Title:	Exploring cosmological imprints of phantom crossing with dynamical dark energy in Horndeski gravity
Authors:	Tiwari, Yashi Upadhyay, Ujjwal Jain, Rajeev Kumar
Issue Date:	14-Feb-2025
Publisher:	Physical Review D
Citation:	Physical Review D, 2025, Vol. 111(4), AR No. 043530
Abstract:	In the current era of precision cosmology, the persistence of cosmological tensions—most notably the Hubble tension and the S8 tension—challenges the standard lambda-cold dark matter (ΛCDM) model. To reconcile these tensions via late-time modifications to expansion history, various features, such as phantom crossing in the dark energy equation of state, a negative energy density at high redshifts, etc., are favored. However, these scenarios cannot be realized within the framework of general relativity (GR) without introducing ghost or gradient instabilities. In this work, we investigate a dynamical dark energy scenario within the framework of Horndeski gravity, incorporating nonminimal coupling to gravity and selfinteractions. We highlight that the model can exhibit novel features like phantom crossing and negative dark energy densities at high redshifts without introducing any instabilities. For this specific Horndeski model, we perform a comprehensive analysis of the background evolution along with the effects on perturbations, examining observables like growth rate, matter and cosmic microwave background (CMB) power spectrum. To check the consistency of the model with the observational data, we employ Markov chain Monte Carlo analysis using BAO/fσ8, supernovae, and CMB data. While the model does not outperform the standard Λ CDM framework in a combined likelihood analysis, there remains a preference for nonzero values of the model parameters within the data. This suggests that dynamical dark energy scenarios, particularly those with nonminimal couplings, merit further exploration as promising alternatives to GR, offering rich phenomenology that can be tested against a broader range of current and upcoming observational datasets
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/8648
ISSN:	2470-0029
Alternative Location:	https://doi.org/10.48550/arXiv.2412.00931 https://doi.org/10.1103/PhysRevD.111.043530
Copyright:	2025 American Physical Society
Appears in Collections:	Research Papers (A&A)

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