Screenings in modified gravity: a perturbative approach

Short Distance Non-perturbative Effects of Large Distance Modified Gravity

In a model of large distance modified gravity we compare the nonperturbative Schwarzschild solution of hep-th/0407049 to approximate solutions obtained previously. In the regions where there is a good qualitative agreement between the two, the nonperturbative solution yields effects that could have observational significance. These effects reduce, by a factor of a few, the predictions for the a...

γγ → π + π − IN THE MODIFIED PERTURBATIVE APPROACH a

Perturbative Gravity Expansions

I have been asked to describe the status of perturbative expansions of gravity theories. This is a fairly active and interesting subject. I will try to be brief, because I have a lot to say about string theory, which is the main subject of my lectures at this school. The motivation for studying perturbative gravity expansions is to ascertain whether standard methods of quantum field theory are ...

Perturbative Noncommutative Quantum Gravity

We study perturbative noncommutative quantum gravity by expanding the gravitational field about a fixed classical background. A calculation of the one loop gravitational self-energy graph reveals that only the non-planar graviton loops are damped by oscillating internal momentum dependent factors. The noncommutative quantum gravity perturbation theory is not renormalizable beyond one loop for m...

Perturbative approach to the two-dimensional quantum gravity

The main part of this presentation is a review of the original works [14, 15, 16, 17, 18, 19] on the perturbative approach to the 2-dimensional quantum gravity. We discuss the renormalization of the two-dimensional dilaton gravity in a covariant gauge, the form of the quantum corrections to the classical potential, and the conditions of Weyl invariance in a theory of string coupled to 2d quantu...