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The idea of possible time or space variations of the `fundamental' constants of nature, although not new, is only now beginning to be actively considered by large numbers of researchers in the particle physics, cosmology and astrophysics…

Astrophysics · Physics 2009-11-07 C. J. A. P. Martins

Cosmological perturbations due to statistical thermal fluctuations in a single fluid characterized by an arbitrary equation of state are computed. Formulas to predict the scalar and tensor perturbation spectra and nongaussianity parameters…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-09 Tirthabir Biswas , Robert Brandenberger , Tomi Koivisto , Anupam Mazumdar

These notes are intended as an introduction to a study of applications of noncommutative calculus to quantum statistical Physics. Centered on noncommutative calculus we describe the physical concepts and mathematical structures appearing in…

Mathematical Physics · Physics 2018-10-09 W. A. Majewski

This review is an up-to-date account of the use of numerical relativity to study dynamical, strong-gravity environments in a cosmological context. First, we provide a gentle introduction into the use of numerical relativity in solving…

General Relativity and Quantum Cosmology · Physics 2025-06-24 Josu C. Aurrekoetxea , Katy Clough , Eugene A. Lim

We explore some cosmological features of the newly suggested 4D Gauss-Bonnet gravity through two different models assuming a varying cosmological constant. Observational constraints, such as the cosmic transit and the flat curvature, have…

General Relativity and Quantum Cosmology · Physics 2023-03-15 Nasr Ahmed , Ajab A. Alfreedi , Alaa A. Alzulaibani

We compute the cosmological constant in a scale invariant scalar field theory. The gravitational action is also suitably modified to respect scale invariance. Due to scale invariance the theory does not admit a cosmological constant term.…

High Energy Physics - Phenomenology · Physics 2010-11-15 Pankaj Jain , Subhadip Mitra

In this paper, we describe the first steps towards fully non-perturbative cosmology. We explain why the conventional methods used by cosmologists based on the ADM formulation are generally inadequate for this purpose and why it is…

General Relativity and Quantum Cosmology · Physics 2019-01-08 Anna Ijjas , Frans Pretorius , Paul J. Steinhardt

We connect a possible solution for the ``cosmological constant problem'' to the existence of a (postulated) conformal fixed point in a fundamental theory. The resulting cosmology leads to quintessence, where the present acceleration of the…

High Energy Physics - Theory · Physics 2009-11-07 C. Wetterich

We give a pedagogical review of a covariant and fully non-perturbative approach to study nonlinear perturbations in cosmology. In the first part, devoted to cosmological fluids, we define a nonlinear extension of the uniform-density…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 David Langlois , Filippo Vernizzi

A new approach to the phenomenon of large numbers coincidence leads to unexpected results. No matter how strange it might sound, the exact value of cosmological parameters and their analytical expression through fundamental constants have…

General Relativity and Quantum Cosmology · Physics 2007-05-23 V. E. Shemi-Zadeh

We extend vector formalism by including it in the algebra of split octonions, which we treat as the universal algebra to describe physical signals. The new geometrical interpretation of the products of octonionic basis units is presented.…

High Energy Physics - Theory · Physics 2008-11-26 Merab Gogberashvili

Cosmological implications of neutrinos are reviewed. The subjects considered involve: (a) bounds on neutrino mass from the observational limits on the universe age and the Hubble constant both in cosmology with and without cosmological…

High Energy Physics - Phenomenology · Physics 2008-11-26 A. D. Dolgov

This is a brief review for particle physicists on cosmological impact of neutrinos and on restrictions on neutrino properties from cosmology. The paper includes discussion of upper bounds on neutrino mass and possible ways to relax them,…

High Energy Physics - Phenomenology · Physics 2009-01-26 A. D. Dolgov

There has been significant recent progress in observational cosmology. This, in turn, has provided an unprecedented picture of the early universe and its evolution. In this review I will present a (biased) view of how one can use these…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Raul Jimenez

Recently, the research community has been exploring fractional calculus to address problems related to cosmology; in this approach, the gravitational action integral is altered, leading to a modified Friedmann equation, then the resulting…

General Relativity and Quantum Cosmology · Physics 2023-02-07 Bayron Micolta-Riascos , Alfredo D. Millano , Genly Leon , Cristián Erices , Andronikos Paliathanasis

The idea of the quantum state of the Universe described by some density matrix, i.e mixture of at least two vacua, the trivial symmetric and the nontrivial one with spontaneously broken symmetry is discussed. Nonzero cosmological constant…

General Relativity and Quantum Cosmology · Physics 2007-05-23 A. A. Grib

We study the set of algebraic numbers of bounded height and bounded degree where an analytic transcendental function takes algebraic values.

Number Theory · Mathematics 2007-05-23 Andrea Surroca

The cosmological constant problem and brane universes are reviewed briefly. We discuss how the cosmological constant problem manifests itself in various scenarios for brane universes. We review attempts - and their difficulties - that aim…

High Energy Physics - Theory · Physics 2009-11-11 Ulrich Ellwanger

The framework for considering the astronomical and cosmological observations in the context of scalar-tensor quintessence in which the quintessence field also accounts for a time dependence of the gravitational constant is developed. The…

Astrophysics · Physics 2010-05-28 Alain Riazuelo , Jean-Philippe Uzan

It is shown that in the presence of a nonvanishing cosmological constant, Strominger's infinite-dimensional $\mathrm{w_{1+\infty}}$ algebra of soft graviton symmetries is modified in a simple way. The deformed algebra contains a subalgebra…

High Energy Physics - Theory · Physics 2023-12-12 Tomasz R. Taylor , Bin Zhu