The drift velocity in the Rubinstein—Duke model for electrophoresis

The average drift velocity of a polymer chain due to an applied electric field is calculated in the Rubinstein-Duke model for reptation. Imposing periodic boundary conditions on the reptating chain the stationary state is solved exactly from the master equation, and the drift velocity is calculated to first and third order in the field. Finite-size effects are included and the scaling hypothesis of Widom et al. is confirmed to third order in the field. An approximate expression is presented for the scaling function in the whole scaling range.