Jean Alexandre (King’s College London)
Title: Tunnelling and convexity in QFT
Abstract: Tunnelling between degenerate vacua is discussed, with an emphasis on the main following property: the one-particle-irreducible effective action is not extensive in the vicinity of the true – symmetric – vacuum. The derivation of the effective potential is based on a semiclassical approximation, where the contribution of several saddle points leads to convexity. As a potential application, violation of the Null Energy Condition and a resulting bouncing Cosmology scenario are discussed.