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The Universe, far to be homogenous, expands in large empty bubbles of the large-scale structure, but not in mass concentrations like galaxies, so that the Robertson-Walker solution does not fit. We suggest that a symmetry breaking occurred…

General Physics · Physics 2008-12-08 Jean Pierre Petit , Gilles d'Agostini

As is well known, a varying effective gravitational "constant" is one of the common features of most modified gravity theories. Of course, as a modified gravity theory, $f(T)$ theory is not an exception. Noting that the observational…

General Relativity and Quantum Cosmology · Physics 2012-08-31 Hao Wei , Hao-Yu Qi , Xiao-Peng Ma

We present a new model universe based on the junction of FRW to flat Lemaitre-Tolman-Bondi (LTB) solutions of Einstein equations along our past light cone, bringing structures within the FRW models. The model is assumed globally to be…

Astrophysics · Physics 2008-11-26 Sh. Khosravi , E. Kourkchi , R. Mansouri , Y. Akrami

We exhibit a varying speed of light (VSL) theory that implements the recently proposed decaying speed of sound mechanism for generating density fluctuations. We avail ourselves of bimetric VSL theories, where the speed of gravity differs…

General Relativity and Quantum Cosmology · Physics 2010-01-29 Joao Magueijo

A new method of derivation of Lorentz Transformation (LT) is given based on both axioms of special relativity (SR) and physical intuitions. The essence of the transformation is established and the crucial role played by the presumptions is…

General Physics · Physics 2015-06-16 Farid Shahandeh

In this paper we aim to investigate a deformed relativistic dynamics well-known as Symmetrical Special Relativity (SSR) related to a cosmic background field that plays the role of a variable vacuum energy density associated to the…

General Physics · Physics 2020-09-14 Claudio Nassif Cruz , Fernando A. Silva

We consider a hypothetical possibility of the variability of light velocity with time and position in space which is derived from two natural postulates. For the consistent consideration of such variability we generalize translational…

Astrophysics · Physics 2016-08-30 Sergey S. Stepanov

This paper presents a compelling argument for the physical light speed in the homogeneous and isotropic Friedman-Lemaitre-Robertson-Walker (FLRW) universe to vary with the cosmic time coordinate t of FLRW. It will be variable when the…

Astrophysics · Physics 2013-07-23 Robert C. Fletcher

We construct effective field theories in which gravity is modified via spontaneous breaking of local Lorentz invariance. This is a gravitational analogue of the Higgs mechanism. These theories possess additional graviton modes and modified…

High Energy Physics - Theory · Physics 2008-11-26 B. M. Gripaios

Energy Momentum Squared Gravity (EMSG) is a cosmological model where the scale factor is non vanishing at all times and hence does not favor big bang cosmology. However, the profile of density in the radiation dominated universe shows that…

General Relativity and Quantum Cosmology · Physics 2020-01-22 S. Bhattacharjee , P. K. Sahoo

I show that the generalized Beltrami differentials and projective connections which appear naturally in induced light cone $W_n$ gravity are geometrical fields parametrizing in one-to-one fashion generalized projective structures on a fixed…

High Energy Physics - Theory · Physics 2010-04-06 Roberto Zucchini

We study the evolution of a flat Friedmann-Robertson- Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of variable gravitational and cosmological constants. The dimensional analysis of the model suggest a…

General Relativity and Quantum Cosmology · Physics 2009-09-25 J. A. Belinchon , T. Harko , M. K. Mak

Doubly special relativity (DSR) introduces an observer-independent energy scale while preserving a deformed relativistic notion of covariance. In many realizations, this leads to an energy-dependent speed of light (light-speed variation,…

High Energy Physics - Phenomenology · Physics 2026-05-07 Hao Li , Jie Zhu

A new variational approach for general relativity and modified theories of gravity is presented. In addition to the metric tensor, two independent affine connections enter the action as dynamical variables. In the matter action the…

General Relativity and Quantum Cosmology · Physics 2015-06-05 Nicola Tamanini

We derive and discus the equations of motion for spinless matter: relativistic spinless scalar fields, particles and fluids in the recently proposed by A. Saa model of gravity with covariantly constant volume with respect to the transposed…

General Relativity and Quantum Cosmology · Physics 2015-06-25 P. P. Fiziev

We extend our investigation of soft graviton effects on the microscopic dynamics of matter fields in de Sitter space. We evaluate the quantum equation of motion in generic gauge theories. We find that the Lorentz invariance can be respected…

High Energy Physics - Theory · Physics 2013-06-14 Hiroyuki Kitamoto , Yoshihisa Kitazawa

We propose a fibre bundle formulation of the mathematical base of relativistic quantum mechanics. At the present stage the bundle form of the theory is equivalent to its conventional one, but it admits new types of generalizations in…

Quantum Physics · Physics 2007-05-23 Bozhidar Z. Iliev

For variable gravity models the strength of gravity, as measured by Newton's ``constant'' or the Planck mass, depends on the value of a scalar field, the cosmon. We discuss two simple four-parameter models with a quadratic or constant…

Cosmology and Nongalactic Astrophysics · Physics 2014-01-15 C. Wetterich

The unique ghost-free mass and nonlinear potential terms for general relativity are presented in a diffeomorphism and local Lorentz invariant vierbein formalism. This construction requires an additional two-index Stuckelberg field, beyond…

High Energy Physics - Theory · Physics 2013-10-30 Gregory Gabadadze , Kurt Hinterbichler , David Pirtskhalava , Yanwen Shang

We show that it is possible to formulate gravity with a complex vierbein based on SL(2,C) gauge invariance. The proposed action is a four-form where the metric is not introduced but results as a function of the complex vierbein. This…

High Energy Physics - Theory · Physics 2009-11-10 Ali H. Chamseddine