A bound on the cosmic opacity of unparticles from the CMB temperature

• DOI: 10.48550/arxiv.2203.16076
• Publication Date: 2022-01-01
• Authors: Maurice H. P. M. ...; Maryam Aghaei Abc...
• Keywords: Unparticle physics

Unparticle cosmology gives an unconventional outlook on the dark sector of cosmology, increasingly challenging $\Lambda\mbox{CDM}$ by $H_0$-tension. This model derives from a finite temperature broken conformal symmetry radiation, described non-radiative correction with unknown sign in energy density. breaking has ambiguity, which corrections about IR fixed point are normal or tachyonic. While first been ruled out recent study, latter possesses late-time $T_c\simeq 4\,T_{CMB}$ associated $\Omega_{\cal U}\simeq 1$ ($\Omega_{\cal U} \simeq 10^4 \Omega_{CMB}$), where $T_{CMB}$ denotes Cosmic Microwave Background (CMB). Thus exposed to enormous heat bath unparticles, is constrained astronomical age Universe $T_{u,0}$. The relative shift $\Delta T/T$ any exchange CMB hereby limited uncertainty few percent bounds effective cross-section unparticles interactions photons $\sigma _{\gamma \mathcal{U}} \lesssim 10^{-40}\ \mbox{m}^2=10^{-3}\ \mbox{nb}$. Assuming standard across broadband mass and spectrum more stringent bound 10^{-3}\,\mbox{pb}$ COBE-FIRAS constraints spectral distortions. midway photon-neutrino $\sigma_{\gamma\nu}$ photon-photon cross sections $\sigma_{\gamma\gamma}$, second par $\sigma_{\gamma\nu}$. These put unparticle if present, at edge model.