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We examine the validity of the $\Lambda$CDM model, and probe for the dynamics of dark energy using latest astronomical observations. Using the $Om(z)$ diagnosis, we find that different kinds of observational data are in tension within the…

Cosmology and Nongalactic Astrophysics · Physics 2017-06-14 Yuecheng Zhang , Hanyu Zhang , Dandan Wang , Yanghan Qi , Yuting Wang , Gong-Bo Zhao

A new parameterization for the dark energy equation of state(EoS) is proposed and some of its cosmological consequences are also investigated. This new parameterization is the modification of Efstathiou' dark energy EoS parameterization. $w…

Cosmology and Nongalactic Astrophysics · Physics 2012-03-12 Lei Feng , Tan Lu

The evolution of dark energy density is a crucial quantity in understanding the nature of dark energy. Often, the quantity is described by the so-called equation of state, that is the ratio of dark energy pressure to its density. In this…

Cosmology and Nongalactic Astrophysics · Physics 2022-01-14 Ahmad Mehrabi , Maryam Vazirnia

Dark energy (DE) models with many free parameters are often considered excessive, as constraining all parameters poses a significant challenge. While such models offer greater flexibility to probe the DE sector in more detail. With the…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-25 Hanyu Cheng , Supriya Pan , Eleonora Di Valentino

We propose and implement a novel test to assess deviations from well-established concordance $\Lambda$CDM cosmology while inferring dark energy properties. In contrast to the commonly implemented parametric forms of the dark energy…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-27 Upala Mukhopadhyay , Sandeep Haridasu , Anjan A Sen , Suhail Dhawan

Using late-Universe observations, we demonstrate that freeing dark energy and dark matter equations of state (EoS) dramatically alters the inferred strength and direction of their interactions. When dark sector EoS are fixed to…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-25 Peng-Ju Wu , Ming Zhang , Shang-Jie Jin

Recently, DESI has released baryon acoustic oscillation (BAO) data, and DES has also published its five-year supernova (SN) data. These observations, combined with cosmic microwave background (CMB) data, support a dynamically evolving dark…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-09 Guo-Hong Du , Peng-Ju Wu , Tian-Nuo Li , Xin Zhang

When CMB data are used to derive cosmological parameters, their very choice does matter: some parameter values can be biased if the parameter space does not cover the "true" model. This is a problem, because of the difficulty to parametrize…

Astrophysics · Physics 2009-06-23 Giuseppe La Vacca , Loris P. L. Colombo , Luca Vergani , Silvio A. Bonometto

We carry out an independent re-analysis of the Dark Energy Spectroscopic Instrument (DESI) public dataset, focusing on extensions to the standard cosmological model, $\Lambda$CDM. Utilizing the dataset and Effective Field Theory (EFT)-based…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-15 Anton Chudaykin , Mikhail M. Ivanov , Oliver H. E. Philcox

A physical mechanism that produces three energy components is proposed as the common origin of dark energy and dark matter. The first two have equations of state W ~ 0 and act like dark matter, while the last has W ~ -1 at low redshifts…

General Relativity and Quantum Cosmology · Physics 2012-12-12 I. Gontijo

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

Recently the Dark Energy Survey (DES) Collaboration presented evidence that the equation of state $w$ of the dark energy is varying, or $w \simeq -0.948$ if it is constant. In either case, the dark energy cannot be due to a cosmological…

High Energy Physics - Phenomenology · Physics 2025-06-23 Hoang Nhan Luu , Yu-Cheng Qiu , S. -H. Henry Tye

Within the frame of cosmologies where Dark Energy (DE) is a self--interacting scalar field, we allow for a CDM--DE coupling and non--zero neutrino masses, simultaneously. In their 0--0 version, i.e. in the absence of coupling and neutrino…

Cosmology and Nongalactic Astrophysics · Physics 2009-09-01 G. La Vacca , J. R. Kristiansen , L. P. L. Colombo , R. Mainini , S. A. Bonometto

Several independent cosmological data, collected within the last twenty years, revealed the accelerated expansion rate of the Universe, usually assumed to be driven by the so called dark energy, which, according to recent estimates,…

Cosmology and Nongalactic Astrophysics · Physics 2020-10-16 Marek Demianski , Elisabeta Lusso , Maurizio Paolillo , Ester Piedipalumbo , Guido Risaliti

We investigate how the properties of dark energy affect the cosmological measurements of neutrino mass and extra relativistic degrees of freedom. We limit ourselves to the most basic extensions of $\Lambda$ cold dark matter (CDM) model,…

Cosmology and Nongalactic Astrophysics · Physics 2017-05-24 Ming-Ming Zhao , Yun-He Li , Jing-Fei Zhang , Xin Zhang

We revisit a cosmological model where dark matter (DM) and dark energy (DE) follow barotropic equations of state, allowing deviations from the standard $\Lambda$CDM framework (i.e. $w_{dm} \neq 0$, $w_{de} \neq -1$), considering both flat…

Cosmology and Nongalactic Astrophysics · Physics 2025-11-24 Dorian Araya , Cristian Castillo , Genly Leon , Juan Magaña , Angie Barr Domínguez , Miguel A. García-Aspeitia

We critically examine the state of current constraints on the dark energy (DE) equation of state (EoS) $w$. Our study is motivated by the observation that, while broadly consistent with the cosmological constant value $w=-1$, several…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-22 Luis A. Escamilla , William Giarè , Eleonora Di Valentino , Rafael C. Nunes , Sunny Vagnozzi

We allow simultaneously for a CDM--DE coupling and non--zero neutrino masses and find that significant coupling and neutrino mass are (slightly) statistically favoured in respect to a cosmology with no coupling and negligible neutrino mass…

Cosmology and Nongalactic Astrophysics · Physics 2009-11-20 G. La Vacca , J. R. Kristiansen , L. P. L. Colombo , R. Mainini , S. A. Bonometto

Cosmology at present provides the nominally strongest constraint on the masses of standard model neutrinos. However, this constraint extremely dependent on the nature of the dark energy component of the Universe. When the dark energy…

Astrophysics · Physics 2008-11-26 Steen Hannestad

This article questions the common assumption of cold dark matter (DM) by exploring the possibility of a non-zero equation of state (EoS) without relying on any parametric approach. In standard cosmological analyses, DM is typically modeled…

Cosmology and Nongalactic Astrophysics · Physics 2026-01-01 Mazaharul Abedin , Luis A. Escamilla , Supriya Pan , Eleonora Di Valentino , Weiqiang Yang