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1. LOCAL DUALITY FOR THE SINGULARITY CATEGORY OF A FINITE DIMENSIONAL GORENSTEIN ALGEBRA

   https://doi.org/10.1017/nmj.2020.2  

   BENSON, DAVE; IYENGAR, SRIKANTH B.; KRAUSE, HENNING; PEVTSOVA, JULIA (March 2020, Nagoya Mathematical Journal)

   A duality theorem for the singularity category of a finite dimensional Gorenstein algebra is proved. It complements a duality on the category of perfect complexes, discovered by Happel. One of its consequences is an analogue of Serre duality, and the existence of Auslander–Reiten triangles for the $$\mathfrak{p}$$ -local and $$\mathfrak{p}$$ -torsion subcategories of the derived category, for each homogeneous prime ideal $$\mathfrak{p}$$ arising from the action of a commutative ring via Hochschild cohomology. 

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2. Pursuing Quantum Difference Equations II: 3D mirror symmetry

   https://doi.org/10.1093/imrn/rnac196  

   Kononov, Yakov; Smirnov, Andrey (July 2022, International Mathematics Research Notices)

   Abstract Let $$\textsf {X}$$ and $$\textsf {X}^{!}$$ be a pair of symplectic varieties dual with respect to 3D mirror symmetry. The $$K$$-theoretic limit of the elliptic duality interface is an equivariant $$K$$-theory class $$\mathfrak {m} \in K(\textsf {X}\times \textsf {X}^{!})$$. We show that this class provides correspondences $$ \begin{align*} & \Phi_{\mathfrak{m}}: K(\textsf{X}) \leftrightarrows K(\textsf{X}^{!}) \end{align*}$$mapping the $$K$$-theoretic stable envelopes to the $$K$$-theoretic stable envelopes. This construction allows us to relate various representation theoretic objects of $$K(\textsf {X})$$, such as action of quantum groups, quantum dynamical Weyl groups, $$R$$-matrices, etc., to those for $$K(\textsf {X}^{!})$$. In particular, we relate the wall $$R$$-matrices of $$\textsf {X}$$ to the $$R$$-matrices of the dual variety $$\textsf {X}^{!}$$. As an example, we apply our results to $$\textsf {X}=\textrm {Hilb}^{n}({{\mathbb {C}}}^2)$$—the Hilbert scheme of $$n$$ points in the complex plane. In this case, we arrive at the conjectures of Gorsky and Negut from [10]. 

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3. Polynomial Representations of the Witt Lie Algebra

   https://doi.org/10.1093/imrn/rnae139  

   Sam, Steven_V; Snowden, Andrew; Tosteson, Philip (June 2024, International Mathematics Research Notices)

   Abstract The Witt algebra  $${\mathfrak{W}}_{n}$$ is the Lie algebra of all derivations of the $$n$$-variable polynomial ring $$\textbf{V}_{n}=\textbf{C}[x_{1}, \ldots , x_{n}]$$ (or of algebraic vector fields on $$\textbf{A}^{n}$$). A representation of $${\mathfrak{W}}_{n}$$ is polynomial if it arises as a subquotient of a sum of tensor powers of $$\textbf{V}_{n}$$. Our main theorems assert that finitely generated polynomial representations of $${\mathfrak{W}}_{n}$$ are noetherian and have rational Hilbert series. A key intermediate result states polynomial representations of the infinite Witt algebra are equivalent to representations of $$\textbf{Fin}^{\textrm{op}}$$, where $$\textbf{Fin}$$ is the category of finite sets. We also show that polynomial representations of $${\mathfrak{W}}_{n}$$ are equivalent to polynomial representations of the endomorphism monoid of $$\textbf{A}^{n}$$. These equivalences are a special case of an operadic version of Schur–Weyl duality, which we establish. 

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4. Cosets of Free Field Algebras via Arc Spaces

   https://doi.org/10.1093/imrn/rnac367  

   Linshaw, Andrew_R; Song, Bailin (January 2023, International Mathematics Research Notices)

   Abstract Using the invariant theory of arc spaces, we find minimal strong generating sets for certain cosets of affine vertex algebras inside free field algebras that are related to classical Howe duality. These results have several applications. First, for any vertex algebra $${{\mathcal {V}}}$$, we have a surjective homomorphism of differential algebras $$\mathbb {C}[J_{\infty }(X_{{{\mathcal {V}}}})] \rightarrow \text {gr}^{F}({{\mathcal {V}}})$$; equivalently, the singular support of $${{\mathcal {V}}}$$ is a closed subscheme of the arc space of the associated scheme $$X_{{{\mathcal {V}}}}$$. We give many new examples of classically free vertex algebras (i.e., this map is an isomorphism), including $$L_{k}({{\mathfrak {s}}}{{\mathfrak {p}}}_{2n})$$ for all positive integers $$n$$ and $$k$$. We also give new examples where the kernel of this map is nontrivial but is finitely generated as a differential ideal. Next, we prove a coset realization of the subregular $${{\mathcal {W}}}$$-algebra of $${{\mathfrak {s}}}{{\mathfrak {l}}}_{n}$$ at a critical level that was previously conjectured by Creutzig, Gao, and the 1st author. Finally, we give some new level-rank dualities involving affine vertex superalgebras. 

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5. Models of G–spectra as presheaves of spectra

   https://doi.org/10.2140/agt.2024.24.1225  

   Guillou, Bertrand J; May, J Peter (January 2024, Algebraic & Geometric Topology)

   Greenlees, John (Ed.)

   Let G be a finite group. We give Quillen equivalent models for the category of G–spectra as categories of spectrally enriched functors from explicitly described domain categories to nonequivariant spectra. Our preferred model is based on equivariant infinite loop space theory applied to elementary categorical data. It recasts equivariant stable homotopy theory in terms of point–set-level categories of G–spans and nonequivariant spectra. We also give a more topologically grounded model based on equivariant Atiyah duality. 

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