FIG. 5. Color online The finite-temperature correction to the optical spectral weight thick curves , for various values of t , as indicated. Also plotted is the analogous quantity for the kinetic energy which, by Eq. 8 , is just −8tg F . Note that the latter is always negative, while the spectral weight becomes positive for a finite electron concentration for electron hole densities below above the van Hove singularity. The magnitude of the anomalous region increases with increasing t .
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