We consider the open string tachyon action in a world-sheet sigma model
approach. We present explicit calculations up to order 8 in derivatives for the
bosonic string, and mimic these to order 6 for the superstring, including terms
with multiple derivatives acting on the tachyon field. We reproduce lower
derivative terms obtained elsewhere, and speculate on the role of the
world-sheet contact terms regularizing the action for the superstring tachyon.Comment: 21 page
