Dimers on a simple-quartic net with a vacancy

TL;DR

This paper investigates the enumeration of dimer configurations on a simple-quartic lattice with a boundary vacancy, establishing independence from vacancy location, deriving a closed-form generating function, and analyzing finite-size effects and conformal properties.

Contribution

It provides the first exact solution for dimer enumeration with a boundary vacancy and reveals a logarithmic correction and a change in conformal central charge.

Findings

Dimer generating function is independent of vacancy position.

Derived a closed-form expression for the dimer generating function.

Identified a logarithmic correction term in large-size expansion.

Abstract

A seminal milestone in lattice statistics is the exact solution of the enumeration of dimers on a simple-quartic net obtained by Fisher,Kasteleyn, and Temperley (FKT) in 1961. An outstanding related and yet unsolved problem is the enumeration of dimers on a net with vacant sites. Here we consider this vacant-site problem with a single vacancy occurring at certain specific sites on the boundary of a simple-quartic net. First, using a bijection between dimer and spanning tree configurations due to Temperley, Kenyon, Propp, and Wilson, we establish that the dimer generating function is independent of the location of the vacancy, and deduce a closed-form expression for the generating function. We next carry out finite-size analyses of this solution as well as that of the FKT solution. Our analyses lead to a logarithmic correction term in the large-size expansion for the vacancy problem with free boundary conditions. A concrete example exhibiting this difference is given. We also find the central charge c=-2 in the language of conformal field theory for the vacancy problem, as versus the value c=1 when there is no vacancy.