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tradition, featuring a core curriculum of chinese and western literature and civilization studies and required courses in physical education and foreign languages. furthermore, while most tsinghua undergraduates must choose a specific major upon entrance, xinya students declare their majors at the end of freshman year, enabling them to explore several different fields of study. in december 2014, tsinghua university established the advisory committee of undergraduate curriculum ( acuc ). it became the first student autonomous organization in mainland china for students to participate in the school ' s management. the tsinghua university academic committee, which was formally established on 8 july 2015, has stipulated in the committee ' s charter that students should be consulted through the acuc for resolutions involving undergraduate students. from then on, tsinghua commenced a new round of academic reform lasting ever since, including establishing gpa grading system, adding the writing classes, critical thinking classes, second foreign languages classes into curriculum, requiring undergrads to be able to swim before graduation, cooperating with the peking university on class cross - registration to supplement each other ' s general education curriculum, reducing fees on class withdraw, transcripts and certificates, and adjusting the graduate school co - terminal admission policies. in 2016, schwarzman scholars was established with almost us $ 400 million endowment by steven schwarzman, the chairman and ceo of the blackstone group and other multinational corporations and global leaders. schwarzman scholars annually selects 100 – 200 scholars across the world to enroll in a one - year fully - funded master ' s degree leadership program designed to cultivate the next generation of global leaders. 40 % students are selected from the united states, 20 % students are selected from china, 40 % are selected from rest of the world. these scholars reside on the university campus at schwarzman college, a residential college built specifically for the program. in 2016, tsinghua ' s expenditures were rmb 13. 7 billion ( us $ 3. 57 billion at purchasing power parity ), the largest budget of any university in china. according to a 2018 financial times report, tsinghua university has been linked to cyber - espionage. in 2024, tsinghua announced that its office of the university president had merged into the university ' s chinese communist party committee, which would directly administer the university henceforth. = = academics = = tsinghua university engages in extensive research and offers 51 bachelor ' s degree programs, 139 master ' s degree programs, and 107 doctoral programs through 20 colleges and 57 departments covering a broad range of subjects, including science, engineering, | https://en.wikipedia.org/wiki/Tsinghua_University |
new computing paradigms, modern feature - rich programming languages and off - the - shelf software libraries enabled the development of new sophisticated malware families. evidence of this phenomena is the recent growth of fileless malware attacks. fileless malware or memory resident malware is an example of an advanced volatile threat ( avt ). in a fileless malware attack, the malware writes itself directly onto the main memory ( ram ) of the compromised device without leaving any trace on the compromised device ' s file system. for this reason, fileless malware presents a difficult challenge for traditional malware detection tools and in particular signature - based detection. moreover, fileless malware forensics and reverse engineering are nearly impossible using traditional methods. the majority of fileless malware attacks in the wild take advantage of ms powershell, however, fileless malware are not limited to ms powershell. in this paper, we designed and implemented a fileless malware by taking advantage of new features in javascript and html5. the proposed fileless malware could infect any device that supports javascript and html5. it serves as a proof - of - concept ( poc ) to demonstrate the threats of fileless malware in web applications. we used the proposed fileless malware to evaluate existing methods and techniques for malware detection in web applications. we tested the proposed fileless malware with several free and commercial malware detection tools that apply both static and dynamic analysis. the proposed fileless malware bypassed all the anti - malware detection tools included in our study. in our analysis, we discussed the limitations of existing approaches / tools and suggested possible detection and mitigation techniques. | arxiv:1911.11276 |
in this paper we extend a method for iteratively improving slow manifolds so that it also can be used to approximate the fiber directions. the extended method is applied to general finite dimensional real analytic systems where we obtain exponential estimates of the tangent spaces to the fibers. the method is demonstrated on the michaelis - menten - henri model and the lindemann mechanism. the latter example also serves to demonstrate the method on a slow - fast system in non - standard slow - fast form. finally, we extend the method further so that it also approximates the curvature of the fibers. | arxiv:1208.6420 |
sit - to - stand ( sts ) is a fundamental daily activity that can be challenging for stroke survivors due to strength, motor control, and proprioception deficits in their lower limbs. existing therapies involve repetitive sts exercises, but these can be physically demanding for therapists while assistive devices may limit patient participation and hinder motor learning. to address these challenges, this work proposes the use of two lower - limb exoskeletons to mediate physical interaction between therapists and patients during a sts rehabilitative task. this approach offers several advantages, including improved therapist - patient interaction, safety enforcement, and performance quantification. the whole body control of the two exoskeletons transmits online feedback between the two users, but at the same time assists in movement and ensures balance, and thus helping subjects with greater difficulty. in this study we present the architecture of the framework, presenting and discussing some technical choices made in the design. | arxiv:2310.06084 |
when global symmetries are spontaneously broken in supersymmetric vacua, there appear quasi - nambu - goldstone ( ng ) fermions as superpartners of ng bosons. in addition to these, there can appear quasi - ng bosons in general. the quasi - ng bosons and fermions together with the ng bosons are organized into chiral multiplets. k \ " ahler potentials of low - energy effective theories were constructed some years ago as supersymmetric nonlinear realizations. it is known that higher derivative terms in the superfield formalism often encounter with the auxiliary field problem ; the auxiliary fields are acted by space - time derivatives and cannot be eliminated. in this paper, we construct higher derivative corrections to supersymmetric nonlinear realizations in the off - shell superfield formalism free from the auxiliary field problem. as an example, we present manifestly supersymmetric chiral lagrangian. | arxiv:1408.4210 |
we provide here a roadmap for modeling silicon nano - devices with one or two group v donors ( d ). we discuss systems containing one or two electrons, that is, d ^ 0, d ^ -, d _ 2 ^ + and d _ 2 ^ 0 centers. the impact of different levels of approximation is discussed. the most accurate instances - - for which we provide quantitative results - - are within multivalley effective mass including the central cell correction and a configuration interaction account of the electron - electron correlations. we also derive insightful, yet less accurate, analytical approximations and discuss their validity and limitations - - in particular, for a donor pair, we discuss the single orbital lcao method, the huckel approximation and the hubbard model. finally we discuss the connection between these results and recent experiments on few dopant devices. | arxiv:1407.8224 |
we consider a class of physiologically structured population models, a first order nonlinear partial differential equation equipped with a nonlocal boundary condition, with a constant external inflow of individuals. we prove that the linearised system is governed by a quasicontraction semigroup. we also establish that linear stability of equilibrium solutions is governed by a generalized net reproduction function. in a special case of the model ingredients we discuss the nonlinear dynamics of the system when the spectral bound of the linearised operator equals zero, i. e. when linearisation does not decide stability. this allows us to demonstrate, through a concrete example, how immigration might be beneficial to the population. in particular, we show that from a nonlinearly unstable positive equilibrium a linearly stable and unstable pair of equilibria bifurcates. in fact, the linearised system exhibits bistability, for a certain range of values of the external inflow, induced potentially by all \ ' { e } e - effect. | arxiv:0906.2180 |
low - dimensional representations, or embeddings, of a graph ' s nodes facilitate several practical data science and data engineering tasks. as such embeddings rely, explicitly or implicitly, on a similarity measure among nodes, they require the computation of a quadratic similarity matrix, inducing a tradeoff between space complexity and embedding quality. to date, no graph embedding work combines ( i ) linear space complexity, ( ii ) a nonlinear transform as its basis, and ( iii ) nontrivial quality guarantees. in this paper we introduce frede ( frequent directions embedding ), a graph embedding based on matrix sketching that combines those three desiderata. starting out from the observation that embedding methods aim to preserve the covariance among the rows of a similarity matrix }, frede iteratively improves on quality while individually processing rows of a nonlinearly transformed ppr similarity matrix derived from a state - of - the - art graph embedding method } and provides, at any iteration, column - covariance approximation guarantees in due course almost indistinguishable from those of the optimal approximation by svd. our experimental evaluation on variably sized networks shows that frede performs almost as well as svd and competitively against state - of - the - art embedding methods in diverse data science tasks, even when it is based on as little as 10 % of node similarities. | arxiv:2006.04746 |
we consider 3 + 1 dimensional quantum field theories ( qfts ) coupled to the dilaton and the graviton. we show that the graviton - dilaton scattering amplitude receives a universal contribution which is helicity flipping and is proportional to $ \ delta c - \ delta a $ along any rg flow, where $ \ delta c $ and $ \ delta a $ are the differences of the uv and ir $ c $ - and $ a $ - trace anomalies respectively. this allows us to relate $ \ delta c - \ delta a $ to spinning massive states in the spectrum of the qft. we test our predictions in two simple examples : in the theory of a massive free scalar and in the theory of a massive dirac fermion ( a more complicated example is provided in a companion paper [ 1 ] ). we discuss possible applications. | arxiv:2312.09308 |
it is known from density functional theory ( dft ) calculations that rhsi has a multifold degenerate dirac point at the fermi energy, with the dominant states in the low - energy region displaying mostly rh $ d $ character. using dft + u, we calculate the band structure by considering an effective local interaction on the rh $ d $ states, with a realistic effective hubbard $ u _ \ textrm { eff } = 2. 5 $ ev derived from a constrained random - phase approximation calculation, and find the emergence of a double hump structure close to the fermi energy. by further deriving a low - energy tight - binding model from our first - principles results, we show that the double hump is a direct consequence of a competition between the rh $ d $ - rh $ d $ and rh $ d $ - si $ p $ interactions, which differ in their momentum dependence. as a consequence, through an artificial tuning of the energy level of the si $ p $ orbitals this hump structure can be suppressed due to the effectively reduced rh $ d $ - si $ p $ interaction. this peculiar low - energy electronic structure additionally results in that a small hole / electron doping ( $ \ sim $ 0. 1 $ \ % $ ) can tune the fermi surface topology, going from closed to open fermi surfaces, which has dramatic consequences for the thermal transport. | arxiv:2403.19370 |
