Shrunk loop theorem for the topology probabilities of closed Brownian (or Feynman) paths on the twice punctured plane

Abstract

The shrunk loop theorem presented here is an integral identity which facilitates the calculation of the relative probability (or probability amplitude) of any given topology that a free, closed Brownian or Feynman path of a given 'duration' might have on the twice punctured plane (the plane with two marked points). The result is expressed as a scattering series of integrals of increasing dimensionality based on the maximally shrunk version of the path. Physically, this applies in different contexts: (i) the topology probability of a closed ideal polymer chain on a plane with two impassable points, (ii) the trace of the Schroedinger Green function, and thence spectral information, in the presence of two Aharonov-Bohm fluxes, (iii) the same with two branch points of a Riemann surface instead of fluxes. Our theorem starts with the Stovicek expansion for the Green function in the presence of two Aharonov-Bohm flux lines, which itself is based on the famous Sommerfeld one puncture point solution of 1896 (the one puncture case has much easier topology, just one winding number). Stovicek's expansion itself can supply the results at the expense of choosing a base point on the loop and then integrating it away. The shrunk loop theorem eliminates this extra two dimensional integration, distilling the topology from the geometry.