Effective action, braneworld scenario and cosmology

The uses of the effective action are discussed in quantum and braneworld cosmology. The braneworld effective action is built in the two-brane Randall-Sundrum model. The radion mode is shown to be a field localizing the essentially nonlocal part of this action. Its non-minimal curvature coupling reflects the violation of AdS/CFT-correspondence for finite values of brane separation. Under small detuning of the brane tension from the Randall-Sundrum value, the radion mode can play the role of inflaton. Inflationary dynamics corresponds to branes moving apart in the field of repelling interbrane radion potential and implies the existence of acceleration stage caused by remnant cosmological constant at late (large brane separation) stages of cosmological evolution. We discuss the possibility of fixing initial conditions in this model within the context of braneworld creation from the tunneling or no-boundary cosmological states, which replaces the conventional moduli stabilization mechanism