Bäcklund transformations, energy shift and the plane wave limit

We discuss basic properties of the Bäcklund transformations for the classical string in AdS space in the context of the null-surface perturbation theory. We explain the relation between the B¨acklund transformations and the energy shift of the dual field theory state. We show that the B¨acklund transformations can be represented as a finite-time evolution generated by a special linear combination of the Pohlmeyer charges. This is a manifestation of the general property of Bäcklund transformations known as spectrality. We also discuss the plane wave limit.

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Published 1 January 2007