Penrose limits, supergravity and brane dynamics

TL;DR

The paper establishes that Penrose limits in supergravity preserve or enhance (super)symmetry and map complex backgrounds (including AdS×S, branes, and black holes) to tractable pp-wave geometries, notably Minkowski space or Cahen–Wallach/Hpp-waves. By combining a rigorous hereditary framework (Geroch-style arguments) with explicit geometric classifications, the authors show that AdS×S limits collapse to a small set of possibilities and that brane and intersecting-brane limits populate continuous families of pp-waves parameterized by null geodesics. The work also elucidates the physical meaning of the limits as large-tension perturbations for branes, and extends the notion of Penrose limits to isometric embeddings and multi-time spacetimes. Overall, these results provide a unifying lens to analyze string/M-theory backgrounds in regimes where the dynamics simplify, enabling exact or near-exact analyses of spectra, worldvolume theories, and holographic correspondences in Penrose-limit backgrounds.

Abstract

We investigate the Penrose limits of classical string and M-theory backgrounds. We prove that the number of (super)symmetries of a supergravity background never decreases in the limit. We classify all the possible Penrose limits of AdS x S spacetimes and of supergravity brane solutions. We also present the Penrose limits of various other solutions: intersecting branes, supersymmetric black holes and strings in diverse dimensions, and cosmological models. We explore the Penrose limit of an isometrically embedded spacetime and find a generalisation to spaces with more than one time. Finally, we show that the Penrose limit is a large tension limit for all branes including those with fields of Born--Infeld type.