4 pi-symmetry of the neutron wave function under space rotation

We analyze the results of the neutron interferometry experiment that showed a 4 pi -symmetry of the neutron wave function under rotation in space produced by slowly rotating adiabatic guide field. In contrast to all previous work the present experiment is of a pure topological nature, i.e. it does not involve the Larmor precession and the result only depends on the topology and not on the value of the magnetic field and the neutron magnetic moment. This is the first experimental observation, which cannot be explained by simply applying the common classical concept of dynamic phase, consistently with the basic principles of quantum mechanics, to each of the energy eigenstates superposed in the neutron wave function. (C) 2001 Published by Elsevier Science B.V