When physics helps mathematics: calculation of the sophisticated   multiple integral
  There exists a remarkable connection between the quantum mechanical Landau-Zener problem and purely classical-mechanical problem of a ball rolling on a Cornu spiral. This correspondence allows us to calculate a complicated multiple integral, a kind of multi-dimensional generalization of Fresnel integrals. A direct method of calculation is also considered but found to be successful only in some low-dimensional cases. As a byproduct of this direct method, an interesting new integral representation for $\zeta(2)$ is obtained. 
A. L. Kholodenko, Z. K. Silagadze
math.CA math-ph math.MP