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the buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. this paper will examine two such effects : multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. both resonances have been studied directly in dipole fields using retarding field analyzers installed in the cornell electron storage ring ( cesr ). these measurements are supported by both analytical models and computer simulations. | arxiv:1603.04817 |
this note concerns tube domains in $ { \ mathbb c } ^ 2 $ with the envelope of holomorphy not equal to the entire space. we construct examples showing that for such domains the sufficient condition for kobayashi hyperbolicity due to m. jarnicki and p. pflug cannot be replaced by its weaker " affine " variant, which is known to be a necessary condition for hyperbolicity. thus, we arrive at the somewhat unexpected conclusion that the obstructions for a domain in the above class to be kobayashi hyperbolic are not just " affine ". | arxiv:1711.04487 |
we consider partially observable markov decision processes ( pomdps ), that are a standard framework for robotics applications to model uncertainties present in the real world, with temporal logic specifications. all temporal logic specifications in linear - time temporal logic ( ltl ) can be expressed as parity objectives. we study the qualitative analysis problem for pomdps with parity objectives that asks whether there is a controller ( policy ) to ensure that the objective holds with probability 1 ( almost - surely ). while the qualitative analysis of pomdps with parity objectives is undecidable, recent results show that when restricted to finite - memory policies the problem is exptime - complete. while the problem is intractable in theory, we present a practical approach to solve the qualitative analysis problem. we designed several heuristics to deal with the exponential complexity, and have used our implementation on a number of well - known pomdp examples for robotics applications. our results provide the first practical approach to solve the qualitative analysis of robot motion planning with ltl properties in the presence of uncertainty. | arxiv:1409.3360 |
in this study, we propose a family of correlation structures for crossover designs with repeated measures for both, gaussian and non - gaussian responses using generalized estimating equations ( gee ). the structure considers two matrices : one that models between - period correlation and another one that models within - period correlation. the overall correlation matrix, which is used to build the gee, corresponds to the kronecker between these matrices. a procedure to estimate the parameters of the correlation matrix is proposed, its statistical properties are studied and a comparison with standard models using a single correlation matrix is carried out. a simulation study showed a superior performance of the proposed structure in terms of the quasi - likelihood criterion, efficiency, and the capacity to explain complex correlation phenomena / patterns in longitudinal data from crossover designs | arxiv:2205.01281 |
to gain insight into the non - abelian born - infeld ( nbi ) action, we study coinciding d - branes wrapped on tori, and turn on magnetic fields on their worldvolume. we then compare predictions for the spectrum of open strings stretching between these d - branes, from perturbative string theory and from the effective nbi action. under some plausible assumptions, we find corrections to the str - prescription for the nbi action at order f ^ 6. in the process we give a way to classify terms in the nbi action that can be written in terms of field strengths only, in terms of permutation group theory. | arxiv:hep-th/0101192 |
deep learning ( dl ) compilers are widely adopted to optimize advanced dl models for efficient deployment on diverse hardware. their quality has profound effect on the quality of compiled dl models. a recent bug study shows that the optimization of high - level intermediate representation ( ir ) is the most error - prone compilation stage. bugs in this stage are accountable for 44. 92 % of the whole collected ones. however, existing testing techniques do not consider high - level optimization related features ( e. g. high - level ir ), and are therefore weak in exposing bugs at this stage. to bridge this gap, we propose hirgen, an automated testing technique that aims to effectively expose coding mistakes in the optimization of high - level ir. the design of hirgen includes 1 ) three coverage criteria to generate diverse and valid computational graphs ; 2 ) full use of high - level irs language features to generate diverse irs ; 3 ) three test oracles inspired from both differential testing and metamorphic testing. hirgen has successfully detected 21 bugs that occur at tvm, with 17 bugs confirmed and 12 fixed. further, we construct four baselines using the state - of - the - art dl compiler fuzzers that can cover the high - level optimization stage. our experiment results show that hirgen can detect 10 crashes and inconsistencies that cannot be detected by the baselines in 48 hours. we further validate the usefulness of our proposed coverage criteria and test oracles in evaluation. | arxiv:2208.02193 |
in this paper, we introduce the notion of strong geometry, a structure composed by both the chirotope of the oriented matroid associated to a set of points x in the d - dimensional space and a new chirotope induced by the hyperplanes spanned by x. with this on hand, we answer positively a strong geometry version of a question due to m. las vergnas about reconstructing polygonal knots via oriented matroids. | arxiv:2504.00197 |
it has been believed that stochastic feedforward neural networks ( sfnns ) have several advantages beyond deterministic deep neural networks ( dnns ) : they have more expressive power allowing multi - modal mappings and regularize better due to their stochastic nature. however, training large - scale sfnn is notoriously harder. in this paper, we aim at developing efficient training methods for sfnn, in particular using known architectures and pre - trained parameters of dnn. to this end, we propose a new intermediate stochastic model, called simplified - sfnn, which can be built upon any baseline dnnand approximates certain sfnn by simplifying its upper latent units above stochastic ones. the main novelty of our approach is in establishing the connection between three models, i. e., dnn - > simplified - sfnn - > sfnn, which naturally leads to an efficient training procedure of the stochastic models utilizing pre - trained parameters of dnn. using several popular dnns, we show how they can be effectively transferred to the corresponding stochastic models for both multi - modal and classification tasks on mnist, tfd, casia, cifar - 10, cifar - 100 and svhn datasets. in particular, we train a stochastic model of 28 layers and 36 million parameters, where training such a large - scale stochastic network is significantly challenging without using simplified - sfnn | arxiv:1704.03188 |
vision - language models ( vlms ) have demonstrated their broad effectiveness thanks to extensive training in aligning visual instructions to responses. however, such training of conclusive alignment leads models to ignore essential visual reasoning, further resulting in failures in meticulous visual problems and unfaithful responses. drawing inspiration from human cognition in solving visual problems ( e. g., marking, zoom in ), this paper introduces chain of manipulations, a mechanism that enables vlms to solve problems step - by - step with evidence. after training, models can solve various visual problems by eliciting intrinsic manipulations ( e. g., grounding, zoom in ) with results ( e. g., boxes, image ) actively without involving external tools, while also allowing users to trace error causes. we study the roadmap to implement this mechanism, including ( 1 ) a flexible design of manipulations upon extensive analysis, ( 2 ) an efficient automated data generation pipeline, ( 3 ) a compatible vlm architecture capable of multi - turn multi - image, and ( 4 ) a model training process for versatile capabilities. with the design, we also manually annotate 6k high - quality samples for the challenging graphical mathematical problems. our trained model, \ textbf { cogcom }, equipped with this mechanism with 17b parameters achieves state - of - the - art performance across 9 benchmarks from 4 categories, demonstrating the effectiveness while preserving the interpretability. our code, model weights, and collected data are publicly available at https : / / github. com / thudm / cogcom. | arxiv:2402.04236 |
let $ \ mathbb { p } $ be the set of prime numbers, $ \ overline { \ mathbb { p } } $ the union $ \ mathbb { p } \ cup \ { 0 \ } $, and for any field $ e $, let char $ ( e ) $ be its characteristic, ddim $ ( e ) $ the diophantine dimension of $ e $, $ \ mathcal { g } _ { e } $ the absolute galois group of $ e $, and cd $ ( \ mathcal { g } _ { e } ) $ the galois cohomological dimension $ \ mathcal { g } _ { e } $. the research presented in this paper is motivated by the open problem of whether cd $ ( \ mathcal { g } _ { e } ) \ le { \ rm ddim } ( e ) $. it proves the existence of quasifinite fields $ \ phi _ { q } \ colon q \ in \ mathbb { p } $, with ddim $ ( \ phi _ { q } ) $ infinity and char $ ( \ phi _ { q } ) = q $, for each $ q $. it shows that for any integer $ m > 0 $ and $ q \ in \ overline { \ mathbb { p } } $, there is a quasifinite field $ \ phi _ { m, q } $ such that char $ ( \ phi _ { m, q } ) = q $ and ddim $ ( \ phi _ { m, q } ) = m $. this is used for proving that for any $ q \ in \ overline { \ mathbb { p } } $ and each pair $ k $, $ \ ell \ in ( \ mathbb { n } \ cup \ { 0, \ infty \ } ) $ satisfying $ k \ le \ ell $, there exists a field $ e _ { k, \ ell ; q } $ with char $ ( e _ { k, \ ell ; q } ) = q $, ddim $ ( e _ { k, \ ell ; q } ) = \ ell $ and cd $ ( \ mathcal { g } _ { e _ { k, \ ell ; q } } ) = k $. finally, we show that the field $ e _ { k, \ ell ; q } $ can be chosen to be perfect unless $ k | arxiv:2303.04112 |
we study selection by vanishing viscosity for the transport of a passive scalar $ f ( x, t ) \ in \ mathbb { r } $ advected by a bounded, divergence - free vector field $ u ( x, t ) \ in \ mathbb { r } ^ 2 $. this is described by the initial value problem to the pde $ \ frac { \ partial f } { \ partial t } + \ nabla \ cdot ( u f ) = 0 $, or with positive viscosity / diffusivity $ \ nu > 0 $, to the pde $ \ frac { \ partial f } { \ partial t } + \ nabla \ cdot ( u f ) - \ nu \ delta f = 0 $. we demonstrate the failure of the vanishing viscosity limit to select ( a ) unique solutions or ( b ) physically admissible solutions in the sense of non - increasing energy / entropy. | arxiv:2307.00809 |
the focus of this paper is providing a description of the spaces of counting functions on free monoids and groups and of the brooks space. these results have been obtained in an earlier publication, however we propose an alternative, simpler approach to proving the theorems concerning the bases. furthermore, one of the theorems at the time of writing this paper contained a slight error, and we correct it here. | arxiv:2306.15520 |
the forecasting of solar energetic particles ( seps ) is a prominent area of space weather research. numerous forecasting models exist that predict sep event properties at proton energies < 100mev. one of these models is the sparx system, a physics - based forecasting tool that calculates > 10mev and > 60mev flux profiles within minutes of a flare being detected. this work describes sparx - h, the extension of sparx to forecast sep events above 300mev. sparx - h predicts fluxes in three high energy channels up to several hundred mev. correlations between sep peak flux and peak intensity of the associated solar flare are seen to be weak at high energies, but improved when events are grouped based on the field polarity during the event. initial results from this new high energy forecasting tool are presented here and the applications of high energy forecasts are discussed. additionally, the new high energy version of sparx is tested on a set of historic sep events. we see that sparx - h performs best when predicting peak fluxes from events with source locations in well - connected regions, where many large sep events tend to originate. | arxiv:2306.01530 |
