Recent content by Sando

For a time independent potential: \langle p \rangle = m \frac{d}{dt} \langle x \rangle which is zero for a bound state.

I'll echo what peteratcam said: shouldn't fermionic creation operators for different species commute? Isn't it fermion creation operators for different modes of the same species that do commute? I.e., shouldn't a proton creation operator and an electron creation operator commute? There's not...

Let \sigma_x = \left( \begin{smallmatrix} 0 & 1 \\ 1 & 0 \end{smallmatrix} \right) , and consider things like e^{i \sigma_x \varphi} where \varphi is some angle. You should find that the matrix exponential of a non-diagonal matrix can, in fact, be diagonal. (You can find a useful /...

Try relating \langle p \rangle to \frac{d}{dt} \langle x \rangle (Ehrenfest's Theorem). If "bound state" means "stationary state in a time-independent potential", then use the fact that \frac{d}{dt} \langle x \rangle = 0 .