Radiative Poincare type eon and its follower

TL;DR

This paper explores how matter in one eon influences the next in Penrose's Conformal Cyclic Cosmology, using Einstein's equations with pure radiation and a Poincaré-Einstein metric analogy, revealing new radiation types in the subsequent eon.

Contribution

It introduces a novel solution to Einstein's equations for a spherical wave in an eon, linking it to the next eon via a reciprocity hypothesis, and characterizes the resulting radiation content.

Findings

The solution depends on one arbitrary function of the radial variable.

The next eon contains a damped wave, an in-going wave from collision, and scattered waves.

The scattered waves resemble a perfect fluid with specific energy and pressure.

Abstract

We consider two consecutive eons $\hat{M}$ and $\check{M}$ from Penrose's Conformal Cyclic Cosmology and study how the matter content of the past eon ($\hat{M}$) determines the matter content of the present eon ($\check{M}$) by means of the reciprocity hypothesis. We assume that the only matter content in the final stages of the past eon is a spherical wave described by Einstein's equations with the pure radiation energy momentum tensor $$\hat{T}^{ij} = \hat{\Phi}K^iK^j, \quad \hat{g}_{ij} K^iK^j = 0,$$ and with cosmological constant $\hat{\Lambda}$ . We solve these Einstein's equations associating to $\hat{M}$ the metric $\hat{g}=t^{-2}\big(-d t^2+h_t\big)$, which is a Lorentzian analog of the Poincar\'e-Einstein metric known from the theory of conformal invariants. The solution is obtained under the assumption that the 3-dimensional conformal structure $[h]$ on the $\mathscr{I}^+$ of $\hat{M}$ is flat, that the metric $\hat{g}$ admits a power series expansion in the time variable $t$, and that $h_0\in [h]$. Such solution depends on one real arbitrary function of the radial variable $r$. Applying the reciprocal hypothesis, $\hat{g}\to \check{g}=t^4\hat{g}$, we show that the new eon $(\check{M},\check{g})$ created from the one containing a single spherical wave, is filled at its initial state with three types of radiation: (i) the damped spherical wave which continues its life from the previous eon, (ii) the in-going spherical wave obtained as a result of a collision of the wave from the past eon with the Bang hypersurface and (3) randomly scattered waves that could be interpreted as perfect fluid with the energy density $\check{\rho}$ and the isotropic pressure $\check{p}$ such that $\check{p}=\tfrac13\check{\rho}$.