H0-tension, CMB temperature and Unparticles

Maryam Aghaei

Department of Physics and Astronomy, Sejong University, South Korea ;

Department of Physics, School of Natural Science,

Ulsan National University of Science and Technology (UNIST), South Korea

 

Abstract: H0-tension is one of the late-time cosmology challenges for ΛCDM alongside cosmological constant problem, missing satellites and many others. Extensions to ΛCDM have been approached mostly by models with an extra parameter. Here, I introduce a framework for evaluating the viability of models of late-time cosmology by investigating unparticle cosmology as a case study. This model derives from a finite temperature broken conformal symmetry of radiation, described by a non-radiative correction with unknown sign in energy density. This symmetry breaking has a sign ambiguity, in which corrections about the IR fixed point are normal or tachyonic. Focusing on H0-tension for positive sign, the model predicts H(z) in the future to be zero or constant, the latter pointing to a stable de Sitter phase for our Universe. Therefore, in this case, unparticle cosmology fails to ameliorate H0-tension, but it provides a pointer to holographic dark energy. That is while negative sign scenario possesses a late-time temperature Tc≃4T_CMB associated with Ω_U≃1 (Ω_U≃10⁴ Ω_CMB). The CMB is hereby exposed to an enormous heat bath, but the age of the Universe constrained by the globular clusters, independently puts a constraint on any heat exchange from unparticles to the CMB in ΛCDM. Accordingly, we estimate the cross section of unparticles interactions with CMB photons to be σγ_U≲10^-40 m²=10^-3 nb.  

 Based on:

1-       Phys. Rev. D 104, 083511

2-       arxiv.org/abs/2203.16076

یکشنبه 25 اردیبهشت 1401، ساعت 15:00

Sunday 15 May 2022 – 15:00 Tehran Time

اتاق سمینار مجازی –Virtual Seminar Room

https://vc.sharif.edu/ch/cosmology

گزینه ورود به صورت مهمان – Enter as a Guest