  In order to actually see the hadron-quark transition happening in a neutron
star, we point out and study two static conditions (the transition hadronic
density must be lower than the neutron star maximum hadronic density; the
neutron star mass at the transition hadronic density must be in the observed
range, of order 1.4 solar mass) and one dynamical condition (nucleation must
occur during the star lifetime). We find that the mini-colapse acompanying the
transition from metastable hadronic matter to quark matter may be relevant to
explain macro-glitches and gamma ray bursts, but that the mecanism increasing
the star density must be relatively fast, e.g. accretion but not slowing down.
This rules out a scenario for gamma ray bursts proposed recently.
