Lecture notes on K3 and Enriques surfaces<br>Notes by S&#322;awomir Rams

Abstract

The main aim of these lectures is to study the connection between symplectic symmetries of $K3$ surfaces and the Mathieu group $M_{24}$, and its Enriques analogy, that is, a conjectural connection between semi-symplectic symmetries of Enriques surfaces and another Mathieu group $M_{12}$.