Where Does the Physics of Extreme Gravitational Collapse Reside?

Abstract

Abstract:The gravitational collapse of massive stars serves to manifest the most severe deviations of general relativity with respect to Newtonian gravity: the formation of horizons and spacetime singularities. Both features have proven to be catalysts of deep physical developments, especially when combined with the principles of quantum mechanics. Nonetheless, it is seldom remarked that it is hardly possible to combine all these developments into a unified theoretical model, while maintaining reasonable prospects for the independent experimental corroboration of its different parts. In this paper we review the current theoretical understanding of the physics of gravitational collapse in order to highlight this tension, stating the position that the standard view on evaporating black holes stands for. This serves as the motivation for the discussion of a recent proposal that offers the opposite perspective, represented by a set of geometries that regularize the classical singular behavior and present modifications of the near-horizon Schwarzschild geometry as the result of the propagation of non-perturbative ultraviolet effects originated in regions of high curvature. We present an extensive exploration of the necessary steps on the explicit construction of these geometries, and discuss how this proposal could change our present understanding of astrophysical black holes and even offer the possibility of detecting genuine ultraviolet effects in gravitational-wave experiments.

A Model of Black Hole Evaporation and 4D Weyl Anomaly

“…This is because the initial collapsing matter came from infinity with a dilute distribution. Then, the region inside the innermost shell in Figure 4 is flat due to the spherical symmetry, and it is almost frozen in time by the large redshift as in (27) 13 . Thus, the boundary conditions for T µν are given by:…”

“…Now, the metric at a spacetime point (U, r) inside the object is obtained by considering the shell that passes the point and evaluating the metric (13). We have at r = r i :…”

“…4 We keep using the term "black hole" even though the system is different from the conventional black hole that has a horizon. 5 See also [13][14][15][16][17]. See, e.g., [18,19] for a black hole as a closed trapped region in the vacuum.…”

“…Finally, using the boundary condition (47), we have: 13 We will check the validity of (30) later. Indeed, (30) becomes almost flat at r ∼ √ σ, and can be connected to the flat spacetime.…”

Born–Infeld inspired modifications of gravity

“…In terms of the energy density and pressure of the matter fluid, we can also compute the degree of anisotropy in theĝ sector, which takes the following from 49) with C = C 1 +C 2 +C 3 . In [191] the quantity Q is used as a parameter in order to obtain the general solution in a parametric form.…”