We developed a finite-size spin-wave calculation on the Heisenberg anti-ferromagnet on the triangular lattice, which, to order 1/s, favors a singlet (for an even number of sites) ground state. Furthermore, we implement the computation of the low-energy excitation spectrum E (S) where S is the total spin. For s = 1/2, the good agreement with the exact diagonalization and quantum Monte Carlo results strengthens the validity of the spin-wave expansion to describe the low-energy spin excitations of the Heisenberg model even in the presence of frustration.
