Supergravity, a field theory that combines the principles of supersymmetry and general relativity
11D supergravity contains a 3-form field C. It also contains an electric 2-brane (M2) and a magnetic 5-brane (M5) under C. These branes are BPS states and they are also black branes.
The Matrix theory they proposed was first suggested as a description of two branes in 11-dimensional supergravity by Bernard de Wit, Jens Hoppe, and Hermann Nicolai.
Arnowitt is also known for his work (with Ali Chamseddine and Pran Nath) which developed the theory of supergravity grand unification (with gravity mediated breaking).
He is pursuing ongoing research into string theory, supersymmetry, and supergravity at the MIT Center for Theoretical Physics.