This result is reversed for non-physical fields whose contributions to virtual processes ensure a unitary theory, called ghost fields. This result takes its usual form in 3 + 1 (“three-plus-one”) dimensions because world lines cannot form knots, making the braid group just the symmetric group; however, (-5[1])the nontrivial braid group in 2 + 1 (“two-plus-one”) dimensions (10[1])causes this result to take a different form obeyed by anyons (10[1])(“ANY-onz”). Proofs of this result require (-5[1])relativistic quantum field theory, (10[1])but topological (10[1])intuition for it is seen in the belt trick, (-5[1])in which a four pi (10[1])rotation returns the belt (10[1]-5[1])to its original state. Per this result, the exchange operator leaves wave functions of one (10[1])class of particles (10[1])unchanged, (-5[2])while wave (10[1])functions of another class of particles pick up a minus (-5[1])sign under exchange. (10[1])For 10 points, name this theorem that states that half-integer spin particles obey the Fermi (-5[2])(“FAIR-mee”)–Dirac (“dih-RACK”) distribution (-5[1])and integer spin particles obey the Bose (10[1])(“boze”)–Einstein distribution. (10[1])■END■ (10[4]0[6])