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We investigate the consequences of the quark deconfinement phase transition on the evolution of proto-neutron stars. Assuming a first order phase transition, we calculate the nucleation time due to thermal and quantum nucleation mechanisms. We introduce the concepts of critical mass Mcr and limiting conversion temperature for proto-hadronic stars. We show that proto-hadronic stars with a mass M < Mcr could survive the early stages of their evolution without decaying to quark stars.

A phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. We study the quark deconfinement phase transition in cold (T = 0) and hot β-stable hadronic matter. Assuming a first order phase transition, we calculate and compare the nucleation rate and the nucleation time due to thermal and quantum nucleation mechanisms. We show that above a threshold value of the central pressure a pure hadronic star (HS) is metastable to the conversion to a quark star (QS) (i.e. hybrid star or strange star). We introduce the concept of critical mass Mcr for cold HSs and proto-hadronic stars (PHSs), and the concept of limiting conversion temperature for PHSs. We show that PHSs with a mass M < Mcr could survive the early stages of their evolution without decaying to QSs. Finally, we discuss the possible evolutionary paths of proto-hadronic stars.

These Proceedings contain the invited and contributed papers presented at the 12th Conference on Theoretical Nuclear Physics in Italy held in Cortona, Italy, from 8–10 October 2008. As usual, the meeting was held at il Palazzone, a 16th century castle owned by the Scuola Normale Superiore di Pisa. The aim of this biennal conference is to bring together Italian theorists working in various fields of Nuclear Physics to discuss their latest results and confront their points of view in a lively and informal way. This offers the opportunity to promote collaborations between different groups. There were about 50 participants at the conference, coming from 14 Italian Universities (Cagliari, Catania, Ferrara, Firenze, Genova, Lecce, Milano, Napoli, Padova, Pavia, Pisa, Roma, Trento, Trieste). The program of the conference, prepared by the Organizing Committee (Ignazio Bombaci, Aldo Covello, Laura Elisa Marcucci and Sergio Rosati) focused on six main topics: Few-Nucleon Systems, Nuclear Matter and Nuclear Dynamics, Nuclear Astrophysics, Structure of Hadrons and Hadronic Matter, Nuclear Structure, Nuclear Physics with Electroweak Probes. Winfried Leidemann, Maria Colonna, Marcello Lissia, Elena Santopinto, Silvia Lenzi and Omar Benhar took the burden of giving general talks on these topics and reviewing the research activities of the various Italian groups. In addition, 19 contributed papers were presented, most of them by young participants. In the last session of the Conference there were two invited talks related to experimental activities of great current interest. Gianfranco Prete from the Laboratori Nazionali di Legnaro spoke about the Italian radioactive ion beam facility SPES and the status of the European project EURISOL, while Nicola Colonna from the INFN, Bari, gave an overview of the perspectives of development of fourth-generation nuclear reactors. We would like to thank the authors of the general reports for their hard work in reviewing the main achievements in the various fields as well as our experimental colleagues for having kindly agreed to talk to an audience consisting only of theoretical physicists. I Bombaci, A Covello, L E Marcucci and S Rosati