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200 papers

We consider a novel mechanism to account for the observed distance-redshift relation. This is done by presenting a toy model for the large-scale matter distribution in a static Universe. Our model mainly concerns particles with masses far…

Cosmology and Nongalactic Astrophysics · Physics 2017-01-13 Nathan W. C. Leigh , Or Graur

The current paper reports an investigation of the cosmological implications of symmetric teleparallel gravity within a modified $f(Q)$ theory. We construct a specific exponential $f(Q)$ model as $f(Q) = Q + \eta_1 Q_0\left(1 - e^{-\eta_2…

General Relativity and Quantum Cosmology · Physics 2025-11-11 Sanjeeda Sultanaa , Surajit Chattopadhyay

We investigate the dynamics of the generalized $\Lambda$CDM model, which the $\Lambda$ term is running with the cosmological time. The $\Lambda(t)$ term emerges from the covariant theory of the scalar field $\phi$ with the self-interacting…

Cosmology and Nongalactic Astrophysics · Physics 2017-09-29 Marek Szydlowski , Aleksander Stachowski

Based on energy conservation in a Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe, on the Legendre transformation between energy density and pressure, and on nonperturbative asymptotic freedom at high temperatures we derive the…

General Physics · Physics 2018-03-14 Steffen Hahn , Ralf Hofmann

It has recently been proposed [M. P. Hertzberg and A. Loeb, arXiv:2302.09090] that the observed value of the cosmological constant can be related to the physical parameters of the Standard Model. In the present compact note we point out…

General Relativity and Quantum Cosmology · Physics 2023-02-23 Shahar Hod

The latest cosmological observables analyses seem to converge to a concordant view of the cosmological model: namely the power law Lambda-CDM. The recent WMAP results comfort this new standard model. Nevertheless, some degeneracy in the CMB…

Astrophysics · Physics 2007-05-23 Marian Douspis

The Hubble Constant measured from the anisotropy in the cosmic microwave background (CMB) is shown to be independent of small changes from the standard model of the redshift dependence of dark energy. Modifications of the Friedmann equation…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Jeremy Mould

In the present paper, we study the capability of interacting dark energy model with pure momentum transfer in the dark sector to reconcile tensions between low redshift observations and cosmic microwave background (CMB) results. This class…

Cosmology and Nongalactic Astrophysics · Physics 2020-02-11 Mahnaz Asghari , Shahram Khosravi , Amir Mollazadeh

In this paper, we propose a new method to use the strong lensing data sets to constrain a cosmological model. By taking the ratio…

Cosmology and Nongalactic Astrophysics · Physics 2013-09-05 Nannan Wang , Lixin Xu

The role of an exponential function of the scalar curvature in the modified gravity is analyzed. Two models are proposed. A toy model that complies with local and cosmological constraints and gives appropriate qualitative description of the…

General Relativity and Quantum Cosmology · Physics 2020-07-15 L. N. Granda

There is now strong evidence that the main contribution to the cosmic energy density is not due to matter, but to another component with negative pressure. Its nature is still unknown: it could be the vacuum energy, manifesting itself as a…

Astrophysics · Physics 2007-05-23 Alberto Cappi

The covariant canonical transformation theory applied to the relativistic Hamiltonian theory of classical matter fields in dynamical space-time yields a novel (first order) gauge field theory of gravitation. The emerging field equations…

General Relativity and Quantum Cosmology · Physics 2023-11-29 David Vasak , Johannes Kirsch , Dirk Kehm , Juergen Struckmeier

New systematic classification of cosmological models of the present Universe is introduced. After making the comparison of these models with all existing observational data three viable models remain: the cold dark matter model with the…

Astrophysics · Physics 2007-05-23 A. A. Starobinsky

We extend the usual gravitational action principle by promoting the bare cosmological constant (CC) from a parameter to a field which can take many possible values. Variation leads to a new integral constraint equation which determines the…

General Relativity and Quantum Cosmology · Physics 2011-03-21 John D. Barrow , Douglas J. Shaw

We analyze cosmography as a tool to constrain modified gravity theories. We take four distinct models and obtain their parameters in terms of the cosmographic parameters favored by observational data of strong gravitational lensing. We…

General Relativity and Quantum Cosmology · Physics 2025-02-06 Mario H. Amante , Andrés Lizardo , Javier Chagoya , C. Ortiz

In light of the most recent cosmological observations, we provide new updated constraints on the slow-roll inflation in different extended scenarios beyond the $\Lambda\rm{CDM}$ cosmological model. Along with the usual six parameters, we…

Cosmology and Nongalactic Astrophysics · Physics 2021-11-25 Matteo Forconi , William Giarè , Eleonora Di Valentino , Alessandro Melchiorri

We study the cosmological implications of gravity models which break diffeomorphisms (Diff) invariance down to transverse diffeomorphisms (TDiff). We start from the most general gravitational action involving up to quadratic terms in…

General Relativity and Quantum Cosmology · Physics 2024-02-02 Antonio G. Bello-Morales , Antonio L. Maroto

We present a generalisation of the charged C-metric conformally coupled with a scalar field in the presence of a cosmological constant. The solution is asymptotically flat or a constant curvature spacetime. The spacetime metric has the…

General Relativity and Quantum Cosmology · Physics 2009-09-29 C. Charmousis , T. Kolyvaris , E. Papantonopoulos

We study dynamics of $\Lambda(t)$ cosmological models which are a natural generalization of the standard cosmological model (the $\Lambda$CDM model). We consider a class of models: the ones with a prescribed form of…

Cosmology and Nongalactic Astrophysics · Physics 2017-09-29 Marek Szydlowski , Aleksander Stachowski

Observational searches for large-scale vorticity modes in the late time Universe are underexplored. Within the standard $\Lambda$CDM model, this is well motivated given the observed properties of the cosmic microwave background (CMB).…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-30 William R. Coulton , Kazuyuki Akitsu , Masahiro Takada