cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
On the robustness of the adaptive lasso to model misspecification
Creators: name: Fine, J. P.
name: Lu, W.
name: Goldberg, Y.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2012

description: Penalization methods have been shown to yield both consistent variable selection and oracle parameter estimation under correct model specification. In this article, we study such methods under model misspecification, where the assumed form of the regression function is incorrect, including generalized linear models for uncensored outcomes and the proportional hazards model for censored responses. Estimation with the adaptive least absolute shrinkage and selection operator, lasso, penalty is proven to achieve sparse estimation of regression coefficients under misspecification. The resulting estimators are selection consistent, asymptotically normal and oracle, where the selection is based on the limiting values of the parameter estimators obtained using the misspecified model without penalization. We further derive conditions under which the penalized estimators from the misspecified model may yield selection consistency under the true model. The robustness is explored numerically via simulation and an application to the Wisconsin Epidemiological Study of Diabetic Retinopathy.
360° Domain Walls: Stability, Magnetic Field and Electric Current Effects
Creators: name: Zhang, Jinshuo
name: Siddiqui, Saima A.
name: Ho, Pin
name: Currivan-Incorvia, Jean Anne
name: Tryputen, Larysa
name: Lage, Enno
name: Bono, David C.
name: Baldo, Marc A.
name: Ross, Caroline A.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The formation of 360° magnetic domain walls (360DWs) in Co and Ni80Fe20 thin film wires was demonstrated experimentally for different wire widths, by successively injecting two 180° domain walls (180DWs) into the wire. For narrow wires (less than 50 nm wide for Co), edge roughness prevented the combination of the 180DWs into a 360DW, and for wide wires (200 nm for Co) the 360DW collapsed, but over an intermediate range of wire widths, reproducible 360DW formation occurred. The annihilation and dissociation of 360DWs was demonstrated by applying a magnetic field parallel to the wire, showing that annihilation fields were several times higher than dissociation fields in agreement with micromagnetic modeling. The annihilation of a 360DW by current pulsing was demonstrated.
description: 17 pages, 6 figures
Predictive accuracy of covariates for event times
Creators: name: Lin, D. Y.
name: Chen, Li
name: Zeng, Donglin
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2012

description: We propose a graphical measure, the generalized negative predictive function, to quantify the predictive accuracy of covariates for survival time or recurrent event times. This new measure characterizes the event-free probabilities over time conditional on a thresholded linear combination of covariates and has direct clinical utility. We show that this function is maximized at the set of covariates truly related to event times and thus can be used to compare the predictive accuracy of different sets of covariates. We construct nonparametric estimators for this function under right censoring and prove that the proposed estimators, upon proper normalization, converge weakly to zero-mean Gaussian processes. To bypass the estimation of complex density functions involved in the asymptotic variances, we adopt the bootstrap approach and establish its validity. Simulation studies demonstrate that the proposed methods perform well in practical situations. Two clinical studies are presented.
A Feshbach resonance in collisions between ultracold ground state molecules
Creators: name: Park, Juliana J.
name: Lu, Yu-Kun
name: Jamison, Alan O.
name: Tscherbul, Timur
name: Ketterle, Wolfgang
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Atomic Physics (physics.atom-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Collisional resonances are an important tool which has been used to modify interactions in ultracold gases, for realizing novel Hamiltonians in quantum simulations, for creating molecules from atomic gases and for controlling chemical reactions. So far, such resonances have been observed for atom-atom collisions, atom-molecule collisions and collisions between Feshbach molecules which are very weakly bound. Whether such resonances exist for ultracold ground state molecules has been debated due to the possibly high density of states and/or rapid decay of the resonant complex. Here we report a very pronounced and narrow (25 mG) Feshbach resonance in collisions between two ground state NaLi molecules. This molecular Feshbach resonance has two special characteristics. First, the collisional loss rate is enhanced by more than two orders of magnitude above the background loss rate which is saturated at the $p$-wave universal value, due to strong chemical reactivity. Second, the resonance is located at a magnetic field where two open channels become nearly degenerate. This implies the intermediate complex predominantly decays to the second open channel. We describe the resonant loss feature using a model with coupled modes which is analogous to a Fabry-Pérot cavity. Our observations prove the existence of long-lived coherent intermediate complexes even in systems without reaction barriers and open up the possibility of coherent control of chemical reactions.
Helicity Selection of the Cycloidal Order in Noncentrosymmetric EuIrGe$_3$
Creators: name: Kurauchi, Kenshin
name: Matsumura, Takeshi
name: Tsukagoshi, Mitsuru
name: Higa, Nonoka
name: Kakihana, Masashi
name: Hedo, Masato
name: Nakama, Takao
name: Ōnuki, Yoshichika
Publisher: name: arXiv
Year: 2023
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: The magnetic helicities of the cycloidal ordering in EuIrGe$_3$, with a noncentrosymmetric tetragonal structure, have been studied by circularly polarized resonant X-ray diffraction. It is shown that the helicity of each cycloidal domain is uniquely determined and satisfies the symmetry relations of the $C_{4v}$ point group of the crystal structure. The result shows that the cycloidal helicity is determined by the Dzyaloshinskii-Moriya type antisymmetric exchange interaction. The domain selection and the phase transition by the external magnetic field along [100] and [110] have also been studied. It is shown that the cycloidal plane prefers to be perpendicular to the field and the transverse conical state is realized.
description: 6 pages, 4 figures, 5 figures in the supplemental material, accepted for publication in J. Phys. Soc. Jpn
Girsanov theory under a finite entropy condition
Creators: name: Léonard, Christian
Publisher: name: arXiv
Year: 2011
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: This paper is about Girsanov's theory. It (almost) doesn't contain new results but it is based on a simplified new approach which takes advantage of the (weak) extra requirement that some relative entropy is finite. Under this assumption, we present and prove all the standard results pertaining to the absolute continuity of two continuous-time processes with or without jumps. We have tried to give as much as possible a self-contained presentation. The main advantage of the finite entropy strategy is that it allows us to replace martingale representation results by the simpler Riesz representations of the dual of a Hilbert space (in the continuous case) or of an Orlicz function space (in the jump case).
(102944) Florence Ellen Imber
Creators: name: Professions, Victorian
Publisher: name: University of Oxford
Year: 2022
Subjects: subject: 220201 Business and Labour History
subject: FOS: Philosophy, ethics and religion
subject: History
subject: 140203 Economic History
subject: FOS: Economics and business

