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we identify a new hydrodynamical instability in protoplanetary discs that may arise due to variations in the dust - to - gas ratio and may lead to concentration of dust grains within a disc. the instability can arise due to dust settling, which produces a vertical compositional entropy gradient. the entropy gradient drives a baroclinic instability that is capable of creating toroidal gas vortices that gather dust into rings. such dust rings are potentially observable via continuum emission of the dust or scattered light. indeed, this instability may offer an explanation for the rings recently observed in the discs around the young stars hl tau and tw hya that does not rely on clearing by protoplanets. the instability may also have wider ramifications, potentially aiding dust agglomeration, altering the radial migration of larger planetesimals, and modifying angular momentum transport within a disc.
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arxiv:1507.05499
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experience replay \ citep { lin1993reinforcement, mnih2015human } is a widely used technique to achieve efficient use of data and improved performance in rl algorithms. in experience replay, past transitions are stored in a memory buffer and re - used during learning. various suggestions for sampling schemes from the replay buffer have been suggested in previous works, attempting to optimally choose those experiences which will most contribute to the convergence to an optimal policy. here, we give some conditions on the replay sampling scheme that will ensure convergence, focusing on the well - known q - learning algorithm in the tabular setting. after establishing sufficient conditions for convergence, we turn to suggest a slightly different usage for experience replay - replaying memories in a biased manner as a means to change the properties of the resulting policy. we initiate a rigorous study of experience replay as a tool to control and modify the properties of the resulting policy. in particular, we show that using an appropriate biased sampling scheme can allow us to achieve a \ emph { safe } policy. we believe that using experience replay as a biasing mechanism that allows controlling the resulting policy in desirable ways is an idea with promising potential for many applications.
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arxiv:2112.04229
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cherenkov telescopes play a major role in the growth of the tev astronomy which, in 20 years, has reached the status of an important branch of astrophysics, because of the observations of the violent, non thermal processes in the extreme band of the electromagnetic spectrum above several tens of gev up to several tens of tev. about one hundred extragalactic sources ( active galactic nuclei, blazars, and radiogalaxies ) and galactic sources ( shell supernovae remnants, pulsar wind nebulae, isolated pulsars, x - ray binaries, and unidentified sources ) have been detected so far. in the near future, an ambitious new array, the cherenkov compton telescope ( cta ) will substitute the present cherenkov telescopes arrays. cta is designed as an array of many ( 50 - 100 ) cherenkov telescopes operated in stereo mode. cta will allow to gain a factor of 10 in sensitivity with respect to the present arrays such as h. e. s. s., magic, and veritas. moreover, cta will connect the tev to the gev energy band covered by space missions such as fermi and agile, and will also explore the highest energy region of the electromagnetic spectrum up to several hundreds of tev.
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arxiv:1010.2208
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in this paper, we propose an optimized field / circuit coupling approach for the simulation of magnetothermal transients in superconducting magnets. the approach improves the convergence of the iterative coupling scheme between a magnetothermal partial differential model and an electrical lumped - element circuit. such a multi - physics, multi - rate and multi - scale problem requires a consistent formulation and a dedicated framework to tackle the challenging transient effects occurring at both circuit and magnet level during normal operation and in case of faults. we derive an equivalent magnet model at the circuit side for the linear and the non - linear settings and discuss the convergence of the overall scheme in the framework of optimized schwarz methods. the efficiency of the developed approach is illustrated by a numerical example of an accelerator dipole magnet with accompanying protection system.
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arxiv:1702.00958
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recent statistical analysis of two extragalactic observational surveys strongly indicate a sublinear kennicutt - schmidt ( ks ) relationship between the star formation rate ( sigsfr ) and molecular gas surface density ( sigmol ). here, we consider the consequences of these results in the context of common assumptions, as well as observational support for a linear relationship between sigsfr and the surface density of dense gas. if the co traced gas depletion time ( tau _ mol ) is constant, and if co only traces star forming giant molecular clouds ( gmcs ), then the physical properties of each gmc must vary, such as the volume densities or star formation rates. another possibility is that the conversion between co luminosity and sigmol, the xco factor, differs from cloud - to - cloud. a more straightforward explanation is that co permeates the hierarchical ism, including the filaments and lower density regions within which gmcs are embedded. a number of independent observational results support this description, with the diffuse gas comprising at least 30 % of the total molecular content. the co bright diffuse gas can explain the sublinear ks relationship, and consequently leads to an increasing tau _ mol with sigmol. if sigsfr linearly correlates with the dense gas surface density, a sublinear ks relationship indicates that the fraction of diffuse gas fdiff grows with sigmol. in galaxies where sigmol falls towards the outer disk, this description suggests that fdiff also decreases radially.
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arxiv:1404.5964
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in a recent work, the cross section measurement of the 64zn ( p, alpha ) 61cu reaction was used to prove that the standard alpha - nucleus optical potentials used in astrophysical network calculation fail to reproduce the experimental data at energies relevant for heavy element nucleosynthesis. in the present paper the analysis of the obtained experimental data is continued by comparing the results with the predictions using different parameters. it is shown that the recently suggested modification of the standard optical potential leads to a better description of the data.
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arxiv:1802.02802
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we study the pure su ( 3 ) gauge theory in 2 + 1 dimensions on the lattice using ' t hooft ' s twisted boundary conditions to force non - vanishing center flux through the finite volume. in this way we measure the free energy of spacelike center vortices as an order parameter for the deconfinement transition. the transition is of 2nd order in the universality class of the 2d 3 - state potts model, which is self - dual. this self - duality can be observed directly in the su ( 3 ) gauge theory, and it can be exploited to extract critical couplings with high precision in rather small volumes. we furthermore obtain estimates for critical exponents and the critical temperature in units of the dimensionful continuum coupling. finally, we also apply our methods to the ( 2 + 1 ) d su ( 4 ) gauge theory which was previously found to have a weak 1st order transition. we nevertheless observe at least approximate q = 4 potts scaling at length scales corresponding to the lattice sizes used in our simulations.
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arxiv:1012.0723
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the growing advancements in autonomous vehicles ( avs ) have emphasized the critical need to prioritize the absolute safety of av maneuvers, especially in dynamic and unpredictable environments or situations. this objective becomes even more challenging due to the uniqueness of every traffic situation / condition. to cope with all these very constrained and complex configurations, avs must have appropriate control architectures with reliable and real - time risk assessment and management strategies ( rams ). these targeted rams must lead to reduce drastically the navigation risks. however, the lack of safety guarantees proves, which is one of the key challenges to be addressed, limit drastically the ambition to introduce more broadly avs on our roads and restrict the use of avs to very limited use cases. therefore, the focus and the ambition of this paper is to survey research on autonomous vehicles while focusing on the important topic of safety guarantee of avs. for this purpose, it is proposed to review research on relevant methods and concepts defining an overall control architecture for avs, with an emphasis on the safety assessment and decision - making systems composing these architectures. moreover, it is intended through this reviewing process to highlight researches that use either model - based methods or ai - based approaches. this is performed while emphasizing the strengths and weaknesses of each methodology and investigating the research that proposes a comprehensive multi - modal design that combines model - based and ai approaches. this paper ends with discussions on the methods used to guarantee the safety of avs namely : safety verification techniques and the standardization / generalization of safety frameworks.
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arxiv:2305.17941
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we report the fabrication of mgb2 with bulk superconducting properties by conventional solid state methods at temperatures as low as 550 c. mg deficiencies of the type mg1 - xb2 were tested. tc was found to decrease by about 1k at large x, though the amount of non - stoichiometry, if any, is likely to be very small. for specific processing conditions, indications of the 25 - 30 k transition often seen in thin films were seen in the bulk materials. the lower temperature transition may be associated with the grain boundaries. these results indicate that it should be possible to fabricate mgb2 with bulk properties in in - situ thin films at temperatures of 600 c or less.
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arxiv:cond-mat/0107534
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we consider an $ n $ - player game where the players control the drifts of their diffusive states which have no interaction in the noise terms. the aim of each player is to minimize the expected value of her cost, which is a function of the player ' s state and the empirical measure of the states of all the players. our aim is to determine the $ n \ to \ infty $ asymptotic behavior of the upper order statistics of the player ' s states under nash equilibrium ( the nash states ). for this purpose, we consider also a system of interacting diffusions which is constructed by using the master pde of the game and approximates the system of the nash states, and we improve an $ l ^ 2 $ estimate for the distance between the drifts of the two systems which has been used for establishing central limit theorems and large deviations principles for the nash states in the past. by differentiating the master pde, we obtain that estimate also in $ l ^ { \ infty } $, which allows us to control the radon - nikodym derivative of a girsanov transformation that connects the two systems. the latter allows us to reduce the problem to the case of $ n $ uncontrolled diffusions with standard mean - field interaction in the drifts, which has been treated in a previous work.
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arxiv:2410.18869
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we consider the question of the amorphization of metallic alloys by melt quenching, as predicted by molecular dynamics simulations with semi - empirical potentials. the parametrization of the potentials is discussed on the example of the ternary cu - ti - zr transition metals alloy, using as reference the ab - initio simulation. the pair structure in the amorphous state is computed from a potential of the stillinger weber form. the transferability of the parameters during the quench is investigated using two parametrizations : from solid state data, as usual, and from a new parametrization on the liquid structure. when the adjustment is made on the pair structure of the liquid, a satisfactory transferability is found between the pure components and their alloys. the liquid structure predicted in this way agrees well with experiment, in contrast with the one obtained using the adjustment on the solid. the final structure, after quenches down to the amorphous state, determined with the new set of parameters is shown to be very close to the ab - initio one, the latter being in excellent agreement with recent x - rays diffraction experiments. the corresponding critical temperature of the glass transition is estimated from the behavior of the heat capacity. discussion of the consistency between the structures predicted using semi - empirical potentials and ab - initio simulation, and comparison of different experimental data underlines the question of the dependence of the final structure on the thermodynamic path followed to reach the amorphous state.
