Kac boundary conditions of the logarithmic minimal models

Abstract

We develop further the implementation and analysis of Kac boundary conditions in the general logarithmic minimal models $\mathcal{LM}(p,p^{\prime })$ with $1\le p<p^{\prime }$ and $p,p^{\prime }$ coprime. Working in a strip geometry, we consider the $(r,s)$ boundary conditions, which are organized into infinitely extended Kac tables labeled by $r,s=1,2,3,...$. They are conjugate to Virasoro Kac representations with conformal dimensions ${\Delta }_{r,s}$ given by the usual Kac formula. On a finite strip of width $N$, built from a square lattice, the associated integrable boundary conditions are constructed by acting on the vacuum $(1,1)$ boundary with an $s$-type seam of width $s-1$ columns and an $r$-type seam of width $\rho -1$ columns. The $r$-type seam contains an arbitrary boundary field $\xi$. The usual fusion construction of the $r$-type seam relies on the existence of Wenzl-Jones projectors restricting its application to $r\le \rho <p^{\prime }$. This limitation was recently removed by Pearce, Rasmussen and Villani who further conjectured that the conformal boundary conditions labeled by $r$ are realized, in particular, for $\rho =\rho (r)=\lfloor \frac{r{p}^{\prime }}{p}\rfloor$. In this paper, we confirm this conjecture by performing extensive numerics on the commuting double row transfer matrices and their associated quantum Hamiltonian chains. Letting $[x]$ denote the fractional part, we fix the boundary field to the specialized values $\xi =\frac{\pi }{2}$ if $[\frac{\rho }{p^{\prime }}]=0$ and $\xi =[\frac{\rho p}{p^{\prime }}]\frac{\pi }{2}$ otherwise. For these boundary conditions, we obtain the Kac conformal weights ${\Delta }_{r,s}$ by numerically extrapolating the finite-size corrections to the lowest eigenvalue of the quantum Hamiltonians out to sizes $N\le 32-\rho -s$. Additionally, by solving local inversion relations, we obtain general analytic expressions for the boundary free energies allowing for more accurate estimates of the conformal data.

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Cited by in corpus (5)

• Boundary algebras and Kac modules for logarithmic minimal models
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• Extended T-systems, Q matrices and T-Q relations for $s\ell (2)$ models at roots of unity
• Critical site percolation on the triangular lattice: From integrability to conformal partition functions
• Logarithmic Minimal Models with Robin Boundary Conditions