Vector fluctuations from multidimensional curvature bounces
  It is argued that in the case of a smooth transition across a (dilaton-driven) curvature bounce the growing mode of the vector fluctuations matches continuously with a decaying mode at later times. Analytical examples of this observation are given both in the presence and in the absence of fluid sources. In the case of multidimensional bouncing models the situation is different, since the system of differential equations describing the vector modes of the geometry has a richer structure. The amplification of the vector modes of the geometry is specifically investigated in a regular five-dimensional bouncing curvature model where scale factors of the external and internal manifolds evolve at a dual rate. Vector fluctuations, in this case, can be copiously produced and are continuous across the bounce. The relevance of these results is critically illustrated. 
Massimo Giovannini