Isotropic assumption (v,/(v,)(2)=m2)=V2+y+n2) The solution is (v,)=Cexp(2/a2) The probability should be normalized dnIsotropic assumption ( ) ( ) ( ) ( ) ( ) 2 2 2 2 x y z x y z f v f v f v = v = v + v + v ( ) ( ) 2 2 f vx =Cexp − vx  The solution is The probability should be normalized   = N dn 1