Signatures of Irreversibility in Models of Flocks

• Federica Ferretti

Flocking is one of the most startling collective behaviours in active matter. Typical agent-based models used to describe such phenomenon are similar to classical spin models for ferromagnets, but with a crucial difference: spins can move. This is activity, which transforms the equilibrium ferromagnet into a non-equilibrium system. Thanks to this property, collective motion can emerge even in d=2, where long range order is prohibited by rigorous theorems for inactive models. In our recent (unpublished) work we try to measure how far from equilibrium a flock is, and try to spot signatures of irreversibility which can be potentially looked for in some experiments.

Dicussion

Nuclear Matter and Neutron Stars: a window into strong interactions.

• Andrea Sabatucci (Sapienza)

A detailed description of the properties of dense matter in extreme conditions, as those within Neutron Star cores, is still an open problem, whose solution is hampered by both the lack of empirical data, and by the difficulties in developing a suitable theoretical framework for the microscopic nuclear dynamics in such regimes. The detection of gravitational waves from the first observed coalescence of two neutron stars has opened the possibility to exploit gravitational waves as a new window to understand the behavior of nuclear matter. In this seminar I will present a pedagogical discussion about the microscopic description of nuclear matter and its relation to the observed properties of Neutron Stars, together with a quick look at our work on these topics.

Discussion