carbon and nitrogen into the solid particles. the pressure and flow rate affect the amount of time of the gas mixture exposed to the energy source and therefore impact the n2 - ch4 chemistry initiated by the plasma discharge, emphasizing the influence of the energy flux in titan atmospheric chemistry. | arxiv:2209.11264 |
superconductor / ferromagnet / superconductor josephson junctions with anomalous phase shift $ \ varphi _ 0 $ ( $ \ varphi _ 0 $ - s / f / s jjs ) implement a coupling between the superconducting phase and the spin degrees of freedom. here we investigate the dynamics of voltage - biased coupled chains of $ \ varphi _ 0 $ - s / f / s jjs and predict that the presence of $ \ varphi _ 0 $ makes the conventional regime corresponding to the linear growth of the superconducting phase at each of the junctions and oscillating josephson current unstable. new stable regimes are found and investigated. the changes of the dynamic behavior are clearly seen in the iv - characteristics of the system and can serve as a fingerprint of the presence of the magnetoelectric coupling $ \ varphi _ 0 $. moreover, the collective magnetic excitations of the chains of $ \ varphi _ 0 $ - s / f / s jjs, which were reported by g. a. bobkov { \ it et. al. } [ jetp lett. { \ bf 119 }, 251 ( 2024 ) ] also manifest themselves in the iv - characteristics. this provides a method for their experimental detection and direct measurement of the constant quantifying the strength of the coupling between the superconducting phase and the spin degrees of freedom. | arxiv:2406.01207 |
a key pre - distribution scheme ( kps ) based on multiple codewords of block codes is presented for wireless sensor networks. the connectivity and security of the proposed kps, quantified in terms of probabilities of sharing common keys for communications of pairs of nodes and their resilience against colluding nodes, are analytically assessed. the analysis is applicable to both linear and nonlinear codes and is simplified in the case of maximum distance separable codes. it is shown that the multiplicity of codes significantly enhances the security and connectivity of kps at the cost of a modest increase of the nodes storage. numerical and simulation results are provided, which sheds light on the effect of system parameters of the proposed kps on its complexity and performance. specifically, it is shown that the probability of resilience of secure pairs against collusion of other nodes only reduces slowly as the number of colluding nodes increase. | arxiv:1407.7011 |
( abridged ) a new method is presented to identify transient candidates in large - scale surveys based on the variability pattern in their light curves. the method is based on the abbe value, that estimates the smoothness of a light curve, and on a newly introduced value called the excess abbe that estimates the regularity of the light curve variability pattern over the duration of the observations. based on simulated light curves, transients are shown to occupy a specific region in the abbe versus excess abbe diagram, distinct from sources presenting pulsating - like features in their light curves or having featureless light curves. the method is tested on real light curves taken from eros - 2 and ogle - ii surveys in a 0. 50deg x 0. 17deg field of the sky in the lmc. the method identifies 43 eros - 2 transient candidates out of a total of ~ 1300 variable stars, and 19 more ogle - ii candidates. the efficiency of the method is further tested by comparing the list of transient candidates with known be stars in the literature. it is shown that all be stars known in the studied field of view with detectable bursts or outbursts are successfully extracted by the method. in addition, four new transient candidates displaying bursts and / or outbursts are found in the field, of which at least two are good new be candidates. the new method proves to be a potentially powerful tool to extract transient candidates from large - scale multi - epoch surveys. the better the photometric measurement uncertainties are, the cleaner the list of detected transient candidates is. in addition, the diagram is shown to be a good diagnostic tool to check the data quality of multi - epoch photometric surveys. a trend of instrumental and / or data reduction origin, for example, will manifest itself by an unexpected distribution of points in the diagram. | arxiv:1406.7785 |
