Violation of fluctuation-dissipation theorem in the off-equilibrium dynamics of a system with non additive interactions

PINTO O. A; ROMA F.; RAMÍREZ-PASTOR A.J.; NIETO F. D.

en La Herradura, Granada, España

Seminario; 11th Granada Seminar on Computational and Statistical Physics; 2010

In this work we study the critical equilibrium properties and the off-equilibrium dynamics of an Ising system with non additive interactions.  The traditional assumption of additivity is modified for one more general, where the energy of exchange J between two spins depends on their neighbourhood.  First, for several non additive situations, we calculated the critical temperature Tc by using paralell tempering Monte Carlo in the canonical assemble and standard finite-size scaling techniques. Then, we carry out a quench from infinite temperature to a low temperature below Tc (off-equilibrium dynamics protocol) and we compute two-time correlation and response functions.   We find a violation of fluctuation-dissipation theorem like coarsening systems. All this was done for several waiting time and several non additive situations. Finally, we analyze the scaling of correlation and response functions for a critical quench from infinite temperature.