Found 2 result(s)

### 05.11.2020 (Thursday)

#### Stringy resurgence: modular graph functions and Poincare series

Regular Seminar Daniele Dorigoni (Durham University)

 at: 15:00 QMWroom Zoom abstract: Zoom link: Please email Silvia Nagy (s.nagyATqmul.ac.uk) or Jungwook Kim (jung-wook.kimATqmul.ac.uk) for the zoom link. Abstract:In string theory SL(2,Z) invariant functions, such as modular graph functions or coefficient functions of higher derivative corrections, are ubiquitous. Using a representation in terms of PoincarÃ© series we can combine different methods for asymptotic expansions and obtain the complete perturbative and non-perturbative expansion. In the case of the higher derivative corrections, these terms have an interpretation in terms of perturbative string loop effects and pairs of instantons/anti-instantons. There will also be a pre-seminar for the students which will begin at 2:30 pm.

### 23.10.2013 (Wednesday)

#### Resurgence in QFT: the Principal Chiral Model

Regular Seminar Daniele Dorigoni (DAMTP, Cambridge)

 at: 14:00 ICroom H503 abstract: I will review the concept of Borel transform and resurgence behavior for the perturbative expansion of generic physical observables presenting particular examples coming from quantum mechanics and supersymmetric localized QFT. I will then discuss more in details the physical role of non-perturbative saddle points of path integrals in theories without instantons, using the example of the asymptotically free two-dimensional principal chiral model (PCM). Standard topological arguments based on homotopy considerations suggest no role for non-perturbative saddles in such theories. However, resurgence theory, unifying perturbative and non-perturbative physics, predicts the existence of several types of non-perturbative saddles associated with features of the large-order structure of perturbation theory. These points are illustrated in the PCM, where we found new non-perturbative fractionalized saddle point field configurations, and give a quantum interpretation of previously discovered `uniton’ unstable classical solutions.