Sterile neutrinos in neutrinoless double beta decay

We study possible contribution of the Majorana neutrino mass eigenstate νₕ, dominated by a sterile neutrino component, to neutrinoless double beta (0νββ) decay. A special emphasis is made on accurate calculation of the corresponding nuclear matrix elements. From the current experimental lower bound on the 0νββ-decay half-life of $76$ Ge we derive stringent constraints on the νₕ-νₑ mixing in a wide region of the values of νₕ mass. We discuss cosmological and astrophysical status of νₕ in this mass region.