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A M Semikhatov

Publications and source records attributed to A M Semikhatov.

18 recordsLinked to original sources
arXiv2016

Quantum walled Brauer algebra: commuting families, Baxterization, and representations

For the quantum walled Brauer algebra, we construct its Specht modules and (for generic parameters of the algebra) seminormal modules. The latter construction yields the spectrum of a commuting family of Jucys--Murphy elements. We also propose a Baxterization prescription; it involves representing the quantum walled Brauer algebra in terms of morphisms in a braided monoidal category and introducing parameters into these morphisms, which allows constructing a "universal transfer matrix" that generates commuting elements of the algebra.

math.QA↗
arXiv2013

Representations of $\bar{U}_q s\ell(2|1)$ at even roots of unity

We construct all projective modules of the restricted quantum group $\bar{U}_q s\ell(2|1)$ at an even, $2p$th, root of unity. This $64p^4$-dimensional Hopf algebra is a common double bosonization, $B(X^*)\otimes B(X)\otimes H$, of two rank-2 Nichols algebras $B(X)$ with fermionic generator(s), with $H=Z_{2p}\otimes Z_{2p}$. The category of $\bar{U}_q s\ell(2|1)$-modules is equivalent to the category of Yetter--Drinfeld $B(X)$-modules in $C_ρ={}^H_H\!YD$, where coaction is defined by a universal $R$-matrix $ρ$. As an application of the projective module construction, we find the associative algebra structure and the dimension, $5p^2-p+4$, of the $\bar{U}_q s\ell(2|1)$ center.

math.QA↗
arXiv1998

Free-Field Resolutions of the Unitary N=2 Super-Virasoro Representations

We construct free-field resolutions of unitary representations of the N=2 superconformal algebra. The irreducible representations are singled out from free-field spaces as the cohomology of fermionic screening operators. We construct and evaluate the cohomology of the resolution associated with one fermionic screening (which is related to the representation theory picture of ``gravitational descendants''), and a {\it butterfly} resolution associated with two fermionic screenings.

hep-th↗
arXiv1998

A Kaehler Structure of the Triplectic Geometry

We study the geometry of the triplectic quantization of gauge theories. We show that underlying the triplectic geometry is a Kaehler manifold N endowed with a pair of transversal polarizations. The antibrackets can be brought to the canonical form if and only if N admits a flat symmetric connection that is compatible with the complex structure and the polarizations.

hep-th↗
arXiv1998

All Singular Vectors of the N=2 Superconformal Algebra via the Algebraic Continuation Approach

We give general expressions for singular vectors of the N=2 superconformal algebra in the form of {\it monomials} in the continued operators by which the universal enveloping algebra of N=2 is extended. We then show how the algebraic relations satisfied by the continued operators can be used to transform the monomials into the standard Verma-module expressions. Our construction is based on continuing the extremal diagrams of N=2 Verma modules to the states satisfying the twisted \hw{} conditions with complex twists. It allows us to establish recursion relations between singular vectors of different series and at different levels. Thus, the N=2 singular vectors can be generated from a smaller set of the so-called topological singular vectors, which are distinguished by being in a 1:1 correspondence with singular vectors in affine sl(2) Verma modules. The method of `continued products' of fermions is a counterpart of the method of complex powers used in the constructions of singular vectors for affine Lie algebras.

hep-th↗
arXiv1998

Resolutions and Characters of Irreducible Representations of the N=2 Superconformal Algebra

We evaluate characters of irreducible representations of the N=2 supersymmetric extension of the Virasoro algebra. We do so by deriving the BGG-resolution of the admissible N=2 representations and also a new 3,5,7...-resolution in terms of twisted massive Verma modules. We analyse how the characters behave under the automorphisms of the algebra, whose most significant part is the spectral flow transformations. The possibility to express the characters in terms of theta functions is determined by their behaviour under the spectral flow. We also derive the identity expressing every $\hat{sl}(2)$ character as a linear combination of spectral-flow transformed N=2 characters; this identity involves a finite number of N=2 characters in the case of unitary representations. Conversely, we find an integral representation for the admissible N=2 characters as contour integrals of admissible $\hat{sl}(2)$ characters.

hep-th↗
arXiv1998

Gauge Symmetries of the Master Action

We study the geometry of the Lagrangian Batalin--Vilkovisky theory on an antisymplectic manifold. We show that gauge symmetries of the BV-theory are essentially the symmetries of an even symplectic structure on the stationary surface of the master action.

hep-th↗
arXiv1998

The Structure of Verma Modules over the N=2 Superconformal Algebra

We classify degeneration patterns of Verma modules over the N=2 superconformal algebra in two dimensions. Explicit formulae are given for singular vectors that generate maximal submodules in each of the degenerate cases. The mappings between Verma modules defined by these singular vectors are embeddings; in particular, their compositions never vanish. As a by-product, we also obtain general formulae for N=2 subsingular vectors.

hep-th↗
arXiv1997

Embedding Diagrams of N=2 Verma Modules and Relaxed ^sl(2) Verma Modules

We classify and explicitly construct the embedding diagrams of Verma modules over the N=2 supersymmetric extension of the Virasoro algebra. The essential ingredient of the solution consists in drawing the distinction between two different types of submodules appearing in N=2 Verma modules. The problem is simplified by associating to every N=2 Verma module a relaxed Verma module over the affine algebra ^sl(2) with an isomorphic embedding diagram. We then make use of the mechanism according to which the structure of the N=2/relaxed-sl(2) embedding diagrams can be found knowing the standard embedding diagrams of ^sl(2) Verma modules. The resulting classification of the N=2/relaxed-^sl(2) embedding diagrams follows the I-II-III pattern extended by an additional indication of the number (0, 1, or 2) and the twists of the standard ^sl(2) embedding diagrams contained in a given N=2/relaxed-^sl(2) embedding diagram.

