On classification of global dynamics for energy-critical equivariant harmonic map heat flows and radial nonlinear heat equation

TL;DR

This paper classifies the global dynamics of energy-critical equivariant harmonic map heat flows and radial nonlinear heat equations, revealing universal bubble formation rates and energy-based solution behaviors.

Contribution

It provides the first rigorous classification of bubble tree dynamics in symmetry settings using a novel energy method approach.

Findings

Finite energy solutions decompose into bubbles and a body map.

Solutions exist globally with bubble scales following universal rates.

Complete classification of radial solutions in high dimensions.

Abstract

We consider the global dynamics of finite energy solutions to energy-critical equivariant harmonic map heat flow (HMHF) and radial nonlinear heat equation (NLH). It is known that any finite energy equivariant solutions to (HMHF) decompose into finitely many harmonic maps (bubbles) separated by scales and a body map, as approaching to the maximal time of existence. Our main result for (HMHF) gives a complete classification of their dynamics for equivariance indices $D\geq3$; (i) they exist globally in time, (ii) the number of bubbles and signs are determined by the energy class of the initial data, and (iii) the scales of bubbles are asymptotically given by a universal sequence of rates up to scaling symmetry. In parallel, we also obtain a complete classification of $\dot{H}^{1}$-bounded radial solutions to (NLH) in dimensions $N\geq7$, building upon soliton resolution for such solutions. To our knowledge, this provides the first rigorous classification of bubble tree dynamics within symmetry. We introduce a new approach based on the energy method that does not rely on maximum principle. The key ingredient of the proof is a monotonicity estimate near any bubble tree configurations, which in turn requires a delicate construction of modified multi-bubble profiles also.