Lozenge tilings of hexagons with removed core and satellites

TL;DR

This paper derives simple product formulas for counting lozenge tilings of symmetric hexagon regions with removed cores and satellites, introduces a new proof method, and generalizes a longstanding tiling formula.

Contribution

It presents a novel approach for proving tiling formulas and extends a classic tiling result, with detailed analysis of symmetric regions with holes.

Findings

Product formulas for tilings of symmetric hexagons with removed parts

A new method for proving tiling enumeration formulas

Generalization of a 20-year-old tiling formula

Abstract

We consider regions obtained from 120 degree rotationally invariant hexagons by removing a core and three equal satellites (all equilateral triangles) so that the resulting region is both vertically symmetric and 120 degree rotationally invariant, and give simple product formulas for the number of their lozenge tilings. We describe a new method of approach for proving these formulas, and give the full details for an illustrative special case. As a byproduct, we are also able to generalize this special case in a different direction, by finding a natural counterpart of a twenty year old formula due to Ciucu, Eisenk\"olbl, Krattenthaler and Zare, which went unnoticed until now. The general case of the original problem will be treated in a subsequent paper. We then work out consequences for the correlation of holes, which were the original motivation for this study.