Explicit universal deformations of even Galois representations

We investigate the case of deformations of even Galois representations. Our methods are the group theoretic ones mainly developed by NIGEL BOSTON to s tudy odd representations. We present conditions for Borel and tame cases un der which the universal deformation ring is isomorphic to Zp[[T]] and where we compute the universal deformation explicitly. Furthermore we produce a family of examples of totally real SQ extensions which satisfy the above co nditions in the tame case and we give examples in the Borel case. Finally w e study the change of the deformation space under enlarging the ramificatio n and thus give an example of an even representation that is not twist - fi nite.