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lung cancer has the highest rate of cancer - caused deaths, and early - stage diagnosis could increase the survival rate. lung nodules are common indicators of lung cancer, making their detection crucial. various lung nodule detection models exist, but many lack efficiency. hence, we propose a more efficient approach by leveraging 2d ct slices, reducing computational load and complexity in training and inference. we employ the tiny version of swin transformer to benefit from vision transformers ( vit ) while maintaining low computational cost. a feature pyramid network is added to enhance detection, particularly for small nodules. additionally, transfer learning is used to accelerate training. our experimental results show that the proposed model outperforms state - of - the - art methods, achieving higher map and mar for small nodules by 1. 3 % and 1. 6 %, respectively. overall, our model achieves the highest map of 94. 7 % and mar of 94. 9 %. | arxiv:2503.01592 |
quantum metrology comprises a set of techniques and protocols that utilize quantum features for parameter estimation which can in principle outperform any procedure based on classical physics. we formulate the quantum metrology in terms of an optimal control problem and apply pontryagin ' s maximum principle to determine the optimal protocol that maximizes the quantum fisher information for a given evolution time. as the quantum fisher information involves a derivative with respect to the parameter which one wants to estimate, we devise an augmented dynamical system that explicitly includes gradients of the quantum fisher information. the necessary conditions derived from pontryagin ' s maximum principle are used to quantify the quality of the numerical solution. the proposed formalism is generalized to problems with control constraints, and can also be used to maximize the classical fisher information for a chosen measurement. | arxiv:2105.06931 |
we introduce collinear drop jet substructure observables, which are unaffected by contributions from collinear radiation, and systematically probe soft radiation within jets. these observables can be designed to be either sensitive or insensitive to process - dependent soft radiation originating from outside the jet. such collinear drop observables can be exploited as variables to distinguish quark, gluon, and color neutral initiated jets, for testing predictions for perturbative soft radiation in monte carlo simulations, for assessing models and universality for hadronization corrections, for examining the efficiency of pileup subtraction methods, and for any other application that leaves an imprint on soft radiation. we discuss examples of collinear drop observables that are based both on clustering and on jet shapes. using the soft - collinear effective theory we derive factorization expressions for collinear drop observables from qcd jets, and carry out a resummation of logarithmically enhanced contributions at next - to - leading - logarithmic order. we also identify an infinite class of collinear drop observables for which the leading double logarithms are absent. | arxiv:1907.11107 |
estimation of the centre of pressure ( cop ) is an important part of the gait analysis, for example, when evaluating the functional capacity of individuals affected by motor impairment. inertial measurement units ( imus ) and force sensors are commonly used to measure gait characteristic of healthy and impaired subjects. we present a methodology for estimating the cop solely from raw gyroscope, accelerometer, and magnetometer data from imus using statistical modelling. we demonstrate the viability of the method using an example of two models : a linear model and a non - linear long - short - term memory ( lstm ) neural network model. models were trained on the cop ground truth data measured using an instrumented treadmill and achieved the average intra - subject root mean square ( rms ) error between estimated and ground truth cop of 12. 3mm and the average inter - subject rms error of 23. 7mm which is comparable or better than similar studies so far. we show that the calibration procedure in the instrumented treadmill can be as short as a couple of minutes without the decrease in our model performance. we also show that the magnetic component of the recorded imu signal, which is most sensitive to environmental changes, can be safely dropped without a significant decrease in model performance. finally, we show that the number of imus can be reduced to five without deterioration in the model performance. | arxiv:2011.01303 |
we calculate the relaxation rate of a nuclear spin in s - wave superconductor with nonmagnetic impurities, including the strong - coupling effects. we show that in a weakly disordered three - dimensional system the corrections due to disorder are negligibly small. | arxiv:cond-mat/0612666 |
the biaxial phase in nematic liquid crystals has been elusive for several decades after its prediction in the 1970s. a recent experimental breakthrough was achieved by liu et al. [ pnas 113, 10479 ( 2016 ) ] in a liquid crystalline medium with magnetic nanoparticles ( mnps ). they exploited the different length scales of dipolar and magneto - nematic interactions to obtain an equilibrium state where the magnetic moments are at an angle to the nematic director. this tilt introduces a second distinguished direction for orientational ordering or biaxiality in the two - component system. using coarse - grained ginzburg - landau free energy models for the nematic and magnetic fields, we provide a theoretical framework which allows for the manipulation of morphologies and quantitative estimates of biaxial order. | arxiv:2210.03467 |
multi - modal image registration spatially aligns two images with different distributions. one of its major challenges is that images acquired from different imaging machines have different imaging distributions, making it difficult to focus only on the spatial aspect of the images and ignore differences in distributions. in this study, we developed a self - supervised approach, indescribable multi - model spatial evaluator ( imse ), to address multi - modal image registration. imse creates an accurate multi - modal spatial evaluator to measure spatial differences between two images, and then optimizes registration by minimizing the error predicted of the evaluator. to optimize imse performance, we also proposed a new style enhancement method called shuffle remap which randomizes the image distribution into multiple segments, and then randomly disorders and remaps these segments, so that the distribution of the original image is changed. shuffle remap can help imse to predict the difference in spatial location from unseen target distributions. our results show that imse outperformed the existing methods for registration using t1 - t2 and ct - mri datasets. imse also can be easily integrated into the traditional registration process, and can provide a convenient way to evaluate and visualize registration results. imse also has the potential to be used as a new paradigm for image - to - image translation. our code is available at https : / / github. com / kid - liet / imse. | arxiv:2303.00369 |
this paper introduces the retrieval - augmented large language model with definite finite automaton ( dfa - rag ), a novel framework designed to enhance the capabilities of conversational agents using large language models ( llms ). traditional llms face challenges in generating regulated and compliant responses in special scenarios with predetermined response guidelines, like emotional support and customer service. our framework addresses these challenges by embedding a definite finite automaton ( dfa ), learned from training dialogues, within the llm. this structured approach acts as a semantic router which enables the llm to adhere to a deterministic response pathway. the routing is achieved by the retrieval - augmentation generation ( rag ) strategy, which carefully selects dialogue examples aligned with the current conversational context. the advantages of dfa - rag include an interpretable structure through human - readable dfa, context - aware retrieval for responses in conversations, and plug - and - play compatibility with existing llms. extensive benchmarks validate dfa - rag ' s effectiveness, indicating its potential as a valuable contribution to the conversational agent. | arxiv:2402.04411 |
the spatial ' t hooft loop measuring the electric flux and the spatial wilsonloop measuring the magnetic flux are analyzed in hot su ( n ) gauge theory. both display area laws. on one hand the tension of the ' t hooft loop is perturbatively calculable, in the same sense as the pressure. we show that the o ( g ^ 3 ) contribution is absent. the ratio of multi - charged ' t hooft loops have a remarkably simple dependence on the charge, true up to, but not including, o ( g ^ 4 ). this dependence follows also from a simple model of free screened colour charges. on the other hand the surface tension of the wilsonloop is non - perturbative. but in a model of screened free monopoles at very high temperature the known area law follows. the density of these monopoles starts to contribute to o ( g ^ 6 ) to the pressure. the ratio of the multicharged wilson loops is calculable and identical to that of the ' t hooft loops. | arxiv:hep-ph/0102022 |
the transition towards designs which co - package electronic and photonic die together in data center switch packages has created a scaling path to petabyte per second ( pbps ) input / output ( i / o ) in such systems. in a co - packaged design, the scaling of bandwidth, cost, and energy will be governed by the number of optical i / o channels and the data rate per channel. while optical communication provide an opportunity to exploit wavelength division multiplexing ( wdm ) to scale data rate, the limited 127 $ \ mu $ m pitch of v - groove based single mode fiber arrays and the use of active alignment and bonding for their packaging present challenges to scaling the number of optical channels. flip - chip optical couplers which allow for low loss, broadband operation and automated passive assembly represent a solution for continued scaling. in this paper, we propose a novel scheme to vertically couple between silicon based waveguides on separate chips using graded index ( grin ) couplers in combination with an evanescent coupler. simulation results using a 3d finite - difference time - domain ( fdtd ) solver are presented, demonstrating coupling losses below 0. 27 db for a chip - to - chip gap of 11 $ \ mu $ m ; 1 - db vertical and lateral alignment tolerances of approximately 2. 38 $ \ mu $ m and $ \ pm $ 2. 24 $ \ mu $ m, respectively ; and a greater than 360 nm 1 - db bandwidth. these results demonstrate the potential of our coupler as a universal interface in future co - packaged optics systems. | arxiv:2503.00121 |
in this paper we develop a numerical scheme for approximating a $ d $ - dimensional chemotaxis - navier - stokes system, $ d = 2, 3 $, modeling cellular swimming in incompressible fluids. this model describes the chemotaxis - fluid interaction in cases where the chemical signal is consumed with a rate proportional to the amount of organisms. we construct numerical approximations based on the finite element method and analyze some error estimates and convergence towards weak solutions. in order to construct the numerical scheme, we use a splitting technique to deal with the chemo - attraction term in the cell - density equation, leading to introduce a new variable given by the gradient of the chemical concentration. having the equivalent model, we consider a fully discrete finite element approximation which is well - posed and it is mass - conservative. we obtain uniform estimates and analyze the convergence of the scheme. finally, we present some numerical simulations to verify the good behavior of our scheme, as well as to check numerically the error estimates proved in our theoretical analysis. | arxiv:1908.03639 |
the system in which a small rigid ball is bouncing repeatedly on a massive at table vibrating vertically, so - called the bouncing ball system, has been widely studied. under the assumption that the table is vibrating with a piecewise polynomial function of time, the bifurcation diagram changes qualitatively depending on the order of the polynomial function. we elucidate the mechanism of the difference in the bifurcation diagrams by focusing on the two - period solution. in addition, we derive the approximate curve of the branch close to the period - doubling bifurcation point in the case of the piecewise cubic function of time for the table vibration. we also performed numerical calculation, and we demonstrate that the approximations well reproduce the numerical results. | arxiv:2004.10633 |