in wireless communications, estimation of channels in ofdm systems spans frequency and time, which relies on sparse collections of pilot data, posing an ill - posed inverse problem. moreover, deep learning estimators require large amounts of training data, computational resources, and true channels to produce accurate channel estimates, which are not realistic. to address this, a convolutional neural tangent kernel ( cntk ) is derived from an infinitely wide convolutional network whose training dynamics can be expressed by a closed - form equation. this cntk is used to impute the target matrix and estimate the missing channel response using only the known values available at pilot locations. this is a promising solution for channel estimation that does not require a large training set. numerical results on realistic channel datasets demonstrate that our strategy accurately estimates the channels without a large dataset and significantly outperforms deep learning methods in terms of speed, accuracy, and computational resources. | arxiv:2504.08660 |
according to quantum mechanics chiral molecules, that is molecules that rotate the polarization of light, should not exist. the simplest molecules which can be chiral have four or more atoms with two arrangements of minimal potential energy that are equivalent up to a parity operation. chiral molecules correspond to states localized in one potential energy minimum and can not be stationary states of the schr \ " odinger equation. a possible solution of the paradox can be founded on the idea of spontaneous symmetry breaking. this idea was behind work we did previously involving a localization phase transition : at low pressure the molecules are delocalized between the two minima of the potential energy while at higher pressure they become localized in one minimum due to the intermolecular dipole - dipole interactions. evidence for such a transition is provided by measurements of the inversion spectrum of ammonia and deuterated ammonia at different pressures. a previously proposed model gives a satisfactory account of the empirical results without free parameters. in this paper, we extend this model to gas mixtures. we find that also in these systems a phase transition takes place at a critical pressure which depends on the composition of the mixture. moreover, we derive formulas giving the dependence of the inversion frequencies on the pressure. these predictions are susceptible to experimental test. | arxiv:1501.02099 |
we present the discovery of a plausible disk - eclipse system ogle - blg182. 1. 162852. the ogle light curve for ogle - blg182. 1. 162852 shows three episodes of dimming by $ i \ simeq 2 - 3 $ magnitudes, separated by 1277 days. the shape of the light curve during dimming events is very similar to that of known disk eclipse system ogle - lmc - ecl - 11893 ( dong et al. 2014 ). the event is presently undergoing a dimming event, predicted to end on december 30th, 2014. we encourage spectroscopic and multi - band photometric observations now. the next dimming episode for ogle - blg182. 1. 162852 is expected to occur in march 2018. | arxiv:1410.2643 |
we investigate topologically biased failure in scale - free networks with degree distribution $ p ( k ) \ propto k ^ { - \ gamma } $. the probability $ p $ that an edge remains intact is assumed to depend on the degree $ k $ of adjacent nodes $ i $ and $ j $ through $ p _ { ij } \ propto ( k _ { i } k _ { j } ) ^ { - \ alpha } $. by varying the exponent $ \ alpha $, we interpolate between random ( $ \ alpha = 0 $ ) and systematic failure. for $ \ alpha > 0 $ ( $ < 0 $ ) the most ( least ) connected nodes are depreciated first. this topological bias introduces a characteristic scale in $ p ( k ) $ of the depreciated network, marking a crossover between two distinct power laws. the critical percolation threshold, at which global connectivity is lost, depends both on $ \ gamma $ and on $ \ alpha $. as a consequence, network robustness or fragility can be controlled through fine tuning of the topological bias in the failure process. | arxiv:0812.3591 |
it has been considered that feas - based high transition temperature ( high - tc ) superconductors need electron or hole doping by aliovalent ion substitution or large off - stoichiometry in order to induce superconductivity. we report that exposure of undoped srfe2as2 epitaxial thin films to water vapor induces a superconducting transition. these films exhibit a higher onset - tc ( 25 k ) and larger magnetic field anisotropy than those of cobalt - doped srfe2as2 epitaxial films, suggesting that the mechanism for the observed superconducting transition differs from that of the aliovalent - ion doped srfe2as2. the present finding provides a new approach to induce superconductivity with a higher tc in feas - based superconductors. | arxiv:0903.3710 |
we have detected 506 i - dropouts ( z ~ 6 galaxies ) in deep, wide - area hst acs fields : hudf, enhanced goods, and hudf - parallel acs fields ( hudf - ps ). the contamination levels are < = 8 % ( i. e., > = 92 % are at z ~ 6 ). with these samples, we present the most comprehensive, quantitative analyses of z ~ 6 galaxies yet and provide optimal measures of the uv luminosity function ( lf ) and luminosity density at z ~ 6, and their evolution to z ~ 3. we redetermine the size and color evolution from z ~ 6 to z ~ 3. field - to - field variations ( cosmic variance ), completeness, flux, and contamination corrections are modelled systematically and quantitatively. after corrections, we derive a rest - frame continuum uv ( ~ 1350 a ) lf at z ~ 6 that extends to m _ { 1350, ab } ~ - 17. 5 ( 0. 04l * ( z = 3 ) ). there is strong evidence for evolution of the lf between z ~ 6 and z ~ 3, most likely through a brightening ( 0. 6 + / - 0. 2 mag ) of m * ( at 99. 7 % confidence ) though the degree depends upon the faint - end slope. as expected from hierarchical models, the most luminous galaxies are deficient at z ~ 6. density evolution ( phi * ) is ruled out at > 99. 99 % confidence. despite large changes in the lf, the luminosity density at z ~ 6 is similar ( 0. 82 + / - 0. 21x ) to that at z ~ 3. changes in the mean uv color of galaxies from z ~ 6 to z ~ 3 suggest an evolution in dust content, indicating the true evolution is substantially larger : at z ~ 6 the star formation rate density is just ~ 30 % of the z ~ 3 value. our uv luminosity function is consistent with z ~ 6 galaxies providing the necessary uv flux to reionize the universe. | arxiv:astro-ph/0509641 |
the causal dependence in data is often characterized by directed acyclic graphical ( dag ) models, widely used in many areas. causal discovery aims to recover the dag structure using observational data. this paper focuses on causal discovery with multi - variate count data. we are motivated by real - world web visit data, recording individual user visits to multiple websites. building a causal diagram can help understand user behavior in transitioning between websites, inspiring operational strategy. a challenge in modeling is user heterogeneity, as users with different backgrounds exhibit varied behaviors. additionally, social network connections can result in similar behaviors among friends. we introduce personalized binomial dag models to address heterogeneity and network dependency between observations, which are common in real - world applications. to learn the proposed dag model, we develop an algorithm that embeds the network structure into a dimension - reduced covariate, learns each node ' s neighborhood to reduce the dag search space, and explores the variance - mean relation to determine the ordering. simulations show our algorithm outperforms state - of - the - art competitors in heterogeneous data. we demonstrate its practical usefulness on a real - world web visit dataset. | arxiv:2406.06829 |
we present a detailed study of the galaxy cluster abell 795 and of its central fanaroff - riley type 0 ( fr0 ) radio galaxy. from an archival chandra observation, we found a dynamically disturbed environment with evidences for sloshing of the intracluster medium. we argue that the environment alone cannot explain the compactness of the radio galaxy, as similar conditions are also found around extended sources. we identified a pair of putative x - ray cavities in the proximity of the center : these could have been created in a past outburst of the fr0, and dragged away by the large - scale gas movement. the presence of x - ray cavities associated with a fr0 could open a new window on the study of jet power and feedback properties of this recently discovered class of compact radio galaxies. | arxiv:2111.02160 |
we investigate the two - dimensional lattice u ( 1 ) gauge - higgs model with a topological term, employing l \ " uscher ' s admissibility condition. the standard monte carlo simulation for this model is hindered not only by the complex action problem due to the topological term but also by the topological freezing problem originating from the admissibility condition. resolving both obstacles simultaneously with the tensor renormalization group approach, we show the advantage of the admissibility condition in dealing with the topological term discretized with the so - called field - theoretical definition. | arxiv:2501.15352 |
we present a collection of selected phenomena observed in j / psi production from proton - nucleus and heavy ion collisions at energies, ranging between the sps and lhc. the emphasis is placed on the related theoretical ideas or techniques, which are either not widely known, or offer an alternative explanation to the observed nuclear effects. | arxiv:1210.6281 |
using wide - field $ bvr _ ci $ imaging for a sample of 16 intermediate redshift ( $ 0. 17 < z < 0. 55 $ ) galaxy clusters from the canadian network for observational cosmology ( cnoc1 ) survey, we investigate the dependence of cluster galaxy populations and their evolution on environment. galaxy photometric redshifts are estimated using an empirical photometric redshift technique and galaxy groups are identified using a modified friends - of - friends algorithm in photometric redshift space. we utilize the red galaxy fraction ( \ fred ) to infer the evolutionary status of galaxies in clusters, using both individual galaxies and galaxies in groups. we apply the local galaxy density, \ sig5, derived using the fifth nearest - neighbor distance, as a measure of local environment, and the cluster - centric radius, \ rcl, as a proxy for global cluster environment. our cluster sample exhibits a butcher - oemler effect in both luminosity - selected and stellar - mass - selected samples. we find that \ fred depends strongly on \ sig5 and \ rcl, and the butcher - oemler effect is observed in all \ sig5 and \ rcl bins. however, when the cluster galaxies are separated into \ rcl bins, or into group and non - group subsamples, the dependence on local galaxy density becomes much weaker. this suggests that the properties of the dark matter halo in which the galaxy resides have a dominant effect on its galaxy population and evolutionary history. we find that our data are consistent with the scenario that cluster galaxies situated in successively richer groups ( i. e., more massive dark matter halos ) reach a high \ fred value at earlier redshifts. associated with this, we observe a clear signature of ` pre - processing ', in which... < and more > | arxiv:0904.0831 |
topological spin textures such as magnetic skyrmions hold considerable promise as robust, nanometre - scale, mobile bits for sustainable computing. a longstanding roadblock to unleashing their potential is the absence of a device enabling deterministic electrical readout of individual spin textures. here we present the wafer - scale realization of a nanoscale chiral magnetic tunnel junction ( mtj ) hosting a single, ambient skyrmion. using a suite of electrical and multi - modal imaging techniques, we show that the mtj nucleates skyrmions of fixed polarity, whose large readout signal - 20 - 70 % relative to uniform states - corresponds directly to skyrmion size. further, the mtj exploits complementary mechanisms to stabilize distinctly sized skyrmions at zero field, thereby realizing three nonvolatile electrical states. crucially, it can write and delete skyrmions using current densities 1, 000 times lower than state - of - the - art. these results provide a platform to incorporate readout and manipulation of skyrmionic bits across myriad device architectures, and a springboard to harness chiral spin textures for multi - bit memory and unconventional computing. | arxiv:2302.08020 |
we describe the design of a low - phase - modulated ( pm ) noise, 40 ghz oscillator that uses a conventional air - dielectric cavity resonator as a frequency discriminator to improve the pm noise of a commercial 10 ghz dielectric resonator oscillator ( dro ) frequency multiplied by four. the main features of this design incorporate ( 1 ) unloaded cavity quality factor ( q ) of 30, 000, ( 2 ) high coupling coefficient, ( 3 ) large carrier suppression by use of interferometric signal processing, ( 4 ) large operating signal power of approximately 1 watt ( w ), and ( 5 ) relatively small size. in addition, we report the pm noise of several ka - band components. | arxiv:1404.4828 |
we study the possibility of orbital synchronization capture for a hierarchical quadrupole stellar system composed by two binaries emitting gravitational waves. based on a simple model including the mass transfer for white dwarf binaries, we find that the capture might be realized for inter - binary distances less than their gravitational wavelength. we also discuss related intriguing phenomena such as a parasitic relation between the coupled white dwarf binaries and significant reductions of gravitational and electromagnetic radiations. | arxiv:1801.02286 |
