The Double Copy of Maximal Supersymmetry in $D=4$

TL;DR

This paper constructs an off-shell, gauge-invariant formulation of N=8 supergravity in four dimensions as a double copy of N=4 super Yang-Mills theory, using homotopy algebra techniques to realize supersymmetry and R-symmetry enhancements.

Contribution

It demonstrates the first off-shell, local, gauge-invariant N=8 supergravity in D=4 as a double copy of N=4 SYM using homotopy algebra methods.

Findings

Realizes N=8 supergravity as a double copy of N=4 SYM.

Shows compatibility of kinematic algebra with supersymmetry.

Identifies an L-infinity algebra structure linking the theories.

Abstract

We realize off-shell, local and gauge invariant $N=8$ supergravity in $D=4$, to cubic order in fields, as the double copy of $N=4$ super Yang-Mills theory (SYM). Employing the homotopy algebra approach, we show that, thanks to a redundant formulation for the fermionic fields, the kinematic algebra $K$ of $N=4$ SYM is compatible with an action of the global supersymmetry algebra. The double copy space is then a subspace of $K\otimes{\widetilde K}$ that inherits an $L_{\infty}$ algebra on which the two copies of the $N=4$ action combine into an action of the $N=8$ supersymmetry algebra, with a corresponding enhancement of the $R$-symmetry group to $SU(8)$.