#### Document Type

Article

#### Rights

This item is available under a Creative Commons License for non-commercial use only

#### Disciplines

Applied mathematics

#### Abstract

A G-strand is a map g : **R**** x R** --> G for a Lie group G that follows from Hamilton's principle for a certain class of G-invariant Lagrangians. Some G-strands on finite-dimensional groups satisfy 1+1 space-time evolutionary equations that admit soliton solutions as completely integrable Hamiltonian systems. For example, the SO(3)-strand equations may be regarded physically as integrable dynamics for solitons on a continuous spin chain. Previous work has shown that G-strands for diffeomorphisms on the real line possess solutions with singular support (e.g. peakons). This paper studies collisions of such singular solutions of G-strands when G = Diff(**R**) is the group of diffeomorphisms of the real line R, for which the group product is composition of smooth invertible functions. In the case of peakon-antipeakon collisions, the solution reduces to solving either Laplace's equation or the wave equation (depending on a sign in the Lagrangian) and is written in terms of their solutions. We also consider the complexified systems of G-strand equations for G = Diff(**R**) corresponding to a harmonic map g : **C** --> Diff(**R**) and find explicit expressions for its peakon-antipeakon solutions, as well.

#### Recommended Citation

D. Holm and R. Ivanov, G-Strands and Peakon Collisions on Diff(R), SIGMA 9 (2013), 027, 14 pages, DOI: 10.3842/SIGMA.2013.027

#### Included in

Dynamic Systems Commons, Mathematics Commons, Non-linear Dynamics Commons, Partial Differential Equations Commons

## Publication Details

SIGMA, vol.9 (2013), 027, 14 pages

DOI: 10.3842/SIGMA.2013.027