Activated sphalerons and large extra dimensions

We present a new scenario for baryon number violation that may take place in models with large extra dimensions. Our idea is interesting because leptogenesis with a low reheating temperature requires an alternative source of $B+L$ violation to convert the produced leptons into baryons. If one considers a model with an intermediate compactification radius, the reheating temperature may be allowed to become higher than the critical temperature of the conventional electroweak phase transition. Our mechanism is still important in this case, because it provides the phase boundary, which is an essential ingredient of electroweak baryogenesis.