we study the electronic states of giant single - shell and the recently discovered nested multi - shell carbon fullerenes within the tight - binding approximation. we use two different approaches, one based on iterations and the other on symmetry, to obtain the $ \ pi $ - state energy spectra of large fullerene cages : $ c _ { 240 } $, $ c _ { 540 } $, $ c _ { 960 } $, $ c _ { 1500 } $, $ c _ { 2160 } $ and $ c _ { 2940 } $. our iteration technique reduces the dimensionality of the problem by more than one order of magnitude ( factors of $ \ sim 12 $ and $ 20 $ ), while the symmetry - based approach reduces it by a factor of $ 10 $. we also find formulae for the highest occupied and lowest unoccupied molecular orbital ( homo and lumo ) energies of $ c _ { 60 { \ cdot } n ^ { 2 } } $ fullerenes as a function of $ n $, demonstrating a tendency towards metallic regime for increasing $ n $. for multi - shell fullerenes, we analytically obtain the eigenvalues of the intershell interaction. | arxiv:cond-mat/9312040 |
theoretical and numerical calculations of the optical absorption spectra of excitons interacting with longitudinal - optical phonons in quasi - 2d polar semiconductors are presented. in ii - vi semiconductor quantum wells, exciton binding energy can be tuned on - and off - resonance with the longitudinal - optical phonon energy by varying the quantum well width. a comprehensive picture of this tunning effect on the temperature - dependent exciton absorption spectrum is derived, using the exciton green ' s function formalism at finite temperature. the effective exciton - phonon interaction is included in the bethe - salpeter equation. numerical results are illustrated for znse - based quantum wells. at low temperatures, both a single exciton peak as well as a continuum resonance state are found in the optical absorption spectra. by contrast, at high enough temperatures, a splitting of the exciton line due to the real phonon absorption processes is predicted. possible previous experimental observations of this splitting are discussed. | arxiv:cond-mat/0106078 |
let $ \ mathfrak { g } $ be a solvable lie algebra and $ q $ an $ ad \ mathfrak { g } $ - stable prime ideal of the symmetric algebra $ s ( \ mathfrak { g } ) $ of $ \ mathfrak { g } $. if $ e $ is the set of non zero elements of $ s ( \ mathfrak { g } ) / q $ which are eigenvectors for the adjoint action of $ \ mathfrak { g } $ in $ s ( \ mathfrak { g } ) / q $, the localised algebra $ ( s ( \ mathfrak { g } ) / q ) _ { e } $ has a natural structure of poisson algebra. we study this algebra here. | arxiv:math/0702615 |
a number of time resolved optical experiments probing and controlling the spin and charge dynamics of the high mobility two - dimensional electron gas in a gaas / algaas heterojunction are discussed. these include time resolved reflectivity, luminescence, transient grating, magneto - optical kerr effect, and electro - optical kerr effect experiments. the optical experiments provide information on the carrier lifetimes and spin dephasing times, as well as on the carrier diffusion coefficient which directly gives the charge mobility. a combination of the two types of kerr experiments, shows to be useful in extracting both the carrier lifetimes and spin dephasing times in a single experiment. | arxiv:cond-mat/0610783 |
the collective tunneling of a small cluster of spins between two degenerate ground state configurations of the kagom \ ' { e } - lattice quantum heisenberg antiferromagnet is \ mbox { studied }. the cluster consists of the six spins on a hexagon of the lattice. the resulting tunnel splitting energy $ \ delta $ is calculated in detail, including the prefactor to the exponential $ \ exp ( - \ sso / \ hbar ) $. this is done by setting up a coherent spin state path integral in imaginary time and evaluating it by the method of steepest descent. the hexagon tunneling problem is mapped onto a much simpler tunneling problem, involving only one collective degree of freedom, which can be treated by known methods. it is found that for half - odd - integer spins, the tunneling amplitude and the tunnel splitting energy are exactly zero, because of destructive interference between symmetry - related $ ( + ) $ - instanton and $ ( - ) $ - instanton tunneling paths. this destructive interference is shown to occur also for certain larger loops of spins on the kagom \ ' { e } lattice. for small, integer spins, our results suggest that tunneling strongly competes with \ mbox { in - plane } order - from - disorder selection effects ; it constitutes a disordering mechanism that might drive the system into a partially disordered ground state, related to a spin nematic. | arxiv:cond-mat/9211002 |
interlaced spin grating is a scheme for the preparation of spectro - spatial periodic absorption gratings in a inhomogeneously broadened absorption profile. it relies on the optical pumping of atoms in a nearby long - lived ground state sublevel. the scheme takes advantage of the sublevel proximity to build large contrast gratings with unlimited bandwidth and preserved average optical depth. it is particularly suited to tm - doped crystals in the context of classical and quantum signal processing. in this paper, we study the optical pumping dynamics at play in an interlaced spin grating and describe the corresponding absorption profile shape in an optically thick atomic ensemble. we show that, in tm : yag, the diffraction efficiency of such a grating can reach 18. 3 % in the small angle, and 11. 6 % in the large angle configuration when the excitation is made of simple pulse pairs, considerably outperforming conventional gratings. | arxiv:1407.3944 |
understanding the thermodynamic state of the hot intracluster medium ( icm ) in a galaxy cluster requires a knowledge of the plasma transport processes, especially thermal conduction. the basic physics of thermal conduction in plasmas with icm - like conditions has yet to be elucidated, however. we use particle - in - cell simulations and analytic models to explore the dynamics of an icm - like plasma ( with small gyroradius, large mean - free - path, and strongly sub - dominant magnetic pressure ) driven by the diffusive heat flux associated with thermal conduction. lin - ear theory reveals that whistler waves are driven unstable electron heat flux, even when the heat flux is weak. the resonant interaction of electrons with these waves then plays a critical role in scattering electrons and suppressing the heat flux. in a 1d model where only whistler modes that are parallel to the magnetic field are captured, the only resonant electrons are moving in the opposite direction to the heat flux and the electron heat flux suppression is small. in 2d or more, oblique whistler modes also resonate with electrons moving in the direction of the heat flux. the overlap of resonances leads to effective symmetrization of the electron distribution function and a strong suppression of heat flux. the results suggest that thermal conduction in the icm might be strongly suppressed, possibly to negligible levels. | arxiv:1606.05261 |
conditional flow matching ( cfm ) models can generate high - quality samples from a non - informative prior, but they can be slow, often needing hundreds of network evaluations ( nfe ). to address this, we propose implicit dynamical flow fusion ( idff ) ; idff learns a new vector field with an additional momentum term that enables taking longer steps during sample generation while maintaining the fidelity of the generated distribution. consequently, idffs reduce the nfes by a factor of ten ( relative to cfms ) without sacrificing sample quality, enabling rapid sampling and efficient handling of image and time - series data generation tasks. we evaluate idff on standard benchmarks such as cifar - 10 and celeba for image generation, where we achieve likelihood and quality performance comparable to cfms and diffusion - based models with fewer nfes. idff also shows superior performance on time - series datasets modeling, including molecular simulation and sea surface temperature ( sst ) datasets, highlighting its versatility and effectiveness across different domains. \ href { https : / / github. com / mrrezaeiuoft / idff } { github repository } | arxiv:2409.14599 |
we point out that luminous magnetic flares, thought to occur in standard agn accretion disks, cannot be located much higher than few pressure scale heights above the disk. using this fact, we estimate the fraction of the disk surface illuminated by a typical flare. this fraction turns out to be very small for geometrically thin disks, which implies that the instantaneous fe k - alpha emission line from a specific magnetic flare is narrow. the line is red - or blue - shifted depending on the position of the observer relative to the flare and sweeps across the line band with time. we present several examples of theoretical time - resolved line profiles from such flares for a non - rotating black hole. the observations of such moving features with future x - ray telescopes will present a powerful test of the accretion disk geometry and may also test general relativity in the strong field limit. | arxiv:astro-ph/0101312 |
atomic scale computer simulations on structures and photo induced volume changes of flatly and obliquely deposited amorphous selenium films have been carried out in order to understand how the properties of chalcogenide glasses are influenced by their preparation method. obliquely deposited a - se thin films contain more coordination defects, larger voids than the flatly deposited ones. to model the photo induced volume changes the electron excitation and hole creation were treated independently within the framework of tight - binding formalism. covalent and interchain bond breakings and formations were found. the obliquely deposited samples containing voids showed a wide spectrum of photo induced structural changes in microscopic and volume changes in macroscopic levels. | arxiv:0806.4066 |
a primary source of increased read time on nand flash comes from the fact that in the presence of noise, the flash medium must be read several times using different read threshold voltages for the decoder to succeed. this paper proposes an algorithm that uses a limited number of re - reads to characterize the noise distribution and recover the stored information. both hard and soft decoding are considered. for hard decoding, the paper attempts to find a read threshold minimizing bit - error - rate ( ber ) and derives an expression for the resulting codeword - error - rate. for soft decoding, it shows that minimizing ber and minimizing codeword - error - rate are competing objectives in the presence of a limited number of allowed re - reads, and proposes a trade - off between the two. the proposed method does not require any prior knowledge about the noise distribution, but can take advantage of such information when it is available. each read threshold is chosen based on the results of previous reads, following an optimal policy derived through a dynamic programming backward recursion. the method and results are studied from the perspective of an slc flash memory with gaussian noise for each level but the paper explains how the method could be extended to other scenarios. | arxiv:2202.05661 |
within the framework of lorentz model for description of viscoelastic medium the influence of deformational defect of the shear modulus is studied on melting of ultrathin lubricant film confined between the atomically flat solid surfaces. the possibility of jump - like and continuous melting is shown. three modes of lubricant behavior are found, which correspond to the zero shear stress, the hooke section of loading diagram, and the domain of plastic flow. transition between these modes can take place according to mechanisms of first - order and second - order phase transitions. hysteresis of dependences of stationary stresses on strain and friction surfaces temperature is described. phase kinetics of the system is investigated. it is shown that ratio of the relaxation times for the studied quantities influences qualitatively on the character of the stationary mode setting. | arxiv:cond-mat/0610144 |
we review and update some aspects of deuterium chemistry in the post - recombination universe with particular emphasis on the formation and destruction of hd. we examine in detail the available theoretical and experimental data for the leading reactions of deuterium chemistry and we highlight the areas where improvements in the determination of rate coefficients are necessary to reduce the remaining uncertainties. we discuss the cooling properties of hd and the modifications to the standard cooling function introduced by the presence of the cosmological radiation field. finally, we consider the effects of deuterium chemistry on the dynamical collapse of primordial clouds in a simple ` ` top - hat ' ' scenario, and we speculate on the minimum mass a cloud must have in order to be able to cool in a hubble time. | arxiv:astro-ph/0202329 |
