CyberSec Research

We provide and discuss complex analytic methods for overcoming the formal character of formal deformation quantization. This is a necessity for returning to physically meaningful statements, and accounts for the fact that the formal parameter $\hbar$ carries the interpretation of Planck's constant. As formal star products are given by a formal power series, this naturally leads into the realm of holomorphic functions and analytic continuation, both in finite and infinite dimensions. We propose a general notion of strict deformation quantization and investigate how one can use established results from complex analysis to think about the resulting objects. Within the main body of the text, the outlined program is then put into practice for strict deformation quantizations of constant Poisson structures on locally convex vector spaces and the strict deformation quantization of canonical mechanics on the cotangent bundle of a Lie group. Numerous auxiliary results, many of which are well-known yet remarkable in their own right, are provided throughout.

Suppose a Lie group $G$ acts on a vertex algebra $V$. In this article we construct a vertex algebra $\tilde{V}$, which is an extension of $V$ by a big central vertex subalgebra identified with the algebra of functionals on the space of regular $\mathfrak{g}$-connections $(d+A)$. The category of representations of $\tilde{V}$ fibres over the set of connections, and the fibres should be viewed as $(d+A)$-twisted modules of $V$, generalizing the familiar notion of $g$-twisted modules. In fact, another application of our result is that it proposes an explicit definition of $(d+A)$-twisted modules of $V$ in terms of a twisted commutator formula, and we feel that this subject should be pursued further. Vertex algebras with big centers appear in practice as critical level or large level limits of vertex algebras. I particular we have in mind limits of the generalized quantum Langlands kernel, in which case $G$ is the Langland dual and $V$ is conjecturally the Feigin-Tipunin vertex algebra and the extension $\tilde{V}$ is conjecturally related to the Kac-DeConcini-Procesi quantum group with big center. With the current article, we can give a uniform and independent construction of these limits.

Generalized Legendrian racks are nonassociative algebraic structures based on the Legendrian Reidemeister moves. We study algebraic aspects of GL-racks and coloring invariants of Legendrian links. We answer an open question characterizing the group of GL-structures on a given rack. As applications, we classify several infinite families of GL-racks. We also compute automorphism groups of dihedral GL-quandles and the categorical center of GL-racks. Then we construct an equivalence of categories between racks and GL-quandles. We also study tensor products of racks and GL-racks coming from universal algebra. Surprisingly, the categories of racks and GL-racks have tensor units. The induced symmetric monoidal structure on medial racks is closed, and similarly for medial GL-racks. Answering another open question, we use GL-racks to distinguish Legendrian knots whose classical invariants are identical. In particular, we complete the classification of Legendrian $8_{13}$ knots. Finally, we use exhaustive search algorithms to classify GL-racks up to order 8.

In this paper, we study the classification of finite GK-dimensional pre-Nichols algebras in the twisted Yetter-Drinfeld module category $_{\k G}^{\k G} \mathcal{YD}^\Phi$, where $G$ is a finite abelian group and $\Phi$ is a $3$-cocycle on $G$. These algebras naturally arise from quasi-quantum groups over finite abelian groups. We prove that all pre-Nichols algebras of nondiagonal type in $_{\k G}^{\k G} \mathcal{YD}^\Phi$ are infinite GK-dimensional, and every graded pre-Nichols algebra in $_{\k G}^{\k G} \mathcal{YD}^\Phi$ with finite GK-dimension is twist equivalent to a graded pre-Nichols algebra in an ordinary Yetter-Drinfeld module category $_{\k G}^{\k G} \mathcal{YD}^\Phi$, where $\mathbb{G}$ is a finite abelian group determined by $G$. In particular, we obtain a complete classification of finitely generated Nichols algebras with finite GK-dimension in $_{\k G}^{\k G} \mathcal{YD}^\Phi$. We prove that a finitely generated Nichols algebra in $_{\k G}^{\k G} \mathcal{YD}^\Phi$ is finite GK-dimensional if and only if it is of diagonal type and the corresponding root system is finite, i.e., an arithmetic root system. Via bosonization, this yields a large class of infinite quasi-quantum groups over finite abelian groups.

We define new crystal maps on $B(\infty)$ using its polyhedral realization, and show that the crystal $B(\infty)$ equipped with the new crystal maps is isomorphic to Kashiwara's $B(\infty)$ as bicrystals. In addition, we combinatorially describe the bicrystal structure of $B(\infty)$, which is called a sliding diamond rule. Using the bicrystal structure on $B(\infty)$, we define the extended crystal and show that it is isomorphic to the extended crystal introduced by Kashiwara and Park.

