The hyperbolic Yang--Mills equation for connections in an arbitrary topological class

TL;DR

This paper develops tools to analyze the hyperbolic Yang--Mills equation in arbitrary topological classes at optimal regularity, extending existing theories and providing new methods for localization and well-posedness in higher dimensions.

Contribution

It generalizes topological class definitions to rough connections, introduces excision and extension techniques for the Yang--Mills constraint, and proves local well-posedness in arbitrary classes at optimal regularity.

Findings

Established local well-posedness in arbitrary topological classes for d ≥ 4.

Provided an alternative proof of classical global well-posedness in the energy subcritical case d=3.

Removed smallness assumptions in the temporal-gauge local well-posedness theorem.

Abstract

This is the third part of a four-paper sequence, which establishes the Threshold Conjecture and the Soliton-Bubbling vs.~Scattering Dichotomy for the energy critical hyperbolic Yang--Mills equation in the $(4+1)$-dimensional Minkowski space-time. This paper provides basic tools for considering the dynamics of the hyperbolic Yang--Mills equation in an arbitrary topological class at an optimal regularity. We generalize the standard notion of a topological class of connections on $\mathbb R^{d}$, defined via a pullback to the one-point compactification $\mathbb S^{d} = \mathbb R^{d} \cup \{\infty\}$, to rough connections with curvature in the critical space $L^{\frac{d}{2}}(\mathbb R^{d})$. Moreover, we provide excision and extension techniques for the Yang--Mills constraint (or Gauss) equation, which allow us to efficiently localize Yang--Mills initial data sets. Combined with the results in the previous paper \cite{OTYM2}, we obtain local well-posedness of the hyperbolic Yang--Mills equation on $\mathbb R^{1+d}$ $(d \geq 4)$ in an arbitrary topological class at optimal regularity in the temporal gauge (where finite speed of propagation holds). In addition, in the energy subcritical case $d = 3$, our techniques provide an alternative proof of the classical finite energy global well-posedness theorem of Klainerman--Machedon \cite{KlMa2}, while also removing the smallness assumption in the temporal-gauge local well-posedness theorem of Tao \cite{TaoYM}. Although this paper is a part of a larger sequence, the materials presented in this paper may be of independent and general interest. For this reason, we have organized the paper so that it may be read separately from the sequence.