  We study the 2D massive fields in the presence of moving mirrors. We do that
for standing mirror and mirror moving with constant velocity. We calculate the
modes and commutation relations of the field operator with the corresponding
conjugate momentum in each case. We find that in case of the ideal mirror,
which reflects modes with all momenta equally well, the commutation relations
do not have their canonical form. However, in the case of non-ideal mirror,
which is transparent for the modes with high enough momenta, the commutation
relations of the field operator and its conjugate momentum have their canonical
form. Then we calculate the free Hamiltonian and the expectation value of the
stress-energy tensor in all the listed situations. In the presence of moving
mirrors the diagonal form in terms of the creation and annihilation operators
has the operator that performs translations along the mirror's world line
rather than the one which does translations along the time-line. For the
massive fields in the presence of a mirror moving with constant velocity the
expectation value of the stress-energy tensor has a non-diagonal contribution
which decays with the distance from the mirror.
