  Subvacuum phenomena on a massive particle induced by a squeezed vacuum state
of strongly coupled critical fields with a dynamical scaling $z$ are studied by
employing the holographic approach. The corresponding dual description is the
string moving in the 4+1-dimensional Lifshitz geometry. The squeezed vacuum
state is constructed from the Bogoliubov transformations of the creation and
annihilation operators of the pure vacuum state as a result from the perturbed
geometry. Then the influence on particle's velocity dispersion from the
squeezed vacuum is studied. With appropriate choices of squeezing parameters,
the velocity dispersion is found smaller than the value caused by the normal
vacuum fluctuations. This leads to a subvacuum effect. We find that the
reduction in the velocity dispersion is suppressed by a large coupling constant
of quantum critical fields, but is in principle observable. We then investigate
the effect of the squeezed vacuum to the decoherence dynamics of a quantum
particle. It is found possible for this decoherence to be below the level from
the pure vacuum, rendering another subvacuum phenomenon of recoherence. We make
some estimates of the degree of recoherence, and show that, in contrary to the
velocity dispersion, the recoherence effect is proportional to the large
coupling constant, and can potentially be observed. Finally we make a
comparison with the effect on the particle influenced by a relativistic free
field with the dynamical scaling $z=1$.
