English

Equivariant maps for measurable cocycles with values into higher rank Lie groups

Geometric Topology 2021-09-01 v3

Abstract

Let GG a semisimple Lie group of non-compact type and let XG\mathcal{X}_G be the Riemannian symmetric space associated to it. Suppose XG\mathcal{X}_G has dimension nn and it has no factor isometric to either H2\mathbb{H}^2 or SL(3,R)/SO(3)\text{SL}(3,\mathbb{R})/\text{SO}(3). Given a closed nn-dimensional Riemannian manifold NN, let Γ=π1(N)\Gamma=\pi_1(N) be its fundamental group and YY its universal cover. Consider a representation ρ:ΓG\rho:\Gamma \rightarrow G with a measurable ρ\rho-equivariant map ψ:YXG\psi:Y \rightarrow \mathcal{X}_G. Connell-Farb described a way to construct a map F:YXGF:Y\rightarrow \mathcal{X}_G which is smooth, ρ\rho-equivariant and with uniformly bounded Jacobian. In this paper we extend the construction of Connell-Farb to the context of measurable cocycles. More precisely, if (Ω,μΩ)(\Omega,\mu_\Omega) is a standard Borel probability Γ\Gamma-space, let σ:Γ×ΩG\sigma:\Gamma \times \Omega \rightarrow G be a measurable cocycle. We construct a measurable map F:Y×ΩXGF: Y \times \Omega \rightarrow \mathcal{X}_G which is σ\sigma-equivariant, whose slices are smooth and they have uniformly bounded Jacobian. For such equivariant maps we define also the notion of volume and we prove a sort of mapping degree theorem in this particular context.

Keywords

Cite

@article{arxiv.1911.05529,
  title  = {Equivariant maps for measurable cocycles with values into higher rank Lie groups},
  author = {Alessio Savini},
  journal= {arXiv preprint arXiv:1911.05529},
  year   = {2021}
}

Comments

19 pages; Added Lemma 3.1 + new references + corrected typo; to appear on Pacific J. Math