Daniele Teresi "Symmetry-Improved 2PI Effective Action"

Thursday 14 Feb 2019, 15:00 → 16:00 Europe/Rome

248 (Ed. C primo piano)

The 2PI effective action is a powerful theoretical tool that resums automatically infinite sets of perturbation-theory contributions, in a consistent and systematic way. A major obstacle to its application to a wide range of situations was that symmetries are not encoded properly in the formalism, giving rise, for instance, to massive Goldstone bosons. We solved this long-standing problem, in the case of global symmetries, by developing the so-called Symmetry-Improved 2PI (SI2PI) Effective Action. I will discuss its satisfactory field-theoretical properties and its application to the recently pointed out issue of IR divergences of the Standard-Model effective potential due to Goldstone bosons. I will finally show that the SI2PI effective potential is exactly invariant under renormalization-group running, as opposed to the more familiar 1PI case, which is so only up to higher orders.