KP solitons and total positivity for the Grassmannian
Abstract
Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili proposed a twodimensional dispersive wave equation now known as the KP equation. It is wellknown that one can use the Wronskian method to construct a soliton solution to the KP equation from each point of the real Grassmannian Gr_kn. More recently several authors have studied the regular solutions that one obtains in this way: these come from points of the totally nonnegative part of the Grassmannian (Gr_kn)_{>= 0}. In this paper we exhibit a surprising connection between the theory of total positivity for the Grassmannian, and the structure of regular soliton solutions to the KP equation. By exploiting this connection, we obtain new insights into the structure of KP solitons, as well as new interpretations of the combinatorial objects indexing cells of (Gr_kn)_{>= 0}. In particular, we completely classify the spatial patterns of the soliton solutions coming from (Gr_2n)_{>0}, as well as those coming from (Gr_kn)_{>= 0} when the absolute value of the time parameter is sufficiently large. We also demonstrate an intriguing connection between soliton graphs for (Gr_kn)_{>0} and the cluster algebras of Fomin and Zelevinsky, and we use this connection to solve the inverse problem for generic KP solitons coming from (Gr_kn)_{>0}. Finally we construct all the soliton graphs for (Gr_2n)_{>0} using the triangulations of ngon.
 Publication:

arXiv eprints
 Pub Date:
 May 2011
 arXiv:
 arXiv:1106.0023
 Bibcode:
 2011arXiv1106.0023K
 Keywords:

 Mathematics  Combinatorics;
 High Energy Physics  Theory;
 Mathematical Physics;
 Mathematics  Algebraic Geometry;
 Nonlinear Sciences  Exactly Solvable and Integrable Systems;
 37K10;
 05Exx;
 14T05;
 13F60;
 14P10
 EPrint:
 47 pages, 37 figures