Supramaximal Representations of Planar Surface Groups
Presenter
June 14, 2021
Abstract
Recently Deroin, Tholozan and Toulisse found connected components of
relative character varieties of surface group representations in a Hermitian
Lie grop G with remarkable properties.
For example, although the Lie groups are noncompact,
these components are compact.
In this way they behave more like relative character varieties for compact Lie
groups. (A relative character variety comprises equivalence classes of
homomorphisms of the fundamental group of a surface S,
where the holonomy around each boundary component of S is constrained
to a fixed conjugacy class in G.)
The first examples were found by Robert Benedetto and myself in an REU
in the summer of 1992, and published in Experimental Mathematics in 1999.
Here S is the 4-holed sphere and G = SL(2,R).
Although computer visualization played an important role in the discovery of
these unexpected compact components,
computation was invisible in the final proof, and its subsequent extensions.