On asymptotic stability of stable Good Boussinesq solitary waves (2501.13649v2)

Abstract: We consider the generalized Good-Boussinesq (GB) model in one dimension, with subcritical power nonlinearity $1<p\<5$ and data in the energy space $H^1\times L^2$. This model has solitary waves with speeds $c\in (-1,1)$. If $c^2>\frac{p-1}{4}$, Bona and Sachs showed the orbital stability of such waves. Previously, one of us proved that unstable GB standing waves can be perturbed with particular odd-even data in a suitable submanifold of the energy space, leading to the asymptotic stability property if $p\ge 2$. In this paper we prove that stable GB solitary waves are asymptotically stable in the case of general initial data placed in the energy space for any $p\ge 2$ and speeds $|c|>c_+(p)\geq \sqrt{\frac{p-1}{4}}$. The proof involves the introduction of a new set of virial estimates specifically adapted to the GB system in a moving setting. In particular, a new virial estimate with mixed variables is considered to treat arbitrary scaling and shift modulations. Another new ingredient is the understanding the corresponding linear matrix operator under mixed orthogonality conditions, a feature absent in our previous works.