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Hadi Salmasian

Publications and source records attributed to Hadi Salmasian.

At least 19 recordsLinked to original sources
arXiv2026

The disoriented skein and iquantum Brauer categories

We develop a diagrammatic approach to the representation theory of the quantum symmetric pairs corresponding to orthosymplectic Lie superalgebras inside general linear Lie superalgebras. Our approach is based on the disoriented skein category, which we define as a module category over the framed HOMFLYPT skein category. The disoriented skein category admits full incarnation functors to the categories of modules over the iquantum enveloping algebras corresponding to the quantum symmetric pairs, and it can be viewed as an interpolating category for these categories of modules. We define an equivalence of module categories between the disoriented skein category and the iquantum Brauer category (also known as the $q$-Brauer category), after endowing the latter with the structure of a module category over the framed HOMFLYPT skein category. The disoriented skein category has some advantages over the iquantum Brauer category, possessing duality structure and allowing the incarnation functors to be strict morphisms of module categories. Finally, we construct explicit bases for the morphism spaces of the disoriented skein and iquantum Brauer categories.

math.QA↗
arXiv2026

Counting $\mathbb F_q$-points of orbital varieties in ad-nilpotent ideals of type $A_n$

Let $\mathfrak b_n(\mathbb F_q)$ denote the Lie algebra of upper triangular $n\times n$ matrices over the finite field $\mathbb F_q$, and let $\mathfrak u_n(\mathbb F_q)$ be the nilradical of $\mathfrak b_n$. For every $\mathfrak b_n(\mathbb F_q)$-stable ideal $\mathfrak a$ of $\mathfrak u_n(\mathbb F_q)$, and every partition $μ$ of $n$, we prove two formulas for the number of elements of $\mathfrak a$ of Jordan type $μ$: the first one is the Hall scalar product of a modified Hall-Littlewood function indexed by $μ$ and a chromatic quasisymmetric function associated to $\mathfrak a$, and the second one is in terms of an explicit collection of standard tableaux. In the special case that $\mathfrak a$ is the nilradical $\mathfrak u_Λ(\mathbb F_q)$ of the parabolic subalgebra associated to a composition $Λ$ of $n$, our first formula reduces to a result of Karp and Thomas: up to an explicit polynomial factor in $q$, the number of elements in $\mathfrak u_Λ(\mathbb F_q)$ of Jordan type $μ$ is equal to the coefficient of the monomial $\mathsf x^Λ$ in the specialization of the dual Macdonald symmetric function $\mathrm Q_{μ'}(\mathsf x;q^{-1},t)$ at $t=0$. We give three applications: (1) a formula for the number of points of a nilpotent Hessenberg variety, (2) a formula for the number of $X\in \mathfrak u_Λ(\mathbb F_q)$ that satisfy $X^2=0$, which in the special case $Λ=(1^n)$ is different from the Kirillov-Melnikov-Ekhad-Zeilberger formula, and (3) a formula for the number of double cosets $\mathrm U_1\backslash\mathrm{GL}_n(\mathbb F_q)/\mathrm U_2$ where $\mathrm U_1$ and $\mathrm U_2$ are unipotent subgroups corresponding to two $\mathfrak b_n(\mathbb F_q)$-stable ideals.

math.CO↗
arXiv2026

Classification of irreducible real modules of real Lie superalgebras

We classify irreducible finite-dimensional modules of a collection of real Lie superalgebras that includes the simple ones, their classical variants, complex Lie superalgebras after restriction of scalars, and all real Lie algebras. Our strategy is to reduce this classification to determining the orbits of the parity and conjugation functors on irreducible modules of the complexifications of the aforementioned algebras. Then we provide explicit results for the computation of these orbits. For Lie superalgebras of basic type or of type $\mathbf Q(n)$, our classification applies to any highest-weight parametrization of irreducible complex modules with respect to an arbitrary Borel subalgebra. As a consequence, in the special case of real simple Lie algebras we obtain a new perspective on the classification of real simple modules and establish a conceptual connection with Kostant's cascade of strongly orthogonal roots.

