The Off-Shell Recursion for Gravity and the Classical Double Copy for currents

Understand

We construct the off-shell recursion for gravity and the graviton current for the perturbative double field theory (DFT).

• We first formulate the perturbative DFT, which is equivalent but simpler to perturbative general relativity, to all-orders in fluctuations of generalised metric.
• The perturbative action and equations of motion (EoM) are derived to arbitrary order for pure gravity case.
• We then derive the graviton off-shell recursion, the gravity counterpart of the Berends-Giele recursion in Yang-Mills theory, through the so-called perturbiner method using the EoM of the perturbative DFT.