Results 11 to 20 of about 193,127 (291)

Fractal Bubble cosmology: a concordant cosmological model? [PDF]

Monthly Notices of the Royal Astronomical Society: Letters, 2009
Abstract The Fractal Bubble model has been proposed as a viable cosmology that does not require dark energy to account for cosmic acceleration, but rather attributes its observational signature to the formation of structure. In this Letter, it is demonstrated that, in contrast to previous findings, this model is not a good fit to ...
Kwan, Juliana, Francis, Matthew J., Lewis, Geraint F.   +2 more
openaire   +2 more sources

FLRW Cosmological Models with Dynamic Cosmological Term in Modified Gravity

Universe, 2021
Although the standard lambda cold dark matter cosmological model is quite successful in describing the universe, there are still several issues that are still not resolved.
Rishi Kumar Tiwari, Aroonkumar Beesham, Bhupendra Kumar Shukla   +2 more
doaj   +1 more source

Cosmological Tensions and the Transitional Planck Mass Model

The Astrophysical Journal, 2023
In this follow-up analysis, we update previous constraints on the transitional Planck mass (TPM) modified gravity model using the latest version of EFTCAMB and provide new constraints using South Pole Telescope (SPT) and Planck anisotropy data along with
Joshua A. Kable, Giampaolo Benevento, Graeme E. Addison, Charles L. Bennett   +3 more
doaj   +1 more source

Singularities in Inflationary Cosmological Models

Universe, 2021
Due to the accelerated expansion of the universe, the possibilities for the formation of singularities has changed from the classical Big Bang and Big Crunch singularities to include a number of new scenarios. In recent papers it has been shown that such
Leonardo Fernández-Jambrina
doaj   +1 more source

Stochastic semiclassical cosmological models [PDF]

, 1997
We consider the classical stochastic fluctuations of spacetime geometry induced by quantum fluctuations of massless non-conformal matter fields in the Early Universe.
A. A. Starobinsky, A. A. Starobinsky, A. A. Starobinsky, A. Campos, A. Campos, A. Matacz, Antonio Campos, B. L. Hu, B. L. Hu, B.-L. Hu, B.-L. Hu, B.-L. Hu, C. Misner, C.-I. Kuo, E. Calzetta, E. Calzetta, E. Calzetta, E. Calzetta, E. Calzetta, E. Calzetta, E. Calzetta, E. Calzetta, E. E. Flanagan, E. S. Abers, Enric Verdaguer, Esteban Calzetta, F. Lombardo, G. T. Horowitz, H. Callen, J. A. Frieman, J. B. Hartle, J. B. Hartle, J. B. Hartle, J. P. Boon, J. P. Paz, J. Schwinger, J. Z. Simon, K. Chou, L. Kadanoff, L. Landau, L. P. Grishchuk, L. Parker, L. Rosenfeld, L. V. Keldysh, M. Gell-Mann, M. Morikawa, M. V. Fischetti, N. D. Birrell, N. D. Birrell, P. Anderson, P. Anderson, P. M. Bakshi, R. D. Jordan, R. P. Feynman, R. P. Feynman, R. Wald, S. K. Ma, V. N. Lukash, V. N. Lukash, Y. B. Zeldovich   +59 more
core   +2 more sources

Crossing of Phantom Divide Line in Model of Interacting Tsallis Holographic Dark Energy

Universe, 2022
We consider a Tsallis holographic dark energy model with interaction between dark energy and matter. The density of dark energy is taken as ρd∼3C2/L4−2γ, where C, γ are constants. The event horizon is chosen as the characteristic scale L.
Artyom V. Astashenok, Alexander Tepliakov   +1 more
doaj   +1 more source

Homogeneous Cosmological Models in Weyl’s Geometrical Scalar–Tensor Theory

Universe, 2023
In this paper, we consider homogeneous cosmological solutions in the context of the Weyl geometrical scalar–tensor theory. Firstly, we exhibit an anisotropic Kasner type solution taking advantage of some similarities between this theory and the Brans ...
Adriano Barros, Carlos Romero
doaj   +1 more source

Cosmological models from quintessence [PDF]

, 2000
A generalized quintessence model is presented which corresponds to a richer vacuum structure that, besides a time-dependent, slowly varying scalar field, contains a varying cosmological term.
A. G. Riess, A. Mariero, B. P. Schmidth, B. Ratra, C. J. Hogan, C. Kolda, G. Huey, I. Zehavi, I. Zlatev, I. Zlatev, J. A. Frieman, J. E. Gunn, J. P. Ostriker, K. Coble, L. Wang, L. Wang, M. Abramowitz, M. S. Turner, P. Binétruy, P. Binétruy, P. Brax, P. Brax, P. J. E. Peebles, P. J. Steinhardt, P. J. Steinhardt, Pedro F. González-Díaz, R. R. Caldwell, R. R. Caldwell, S. Perlmutter, S. Perlmutter, S. Weinberg, T. Barreiro   +31 more
core   +2 more sources

Effects of Quantum Metric Fluctuations on the Cosmological Evolution in Friedmann-Lemaitre-Robertson-Walker Geometries

Physics, 2021
In this paper, the effects of the quantum metric fluctuations on the background cosmological dynamics of the universe are considered. To describe the quantum effects, the metric is assumed to be given by the sum of a classical component and a fluctuating
Zahra Haghani, Tiberiu Harko
doaj   +1 more source

Cosmological Model with Ω M -Dependent Cosmological Constant [PDF]

General Relativity and Gravitation, 2003
The idea here is to set the cosmical constant $ $ proportional to the scalar of the stress-energy tensor of the ordinary matter. We investigate the evolution of the scale factor in a cosmological model in which the cosmological constant is proportional to the scalar of the stress-energy tensor.
openaire   +3 more sources