EXACT-SOLUTIONS AND THE EFFECTIVE EQUATION OF STATE IN KALUZA-KLEIN THEORY

A generalization of the standard class of solutions in the Kaluza-Klei n (4 + 1) gravity, wherein the spherically symmetric metric depends no t only on the radius but also on the extra coordinate, is considered. Two new classes of exact solutions of the empty Kaluza-Klein field equ ations are given. However, it is known that apparently empty solutions of the (4 + 1) Kaluza-Klein equations can be interpreted as solutions with effective matter properties of the (3 + 1) Einstein equations. T he physical importance of the new solutions is that in this approach t he dependency on the extra coordinate allows us to obtain more general equations of state than before, including ones for radiation, dust, v acuum, and stiff matter.