Numerical renormalization group study of the Bose-Fermi Kondo model

The Bose-Fermi Kondo model (BFKM) is of current interest in the context of non-Fermi liquid behaviour in quantum critical heavy fermion systems [1]. We study the Ising-symmetry BFKM, employing a novel extension of Wilson's numerical renormalization group to include coupling of a quantum impurity to {\it both} a conduction electron band {\it and} a dissipative bosonic bath described by the spectral function $\eta(\omega)\propto \omega^s$ ($0<\omega<\omega_c$). For sub-Ohmic bath exponents $0g_{c}$) where the effective Kondo coupling flows to zero. Various critical exponents are computed and shown to obey hyperscaling relations for $0