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Combining the equivalence between cosmological particle creation and an effective viscous fluid pressure with the fact that the latter represents a dynamical degree of freedom within the second-order Israel-Stewart theory for imperfect…

Astrophysics · Physics 2009-10-31 Winfried Zimdahl

Modified theories of gravity encompass a class of $f(R)$-models that seek to elucidate the observed late time accelerated expansion of the universe. In this study, we examine a set of viable $f(R)$ models (Hu-Sawicki: two cases,…

Cosmology and Nongalactic Astrophysics · Physics 2023-12-15 Kumar Ravi , Anirban Chatterjee , Biswajit Jana , Abhijit Bandyopadhyay

The article investigates cosmological applications of $f(Q)$ theories in a non-coincident formalism. We explore a new $f(Q)$ theory dynamics utilizing a non-vanishing affine connection involving a non-constant function…

General Relativity and Quantum Cosmology · Physics 2024-10-03 Sneha Pradhan , Raja Solanki , P. K. Sahoo

We develop a novel framework for describing quantum fluctuations in field theory, with a focus on cosmological applications. Our method uniquely circumvents the use of operator/Hilbert-space formalism, instead relying on a systematic…

General Relativity and Quantum Cosmology · Physics 2024-06-25 Ding Ding , Zhao Yu , Yidun Wan

In order to explore the generic properties of a backreaction model for explaining the accelerated expansion of the Universe, we exploit two metrics to describe the late time Universe. Since the standard FLRW metric cannot precisely describe…

Cosmology and Nongalactic Astrophysics · Physics 2020-05-27 Shu-Lei Cao , Huan-Yu Teng , Hao-Ran Yu , Hao-Yi Wan , Tong-Jie Zhang

The dispersion measure-redshift relation of fast radio bursts (FRBs) provides a valuable cosmological probe for constraining the Hubble constant, offering an independent measurement that could help resolve the ongoing Hubble tension. In…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-28 Chenyuan Xu , Yi Feng , Jiaying Xu

Non-extensive Tsallis thermostatistics is a widespread paradigm to describe large-scale gravitational systems. In this work we use Tsallis Cosmology to study thermodynamic gravity and derive modified Friedmann equations. We show that…

General Relativity and Quantum Cosmology · Physics 2025-03-25 Giuseppe Gaetano Luciano , Jaume Gine

In earlier papers we showed that a frame dependent effective action motivated by the postulates of three-space general coordinate invariance and Weyl scaling invariance exactly mimics a cosmological constant in Friedmann-Robertson-Walker…

Cosmology and Nongalactic Astrophysics · Physics 2020-08-25 Stephen L. Adler

The particle production in relativistic heavy-ion collisions seems to be created in a dynamically disordered system which can be best described by an extended exponential entropy. In distinguishing between the applicability of this and…

Nuclear Theory · Physics 2018-05-29 Abdel Nasser Tawfik , Hayam Yassin , Eman R. Abo Elyazeed

Causal inference is central to statistics and scientific discovery, enabling researchers to identify cause-and-effect relationships beyond associations. While traditionally studied within Euclidean spaces, contemporary applications…

Methodology · Statistics 2025-07-01 Satarupa Bhattacharjee , Bing Li , Xiao Wu , Lingzhou Xue

A linear relationship between the Hubble expansion parameter and the time derivative of the scalar field is explored in order to derive exact cosmological, attractor-like solutions, both in Einstein's theory and in Brans-Dicke gravity with…

General Relativity and Quantum Cosmology · Physics 2010-10-27 Olga Arias , Tame Gonzalez , Yoelsy Leyva , Israel Quiros

Based on the assumption that some apparent properties of the observable universe are accurate at a reasonable level of approximation, a tentative is made to independently derive the values of the baryon density parameter, the Hubble…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 A. Dinculescu

The increasing precision in the determination of the Hubble parameter has reached a per cent level at which large-scale cosmic flows induced by inhomogeneities of the matter distribution become non-negligible. Here we use large-scale…

Cosmology and Nongalactic Astrophysics · Physics 2017-06-28 Radoslaw Wojtak , Alexander Knebe , William A. Watson , Ilian T. Iliev , Steffen Hess , David Rapetti , Gustavo Yepes , Stefan Gottloeber

We propose an analytical parametrization of the comoving distance and Hubble parameter to study the cosmic expansion history beyond the vanilla $\Lambda$CDM model. The parametrization is generalized enough to include the contribution of…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-22 Bikash R. Dinda

In this paper, after reconstructing the redshift evolution of the Hubble function by adopting Gaussian process techniques, we estimate the best-fit parameters for some flat Friedmann cosmological models based on a Modified Chaplygin Gas…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-28 Muhsin Aljaf , Daniele Gregoris , Martiros Khurshudyan

We constrain two non-flat time-evolving dark energy cosmological models by using Hubble parameter data, Type Ia supernova apparent magnitude measurements, and baryonic acoustic oscillation peak length scale observations. The inclusion of…

Cosmology and Nongalactic Astrophysics · Physics 2017-03-22 Omer Farooq , Data Mania , Bharat Ratra

We considered the Tsallis holographic dark energy model in frames of Nojiri-Odintsov gravity with $f(R)=R+\lambda R^2-\sigma{\mu}/{R}$. For IR cutoff event horizon is taken. The cosmological evolution of such universe is investigated for…

General Relativity and Quantum Cosmology · Physics 2023-01-11 Artyom V. Astashenok , Alexander S. Tepliakov

We construct a theoretical framework to interpret the Hubble tension by means of a slow-rolling dynamics of a self-interacting scalar field. In particular, we split the Friedmann equation in order to construct a system for the three…

General Relativity and Quantum Cosmology · Physics 2024-04-25 Giovanni Montani , Nakia Carlevaro , Maria G. Dainotti

Bearing holographic dark energy hypothesis in mind, the ability of vacuum energy in describing the current accelerated universe is studied in the framework of Rastall theory. Here, in addition to the ordinary approach in which it is…

General Relativity and Quantum Cosmology · Physics 2020-11-17 S. Ghaffari , A. A. Mamon , H. Moradpour , A. H. Ziaie

Nojiri \& Odintsov \cite{noj1} and Hu \& Sawicki \cite{hu} have studied non-linear functions in modified gravity that explain the cosmic acceleration without cosmological constant, fulfil the conditions of local gravity \& stability and…

General Relativity and Quantum Cosmology · Physics 2019-08-14 Gauranga C Samanta , Nisha Godani