<P> The position - space wave function of a single particle without spin in three spatial dimensions is similar to the case of one spatial dimension above: </P> <Dl> <Dd> Ψ (r, t) (\ displaystyle \ Psi (\ mathbf (r), t)) </Dd> </Dl> <Dd> Ψ (r, t) (\ displaystyle \ Psi (\ mathbf (r), t)) </Dd> <P> where r is the position vector in three - dimensional space, and t is time . As always Ψ (r, t) is a complex - valued function of real variables . As a single vector in Dirac notation </P>

What is the significance of psi and psi squared