Year: 2019
Type: preprint
Abstract: We introduce coordinates on the spaces of framed and decorated representations of the fundamental group of a surface with nonempty boundary into the symplectic group $Sp(2n,\mathbf R)$. These coordinates provide a noncommutative generalization of the parametrizations of the spaces of representations into $SL(2,\mathbf R)$ or $PSL(2,\mathbf R)$ given by Thurston, Penner, Kashaev, and Fock-Goncharov. On the space of decorated symplectic representations the coordinates give a geometric realization of the noncommutative cluster-like structures introduced by Berenstein-Retakh. The locus of positive coordinates maps to the space of framed maximal representations. We use this to determine an explicit homeomorphism between the space of framed maximal representations and a quotient by the group $O(n)$. This allows us to describe the homotopy type and, when $n=2$, to give an exact description of the singularities. Along the way, we establish a complete classification of pairs of nondegenerate quadratic forms.
Source: arXiv (Cornell University)
Language: English
Subfield: Geometry and Topology
Field: Mathematics
Domain: Physical Sciences
Open Access status: green
Awards: Dynamics and geometric structures, G1620761618, RNMS: Geometric structures and representation varieties, G202495085, G2418827033, G4929423962, G5148239254, G5420063140, Deformation Spaces of Geometric Structures, RNMS: Geometric Structures and Representation Varieties, EXC 2181: STRUKTUREN: Emergenz in Natur, Mathematik und komplexen Daten, G7278058915, G7695612773, Mathematical Sciences Research Institute (MSRI), RNMS: Geometric Structures and Representation Varieties
OpenAlex ID: W2989855468