math.AT cs.CG math.CO math.MG 55N31 (Primary), 55-08, 05C05, 05C38, 05C40, 05C63, 05C85, 05C90,
  05C92, 52C22, 68W05, 92E10 (Secondary) G.2.2; G.2.3; F.2.2
Merge Trees of Periodic Filtrations
Herbert Edelsbrunner Teresa Heiss