Dynamical phase transitions for the activity biased Ising model in a magnetic field

Understand

We consider large deviations of the dynamical activity -- defined as the total number of configuration changes within a time interval -- for mean-field and one-dimensional Ising models, in the presence of a magnetic field.

• We identify several dynamical phase transitions that appear as singularities in the scaled cumulant generating function of the activity.
• In particular, we find low-activity ferromagnetic states and a novel high-activity phase, with associated first- and second-order phase transitions.
• The high-activity phase has a negative susceptibility to the magnetic field.