Within the universality class of ferromagnetic vector models with O(n) symmetry and purely dissipative dynamics, we study the non-equilibrium critical relaxation from a magnetized initial state. Transverse correlation and response functions are exactly computed for Gaussian fluctuations and in the limit of infinite number n of components of the order parameter. We find that the fluctuation-dissipation ratios (FDRs) for longitudinal and transverse modes differ already at the Gaussian level. In these two exactly solvable cases we completely describe the crossover from the short-time to the long-time behaviour, corresponding to a disordered and a magnetized initial condition, respectively. The effects of non-Gaussian fluctuations on longitudinal and transverse quantities are calculated in the first order in the epsilon-expansion (epsilon = 4-d) and reliable three-dimensional estimates of the two FDRs are obtained.
|Autori:||Calabrese P; Gambassi A|
|Titolo:||Slow dynamics in critical ferromagnetic vector models relaxing from a magnetized initial state|
|Anno del prodotto:||2007|
|Digital Object Identifier (DOI):||10.1088/1742-5468/2007/01/P01001|
|Appare nelle tipologie:||1.1 Articolo in rivista|