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We study Friedmann--Robertson--Walker models with a perfect fluid matter source and a scalar field nonminimally coupled to matter. We prove that a general class of bounded from above potentials which fall to minus infinity as the field goes…

General Relativity and Quantum Cosmology · Physics 2015-06-23 Roberto Giambò , John Miritzis , Koralia Tzanni

Cosmological models with time dependent $\Lambda$ (read as $\Lambda (t)$) have been investigated widely in the literature. Models that solve background dynamics analytically, are of special interest. Additionally, the allowance of past or…

General Relativity and Quantum Cosmology · Physics 2018-01-08 Supriya Pan

It is shown that a physically reasonable spacetime that is eternally inflating to the future must possess an initial singularity.

General Relativity and Quantum Cosmology · Physics 2010-04-06 Arvind Borde , Alexander Vilenkin

Complex structures can only form in a universe that allows for bound states. While this is clearly observed in three-dimensions, added degrees of freedom in a higher-dimensional space preclude the immediate assumption that binding…

We study the statistical mechanics of the early radiation dominated universe in the context of a generalized uncertainty principle which supports the existence of a minimal length scale. Utilizing the resultant modified thermodynamical…

General Relativity and Quantum Cosmology · Physics 2016-01-22 B. Vakili , M. A. Gorji

With this note we want to point out that already in the early days of cosmology it was understood that negative pressure could eliminate gravitational singularities in a natural way e.g. E.B. Gliner, Sov. Phys. JETP 22(1966)378 and M.A.…

Cosmology and Nongalactic Astrophysics · Physics 2009-10-14 Gustaf Rydbeck

Singularity theorems demonstrate the inevitable breakdown of the concept of continuous, classical spacetime under highly general conditions. Quantum gravity is expected to intervene to avoid singularities and models so far hint towards…

General Relativity and Quantum Cosmology · Physics 2024-08-30 Raúl Carballo-Rubio , Stefano Liberati , Vania Vellucci

Some relevant aspects of a new form of generalized entropic cosmology, recently introduced by Nojiri, Odintsov and Faraoni, are considered. The setup is a logarithmic equation of state for a viscous dark fluid coupled with dark matter, in…

General Relativity and Quantum Cosmology · Physics 2026-05-05 E. Elizalde , A. V. Yurov , A. V. Timoshkin

Asymptotic safety (an ultraviolet fixed point with finite-dimensional critical surface) offers the possibility that a predictive theory of quantum gravity can be obtained from the quantization of classical general relativity. However, it is…

General Relativity and Quantum Cosmology · Physics 2011-06-27 Roberto Casadio , Stephen D. H. Hsu , Behrouz Mirza

A flat Friedmann universe filled with a mixture of anti-Chaplygin gas and dust-like matter evolves into a future soft singularity, where despite infinite tidal forces the geodesics can be continued. In the singularity the pressure of the…

General Relativity and Quantum Cosmology · Physics 2014-12-23 A. Kamenshchik , Z. Keresztes , L. Gergely

We propose a new notion of singularity in General Relativity which complements the usual notions of geodesic incompleteness and curvature singularities. Concretely, we say that a spacetime has a volume singularity if there exist points…

General Relativity and Quantum Cosmology · Physics 2024-05-30 Leonardo García-Heveling

We study a 1D transport equation with nonlocal velocity and show the formation of singularities in finite time for a generic family of initial data. By adding a diffusion term the finite time singularity is prevented and the solutions exist…

Analysis of PDEs · Mathematics 2007-06-14 Antonio Cordoba , Diego Cordoba , Marco A. Fontelos

We study the future evolution of quintessence/phantom dominated epoch in modified $F(R)$-gravity which unifies the early-time inflation with late-time acceleration and which is consistent with observational tests. Using the reconstruction…

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

We show that in tilting perfect fluid cosmological models with an ultra-radiative equation of state, generically the tilt becomes extreme at late times and, as the tilt instability sets in, observers moving with the tilting fluid will…

General Relativity and Quantum Cosmology · Physics 2009-11-11 A. A. Coley , S. Hervik , W. C. Lim

The knowledge of the universe future is of fundamental importance for any advanced civilization. We study the future of singular dark universe where thermal effects due to the Hawking radiation on the apparent horizon of the FRW universe…

General Relativity and Quantum Cosmology · Physics 2020-07-27 Shin'ichi Nojiri , Sergei D. Odintsov

We point out that spacetime singularities play a useful role in gravitational theories by eliminating unphysical solutions. In particular, we argue that any modification of general relativity which is completely nonsingular cannot have a…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Gary T. Horowitz , Robert Myers

When gravity couples to scalar fields in Anti-de Sitter space, the geometry becomes non-AdS and develops singularities generally. We propose a criterion that the singularity is physically admissible if the integral of the on-shell…

High Energy Physics - Theory · Physics 2009-10-31 Hyung Do Kim

We argue that many future-eternal inflating spacetimes are likely to violate the weak energy condition. It is possible that such spacetimes may not enforce any of the known averaged conditions either. If this is indeed the case, it may open…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Arvind Borde , Alex Vilenkin

Discussions on indeterminism in physics focus on the possibility of an open future, i.e. the possibility of having potential alternative future events, the realisation of one of which is not fully determined by the present state of affairs.…

History and Philosophy of Physics · Physics 2023-02-21 Flavio Del Santo , Nicolas Gisin

Spacetime singularities in general relativity are commonly thought to be problematic, in that they signal a breakdown in the theory. We address the question of how to interpret this breakdown, restricting our attention to classical…

History and Philosophy of Physics · Physics 2021-02-03 Feraz Azhar , Mohammad Hossein Namjoo
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