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arxiv:1506.06530
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the host galaxies of the five local, z < 0. 25, long - duration gamma - ray bursts, each of which had a well - documented associated supernova, are all faint and metal - poor compared to the population of local star - forming galaxies. we quantify this statement by using a previous analysis of star - forming galaxies ( z < 0. 2 ) from the sloan digital sky survey to estimate the fraction of local star formation as a function of host galaxy oxygen abundance. we find that only a small fraction ( < 25 % ) of current star formation occurs in galaxies with oxygen abundance 12 + log ( o / h ) < 8. 6, i. e., about half that of the milky way. however, all five low - z grb hosts have oxygen abundance below this limit, in three cases very significantly so. if grbs traced local star formation independent of metallicity, the probability of obtaining such low abundances for all five hosts would be p ~ 0. 1 %. we conclude that grbs trace only low - metallicity star formation, and that the milky way has been too metal rich to host long grbs for at least the last several billion years. this result has implications for the potential role of grbs in mass extinctions, for searches for recent burst remnants in the milky way and other large galaxies, for non - detections of late radio emission from local core - collapse supernovae, and for the production of cosmic rays in the local universe. we also find that the isotropic energy release of these five grbs, e _ iso, steeply decreases with increasing host oxygen abundance, suggesting an upper metallicity limit for ` ` cosmological ' ' grbs at ~ 0. 15 z _ solar. ( abridged )
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arxiv:astro-ph/0604113
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ldp deployments are vulnerable to inference attacks as an adversary can link the noisy responses to their identity and subsequently, auxiliary information using the order of the data. an alternative model, shuffle dp, prevents this by shuffling the noisy responses uniformly at random. however, this limits the data learnability - - only symmetric functions ( input order agnostic ) can be learned. in this paper, we strike a balance and show that systematic shuffling of the noisy responses can thwart specific inference attacks while retaining some meaningful data learnability. to this end, we propose a novel privacy guarantee, d - sigma - privacy, that captures the privacy of the order of a data sequence. d - sigma - privacy allows tuning the granularity at which the ordinal information is maintained, which formalizes the degree the resistance to inference attacks trading it off with data learnability. additionally, we propose a novel shuffling mechanism that can achieve \ name - privacy and demonstrate the practicality of our mechanism via evaluation on real - world datasets.
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arxiv:2106.06603
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in the 1970s and 1980s, searches performed by l. carter, c. lam, l. thiel, and s. swiercz showed that projective planes of order ten with weight 16 codewords do not exist. these searches required highly specialized and optimized computer programs and required about 2, 000 hours of computing time on mainframe and supermini computers. in 2011, these searches were verified by d. roy using an optimized c program and 16, 000 hours on a cluster of desktop machines. we performed a verification of these searches by reducing the problem to the boolean satisfiability problem ( sat ). our verification uses the cube - and - conquer sat solving paradigm, symmetry breaking techniques using the computer algebra system maple, and a result of carter that there are ten nonisomorphic cases to check. our searches completed in about 30 hours on a desktop machine and produced nonexistence proofs of about 1 terabyte in the drat ( deletion resolution asymmetric tautology ) format.
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arxiv:2001.11973
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in order to fully exploit the physics potential of a future high energy e + e - linear collider, a vertex tracker, providing high resolution track reconstruction, is required. hybrid silicon pixel sensors are an attractive option, for the sensor technology, due to their read - out speed and radiation hardness, favoured in the high rate environment of the tesla e + e - linear collider design but have been so far limited by the achievable single point space resolution. in this paper, a conceptual design of the tesla vertex tracker, based on a novel layout of hybrid pixel sensors with interleaved cells to improve their spatial resolution, is presented.
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arxiv:hep-ex/9911013
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a novel method, the gaussian integral method ( gim ), is presented for calculating void fractions in computational fluid dynamics - discrete element method ( cfd - dem ) simulations. gim is versatile and applicable to various grid types, including structured and unstructured polyhedral meshes, without requiring special boundary treatments. an optimization technique is introduced to make gim independent of grid resolution and type. the method is validated against experimental data from a fluidized bed, demonstrating that gim produces realistic simulations closely resembling experimental observations. additionally, unstructured polyhedral grids using gim outperform structured grids of equivalent resolution, yielding results more aligned with experimental data. the gradient of the void fraction is computed in the cfd solver and utilized in the dem solver for precise estimation at particle locations. overall, gim provides an effective solution for void fraction calculations in particulate media simulations with complex geometries, enhancing the accuracy and applicability of cfd - dem simulations in industrial applications.
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arxiv:2408.00909
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sums of walks for charged particles ( e. g. hofstadter electrons ) on a square lattice in the presence of a magnetic field are evaluated. returning loops are systematically added to directed paths to obtain the unrestricted propagators. expressions are obtained for special values of the magnetic flux - per - plaquette commensurate with the flux quantum. for commensurate and incommensurate values of the flux, the addition of small returning loops does not affect the general features found earlier for directed paths. lattice green ' s functions are also obtained for staggered flux configurations encountered in models of high - tc superconductors.
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arxiv:cond-mat/9310024
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and irrigation in the alluvial south, and catchment systems stretching for tens of kilometers in the hilly north. their palaces had sophisticated drainage systems. writing was invented in mesopotamia, using the cuneiform script. many records on clay tablets and stone inscriptions have survived. these civilizations were early adopters of bronze technologies which they used for tools, weapons and monumental statuary. by 1200 bc they could cast objects 5 m long in a single piece. several of the six classic simple machines were invented in mesopotamia. mesopotamians have been credited with the invention of the wheel. the wheel and axle mechanism first appeared with the potter ' s wheel, invented in mesopotamia ( modern iraq ) during the 5th millennium bc. this led to the invention of the wheeled vehicle in mesopotamia during the early 4th millennium bc. depictions of wheeled wagons found on clay tablet pictographs at the eanna district of uruk are dated between 3700 and 3500 bc. the lever was used in the shadoof water - lifting device, the first crane machine, which appeared in mesopotamia circa 3000 bc, and then in ancient egyptian technology circa 2000 bc. the earliest evidence of pulleys date back to mesopotamia in the early 2nd millennium bc. the screw, the last of the simple machines to be invented, first appeared in mesopotamia during the neo - assyrian period ( 911 – 609 ) bc. the assyrian king sennacherib ( 704 – 681 bc ) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two - part clay molds rather than by the ' lost wax ' process. the jerwan aqueduct ( c. 688 bc ) is made with stone arches and lined with waterproof concrete. the babylonian astronomical diaries spanned 800 years. they enabled meticulous astronomers to plot the motions of the planets and to predict eclipses. the earliest evidence of water wheels and watermills date back to the ancient near east in the 4th century bc, specifically in the persian empire before 350 bc, in the regions of mesopotamia ( iraq ) and persia ( iran ). this pioneering use of water power constituted the first human - devised motive force not to rely on muscle power ( besides the sail ). = = = = egypt = = = = the egyptians, known for building pyramids centuries before the creation of modern tools, invented and used many simple machines, such as the ramp to aid construction processes. historians and archaeologists have found evidence that the pyramids were built using
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https://en.wikipedia.org/wiki/History_of_technology
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we introduce a system of monadic affine sized types, which substantially generalise usual sized types, and allows this way to capture probabilistic higher - order programs which terminate almost surely. going beyond plain, strong normalisation without losing soundness turns out to be a hard task, which cannot be accomplished without a richer, quantitative notion of types, but also without imposing some affinity constraints. the proposed type system is powerful enough to type classic examples of probabilistically terminating programs such as random walks. the way typable programs are proved to be almost surely terminating is based on reducibility, but requires a substantial adaptation of the technique.
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arxiv:1701.04089
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organosulfur species are potential major carriers of sulfur in the interstellar medium, as well as interesting ingredients in prebiotic chemistry. the most fundamental question regarding these species is under which conditions they reside in the gas versus solid phase. here, we characterize the thermal desorption kinetics, binding energies, and entrapment of the organosulfur methyl mercaptan ( ch $ _ 3 $ sh, or mesh ) in different ice environments, comparing them with those of methanol ( ch $ _ 3 $ oh, or meoh ) ices. the derived multi - layer ( pure mesh - mesh ) and sub - monolayer ( layered mesh - h $ _ 2 $ o ) binding energies are surprisingly similar, corresponding to snow line locations where the disk midplane temperature is ~ 105 k. in both h $ _ 2 $ o - dominated and more realistic h $ _ 2 $ o : co $ _ 2 $ - dominated ices, 100 % of the mesh is entrapped, almost exclusively desorbing at the molecular volcano desorption peak, indicating that mesh is retained at the water snow line if initially mixed with water ice during formation. additionally, the presence of mesh in an ice mixture enhances the entrapment of co $ _ 2 $ and meoh ( up to 100 % ) until the onset of volcano desorption ; without mesh, both desorb at their respective pure desorption temperatures and also co - desorb with water. compared to meoh, mesh binds less well to water, explaining why mesh escapes during water ice crystallization rather than co - desorbing with water. these results show the larger relative size of mesh compared to meoh significantly impacts its ability to bind to water and its entrapment efficiency. therefore, molecular size plays an important role in the adsorption and retention of s - bearing organics and, in turn, other volatiles in ices.
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arxiv:2504.01102
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each triangle has three exterior or external circles tangential to the three straight lines containing the three sides of the triangle. among the preliminaries in this paper, is deriving formulas for the radii of the three exterior circles in terms of the triangle ' s sidelengths. after that we focus on heron triangles. heron triangles are known in the literature as triangles with integer sidelengths and integral area. pythagorean triangles are examples of heron triangles. in the first part of the paper, we parametrically describe all heron isosceles triangles. in the second part, we parametrically ( in terms of three independent parameters ) describe the subfamily which consists of all heron isosceles triangles which also have integral external radii. we provide numerical examples and tables.
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arxiv:0804.4640
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electric - field controls of dzyaloshinskii - moriya interactions ( dmis ) have recently been discussed from the microscopic viewpoint. since the dmi plays a critical role in generating topological spin textures ( tsts ) such as the chiral soliton, the magnetic skyrmion, and the magnetic hedgehog, electric - field controls of these tsts have become an important issue. this paper shows that such electric - field - induced dmi indeed creates and annihilates tsts by numerically solving the landau - lifshitz - gilbert ( llg ) equation for many - body spin systems at finite temperatures. we show that when a strong electric field is applied in a proper way to one - or two - dimensional ferromagnets, the hamiltonians are changed into the well - known spin models for the chiral soliton or the skyrmion lattice, and the tst states emerge. we utilize a machine - learning method to count the number of generated tsts. in the three - dimensional ( 3d ) case, we demonstrate the electric - field induction of a magnetic hedgehog structure as follows : applying a strong enough electric field along a proper direction to a skyrmion - string state ( a triple - $ \ boldsymbol { q } $ state ) at low but finite temperatures, we find that the field - induced dmi can drive a quadruple - $ \ boldsymbol { q } $ state with hedgehog - antihedgehog pairs. this result indicates that we have succeeded in constructing a simple 3d short - range interacting spin model hosting a magnetic hedgehog structure.
