On unimodular quantum gravity

Unimodular gravity is classically equivalent to standard Einstein gravity, but differs when it comes to the quantum theory: the conformal factor is non-dynamical, and the gauge symmetry consists of transverse diffeomorphisms only. Furthermore, the cosmological constant is not renormalized. Thus the quantum theory is distinct from a quantization of standard Einstein gravity. Here we show that within a truncation of the full renormalization group flow of unimodular quantum gravity, there is a non-trivial ultraviolet (UV)-attractive fixed point, yielding a UV completion for unimodular gravity. We discuss important differences to the standard asymptotic-safety scenario for gravity, and provide further evidence for this scenario by investigating a new form of the gauge-fixing and ghost sector.