Failures of the Integral Hasse Principle for Affine Quadric Surfaces
  Quadric hypersurfaces are well-known to satisfy the Hasse principle. However, this is no longer true in the case of the Hasse principle for integral points, where counter-examples are known to exist in dimension 1 and 2. This work explores the frequency that such counter-examples arise in a family of affine quadric surfaces defined over the integers. 
Vladimir Mitankin
math.NT