pp-waves in 11-dimensions with extra supersymmetry

Abstract

The Killing spinor equations for pp-wave solutions of eleven dimensional supergravity are analysed and it is shown that there are solutions that preserve 18,20,22 and 24 supersymmetries, in addition to the generic solution preserving 16 supersymmetries and the Kowalski-Glikman solution preserving 32 supersymmetries.Comment: 13 pages. Reference added, typos corrected, new examples of 7-parameter case presente