asymmetric dark matter under certain conditions could form compact star - like objects, which can be searched either through gravitational lensing or by observation of gravitational waves from binaries involving such compact objects. in this paper we analyze possible signatures of such dark stars made of asymmetric dark matter with a portal to the standard model. we argue that compact dark stars could capture protons and electrons from the interstellar medium, which then accumulate in the core of the dark star, forming a very hot gas that emits x - rays or $ \ gamma $ - rays. for dark matter parameters compatible with current laboratory constraints, compact dark stars could be sufficiently luminous to be detected at the earth as point sources in the x - ray or $ \ gamma $ - ray sky. | arxiv:2211.05845 |
this thesis presents the evidence, at 3. 08 sigma, for the associate production of massive vector bosons ( w and z ) in a final state with one lepton, met and hf - tagged jets, measured with the complete cdf ii dataset ( 9. 4fb ^ - 1 of data ). the signals, both inclusive diboson production and ww vs wz / zz separately, were extracted from the invariant mass distribution, m _ inv ( jet1, jet2 ), of single and double hf - tagged jet pairs. for single - tagged events the b quark vs c quark discrimination was obtained by using a bi - dimensional distribution m _ inv ( jet1, jet2 ) vs a flavor - serapator nn. the results, consistent with the sm prediction, confirm the cdf capability of identify a small signal in this challenging final state. in particular we also report the previous version of this analysis, performed with a dataset of 7. 5fb ^ - 1 that was the first evidence of diboson production in lnu + hf final state at a hadron collider. beyond the pure testing of sm predicted processes, several of the techniques developed for this thesis were also applied to the wh search at cdf, with a relevant improvement of the sensitivity to this process. | arxiv:1302.0389 |
we study products of functions evaluated at self - adjoint polynomials in deterministic matrices and independent wigner matrices ; we compute the deterministic approximations of such products and control the fluctuations. we focus on minimizing the assumption of smoothness on those functions while optimizing the error term with respect to $ n $, the size of the matrices. as an application, we build on the idea that the long - time heisenberg evolution associated to wigner matrices generates asymptotic freeness as first shown in $ [ 9 ] $. more precisely given $ p $ a self - adjoint non - commutative polynomial and $ y ^ n $ a $ d $ - tuple of independent wigner matrices, we prove that the quantum evolution associated to the operator $ p ( y ^ n ) $ yields asymptotic freeness for large times. | arxiv:2208.02118 |
in this paper we show how the relaxation techniques can be used to establish the existence of an optimal contract in presence of information asymmetry. the method we illustrate was initially motivated by the problem of designing optimal brokerage fees, but it does apply to other optimal contract problems, in which ( i ) the agent controls linearly the drift of a diffusion process, ( ii ) the direct dependence of the principal ' s and the agent ' s objectives on the strategy of the agent is of a special form, and ( iii ) the space of admissible contracts is compact. this method is then applied to establish existence of an optimal brokerage fee in a market model with a private trading signal observed by the broker ' s client but not by the broker. | arxiv:2307.07010 |
we study the su ( 3 ) extension of the skyrme model with vector mesons in the collective quantization scheme. the parameters of the model are fixed in its mesonic sector. fields which are excited by the collective rotation of the classical soliton are determined by a variational method. the resulting collective hamiltonian which includes various symmetry breaking terms is diagonalized exactly. this yields reasonable predictions for the mass differences of the low - lying baryons. we furthermore investigate static properties of these baryons in this model by evaluating all relevant matrix elements using the exact eigenstates of the collective hamiltonian. electromagnetic observables are found to approximately obey the predictions obtained from su ( 3 ) symmetry. strong deviations from su ( 3 ) symmetry are, however, found for the matrix elements of strange vector and scalar operators indicating a small amount of strangeness in the proton. the exploration of axial currents shows that the results of the emc experiment may be explained with a small polarization of the strange sea of the proton without violating the successful cabibbo model for semileptonic hyperon decays. | arxiv:hep-ph/9211259 |
