Removing Static Black Hole Singularity without QM (paper)

[MTd2]

I thought of posting this on astrophysics or general relativity forums since it seems completely classical, but given the extraordinary claim, I am posting here. Note that one of the guys is a notable string theorist.

http://arxiv.org/abs/1510.03396v1

Journey Beyond the Schwarzschild Black Hole Singularity
Ignacio J. Araya, Itzhak Bars, Albin James
(Submitted on 12 Oct 2015)
We present the geodesical completion of the Schwarzschild black hole in four dimensions which covers the entire space in (u,v) Kruskal-Szekeres coordinates, including the spacetime behind the black and white hole singularities. The gravitational constant switches sign abruptly at the singularity, thus we interpret the other side of the singularity as a region of antigravity. The presence of such sign flips is a prediction of local (Weyl) scale invariant geodesically complete spacetimes which improve classical general relativity and string theory. We compute the geodesics for our new black hole and show that all geodesics of a test particle are complete. Hence, an ideal observer, that starts its journey in the usual space of gravity, can reach the other side of the singularity in a finite amount of proper time. As usual, an observer outside of the horizon cannot verify that such phenomena exist. However, the fact that there exist proper observers that can see this, is of fundamental significance for the construction of the correct theory and the interpretation of phenomena pertaining to black holes and cosmology close to and beyond the singularities.

 

[martinbn]

The suggestion is that the gravitational constant $G$ changes sign. How reasonable is that and how physical is that?

 

[I. J. Araya]

Hi. I am Ignacio J. Araya (co-author of the paper).
So for observers in the usual gravity region, the sign of G is the usual one, and the physics of things that happen beyond the singularity (even beyond the horizon) won't be accessible to them due to the infinite time-dilation between the observer at infinity and the infalling observer at horizon-crossing. Therefore, the physics in our gravity region is unchanged. Also, the motivation for requiring the sign-change is that in the context of the Weyl-symmetric version of the Standard Model coupled to GR, the term in the action that conformally couples the scalar fields does change sign in generic solutions, and therefore, fixing the gauge by choosing the term to be a constant (to recover usual gravity) leads to an incomplete evolution in field-space by choice, and therefore, it leads to geodesically incomplete trajectories of particles in the corresponding background.