description: This three-year research project began in January 2014 and investigated whether, during the Victorian period, the professions formed a distinct self-sustaining social group with its own mores and values. The project looked at 16,000 individuals drawn from census data for Alnwick, Brighton, Bristol, Dundee, Greenock, Leeds, Merthyr Tydfil, Morpeth, and Winchester. The research project was funded by the UK Economic & Social Research Council and was based at the Universities of Oxford and Northumbria.
Generalized quantum phase spaces for the $κ$-deformed extended Snyder model
Creators: name: Lukierski, Jerzy
name: Meljanac, Stjepan
name: Mignemi, Salvatore
name: Pachoł, Anna
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: We describe, in an algebraic way, the $κ$-deformed extended Snyder models, that depend on three parameters $β, κ$ and $λ$, which in a suitable algebra basis are described by the de Sitter algebras ${o}(1,N)$. The commutation relations of the algebra contain a parameter $λ$, which is used for the calculations of perturbative expansions. For such $κ$-deformed extended Snyder models we consider the Heisenberg double with dual generalized momenta sector, and provide the respective generalized quantum phase space depending on three parameters mentioned above. Further, we study for these models an alternative Heisenberg double, with the algebra of functions on de Sitter group. In both cases we calculate the formulae for the cross commutation relations between generalized coordinate and momenta sectors, at linear order in $λ$. We demonstrate that in the commutators of quantum space-time coordinates and momenta of the quantum-deformed Heisenberg algebra the terms generated by $κ$-deformation are dominating over $β$-dependent ones for small values of $λ$.
description: 11 pages, no figures, accepted version
More efficient estimators for case-cohort studies
Creators: name: Kim, S.
name: Cai, J.
name: Lu, W.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2013

description: The case-cohort study design, used to reduce costs in large cohort studies, is a random sample of the entire cohort, named the subcohort, augmented with subjects having the disease of interest but not in the subcohort sample. When several diseases are of interest, several case-cohort studies may be conducted using the same subcohort, with each disease analyzed separately, ignoring the additional exposure measurements collected on subjects with the other diseases. This is not an efficient use of the data, and in this paper, we propose more efficient estimators. We consider both joint and separate analyses for the multiple diseases. We propose an estimating equation approach with a new weight function, and we establish the consistency and asymptotic normality of the resulting estimator. Simulation studies show that the proposed methods using all available information gain efficiency. We apply our proposed method to the data from the Busselton Health Study.
(102943) Arthur Victor Lloyd
Creators: name: Professions, Victorian
Publisher: name: University of Oxford
Year: 2022
Subjects: subject: 220201 Business and Labour History
subject: FOS: Philosophy, ethics and religion
subject: History
subject: 140203 Economic History
subject: FOS: Economics and business

