Iwahori-Coulomb branches, stable envelopes, and quantum cohomology of cotangent bundles of flag varieties
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| Format: | Preprint |
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2026
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| _version_ | 1866911519163285504 |
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| author | Chan, Ki Fung Chan, Kwokwai Chow, Chi Hong Lam, Chin Hang Eddie |
| author_facet | Chan, Ki Fung Chan, Kwokwai Chow, Chi Hong Lam, Chin Hang Eddie |
| contents | We consider Iwahori-Coulomb branches $\mathcal{A}_{G,\mathbf{N},\mathbf{V}}^{\mathrm{Fl}}$, which are the affine flag analogs of the original Coulomb branches $\mathcal{A}_{G,\mathbf{N}}^{\mathrm{Gr}}$ defined by Braverman, Finkelberg, and Nakajima. For any conical symplectic resolution $X$, we prove that the $\mathcal{A}_{G,\mathbf{N},\mathbf{V}}^{\mathrm{Fl}}$-action on the localized equivariant quantum cohomology of $X$, induced by shift operators, satisfies a polynomiality property in terms of stable envelopes.
We then study the case $X = T^*(G/P)$, the cotangent bundle of a flag variety, for which the Iwahori-Coulomb branch is isomorphic to the trigonometric double affine Hecke algebra $\mathcal{H}_{G,\hbar,k}$. The polynomiality property enables us to compute explicitly the above action in terms of the Demazure-Lusztig elements and stable envelopes. Applications include:
(1) Computation of the Iwarhori-Coulomb branch action for $G/P$ by taking the confluent limit, recovering Peterson-Lam-Shimozono's theorem.
(2) Construction of an explicit Namikawa-Weyl group action on the equivariant quantum cohomology of $T^*(G/P)$ that preserves the quantum product, extending a result of Li-Su-Xiong.
(3) Proof of a conjecture of Braverman-Finkelberg-Nakajima stating that, up to a shift of the dilation parameter, $\mathcal{A}_{G,\mathfrak{g}^*}^{\mathrm{Gr}}$ is isomorphic to the spherical subalgebra of $\mathcal{H}_{G,\hbar,k}$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2601_19691 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Iwahori-Coulomb branches, stable envelopes, and quantum cohomology of cotangent bundles of flag varieties Chan, Ki Fung Chan, Kwokwai Chow, Chi Hong Lam, Chin Hang Eddie Algebraic Geometry Mathematical Physics Representation Theory We consider Iwahori-Coulomb branches $\mathcal{A}_{G,\mathbf{N},\mathbf{V}}^{\mathrm{Fl}}$, which are the affine flag analogs of the original Coulomb branches $\mathcal{A}_{G,\mathbf{N}}^{\mathrm{Gr}}$ defined by Braverman, Finkelberg, and Nakajima. For any conical symplectic resolution $X$, we prove that the $\mathcal{A}_{G,\mathbf{N},\mathbf{V}}^{\mathrm{Fl}}$-action on the localized equivariant quantum cohomology of $X$, induced by shift operators, satisfies a polynomiality property in terms of stable envelopes. We then study the case $X = T^*(G/P)$, the cotangent bundle of a flag variety, for which the Iwahori-Coulomb branch is isomorphic to the trigonometric double affine Hecke algebra $\mathcal{H}_{G,\hbar,k}$. The polynomiality property enables us to compute explicitly the above action in terms of the Demazure-Lusztig elements and stable envelopes. Applications include: (1) Computation of the Iwarhori-Coulomb branch action for $G/P$ by taking the confluent limit, recovering Peterson-Lam-Shimozono's theorem. (2) Construction of an explicit Namikawa-Weyl group action on the equivariant quantum cohomology of $T^*(G/P)$ that preserves the quantum product, extending a result of Li-Su-Xiong. (3) Proof of a conjecture of Braverman-Finkelberg-Nakajima stating that, up to a shift of the dilation parameter, $\mathcal{A}_{G,\mathfrak{g}^*}^{\mathrm{Gr}}$ is isomorphic to the spherical subalgebra of $\mathcal{H}_{G,\hbar,k}$. |
| title | Iwahori-Coulomb branches, stable envelopes, and quantum cohomology of cotangent bundles of flag varieties |
| topic | Algebraic Geometry Mathematical Physics Representation Theory |
| url | https://arxiv.org/abs/2601.19691 |