Séminaire du LPTMS : Rupak Majumder (TIFR Mumbai)

Consider a thermodynamic system that shows phase transition between an ordered and a disordered phase. We ask: In the parameter regime in which the system exhibits a disordered phase, can we induce order in the entire system by repeatedly resetting only a specific part of the system into an ordered state at random times? If yes, then we can control the macroscopic phase of a system by controlling only a (extensive) part of the system. More generally, can the macroscopic phase of a system be altered by resetting a part of it into a suitable phase?

We study these questions in different spin and oscillator models, both equilibrium and non-equilibrium, mean-field and non-mean-field, with and without quenched disorder. We observe that, just by changing a few control parameters–the size of the subsystem we reset, how fast we reset, and at what configuration we reset–we can not only modify the system’s phases but also shift transition points and alter the nature of the transitions. Furthermore, despite the non-reset subsystem retaining memory of the entire dynamics, we obtain analytical predictions that are validated by simulations.