using a combination of deep mid - ir observations obtained by irac, mips and irs on board spitzer we investigate the mid - ir properties of lyman break galaxies ( lbgs ) at z ~ 3, establish a better understanding of their nature and attempt a complete characterisation of the population. with deep mid - infrared and optical observations of ~ 1000 lbgs covered by irac / mips and from the ground respectively, we extend the spectral energy distributions ( seds ) of the lbgs to mid - infrared. spitzer data reveal for the first time that the mid - infrared properties of the population are inhomogeneous ranging from those with marginal irac detections to those with bright rest - frame near - infrared colors and those detected at 24mu mips band revealing the newly discovered population of the infrared luminous lyman break galaxies ( illbgs ). to investigate this diversity, we examine the photometric properties of the population and we use stellar population synthesis models to probe the stellar content of these galaxies. we find that a fraction of lbgs have very red colors and large estimated stellar masses m * > 5x10 ^ 10mo. we discuss the link between these lbgs and submm - luminous galaxies and we report the detection of rest frame 6. 2 and 7. 7mu emission features arising from polycyclic aromatic hydrocarbons ( pah ) in the spitzer / irs spectrum of an infrared - luminous lyman break galaxy at z = 3. 01. | arxiv:0710.0506 |
the three level photon echo has been described in different works by using rotating wave approximation but none of them did not get results which show the effects of field ' s frequencies on frequency of ground level of system. in this work, we studied a lambda type system theoretically and numerically. by considering the doppler effect in environment, we get different equation for polarization of echo signal and its intensity. | arxiv:1405.7674 |
we propose to use the thermal x - ray emission from young supernova remnants ( snrs ) originated in type ia supernovae ( sne ) to extract relevant information concerning the explosion mechanism. we focus on the differences between numerical 1d and 3d explosion calculations, and the impact that these differences could have on young snrs. we use the remnant of the tycho supernova ( sn 1572 ) as a test case to compare with our predictions, discussing the observational features that allow to accept or discard a given model. | arxiv:astro-ph/0309013 |
an essential factor to achieve high accuracies in fingerprint recognition systems is the quality of its samples. previous works mainly proposed supervised solutions based on image properties that neglects the minutiae extraction process, despite that most fingerprint recognition techniques are based on detected minutiae. consequently, a fingerprint image might be assigned a high quality even if the utilized minutia extractor produces unreliable information. in this work, we propose a novel concept of assessing minutia and fingerprint quality based on minutia detection confidence ( midecon ). midecon can be applied to an arbitrary deep learning based minutia extractor and does not require quality labels for learning. we propose using the detection reliability of the extracted minutia as its quality indicator. by combining the highest minutia qualities, midecon also accurately determines the quality of a full fingerprint. experiments are conducted on the publicly available databases of the fvc 2006 and compared against several baselines, such as nist ' s widely - used fingerprint image quality software nfiq1 and nfiq2. the results demonstrate a significantly stronger quality assessment performance of the proposed midecon - qualities as related works on both, minutia - and fingerprint - level. the implementation is publicly available. | arxiv:2106.05601 |
in this work, we present a literature review for full - text and keyword indexes as well as our contributions ( which are mostly practice - oriented ). the first contribution is the fm - bloated index, which is a modification of the well - known fm - index ( a compressed, full - text index ) that trades space for speed. in our approach, the count table and the occurrence lists store information about selected $ q $ - grams in addition to the individual characters. two variants are described, namely one using $ o ( n \ log ^ 2 n ) $ bits of space with $ o ( m + \ log m \ log \ log n ) $ average query time, and one with linear space and $ o ( m \ log \ log n ) $ average query time, where $ n $ is the input text length and $ m $ is the pattern length. we experimentally show that a significant speedup can be achieved by operating on $ q $ - grams ( albeit at the cost of very high space requirements, hence the name " bloated " ). in the category of keyword indexes we present the so - called split index, which can efficiently solve the $ k $ - mismatches problem, especially for 1 error. our implementation in the c + + language is focused mostly on data compaction, which is beneficial for the search speed ( by being cache friendly ). we compare our solution with other algorithms and we show that it is faster when the hamming distance is used. query times in the order of 1 microsecond were reported for one mismatch for a few - megabyte natural language dictionary on a medium - end pc. a minor contribution includes string sketches which aim to speed up approximate string comparison at the cost of additional space ( $ o ( 1 ) $ per string ). they can be used in the context of keyword indexes in order to deduce that two strings differ by at least $ k $ mismatches with the use of fast bitwise operations rather than an explicit verification. | arxiv:1508.06610 |
( abridged ) we present here the second half of an eso large programme, which exploits the unique combination of area and sensitivity provided in the near - ir by the camera hawk - i at the vlt. we have obtained - 30 observing hours with hawk - i in the y - band of two high galactic latitude fields. we combined the y - band data with deep j and k hawk - i observations, and with fors1 / fors2 u, b, v, r, i, and z observations to select z - drop galaxies having z - y > 1, no optical detection and flat y - j and y - k colour terms. we detect 8 high - quality candidates in the magnitude range y = 25. 5 - 26. 5 that we add to the z - drop candidates selected in two hawk - i pointings over the goods - south field. we use this full sample of 15 objects found in - 161 arcmin ^ 2 of our survey to constrain the average physical properties and the evolution of the number density of z ~ 7 lbgs. a stacking analysis yields a best - fit sed with photometric redshift z = 6. 85 + 0. 20 - 0. 15 and an e ( b - v ) = 0. 05 + 0. 15 - 0. 05. we compute a binned estimate of the z ~ 7 lf and explore the effects of photometric scatter and model uncertainties on the statistical constraints. after accounting for the expected incompleteness through montecarlo simulations, we strengthen our previous finding that a schechter luminosity function constant from z = 6 to z = 7 is ruled out at a > 99 % confidence level, even including the effects of cosmic variance. for galaxies brighter than m _ 1500 = - 19. 0, we derive a luminosity density rho _ uv = 1. 5 ^ { + 2. 1 } { - 0. 8 } x 10 ^ 25 erg / s / hz / mpc ^ 3, implying a decrease by a factor 3. 5 from z = 6 to z = 6. 8. we find that, under standard assumptions, the emission rate of ionizing photons coming from uv bright galaxies is lower by at least a factor of two than the value required for reionization. finally, we exploit deep hawk - i j and k band observations to derive an upper limit on the number density of m1500 < ~ - 22. 0 lbgs at z - 8 ( y | arxiv:1007.5396 |
in the minimum consistent subset ( mcs ) problem, we are presented with a connected simple undirected graph $ g = ( v, e ) $, consisting of a vertex set $ v $ of size $ n $ and an edge set $ e $. each vertex in $ v $ is assigned a color from the set $ \ { 1, 2, \ ldots, c \ } $. the objective is to determine a subset $ v ' \ subseteq v $ with minimum possible cardinality, such that for every vertex $ v \ in v $, at least one of its nearest neighbors in $ v ' $ ( measured in terms of the hop distance ) shares the same color as $ v $. the decision problem, indicating whether there exists a subset $ v ' $ of cardinality at most $ l $ for some positive integer $ l $, is known to be np - complete even for planar graphs. in this paper, we establish that the mcs problem for trees, when the number of colors $ c $ is considered an input parameter, is np - complete. we propose a fixed - parameter tractable ( fpt ) algorithm for mcs on trees running in $ o ( 2 ^ { 6c } n ^ 6 ) $ time, significantly improving the currently best - known algorithm whose running time is $ o ( 2 ^ { 4c } n ^ { 2c + 3 } ) $. in an effort to comprehensively understand the computational complexity of the mcs problem across different graph classes, we extend our investigation to interval graphs. we show that it remains np - complete for interval graphs, thus enriching graph classes where mcs remains intractable. | arxiv:2404.15487 |
recent works have demonstrated success in controlling sentence attributes ( $ e. g. $, sentiment ) and structure ( $ e. g. $, syntactic structure ) based on the diffusion language model. a key component that drives theimpressive performance for generating high - quality samples from noise is iteratively denoise for thousands of steps. while beneficial, the complexity of starting from the noise and the learning steps has limited its implementation to many nlp real - world applications. this paper proposes language rectified flow ( { \ ours } ). our method is based on the reformulation of the standard probabilistic flow models. language rectified flow learns ( neural ) ordinary differential equation models to transport between the source distribution and the target distribution, hence providing a unified and effective solution to generative modeling and domain transfer. from the source distribution, our language rectified flow yields fast simulation and effectively decreases the inference time. experiments on three challenging fine - grained control tasks and multiple high - quality text editing show that our method consistently outperforms its baselines. extensive experiments and ablation studies demonstrate that our method can be general, effective, and beneficial for many nlp tasks. | arxiv:2403.16995 |
motile eukaryotic cells propel themselves in viscous fluids by passing waves of bending deformation down their flagella. an infinitely long flagellum achieves a hydrodynamically optimal low - reynolds number locomotion when the angle between its local tangent and the swimming direction remains constant along its length. optimal flagella therefore adopt the shape of a helix in three dimensions ( smooth ) and that of a sawtooth in two dimensions ( non - smooth ). physically, biological organisms ( or engineered micro - swimmers ) must expend internal energy in order to produce the waves of deformation responsible for the motion. here we propose a physically - motivated derivation of the optimal flagellum shape. we determine analytically and numerically the shape of the flagellar wave which leads to the fastest swimming while minimizing an appropriately - defined energetic expenditure. our novel approach is to define an energy which includes not only the work against the surrounding fluid, but also ( 1 ) the energy stored elastically in the bending of the flagellum, ( 2 ) the energy stored elastically in the internal sliding of the polymeric filaments which are responsible for the generation of the bending waves ( microtubules ), and ( 3 ) the viscous dissipation due to the presence of an internal fluid. this approach regularizes the optimal sawtooth shape for two - dimensional deformation at the expense of a small loss in hydrodynamic efficiency. the optimal waveforms of finite - size flagella are shown to depend upon a competition between rotational motions and bending costs, and we observe a surprising bias towards half - integer wave - numbers. their final hydrodynamic efficiencies are above 6 %, significantly larger than those of swimming cells, therefore indicating available room for further biological tuning. | arxiv:0909.4826 |
we present an automatic procedure to perform reliable photometry of galaxies on sdss images. we selected a sample of 5853 galaxies in the coma and virgo superclusters. for each galaxy, we derive petrosian g and i magnitudes, surface brightness profiles and color profiles. unlike the sdss pipeline, our procedure is not affected by the well known shredding problem and efficiently extracts petrosian magnitudes for all galaxies. hence we derived magnitudes even from the population of galaxies missed by the sdss that represents 25 % of all local supercluster galaxies and ~ 95 % of galaxies with g < 11 mag. after correcting the g and i magnitudes for galactic and internal extinction, the blue and red sequences in the color magnitude diagram are well separated, with similar slopes. in addition, we study ( i ) the color - magnitude diagrams in different galaxy regions, the inner ( r < = 1 kpc ), intermediate ( 0. 2r { pet } < = r < = 0. 3r { pet } ) and outer, disk - dominated ( r > = 0. 35r { pet } ) ) zone, and ( ii ), we compute template color profiles, discussing the dependences of the templates on the galaxy masses and on their morphological type. the two analyses consistently lead to a picture where elliptical galaxies show no color gradients, irrespective of their masses. spirals, instead, display a steeper gradient in their color profiles with increasing mass, consistently with the growing relevance of a bulge and / or a bar component above 10 ^ { 10 } modot. | arxiv:1603.07753 |
