English

Unimodality of $q$-Fibonomial coefficients for small cases

Combinatorics 2026-05-14 v1

Abstract

Bergeron--Ceballos--K\"ustner introduced the qq-Fibonomial coefficients \qfibonomm+nn \qfibonom{m+n}{n}, gave a combinatorial interpretation of the qq-Fibonomial coefficients via a weighted path-domino tiling model, and conjectured that these polynomials are unimodal. We prove the conjecture for n3n\leq3. For the n=2n=2 case, we give a combinatorial proof of both unimodality and symmetry by defining a nearly symmetric saturated chain decomposition on the set of tilings. For all three cases, we give an algebraic proof. Finally, for the n=3n=3 case, we establish a more general unimodality result for certain products of qq-analogs and propose several related conjectures.

Keywords

Cite

@article{arxiv.2605.12822,
  title  = {Unimodality of $q$-Fibonomial coefficients for small cases},
  author = {Brendan B. Connelly and Ezekiel Ito and Thomas C. Martinez and Olha Shevchenko and Kacey Yang},
  journal= {arXiv preprint arXiv:2605.12822},
  year   = {2026}
}