By promoting the mass, m, in the dRGT theory of massive gravity to a dynamical scalar field, we have a ghost-free theory of a massive spin-2 particle coupled to a spin-0 particle. The strong coupling scale is now set by the value of the scalar field rather than a fixed mass scale. This can describe cosmologies with both early and late time acceleration (inflation and dark energy domination), where the scalar acts as the slowly-rolling inflaton.

When studying inflation in the context of massive gravity, an additional scalar field, the inflaton, is usually postulated. Here, that scalar is naturally incorporated into the dRGT theory, setting the scale at which the graviton mass becomes important. This could have a variety of interesting cosmological effects.