the intrinsic ferroelectricity and related dielectric properties of m - type barium hexaferrite ( bafe12o19 ) with excellent magnetic performance are reported in this paper. a classic electric polarization ( p - e ) hysteresis loop with full saturation, together with two nonlinear reversal current peaks in the i - v curve and huge change of dielectric constant in the vicinity of curie temperature, have all demonstrated themselves as sufficient experimental evidences to verify the ferroelectricity of bafe12o19 ceramics. it holds a large remnant polarization at 108 uc / cm2 and a suitable coercive field at 117 kv / cm. two peaks at 194c and 451c in the temperature - dependent dielectric spectrum of bafe12o19 ceramics are considered to be the phase transition from ferro - to antiferro - and antiferro - to para - electric structures. a conventional strong magnetic hysteresis loop was also observed. the magnetically induced polarization upon the bafe12o19 ceramics was achieved in the form of alternating spin current waves. a me - coupling voltage with an amplitude of 23mv on an applied magnetic field at 500mt was achieved. these combined multiple functional responses of large ferroelectrics and strong ferromagnetism reveal the excellent multiferroic features of bafe12o19, which would bring forth the great opportunity to create novel electric devices with active coupling effect between magnetic and electric orders. | arxiv:2002.11412 |
topological materials which are also superconducting are of great current interest, since they may exhibit a non - trivial topologically - mediated superconducting phase. although there have been many reports of pressure - tuned or chemical - doping - induced superconductivity in a variety of topological materials, there have been few examples of intrinsic, ambient pressure superconductivity in a topological system having a stoichiometric composition. here, we report that the pure intermetallic casn3 not only exhibits topological fermion properties but also has a superconducting phase at 1. 178 k under ambient pressure. the topological fermion properties, including the nearly zero quasi - particle mass and the non - trivial berry phase accumulated in cyclotron motions, were revealed from the de haas - van alphen ( dhva ) quantum oscillation studies of this material. although casn3 was previously reported to be superconducting at 4. 2k, our studies show that the superconductivity at 4. 2k is extrinsic and caused by sn on the degraded surface, whereas its intrinsic bulk superconducting transition occurs at 1. 178 k. these findings make casn3 a promising candidate for exploring new exotic states arising from the interplay between non - trivial band topology and superconductivity, e. g. topological superconductivity | arxiv:1811.11638 |
we propose a realistic model for the evolution of the covid - 19 pandemic subject to the lockdown and quarantine measures, which takes into account the time - delay for recovery or death processes. the dynamic equations for the entire process are derived by adopting a kinetic - type reaction approach. more specifically, the lockdown and the quarantine measures are modelled by some kind of inhibitor reactions where susceptible and infected individuals can be trapped into inactive states. the dynamics for the recovered people is obtained by accounting people who are only traced back to hospitalised infected people. to get the evolution equation we take inspiration from the michaelis - menten enzyme - substrate reaction model ( the so - called mm reaction ) where the enzyme is associated to the available hospital beds, the substrate to the infected people, and the product to the recovered people, respectively. in other words, everything happens as if the hospitals beds act as a catalyser in the hospital recovery process. of course, in our case the reverse mm reactions has no sense in our case and, consequently, the kinetic constant is equal to zero. finally, the o. d. e. s for people tested positive to covid - 19 is simply modelled by the following kinetic scheme s + i = > 2i with i = > r or i = > d, with s, i, r, and d denoting the compartments susceptible, infected, recovered, and deceased people, respectively. the resulting kinetic - type equation } provide the o. d. e. s, for elementary reaction steps, describing the number of the infected people, the total number of the recovered people previously hospitalised, subject to the lockdown and the quarantine measure, and the total number of deaths. the model foresees also the second wave of infection by coronavirus. the tests carried out on real data for belgium, france and germany confirmed the correctness of our model. | arxiv:2101.05596 |
in order to increase the ability to build complex, software - intensive systems, as well as to decrease time - to - market for new functionality, automotive companies aim to scale agile methods beyond individual teams. this is challenging, given the specifics of automotive systems that are often safety - critical and consist of software, hardware, and mechanical components. this paper investigates the concrete reasons for scaling agility beyond teams, the strategies that support such scaling, and foreseeable implications that such a drastic organizational change will entail. the investigation is based on a qualitative case study, with data from 20 semi - structured interviews with managers and technical experts at two automotive companies. at the core of our findings are observations about establishing an agile vehicle - level feedback loop beyond individual teams. ( i ) we find that automotive oems aim to decrease lead - time of development. ( ii ) we also identify 7 strategies that aim to enable scaled - agile beyond teams. ( iii ) finally, we extract 6 foreseeable implications and side - effects of scaling agile beyond teams in automotive. by charting the landscape of expected benefits, strategies, and implications of scaling agile beyond teams in automotive, we enable further research and process improvements. | arxiv:2203.13130 |
quantum spin networks overcome the challenges of traditional charge - based electronics by encoding the information into spin degrees of freedom. although beneficial for transmitting information with minimal losses when compared to their charge - based counterparts, the mathematical formalization of the information propagation in a spin ( tronic ) network is challenging due to its complicated scaling properties. in this paper, we propose a geometric approach - - - specific to finite networks - - - for unraveling the information - theoretic phenomena of spin chains and rings by abstracting them as weighted graphs, where the vertices correspond to the spin excitation states and the edges represent the information theoretic distance between pair of nodes. the weighted graph representation of the quantum spin network dynamics exhibits a complex self - similar structure ( where subgraphs repeat to some extent over various space scales ). to quantify this complex behavior, we develop a new box counting inspired algorithm which assesses the mono - fractal versus multi - fractal properties of quantum spin networks. besides specific to finite networks, multi - fractality is further compounded by " engineering " or " biasing " the network for selective transfer, as selectivity makes the network more heterogeneous. to demonstrate criticality in finite size systems, we define a thermodynamics inspired framework for describing information propagation and show evidence that some spin chains and rings exhibit an informational phase transition phenomenon, akin to the metal - to - insulator phase transition in anderson localization in finite media. } | arxiv:1608.08192 |
i numerically simulate and compare the entanglement of two quanta using the conventional formulation of quantum mechanics and a time - symmetric formulation that has no collapse postulate. the experimental predictions of the two formulations are identical, but the entanglement predictions are significantly different. the time - symmetric formulation reveals an experimentally testable discrepancy in the original quantum analysis of the hanbury brown - twiss experiment, suggests solutions to some parts of the nonlocality and measurement problems, fixes known time asymmetries in the conventional formulation, and answers bell ' s question " how do you convert an ' and ' into an ' or '? ' " | arxiv:2003.07183 |
we show how standard metadynamics coupled with classical molecular dynamics can be successfully ap - plied to sample the configurational and free energy space of metallic and bimetallic nanopclusters via the implementation of collective variables related to the pair distance distribution function of the nanoparticle itself. as paradigmatic examples we show an application of our methodology to ag147, pt147 and their alloy agshellptcore at 1 : 1 and 2 : 1 chemical compositions. the proposed scheme is not only able to reproduce known structural transformation pathways, as the five and the six square - diamond mechanisms both in pure and core - shell nanoparticles but also to predict a new route connecting icosahedron to anti - cuboctahedron. | arxiv:1507.03505 |
screenshots are prevalent on social media as a common approach for information sharing. users rarely verify before sharing a screenshot whether the post it contains is fake or real. information sharing through fake screenshots can be highly responsible for misinformation and disinformation spread on social media. our ultimate goal is to develop a tool that could take a screenshot of a tweet and provide a probability that the tweet is real, using resources found on the live web and in web archives. this paper provides methods for extracting the tweet text, timestamp, and twitter handle from a screenshot of a tweet. | arxiv:2306.08236 |
the paper deals with dynamics of expanding lorenz maps, which appear in a natural way as poincar \ ` e maps in geometric models of well - known lorenz attractor. using both analytical and symbolic approaches, we study connections between periodic points, completely invariant sets and renormalizations. we show that some renormalizations may be connected with completely invariant sets while some others don ' t. we provide an algorithm to detect the renormalizations that can be recovered from completely invariant sets. furthermore, we discuss the importance of distinguish one - side and double - side preimage. this way we provide a better insight into the structure of renormalizations in lorenz maps. these relations remained unnoticed in the literature, therefore we are correcting some gaps existing in the literature, improving and completing to some extent the description of possible dynamics in this important field of study. | arxiv:2104.00110 |
the shape and the dynamics of reversals of the magnetic field in a turbulent dynamo experiment are investigated. we report the evolution of the dipolar and the quadrupolar parts of the magnetic field in the vks experiment, and show that the experimental results are in good agreement with the predictions of a recent model of reversals : when the dipole reverses, part of the magnetic energy is transferred to the quadrupole, reversals begin with a slow decay of the dipole and are followed by a fast recovery, together with an overshoot of the dipole. random reversals are observed at the borderline between stationary and oscillatory dynamos. | arxiv:1010.4771 |
we present breizhcrops, a novel benchmark dataset for the supervised classification of field crops from satellite time series. we aggregated label data and sentinel - 2 top - of - atmosphere as well as bottom - of - atmosphere time series in the region of brittany ( breizh in local language ), north - east france. we compare seven recently proposed deep neural networks along with a random forest baseline. the dataset, model ( re - ) implementations and pre - trained model weights are available at the associated github repository ( https : / / github. com / dl4sits / breizhcrops ) that has been designed with applicability for practitioners in mind. we plan to maintain the repository with additional data and welcome contributions of novel methods to build a state - of - the - art benchmark on methods for crop type mapping. | arxiv:1905.11893 |
we discuss implications on the $ h _ 0 $ tension due to preferred - frame effects in the context of ho \ v { r } ava - lifshitz gravity. by using a combination of low - redshift data ( sne1a, elliptical and lenticular galaxies, grb ' s, and quasars ) we study the $ h _ 0 $ tension and its appearance as a preferred - frame effect, as well as present new constraints on the model parameter $ \ lambda $. moreover, from the structure of the friedmann equations, we argue that up to $ 38 \ % $ of the hubble tension can be explained by lorentz - violating effects in a ho \ v { r } ava - lifshitz scenario. | arxiv:1910.14414 |
