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Say S is a compact three-manifold with non-positive Yamabe invariant. We prove that in any long time constant mean curvature Einstein flow over S, having bounded C^{\alpha} space-time curvature at the cosmological scale, the reduced volume…

General Relativity and Quantum Cosmology · Physics 2009-11-13 Martin Reiris

We consider spatially homogeneous and isotropic cosmologies with non-zero torsion. Given the high symmetry of these universes, we adopt a specific form for the torsion tensor that preserves the homogeneity and isotropy of the spatial…

General Relativity and Quantum Cosmology · Physics 2019-05-01 D. Kranas , C. G. Tsagas , J. D. Barrow , D. Iosifidis

We consider a new variant of cosmological perturbation theory that has been designed specifically to include non-linear density contrasts on scales 100 Mpc, while still allowing for linear fluctuations on larger scales. This theory is used…

General Relativity and Quantum Cosmology · Physics 2019-04-08 Christopher S. Gallagher , Timothy Clifton

A spherically symmetric comoving fluid solution of Einstein's equations is adapted for cosmological application by extending the geometry of standard FRW cosmology using a generalised curvature term. The resulting model retains many of the…

General Relativity and Quantum Cosmology · Physics 2009-09-15 Ron Wiltshire

An important open question in cosmology is the degree to which the Friedmann-Lemaitre-Robertson-Walker (FLRW) solutions of Einstein's equations are able to model the large-scale behaviour of the locally inhomogeneous observable universe. We…

General Relativity and Quantum Cosmology · Physics 2013-08-29 Timothy Clifton , Kjell Rosquist , Reza Tavakol

A recent paper [CGT] studies the evolution of star-shaped mean convex hypersurfaces of the Euclidean space by a class of nonhomogeneous expanding curvature flows. In the present paper we consider the same problem in the real, complex and…

Differential Geometry · Mathematics 2020-10-08 Giuseppe Pipoli

In the full nonlinear cosmological perturbation theory in the leading order of the gradient expansion, all the types of the gauge invariant perturbation variables are defined. The metric junction conditions across the spacelike transition…

Cosmology and Nongalactic Astrophysics · Physics 2011-08-05 Takashi Hamazaki

The solution of the problem of describing the Friedmann observables (the Hubble law, the red shift, etc.) in quantum cosmology is proposed on the basis of the method of gaugeless Hamiltonian reduction in which the gravitational part of the…

General Relativity and Quantum Cosmology · Physics 2009-10-30 A. M. Khvedelidze , V. V. Papoyan , Yu. G. Palii , V. N. Pervushin

According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-14 Gábor Rácz , László Dobos , Róbert Beck , István Szapudi , István Csabai

We consider the quantum evolution of a fermion-hole pair in a d-dimensional gas of non-interacting fermions in the presence of random phase scattering. This system is mapped onto an effective Ising model, which enables us to show rigorously…

Disordered Systems and Neural Networks · Physics 2023-08-31 Klaus Ziegler

Bounce cosmological models containing a dark viscous fluid in a spatially flat Friedmann-Robertson-Walker (FRW) universe are considered. The universe evolution is described in terms of generalized equation of state (EoS) parameters, in…

General Relativity and Quantum Cosmology · Physics 2024-11-19 E. Elizalde , A. V. Yurov , A. V. Timoshkin

We present numerical solutions to Einstein's equations describing large spherical cosmic voids constituted by two components; dark matter and baryons, with a non-vanishing initial relative velocity, in an asymptotically homogeneous…

General Relativity and Quantum Cosmology · Physics 2023-06-06 Fernando A. Pizaña , Juan Carlos Hidalgo , Ismael Delgado Gaspar , Roberto A. Sussman

An emergence of cosmic space has been suggested by Padmanabhan in [arXiv:1206.4916]. This new interesting approach argues that the expansion of the universe is due to the difference between the number of degrees of freedom on a holographic…

High Energy Physics - Theory · Physics 2014-04-17 Ahmed Farag Ali

We investigate the weakly non-linear evolution of cosmic gravitational clustering in phase space by looking at the Zel'dovich solution in the discrete wavelet transform (DWT) representation. We show that if the initial perturbations are…

Astrophysics · Physics 2009-11-06 J. Pando , L. Feng , L. Z. Fang

We compute the time variation of the fundamental constants (such as the ratio of the proton mass to the electron mass, the strong coupling constant, the fine structure constant and Newton's constant) within the context of the so-called…

High Energy Physics - Phenomenology · Physics 2017-04-03 Harald Fritzsch , Joan Sola , Rafael C. Nunes

We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and…

General Relativity and Quantum Cosmology · Physics 2007-05-23 J. Hwang , H. Noh

In this paper, we study $F(R)$ gravity by Hu-Sawicki model in Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) background. The Friedmann equations are calculated by modified gravity action, and then the obtained Friedmann equations are…

General Relativity and Quantum Cosmology · Physics 2016-05-25 Ali R. Amani

A new method for constructing exact inhomogeneous universes is presented, that allows variation in 3 dimensions. The resulting spacetime may be statistically uniform on average, or have random, non-repeating variation. The construction…

General Relativity and Quantum Cosmology · Physics 2012-03-19 Charles Hellaby

Recently it was shown that the exact cosmological solutions known as the vacuum plane-wave solutions are late-time attractors for an open set of the spatially homogeneous Bianchi universes containing a non-inflationary $\gamma$-law perfect…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Sigbjorn Hervik , Alan Coley

Cosmological N-Body simulations are used for a variety of applications. Indeed progress in the study of large scale structures and galaxy formation would have been very limited without this tool. For nearly twenty years the limitations…

Astrophysics · Physics 2010-05-07 J. S. Bagla , Nishikanta Khandai
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