  The giant magnons are classical solitons of the O(N) sigma-model, which play
an important role in the AdS/CFT correspondence. We study quantum giant magnons
first at large N and then exactly using Bethe Ansatz, where giant magnons can
be interpreted as holes in the Fermi sea. We also identify a solvable limit of
Bethe Ansatz in which it describes a weakly-interacting Bose gas at zero
temperature. The examples include the O(N) model at large N, weakly interacting
non-linear Schrodinger model, and nearly isotropic XXZ spin chain in the
magnetic field.