in this paper, we compare and analyze clustering methods with missing data in health behavior research. in particular, we propose and analyze the use of compressive sensing ' s matrix completion along with spectral clustering to cluster health related data. the empirical tests and real data results show that these methods can outperform standard methods like lpa and fiml, in terms of lower misclassification rates in clustering and better matrix completion performance in missing data problems. according to our examination, a possible explanation of these improvements is that spectral clustering takes advantage of high data dimension and compressive sensing methods utilize the near - to - low - rank property of health data. | arxiv:1404.5899 |
we study lie subalgebras $ l $ of the vector fields $ \ mathrm { vec } ^ { c } ( { \ mathbb a } ^ { 2 } ) $ of affine 2 - space $ { \ mathbb a } ^ { 2 } $ of constant divergence, and we classify those $ l $ which are isomorphic to the lie algebra $ \ mathfrak { aff } _ { 2 } $ of the group $ \ mathrm { aff } _ { 2 } ( k ) $ of affine transformations of $ { \ mathbb a } ^ { 2 } $. we then show that the following three statements are equivalent : ( i ) the jacobian conjecture holds in dimension 2 ; ( ii ) all lie subalgebras $ l \ subset \ mathrm { vec } ^ { c } ( { \ mathbb a } ^ { 2 } ) $ isomorphic to $ \ mathfrak { aff } _ { 2 } $ are conjugate under $ \ mathrm { aut } ( { \ mathbb a } ^ { 2 } ) $ ; ( iii ) all lie subalgebras $ l \ subset \ mathrm { vec } ^ { c } ( { \ mathbb a } ^ { 2 } ) $ isomorphic to $ \ mathfrak { aff } _ { 2 } $ are algebraic. | arxiv:1311.0232 |
optical microscopy offers a unique insight of biological structures with a sub - micrometer resolution and a minimum invasiveness. however, the inhomogeneities of the specimen itself can induce multiple scattering of light and optical aberrations which limit the observation to depths close to the surface. to predict quantitatively the penetration depth in microscopy, we theoretically derive the single - to - multiple scattering ratio in reflection. from this key quantity, the multiple scattering limit is deduced for various microscopic imaging techniques such as confocal microscopy, optical coherence tomography and related methods. | arxiv:1709.03386 |
has been criticized because normal integers may also lead with zero. as such, python, ruby, haskell, and ocaml prefix octal values with 0o or 0o, following the layout used by hexadecimal values. several languages, including java, c #, scala, python, ruby, ocaml, c ( starting from c23 ) and c + + can represent binary values by prefixing a number with 0b or 0b. = = extreme values = = in many programming languages, there exist predefined constants representing the least and the greatest values representable with a given integer type. names for these include smallbasic : maxint java : java. lang. integer. max _ value, java. lang. integer. min _ value corresponding fields exist for the other integer classes in java. c : int _ max, etc. glib : g _ minint, g _ maxint, g _ maxuint,... haskell : minbound, maxbound pascal : maxint python 2 : sys. maxint turing : maxint = = see also = = arbitrary - precision arithmetic binary - coded decimal ( bcd ) c data types integer overflow signed number representations = = notes = = = = references = = | https://en.wikipedia.org/wiki/Integer_(computer_science) |
the reactive optimal power flow ( ropf ) problem consists in computing an optimal power generation dispatch for an alternating current transmission network that respects power flow equations and operational constraints. some means of action on the voltage are modelled in the ropf problem such as the possible activation of shunts, which implies discrete variables. the ropf problem belongs to the class of nonconvex minlps ( mixed - integer nonlinear problems ), which are np - hard problems. in this paper, we solve three new variants of the ropf problem by using a semidefinite optimization - based branch - and - bound algorithm. we present results on matpower instances and we show that this method can solve to global optimality most instances. on the instances not solved to optimality, our algorithm is able to find solutions with a value better than the ones obtained by a rounding algorithm. we also demonstrate that applying an appropriate clique merging algorithm can significantly speed up the resolution of semidefinite relaxations of ropf large instances. | arxiv:2103.13648 |
sufficiency of jets is a very important notion introduced by rene thom in order to establish the structural stability theory. the criteria for some sufficiency of jets are known as the kuo condition and thom type inequality, which are defined using the kuo quantity and thom quantity. therefore these quantities are meaningful. in this paper we show the equivalence of kuo and thom quantities. then we apply this result to the relative conditions to a given closed set. | arxiv:2003.02127 |
their son was born, leaving her penniless ; and as a result of her poor health she lost custody of the boy when he was four. she married again, and her new husband promised to become the child ' s legal guardian, but after their marriage he refused to sign the needed papers and the boy was taken to minnesota and told his mother had died. eddy, then known as mary patterson, and her husband moved to rural new hampshire, where eddy continued to suffer from health problems which often kept her bedridden. eddy tried various cures for her health problems, including conventional medicine as well as many forms of alternative medicine such as grahamism, electrotherapy, homeopathy, hydropathy, and finally mesmerism under phineas quimby. she was later accused by critics, beginning with julius dresser, of borrowing ideas from quimby in what biographer gillian gill would call the " single most controversial issue " of her life. in february 1866, eddy fell on the ice in lynn, massachusetts. evidence suggests she had severe injuries, but a few days later she apparently asked for her bible, opened it to an account of one of jesus ' miracles, and left her bed telling her friends that she was healed through prayer alone. the moment has since been controversial, but she considered this moment one of the " falling apples " that helped her to understand christian science, although she said she did not fully understand it at the time. in 1866, after her fall on the ice, eddy began teaching her first student and began writing her ideas which she eventually published in science and health with key to the scriptures, considered her most important work. her students voted to form a church called the church of christ ( scientist ) in 1879, later reorganized as the first church of christ, scientist, also known as the mother church, in 1892. she founded the massachusetts metaphysical college in 1881 to continue teaching students, eddy started a number of periodicals : the christian science journal in 1883, the christian science sentinel in 1898, the herald of christian science in 1903, and the christian science monitor in 1908, the latter being a secular newspaper. the monitor has gone on to win seven pulitzer prizes as of 2011. she also wrote numerous books and articles in addition to science and health, including the manual of the mother church which contained by - laws for church government and member activity, and founded the christian science publishing society in 1898 in order to distribute christian science literature. although the movement started in boston, the first purpose - built christian science church building was erected in | https://en.wikipedia.org/wiki/Christian_Science |
quiver flag zero loci are subvarieties of quiver flag varieties cut out by sections of homogeneous vector bundles. we prove the abelian / non - abelian correspondence in this context : this allows us to compute genus zero gromov - - witten invariants of quiver flag zero loci. we determine the ample cone of a quiver flag variety, disproving a conjecture of craw. in the appendices, which are joint work with tom coates and alexander kasprzyk, we use these results to find four - dimensional fano manifolds that occur as quiver flag zero loci in ambient spaces of dimension up to 8, and compute their quantum periods. in this way we find at least 141 new four - dimensional fano manifolds. | arxiv:1808.00311 |
the general hamiltonian expression, up to the first - order relativistic correction, was derived by breaking the four - component dirac equation into the two - component dirac - pauli equation. this hamiltonian incorporates the first - order relativistic correction to the electromagnetic interaction with the spin and orbital magnetic moments of the charged lepton, distinguishing it from other generic hamiltonians. notably, our hamiltonian is applicable to scenarios involving non - uniform magnetic fields, providing a more general framework for describing relativistic effects. using this generalized hamiltonian, we calculated the first - order relativistic adjustment to the land \ ' e \ ( g \ ) - factor ( or equivalently, the magnetic moment ) for hydrogen - like atoms in the presence of an external magnetic field. our results provide a novel expression for the relativistic correction of order \ ( \ alpha ^ 2 \ ) to the \ ( g \ ) factor, which explicitly depends on the azimuthal quantum number as \ ( m ^ 2 _ j \ ) and reduces to the well - known breit result for specific states. both quantum field theory ( qft ) and relativistic corrections contribute to the \ ( g \ ) factor of hydrogen - like ions. the qft contribution is intrinsic, while the relativistic correction depends on the particle ' s kinematics and external electromagnetic field. for highly charged ions with \ ( z \ approx \ sqrt { 1 / \ alpha } \ ), relativistic effects become comparable to qft corrections and play a significant role. | arxiv:2501.07610 |
we demonstrate how concepts of statistical mechanics of interacting particles can have important implications in the choice of interaction potentials to model qualitative properties of cell aggregates in theoretical biology. we illustrate this by showing cell sorting phenomena for cell groups with different adhesiveness parameters : ranging from well - mixed cells aggregates to full segregation of cell type passing through engulfment via adhesiveness tuning. | arxiv:1706.08969 |
a microscopic optical potential ( op ) is derived from nn chiral potentials at the first - order term within the spectator expansion of the multiple scattering theory and adopting the impulse approximation. the performances of our op are compared with those of a phenomenological op in the description of elastic proton scattering data on different isotopic chains. an analogous scheme is adopted to construct a microscopic op for elastic antiproton - nucleus scattering. the results of our ops are in reasonably good agreement with the experimental data, for both elastic proton and antiproton - nucleus scattering. | arxiv:1912.09415 |
we show uniqueness for overdetermined elliptic problems defined on topological disks $ \ omega $ with $ c ^ 2 $ boundary, i. e., positive solutions $ u $ to $ \ delta u + f ( u ) = 0 $ in $ \ omega \ subset ( m ^ 2, g ) $ so that $ u = 0 $ and $ \ frac { \ partial u } { \ partial \ vec \ eta } = cte $ along $ \ partial \ omega $, $ \ vec \ eta $ the unit outward normal along $ \ partial \ omega $ under the assumption of the existence of a candidate family. to do so, we adapt the g \ ' alvez - mira generalized hopf - type theorem to the realm of overdetermined elliptic problem. when $ ( m ^ 2, g ) $ is the standard sphere $ \ mathbb s ^ 2 $ and $ f $ is a $ c ^ 1 $ function so that $ f ( x ) > 0 $ and $ f ( x ) \ ge x \, f ' ( x ) $ for any $ x \ in \ mathbb r _ + ^ * $, we construct such candidate family considering rotationally symmetric solutions. this proves the berestycki - caffarelli - nirenberg conjecture in $ \ mathbb s ^ 2 $ for this choice of $ f $. more precisely, this shows that if $ u $ is a positive solution to $ \ delta u + f ( u ) = 0 $ on a topological disk $ \ omega \ subset \ mathbb s ^ 2 $ with $ c ^ 2 $ boundary so that $ u = 0 $ and $ \ frac { \ partial u } { \ partial \ vec \ eta } = cte $ along $ \ partial \ omega $, then $ \ omega $ must be a geodesic disk and $ u $ is rotationally symmetric. in particular, this gives a positive answer to the schiffer conjecture d for the first dirichlet eigenvalue and classifies simply - connected harmonic domains, also called { \ it serrin problem } ) in $ \ mathbb s ^ 2 $. | arxiv:1610.09833 |