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arxiv:2505.07210
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we investigate the interplay between pre - stress and mechanical properties in random elastic networks. to do this in a controlled fashion, we introduce an algorithm for creating random freestanding frames that support exactly one state of self stress. by multiplying all the bond tensions in this state of self stress by the same number - - - which with the appropriate normalization corresponds to the physical pre - stress inside the frame - - - we systematically evaluate the linear mechanical response of the frame as a function of pre - stress. after proving that the mechanical moduli of affinely deforming frames are rigourously independent of pre - stress, we turn to non - affinely deforming frames. in such frames, pre - stress has a profound effect on linear response : not only can it change the values of the linear modulus - - - an effect we demonstrate to be related to a suppressive effect of pre - stress on non - affinity - - - but pre - stresses also generically trigger bistable mechanical response. thus, pre - stress can be leveraged to both augment the mechanical response of network architectures on the fly, and to actuate finite deformations. these control modalities may be of use in the design of both novel responsive materials and soft actuators.
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arxiv:1812.00611
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let bg be the classifying space of an algebraic group over the complex field c. we compute a new stable rational invariant defined by the difference of two coniveau filtrations ( by benoist and ottem ) of a ( projective ) approximation for bg.
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arxiv:2106.07061
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this paper describes a comprehensive measurement model for the error budget of pulse arrival times with emphasis on intrinsic pulse jitterand plasma propagation effects ( particularly interstellar scattering ), which are stochastic in time and have diverse dependences on radio frequency. to reduce their contribution, timing measurements can be made over a range of frequencies that depends on a variety of pulsar and instrumentation - dependent factors that we identify. a salient trend for high signal - to - noise measurements of millisecond pulsars is that time - of - arrival precision is limited either by irreducible interstellar scattering or by pulse - phase jitter caused by variable emission within pulsar magnetospheres. a cap on timing errors implies that pulsars must be confined to low dispersion measures ( dms ) and observed at high frequencies. use of wider bandwidths that increase signal - to - noise ratios will degrade timing precision if nondispersive chromatic effects are not mitigated. the allowable region in the dm - frequency plane depends on how chromatic timing perturbations are addressed. without mitigation, observations at 1. 4 ~ ghz or 5 ~ ghz are restricted to $ \ dm \ lesssim 30 $ and $ \ lesssim 100 ~ \ dmu $, respectively. with aggressive mitigation of interstellar scattering and use of large telescopes to provide adequate sensitivity at high frequencies ( e. g. arecibo, fast, phase 1 of the ska, and the ska ), pulsars with dms up to 500 ~ $ \ dmu $ can be used in precision timing applications. we analyze methods that fit arrival times vs. frequency at a given epoch prior to multi - epoch fitting. while the terms of greatest astrophysical interest are achromatic ( e. g. orbital and gravitational wave perturbations ), measurements may ultimately be limited by similarly achromatic stochasticity in a pulsar ' s spin rate.
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arxiv:1010.3785
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metallic systems exhibit plasmons as elementary charge excitations. this fundamental concept was reinforced also in high - temperature cuprate superconductors recently, although cuprates are not only layered systems but also strongly correlated electron systems. here, we study how such ubiquitous plasmons leave their marks on the electron dispersion in cuprates. in contrast to phonons and magnetic fluctuations, plasmons do not yield a kink in the electron dispersion. instead, we find that the optical plasmon accounts for an emergent band - - plasmarons - - in the one - particle excitation spectrum ; acoustic - like plasmons typical to a layered system are far less effective. because of strong electron correlations, the plasmarons are generated by bosonic fluctuations associated with the local constraint, not by the usual charge - density fluctuations. apart from this physical mechanism, the plasmarons are similar to those discussed in alkali metals, bi, graphene, monolayer transition - metal dichalcogenides, semiconductors, diamond, two - dimensional electron systems, and sriro3 films, establishing a concept of plasmarons in metallic systems in general. plasmarons are realized below ( above ) the quasiparticle band in electron - doped ( hole - doped ) cuprates, including a region around ( pi, 0 ) and ( 0, pi ) where the superconducting gap and the pseudogap are most enhanced.
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arxiv:2208.11421
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we present broadband imaging polarimetry of dr21 at 2. 2 $ \ mu $ m. background stars shining through the lobes of the bipolar outflow show polarization aligned with the long axis of the outflow, indicating a magnetic field geometry oriented along the flow axis. there is no indication of a spiral or turbulent magnetic field geometry in the lobes. the polarization of stars in the central cluster has a different position angle than the lobes and is in good agreement with millimeter polarimetry. the nebulosity in the eastern lobe has moderate to high polarization consistent with scattering of continuum light from the central cluster. we were unable to detect polarization of the nebulosity in the western lobe at the 4. 2 % ( 3sigma ) level.
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arxiv:astro-ph/0301217
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reputation systems are currently used, often with success, to ensure the functioning of online services as well as of e - commerce sites. despite the relationship between reputation and material cooperative behaviours is quite supported, less obvious appears the relationship with informative behaviours, which are crucial for the transmission of reputational information and therefore for the maintenance of cooperation among individuals. the purpose of this study was to verify how reputation affects cooperation dynamics in virtual environment, within a social dilemma situation ( i. e., where there are incentives to act selfishly ). the results confirm that reputation can activate prosocial conducts, however it highlights also the limitations and distortions that reputation can create.
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arxiv:1609.04659
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if $ g $ is a compact lie group, $ t $ a maximal torus in $ g $ ( with lie algebras $ \ mathfrak { g } $ and $ \ mathfrak { t } $ respectively ) and $ w $ the corresponding weyl group, then the berry - robbins problem for $ g $, as formulated by sir michael atiyah and roger bielawski, asks whether there exists a continuous $ su ( 2 ) \ times w $ equivariant map from the space of regular cartan triples ( an open subset of $ \ mathfrak { t } \ otimes \ mathbb { r } ^ 3 $ ) to $ g / t $, where $ su ( 2 ) $ acts via a regular lie group homomorphism $ su ( 2 ) \ to g $. this was settled positively by atiyah and bielawski, and their maps are even smooth, but they are not explicit. for $ g = u ( n ) $, there exists another construction due to sir michael atiyah and developed further with paul sutcliffe, which is explicit, but relies on a linear independence conjecture. the author had previously found a similar type of construction for $ g = sp ( m ) $, also relying on a linear independence conjecture. in this paper, similar constructions are done for $ so ( 2m + 1 ) $ and $ so ( 2m ) $, thus exhausting the list of classical groups.
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arxiv:1508.04076
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efficient symbol detection algorithms carry critical importance for achieving the spatial multiplexing gains promised by multi - input multi - output ( mimo ) systems. in this paper, we consider a maximum a posteriori probability ( map ) based symbol detection algorithm, called m - blast, over uncoded quasi - static mimo channels. relying on the successive interference cancellation ( sic ) receiver, m - blast algorithm offers a superior error performance over its predecessor v - blast with a signal - to - noise ratio ( snr ) gain of as large as 2 db under various settings of recent interest. performance analysis of the m - blast algorithm is very complicated since the proposed detection order depends on the decision errors dynamically, which makes an already complex analysis of the conventional ordered sic receivers even more difficult. to this end, a rigorous analytical framework is proposed to analyze the outage behavior of the m - blast algorithm over binary complex alphabets and two transmitting antennas, which has a potential to be generalized to multiple transmitting antennas and multidimensional constellation sets. the numerical results show a very good match between the analytical and simulation data under various snr values and modulation alphabets.
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arxiv:1710.01189
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quarkonium has long been proposed as one of the golden probes to identify the phase transition from confined hadronic matter to the deconfined quark - gluon plasma in heavy - ion collisions. since then, we have achieved a better understanding, not only about the propagation of quarkonium in - medium, but also about its production. recent theoretical developments in our comprehension of the quarkonium production mechanism in proton - proton collisions and on the propagation of quarkonia in proton - nucleus and nucleus - nucleus collisions are reviewed and discussed.
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arxiv:1810.00477
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for acute ischemic stroke ( ais ) patients with large vessel occlusions, clinicians must decide if the benefit of mechanical thrombectomy ( mtb ) outweighs the risks and potential complications following an invasive procedure. pre - treatment computed tomography ( ct ) and angiography ( cta ) are widely used to characterize occlusions in the brain vasculature. if a patient is deemed eligible, a modified treatment in cerebral ischemia ( mtici ) score will be used to grade how well blood flow is reestablished throughout and following the mtb procedure. an estimation of the likelihood of successful recanalization can support treatment decision - making. in this study, we proposed a fully automated prediction of a patient ' s recanalization score using pre - treatment ct and cta imaging. we designed a spatial cross attention network ( scanet ) that utilizes vision transformers to localize to pertinent slices and brain regions. our top model achieved an average cross - validated roc - auc of 77. 33 $ \ pm $ 3. 9 \ %. this is a promising result that supports future applications of deep learning on ct and cta for the identification of eligible ais patients for mtb.
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arxiv:2302.04143
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the quantum hall effect is observed in a two - dimensional electron gas formed in millimeter - scale hydrogenated graphene, with a mobility less than 10 $ \ mathrm { cm ^ { 2 } / v \ cdot s } $ and corresponding ioffe - regel disorder parameter $ ( k _ { f } \ lambda ) ^ { - 1 } \ gg1 $. in zero magnetic field and low temperatures, the hydrogenated graphene is insulating with a two - point resistance of order of $ 250 h / e ^ 2 $. application of a strong magnetic field generates a negative colossal magnetoresistance, with the two - point resistance saturating within 0. 5 % of $ h / 2e ^ { 2 } $ at 45t. our observations are consistent with the opening of an impurity - induced gap in the density of states of graphene. the interplay between electron localization by defect scattering and magnetic confinement in two - dimensional atomic crystals is discussed.
