  Answering Vershik's question we show that quasi-similarity does not conserve
the entropy, proving quasi-similarity of all Bernoulli actions of a countable
infinite group. We prove also the following generalization of Pinsker's
theorem: the actions with zero Kirillov-Kushnirenko $P$-entropy and the actions
with completely positive $P$-entropy are disjoint. Poisson suspensions are used
as examples.
