Inhomogeneous cosmological model in Kaluza-Klein spacetime

Sujit Chatterjee
New Alipore College, Kolkata - 700 053, India
Relativity & Cosmology Research Center
Jadavpur University, Kolkata - 700 032, India
e mail sujit @juphys.ernet.in
chat_sujit1@yahoo.com

Exact cosmological solutions are obtained in a 5D Kaluza Klein type of spacetime in an inhomogeneous distribution of fluid obeying an equation of state.The set of solutions includes those of dust,radiation and stiff fluid confined to the usual 3D space while the fifth dimensional pressure monotonically decreases with time.Depending on the signature of the 4-space curvature one can show that while the 3-space expands the extra space shrinks with time, which is desirable in the context of higher dimensional cosmology.Entropy generation resulting from the compactification of the fifth dimension is discussed and its relevance to the inflationary scenario is popinted out.Interestingly,apart from the usual big bang singularity our inhomogeneous model is spatially regular everywhere including the origin of the fluid distribution.Further our model seems to suggest an alternative mechanism pointing to a smooth passover from a primordial multidimensional,inhomogeneous phase to a 4D homogeneous one without forcing ourselves to assume very special initial conditions as is customary in standard models.