description: This three-year research project began in January 2014 and investigated whether, during the Victorian period, the professions formed a distinct self-sustaining social group with its own mores and values. The project looked at 16,000 individuals drawn from census data for Alnwick, Brighton, Bristol, Dundee, Greenock, Leeds, Merthyr Tydfil, Morpeth, and Winchester. The research project was funded by the UK Economic & Social Research Council and was based at the Universities of Oxford and Northumbria.
Continuity as a computational effect
Creators: name: Neves, Renato
name: Barbosa, Luis S.
name: Hofmann, Dirk
name: Martins, Manuel A.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Logic in Computer Science (cs.LO)
subject: Software Engineering (cs.SE)
subject: FOS: Computer and information sciences

description: The original purpose of component-based development was to provide techniques to master complex software, through composition, reuse and parametrisation. However, such systems are rapidly moving towards a level in which software becomes prevalently intertwined with (continuous) physical processes. A possible way to accommodate the latter in component calculi relies on a suitable encoding of continuous behaviour as (yet another) computational effect. This paper introduces such an encoding through a monad which, in the compositional development of hybrid systems, may play a role similar to the one played by the 1+, powerset, and distribution monads in the characterisation of partial, non deterministic and probabilistic components, respectively. This monad and its Kleisli category provide a setting in which the effects of continuity over (different forms of) composition can be suitably studied.
description: Journal of Logical and Algebraic Methods in Programming, 2016
A survey of the Schrödinger problem and some of its connections with optimal transport
Creators: name: Léonard, Christian
Publisher: name: arXiv
Year: 2013
Subjects: subject: Probability (math.PR)
subject: Functional Analysis (math.FA)
subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: This article is aimed at presenting the Schrödinger problem and some of its connections with optimal transport. We hope that it can be used as a basic user's guide to Schrödinger problem. We also give a survey of the related literature. In addition, some new results are proved.
description: To appear in Discrete \& Continuous Dynamical Systems - Series A. Special issue on optimal transport
(102942) Winifred Daisy Ethel Lloyd
Creators: name: Professions, Victorian
Publisher: name: University of Oxford
Year: 2022
Subjects: subject: 220201 Business and Labour History
subject: FOS: Philosophy, ethics and religion
subject: History
subject: 140203 Economic History
subject: FOS: Economics and business

description: This three-year research project began in January 2014 and investigated whether, during the Victorian period, the professions formed a distinct self-sustaining social group with its own mores and values. The project looked at 16,000 individuals drawn from census data for Alnwick, Brighton, Bristol, Dundee, Greenock, Leeds, Merthyr Tydfil, Morpeth, and Winchester. The research project was funded by the UK Economic & Social Research Council and was based at the Universities of Oxford and Northumbria.
(102941) Mabel Agnes Lloyd
Creators: name: Professions, Victorian
Publisher: name: University of Oxford
Year: 2022
Subjects: subject: 220201 Business and Labour History
subject: FOS: Philosophy, ethics and religion
subject: History
subject: 140203 Economic History
subject: FOS: Economics and business

description: This three-year research project began in January 2014 and investigated whether, during the Victorian period, the professions formed a distinct self-sustaining social group with its own mores and values. The project looked at 16,000 individuals drawn from census data for Alnwick, Brighton, Bristol, Dundee, Greenock, Leeds, Merthyr Tydfil, Morpeth, and Winchester. The research project was funded by the UK Economic & Social Research Council and was based at the Universities of Oxford and Northumbria.
Nonparametric estimation of the mean function for recurrent event data with missing event category
Creators: name: Fine, Jason P.
name: Cai, Jianwen
name: Lai, Huichuan J.
name: Lin, Feng Chang
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2013

description: Recurrent event data frequently arise in longitudinal studies when study subjects possibly experience more than one event during the observation period. Often, such recurrent events can be categorized. However, part of the categorization may be missing due to technical difficulties. If the event types are missing completely at random, then a complete case analysis may provide consistent estimates of regression parameters in certain regression models, but estimates of the baseline event rates are generally biased. Previous work on nonparametric estimation of these rates has utilized parametric missingness models. In this paper, we develop fully nonparametric methods in which the missingness mechanism is completely unspecified. Consistency and asymptotic normality of the nonparametric estimators of the mean event functions accommodate nonparametric estimators of the event category probabilities, which converge more slowly than the parametric rate. Plug-in variance estimators are provided and perform well in simulation studies, where complete case estimators may exhibit large biases and parametric estimators generally have a larger mean squared error when the model is misspecified. The proposed methods are applied to data from a cystic fibrosis registry.
A double-edged sword: Benefits and pitfalls of heterogeneous punishment in evolutionary inspection games
Creators: name: Perc, Matjaz
name: Szolnoki, Attila
Publisher: name: arXiv
Year: 2015
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Adaptation and Self-Organizing Systems (nlin.AO)
subject: Populations and Evolution (q-bio.PE)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: As a simple model for criminal behavior, the traditional two-strategy inspection game yields counterintuitive results that fail to describe empirical data. The latter shows that crime is often recurrent, and that crime rates do not respond linearly to mitigation attempts. A more apt model entails ordinary people who neither commit nor sanction crime as the third strategy besides the criminals and punishers. Since ordinary people free-ride on the sanctioning efforts of punishers, they may introduce cyclic dominance that enables the coexistence of all three competing strategies. In this setup ordinary individuals become the biggest impediment to crime abatement. We therefore also consider heterogeneous punisher strategies, which seek to reduce their investment into fighting crime in order to attain a more competitive payoff. We show that this diversity of punishment leads to an explosion of complexity in the system, where the benefits and pitfalls of criminal behavior are revealed in the most unexpected ways. Due to the raise and fall of different alliances no less than six consecutive phase transitions occur in dependence on solely the temptation to succumb to criminal behavior, leading the population from ordinary people-dominated across punisher-dominated to crime-dominated phases, yet always failing to abolish crime completely.
description: 9 two-column pages, 5 figures; accepted for publication in Scientific Reports
Robust analysis of semiparametric renewal process models
Creators: name: Lin, Feng Chang
name: Truong, Young K.
name: Fine, Jason P.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2013

