  We introduce a generalized tetrad which plays the role of a potential for
torsion and makes torsion dynamic. Starting from the Einstein-Cartan action
with torsion, we get two field equations, the Einstein equation and the torsion
field equation by using the metric tensor and the torsion potential as
independent variables; in the former equation the torsion potential plays the
role of a matter field. We also discuss properties of local linear
transformations of the torsion potential and give a simple example in which the
torsion potential is described by a scalar field.
