MG14 - Talk detail

Back to previous page

 Participant

Institution

Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

We present a class of weakly non-local higher derivative theories of gravity as a step forward with Einstein general relativity. These theories are unitary (ghost-free) and finite at quantum level in even and odd dimension. In D=4 we explicitly evaluated the beta functions showing quantum scale invariance (all the beta functions vanish). These results can be easily extended in any even dimension and it is likely, that the higher dimensional theory can be made finite too. Therefore we have the possibility for ``finite quantum gravity" in any dimension.

Pdf file

Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

We propose a ultraviolet completion of the bosonic sector of 11-dimensional supergravity motivated by string field theory. We start from a general class of theories characterized by an entire nonpolynomial form factor which allows one to avoid new poles in the propagator and improves the high-energy behavior of the loops amplitudes. Comparing these models with effective string field theory, a unique form factor is selected out. In view of this, we modify 10-dimensional supergravity and finally get a ultraviolet completion of 11-dimensional supergravity by an oxidation process. The result is a candidate for a finite and unitary particle-field limit of M-theory.

Pdf file

Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

In a class of weakly nonlocal theories of gravity we investigate the gravitational collapse and the formation of singularity-free black holes. The classical singularity inside the matter region is replaced by a bounce, after which the body starts expanding again. A black hole never forms, and the gravitational collapse only creates an apparent horizon, which can be interpreted as an event horizon when the observational timescale is shorter than the lifetime of the apparent horizon. We also exactly solve truncated equations of motion in the region outside the collapsing body and we reconstruct the solution in the whole spacetime. Now the gravitational collapse creates a singularity-free black hole in a finite amount of time, but the singularity is approached in an infinite amount of time. We argue that these black holes should be unstable providing a link between the two scenarios here presented.

Pdf file

Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

We give a list of exact classical solutions for a large class of weakly nonlocal theories of gravity, which are unitary and super-renormalizable (or finite) at quantum level. It is explicitly shown that flat and Ricci-flat spacetimes as well as maximally symmetric manifolds are exact solutions of the equations of motion. Therefore, well-known physical spacetimes like Schwarzschild, Kerr, (Anti-)de Sitter serve as solutions for standard matter content. In dimension higher than four we can also have Anti-de Sitter solutions in the presence of positive cosmological constant. We pedagogically show how to obtain these exact solutions. Furthermore, for another version of the theory written in the Weyl basis, Friedmann-Robertson-Walker (FRW) spacetimes are also exact solutions, when the matter content is given by conformal matter (radiation). We also comment on the presence of singularities and possible resolution of them in finite and conformally invariant theories. ``Delocalization" is proposed as a way to solve the black holes singularity problem. In order to solve cosmological Big-Bang singularity it seems crucial to have a conformally invariant quantum gravitational theory or an asymptotically free theory.

Pdf file

Back to previous page