arXiv subjects

K. B. Alkalaev

Publications and source records attributed to K. B. Alkalaev.

At least 19 recordsLinked to original sources

arXiv2026

Wilson network expansion for four-point contact and exchange scalar Feynman diagrams in AdS$_2$

We derive new integral identities for AdS propagators and further develop the Wilson network expansion for AdS Feynman diagrams. In particular, we demonstrate that four-point contact and exchange scalar diagrams in two dimensions can be expanded into several infinite series of matrix elements of Wilson line network operators with running conformal weights. Each series is characterized by specific multi-trace operators associated with the external and intermediate edges of the corresponding graphs. The resulting expansions near the conformal boundary reproduce the well-known decompositions of the corresponding four-point Witten diagrams into conformal blocks.

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arXiv2026

Thermal conformal partial waves from flat-space and defect CFT

We establish a correspondence between conformal partial waves on flat, thermal, and defect backgrounds using the shadow formalism. We demonstrate that scalar one-point thermal blocks can be systematically obtained from their four-point flat-space and two-point defect counterparts by considering specific operator configurations. This framework allows us to derive the thermal Casimir equation as a diagonal reduction of the flat-space Casimir system without introducing chemical potentials. We further show that defect two-point blocks with a spin-$l$ exchange operator correspond to thermal one-point blocks for an external spin-$l$ operator.

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arXiv2025

Wilson network decomposition of AdS Feynman diagrams in two dimensions

We show that Feynman diagrams in AdS$_2$ space can be decomposed into infinite series of matrix elements of Wilson line network operators. The case of the 3-point scalar Feynman diagram with endpoints in the bulk is studied in detail. The resulting decomposition is similar to the conformal block decomposition of Witten diagrams, i.e. it comprises a single-trace term and infinite sums of double-trace terms. We derive a number of AdS propagator identities which relate the standard bulk-to-bulk propagators with the modified bulk-to-bulk propagators of two different types responsible for extracting single-trace and double-trace terms.

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arXiv2025

Multipoint conformal integrals in $D$ dimensions. Part II: Polygons and basis functions

We explicitly construct a class of multivariate generalized hypergeometric series which is conjectured in our previous paper [Alkalaev & Mandrygin 2025] to calculate multipoint one-loop parametric conformal integrals in $D$ dimensions. Our approach is based on a simple diagrammatic algorithm which systematically builds both arguments and series coefficients in terms of a convex polygon which is part of the Baxter lattice. The examples of the box, pentagon, and hexagon integrals are considered in detail.

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arXiv2025

Multipoint conformal integrals in $D$ dimensions. Part I: Bipartite Mellin-Barnes representation and reconstruction

We propose a systematic approach to calculating $n$-point one-loop parametric conformal integrals in $D$ dimensions which we call the reconstruction procedure. It relies on decomposing a conformal integral over basis functions which are generated from a set of master functions by acting with the cyclic group $\mathbb{Z}_n$. In order to identify the master functions we introduce a bipartite Mellin-Barnes representation by means of splitting a given conformal integral into two additive parts, one of which can be evaluated explicitly in terms of multivariate generalized hypergeometric series. For the box and pentagon integrals (i.e. $n=4,5$) we show that a computable part of the bipartite representation contains all master functions. In particular, this allows us to evaluate the parametric pentagon integral as a sum of ten basis functions generated from two master functions by the cyclic group $\mathbb{Z}_5$. The resulting expression can be tested in two ways. First, when one of propagator powers is set to zero, the pentagon integral is reduced to the known box integral, which is also rederived through the reconstruction procedure. Second, going to the non-parametric case, we reproduce the known expression for the pentagon integral given in terms of logarithms derived earlier within the geometric approach to calculating conformal integrals. We conclude by considering the hexagon integral ($n=6$) for which we show that those basis functions which follow from the computable part of the bipartite representation are not enough and more basis functions are required. In the second part of our project we will describe a method of constructing a complete set of master/basis functions in the $n$-point case.

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arXiv2025

Holographic reconstruction for AdS Wilson line networks and scalar Witten diagrams

We find a holographic reconstruction formula for gravitational Wilson line network operators in AdS$_2$ evaluated between Ishibashi states of the algebra $sl(2,\mathbb{R})$. It is given in integral form where the integrand is the global conformal block multiplied by a smearing function which is the product of the scalar bulk-to-boundary propagators. The integral can be explicitly calculated as multidimensional series of which arguments are rational functions of endpoint coordinates. In the case of two and three endpoints the resulting expressions allow one to establish a number of relations between the gravitational Wilson line networks and Witten diagrams for massive scalar fields in AdS$_2$.

