S. Hayakawa

Low energy effective action on a self-gravitating D-brane

Recently the study of braneworld on the self-gravitating D-brane has been initiated and derived the gravitational equation on the brane by holographic and geometrical projection methods. Surprisingly, in common with these two methods, the matter on the brane cannot be the source of the gravity on the brane at leading order. In this paper we will propose the low energy effective action on the D-brane coupled with gravity which derives the same results.

Warped Compactification with a Four-Brane

Warped compactification of the six-dimensional bulk with a negative cosmological constant is realized with a 4-brane along with an abelian gauge theory. No fine tuning of couplings are needed to obtain the vanishing cosmological constant in four dimensions, as is the case for the bulk with a positive cosmological constant.

Gravitation in the Codimension Two Brane World

We derive the gravitational field equations on the three-brane in six dimensions. In a covariant manner, we show how Einstein gravity is recovered in the low energy limit. The Einstein equations are modified in the same way as in the five-dimensional model, adding two terms: the quadratic stress-energy term and the Weyl term. We show that the Weyl term is negligible in llinearized gravity.