merging mobile edge computing ( mec ), which is an emerging paradigm to meet the increasing computation demands from mobile devices, with the dense deployment of base stations ( bss ), is foreseen as a key step towards the next generation mobile networks. however, new challenges arise for designing energy efficient networks since radio access resources and computing resources of bss have to be jointly managed, and yet they are complexly coupled with traffic in both spatial and temporal domains. in this paper, we address the challenge of incorporating mec into dense cellular networks, and propose an efficient online algorithm, called engine ( energy constrained offloading and sleeping ) which makes joint computation offloading and bs sleeping decisions in order to maximize the quality of service while keeping the energy consumption low. our algorithm leverages lyapunov optimization technique, works online and achieves a close - to - optimal performance without using future information. our simulation results show that our algorithm can effectively reduce energy consumption without sacrificing the user quality of service. | arxiv:1701.07405 |
we study the high - energy limit of tree - level string production amplitudes from decaying d - branes in bosonic string theory, interpreting the vertex operators as external charges interacting with a coulomb gas corresponding to the rolling tachyon background, and performing an electrostatic analysis. in particular, we consider two open string - one closed string amplitudes and four open string amplitudes, and calculate explicit formulas for the leading exponential behavior. | arxiv:1008.4743 |
we have performed a statistical analysis of a sample of 1100 extra - galactic rotation measures ( rms ) obtained from the literature. using a subsample of approximately 800 reliable rms we compute a rotation measure sky and determine reliable large scale features for the line of sight galactic magnetic field. we find that the influence of the milky way can be seen up to roughly 30 degrees on either side of the galactic plane. furthermore we observe an excess of rm on spatial scales between 30 degrees and 50 degrees in the region of the galactic plane. additionally, the support for a bisymmetric spiral galactic magnetic field is significantly reduced in our analysis. | arxiv:astro-ph/0410659 |
this article investigates the concept of dominant metric dimensions in zero divisor graphs ( zd - graphs ) associated with rings. consider a finite commutative ring with unity, denoted as r, where nonzero elements x and y are identified as zero divisors if their product results in zero ( x. y = 0 ). the set of zero divisors in ring r is referred to as l ( r ). to analyze various algebraic properties of r, a graph known as the zero - divisor graph is constructed using l ( r ). this manuscript establishes specific general bounds for the dominant metric dimension ( ddim ) concerning the zd - graph of r. to achieve this objective, we examine the zero divisor graphs for specific rings, such as the ring of gaussian integers modulo m, denoted as zm [ i ], the ring of integers modulo n, denoted as zn, and some quotient polynomial rings. additionally, we present a general result outlining bounds for the dominant metric dimension expressed in terms of the maximum degree, girth, clique number, and diameter of the associated zd - graphs. finally, we provide insights into commutative rings that share identical metric dimensions and dominant metric dimensions. this exploration contributes to a deeper understanding of the structural characteristics of zd - graphs and their implications for the algebraic properties of commutative rings. | arxiv:2312.16005 |
there are a number of studies about extraction of bottleneck ( bn ) features from deep neural networks ( dnns ) trained to discriminate speakers, pass - phrases and triphone states for improving the performance of text - dependent speaker verification ( td - sv ). however, a moderate success has been achieved. a recent study [ 1 ] presented a time contrastive learning ( tcl ) concept to explore the non - stationarity of brain signals for classification of brain states. speech signals have similar non - stationarity property, and tcl further has the advantage of having no need for labeled data. we therefore present a tcl based bn feature extraction method. the method uniformly partitions each speech utterance in a training dataset into a predefined number of multi - frame segments. each segment in an utterance corresponds to one class, and class labels are shared across utterances. dnns are then trained to discriminate all speech frames among the classes to exploit the temporal structure of speech. in addition, we propose a segment - based unsupervised clustering algorithm to re - assign class labels to the segments. td - sv experiments were conducted on the reddots challenge database. the tcl - dnns were trained using speech data of fixed pass - phrases that were excluded from the td - sv evaluation set, so the learned features can be considered phrase - independent. we compare the performance of the proposed tcl bottleneck ( bn ) feature with those of short - time cepstral features and bn features extracted from dnns discriminating speakers, pass - phrases, speaker + pass - phrase, as well as monophones whose labels and boundaries are generated by three different automatic speech recognition ( asr ) systems. experimental results show that the proposed tcl - bn outperforms cepstral features and speaker + pass - phrase discriminant bn features, and its performance is on par with those of asr derived bn features. moreover,.... | arxiv:1905.04554 |
