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A numerical molecular dynamics experiment measuring the two-time correlation function of the transversal velocity field in the homogeneous cooling state of a granular gas is reported. By measuring the decay rate and the amplitude of the…

Statistical Mechanics · Physics 2009-11-13 J. J. Brey , M. I. Garcia de Soria , P. Maynar

Recent experimental advances in ultrafast phenomena have triggered renewed interest in the dynamics of correlated quantum systems away from equilibrium. We review nonequilibrium dynamical mean-field theory studies of both the transient and…

Strongly Correlated Electrons · Physics 2020-05-25 Herbert F. Fotso , James K. Freericks

We analyze the validity of the fluctuation-dissipation theorem for slow relaxation systems in the context of mesoscopic nonequilibrium thermodynamics. We demonstrate that the violation arises as a natural consequence of the elimination of…

Statistical Mechanics · Physics 2009-11-07 A. Perez-Madrid , D. Reguera , J. M. Rubi

In this paper the scalar-tensor theory is applied to the study of perturbations in a multi-fluid universe, using the 1+3 covariant approach. Both scalar and harmonic decompositions are instituted on the perturbation equations. In…

General Relativity and Quantum Cosmology · Physics 2020-11-30 Joseph Ntahompagaze , Shambel Sahlu , Amare Abebe , Manasse R. Mbonye

The driving force of the dynamical system can be decomposed into the gradient of a potential landscape and curl flux (current). The fluctuation-dissipation theorem (FDT) is often applied to near equilibrium systems with detailed balance.…

Statistical Mechanics · Physics 2015-05-30 Haidong Feng , Jin Wang

The cosmological constant (vacuum energy) problem is analyzed within the scope of quantum theories with UV-cut-off or fundamental length. Various cases associated with the appearance of the latter are considered both using the Generalized…

General Relativity and Quantum Cosmology · Physics 2007-12-20 A. E. Shalyt-Margolin

In this review, we scrutinize historical and modern results on the linear response of dynamical systems to external perturbations with a particular emphasis on the celebrated relationship between fluctuations and dissipation expressed by…

Using the concept of open systems where the classical geometry is treated as the system and the quantum matter field as the environment, we derive a fluctuation-dissipation theorem for semiclassical cosmology. This theorem which exists…

General Relativity and Quantum Cosmology · Physics 2008-11-26 B. L. Hu , Sukanya Sinha

The theoretical foundations of the phenomenon known as super-radiance still continues to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate…

General Relativity and Quantum Cosmology · Physics 2014-09-17 Petarpa Boonserm , Tritos Ngampitipan , Matt Visser

We extend previous conduction-based analogies between ice growth in a lake and cosmological expansion by incorporating buoyancy-driven heat transport. Reformulating the Stefan problem with both conductive and convective fluxes yields an…

General Relativity and Quantum Cosmology · Physics 2026-03-17 Lorens F. Niehof , Ananya Venkatasubramanian , Federico Toschi , Stefano Liberati

We discuss from the condensed-matter point of view the recent idea that the Poisson fluctuations of cosmological constant about zero could be a source of the observed dark energy. We argue that the thermodynamic fluctuations of Lambda are…

General Relativity and Quantum Cosmology · Physics 2009-11-10 G. E. Volovik

We consider the generic scenario of dark energy which arises through the latent heat of a hidden sector first order cosmological phase transition. This field could account for the extra radiation degree of freedom suggested by the CMB. We…

Cosmology and Nongalactic Astrophysics · Physics 2014-03-26 Ue-Li Pen , Pengjie Zhang

I consider some of the issues we face in trying to understand dark energy. Huge fluctuations in the unknown dark energy equation of state can be hidden in distance data, so I argue that model-independent tests which signal if the…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Chris Clarkson

A phenomenological model of dark energy that tracks the baryonic and cold dark matter at early times but resembles a cosmological constant at late times is explored. In the transition between these two regimes, the dark energy density drops…

Cosmology and Nongalactic Astrophysics · Physics 2013-11-13 Jannis Bielefeld , W. L. Kimmy Wu , Robert R. Caldwell , Olivier Dore

We revisit the cosmic evolution of the energy density of a quantized free scalar field and assess under what conditions the particle production and classical field approximations reproduce its correct value. Because the unrenormalized…

General Relativity and Quantum Cosmology · Physics 2023-05-26 Cristian Armendariz-Picon , Alberto Diez-Tejedor

Within the framework of unified approach we study the Casimir-Lifshitz interaction, the van der Waals friction force and the radiative heat transfer at nonequilibrium conditions, when the interacting bodies are at different temperatures,…

Other Condensed Matter · Physics 2010-05-06 A. I. Volokitin , B. N. J. Persson

In order to understand the nature of the accelerating expansion of the late-time universe, it is important to experimentally determine whether dark energy is a cosmological constant or dynamical in nature. If dark energy already exists…

Cosmology and Nongalactic Astrophysics · Physics 2019-04-02 Chien-Ting Chen , Pisin Chen

Using real-time holography, we investigate fluctuation-dissipation relations in holographic systems at finite density. In the bulk, it corresponds to the study of scattering of a charged scalar field against a charged black hole background,…

High Energy Physics - Theory · Physics 2025-08-12 Shivam K. Sharma

The stochastic model that describes radiative heat transfer in dielectric medium is built. The model is based on the representation that heat transfer is realized both by heat conductivity mechanism in it and due to the electromagnetic…

Statistical Mechanics · Physics 2017-03-20 Yuri Petrovich Virchenko , Lam Tan Phat

Inspired by one--dimensional light--particle systems, the dynamics of a non-Hamiltonian system with long--range forces is investigated. While the molecular dynamics does not reach an equilibrium state, it may be approximated in the…

Statistical Mechanics · Physics 2019-01-23 Romain Bachelard , Nicola Piovella , Shamik Gupta