When a particle's position is measured, if one considers the wavefunction to collapse then one can assume it collapses into a delta function peaked at the measured position, and then after some finite time the wavefunciton 'evolves' outward away from this position.
Does a similar thing happen to spin?
From reading, it seems that instead if one measures a particle to be 'spin up' in the z-direction, and then wait some finite time, so long as you measure the particle in the z-direction again, it will always measure spin up. This would suggest that the particle's spin doesn't 'evolve into randomness after measurement'?
Is this correct?
One idea I had was that if we assume the wavefunctions only evolve due to the Hamiltonian in the TISE, if we assume a free particle Hamiltonian, this would indeed affect the spatial part of the wavefunciton but not the spin part.