we present a necessary and sufficient product criterion for bipartite quantum states based on the rank of realignment matrix of density matrix. then, this approach is generalized to multipartite systems. we first introduce the concept of semiproduct in a similar manner to the semiseparable and prove that semiproduct is equivalent to fully product. therefore, a quantum state is bipartite product with respect to all possible partitions implies fully product which is different from the case of separability. for pure states, it can easily be seen that several necessary and sufficient separability criteria for multipartite systems are derived as a special case of our results. several specific examples illustrate that our criteria are convenient and operational. | arxiv:1706.04705 |
the main goal of this work is to relate weak and pathwise mild solutions for parabolic quasilinear stochastic partial differential equations ( spdes ). extending in a suitable way techniques from the theory of nonautonomous semilinear spdes to the quasilinear case, we prove the equivalence of these two solution concepts. | arxiv:2008.10318 |
quasi parton distributions ( quasi - pdfs ) are currently under intense investigation. quasi - pdfs are defined through spatial correlation functions and are thus accessible in lattice qcd. they gradually approach their corresponding standard ( light - cone ) pdfs as the hadron momentum increases. recently, we investigated the concept of quasi - distributions in the case of generalized parton distributions ( gpds ) by calculating the twist - 2 vector gpds in the scalar diquark spectator model. in the present work, we extend this study to the remaining six leading - twist gpds. for large hadron momenta, all quasi - gpds analytically reduce to the corresponding standard gpds. we also study the numerical mismatch between quasi - gpds and standard gpds for finite hadron momenta. furthermore, we present results for quasi - pdfs, and explore higher - twist effects associated with the parton momentum and the longitudinal momentum transfer to the target. we study the dependence of our results on the model parameters as well as the type of diquark. finally, we discuss the lowest moments of quasi distributions, and elaborate on the relation between quasi - gpds and the total angular momentum of quarks. the moment analysis suggests a preferred definition of several quasi - distributions. | arxiv:1903.05721 |
gromov - wasserstein ( gw ) transport is inherently invariant under isometric transformations of the data. having this property in mind, we propose to estimate dynamical systems by transfer operators derived from gw transport plans, when merely the initial and final states are known. we focus on entropy regularized gw transport, which allows to utilize the fast sinkhorn algorithm and a spectral clustering procedure to extract coherent structures. moreover, the gw framework provides a natural quantitative assessment on the shape - coherence of the extracted structures. we discuss fused and unbalanced variants of gw transport for labelled and noisy data, respectively. our models are verified by three numerical examples of dynamical systems with governing rotational forces. | arxiv:2301.12880 |
keck spectropolarimetry, giving spectral coverage from ly - $ \ alpha $ to beyond ciii ], and hst imaging of a sample of powerful radio galaxies with $ z \ sim2. 5 $ \ has been obtained. these data are giving us a clear picture of the nature of the ` alignment effect ' and are revealing new correlations between polarization and emission line ratios which may be interpreted in the context of the stellar evolutionary histories of these massive galaxies. in particular, we see the 2200 \ aa dust absorption feature in the radio galaxy continua and a large variation in the nv / civ line ratio amongst objects having a similar ionization level. vlt infrared spectroscopy of this and similar samples will give us a view of a period of galaxy history during which rapid chemical evolution was taking place. | arxiv:astro-ph/9808066 |
recent experimental and theoretical interest in the superconducting phase of the heavy fermion material uru $ _ 2 $ si $ _ 2 $ has led to a number of proposals in which the superconducting order parameter breaks time - reversal symmetry ( trs ). in this study we measured polar kerr effect ( pke ) as a function of temperature for several high - quality single crystals of uru $ _ 2 $ si $ _ 2 $. we find an onset of pke below the superconducting transition that is consistent with a trs - breaking order parameter. this effect appears to be independent of an additional, possibly extrinsic, pke generated above the hidden order transition at $ t _ { ho } = 17. 5 $ k, and contains structure below $ t _ c $ suggestive of additional physics within the superconducting state. | arxiv:1410.1479 |
we classify complex projective varieties of dimension $ 2r \ geq 8 $ swept out by a family of codimension two grassmannians of lines $ \ mathbb { g } ( 1, r ) $. they are either fibrations onto normal surfaces such that the general fibers are isomorphic to $ \ g ( 1, r ) $ or the grassmannian $ \ mathbb { g } ( 1, r + 1 ) $. the cases $ r = 2 $ and $ r = 3 $ are also considered in the more general context of varieties swept out by codimension two linear spaces or quadrics. | arxiv:0810.0129 |
classical properties of 1 / 4 bps dyons were previously well understood both in field theory context and in string theory context. its quantum properties, however, have been more difficult to probe, although the elementary information of the supermultiplet structures is known from a perturbative construction. recently, a low energy effective theory of monopoles was constructed and argued to contain these dyons as quantum bound states. in this paper, we find these dyonic bound states explicitly in the n = 4 supersymmetric low energy effective theory. after identifying the correct angular momentum operators, we motivate an anti - self - dual ansatz for all bps bound states. the wavefunctions are found explicitly, whose spin contents and degeneracies match exactly the expected results. | arxiv:hep-th/9907090 |
##c { 13, 983, 815 } { 13, 983, 816 } } \ \ & \ approx 1. 0317 \ times 10 ^ { - 7 } { \ text { shannons } }. \ end { aligned } } } the information entropy of a lottery probability distribution is also easy to calculate as the expected value of the information content. h ( x ) = x − p x ( x ) log p x ( x ) = x p x ( x ) i x ( x ) = d e f e [ i x ( x ) ] { \ displaystyle { \ begin { alignedat } { 2 } \ mathrm { h } ( x ) & = \ sum _ { x } { - p _ { x } { \ left ( x \ right ) } \ log { p _ { x } { \ left ( x \ right ) } } } \ & = \ sum _ { x } { p _ { x } { \ left ( x \ right ) } \ operatorname { i } _ { x } ( x ) } \ \ & { \ overset { \ underset { \ mathrm { def } } { } } { = } } \ \ mathbb { e } { \ left [ \ operatorname { i } _ { x } ( x ) \ right ] } \ end { alignedat } } } oftentimes the random variable of interest in the lottery is a bernoulli trial. in this case, the bernoulli entropy function may be used. using x { \ displaystyle x } representing winning the 6 - of - 49 lottery, the shannon entropy of 6 - of - 49 above is h ( x ) = − p log ( p ) − q log ( q ) = − 1 13, 983, 816 log 1 13, 983, 816 − 13, 983, 815 13, 983, 816 log 13, 983, 815 13, 983, 816 ≈ 1. 80065 × 10 − 6 shannons. { \ displaystyle { \ begin { aligned } \ mathrm { h } ( x ) & = - p \ log ( p ) - q \ log ( q ) = - { \ tfrac { 1 } { 13, 983, 816 } } \ log \! { \ tfrac { 1 } { 13, 983, 816 } } - { \ tfrac { 13, 983 | https://en.wikipedia.org/wiki/Lottery_mathematics |
we show the existence of solution for some classes of nonlocal problems. our proof combines the presence of sub and supersolution with the pseudomonotone operators theory. | arxiv:1306.1211 |
the shigesada - kawasaki - teramoto system, which consists of two reaction - diffusion equations with variable cross - diffusion and quadratic nonlinearities, is considered. the system is the most important case of the biologically motivated model proposed by shigesada et al. a complete description of lie symmetries for this system is derived. it is proved that the shigesada - kawasaki - teramoto system admits a wide range of different lie symmetries depending on coefficient values. in particular, the lie symmetry operators with highly unusual structure are unveiled and applied for finding exact solutions of the relevant nonlinear system with cross - diffusion. | arxiv:1611.08801 |
an extensive series of neutron diffraction experiments and molecular dynamics simulations has shown that mixtures of methanol and water exhibit extended structures in solution despite the components being fully miscible in all proportions. of particular interest is a concentration region ( methanol mole fraction between 0. 27 and 0. 54 ) where { \ em both } methanol and water appear to form separate, percolating networks. this is the concentration range where many transport properties and thermodynamic excess functions reach extremal values. the observed concentration dependence of several of these material properties of the solution may therefore have a structural origin. | arxiv:cond-mat/0412436 |
we introduce a ramified covering of small categories, and we show three properties of the notion : the riemann - hurwitz formula holds for a ramified covering of finite categories, the zeta function of $ c $ divides that of $ \ widetilde { c } $ for a ramified covering $ \ map { p } { \ widetilde { c } } { c } $ of finite categories, and the classifying space of a $ d $ - fold ramified covering of small categories is also a $ d $ - fold ramified covering in the sense of dold \ cite { dol86 }. | arxiv:1303.7046 |
uniaxial strain affects pairing symmetry states in superconductors by changing the lattice symmetry, and by altering fermi surface topology. here, we present a systematic study of these effects within a one - band negative - u hubbard model for s, p and d - wave pairing states. we consider a general 2d model that can be applied to superconductors under uniaxial strain, modelled via hopping anisotropy, on a square lattice. the results presented here model an in plane compression along the x - axis, which reduces the lattice symmetry from a tetragonal to an orthorhombic crystal space group. the effects of hopping anisotropy on the different types of gap pairings are explored. we show that changes in tc are tunable with hopping anisotropy and depend on the orientation of the gap function in relation to the opening of the fermi surface during the lifshitz transition. in comparing the model results to experimental data for the case of sr2ruo4 it is found that both the d + id and d + ig pairings best describe the changes in tc for the superconducting state in regards to its response to small uniaxial strain. | arxiv:2209.00300 |
signature effects observed in rotational bands are a consequence of an inherent d2 - symmetry. this symmetry is naturally broken by the mean field cranking approximation when a tilted ( non - principal ) axis orientation of the nuclear spin becomes stable. the possible tunneling forth and back between the two symmetry - related minima in the double - humped potential - energy surface appears as a typical bifurcation of the rotational band. we describe this many - body process in which all nucleons participate by diagonalizing the nuclear hamiltonian within a selected set of tilted and non - tilted cranking quasiparticle states. this microscopic approach is able to restore the broken d2 symmetry and reproduce the quantum fluctuations between symmetry - related hfb states which emerge as splitting of the band energies and in parallel staggering in intraband m1 transitions. | arxiv:nucl-th/9809045 |
the advent of social media has provided data and insights about how people relate to information and culture. while information is composed by bits and its fundamental building bricks are relatively well understood, the same cannot be said for culture. the fundamental cultural unit has been defined as a " meme ". memes are defined in literature as specific fundamental cultural traits, that are floating in their environment together. just like genes carried by bodies, memes are carried by cultural manifestations like songs, buildings or pictures. memes are studied in their competition for being successfully passed from one generation of minds to another, in different ways. in this paper we choose an empirical approach to the study of memes. we downloaded data about memes from a well - known website hosting hundreds of different memes and thousands of their implementations. from this data, we empirically describe the behavior of these memes. we statistically describe meme occurrences in our dataset and we delineate their fundamental traits, along with those traits that make them more or less apt to be successful. | arxiv:1304.1712 |