hep-th↗
arXiv1997

Past the Highest-Weight, and What You Can Find There

The properties of highest-weight representations of the N=2 superconformal algebra in two dimensions can be considerably simplified when re-expressed in terms of relaxed ^sl(2) representations. This applies to the appearance of submodules and hence, of singular vectors, and to the structure of the embedding diagrams and the BGG-type resolution. I also discuss the realization of these representations in the bosonic string, where the generalized DDK prescription amounts to the requirement that the representations have a charged singular vector, and the role of the fermionic screening operator.

q-alg↗
arXiv1997

On the Canonical Form of a Pair of Compatible Antibrackets

In the triplectic quantization of general gauge theories, we prove a `triplectic' analogue of the Darboux theorem: we show that the doublet of compatible antibrackets can be brought to a weakly-canonical form provided the general triplectic axioms of [BMS] are imposed together with some additional requirements that can be formulated in terms of marked functions of the antibrackets. The weakly-canonical antibrackets involve an obstruction to bringing them to the canonical form. We also classify the `triplectic' odd vectors fields compatible with the weakly-canonical antibrackets and construct the Poisson bracket associated with the antibrackets and the odd vector fields. We formulate the Sp(2)-covariance requirement for the antibrackets and the vector fields; whenever the obstruction to the canonical form of the antibrackets vanishes, the Sp(2)-covariance condition implies the canonical form of the triplectic vector fields.

hep-th↗
arXiv1997

On the Equivalence of Affine sl(2) and N=2 Superconformal Representation Theories

There exist two different languages, the ^sl(2) and N=2 ones, to describe similar structures; a dictionary is given translating the key representation-theoretic terms related to the two algebras. The main tool to describe the structure of ^sl(2) and N=2 modules is provided by diagrams of extremal vectors. The ^sl(2) and N=2 representation theories of certain highest-weight types turn out to be equivalent modulo the respective spectral flows.

hep-th↗
arXiv1996

Singular Vectors of the Topological Conformal Algebra

A general construction is found for `topological' singular vectors of the twisted N=2 superconformal algebra. It demonstrates many parallels with the known construction for sl(2) singular vectors due to Malikov--Feigin--Fuchs, but is formulated independently of the latter. The two constructions taken together provide an isomorphism between topological and sl(2)- singular vectors. The general formula for topological singular vectors can be reformulated as a chain of direct recursion relations that allow one to derive a given singular vector |S(r,s)> from the lower ones |S(r,s' . We also introduce generalized Verma modules over the twisted N=2 algebra and show that they provide a natural setup for the new construction for topological singular vectors.

hep-th↗
arXiv1995

$sl(2)_{-4}$ WZW Model as an N=4 Supersymmetric Bosonic String with $c=-2$ matter

We consider the sl(2) current algebra at level k=-4 when the sl(2) BRST operator is nilpotent. We formulate a spectral sequence converging to the cohomology of this BRST operator. At the second term of the spectral sequence, we observe an N=4 algebra. This algebra is generated in a c=-2 bosonic string whose BRST operator Q_{string} represents the next term in the spectral sequence. We realize the cohomology of the irreducible modules as Q_{string}-primitives of the N=4 singular vectors and point out their relation to Lian--Zuckerman states of c=-2 matter. The relation between sl(2)_{-4} WZW model and c=-2 bosonic string is established both at the level of BRST cohomology and at the level of an explicit operator construction. The relation of the N=4 algebra to the known symmetries of matter+gravity systems is also investigated.

hep-th↗
arXiv1994

Inverting the Hamiltonian Reduction in String Theory

It is well known that many interesting realisations of string theories can be obtained via hamiltonian reduction from WZW models. I want to point out that string theories do in certain cases also provide the recipe to reconstruct the ambient space of the hamiltonian reduction, including Kac--Moody currents and the associated ghosts. The procedure of reconstructing the Kac--Moody currents is closely related to properties of matter+gravity multiplets in noncritical string theories. In application to KPZ gravity and its N=1 supersymmetric extension, the `inverted hamiltonian reduction' constructions serve to establish relation with the DDK-type formalism for matter + gravity.

hep-th↗
arXiv1993

Singular Vectors and Topological Theories from Virasoro Constraints via the Kontsevich-Miwa Transform

We use the Kontsevich-Miwa transform to relate the different pictures describing matter coupled to topological gravity in two dimensions: topological theories, Virasoro constraints on integrable hierarchies, and a DDK-type formalism. With the help of the Kontsevich-Miwa transform, we solve the Virasoro constraints on the KP hierarchy in terms of minimal models dressed with a (free) Liouville-like scalar. The dressing prescription originates in a topological (twisted N=2) theory. The Virasoro constraints are thus related to essentially the N=2 null state decoupling equations. The N=2 generators are constructed out of matter, the `Liouville' scalar, and $c=-2$ ghosts. By a `dual' construction involving the reparametrization $c=-26$ ghosts, the DDK dressing prescription is reproduced from the N=2 symmetry. As a by-product we thus observe that there are two ways to dress arbitrary $d\leq1$ or $d\geq25$ matter theory, that allow its embedding into a topological theory. By th e Kontsevich-Miwa transform, which introduces an infinite set of `time' variables $t_r$, the equations ensuring the vanishing of correlators that involve BRST-exact primary states, factorize through the Virasoro generators expressed in terms of the $t_r$. The background charge of these Virasoro generators is determined by the topological central charge.

hep-th↗