Ignacio Navarro

We consider solutions of $d$ dimensional Einstein equations with $d-4$ compact dimensions. It is shown that one can introduce codimension 2 branes in this background in such a way that the effective four dimensional cosmological constant is completely independent of the brane tension. These tension is completely arbitrary, without requiring any fine tuning. We must, however, fine tune bulk parameters in order to obtain a sufficiently small value for the observable cosmological constant. We also comment on different possibilities for generating the spontaneous compactification of the extra dimensions.

Seminario de Física Teórica, Facultad de Ciencias, 3rd Floor, Universidad de Zaragoza