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We present a method for constructing dynamical models of stellar systems described by distribution functions and constrained by discrete-kinematic data. We implement various improvements compared to earlier applications of this approach,…

Astrophysics of Galaxies · Physics 2026-04-28 Eugene Vasiliev , Anja Feldmeier-Krause , Mattia C. Sormani

We derive a hierarchy of kinetic and macroscopic models from a noisy variant of the heuristic behavioral Individual-Based Model of Moussaid et al, PNAS 2011, where the pedestrians are supposed to have constant speeds. This IBM supposes that…

Mathematical Physics · Physics 2017-09-20 Pierre Degond , Cécile Appert-Rolland , Mehdi Moussaid , Julien Pettré , Guy Theraulaz

This paper presents an {\it ab initio} derivation of the expression given by irreversible thermodynamics for the rate of entropy production for different classes of diffusive processes. The first class are Lorentz gases, where…

Chaotic Dynamics · Physics 2009-11-07 J. R. Dorfman , P. Gaspard , T. Gilbert

This paper is about models for a vector of probabilities whose elements must have a multiplicative structure and sum to 1 at the same time; in certain applications, as basket analysis, these models may be seen as a constrained version of…

Statistics Theory · Mathematics 2018-04-17 Antonio Forcina

Molecular dynamics simulations are used to investigate the atomic mobility and diffusivity of a generalized Frenkel-Kontorova model which takes into account anharmonic (exponential) interaction of atoms subjected to a three-dimensional…

patt-sol · Physics 2015-04-09 Oleg M. Braun , Thierry~Dauxois , Maxim V. Paliy , Michel Peyrard

Carnot's four-part ideal-gas cycle includes both isothermal and adiabatic expansions and compressions. Analyzing this cycle provides the fundamental basis for statistical thermodynamics. We explore the cycle here from a pedagogical view in…

Statistical Mechanics · Physics 2022-02-11 William Graham Hoover , Carol Griswold Hoover

The probability distribution function (PDF) of the mass surface density of molecular clouds provides essential information about the structure of molecular cloud gas and condensed structures out of which stars may form. In general, the PDF…

Astrophysics of Galaxies · Physics 2015-06-22 Jörg Fischera

Global and local regularities of functions are analyzed in anisotropic function spaces, under a common framework, that of hyperbolic wavelet bases. Local and directional regularity features are characterized by means of global quantities…

Functional Analysis · Mathematics 2012-10-09 Patrice Abry , Marianne Clausel , Stéphane Jaffard , Stéphane Roux , Béatrice Vedel

We present a three-dimensional lattice-gas model with trivial thermodynamics, but nontrivial dynamics. The model is characterized by each particle having its own random energy landscape. The equilibrium dynamics of the model were…

Soft Condensed Matter · Physics 2012-03-27 Ulf R. Pedersen , Tina Hecksher , Jeppe C. Dyre , Thomas B. Schrøder

We report the results of simulations of dense rotating stellar systems whose members suffer collisions and undergo stellar evolution processes. The initial configuration for each experiment is an isotropic Kuzmin-Kutuzov model. The…

Astrophysics · Physics 2007-05-23 John S. Arabadjis , Douglas O. Richstone

Generative models emerge as promising candidates for novel sequence-data driven approaches to protein design, and for the extraction of structural and functional information about proteins deeply hidden in rapidly growing sequence…

Biomolecules · Quantitative Biology 2021-11-10 Jeanne Trinquier , Guido Uguzzoni , Andrea Pagnani , Francesco Zamponi , Martin Weigt

The truncated Israel-Stewart theory of irreversible thermodynamics is used to describe the bulk viscous pressure and the anisotropic stress in a class of spatially homogeneous viscous fluid cosmological models. The governing system of…

General Relativity and Quantum Cosmology · Physics 2010-04-06 R. J. van den Hoogen , A. A. Coley

.Stochastic models based on random diffusivities, such as the diffusing-diffusivity approach, are popular concepts for the description of non-Gaussian diffusion in heterogeneous media. Studies of these models typically focus on the moments…

Statistical Mechanics · Physics 2020-08-26 V. Sposini , D. S. Grebenkov , R. Metzler , G. Oshanin , F. Seno

A method of modelling the three-dimensional microstructure of random isotropic two-phase materials is proposed. The information required to implement the technique can be obtained from two-dimensional images of the microstructure. The…

Disordered Systems and Neural Networks · Physics 2009-10-31 Anthony Roberts

We present a numerical method for learning the dynamics of slow components of unknown multiscale stochastic dynamical systems. While the governing equations of the systems are unknown, bursts of observation data of the slow variables are…

Machine Learning · Computer Science 2024-08-28 Yuan Chen , Dongbin Xiu

We present a class of thermodynamic systems with constant thermodynamic curvature which, within the context of geometric approaches of thermodynamics, can be interpreted as constant thermodynamic interaction among their components. In…

Mathematical Physics · Physics 2013-09-05 A. C. Gutiérrez-Piñeres , C. S. López-Monsalvo , F. Nettel

We consider a generic class of stochastic particle-based models whose state at an instant in time is described by a set of continuous degrees of freedom (e.g. positions), and the length of this set changes stochastically in time due to…

Statistical Mechanics · Physics 2025-09-03 Samuel Cameron , Elsen Tjhung

Polytropic models play a very important role in galactic dynamics and in the theory of stellar structure and evolution. However, in general, the solution of the Lane-Emden equation can not be given analytically but only numerically. In the…

Astrophysics · Physics 2015-06-24 F. K. Liu

Triangular systems with nonadditively separable unobserved heterogeneity provide a theoretically appealing framework for the modelling of complex structural relationships. However, they are not commonly used in practice due to the need for…

Econometrics · Economics 2019-10-08 Victor Chernozhukov , Iván Fernández-Val , Whitney Newey , Sami Stouli , Francis Vella

Functional data that are nonnegative and have a constrained integral can be considered as samples of one-dimensional density functions. Such data are ubiquitous. Due to the inherent constraints, densities do not live in a vector space and,…

Statistics Theory · Mathematics 2016-01-13 Alexander Petersen , Hans-Georg Müller