creation of high quality p - n junctions in graphene monolayer is vital in studying many exotic phenomena of massless dirac fermions. however, even with the fast progress of graphene technology for more than ten years, it remains conspicuously difficult to generate nanoscale and atomically - sharp p - n junctions in graphene. here, we employ monolayer - vacancy - island engineering of cu surface to realize nanoscale p - n junctions with atomically - sharp boundaries in graphene monolayer. the variation of graphene - cu separations around the edges of the cu monolayer - vacancy - island affects the positions of the dirac point in graphene, which consequently lead to atomically - sharp p - n junctions with the height as high as 660 mev in graphene. the generated sharp p - n junctions isolate the graphene above the cu monolayer - vacancy - island as nanoscale graphene quantum dots ( gqds ) in a continuous graphene sheet. massless dirac fermions are confined by the p - n junctions for a finite time to form quasi - bound states in the gqds. by using scanning tunneling microscopy, we observe resonances of quasi - bound states in the gqds with various sizes and directly visualize effects of geometries of the gqds on the quantum interference patterns of the quasi - bound states, which allow us to test the quantum electron optics based on graphene in atomic scale. | arxiv:1705.10952 |
subspace codes have received an increasing interest recently due to their application in error - correction for random network coding. in particular, cyclic subspace codes are possible candidates for large codes with efficient encoding and decoding algorithms. in this paper we consider such cyclic codes and provide constructions of optimal codes for which their codewords do not have full orbits. we further introduce a new way to represent subspace codes by a class of polynomials called subspace polynomials. we present some constructions of such codes which are cyclic and analyze their parameters. | arxiv:1404.7739 |
we calculate the gluon structure function of a color dipole in near - light - cone su ( 2 ) lattice qcd as a function of $ x _ b $. the quark and antiquark are external non - dynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. we compute the color dipole matrix element of transversal chromo - electric and chromo - magnetic field operators separated along a direction close to the light cone, the fourier transform of which is the gluon structure function. as vacuum state in the pure glue sector, we use a variational ground state of the near - light - cone hamiltonian. we derive a recursion relation for the gluon structure function on the lattice similar to the perturbative dglap equation. it depends on the number of transversal links assembling the schwinger string of the dipole. fixing the mean momentum fraction of the gluons to the " experimental value " in a proton, we compare our gluon structure function for a dipole state with four links with the nlo \ emph { mrst } 2002 and the \ emph { cteqab - 0 } parameterizations at $ q ^ 2 = 1. 5 \ mathrm { gev } ^ 2 $. within the systematic uncertainty we find rather good agreement. we also discuss the low $ x _ b $ behavior of the gluon structure function in our model calculation. | arxiv:0908.0715 |
in this short paper, we establish a reverse of the derived inequalities for sector matrices by tan and xie, with kantorovich constant. then, as application of our main theorem, some inequalities for determinant and unitarily invariant norm are presented. | arxiv:2001.00683 |
in this paper it is shown that the mathematical form which most precisely describes the blazhko rr lyrae light curves is connected to almost periodic functions and not to the mathematics of modulation. that is, the blazhko effect is more than a simple external modulation of the pulsation signal. the mathematical framework of almost periodic functions predicts a new observable effect : a shift of the fourier harmonics of the main pulsation frequency from the exact harmonic position. this phenomenon is called as harmonic detuning effect ( hde ). the published deviations of the harmonics of v445 lyr are explained with this effect. hde is also found for v2178 cyg, another blazhko star observed by the kepler space telescope. hde is detectable only if the phase variation part of the blazhko effect is of large amplitude and non - periodic enough, additionally, the time span of the observed light curve is sufficiently long for obtaining precise frequencies. these three conditions restrict the number of stars showing detectable hde and explain why this effect has not been discovered up to now. | arxiv:1709.02143 |
