Renormalization group for network models of Quantum Hall transitions

We analyze in detail the renormalization group flows which follow from the recently proposed all orders beta functions for the Chalker-Coddington network model. The flows in the physical regime reach a true singularity after a finite scale transformation. Other flows are regular and we identify the asymptotic directions. One direction is in the same universality class as the disordered XY model. The all orders beta function is computed for the network model of the spin Quantum Hall transition and the flows are shown to have similar properties. It is argued that fixed points of general current-current interactions in 2d should correspond to solutions of the Virasoro master equation. Based on this we identify two coset conformal field theories osp(2N|2N)_1 /u(1)_0 and osp(4N|4N)_1/su(2)_0 as possible fixed points and study the resulting multifractal properties. We also obtain a scaling relation between the typical amplitude exponent alpha_0 and the typical point contact conductance exponent X_t which is expected to hold when the density of states is constant.Comment: 35 pages, 5 color figures, v2: references adde

Affine Lie Algebra Symmetry of Sine-Gordon Theory at Reflectionless Points

The quantum affine symmetry of the sine-Gordon theory at q^2 = 1, which occurs at the reflectionless points, is studied. Conserved currents that correspond to the closure of simple root generators are considered, and shown to be local. We argue that they satisfy the affine sl(2) algebra. Examples of these currents are explicitly constructed.Comment: 8 pages, plaintex, uses harvma

Strong-weak coupling duality in anisotropic current interactions

The recently proposed all orders beta function is further investigated. By using a strong-weak coupling duality of the beta function, and some added topology of the space of couplings we are able to extend the flows to arbitrarily large or small scales. Using a non-trivial RG invariant we are able to identify sine-Gordon, sinh-Gordon and Kosterlitz-Thouless phases. We also find an additional phase with cyclic or roaming RG trajectories.Comment: 10 pages, 1 color figure v2: additional check with both UV and IR fixed points include