description: A rate model is proposed for a modulated renewal process comprising a single long sequence, where the covariate process may not capture the dependencies in the sequence as in standard intensity models. We consider partial likelihood-based inferences under a semiparametric multiplicative rate model, which has been widely studied in the context of independent and identical data. Under an intensity model, gap times in a single long sequence may be used naively in the partial likelihood with variance estimation utilizing the observed information matrix. Under a rate model, the gap times cannot be treated as independent and studying the partial likelihood is much more challenging. We employ a mixing condition in the application of limit theory for stationary sequences to obtain consistency and asymptotic normality. The estimator's variance is quite complicated owing to the unknown gap times dependence structure. We adapt block bootstrapping and cluster variance estimators to the partial likelihood. Simulation studies and an analysis of a semiparametric extension of a popular model for neural spike train data demonstrate the practical utility of the rate approach in comparison with the intensity approach.
Hyperfine structure of P-states in muonic deuterium
Creators: name: Faustov, R. N.
name: Martynenko, A. P.
name: Martynenko, G. A.
name: Sorokin, V. V.
Publisher: name: arXiv
Year: 2015
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: On the basis of quasipotential approach to the bound state problem in quantum electrodynamics we calculate hyperfine structure intervals Delta E^{hfs}(2P_{1/2}) and Delta E^{hfs}(2P_{3/2}) for P-states in muonic deuterium. The tensor method of projection operators for the calculation of the hyperfine structure of P-states with definite quantum numbers of total atomic momentum F and total muon momentum j in muonic deuterium is formulated. We take into account vacuum polarization, relativistic, quadrupole and structure corrections of orders alpha^4, alpha^5 and alpha^6. The obtained numerical values of hyperfine splittings are useful for the analysis of new experimental data of the CREMA collaboration regarding to muonic deuterium.
description: 21 pages, 2 figures
The optimal power puzzle: scrutiny of the monotone likelihood ratio assumption in multiple testing
Creators: name: Sun, Wenguang
name: Kosorok, Michael R.
name: Cao, Hongyuan
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2013