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arxiv:1301.1257
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in this paper, we investigate the stability of the particle trajectories in fixed field alternating gradient accelerators ( ffa ) in the presence of field errors : the emphasis is on the scaling radial sector ffa type : a collaboration work is on - going in view of better understanding the properties of the 150 mev scaling ffa at kurri in japan, and progress towards high intensity operation. analysis of certain types of field imperfections revealed some interesting features about this machine that explain some of the experimental results and generalize the concept of a scaling ffa to a non - scaling one for which the tune variations obey a well defined law. a compensation scheme of tune variations in imperfect scaling ffas is presented. this is the cornerstone of a novel concept of a non - linear non - scaling radial sector fixed tune ffa that we present and discuss in details in the last part of this paper.
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arxiv:1710.08772
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neutrinos can scatter electrons in water detectors through their magnetic moments and charge radii in addition to the charged and neutral currents channels. the recent solar neutrino charged current event rates announced by sno with the earlier solar and atmospheric neutrino observations from super - kamiokande allows us to put upper bounds of $ \ mu < 10 ^ { - 9 } \ mu _ b $ on neutrino magnetic moments and $ < r ^ 2 > < 10 ^ { - 31 } cm ^ 2 $ on the neutrino charge radii. for the electron and muon neutrinos these bounds are comparable with existing bounds but for tau neutrinos these bounds are three orders of magnitude more stringent than earlier terrestrial bounds. these bounds are independent of any specific model of neutrino oscillations.
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arxiv:hep-ph/0108018
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inspired by kernel methods that have been used extensively in achieving efficient facial animation retargeting, this paper presents a solution to retargeting facial animation in virtual character ' s face model based on the kernel projection of latent structure ( kpls ) regression between semantically similar facial expressions. specifically, a given number of corresponding semantically similar facial expressions are projected into the latent space. by using the nonlinear iterative partial least square method, decomposition of the latent variables is achieved. finally, the kpls is achieved by solving a kernalized version of the eigenvalue problem. by evaluating our methodology with other kernel - based solutions, the efficiency of the presented methodology in transferring facial animation to face models with different morphological variations is demonstrated.
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arxiv:1707.09629
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in the design of brain - computer interface systems, classification of electroencephalogram ( eeg ) signals is the essential part and a challenging task. recently, as the marginalized discrete wavelet transform ( mdwt ) representations can reveal features related to the transient nature of the eeg signals, the mdwt coefficients have been frequently used in eeg signal classification. in our previous work, we have proposed a super - dirichlet distribution - based classifier, which utilized the nonnegative and sum - to - one properties of the mdwt coefficients. the proposed classifier performed better than the state - of - the - art support vector machine - based classifier. in this paper, we further study the neutrality of the mdwt coefficients. assuming the mdwt vector coefficients to be a neutral vector, we transform them non - linearly into a set of independent scalar coefficients. feature selection strategy is proposed on the transformed feature domain. experimental results show that the feature selection strategy helps improving the classification accuracy.
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arxiv:1808.00814
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daily progress notes are common types in the electronic health record ( ehr ) where healthcare providers document the patient ' s daily progress and treatment plans. the ehr is designed to document all the care provided to patients, but it also enables note bloat with extraneous information that distracts from the diagnoses and treatment plans. applications of natural language processing ( nlp ) in the ehr is a growing field with the majority of methods in information extraction. few tasks use nlp methods for downstream diagnostic decision support. we introduced the 2022 national nlp clinical challenge ( n2c2 ) track 3 : progress note understanding - assessment and plan reasoning as one step towards a new suite of tasks. the assessment and plan reasoning task focuses on the most critical components of progress notes, assessment and plan subsections where health problems and diagnoses are contained. the goal of the task was to develop and evaluate nlp systems that automatically predict causal relations between the overall status of the patient contained in the assessment section and its relation to each component of the plan section which contains the diagnoses and treatment plans. the goal of the task was to identify and prioritize diagnoses as the first steps in diagnostic decision support to find the most relevant information in long documents like daily progress notes. we present the results of 2022 n2c2 track 3 and provide a description of the data, evaluation, participation and system performance.
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arxiv:2303.08038
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this paper investigates the hypothesis that the lensing objects towards the large magellanic cloud ( lmc ) are brown dwarfs by analysing the effects of velocity anisotropy on the inferred microlensing masses. to reduce the masses, the transverse velocity of the lenses with respect to the microlensing tube must be minimised. in the outer halo, radial anisotropy is best for doing this ; closer to the solar circle, azimuthal anisotropy is best. by using a constraint on the total kinetic energy of the tracer population from the jeans equations, the microlensing mass is minimised over orientations of the velocity dispersion tensor. this minimum mass is about a tenth of a solar mass, which lies above the hydrogen burning limit. this demonstrates explicitly that populations of brown dwarfs with smoothly decreasing densities and dynamically mixed velocity distributions cannot be responsible for the microlensing events. brown dwarfs are no white knights! there is one caveat. if there are demons sitting on the microlensing tube, they can drop brown dwarfs so as to reproduce the microlensing data - set exactly. such a distribution is not smooth and does not give well - mixed velocities in phase space. it is a permissible solution only if the outer halo is dynamically young and lumpy. in such a case, theorists cannot rule out brown dwarfs. only exorcists can!
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arxiv:astro-ph/9805304
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we study existence, uniqueness, and distributional aspects of generalized solutions to the cauchy problem for first - order symmetric ( or hermitian ) hyperbolic systems of partial differential equations with colombeau generalized functions as coefficients and data. the proofs of solvability are based on refined energy estimates on lens - shaped regions with spacelike boundaries. we obtain several variants and also partial extensions of previous results and provide aspects accompanying related recent work by c. garetto and m. oberguggenberger.
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arxiv:1107.5967
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for $ 0 < \ lambda \ le 1 $, let $ \ mathcal { u } ( \ lambda ) $ be the class analytic functions $ f ( z ) = z + \ sum _ { n = 2 } ^ { \ infty } a _ n z ^ n $ in the unit disk $ \ mathbb { d } $ satisfying $ | f ' ( z ) ( z / f ( z ) ) ^ 2 - 1 | < \ lambda $ and $ \ mathcal { u } : = \ mathcal { u } ( 1 ) $. in the present article, we prove that the class $ \ mathcal { u } $ is contained in the closed convex hull of the class of starlike functions and using this fact, we solve some extremal problems such as integral mean problem and arc length problem for functions in $ \ mathcal { u } $. by means of the so - called theory of star functions, we also solve the integral mean problem for functions in $ \ mathcal { u } ( \ lambda ) $. we also obtain the estimate of the fekete - szeg \ " { o } functional and the pre - schwarzian norm of certain nonlinear integral transform of functions in $ \ mathcal { u } ( \ lambda ) $. further, for the class of meromorphic functions which are defined in $ \ delta : = \ { \ zeta \ in \ mathbb { \ widehat { c } } : | \ zeta | > 1 \ } $ and associated with the class $ \ mathcal { u } ( \ lambda ) $, we obtain a sufficient condition for a function $ g $ to be an extreme point of this class.
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arxiv:2006.15577
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we bound the second eigenvalue of random $ d $ - regular graphs, for a wide range of degrees $ d $, using a novel approach based on fourier analysis. let $ g _ { n, d } $ be a uniform random $ d $ - regular graph on $ n $ vertices, and let $ \ lambda ( g _ { n, d } ) $ be its second largest eigenvalue by absolute value. for some constant $ c > 0 $ and any degree $ d $ with $ \ log ^ { 10 } n \ ll d \ leq c n $, we show that $ \ lambda ( g _ { n, d } ) = ( 2 + o ( 1 ) ) \ sqrt { d ( n - d ) / n } $ asymptotically almost surely. combined with earlier results that cover the case of sparse random graphs, this fully determines the asymptotic value of $ \ lambda ( g _ { n, d } ) $ for all $ d \ leq c n $. to achieve this, we introduce new methods that use mechanisms from discrete fourier analysis, and combine them with existing tools and estimates on $ d $ - regular random graphs - especially those of liebenau and wormald.
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arxiv:2201.02015
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we show that the mapping class group of a handlebody of genus at least 2 ( with any number of marked points or spots ) is exponentially distorted in the mapping class group of its boundary surface. the same holds true for solid tori with at least two marked points or spots.
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arxiv:1101.1838
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berkeley 59 is a nearby ( $ \ sim $ 1 kpc ) young cluster associated with the sh2 - 171 h { \ sc ii } region. we present deep optical observations of the central $ \ sim $ 2. 5 $ \ times $ 2. 5 pc $ ^ 2 $ area of the cluster, obtained with the 3. 58 - m telescopio nazionale galileo. the $ v $ / ( $ v $ - $ i $ ) color - magnitude diagram manifests a clear pre - main - sequence ( pms ) population down to $ \ sim $ 0. 2 m $ _ \ odot $. using the near - infrared and optical colors of the low - mass pms members we derive a global extinction of a $ _ v $ = 4 mag and a mean age of $ \ sim $ 1. 8 myr, respectively, for the cluster. we constructed the initial mass function and found that its global slopes in the mass ranges of 0. 2 - 28 m $ _ \ odot $ and 0. 2 - 1. 5 m $ _ \ odot $ are - 1. 33 and - 1. 23, respectively, in good agreement with the salpeter value in the solar neighborhood. we looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. the dynamical status of the cluster suggests that the mass segregation is likely primordial. the age distribution of the pms sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star - forming clouds is discussed. within the observed area, we derive a total mass of $ \ sim $ 10 $ ^ 3 $ m $ _ \ odot $ for the cluster. comparing the properties of berkeley 59 with other young clusters, we suggest it resembles more to the trapezium cluster.
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arxiv:1711.09353
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developers are starting to write large and complex applications in typescript, a typed dialect of javascript. typescript applications integrate javascript libraries via typed descriptions of their apis called declaration files. definitelytyped is the standard public repository for these files. the repository is populated and maintained manually by volunteers, which is error - prone and time consuming. discrepancies between a declaration file and the javascript implementation lead to incorrect feedback from the typescript ide and, thus, to incorrect uses of the underlying javascript library. this work presents dts - generate, a tool that generates typescript declaration files for javascript libraries uploaded to the npm registry. it extracts code examples from the documentation written by the developer, executes the library driven by the examples, gathers run - time information, and generates a declaration file based on this information. to evaluate the tool, 249 declaration files were generated directly from an npm module and 111 of these were compared with the corresponding declaration file provided on definitelytyped. all these files either exhibited no differences at all or differences that can be resolved by extending the developer - provided examples.
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arxiv:2108.08027
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%. our dcnn models could be further extended to determine additional parameters needed to model dynamics of interacting galaxy pairs, which is currently accomplished by trial and error method.
