Exponential decay for the Korteweg-de Vries equation on the real line with new classes of localized damping
Korteweg-de Vries; KdV equation; exponential decay; localized damping; Bourgain spaces
This master's thesis investigates the results of exponential decay in the \(L^2\) norm of the Korteweg-de Vries (KdV) equation on the real line with localized damping, as established by M.~Wang and D.~Xhou in \cite{Wang1}. Initially, it is proven that for the linear KdV equation, the exponential decay occurs if and only if the average of the damping coefficient across all intervals of a fixed length has a positive lower bound. Subsequently, Bourgain spaces \( X^{s,b} \) are introduced to demonstrate that, under the same damping conditions, exponential decay is also valid for the (nonlinear) KdV equation with small initial data. Finally, with the help of certain properties of regularity propagation in Bourgain spaces for solutions of the associated linear system and the unique continuation property, it is established that the exponential decay for the KdV equation with large initial data holds if the damping coefficient has a positive lower bound in \(E\subset\mathbb{R}\), where \(E\) is equidistributed over the real line and the complement \(E^{c}\) has finite Lebesgue measure.