On stable and finite Morse index solutions of the fractional Toda system

TL;DR

This paper establishes Liouville type theorems for stable solutions of the fractional Toda system using a monotonicity formula, integral estimates, and blow-down analysis, extending understanding of solutions with finite Morse index.

Contribution

It introduces a new monotonicity formula and applies it to classify stable solutions of the fractional Toda system for certain dimensions and parameters.

Findings

Liouville theorems for finite Morse index solutions

Classification of stable homogeneous solutions

Conditions under which solutions are trivial or non-trivial

Abstract

We develop a monotonicity formula for solutions of the fractional Toda system $$ (-\Delta)^s f_\alpha = e^{-(f_{\alpha+1}-f_\alpha)} - e^{-(f_\alpha-f_{\alpha-1})} \quad \text{in} \ \ \mathbb R^n,$$ when $0<s<1$, $\alpha=1,\cdots,Q$, $f_0=-\infty$, $f_{Q+1}=\infty$ and $Q \ge2$ is the number of equations in this system. We then apply this formula, technical integral estimates, classification of stable homogeneous solutions, and blow-down analysis arguments to establish Liouville type theorems for finite Morse index (and stable) solutions of the above system when $n > 2s$ and $$ \dfrac{\Gamma(\frac{n}{2})\Gamma(1+s)}{\Gamma(\frac{n-2s}{2})} \frac{Q(Q-1)}{2} > \frac{ \Gamma(\frac{n+2s}{4})^2 }{ \Gamma(\frac{n-2s}{4})^2} . $$ Here, $\Gamma$ is the Gamma function. When $Q=2$, the above equation is the classical (fractional) Gelfand-Liouville equation.