Constraining bouncing cosmology caused by the Casimir effect

We constrain the Friedmann-Robertson-Walker (FRW) model with a “radiation-like” contribution to the Friedmann equation against the astronomical data. We analyze the observational bounds on a (1 + z ) 4 term from type Ia supernovae (SNIa) data, Fanaroff-Riley type IIb (FRIIb) radio galaxy (RG) data, baryon oscillation peak and cosmic microwave background radiation (CMBR) observations. We argue that it is not possible to determine the energy densities of individual components scaling like radiation from a kinematic astronomical test. The bounds for the density parameter of the total radiation-like term can be obtained. We find different interpretations of the presence of a scaling-like radiation term: the FRW universe filled with a massless scalar field in a quantum regime (the Casimir effect), the FRW model in a semiclassical approximation of loop quantum gravity, the FRW model in the Randall-Sundrum scenario with dark radiation or a cosmological model with global rotation. In this paper, we mainly concentrate on the Casimir effect arising from quantum effects of a scalar field. This contribution can describe a decaying part of the cosmological constant. We discuss the back-reaction of gravity on the Casimir-type force which is a manifestation of the vacuum fluctuations of the quantum scalar field at low temperature. It is shown that, while the Casimir energy gives rise to the accelerating Universe, the cosmological constant term is still required. We argue that a small negative contribution of a radiation-like term can reconcile the tension between the observed primordial 4 He and D abundances. Moreover, the presence of such a contribution can also remove the disagreement between the Hubble parameter H 0 values obtained from the SNIa and Wilkinson Microwave Anisotropy Probe (WMAP) satellite data.