description: In single hypothesis testing, power is a non-decreasing function of type I error rate; hence it is desirable to test at the nominal level exactly to achieve optimal power. The puzzle lies in the fact that for multiple testing, under the false discovery rate paradigm, such a monotonic relationship may not hold. In particular, exact false discovery rate control may lead to a less powerful testing procedure if a test statistic fails to fulfil the monotone likelihood ratio condition. In this article, we identify different scenarios wherein the condition fails and give caveats for conducting multiple testing in practical settings.
Majorana Neutrinos and Clockworked Yukawa Couplings contribution to non-observation of the rare leptonic decay $ l_{i}\rightarrow l_{j} γ$, Clockwork Photon and Clockwork Graviton
Creators: name: Ghosh, Gayatri
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The clockwork is an extra-dimensional set-up for generating light particles with exponentially suppressed or hierarchical couplings of light particles with N massive states having comparable masses near the threshold scale of the mechanism in theories which contain no small parameters at the fundamental level. We explore the prospect of charged lepton flavour violation (cLFV) in a clockwork framework which encompasses Dirac mass terms as well as Majorana mass terms for the new clockwork fermions. We deive the masses of the non zero clockwork Majorana masses, and new particles in a clockwork framework and for their Yukawa couplings to the lepton doublets, in the framework where the clockwork parameters are universal. When the new clockwork Majorana masses are non zero, neutrino masses are generated as a result from the exchange of heavy messenger particles such as right handed iso$-$singlet neutrinos or iso$ - $triplet scalar bosons known as the seesaw mechanism. In the case of non zero clockwork Majorana masses, owing to the sizable effective Yukawa couplings of the higher mass modes neutrino masses can only be made tiny by conjecturing large Majorana mass in the teraelectron volt range for allthe clockwork gears. This is apparent from the constraints on the mass scale of the clockwork fermions due to the non-observation of the rare cLFV decay $ μ\rightarrow eγ$, $ τ\rightarrow μγ$, $ τ\rightarrow eγ$. A general description of the clockwork mechanism valid for fermions, gauge bosons, and gravitons is discussed here. This mechanism can be implemented with a discrete set of new fields or, in its continuum version, through an extra spatial dimension.
description: 14 pages, 7 figures, presented at NuFact 2022, The 23rd International Workshop on Neutrinos from Accelerators, University of UTAH, USA
Comprehensive analysis of a symbiotic candidate V503 Her
Creators: name: Merc, J.
name: Gális, R.
name: Wolf, M.
name: Dubovský, P. A.
name: Kára, J.
name: Sims, F.
name: Foster, J. R.
name: Medulka, T.
name: Boussin, C.
name: Coffin, J. P.
name: Buil, C.
name: Boyd, D.
name: Montier, J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: V503 Her was previously proposed as an eclipsing symbiotic candidate based on photometric behavior and spectroscopic appearance indicating the composite optical spectrum. To investigate its nature, we analyzed long-term photometric observations covering one hundred years of its photometric history and new low-resolution optical spectroscopic data, supplemented with the multifrequency measurements collected from several surveys and satellites. Based on the analysis presented in this paper, we claim that V503 Her is not an eclipsing binary star. The optical and infrared wavelengths are dominated by a K-type bright giant with an effective temperature of 4 500 K, luminosity of 1 900 L$_\odot$, and sub-solar metallicity on the asymptotic giant branch showing semiregular complex multi-periodic pulsation behavior. V503 Her does not show the characteristics of strongly interacting symbiotic variables, but some pieces of evidence suggest that it could still be one of the 'hidden' accreting-only symbiotic systems. However, the currently available data do not allow us to fully confirm or constrain the parameters of a possible companion.
description: 16 pages, 10 figures, 4 tables; accepted in the Astronomical Journal
Lazy random walks and optimal transport on graphs
Creators: name: Léonard, Christian
Publisher: name: arXiv
Year: 2013
Subjects: subject: Metric Geometry (math.MG)
subject: Probability (math.PR)
subject: FOS: Mathematics

description: This paper is about the construction of displacement interpolations on a discrete metric graph. Our approach is based on the approximation of any optimal transport problem whose cost function is a distance on a discrete graph by a sequence of Schrödinger problems associated with random walks whose jump frequencies tend down to zero. Displacement interpolations are defined as the limit of the time-marginal flows of the solutions to the Schrödinger problems. This allows to work with these interpolations by doing stochastic calculus on the approximating random walks which are regular objects, and then to pass to the limit in a slowing down procedure. The main convergence results are based on Gamma-convergence of entropy minimization problems. As a by-product, we obtain new results about optimal transport on graphs.
Reciprocal processes. A measure-theoretical point of view
Creators: name: Léonard, Christian
name: Roelly, Sylvie
name: Zambrini, Jean-Claude
Publisher: name: arXiv
Year: 2013
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: This is a survey paper about reciprocal processes. The bridges of a Markov process are also Markov. But an arbitrary mixture of these bridges fails to be Markov in general. However, it still enjoys the interesting properties of a reciprocal process. The structures of Markov and reciprocal processes are recalled with emphasis on their time-symmetries. A review of the main properties of the reciprocal processes is presented. Our measure-theoretical approach allows for a unified treatment of the diffusion and jump processes. Abstract results are illustrated by several examples and counter-examples.
Convergence of sample eigenvalues, eigenvectors, and principal component scores for ultra-high dimensional data
Creators: name: Lee, Seunggeun
name: Wright, Fred A.
name: Zou, Fei
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2014

description: The development of high-throughput biomedical technologies has led to increased interest in the analysis of high-dimensional data where the number of features is much larger than the sample size. In this paper, we investigate principal component analysis under the ultra-high dimensional regime, where both the number of features and the sample size increase as the ratio of the two quantities also increases. We bridge the existing results from the finite and the high-dimension low sample size regimes, embedding the two regimes in a more general framework. We also numerically demonstrate the universal application of the results from the finite regime.
Hypothesis testing for band size detection of high-dimensional banded precision matrices
Creators: name: Liu, Yufeng
name: Guo, Jianhua
name: An, Baiguo
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2014

