# Global well-posedness of partially periodic KP-I equation in the energy space and application

## TL;DR

This paper proves the global well-posedness of the partially periodic KP-I equation in the energy space and demonstrates the orbital stability of small-speed KdV solitons under this flow.

## Contribution

It establishes the first global well-posedness result for KP-I with periodic y in the energy space and analyzes the stability of KdV solitons in this setting.

## Key findings

- Global well-posedness in energy space for KP-I with periodic y
- Orbital stability of small-speed KdV solitons under KP-I flow
- Extension of KP-I analysis to partially periodic domain

## Abstract

In this article, we address the Cauchy problem for the KP-I equation \[\partial_t u + \partial_x^3 u -\partial_x^{-1}\partial_y^2u + u\partial_x u = 0\] for functions periodic in $y$. We prove global well-posedness of this problem for any data in the energy space $\mathbb{E} = \left\{u\in L^2\left(\mathbb{R}\times\mathbb{T}\right),~\partial_x u \in L^2\left(\mathbb{R}\times\mathbb{T}\right),~\partial_x^{-1}\partial_y u \in L^2\left(\mathbb{R}\times\mathbb{T}\right)\right\}$. We then prove that the KdV line soliton, seen as a special solution of KP-I equation, is orbitally stable under this flow, as long as its speed is small enough.

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Source: https://tomesphere.com/paper/1706.06903