# Quantum Mechanics - Leonard Susskind on Integration by Parts

1. Oct 2, 2011

### Jonnyb42

I'm watching the video series on Quantum Mechanics taught by Leonard Susskind, (from Stanford).

On Lecture #3, Dr. Susskind says that integration by parts is:

∫FG' = -∫GF'

However from what I know integral by parts to be, there i missing a +FG on the righthand side, or something... since I don't recognize that as the same as
∫FdG = FG - ∫GdF

The specific function that was being dealt with was the wavefunction ψ, (where F = G = ψ) so maybe that could have to do with it... I don't think ψ^2 = 0 though.

Thanks

2. Oct 2, 2011

### Pengwuino

The "FG" part is evaluated at the boundary. I assume there are boundary conditions that make that term vanish.

3. Oct 2, 2011

### Jonnyb42

He mentioned something about boundary conditions, could you explain to me what you mean? What boundary conditions could make the term vanish?

4. Oct 2, 2011

### grzz

If F or G is some wavefunction ψ then the boundary condition says that ψ goes to 0 at x = + or - infinity.

5. Oct 2, 2011

### Jonnyb42

Right ok thanks, I lost my mind there a little bit!