Lucas Gagnon

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math.AG2026

The Quasisymmetric Grassmannian

Nantel Bergeron, Lucas Gagnon, Hunter Spink +1

We construct a complex of toric varieties we call the quasisymmetric Grassmannian inside the Grassmannian of $r$ -planes in $C^{n}$ . Each irreducible component is a positroid…

math.AG2026

The Coxeter Flag Variety

Nantel Bergeron, Lucas Gagnon, Hunter Spink +1

For a Coxeter element $c$ in a Weyl group $W$ , we define the $c$ -Coxeter flag variety $CFl_{c} \subset G / B$ as the union of left-translated Richardson varieties $w^{-1}…

math.AG2025

The quasisymmetric flag variety: a toric complex on noncrossing partitions

Nantel Bergeron, Lucas Gagnon, Philippe Nadeau +2

We develop the geometric theory of equivariant quasisymmetry via a new ``quasisymmetric flag variety''. This is a toric complex in the flag variety whose fixed point set is the set…