Critical-point-free energy for fractional-Toledo representations

Abstract

Let $S_g$ be a closed oriented surface of genus $g\ge 2$. For a reductive representation $ρ:π_1(S_g)\to\PU(2,1)$, let $E_{\rho }$ be the energy function on Teichmüller space associated to equivariant harmonic maps into $\CH^2$. For every positive integer $d$ with $3\nmid d$, all sufficiently large $h$, and every $g>h$, we construct an irreducible reductive representation \[ ρ_{g,h,d}:π_1(S_g)\to\PU(2,1) \] with \[ τ(ρ_{g,h,d})=2h-2-\frac{2d}{3}\notin\mathbb Z, \qquad \operatorname{Crit}(E_{ρ_{g,h,d}})=\varnothing. \] Consequently, the associated branched-minimal-surface forgetful map is not surjective in these nonintegral Toledo components.

14 pages