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We study the quantum evolution of the early universe, its semi-classical analogue together with inflationary regime, in view of a generalized modified theory of gravity. The action is built by supplementing the non-minimally coupled…

High Energy Physics - Theory · Physics 2021-01-11 Ranajit Mandal , Dalia Saha , Mohosin Alam , Abhik Kumar Sanyal

A new class of gravity-matter models defined in terms of two independent non-Riemannian volume forms (alternative generally covariant integration measure densities) on the space-time manifold are studied in some detail. These models involve…

General Relativity and Quantum Cosmology · Physics 2015-06-22 Eduardo Guendelman , Ramón Herrera , Pedro Labraña , Emil Nissimov , Svetlana Pacheva

Deformations of minimal surfaces lying in constant time slices in static space-times are studied. An exact and universal formula for a change of the area of a minimal surface under shifts of nearby point-like particles is found. It allows…

High Energy Physics - Theory · Physics 2014-11-21 Dmitri V. Fursaev

We consider the modified gravity non-minimally coupled with matter Lagrangian for the description of early-time and late-time universe. Such $F(R)$ ($F(G)$) gravity in the absence of non-minimal coupling is viable theory which passes the…

High Energy Physics - Theory · Physics 2008-11-26 Shin'ichi Nojiri , Sergei D. Odintsov , Petr V. Tretyakov

A theory of exponential modified gravity which explains both early-time inflation and late-time acceleration, in a unified way, is proposed. The theory successfully passes the local tests and fulfills the cosmological bounds and,…

High Energy Physics - Theory · Physics 2011-04-22 E. Elizalde , S. Nojiri , S. D. Odintsov , L. Sebastiani , S. Zerbini

We investigate the possible effects on the evolution of perturbations in the inflationary epoch due to short distance physics. We introduce a suitable non local action for the inflaton field, suggested by Noncommutative Geometry, and…

High Energy Physics - Theory · Physics 2009-11-07 Fedele Lizzi , Gianpiero Mangano , Gennaro Miele , Marco Peloso

Many body gravity (MBG) is a novel modified theory of gravity formulated in a 5-D space-time-temperature framework, in which the variation in temperature is recast as a variation in the 5-D metric. Previous work on MBG has shown that it can…

General Relativity and Quantum Cosmology · Physics 2026-04-17 S Ganesh

Inspired by Verlinde's idea, some modified versions of entropic gravity have appeared in the literature. Extending them in a unified formalism, we derive the generalized gravitational equations accordingly. From gravitational equations, the…

High Energy Physics - Theory · Physics 2012-11-27 Tower Wang

Noncommutative geometry, as conceptualized by Nicolini, Smailagic, and Spallucci, may be viewed as a slight modification of Einstein's theory. The same can be said for $f(R)$ modified gravity for an appropriate choice of the function…

General Relativity and Quantum Cosmology · Physics 2021-01-05 Peter K. F. Kuhfittig

We study the evolution of quantum fluctuations of gravity around an inflationary solution in renormalizable quantum gravity, in which the initial scalar-fluctuation dominance is shown by the background-free nature expressed by a special…

High Energy Physics - Theory · Physics 2024-01-19 Ken-ji Hamada

The pre-inflationary evolution of the universe describes the beginning of the expansion from a static initial state, such that the Hubble parameter is initially zero, but increases to an asymptotic constant value, in which it could achieve…

General Relativity and Quantum Cosmology · Physics 2016-05-30 Marcos R. A. Arcodía , Mauricio Bellini

We discuss the possibility that spacetime geometry may be an emergent phenomenon. This idea has been motivated by the Analogue Gravity programme. These are systems where the kinematics of small perturbations are dominated by an effective…

General Relativity and Quantum Cosmology · Physics 2007-11-29 Silke Weinfurtner

Noncommutative geometry is a mathematical framework that expresses the structure of space-time in terms of operator algebras. By using the tools of quantum mechanics to describe the geometry, noncommutative space-times are expected to give…

Mathematical Physics · Physics 2024-07-03 Kilian Hersent

We experience some challenges in general gravitational theory owing to Einstein to explain late time acceleration of universe. To address this issue, geometric components of gravity have been modified in quite a few occasions to have a more…

General Relativity and Quantum Cosmology · Physics 2024-10-04 Santanu Das , Nilanjana Mahata , Priyanka Ray

Non commutative geometry is creating new possibilities for physics. Quantum spacetime geometry and post inflationary models of the universe with matter creation have an enormous range of scales of time, distance and energy in between. There…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Ajay Patwardhan

We argue that a field theory defined on noncommutative (NC) spacetime should be regarded as a theory of gravity, which we refer to as the emergent gravity. A whole point of the emergent gravity is essentially originated from the basic…

High Energy Physics - Theory · Physics 2009-11-13 Hyun Seok Yang

The huge amounts of undetected and exotic dark matter and dark energy needed to make general relativity work on large scales argue that we should investigate modifications of gravity. The only stable, metric-based and invariant alternative…

General Relativity and Quantum Cosmology · Physics 2018-07-06 R. P. Woodard

We propose a modified gravity theory by extending the Einstein-Hilbert action with an arbitrary function of the Ricci scalar and the Kretschmann scalar invariants. The resulting modified Friedmann equations for a spatially flat FRW universe…

General Relativity and Quantum Cosmology · Physics 2026-05-29 A. Dehyadegari , A. Sheykhi

It is an old idea to realize Einstein's equations as a thermodynamical equation of state. Since then, there has been new conjectures to understand gravity from another point of view. In this way we can accept that the gravitational field is…

High Energy Physics - Theory · Physics 2017-08-16 Everton M. C. Abreu , Jorge Ananias Neto , Albert C. R. Mendes , Daniel O. Souza

I describe the conceptual and mathematical basis of an approach which describes gravity as an emergent phenomenon. Combining principle of equivalence and principle of general covariance with known properties of local Rindler horizons,…

General Relativity and Quantum Cosmology · Physics 2009-11-22 T. Padmanabhan