This paper studies giant magnons in CP 3 , which in all known cases are old solutions from S 5 placed into two-and three-dimensional subspaces of CP 3 , namely CP 1 , RP 2 and RP 3 . We clarify some points about these subspaces, and other potentially interesting three-and four-dimensional subspaces. After confirming that ∆ − (J 1 − J 4 )/2 is a Hamiltonian for small fluctuations of the relevant 'vacuum' point particle solution, we use it to calculate the dispersion relation of each of the inequivalent giant magnons. We comment on the embedding of finite-J solutions, and use these to compare string solutions to giant magnons in the algebraic curve.
Groups in ABJM theoryThe N = 6 superconformal Chern-Simons-matter theory 2 of ABJM [4] of interest here has gauge symmetry U (N ) × U (N ). We will only study its scalars A i , B i . The fields A 1 , A 2 are matrices in the (N,N ) representation of this (one fundamental index, one anti-fundamental), and the fields B 1 , B 2 in the (N , N ). There is a manifest SU (2) A R-symmetry in which the As form a doublet, and SU (2) B acting on the Bs. There is also the conformal group SO(2, 3), since we are 1 Section 7, and the discussion of finite J in section 8, are new in version 2 of this paper.2 These of theories were discovered after the explorations of 3-dimensional superconformal theories with non-Lie-algebra guage symmetry by BLG, [18] and build on earlier work on Chern-Simons-matter theories by [19]. 4 i=1 J i = 0 follows trivially from the definition (12).