Transport in a classical model of an one-dimensional Mott insulator: Influence of conservation laws

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We study numerically how conservation laws affect the optical conductivity sigma(w) of a slightly doped one-dimensional Mott insulator. We investigate a regime where the average distance between charge excitations is large compared to their thermal de Broglie wave length and a classical description is possible. Due to conservation laws, the dc-conductivity is infinite and the Drude weight D is finite even at finite temperatures. Our numerical results test and confirm exact theoretical predictions for D both for integrable and non-integrable models. Small deviations from integrability induce slowly decaying modes and, consequently, low-frequency peaks in sigma(w) which can be described by a memory matrix approach.