Thermal unparticles: a new form of energy density in the universe期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

Thermal unparticles: a new form of energy density in the universe

Authors:	Shao-Long Chen Xiao-Gang He Xue-Peng Hu Yi Liao

Affiliation:	(1) Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei, Taiwan;(2) Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei, Taiwan;(3) Department of Physics, Nankai University, Tianjin, 300071, China

Abstract:	An unparticle with scaling dimension $d_{{mathcal {U}}}$ has peculiar thermal properties due to its unique phase space structure. We find that the equation of state parameter $omega_{{mathcal {U}}}$ , the ratio of pressure to energy density, is given by $1/(2d_{{mathcal {U}}}+1),$ providing a new form of energy in our universe. In an expanding universe, the unparticle energy density $rho_{{mathcal {U}}}(T)$ evolves dramatically differently from that for photons. For $d_{{mathcal {U}}}>1$ , even if $rho_{{mathcal {U}}}(T_{mathrm{D}})$ at a high decoupling temperature T _D is very small, it is possible to have a large relic density $rho_{{mathcal {U}}}(T^{0}_{gamma})$ at present photon temperature T _γ⁰, large enough to play the role of dark matter. We calculate T _D and $rho_{{mathcal {U}}}(T^{0}_{gamma})$ using photon–unparticle interactions for illustration.

Keywords:	KeywordHeading" >PACS 98.80.Cq 11.15.Tk 11.25.Hf 14.80.-j
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