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We discuss the Buchert equations, which describe the average expansion of an inhomogeneous dust universe. In the limit of small perturbations, they reduce to the Friedmann-Robertson-Walker equations. However, when the universe is very…

Astrophysics · Physics 2008-11-26 Syksy Rasanen

We present an approach to cosmological perturbations based on a covariant perturbative expansion between two worldlines in the real inhomogeneous universe. As an application, at an arbitrary order we define an exact scalar quantity which…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Kari Enqvist , Janne Hogdahl , Sami Nurmi , Filippo Vernizzi

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

As galaxy redshift surveys probe deeper into the universe, they uncover ever more dramatic structures in the large-scale distribution of galaxies. In particular, the CfA2 and SSRS2 surveys to an apparent magnitude limit of 15.5 exhibit an…

Astrophysics · Physics 2008-02-03 Sergei F. Shandarin

We analyse the evolution of cosmological perturbations which leads to the formation of large isolated voids in the Universe. We assume that initial perturbations are spherical and all components of the Universe (radiation, matter and dark…

Cosmology and Nongalactic Astrophysics · Physics 2016-12-14 Bohdan Novosyadlyj , Maksym Tsizh , Yurij Kulinich

We examine the growth of structure in three different cosmological models with interacting dark matter and vacuum energy. We consider the case of geodesic dark matter with zero sound speed, where the relativistic growing mode in…

Cosmology and Nongalactic Astrophysics · Physics 2020-05-20 Humberto A Borges , David Wands

Growing Neutrino quintessence describes a form of dynamical dark energy that could explain why dark energy dominates the universe only in recent cosmological times. This scenario predicts the formation of large scale neutrino lumps which…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Marco Baldi , Valeria Pettorino , Luca Amendola , Christof Wetterich

In this work, we analyze the possibility of gravitationally induced matter creation in the so-called Energy-Momentum-Squared gravity (EMSG), i.e. $f(R,T_{\mu\nu}T^{\mu\nu})$ gravity, in its dynamically equivalent scalar-tensor…

General Relativity and Quantum Cosmology · Physics 2024-03-15 Ricardo A. C. Cipriano , Tiberiu Harko , Francisco S. N. Lobo , Miguel A. S. Pinto , João Luís Rosa

The effect of capture of a cosmic object by the central gravitational field of a galaxy cluster is described in the expanding Universe. The cosmic evolution can be the origin of the capture explaining formation of galaxies and their…

Astrophysics · Physics 2007-06-07 Piotr Flin , Victor Pervushin , Andrey Zorin

We have found some analytical cosmological solutions to MOdified Gravity (MOG). These solutions describe different evolutionary epochs of an isotropic and homogeneous universe. During each epoch, the evolution of cosmological perturbation…

General Relativity and Quantum Cosmology · Physics 2017-05-04 Fatimah Shojai , Samira Cheraghchi , Hamed Bouzari Nezhad

The formation and evolution of disk galaxies in the cosmological context is studied. We consider the observable properties of disk galaxies and treat the disk formation and galactic evolutionary processes in a self-consistent fashion. We…

Astrophysics · Physics 2007-05-23 Claudio Firmani , Vladimir Avila-Reese , Xavier Hernández

Peculiar velocities are an important probe of the growth rate of mass density fluctuations in the Universe. Most previous studies have focussed exclusively on measuring peculiar velocities at intermediate ($0.2 < z < 1$) redshifts using…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-04 Michael J. Hudson , Stephen J. Turnbull

We develop the reconstruction program for the number of modified gravities: scalar-tensor theory, $f(R)$, $F(G)$ and string-inspired, scalar-Gauss-Bonnet gravity. The known (classical) universe expansion history is used for the explicit and…

High Energy Physics - Theory · Physics 2010-04-06 Shin'ichi Nojiri , Sergei D. Odintsov

The cosmic large scale structure encodes the formation and evolution of a weblike network of dark matter and galaxies within the Universe. The cosmological information is wrapped up in non-Gaussian statistics requiring characterisation…

Cosmology and Nongalactic Astrophysics · Physics 2024-11-26 Alex Gough

This article provides a discussion on the construction of conformal Gaussian gauge systems to study the evolution of solutions to the Einstein field equations with positive Cosmological constant. This is done by means of a gauge based on…

General Relativity and Quantum Cosmology · Physics 2023-08-10 Marica Minucci

In the framework of the recently proposed models of massive gravity, defined with respect to a de Sitter reference metric, we obtain new homogeneous and isotropic solutions for arbitrary cosmological matter and arbitrary spatial curvature.…

High Energy Physics - Theory · Physics 2015-06-05 David Langlois , Atsushi Naruko

We study the late-time evolution of the Universe where dark energy (DE) is parametrized by a modified generalized Chaplygin gas (mGCG) on top of cold dark matter (CDM). We also take into account the radiation content of the Universe. In…

General Relativity and Quantum Cosmology · Physics 2015-12-22 Mariam Bouhmadi-López , Maxim Brilenkov , Ruslan Brilenkov , João Morais , Alexander Zhuk

Cosmological backreaction suggests a link between structure formation and the expansion history of the Universe. In order to quantitatively examine this connection, we dynamically investigate a volume partition of the Universe into over--…

Cosmology and Nongalactic Astrophysics · Physics 2010-08-18 Alexander Wiegand , Thomas Buchert

We investigate the dynamics of the FLRW flat cosmological models in which the vacuum energy varies with redshift. A particularly well motivated model of this type is the so-called quantum field vacuum, in which both kind of terms $H^{2}$…

Cosmology and Nongalactic Astrophysics · Physics 2015-07-15 Spyros Basilakos

A modified gravitational theory explains early universe and late time cosmology, galaxy and galaxy cluster dynamics. The modified gravity (MOG) theory extends general relativity (GR) by three extra degrees of freedom: a scalar field $G$,…

General Relativity and Quantum Cosmology · Physics 2020-10-30 J. W. Moffat
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