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In this work we establish the correspondence between solutions to the Friedmann--Robertson--Walker cosmologies for perfect fluid and scalar field sources, where both ones fulfill state equations of the form $p+\rho=\gamma f(\rho)$, not…

High Energy Physics - Theory · Physics 2009-11-10 A. Garcia , M. Cataldo , S. del Campo

Diagrammatic Monte Carlo approach is applied to a problem of a single spin-down fermion resonantly interacting with the sea of ideal spin-up fermions. On one hand, we develop a generic, sign-problem tolerant, method of exact numerical…

Statistical Mechanics · Physics 2009-11-13 Nikolay Prokof'ev , Boris Svistunov

We give a counterexample to a recently conjectured variant of the Penrose inequality.

Differential Geometry · Mathematics 2026-04-30 Sven Hirsch , Yipeng Wang

This paper has been withdrawn by the authors due to the too limited range of the current version of the model (the dark energy fraction is constant, but it has to be a function of the scale factor). We will resubmit the paper after…

General Relativity and Quantum Cosmology · Physics 2008-11-25 Torsten Asselmeyer-Maluga , Helge Rosé

Simple linear second-order differential equations have been written down for FRW cosmologies with barotropic fluids by Faraoni. His results have been extended by Rosu, who employed techniques belonging to nonrelativistic supersymmetry to…

General Relativity and Quantum Cosmology · Physics 2016-08-31 H. C. Rosu , O. Cornejo , M. Reyes , D. Jimenez

Fluid cosmologies are consistent with the generally accepted observational evidence during intermediate and late times, and they need not have singular behavior in primordial times. A general form for fluid cosmology consistent with…

General Relativity and Quantum Cosmology · Physics 2009-01-20 James Lindesay

For non-zero cosmological constant Lambda, we show that the barotropic FRW cosmologies as worked out in the comoving time lead in the radiation-dominated case to scale factors of identical form as for the Chiellini dissipative scale factors…

Mathematical Physics · Physics 2015-06-17 Haret C. Rosu , Stefan C. Mancas , Pisin Chen

The present discussion contribution is some remarks concerning and review of the proposal by one of us (C. Balazs) to explain the cosmological constant by a/the principle of entropy. Used without further comment this principle of entropy…

Cosmology and Nongalactic Astrophysics · Physics 2013-06-26 H. B. Nielsen , C. Balazs

Generic models of cosmological inflation and the recently proposed scenarios of a recycling universe and the string theory landscape predict spacetimes whose global geometry is a stochastic, self-similar fractal. To visualize the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Sergei Winitzki

The Cosmological Principle (CP) -- the notion that the Universe is spatially isotropic and homogeneous on large scales -- underlies a century of progress in cosmology. It is conventionally formulated through the…

A generally anisotropic equation of state originally derived in the context of Newman-Janis rotating systems allows for vacuum energy at a specific density. In this paper we examine the possibility of using that equation of state for…

General Relativity and Quantum Cosmology · Physics 2023-09-08 Philip Beltracchi

Bianchi I cosmological solutions in f(T) gravity are discussed. We start from diagonal metrics and tetrads and show that their dynamical equations are pretty much tractable analytically, with a possible arena for physical applications. Then…

General Relativity and Quantum Cosmology · Physics 2026-02-24 Alexey Golovnev , Mustafa M. Hemida

We find an exact convergence in the local dynamics described by two supposedly antagonistic approaches in modern cosmology: one starting from an expanding universe perspective such as FLRW, the other based on a local model ignoring any…

General Relativity and Quantum Cosmology · Physics 2021-12-08 J. M. Pons , P. Talavera

In this paper, we study the main cosmological properties of the classical Friedmann equations in the case of homogeneous and isotropic Friedmann-Robertson-Walker Universe and we also generalized the expression of the Friedmann equation in…

General Relativity and Quantum Cosmology · Physics 2014-03-13 S. Chattopadhyay , A. Ashurov , M. Khurshudyan , K. Myrzakulov , A. Pasqua , R. Myrzakulov

We compare the cosmology of conformal gravity (CG), (Mannheim 2006), to $\Lambda$CDM. CG cosmology has repulsive matter and radiation on cosmological scales, while retaining attractive gravity at local scales. Mannheim (2003) finds that CG…

Cosmology and Nongalactic Astrophysics · Physics 2017-11-29 Carl Roberts , Keith Horne , Alistair O. Hodson , Alasdair Dorkenoo Leggat

It is described dynamics of a large class of accelerating cosmological models in terms of dynamical systems of the Newtonian type. The evolution of the models is reduced to the motion of a particle in a potential well parameterized by the…

Astrophysics · Physics 2017-09-29 Marek Szydlowski , Aleksandra Kurek

The subject of cosmological backreaction in General Relativity is often approached by coordinate-dependent and metric-based analyses. We present in this letter an averaging formalism for the scalar parts of Einstein's equations that is…

General Relativity and Quantum Cosmology · Physics 2018-12-04 Thomas Buchert , Pierre Mourier , Xavier Roy

In this paper we consider Chameleonic Generalized Brans--Dicke Cosmology in the framework of FRW universes. The bouncing solution and phantom crossing is investigated for the model. Two independent cosmological tests: Cosmological Redshift…

General Relativity and Quantum Cosmology · Physics 2012-01-20 H. Farajollahi , M. Farhoudi , A. Salehi , H. Shojaie

A systematic dynamical system approach is applied to study the cosmology of anisotropic Bianchi I universes in which a vector field is assumed to operate on a disformal frame. This study yields a number of new fixed points, among which…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-02 Tomi S. Koivisto , Federico R. Urban

We consider properties and applications of a sequence of polynomials known as complementary Romanovski-Routh polynomials (CRR polynomials for short). These polynomials, which follow from the Romanovski-Routh polynomials or complexified…

Classical Analysis and ODEs · Mathematics 2018-06-08 A. Martínez-Finkelshtein , L. L. Silva Ribeiro , A. Sri Ranga , M. Tyaglov