Investigation of the pion condensation threshold in finite nuclei

The threshold condition for pionic instabilities in finite nuclei is investigated by evaluating the response function for pion-like nuclear excitations (i.e. isovector J^π=0^-, 1⁺, 2^-, ... excitations). The onset of pion condensation is then defined as the point where the response function for given J^π becomes infinite at frequency ω=0. Using a momentum space representation for the response function which allows to establish clear connections to the nuclear matter case, we find that for angular momenta J smaller than a maximum value which depends on the size of the nucleus, the threshold condition is almost the same as for infinite matter. We also study the systematics of this phenomenon as a function of nuclear mass number.