phase change material ( pcm ) features distinct optical or electronic properties between amorphous and crystalline states. recently, it starts to play a key role in the emerging photonic applications like optoelectronic display, dynamic wavefront control, on - chip photonic memory and computation. however, current pcms do not refract effectively at visible wavelengths and suffer from deformation and decomposition, limiting the repeatability and vast visible wavelength applications. silicon as the fundamental material for electronics and photonics, has never been considered as phase change material, due to its ultrafast crystallization kinetics. here we show the striking fact that nanoscale silicon domains can be reversibly crystallized and amorphized under nanosecond laser pulses. for a typical disk resonator, it also provides a 25 % non - volatile modulation at nanosecond time scale. we further show proof - of - concept experiments that such attributes could enable ultra - high resolution dielectric color display and dynamic visible wavefront control. | arxiv:1904.11691 |
both the original temperley - lieb algebras $ \ mathsf { tl } _ { n } $ and their dilute counterparts $ \ mathsf { dtl } _ { n } $ form families of filtered algebras : $ \ mathsf { tl } _ { n } \ subset \ mathsf { tl } _ { n + 1 } $ and $ \ mathsf { dtl } _ { n } \ subset \ mathsf { dtl } _ { n + 1 } $, for all $ n \ geq 0 $. for each such inclusion, the restriction and induction of every finite - dimensional indecomposable module over $ \ mathsf { tl } _ { n } $ ( or $ \ mathsf { dtl } _ { n } $ ) is computed. to accomplish this, a thorough description of each indecomposable is given, including its projective cover and injective hull, some short exact sequences in which it appears, its socle and head, and its extension groups with irreducible modules. these data are also used to prove the completeness of the list of indecomposable modules, up to isomorphism. in fact, two completeness proofs are given, the first is based on elementary homological methods and the second uses auslander - reiten theory. the latter proof offers a detailed example of this algebraic tool that may be of independent interest. | arxiv:1605.05159 |
in this paper we investigate the construction of state models for link invariants using representations of the braid group obtained from various gauge choices for a solution of the trigonometric yang - baxter equation. our results show that it is possible to obtain invariants of regular isotopy ( as defined by kauffman ) which may not be ambient isotopic. we illustrate our results with explicit computations using solutions of the trigonometric yang - baxter equation associated with the one - parameter family of minimal typical representations of the quantum superalgebra u _ q [ gl ( 2 | 1 ) ]. we have implemented mathematica code to evaluate the invariants for all prime knots up to 10 crossings. | arxiv:math/0004169 |
in the context of spinfoam models for quantum gravity, we investigate the asymptotical behavior of the 6j - symbol at next - to - leading order. we compute it analytically and check our results against numerical calculations. the 6j - symbol is the building block of the ponzano - regge amplitudes for 3d quantum gravity, and the present analysis is directly relevant to deriving the quantum corrections to gravitational correlations in the spinfoam formalism. | arxiv:0905.4188 |
liko and wesson have recently introduced a new 5 - dimensional induced matter solution of the einstein equations, a negative curvature robertson - walker space embedded in a riemann flat 5 - dimensional manifold. we show that this solution is a special case of a more general theorem prescribing the structure of certain n + 1 - dimensional riemann flat spaces which are all solutions of the einstein equations. these solutions encapsulate n - dimensional curved manifolds. such spaces are said to " induce matter " in the sub - manifolds by virtue of their geometric structure alone. we prove that the n - manifold can be any maximally symmetric space. | arxiv:gr-qc/0511012 |
we propose a positivity preserving entropy decreasing finite volume scheme for nonlinear nonlocal equations with a gradient flow structure. these properties allow for accurate computations of stationary states and long - time asymptotics demonstrated by suitably chosen test cases in which these features of the scheme are essential. the proposed scheme is able to cope with non - smooth stationary states, different time scales including metastability, as well as concentrations and self - similar behavior induced by singular nonlocal kernels. we use the scheme to explore properties of these equations beyond their present theoretical knowledge. | arxiv:1402.4252 |
warfare dramatically improved with use of railways and telegraphs. industrialization provided a base of factories that could be converted to produce munitions, as well as uniforms, tents, wagons and essential supplies. medical facilities were enlarged and reorganized based on improved hospitals and the creation of modern nursing, typified by florence nightingale in britain during the crimean war of 1854 – 56. = = = = naval = = = = naval warfare was transformed by many innovations, most notably the coal - based steam engine, highly accurate long - range naval guns, heavy steel armour for battleships, mines, and the introduction of the torpedo, followed by the torpedo boat and the destroyer. coal after 1900 was eventually displaced by more efficient oil, but meanwhile navies with an international scope had to depend on a network of coaling stations to refuel. the british empire provided them in abundance, as did the french empire to a lesser extent. war colleges developed, as military theory became a specialty ; cadets and senior commanders were taught the theories of jomini, clausewitz and mahan, and engaged in tabletop war games. around 1900, entirely new innovations such as submarines and airplanes appeared, and were quickly adapted to warfare by 1914. the british hms dreadnought ( 1906 ) incorporated so much of the latest technology in weapons, propulsion and armour that it at a stroke made all other battleships obsolescent. = = = = organization and finance = = = = new financial tools were developed to fund the rapidly increasing costs of warfare, such as popular bond sales and income taxes, and the funding of permanent research centers. many 19th century innovations were largely invented and promoted by lone individuals with small teams of assistants, such as david bushnell and the submarine, john ericsson and the battleship, hiram maxim and the machine gun, and alfred nobel and high explosives. by 1900 the military began to realize that they needed to rely much more heavily on large - scale research centers, which needed government funding. they brought in leaders of organized innovation such as thomas edison in the u. s. and chemist fritz haber of the kaiser wilhelm institute in germany. = = postmodern technology = = the postmodern stage of military technology emerged in the 1940s, and one with recognition thanks to the high priority given during the war to scientific and engineering research and development regarding nuclear weapons, radar, jet engines, proximity fuses, advanced submarines, aircraft carriers, and other weapons. the high - priority continues into the 21st century. it involves the military application of advanced scientific research regarding nuclear weapons, jet engines | https://en.wikipedia.org/wiki/Military_technology |
we show that a dilute ensemble of epoxy - bonded adatoms on graphene has a tendency to form a spatially correlated state accompanied by a gap in graphene ' s electron spectrum. this effect emerges from the electron - mediated interaction between adatoms with a peculiar $ 1 / r ^ 3 $ distance dependence. the partial ordering transition is described by a random bond three state potts model. | arxiv:0909.2988 |
in this paper, we show that the $ c ^ 1 $ - differentiability of the norm of a two - dimensional normed space depends only on distances between points of the unit sphere in two different ways. as a consequence, we see that any isometry between the spheres of normed planes $ \ tau : s _ x \ to s _ y $ is linear, provided that there exist linearly independent $ x, \ overline { x } \ in s _ x $ where $ s _ x $ is not differentiable and that $ s _ x $ is piecewise differentiable. we end this work by showing that the isometry $ \ tau : c _ x \ to c _ y $ is linear even if it is not an isometry between spheres : every isometry between ( planar ) jordan piecewise $ c ^ 1 $ - differentiable convex curves extends to $ x $ whenever $ x $ and $ y $ are strictly convex and the amount of non - differentiability points of $ s _ x $ and $ s _ y $ is finite and greater than 2. | arxiv:2102.11226 |
let $ f $ be the infinitesimal generator of a one - parameter semigroup $ \ left \ { f _ { t } \ right \ } _ { t \ ge0 } $ of holomorphic self - mappings of the open unit disk $ \ delta $. in this paper we study properties of the family $ r $ of resolvents $ ( i + rf ) ^ { - 1 } : \ delta \ to \ delta ~ ( r \ ge0 ) $ in the spirit of geometric function theory. we discovered, in particular, that $ r $ forms an inverse l \ " owner chain of hyperbolically convex functions. moreover, each element of $ r $ satisfies the noshiro - warschawski condition and is a starlike function of order at least $ \ frac12 $,. this, in turn, implies that each element of $ r $ is also a holomorphic generator. we mention also quasiconformal extension of an element of $ r. $ finally we study the existence of repelling fixed points of this family. | arxiv:1901.02142 |
the orbits of the group b of upper - triangular matrices acting on 2 - nilpotent complex matrices via conjugation are classified via oriented link patterns, generalizing a. melnikov ' s classification of the b - orbits on upper - triangular such matrices. the orbit closures as well as the " building blocks " of minimal degenerations of orbits are described. the classification uses the theory of representations of finite - dimensional algebras. furthermore, we initiate the study of the b - orbits on arbitrary nilpotent matrices. | arxiv:1004.1996 |
on the basis of a suggestive definition of a classical extension of quantum mechanics in terms of statistical models, we prove that every such classical extension is essentially given by the so - called misra - bugajski reduction map. we consider how this map enables one to understand quantum mechanics as a reduced classical statistical theory on the projective hilbert space as phase space and discuss features of the induced hidden - variables model. moreover, some relevant technical results on the topology and borel structure of the projective hilbert space are reviewed. | arxiv:0708.1539 |
it has been shown that it is theoretically possible for there to exist higher - order quantum processes in which the operations performed by separate parties cannot be ascribed a definite causal order. some of these processes are believed to have a physical realization in standard quantum mechanics via coherent control of the times of the operations. a prominent example is the quantum switch, which was recently demonstrated experimentally. however, the interpretation of such experiments as realizations of a process with indefinite causal structure as opposed to some form of simulation of such a process has remained controversial. where exactly are the local operations of the parties in such an experiment? on what spaces do they act given that their times are indefinite? can we probe them directly rather than assume what they ought to be based on heuristic considerations? how can we reconcile the claim that these operations really take place, each once as required, with the fact that the structure of the presumed process implies that they cannot be part of any acyclic circuit? here, i offer a precise answer to these questions : the input and output systems of the operations in such a process are generally nontrivial subsystems of hilbert spaces that are tensor products of hilbert spaces associated with systems at different times - - - a fact that is directly experimentally verifiable. with respect to these time - delocalized subsystems, the structure of the process is one of a circuit with a causal cycle. i also identify a whole class of isometric processes, of which the quantum switch is a special case, that admit a physical realization on time - delocalized subsystems. these results unveil a novel structure within quantum mechanics, which may have important implications for physics and information processing. | arxiv:1801.07594 |
