Density perturbation of unparticle dark matter in the flat Universe

• Published in: The European physical journal. C, Particles and fields Vol. 64; no. 1; pp. 107 - 112
• Main Authors: Chen, Songbai, Fu, Xiangyun, Jing, Jiliang
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.11.2009; Springer; Springer Nature B.V
• Subjects: Approximation; Astronomy; Astrophysics and Cosmology; Big Bang theory; Cold dark matter; Dark matter; Density; Elementary Particles; Equations of state; Evolution; Exact sciences and technology; Growth factors; Hadrons; Heavy Ions; Mathematical models; Measurement Science and Instrumentation; Nuclear Energy; Nuclear Physics; Perturbation; Perturbation methods; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Regular Article - Theoretical Physics; String Theory; The physics of elementary particles and fields; Universe; 95.36.+x; 98.80.-k; Equations of state; Dark matter; Growth rate; Cold dark matter; Density perturbation; Elementary particles; Models; Mathematical physics; Flat metric
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1140/epjc/s10052-009-1141-9

The unparticle has been suggested as a candidate of dark matter. We investigated the growth rate of the density perturbation for unparticle dark matter in the flat Universe. First, we consider the model in which the unparticle is the sole dark matter and find that the growth factor can be approximated well by f =(1+3 ω u ) Ω u γ , where ω u is the equation of state of unparticle. Our results show that the presence of ω u modifies the behavior of the growth factor  f . For the second model where the unparticle co-exists with cold dark matter, the growth factor has a new approximation f =(1+3 ω u ) Ω u γ + α Ω m and α is a function of ω u . Thus the growth factor of the unparticle is quite different from that of the usual dark matter. This information can help us know more about unparticle and the early evolution of the Universe.