We prove the existence and give a classification of toric non-commutative crepant resolutions (NCCRs) of Gorenstein toric singularities with divisor class group of rank one. We prove that they correspond bijectively to non-trivial upper sets in a certain quotient of the divisor class group equipped with a certain partial order. By this classification, we show that for such toric singularities, all toric NCCRs are connected by iterated Iyama-Wemyss mutations.

The ongoing progress in quantum technologies has fueled a sustained exploration of their potential applications across various domains. One particularly promising field is quantitative finance, where a central challenge is the pricing of financial derivatives-traditionally addressed through Monte Carlo integration techniques. In this work, we introduce two hybrid classical-quantum methods to address the option pricing problem. These approaches rely on reconstructing Fourier series representations of statistical distributions from the outputs of Quantum Machine Learning (QML) models based on Parametrized Quantum Circuits (PQCs). We analyze the impact of data size and PQC dimensionality on performance. Quantum Accelerated Monte Carlo (QAMC) is employed as a benchmark to quantitatively assess the proposed models in terms of computational cost and accuracy in the extraction of Fourier coefficients. Through the numerical experiments, we show that the proposed methods achieve remarkable accuracy, becoming a competitive quantum alternative for derivatives valuation.

In his $1994$ survey, Kleinert defined formally and formulated the problem to obtain unit theorems for unit groups of orders in a semisimple algebra $A$. If $A$ is a group algebra $FG$, it boils down to classifying all finite groups $G$ such that the unit groups of most orders in $FG$ belong to a prescribed class $\mathcal{G}$ of infinite groups. We solve this problem for $\mathcal{G}$ consisting of the groups which are virtually a direct product of groups whose Cayley graph has more than one end. Subsequently, we obtain two types of applications. A first type being about the existence of torsion-free normal complements and a second about obtaining short and uniform proofs of some of the main results in [13,18,14,15].

Webs are a kind of planar, directed, edge-labeled graph that encode invariant vectors for quantum representations of $\mathfrak{sl}_n$. The theory of webs developed organically for $\mathfrak{sl}_2$, where they are also known as noncrossing matchings and the Temperley-Lieb algebra, before being formalized by Kuperberg for $\mathfrak{sl}_2$ and $\mathfrak{sl}_3$ as the morphisms in a diagrammatic categorification of quantum representations called the spider category. Various models extend webs to $n \geq 4$. Only Cautis-Kamnitzer-Morrison prove a full set of relations for their webs, though Fontaine's webs are better adapted to computations, more graph-theoretically natural, and directly generalize webs for $n=2$ and $n=3$. This paper formalizes the theory of Fontaine's webs, proving the existence of a deep and powerful global structure on these webs called strandings. We do three key things: 1) give a state-sum formula to construct ($U_q(\mathfrak{sl}_n)$-invariant) web vectors from the orientation of strandings on Fontaine's webs; 2) list and prove a complete set of relations, connecting strandings to the local data of binary labelings that are well-established in the literature; and 3) provide applications and examples of how strandings facilitate computations.

Building on the Atiyah--Singer holomorphic Lefschetz fixed-point theorem, we define ramification modules associated to the fixed loci of a finite group acting on a compact complex manifold. This allows us to generalize the Chevalley--Weil formula for compact Riemann surfaces to higher dimensions. More precisely, let $G$ be a finite group acting on a compact complex manifold $X$, and let $\mathcal{E}$ be a $G$-equivariant locally free sheaf on $X$. Then, in the representation ring $R(G)_\mathbb{Q}$, we have $$\chi_G(X, \mathcal{E}):=\sum_{i=0}^{\dim X}(-1)^i[H^i(X, \mathcal{E})]=\frac{1}{|G|}\chi(X,\mathcal{E})[\mathbb{C}[G]] + \sum_Z\Gamma(\mathcal{E})_Z$$ where $Z$ runs over all connected components of the fixed-point sets $X^g$ for $g\in G$, and each $\Gamma(\mathcal{E})_Z\in R(X)_\mathbb{Q}$, called the \emph{ramification module} at $Z$, depends only on the restriction $\mathcal{E}|_Z$ and the normal bundle $N_{Z/X}$ as $G_Z$-equivariant bundles. We illustrate the computation of $\Gamma(\mathcal{E})_Z$ in several special cases and provide a detailed example for faithful actions of $G\cong(\mathbb{Z}/2\mathbb{Z})^n$ on a compact complex surface.