secondary = = = e - learning is increasingly being utilized by students who may not want to go to traditional brick - and - mortar schools due to severe allergies or other medical issues, fear of school violence and school bullying, and students whose parents would like to homeschool but do not feel qualified. online schools create a haven for students to receive a quality education while almost completely avoiding these common problems. online charter schools also often are not limited by location, income level, or class size in the way brick and mortar charter schools are. e - learning also has been rising as a supplement to the traditional classroom. students with special talents or interests outside of the available curricula use e - learning to advance their skills or exceed grade restrictions. virtual education in k - 12 schooling often refers to virtual schools, and in higher education to virtual universities. virtual schools are " cybercharter schools " with innovative administrative models and course delivery technology. education technology also seems to be an interesting method of engaging gifted youths that are under - stimulated in their current educational program. this can be achieved with after - school programs or even technologically - integrated curricula. 3d printing integrated courses ( 3dpic ) can also give youths the stimulation they need in their educational journey. universite de montreal ' s projet seur in collaboration with college mont - royal and la variable are heavily developing this field. = = = higher education = = = online college course enrollment has seen a 29 % increase in enrollment with nearly one - third of all college students, or an estimated 6. 7 million students are currently enrolled in online classes. in 2009, 44 % of post - secondary students in the us were taking some or all of their courses online, which was projected to rise to 81 % by 2014. although a large proportion of for - profit higher education institutions now offer online classes, only about half of private, non - profit schools do so. private institutions may become more involved with online presentations as the costs decrease. properly trained staff must also be hired to work with students online. these staff members need to understand the content area, and also be highly trained in the use of the computer and internet. online education is rapidly increasing, and online doctoral programs have even developed at leading research universities. although massive open online courses ( moocs ) may have limitations that preclude them from fully replacing college education, such programs have significantly expanded. mit, stanford and princeton university offer classes to a global audience, but not for college credit. university - level programs, like edx | https://en.wikipedia.org/wiki/Educational_technology |
[ abridged ] we study supermassive black hole binary mergers driven by angular momentum loss to small - scale gas discs. such binaries form after major galaxy mergers, but their fate is unclear since hardening through stellar scattering becomes very inefficient at sub - parsec distances. gas discs may dominate binary dynamics on these scales, and promote mergers. using numerical simulations, we investigate the evolution of the orbits of binaries embedded within geometrically thin gas discs. our simulations directly resolve angular momentum transport within the disc, which at the radii of interest is likely dominated by disc self - gravity. we show that the binary decays at a rate which is in good agreement with analytical estimates, while the eccentricity grows. saturation of eccentricity growth is not observed up to values e > 0. 35. accretion onto the black holes is variable, and is roughly modulated by the binary orbital frequency. scaling our results, we analytically estimate the maximum rate of binary decay that is possible without fragmentation occuring within the surrounding gas disc, and compare that rate to an estimate of the stellar dynamical hardening rate. for binary masses in the range 10 ^ 5 < m / msun < 10 ^ 8 we find that decay due to gas discs may dominate for separations below a ~ 0. 01 - - 0. 1 pc, where the disc is optically thick. the minimum merger time scale is shorter than the hubble time for m < 10 ^ 7 msun. this implies that gas discs could commonly attend relatively low mass black hole mergers, and that a significant population of binaries might exist at separations of a few hundredths of a pc, where the combined decay rate is slowest. for more massive binaries, we suggest that scattering of stars formed within a fragmenting gas disc could act as a significant additional sink of binary angular momentum. | arxiv:0809.0311 |
we analysed red giant branch stars in 16 galactic globular clusters, computing their atmospheric parameters both from the photometry and from excitation and ionisation balances. the spectroscopic parameters are lower than the photometric ones and this discrepancy increases decreasing the metallicity, reaching, at [ fe / h ] ~ - 2. 5 dex, differences of ~ 350 k in effective temperature and ~ 1 dex in surface gravity. we demonstrate that the spectroscopic parameters are inconsistent with the position of the stars in the colour - magnitude diagram, providing too low temperatures and gravities, and predicting that the stars are up to about 2. 5 magnitudes brighter than the observed magnitudes. the parameter discrepancy is likely due to the inadequacies of the adopted physics, in particular the assumption of 1 - dimensional geometry can be the origin of the observed slope between iron abundances and excitation potential that leads to low temperatures. however, the current modelling of 3d / nlte radiative transfer for giant stars seems to be not able to totally erase this slope. we conclude that the spectroscopic parameters are wrong for metallicity lower than - 1. 5 dex and for these red giant stars photometric temperatures and gravities should be adopted. we provide a simple relation to correct the spectroscopic temperatures in order to put them onto a photometric scale. | arxiv:2003.07390 |
we demonstrate theoretically and numerically how to control the nmr relaxation rate after application of the standard spin echo technique. using radiation damping, we return the nuclear magnetization to its equilibrium state during a time interval that is negligible compared to the relaxation time. we obtain an estimate for optimal radiation damping which is consistent with our numerical simulations. | arxiv:1111.7060 |
given a map $ f \ colon x \ to y $, we extend a gottlieb ' s result to the generalized gottlieb group $ g ^ f ( y, f ( x _ 0 ) ) $ and show that the canonical isomorphism $ \ pi _ 1 ( y, f ( x _ 0 ) ) \ xrightarrow { \ approx } \ mathcal { d } ( y ) $ restricts to an isomorphism $ g ^ f ( y, f ( x _ 0 ) ) \ xrightarrow { \ approx } \ mathcal { d } ^ { \ tilde { f } _ 0 } ( y ) $, where $ \ mathcal { d } ^ { \ tilde { f } _ 0 } ( y ) $ is some subset of the group $ \ mathcal { d } ( y ) $ of deck transformations of $ y $ for a fixed lifting $ \ tilde { f } _ 0 $ of $ f $ with respect to universal coverings of $ x $ and $ y $, respectively. | arxiv:1708.04708 |
this article aims to provide insights into the qualitative analysis of some nonlinear reaction - diffusion ( rd ) systems arising in neuroscience. we first introduce a non - homogeneous fitzhugh - nagumo ( nhfhn ) featuring excitability and oscillatory properties. then, we discuss the qualitative analysis of a toy model related to nhfhn. in particular, we focus on the convergence of solutions of the toy model toward different solutions ( fixed point, periodic ) and show the existence of a cascade of hopf bifurcations. finally, we connect this analysis to the nhfhn system. | arxiv:1903.05754 |
complex network formalism allows to explain the behavior of systems composed by interacting units. several prototypical network models have been proposed thus far. the small - world model has been introduced to mimic two important features observed in real - world systems : i ) local clustering and ii ) the possibility to move across a network by means of long - range links that significantly reduce the characteristic path length. a natural question would be whether there exist several " types " of small - world architectures, giving rise to a continuum of models with properties ( partially ) shared with other models belonging to different network families. here, we take advantage of the interplay between network theory and time series analysis and propose to investigate small - world signatures in complex networks by analyzing multifractal characteristics of time series generated from such networks. in particular, we suggest that the degree of right - sided asymmetry of multifractal spectra is linked with the degree of small - worldness present in networks. this claim is supported by numerical simulations performed on several parametric models, including prototypical small - world networks, scale - free, fractal and also real - world networks describing protein molecules. our results also indicate that right - sided asymmetry emerges with the presence of the following topological properties : low edge density, low average shortest path, and high clustering coefficient. | arxiv:1705.07801 |
knowledge distillation ( kd ) in transformers often faces challenges due to misalignment in the number of attention heads between teacher and student models. existing methods either require identical head counts or introduce projectors to bridge dimensional gaps, limiting flexibility and efficiency. we propose squeezing - heads distillation ( shd ), a novel approach that enables seamless knowledge transfer between models with varying head counts by compressing multi - head attention maps via efficient linear approximation. unlike prior work, shd eliminates alignment barriers without additional parameters or architectural modifications. our method dynamically approximates the combined effect of multiple teacher heads into fewer student heads, preserving fine - grained attention patterns while reducing redundancy. experiments across language ( llama, gpt ) and vision ( dit, mdt ) generative and vision ( deit ) discriminative tasks demonstrate shd ' s effectiveness : it outperforms logit - based and feature - alignment kd baselines, achieving state - of - the - art results in image classification, image generation language fine - tuning, and language pre - training. the key innovations of flexible head compression, projector - free design, and linear - time complexity make shd a versatile and scalable solution for distilling modern transformers. this work bridges a critical gap in kd, enabling efficient deployment of compact models without compromising performance. | arxiv:2502.07436 |
we introduce and study the number of tilings of unit height rectangles with irrational tiles. we prove that the class of sequences of these numbers coincides with the class of diagonals of n - rational generating functions and a class of certain binomial multisums. we then give asymptotic applications and establish connections to hypergeometric functions and catalan numbers. | arxiv:1407.8222 |
the model of programs over ( finite ) monoids, introduced by barrington and th \ ' erien, gives an interesting way to characterise the circuit complexity class $ \ mathsf { nc ^ 1 } $ and its subclasses and showcases deep connections with algebraic automata theory. in this article, we investigate the computational power of programs over monoids in $ \ mathbf { j } $, a small variety of finite aperiodic monoids. first, we give a fine hierarchy within the class of languages recognised by programs over monoids from $ \ mathbf { j } $, based on the length of programs but also some parametrisation of $ \ mathbf { j } $. second, and most importantly, we make progress in understanding what regular languages can be recognised by programs over monoids in $ \ mathbf { j } $. to this end, we introduce a new class of restricted dot - depth one languages, threshold dot - depth one languages. we show that programs over monoids in $ \ mathbf { j } $ actually can recognise all languages from this class, using a non - trivial trick, and conjecture that threshold dot - depth one languages with additional positional modular counting suffice to characterise the regular languages recognised by programs over monoids in $ \ mathbf { j } $. finally, using a result by j. c. costa, we give an algebraic characterisation of threshold dot - depth one languages that supports that conjecture and is of independent interest. | arxiv:1912.07992 |
we report secondary eclipse photometry of the hot jupiter xo - 3b in the 4. 5 ~ $ \ mu $ m band taken with the infrared array camera ( irac ) on the spitzer space telescope. we measure individual eclipse depths and center of eclipse times for a total of twelve secondary eclipses. we fit these data simultaneously with two transits observed in the same band in order to obtain a global best - fit secondary eclipse depth of $ 0. 1580 \ pm 0. 0036 \ % $ and a center of eclipse phase of $ 0. 67004 \ pm 0. 00013 $. we assess the relative magnitude of variations in the dayside brightness of the planet by measuring the size of the residuals during ingress and egress from fitting the combined eclipse light curve with a uniform disk model and place an upper limit of 0. 05 $ \ % $. the new secondary eclipse observations extend the total baseline from one and a half years to nearly three years, allowing us to place an upper limit on the periastron precession rate of $ 2. 9 \ times 10 ^ { - 3 } $ degrees / day the tightest constraint to date on the periastron precession rate of a hot jupiter. we use the new transit observations to calculate improved estimates for the system properties, including an updated orbital ephemeris. we also use the large number of secondary eclipses to obtain the most stringent limits to date on the orbit - to - orbit variability of an eccentric hot jupiter and demonstrate the consistency of multiple - epoch spitzer observations. | arxiv:1407.1313 |
