Spherical collapse model in time varying vacuum cosmologies
- Academy of Athens, Research Center for Astronomy and Applied Mathematics, Soranou Efesiou 4, 11527, Athens (Greece)
- Institute of Astronomy and Astrophysics, National Observatory of Athens, Thessio 11810, Athens (Greece) and Instituto Nacional de Astrofisica, Optica y Electronica, 72000 Puebla (Mexico)
- High Energy Physics Group, Department Estructura i Constituents de la Materia, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Catalonia, Spain and Institut de Ciencies del Cosmos, UB, Barcelona (Spain)
We investigate the virialization of cosmic structures in the framework of flat Friedmann-Lemaitre-Robertson-Walker cosmological models, in which the vacuum energy density evolves with time. In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, 'turn around', and finally collapse. We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, {Lambda}={Lambda}(H). A particularly well-motivated model of this type is the so-called quantum field vacuum, in which {Lambda}(H) is a quadratic function, {Lambda}(H)=n{sub 0}+n{sub 2}H{sup 2}, with n{sub 0{ne}}0. This model was previously studied by our team using the latest high quality cosmological data to constrain its free parameters, as well as the predicted cluster formation rate. It turns out that the corresponding Hubble expansion history resembles that of the traditional {Lambda}CDM cosmology. We use this {Lambda}(t)CDM framework to illustrate the fact that the properties of the spherical collapse model (virial density, collapse factor, etc.) depend on the choice of the considered vacuum energy (homogeneous or clustered). In particular, if the distribution of the vacuum energy is clustered, then, under specific conditions, we can produce more concentrated structures with respect to the homogeneous vacuum energy case.
- OSTI ID:
- 21433005
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 82, Issue 8; Other Information: DOI: 10.1103/PhysRevD.82.083512; (c) 2010 American Institute of Physics; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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