Truncated Hilbert space approach to the 2d ϕ4\phi^{4} theory

We apply the massive analogue of the truncated conformal space approach to study the two dimensional $\phi^{4}$ theory in finite volume. We focus on the broken phase and determine the finite size spectrum of the model numerically. We interpret the results in terms of the Bethe-Yang spectrum, from which we extract the infinite volume masses and scattering matrices for various couplings. We compare these results against semiclassical analysis and perturbation theory. We also analyze the critical point of the model and confirm that it is in the Ising universality class.Comment: pdflatex, 35 pages with 29 pdf figures. Binary program is also attached, run on linux as: phi4 config.dat, v2: typos corrected, comparison to other works and references added, vacuum splitting analysis corrected, comparison to sine-Gordon TCSA added, v3: improved numerics, analysis on excited kink added, critical point investigate

Symplectic leaves of W-algebras from the reduced Kac-Moody point of view

The symplectic leaves of W-algebras are the intersections of the symplectic leaves of the Kac-Moody algebras and the hypersurface of the second class constraints, which define the W-algebra. This viewpoint enables us to classify the symplectic leaves and also to give a representative for each of them. The case of the (W_{2}) (Virasoro) algebra is investigated in detail, where the positivity of the energy functional is also analyzed.Comment: Latex, 6 pages, Talk presented by Z. Bajnok at the Second International Conference on Geometry, Integrability and Quantization, Varna, 200

Explicit boundary form factors: the scaling Lee-Yang model

We provide explicit expressions for boundary form factors in the boundary scaling Lee-Yang model for operators with the mildest ultraviolet behavior for all integrable boundary conditions. The form factors of the boundary stress tensor take a determinant form, while the form factors of the boundary primary field contain additional explicit polynomials.Comment: 18 pages, References adde

Boundary reduction formula

An asymptotic theory is developed for general non-integrable boundary quantum field theory in 1+1 dimensions based on the Langrangean description. Reflection matrices are defined to connect asymptotic states and are shown to be related to the Green functions via the boundary reduction formula derived. The definition of the $R$-matrix for integrable theories due to Ghoshal and Zamolodchikov and the one used in the perturbative approaches are shown to be related.Comment: 12 pages, Latex2e file with 5 eps figures, two Appendices about the boundary Feynman rules and the structure of the two point functions are adde

A2 Toda theory in reduced WZNW framework and the representations of the W algebra

Using the reduced WZNW formulation we analyse the classical $W$ orbit content of the space of classical solutions of the $A_2$ Toda theory. We define the quantized Toda field as a periodic primary field of the $W$ algebra satisfying the quantized equations of motion. We show that this local operator can be constructed consistently only in a Hilbert space consisting of the representations corresponding to the minimal models of the $W$ algebra.Comment: 38 page

C2C_2 Toda theory in the reduced WZNW framework

We consider the $C_2$ Toda theory in the reduced WZNW framework. Analysing the classical representation space of the symmetry algebra (which is the corresponding $C_2$ $W$ algebra) we determine its classical highest weight representations. We quantise the model promoting only the relevant quantities to operators. Using the quantised equation of motion we determine the selection rules for the $u$ field that corresponds to one of the Toda fields and give restrictions for its amplitude functions and for the structure of the Hilbert space of the model

C2 TODA THEORY IN THE REDUCED WZNW FRAMEWORK

We consider the $C_2$ Toda theory in the reduced WZNW framework. Analysing the classical representation space of the symmetry algebra (which is the corresponding $C_2$ $W$ algebra) we determine its classical highest weight representations. We quantise the model promoting only the relevant quantities to operators. Using the quantised equation of motion we determine the selection rules for the $u$ field that corresponds to one of the Toda fields and give restrictions for its amplitude functions and for the structure of the Hilbert space of the model.Comment: 26 pages, TeX, ITP Budapest 501, minor modification

Finite size effects in quantum field theories with boundary from scattering data

We derive a relation between leading finite size corrections for a 1+1 dimensional quantum field theory on a strip and scattering data, which is very similar in spirit to the approach pioneered by Luscher for periodic boundary conditions. The consistency of the results is tested both analytically and numerically using thermodynamic Bethe Ansatz, Destri-de Vega nonlinear integral equation and classical field theory techniques. We present strong evidence that the relation between the boundary state and the reflection factor one-particle couplings, noticed earlier by Dorey et al. in the case of the Lee-Yang model extends to any boundary quantum field theory in 1+1 dimensions.Comment: 24 pages, 1 eps figure. Clarifying comments and a reference adde