itle: Bions and resurgence in CP^N model
Abstract:
Perturbation series in quantum field theory are generically divergent asymptotic series.
Resurgence theory relates such perturbation series and non-perturbative effects
which cannot be captured by the perturbative expansion.
It has been shown that the so-called bion saddle points,
which consist of instanton-antiinstanton pair,
plays an important role in resurgence theory in a certain class of quantum systems.
In this talk, I will overview the recent development of
the resurgence theory based on the complexified path integral and the bion saddle points.
I will talk about the bion contributions in the 2d CP^{N-1} models
on R \times S1 with twisted boundary conditions
and show that the semi-classical bion contributions
is consistent with the expected IR-renormalon ambiguity.