OP-00393 Open Sunada’s no-gap conjecture for abelian covers SP · abelian coverings · AIM Open Applied Problems · hyperbolic surfaces · spectral gaps
OP-00527 Open The sharp number of directions illuminating a convex body MG · AIM Open Applied Problems · convex bodies · homothetic coverings · illumination numbers
OP-01036 Open How many rotated pyjama sets cover the plane CO · coverings · pyjama problem · quantitative bounds · topological dynamics