Published online by Cambridge University Press: 05 April 2022
In this paper, we prove several results on the exponential decay in $L^{2}$ norm of the KdV equation on the real line with localized dampings. First, for the linear KdV equation, the exponential decay holds if and only if the averages of the damping coefficient on all intervals of a fixed length have a positive lower bound. Moreover, under the same damping condition, the exponential decay holds for the (nonlinear) KdV equation with small initial data. Finally, with the aid of certain properties of propagation of regularity in Bourgain spaces for solutions of the associated linear system and the unique continuation property, the exponential decay for the KdV equation with large data holds if the damping coefficient has a positive lower bound on $E$
 norm of the KdV equation on the real line with localized dampings. First, for the linear KdV equation, the exponential decay holds if and only if the averages of the damping coefficient on all intervals of a fixed length have a positive lower bound. Moreover, under the same damping condition, the exponential decay holds for the (nonlinear) KdV equation with small initial data. Finally, with the aid of certain properties of propagation of regularity in Bourgain spaces for solutions of the associated linear system and the unique continuation property, the exponential decay for the KdV equation with large data holds if the damping coefficient has a positive lower bound on $E$ , where $E$
, where $E$ is equidistributed over the real line and the complement $E^{c}$
 is equidistributed over the real line and the complement $E^{c}$ has a finite Lebesgue measure.
 has a finite Lebesgue measure.
 with relatively dense damping. Proc. Am. Math. Soc. 148 (2020), 4745–4753.CrossRefGoogle Scholar
 with relatively dense damping. Proc. Am. Math. Soc. 148 (2020), 4745–4753.CrossRefGoogle Scholar . J. Math. Pure Appl. 126 (2019), 144–194.Google Scholar
. J. Math. Pure Appl. 126 (2019), 144–194.Google Scholar has a finite fractal dimension. Math. Methods Appl. Sci. 43 (2020), 4567–4584.Google Scholar
 has a finite fractal dimension. Math. Methods Appl. Sci. 43 (2020), 4567–4584.Google Scholar