5d cosmological model with 3 - brane with matter is considered. the brane divides bulk in two ads half spaces. geometry of the model can be described by two types of coordinates : in the first setting the metric is static and the brane is moving in the bulk, in the second approach the metric is time - dependent and the brane is located at a fixed position in the bulk. coordinate transformation connecting two coordinate systems is constructed. | arxiv:1204.2351 |
post - training quantization ( ptq ) for vision transformers ( vits ) has received increasing attention from both academic and industrial communities due to its minimal data needs and high time efficiency. however, many current methods fail to account for the complex interactions between quantized weights and activations, resulting in significant quantization errors and suboptimal performance. this paper presents erq, an innovative two - step ptq method specifically crafted to reduce quantization errors arising from activation and weight quantization sequentially. the first step, activation quantization error reduction ( aqer ), first applies reparameterization initialization aimed at mitigating initial quantization errors in high - variance activations. then, it further mitigates the errors by formulating a ridge regression problem, which updates the weights maintained at full - precision using a closed - form solution. the second step, weight quantization error reduction ( wqer ), first applies dual uniform quantization to handle weights with numerous outliers, which arise from adjustments made during reparameterization initialization, thereby reducing initial weight quantization errors. then, it employs an iterative approach to further tackle the errors. in each iteration, it adopts rounding refinement that uses an empirically derived, efficient proxy to refine the rounding directions of quantized weights, complemented by a ridge regression solver to reduce the errors. comprehensive experimental results demonstrate erq ' s superior performance across various vits variants and tasks. for example, erq surpasses the state - of - the - art gptq by a notable 36. 81 % in accuracy for w3a4 vit - s. our codes are available at https : / / github. com / zysxmu / erq. | arxiv:2407.06794 |
in this paper, a noncommutative gravitational theory is constructed by applying moyal deformation quantization and the seiberg - witten map to teleparallel gravity, a classical gravitational theory, as a gauge theory of local translational symmetry. since our model is based on teleparallel gravity, it is an extremely simple noncommutative gravitational theory. we also clearly divide the role of the products, such that the metric is responsible for the rule of the inner product ( which is calculated by taking the sum over the subscripts ) and the moyal product is responsible for tensor and field noncommutativity. this solves problems related to the order of the products and the relationship between the metric and the moyal product. furthermore, we analyze the cosmic evolution of the very early universe and the spacetime features around black holes using the constructed noncommutative gravitational theory, and find that gravity acts repulsively in the extreme region where its quantum effects become prominent. | arxiv:1806.08062 |
we provide the microscopic explanation for the localized f state observed in a heavy fermion metal ybrh2si2 by prof. f. steglich ' s group, reported recently in phys. rev. lett. 91 ( 2003 ) 156401, as associated with the strongly - correlated 4f13 configuration of the yb atom. we derived to ground - state eigenfunctions that perfectly reproduce the observed esr values of g _ perp = 3. 561 and g _ par = 0. 17 : 1 ) g _ 7 ^ 1 = 0. 803 | + - 3 / 2 > + 0. 595 | - + 5 / 2 > - 0. 026 | - + 1 / 2 > - 0. 008 | + - 7 / 2 > ( crystal field parameters : b _ 2 ^ 0 = + 14k, b _ 4 ^ 0 = + 60 mk, b _ 6 ^ 0 = - 0. 5 mk, b _ 4 ^ 4 = - 2. 3 k, b _ 6 ^ 4 = - 10 mk with a small orthorhombic distortion b _ 2 ^ 2 = + 0. 22 k, or 2 ) g _ 6 ^ 1 = 0. 944 | + - 1 / 2 > + 0. 322 | - + 7 / 2 > - 0. 052 | - + 3 / 2 > - 0. 046 | + - 5 / 2 > ( b _ 2 ^ 0 = + 8 k, b _ 4 ^ 0 = - 60 mk, b _ 6 ^ 0 = + 6 mk, b _ 4 ^ 4 = - 1. 78 k and b _ 6 ^ 4 = - 5 mk with a b _ 2 ^ 2 = + 0. 475 k ). we express our feeling that the paper of ref. 1 will be the turning point in the heavy - fermion subject. | arxiv:cond-mat/0401127 |
