REVIEW
Affine sl(N) conformal blocks from N=2 SU(N) gauge theories
High Energy Physics - Theory · Submitted 8 Aug 2010 · 53 references
Pith's verdict: Honest, useful sl(N) extension of Alday–Tachikawa; the checks are real but stop short of the terms that would actually test the guessed K† insertion.
T0 · AI review
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Referee report
The paper
The paper claims
Conformal blocks of the affine $sl(N)$ current algebra, with a specific operator inserted, are proposed to equal the instanton partition functions of $N=2$ $SU(N)$ quiver gauge theories in the presence of a full surface operator.
The reading
What carries the argument
Two ingredients carry the argument. First, the character formula for instanton counting in the presence of a full surface operator, taken from the mathematics literature, which replaces the usual sum over $N$-vectors of Young tableaux by a periodic structure $lambda_i equiv lambda_{i+N}$, $a_i equiv a_{i+N}$ with instanton numbers $k_i = sum_{j geq 1} lambda^{i-j+1}_j$; this is what produces the $N$ separate expansion variables $y_i$ and the characteristic floor functions $lfloor cdot/N rfloor$ that single out $y_N$. Second, the decomposition of the affine conformal block over a complete set of descendants with the inverse Gram (Shapovalov) matrix $X^{-1}$, which turns the block into a sum of hypergeometric functions whose parameters are read off from the differential-operator realisation of the $sl(N)$ generators on $N-1$ isospin variables. The operator $K^dagger$, an exponential of raising and Cartan modes with coefficients $1/(2n-1)$, is the device that aligns the argument of each hypergeometric function with the instanton series; its zero-mode part factorises as $e^{J^1_+} e^{-J^{2,1}_0} cdots e^{-J^{N-1,N-2}_0}$.
Extended reading notes
Core claim
The central claim is that the instanton partition function of a conformal $N=2$ $SU(N)$ quiver gauge theory with a full surface operator is, up to a prefactor, an affine $sl(N)$ conformal block. Concretely, the authors conjecture that the four-point block $sum_{n,A;n',A'} langle j_1| V_{chi_2}(1,1) |n,A;j rangle X^{-1}_{n,A;n',A'}(j) langle n',A';j| V_{chi_3}(x,z) |j_4 rangle$ equals the $N_f = 2N$ instanton partition function with a full surface operator, where the external insertions $V_chi$ carry the special weights $chi_i = kappa_i Lambda_{N-1}$ (or $kappa_i Lambda_1$) and are dressed by an operator $K$ or $K^dagger$. The dictionary identifies the $N-1$ surface-operator couplings with the isospin coordinates through $y_1 = x_1$, $y_{i+1} = x_{i+1}/x_i$, $y_N = z/x_{N-1}$, the internal affine weight with the Coulomb moduli through $j_i = -1/2 + (a_i - a_{i+1})/(2 epsilon_1)$, and the level with the deformation parameters through $k = -N - epsilon_2/epsilon_1$. The matching is exhibited explicitly for the hypergeometric pieces of the four-point block, for the four hypergeometric families of the five-point block, and for the torus one-point block, and it is extended to pure $SU(N)$ via a state annihilated by $J^1_+$, $J^{N-1,-1}$ and the intermediate raising operators.
Load-bearing premise
The dressing operator $K^dagger$ written down in equation (4.16) is a guess fixed only by $sl(N)$ covariance and by analogy with the $SU(2)$ case, and the reported checks exercise only those pieces of it that act on the states examined.
Editorial extensions
If this is right
- Any conformal $N=2$ $SU(N)$ quiver gauge theory with a full surface operator acquires a two-dimensional computational route: expand the affine block instead of evaluating localisation integrals over the defect moduli space.
- The $N-1$ continuous parameters of the surface operator are identified with ratios of isospin variables, so the defect's coupling space is mapped onto the coordinate space of the current-algebra insertion.
- Asymptotically free $SU(N)$ theories with a full surface operator obtain a Whittaker-vector construction analogous to the Gaiotto state, with the state fixed by $J^1_+|vec{x},z;jrangle = sqrt{x_1}|vec{x},z;jrangle$ and $J^{N-1,-1}|vec{x},z;jrangle = sqrt{z/x_{N-1}}|vec{x},z;jrangle$.
- The subsector with $k_N = 0$ depends only on $epsilon_1$ and not $epsilon_2$, matching the known statement that this piece is an eigenfunction of the quantum trigonometric Calogero-Sutherland model and explaining the absence of $epsilon_2$ as a restriction to zero modes of the affine current.
