# Homework Help: Hamiltonian commutator

1. Feb 2, 2012

### v_pino

1. The problem statement, all variables and given/known data

How do I obtain [H,P_x]? P_x is the polarization operator.

2. Relevant equations

$$H=-\frac{\hbar^2}{2m}\frac{\partial^2 }{\partial x^2}+V(x)$$

$$P_x=2Re[c_+^*c_-]$$

3. The attempt at a solution

I know how to commute H and x. But somehow can't think of a way to do the same for H and P_x.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Feb 2, 2012

### ardie

write P_x instead of x; then do the commutation just as you do for x