We investigate the system of polynomial equations, known as $QQ$-systems, which are closely related to the so-called Bethe ansatz equations of the XXZ spin chain, using the methods of tropical geometry.

We study the large $r$ asymptotic behaviour of the Turaev-Viro invariants of oriented Seifert fibered 3-manifolds at the root $q=e^\frac{2\pi i}{r}$. As an application, we prove the volume conjecture for large families of oriented Seifert fibered 3-manifolds with empty and non-empty boundary.

We formulate two new $\mathbb Z[q,q^{-1}]$-linear diagrammatic monoidal categories, the affine $q$-web category and the affine $q$-Schur category, as well as their respective cyclotomic quotient categories. Diagrammatic integral bases for the Hom-spaces of all these categories are established. In addition, we establish the following isomorphisms, providing diagrammatic presentations of these $q$-Schur algebras for the first time: (i)~ the path algebras of the affine $q$-web category to R.~Green's affine $q$-Schur algebras, (ii)~ the path algebras of the affine $q$-Schur category to Maksimau-Stroppel's higher level affine $q$-Schur algebras, and most significantly, (iii)~ the path algebras of the cyclotomic $q$-Schur categories to Dipper-James-Mathas' cyclotomic $q$-Schur algebras.

Let $Q$ be an affine quiver of type $A_2^{(1)}$. We explicitly construct the cluster multiplication formulas for the quantum cluster algebra of $Q$ with principal coefficients. As applications, we obtain: (1)\ an exact expression for every quantum cluster variable as a polynomial in terms of the quantum cluster variables in clusters which are one-step mutations from the initial cluster; (2)\ an explicit bar-invariant positive $\mathbb{ZP}$-basis.

A three-functor formalism is the half of a six-functor formalism that supports the projection and base change formulas. In this paper, we provide a three-functor formalism for commutative von Neumann algebras and their modules. Using the Gelfand-Naimark theorem, this gives rise to a three-functor formalism for measure spaces and measurable bundles of Hilbert spaces. We use this to prove Fell absorption for unitary representations of measure groupoids. The three-functor formalism for commutative von Neumann algebras takes values in W*-categories, and we discuss in what sense it is a unitary three-functor formalism.

The mirror symmetry among Calabi-Yau manifolds is mysterious, however, the mirror operation in 2d N=(2,2) supersymmetric conformal field theory (SCFT) is an elementary operation. In this paper, we mathematically formulate SCFTs using unitary full vertex operator superalgebras (full VOAs) and develop a cohomology theory of unitary SCFTs (aka holomorphic / topological twists). In particular, we introduce cohomology rings, Hodge numbers, and the Witten index of a unitary $N=(2,2)$ full VOA, and prove that the cohomology rings determine 2d topological field theories and give relations between them (Hodge duality and T-duality). Based on this, we propose a possible approach to prove the existence of mirror Calabi-Yau manifolds for the Hodge numbers using SCFTs. For the proof, one need a construction of sigma models connecting Calabi-Yau manifolds and SCFTs which is still not rigorous, but expected properties are tested for the case of Abelian varieties and a special K3 surface based on some unitary $N=(2,2)$ full VOAs.

We study certain overlap coefficients appearing in representation theory of the quantum algebra $\U_q(\mathfrak{sl}_2(\C))$. The overlap coefficients can be identified as products of Askey-Wilson functions, leading to an algebraic interpretation of the multivariate Askey-Wilson functions introduced by Geronimo and Iliev. We use the underlying coalgebra structure to derive $q$-difference equations satisfied by the multivariate Askey-Wilson functions.

Isoclinism was introduced by Hall and is an important concept in group theory. More generally, there is the notion of $n$-isoclinism for every natural number $n$. Recently, Letourmy and Vendramin (2023) extended the notions of isoclinism and also stem groups to the setting of skew braces. In this paper, we shall propose two analogs of $n$-isoclinism and $n$-stem groups for skew braces. We shall prove that for the ``weak" version, analogous to the case of groups, weak $n$-isoclinism implies weak $(n+1)$-isoclinism.

