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Total Positivity is a Quantum Phenomenon: The Grassmannian Case

About this Title

S. Launois, T. H. Lenagan and B. M. Nolan

Publication: Memoirs of the American Mathematical Society
Publication Year: 2023; Volume 291, Number 1448
ISBNs: 978-1-4704-6694-7 (print); 978-1-4704-7681-6 (online)
DOI: https://doi.org/10.1090/memo/1448
Published electronically: November 8, 2023
Keywords: Quantum grassmannian, totally nonnegative grassmannian, torus-invariant prime ideals, positroids, quantum minors, Cauchon-Le diagrams, partition subalgebras

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Table of Contents

Chapters

  • 1. Introduction
  • 2. Quantum matrices and partition subalgbras thereof
  • 3. Quantum Nilpotent Algebras and their $\mathcal {H}$-primes
  • 4. Cauchon-Le diagrams and Postnikov graphs
  • 5. $\mathcal {H}$-primes in partition subalgebras: membership
  • 6. Primes in $\mathcal {O}_q(M_{m,n}(R))$ from Cauchon-Le diagrams
  • 7. $\mathcal {H}$-primes in partition subalgebras: generation
  • 8. Primes in $\mathcal {O}_q(Y_\lambda (R))$ from Cauchon-Le diagrams
  • 9. $\mathcal {H}$-primes in the quantum grassmannian: membership
  • 10. $\mathcal {H}$-primes in ${\mathcal O}_q(G_{mn}(\mathbb {K}))$: generation
  • 11. The link with the total nonnegative grassmannian and applications

Abstract

The main aim of this paper is to establish a deep link between the totally nonnegative grassmannian and the quantum grassmannian. More precisely, under the assumption that the deformation parameter $q$ is transcendental, we show that “quantum positroids” are completely prime ideals in the quantum grassmannian ${\mathcal O}_q(G_{mn}(\mathbb {F}))$. As a consequence, we obtain that torus-invariant prime ideals in the quantum grassmannian are generated by polynormal sequences of quantum Plücker coordinates and give a combinatorial description of these generating sets. We also give a topological description of the poset of torus-invariant prime ideals in ${\mathcal O}_q(G_{mn}(\mathbb {F}))$, and prove a version of the orbit method for torus-invariant objects. Finally, we construct separating Ore sets for all torus-invariant primes in ${\mathcal O}_q(G_{mn}(\mathbb {F}))$. The latter is the first step in the Brown-Goodearl strategy to establish the orbit method for (quantum) grassmannians.

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