We obtain the giant magnon of Hofman-Maldacena and its dyonic generalisation on R × S 3 ⊂ AdS 5 × S 5 from the general elliptic finite-gap solution by degenerating its elliptic spectral curve into a singular curve. This alternate description of giant magnons as finite-gap solutions associated to singular curves is related through a symplectic transformation to their already established description in terms of condensate cuts developed in hep-th/0606145.
IntroductionRecently, a certain limit of the AdS/CFT correspondence was proposed by Hofman and Maldacena [1] in which the 't Hooft coupling λ is held fixed allowing for a direct interpolation between the gauge theory (λ ≪ 1) and string theory (λ ≫ 1). In the Hofman-Maldacena (HM) limit, the energy E (or conformal dimension ∆ = E) and a U(1) R-charge J 1 both become infinite with the difference E − J 1 held fixed. On the string side, using static gauge X 0 = κτ , the energy density E = √ λκ/2π is uniform along the string so that the string effectively becomes infinitely long in this limit. Likewise on the gauge side, the dual singletrace conformal operator of the form tr(Z J 1 W J 2 ) clearly becomes infinitely long in this limit. If we relax the trace condition then we are able to consider elementary excitations on the gauge side given by infinitely long operators of the formThe trace condition is equivalent to the requirement that the total momentum of all excitations should vanish. The single excitation (0.1), which violates the momentum condition, describes a 'magnon' of momentum p with dispersion relation [2,3,4,5,6] E − J 1 = 1 + λ π 2 sin 2 p 2 .At large λ this state is described by a classical string solution on the real line called a 'giant magnon' which was identified in [1]. It corresponds to a solitonic solution of the infinite string embedded in an R × S 2 subsector of AdS 5 × S 5 .Subsequently, solitonic solutions of the infinite string moving through R × S 3 referred to as 'dyonic giant magnons' were identified in [2] and constructed in [7]. These solutions carry an extra finite U(1) R-charge J 2 and have the following dispersion relationThey correspond on the gauge side to bound states of J 2 magnons given by infinitely long operators of the form
.).A general description of such dyonic giant magnons was then proposed in [8] using the language of finite-gap solutions and spectral curves [9,10,11,12,13], still restricting attention to the R × S 3 sector. In this framework, every solution is characterised by a spectral curve Σ equipped with an Abelian integral p called the quasi-momentum, such that the pair (Σ, dp) encodes the integrals of motion of the solution. A single dyonic giant magnon can 1 be described by a condensate cut B 1 from x 1 tox 1 on the spectral curve [8], whose presence can be traced down to the existence of a nonvanishing a-period for the differential of the quasi-momentum a dp ∈ 2πZ.The ensuing multivaluedness of the Abelian integral p(x) can equivalently be described in terms of simple poles of p(x) at the end points x 1...