Timescape cosmology with radiation fluid

Abstract

Abstract. The timescape cosmology represents a potentially viable alternative to the standard homogeneous cosmology, without the need for dark energy. Although average cosmic evolution in the timescape scenario only differs substantially from that of Friedmann-Lemaître model at relatively late epochs when the contribution from the energy density of radiation is negligible, a full solution of the Buchert equations to incorporate radiation is necessary to smoothly match parameters to the epoch of photon decoupling and to obtain constraints from cosmic microwave background data. Here we extend the matter-dominated solution found in earlier work to include radiation, providing series solutions at early times and an efficient numerical integration strategy for generating the complete solution. The numerical solution is used to directly calculate the scale of the sound horizon at decoupling, and at the baryon drag epoch. The constraints on these scales from the Planck satellite data yield bounds on the timescape cosmological parameters, which are found to also agree with the best-fit values from a recent analysis of SDSS-II supernova data, while avoiding the problem of a primordial lithium-7 abundance anomaly.PACS numbers: 04.20.Cv, 98.80.Jk, 98.80.Es Timescape cosmology with radiation fluid 2

Curvature versus distances: Testing the FLRW cosmology

“…12 a) of [23] and is courtesy of Mikko Lavinto and Syksy Räsänen. The green dot-dashed line corresponds to the timescape scenario, see [16,62] and is courtesy of David Wiltshire.…”

Future evolution in a backreaction model and the analogous scalar field cosmology

“…It has been argued that confronting the backreaction models using the cosmological observational data may require more sophisticated approaches [36][37][38][39] than what one generally does in case of dark energy models. However, in the present case we have mapped the scalar field originating due to differential scale factors of the local domains into a large global domain such that it can fit the Friedmannian cosmology at the relevant large scales.…”

The background Friedmannian Hubble constant in relativistic inhomogeneous cosmology and the age of the Universe

“…pec_expan-bbl tions of emerging average negative curvature models, include, e.g., toy models of collapsing and expanding spheres (Räsänen 2006) or Lemaître-Tolman-Bondi (LTB) regions (Nambu & Tanimoto 2005;Kai et al 2007), a peak model (Räsänen 2008), a metric template model (Larena et al 2009;Chiesa et al 2014), bi-scale or more general multi-scale models (Wiegand & Buchert 2010;Buchert & Räsänen 2012), the Timescape model (Wiltshire 2009;Duley, Nazer, & Wiltshire 2013;Nazer & Wiltshire 2015), the virialisation approximation (Roukema, Ostrowski, & Buchert 2013), an effective viscous pressure approach , and Swiss cheese models that paste exact inhomogeneous solutions into holes in a homogeneous (FLRW) background (Bolejko & Célérier 2010; the Tardis model of Lavinto, Räsänen, & Szybka 2013). Updates to many of these models should benefit from an observationally justified estimate of H bg 1 .…”