in this article, we study boundary null controllability properties of the linearized compressible navier - stokes equations in the interval $ ( 0, 2 \ pi ) $ for both barotropic and non - barotropic fluids using only one boundary control. we consider all the possible cases of the act of control for both systems ( density, velocity and temperature ). these controls are acting on the boundary and are given as the difference of the values at $ x = 0 $ and $ x = 2 \ pi $. in this setup, using a boundary control acting in density, we first prove null controllability of both the barotropic and non - barotropic systems at large time in the spaces $ ( \ dot { l } ^ 2 ( 0, 2 \ pi ) ) ^ 2 $ and $ ( \ dot { l } ^ 2 ( 0, 2 \ pi ) ) ^ 3 $ respectively ( where the dot represents functions with mean value zero ). when the control is acting in the velocity component, we prove null controllability at large time in the spaces $ \ dot { h } ^ 1 _ { \ text { per } } ( 0, 2 \ pi ) \ times \ dot { l } ^ 2 ( 0, 2 \ pi ) $ and $ \ dot { h } ^ 1 _ { \ text { per } } ( 0, 2 \ pi ) \ times ( \ dot { l } ^ 2 ( 0, 2 \ pi ) ) ^ 2 $ respectively. further, in both cases, we prove that these null controllability results are sharp with respect to the regularity of the initial states in velocity / temperature case, and time in the density case. finally, for both barotropic and non - barotropic fluids, we prove that, under some assumptions, the system cannot be approximately controllable at any time, whether there is a control acting in density, velocity or temperature. | arxiv:2301.04080 |
in many practical applications of clustering, the objects to be clustered evolve over time, and a clustering result is desired at each time step. in such applications, evolutionary clustering typically outperforms traditional static clustering by producing clustering results that reflect long - term trends while being robust to short - term variations. several evolutionary clustering algorithms have recently been proposed, often by adding a temporal smoothness penalty to the cost function of a static clustering method. in this paper, we introduce a different approach to evolutionary clustering by accurately tracking the time - varying proximities between objects followed by static clustering. we present an evolutionary clustering framework that adaptively estimates the optimal smoothing parameter using shrinkage estimation, a statistical approach that improves a naive estimate using additional information. the proposed framework can be used to extend a variety of static clustering algorithms, including hierarchical, k - means, and spectral clustering, into evolutionary clustering algorithms. experiments on synthetic and real data sets indicate that the proposed framework outperforms static clustering and existing evolutionary clustering algorithms in many scenarios. | arxiv:1104.1990 |
probabilistic quantum cloning and identifying machines can be constructed via unitary - reduction processes [ duan and guo, phys. rev. lett. 80, 4999 ( 1998 ) ]. given the cloning ( identifying ) probabilities, we derive an explicit representation of the unitary evolution and corresponding hamiltonian to realize probabilistic cloning ( identification ). the logic networks are obtained by decomposing the unitary representation into universal quantum logic operations. the robustness of the networks is also discussed. our method is suitable for a $ k $ - partite system, such as quantum computer, and may be generalized to general state - dependent cloning and identification. | arxiv:quant-ph/9907097 |
the emphasis in the developmet of theories with more than three spatial dimensions has recently shifted towards ` ` brane world ' ' picture, which assumes that ordinary matter ( with possible exceptions of gravitons and other, hypothetic, particles which interact very weakly with matter ) is trapped to a three - dimensional submanifold - - - brane - - - embedded in fundamental multi - dimensional space. in the brane world scenario, extra dimensions may be large, and even infinite ; they may have effects, directly observable in current or fothcoming experiments. on the basis of simple field - theoretic models, various ideas in this direction are exposed at a non - expert level. | arxiv:hep-ph/0104152 |
we prove that a composition operator is bounded on the hardy space $ h ^ 2 $ of the right half - plane if and only if the inducing map fixes the point at infinity non - tangentially, and has a finite angular derivative $ \ lambda $ there. in this case the norm, essential norm, and spectral radius of the operator are all equal to $ \ sqrt { \ lambda } $. | arxiv:0907.0350 |
we consider systems under uncertainty whose dynamics are partially unknown. our aim is to study satisfaction of temporal logic properties by trajectories of such systems. we express these properties as signal temporal logic formulas and check if the probability of satisfying the property is at least a given threshold. since the dynamics are parameterized and partially unknown, we collect data from the system and employ bayesian inference techniques to associate a confidence value to the satisfaction of the property. the main novelty of our approach is to combine both data - driven and model - based techniques in order to have a two - layer probabilistic reasoning over the behavior of the system : one layer is related to the stochastic noise inside the system and the next layer is related to the noisy data collected from the system. we provide approximate algorithms for computing the confidence for linear dynamical systems. | arxiv:2005.05040 |
we have measured the water and hydrogen outgassing rates of seven vacuum chambers of identical geometry but constructed of different materials and heat treatments. chambers of five different materials were tested : 304l, 316l, and 316ln stainless steels ; titanium ( astm grade 2 ) ; and 6061 aluminum. in addition, chambers constructed of 316l and 316ln stainless steel were subjected to a vacuum - fire process, where they were heated to approximately 950 { \ deg } c for 24 hours while under vacuum ; these two chambers are designated as 316l - xhv and 316ln - xhv. all chambers were of identical geometry and made by the same manufacturer, thus a relative comparison of the outgassing rates among these chambers can be made. water outgassing rates were measured as a function of time using the throughput technique. the water outgassing results for the 316l, 316ln, 316l - xhv, 316ln - xhv were all similar, but lower than those of 304l by a factor of 3 to 5 lower at 10 ^ 4 s. the water outgassing results for ti and al chambers were close to that of 304l, ti being slightly lower. hydrogen outgassing rates were measured using the rate - of - rise method and performed after a low - temperature bake of 125 { \ deg } c to 150 { \ deg } c for a minimum of 72 hours. the ti, al, 316l - xhv, and 316ln - xhv chambers all have specific outgassing rates below 1 x 10 ^ - 11 pa l s ^ - 1 cm ^ - 2 and are at least a factor of 100 or better than the 304l chamber. the 304l, 316l, and 316ln chambers without vacuum - fire heat treatment have larger hydrogen outgassing rates than the other chambers, with specific outgassing rates ranging between 4. 0 x 10 ^ - 11 pa l s ^ - 1 cm ^ - 2 and 8. 0 x 10 ^ - 11 pa l s ^ - 1 cm ^ - 2. we conclude that ti, al, 316l - xhv, and 316ln - xhv have hydrogen outgassing rates that make them excellent choices for ultra - high vacuum ( uhv ) and extreme - high vacuum ( xhv ) applications, the choice depending on cost and other material properties. | arxiv:2009.10560 |
we introduce a stochastic model of binary opinion dynamics in which the opinions are determined by the size of the neighbouring domains. the exit probability here shows a step function behaviour indicating the existence of a separatrix distinguishing two different regions of basin of attraction. this behaviour, in one dimension, is in contrast to other well known opinion dynamics models where no such behaviour has been observed so far. the coarsening study of the model also yields novel exponent values. a lower value of persistence exponent is obtained in the present model, which involves stochastic dynamics, when compared to that in a similar type of model with deterministic dynamics. this apparently counter - intuitive result is justified using further analysis. based on these results it is concluded that the proposed model belongs to a unique dynamical class. | arxiv:1306.6813 |
generative adversarial network ( gan ) is a useful type of neural networks in various types of applications including generative models and feature extraction. various types of gans are being researched with different insights, resulting in a diverse family of gans with a better performance in each generation. this review focuses on various gans categorized by their common traits. | arxiv:2009.09579 |
discriminant ideals of noncommutative algebras $ a $, which are module finite over a central sublagebra $ c $, are key invariants that carry important information about $ a $, such as the sum of the squares of the dimensions of its irreducible modules with a given central character. there has been substantial research on the computation of discriminants, but very little is known about the computation of discriminant ideals. in this paper we carry out a detailed investigation of the lowest discriminant ideals of cayley - hamilton hopf algebras in the sense of de concini, reshetikhin, rosso and procesi, whose identity fiber algebras are basic. the lowest discriminant ideals are the most complicated ones, because they capture the most degenerate behaviour of the fibers in the exact opposite spectrum of the picture from the azumaya locus. we provide a description of the zero sets of the lowest discriminant ideals of cayley - hamilton hopf algebras in terms of maximally stable modules of hopf algebras, irreducible modules that are stable under tensoring with the maximal possible number of irreducible modules with trivial central character. in important situations, this is shown to be governed by the actions of the winding automorphism groups. the results are illustrated with applications to the group algebras of central extensions of abelian groups, big quantum borel subalgebras at roots of unity and quantum coordinate rings at roots of unity. | arxiv:2307.15477 |
recently, digitized - counterdiabatic ( cd ) corrections to the quantum approximate optimization algorithm ( qaoa ) have been proposed, yielding faster convergence within the desired accuracy than standard qaoa. in this manuscript, we apply this approach to a fully - connected spin model with random couplings. we show that the performances of the algorithm are related to the spectral properties of the instances analyzed. in particular, the larger the gap between the ground state and the first excited states, the better the convergence to the exact solution. | arxiv:2409.03503 |
an edge - coloring of a complete graph with a set of colors $ c $ is called completely balanced if any vertex is incident to the same number of edges of each color from $ c $. erd \ h { o } s and tuza asked in $ 1993 $ whether for any graph $ f $ on $ \ ell $ edges and any completely balanced coloring of any sufficiently large complete graph using $ \ ell $ colors contains a rainbow copy of $ f $. this question was restated by erd \ h { o } s in his list of ` ` some of my favourite problems on cycles and colourings ' '. we answer this question in the negative for most cliques $ f = k _ q $ by giving explicit constructions of respective completely balanced colorings. further, we answer a related question concerning completely balanced colorings of complete graphs with more colors than the number of edges in the graph $ f $. | arxiv:2209.13867 |
marstrand ' s projection theorem from $ 1954 $ states that if $ k \ subset \ mathbb { r } ^ { 3 } $ is an analytic set, then, for $ \ mathcal { h } ^ { 2 } $ almost every $ e \ in s ^ { 2 } $, the orthogonal projection $ \ pi _ { e } ( k ) $ of $ k $ to the line spanned by $ e $ has hausdorff dimension $ \ min \ { \ dim _ { \ mathrm { h } } k, 1 \ } $. this paper contains the following sharper version of marstrand ' s theorem. let $ v \ subset \ mathbb { r } ^ { 3 } $ be any $ 2 $ - plane, which is not a subspace. then, for $ \ mathcal { h } ^ { 1 } $ almost every $ e \ in s ^ { 2 } \ cap v $, the projection $ \ pi _ { e } ( k ) $ has hausdorff dimension $ \ min \ { \ dim _ { \ mathrm { h } } k, 1 \ } $. for $ 0 \ leq t < \ dim _ { \ mathrm { h } } k $, we also prove an upper bound for the hausdorff dimension of those vectors $ e \ in s ^ { 2 } \ cap v $ with $ \ dim _ { \ mathrm { h } } \ rho _ { e } ( k ) \ leq t < \ dim _ { \ mathrm { h } } k $. | arxiv:1708.04859 |
holm 15a, the brightest cluster galaxy ( bcg ) of the galaxy cluster abell 85, has an ultra - diffuse central region, 2 mag fainter than the faintest depleted core of any early - type galaxy ( etg ) that has been dynamically modelled in detail. we use orbit - based, axisymmetric schwarzschild models to analyse the stellar kinematics of holm 15a from new high - resolution, wide - field spectral observations obtained with muse at the vlt. we find a supermassive black hole ( smbh ) with a mass of ( 4. 0 + - 0. 80 ) x 10 ^ 10 solar masses at the center of holm 15a. this is the most massive black hole with a direct dynamical detection in the local universe. we find that the distribution of stellar orbits is increasingly biased towards tangential motions inside the core. however, the tangential bias is less than in other cored elliptical galaxies. we compare holm 15a with n - body simulations of mergers between galaxies with black holes and find that the observed amount of tangential anisotropy and the shape of the light profile are consistent with a formation scenario where holm 15a is the remnant of a merger between two etgs with pre - existing depleted cores. we find that black hole masses in cored galaxies, including holm 15a, scale inversely with the central stellar surface brightness and mass density, respectively. these correlation are independent of a specific parameterization of the light profile. | arxiv:1907.10608 |
