paper

Modular invariance, lattice field theories and finite size corrections

arXiv:hep-th/9606137 · doi:10.1006/aphy.1998.5868

Abstract

We give a lattice theory treatment of certain one and two dimensional quantum field theories. In one dimension we construct a combinatorial version of a non-trivial field theory on the circle which is of some independent interest in itself while in two dimensions we consider a field theory on a toroidal triangular lattice. We take a continuous spin Gaussian model on a toroidal triangular lattice with periods and where the spins carry a representation of the fundamental group of the torus labeled by phases and . We compute the {\it exact finite size and lattice corrections}, to the partition function , for arbitrary mass and phases . Summing over a specified set of phases gives the corresponding result for the Ising model on a torus. An interesting property of the model is that the limits and do not commute. Also when the model exhibits a {\it vortex critical phase} when at least one of the is non-zero. In the continuum or scaling limit, for arbitrary , the finite size corrections to are {\it modular invariant} and for the critical phase are given by elliptic theta functions. In the cylinder limit the ``cylinder charge'' is a non-monotonic function of that ranges from for to zero for but from which one can determine the central charge . The study of the continuum limit of these field theories provides a kind of quantum theoretic analog of the link between certain combinatorial and analytic topological quantities.

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