Let $N(\Gamma,G)$ be the number of homomorphisms from $\Gamma$ to $G$ up to conjugation by $G$. Physics of four-dimensional $\mathcal{N}=4$ supersymmetric gauge theories predicts that $N(\Gamma,G)=N(\Gamma , \tilde G)$ when $\Gamma$ is a finite subgroup of $SU(2)$, $G$ is a connected compact simple Lie group and $\tilde G$ is its Langlands dual. This statement is known to be true when $\Gamma=\mathbb{Z}_n$, but the statement for non-Abelian $\Gamma$ is new, to the knowledge of the authors. To lend credence to this conjecture, we prove this equality in a couple of examples, namely $(G,\tilde G)=(SU(n),PU(n))$ and $(Sp(n),SO(2n+1))$ for arbitrary $\Gamma$, and $(PSp(n),Spin(2n+1))$ for exceptional $\Gamma$. A more refined version of the conjecture, together with proofs of some concrete cases, will also be presented. The authors would like to ask mathematicians to provide a more uniform proof applicable to all cases.

We construct a graded cluster algebra structure on the Cox ring of a smooth complex variety $Z$, depending on a base cluster structure on the ring of regular functions of an open subset $Y$ of $Z$. After considering some elementary examples of our construction, including toric varieties, we discuss the two main applications. First: if $Z$ is a flag variety and $Y$ is the open Schubert cell, we prove that our results recover, by geometric methods, a well known construction of Geiss, Leclerc and Schröer. Second: we define the diagonal partial compactification of a (finite type) cluster variety, and prove that its Cox ring is a graded upper cluster algebra. Along the way, we explain how similar constructions can be done if we replace the Cox ring with a ring of global sections of a sheaf of divisorial algebras on $Z$.

The purpose of this article is threefold: Firstly, we propose some enhancements to the existing definition of 6-functor formalisms. Secondly, we systematically study the category of kernels, which is a certain 2-category attached to every 6-functor formalism. It provides powerful new insights into the internal structure of the 6-functor formalism and allows to abstractly define important finiteness conditions, recovering well-known examples from the literature. Finally, we apply our methods to the theory of smooth representations of $p$-adic Lie groups and, as an application, construct a canonical anti-involution on derived Hecke algebras generalizing results of Schneider--Sorensen. In an appendix we provide the necessary background on $\infty$-categories, higher algebra, enriched $\infty$-categories and $(\infty,2)$-categories. Among others we prove several new results on adjunctions in an $(\infty,2)$-category and in particular show that passing to the adjoint morphism is a functorial operation.

We prove new fundamental lemma and arithmetic fundamental lemma identities for general linear groups over quaternion division algebras. In particular, we verify the transfer conjeture and the arithmetic transfer conjecture from arXiv:2307.11716 in cases of Hasse invariant 1/2.

We compute the Jantzen filtration of a D-module on the flag variety of $\mathrm{SL}_2(\mathbb{C})$. At each step in the computation, we illustrate the $\mathfrak{sl}_2(\mathbb{C})$-module structure on global sections to give an algebraic picture of this geometric computation. We conclude by showing that the Jantzen filtration on the D-module agrees with the algebraic Jantzen filtration on its global sections, demonstrating a famous theorem of Beilinson--Bernstein.

We show that DSSYK amplitudes are reproduced by considering the quantum mechanics of a constrained particle on the quantum group SU$_q(1,1)$. We construct its left-and right-regular representations, and show that the representation matrices reproduce two-sided wavefunctions and correlation functions of DSSYK. We then construct a dynamical action and path integral for a particle on SU$_q(1,1)$, whose quantization reproduces the aforementioned representation theory. By imposing boundary conditions or constraining the system we find the $q$-analog of the Schwarzian and Liouville boundary path integral descriptions. This lays the technical groundwork for identifying the gravitational bulk description of DSSYK. We find evidence the theory in question is a sine dilaton gravity, which interestingly is capable of describing both AdS and dS quantum gravity.

In this paper we introduce a notion of Poincar\'e exponent for isometric representations of discrete groups on Hilbert spaces. Similarly as growth exponents control the geometry this exponent is shown to control the size of spectral gaps. Following similar ideas as Patterson and Sullivan it is used in the case of negatively curved groups to construct weakly contained boundary representations reflecting the spectral properties of the original representation analogously as complementary series representations in the case of semi-simple Lie groups. This is exploited to deduced sharp estimates on spectral invariants. A quantitive property (T) \'a la Cowling is also established proving uniform bound on the mixing rate of representations of hyperbolic groups with property (T). Along the way some properties of boundary representations are discussed. A original characterisation of the positivity of the so-called Knapp-Stein operators and certain fusion rules on the boundary complementary series representations are established.

We study the mod $p$ equivariant quantum cohomology of conical symplectic resolutions. Using symplectic genus zero enumerative geometry, Fukaya and Wilkins defined operations on mod $p$ quantum cohomology deforming the classical Steenrod operations on mod $p$ cohomology. We conjecture that these quantum Steenrod operations on divisor classes agree with the $p$-curvature of the mod $p$ equivariant quantum connection, and verify this in the case of the Springer resolution. The key ingredient is a new compatibility relation between the quantum Steenrod operations and the shift operators.

