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Igor Frenkel

Publications and source records attributed to Igor Frenkel.

At least 19 recordsLinked to original sources
arXiv2026

Reduction of Symmetry in Quaternionic Analysis and Invariant Trilinear Forms

In our previous papers we repeatedly emphasized the special role in Quaternionic Analysis of the conformal group SU(2,2) and other real forms of its complexification SL(4,C). In particular, the natural product map of the left and right regular functions into a larger representation that contains the doubly regular functions as a subquotient is an intertwining operator. In this paper we show, however, that the spaces of regular and doubly regular functions do not "interact" - there is no invariant trilinear form on the tensor product of these representations. To construct a natural invariant trilinear form, we reduce the conformal group symmetry to the symplectic subgroup Sp(4,R). This suggests a new approach to the Quaternionic Analysis in general, and we make the first steps in this paper. It turns out that the spaces of regular and doubly regular functions are still irreducible after the restriction to the symplectic subgroup and have a composed structure arising from the metaplectic representation of the double cover of Sp(4,R) - the metaplectic group. This also leads us to consider the double covers of the quaternionic spaces and non-trivial pairings between them. Our study of Quaternionic Analysis based on the symplectic symmetry group culminates in the construction of the invariant trilinear forms on the products of spaces of doubly regular functions and certain counterparts of regular and quasi regular functions. Additional motivation for constructing invariant trilinear forms comes from their application to spinor representations of certain quaternionic algebras based on the doubly regular functions. The latter can be viewed as the space of solutions of the Maxwell equation, and their spinor representations are of a great importance to quantum field theory. These spinor representations will be the subject of a forthcoming paper.

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arXiv2024

Quasi Regular Functions in Quaternionic Analysis

We study a new class of functions that arise naturally in quaternionic analysis, we call them "quasi regular functions". Like the well-known quaternionic regular functions, these functions provide representations of the quaternionic conformal group. However, unlike the regular functions, the quasi regular ones do not admit an invariant unitary structure but rather a pseudounitary equivalent. The reproducing kernels of these functions have an especially simple form: (Z-W)^{-1}. We describe the K-type bases of quasi regular functions and derive the reproducing kernel expansions. We also show that the restrictions of the irreducible representations formed from the quasi regular functions to the Poincare group have three irreducible components. Our interest in the quasi regular functions arises from an application to the study of conformal-invariant algebras of quaternionic functions. We also introduce a factorization of certain intertwining operators between tensor products of spaces of quaternionic functions. This factorization is obtained using fermionic Fock spaces constructed from the quasi regular functions.

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arXiv2020

Sketch of a Program for Universal Automorphic Functions to Capture Monstrous Moonshine

We review and reformulate old and prove new results about the triad $ {\rm PPSL}_2({\mathbb Z})\subseteq{\rm PPSL}_2({\mathbb R})\circlearrowright ppsl_2({\mathbb R}) $, which provides a universal generalization of the classical automorphic triad ${\rm PSL}_2({\mathbb Z})\subseteq{\rm PSL}_2({\mathbb R})\circlearrowright psl_2({\mathbb R})$. The leading P or $p$ in the universal setting stands for $piecewise$, and the group ${\rm PPSL}_2({\mathbb Z})$ plays at once the role of universal modular group, universal mapping class group, Thompson group $T$ and Ptolemy group. We produce a new basis of the Lie algebra $ppsl_2({\mathbb R})$, compute its structure constants, define a central extension which is compared with the Weil-Petersson 2-form, and discuss its representation theory. We construct and study new framed holographic coordinates on the universal Teichmüller space and its symmetry group ${\rm PPSL}_2({\mathbb R})$, and construct an invariant 1-form as its Maurer-Cartan form analogous to the invariant Eisenstein 1-form $E_2(z)dz$, which gives rise to the spin 1 representation of $psl_2({\mathbb R})$ extended by the trivial representation. This suggests the full program for developing the theory of universal automorphic functions conjectured to yield the bosonic CFT$_2$. Relaxing the automorphic condition to the commutant leads to our ultimate conjecture on realizing the Monster CFT$_2$ via the automorphic representation for the universal triad. This conjecture is also bolstered by the links of both the universal Teichmüller and the Monster CFT$_2$ theories to the three-dimensional quantum gravity.

