  Condensation of fluctuations is an interesting phenomenon conceptually
distinct from condensation on average. One stricking feature is that, contrary
to what happens on average, condensation of fluctuations may occurr even in the
absence of interaction. The explanation emerges from the duality between large
deviation events in the given system and typical events in a new and
appropriately biased system. This surprising phenomenon is investigated in the
context of the Gaussian model, chosen as paradigmatical non interacting system,
before and after an istantaneous temperature quench. It is shown that the bias
induces a mean-field-like effective interaction responsible of the condensation
on average. Phase diagrams, covering both the equilibrium and the
off-equilibrium regimes, are derived for observables representative of generic
behaviors.