without recourse to the sophisticated machinery of twisted group algebras, projective character tables and explicit values of 2 - cocycles, we here present a simple algorithm to study the gauge theory data of d - brane probes on a generic orbifold g with discrete torsion turned on. we show in particular that the gauge theory can be obtained with the knowledge of no more than the ordinary character tables of g and its covering group g *. subsequently we present the quiver diagrams of certain illustrative examples of su ( 3 ) - orbifolds which have non - trivial schur multipliers. the paper serves as a companion to our earlier work ( arxiv : hep - th / 0010023 ) and aims to initiate a systematic and computationally convenient study of discrete torsion. | arxiv:hep-th/0011192 |
computing education widely applies general learning theories and pedagogical practices. however, computing also includes specific disciplinary knowledge and skills, e. g., programming and software development methods, for which there has been a long history of development and application of specific pedagogical practices. in recent years, there has also been substantial interest in developing computing - specific theoretical models, which seek to describe and explain the complex interactions within teaching and learning computing in various contexts. in this paper, we explore connections between computing - specific pedagogies and theoretical models as reported in the literature. our goal is to enrich computing education research and practice by illustrating how explicit use of field - specific theories and pedagogies can further the whole field. we have collected a list of computing - specific pedagogical practices and theoretical models from a literature search, identifying source papers where they have been first introduced or well described. we then searched for papers in the acm digital library that cite source papers from each list, and analyzed the type of interaction between the model and pedagogy in each paper. we developed a categorization of how theoretical models and pedagogies have supported or discounted each other, have been used together in empirical studies or used to build new artefacts. our results showed that pair programming and parsons problems have had the most interactions with theoretical models in the explored papers, and we present findings of the analysis of these interactions. | arxiv:2409.12245 |
we show that the sets of periods of multidimensional shifts of finite type ( sfts ) are exactly the sets of integers of the complexity class $ \ ne $. we also show that the functions counting their number are the functions of # e. we also give characterizations of some other notions of periodicity. we finish the paper by giving some characterizations for sofic and effective subshifts. | arxiv:1303.2462 |
we introduce a model for non - standard neutral current interaction ( nsi ) between neutrinos and the matter fields, with an arbitrary coupling to the up and down quarks. the model is based on a new $ u ( 1 ) $ gauge symmetry with a light gauge boson that mixes with the photon. we show that the couplings to the $ u $ and $ d $ quarks can have a ratio such that the contribution from nsi to the coherent elastic neutrino - nucleus scattering ( ce $ \ nu $ ns ) amplitude vanishes, relaxing the bound on the nsi from the ce $ \ nu $ ns experiments. additionally, the deviation of the measured value of the anomalous magnetic dipole moment of the muon from the standard - model prediction can be fitted. the most limiting constraints on our model come from the search for the decay of the new gauge boson to $ e ^ - e ^ + $ and invisible particles, carried out by na48 / 2 and na64, respectively. we show that these bounds can be relaxed by opening up the decay of the new gauge boson to new light scalars that eventually decay into the $ e ^ - e ^ + $ pairs. we show that there are ranges that can lead to both a solution to the $ ( g - 2 ) _ \ mu $ anomaly and values of $ \ epsilon _ { \ mu \ mu } = \ epsilon _ { \ tau \ tau } $ large enough to be probed by future solar neutrino experiments. | arxiv:2211.15686 |
graph neural networks ( gnns ) have gained traction in high - energy physics ( hep ) for their potential to improve accuracy and scalability. however, their resource - intensive nature and complex operations have motivated the development of symmetry - equivariant architectures. in this work, we introduce euclidnet, a novel symmetry - equivariant gnn for charged particle tracking. euclidnet leverages the graph representation of collision events and enforces rotational symmetry with respect to the detector ' s beamline axis, leading to a more efficient model. we benchmark euclidnet against the state - of - the - art interaction network on the trackml dataset, which simulates high - pileup conditions expected at the high - luminosity large hadron collider ( hl - lhc ). our results show that euclidnet achieves near - state - of - the - art performance at small model scales ( < 1000 parameters ), outperforming the non - equivariant benchmarks. this study paves the way for future investigations into more resource - efficient gnn models for particle tracking in hep experiments. | arxiv:2304.05293 |
in a series of papers, avraham, filtser, kaplan, katz, and sharir ( socg ' 14 ), kaplan, katz, saban, and sharir ( esa ' 23 ), and katz, saban, and sharir ( esa ' 24 ) studied a class of geometric optimization problems - - including reverse shortest path in unweighted and weighted unit - disk graphs, discrete fr \ ' { e } chet distance with one - sided shortcuts, and reverse shortest path in visibility graphs on 1. 5 - dimensional terrains - - for which standard parametric search does not work well due to a lack of efficient parallel algorithms for the corresponding decision problems. the best currently known algorithms for all the above problems run in $ o ^ * ( n ^ { 6 / 5 } ) = o ^ * ( n ^ { 1. 2 } ) $ time ( ignoring subpolynomial factors ), and they were obtained using a technique called \ emph { shrink - and - bifurcate }. we improve the running time to $ \ tilde { o } ( n ^ { 8 / 7 } ) \ approx o ( n ^ { 1. 143 } ) $ for these problems. furthermore, specifically for reverse shortest path in unweighted unit - disk graphs, we improve the running time further to $ \ tilde { o } ( n ^ { 9 / 8 } ) = \ tilde { o } ( n ^ { 1. 125 } ) $. | arxiv:2504.06434 |
. batching is the process of weighing the oxides according to recipes, and preparing them for mixing and drying. mixing occurs after batching and is performed with various machines, such as dry mixing ribbon mixers ( a type of cement mixer ), resonantacoustic mixers, mueller mixers, and pug mills. wet mixing generally involves the same equipment. forming is making the mixed material into shapes, ranging from toilet bowls to spark plug insulators. forming can involve : ( 1 ) extrusion, such as extruding " slugs " to make bricks, ( 2 ) pressing to make shaped parts, ( 3 ) slip casting, as in making toilet bowls, wash basins and ornamentals like ceramic statues. forming produces a " green " part, ready for drying. green parts are soft, pliable, and over time will lose shape. handling the green product will change its shape. for example, a green brick can be " squeezed ", and after squeezing it will stay that way. drying is removing the water or binder from the formed material. spray drying is widely used to prepare powder for pressing operations. other dryers are tunnel dryers and periodic dryers. controlled heat is applied in this two - stage process. first, heat removes water. this step needs careful control, as rapid heating causes cracks and surface defects. the dried part is smaller than the green part, and is brittle, necessitating careful handling, since a small impact will cause crumbling and breaking. sintering is where the dried parts pass through a controlled heating process, and the oxides are chemically changed to cause bonding and densification. the fired part will be smaller than the dried part. = = forming methods = = ceramic forming techniques include throwing, slipcasting, tape casting, freeze - casting, injection molding, dry pressing, isostatic pressing, hot isostatic pressing ( hip ), 3d printing and others. methods for forming ceramic powders into complex shapes are desirable in many areas of technology. such methods are required for producing advanced, high - temperature structural parts such as heat engine components and turbines. materials other than ceramics which are used in these processes may include : wood, metal, water, plaster and epoxy — most of which will be eliminated upon firing. a ceramic - filled epoxy, such as martyte, is sometimes used to protect structural steel under conditions of rocket exhaust impingement. these forming techniques are well known for providing tools and other components with dimensional stability, surface quality | https://en.wikipedia.org/wiki/Ceramic_engineering |
attached to a weight space in an integrable highest weight representation of a simply - laced kac - moody algebra $ \ mathfrak { g } $, there are two natural commutative algebras : the cohomology ring of a quiver variety and the center of a cyclotomic klr algebra. in this note, we describe a natural geometric map between these algebras in terms of quantum coherent sheaves on quiver varieties. the cohomology ring of an algebraic symplectic variety can be interpreted as the hochschild cohomology of a quantization of this variety in the sense of bezrukavnikov and kaledin. on the other hand, cyclotomic klr algebras appear as ext - algebras of certain particular sheaves, and thus its center receives a canonical map from the hochschild cohomology of the category. we show that this map is an isomorphism in finite type, and injective in general. we further note that the kirwan surjectivity theorem for quivers of finite type is an easy corollary of these results. the most important property of this map is its compatibility with actions of the current algebra on both the cohomology of quiver varieties and on the hochschild cohomology of any category with a categorical action of $ \ mathfrak { g } $. the structure of these current algebra actions allow us to show the desired results. | arxiv:1504.04401 |
neutron matter is an intriguing nuclear system with multiple connections to other areas of physics. considerable progress has been made over the last two decades in exploring the properties of pure neutron fluids. here we begin by reviewing work done to explore the behavior of very low density neutron matter, which forms a strongly paired superfluid and is thus similar to cold fermi atoms, though at energy scales differing by many orders of magnitude. we then increase the density, discussing work that ties the study of neutron matter with the determination of the properties of neutron - rich nuclei and neutron - star crusts. after this, we review the impact neutron matter at even higher densities has on the mass - radius relation of neutron stars, thereby making contact with astrophysical observations. | arxiv:1501.05675 |
visual localization is a fundamental task for various applications including autonomous driving and robotics. prior methods focus on extracting large amounts of often redundant locally reliable features, resulting in limited efficiency and accuracy, especially in large - scale environments under challenging conditions. instead, we propose to extract globally reliable features by implicitly embedding high - level semantics into both the detection and description processes. specifically, our semantic - aware detector is able to detect keypoints from reliable regions ( e. g. building, traffic lane ) and suppress unreliable areas ( e. g. sky, car ) implicitly instead of relying on explicit semantic labels. this boosts the accuracy of keypoint matching by reducing the number of features sensitive to appearance changes and avoiding the need of additional segmentation networks at test time. moreover, our descriptors are augmented with semantics and have stronger discriminative ability, providing more inliers at test time. particularly, experiments on long - term large - scale visual localization aachen day - night and robotcar - seasons datasets demonstrate that our model outperforms previous local features and gives competitive accuracy to advanced matchers but is about 2 and 3 times faster when using 2k and 4k keypoints, respectively. | arxiv:2304.14845 |