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arXiv2026

Classifying submodules over monoidal categories

We study the classification of submodules of module categories over monoidal categories, extending ideas of Coulembier on the classification of tensor ideals in monoidal categories. We develop a framework that applies to module categories equipped with a twisted cylinder twist, a structure closely related to the twisted reflection equation and quantum symmetric pairs. Under mild assumptions, we establish an order-preserving bijection between submodules of a module category $\mathcal{M}$ and submodules of the path-algebra module $\mathcal{M}(1,-)$. We show that this correspondence is compatible with idempotent completion and analyze its behavior under decategorification to the split Grothendieck group, giving criteria for classification in terms of indecomposable objects. As an application, we study the disoriented skein category as a module category over the oriented skein category, describe its indecomposable objects, and obtain a complete classification of its submodules.

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arXiv2025

Radial restriction of spherical functions on supergroups

Using the Hopf superalgebra structure of the enveloping algebra $U(\mathfrak g)$ of a Lie superalgebra $\mathfrak=\mathrm{Lie}(G)$, we give a purely algebraic treatment of $K$-bi-invariant functions on a Lie supergroup $G$, where $K$ is a sub-supergroup of $G$. We realize $K$-bi-invariant functions as a subalgebra $\mathcal A(\mathfrak g,\mathfrak k)$ of the dual of $U(\mathfrak g)$ whose elements vanish on the coideal $\mathcal I=\mathfrak kU(\mathfrak g)+U(\mathfrak g)\mathfrak k$, where $\mathfrak k=\mathrm{Lie}(K)$. Next, for a general class of supersymmetric pairs $(\mathfrak g,\mathfrak k)$, we define the radial restriction of elements of $\mathcal A(\mathfrak g,\mathfrak k)$ and prove that it is an injection into $S(\mathfrak a)^*$, where $\mathfrak a$ is the Cartan subspace of $(\mathfrak g,\mathfrak k)$. Finally, we compute a basis for $\mathcal I$ in the case of the pair $(\mathfrak{gl}(1|2), \mathfrak{osp}(1|2))$, and uncover a connection with the Bernoulli and Euler zigzag numbers.

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arXiv2024

The Capelli eigenvalue problem for quantum groups

We introduce and study quantum Capelli operators inside newly constructed quantum Weyl algebras associated to three families of symmetric pairs. Both the center of a particular quantized enveloping algebra and the Capelli operators act semisimply on the polynomial part of these quantum Weyl algebras. We show how to transfer well-known properties of the center arising from the theory of quantum symmetric pairs to the Capelli operators. Using this information, we provide a natural realization of Knop-Sahi interpolation polynomials as functions that produce eigenvalues for quantum Capelli operators.

math.QA↗
arXiv2024

The refined solution to the Capelli eigenvalue problem for $\mathfrak{gl}(m|n)\oplus\mathfrak{gl}(m|n)$ and $\mathfrak{gl}(m|2n)$

Let $\mathfrak g$ be either the Lie superalgebra $\mathfrak{gl}(V)\oplus\mathfrak{gl}(V)$ where $V:=\mathbb C^{m|n}$ or the Lie superalgebra $\mathfrak{gl}(V)$ where $V:=\mathbb C^{m|2n}$. Furthermore, let $W$ be the $\mathfrak g$-module defined by $W:=V\otimes V^*$ in the former case and $W:=\mathcal S^2(V)$ in the latter case. Associated to $(\mathfrak g,W)$ there exists a distinguished basis of Capelli operators $\left\{D^λ\right\}_{λ\inΩ}$, naturally indexed by a set of hook partitions $Ω$, for the subalgebra of $\mathfrak g$-invariants in the superalgebra $\mathcal{PD}(W)$ of superdifferential operators on $W$. Let $\mathfrak b$ be a Borel subalgebra of $\mathfrak g$. We compute eigenvalues of the $D^λ$ on the irreducible $\mathfrak g$-submodules of $\mathcal{P}(W)$ and obtain them explicitly as the evaluation of the interpolation super Jack polynomials of Sergeev--Veselov at suitable affine functions of the $\mathfrak b$-highest weight. While the former case is straightforward, the latter is significantly more complex. This generalizes a result by Sahi, Salmasian and Serganova for these cases, where such formulas were given for a fixed choice of Borel subalgebra.

