  With cooling of the cosmological plasma during phase transitions in the early
Universe vacuum condensates of quantum fields were produced with negative
energy density. Probably these condensates have compensated the initial vacuum
energy. The present vacuum is the vacuum condensate of the last relativistic
phase transition ($T_{cr}\sim 100$ MeV) (its information is carried by
pseudo-Goldstone bosons ($\pi $-mesons)). This allows us to use Zeldovich's
formula that can calculate exactly the value of the cosmological constant in
the present epoch. If the most likely values $\Omega_\Lambda $ are 0.7-0.8 then
$H_0$ falls in the range from 72.5 to 67.8 (km/s)/Mpc.