The stated ${\rm SL}_n$-skein algebra $\mathscr{S}_{\hat{q}}(\mathfrak{S})$ of a surface $\mathfrak{S}$ is a quantization of the ${\rm SL}_n$-character variety, and is spanned over $\mathbb{Z}[\hat{q}^{\pm 1}]$ by framed tangles in $\mathfrak{S} \times (-1,1)$. If $\hat{q}$ is evaluated at a root of unity $\hat{\omega}$ with the order of $\hat{\omega}^{4n^2}$ being $N$, then for $\hat{\eta} = \hat{\omega}^{N^2}$, the Frobenius homomorphism $\Phi : \mathscr{S}_{\hat{\eta}}(\mathfrak{S}) \to \mathscr{S}_{\hat{\omega}}(\mathfrak{S})$ is a surface generalization of the well-known Frobenius homomorphism between quantum groups. We show that the image under $\Phi$ of a framed oriented knot $\alpha$ is given by threading along $\alpha$ of the reduced power elementary polynomial, which is an ${\rm SL}_n$-analog of the Chebyshev polynomial $T_N$. This generalizes Bonahon and Wong's result for $n=2$, and confirms a conjecture of Bonahon and Higgins. Our proof uses representation theory of quantum groups and its skein theoretic interpretation, and does not require heavy computations. We also extend our result to marked 3-manifolds.

We define the concept of an $\mathbb{A}_n$-schober as a categorification of classification data for perverse sheaves on $\mathrm{Sym}^{n+1}(\mathbb{C})$ due to Kapranov-Schechtman. We show that any $\mathbb{A}_n$-schober gives rise to a categorical action of the Artin braid group $\mathrm{Br}_{n+1}$ and demonstrate how this recovers familiar examples of such actions arising from Seidel-Thomas $\mathbb{A}_n$-configurations of spherical objects in categorical Picard-Lefschetz theory and Rickard complexes in link homology theory. As a key example, we use singular Soergel bimodules to construct a factorizing family of $\mathbb{A}_n$-schobers which we refer to as Soergel schobers. We expect such families to give rise to a categorical analog of a graded bialgebra valued in a suitably defined freely generated braided monoidal $(\infty,2)$-category.

In this paper we give a combinatorial description of the Cauchy completion of the categories $\mathcal{E}_q$ and $\overline{\mathcal{SE}_N}$ recently introduced by the first author and Snyder. This in turns gives a combinatorial description of the categories $\overline{\operatorname{Rep}(U_q(\mathfrak{sl}_N))}_{A}$ where $A$ is the \`etale algebra object corresponding to the conformal embedding $\mathfrak{sl}_N$ level $N$ into $\mathfrak{so}_{N^2-1}$ level 1. In particular we give a classification of the simple objects of these categories, a formula for their quantum dimensions, and fusion rules for tensoring with the defining object. Our method of obtaining these results is the Schur-Weyl approach of studying the representation theory of certain endomorphism algebras in $\mathcal{E}_q$ and $\mathcal{SE}_N$, which are known to be subalgebras of Hecke-Clifford algebras. We build on existing literature to study the representation theory of the Hecke-Clifford algebras at roots of unity.

We introduce the notion of a \emph{braided dihedral set} (BDS) to describe set-theoretical solutions of the Yang-Baxter equation (YBE) that furnish representations of the infinite dihedral group on the Cartesian square of the underlying set. BDS which lead to representations of the symmetric group on three objects are called \emph{braided triality sets} (BTS). Basic examples of BDS come from symmetric spaces. We show that Latin BDS (LBDS) can be described entirely in terms of involutions of uniquely 2-divisible Bruck loops. We show that isomorphism classes of LBDS are in one-to-one correspondence with conjugacy classes of involutions of uniquely 2-divisible Bruck loops. We describe all LBDS of prime, prime-square and 3 times prime-order, up to isomorphism. Using \texttt{GAP}, we enumerate isomorphism classes of LBDS of orders 27 and 81. Latin BTS, or LBTS, are shown to be in one-to-one correspondence with involutions of commutative Moufang loops of exponent 3 (CML3), and, as with LBDS, isomorphisms classes of LBTS coincide with conjugacy classes of CML3-involutions. We classify all LBTS of order at most 81.

Abstract spin chains axiomatize the structure of local observables on the 1D lattice which are invariant under a global symmetry, and arise at the physical boundary of 2+1D topologically ordered spin systems. In this paper, we study tensor categorical properties of DHR bimodules over abstract spin chains. Assuming that the charge transporters generate the algebra of observables, we prove that the associated category has a structure of modular tensor category with respect to the natural braiding. Under an additional assumption of algebraic Haag duality, this category becomes the Drinfeld center of the half-line fusion category.