  In the Einstein-Cartan space $U_4$, an axial vector torsion together with a
scalar field connected to a local scale factor have been considered. By
combining two particular terms from the SO(4,1) Pontryagin density and then
modifying it in a SO(3,1) invariant way, we get a Lagrangian density with
Lagrange multipliers. Then under FRW-cosmological background, where the scalar
field is connected to the source of gravitation, the Euler-Lagrange equations
ultimately give the constancy of the gravitational constant together with only
three kinds of energy densities representing mass, radiation and cosmological
constant. The gravitational constant has been found to be linked with the
geometrical Nieh-Yan density.