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arXiv2024

Quantized Weyl algebras, the double centralizer property, and a new First Fundamental Theorem for $U_q(\mathfrak{gl}_n)$

Let $\mathcal P:=\mathcal P_{m\times n}$ denote the quantized coordinate ring of the space of $m\times n$ matrices, equipped with natural actions of the quantized enveloping algebras $U_q(\mathfrak{gl}_m)$ and $U_q(\mathfrak{gl}_n)$. Let $\mathcal L$ and $\mathcal R$ denote the images of $U_q(\mathfrak{gl}_m)$ and $U_q(\mathfrak{gl}_n)$ in $\mathrm{End}(\mathcal P)$, respectively. We define a $q$-analogue of the algebra of polynomial-coefficient differential operators inside $\mathrm{End}(\mathcal P)$, henceforth denoted by $\mathcal{PD}$, and we prove that $\mathcal L\cap \mathcal{PD}$ and $\mathcal{R}\cap \mathcal{PD}$ are mutual centralizers inside $\mathcal{PD}$. Using this, we establish a new First Fundamental Theorem of invariant theory for $U_q(\mathfrak{gl}_n)$. We also compute explicit formulas in terms of $q$-determinants for generators of the intersections with $\mathcal{PD}$ of the images of the Cartan subalgebras of $U_q(\mathfrak{gl}_m)$ and $U_q(\mathfrak{gl}_n)$.

math.QA↗
arXiv2023

Polynomiality of the faithful dimension of nilpotent groups over finite truncated valuation rings

The faithful dimension of a finite group $\mathrm G$ over $\mathbb C$, denoted by $m_\mathrm{faithful}(\mathrm G)$, is the smallest integer $n$ such that $\mathrm G$ can be embedded in $\mathrm{GL}_n(\mathbb C)$. Continuing our previous work (arXiv:1712.02019), we address the problem of determining the faithful dimension of a finite $p$-group of the form $\mathcal G_R:=\exp(\mathfrak g_R)$ associated to $\mathfrak g_R:=\mathfrak g \otimes_\mathbb Z R $ in the Lazard correspondence, where $\mathfrak g$ is a nilpotent $\mathbb Z$-Lie algebra and $R$ ranges over finite truncated valuation rings. Our first main result is that if $R$ is a finite field with $p^f$ elements and $p$ is sufficiently large, then $m_\mathrm{faithful}(\mathcal G_R)=fg(p^f)$ where $g(T)$ belongs to a finite list of polynomials $g_1,\ldots,g_k$, with non-negative integer coefficients. The list of polynomials is uniquely determined by the Lie algebra $\mathfrak g$. Furthermore, for $1\leq i\leq k$ the set of pairs $(p,f)$ for which $g=g_i$ is a finite union of Cartesian products $\mathcal P\times \mathcal F$, where $\mathcal P$ is a Frobenius set of prime numbers and $\mathcal F$ is a subset of $\mathbb N$ that belongs to the Boolean algebra generated by arithmetic progressions. Next we formulate a conjectural polynomiality property for $m_\mathrm{faithful}(\mathcal G_R)$ in the more general setting where $R$ is a finite truncated valuation ring, and prove special cases of this conjecture. In particular, we show that for a vast class of Lie algebras $\mathfrak g $ that are defined by partial orders, $m_\mathrm{faithful}(\mathcal G_R)$ is given by a single polynomial-type formula. Finally, we compute $m_\mathrm{faithful}(\mathcal G_R)$ precisely in the case where $\mathfrak g$ is the free metabelian nilpotent Lie algebra of class $c$ on $n$ generators and $R$ is a finite truncated valuation ring.

