Abstract. An alternative Lagrangian definition of an integrable defect is provided and analysed. The new approach is sufficiently broad to allow a description of defects within the Tzitzéica model, which was not possible in previous approaches, and may be generalizable. New, two-parameter, sine-Gordon defects are also described, which have characteristics resembling a pair of 'fused' defects of a previously considered type. The relationship between these defects and Bäcklund transformations is described and a Hamiltonian description of integrable defects is proposed.

PACS numbers: 02.30.Ik, 03.50 −z, 05.45 Yv

Print publication: Issue 47 (27 November 2009)
Received 21 August 2009
Published 4 November 2009