description: Many statistical analysis procedures require a good estimator for a high-dimensional covariance matrix or its inverse, the precision matrix. When the precision matrix is banded, the Cholesky-based method often yields a good estimator of the precision matrix. One important aspect of this method is determination of the band size of the precision matrix. In practice, crossvalidation is commonly used; however, we show that crossvalidation not only is computationally intensive but can be very unstable. In this paper, we propose a new hypothesis testing procedure to determine the band size in high dimensions. Our proposed test statistic is shown to be asymptotically normal under the null hypothesis, and its theoretical power is studied. Numerical examples demonstrate the effectiveness of our testing procedure.
Phase Separation in Wetting Ridges of Sliding Drops on Soft and Swollen Surfaces
Creators: name: Hauer, Lukas
name: Cai, Zhuoyun
name: Vollmer, Doris
name: Pham, Jonathan T.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: Drops in contact with swollen, elastomeric substrates can induce a capillary-mediated phase separation in wetting ridges. Using laser scanning confocal microscopy, we visualize phase separation of oligomeric silicone oil from a crosslinked silicone network during steady-state sliding of water drops. We find an inverse relationship between the oil tip height and the drop sliding speed, which is rationalized by competing transport timescales of oil molecules: separation rate and drop-advection speed. Separation rates in highly swollen networks are as fast as diffusion in pure melts.
Subhalo abundance matching and assembly bias in the EAGLE simulation
Creators: name: Chaves-Montero, Jonás
name: Angulo, Raul E.
name: Schaye, Joop
name: Schaller, Matthieu
name: Crain, Robert A.
name: Furlong, Michelle
name: Theuns, Tom
Publisher: name: arXiv
Year: 2015
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: Subhalo abundance matching (SHAM) is a widely-used method to connect galaxies with dark matter structures in numerical simulations. SHAM predictions agree remarkably well with observations, yet they still lack strong theoretical support. We examine the performance, implementation, and assumptions of SHAM using the EAGLE project simulations. We find that $V_{\rm relax}$, the highest value of the circular velocity attained by a subhalo while it satisfies a relaxation criterion, is the subhalo property that correlates most strongly with galaxy stellar mass ($M_{\rm star}$). Using this parameter in SHAM, we retrieve the real-space clustering of EAGLE to within our statistical uncertainties on scales greater than $2$ Mpc for galaxies with $8.77
description: 20 pages, 14 figures
On the convexity of the entropy along entropic interpolations
Creators: name: Léonard, Christian
Publisher: name: arXiv
Year: 2013
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: Convexity properties of the entropy along displacement interpolations are crucial in the Lott-Sturm-Villani theory of lower bounded curvature of geodesic measure spaces. As discrete spaces fail to be geodesic, an alternate analogous theory is necessary in the discrete setting. Replacing displacement interpolations by entropic ones allows for developing a rigorous calculus, in contrast with Otto's informal calculus. When the underlying state space is a Riemannian manifold, we show that the first and second derivatives of the entropy as a function of time along entropic interpolations are expressed in terms of the standard Bakry-Émery operators $Γ$ and $ Γ_2$. On the other hand, in the discrete setting new operators appear. Our approach is probabilistic; it relies on the Markov property and time reversal. We illustrate these calculations by means of Brownian diffusions on manifolds and random walks on graphs. We also give a new unified proof, covering both the manifold and graph cases, of a logarithmic Sobolev inequality in connection with convergence to equilibrium.
Enhancing Deep Learning Performance of Massive MIMO CSI Feedback
Creators: name: Ji, Sijie
name: Li, Mo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Information Theory (cs.IT)
subject: Artificial Intelligence (cs.AI)
subject: Signal Processing (eess.SP)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: CSI feedback is an important problem of Massive multiple-input multiple-output (MIMO) technology because the feedback overhead is proportional to the number of sub-channels and the number of antennas, both of which scale with the size of the Massive MIMO system. Deep learning-based CSI feedback methods have been widely adopted recently owing to their superior performance. Despite the success, current approaches have not fully exploited the relationship between the characteristics of CSI data and the deep learning framework. In this paper, we propose a jigsaw puzzles aided training strategy (JPTS) to enhance the deep learning-based Massive MIMO CSI feedback approaches by maximizing mutual information between the original CSI and the compressed CSI. We apply JPTS on top of existing state-of-the-art methods. Experimental results show that by adopting this training strategy, the accuracy can be boosted by 12.07% and 7.01% on average in indoor and outdoor environments, respectively. The proposed method is ready to adopt to existing deep learning frameworks of Massive MIMO CSI feedback. Codes of JPTS are available on GitHub for use.
description: This work has been accepted by IEEE ICC 2023. Copyright has been transferred to IEEE
Multicategory angle-based large-margin classification
Creators: name: Zhang, Chong
name: Liu, Yufeng
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2014

