On the uniqueness of multi-breathers of the modified Korteweg-de Vries equation

Alexander Semenov (1)

1 IRMA - Institut de Recherche Mathématique Avancée

We consider the modified Korteweg-de Vries equation (mKdV) and prove that given any sum P of solitons and breathers of (mKdV) (with distinct velocities), there exists a solution p of (mKdV) such that p(t) − P(t) → 0 when t → +∞, which we call multi-breather. In order to do this, we work at the H^2 level (even if usually solitons are considered at the H^1 level). We will show that this convergence takes place in any H^s space and that this convergence is exponentially fast in time. We also show that the constructed multi-breather is unique in two cases: in the class of solutions which converge to the profile P faster than the inverse of a polynomial of a large enough degree in time (we will call this a super polynomial convergence), or (without hypothesis on the convergence rate), when all the velocities are positive.

Domaines: Equations aux dérivées partielles [math.AP]

Alexander Semenov. On the uniqueness of multi-breathers of the modified Korteweg-de Vries equation. 2022. ⟨hal-03337323v4⟩