Quantum groups and Thermo Field Dynamics

The algebraic structure of Thermo Field Dynamics for bosons can be fully incorporated in the q-deformation of the Weyl-Heisenberg algebra h(q)(1). The doubling of the degrees of freedom, the set of the tilde-conjugation rules, the Bogoliubov transformation and its generator have a direct and simple interpretation in terms of operators and of properties of h(q)(1). The notion of ''thermal degree of freedom'' introduced by Umezawa also finds a more specific formalization since the corresponding ''thermal conjugate momentum'' can be formally introduced, thus providing us with a set of canonical ''thermal'' variables.