title: Observable-dependence of the effective temperature in off-equilibrium diatomic molecular liquids.
abstract: We discuss the observable-dependence of the effective temperature Teff, defined via the fluctuation-dissipation relation, of an out-of-equilibrium system composed by homonuclear dumbbell molecules. Teff is calculated by evaluating the fluctuation and the response for two observables associated, respectively, to translational and to rotational degrees of freedom, following a sudden temperature quench. We repeat our calculations for different dumbbell elongations ζ. At high elongations (ζ > 0.4), we find the same Teff for the two observables. At low elongations (ζ ⩽ 0.4), only for very deep quenches Teff coincides. The observable-dependence of Teff for low elongations and shallow quenches stresses the importance of a strong coupling between orientational and translational variables for a consistent definition of the effective temperature in glassy systems.
authors.affiliation: Dipartimento di Fisica, "Sapienza" Università di Roma, Piazzale A. Moro 2, 00186 Roma, Italy.
authors.forename: Andrea Saverio
authors.initials: AS
authors.lastname: Ninarello
authors.affiliation: CNR-ISC Uos "Sapienza," Piazzale A. Moro 2, 00186 Roma, Italy.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Gnan
authors.affiliation: Dipartimento di Fisica, "Sapienza" Università di Roma, Piazzale A. Moro 2, 00186 Roma, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Sciortino