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arXiv2024

One-point thermal conformal blocks from four-point conformal integrals

We develop the thermal shadow formalism to study the conformal blocks decomposition in $D$-dimensional conformal field theory on $\mathbb{S}_β^{1} \times \mathbb{S}^{D-1}$, where the temperature is $T = β^{-1}$. It is demonstrated that both the 1-point thermal ($T\neq 0$) conformal blocks and the 4-point plane ($T=0$) conformal blocks are defined by the same 4-point conformal integral. It is shown that up to power prefactors the 1-point thermal conformal block is given by the fourth Appell function.

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arXiv2024

A note on the large-$c$ conformal block asymptotics and $α$-heavy operators

We consider $α$-heavy conformal operators in CFT$_2$ which dimensions grow as $h = O(c^α)$ with $α$ being non-negative rational number and conjecture that the large-$c$ asymptotics of the respective 4-point Virasoro conformal block is exponentiated similar to the standard case of $α=1$. It is shown that the leading exponent is given by a Puiseux polynomial which is a linear combination of power functions in the central charge with fractional powers decreasing from $α$ to $0$ according to some pattern. Our analysis is limited by considering the first six explicit coefficients of the Virasoro block function in the coordinate. For simplicity, external primary operators are chosen to be of equal conformal dimensions that, therefore, includes the case of the vacuum conformal block. The consideration is also extended to the 4-point ${\cal W}_3$ conformal block of four semi-degenerate operators, in which case the exponentiation hypothesis works the same way. Here, only the first three block coefficients can be treated analytically.

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arXiv2023

Wilson networks in AdS and global conformal blocks

We develop the relation between gravitational Wilson line networks, defined as a particular product of Wilson line operators averaged over the cap states, and conformal correlators in the context of the AdS$_2$/CFT$_1$ correspondence. The $n$-point $sl(2, \mathbb{R})$ comb channel global conformal block in CFT$_1$ is explicitly calculated by means of the extrapolate dictionary relation from the gravitational Wilson line network with $n$ boundary endpoints stretched in AdS$_2$. Remarkably, the Wilson line calculation directly yields the conformal block in a particularly simple form which up to the leg factor is given by the comb function of cross-ratios. It is also found that the comb channel structure constants are expressed in terms of factorials and triangle functions of conformal weights whose form determines fusion rules for a given 3-valent vertex. We obtain analytic expressions for the Wilson line matrix elements in AdS$_2$ which are building blocks of the Wilson line networks. We analyze general cap states and specify those which lead to asymptotic values of the Wilson line networks interpreted as boundary correlators of CFT$_1$ primary operators. The cases of (in)finite-dimensional $sl(2, \mathbb{R})$ modules carried by Wilson lines are treated on equal footing that boils down to consideration of singular submodules and their contributions to the Wilson line matrix elements.

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arXiv2023

Torus shadow formalism and exact global conformal blocks

Using the shadow formalism we find global conformal blocks of torus CFT$_2$. It is shown that $n$-point torus blocks in the ``necklace'' channel (a loop with $n$ legs) are expressed in terms of a hypergeometric-type function which we refer to as the necklace function.

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arXiv2022

Torus conformal blocks and Casimir equations in the necklace channel

We consider the conformal block decomposition in arbitrary exchange channels of a two-dimensional conformal field theory on a torus. The channels are described by diagrams built of a closed loop with external legs (a necklace sub-diagram) and trivalent vertices forming trivalent trees attached to the necklace. Then, the $n$-point torus conformal block in any channel can be obtained by acting with a number of OPE operators on the $k$-point torus block in the necklace channel at $k=1,...,n$. Focusing on the necklace channel, we go to the large-$c$ regime, where the Virasoro algebra truncates to the $sl(2, \mathbb{R})$ subalgebra, and obtain the system of the Casimir equations for the respective $k$-point global conformal block. In the plane limit, when the torus modular parameter $q\to 0$, we explicitly find the Casimir equations on a plane which define the $(k+2)$-point global conformal block in the comb channel. Finally, we formulate the general scheme to find Casimir equations for global torus blocks in arbitrary channels.

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arXiv2022

Color decorations of Jackiw-Teitelboim gravity

We introduce the colored version of Jackiw-Teitelboim (JT) gravity which is the two-dimensional dilaton gravity model with matrix-valued fields. It is straightforwardly formulated in terms of BF action with $su(N,N)$ gauge algebra so that the standard JT gravity is embedded as $su(1,1) \subset su(N,N)$ subsector. We also elaborate on the respective metric formulation which is shown to involve the JT fields plus $su(N)$ non-Abelian fields as well as $su(N)$-matrix valued metric and dilaton fields. Their interactions are governed by minimal couplings and potential terms of cubic and quartic orders involving derivatives.

