Deforming reducible representations of surface and 2-orbifold groups

Abstract

For a compact 2-orbifold with negative Euler characteristic $\mathcal O^2$, the variety of characters of $\pi_1(\mathcal O^2)$ in $\mathrm{SL}_{n}(\mathbb R)$ is a non-singular manifold at $\mathbb C$-irreducible representations. In this paper we prove that when a $\mathbb C$-irreducible representation of $\pi_1(\mathcal O^2)$ in $\mathrm{SL}_{n}(\mathbb R)$ is viewed in $\mathrm{SL}_{n+1}(\mathbb R)$, then the variety of characters is singular, and we describe the singularity.