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We propose a completely new parametrisation of the dark energy equation of state, which uses the dark energy density, $\Omega_e$ as a cosmic clock. We expand the equation of state in a series of orthogonal polynomials, with $\Omega_e$ as…

Cosmology and Nongalactic Astrophysics · Physics 2013-12-13 Ewan R. M. Tarrant , Edmund J. Copeland , Antonio Padilla , Constantinos Skordis

We review the implications of having a non-trivial matter component in the universe and the potential for detecting such a component through the matter power spectrum and ISW effect. We adopt a phenomenological approach and consider the…

Astrophysics · Physics 2009-07-09 Rachel Bean , Olivier Doré

In this work, we present a study on cosmological constraints of dark energy (DE) parametrizations after the observations of Dark Energy Spectroscopic Instruments (DESI) for Baryon Acoustic Oscillations (BAO) in 2024, suggesting potential…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-07 M. Malekjani , Z. Davari , S. Pourojaghi

Dynamical dark energy has gained renewed interest due to recent theoretical and observational developments. In the present paper, we focus on a string-motivated dark energy set-up, and perform a detailed cosmological analysis of exponential…

Cosmology and Nongalactic Astrophysics · Physics 2024-06-04 Sukannya Bhattacharya , Giulia Borghetto , Ameek Malhotra , Susha Parameswaran , Gianmassimo Tasinato , Ivonne Zavala

We constrain the dark energy equation of state parameter, $w$, using the power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect. We improve upon previous analyses by taking into account the trispectrum in the covariance matrix and…

Cosmology and Nongalactic Astrophysics · Physics 2018-04-11 Boris Bolliet , Barbara Comis , Eiichiro Komatsu , Juan Francisco Macías-Pérez

We present updated observational constraints on the spatially flat $\phi$CDM model, where dark energy is described by a minimally coupled scalar field $\phi$ with an inverse power-law potential $V=V_0 \phi^{-\alpha}$. Using Planck 2018 CMB…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-01 Chan-Gyung Park , Bharat Ratra

The predicted present-day amplitude of matter fluctuations based on cosmic microwave background (CMB) anisotropy data has sometimes been found discrepant with more direct measurements of late-time structure. This has motivated many…

Cosmology and Nongalactic Astrophysics · Physics 2024-02-14 Alex Laguë , Fiona McCarthy , Mathew Madhavacheril , J. Colin Hill , Frank J. Qu

We have reanalysed constraints on the equation of state parameter, w_Q = P/rho, of the dark energy, using several cosmological data sets and relaxing the usual constraint w_Q > -1. We find that combining Cosmic Microwave Background, large…

Astrophysics · Physics 2009-11-07 Steen Hannestad , Edvard Mortsell

Measurements of the cosmic microwave background (CMB) radiation provide a unique opportunity for a direct study of the primordial cosmic plasma at redshift z ~1000. The angular power spectra of temperature and polarisation fluctuations are…

Astrophysics · Physics 2009-11-10 Marco Bersanelli , Davide Maino , Aniello Mennella

We use late Universe probes - Type Ia Supernovae from the PantheonPlus compilation, Quasars, and Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) BAO data - along with Cosmic Chronometers or Megamasers to constrain various…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-02 Shubham Barua , Shantanu Desai

We consider the CMB bispectrum signal induced by structure formation through the correlation between the Integrated Sachs-Wolfe and the weak lensing effect. We investigate how the bispectrum knowledge can improve our knowledge of the most…

Astrophysics · Physics 2009-11-10 F. Giovi , C. Baccigalupi

We investigate the clustering properties of dynamical dark energy using the latest cosmological observations. We describe the dark energy perturbation within two complementary frameworks, namely the Parameterized Post-Friedmann (PPF)…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-02 Yuhang Yang , Qingqing Wang , Xin Ren , Emmanuel N. Saridakis , Yi-Fu Cai

Dark energy affects the CMB through its perturbations and affects both CMB and Sn-Ia through its background evolution. Using recent CMB and Sn-Ia data sets, together with the most general parameterization of the dark energy equation of…

We derive multiple constraints on dark energy and compare dynamical dark energy models with a time-varying equation of state ($w_0 w_a$CDM) versus a cosmological constant model ($\Lambda$CDM). We use Baryon Acoustic Oscillation (BAO) from…

Cosmology and Nongalactic Astrophysics · Physics 2025-10-24 Mustapha Ishak , Leonel Medina-Varela

The dynamics of expansion and large scale structure formation of the Universe are analyzed for models with dark energy in the form of a phantom scalar field which initially mimics a $\Lambda$-term and evolves slowly to the Big Rip…

Cosmology and Nongalactic Astrophysics · Physics 2013-05-30 Bohdan Novosyadlyj , Olga Sergijenko , Ruth Durrer , Volodymyr Pelykh

The lack of power anomaly is an intriguing feature at the largest angular scales of the CMB anisotropy temperature pattern, whose statistical significance is not strong enough to claim any new physics beyond the standard cosmological model.…

Cosmology and Nongalactic Astrophysics · Physics 2019-06-11 M. Billi , A. Gruppuso , N. Mandolesi , L. Moscardini , P. Natoli

We study the $(w_0, \, w_a)$ parametrization of the dark energy (DE) equation of state, with and without the effective field theory of dark energy (EFTofDE) framework to describe the DE perturbations, parametrized here by the braiding…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-19 Zhiyu Lu , Théo Simon

We investigate a phenomenological extension of the standard $\Lambda$CDM framework, the $\Omega_1\Omega_2$-$\Lambda$CDM model, in which the total energy density of the universe is expanded in powers of $1+z$. This parameterization recovers…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-20 Suresh Kumar

This study investigates the potential of a cosmological model termed $\Lambda w$DM, in which a cosmological constant play the role of dark energy and dark matter is barotropic and has a constant equation of state parameter ($w_{\rm dm}$),…

Cosmology and Nongalactic Astrophysics · Physics 2025-07-02 Yan-Hong Yao , Jian-Qi Liu

We use six tilted spatially-flat and untilted non-flat dark energy cosmological models in analyses of South Pole Telescope polarization (SPTpol) cosmic microwave background (CMB) data, alone and in combination with Planck 2015 CMB data and…

Cosmology and Nongalactic Astrophysics · Physics 2020-04-10 Chan-Gyung Park , Bharat Ratra