Math of QM: 4.1. Definition of Symmetric and (Essentially) Selfadjoint Operators

The lecture notes of the course can be found at https://rolandspeicher.com/wp-content/uploads/2024/10/mathematicalaspects.pdf Definition of symmetric, selfadjoint, essentially selfadjoint. This is part 1 of Lecture 4 in the lecture series "Mathematical Aspects of Quantum Mechanics" of Roland Speicher in the winter term 2020/21 at Saarland University, Germany. Lecture 4, which is split into 6 parts, deals with the distinction between symmetric and selfadjoint for unbounded operators.