math.GR↗
arXiv2023

Classification and double commutant property for dual pairs in an orthosymplectic Lie supergroup

In this paper, we obtain a full classification of reductive dual pairs in a, real or complex, Lie superalgebra $\mathfrak{spo}(E)$ and Lie supergroup $\textbf{SpO}(E)$. Moreover, by looking at the natural action of the orthosymplectic Lie supergroup $\textbf{SpO}(E)$ on the Weyl-Clifford algebra $\textbf{WC}(E)$, we prove that for a reductive dual pair $(\mathscr{G}\,, \mathscr{G}') = ((G\,, \mathfrak{g})\,, (G'\,, \mathfrak{g}'))$ in $\textbf{SpO}(E)$, the superalgebra $\textbf{WC}(E)^{\mathscr{G}}$ consisting of $\mathscr{G}$-invariant elements in $\textbf{WC}(E)$ is generated by the Lie superalgebra $\mathfrak{g}'$. We obtain a full classification of reductive dual pairs in the (real or complex) Lie superalgebra $\mathfrak{spo}(\mathrm E)$ and the Lie supergroup $\textbf{SpO}(\mathrm E)$. Using this classification we prove that for a reductive dual pair $(\mathscr{G}\,, \mathscr{G}') = ((\mathrm G\,, \mathfrak{g})\,, (\mathrm G'\,, \mathfrak{g}'))$ in $\textbf{SpO}(\mathrm E)$, the superalgebra $\textbf{WC}(\mathrm E)^{\mathscr{G}}$ consisting of $\mathscr{G}$-invariant elements in the Weyl-Clifford algebra $\textbf{WC}(\mathrm E)$, equipped with the natural action of the orthosymplectic Lie supergroup $\textbf{SpO}(\mathrm E)$, is generated by the Lie superalgebra $\mathfrak{g}'$. As an application, we prove that Howe duality holds for the dual pairs $({\textbf{SpO}}(2n|1)\,, {\textbf{OSp}}(2k|2l)) \subseteq {\textbf{SpO}}(\mathbb{C}^{2k|2l} \otimes \mathbb{C}^{2n|1})$.

math.RT↗
arXiv2022

Weyl algebras for quantum homogeneous spaces

We present a new family of quantum Weyl algebras where the polynomial part is the quantum analog of functions on homogeneous spaces corresponding to symmetric matrices, skew symmetric matrices, and the entire space of matrices of a given size. The construction uses twisted tensor products and their deformations combined with invariance properties derived from quantum symmetric pairs. These quantum Weyl algebras admit $U_q(\mathfrak{gl}_N)$-module algebra structures compatible with standard ones on the polynomial part, have relations that are expressed nicely via matrices, and are closely related to an algebra arising in the theory of quantum bounded symmetric domains.

math.QA↗
arXiv2021

Capelli operators for spherical superharmonics and the Dougall-Ramanujan identity

Let $(V,ω)$ be an orthosympectic $\mathbb Z_2$-graded vector space and let $\mathfrak g:=\mathfrak{gosp}(V,ω)$ denote the Lie superalgebra of similitudes of $(V,ω)$. When the space $\mathscr P(V)$ of superpolynomials on $V$ is \emph{not} a completely reducible $\mathfrak g$-module, we construct a natural basis $D_λ$ of Capelli operators for the algebra of $\mathfrak g$-invariant superpolynomial superdifferential operators on $V$, where the index set $\mathcal P$ is the set of integer partitions of length at most two. We compute the action of the operators $D_λ$ on maximal indecomposable components of $\mathscr P(V)$ explicitly, in terms of Knop-Sahi interpolation polynomials. Our results show that, unlike the cases where $\mathscr P(V)$ is completely reducible, the eigenvalues of a subfamily of the $D_λ$ are \emph{not} given by specializing the Knop-Sahi polynomials. Rather, the formulas for these eigenvalues involve suitably regularized forms of these polynomials. In addition, we demonstrate a close relationship between our eigenvalue formulas for this subfamily of Capelli operators and the Dougall-Ramanujan hypergeometric identity. We also transcend our results on the eigenvalues of Capelli operators to the Deligne category $\mathsf{Rep}(O_t)$. More precisely, we define categorical Capelli operators $\{\mathbf D_{t,λ}\}_{λ\in\mathcal P}^{}$ that induce morphisms of indecomposable components of symmetric powers of $\mathsf V_t$, where $\mathsf V_t$ is the generating object of $\mathsf{Rep}(O_t)$. We obtain formulas for the eigenvalue polynomials associated to the $\left\{\mathbf D_{t,λ}\right\}_{λ\in\mathcal P}$ that are analogous to our results for the operators $\{D_λ\}_{λ\in\mathcal P}^{}$.

