On the initial-boundary value problems for soliton equations
A. Degasperis+*, S. V. Manakov, P. M. Santini+* 1)
+Dipartimento di Fisica, Universitàdi Roma "La Sapienza", I-00185 Roma, Italy *Istituto Nazionale di Fisica Nucleare, Sezione di Roma, I-00185 Roma, Italy Landau Institute for Theoretical Physics RAS, 117334 Moscow, Russia
PACS: 02.60.Lj, 03.40.Kf
Abstract
We present a novel approach to solve initial-boundary value
problems on the segment and on the half line for soliton equations. Our
method is illustrated by solving a prototype, and widely applicable,
dispersive soliton equation: the celebrated nonlinear Schroedinger equation.
It is well-known that the
basic difficulty associated with boundaries is that some coefficients of
the evolution equation of the
(x-) scattering matrix S(k,t) depend on
unknown
boundary data. In this paper we overcome this difficulty by expressing
the unknown boundary data in terms of elements of the scattering matrix
itself, so obtaining a nonlinear integro - differential evolution
equation for S(k,t). We also sketch an alternative approach, in the
semiline case, based on a nonlinear
equation for S(k,t) which does not contain unknown boundary data; in this
way, the "linearizable" boundary value problems correspond to the
cases in which S(k,t) can be found by solving
a linear Riemann - Hilbert problem.
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