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arxiv:2002.01238
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reverse osmosis and nanofiltration are membrane - based methods that remove solutes from solvent, for instance they remove salts from water ( desalination ). in these methods, an applied pressure is the driving force for solvent to pass the membrane, while most of the solutes are blocked. very important in the theory of mass transport is the concentration polarization layer ( cp layer ), which develops on the upstream side of the membrane. because of the cp layer, the solvent flux through the membrane is reduced while leakage of solutes through the membrane increases, and both these effects must be minimized. so it is very important to understand and describe the nature of the cp layer accurately, especially to find a good estimate of the cp layer mass transfer coefficient, $ k $. this is also important for the accurate characterization of membranes in a test cell geometry. we theoretically analyze the structure of the cp layer using three levels of mathematical models. first, we present a modification of an equation for $ k $ by sherwood et al. ( 1965 ) and show that it works very well in a zero dimensional model. second, we evaluate a one - dimensional model that is more accurate, which can incorporate any equation for the flow of solvent and solutes through the membrane, and which also makes use of the new modified sherwood equation. finally, we fully resolve the complete channel in a two - dimensional geometry, to validate the lower - order models and to illustrate the structure of the cp layer. the overall conclusion is that for typical test cell conditions, the modified sherwood equation can be used to characterize the cp layer, also when solvent flux through the membrane changes between inlet and outlet of the test cell. furthermore, the one - dimensional model accurately describes solute removal ( for instance water desalination ) not just in a short test cell but also in a longer module.
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arxiv:2401.11527
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in the minimal supersymmetric standard model ( mssm ) extended by a singlet superfield, when the coupling between the singlet sector and the mssm sector is tiny, the singlet sector can be a quasi dark sector with supersymmetry ( susy ). we investigate the cosmological phenomena in this scenario and obtain the following observations : ( i ) in the parameter space solving the small cosmological scale anomalies via self - interacting singlino dark matter ( sidm ), a first - order phase transition ( fopt ) can readily happen but requires rather light dark matter below mev ; ( ii ) the corresponding parameter space indicated by fopt and sidm can be partially covered by detecting the phase - transition gravitational waves ( gws ) at the near - future projects, such as lisa, tianqin and taiji. therefore, the recently developed gw astronomy could be a novel probe to such a susy scenario.
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arxiv:2204.01928
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let $ k $ be an algebraically closed field of characteristic $ 0 $. for a log curve $ x / k ^ { \ times } $ over the standard log point, we define ( algebraically ) a combinatorial monodromy operator on its log - de rham cohomology group. the invariant part of this action has a cohomological description, it is the du bois cohomology of $ x $. this can be seen as an analogue of the invariant cycles exact sequence for a semistable family ( as in the complex, \ ' etale and $ p $ - adic settings ). in the specific case in which $ k = \ mathbb c $ and $ x $ is the central fiber of a semistable degeneration over the complex disc, our construction recovers the topological monodromy and the classical local invariant cycles theorem. in particular, our description allows an explicit computation of the monodromy operator in this setting.
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arxiv:1810.11627
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vela x is the prototypical example of a pulsar wind nebula whose morphology and detailed structure have been affected by the interaction with the reverse shock of its host supernova remnant. the resulting complex of filamentary structure and mixed - in ejecta embedded in a nebula that is offset from the pulsar provides the best example we have of this middle - age state that characterizes a significant fraction of composite snrs, and perhaps all of the large - diameter pwne seen as tev sources. here we report on an xmm - newton large project study of vela x, supplemented by additional chandra observations. through broad spectral modeling as well as detailed spectral investigations of discrete emission regions, we confirm previous studies that report evidence for ejecta material within vela x, and show that equivalent width variations of o vii and o viii are consistent with temperature maps within the pwn that show low - temperature regions where the projected snr emission appears to dominate emission from the ejecta. we identify spectral variations in the nonthermal emission, with hard emission being concentrated near the pulsar. we carry out investigations of the vela x " cocoon " structure and, with hydrodynamical simulations, show that its overall properties are consistent with structures formed in the late - phase evolution of a composite snr expanding into a surrounding medium with a density gradient, with ejecta material being swept beyond the pulsar and compressed into an elongated structure in the direction opposite the high external density.
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arxiv:1808.03878
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the perturbation theory by l. ge et al. [ phys. rev. a 87, 023833 ] for transverse - electric polarized modes in weakly deformed microdisks omits terms related to the variation of the normal derivative of the magnetic field along the boundary. here we show that these terms are necessary to accurately describe microdisks with a strongly winding boundary. in particular, it is demonstrated that the corrected perturbation theory allows to describe the counterintuitive phenomenon of q - factor enhancement due to weak boundary deformation. we discuss in detail the microflower cavity and the limacon cavity. good agreement of the corrected perturbation theory with full numerical results is observed.
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arxiv:1811.11631
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we formulate a general sufficiency criterion for discreteness of the spectrum of both supersymmmetric and non - su - persymmetric theories with a fermionic contribution. this criterion allows an analysis of hamiltonians in complete form rather than just their semiclassical limits. in such a framework we examine spectral properties of various ( 1 + 0 ) matrix models. we consider the bmn model of m - theory compactified on a maximally supersymmetric pp - wave background, different regularizations of the supermembrane with central charges and a non - supersymmetric model comprising a bound state of n d2 with m d0. while the first two examples have a purely discrete spectrum, the latter has a continuous spectrum with a lower end given in terms of the monopole charge.
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arxiv:1011.4791
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we report on the observation of half - quantum vortices ( hqvs ) in the easy - plane polar phase of an antiferromagnetic spinor bose - einstein condensate. using in situ magnetization - sensitive imaging, we observe that pairs of hqvs with opposite core magnetization are generated when singly charged quantum vortices are injected into the condensate. the dynamics of hqv pair formation is characterized by measuring the temporal evolutions of the pair separation distance and the core magnetization, which reveals the short - range nature of the repulsive interactions between the hqvs. we find that spin fluctuations arising from thermal population of axial magnon excitations do not significantly affect the hqv pair formation dynamics. our results demonstrate the instability of a singly charged vortex in the antiferromagnetic spinor condensate.
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arxiv:1503.05648
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5 $ \ mu $ m thick smco films were deposited onto si substrates using triode sputtering. a study of the influence of deposition temperature ( tdep < = 600 degrees c ) on the structural, magnetic and mechanical properties has shown that optimum properties ( highest degree of in - plane texture, maximum in - plane coercivity and remanence ( 1. 3 and 0. 8 t, respectively ), no film peel - off ) are achieved for films deposited at the relatively low temperature of 350 degrees c. this temperature is compatible with film integration into micro - electro - mechanical - systems ( mems ). the deposition rate was increased from 3. 6 to 18 $ \ mu $ m / h by increasing the surface area of the target from 7 to 81 cm2. mechanically stable films could be prepared by deposition onto pre - patterned films or deposition through holes in a mask.
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arxiv:0804.1992
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a conducting two - dimensional periodic composite of two anisotropic phases with anisotropic, not necessarily symmetric, conductivity tensors is considered. by finding approximate representations for the relevant operators, an approximation formula is derived for the effective matrix valued conductivity as a function of the two matrix valued conductivity tensors of the phases. this approximation should converge to the exact effective conductivity function as the number of basis fields tends to infinity. using the approximations for the relevant operators one can also directly obtain approximations, with the same geometry, for the effective tensors of coupled field problems, including elasticity, piezoelectricity, and thermoelectricity. to avoid technical complications we assume that the phase geometry is symmetric under reflection about one of the centerlines of the unit cell.
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arxiv:1705.02633
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there has been some evidence that agility is connected to the group maturity of software development teams. this study aims at conducting group development psychology training with student teams, participating in a project course at university, and compare their group effectiveness score to their agility usage over time in a longitudinal design. seven xp student teams were measured twice ( 43 + 40 ), which means 83 data points divided into two groups ( an experimental group and one control group ). the results showed that the agility measurement was not possible to increase by giving a 1. 5 - hour of group psychology lecture and discussion over a two - month period. the non - significant result was probably due to the fact that 1. 5 hours of training were not enough to change the work methods of these student teams, or, a causal relationship does not exist between the two concepts. a third option could be that the experiential setting of real teams, even at a university, has many more variables not taken into account in this experiment that affect the two concepts. we therefore have no conclusions to draw based on the expected effects. however, we believe these concepts have to be connected since agile software development is based on teamwork to a large extent, but there are probably many more confounding or mediating factors.
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arxiv:1904.02466
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this work relates quantitatively homogenization to anderson localization for acoustic operators in disordered media. by blending dispersive estimates for homogenized operators and quantitative homogenization of the wave equation, we derive large - scale dispersive estimates for waves in disordered media that we apply to the spreading of low - energy eigenstates. this gives a short and direct proof that the lower spectrum of the acoustic operator is purely absolutely continuous in case of periodic media, and it further provides new lower bounds on the localization length of possible eigenstates in case of quasiperiodic or random media.
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arxiv:2304.14046
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recent research dealing with magnetocaloric effect ( mce ) study of antiferromagnetic ( afm ) low dimensional spin systems have revealed a number of fascinating ground - state crossover characteristics upon application of external magnetic field. herein, through mce investigation we have explored field - induced quantum level - crossing characteristics of one such spin system : nh4cupo4. h2o ( ncp ), an afm spin 1 / 2 dimer. experimental magnetization and specific heat data are presented and the data have been employed to evaluate entropy, magnetic energy and magnetocaloric properties. we witness a sign change in magnetic grueneisen parameter across the level - crossing field b _ c. an adiabatic cooling is observed at low temperature by tracing the isentropic curves in temperature - magnetic field plane. energy - level crossover characteristics in ncp interpreted through mce analysis are well consistent with the observations made from magnetization and specific heat data.
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arxiv:1812.11298
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based on the digitized electron micrographs, we investigate a temperature evolution of co / c film. the simple in usage quantitative characterization of the spatial disorder for systems of point objects has been employed. we show that a dominant increase of spatial inhomogeneity of cobalt phase is shifted towards the larger length scales along the sample heating temperature. the results allow the subtle differences of spatial inhomogeneity in thin metallic films to be explored.
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arxiv:cond-mat/0101144
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we present an empirical method for converting single - point near - infrared j, h, and k measurements of fundamental - mode cepheids to mean magnitudes, using complete light curves in v or i bands. the algorithm is based on the template light curves in the near - infrared bandpasses. the mean uncertainty of the method is estimated to about 0. 03 mag, which is smaller than the uncertainties obtained in other approaches to the problem in the literature.