the electronic structure of heterointerfaces play a pivotal role in their device functionality. recently, highly crystalline ultrathin films of superconducting nbn have been integrated by molecular beam epitaxy with the semiconducting gan. we use soft x - ray angle - resolved photoelectron spectroscopy to directly measure the momentum - resolved electronic band structures for both nbn and gan constituents of this schottky heterointerface, and determine their momentum - dependent interfacial band offset as well as the band - bending profile into gan. we find, in particular, that the fermi states in nbn are aligned against the band gap in gan, which excludes any significant electronic cross - talk of the superconducting states in nbn through the interface to gan. we support the experimental findings with first - principles calculations for bulk nbn and gan. the schottky barrier height obtained from photoemission is corroborated by electronic transport and optical measurements. the momentum - resolved understanding of electronic properties elucidated by the combined materials advances and experimental methods in our work opens up new possibilities in systems where interfacial states play a defining role. | arxiv:2103.07021 |
observations by the voyager and cassini spacecrafts have revealed various striking features of the gap structure in saturn ' s ring, such as the density waves, sharp edge, and vertical wall structure. in order to explain these features in a single simulation, we perform a high - resolution ( n ~ 10 ^ 6 - 10 ^ 7 ) global full n - body simulation of gap formation by an embedded satellite considering gravitational interactions and inelastic collisions among all ring particles and the satellite, while these features have been mostly investigated separately with different theoretical approaches : the streamline models, 1d diffusion models, and local n - body simulation. as a first attempt of a series of papers, we here focus on the gap formation by separating satellite migration with fixing the satellite orbit in a keplerian circular orbit. we reveal how the striking gap features - the density waves, sharp edge, and vertical wall structure - are simultaneously formed by an interplay of the satellite - ring and ring particle - particle interactions. in particular, we propose a new mechanism to quantitatively explain the creation of the vertical wall structure at the gap edge. inelastic collisions between ring particles damp their eccentricity excited by the satellite ' s perturbations to enhance the surface density at the gap edge, making its sharp edges more pronounced. we find the eccentricity damping process inevitably raises the vertical wall structures the most effectively in the second epicycle waves. particle - particle collisions generally convert their lateral epicyclic motion into vertical motion. because the excited epicyclic motion is the greatest near the ring edge and the epicycle motions are aligned in the first waves, the conversion is the most efficient in the gap edge of the second waves and the wall height is scaled by the satellite hill radius, which are consistent with the observations. | arxiv:2403.03012 |
we have applied the fast fourier transform ( fft ), which allows to compute efficiently convolution sums, to solve the set of self - consistent t - matrix equations to get the green function of the two dimensional attractive - u hubbard modelbelow $ t _ c $, extending previous calculations of the same authors. using a constant order parameter $ \ delta ( t ) $, we calculated $ t _ c $ as a function of electron density and interaction strength $ u $. these global results deviate from the bcs behavior remarkably. | arxiv:cond-mat/9612246 |
the structure of nafion, the polymer electrolyte membrane used in some fuel cells, has been extensively debated over recent decades. now, a newly proposed model reveals the nanoscale arrangement that could explain the excellent transport properties of the material. | arxiv:0807.3407 |
clustering measurements of gravitational wave ( gw ) mergers in luminosity distance space can be used in the future as a powerful tool for cosmology. we consider tomographic measurements of the angular power spectrum of mergers both in an einstein telescope - like detector network and in some more advanced scenarios ( more sources, better distance measurements, better sky localization ). we produce fisher forecasts for both cosmological ( matter and dark energy ) and merger bias parameters. our fiducial model for the number distribution and bias of gw events is based on results from hydrodynamical simulations. the cosmological parameter forecasts with einstein telescope are less powerful than those achievable in the near future via galaxy clustering observations with, e. g., euclid. however, in the more advanced scenarios we see significant improvements. moreover, we show that bias can be detected at high statistical significance. regardless of the specific constraining power of different experiments, many aspects make this type of analysis interesting anyway. for example, compact binary mergers detected by einstein telescope will extend up to very high redshifts. furthermore, luminosity distance space distortions in the gw analysis have a different structure with respect to redshift - space distortions in galaxy catalogues. finally, measurements of the bias of gw mergers can provide useful insight into their physical nature and properties. | arxiv:2007.06905 |
