- 95-21 Bruno Nachtergaele
- Bounds on the mass gap of the ferromagnetic XXZ chain
(79K, LaTeX, 1 figure appended as uuencoded compressed Postscript file)
Jan 23, 95
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Abstract. We prove rigorous lower and upper bounds for the mass gap
of the ferromagnetic spin 1/2 XXZ chain. The two bounds coincide
asymptotically in the Ising limit $\Delta\to\infty$. Near the
isotropic point, $\Delta=1$, the estimates are good enough to
determine the critical behaviour of the mass gap unambiguously.
The derivation does not rely on exact solutions.