description: Large-margin classifiers are popular methods for classification. Among existing simultaneous multicategory large-margin classifiers, a common approach is to learn k different functions for a k-class problem with a sum-to-zero constraint. Such a formulation can be inefficient. We propose a new multicategory angle-based large-margin classification framework. The proposed angle-based classifiers consider a simplex-based prediction rule without the sum-to-zero constraint, and enjoy more efficient computation. Many binary large-margin classifiers can be naturally generalized for multicategory problems through the angle-based framework. Theoretical and numerical studies demonstrate the usefulness of the angle-based methods.
The solid phase of He-4: A Monte Carlo simulation study
Creators: name: Boninsegni, Massimo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: The thermodynamics of solid (hcp) He-4 is studied theoretically by means of unbiased Monte Carlo simulations at finite temperature, in a wide range of density. This study complements and extends previous theoretical work, mainly by obtaining results at significantly lower temperatures (down to 60 mK) and for systems of greater size, by including in full the effect of quantum statistics, and by comparing estimates yielded by different pair potentials. All the main thermodynamic properties of the crystal, e.g., the kinetic energy per atom, are predicted to be essentially independent of temperature below 1 K. Quantum-mechanical exchanges are virtually non-existent in this system, even at the lowest temperature considered. However, effects of quantum statistics are detectable in the momentum distribution. Comparison with available measurements shows general agreement within the experimental uncertainties.
description: Replaced with published version
Diagnostic measures for the Cox regression model with missing covariates
Creators: name: Zhu, Hongtu
name: Chen, Ming Hui
name: Ibrahim, Joseph G.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2015

description: This paper investigates diagnostic measures for assessing the influence of observations and model misspecification in the presence of missing covariate data for the Cox regression model. Our diagnostics include case-deletion measures, conditional martingale residuals, and score residuals. The Q-distance is proposed to examine the effects of deleting individual observations on the estimates of finite-dimensional and infinite-dimensional parameters. Conditional martingale residuals are used to construct goodness of fit statistics for testing possible misspecification of the model assumptions. A resampling method is developed to approximate the p-values of the goodness of fit statistics. Simulation studies are conducted to evaluate our methods, and a real data set is analyzed to illustrate their use.
Bridges of Markov counting processes. Reciprocal classes and duality formulas
Creators: name: Conforti, Giovanni
name: Léonard, Christian
name: Murr, Rüdiger
name: Roelly, Sylvie
Publisher: name: arXiv
Year: 2014
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: Processes having the same bridges are said to belong to the same reciprocal class. In this article we analyze reciprocal classes of Markov counting processes by identifying their reciprocal invariants and we characterize them as the set of counting processes satisfying some duality formula.
Oxygen Isotope Exchange Between Molten Silicate Spherules and Ambient Water Vapor with Nonzero Relative Velocity: Implication for Chondrule Formation Environment
Creators: name: Arakawa, Sota
name: Yamamoto, Daiki
name: Ushikubo, Takayuki
name: Kaneko, Hiroaki
name: Tanaka, Hidekazu
name: Hirose, Shigenobu
name: Nakamoto, Taishi
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Soft Condensed Matter (cond-mat.soft)
subject: Chemical Physics (physics.chem-ph)
subject: Geophysics (physics.geo-ph)
subject: FOS: Physical sciences

description: Oxygen isotope compositions of chondrules reflect the environment of chondrule formation and its spatial and temporal variations. Here, we present a theoretical model of oxygen isotope exchange reaction between molten silicate spherules and ambient water vapor with finite relative velocity. We found a new phenomenon, that is, mass-dependent fractionation caused by isotope exchange with ambient vapor moving with nonzero relative velocity. We also discussed the plausible condition for chondrule formation from the point of view of oxygen isotope compositions. Our findings indicate that the relative velocity between chondrules and ambient vapor would be lower than several 100 m/s when chondrules crystallized.
description: 15 pages, 8 figures. Accepted for publication in Icarus
Survival Probability of the Néel State in Clean and Disordered Systems: an Overview
Creators: name: Torres-Herrera, E. J.
name: Távora, Marco
name: Santos, Lea F.
Publisher: name: arXiv
Year: 2015
Subjects: subject: Disordered Systems and Neural Networks (cond-mat.dis-nn)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: In this work we provide an overview of our recent results about the quench dynamics of one-dimensional many-body quantum systems described by spin-1/2 models. To illustrate those general results, here we employ a particular and experimentally accessible initial state, namely the Néel state. Both cases are considered: clean chains without any disorder and disordered systems with static random on-site magnetic fields. The quantity used for the analysis is the probability for finding the initial state later in time, the so-called survival probability. At short times, the survival probability may decay faster than exponentially, Gaussian behaviors and even the limit established by the energy-time uncertainty relation are displayed. The dynamics at long times slows down significantly and shows a powerlaw behavior. For both scenarios, we provide analytical expressions that agree very well with our numerical results.
description: 9 pages, 3 figures. Contribution to the special issue of the Brazilian Journal of Physics for the Workshop: Quantum Information and Thermodynamics
Reciprocal classes of random walks on graphs
Creators: name: Conforti, Giovanni
name: Léonard, Christian
Publisher: name: arXiv
Year: 2015
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics
subject: 60J27, 60J75

