Quantum-Ordering Ambiguities in Weak Chern-Simons 4D Gravity and Metastability of the Condensate-Induced Inflation

Understand

In this work, we elaborate further on a 4D cosmological Running-Vacuum-type Model (RVM) of inflation that characterises string-inspired Chern-Simons (CS) gravity.

• It has been shown that inflation in such models is caused by a condensation of the gravitational CS (gCS) terms induced by primordial gravitational waves (GW), which leads to a linear-axion potential, thus breaking the shift symmetry, and lifting its periodicity (monodromy).
• We demonstrate here that this inflationary phase may be metastable, due to the existence of non-trivial imaginary parts of the gCS condensate.
• These imaginary parts are quantum effects, proportional to appropriate commutators of GW perturbations.