there are no limits for the speeds of light and particles in general relativity ( gr ). four examples illustrate this basic result, which is too often neglected. | arxiv:1201.0114 |
correlation matrices are the sub - class of positive definite real matrices with all entries on the diagonal equal to unity. earlier work has exhibited a parametrisation of the corresponding cholesky factorisation in terms of partial correlations, and also in terms of hyperspherical co - ordinates. we show how the two are relating, starting from the definition of the partial correlations in terms of the schur complement. we extend this to the generalisation of correlation matrices to the cases of complex and quaternion entries. as in the real case, we show how the hyperspherical parametrisation leads naturally to a distribution on the space of correlation matrices $ \ { r \ } $ with probability density function proportional to $ ( \ det r ) ^ a $. for certain $ a $, a construction of random correlation matrices realising this distribution is given in terms of rectangular standard gaussian matrices. | arxiv:1812.07685 |
a new quantum ontology of quantum mechanics has been proposed recently. this ontology is based on impossible to realize measurements which need to be performed repeatedly on the same single physical system or on the same pair of physical systems. we agree that quantum mechanics is a contextual theory and that the experimental contexts have to be a part of any description of quantum phenomena but in our opinion this new ontology is neither convincing nor useful. in particular the authors claim that their ontology explains the peaceful coexistence between quantum mechanics and relativity in spin polarization correlation experiments. we show that, contrary to their claim, the authors are unable to explain why strong correlations, between the outcomes of distant local measurements, do exist and why they preserve a condition of parameter independence ( non - signaling ). strangely enough the authors ignore that these strong but imperfect correlations can be explained in a local and causal way using statistical contextual interpretation of quantum mechanics what was demonstrated in several articles. | arxiv:1602.03495 |
when a square tube is brought in contact with bulk liquid, the liquid wets the corners of the tube, and creates finger - like wetted region. the wetting of the liquid then takes place with the growth of two parts, the bulk part where the cross section is entirely filled with the liquid and the finger part where the cross section of the tube is partially filled. in the previous works, the growth of these two parts has been discussed separately. here we conduct the analysis by explicitly accounting for the coupling of the two parts. we propose coupled equations for the liquid imbibition in both parts and show that ( a ) the length of each part, $ h _ 0 $ and $ h _ 1 $, both increases in time $ t $ following the lucas - washburn ' s law, $ h _ 0 \ sim t ^ { 1 / 2 } $ and $ h _ 1 \ sim t ^ { 1 / 2 } $, but that ( b ) the coefficients are different from those obtained in the previous analysis which ignored the coupling. | arxiv:1810.12487 |
two dimensional ( 2d ) materials provide a unique platform to explore the full potential of magnetic proximity driven phenomena, which can be further used for applications in next generation spintronic devices. of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene / ferromagnetic - insulator ( fmi ) heterostructures. here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to fmi magnetization. owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. this is manifested as an unusually strong temperature dependence of the non - local spin signals in graphene, which is due to spin relaxation by thermally - induced transverse fluctuations of the fmi magnetization. | arxiv:1610.08017 |
we report the magnetic field dependence of resistivity ( $ \ rho $ ) and specific heat ( $ c $ ) for the non - superconducting prfeaso compound. our study shows a hitherto unobserved anomaly at $ t _ { sr } $ in the resistivity and specific heat data which arises as a result of the interplay of antiferromagnetic ( afm ) pr and fe sublattices. below the afm transition temperature ( $ t _ n ^ { \ rm { pr } } $ ), pr moment orders along the crystallographic c axis and its effect on the iron subsystem causes a reorientation of the ordered inplane fe moments in a direction out of the $ ab $ plane. application of magnetic field introduces disorder in the afm pr sublattice, which, in turn, reduces the out - of - plane pr - fe exchange interaction responsible for fe spin reorientation. both in $ \ rho $ ( $ t $ ) and $ d ( c / t ) / dt $ curves, the peak at $ t _ { sr } $ broadens with the increase of $ h $ due to the introduction of the disorder in the afm pr sublattice by magnetic field. in $ \ rho $ ( $ t $ ) curve, the peak shifts towards lower temperature with $ h $ and disappears above 6 t while in $ d ( c / t ) / dt $ curve the peak remains visible up to 14 t. the broadening of the anomaly at $ t _ n ^ { \ rm { pr } } $ in $ c ( t ) $ with increasing $ h $ further confirms that magnetic field induces disorder in the afm pr sublattice. | arxiv:1110.6266 |
in this article we study analogues of the weak expectation property of discrete group c * - algebras and their crossed products, in the discrete quantum group setting, i. e., discrete quantum group c * - algebras and crossed products of c * - algebras with amenable discrete quantum groups. | arxiv:2208.14009 |
lindenbaum method is named after the polish logician adolf lindenbaum who prematurely and without a clear trace disappeared in the turmoil of the second world war at the age of about 37. the method is based on the symbolic nature of formalized languages of deductive systems and opens a gate for applications of algebra to logic and, thereby, to abstract algebraic logic. | arxiv:1609.07379 |
phase diagram of the spin - 1 quantum heisenberg model with both exchange as well as single - ion anisotropy is constructed within the framework of pair approximation formulated as a variational procedure based on the gibbs - bogoliubov inequality. in this form adapted variational approach is used to obtain the results equivalent with the oguchi ' s pair approximation. it is shown that the single - ion anisotropy induces a tricritical behaviour in the considered model system and a location of tricritical points is found in dependence on the exchange anisotropy strength. | arxiv:cond-mat/0611254 |
algebras of generalized functions offer possibilities beyond the purely distributional approach in modelling singular quantities in non - smooth differential geometry. this article presents an introductory survey of recent developments in this field and highlights some applications in mathematical physics. | arxiv:math/0312487 |
this study addresses limited attention allocation in a stochastic linear quadratic system with multiplicative noise. our approach enables strategic resource allocation to enhance noise estimation and improve control decisions. we provide analytical optimal control and propose a numerical method for optimal attention allocation. additionally, we apply our ffndings to dynamic mean - variance portfolio selection, showing effective resource allocation across time periods and factors, providing valuable insights for investors. | arxiv:2403.18528 |
best practices for high conflict conversations like counseling or customer support almost always include recommendations to paraphrase the previous speaker. although paraphrase classification has received widespread attention in nlp, paraphrases are usually considered independent from context, and common models and datasets are not applicable to dialog settings. in this work, we investigate paraphrases in dialog ( e. g., speaker 1 : " that book is mine. " becomes speaker 2 : " that book is yours. " ). we provide an operationalization of context - dependent paraphrases, and develop a training for crowd - workers to classify paraphrases in dialog. we introduce a dataset with utterance pairs from npr and cnn news interviews annotated for context - dependent paraphrases. to enable analyses on label variation, the dataset contains 5, 581 annotations on 600 utterance pairs. we present promising results with in - context learning and with token classification models for automatic paraphrase detection in dialog. | arxiv:2404.06670 |
in a unified system of passive radar and communication systems of joint transmitter platform, information intended for a communication receiver may be eavesdropped by a passive radar receiver ( rr ), thereby undermining the security of communications system. to minimize this information security risk, in this paper, we propose a unified passive radar and communications system wherein the signal - to - interference and noise ratio ( sinr ) at the rr is maximized while ensuring that the information secrecy rate is above a certain threshold value. we consider both scenarios wherein transmissions of the radar waveform and information signals are scheduled with the disjoint ( non - overlapping case ) as well as with the same set of resources ( overlapping case ). in both cases, the underlying optimization problems are non - convex. in the former case, we propose alternating optimization ( ao ) techniques that employ semidefinite programming and computationally efficient semi - analytical approaches. in the latter case, ao method based on semi - definite relaxation approach is proposed to solve the optimization problem. by changing the threshold value of the information secrecy rate, we then characterize the performance tradeoff between passive radar and communication systems with the boundaries of the sinr - secrecy capacity regions. the performance comparison of the proposed optimization methods demonstrate the importance of the semi - analytical approach and the advantage of overlapping case over non - overlapping one. | arxiv:1808.09527 |
we define an elementary relatively $ \ mathbb z / 4 $ graded lagrangian - floer chain complex for restricted immersions of compact 1 - manifolds into the pillowcase, and apply it to the intersection diagram obtained by taking traceless $ su ( 2 ) $ character varieties of 2 - tangle decompositions of knots. calculations for torus knots are explained in terms of pictures in the punctured plane. the relation to the reduced instanton homology of knots is explored. | arxiv:1501.00028 |
a com - prelie bialgebra is a commutative bialgebra with an extra prelie product satisfying some compatibilities with the product and coproduct. we here give a classification of connected, cocommutative com - prelie bialgebras over a field of characteristic zero : we obtain a main family of symmetric algebras on a space v of any dimension, and another family available only if v is one - dimensional. we also explore the case of com - prelie bialgebras over a group algebra and over a tensor product of a group algebra and of a symmetric algebra. | arxiv:1802.08171 |
we investigate the [ o ii ] emission line properties of 18, 508 quasars at z < 1. 6 drawn from the sloan digital sky survey ( sdss ) quasar sample. the quasar sample has been separated into 1, 692 radio - loud and 16, 816 radio - quiet quasars ( rlqs and rqqs hereafter ) matched in both redshift and i ' - band absolute magnitude. we use the [ o ii ] \ lambda3726 + 3729 line as an indicator of star formation. based on these measurements we find evidence that star - formation activity is higher in the rlq population. the mean equivalent widths ( ew ) for [ o ii ] are ew ( [ o ii ] ) _ rl = 7. 80 \ pm0. 30 \ aa, and ew ( [ o ii ] ) _ rq = 4. 77 \ pm0. 06 \ aa, for the rlq and rqq samples respectively. the mean [ o ii ] luminosities are \ log [ l ( [ o ii ] ) _ rl / w ] = 34. 31 \ pm0. 01 and \ log [ l ( [ o ii ] ) _ rq / w ] = 34. 192 \ pm0. 004 for the samples of rlqs and rqqs respectively. finally, to overcome possible biases in the ew measurements due to the continuum emission below the [ o ii ] line being contaminated by young stars in the host galaxy, we use the ratio of the [ o ii ] luminosity to rest - frame i ' - band luminosity, in this case, we find for the rlqs \ log [ l ( [ o ii ] ) _ rl / l _ opt ] = - 3. 89 \ pm0. 01 and \ log [ l ( [ o ii ] ) _ rq / l _ opt ] = - 4. 011 \ pm0. 004 for rqqs. however the results depend upon the optical luminosity of the quasar. rlqs and rqqs with the same high optical luminosity \ log ( l _ opt / w ) > 38. 6, tend to have the same level of [ o ii ] emission. on the other hand, at lower optical luminosities \ log ( l _ opt / w ) < 38. 6, there is a clear [ o ii ] | arxiv:1209.2329 |
