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Observational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating `dark energy', of which the…

Astrophysics · Physics 2010-03-26 Luke Barnes , Matthew J. Francis , Geraint F. Lewis , Eric V. Linder

Despite the significant accomplishments of general relativity, numerous unresolved issues persist in our understanding of the cosmos. One of the most perplexing challenges is the ongoing accelerated expansion of the Universe, which…

Cosmology and Nongalactic Astrophysics · Physics 2023-11-22 M. Koussour , N. Myrzakulov , Alnadhief H. A. Alfedeel , Amare Abebe

Understanding the accelerating expansion of the Universe remains a fundamental challenge in modern cosmology. In this paper, we investigate a cosmological model parametrized by a generalized variable deceleration parameter to elucidate the…

General Relativity and Quantum Cosmology · Physics 2023-09-29 M. Koussour , N. Myrzakulov , Alnadhief H. A. Alfedeel , F. Awad , M. Bennai

We explore the equation of state (EoS) for dark energy $w_{\mathrm{DE}}$ in modified gravitational theories to explain the current accelerated expansion of the universe. We explicitly demonstrate that the future crossings of the phantom…

General Relativity and Quantum Cosmology · Physics 2017-08-23 Kazuharu Bamba

In view of late-time cosmic acceleration, a dark energy cosmological model is revisited wherein Einstein's cosmological constant is considered as a candidate of dark energy. Exact solution of Einstein field equations (EFEs) is derived in a…

General Relativity and Quantum Cosmology · Physics 2019-11-22 S. K. J. Pacif , Md Salahuddin Khan , L. K. Paikroy , Shalini Singh

In this article, we attempt to describe cosmic late-time acceleration of the universe in the framework of $f(R,L_m)$ gravity by using an effective equation of state when the account is taken of bulk viscosity. We presume a non-linear…

General Relativity and Quantum Cosmology · Physics 2023-03-31 Lakhan V. Jaybhaye , Raja Solanki , Sanjay Mandal , Pradyumn Kumar Sahoo

In this study, we have explored a transitioning cosmological model of universe's expansion in $f(R,\mathcal{L}_{m})$ gravity. The quadratic type of equation of state parameter in the form $\omega=-1 + \alpha (1 + z) + \beta (1 + z)^2$,…

General Relativity and Quantum Cosmology · Physics 2025-04-16 Vinod Kumar Bhardwaj , Saibal Ray

This paper rigorously examines the potential of the $f(T, \mathcal{T})$ theory as a promising framework for understanding the dark sector of the universe, particularly in relation to cosmic acceleration. The $f(T, \mathcal{T})$ theory…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-28 M. Koussour , O. Donmez , S. Bekov , A. Syzdykova , S. Muminov , A. I. Ashirova

In this article, we investigate a new parametrization of the dark energy equation of state (EoS) with a single parameter for a barotropic fluid that deviates from the standard $\Lambda$CDM cosmology. We derive observational constraints on…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-31 D. Revanth Kumar , Santosh Kumar Yadav

Recent analysis of the DESI Collaboration challenges the $\Lambda$-Cold Dark Matter ($\Lambda$CDM) model, suggesting evidence for a dynamic dark energy. These results are obtained in the context of generic parameterizations of the dark…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-21 Rayff de Souza , Gabriel Rodrigues , Jailson Alcaniz

We discuss deep learning inference for the neutron star equation of state (EoS) using the real observational data of the mass and the radius. We make a quantitative comparison between the conventional polynomial regression and the neural…

Nuclear Theory · Physics 2021-06-14 Yuki Fujimoto , Kenji Fukushima , Koichi Murase

In this paper, we combine the latest observational data, including the WMAP five-year data (WMAP5), BOOMERanG, CBI, VSA, ACBAR, as well as the Baryon Acoustic Oscillations (BAO) and Type Ia Supernoave (SN) "Union" compilation (307 sample)…

Astrophysics · Physics 2008-11-26 Jun-Qing Xia , Hong Li , Gong-Bo Zhao , Xinmin Zhang

We review various theoretical approaches for the equation of state (EoS) of dense matter, relevant for the description of core-collapse supernovae, compact stars and compact star mergers. The emphasis is put on models that are applicable to…

High Energy Astrophysical Phenomena · Physics 2017-04-05 M. Oertel , M. Hempel , T. Klähn , S. Typel

Among the various possibilities to probe the theory behind the recent accelerated expansion of the universe, the energy conditions (ECs) are of particular interest, since it is possible to confront and constrain the many models, including…

General Relativity and Quantum Cosmology · Physics 2018-09-17 M. E. S. Alves , F. C. Carvalho , J. C. N. de Araujo , M. Penna-Lima , S. D. P. Vitenti

We use the Constitution supernova, the baryon acoustic oscillation, the cosmic microwave background, and the Hubble parameter data to analyze the evolution property of dark energy. We obtain different results when we fit different baryon…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Yungui Gong , Rong-Gen Cai , Yun Chen , Zong-Hong Zhu

The equation of state (EoS) of the neutron star (NS) matter remains an enigma. In this work we perform the Bayesian parameter inference with the gravitational wave data (GW170817) and mass-radius observations of some NSs (PSR J0030+0451,…

High Energy Astrophysical Phenomena · Physics 2021-03-23 Shao-Peng Tang , Jin-Liang Jiang , Wei-Hong Gao , Yi-Zhong Fan , Da-Ming Wei

We have conducted an extensive study using a diverse set of equations of state (EoSs) to uncover strong relationships between neutron star (NS) observables and the underlying EoS parameters using symbolic regression method. These EoS…

Nuclear Theory · Physics 2025-04-17 N. K. Patra , Tuhin Malik , Helena Pais , Kai Zhou , B. K. Agrawal , Constança Providência

Understanding the equation of state (EOS) of neutron stars (NSs) is a fundamental challenge in astrophysics and nuclear physics. A first-order phase transition (FOPT) at high densities could lead to the formation of a quark core,…

High Energy Astrophysical Phenomena · Physics 2025-02-11 Zuhua Ji , Jiarui Chen

Modern multi-messenger astronomical observations and heavy ion experiments provide new insights into the structure of compact objects. Nevertheless, much ambiguity remains when it comes to super dense matter above the nuclear saturation…

General Relativity and Quantum Cosmology · Physics 2021-02-03 Victor I. Danchev , Daniela D. Doneva

Here we test different models of dark energy beyond the standard cosmological constant scenario. We start considering the CPL parameterization of the equation of state (EOS), then we consider a dark energy scalar field (Quintessense).…

High Energy Astrophysical Phenomena · Physics 2018-02-07 Marek Demianski , Ester Piedipalumbo , Disha Sawant , Lorenzo Amati