- The comparison of two-dimensional-defect and four-dimensional-defect realisations becomes a sharp question at higher rank, since the two agree for $SU(2)$ but appear to differ already for a two-node $SU(2)$ quiver.
Reading between the lines
- The $K^dagger$ insertion reads like a stand-in for spectral flow. The paper itself observes that replacing one primary by its spectrally flowed version could substitute for $K$, which suggests the operator is bookkeeping for a choice of affine coordinate patch rather than additional physical input; if so, the correspondence may be stated more invariantly without it.
- If the equality holds beyond the checked orders, the factorised structure of the affine block predicts recursive patterns in the surface-operator instanton series that localisation could test independently, without ever computing a conformal block.
- The failure of the two-dimensional/three-dimensional defect coincidence at quiver level for $SU(2)$ may be an artefact of $SU(2)$ having a single Levi type; a rank-two check with a simple surface operator breaking $SU(3)$ to $SU(2) times U(1)$ would settle whether the coincidence is generic or accidental.
- Because the dictionary fixes $j_i$ from differences $a_i - a_{i+1}$, the affine block is sensitive only to the $SU(N)$ Cartan of the Coulomb branch, so the overall $U(1)$ decoupled from the $N_f = 2N$ matter content should appear only as a prefactor, which is a check the paper does not spell out.
Original abstract
Recently Alday and Tachikawa proposed a relation between conformal blocks in a two-dimensional theory with affine sl(2) symmetry and instanton partition functions in four-dimensional conformal N=2 SU(2) quiver gauge theories in the presence of a certain surface operator. In this paper we extend this proposal to a relation between conformal blocks in theories with affine sl(N) symmetry and instanton partition functions in conformal N=2 SU(N) quiver gauge theories in the presence of a surface operator. We also discuss the extension to non-conformal N=2 SU(N) theories.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
Recently Alday and Tachikawa proposed a relation between conformal blocks in a two-dimensional theory with affine sl(2) symmetry and instanton partition functions in four-dimensional conformal N=2 SU(2) quiver gauge theories in the presence of a certain surface operator. In this paper we extend this proposal to a relation between conformal blocks in theories with affine sl(N) symmetry and instanton partition functions in conformal N=2 SU(N) quiver gauge theories in the presence of a surface operator. We also discuss the extension to non-conformal N=2 SU(N) theories.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Recently Alday and Tachikawa proposed a relation between conformal blocks in a two-dimensional theory with affine sl(2) symmetry and instanton partition functions in four-dimensional conformal N=2 SU(2) quiver gauge theories in the presence of a certain surface operator. | background 1.00 | 0.03 | 0.05 | asserted 0.99 |
| s1 | In this paper we extend this proposal to a relation between conformal blocks in theories with affine sl(N) symmetry and instanton partition functions in conformal N=2 SU(N) quiver gauge theories in the presence of a surface operator. | contribution 1.00 | 0.90 | 0.86 | asserted 0.99 |
| s2 | We also discuss the extension to non-conformal N=2 SU(N) theories. | contribution 0.97 | 0.82 | 0.07 | asserted 0.71 |
What was examined, and what was not
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- P abstract
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References
How the literature uses it
52 arXiv papers cite this in 112 sentences
Papers citing it · 84 sentences without a confident label
Builds on it 2 papers
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In this section we extend the analysis in [ref] to general $N$.
Instanton partition functions in N=2 SU(N) gauge theories with a general surface operator, and their W-algebra duals · The case of $N=1+(N-1)$ surface operators · 1.00
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This relation is extended to the theory with the generalized $W$ algebra [ref] [ref] [ref] , which is obtained from the quantum Drinfeld-Sokolov reduction applied to an affine Lie algebra $(n)$ [ref] .
Matrix model from N = 2 orbifold partition function · String theory perspective · 0.95
Uses its method or tool 1 paper
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These can be defined for the quasi-superconformal algebras in a way completely analogous to the construction in [ref] (see also [ref] and section 5 in [ref] ).
Instanton partition functions in N=2 SU(N) gauge theories with a general surface operator, and their W-algebra duals · The case of $N=1+…+1+2$ surface operators · 0.82
Compares with it 4 papers
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We note that to make our results compatible with those in [ref] the following redefinition of the parameters is required [equation] and [equation]
Conformal blocks of Chiral fields in N=2 SUSY CFT and Affine Laumon Spaces · Affine $sl(2)$ blocks and instanton partition functions · 0.98
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For instance, the specialization of the primary fields $V_χ$, $χ=κΛ_1, κΛ_N-1$ in [ref] for the simple punctures agrees with the choice of the spectral type $(N-1,1)$.