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arXiv2020

n-Regular Functions in Quaternionic Analysis

In this paper we study left and right n-regular functions that originally were introduced in [FL4]. When n=1, these functions are the usual quaternionic left and right regular functions. We show that n-regular functions satisfy most of the properties of the usual regular functions, including the conformal invariance under the fractional linear transformations by the conformal group and the Cauchy-Fueter type reproducing formulas. Arguably, these Cauchy-Fueter type reproducing formulas for n-regular functions are quaternionic analogues of Cauchy's integral formula for the n-th order pole expressing the (n-1)-st derivative of a holomorphic function. We also find two expansions of the Cauchy-Fueter kernel for n-regular functions in terms of certain basis functions, we give an analogue of Laurent series expansion for n-regular functions, we construct an invariant pairing between left and right n-regular functions and we describe the irreducible representations associated to the spaces of left and right n-regular functions of the conformal group and its Lie algebra.

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arXiv2019

Quaternionic Analysis, Representation Theory and Physics II

We develop further quaternionic analysis introducing left and right doubly regular functions. We derive Cauchy-Fueter type formulas for these doubly regular functions that can be regarded as another counterpart of Cauchy's integral formula for the second order pole, in addition to the one studied in the first paper with the same title. We also realize the doubly regular functions as a subspace of the quaternionic-valued functions satisfying a Euclidean version of Maxwell's equations for the electromagnetic field. Then we return to the study of the original quaternionic analogue of Cauchy's second order pole formula and its relation to the polarization of vacuum. We find the decomposition of the space of quaternionic-valued functions into irreducible components that include the spaces of doubly left and right regular functions. Using this decomposition, we show that a regularization of the vacuum polarization diagram is achieved by subtracting the component corresponding to the one-dimensional subrepresentation of the conformal group. After the regularization, the vacuum polarization diagram is identified with a certain second order differential operator which yields a quaternionic version of Maxwell equations. Next, we introduce two types of quaternionic algebras consisting of spaces of scalar-valued and quaternionic-valued functions. We emphasize that these algebra structures are invariant under the action of the conformal Lie algebra. This uses techniques from our study of the vacuum polarization diagram. These algebras are not associative, but we can define an infinite family of n-multiplications, and we conjecture that they have structures of weak cyclic A-infinity algebras. We also conjecture the relation between the multiplication operations of the scalar and non-scalar quaternionic algebras with the n-photon Feynman diagrams in the scalar and ordinary conformal QED.

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arXiv2014

A categorification of the boson-fermion correspondence via representation theory of $sl(\infty)

In recent years different aspects of categorification of the boson-fermion correspondence have been studied. In this paper we propose a categorification of the boson-fermion correspondence based on the category of tensor modules of the Lie algebra $sl(\infty)$ of finitary infinite matrices. By $\mathbb T^+$ we denote the category of "polynomial" tensor $sl(\infty)$-modules. There is a natural "creation" functor $\mathcal T_N: \mathbb T^+\to \mathbb T^+$, $M\mapsto N\otimes M,\quad M,N\in \mathbb T^+$. The key idea of the paper is to employ the entire category $\mathbb T$ of tensor $sl(\infty)$-modules in order to define the "annihilation" functor $\mathcal D_N: \mathbb T^+\to \mathbb T^+$ corresponding to $\mathcal T_N$. We show that the relations allowing to express fermions via bosons arise from relations in the cohomology of complexes of linear endofunctors on $\mathbb T^+$.

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arXiv2014

Anti De Sitter Deformation of Quaternionic Analysis and the Second Order Pole

This is a continuation of a series of papers [FL1, FL2, FL3], where we develop quaternionic analysis from the point of view of representation theory of the conformal Lie group and its Lie algebra. In this paper we continue to study the quaternionic analogues of Cauchy's formula for the second order pole. These quaternionic analogues are closely related to regularization of infinities of vacuum polarization diagrams in four-dimensional quantum field theory. In order to add some flexibility, especially when dealing with Cauchy's formula for the second order pole, we introduce a one-parameter deformation of quaternionic analysis. This deformation of quaternions preserves conformal invariance and has a geometric realization as anti de Sitter space sitting inside the five-dimensional Euclidean space. We show that many results of quaternionic analysis - including the Cauchy-Fueter formula - admit a simple and canonical deformation. We conclude this paper with a deformation of the quaternionic analogues of Cauchy's formula for the second order pole.

