Marshall-Peierls sign rule for excited states of the frustrated J(1)-J(2) Heisenberg antiferromagnet

We present analytical and numerical calculations for some exited states of the frustrated J(1)-J(2) spin-1/2 Heisenberg model for linear chains and square lattices. We consider the lowest eigenstates the subspaces determined by the eigenvalue M of the spin operator S-total(z). Because of the reduced number of Ising basis states in the subspaces with higher M we are able to diagonalize systems with up to N = 144 spins. We find evidence that the Marshall-Peierls sign rule survives for a relatively large frustration parameter J(2).