In this paper, we study a two-parameter family of convex billiard tables, by taking the intersection of two round disks (with different radii) in the plane. These tables give a generalization of the one-parameter family of lemon-shaped billiards. Initially, there is only one ergodic table among all lemon tables. In our generalized family, we observe numerically the prevalence of ergodicity among the some perturbations of that table. Moreover, numerical estimates of the mixing rate of the billiard dynamics on some ergodic tables are also provided.
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Chaos
January 2025
Departamento de Física, Universidad Nacional de Colombia, Bogotá, Colombia.
We consider a discrete-time Markovian random walk with resets on a connected undirected network. The resets, in which the walker is relocated to randomly chosen nodes, are governed by an independent discrete-time renewal process. Some nodes of the network are target nodes, and we focus on the statistics of first hitting of these nodes.
View Article and Find Full Text PDFJ Chem Phys
January 2025
CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China.
While most thermostats in molecular dynamics are designed for equilibrium systems, their extension to non-equilibrium simulations has little theoretical justification. In the literature, an artifact referred to as "lane formation" was discovered; however, its cause remained unclear and was simply attributed to a constraint on velocity fluctuations or non-ergodicity in thermostats. In addition, global deterministic thermostatted dynamics was found to exhibit unceasing phase-space compression in steady states, incompatible with their expected stationary distributions and Gibbs entropy, which was mistakenly perceived as inescapable.
View Article and Find Full Text PDFEntropy (Basel)
December 2024
Centro de Investigación Operativa, Universidad Miguel Hernández de Elche, 03202 Elche, Spain.
Since its origin in the thermodynamics of the 19th century, the concept of entropy has also permeated other fields of physics and mathematics, such as Classical and Quantum Statistical Mechanics, Information Theory, Probability Theory, Ergodic Theory and the Theory of Dynamical Systems. Specifically, we are referring to the classical entropies: the Boltzmann-Gibbs, von Neumann, Shannon, Kolmogorov-Sinai and topological entropies. In addition to their common name, which is historically justified (as we briefly describe in this review), another commonality of the classical entropies is the important role that they have played and are still playing in the theory and applications of their respective fields and beyond.
View Article and Find Full Text PDFChaos
December 2024
Department of Atomic Physics, Eötvös Loránd University, 1117 Pázmány Péter sétány 1A, Budapest, Hungary.
We investigate how the magnetic structures of the plasma change in a large aspect ratio tokamak perturbed by an ergodic magnetic limiter, when a system parameter is non-adiabatically varied in time. We model such a scenario by considering the Ullmann-Caldas nontwist map, where we introduce an explicit time-dependence to the ratio of the limiter and plasma currents. We apply the tools developed recently in the field of chaotic Hamiltonian systems subjected to parameter drift.
View Article and Find Full Text PDFStat Sci
November 2024
Department of Statistics and Data Science, University of Texas at Austin, Austin, Texas 78705, USA.
Consider a Bayesian setup in which we observe , whose distribution depends on a parameter , that is, . The parameter is unknown and treated as random, and a prior distribution chosen from some parametric family , is to be placed on it. For the subjective Bayesian there is a single prior in the family which represents his or her beliefs about , but determination of this prior is very often extremely difficult.
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