Gravitation, group theory, and the unification of physical laws

In order to deal with the problem of the unification of electromagnetic and gravitational field one can utilize group theory, through a 5-dimensional hyperspherical model of Universe S5; the group of motions of this latter coincides with the 15-parameters group of 6-dimensional rotations. In this Universe the physical laws are given by generalized Maxwell equations, which describe a 15-components field; this latter can be interpreted as a unified magnetohydrodynamical-gravitational field. 7 refs