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math.CO2025

Propp's benzels and Lai's nearly symmetric hexagons with holes

Seok Hyun Byun, Mihai Ciucu, Yi-Lin Lee

In this paper we present a new version of the second author's factorization theorem for perfect matchings of symmetric graphs. We then use our result to solve four open problems of…

math.CO2025

A reflection principle for nonintersecting paths and lozenge tilings with free boundaries

Seok Hyun Byun

Okada and Stembridge's Pfaffian formula for the enumeration of families of nonintersecting paths with fixed starting points and unfixed ending points has been widely used to resolv…

math.CO2025

A short combinatorial proof of Di Francesco's conjecture on Aztec triangles

Seok Hyun Byun, Mihai Ciucu

Di Francesco conjectured in 2021 that the number of domino tilings of a certain family of regions -- called Aztec triangles -- on the square lattice is given by a product formula r…

math.CO2025

A Note on One-Hole Domino Tilings of Squares and Rectangles

Seok Hyun Byun, Wayne Goddard

We consider the number of domino tilings of an odd-by-odd rectangle that leave one hole. This problem is equivalent to the number of near-perfect matchings of the odd-by-odd rectan…

math.CO2025

Block diagonally symmetric lozenge tilings

Seok Hyun Byun, Yi-Lin Lee

We introduce a new symmetry class of both plane partitions and lozenge tilings of a hexagon, called the \textit{-block diagonal symmetry class}, where is a…

math.CO2024

Perfect matchings and spanning trees: squarishness, bijections and independence

Seok Hyun Byun, Mihai Ciucu

A number which is either the square of an integer or two times the square of an integer is called squarish. There are two main results in the literature on graphs whose number of p…