Vanishing of the conformal anomaly for strings in a gravitational wave

Abstract

Using the non-symmetric-connection approach proposed by Osborn, we demonstrate that, for a bosonic string in a specially chosen plane-fronted gravitational wave and an axion background, the conformal anomaly vanishes at the two-loop level. Under some conditions, the anomaly vanishes at all orders.

Previously not available in hep-th. Published as Physics Letters B 313, 10 (1993). Plain TeX 6 pages. No figures