What is the name of this symbol used often in quantum mechanics?
Answers
quantum state of an isolated quantum system. The wave function is a complex-valued probability amplitude, and the probabilities for the possible results of measurements made on the system can be derived from it. The most common symbols for a wave function are the Greek letters ψ and Ψ (lower-case and capital psi, respectively).
x and y are functions. In quantum mechanics, they are generally wave functions, maybe probability density functions for electrons in an atom, molecule or solid.
V over h-bar is an operator. In physics, V is usually a potential energy.
The angle brackets are shorthand for integration over an implied independent variable.
This notation is used instead of writing out the integral because it's compact and it's easy to see each part at a glance.
More importantly, the notation is very general.
x and y could be functions of one variable or many. They could be vector functions.