Stochastic gravitational waves from a new type of modified Chaplygin gas

Abstract

We propose a new scenario for the early universe where there is a smooth transition between an early de Sitter-like phase and a radiation dominated era. In this model, the matter content is modelled by a new type of generalised Chaplygin gas for the early universe, with an underlying scalar field description. We study the gravitational waves generated by the quantum fluctuations. In particular, we calculate the gravitational wave power spectrum, as it would be measured today, following the method of the Bogoliubov coefficients. We show that the high frequencies region of the spectrum depends strongly on one of the parameters of the model. On the other hand, we use the number of e-folds, along with the power spectra and spectral index of the scalar perturbations, to constrain the model observationally.Comment: 8 pages, 6 figures, RevTeX 4. Published in PR

Slow-roll inflation preceded by a topological defect phaseà laChaplygin gas

“…(2.5b) was previously studied within an inflationary framework in Ref. [22] (see also Ref. [18]) and, under suitable constraints on A 2 , B 2 , and α 2 , can depict the transition from the de Sitter-like era to the radiation dominated era.…”

“…We can as well impose a bound on the number of e-folds, N c , since a given mode exits the horizon until the end of inflation as done in Ref. [22]. This gives the best-fit values for α 2 , V 0 , and, therefore, A 2 .…”

“…the potentials (2.13) and (2.14), using the methodology used by one of us in Ref. [22]. More precisely, we can use the WMAP7 observation of the power spectrum of the comoving curvature perturbation, P s = 2.45×10 −9 , and the spectral index, n s = 0.963, at the pivot scale k 0 = 0.002 Mpc −1 to fix the parameters in our model [28].…”

“…[19] (see also [20,21]) and later extended in Refs. [22][23][24]. The energy density of a network of frustrated topological defects (NFTD) can be described in a compact way, for example, as…”

Eddington–Born–Infeld cosmology: a cosmographic approach, a tale of doomsdays and the fate of bound structures

“…Indeed, the GCG can unify the role of dark matter and dark energy [66,67] (for a recent update of the subject see Ref. [68]), avoid the big rip singularity [69], describe some primitive epoch of the universe [70] and alleviate the observed low quadruple of the CMB [71]. We will complete our analyses by considering as well the possible avoidance of the little rip event [72] in the above mentioned setup.…”