Inflation and Scale-invariant $R^2$-Gravity

Understand

In scale-invariant models of fundamental physics, mass scales are generated by spontaneous symmetry breaking.

• In this work, we study inflation in scale-invariant $R^2$ gravity, in which the Planck mass is generated by a scalar field, which is responsible for spontaneous breaking of scale--symmetry.
• If the self-interactions of the scalar field are non-zero, a cosmological constant is generated, which can be potentially quite large.
• To avoid fine-tuning at late times, we introduce another scalar field which drives the classical cosmological constant to zero during inflation.