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arXiv2011

Quaternionic Analysis and the Schrodinger Model for the Minimal Representation of O(3,3)

In the series of papers [FL,FL2] we approach quaternionic analysis from the point of view of representation theory of the conformal group SL(4,C) and its real forms. This approach has proven very fruitful and pushed further the parallel with complex analysis and develop a rich theory. In [FL2] we study the counterparts of Cauchy-Fueter and Poisson formulas on the spaces of split quaternions H_R and Minkowski space M and show that they solve the problem of separation of the discrete and continuous series on SL(2,R) and the imaginary Lobachevski space SL(2,C)/SL(2,R). In particular, we introduce an operator Pl_R, compute its effect on the discrete and continuous series components of the space of functions H(H_R) and obtain a surprising formula for the Plancherel measure of SL(2,R). The proof is based on a transition to the Minkowski space M and some pretty lengthy computations. In this paper we introduce an operator d/dR Pl_R on H(H_R) and show that its effect on the discrete and continuous series components can be easily computed using the Schrodinger model for the minimal representation of O(p,q) (with p=q=3) and the results of Kobayashi-Mano from [KM], particularly their computation of the integral expression for the operator F_C. This provides an independent verification of the coefficients involved in the formula for Pl_R. This paper once again demonstrates a close connection between quaternionic analysis and representation theory of various O(p,q)'s.

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arXiv2011

Quaternionic Analysis, Representation Theory and Physics

We develop quaternionic analysis using as a guiding principle representation theory of various real forms of the conformal group. We first review the Cauchy-Fueter and Poisson formulas and explain their representation theoretic meaning. The requirement of unitarity of representations leads us to the extensions of these formulas in the Minkowski space, which can be viewed as another real form of quaternions. Representation theory also suggests a quaternionic version of the Cauchy formula for the second order pole. Remarkably, the derivative appearing in the complex case is replaced by the Maxwell equations in the quaternionic counterpart. We also uncover the connection between quaternionic analysis and various structures in quantum mechanics and quantum field theory, such as the spectrum of the hydrogen atom, polarization of vacuum, one-loop Feynman integrals. We also make some further conjectures. The main goal of this and our subsequent paper is to revive quaternionic analysis and to show profound relations between quaternionic analysis, representation theory and four-dimensional physics.

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arXiv2011

Split Quaternionic Analysis and Separation of the Series for SL(2,R) and SL(2,C)/SL(2,R)

We extend our previous study of quaternionic analysis based on representation theory to the case of split quaternions H_R. The special role of the unit sphere in the classical quaternions H identified with the group SU(2) is now played by the group SL(2,R) realized by the unit quaternions in H_R. As in the previous work, we use an analogue of the Cayley transform to relate the analysis on SL(2,R) to the analysis on the imaginary Lobachevski space SL(2,C)/SL(2,R) identified with the one-sheeted hyperboloid in the Minkowski space M. We study the counterparts of Cauchy-Fueter and Poisson formulas on H_R and M and show that they solve the problem of separation of the discrete and continuous series. The continuous series component on H_R gives rise to the minimal representation of the conformal group SL(4,R), while the discrete series on M provides its K-types realized in a natural polynomial basis. We also obtain a surprising formula for the Plancherel measure on SL(2,R) in terms of the Poisson integral on the split quaternions H_R. Finally, we show that the massless singular functions of four-dimensional quantum field theory are nothing but the kernels of projectors onto the discrete and continuous series on the imaginary Lobachevski space SL(2,C)/SL(2,R). Our results once again reveal the central role of the Minkowski space in quaternionic and split quaternionic analysis as well as a deep connection between split quaternionic analysis and the four-dimensional quantum field theory.

