Memoirs of the American Mathematical Society 2005; 144 pp; softcover Volume: 178 ISBN10: 082183794X ISBN13: 9780821837948 List Price: US$70 Individual Members: US$42 Institutional Members: US$56 Order Code: MEMO/178/839
 The two parts of this Memoir contain two separate but closely related papers. In the paper in Part A we study the correlation of holes in random lozenge (i.e., unit rhombus) tilings of the triangular lattice. More precisely, we analyze the joint correlation of these triangular holes when their complement is tiled uniformly at random by lozenges. We determine the asymptotics of the joint correlation (for large separations between the holes) in the case when one of the holes has side 1, all remaining holes have side 2, and the holes are distributed symmetrically with respect to a symmetry axis. Our result has a striking physical interpretation. If we regard the holes as electrical charges, with charge equal to the difference between the number of downpointing and uppointing unit triangles in a hole, the logarithm of the joint correlation behaves exactly like the electrostatic potential energy of this twodimensional electrostatic system: it is obtained by a Superposition Principle from the interaction of all pairs, and the pair interactions are according to Coulomb's law. The starting point of the proof is a pair of exact lozenge tiling enumeration results for certain regions on the triangular lattice, presented in the second paper. The paper in Part B was originally motivated by the desire to find a multiparameter deformation of MacMahon's simple product formula for the number of plane partitions contained in a given box. By a simple bijection, this formula also enumerates lozenge tilings of hexagons of sidelengths \(a,b,c,a,b,c\) (in cyclic order) and angles of 120 degrees. We present a generalization in the case \(b=c\) by giving simple product formulas enumerating lozenge tilings of regions obtained from a hexagon of sidelengths \(a,b+k,b,a+k,b,b+k\) (where \(k\) is an arbitrary nonnegative integer) and angles of 120 degrees by removing certain triangular regions along its symmetry axis. The paper in Part A uses these formulas to deduce that in the scaling limit the correlation of the holes is governed by two dimensional electrostatics. Readership Graduate students and research mathematicians interested in mathematical physics and probability. Table of Contents Part A. A Random Tiling Model for Two Dimensional Electrostatics  Introduction
 Definitions, statement of results and physical interpretation
 Reduction to boundaryinfluenced correlations
 A simple product formula for correlations along the boundary
 A \((2m+2n)\)fold sum for \(\omega_b\)
 Separation of the \((2m+2n)\)fold sum for \(\omega_b\) in terms of \(4mn\)fold integrals
 The asymptotics of the \(T^{(n)}\)'s and \({T'}^{(n)}\)'s
 Replacement of the \(T^{(k)}\)'s and \({T'}^{(k)}\)'s by their asymptotics
 Proof of Proposition 7.2
 The asymptotics of a multidimensional Laplace integral
 The asymptotics of \(\omega_b\). Proof of Theorem 2.2
 Another simple product formula for correlations along the boundary
 The asymptotics of \(\bar{\omega}_b\). Proof of Theorem 2.1
 A conjectured general two dimensional Superposition Principle
 Three dimensions and concluding remarks
 Bibliography
Part B. Plane Partitions I: A Generalization of MacMahon's Formula  Introduction
 Two families of regions
 Reduction to simplyconnected regions
 Recurrences for \(\mathrm{M}(R_{{\bf l},{\bf q}}(x))\) and \(\mathrm{M}(\bar{R}_{{\bf l},{\bf q}}(x))\)
 Proof of Proposition 2.1
 The guessing of \(\mathrm{M}(R_{{\bf l},{\bf q}}(x))\) and \(\mathrm{M}(\bar{R}_{{\bf l},{\bf q}}(x))\)
 Bibliography
