Abstract
The one-dimensional Hubbard model at half-filling is studied in theframework of the Composite Operator Method using a static approximation.A solution characterized by strong antiferromagnetic correlations and agap for any non-zero on-site interaction U is found. The correspondingground-state energy, double occupancy and specific heat are in excellentagreement with those obtained within the Bethe Ansatz. These resultsshow that the Composite Operator Method is an appropriate framework forthe half-filled Hubbard chain and can be applied to evaluate properties,like the correlation functions, which cannot be obtained by means of theBethe Ansatz, except for some limiting cases.
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