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-00939 Open Covering a cyclic group by few translates of a random set CO · covering · cyclic groups of prime order · random sets · translates
OP-00940 Open Density of linear covering codes of large radius CO · coding theory · covering codes · Hamming balls · linear codes
OP-00942 Open Covering every integer up to N ten times by one residue class per prime NT · covering systems · Erdős problems · residue classes · sieve theory