Nonsingular bouncing cosmology in general relativity: physical analysis of the spacetime defect

Abstract

In this paper, we describe physical effects occurring in the regularized Robertson–Walker spacetime which can reveal the presence of the defect. Our analysis is based on two main physical quantities: the compressive forces acting on (human) observers and the energy possessed by massive particles and photons during their dynamical evolution. In section , we claim that with a characteristic length scale of the order of the Planck length compressive forces become so intense near the defect that no (human) observer is able to cross it. In section , we show that the energy exhibits an unusual character over a small time interval around the bounce contrasting with the behaviour in the standard cosmology picture. We conclude the paper with some considerations and open problems related to our results.

Geodesic congruences in modified Schwarzschild black holes

“…There is another issue we would like to address here. The procedure of the spacetime-defect regularization of the Schwarzschild solution can actually be applied to the singular Friedmann solution in cosmology [12,13,22]. The expansion of geodesic congruence could remain finite at cosmic time t = 0 for this regularized FLRW universe [15], while it is divergent at the big bang singularity for the standard FLRW universe.…”

On the propagation across the big bounce in an open quantum FLRW cosmology

“…where Π is the conserved momentum associated to the -translational Killing vector field underlying the geometry (6). The numerical analysis of the solution of the above equation reveals that timelike geodesics are well-behaved at the BB (see Fig.…”

“…In this second part of the paper, we perform a quantum analysis by computing the propagator of a scalar field evolving along the FLRW background (6). The starting point of our study will be the 2-point function defined by a Gaussian integral in the matrix model, i.e.,…”

Spacetime geometry of spin, polarization, and wavefunction collapse

“…Degenerate spacetime metrics have appeared in other contexts in the literature, such as in the regularization of the big bang singularity [Ba,K1,K2,K3,KW] and loop quantum gravity [LW]. Our use of metric degeneracy originates from nonnoetherian algebraic geometry, which in turn arose from the vacuum geometry of certain quiver gauge theories in string theory (see [F-K, B3] and references therein).…”