# Identical particles

1. Oct 21, 2011

### center o bass

Hey I'm tring to grasp the symmetrization principle for identical particles. If the particles are indistinguishble, for example two electrons (not regarding spin), then $$\psi(x_1,x_2)$$ must correspond to the same physical situation as $$\psi(x_2,x_1)$$. It follows that

$$|\psi(x_1,x_2)|^2 = |\psi(x_2,x_1)|^2$$

and from this the symmetrization priciple follows as

$$\psi(x_1,x_2) = \pm \psi(x_2,x_1)$$.

This is all okay... However, if we had two electrons 1 and 2 with differents spins along the z-axis m1 and m2. Then how could the physical situation of 1 being at x1 with z-spin m1 and 2 being at x2 with spin m2 be the same as the situation of 2 being at x1 with spin m2 while 1 is at x2 with spin m1?

That is how could the physical situation of

$$\psi_{m_1,m_2}(x_1,x_2)$$
be the same as the situation

$$\psi_{m_2,m_1}(x_2,x_1)?$$

Could'nt we just mesure the z-spin of the particle at x1 in the two situations and determine the difference?

2. Oct 21, 2011

### Bill_K

It's more like this... ψ(x1,m1; x2,m2) = -ψ(x2,m2; x1,m1). In both cases the electron at x1 has spin m1, and the electron at x2 has spin m2. What is being interchanged is the identity of the particles.