the through silicon via ( tsv ) process developed by silex provides down to 30 micrometers pitch for through wafer connections in up to 600 micrometers thick substrates. integrated with mems designs it enables significantly reduced die size and true " wafer level packaging " - features that are particularly important in consumer market applications. the tsv technology also enables integration of advanced interconnect functions in optical mems, sensors and microfluidic devices. in addition the via technology opens for very interesting possibilities considering integration with cmos processing. with several companies using the process already today, qualified volume manufacturing in place and a line - up of potential users, the process is becoming a standard in the mems industry. we provide a introduction to the via formation process and also present some on the novel solutions made available by the technology. | arxiv:0805.0922 |
we present radio observations of the most slowly rotating known radio pulsar psr j0250 + 5854. with a 23. 5 s period, it is close, or even beyond, the $ p $ - $ \ dot { p } $ diagram region thought to be occupied by active pulsars. the simultaneous observations with fast, the chilbolton and effelsberg lofar international stations, and nenufar represent a five - fold increase in the spectral coverage of this object, with the detections at 1250 mhz ( fast ) and 57 mhz ( nenufar ) being the highest - and lowest - frequency published respectively to date. we measure a flux density of $ 4 \ pm2 $ $ \ mu $ jy at 1250 mhz and an exceptionally steep spectral index of $ - 3. 5 ^ { + 0. 2 } _ { - 1. 5 } $, with a turnover below $ \ sim $ 95 mhz. in conjunction with observations of this pulsar with the gbt and the lofar core, we show that the intrinsic profile width increases drastically towards higher frequencies, contrary to the predictions of conventional radius - to - frequency mapping. we examine polarimetric data from fast and the lofar core and conclude that its polar cap radio emission is produced at an absolute height of several hundreds of kilometres around 1. 5 ghz, similar to other rotation - powered pulsars across the population. its beam is significantly underfilled at lower frequencies, or it narrows because of the disappearance of conal outriders. finally, the results for psr j0250 + 5854 and other slowly spinning rotation - powered pulsars are contrasted with the radio - detected magnetars. we conclude that magnetars have intrinsically wider radio beams than the slow rotation - powered pulsars, and that consequently the latter ' s lower beaming fraction is what makes objects such as psr j0250 + 5854 so scarce. | arxiv:2109.00266 |
exact discrete symmetries, if non - linearly realized, can reduce the ultraviolet sensitivity of a given theory. the scalars stemming from spontaneous symmetry breaking are massive without breaking the discrete symmetry, and those masses are protected from divergent quadratic corrections. this is in contrast to non - linearly realized continuous symmetries, for which the masses of pseudo - goldstone bosons require an explicit breaking mechanism. the symmetry - protected masses and potentials of those discrete goldstone bosons offer promising physics avenues, both theoretically and in view of the blooming experimental search for alps. we develop this theoretical setup using invariant theory and focusing on the maximally natural minima of the potential. for these, we show that typically a subgroup of the ultraviolet discrete symmetry remains explicit in the spectrum, i. e. realized " \ ` a la wigner " ; this subgroup can be either abelian or non - abelian. this suggests tell - tale experimental signals for those minima : at least two ( three ) degenerate scalars produced simultaneously if abelian ( non - abelian ), while the specific ratios of multi - scalar amplitudes provide a hint of the full ultraviolet discrete symmetry. examples of exact ultraviolet $ a _ 4 $ and $ a _ 5 $ symmetries are explored in substantial detail. | arxiv:2205.09131 |
a mean field method to study heteroepitaxial thin film growth is applied to growth, intermixing and surface reconstructions of $ au $ on $ ag ( 110 ) $. the results are in accordance with experimentally observed ` ` burrowing ' ' at submonolayer coverages and growth of elongated, $ ( 1 \ times 3 ) $ reconstructed, $ au $ clusters at higher coverages. at coverages of few monolayers the surface between the clusters has a high concentration of $ ag $, and ordered rows of $ au $ are formed just beneath the surface. | arxiv:cond-mat/9512029 |
detecting the subtle yet phase defining features in scanning tunneling microscopy and spectroscopy data remains an important challenge in quantum materials. we meet the challenge of detecting nematic order from local density of states data with supervised machine learning and artificial neural networks for the difficult scenario without sharp features such as visible lattice bragg peaks or friedel oscillation signatures in the fourier transform spectrum. we train the artificial neural networks to classify simulated data of isotropic and anisotropic two - dimensional metals in the presence of disorder. the supervised machine learning succeeds only with at least one hidden layer in the ann architecture, demonstrating it is a higher level of complexity than nematic order detected from bragg peaks which requires just two neurons. we apply the finalized ann to experimental stm data on cafe2as2, and it predicts nematic symmetry breaking with 99 % confidence ( probability 0. 99 ), in agreement with previous analysis. our results suggest anns could be a useful tool for the detection of nematic order in stm data and a variety of other forms of symmetry breaking. | arxiv:1901.11042 |
for an acyclic quiver q, we solve the clebsch - gordan problem for the projective representations by computing the multiplicity of a given indecomposable projective in the tensor product of two indecomposable projectives. motivated by this problem for arbitrary representations, we study idempotents in the representation ring of q ( the free abelian group on the indecomposable representations, with multiplication given by tensor product ). we give a general technique for constructing such idempotents and for decomposing the representation ring into a direct product of ideals, utilizing morphisms between quivers and categorical moebius inversion. | arxiv:1009.0029 |
radiation of gluons gives rise to extra jets in top quark events that can lead to complications in event reconstruction and mass measurement. i review recent results for gluon radiation in top quark production and decay, and discuss their implications for top quark physics. | arxiv:hep-ph/9609354 |
we show that the strongly symmetric spectral convex compact sets are precisely the normalized state spaces of finite - dimensional simple euclidean jordan algebras and the simplices. spectrality is the property that every state has a convex decomposition into perfectly distinguishable pure states ; strong symmetry is transitivity, for each integer n, of the affine automorphism group of the state space on lists of n perfectly distinguishable pure states. additional assumptions combine with this theorem to give simple characterizations of finite - dimensional complex quantum state space. important aspects of quantum and classical thermodynamics and of query complexity have been generalized to classes of general probabilistic theories ( gpts ) satisfying natural postulates including or implying spectrality and strong symmetry ; our result shows that these apply to a narrower class of theories than might have been hoped. sorkin ' s notion of irreducibly k - th order interference has been studied in the gpt framework and looked for in experiments. our result shows that the assumption of no higher - order ( k > 2 ) interference, used along with spectrality and strong symmetry to characterize the same class of jordan - algebraic convex sets by barnum, mueller, and ududec in arxiv : 1403. 4147, was superfluous. it also implies that lee and selby ' s extension, on the assumption that interference has fixed maximal degree k, of the important order square root of n lower bound on the quantum black - box query complexity of searching n possibilities for one having a desired property ( which is achieved by grover ' s quantum algorithm ), to a class of theories satisfying certain postulates allowing the formulation of a generalized notion of query algorithm, actually applies in the jordan - algebraic setting where higher - order interference is not possible. | arxiv:1904.03753 |
in quantum error - correcting code ( qecc ), many quantum operations and measurements are necessary to correct errors in logical qubits. in the stabilizer formalism, which is widely used in qecc, generators $ g _ i ( i = 1, 2,.. ) $ consist of multiples of pauli matrices and perform encoding, decoding and measurement. in order to maintain encoding states, the stabilizer hamiltonian $ h _ { \ rm stab } = - \ sum _ i g _ i $ is suitable because its ground state corresponds to the code space. on the other hand, hamiltonians of most solid - state qubits have two - body interactions and show their own dynamics. in addition solid - state qubits are fixed on substrate and qubit - qubit operation is restricted in their neighborhood. the main purpose of this paper is to show how to directly generate the stabilizer hamiltonian $ h _ { \ rm stab } $ from conventional two - body hamiltonians with ising interaction and xy interaction by applying a pulse control method such as an nmr technique. we show that generation times of $ h _ { \ rm stab } $ for nine - qubit code, five - qubit code and steane code are estimated to be less than 300 ns when typical experimental data of superconducting qubits are used, and sufficient pulse control is assumed. we also show how to prepare encoded states from an initial state $ | 0.... 0 > $. in addition, we discuss an appropriate arrangement of two - or three - dimensional arrayed qubits. | arxiv:1307.6970 |
a wide range of decision problems can be formulated as bilevel programs with independent followers, which as a special case include two - stage stochastic programs. these problems are notoriously difficult to solve especially when a large number of followers present. motivated by a real - world cycling infrastructure planning application, we present a general approach to solving such problems. we propose an optimization model that explicitly considers a sampled subset of followers and exploits a machine learning model to estimate the objective values of unsampled followers. we prove bounds on the optimality gap of the generated leader decision as measured by the original objective function that considers the full follower set. we then develop follower sampling algorithms to tighten the bounds and a representation learning approach to learn follower features, which are used as inputs to the embedded machine learning model. through numerical studies, we show that our approach generates leader decisions of higher quality compared to baselines. finally, in collaboration with the city of toronto, we perform a real - world case study in toronto where we solve a cycling network design problem with over one million followers. compared to the current practice, our approach improves toronto ' s cycling accessibility by 19. 2 %, equivalent to $ 18m in potential cost savings. our approach is being used to inform the cycling infrastructure planning in toronto and outperforms the current practice by a large margin. it can be generalized to any decision problems that are formulated as bilevel programs with independent followers. | arxiv:2209.09404 |
this paper studies how to learn variational autoencoders with a variety of divergences under differential privacy constraints. we often build a vae with an appropriate prior distribution to describe the desired properties of the learned representations and introduce a divergence as a regularization term to close the representations to the prior. using differentially private sgd ( dp - sgd ), which randomizes a stochastic gradient by injecting a dedicated noise designed according to the gradient ' s sensitivity, we can easily build a differentially private model. however, we reveal that attaching several divergences increase the sensitivity from o ( 1 ) to o ( b ) in terms of batch size b. that results in injecting a vast amount of noise that makes it hard to learn. to solve the above issue, we propose term - wise dp - sgd that crafts randomized gradients in two different ways tailored to the compositions of the loss terms. the term - wise dp - sgd keeps the sensitivity at o ( 1 ) even when attaching the divergence. we can therefore reduce the amount of noise. in our experiments, we demonstrate that our method works well with two pairs of the prior distribution and the divergence. | arxiv:2006.11204 |