we study the critical effect of quarantine on the propagation of epidemics on an adaptive network of social contacts. for this purpose, we analyze the susceptible - infected - recovered ( sir ) model in the presence of quarantine, where susceptible individuals protect themselves by disconnecting their links to infected neighbors with probability w, and reconnecting them to other susceptible individuals chosen at random. starting from a single infected individual, we show by an analytical approach and simulations that there is a phase transition at a critical rewiring ( quarantine ) threshold w _ c separating a phase ( w < w _ c ) where the disease reaches a large fraction of the population, from a phase ( w > = w _ c ) where the disease does not spread out. we find that in our model the topology of the network strongly affects the size of the propagation, and that w _ c increases with the mean degree and heterogeneity of the network. we also find that w _ c is reduced if we perform a preferential rewiring, in which the rewiring probability is proportional to the degree of infected nodes. | arxiv:1010.1514 |
theoretical studies and current observations of the high - redshift intergalactic medium ( igm ) indicate that at least two cosmic transitions occur by the time the universe reaches gas metallicities of about $ 10 ^ { - 3 } $ of solar values. these are the cosmological reionization of the igm, and the transition from a primordial to present - day mode of star formation. we quantify this relation through new calculations of the ionizing radiation produced in association with the elements carbon, oxygen and silicon observed in galactic metal - poor halo stars, which are likely second - generation objects formed in the wake of primordial supernovae. we demonstrate that sufficient ionizing photons per baryon are created by enrichment levels of [ fe / h ] of about - 3 in the environment of metal - poor halo stars to provide the optical depth in the cosmic microwave background of about 0. 1 detected by $ wmap $. we show, on a star by star basis, that a genuine cosmic milestone in igm ionization and star formation mode occurred at metallicities of $ 10 ^ { - 4 } $ to $ 10 ^ { - 3 } $ solar in these halo stars. this provides an important link in the chain of evidence for metal - free first stars having dominated the process of reionization by redshift 6. we conclude that many of the fe - poor halo stars formed close to the end of or soon after cosmological reionization, making them the ideal probe of the physical conditions under which the transition from first - to second - generation star formation happened in primordial galaxies. | arxiv:astro-ph/0601002 |
we analyze the low - voltage transport response of large molecular wires bridging graphene electrodes, where the molecules are physisorbed onto the graphene sheets by planar anchor groups. in our study, the sheets are pulled away to vary the gap length and the relative atomic positions. the molecular wires are also translated in directions parallel and perpendicular to the sheets. we show that the energy position of the breit - wigner molecular resonances is universal for a given molecule, in the sense that it is independent of the details of the graphene edges, gaps lengths or of the molecule positions. we discuss the need to converge carefully the k - sampling to provide reasonable values of the conductance. | arxiv:1303.1386 |
we study squeezed quantum states of phonons, which allow the possibility of modulating the quantum fluctuations of atomic displacements below the zero - point quantum noise level of coherent phonon states. we calculate the corresponding expectation values and fluctuations of both the atomic displacement and the lattice amplitude operators, and also investigate the possibility of generating squeezed phonon states using a three - phonon parametric amplification process based on phonon - phonon interactions. furthermore, we also propose a detection scheme based on reflectivity measurements. | arxiv:cond-mat/9609188 |
nonlinearity of density stratification modulates buoyancy effects. we report results from a body - inclusive large eddy simulation ( les ) of a wake in nonlinear stratification, specifically for a circular disk at diameter - based reynolds number ( $ re $ ) of $ 5000 $. five density profiles are considered ; the benchmark has linear stratification and the other four have hyperbolic tangent profiles to model a pycnocline. the disk moves inside the central core of the pycnocline in two of those four cases and, in the other two cases with { a } shifted density profile, the disk moves partially / completely outside the pycnocline. the maximum buoyancy frequency ( $ n _ { max } $ ) for all the profiles is the same. the first part of the study investigates the centered cases. nonuniform stratification results in increasing wake turbulence relative to the benchmark owing to reduced suppression of turbulence production as well as the wave trapping in the pycnocline. steady lee waves are also quantified to understand limitations of linear theory. the second part pays attention to the effect of a relative shift between the pycnocline and the disk. the wake defect velocity decays faster in the cases with a shift. the effect of disk location on the kelvin wake waves ( a family of steady waves within the pycnocline ) and its modal form is obtained and explained by solving the taylor - goldstein equation. the family of unsteady internal gravity waves that are generated by the wake is also studied and the effect of disk shift is quantified. | arxiv:2208.12442 |
1e 0102. 2 - - 7219 ( hereafter e0102 ) is a young supernova remnant ( snr ) in the small magellanic cloud ( smc ). it contains oxygen - rich sn ejecta, a possible neutron star ( ns ), and a small amount of fast - moving h - rich ejecta material. these properties are also seen in cas a, it has thus been suggested that e0102 is also a type iib snr, whose sn progenitor ' s hydrogen envelope was stripped off possibly via interactions with a companion star. to search for a surviving companion of e0102 ' s sn progenitor, we have used archival hubble space telescope ( hst ) continuum images to make photometric measurements of stars projected in the snr to construct color - magnitude diagrams and compare the stars with those expected from surviving companions of type iib sne. we have also used the multi - unit spectroscopic explorer observations taken with the very large telescope to perform spectroscopic analyses of stars and search for peculiar radial velocities as diagnostics of surviving companions. we further use the hst and gaia data to inspect proper motions of stars for complementary kinetic studies. no plausible companion candidates are found if the sn explosion site was near the ns, while the b3 v star 34a may be a plausible companion candidate if the sn explosion site is near the sn ejecta ' s expansion center. if the ns is real and associated with e0102, it needs a ~ 1000 km / s runaway velocity, which has been observed in other snrs and can be acquired from an asymmetric sn explosion or a kick by the sn explosion of a massive companion. | arxiv:2104.04835 |
the paper exploits an isomorphism between the natural numbers n and a space u of periodic sequences of the roots of unity in constructing a recursive procedure for representing and computing the prime numbers. the nth wave number $ { \ bf u } _ n $ is the countable sequence of the nth roots of unity having frequencies k / n for all integer phases k. the space u is closed under a commutative and associative binary operation $ { \ bf u } _ m \ odot { \ bf u } _ n = { \ bf u } _ { mn } $, termed the circular product, and is isomorphic with n under their respective product operators. functions are defined on u that partition wave numbers into two complementary sequences, of which the co - number $ { \ overset { \ bf \ ast } { \ bf u } } _ n $ is a function of a wave number in which zeros replace its positive roots of unity. the recursive procedure $ { \ overset { \ bf \ ast } { \ bf u } } _ { n + 1 } = { \ overset { \ bf \ ast } { \ bf u } } _ { n } \ odot { \ overset { \ bf \ ast } { \ bf u } } _ { { n + 1 } } $ represents prime numbers explicitly in terms of preceding prime numbers, starting with $ p _ 1 = 2 $, and is shown never to terminate. if $ { p } _ 1,..., { p } _ { n + 1 } $ are the first $ n + 1 $ prime phases, then the phases in the range $ p _ { n + 1 } \ leq k < p ^ 2 _ { n + 1 } $ that are associated with the non - zero terms of $ { \ overset { \ bf \ ast } { \ bf u } } _ { n } $ are, together with $ p _ 1,..., p _ n $, all of the prime phases less than $ p ^ 2 _ { n + 1 } $. when applied with all of the primes identified at the previous step, the recursive procedure identifies approximately $ 7 ^ { 2 ( n - 1 ) } / ( 2 ( n - 1 ) ln7 ) $ primes at each iteration for $ n > 1 $. when the phases of wave numbers are represented in modular arithmetic, the prime phases are represent | arxiv:2209.09313 |
$ \ delta $ - machine learning ( $ \ delta $ - ml ) has been shown to effectively and efficiently bring a low - level ml potential energy surface to ccsd ( t ) quality. here we propose extending this approach to general force fields, which implicitly or explicitly contain many - body effects. after describing this general approach, we illustrate it for the mb - pol water potential which contains ccsd ( t ) 2 - body and 3 - body interactions but relies on the ttm4 - f 4 - body and higher body interactions. the 4 - body mb - pol ( ttm4 - f ) interaction fails at a very short range and for the water hexamer errors up to 0. 84 kcal / mol are seen for some isomers, owing mainly to 4 - body errors. we apply $ \ delta $ - ml for the 4 - body interaction, using a recent dataset of ccsd ( t ) 4 - body energies that we used to develop a new water potential, q - aqua. this 4 - body correction is shown to improve the accuracy of the mb - pol potential for the relative energies of 8 isomers of the water hexamer as well as the harmonic frequencies. the new potential is robust in the very short range and so should be reliable for simulations at high pressure and / or high temperature. | arxiv:2206.04254 |
bismuth ( bi ) films hold potential for spintronic devices and topological one - dimensional edge transport. large - area high - quality ( 111 ) bi ultrathin films are grown on insb ( 111 ) b substrates. strong film - substrate interactions epitaxially stabilize the ( 111 ) orientation and lead to inversion symmetry breaking. we resolve the longstanding controversy over the z _ 2 topological assignment of bismuth and show that the surface states are topologically trivial. our results demonstrate that interfacial bonds prevent the semimetal - to - semiconductor transition predicted for freestanding bismuth layers, highlighting the importance of controlled functionalization and surface passivation in two - dimensional materials. | arxiv:2302.00803 |
we say that a finite almost simple $ g $ with socle $ s $ is admissible ( with respect to the spectrum ) if $ g $ and $ s $ have the same sets of orders of elements. let $ l $ be a finite simple linear or unitary group of dimension at least three over a field of odd characteristic. we describe admissible almost simple groups with socle $ l $. also we calculate the orders of elements of the coset $ l \ tau $, where $ \ tau $ is the inverse - transpose automorphism of $ l $. | arxiv:1609.00518 |
racks do not give us invariants of surface - knots in general. for example, if a surface - knot diagram has branch points ( and a rack which we use satisfies some mild condition ), then it admits no rack colorings. in this paper, we investigate rack colorings for surface - knot diagrams without branch points and prove that rack colorings are invariants of $ s ^ 2 $ - knots. we also prove that rack colorings for $ s ^ 2 $ - knots can be interpreted in terms of quandles, and discuss a relationship with regular - equivalences of surface - knot diagrams. | arxiv:1406.3543 |
a study of the semi - analytical approach to four - fermion production in $ e ^ + e ^ - $ annihilation is presented. we classify all possible four - fermion final states and present results of new calculations for the ` basic ' processes with the $ ww, zz $, and $ zh $ off - shell production together with some examples of ` background ' processes. the initial state radiative corrections are included for the basic processes. several numerical examples are given in the energy range from lep2 up to $ \ sqrt { s } = 1 $ tev. | arxiv:hep-ph/9406340 |
we consider the conjecture of chen and nie concerning the space forms for canonical metric connections of compact hermitian manifolds. we verify the conjecture for two special types of hermitian manifolds : complex nilmanifolds with nilpotent $ j $, and non - balanced bismut torsion - parallel manifolds. | arxiv:2501.03032 |
we introduce and analyze a new family of first - order optimization algorithms which generalizes and unifies both mirror descent and dual averaging. within the framework of this family, we define new algorithms for constrained optimization that combines the advantages of mirror descent and dual averaging. our preliminary simulation study shows that these new algorithms significantly outperform available methods in some situations. | arxiv:1910.13742 |