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arxiv:astro-ph/0503598
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many scientific papers such as those in arxiv and pubmed data collections have abstracts with varying lengths of 50 - 1000 words and average length of approximately 200 words, where longer abstracts typically convey more information about the source paper. up to recently, scientific summarization research has typically focused on generating short, abstract - like summaries following the existing datasets used for scientific summarization. in domains where the source text is relatively long - form, such as in scientific documents, such summary is not able to go beyond the general and coarse overview and provide salient information from the source document. the recent interest to tackle this problem motivated curation of scientific datasets, arxiv - long and pubmed - long, containing human - written summaries of 400 - 600 words, hence, providing a venue for research in generating long / extended summaries. extended summaries facilitate a faster read while providing details beyond coarse information. in this paper, we propose tstr, an extractive summarizer that utilizes the introductory information of documents as pointers to their salient information. the evaluations on two existing large - scale extended summarization datasets indicate statistically significant improvement in terms of rouge and average rouge ( f1 ) scores ( except in one case ) as compared to strong baselines and state - of - the - art. comprehensive human evaluations favor our generated extended summaries in terms of cohesion and completeness.
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arxiv:2206.00847
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with an excellent balance between speed and accuracy, cutting - edge yolo frameworks have become one of the most efficient algorithms for object detection. however, the performance of using yolo networks is scarcely investigated in brain tumor detection. we propose a novel yolo architecture with reparameterized convolution based on channel shuffle ( rcs - yolo ). we present rcs and a one - shot aggregation of rcs ( rcs - osa ), which link feature cascade and computation efficiency to extract richer information and reduce time consumption. experimental results on the brain tumor dataset br35h show that the proposed model surpasses yolov6, yolov7, and yolov8 in speed and accuracy. notably, compared with yolov7, the precision of rcs - yolo improves by 1 %, and the inference speed by 60 % at 114. 8 images detected per second ( fps ). our proposed rcs - yolo achieves state - of - the - art performance on the brain tumor detection task. the code is available at https : / / github. com / mkang315 / rcs - yolo.
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arxiv:2307.16412
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transmission spectroscopy of exoplanets has revealed signatures of water vapor, aerosols, and alkali metals in a few dozen exoplanet atmospheres. however, these previous inferences with the hubble and spitzer space telescopes were hindered by the observations ' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species $ - $ in particular the primary carbon - bearing molecules. here we report a broad - wavelength 0. 5 - 5. 5 $ \ mu $ m atmospheric transmission spectrum of wasp - 39 b, a 1200 k, roughly saturn - mass, jupiter - radius exoplanet, measured with jwst nirspec ' s prism mode as part of the jwst transiting exoplanet community early release science team program. we robustly detect multiple chemical species at high significance, including na ( 19 $ \ sigma $ ), h $ _ 2 $ o ( 33 $ \ sigma $ ), co $ _ 2 $ ( 28 $ \ sigma $ ), and co ( 7 $ \ sigma $ ). the non - detection of ch $ _ 4 $, combined with a strong co $ _ 2 $ feature, favours atmospheric models with a super - solar atmospheric metallicity. an unanticipated absorption feature at 4 $ \ mu $ m is best explained by so $ _ 2 $ ( 2. 7 $ \ sigma $ ), which could be a tracer of atmospheric photochemistry. these observations demonstrate jwst ' s sensitivity to a rich diversity of exoplanet compositions and chemical processes.
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arxiv:2211.10487
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we explore the task of language - guided video segmentation ( lvs ). previous algorithms mostly adopt 3d cnns to learn video representation, struggling to capture long - term context and easily suffering from visual - linguistic misalignment. in light of this, we present locater ( local - global context aware transformer ), which augments the transformer architecture with a finite memory so as to query the entire video with the language expression in an efficient manner. the memory is designed to involve two components - - one for persistently preserving global video content, and one for dynamically gathering local temporal context and segmentation history. based on the memorized local - global context and the particular content of each frame, locater holistically and flexibly comprehends the expression as an adaptive query vector for each frame. the vector is used to query the corresponding frame for mask generation. the memory also allows locater to process videos with linear time complexity and constant size memory, while transformer - style self - attention computation scales quadratically with sequence length. to thoroughly examine the visual grounding capability of lvs models, we contribute a new lvs dataset, a2d - s +, which is built upon a2d - s dataset but poses increased challenges in disambiguating among similar objects. experiments on three lvs datasets and our a2d - s + show that locater outperforms previous state - of - the - arts. further, we won the 1st place in the referring video object segmentation track of the 3rd large - scale video object segmentation challenge, where locater served as the foundation for the winning solution. our code and dataset are available at : https : / / github. com / leonnnop / locater
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arxiv:2203.09773
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the notion of nondeterminism has disappeared from the current definition of np, which has led to ambiguities in understanding np, and caused fundamental difficulties in studying the relation p versus np. in this paper, we question the equivalence of the two definitions of np, the one defining np as the class of problems solvable by a nondeterministic turing machine in polynomial time, and the other defining np as the class of problems verifiable by a deterministic turing machine in polynomial time, and reveal cognitive biases in this equivalence. inspired from a famous chinese paradox white horse is not horse, we further analyze these cognitive biases. the work shows that these cognitive biases arise from the confusion between different levels of nondeterminism and determinism, due to the lack of understanding about the essence of nondeterminism. therefore, we argue that fundamental difficulties in understanding p versus np lie firstly at cognition level, then logic level.
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arxiv:1501.01906
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recently, there emerged revived interests of designing automatic programs ( e. g., using genetic / evolutionary algorithms ) to optimize the structure of convolutional neural networks ( cnns ) for a specific task. the challenge in designing such programs lies in how to balance between large search space of the network structures and high computational costs. existing works either impose strong restrictions on the search space or use enormous computing resources. in this paper, we study how to design a genetic programming approach for optimizing the structure of a cnn for a given task under limited computational resources yet without imposing strong restrictions on the search space. to reduce the computational costs, we propose two general strategies that are observed to be helpful : ( i ) aggressively selecting strongest individuals for survival and reproduction, and killing weaker individuals at a very early age ; ( ii ) increasing mutation frequency to encourage diversity and faster evolution. the combined strategy with additional optimization techniques allows us to explore a large search space but with affordable computational costs. our results on standard benchmark datasets ( mnist, svhn, cifar - 10, cifar - 100 ) are competitive to similar approaches with significantly reduced computational costs.
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arxiv:1806.00851
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ellis ( 1913 – 2007 ) : american psychologist who in 1955 developed rational emotive behavior therapy. paul erdos ( 1913 – 1996 ) : hungarian mathematician. he published more papers than any other mathematician in history, working with hundreds of collaborators. he worked on problems in combinatorics, graph theory, number theory, classical analysis, approximation theory, set theory, and probability theory. daniel everett ( 1951 – ) : american linguistic anthropologist and author best known for his study of the amazon basin ' s piraha people and their language. hugh everett iii ( 1930 – 1982 ) : american physicist who first proposed the many - worlds interpretation ( mwi ) of quantum physics, which he termed his " relative state " formulation. hans eysenck ( 1916 – 1997 ) : german psychologist and author who is best remembered for his work on intelligence and personality, though he worked in a wide range of areas. he was the founding editor of the journal personality and individual differences, and authored about 80 books and more than 1600 journal articles. = = f = = gustav fechner ( 1801 – 1887 ) : german experimental psychologist. an early pioneer in experimental psychology and founder of psychophysics. leon festinger ( 1919 – 1989 ) : american social psychologist famous for his theory of cognitive dissonance. richard feynman ( 1918 – 1988 ) : american theoretical physicist, best known for his work in renormalizing quantum electrodynamics ( qed ) and his path integral formulation of quantum mechanics. he won the nobel prize in physics in 1965. irving finkel ( 1951 – ) : british philologist, assyriologist, and the assistant keeper of ancient mesopotamian script, languages and cultures in the department of the middle east in the british museum, where he specialises in cuneiform inscriptions on tablets of clay from ancient mesopotamia. sir raymond firth cnzm, fba ( 1901 – 2002 ) : new zealand ethnologist, considered to have singlehandedly created a form of british economic anthropology. helen fisher ( 1945 - 2024 ) : american biological anthropologist and member of the center for human evolutionary studies at rutgers university. james franck ( 1882 – 1964 ) : german physicist. won the nobel prize in physics in 1925. carlos frenk ( 1951 – ) : mexican - british cosmologist and the ogden professor of fundamental physics at durham university, whose main interests lie in the field of cosmology, studying galaxy formation and computer simulations of cosmic structure formation. sigmund freud ( 1856 – 1939 ) : austrian ne
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https://en.wikipedia.org/wiki/List_of_atheists_in_science_and_technology
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diagnostic captioning ( dc ) automatically generates a diagnostic text from one or more medical images ( e. g., x - rays, mris ) of a patient. treated as a draft, the generated text may assist clinicians, by providing an initial estimation of the patient ' s condition, speeding up and helping safeguard the diagnostic process. the accuracy of a diagnostic text, however, strongly depends on how well the key medical conditions depicted in the images are expressed. we propose a new data - driven guided decoding method that incorporates medical information, in the form of existing tags capturing key conditions of the image ( s ), into the beam search of the diagnostic text generation process. we evaluate the proposed method on two medical datasets using four dc systems that range from generic image - to - text systems with cnn encoders and rnn decoders to pre - trained large language models. the latter can also be used in few - and zero - shot learning scenarios. in most cases, the proposed mechanism improves performance with respect to all evaluation measures. we provide an open - source implementation of the proposed method at https : / / github. com / nlpaueb / dmmcs.
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arxiv:2406.14164
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data drifts pose a critical challenge in the lifecycle of machine learning ( ml ) models, affecting their performance and reliability. in response to this challenge, we present a microbenchmark study, called d3bench, which evaluates the efficacy of open - source drift detection tools. d3bench examines the capabilities of evidently ai, nannyml, and alibi - detect, leveraging real - world data from two smart building use cases. we prioritize assessing the functional suitability of these tools to identify and analyze data drifts. furthermore, we consider a comprehensive set of non - functional criteria, such as the integrability with ml pipelines, the adaptability to diverse data types, user - friendliness, computational efficiency, and resource demands. our findings reveal that evidently ai stands out for its general data drift detection, whereas nannyml excels at pinpointing the precise timing of shifts and evaluating their consequent effects on predictive accuracy.