multicasting, where a base station ( bs ) wishes to convey the same message to several user equipments ( ues ), represents a common yet highly challenging wireless scenario. in fact, guaranteeing decodability by the whole ue population proves to be a major performance bottleneck since the ues in poor channel conditions ultimately determine the achievable rate. to overcome this issue, two - phase cooperative multicasting schemes, which use conventional multicasting in a first phase and leverage device - to - device ( d2d ) communications in a second phase to effectively spread the message, have been extensively studied. however, most works are limited either to the simple case of single - antenna bs or to a specific channel state information at the transmitter ( csit ) setup. this paper proposes a general two - phase framework that is applicable to the cases of perfect, statistical, and topological csit in the presence of multiple antennas at the bs. the proposed method exploits the precoding capabilities at the bs, which enable targeting specific ues that can effectively serve as d2d relays towards the remaining ues, and maximize the multicast rate under some outage constraint. numerical results show that our schemes bring substantial gains over traditional single - phase multicasting and overcome the worst - ue bottleneck behavior in all the considered csit configurations. | arxiv:2102.01624 |
we apply ideas from intersection theory on toric varieties to tropical intersection theory. we introduce mixed minkowski weights on toric varieties which interpolate between equivariant and ordinary chow cohomology classes on complete toric varieties. these objects fit into the framework of tropical intersection theory developed by allermann and rau. standard facts about intersection theory on toric varieties are applied to show that the definitions of tropical intersection product on tropical cycles in $ \ r ^ n $ given by allermann - rau and mikhalkin are equivalent. we introduce an induced tropical intersection theory on subvarieties on a toric variety. this gives a conceptional proof that the intersection of tropical $ \ psi $ - classes on $ \ cmbar _ { 0, n } $ used by kerber and markwig computes classical intersection numbers. | arxiv:0907.2488 |
we investigate dissipative anomalies in a turbulent fluid governed by the compressible navier - stokes equation. we follow an exact approach pioneered by onsager, which we explain as a non - perturbative application of the principle of renormalization - group invariance. in the limit of high reynolds and p \ ' eclet numbers, the flow realizations are found to be described as distributional or " coarse - grained " solutions of the compressible euler equations, with standard conservation laws broken by turbulent anomalies. the anomalous dissipation of kinetic energy is shown to be due not only to local cascade, but also to a distinct mechanism called pressure - work defect. irreversible heating in stationary, planar shocks with an ideal - gas equation of state exemplifies the second mechanism. entropy conservation anomalies are also found to occur by two mechanisms : an anomalous input of negative entropy ( negentropy ) by pressure - work and a cascade of negentropy to small scales. we derive " 4 / 5th - law " - type expressions for the anomalies, which allow us to characterize the singularities ( structure - function scaling exponents ) required to sustain the cascades. we compare our approach with alternative theories and empirical evidence. it is argued that the " big power - law in the sky " observed in electron density scintillations in the interstellar medium is a manifestation of a forward negentropy cascade, or an inverse cascade of usual thermodynamic entropy. | arxiv:1704.03532 |
we construct models hosting classical fractal spin liquids on two realistic three - dimensional ( 3d ) lattices of corner - sharing triangles : trillium and hyperhyperkagome ( hhk ). both models involve the same form of three - spin ising interactions on triangular plaquettes as the newman - moore ( nm ) model on the 2d triangular lattice. however, in contrast to the nm model and its 3d generalizations, their degenerate ground states and low - lying excitations cannot be described in terms of scalar cellular automata ( ca ), because the corresponding fractal structures lack a simplifying algebraic property, often termed the ' freshman ' s dream '. by identifying a link to matrix cas - - that makes essential use of the crystallographic structure - - we show that both models exhibit fractal symmetries of a distinct class to the nm - type models. we devise a procedure to explicitly construct low - energy excitations consisting of finite sets of immobile defects or " fractons ", by flipping arbitrarily large self - similar subsets of spins, whose fractal dimensions we compute analytically. we show that these excitations are associated with energetic barriers which increase logarithmically with system size, leading to " fragile " glassy dynamics, whose existence we confirm via classical monte carlo simulations. we also discuss consequences for spontaneous fractal symmetry breaking when quantum fluctuations are introduced by a transverse magnetic field, and propose multi - spin correlation function diagnostics for such transitions. our findings suggest that matrix cas may provide a fruitful route to identifying fractal symmetries and fracton - like behaviour in lattice models, with possible implications for the study of fracton topological order. | arxiv:2109.06207 |
much of earth ' s charismatic megafauna is endangered by human activities, particularly the rhino, which is at risk of extinction due to the poaching crisis in africa. monitoring rhinos ' movement is crucial to their protection but has unfortunately proven difficult because rhinos are elusive. therefore, instead of tracking rhinos, we propose the novel approach of mapping communal defecation sites, called middens, which give information about rhinos ' spatial behavior valuable to anti - poaching, management, and reintroduction efforts. this paper provides the first - ever mapping of rhino midden locations by building classifiers to detect them using remotely sensed thermal, rgb, and lidar imagery in passive and active learning settings. as existing active learning methods perform poorly due to the extreme class imbalance in our dataset, we design multimodal, an active learning system employing a ranking technique and multimodality to achieve competitive performance with passive learning models with 94 % fewer labels. our methods could therefore save over 76 hours in labeling time when used on a similarly - sized dataset. unexpectedly, our midden map reveals that rhino middens are not randomly distributed throughout the landscape ; rather, they are clustered. consequently, rangers should be targeted at areas with high midden densities to strengthen anti - poaching efforts, in line with un target 15. 7. | arxiv:2409.18104 |
the physical foundations of the dissipation of energy and the associated heating in weakly collisional plasmas are poorly understood. here, we compare and contrast several measures that have been used to characterize energy dissipation and kinetic - scale conversion in plasmas by means of a suite of kinetic numerical simulations describing both magnetic reconnection and decaying plasma turbulence. we adopt three different numerical codes that can also include interparticle collisions : the fully kinetic particle - in - cell vpic, the fully kinetic continuum gkeyll, and the eulerian hybrid vlasov - maxwell ( hvm ) code. we differentiate between ( i ) four energy - based parameters, whose definition is related to energy transfer in a fluid description of a plasma, and ( ii ) four distribution function - based parameters, requiring knowledge of the particle velocity distribution function. there is an overall agreement between the dissipation measures obtained in the pic and continuum reconnection simulations, with slight differences due to the presence / absence of secondary islands in the two simulations. there are also many qualitative similarities between the signatures in the reconnection simulations and the self - consistent current sheets that form in turbulence, although the latter exhibits significant variations compared to the reconnection results. all the parameters confirm that dissipation occurs close to regions of intense magnetic stresses, thus exhibiting local correlation. the distribution function - based measures show a broader width compared to energy - based proxies, suggesting that energy transfer is co - localized at coherent structures, but can affect the particle distribution function in wider regions. the effect of interparticle collisions on these parameters is finally discussed. | arxiv:2101.00722 |
based on the expectile loss function and the adaptive lasso penalty, the paper proposes and studies the estimation methods for the accelerated failure time ( aft ) model. in this approach, we need to estimate the survival function of the censoring variable by the kaplan - meier estimator. the aft model parameters are first estimated by the expectile method and afterwards, when the number of explanatory variables can be large, by the adaptive lasso expectile method which directly carries out the automatic selection of variables. we also obtain the convergence rate and asymptotic normality for the two estimators, while showing the sparsity property for the censored adaptive lasso expectile estimator. a numerical study using monte carlo simulations confirms the theoretical results and demonstrates the competitive performance of the two proposed estimators. the usefulness of these estimators is illustrated by applying them to three survival data sets. | arxiv:2402.03203 |
1. i update my previous comparison of the theoretical value of the muon anomaly with the new measurement and found $ \ delta a _ \ mu \ equiv a _ \ mu ^ { exp } - a _ \ mu ^ { th } = ( 143 \ pm 42 _ { th } \ pm 22 _ { exp } ) \ times 10 ^ { - 11 } $ which is about 3 $ \ sigma $ discrepancy between the sm predictions and experiment. 2. i improve the estimate of qcd power corrections up to dimension d = 12 and provide a new estimate of the ones up to d = 20 within the svz expansion by combining the ratio of the laplace sum rules ( lsr ) with the bnp $ \ tau $ - like decay moments for the i = 1 vector current. the results in table 1 confirm a violation of the factorization of the four - quark condensates and the value of the gluon one $ < \ alpha _ s g ^ 2 > $ from some other sources. up to d = 20, i there is not any factorial nor exponential growth of the size of these power corrections. 3. i use these new values of power corrections to extract $ \ alpha _ s $ from the bnp lowest moment. to order $ \ alpha _ s ^ 4 $, i find within the svz expansion : $ \ alpha _ s ( m _ \ tau ) = 0. 3081 ( 50 ) _ { fit } ( 71 ) _ { \ alpha _ s ^ 5 } $ [ resp. $ 0. 3260 ( 47 ) _ { fit } ( 62 ) _ { \ alpha _ s ^ 5 } ] $ implying $ \ alpha _ s ( m _ z ) = 0. 1170 ( 6 ) ( 3 ) _ { evol } $ [ resp. $ 0. 1192 ( 6 ) ( 3 ) _ { evol } $ ] for fixed order ( fo ) [ resp. contour improved ( ci ) ] pt series. they lead to the mean : $ \ alpha _ s ( m _ \ tau ) \ vert _ { svz } = 0. 3179 ( 58 ) _ { fit } ( 81 ) _ { syst } $ and $ \ alpha _ s ( m _ z ) \ vert _ { svz } = 0. 1182 ( 12 ) ( 3 ) _ { evol } $ where the systematic error ( syst ) takes into account the | arxiv:2402.13983 |
this paper studies the design of codes for distributed storage systems ( dss ) that enable local repair in the event of node failure. this paper presents locally repairable codes based on low degree multivariate polynomials. its code construction mechanism extends work on noisy interpolating set by dvir et al. \ cite { dvir2011 }. the paper presents two classes of codes that allow node repair to be performed by contacting 2 and 3 surviving nodes respectively. it further shows that both classes are good in terms of their rate and minimum distance, and allow their rate to be bartered for greater flexibility in the repair process. | arxiv:1204.6098 |