let $ \ mathcal { a } $ consists of analytic functions $ f : \ mathbb { d } \ to \ mathbb { c } $ satisfying $ f ( 0 ) = f ' ( 0 ) - 1 = 0 $. let $ \ mathcal { s } ^ * _ { ne } $ be the recently introduced ma - minda type functions family associated with the $ 2 $ - cusped kidney - shaped { \ it nephroid } curve $ \ left ( ( u - 1 ) ^ 2 + v ^ 2 - \ frac { 4 } { 9 } \ right ) ^ 3 - \ frac { 4 v ^ 2 } { 3 } = 0 $ given by \ begin { align * } \ mathcal { s } ^ * _ { ne } : = \ left \ { f \ in \ mathcal { a } : \ frac { zf ' ( z ) } { f ( z ) } \ prec \ varphi _ { \ scriptscriptstyle { ne } } ( z ) = 1 + z - z ^ 3 / 3 \ right \ }. \ end { align * } in this paper, we adopt a novel technique that uses the geometric properties of { \ it hypergeometric functions } to determine sharp estimates on $ \ beta $ so that each of the differential subordinations \ begin { align * } p ( z ) + \ beta zp ' ( z ) \ prec \ begin { cases } \ sqrt { 1 + z } ; 1 + z ; e ^ z ; \ end { cases } \ end { align * } imply $ p ( z ) \ prec \ varphi _ { \ scriptscriptstyle { ne } } ( z ) $, where $ p ( z ) $ is analytic satisfying $ p ( 0 ) = 1 $. as applications, we establish conditions that are sufficient to deduce that $ f \ in \ mathcal { a } $ is a member of $ \ mathcal { s } ^ * _ { ne } $. | arxiv:2104.04890 |
recent advancements in observational techniques have led to new tests of the general relativistic predictions for black - hole spacetimes in the strong - field regime. one of the key ingredients for several tests is a metric that allows for deviations from the kerr solution but remains free of pathologies outside its event horizon. existing metrics that have been used in the literature often do not satisfy the null convergence condition that is necessary to apply the strong rigidity theorem and would have allowed us to calculate the location of the event horizon by identifying it with an appropriate killing horizon. this has led earlier calculations of event horizons of parametrically deformed metrics to either follow numerical techniques or simply search heuristically for coordinate singularities. we show that several of these metrics, almost by construction, are circular. we can, therefore, use the weak rigidity and carter ' s rotosurface theorem and calculate algebraically the locations of their event horizons, without relying on expansions or numerical techniques. we apply this approach to a number of parametrically deformed metrics, calculate the locations of their event horizons, and place constraints on the deviation parameters such that the metrics remain regular outside their horizons. we show that calculating the angular velocity of the horizon and the effective gravity there offers new insights into the observational signatures of deformed metrics, such as the sizes and shapes of the predicted black - hole shadows. | arxiv:2205.12994 |
the analogue of the poisson bracket for the de donder - weyl ( dw ) hamiltonian formulation of field theory is proposed. we start from the hamilton - poincar \ ' { e } - cartan ( hpc ) form of the multidimensional variational calculus and define the bracket on the differential forms over the space - time ( = horizontal forms ). this bracket is related to the schouten - nijenhuis bracket of the multivector fields which are associated with the horizontal forms by means of the " polysymplectic form ". the latter is given by the hpc form and generalizes the symplectic form to field theory. we point out that the algebra of forms with respect to our poisson bracket and the exterior product has the structure of the gerstenhaber graded algebra. it is shown that the poisson bracket with the dw hamiltonian function generates the exterior differential thus leading to the bracket representation of the dw hamiltonian field equations. few illustrative examples are also presented. | arxiv:hep-th/9312162 |
the stability of the $ \ beta $ - equilibrated dense nuclear matter is analyzed with respect to the thermodynamic stability conditions. based on the density dependent m3y effective nucleon - nucleon interaction, the effects of the nuclear incompressibility on the proton fraction in neutron stars and the location of the inner edge of their crusts and core - crust transition density and pressure are investigated. the high - density behavior of symmetric and asymmetric nuclear matter satisfies the constraints from the observed flow data of heavy - ion collisions. the neutron star properties studied using $ \ beta $ - equilibrated neutron star matter obtained from this effective interaction for a pure hadronic model agree with the recent observations of the massive compact stars. the density, pressure and proton fraction at the inner edge separating the liquid core from the solid crust of neutron stars are determined to be $ \ rho _ t = $ 0. 0938 fm $ ^ { - 3 } $, p $ _ t = $ 0. 5006 mev fm $ ^ { - 3 } $ and x $ _ { p ( t ) } = $ 0. 0308, respectively. | arxiv:1406.5302 |
in this paper, we explore the possibilities of realizing weak value amplification ( wva ) using purely atomic degrees of freedom. our scheme identifies the internal electronic states and external motional states of a single trapped $ ^ { 40 } $ ca $ ^ + $ ion as the system degree and pointer degree respectively, and their controllable weak coupling is provided by a bichromatic light field. in our experimental demonstration, by performing appropriate postselection on the internal states, a position displacement of 4 angstroms ( in phase space ) of the trapped ion is amplified to 10 nanometers. the sensitivity of the amplification effect to the relative phase of the quantum state is also demonstrated. the high operational flexibility of this procedure allows fully exploration of the peculiarities of wva. | arxiv:1811.06170 |
continuous monitoring of non - invasive skin sympathetic nerve activity ( skna ) holds promise for understanding the sympathetic nervous system ( sns ) dynamics in various physiological and pathological conditions. however, muscle noise artifacts present a challenge in accurate skna analysis, particularly in real - life scenarios. this study proposes a deep convolutional neural network ( cnn ) approach to detect and remove muscle noise from skna recordings obtained via ecg electrodes. twelve healthy participants underwent controlled experimental protocols involving cognitive stress induction and voluntary muscle movements, while collecting skna data. power spectral analysis revealed significant muscle noise interference within the skna frequency band ( 500 - 1000 hz ). a 2d cnn model was trained on the spectrograms of the data segments to classify them into baseline, stress - induced skna, and muscle noise - contaminated periods, achieving an average accuracy of 89. 85 % across all subjects. our findings underscore the importance of addressing muscle noise for accurate skna monitoring, advancing towards wearable skna sensors for real - world applications. | arxiv:2410.21319 |
we compute the first curvature corrections to the spectrum of light - cone gauge type iia string theory that arise in the expansion of $ ads _ 4 \ times \ mathbb { cp } ^ 3 $ about a plane - wave limit. the resulting spectrum is shown to match precisely, both in magnitude and degeneration that of the corresponding solutions of the all - loop gromov - - vieira bethe ansatz. the one - loop dispersion relation correction is calculated for all the single oscillator states of the theory, with the level matching condition lifted. it is shown to have all logarithmic divergences cancelled and to leave only a finite exponentially suppressed contribution, as shown earlier for light bosons. we argue that there is no ambiguity in the choice of the regularization for the self - energy sum, since the regularization applied is the only one preserving unitarity. interaction matrices in the full degenerate two - oscillator sector are calculated and the spectrum of all two light magnon oscillators is completely determined. the same finite - size corrections, at the order 1 / j, where $ j $ is the length of the chain, in the two - magnon sector are calculated from the all loop bethe ansatz. the corrections obtained by the two completely different methods coincide up to the fourth order in $ \ lambda ' = \ lambda / j ^ 2 $. we conjecture that the equivalence extends to all orders in $ \ lambda $ and to higher orders in 1 / j. | arxiv:1111.6628 |
body weight, as an essential physiological trait, is of considerable significance in many applications like body management, rehabilitation, and drug dosing for patient - specific treatments. previous works on the body weight estimation task are mainly vision - based, using 2d / 3d, depth, or infrared images, facing problems in illumination, occlusions, and especially privacy issues. the pressure mapping mattress is a non - invasive and privacy - preserving tool to obtain the pressure distribution image over the bed surface, which strongly correlates with the body weight of the lying person. to extract the body weight from this image, we propose a deep learning - based model, including a dual - branch network to extract the deep features and pose features respectively. a contrastive learning module is also combined with the deep - feature branch to help mine the mutual factors across different postures of every single subject. the two groups of features are then concatenated for the body weight regression task. to test the model ' s performance over different hardware and posture settings, we create a pressure image dataset of 10 subjects and 23 postures, using a self - made pressure - sensing bedsheet. this dataset, which is made public together with this paper, together with a public dataset, are used for the validation. the results show that our model outperforms the state - of - the - art algorithms over both 2 datasets. our research constitutes an important step toward fully automatic weight estimation in both clinical and at - home practice. our dataset is available for research purposes at : https : / / github. com / ustcwzy / massestimation. | arxiv:2303.10136 |
we apply a type of background independent " polymer " quantization to a free scalar field in a flat spacetime. using semi - classical states, we find an effective wave equation that is both nonlinear and lorentz invariance violating. we solve this equation perturbatively for several cases of physical interest, and show that polymer corrections to solutions of the klein - gordon equation depend on the amplitude of the field. this leads to an effective dispersion relation that depends on the amplitude, frequency and shape of the wave - packet, and is hence distinct from other modified dispersion relations found in the literature. we also demonstrate that polymer effects tend to accumulate with time for plane - symmetric waveforms. we conclude by discussing the possibility of measuring deviations from the klein - gordon equation in particle accelerators or astrophysical observations. | arxiv:0906.4046 |
the nuclear medium effects are studied in the $ \ nu _ \ tau / \ bar \ nu _ \ tau $ interactions from nuclei in the deep inelastic scattering ( dis ) region and applied to the $ ^ { 40 } ar $ nucleus to obtain the scattering cross sections in the energy region of the proposed dune experiment. the free nucleon structure functions ( $ f _ { in } ( x, q ^ 2 ) ; ~ ( i = 1 - 5 ) $ ) have been calculated at the next - to - leading order ( nlo ) using martin - motylinski - harland lang - thorne 2014 as well as the coordinated theoretical - experimental project on qcd parameterizations for parton distribution functions ( pdfs ) and including the effect of perturbative and nonperturbative qcd corrections \ cite { ansari : 2020xne }. these free nucleon structure functions are then convoluted with the nucleon spectral function in the nucleus to obtain the nuclear structure functions ( $ f _ { ia } ( x, q ^ 2 ) ; ~ ( i = 1 - 5 ) $ ). the nucleon spectral function takes into account the fermi motion and the binding energy of the nucleons as well as the nucleon correlations within the nucleus. these nuclear structure functions are then used to calculate the deep inelastic scattering cross sections. moreover, the contribution of $ \ pi $ and $ \ rho $ mesons as well as the corrections due to the shadowing and antishadowing effects in the relevant kinematic region of the bjorken variable $ x $ are also included. the numerical results for the cross sections have been presented and compared with the results obtained in the phenomenological approach using nuclear structure functions from ncteqnu. | arxiv:2111.07609 |
we study overdetermined problems for fully nonlinear elliptic equations in subdomains $ \ o $ of the euclidean sphere $ \ mathbb { s } ^ { n } $ and the hyperbolic space $ \ mathbb { h } ^ { n } $. we prove, the existence of a classical solution to the underlined equation forces $ \ o $ to be a geodesic ball in the ambient space. our result extends to fully nonlinear equations, a similar result in the case of semilinear equations with the laplace operator due to kumaresan and prajapat. | arxiv:2010.13945 |
