We use Quantum Monte Carlo methods to determine T = 0 Green functions, G(r,ω), on lattices up to 16 × 16 for the 2D Hubbard model at U/t = 4. For chemical potentials, µ, within the Hubbard gap, |µ | < µc, and at long distances, r, G(r,ω = µ) ∼ e −|r|/ξl with critical behavior: ξl ∼ |µ − µc | −ν, ν = 0.26±0.05. This result stands in agreement with the assumption of hyperscaling with correlation exponent ν = 1/4 and dynamical exponent z = 4. In contrast, the generic band insulator as well as the metal-insulator transition in the 1D Hubbard model are characterized by ν = 1/2 and z = 2. PACS numbers: 71.27.+a, 71.30.+h, 71.10.+x 1 At zero-temperature a continuous metal-insulator transition driven by a change in chemical potential may be characterized by the compressibility, χc, or the Drude weight, D. In the Mott insulating phase both D and χc vanish while they remain finite in the metallic phase [1,2]. In order to describe the metal-insulator transition from the insulator side, we consider the zero-temperature Green function G(r, ω) . At long distances, |r|, and for values of th
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