we present a cnn - based technique to estimate high - dynamic range outdoor illumination from a single low dynamic range image. to train the cnn, we leverage a large dataset of outdoor panoramas. we fit a low - dimensional physically - based outdoor illumination model to the skies in these panoramas giving us a compact set of parameters ( including sun position, atmospheric conditions, and camera parameters ). we extract limited field - of - view images from the panoramas, and train a cnn with this large set of input image - - output lighting parameter pairs. given a test image, this network can be used to infer illumination parameters that can, in turn, be used to reconstruct an outdoor illumination environment map. we demonstrate that our approach allows the recovery of plausible illumination conditions and enables photorealistic virtual object insertion from a single image. an extensive evaluation on both the panorama dataset and captured hdr environment maps shows that our technique significantly outperforms previous solutions to this problem. | arxiv:1611.06403 |
this study presents an architectural analysis of yolov11, the latest iteration in the yolo ( you only look once ) series of object detection models. we examine the models architectural innovations, including the introduction of the c3k2 ( cross stage partial with kernel size 2 ) block, sppf ( spatial pyramid pooling - fast ), and c2psa ( convolutional block with parallel spatial attention ) components, which contribute in improving the models performance in several ways such as enhanced feature extraction. the paper explores yolov11 ' s expanded capabilities across various computer vision tasks, including object detection, instance segmentation, pose estimation, and oriented object detection ( obb ). we review the model ' s performance improvements in terms of mean average precision ( map ) and computational efficiency compared to its predecessors, with a focus on the trade - off between parameter count and accuracy. additionally, the study discusses yolov11 ' s versatility across different model sizes, from nano to extra - large, catering to diverse application needs from edge devices to high - performance computing environments. our research provides insights into yolov11 ' s position within the broader landscape of object detection and its potential impact on real - time computer vision applications. | arxiv:2410.17725 |
rapid advancements in machine - learning methods have led to the emergence of machine - learning - based interatomic potentials as a new cutting - edge tool for simulating large systems with ab initio accuracy. still, the community awaits universal inter - atomic models that can be applied to a wide range of materials without tuning neural network parameters. we develop a unified deep - learning inter - atomic potential ( the dpa - semi model ) for 19 semiconductors ranging from group iib to via, including si, ge, sic, bas, bn, aln, alp, alas, inp, inas, insb, gan, gap, gaas, cdte, inte, cdse, zns, and cds. in addition, independent deep potential models for each semiconductor are prepared for detailed comparison. the training data are obtained by performing density functional theory calculations with numerical atomic orbitals basis sets to reduce the computational costs. we systematically compare various properties of the solid and liquid phases of semiconductors between different machine - learning models. we conclude that the dpa - semi model achieves gga exchange - correlation functional quality accuracy and can be regarded as a pre - trained model towards a universal model to study group iib to via semiconductors. | arxiv:2311.11305 |
the aim of this chapter is to describe two situations where positive noise correlations can be directly monitored using a transport experiment, either with a superconductor or with a correlated electron system. to be more precise, the present text reflects the presentations made by the three authors during the delft nato workshop. bell inequalities and quantum mechanical non - locality with electrons injected from a superconductor will be addressed first. next, noise correlations will be computed in a carbon nanotube where electrons are injected in the bulk from a stm tip. the first topic is the result of an ongoing collaboration with g. lesovik and g. blatter over the years. the unifying theme is that in both branched quantum circuits, entanglement is explicit and can be illustrated via noise correlations. entanglement can be achieved either for pairs of electrons in the case of superconductor sources connected to fermi liquid leads, or alternatively for pairs of quasiparticle excitations of the correlated electron fluid. | arxiv:cond-mat/0209517 |
we propose heavy axions as a natural superheavy dark matter candidate in string theory, with the relic density of dark matter originating in quantum fluctuations during cosmic inflation. string theory is well known for the possibility of having tens to hundreds of axion - like particles - - the axiverse. moduli stabilization generates high - scale masses for many of these, placing them naturally in the superheavy regime of particle physics. we consider moduli stabilization in the kklt framework, featuring a single volume modulus and $ c _ 4 $ axion, and a fiducial inflation model minimally coupled to the volume modulus. we demonstrate that both the volume modulus and the axion can be abundantly produced through gravitational particle production. the former is unstable and readily decays to standard model particles while the latter ( the axion ) can be stable and survives to constitute the present day dark matter. | arxiv:2504.13256 |
transport and magnetic studies of ca3ru2o7 for temperatures ranging from 0. 4 k to 56 k and magnetic fields, b, up to 45 t leads to strikingly different behavior when the field is applied along the different crystal axes. a ferromagnetic ( fm ) state with full spin polarization is achieved for b | | a - axis, but colossal magnetoresistance is realized only for b | | b - axis. for b | | c - axis, shubnikov - de haas oscillations are observed and followed by a less resistive state than for b | | a. hence, in contrast to standard colossal magnetoresistive materials, the fm phase is the least favorable for electron hopping. these properties together with highly unusual spin - charge - lattice coupling near the mott transition ( 48 k ) are driven by the orbital degrees of freedom. | arxiv:cond-mat/0503708 |
we introduce new models that incorporate layer corrugation and interface roughness into standard approaches for measuring interface stress in nanomultilayers ( nmls ). applied to cu / w nmls, these models show that ignoring such features can inflate measured interface stress by up to 0. 4 j / m ^ 2. however, corrugation and roughness alone cannot account for the extreme stresses reported, suggesting that atomic - scale phenomena ( e. g., intermixing and metastable phase formation at the interfaces ) dominate. these findings highlight the importance of balancing bilayer counts and thickness - to - roughness ratios for reliable stress quantification, providing a practical pathway to designing and characterizing advanced nanocomposite coatings with improved accuracy. | arxiv:2501.18247 |
we study disk - instantons ending on coisotropic branes preserved by real torus action in toric calabi - yau 3 - folds. in particular, we find fermion zero modes on disk multi - covers ending on a coisotropic brane in local p ^ 1 geometry with normal bundle ( - a, a - 2 ). it turns out that, independent of a, disk multi - cover formula is the same as for disks ending on a lagrangian brane in resolved conifold. we further construct an example of a coisotropic brane in calabi - yau 3 - fold used in geometric engineering of 4d n = 2 su ( k ) gauge theory, where this brane provides a surface defect. | arxiv:1410.2340 |
in this paper we consider a class of einstein warped product semi - riemannian manifolds $ \ widehat { m } = m ^ { n } \ times _ { f } n ^ { m } $ with $ n \ geq 3 $ and $ m \ geq 2 $. for $ \ widehat { m } $ with compact base and ricci - flat fiber, we prove that $ \ widehat { m } $ is simply a riemannian product space. then, when the base $ m $ is conformal to a pseudo - euclidean space which is invariant under the action of a $ ( n - 1 ) $ - dimensional translation group, we classify all such spaces. furthermore, we get new examples of complete einstein warped products riemannian manifolds. | arxiv:1708.04720 |
we study conformational transitions of simple coarse - grained models for protein - like heteropolymers on the simple cubic lattice and off - lattice, respectively, by means of multicanonical sampling algorithms. the effective hydrophobic / polar models do not require the knowledge of the native topology for a given sequence of residues as input. therefore these models are eligible to investigate general properties of the tertiary folding behaviour of such protein - like heteropolymers. | arxiv:0710.4095 |
we study the spectroscopic appearance of very massive stars and their effect on the integrated light of starbursts at low metallicity ( z ). we adopt two frameworks for the mass loss rates of vms : in one case we assume no z dependence, in the other case we assume a linear scaling with z. we compute evolutionary models for masses 150, 200, 250 and 300 msun at z = 0. 2, 0. 1 and 0. 01 zsun. we compute the associated synthetic spectra at selected points along the evolutionary tracks. finally we build population synthesis models including vms. we find that the evolution of vms critically depends on the assumptions regarding mass loss rates. in case of no z dependence vms remain hot for all their lifetime. conversely when mass loss rates are reduced because of lower z vms follow a classical evolution towards the red part of the hr diagram. vms display heii 1640 emission in most phases of their evolution, except when they become too cool. this line is present in the integrated light of population synthesis models down to 0. 1 zsun whatever the star formation history, and is also sometimes seen at z = 0. 01 zsun. heii 1640 is weaker in models that include a z scaling of the mass loss rates. the optical spectra of starbursts, especially the wolf - rayet bumps, sometimes display vms signatures when these stars are present. at low z, adding vms to population synthesis models produces more ionising photons down to 45 ev. at higher energy the ionising flux depends on age, z, assumption regarding vms mass loss rates, and on the very short phases at the end of vms evolution. heii ionising fluxes large enough to produce some amount of nebular heii 4686 emission can be produced under specific circumstances. our models are able to reproduce qualitatively and sometimes also quantitatively the uv spectra of star - forming regions. however we are not able to clearly identify which mass loss framework is favoured. | arxiv:2505.02993 |
coded caching is an effective technique to reduce the redundant traffic in wireless networks. the existing coded caching schemes require the splitting of files into a possibly large number of subfiles, i. e., they perform coded subfile caching. keeping the files intact during the caching process would actually be appealing, broadly speaking because of its simpler implementation. however, little is known about the effectiveness of this coded file caching in reducing the data delivery rate. in this paper, we propose such a file caching scheme which uses a decentralized algorithm for content placement and either an online clique cover or matching algorithm for the delivery of missing data. we derive approximations for the expected delivery rate of both schemes using the differential equations method, and show them to be tight through concentration analysis and computer simulations. our numerical results demonstrate that the proposed coded file caching is significantly more effective than uncoded caching in reducing the delivery rate. we furthermore show the additional improvement in the performance of the proposed scheme when its application is extended to subfile caching with a small number of subfiles. | arxiv:1708.07493 |
in the present work we present a general framework which guarantees the existence of optimal domains for isoperimetric problems within the class of $ c ^ { 1, 1 } $ - regular domains satisfying a uniform ball condition as long as the desired objective function satisfies certain properties. we then verify that the helicity isoperimetric problem studied in [ j. cantarella, d. deturck, h. gluck and m. teytel, j. math. phys. 41, 5615 ( 2000 ) ] satisfies the conditions of our framework and hence establish the existence of optimal domains within the given class of domains. we additionally use the same framework to prove the existence of optimal domains among uniform $ c ^ { 1, 1 } $ - domains for a first curl eigenvalue problem which has been studied recently for other classes of domains in [ a. enciso, w. gerner and d. peralta - salas, trans. amer. math. soc. 377, 4519 - 4540 ( 2024 ) ]. | arxiv:2305.13642 |
