The Trace-Free Einstein Equations and inflation

Abstract

The trace-free version of the Einstein Gravitational equations, essentially equivalent to unimodular gravity, can solve the troubling issue of the huge discrepancy between quantum field theory estimates of the vacuum energy density and the astronomically observed value of the cosmological constant. However it has been suggested that this proposal cannot work because it prevents the inflaton potential energy from driving inflation. It is shown here that that concern is unjustified: inflation proceeds as usual if we adopt the trace free gravitational equations.