  The nonlocal response functions to quantum fluctuations are used to find
asymptotic expressions for the Casimir free energy and entropy at arbitrarily
low temperature in the configuration of two parallel metallic plates. It is
shown that by introducing an alternative nonlocal response to the
off-the-mass-shell fluctuations the Lifshitz theory is brought into agreement
with the requirements of thermodynamics. According to our results, the Casimir
entropy calculated using the nonlocal response functions, which take into
account dissipation of conduction electrons, remains positive and monotonously
goes to zero with vanishing temperature, i.e., satisfies the Nernst heat
theorem. This is true for both plates with perfect crystal lattices and for
lattices with defects of structure. The obtained results are discussed in the
context of the Casimir puzzle.