this document is one of the deliverable reports created for the escape project. escape stands for energy - efficient scalable algorithms for weather prediction at exascale. the project develops world - class, extreme - scale computing capabilities for european operational numerical weather prediction and future climate models. this is done by identifying weather & climate dwarfs which are key patterns in terms of computation and communication ( in the spirit of the berkeley dwarfs ). these dwarfs are then optimised for different hardware architectures ( single and multi - node ) and alternative algorithms are explored. performance portability is addressed through the use of domain specific languages. this deliverable provides an evaluation of the work performed within escape to port different dwarfs to accelerators, using different programming models. a key metric of the evaluation is the performance portability of the resulting porting efforts. portability means that a single source code containing the numerical operators can be compiled and run in multiple architectures, while performance portability additionally requires that the single source code runs efficiently in all the different architectures. as results of other deliverables like d2. 1, d2. 4 escape provides a collection of dwarfs ported to different computing architectures like traditional cpus, intel xeonphi and nvidia gpus. additionally d3. 3 went through an optimization process to obtain efficient and energy efficient dwarfs. in this deliverable we present a review of the different programming models employed and their use to port various dwarfs of escape. a final evaluation of the different approaches based on different metrics like performance portability, readability of the numerical methods, efforts to port a dwarf and efficiency of the implementation obtained is reported. | arxiv:1908.06094 |
the celebrated erd \ h { o } s - ko - rado theorem determines the maximum size of a $ k $ - uniform intersecting family. the hilton - milner theorem determines the maximum size of a $ k $ - uniform intersecting family that is not a subfamily of the so - called erd \ h { o } s - ko - rado family. in turn, it is natural to ask what the maximum size of an intersecting $ k $ - uniform family that is neither a subfamily of the erd \ h { o } s - ko - rado family nor of the hilton - milner family is. for $ k \ ge 4 $, this was solved ( implicitly ) in the same paper by hilton - milner in 1967. we give a different and simpler proof, based on the shifting method, which allows us to solve all cases $ k \ ge 3 $ and characterize all extremal families achieving the extremal value. | arxiv:1509.05464 |
we present a measurement of the evolution of the stellar mass function ( mf ) of galaxies and the evolution of the total stellar mass density at 0 < z < 5. we use deep multicolor data in the fors deep field ( fdf ; i - selected reaching i _ ab = 26. 8 ) and the goods - s / cdfs region ( k - selected reaching k _ ab = 25. 4 ) to estimate stellar masses based on fits to composite stellar population models for 5557 and 3367 sources, respectively. the mf of objects from the goods - s sample is very similar to that of the fdf. near - ir selected surveys hence detect the more massive objects of the same principal population as do i - selected surveys. we find that the most massive galaxies harbor the oldest stellar populations at all redshifts. at low z, our mf follows the local mf very well, extending the local mf down to 10 ^ 8 msun. the faint end slope is consistent with the local value of alpha ~ 1. 1 at least up to z ~ 1. 5. our mf also agrees very well with the munics and k20 results at z < 2. the mf seems to evolve in a regular way at least up to z ~ 2 with the normalization decreasing by 50 % to z = 1 and by 70 % to z = 2. objects having m > 10 ^ 10 msun which are the likely progenitors of todays l * galaxies are found in much smaller numbers above z = 2. however, we note that massive galaxies with m > 10 ^ 11 msun are present even to the largest redshift we probe. beyond z = 2 the evolution of the mass function becomes more rapid. we find that the total stellar mass density at z = 1 is 50 % of the local value. at z = 2, 25 % of the local mass density is assembled, and at z = 3 and z = 5 we find that at least 15 % and 5 % of the mass in stars is in place, respectively. the number density of galaxies with m > 10 ^ 11 msun evolves very similarly to the evolution at lower masses. it decreases by 0. 4 dex to z = 1, by 0. 6 dex to z = 2, and by 1 dex to z = 4. | arxiv:astro-ph/0412167 |
green illusions, university of nebraska press, 2012. = = external links = = appropedia – the sustainability wiki – world wide wiki of sustainable technology ( appropriate technology portal ) akvopedia — the open water and sanitation knowledge resource aprovecho – an environmental education center with a focus on living with appropriate technologies. the appropriate technology collaborative – an appropriate technology design and dissemination nonprofit. the whole earth catalog : access to tools and ideas archived 2009 - 01 - 06 at the wayback machine guide des innovations pour lutter contre la pauvrete ( innovation guide to tackle poverty ) / available in french, german and portuguese, this guide features 100 innovations designed to improve the living conditions of the poor. | https://en.wikipedia.org/wiki/Appropriate_technology |
plasma densification through magnetic compression has been suggested for time - resolved control of the wave properties in plasma - based accelerators. using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro - period is investigated. for compression times shorter than the transit time of a compressional alfven wave across the plasma slab, results show the formation of two counter - propagating shock waves, leading to a highly non - uniform plasma density profile. furthermore, the plasma slab displays large hydromagnetic like oscillations after the driving field has reached steady state. peak compression is obtained when the two shocks collide in the mid - plane. at this instant, very large plasma heating is observed, and plasma $ \ beta $ is estimated to be about $ 1 $. although these results point out a densification mechanism quite different and more complex than initially envisioned, these features could possibly be advantageous in particle accelerators. | arxiv:1601.06883 |
the current status of electroweak physics results from lep is reviewed. particular emphasis is placed on the latest results on the properties of the z and w bosons. the updated status of the global electroweak fit to the standard model and the resulting standard model higgs mass limits are presented. | arxiv:hep-ex/0605093 |
we prove a a formula for the first variation of the integral of a log - concave function, which allows us to define the surface area measure of such a function. the formula holds in complete generality with no regularity assumptions, and is intimately related to the notion of anisotropic total variation and to anisotropic coarea formulas. this improves previous partial results by colesanti and fragal \ ` a, by cordero - erausquin and klartag and by the author. | arxiv:2206.13146 |
a large decrease is observed in the critical current density of ybco coated conductors ( cc ) and related compounds when a strong perpendicular magnetic field is applied. while measurements are generally carried out at 77k only, here we present a magnetic technique permitting to determine the critical current per unit width of conductor ( icr / w ) in a large temperature range. we report measurements carried out on various ccs that show that, in addition to the reduction in the critical temperature that can be attributed to the low value of the irreversibility field near tc, the field application results in a large decrease of icr / w at all temperatures. we ascribe this reduction to the josephson behaviour of the twin boundaries included in the ybco layer. | arxiv:1207.5691 |
a cascade of dihedral symmetries is hidden in young ' s lattice of integer partitions. in fact, for each integer n > 2 the hasse graph of the subposet consisting of the partitions with maximal hook length strictly less than n has the dihedral group of order 2n as its symmetry group. here a new interpretation of those hasse graphs is presented, namely as the 1 - skeleta of the injective hulls of certain finite metric spaces. | arxiv:1212.4463 |
quantum darwinism ( qd ) proposes that classical objectivity emerges from the broadcast of information about a microscopic degree of freedom into multiple fractions of a many - body environment. such a broadcast of information is in sharp contrast with its scrambling under strong interaction. it was recently shown that quantum dynamics interpolating between broadcasting and scrambling may display sharp phase transitions of information propagation, named qd - encoding transitions. here, we initiate their systematic study in generic, non - clifford settings. first, in a general theoretical setup where the information propagation is modeled as an isometry, whose input qudit is entangled with a reference, we propose a probe of the transitions - - the distribution of the density matrix of the reference after measuring an environment fraction. this probe measures the classical correlation between the fraction and the injected information. we then apply the framework to two similar models defined by a tensor network on an expanding tree, modeling a noisy apparatus that attempts to broadcast the $ z $ component of a spin - half. we derive an exact recursion relation of the density matrix distribution, which we analyze analytically and numerically. as a result we find three phases : qd, intermediate and encoding, and two continuous transitions. the encoding - intermediate transition describes the establishment of nonzero correlation between the reference and a small environment fraction, and can be probed by a ` ` coarse - grained ' ' measure of the total spin - $ z $ of the fraction, which becomes non - gaussian and symmetry breaking in the intermediate space. the qd - intermediate transition is about whether the correlation is perfect. it must be probed by fined - grained measures, and corresponds to a more subtle symmetry breaking in the replica space. | arxiv:2312.04284 |
the complementary characteristics of active and passive depth sensing techniques motivate the fusion of the li - dar sensor and stereo camera for improved depth perception. instead of directly fusing estimated depths across lidar and stereo modalities, we take advantages of the stereo matching network with two enhanced techniques : input fusion and conditional cost volume normalization ( ccvnorm ) on the lidar information. the proposed framework is generic and closely integrated with the cost volume component that is commonly utilized in stereo matching neural networks. we experimentally verify the efficacy and robustness of our method on the kitti stereo and depth completion datasets, obtaining favorable performance against various fusion strategies. moreover, we demonstrate that, with a hierarchical extension of ccvnorm, the proposed method brings only slight overhead to the stereo matching network in terms of computation time and model size. for project page, see https : / / zswang666. github. io / stereo - lidar - ccvnorm - project - page / | arxiv:1904.02917 |
a two - component model of radio emission has been used to explain some radio observational properties of active galactic nuclei ( agns ) and, in particular, of blazars. in this work, we extend the two - component idea to the $ \ gamma $ - ray emission and assume that the total $ \ gamma $ - ray output of blazars consists of relativistically beamed and unbeamed components. the basic idea leverages the correlation between the radio core - dominance parameter and the $ \ gamma $ - ray beaming factor. to do so, we evaluate this correlation for a large sample of 584 blazars taken from the fourth source catalog of the fermi large area telescope ( fermi - lat ) and correlated their $ \ gamma $ - ray core - dominance parameters with radio core - dominance parameters. the $ \ gamma $ - ray beaming factor is then used to estimate the beamed and unbeamed components. our analysis confirms that the $ \ gamma $ - ray emission in blazars is mainly from the beamed component. | arxiv:2009.06624 |
