  Using quantum liquids one can simulate the behavior of the quantum vacuum in
the presence of the event horizon. The condensed matter analogs demonstrate
that in most cases the quantum vacuum resists to formation of the horizon, and
even if the horizon is formed different types of the vacuum instability
develop, which are faster than the process of Hawking radiation. Nevertheless,
it is possible to create the horizon on the quantum-liquid analog of the brane,
where the vacuum life-time is long enough to consider the horizon as the
quasistationary object. Using this analogy we calculate the Bekenstein entropy
of the nearly extremal and extremal black holes, which comes from the fermionic
microstates in the region of the horizon -- the fermion zero modes. We also
discuss how the cancellation of the large cosmological constant follows from
the thermodynamics of the vacuum.