description: The reciprocal class of a Markov path measure is the set of all mixtures of its bridges. We give characterizations of the reciprocal class of a continuous-time Markov random walk on a graph. Our main result is in terms of some reciprocal characteristics whose expression only depends on the jump intensity. We also characterize the reciprocal class by means of Taylor expansions in small time of some conditional probabilities. Our measure-theoretical approach allows to extend significantly already known results on the subject. The abstract results are illustrated by several examples.
description: This second version of the paper is shorter than the first one. It only considers the easiest situation where the graph is non-directed. This restricted setting avoids many technicalities and provides an easier presentation, keeping the essential features of the proof. The reader interested in directed random walks (for instance, on directed trees) should read the first version
An entropic interpolation problem for incompressible viscid fluids
Creators: name: Arnaudon, Marc
name: Cruzeiro, Ana Bela
name: Léonard, Christian
name: Zambrini, Jean-Claude
Publisher: name: arXiv
Year: 2017
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: In view of studying incompressible inviscid fluids, Brenier introduced in the late 80's a relaxation of a geodesic problem addressed by Arnold in 1966. Instead of inviscid fluids, the present paper is devoted to incompressible viscid fluids. A natural analogue of Brenier's problem is introduced, where generalized flows are no more supported by absolutely continuous paths, but by Brownian sample paths. It turns out that this new variational problem is an entropy minimization problem with marginal constraints entering the class of convex minimization problems. This paper explores the connection between this variational problem and Brenier's original problem. Its dual problem is derived and the general shape of its solution is described. Under the restrictive assumption that the pressure is a nice function, the kinematics of its solution is made explicit and its connection with the Navier-Stokes equation is established.
Cities through the Prism of People's Spending Behavior
Creators: name: Sobolevsky, Stanislav
name: Sitko, Izabela
name: Combes, Remi Tachet des
name: Hawelka, Bartosz
name: Arias, Juan Murillo
name: Ratti, Carlo
Publisher: name: arXiv
Year: 2015
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Social and Information Networks (cs.SI)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Scientific studies of society increasingly rely on digital traces produced by various aspects of human activity. In this paper, we use a relatively unexplored source of data, anonymized records of bank card transactions collected in Spain by a big European bank, in order to propose a new classification scheme of cities based on the economic behavior of their residents. First, we study how individual spending behavior is qualitatively and quantitatively affected by various factors such as customer's age, gender, and size of a home city. We show that, similar to other socioeconomic urban quantities, individual spending activity exhibits a statistically significant superlinear scaling with city size. With respect to the general trends, we quantify the distinctive signature of each city in terms of residents' spending behavior, independently from the effects of scale and demographic heterogeneity. Based on the comparison of city signatures, we build a novel classification of cities across Spain in three categories. That classification is, with few exceptions, stable over different ways of city definition and connects with a meaningful socioeconomic interpretation. Furthermore, it appears to be related with the ability of cities to attract foreign visitors, which is a particularly remarkable finding given that the classification was based exclusively on the behavioral patterns of city residents. This highlights the far-reaching applicability of the presented classification approach and its ability to discover patterns that go beyond the quantities directly involved in it.
Beam Alignment for Millimetre Wave Links with Motion Prediction of Autonomous Vehicles
Creators: name: Mavromatis, Ioannis
name: Tassi, Andrea
name: Piechocki, Robert J.
name: Nix, Andrew
Publisher: name: arXiv
Year: 2017
Subjects: subject: Networking and Internet Architecture (cs.NI)
subject: FOS: Computer and information sciences

description: Intelligent Transportation Systems (ITSs) require ultra-low end-to-end delays and multi-gigabit-per-second data transmission. Millimetre Waves (mmWaves) communications can fulfil these requirements. However, the increased mobility of Connected and Autonomous Vehicles (CAVs), requires frequent beamforming - thus introducing increased overhead. In this paper, a new beamforming algorithm is proposed able to achieve overhead-free beamforming training. Leveraging from the CAVs sensory data, broadcast with Dedicated Short Range Communications (DSRC) beacons, the position and the motion of a CAV can be estimated and beamform accordingly. To minimise the position errors, an analysis of the distinct error components was presented. The network performance is further enhanced by adapting the antenna beamwidth with respect to the position error. Our algorithm outperforms the legacy IEEE 802.11ad approach proving it a viable solution for the future ITS applications and services.
description: Proc. of IET Colloquium on Antennas, Propagation & RF Technology for Transport and Autonomous Platforms, to appear