# Relativistc probability current

1. Jan 2, 2008

### opous

[SOLVED] Relativistc probability current

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

I've got two formulae here and I'm not sure how you get from the first to the second:

$$\textbf{j}(\textbf{x},t) = Re[\Psi^{*}(x,t)(-i/m)\nabla\Psi(x,t)]$$

$$= \frac{-i}{2m}[\Psi^{*}(\nabla\Psi) - (\nabla\Psi^{*})\Psi]$$

Can anyone suggest a relationship I need to bridge the gap? Thanks.

2. Relevant equations

3. The attempt at a solution

2. Jan 2, 2008

### Dick

Try Re(z)=(z+z*)/2.

3. Jan 3, 2008

### opous

Got it! Thanks Dick :)