Exact Results in Quantum Theory

Perturbative expansions are ubiquitous in physics, often resulting inasymptotic series with zero radius of convergence. In order for theassociated observables to become nonperturbatively well-defined oneneeds to use theory of resurgence. In this seminar, I will give anincomers view on the theory of resurgence functions illustrating basicconcepts with simplest examples. Some applications in physics will beshortly reviewed.