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arXiv2011

Categorifying fractional Euler characteristics, Jones-Wenzl projector and $3j$-symbols

We study the representation theory of the smallest quantum group and its categorification. The first part of the paper contains an easy visualization of the 3j-symbols in terms of weighted signed line arrangements in a fixed triangle and new binomial expressions for the 3j-symbols. All these formulas are realized as graded Euler characteristics. The 3j-symbols appear as new generalizations of Kazhdan-Lusztig polynomials. A crucial result of the paper is that complete intersection rings can be employed to obtain rational Euler characteristics, hence to categorify rational quantum numbers. This is the main tool for our categorification of the Jones-Wenzl projector, Theta-networks and tetrahedron networks. Networks and their evaluations play an important role in the Turaev-Viro construction of 3-manifold invariants, \cite{TV}. We categorify these evaluations by Ext-algebras of certain simple Harish-Chandra bimodules. The relevance of this construction to categorified colored Jones invariants and invariants of 3-manifolds will be studied in detail in subsequent papers.

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arXiv2011

Gelfand-Tsetlin algebras and cohomology rings of Laumon spaces

Laumon moduli spaces are certain smooth closures of the moduli spaces of maps from the projective line to the flag variety of GL_n. We calculate the equivariant cohomology rings of the Laumon moduli spaces in terms of Gelfand-Tsetlin subalgebra of U(gl_n), and formulate a conjectural answer for the small quantum cohomology rings in terms of certain commutative shift of argument subalgebras of U(gl_n).

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arXiv2010

Vertex operator algebras associated to modified regular representations of the Virasoro algebra

We give an abstract construction, based on the Belavin-Polyakov-Zamolodchikov equations, of a family of vertex operator algebras of rank $26$ associated to the modified regular representations of the Virasoro algebra. The vertex operators are obtained from the tensor products of intertwining operators for a pair of Virasoro algebras. We explicitly determine the structure coefficients that yield the axioms of VOAs. In the process of our construction, we obtain new hypergeometric identities.

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arXiv2005

A categorification of finite-dimensional irreducible representations of quantum sl(2) and their tensor products

The purpose of this paper is to study categorifications of tensor products of finite dimensional modules for the quantum group for sl(2). The main categorification is obtained using certain Harish-Chandra bimodules for the complex Lie algebra gl(n). For the special case of simple modules we naturally deduce a categorification via modules over the cohomology ring of certain flag varieties. Further geometric categorifications and the relation to Steinberg varieties are discussed. We also give a categorical version of the quantised Schur-Weyl duality and an interpretation of the (dual) canonical bases and the (dual) standard bases in terms of projective, tilting, standard and simple Harish-Chandra bimodules.

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arXiv2005

Level 1 Perfect Crystals and Path Realizations of Basic Representations at q=0

We present a uniform construction of level 1 perfect crystals $\mathcal B$ for all affine Lie algebras. We also introduce the notion of a crystal algebra and give an explicit description of its multiplication. This allows us to determine the energy function on $\mathcal B \otimes \mathcal B$ completely and thereby give a path realization of the basic representations at $q=0$ in the homogeneous picture.

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arXiv2005

Complex Counterpart of Chern-Simons-Witten Theory and Holomorphic Linking

In this paper we are begining to explore the complex counterpart of the Chern-Simon-Witten theory. We define the complex analogue of the Gauss linking number for complex curves embedded in a Calabi-Yau threefold using the formal path integral that leads to a rigorous mathematical expression. We give an analytic and geometric interpretation of our holomorphic linking following the parallel with the real case. We show in particular that the Green kernel that appears in the explicit integral for the Gauss linking number is replaced by the Bochner-Martinelli kernel. We also find canonical expressions of the holomorphic linking using the Grothendieck-Serre duality in local cohomology, the latter admits a generalization for an arbitrary field.

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arXiv2004

Complex ADHM equations, sheaves on P^3 and quantum instantons

We use a complex version of the celebrated Atiyah-Hitchin-Drinfeld-Manin matrix equations to construct admissible torsion-free sheaves on $\p^3$ and complex quantum instantons over our quantum Minkowski space-time. We identify the moduli spaces of various subclasses of sheaves on $\p^3$, and prove their smoothness. We also define the Laplace equation in the quantum Minkowski space-time, study its solutions and relate them to the admissibility condition for sheaves on $\p^3$.

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