math.RT↗
arXiv2019

Kirillov's orbit method and polynomiality of the faithful dimension of $p$-groups

Given a finite group $\mathrm{G}$ and a field $K$, the faithful dimension of $\mathrm{G}$ over $K$ is defined to be the smallest integer $n$ such that $\mathrm{G}$ embeds into $\mathrm{GL}_n(K)$. In this paper we address the problem of determining the faithful dimension of a $p$-group of the form $\mathscr{G}_q:=\exp(\mathfrak{g} \otimes_\mathbb{Z}\mathbb{F}_q)$ associated to $\mathfrak{g}_q:=\mathfrak{g} \otimes_\mathbb{Z}\mathbb{F}_q$ in the Lazard correspondence, where $\mathfrak{g}$ is a nilpotent $\mathbb{Z}$-Lie algebra which is finitely generated as an abelian group. We show that in general the faithful dimension of $\mathscr{G}_p$ is a piecewise polynomial function of $p$ on a partition of primes into Frobenius sets. Furthermore, we prove that for $p$ sufficiently large, there exists a partition of $\mathbb{N}$ by sets from the Boolean algebra generated by arithmetic progressions, such on each part the faithful dimension of $\mathscr{G}_q$ for $q:=p^f$ is equal to $f g(p^f)$ for a polynomial $g(T)$. We show that for many naturally arising $p$-groups, including a vast class of groups defined by partial orders, the faithful dimension is given by a single formula of the latter form. The arguments rely on various tools from number theory, model theory, combinatorics and Lie theory.

math.RT↗
arXiv2019

The Capelli eigenvalue problem for Lie superalgebras

For a finite dimensional unital complex simple Jordan superalgebra $J$, the Tits-Kantor-Koecher construction yields a 3-graded Lie superalgebra $\mathfrak g_\flat\cong \mathfrak g_\flat(-1)\oplus\mathfrak g_\flat(0)\oplus\mathfrak g_\flat(1)$, such that $\mathfrak g_\flat(-1)\cong J$. Set $V:=\mathfrak g_\flat(-1)^*$ and $\mathfrak g:=\mathfrak g_\flat(0)$. In most cases, the space $\mathcal P(V)$ of superpolynomials on $V$ is a completely reducible and multiplicity-free representation of $\mathfrak g$, with a decomposition $\mathcal P(V):=\bigoplus_{λ\inΩ}V_λ$, where $\left(V_λ\right)_{λ\inΩ}$ is a family of irreducible $\mathfrak g$-modules parametrized by a set of partitions $Ω$. In these cases, one can define a natural basis $\left(D_λ\right)_{λ\inΩ}$ of "Capelli operators" for the algebra $\mathcal{PD}(V)^{\mathfrak g}$. In this paper we complete the solution to the Capelli eigenvalue problem, which is to determine the scalar $c_μ(λ)$ by which $D_μ$ acts on $V_λ$. We associate a restricted root system $\mathitΣ$ to the symmetric pair $(\mathfrak g,\mathfrak k)$ that corresponds to $J$, which is either a deformed root system of type $\mathsf{A}(m,n)$ or a root system of type $\mathsf{Q}(n)$. We prove a necessary and sufficient condition on the structure of $\mathitΣ$ for $\mathcal{P}(V)$ to be completely reducible and multiplicity-free. When $\mathitΣ$ satisfies the latter condition we obtain an explicit formula for the eigenvalue $c_μ(λ)$, in terms of Sergeev-Veselov's shifted super Jack polynomials when $\mathitΣ$ is of type $\mathsf{A}(m,n)$, and Okounkov-Ivanov's factorial Schur $Q$-polynomials when $\mathitΣ$ is of type $\mathsf{Q}(n)$.

