English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We exploit the gauge-invariant formalism to analyse the perturbativebehaviour of two cosmological models based on the generalized Chaplygin gasdescribing both dark matter and dark energy in the present Universe. In thefirst model we consider the generalized Chaplygin gas alone, while in thesecond one we add a baryon component to it. We extend our analysis also intothe parameter range $\alpha > 1$, where the generalized Chaplygin gas soundvelocity can be larger than that of light. In the first model we find that thematter power spectrum is compatible with the observed one only for $\alpha <10^{-5}$, which makes the generalized Chaplygin gas practicallyindistinguishable from $\Lambda$CDM. In the second model we study the evolutionof inhomogeneities of the baryon component. The theoretical power spectrum isin good agreement with the observed one for almost all values of $\alpha$.However, the growth of inhomogeneities seems to be particularly favoured eitherfor sufficiently small values of $\alpha$ or for $\alpha \gtrsim 3$. Thus, itappears that the viability of the generalized Chaplygin gas as a cosmologicalmodel is stronger when its sound velocity is superluminal. We show that in thiscase the generalized Chaplygin gas equation of state can be changed in anunobservable region in such a way that its equivalent $k$-essence microscopicalmodel has no problems with causality.

Gauge-invariant analysis of perturbations in Chaplygin gas unified models of dark matter and dark energy