Unitary time evolution in the Gowdy T3 model

Abstract

The polarized Gowdy T3 model is a classically solvable cosmological model with local degrees of freedom. This explains the increasing interest in its quantization. After gauge fixing, the system can be described in terms of a point particle and a massless scalar field propagating in an expanding torus. A Fock space representation has been proposed for the quantization of the model, but the classical dynamics for the scalar field cannot be unitarily implemented in this quantum theory. We show that, nevertheless, unitarity can be regained by slightly modifying the dynamics with quantum corrections. Moreover, a time-dependent rescaling of the scalar field leads to new evolution equations that can be unitarily implemented.