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arxiv:2404.18673
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the concept of generalized cross - validation ( gcv ) is applied to modified total generalized variation ( mtgv ) regularization. current implementations of the mtgv regularization rely on manual ( or semi - manual ) hyperparameter optimization, which is both time - consuming and subject to bias. the combination of mtgv - regularization and gcv allows for a straightforward hyperparameter search during regularization. this significantly increases the efficiency of the mtgv - method, because it limits the number of hyperparameters, which have to be tested and, improves the practicality of mtgv regularization as a standard technique for inversion of nmr signals. the combined method is applied to simulated and experimental nmr data and the resulting reconstructed distributions are presented. it is shown that for all data sets studied the proposed combination of mtgv and gcv minimizes the gcv score allowing an optimal hyperparameter choice.
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arxiv:2311.11442
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we consider self - similar profiles to smoluchowski ' s coagulation equation for which we derive the precise asymptotic behaviour at infinity. more precisely, we look at so - called fat - tailed profiles which decay algebraically and as a consequence have infinite total mass. the results only require mild assumptions on the coagulation kernel and thus cover a large class of rate kernels.
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arxiv:1703.09192
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a class of equations with exponential nonlinearities on a compact riemannian surface is considered. more precisely, we study an asymmetric sinh - gordon problem arising as a mean field equation of the equilibrium turbulence of vortices with variable intensities. we start by performing a blow - up analysis in order to derive some information on the local blow - up masses. as a consequence we get a compactness property in a supercritical range. we next introduce a variational argument based on improved moser - trudinger inequalities which yields existence of solutions for any choice of the underlying surface.
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arxiv:1609.05373
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moessbauer transmission spectra for the 14. 41 - kev resonant line in 57fe have been collected at room temperature by using 57co ( rh ) commercial source and alpha - fe strain - free single crystal as an absorber. the absorber was magnetized to saturation in the absorber plane perpendicular to the gamma - ray beam axis applying small external magnetic field. spectra were collected for various orientations of the magnetizing field, the latter lying close to the [ 110 ] crystal plane. a positive electric quadrupole coupling constant was found practically independent on the field orientation. one obtains the following value vzz = + 1. 61 ( 4 ) x10 ^ 19 v / m ^ 2 for the ( average ) principal component of the electric field gradient ( efg ) tensor under assumption that the efg tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the 57fe nucleus. the nuclear spectroscopic electric quadrupole moment for the first excited state of the 57fe nucleus was adopted as + 0. 17 b. similar measurement was performed at room temperature using as - rolled polycrystalline alpha - fe foil of high purity in the zero external field. corresponding value for the principal component of the efg was found as vzz = + 1. 92 ( 4 ) x10 ^ 19 v / m ^ 2. hence, it seems that the origin of the efg is primarily due to the local ( atomic ) electronic wave function distortion caused by the spin - orbit interaction between effective electronic spin s and incompletely quenched electronic angular momentum l. it seems as well that the lowest order term proportional to the product l. lambda. s dominates, as no direction dependence of the efg principal component is seen. the lowest order term is isotropic for a cubic symmetry as one has lambda = lambda. 1 for cubic systems with the symbol 1 denoting unit operator and lambda being the coupling parameter.
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arxiv:1511.04933
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we investigate internal localized eigenmodes of the linearized equation around spin discrete breathers in 1d antiferromagnets with on - site easy axis anisotropy. the threshold of occurrence of the internal localized eigenmodes has a typical structure in parameter space depending on the frequency of the spin discrete breather. we also performed molecular dynamics simulation in order to show the validity of our linear analysis.
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arxiv:cond-mat/0207053
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motivated by realization of the dissipative quantum point contact in ultracold atomic gases, we investigate a two - terminal mesoscopic transport system in which a single - particle loss is locally present in a one - dimensional chain. by means of the dyson equation approach in the keldysh formalism that can incorporate dissipative effects, we reveal analytic structures of the particle and energy currents whose formal expressions correspond to ones in certain three - terminal systems where the particle loss is absent. the obtained formulas are also consistent with non - hermitian and three - terminal landauer - b \ " { u } ttiiker analyses. the universality on the current expressions holds regardless of quantum statistics and may be useful for understanding lossy two - terminal transport in terms of three - terminal transport and vice versa.
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arxiv:2206.09088
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pattern of confined chemical garden was controlled by the speed of injected fluid, and their mechanism is discussed. a confined chemical garden system was constructed where an aqueous solution of cobalt chloride was injected into a cell filled with sodium silicate solution. the reaction of these two solutions resulted in the formation of precipitation. the viscosities of the prepared aqueous solutions were set to be similar in order to rule out the possibility of saffman - taylor instability. the injection front showed three distinctive patterns : algaes, shells, and filaments, which were dependent on injection speed. the injection pressure and the spatio - temporal pattern of the injected fluid were measured, and a significant increase in the injection pressure was observed when the filament pattern appeared, which indicated the existence of thin lubrication layer between the precipitation and the substrate. the filament pattern was further analyzed quantitatively, and the number of active filaments was determined to be proportional to the injection speed. a mathematical model was constructed that considered both the viscous effect from the thin luburiation layer and the laplace pressure. this model successfully reproduced the characteristic filament dynamics.
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arxiv:1612.04181
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we consider the twistor space $ { \ cal p } ^ 6 \ cong { \ mathbb r } ^ 4 { \ times } { \ mathbb c } p ^ 1 $ of $ { \ mathbb r } ^ 4 $ with a non - integrable almost complex structure $ { \ cal j } $ such that the canonical bundle of the almost complex manifold $ ( { \ cal p } ^ 6, { \ cal j } ) $ is trivial. it is shown that $ { \ cal j } $ - holomorphic chern - simons theory on a real $ ( 6 | 2 ) $ - dimensional graded extension $ { \ cal p } ^ { 6 | 2 } $ of the twistor space $ { \ cal p } ^ 6 $ is equivalent to self - dual yang - mills theory on euclidean space $ { \ mathbb r } ^ 4 $ with lorentz invariant action. it is also shown that adding a local term to a chern - simons - type action on $ { \ cal p } ^ { 6 | 2 } $, one can extend it to a twistor action describing full yang - mills theory.
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arxiv:2103.11840
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the event horizon telescope ( eht ) observations of sgr \, a * resolved the shadow image and emission ring - like structure, which is associated to the photon ring of the supermassive black hole, at the galactic centre, revealing a diameter of $ 51. 8 ~ \ mu \ text { as } $. the ring - like structure is consistent with that of a kerr black hole. however, the source of the high bright regions in the image and the time variability remain an open question. besides the plasma properties and emission models, the spacetime geometry also holds an important role. we present an image depicting the bright hot spots consistent with sgr \, a * observations at a wavelength $ \ lambda = 1. 3 \, { \ rm mm } $. the image is the result of an eclipsing schwarzschild black hole situated along the line of sight between the galactic centre and earth. the separation from both, primary ( sgr \, a * ) and secondary ( eclipsing ) black holes is $ 10233 \, { \ rm au } $. the central supermassive black hole located at the centre of the galaxy has an observational mass of $ 4. 14 \ times10 ^ 6 \, m _ { \ odot } $ and the secondary eclipsing black hole has an inferred mass of $ 1035 \, m _ { \ odot } $.
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arxiv:2502.16058
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we analyze the algebraic structure of the connes fusion tensor product ( cftp ) in the case of bi - finite hilbert modules over a von neumann algebra m. it turns out that all complications in its definition disappear if one uses the closely related bi - modules of bounded vectors. we construct an equivalence of monoidal categories with duality between a category of hilbert bi - modules over m with cftp and some natural category of bi - modules over m with the usual relative algebraic tensor product. the results are surely well - known to the experts. we hope that the exposition and presentation is useful for those who want to learn about the cftp.
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arxiv:math/0601045
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we determine the jordan - holder decomposition multiplicities of projective and cell modules over periplectic brauer algebras in characteristic zero. these are obtained by developing the combinatorics of certain skew young diagrams. we also establish a useful relationship with the kazhdan - lusztig multiplicities of the periplectic lie superalgebra.
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arxiv:1701.04606
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probe requests help mobile devices discover active wi - fi networks. they often contain a multitude of data that can be used to identify and track devices and thereby their users. the past years have been a cat - and - mouse game of improving fingerprinting and introducing countermeasures against fingerprinting. this paper analyses the content of probe requests sent by mobile devices and operating systems in a field experiment. in it, we discover that users ( probably by accident ) input a wealth of data into the ssid field and find passwords, e - mail addresses, names and holiday locations. with these findings we underline that probe requests should be considered sensitive data and be well protected. to preserve user privacy, we suggest and evaluate a privacy - friendly hash - based construction of probe requests and improved user controls.
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arxiv:2206.03745
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we present models of the evolution of the gaseous and stellar content of galaxies incorporating the formation of h _ 2 out of hi gas as part of such a model. we do so by formulating a subgrid model for gas clouds that uses well - known cloud scaling relations and solves for the hi - h _ 2 balance set by the h _ 2 formation on dust grains and its fuv - induced photodissociation by the temporally and spatially varying interstellar radiation field. this allows the seamless tracking of the evolution of the h _ 2 gas phase, its precursor cold neutral medium ( cnm ) hi gas, simultaneously with the star formation. our most important findings are : a ) a significant dependence of the hi - h _ 2 transition and the resultant h _ 2 gas mass on the ambient metallicity and the h _ 2 formation rate, b ) the important influence of the characteristic star formation timescale ( regulating the ambient fuv radiation field ) on the equilibrium h _ 2 gas mass and c ) the possibility of a diffuse h _ 2 gas phase. finally, we implement and briefly explore a novel approach of using the ambient h _ 2 gas mass fraction as a criterion for the onset of star formation. ( abridged )
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arxiv:astro-ph/0603581
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we compare optimal static and dynamic solutions in trade execution. an optimal trade execution problem is considered where a trader is looking at a short - term price predictive signal while trading. when the trader creates an instantaneous market impact, it is shown that transaction costs of optimal adaptive strategies are substantially lower than the corresponding costs of the optimal static strategy. in the same spirit, in the case of transient impact it is shown that strategies that observe the signal a finite number of times can dramatically reduce the transaction costs and improve the performance of the optimal static strategy.
