I. Andrew Affleck

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Boundary critical phenomena are studied in the 3-State Potts model in 2 dimensions using conformal field theory, duality and renormalization group methods. A presumably complete set of boundary conditions is obtained using both fusion and orbifold methods. Besides the previously known free, fixed and mixed boundary conditions a new one is obtained. This(More)
Using the density matrix renormalization group and a bosonization approach, we study a spin-1/2 antiferromagnetic Heisenberg chain with near-neighbor coupling J 1 and frustrating second-neighbor coupling J 2 , particularly in the limit J 2 >> J 1. This system exhibits both dimerization and incommensurate spiral spin correlations. We argue that this system(More)
A systematic field-theory approach to Electron Spin Resonance (ESR) in the S = 1/2 quantum antiferromagnetic chain at low temperature T (compared to the exchange coupling J) is developed. In particular, effects of a transverse staggered field h and an exchange anisotropy (including a dipolar interaction) δ on the ESR lineshape are discussed. In the lowest(More)
Non-magnetic impurities in an S=1/2 Heisenberg antiferromagnetic chain are studied using boundary conformal field theory techniques and finite-temperature quantum Monte Carlo simulations. We calculate the static structure function, S imp (k), measured in neutron scattering and the local susceptibility , χ i measured in Knight shift experiments. S imp (k)(More)