  This work contributes to the study of non-equilibrium aspects of the Casimir
forces with the introduction of squeezed states in the calculations. Throughout
this article two main results can be found, being both strongly correlated.
Primarily, the more formal result involves the development of a
first-principles canonical quantization formalism to study the vacuum in
presence different dissipative bodies in completely general scenarios. We
considered a one-dimensional quantum scalar field interacting with the volume
elements' degrees of freedom of the material bodies, which are modeled as
composite systems consisting in a harmonic oscillators interacting with an
environment. Solving the full dynamics of the composite system through its
Heisenberg equations, we studied each contribution to the field operator by
employing general properties of the Green function. We deduced the long-time
limit of the field operator. In agreement with previous works, we showed that
the expectation values of the components of the energy-momentum tensor present
two contributions, one associated to the thermal baths and the other one
associated to the field's initial conditions. This allows us to the direct
study of steady situations involving different initial states for the field and
arbitrary thermal states for the baths. This leads to the other main result,
consisting in computing the Casimir force when the field is initially in
thermal or continuum-single-mode squeezed states (characterized by a given
bandwidth and frequency). Time-averaging is required for the squeezed case,
showing both results in a unified way. For the thermal state, all the
well-known equilibrium results can be successfully reproduced. Finally, we
compared the initial conditions' contribution and the total force for each
case, showing that the latter can be tuned in a wide range of values through
varying the size of the bandwidth.
