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math.CO2025
Hybrid pipe dreams for the lower-upper scheme
Allen Knutson, Paul Zinn-Justin
In [KU23] were introduced hybrid pipe dreams interpolating between classic and bumpless pipe dreams, each hybridization giving a different formula for double Schubert polynomials.…
math.CO2024
Generic pipe dreams, lower-upper varieties, and Schwartz-MacPherson classes
Allen Knutson, Paul Zinn-Justin
We recall the lower-upper varieties from [Knutson '05] and give a formula for their equivariant cohomology classes, as a sum over generic pipe dreams. We recover as limits the clas…
math.CO2024
The commutant of divided difference operators, Klyachko's genus, and the comaj statistic
Christian Gaetz, Rebecca Goldin, Allen Knutson
In [Hamaker-Pechenik-Speyer-Weigandt, Nenashev, Pechenik-Weigandt] are studied certain operators on polynomials and power series that commute with all divided difference operators…