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Event Type:

Geometry-Topology Seminar

Date/Time:

Monday, May 6, 2019 - 12:00 to 12:50

Location:

Kidd 280

Abstract:

We will describe two combinatorial problems inspired by finite automorphism groups of compact Riemann surfaces of genus two or greater: enumerating the topological actions of a finite group on surfaces and determining the set of genera of surfaces admitting such a group action, called the genus spectrum. We will illustrate results in the important case of quasiplatonic cyclic group actions (i.e., quotient genus zero and three branch values). Specifically, using formulas of Benim and Wootton (2014), we show that the number of quasiplatonic cyclic group actions is roughly one-sixth the number of regular dessins d'enfants with a cyclic group of symmetries. In addition, by optimizing the Riemann-Hurwitz formula under certain conditions, we discuss the second-smallest genus of surfaces admitting a quasiplatonic cyclic group action, which appears to resemble the known minimal genus action discovered by Harvey (1966).