we present the results of an experiment on measuring the gradient of the casimir force between an au - coated hollow glass microsphere and graphene - coated fused silica plate by means of a modified atomic force microscope cantilever based technique operated in the dynamic regime. these measurements were performed in high vacuum at room temperature. the energy gap and the concentration of impurities in the graphene sample used have been measured utilizing scanning tunnelling spectroscopy and raman spectroscopy, respectively. the measurement results for the gradients of the casimir force are found to be in a very good agreement with theory using the polarization tensor of graphene at nonzero temperature depending on the energy gap and chemical potential with no fitting parameters. the theoretical predictions of the same theory at zero temperature are experimentally excluded over the measurement region from 250 to 517 nm. we have also investigated a dependence of the thermal correction to the casimir force gradient on the values of the energy gap, chemical potential, and on the presence of a substrate supporting the graphene sheet. it is shown that the observed thermal effect is consistent in size with that arising for pristine graphene sheets if the impact of real conditions such as nonzero values of the energy gap, chemical potential, and the presence of a substrate is included. implications of the obtained results to the resolution of the long - standing problems in casimir physics are discussed. in addition to the paper published previously [ m. liu { \ it et al }., phys. rev. lett. { \ bf 126 }, 206802 ( 2021 ) ], we present measurement results for the energy gap of the graphene sample, double the experimental data for the casimir force, and perform a more complete theoretical analysis. | arxiv:2108.07558 |
this paper deals with the theoretical modeling of anisotropic compact stars in the framework of $ f ( t ) $ theory of gravity, where $ t $ is torsion scalar. to this end, we have used the exact solutions of krori and barua metric to a static spherically symmetric metric. the unknown constants involved in the krori and barua metric have been specified by using the masses and radii of compact stars 4 $ u $ 1820 - 30, her x - 1, sax j 1808 - 3658. the physical properties of these stars have been analyzed in the framework of $ f ( t ) $ theory. in this setting, we have checked the anisotropic behavior, regularity conditions, stability and surface redshift of the compact stars. | arxiv:1501.05829 |
the primal - dual hybrid gradient ( pdhg ) method is a powerful optimization scheme that breaks complex problems into simple sub - steps. unfortunately, pdhg methods require the user to choose stepsize parameters, and the speed of convergence is highly sensitive to this choice. we introduce new adaptive pdhg schemes that automatically tune the stepsize parameters for fast convergence without user inputs. we prove rigorous convergence results for our methods, and identify the conditions required for convergence. we also develop practical implementations of adaptive schemes that formally satisfy the convergence requirements. numerical experiments show that adaptive pdhg methods have advantages over non - adaptive implementations in terms of both efficiency and simplicity for the user. | arxiv:1305.0546 |
we have studied the hadron spectrum while varying the number of light dynamical quarks when the physical lattice spacing and volume are held fixed relative to the rho mass. for two and zero flavors of staggered fermions, we find the nucleon to rho mass ratios ( extrapolated to zero valence quark mass ) are very similar. however, for four flavors the ratio is 7 % ( 2 standard deviations ) above the two flavor result. | arxiv:hep-lat/9705029 |
a constituent quark model is developed for an arbitrary light - cone direction \ omega. form factors are obtained from free one - body electromagnetic current matrix elements. they are found to be \ omega - independent for spin - 0 mesons, the nucleon and \ lambda hyperon, while there is \ omega - dependence for spin - 1 systems like the deuteron. | arxiv:hep-ph/9512382 |
in this work, we examine recently developed methods for bayesian inference of optimal dynamic treatment regimes ( dtrs ). dtrs are a set of treatment decision rules aimed at tailoring patient care to patient - specific characteristics, thereby falling within the realm of precision medicine. in this field, researchers seek to tailor therapy with the intention of improving health outcomes ; therefore, they are most interested in identifying optimal dtrs. recent work has developed bayesian methods for identifying optimal dtrs in a family indexed by $ \ psi $ via bayesian dynamic marginal structural models ( msms ) ( rodriguez duque et al., 2022a ) ; we review the proposed estimation procedure and illustrate its use via the new bayesdtr r package. although methods in ( rodriguez duque et al., 2022a ) can estimate optimal dtrs well, they may lead to biased estimators when the model for the expected outcome if everyone in a population were to follow a given treatment strategy, known as a value function, is misspecified or when a grid search for the optimum is employed. we describe recent work that uses a gaussian process ( $ gp $ ) prior on the value function as a means to robustly identify optimal dtrs ( rodriguez duque et al., 2022b ). we demonstrate how a $ gp $ approach may be implemented with the bayesdtr package and contrast it with other value - search approaches to identifying optimal dtrs. we use data from an hiv therapeutic trial in order to illustrate a standard analysis with these methods, using both the original observed trial data and an additional simulated component to showcase a longitudinal ( two - stage dtr ) analysis. | arxiv:2303.15281 |
we present xmm - newton epic observations of warm absorbers in the quasars pg 1114 + 445 and pg 1309 + 355, both of which exhibit evidence for absorption by warm material in the line - of - sight. we find the absorption in pg 1114 + 445 to be in two phases, a ` hot ' phase with a log ionisation parameter xi of 2. 57, and a ` cooler ' phase with log xi of 0. 83 ; an unresolved transition array ( uta ) of m - shell iron is observed in the cooler phase. the absorption in this quasar is similar to that observed in the seyfert 1 ngc 3783. the absorption in pg 1309 + 355 consists of a single phase, with log xi of 1. 87. the absorbing gas lies at distances of 10 ^ { 18 } - 10 ^ { 22 } cm from the continuum radiation sources in these agn, which suggests that it could originate in a wind emanating from a molecular torus. we derive distances assuming that these x - ray warm absorbers have the same velocity as the uv warm absorbers observed in these quasars. the distances to the warm absorbers from the central continuum source scale approximately with the square root of the agn ionising luminosity, a result consistent with the warm absorber originating as a torus wind. the kinetic luminosities of these outflowing absorbers represent insignificant fractions ( < 10 ^ { - 3 } ) of the energy budgets of the agn. | arxiv:astro-ph/0408160 |
despite the performance advantages of modern sampling - based motion planners, solving high dimensional planning problems in near real - time remains a challenge. applications include hyper - redundant manipulators, snake - like and humanoid robots. based on the intuition that many of these problem instances do not require the robots to exercise every degree of freedom independently, we introduce an enhancement to popular sampling - based planning algorithms aimed at circumventing the exponential dependence on dimensionality. we propose beginning the search in a lower dimensional subspace of the configuration space in the hopes that a simple solution will be found quickly. after a certain number of samples are generated, if no solution is found, we increase the dimension of the search subspace by one and continue sampling in the higher dimensional subspace. in the worst case, the search subspace expands to include the full configuration space - making the completeness properties identical to the underlying sampling - based planer. our experiments comparing the enhanced and traditional version of rrt, rrt - connect, and bidirectionalt - rrt on both a planar hyper - redundant manipulator and the baxter humanoid robot indicate that a solution is typically found much faster using this approach and the run time appears to be less sensitive to the dimension of the full configuration space. we explore important implementation issues in the sampling process and discuss its limitations. | arxiv:1802.00328 |
entropy is the distinguishing and most important concept of our efforts to understand and regularize our observations of a very large class of natural phenomena, and yet, it is one of the most contentious concepts of physics. in this article, we review two expositions of thermodynamics, one without reference to quantum theory, and the other quantum mechanical without probabilities of statistical mechanics. in the first, we show that entropy is an inherent property of any system in any state, and that its analytical expression must conform to eight criteria. in the second, we recognize that quantum thermodynamics : ( i ) admits quantum probabilities described either by wave functions or by nonstatistical density operators ; and ( ii ) requires a nonlinear equation of motion that is delimited by but more general than the schroedinger equation, and that accounts for both reversible and irreversible evolutions of the state of the system in time. both the more general quantum probabilities, and the equation of motion have been defined, and the three laws of thermodynamics are shown to be theorems of this equation. | arxiv:quant-ph/0512251 |
the use of supersymmetric localisation has recently led to modular covariant expressions for certain integrated correlators of half - bps operators in $ \ mathcal { n } = 4 $ supersymmetric yang - mills theory with a general classical gauge group $ g _ n $. here we determine generating functions that encode such integrated correlators for any classical gauge group and provide a proof of previous conjectured formulae. this gives a systematic understanding of the relation between properties of these correlators at finite $ n $ and their expansions at large $ n $. in particular, it determines a duality - invariant non - perturbative completion of the large - $ n $ expansion in terms of a sum of novel non - holomorphic modular functions. these functions are exponentially suppressed at large $ n $ and have the form of a sum of contributions from coincident $ ( p, q ) $ - string world - sheet instantons. | arxiv:2210.14038 |
let $ h _ { a, b } ^ n $ denote the component of the hilbert scheme whose general point parameterizes an $ a $ - plane union a $ b $ - plane meeting transversely in $ \ mathbf { p } ^ n $. we describe the effective and nef cones of $ h _ { a, b } ^ n $ and determine when the component is fano. moreover, we show that $ h _ { a, b } ^ n $ is a mori dream space for all values of $ a, b, n $. | arxiv:2006.06211 |
let $ \ pi : sl ( n | n ) \ to a ( n - 1, n - 1 ) $ be the natural epimorphism of lie superalgebra. then $ \ dim \ ker \ pi = 1 $. let $ \ pi ^ { ( t ) } : sl ^ { ( t ) } ( n | n ) \ to a ^ { ( t ) } ( n - 1, n - 1 ) $ be the natural epimorphism, where $ t = 1, 2, 4 $. let $ \ { e _ k | k \ in { \ mathbb { z } } \ } $ be the basis of $ \ ker \ pi ^ { ( t ) } $ with $ e _ k \ in sl ^ { ( t ) } ( n | n ) _ { ( a _ tk + b _ t ) \ delta } $, where $ ( a _ 1, b _ 1 ) = ( 1, 0 ) $, $ ( a _ 2, b _ 2 ) = ( 2, - 1 ) $ and $ ( a _ 4, b _ 4 ) = ( 4, - 2 ) $. the main result of this paper is to explicitly describe an element of $ u _ q ( sl ^ { ( t ) } ( n | n ) ) $ ( and its multi - parameter version ) corresponding to $ e _ 1 $ ( i. e., $ k = 1 $ ). as for $ u _ q ( sl ^ { ( 1 ) } ( n | n ) ) $ ( i. e., $ t = 1 $ ), the author had already had explicit description for every $ k $ in 1999. | arxiv:1809.03223 |