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arxiv:1811.11265
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this is a pedagogical paper which explains some ideas in cosmology at a level accessible to undergraduate students. it does not use general relativity, but uses the ideas of newtonian cosmology worked out by milne and mccrea. the cosmological constant is also introduced within a newtonian framework. following standard quantization procedures the wheeler - dewitt equation in the minisuperspace approximation is derived for empty and non - empty universes.
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arxiv:physics/9806004
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a dynamical system is controllable if by imposing appropriate external signals on a subset of its nodes, it can be driven from any initial state to any desired state in finite time. here we study the impact of various network characteristics on the minimal number of driver nodes required to control a network. we find that clustering and modularity have no discernible impact, but the symmetries of the underlying matching problem can produce linear, quadratic or no dependence on degree correlation coefficients, depending on the nature of the underlying correlations. the results are supported by numerical simulations and help narrow the observed gap between the predicted and the observed number of driver nodes in real networks.
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arxiv:1203.5161
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we consider interactions of fermions with the domain wall bubbles produced during the first order phase transitions. new exact solution of dirac equations and reflection coefficient are obtained.
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arxiv:hep-ph/9603395
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given a spectral triple $ ( \ mathcal { a }, \ mathcal { h }, d ) \, $ connes associated a canonical differential graded algebra $ \, \ omega _ d ^ \ bullet ( \ mathcal { a } ) $. however, so far this has been computed for very few special cases. we identify suitable hypotheses on a spectral triple that helps one to compute the associated connes ' calculus for its quantum double suspension. this allows one to compute $ \, \ omega _ d ^ \ bullet $ for spectral triples obtained by iterated quatum double suspension of the spectral triple associated with a first order differential operator on a compact smooth manifold. this gives the first systematic computation of connes ' calculus for a large family of spectral triples.
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arxiv:1404.2708
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this work proposes a robust data - driven predictive control approach for unknown nonlinear systems in the presence of bounded process and measurement noise. data - driven reachable sets are employed for the controller design instead of using an explicit nonlinear system model. although the process and measurement noise are bounded, the statistical properties of the noise are not required to be known. by using the past noisy input - output data in the learning phase, we propose a novel method to over - approximate reachable sets of an unknown nonlinear system. then, we propose a data - driven predictive control approach to compute safe and robust control policies from noisy online data. the constraints are guaranteed in the control phase with robust safety margins through the effective use of the predicted output reachable set obtained in the learning phase. finally, a numerical example validates the efficacy of the proposed approach and demonstrates comparable performance with a model - based predictive control approach.
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arxiv:2211.05867
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a kinetic theory of the bohm criterion is developed that is based on positive - exponent velocity moments of the plasma kinetic equation. this result is contrasted with the conventional kinetic bohm criterion that is based on a v ^ { - 1 } moment of the vlasov equation. the salient difference between the two results is that low velocity particles dominate in the conventional theory, but are essentially unimportant in the new theory. it is shown that the derivation of the conventional kinetic bohm criterion is flawed. low velocity particles can cause unphysical divergences in the conventional theory. these divergent contributions are avoided with this new approach. the two theories are compared using example distribution functions from previous presheath models. the importance of ion - ion and electron - electron collisions to determining the particle distribution functions throughout the presheath is also discussed. a kinetic equation that accounts for wave - particle scattering by convective instabilities is used to show that ion - acoustic instabilities in the presheath of low temperature plasmas ( where t _ e \ gg t _ i ) can cause both ions and electrons to obtain maxwellian distribution functions near the sheath.
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arxiv:1301.5700
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in these notes, we review some recent mathematical results concerning the derivation of effective evolution equations from many body quantum mechanics. in particular, we discuss the emergence of the hartree equation in the so - called mean field regime ( for example, for systems of gravitating bosons ), and we show that the gross - pitaevskii equation approximates the dynamics of initially trapped bose - einstein condensates. we explain how effective evolution equations can be derived, on the one hand, by analyzing the so called bbgky hierarchy, describing the time - evolution of reduced density matrices, and, on the other hand, by studying the dynamics of coherent initial states in a fock - space representation of the many body system.
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arxiv:1111.6995
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standard solar models predict a solar luminosity that gradually increased by about 30 % over the past 4. 5 billion years. under the faint sun, earth should have been frozen solid for most of its existence. yet, running water is observed to have been present since very early in earth ' s history. this enigma is known as the faint sun paradox. we show here that it can be partially resolved once we consider the cooling effect that cosmic rays are suspected to have on the global climate and that the younger sun must have had a stronger solar wind, such that it was more effective at stopping cosmic rays from reaching earth. the paradox can then be completely resolved with the further contribution of modest greenhouse gas warming. when we add the cosmic ray flux modulation by a variable star formation rate in the milky way, we recover the long term glacial activity on earth. as to the future, we find that the average global temperature will increase by typically 10k in the coming 2 gyr.
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arxiv:astro-ph/0306477
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we study the class of endlessly single - mode all - silica photonic crystal fibers with a triangular air - hole cladding. we consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low - loss large - mode area photonic crystal fibers. we also discuss the dominating scattering mechanism and experimentally we confirm that both macro and micro - bending can be the limiting factor.
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arxiv:physics/0302072
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the optimal state determination ( or tomography ) is studied for a composite system of two qubits when measurements can be performed on one of the qubits and interactions of the two qubits can be implemented. the goal is to minimize the number of interactions to be used. the algebraic method applied in the paper leads to an extension of the concept of mutually unbiased measurements.
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arxiv:quant-ph/0605049
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knowledge tracing ( kt ) is to trace the knowledge of students as they solve a sequence of problems represented by their related skills. this involves abstract concepts of students ' states of knowledge and the interactions between those states and skills. therefore, a kt model is designed to predict whether students will give correct answers and to describe such abstract concepts. however, existing methods either give relatively low prediction accuracy or fail to explain those concepts intuitively. in this paper, we propose a new model called knowledge query network ( kqn ) to solve these problems. kqn uses neural networks to encode student learning activities into knowledge state and skill vectors, and models the interactions between the two types of vectors with the dot product. through this, we introduce a novel concept called \ textit { probabilistic skill similarity } that relates the pairwise cosine and euclidean distances between skill vectors to the odds ratios of the corresponding skills, which makes kqn interpretable and intuitive. on four public datasets, we have carried out experiments to show the following : 1. kqn outperforms all the existing kt models based on prediction accuracy. 2. the interaction between the knowledge state and skills can be visualized for interpretation. 3. based on probabilistic skill similarity, a skill domain can be analyzed with clustering using the distances between the skill vectors of kqn. 4. for different values of the vector space dimensionality, kqn consistently exhibits high prediction accuracy and a strong positive correlation between the distance matrices of the skill vectors.
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arxiv:1908.02146
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jieao song recently conjectured a formula for the class of a lagrangian plane on a hyperk \ " ahler variety of $ k3 ^ { [ n ] } $ - type in terms of the class of a line on it. we give a proof of this conjecture if the line class is primitive.
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arxiv:2206.10288
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an invisibility cloak that can hide an arbitrary object external to the cloak itself has not been devised before. in this letter, we introduce a novel way to design a remote cloaking device that makes any object located at a certain distance invisible. this is accomplished using multi - folded transformation optics to remotely generate a hidden region around the object that no field can penetrate and that does not disturb the far - field scattering electromagnetic field. as a result, any object in the hidden region can stay in position or move freely within that region and remain invisible. our idea is further extended in order to design a remote illusion optics that can transform any arbitrary object into another one. unlike other cloaking methods, this method would require no knowledge of the details of the object itself. the proposed multi - folded transformation optics will be crucial in the design of remote devices in a variety of contexts.
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arxiv:1511.07577
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nowadays, the current neural network models of dialogue generation ( chatbots ) show great promise for generating answers for chatty agents. but they are short - sighted in that they predict utterances one at a time while disregarding their impact on future outcomes. modelling a dialogue ' s future direction is critical for generating coherent, interesting dialogues, a need that has led traditional nlp dialogue models that rely on reinforcement learning. in this article, we explain how to combine these objectives by using deep reinforcement learning to predict future rewards in chatbot dialogue. the model simulates conversations between two virtual agents, with policy gradient methods used to reward sequences that exhibit three useful conversational characteristics : the flow of informality, coherence, and simplicity of response ( related to forward - looking function ). we assess our model based on its diversity, length, and complexity with regard to humans. in dialogue simulation, evaluations demonstrated that the proposed model generates more interactive responses and encourages a more sustained successful conversation. this work commemorates a preliminary step toward developing a neural conversational model based on the long - term success of dialogues.
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arxiv:2212.14117
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a sufficient condition for the infinite dimensionality of the bergman space of a pseudoconvex domain is given. this condition holds on any pseudoconvex domain that has at least one smooth boundary point of finite type in the sense of d ' angelo.
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arxiv:1603.09099
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inspired by simulated annealing algorithm, we propose a quantum cooling protocol which includes an annealing process. this protocol can be universally and efficiently applied to various quantum simulators, driving the system from an arbitrary initial state to the ground state with high fidelity. we have described the cooling process based on perturbation theory, validated the advantages of bath under time - modulated zeeman field compared to bath under static one, and provided a justification for the necessity of an annealing process when the system to be cooled is unknown. we applied tensor network methods to numerically simulate our cooling protocol, using the transverse field ising model ( tfim ) as an example to verify the effectiveness of the protocol in cooling one - dimensional systems, two - dimensional systems, and systems with quantum noise. we compared the overall performance of cooling protocols with and without the annealing process on a test set generated with random parameters $ g _ p $. the results indicate that the cooling protocol with annealing process can achieve both accuracy and efficiency. our results also show that the cooling protocol ' s resistance to noise depends on the type of quantum noise.
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arxiv:2501.05268
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we consider the problem of predicting power outages in an electrical power grid due to hazards produced by convective storms. these storms produce extreme weather phenomena such as intense wind, tornadoes and lightning over a small area. in this paper, we discuss the application of state - of - the - art machine learning techniques, such as random forest classifiers and deep neural networks, to predict the amount of damage caused by storms. we cast this application as a classification problem where the goal is to classify storm cells into a finite number of classes, each corresponding to a certain amount of expected damage. the classification method use as input features estimates for storm cell location and movement which has to be extracted from the raw data. a main challenge of this application is that the training data is heavily imbalanced as the occurrence of extreme weather events is rare. in order to address this issue, we applied smote technique.
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arxiv:1805.07897
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