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In this letter, we consider the possibility of reconciling metric theories of gravitation with violation of the conservation of energy-momentum. Under some circumstances, this can be achieved in the context of unimodular gravity, and it…

General Relativity and Quantum Cosmology · Physics 2017-01-18 Thibaut Josset , Alejandro Perez , Daniel Sudarsky

In previous work [L. Blanchet and A. Le Tiec, Phys. Rev. D 78, 024031 (2008)], a model of dark matter and dark energy based on the concept of gravitational polarization was investigated. This model was shown to recover the concordance…

Cosmology and Nongalactic Astrophysics · Physics 2010-04-15 Luc Blanchet , Alexandre Le Tiec

We show that, contrary to some recent claims, relativistic effects cannot mimic dark matter in the galactic rotation curves and gravitational lensing.

General Relativity and Quantum Cosmology · Physics 2026-04-03 L. Filipe O. Costa , José Natário

We present a brief review of various approaches to late time acceleration of universe. The cosmological relevance of scaling solutions is emphasized in case of scalar field models of dark energy. The underlying features of a variety of…

High Energy Physics - Theory · Physics 2009-01-21 M. Sami

This thesis is mainly about how to set up and carry out in a physically meaningful way the idea of back-reaction, according to which dark energy could be an effective source. There are, broadly speaking, two distinct approaches. One is…

Astrophysics · Physics 2008-10-03 Valerio Marra

One of the unresolved questions currently in cosmology is that of the non-linear accelerated expansion of the universe. This has been attributed to the so called Dark Energy (DE). The accelerated expansion of the universe is deduced from…

General Physics · Physics 2017-08-31 Kenath Arun , S B Gudennavar , A Prasad , C Sivaram

We present a dark energy model with a double exponential potential for a minimally coupled scalar field, which allows general exact integration of the cosmological equations. The solution can perfectly emulate a $\Lambda$-term model at…

Astrophysics · Physics 2008-11-26 C. Rubano , P. Scudellaro , E. Piedipalumbo , S. Capozziello

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational…

Cosmology and Nongalactic Astrophysics · Physics 2021-04-13 V. Motta , Miguel A. García-Aspeitia , A. Hernández-Almada , J. Magaña , Tomás Verdugo

In this paper, basics and some theoretical models of dark energy are reviewed. Theoretical models include cosmological constant, vacuum fluctuations of quantum fields, scalar field models, chaplygin gas, vector field models and Brane world…

General Relativity and Quantum Cosmology · Physics 2009-10-29 R. Rakhi , K. Indulekha

The Einstein-locality of our EPR model has been questioned. We show that our model obeys Einstein locality and that the questions are without basis.

Quantum Physics · Physics 2007-05-23 Karl Hess , Walter Philipp

We show the importance of properly including the perturbations of the dark energy component in the dynamical dark energy models based on a scalar field and modified gravity theories in order to meet with present and future observational…

Cosmology and Nongalactic Astrophysics · Physics 2009-10-29 Chan-Gyung Park , Jai-chan Hwang , Jae-heon Lee , Hyerim Noh

In this paper we clear up misconceptions concerning the dark bubble model as a realization of dark energy in string theory. In particular we point out important differences with Randall-Sundrum, and explain why gravity neither is, nor need…

High Energy Physics - Theory · Physics 2023-12-18 Souvik Banerjee , Ulf Danielsson , Suvendu Giri

We discuss the implications of the time-energy uncertainty relation to recoillessly emitted and captured neutrinos (Mossbauer neutrinos) and show that it does not preclude oscillations of these neutrinos, contrary to a recent claim (J.…

High Energy Physics - Phenomenology · Physics 2009-05-01 Evgeny Kh. Akhmedov , Joachim Kopp , Manfred Lindner

It is argued that in the paper by A.A. Garcia-Diaz and G. Gutierrez-Cano [Phys. Rev. D 100, 064068 (2019)] on nonlinear electrodynamics coupled to general relativity, along with some interesting results and useful observations, many…

General Relativity and Quantum Cosmology · Physics 2020-07-01 K. A. Bronnikov

In this recent Letter [1], we studied the implications of string Swampland conjectures for quintessence models of dark energy. A couple of days ago, a paper appeared [2] which refers to our work but misrepresents what we have done. Here, we…

Cosmology and Nongalactic Astrophysics · Physics 2018-09-05 Lavinia Heisenberg , Matthias Bartelmann , Robert Brandenberger , Alexandre Refregier

We consider a generalization of the standard model which respects quantum conformal invariance. This model leads to identically zero vacuum energy. We show how non-relativistic matter and dark energy arises in this model. Hence the model is…

General Relativity and Quantum Cosmology · Physics 2019-12-09 Pankaj Jain , Gopal Kashyap , Subhadip Mitra

In this paper, it is shown that the cosmological model that was introduced in a sequence of three earlier papers under the title, A Dust Universe Solution to the Dark Energy Problem, can be used to resolve the problem of the great mismatch…

General Physics · Physics 2010-07-21 James G. Gilson

There is now strong observational evidence that the expansion of the universe is accelerating. The standard explanation invokes an unknown "dark energy" component. But such scenarios are faced with serious theoretical problems, which has…

Astrophysics · Physics 2008-11-26 Martin Kunz , Domenico Sapone

We discuss a model of non perturbative decay of dark energy into hot and cold dark matter. This model provides a mechanism from the field theory to realize the energy transfer from dark energy into dark matter, which is the requirement to…

General Relativity and Quantum Cosmology · Physics 2015-06-04 Elcio Abdalla , Leila Graef , Bin Wang

The mass varying neutrino scenario is a model that successfully explains the origin of dark energy while at the same time solves the coincidence problem. The model is, however, heavily constrained by its stability towards the formation of…

Astrophysics · Physics 2010-05-18 Ole Eggers Bjaelde , Steen Hannestad