504 citations · 2.7k across the 41 of their papers we have counts for
42 papers
The Kerr/CFT energy gap
Robert Penna
Noether charges in gravity are always defined with respect to a reference metric, but the near-horizon extremal Kerr (NHEK) solution does not come with an obvious choice of referen…
Scattering amplitudes for cylindrical gravitational waves
Robert Penna
Cylindrical gravitational waves are interesting because they enjoy an infinite dimensional symmetry called Geroch symmetry. In this paper, we compute the 2-particle tree-level S-ma…
Gravitational Pulse Wave Scattering and the Geroch group
Robert F. Penna
Cylindrical gravitational pulse waves are cylindrical gravitational waves with a pulse profile in the radial direction. The dynamics of cylindrical gravitational pulse waves is gov…
The Geroch Group in One Dimension
Robert F. Penna
We study the dimensional reduction of general relativity to a single null spacetime dimension. The dimensionally reduced theory is a theory of six scalar fields governed by three c…
A Lax Operator for Supergravity
Robert F. Penna
General relativity and supergravity become integrable systems after dimensional reduction to two spacetime dimensions. This means the equations of motion can be encoded in the flat…
Einstein-Rosen Waves and the Geroch Group
Robert F. Penna
Under the action of the Geroch group, the Minkowski metric can be transformed into any vacuum metric with two commuting Killing vectors. In principle, this reduces the problem of d…