Large N as a classical limit (1/N ≈ ∋) of mixed valence

Abstract

Abstract Earlier work has shown that the infinite U Anderson model for mixed valence is contained within a broader ‘slave boson’ field theory. For large spin degeneracy N , the slave boson theory behaves classically with 1/ N playing the role of Planck's constant. Thermal equilibrium is studied in this classical limit. A 2nd order phase transition seperates weak coupling from a strong coupling regime where the boson field has a definite vacuum expectation value, forming a heavy band in the lattice. Quantum fluctuations at finite N convert this phase transition into a smooth crossover characterized by the development of power law correlations in the Bose field.