A quantum isomonodromy equation and its application to N=2 SU(N) gauge theories · Summary and discussions · 0.81
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For example in the case corresponding to $N=1+…+1$ with $k_N=0$ the character obtained in [ref] reduces to the character in [ref] (see e.g. [ref] for a discussion).
Instanton partition functions in N=2 SU(N) gauge theories with a general surface operator, and their W-algebra duals · Preliminaries and statement of the main conjecture · 0.94
Cites it as support 2 papers
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We are now going to propose the following conjecture: There exists a choice of twist elements $_e(τ_e,x_e)$ such that we have [equation] assuming that [equation] Evidence for this conjecture is provided by the computations performed in [ref] in the cases $C=C_1,1$ and $C=C_0,4$.
Surface Operators and Separation of Variables · Relation to conformal field theory · 0.99
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This expectation is based on the computations in [ref] for $N=2$ and in [ref] for $N=3$.
Instanton partition functions in N=2 SU(N) gauge theories with a general surface operator, and their W-algebra duals · The case of $N=1+(N-1)$ surface operators · 0.96
Cites it as background 18 papers
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The AGT correspondence [ref] relates $= 2$ supersymmetric gauge theories in four dimensions and conformal field theories with W-algebra symmetry in two dimensions [ref] .
Compactification on the \Omega-background and the AGT correspondence · Introduction · 0.99
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On the conformal blocks in Toda theory which correspond to the instanton part of partition function in gauge theory, the discussion and calculation have been developed [ref] .
Notes on 3-point functions of A_{N-1} Toda theory and AGT-W relation for SU(N) quiver · Introduction · 0.96
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There are other surface operators which, according to [ref] , changes the 2D theories from Liouville or Toda theories to those with affine Lie algebra symmetry.
AGT on the S-duality Wall · Introduction · 0.87
What it cites · 77 sentences without a confident label
Builds on 1 paper
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In this paper we extend the proposal in [ref] to a relation between conformal blocks in theories with affine $(N)$ symmetry and instanton partition functions in conformal $=2$ $(N)$ quiver gauge theories in the presence of a surface operator arising from a $4d$ defect.
Affine SL(2) conformal blocks from 4d gauge theories · Introduction · 1.00
Uses the method or tool of 1 paper
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However, since the $$ operator is crucial when matching the higher-point conformal blocks to instanton partition functions in quiver gauge theories, we will insert a $$ operator, following the prescription in [ref] (note that the expression for $$ written in [ref] is equal to $(1,1)$ in our notation).
Affine SL(2) conformal blocks from 4d gauge theories · Four-point conformal block on the sphere · 0.98
Compares with 4 papers
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Whereas instanton partition functions built from the character ([ref]) are intimately connected with the affine $(N)$ algebra the results in [ref] are based on the ordinary $(N)$ algebra.
Laumon Spaces and the Calogero-Sutherland Integrable System · $(N)$ instanton counting in the presence of a full surface operator · 0.99
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An important thing to note is that the $y_N$-independent terms only depend on $_1$ and not on $_2$, which is similar to the setting in [ref] (see also [ref] ).
Quantization of Integrable Systems and Four Dimensional Gauge Theories · $(N)$ instanton counting in the presence of a full surface operator · 0.92
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An important thing to note is that the $y_N$-independent terms only depend on $_1$ and not on $_2$, which is similar to the setting in [ref] (see also [ref] ).
Nekrasov Functions and Exact Bohr-Sommerfeld Integrals · $(N)$ instanton counting in the presence of a full surface operator · 0.92
Cites as background 23 papers
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In [ref] it was conjectured that a simple surface operator in a (mass-deformed) conformal $(2)$ theory has a dual description in the Liouville theory in terms of the insertion of a certain degenerate field.
Loop and surface operators in N=2 gauge theory and Liouville modular geometry · $(N)$ instanton counting in the presence of a simple surface operator · 0.86
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In [ref] the following terminology was used: a full surface operator corresponds to the breaking of $(N)$ to $(1)^N-1$ and depends on $N-1$ continuous parameters (this is the maximal number of parameters possible), whereas a simple surface operator corresponds to the breaking of $(N)$ to $(N-1)×(1)$ and depends on one parameter.
Affine SL(2) conformal blocks from 4d gauge theories · Surface operators and instanton counting · 0.96
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Such surface operators were first considered in [ref] and have been further studied in [ref] .
Deformed Prepotential, Quantum Integrable System and Liouville Field Theory · Introduction · 0.82
Discussion
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