Non‐Singular Black Holes Interiors Need Physics Beyond the Standard Model

Abstract

The composition as well as the very existence of the interior of a Schwarzschild black hole (BH) remains at the forefront of interesting, open problems in fundamental physics. To address this issue, we turn to Hawking's "principle of ignorance", which says that, for an observer with limited information about a physical system, all descriptions that are consistent with known physics are equally valid. We compare three different observers who view the BH from the outside and agree on the external Schwarzschild geometry. First, the modernist, who accepts the classical BH as the final state of gravitational collapse, the singularity theorems that underlie this premise and the central singularity that the theorems predict. The modernist is willing to describe matter in terms of quantum fields in curved space but insists on (semi)classical gravity. Second is the skeptic, who wishes to evade any singular behavior by finding a loophole to the singularity theorems within the realm of classical general relativity (GR). The third is a postmodernist who similarly wants to circumvent the singularity theorems but is willing to invoke exotic quantum physics in the gravitational and/or matter sector to do so. The postmodern view suggests that the uncertainty principle can stabilize a classically singular BH in a similar manner to the stabilization of the classically unstable hydrogen atom: Strong quantum effects in the matter and gravitational sectors resolve the would-be singularity over horizon-sized length scales. The postmodern picture then requires a significant departure from (semi)classical gravity, as well as some exotic matter beyond the standard model of particle physics (SM). We find that only the postmodern framework is consistent with what is known so far about BH physics and conclude that a valid description of the BH interior needs matter beyond the SM and gravitational physics beyond (semi)classical GR.

Correspondence between strings in the Hagedorn phase and asymptotically de Sitter space

“…As the FRW evolution starts in a thermal state, an FRW observer might be compelled to invent a prehistory to explain the observable Universe. This is similar to the way that a semiclassical observer invents a description of the BH interior [43] (and see below). Three possible such prehistories are shown in Fig.…”

“…The latter case leads to a duality connecting the string state to dS space and, as shown in our current discussion, implies a duality between dS space and a thermal-scalar condensate. [43]. Indeed, previous studies by Silverstein and collaborators have discussed, in a very different context, how a tachyon condensate can be used to tame spacelike singularities [44][45][46][47].…”

The role of collapsed matter in the decay of black holes

“…The huge discrepancy between N G ∼ 1 and N G ∼ 10 38 at the time of the departure from the semiclassical evolution estimated in the two scenarios leads us to the fundamental questions: What is the shortest scale of gravitational confinement for ordinary matter? In order to answer this question, we need an estimate of the quantum pressure that prevents the baryons from reaching the infinitely dense classical singularity [22,23].…”

Geodesically complete black holes

“…However, it is reasonable to assume that, once that quantum gravity effect are taken into account, singularities will be regularized. The structure and properties of the corresponding non-singular black holes is largely unknown, in part due to our lack of knowledge about the dynamics in quantum gravity, although there have been many and diverse attempts at constructing geometries or toy models that aim at capturing the leading effects beyond general relativity [5][6][7][8][9][10][11][12][13][14][15][16].…”