purpose : swift ( sweep imaging with fourier transformation ) is a non - cartesian mri method with unique features and capabilities. in swift, radiofrequency ( rf ) excitation and reception are performed nearly simultaneously, by rapidly switching between transmit and receive during a frequency - swept rf pulse. because both the transmitted pulse and data acquisition are simultaneously amplitude - modulated in swift ( in contrast to continuous rf excitation and uninterrupted data acquisition in more familiar mri sequences ), crosstalk between different frequency bands occurs in the data. this crosstalk leads to a " bulls - eye " artifact in swift images. we present a method to cancel this inter - band crosstalk by cycling the pulse and receive gap positions relative to the un - gapped pulse shape. we call this strategy " gap cycling. " methods : we carry out theoretical analysis, simulation and experiments to characterize the signal chain, resulting artifacts, and their elimination for swift. results : theoretical analysis reveals the mechanism for gap - cycling ' s effectiveness in canceling inter - band crosstalk. we show phantom and in - vivo results demonstrating bulls - eye artifact free images. conclusion : gap cycling is an effective method to remove bulls - eye artifact resulting from inter - band crosstalk in swift data. | arxiv:1307.2926 |
inductive logic programming ( ilp ) is a form of machine learning. the goal of ilp is to induce a hypothesis ( a set of logical rules ) that generalises training examples. as ilp turns 30, we provide a new introduction to the field. we introduce the necessary logical notation and the main learning settings ; describe the building blocks of an ilp system ; compare several systems on several dimensions ; describe four systems ( aleph, tilde, aspal, and metagol ) ; highlight key application areas ; and, finally, summarise current limitations and directions for future research. | arxiv:2008.07912 |
in this article we derive the average and the variance of the cross - correlation of a noise wavefield. the noise cross - correlation function ( ncf ) is widely used to passively estimate the green ' s function between two probes and is proportional to the cross density of states ( cdos ) in photonic and plasmonic systems. we first explain from the ladder approximation how the diffusion halo plays the role of secondary sources to reconstruct the mean green ' s function. we then show that fluctuations of ncf are governed by several non - gaussian correlations. an infinite - range ncf correlation dominates cdos fluctuations and proves that ncf is not a self averaging quantity with respect to the plurality of noise sources. the link between these correlations and the intensity ones is highlighted. these results are supported by numerical simulations and are of importance for passive imaging applications and material science. | arxiv:1310.5283 |
starting from the general definition of a one - loop tensor n - point function, we use its feynman parametrization to calculate the uv - divergent part of an arbitrary tensor coefficient in the framework of dimensional regularization. in contrast to existing recursion schemes, we are able to present a general analytic result in closed form that enables direct determination of the uv - divergent part of any one - loop tensor n - point coefficient independent from uv - divergent parts of other one - loop tensor n - point coefficients. simplified formulas and explicit expressions are presented for a -, b -, c -, d -, e -, and f - functions. | arxiv:hep-ph/0609282 |
using accurate dissipative dft - negf atomistic - simulation techniques within the wannier - function formalism, we give a fresh look at the possibility of sub - 10 nm scaling for high - performance cmos applications. we show that a combination of good electrostatic control together with a high mobility is paramount to meet the stringent roadmap targets. such requirements typically play against each other at sub - 10 nm gate length for mos transistors made of conventional semiconductor materials like si, ge or iii - v and dimensional scaling is expected to end around 12 nm gate - length. we demonstrate that using alternative 2d channel materials, such as the less explored hfs2 or zrs2, high - drive current down to about 6 nm is, however, achievable. we also propose a novel transistor concept, the dynamically - doped field - effect transistor, that scales better than its mosfet counterpart. used in combination with a high - mobility material such as hfs2, it allows for keeping the stringent high - performance cmos on current and competitive energy - delay performance, when scaling down to 1 nm gate length using a single - gate architecture and an ultra - compact design. the dynamically - doped field - effect transistor further addresses the grand - challenge of doping in ultra - scaled devices and 2d materials in particular. | arxiv:2010.06867 |
we give a criterium of holomorphy for some type formal power series. this gives a stronger form of a rothstein ' s type extension theorem for a particular ring of holomorphic functions. | arxiv:math/0009031 |
molecular dynamics simulations of frictional sliding in an atomic force microscope ( afm ) show a clear dependence of superlubricity between incommensurate surfaces on tip compliance and applied normal force. while the kinetic friction vanishes for rigid tips and low normal force, superlubric behavior breaks down for softer tips and high normal force. the simulations provide evidence that the frenkel - kontorova - tomlinson ( fkt ) scaling applies equally to a more realistic 3 - d incommensurate afm model except in the limit of very low stiffness and high normal load limit. unlike the fkt model in which the breakdown of superlubricity coincides to the emergence of the meta - stable states, in the 3 - d model some meta - stable states appear to reduce frictional force leading to non - monotonic dependence of force on normal load and tip compliance. meta - stable states vary with the slider positions, and the relative stabilities of these meta - stable states result in varying transition mechanisms depending on sliding velocity. | arxiv:0908.4304 |
we theoretically investigate the spin - charge transport in two - terminal device of graphene nanoribbons in the presence of an uniform uniaxial strain, spin - orbit coupling, exchange field and smooth staggered potential. we show that the direction of applied strain can efficiently tune strain - strength induced oscillation of band - gap of armchair graphene nanoribbon ( agnr ). it is also found that electronic conductance in both agnr and zigzag graphene nanoribbons ( zgnrs ) oscillates with rashba spin - orbit coupling akin to the datta - das field effect transistor. two distinct strain response regimes of electronic conductance as function of spin - orbit couplings ( soc ) magnitude are found. in the regime of small strain, conductance of zgnr presents stronger strain dependence along the longitudinal direction of strain. whereas for high values of strain shows larger effect for the transversal direction. furthermore, the local density of states ( ldos ) shows that depending on the smoothness of the staggered potential, the edge state of agnr can either emerge or be suppressed. these emerging states can be determined experimentally by performing spatially scanning tunneling microscope or by scanning tunneling spectroscopy. our findings open up new paradigms of manipulation and control of strained graphene based nanostructure for application on novel topological quantum devices. | arxiv:1405.2497 |
modeling and forecasting of dynamically varying covariances have received much attention in the literature. the two most widely used conditional covariances and correlations models are bekk and dcc. in this paper, we advance a new method to introduce targeting in both models to estimate matrices associated with financial time series. our approach is based on specific groups of highly correlated assets in a financial market, and these relationships remain unaltered over time. based on the estimated parameters, we evaluate our targeting method on simulated series by referring to two well - known loss functions introduced in the literature and network analysis. we find all the maximal cliques in correlation graphs to evaluate the effectiveness of our method. results from an empirical case study are encouraging, mainly when the number of assets is not large. | arxiv:2202.02197 |
we consider the fiber cone of monomial ideals. it is shown that for monomial ideals $ i \ subset k [ x, y ] $ of height $ 2 $, generated by $ 3 $ elements, the fiber cone $ f ( i ) $ of $ i $ is a hypersurface ring, and that $ f ( i ) $ has positive depth for interesting classes of height $ 2 $ monomial ideals $ i \ subset k [ x, y ] $, which are generated by $ 4 $ elements. for these classes of ideals we also show that $ f ( i ) $ is cohen - - macaulay if and only if the defining ideal $ j $ of $ f ( i ) $ is generated by at most 3 elements. in all the cases a minimal set of generators of $ j $ is determined. | arxiv:1904.04988 |
we first prove some basic properties of okounkov bodies, and give a characterization of nakayama and positive volume subvarieties of a pseudoeffective divisor in terms of okounkov bodies. next, we show that each valuative and limiting okounkov bodies of a pseudoeffective divisor which admits the birational good zariski decomposition is a rational polytope with respect to some admissible flag. this is an extension of the result of anderson - k \ " { u } ronya - lozovanu about the rational polyhedrality of okounkov bodies of big divisors with finitely generated section rings. | arxiv:1608.00221 |
a charged tether or wire experiences coulomb drag when inserted into flowing plasma. in the solar wind the coulomb drag can be utilised as efficient propellantless interplanetary propulsion as the electric solar wind sail ( electric sail, e - sail ). in low earth orbit ( leo ) the same plasma physical effect can be utilised for efficient low - thrust deorbiting of space debris objects ( the plasma brake ). the e - sail is rotationally stabilised while the deorbiting coulomb drag devices according to numerical estimates, coulomb drag devices have very promising performance figures, both for interplanetary propulsion and for deorbiting in leo. much of the technology is common to both applications. e - sail technology development was carried out in esail fp7 project ( 2011 - 2013 ) which achieved trl 4 - 5 for key hardware components that can enable 1 n class interplanetary e - sail weighing less than 200 kg. the thrust of the e - sail scales as inverse solar distance and its power consumption ( nominally 700 w / n at 1 au ) scales as the inverse distance squared. as part of the esail project, a continuous 1 km sample of e - sail tether was produced by an automatic and scalable " tether factory ". the manufacturing method uses ultrasonic wire to wire bonding which was developed from ordinary wire to plate bonding for the e - sail purpose. also a " remote unit " device which takes care of deployment and spin rate control was prototyped and successfully environmentally tested. our remote unit prototype is operable in the solar distance range of 0. 9 - 4 au. the 1 - u cubesat estcube - 1 was launched in may 2013 and it will try to measure the coulomb drag acting on a 10 m long tether in leo when charged to 500 v positive or negative. a more advanced version of the experiment with 100 m tether is under preparation and will be launched in 2015 with the aalto - 1 3 - u cubesat to polar leo. | arxiv:1404.7430 |
we describe the integral cohomology of the generalized kummer fourfold giving an explicit basis, using hilbert scheme cohomology and tools developed by hassett and tschinkel. then we apply our results to a ihs variety with singularities, obtained by a partial resolution of the generalized kummer quotiented by a symplectic involution. we calculate the beauville - - bogomolov form of this new variety, presenting the first example of such a form that is odd. | arxiv:1607.03431 |
contact structures, as well as their holomorphic and quaternionic counterparts are the primary examples of strongly bracket generating ( or fat ) distributions. in this article we associate a numerical invariant to corank $ 2 $ fat distribution on manifolds, referred to as \ emph { degree } of the distribution. the real distribution underlying a holomorphic contact structure is of degree $ 2 $. using gromov ' s sheaf theoretic and analytic techniques of $ h $ - principle, we prove the existence of horizontal immersions of an arbitrary manifold into degree $ 2 $ fat distributions and the quaternionic contact structures. we also study immersions of a contact manifold inducing the given contact structure. | arxiv:2007.02058 |
we prove that finitely generated higher dimensional kleinian groups with small critical exponent are always convex - cocompact. along the way, we also prove some geometric properties for any complete pinched negatively curved manifold with critical exponent less than 1. | arxiv:2008.12365 |
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