$SU(2)$ Yang-Mills-Higgs functional with Higgs self-interaction on $3$-manifolds

Abstract

Fixing a constant $\lambda>0$, for any parameter $\varepsilon>0$ we study critical points of the Yang--Mills--Higgs energy \[ \mathcal{Y}_{\varepsilon}(\nabla,\Phi) = \int_M \varepsilon^2|F_{\nabla}|^2 + |\nabla\Phi|^2 + \frac{\lambda}{4\varepsilon^2}(1-|\Phi|^2)^2, \] defined for pairs $(\nabla,\Phi)$, where $\nabla$ is a connection on an $SU(2)$-bundle over an oriented Riemannian $3$-manifold $(M^3, g)$, and $\Phi$ a section of the associated adjoint bundle. When $M$ is closed, we use a $2$-parameter min-max construction to produce, for $\varepsilon\ll_M 1$, non-trivial critical points in the energy regime \[ 1 \lesssim_{\lambda}\varepsilon^{-1}\mathcal{Y}_{\varepsilon}(\nabla_{\varepsilon},\Phi_{\varepsilon}) \lesssim_{\lambda, M} 1. \] When $b_1(M)=0$, these critical points are irreducible: $\nabla_{\varepsilon}\Phi_{\varepsilon}\neq 0$. Next, assuming $M$ has bounded geometry (not necessarily compact), and given critical points with $\varepsilon^{-1}\mathcal{Y}_{\varepsilon}(\nabla_{\varepsilon}, \Phi_{\varepsilon})$ uniformly bounded, we show that as $\varepsilon\to 0$, the energy measures $\varepsilon^{-1}e_{\varepsilon}(\nabla_{\varepsilon}, \Phi_{\varepsilon}) vol_{g}$ converge subsequentially to \[ |h|^2 vol_g + \sum_{x \in S}\Theta(x)\delta_{x}, \] where $h$ is an $L^2$ harmonic $1$-form, $S$ a finite set and each $\Theta(x)$ equals the energy of a finite collection of $\mathcal{Y}_{1}$-critical points on $\mathbb{R}^3$. Finally, the estimates involved also lead to an energy gap for critical points on $3$-manifolds with bounded geometry. As a byproduct of our results, we deduce the existence of non-trivial $\mathcal{Y}_{1}$-critical points over $\mathbb{R}^3$ for any $\lambda>0$.