Unimodular Gauge in Perturbative Gravity and Supergravity
This paper explains the Unimodular gauge fixing of gravity and supergravity in the framework of a perturbative BRST construction. The unphysical sector contains additional BRST-exact quartets to suppress possible ambiguities and impose both the Unimodular gauge fixing condition on the metric and a gauge condition for the reparametrization symmetry of the unimodular part of the metric. The Unimodular gauge choice of the metric must be completed by a $\gamma$-Traceless gauge condition for the Rarita--Schwinger field in the case of supergravity. This gives an interesting new class of gauges for gravity and supergravity.