we present an analysis of high - resolution spectroscopy of several bright t tauri stars using the vlt / crires and keck / nirspec spectrographs, revealing the first detections of emission from hcn and c2h2 in circumstellar disks at near - infrared wavelengths. using advanced data reduction techniques we achieve a dynamic range with respect to the disk continuum of ~ 500 at 3 microns, revealing multiple emission features of h2o, oh, hcn, and c2h2. we also present stringent upper limits for two other molecules thought to be abundant in the inner disk, ch4 and nh3. line profiles for the different detected molecules are broad but centrally peaked in most cases, even for disks with previously determined inclinations of greater than 20 degrees, suggesting that the emission has both a keplerian and non - keplerian component as observed previously for co emission. we apply two different modeling strategies to constrain the molecular abundances and temperatures : we use a simplified single - temperature lte slab model with a gaussian line profile to make line identifications and determine a best - fit temperature and initial abundance ratios, and we compare these values with constraints derived from a detailed disk radiative transfer model assuming lte excitation but utilizing a realistic temperature and density structure. abundance ratios from both sets of models are consistent with each other and consistent with expected values from theoretical chemical models, and analysis of the line shapes suggests the molecular emission originates from within a narrow region in the inner disk ( r < 1 au ). | arxiv:1201.0766 |
we present a network formulation for a traffic flow model with nonlocal velocity in the flux function. the modeling framework includes suitable coupling conditions at intersections to either ensure maximum flux or distribution parameters. based on an upwind type numerical scheme, we prove the maximum principle and the existence of weak solutions on networks. we also investigate the limiting behavior of the proposed models when the nonlocal influence tends to infinity. numerical examples show the difference between the proposed coupling conditions and a comparison to the lighthill - whitham - richards network model. | arxiv:2105.00834 |
sentiment analysis is a fundamental and valuable task in nlp. however, due to limitations in data and technological availability, research into sentiment analysis of african languages has been fragmented and lacking. with the recent release of the afrisenti - semeval shared task 12, hosted as a part of the 17th international workshop on semantic evaluation, an annotated sentiment analysis of 14 african languages was made available. we benchmarked and compared current state - of - art transformer models across 12 languages and compared the performance of training one - model - per - language versus single - model - all - languages. we also evaluated the performance of standard multilingual models and their ability to learn and transfer cross - lingual representation from non - african to african languages. our results show that despite work in low resource modeling, more data still produces better models on a per - language basis. models explicitly developed for african languages outperform other models on all tasks. additionally, no one - model - fits - all solution exists for a per - language evaluation of the models evaluated. moreover, for some languages with a smaller sample size, a larger multilingual model may perform better than a dedicated per - language model for sentiment classification. | arxiv:2310.14120 |
we measured the lifetime of optically created valley polarization in single layer ws2 using transient absorption spectroscopy. the electron valley relaxation is very short ( < 1ps ). however the hole valley lifetime is at least two orders of magnitude longer and exhibits a temperature dependence that cannot be explained by single carrier spin / valley relaxation mechanisms. our theoretical analysis suggests that a collective contribution of two potential processes may explain the valley relaxation in single layer ws2. one process involves direct scattering of excitons from k to k ' valleys with a spin flip - flop interaction. the other mechanism involves scattering through spin degenerate gamma valley. this second process is thermally activated with an arrhenius behavior due to the energy barrier between gamma and k valleys. | arxiv:1405.5141 |