math.RT↗
arXiv2018

Quadratic Capelli operators and Okounkov polynomials

Let $Z$ be the symmetric cone of $r \times r$ positive definite Hermitian matrices over a real division algebra $\mathbb F$. Then $Z$ admits a natural family of invariant differential operators -- the Capelli operators $C_λ$ -- indexed by partitions $λ$ of length at most $r$, whose eigenvalues are given by specialization of Knop--Sahi interpolation polynomials. In this paper we consider a double fibration $Y \longleftarrow X \longrightarrow Z$ where $Y$ is the Grassmanian of $r$-dimensional subspaces of $\mathbb F^n $ with $n \geq 2r$. Using this we construct a family of invariant differential operators $D_{λ,s}$ on $Y$ that we refer to as quadratic Capelli operators. Our main result shows that the eigenvalues of the $D_{λ,s}$ are given by specializations of Okounkov interpolation polynomials.

math.RT↗
arXiv2018

Schur $Q$-functions and the Capelli eigenvalue problem for the Lie superalgebra $\mathfrak q(n)$

Let $\mathfrak l:= \mathfrak q(n)\times\mathfrak q(n)$, where $\mathfrak q(n)$ denotes the queer Lie superalgebra. The associative superalgebra $V$ of type $Q(n)$ has a left and right action of $\mathfrak q(n)$, and hence is equipped with a canonical $\mathfrak l$-module structure. We consider a distinguished basis $\{D_λ\}$ of the algebra of $\mathfrak l$-invariant super-polynomial differential operators on $V$, which is indexed by strict partitions of length at most $n$. We show that the spectrum of the operator $D_λ$, when it acts on the algebra $\mathscr P(V)$ of super-polynomials on $V$, is given by the factorial Schur $Q$-function of Okounkov and Ivanov. This constitutes a refinement and a new proof of a result of Nazarov, who computed the top-degree homogeneous part of the Harish-Chandra image of $D_λ$. As a further application, we show that the radial projections of the spherical super-polynomials corresponding to the diagonal symmetric pair $(\mathfrak l,\mathfrak m)$, where $\mathfrak m:=\mathfrak q(n)$, of irreducible $\mathfrak l$-submodules of $\mathscr P(V)$ are the classical Schur $Q$-functions.

math.RT↗
arXiv2017

Smoothing operators and $C^*$-algebras for infinite dimensional Lie groups

A host algebra of a (possibly infinite dimensional) Lie group $G$ is a $C^*$-algebra whose representations are in one-to-one correspondence with certain continuous unitary representations $π\colon G \to \U(\cH)$. In this paper we present a new approach to host algebras for infinite dimensional Lie groups which is based on smoothing operators, i.e., operators whose range is contained in the space $\cH^\infty$ of smooth vectors. Our first major result is a characterization of smoothing operators $A$ that in particular implies smoothness of the maps $π^A \colon G \to B(\cH), g \mapsto π(g)A$. The concept of a smoothing operator is particularly powerful for representations $(π,\cH)$ which are semibounded, i.e., there exists an element $x_0 \in\g$ for which all operators $i\ddπ(x)$, $x \in \g$, from the derived representation are uniformly bounded from above in some neighborhood of $x_0$. Our second main result asserts that this implies that $\cH^\infty$ coincides with the space of smooth vectors for the one-parameter group $π_{x_0}(t) = π(\exp tx_0)$. We then show that natural types of smoothing operators can be used to obtain host algebras and that, for every metrizable Lie group, the class of semibounded representations can be covered completely by host algebras. In particular, it permits direct integral decompositions.

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