The long-time Spitzer winding theorem states that, for the continuous unwrapped angle of planar Brownian motion started at ,
Here has the standard symmetric Cauchy distribution. The notation means convergence in distribution: for every real ,
Equivalently, expectations converge for every bounded continuous test function. This is a statement about the laws at large deterministic times, without asserting almost-sure convergence of sample paths. The angle is unwrapped; a principal argument is bounded and would instead give zero after division by .