Nonequilibrium mode-coupling theory for uniformly sheared underdamped systems

Abstract

Nonequilibrium mode-coupling theory (MCT) for uniformly sheared underdamped systems is developed, starting from the microscopic thermostatted SLLOD equation, and the corresponding Liouville equation. Special attention is paid to the translational invariance in the sheared frame, which requires an appropriate definition of the transient time-correlators. The derived MCT equation satisfies the alignment of the wavevectors, and is manifestly translationally invariant. Isothermal condition is implemented by the introduction of the current fluctuation in the dissipative coupling to the thermostat. This current fluctation grows in the $α$-relaxation regime, which generates a deviation of the yield stress in the glassy phase from the overdamped case. Response to a perturbation of the shear rate demonstrates an inertia effect which is not observed in the overdamped case. Our theory turns out to be a non-trivial extension of the theory by Fuchs and Cates (J. Rheol. 53(4), 2009) to underdamped systems. Since our starting point is identical to that by Chong and Kim (Phys. Rev. E 79, 2009), the contradictions between Fuchs-Cates and Chong-Kim are resolved.