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- Masaki Oshikawa, Ian Affleck
- 1996

Critical phenomena in the two-dimensional Ising model with a defect line are studied using boundary conformal field theory on the c = 1 orbifold. Novel features of the boundary states arising from the orbifold structure, including continuously varying boundary critical exponents, are elucidated. New features of the Ising defect problem are obtained… (More)

- Ian Affleck, Masaki Oshikawa, Hubert Saleur
- 1998

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)

- Ian Affleck
- 1993

A brief review is given of a new method for studying the critical behavior of quantum impurity problems, based on conformal field theory techniques, which I developed with Andreas Ludwig. Some results on the overscreened Kondo problem are reviewed. It is shown that the simple open and periodic fixed points, which occur in quantum spin chain impurity models,… (More)

- Ian Affleck
- 2008

The boundary conformal field theory approach to quantum impurity problems is used to study the Fermi edge singularity, occuring in the X-ray ad-sorption probablility. The deep-hole creation operator, in the effective low-energy theory, changes the boundary condition on the conduction electrons. By a conformal mapping, the dimension of such an operator is… (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)

- Masaki Oshikawa, Ian Affleck
- 2001

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)

A scaling form for the local susceptibility, derived from renormalization group arguments, is proposed. The scale over which the uniform part of this scaling form varies can be viewed as a definition of the Kondo " screening cloud " ∼ ξ K. The proposed scaling form interpolates between Ruderman-Kittel-Kasuya-Yosida (RKKY) results in the high temperature… (More)

Highly accurate results are presented for the susceptibility, χ(T) of the s = 1/2 Heisenberg antiferromagnetic chain for all temperatures, using the Bethe ansatz and field theory methods. After going through a rounded peak, χ(T) approaches its asympotic zero-temperature value with infinite slope.