we prove the existence of positive solutions to a sys - tem of k non - linear elliptic equations corresponding to standing - wave k - uples solutions to a system of non - linear klein - gordon equations. our solutions are characterised by a small energy / charge ratio, appropriately defined. | arxiv:1110.6495 |
recently, face recognition systems have demonstrated remarkable performances and thus gained a vital role in our daily life. they already surpass human face verification accountability in many scenarios. however, they lack explanations for their predictions. compared to human operators, typical face recognition network system generate only binary decisions without further explanation and insights into those decisions. this work focuses on explanations for face recognition systems, vital for developers and operators. first, we introduce a confidence score for those systems based on facial feature distances between two input images and the distribution of distances across a dataset. secondly, we establish a novel visualization approach to obtain more meaningful predictions from a face recognition system, which maps the distance deviation based on a systematic occlusion of images. the result is blended with the original images and highlights similar and dissimilar facial regions. lastly, we calculate confidence scores and explanation maps for several state - of - the - art face verification datasets and release the results on a web platform. we optimize the platform for a user - friendly interaction and hope to further improve the understanding of machine learning decisions. the source code is available on github, and the web platform is publicly available at http : / / explainable - face - verification. ey. r. appspot. com. | arxiv:2211.13735 |
we show here the separability of hamilton - jacobi equation for a hierarchy of integrable hamiltonian systems obtained from the constrained flows of the jaulent - miodek hierarchy. the classical poisson structure for these hamiltonian systems is constructed. the associated $ r $ - matrices depend not only on the spectral parameters, but also on the dynamical variables and, for consistency, have to obey the classical yang - baxter equations of dynamical type. some new solutions of classical dynamical yang - baxter equations are presented. thus these integrable systems provide examples both for the dynamical $ r $ - matrix and for the separable hamiltonian system not having a natural hamiltonian form. | arxiv:solv-int/9509009 |
in this note we comment on a recent attempt by p. burikham, t. harko, k. pimsamarn and s. shahidi [ phys. rev. d { \ bf 107 }, 064008 ( 2023 ) ] to explain the galactic rotation curves as the result of the motion of time - like test particles in the weyl geometric theory of gravity. we show that the static, spherically symmetric solution found by the authors, which could be the basis of an alternative explanation of the galactic rotation curves, is wrong. | arxiv:2306.11926 |
during infectious disease outbreaks, estimates of time - varying pathogen transmissibility, such as the instantaneous reproduction number r ( t ) or epidemic growth rate r ( t ), are used to inform decision - making by public health authorities. for directly transmitted infectious diseases, the renewal equation framework is a widely used method for measuring time - varying transmissibility. the framework uses information on the typical time elapsing between an infection and the offspring infections ( quantified by the generation time distribution ), and r ( t ), to describe the rate at which currently infected individuals generate new infections. for diseases with transmission cycles involving hosts and vectors, however, renewal equation models have been far less used. this is likely due to difficulties in mechanistically defining generation times that can capture the complexity of multi - stage, human - vector relationships. here, using dengue as an example, we provide general renewal equations that are derived from first principles using age - structured systems of coupled partial differential equations across human and vector sub - populations. our framework tracks the multi - stage transmission cycle over calendar time and across stage - specific ages, resulting in governing renewal equations that quantify how the rate at which new infections are generated from existing infections depends on stage - specific processes. the framework provides a foundation on which to base inferential frameworks for estimating r ( t ) and r ( t ) for infectious diseases with multiple stages in the transmission cycle | arxiv:2409.18726 |
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