# Total positivity is a quantum phenomenon: the grassmannian case

## TL;DR

This paper reveals a deep connection between total positivity and quantum structures in the Grassmannian, showing that quantum positroids form prime ideals and providing a combinatorial and topological framework for their study.

## Contribution

It establishes that quantum positroids are prime ideals in the quantum Grassmannian and offers a combinatorial description of torus-invariant prime ideals, advancing the orbit method in quantum geometry.

## Key findings

- Quantum positroids are completely prime ideals.
- Torus-invariant prime ideals are generated by quantum Plücker coordinates.
- Constructed separating Ore sets for all torus-invariant primes.

## 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 $A$. As a consequence, we obtain that torus-invariant prime ideals in the quantum grassmannian are generated by polynormal sequences of quantum Pl\"ucker 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 $A$, and prove a version of the orbit method for torus-invariant objects. Finally, we construct separating Ore sets for all torus-invariant primes in $A$. The latter is the first step in the Brown-Goodearl strategy to establish the orbit method for (quantum) grassmannians.

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Source: https://tomesphere.com/paper/1906.06199