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We show why the amount of information communicated between the past and future--the excess entropy--is not in general the amount of information stored in the present--the statistical complexity. This is a puzzle, and a long-standing one,…

Statistical Mechanics · Physics 2013-05-29 James P. Crutchfield , Christopher J. Ellison , John R. Mahoney

Entropy production is often interpreted as a proxy for microscopic disorder or environmental roughness in stochastic systems. We test this interpretation using controlled simulations of overdamped stochastic dynamics on curved surfaces in…

Statistical Mechanics · Physics 2026-02-23 Patrick Romanescu

We find ourselves in an extended era of entropy production. Unlike most other observations, the arrow of time is usually regarded as a constraint on initial conditions. I argue, however, that it primarily constrains the vacuum structure of…

High Energy Physics - Theory · Physics 2013-05-30 Raphael Bousso

Gravity is a macroscopic manifestation of a microscopic quantum theory of space-time, just as the theories of elasticity and hydrodynamics are the macroscopic manifestation of the underlying quantum theory of atoms. The connection of…

High Energy Physics - Theory · Physics 2011-01-31 George F. Smoot

If our universe underwent inflation, its entropy during the inflationary phase was substantially lower than it is today. Because a low-entropy state is less likely to be chosen randomly than a high-entropy one, inflation is unlikely to…

General Relativity and Quantum Cosmology · Physics 2011-05-12 Sean M. Carroll , Jennifer Chen

Perturbation theory is used to investigate the evolution of the von Neumann entropy of a subsystem of a bipartite quantum system under the action of a unitary matrix, in the limit where that matrix is close to the unit matrix. The physical…

Quantum Physics · Physics 2025-09-08 Duncan MacIntyre , Gordon W. Semenoff

Curiously, our Universe was born in a low entropy state, with abundant free energy to power stars and life. The form that this free energy takes is usually thought to be gravitational: the Universe is almost perfectly smooth, and so can…

Cosmology and Nongalactic Astrophysics · Physics 2023-06-22 Luke A. Barnes , Geraint F. Lewis

Observational entropy captures both the intrinsic uncertainty of a thermodynamic state and the lack of knowledge due to coarse-graining. We demonstrate two interpretations of observational entropy, one as the statistical deficiency…

Quantum Physics · Physics 2024-11-20 Ge Bai , Dominik Šafránek , Joseph Schindler , Francesco Buscemi , Valerio Scarani

We discuss the treatment, in an effective field theory, of multi-particle correlations within a "large" system. We show that the act of coarse-graining necessarily introduces violations of unitarity in the evolution of states where the…

High Energy Physics - Theory · Physics 2013-09-20 Giorgio Torrieri

The universe time-asymmetry is essentially produced by its low-entropy unstable initial state. Using quanlitative arguments, Paul Davies has demonstrated that the universe expansion may diminish the entropy gap, therefore explaining its…

Quantum Physics · Physics 2015-06-26 Roberto Aquilano , Mario Castagnino

The past entropy is considered as an uncertainty measure for the past lifetime distribution. Generating function approach to entropy become popular in recent time as it generate several well-known entropy measures. In this paper, we…

Information Theory · Computer Science 2023-12-06 Smitha S. , Sudheesh K Kattumannil

Entropy relates the fast, microscopic behaviour of the elements in a system to its slow, macroscopic state. We propose to use it to explain how, as complexity theory suggests, small scale decisions of individuals form cities. For this, we…

Physics and Society · Physics 2017-11-28 Martin Barner , Clémentine Cottineau , Carlos Molinero , Hadrien Salat , Kiril Stanilov , Elsa Arcaute

The universal validity of the second law of thermodynamics is widely attributed to a finely tuned initial condition of the universe. This creates a problem: why is the universe atypical? We suggest that the problem is an artefact created by…

General Relativity and Quantum Cosmology · Physics 2015-07-27 Julian Barbour , Tim Koslowski , Flavio Mercati

We track the evolution of entropy and black holes in a cyclic universe that undergoes repeated intervals of expansion followed by slow contraction and a smooth (non-singular) bounce. In this kind of cyclic scenario, there is no big crunch…

General Relativity and Quantum Cosmology · Physics 2022-05-09 Anna Ijjas , Paul J. Steinhardt

The concept of entropy connects the number of possible configurations with the number of variables in large stochastic systems. Independent or weakly interacting variables render the number of configurations scale exponentially with the…

Statistical Mechanics · Physics 2020-06-25 Sámuel G. Balogh , Gergely Palla , Péter Pollner , Dániel Czégel

We introduce a high dimensional symplectic map, modeling a large system consisting of weakly interacting chaotic subsystems, as a toy model to analyze the interplay between single-particle chaotic dynamics and particles interactions in…

Chaotic Dynamics · Physics 2011-11-10 Massimo Falcioni , Luigi Palatella , Simone Pigolotti , Lamberto Rondoni , Angelo Vulpiani

In this article, we explore properties of pseudo entropy [1] in quantum field theories and spin systems from several approaches. Pseudo entropy is a generalization of entanglement entropy such that it depends on both an initial and final…

High Energy Physics - Theory · Physics 2021-09-22 Ali Mollabashi , Noburo Shiba , Tadashi Takayanagi , Kotaro Tamaoka , Zixia Wei

A large class of technically non-chaotic systems, involving scatterings of light particles by flat surfaces with sharp boundaries, is nonetheless characterized by complex random looking motion in phase space. For these systems one may…

Chaotic Dynamics · Physics 2009-11-10 Henk van Beijeren

We derive a bound for entropy production in terms of the mean of normalizable path-antisymmetric observables. The optimal observable for this bound is shown to be the signum of entropy production, which is often easier determined or…

Statistical Mechanics · Physics 2024-10-07 Gabriel Knotz , Till M. Muenker , Timo Betz , Matthias Krüger

Entropy, and its temporal evolution, play a central role in the foundations of quantum theory and in modern quantum technologies. Here we study, in particular, the relations between the --- in general, non-Markovian --- evolution of an open…

Quantum Physics · Physics 2018-09-18 Paolo Aniello , Joonwoo Bae , Dariusz Chruscinski