free - text rationales justify model decisions in natural language and thus become likable and accessible among approaches to explanation across many tasks. however, their effectiveness can be hindered by misinterpretation and hallucination. as a perturbation test, we investigate how large language models ( llms ) perform rationale generation under the effects of readability level control, i. e., being prompted for an explanation targeting a specific expertise level, such as sixth grade or college. we find that explanations are adaptable to such instruction, though the requested readability is often misaligned with the measured text complexity according to traditional readability metrics. furthermore, the generated rationales tend to feature medium level complexity, which correlates with the measured quality using automatic metrics. finally, our human annotators confirm a generally satisfactory impression on rationales at all readability levels, with high - school - level readability being most commonly perceived and favored. | arxiv:2407.01384 |
in the previous work, zhang et al. proposed a multi - resolution smoothed particle hydrodynamics ( sph ) method for fluid - structure interactions ( fsi ) with achieving an optimized computational efficiency meanwhile maintaining good numerical robustness and accuracy. in the present paper, this multi - resolution sph framework where different spatial - temporal discretizations are applied for different sub - systems is extended to multi - phase flows involving large density ratio and interacting with rigid or flexible structure. to this end, a simple and efficient multi - phase model is introduced by exploiting different density reinitialization strategies other than applying different formulations to implement mass conservation to the light and heavy phases, respectively, to realize the target of using same artificial speed of sound for the both. to eliminate the unnatural voids and unrealistic phase separation meanwhile decrease the numerical dissipation, the transport velocity formulation are rewritten by applying temporal local flow state dependent background pressure. to handle the fsi coupling in both single - and multi - resolution scenarios in the triple point, the one - sided riemann - based solid boundary condition is adopted. a set of examples involving multi - phase flows with high density ratio and complex interface and multi - phase fsi are studied to demonstrate the efficiency, accuracy and robustness of the present method. the validations presented herein and those reported in the original paper of zhang et al. where single - phase fsi is studied put the present multi - resolution sph framework in good stead in terms of computational efficiency for multi - physics applications. | arxiv:2205.00707 |
scanning devices often produce point clouds exhibiting highly uneven distributions of point samples across the surfaces being captured. different point cloud subsampling techniques have been proposed to generate more evenly distributed samples. poisson - disk sampling approaches assign each sample a cost value so that subsampling reduces to sorting the samples by cost and then removing the desired ratio of samples with the highest cost. unfortunately, these approaches compute the sample cost using pairwise distances of the points within a constant search radius, which is very costly for massive point clouds with uneven densities. in this paper, we revisit poisson - disk sampling for point clouds. instead of optimizing for equal densities, we propose to maximize the distance to the closest point, which is equivalent to estimating the local point density as a value inversely proportional to this distance. this algorithm can be efficiently implemented using k nearest - neighbors searches. besides a kd - tree, our algorithm also uses a voxelization to speed up the searches required to compute per - sample costs. we propose a new strategy to minimize cost updates that is amenable for out - of - core operation. we demonstrate the benefits of our approach in terms of performance, scalability, and output quality. we also discuss extensions based on adding orientation - based and color - based terms to the cost function. | arxiv:2311.17604 |
in 1993, chemin proved that vorticity possessing negative holder regularity in directions given by a sufficient family of vector fields ( striated regularity ) maintains such regularity for all time when measured against the push - forward of those vector fields. later work of gamblin and saint raymond, and of danchin, established analogous results in higher dimension. we give an alternative proof of these results, and establish the propagation of striated regularity of the lagrangian velocity in a positive holder space. | arxiv:1508.01915 |
we report on recent developments in the integration of optical microresonators into atom chips and describe some fabrication and implementation challenges. we also review theoretical proposals for quantum computing with single atoms based on the observation of photons leaking through the cavity mirrors. the use of measurements to generate entanglement can result in simpler, more robust and scalable quantum computing architectures. indeed, we show that quantum computing with atom - cavity systems is feasible even in the presence of relatively large spontaneous decay rates and finite photon detector efficiencies. | arxiv:quant-ph/0607197 |
we investigate the magnetic - field effects on a two - orbital hubbard model that describes multiple spin states. cobalt oxides have been investigated as materials possessing spin - state degrees of freedom due to the interplay between the hund coupling interaction and crystalline field effect. in the competing region, quantum hybridizations between distinct spin states are expected to emerge, corresponding to excitonic condensation. applied magnetic fields could also induce such a competition. to understand magnetic - field effects on excitonic condensation in multi - orbital systems, it is crucial to account for contributions from both spin and orbital degrees of freedom to magnetic properties. here, we study field - induced phenomena in the two - orbital hubbard model by focusing on the role of the orbital angular momentum. we comprehensively analyze this model on a square lattice employing the hartree - fock approximation. omitting contributions from the orbital moment, we find that an applied magnetic field gives rise to two excitonic phases, besides the spin - state ordered phase, between the nonmagnetic low - spin and spin - polarized high - spin phases. one of these excitonic phases manifests a staggered - type spin - state order, interpreted as an excitonic supersolid state. conversely, the other phase is not accompanied by it and exhibits only a spin polarization due to the applied magnetic field. when spin - orbit coupling is present, this phase displays a ferrimagnetic spin alignment attributed to spin anisotropy. our analysis also reveals that incorporating the contribution of the orbital magnetic moment to the zeeman term significantly alters the overall structure of the phase diagram. notably, the orbital magnetization destabilizes the excitonic phase in contrast to scenarios without this contribution. we also discuss the relevance of our findings to real materials, such as cobalt oxides. | arxiv:2311.13191 |
we consider theoretically transport in a spinfull one - channel interacting quantum wire placed in an external magnetic field. for the case of two point - like impurities embedded in the wire, under a small voltage bias the spin - polarized current occurs at special points in the parameter space, tunable by a single parameter. at sufficiently low temperatures complete spin - polarization may be achieved, provided repulsive interaction between electrons is not too strong. | arxiv:0909.0025 |
it is shown that tight closure commutes with localization in any two dimensional ring $ r $ of prime characteristic if either $ r $ is a nagata ring or $ r $ possesses a weak test element. moreover, it is proved that tight closure commutes with localization at height one prime ideals in any ring of prime characteristic. | arxiv:math/0502076 |
the gessel number $ p ( n, r ) $ is the number of the paths in plane with $ ( 1, 0 ) $ and $ ( 0, 1 ) $ steps from $ ( 0, 0 ) $ to $ ( n + r, n + r - 1 ) $ that never touch any of the points from the set $ \ { ( x, x ) \ in \ mathbb { z } ^ 2 : x \ geq r \ } $. we show that there is a close relationship between the gessel numbers $ p ( n, r ) $ and the super catalan numbers $ s ( n, r ) $. by using new sums, we prove that an alternating convolution of the gessel numbers $ p ( n, r ) $ is always divisible by \ frac { 1 } { 2 } $ s ( n, r ) $. | arxiv:2206.03808 |
we give a new inequality between the energy of a graph and a weighted sum over the edges of the graph. using this inequality we prove that $ \ mathcal { e } ( g ) \ geq 2r ( h ) $, where $ \ mathcal { e } ( g ) $ is the energy of a graph $ g $ and $ r ( h ) $ is the randi \ ' c index of any subgraph of $ g $ ( not necessarily induced ). in particular, this generalizes well - known inequalities $ \ mathcal { e } ( g ) \ geq 2r ( g ) $ and $ \ mathcal { e } ( g ) \ geq 2 \ mu ( g ) $ where $ \ mu ( g ) $ is the matching number. we give other inequalities as applications to this result. | arxiv:2406.03561 |
deep learning - based cardiac segmentation has seen significant advancements over the years. many studies have tackled the challenge of anatomically incorrect segmentation predictions by introducing auxiliary modules. these modules either post - process segmentation outputs or enforce consistency between specific points to ensure anatomical correctness. however, such approaches often increase network complexity, require separate training for these modules, and may lack robustness in scenarios with poor visibility. to address these limitations, we propose a novel transformer - based architecture that leverages dense associative networks to learn and retain specific patterns inherent to cardiac inputs. unlike traditional methods, our approach restricts the network to memorize a limited set of patterns. during forward propagation, a weighted sum of these patterns is used to enforce anatomical correctness in the output. since these patterns are input - independent, the model demonstrates enhanced robustness, even in cases with poor visibility. the proposed pipeline was evaluated on two publicly available datasets, camus and cardiacnet. experimental results indicate that our model consistently outperforms baseline approaches across all metrics, highlighting its effectiveness and reliability for cardiac segmentation tasks. | arxiv:2502.15128 |
quantum fourier transformation is important in many quantum algorithms. in this paper, we generalize quantum fourier transformation over the abelian group $ \ mathbb { z } _ n $ from two different points to get more efficient unitary transformations. the obtained unitary transformations are given in concise and explicit formula which can be used directly. a relationship between the generalized quantum fourier transformation and the dihedral hidden subgroup problem are discussed in this paper. this may lead a way to solve the dihedral hidden subgroup problem. the second goal of this paper is to give an explicit formula of quantum haar transformation. | arxiv:1712.01350 |
human organs constantly undergo anatomical changes due to a complex mix of short - term ( e. g., heartbeat ) and long - term ( e. g., aging ) factors. evidently, prior knowledge of these factors will be beneficial when modeling their future state, i. e., via image generation. however, most of the medical image generation tasks only rely on the input from a single image, thus ignoring the sequential dependency even when longitudinal data is available. sequence - aware deep generative models, where model input is a sequence of ordered and timestamped images, are still underexplored in the medical imaging domain that is featured by several unique challenges : 1 ) sequences with various lengths ; 2 ) missing data or frame, and 3 ) high dimensionality. to this end, we propose a sequence - aware diffusion model ( sadm ) for the generation of longitudinal medical images. recently, diffusion models have shown promising results in high - fidelity image generation. our method extends this new technique by introducing a sequence - aware transformer as the conditional module in a diffusion model. the novel design enables learning longitudinal dependency even with missing data during training and allows autoregressive generation of a sequence of images during inference. our extensive experiments on 3d longitudinal medical images demonstrate the effectiveness of sadm compared with baselines and alternative methods. the code is available at https : / / github. com / ubc - tea / sadm - longitudinal - medical - image - generation. | arxiv:2212.08228 |
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