accurate risk stratification is key to reducing cancer morbidity through targeted screening and preventative interventions. numerous breast cancer risk prediction models have been developed, but they often give predictions with conflicting clinical implications. integrating information from different models may improve the accuracy of risk predictions, which would be valuable for both clinicians and patients. brcapro and bcrat are two widely used models based on largely complementary sets of risk factors. brcapro is a bayesian model that uses detailed family history information to estimate the probability of carrying a brca1 / 2 mutation, as well as future risk of breast and ovarian cancer, based on mutation prevalence and penetrance ( age - specific probability of developing cancer given genotype ). bcrat uses a relative hazard model based on first - degree family history and non - genetic risk factors. we consider two approaches for combining brcapro and bcrat : 1 ) modifying the penetrance functions in brcapro using relative hazard estimates from bcrat, and 2 ) training an ensemble model that takes as input brcapro and bcrat predictions. we show that the combination models achieve performance gains over brcapro and bcrat in simulations and data from the cancer genetics network. | arxiv:2008.01019 |
the classical and the quantum motion of a massive body in the rotating tube is considered. photon is included. the spin motion described by the bargmann - michel - telegdi equation is considered in the rotation tube and rotating system. | arxiv:1109.1716 |
the structure of the phase diagram of strongly interacting matter at moderate densities is calculated within a 3 - flavor njl - type quark model with realistic quark masses. we focus on the influence of the selfconsistently determined effective strange quark mass on the color - flavor unlocking phase transition. | arxiv:hep-ph/0202098 |
we propose a framework for transferring any existing policy from a potentially unknown source mdp to a target mdp. this framework ( 1 ) enables reuse in the target domain of any form of source policy, including classical controllers, heuristic policies, or deep neural network - based policies, ( 2 ) attains optimality under suitable theoretical conditions, and ( 3 ) guarantees improvement over the source policy in the target mdp. these are achieved by packaging the source policy as a black - box option in the target mdp and providing a theoretically grounded way to learn the option ' s initiation set through general value functions. our approach facilitates the learning of new policies by ( 1 ) maximizing the target mdp reward with the help of the black - box option, and ( 2 ) returning the agent to states in the learned initiation set of the black - box option where it is already optimal. we show that these two variants are equivalent in performance under some conditions. through a series of experiments in simulated environments, we demonstrate that our framework performs excellently in sparse reward problems given ( sub - ) optimal source policies and improves upon prior art in transfer methods such as continual learning and progressive networks, which lack our framework ' s desirable theoretical properties. | arxiv:2012.14942 |
in traffic signal control, flow - based ( optimizing the overall flow ) and pressure - based methods ( equalizing and alleviating congestion ) are commonly used but often considered separately. this study introduces a unified framework using lyapunov control theory, defining specific lyapunov functions respectively for these methods. we have found interesting results. for example, the well - recognized back - pressure method is equal to differential queue lengths weighted by intersection lane saturation flows. we further improve it by adding basic traffic flow theory. rather than ensuring that the control system be stable, the system should be also capable of adaptive to various performance metrics. building on insights from lyapunov theory, this study designs a reward function for the reinforcement learning ( rl ) - based network signal control, whose agent is trained with double deep q - network ( ddqn ) for effective control over complex traffic networks. the proposed algorithm is compared with several traditional and rl - based methods under pure passenger car flow and heterogenous traffic flow including freight, respectively. the numerical tests demonstrate that the proposed method outperforms the alternative control methods across different traffic scenarios, covering corridor and general network situations each with varying traffic demands, in terms of the average network vehicle waiting time per vehicle. | arxiv:2210.02612 |
given a textual passage and an answer, humans are able to ask questions with various expressions, but this ability is still challenging for most question generation ( qg ) systems. existing solutions mainly focus on the internal knowledge within the given passage or the semantic word space for diverse content planning. these methods, however, have not considered the potential of external knowledge for expression diversity. to bridge this gap, we propose rast, a framework for retrieval - augmented style transfer, where the objective is to utilize the style of diverse templates for question generation. for training rast, we develop a novel reinforcement learning ( rl ) based approach that maximizes a weighted combination of diversity reward and consistency reward. here, the consistency reward is computed by a question - answering ( qa ) model, whereas the diversity reward measures how much the final output mimics the retrieved template. experimental results show that our method outperforms previous diversity - driven baselines on diversity while being comparable in terms of consistency scores. our code is available at https : / / github. com / gouqi666 / rast. | arxiv:2310.14503 |
we consider multimodal c ^ 3 interval maps f satisfying a summability condition on the derivatives d _ n along the critical orbits which implies the existence of an absolutely continuous f - invariant probability measure mu. if f is non - renormalizable, mu is mixing and we show that the speed of mixing ( decay of correlations ) is strongly related to the rate of growth of the sequence d _ n as n tends to infinity. we also give sufficient conditions for mu to satisfy the central limit theorem. this applies for example to the quadratic fibonacci map which is shown to have subexponential decay of correlations. | arxiv:math/0208114 |
adapter - style efficient transfer learning ( etl ) has shown excellent performance in the tuning of vision - language models ( vlms ) under the low - data regime, where only a few additional parameters are introduced to excavate the task - specific knowledge based on the general and powerful representation of vlms. however, most adapter - style works face two limitations : ( i ) modeling task - specific knowledge with a single modality only ; and ( ii ) overlooking the exploitation of the inter - class relationships in downstream tasks, thereby leading to sub - optimal solutions. to mitigate that, we propose an effective adapter - style tuning strategy, dubbed graphadapter, which performs the textual adapter by explicitly modeling the dual - modality structure knowledge ( i. e., the correlation of different semantics / classes in textual and visual modalities ) with a dual knowledge graph. in particular, the dual knowledge graph is established with two sub - graphs, i. e., a textual knowledge sub - graph, and a visual knowledge sub - graph, where the nodes and edges represent the semantics / classes and their correlations in two modalities, respectively. this enables the textual feature of each prompt to leverage the task - specific structure knowledge from both textual and visual modalities, yielding a more effective classifier for downstream tasks. extensive experimental results on 11 benchmark datasets reveal that our graphadapter significantly outperforms previous adapter - based methods. the code will be released at https : / / github. com / lixinustc / graphadapter | arxiv:2309.13625 |
we study the topologically twisted osp ( 2 | 2 ) + osp ( 2 | 2 ) conformal superalgebra. the algebra includes the lagrangians which are intrinsic to the topological field theory and composed of fermionic generators. studying the lagrangians through a gauge system of osp ( 2 | 2 ) + osp ( 2 | 2 ), geometrical features inherent to the algebra are revealed : a moduli space associated with the algebra is derived and the crucial roles which the fermionic generators play in the moduli space are clarified it is argued that there exists a specific relation between the topological twist and the moduli problem through a geometrical aspect of the algebra. | arxiv:hep-th/9504135 |
the role of lorentz symmetry in noncommutative field theory is considered. any realistic noncommutative theory is found to be physically equivalent to a subset of a general lorentz - violating standard - model extension involving ordinary fields. some theoretical consequences are discussed. existing experiments bound the scale of the noncommutativity parameter to ( 10 tev ) ^ { - 2 }. | arxiv:hep-th/0105082 |
topology affects physical and biological properties of dna and impacts fundamental cellular processes, such as gene expression, genome replication, chromosome structure and segregation. in all organisms dna topology is carefully modulated and the supercoiling degree of defined genome regions may change according to physiological and environmental conditions. elucidation of structural properties of dna molecules with different topology may thus help to better understand genome functions. whereas a number of structural studies have been published on highly negatively supercoiled dna molecules, only preliminary observations of highly positively supercoiled are available, and a description of dna structural properties over the full range of supercoiling degree is lacking. atomic force microscopy ( afm ) is a powerful tool to study dna structure at single molecule level. we here report a comprehensive analysis by afm of dna plasmid molecules with defined supercoiling degree, covering the full spectrum of biologically relevant topologies, under different observation conditions. our data, supported by statistical and biochemical analyses, revealed striking differences in the behavior of positive and negative plasmid molecules. | arxiv:1711.02443 |
highly collimated outflows ( jets ) are observed across a wide range of astrophysical systems involving the accretion of material onto central objects, from supermassive black holes in active galaxies to proto - brown dwarfs and stellar - mass black holes. despite the diversity of their driving sources, it is believed that all jets are different manifestations of a single universal phenomenon. however, a unified explanation for their ejection and collimation remains elusive. in this study we present the first rotation measure analysis of the polarized synchrotron emission ever performed in a protostellar radio jet, which allows us to reveal its true 3d magnetic structure. unlike extragalactic radio jets, which often exhibit faint counterjets, protostellar radio jets allow both the jet and the counterjet to be analyzed. this exceptional circumstance allows us to unveil the magnetic field structure of both components. our findings provide the first solid evidence for a helical magnetic field within a protostellar jet, supporting the universality of the jet collimation mechanism. | arxiv:2501.07622 |
in this paper we introduce a mass for asymptotically flat manifolds by using the gauss - bonnet curvature. we first prove that the mass is well - defined and is a geometric invariant, if the gauss - bonnet curvature is integrable and the decay order $ \ tau $ satisfies $ \ tau > \ frac { n - 4 } { 3 }. $ then we show a positive mass theorem for asymptotically flat graphs over $ { \ mathbb r } ^ n $. moreover we obtain also penrose type inequalities in this case. | arxiv:1211.3645 |
the power spectrum of primordial tensor perturbations $ \ mathcal { p } _ t $ increases rapidly in high frequency region if the spectral index $ n _ t > 0 $. it is shown that the amplitude of relic gravitational wave $ h _ t $ ( $ 5 \ times10 ^ 9 $ hz ) varies from $ 10 ^ { - 36 } $ to $ 10 ^ { - 25 } $ while $ n _ t $ varies from $ - 6. 25 \ times 10 ^ { - 3 } $ to $ 0. 87 $. high frequency gravitational waves detector that is proposed by f. - y. li detects gravitational waves through observing the perturbed photon flux that is generated by interaction between the relic gravitational waves and electromagnetic system. it is shown that the perturbative photon flux $ n _ x ^ 1 $ ( $ 5 \ times10 ^ 9 $ hz ) varies from $ 1. 40 \ times10 ^ { - 4 } \ rm s ^ { - 1 } $ to $ 2. 85 \ times10 ^ { 7 } \ rm s ^ { - 1 } $ while $ n _ t $ varies from $ - 6. 25 \ times 10 ^ { - 3 } $ to $ 0. 87 $. correspondingly, the ratio of the transverse perturbative photon flux $ n _ x ^ 1 $ to the background photon flux varies from $ 10 ^ { - 28 } $ to $ 10 ^ { - 16 } $. | arxiv:1509.02443 |
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