Abstract :
We construct plane wave backgrounds with time-dependent profiles corresponding to Penrose limits of NS5-branes with transverse space symmetry group broken from SO(4) to SO(2)×ZN. We identify the corresponding exact theory as the five-dimensional logarithmic Conformal Field Theory (CFT) arising from the contraction of the SU(2)N′/U(1)×SL(2,R)−N exact CFT, times R5. We study several general aspects and construct the free field representation in this theory. String propagation and spectra are also considered and explicitly solved in the light-cone gauge.
