ENERGY-LEVEL ORDERING IN THE ONE-DIMENSIONAL T-J MODEL - A RIGOROUS RESULT
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Abstract
Two theorems about the spin properties of the ground state and the ordering of the energy levels for different spins of the one-dimensional t-J model are stated and proved. It is shown that when the number of electrons N=4n + 2 (n an integer) with periodic boundary conditions or N=4n with antiperiodic boundary conditions, the ground state is a nondegenerate singlet.