Let $G$ be a connected reductive algebraic group over an algebraically closed field $k$ of characteristic $p>0$ and let $\ell$ be a prime number different from $p$. Let $U\subset G$ be a maximal unipotent subgroup, and let $T$ be a maximal torus normalizing $U$ with normalizer $N=N_G(T)$. Let $W=N/T$ be the Weyl group of $G$. Let $\mathcal{L}$ be a non-degenerate $\ell$-adic multiplicative local system on $U$. In this paper we prove that the bi-Whittaker category, namely the triangulated monoidal category of $(U,\mathcal{L})$-bi-equivariant complexes on $G$, is monoidally equivalent to an explicit thick triangulated monoidal subcategory $\mathscr{D}^\circ_W(T)\subset \mathscr{D}_W(T)$ of ''$W$-equivariant central sheaves'' on the torus, answering a question raised by Drinfeld. In particular, the bi-Whittaker category has the structure of a symmetric monoidal category. We also study a certain thick triangulated monoidal subcategory $\mathscr{D}^\circ_G(G)\subset \mathscr{D}_G(G)$ of ''vanishing sheaves'' and prove that it is braided monoidally equivalent to an explicit thick triangulated monoidal subcategory $\mathscr{D}^\circ_N(T)\subset \mathscr{D}_N(T)$of ''$N$-equivariant central sheaves'' on the torus. The above equivalence is given by an enhancement of the parabolic restriction functor restricted to the subcategory $\mathscr{D}^\circ_G(G)$.

We define the computational task of detecting projectors in finite dimensional associative algebras with a combinatorial basis, labelled by representation theory data, using combinatorial central elements in the algebra. In the first example, the projectors belong to the centre of a symmetric group algebra and are labelled by Young diagrams with a fixed number of boxes $n$. We describe a quantum algorithm for the task based on quantum phase estimation (QPE) and obtain estimates of the complexity as a function of $n$. We compare to a classical algorithm related to the projector identification problem by the AdS/CFT correspondence. This gives a concrete proof of concept for classical/quantum comparisons of the complexity of a detection task, based in holographic correspondences. A second example involves projectors labelled by triples of Young diagrams, all having $n$ boxes, with non-vanishing Kronecker coefficient. The task takes as input the projector, and consists of identifying the triple of Young diagrams. In both of the above cases the standard QPE complexities are polynomial in $n$. A third example of quantum projector detection involves projectors labelled by a triple of Young diagrams, with $m,n$ and $m+n$ boxes respectively, such that the associated Littlewood-Richardson coefficient is non-zero. The projector detection task is to identify the triple of Young diagrams associated with the projector which is given as input. This is motivated by a two-matrix model, related via the AdS/CFT correspondence, to systems of strings attached to giant gravitons. The QPE complexity in this case is polynomial in $m$ and $n$.

In this paper we prove the isomorphism of the positive half of the quantum toroidal algebra and the positive half of the Maulik-Okounkov quantum affine algebra of affine type $A$ via the monodromy representation for the Dubrovin connection. The main tool is on the proof of the fact that the degeneration limit of the algebraic quantum difference equation is the same as that of the Okounkov-Smirnov geometric quantum difference equation.

Let $Y_2$ be the Yangian associated to the general linear Lie algebra $\mathfrak{gl}_2$, defined over an algebraically closed field $\mathbbm{k}$ of characteristic $p > 0$. In this paper, we study the representation theory of the restricted Yangian $Y^{[p]}_2$. This leads to a description of the representations of $\mathfrak{gl}_{2n}$, whose $p$-character is nilpotent with Jordan type given by a two-row partition $(n, n)$.

Let $Y_2$ be the Yangian associated to the general linear Lie algebra $\mathfrak{gl}_2$, defined over an algebraically closed field $\mathbbm{k}$ of characteristic $p > 0$. In this paper, we study the representation theory of the restricted Yangian $Y^{[p]}_2$. This leads to a description of the representations of $\mathfrak{gl}_{2n}$, whose $p$-character is nilpotent with Jordan type given by a two-row partition $(n, n)$.

Let $\Bbbk$ be an algebraically closed field of characteristic 0 and $H$ a finite-dimensional Hopf algebra over $\Bbbk$ with the dual Chevalley property. In this paper, we show that $\operatorname{gr}^c(H)$ is of tame corepresentation type if and only if $\operatorname{gr}^c(H)\cong (\Bbbk\langle x,y\rangle/I)^* \times H^\prime$ for some finite-dimensional semisimple Hopf algebra $H^\prime$ and some special ideals $I$. Then, by the method of link quiver and bosonization, we discuss which of the above ideals will occur when $(\Bbbk\langle x,y\rangle/I)^* \times H_0$ is a Hopf algebra of tame corepresentation type under some assumptions.