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arXiv2022

Schwarzian for colored Jackiw-Teitelboim gravity

We study the boundary effective action of the colored version of the Jackiw-Teitelboim (JT) gravity. We derive the boundary action, which is the color generalization of the Schwarzian action, from the $su(N,N)$ BF formulation of the colored JT gravity. Using different types of the $SU(N,N)$ group decompositions both the zero and finite temperature cases are elaborated. We provide the semi-classical perturbative analysis of the boundary action and discuss the instability of the spin-1 mode and its implication for the quantum chaos. A rainbow-AdS$_2$ geometry is introduced where the color gauge symmetry is spontaneously broken.

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arXiv2021

AdS$_3$/AdS$_2$ degression of massless particles

We study a 3d/2d dimensional degression which is a Kaluza-Klein type mechanism in AdS$_3$ space foliated into AdS$_2$ hypersurfaces. It is shown that an AdS$_3$ massless particle of spin $s=1,2,...,\infty$ degresses into a couple of AdS$_2$ particles of equal energies $E=s$. Note that the Kaluza-Klein spectra in higher dimensions are always infinite. To formulate the AdS$_3$/AdS$_2$ degression we consider branching rules for AdS$_3$ isometry algebra o$(2,2)$ representations decomposed with respect to AdS$_2$ isometry algebra o$(1,2)$. We find that a given o$(2,2)$ higher-spin representation lying on the unitary bound (i.e. massless) decomposes into two equal o$(1,2)$ modules. In the field-theoretical terms, this phenomenon is demonstrated for spin-2 and spin-3 free massless fields. The truncation to a finite spectrum can be seen by using particular mode expansions, (partial) diagonalizations, and identities specific to two dimensions.

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arXiv2020

More on Wilson toroidal networks and torus blocks

We consider the Wilson line networks of the Chern-Simons $3d$ gravity theory with toroidal boundary conditions which calculate global conformal blocks of degenerate quasi-primary operators in torus $2d$ CFT. After general discussion that summarizes and further extends results known in the literature we explicitly obtain the one-point torus block and two-point torus blocks through particular matrix elements of toroidal Wilson network operators in irreducible finite-dimensional representations of $sl(2,\mathbb{R})$ algebra. The resulting expressions are given in two alternative forms using different ways to treat multiple tensor products of $sl(2,\mathbb{R})$ representations: (1) $3mj$ Wigner symbols and intertwiners of higher valence, (2) totally symmetric tensor products of the fundamental $sl(2,\mathbb{R})$ representation.

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arXiv2020

On BF-type higher-spin actions in two dimensions

We propose a non-abelian higher-spin theory in two dimensions for an infinite multiplet of massive scalar fields and infinitely many topological higher-spin gauge fields together with their dilaton-like partners. The spectrum includes local degrees of freedom although the field equations take the form of flatness and covariant constancy conditions because fields take values in a suitable extension of the infinite-dimensional higher-spin algebra $hs[λ]$. The corresponding action functional is of BF-type and generalizes the known topological higher-spin Jackiw-Teitelboim gravity.

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arXiv2020

Holographic variables for CFT$_2$ conformal blocks with heavy operators

We consider large-$c$ $n$-point Virasoro blocks with $n-k$ background heavy operators and $k$ perturbative heavy operators. Conformal dimensions of heavy operators scale linearly with large $c$, while splitting into background/perturbative operators assumes an additional perturbative expansion. Such conformal blocks can be calculated within the monodromy method that basically reduces to solving auxiliary Fuchsian second-order equation and finding monodromy of solutions. We show that there exist particular variables that we call holographic, use of which drastically simplifies the whole analysis. In consequence, we formulate the uniformization property of the large-$c$ blocks which states that in the holographic variables their form depends only on the number of perturbative heavy operators. On the other hand, the holographic variables encode the metric in the bulk space so that the conformal blocks with the same number of perturbative operators are calculated by the same geodesic trees but on different geometries created by the background operators.

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arXiv2019

Four-point conformal blocks with three heavy background operators

We study CFT$_2$ Virasoro conformal blocks of the 4-point correlation function $\langle \mathcal{O}_L \mathcal{O}_H \mathcal{O}_H \mathcal{O}_H \rangle $ with three background operators $\mathcal{O}_H$ and one perturbative operator $\mathcal{O}_L$ of dimensions $Δ_L/Δ_H \ll1$. The conformal block function is calculated in the large central charge limit using the monodromy method. From the holographic perspective, the background operators create $AdS_3$ space with three conical singularities parameterized by dimensions $Δ_H$, while the perturbative operator corresponds to the geodesic line stretched from the boundary to the bulk. The geodesic length calculates the perturbative conformal block. We propose how to address the block/length correspondence problem in the general case of higher-point correlation functions $\langle \mathcal{O}_L \cdots \mathcal{O}_L \mathcal{O}_H \cdots \mathcal{O}_H \rangle $ with arbitrary numbers of background and perturbative operators.

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