{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/probing-a-steep-eos-for-dark-energy-with","title":"Probing a Steep EoS for Dark Energy with latest observations","arxiv_id":"1708.08529","date":"2017-08-28","proceeding":null,"authors":["Mariana Jaber","Axel de la Macorra"],"abstract":"We present a parametrization for the Dark Energy Equation of State \"EoS\" which has a rich structure, performing a transition at pivotal redshift $z_T$ between the present day value $w_0$ to an early time $w_i=w_a+w_0\\equiv w(z\\gg0)$ with a steepness given in terms of $q$ parameter. The proposed parametrization is $w=w_0+w_a(z/z_T)^q/(1+(z/z_T))^q$, with $w_0$, $w_i$, $q $ and $z_T$ constant parameters. It reduces to the widely used EoS $w=w_0+w_a(1-a)$ for $z_T=q=1$. This transition is motivated by scalar field dynamics such as for example quintessence models. We study if a late time transition is favored by BAO measurements combined with local determination of $H_0$ and information from the CMB. According to our results, an EoS with a present value of $w_0 = -0.92$ and a high redshift value $w_i =-0.99$, featuring a transition at $z_T = 0.28$ with an exponent $q = 9.97$ was favored by data coming from local dynamics of the Universe (BAO combined with $H_0$ determination). We find that a dynamical DE model allows to simultaneously fit $H_0$ from local determinations and Planck CMB measurements, alleviating the tension obtained in a $\\Lambda$CDM model. Additionally to this analysis we solved numerically the evolution of matter over-densities in the presence of dark energy both at background level and when its perturbations were considered. We show that the presence of a steep transition in the DE EoS gets imprinted into the evolution of matter overdensities and that the addition of an effective sound speed term does not erase such feature.","url_abs":"http://arxiv.org/abs/1708.08529v1","url_pdf":"http://arxiv.org/pdf/1708.08529v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"probing-a-steep-eos-for-dark-energy-with","repo_url":"https://github.com/oarodriguez/cosmostat","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}