arXiv subjects

Congkao Wen

Publications and source records attributed to Congkao Wen.

At least 19 recordsLinked to original sources

arXiv2026

Energy-Energy Correlators at Strong Coupling

We study energy-energy correlators (EEC) in planar $\mathcal{N}=4$ super Yang-Mills theory at strong 't Hooft coupling $\lambda$. We consider the EEC in states created by half-BPS operators of arbitrary dimension $p$, and determine the corresponding event-shape function up to order $\lambda^{-3/2}$ from the worldsheet representation of the AdS Virasoro-Shapiro amplitude with Kaluza-Klein external states. For $p=2$ we compute the second curvature correction, which completes the EEC through order $\lambda^{-2}$; the new contribution improves the agreement with recently derived non-perturbative bounds at intermediate coupling. We further develop a complementary method in which the strong-coupling expansion coefficients of the EEC are extracted directly from the Wilson coefficients of low-energy expansion of the AdS Virasoro-Shapiro amplitude, and find the two approaches in perfect agreement.

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arXiv2026

Two-point functions in $4-2\,\varepsilon$ dimensions from localization

We study two-point functions of half-BPS operators in maximally supersymmetric Yang-Mills theory continued to $d=4-2\,\varepsilon$ dimensions. Using supersymmetric localization on $S^d$, we derive perturbative matrix-model expressions for the $\varepsilon$-expansion of these correlators and obtain all-loop results at leading order in $\varepsilon$ in the planar limit, with extensions to finite-$N$ corrections and higher-charge operators. We compare the localization results with direct perturbative computations in flat space. At order $\varepsilon$ the two descriptions agree perfectly, while at higher orders our construction fails to reproduce the perturbative data due to the breaking of conformal symmetry away from four dimensions. Nevertheless, in the case of the dimension-two operator we conjecture an all-loop formula at order $\varepsilon^2$ by exploiting the precise form of the mismatch.

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arXiv2026

Bootstrapping Giant Graviton Correlators

We develop bootstrap methods for mixed heavy-light four-point correlators $\langle GGOO\rangle$ in $\mathcal N=4$ super-Yang--Mills theory at large $N$, where $O\equiv {\cal O}_2$ is the chiral primary operator in the stress-tensor multiplet and $G$ are (dual) giant graviton operators with dimension of order $N$, including the maximal determinant case. The loop integrand is expanded in a basis of labelled $f$-graphs -- necessarily including non-planar topologies due to the dimension-$N$ nature of the giant gravitons -- and the coefficients are fixed by various bootstrap conditions including double-triangle and triangle rules in the cusp and OPE limits, integrated correlators from supersymmetric localization, and a ten-dimensional hidden symmetry, the latter also allowing extension to correlators involving generic chiral primaries $\mathcal{O}_k$. Together, these inputs uniquely determine the correlator through three loops, passing further non-trivial consistency checks. For the maximal determinant operator, we reproduce the known results through two loops and obtain the full three-loop correction.

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arXiv2026

$\mathcal{N}=4$ single-minus superamplitudes and dual superconformal symmetry

We construct the $\mathcal{N}=4$ supersymmetric completion of the recently proposed single-minus gluon amplitudes in $(2,2)$ signature, which are nonvanishing for all multiplicities on a half-collinear kinematic locus. The superamplitude factorises into a permutation-invariant measure $\Delta^{(n-1)}$ with uniform little-group weight that imposes the half-collinearity constraint, a piecewise constant stripped amplitude $\tilde{A}_{1\ldots n}$ that is helicity blind and dual conformal invariant, and (super)momentum conservation delta functions. For $n=3$, our superamplitude reduces to the known $\overline{\rm MHV}$ superamplitude. We prove dual superconformal covariance of the $n$-point superamplitude, and further analyse the $\mathrm{Gr}(k,n)$ Grassmannian integral at $k=1$. Finally, we present the corresponding single-minus superamplitude in $\mathcal{N}=8$ supergravity.

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arXiv2026

Giant graviton integrated correlators at finite coupling and all orders in $1/N$

We study the giant graviton integrated correlator in SU$(N)$ $\mathcal{N}=4$ super Yang-Mills at finite complexified coupling $\tau$. Despite the formidable complexity arising from the heavy nature of the operators considered, the large-$N$ expansion simplifies dramatically and exhibits manifest modular invariance. At each order in $1/N$, the expansion coefficients are linear combinations of non-holomorphic Eisenstein series thus capturing the full spectrum of perturbative and non-perturbative effects in the Yang-Mills coupling. Furthermore, we find additional contributions which are modular functions exponentially suppressed in $N$. In the 't Hooft limit, this yields an all-orders result in the $1/N$ expansion at arbitrary coupling $\lambda$, extending beyond prior results of leading orders. For the U$(N)$ theory, we obtain a closed-form expression valid for all $N$ and $\tau$, and show that the coupling-dependent sector of the large-$N$ expansion is universal between SU$(N)$ and U$(N)$ to all orders. Crucially, we exploit the integrated correlator constraints and determine the giant graviton correlator itself to two-loop order at finite $N$, previously only accessible in the planar limit.

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arXiv2026

Energy-Energy Correlator from the AdS Virasoro-Shapiro Amplitude

We establish a precise formula relating the world-sheet integral of the AdS Virasoro-Shapiro amplitude to the energy-energy correlator (EEC) in $\mathcal{N}=4$ super Yang-Mills theory at strong coupling. This mapping allows us to evaluate the coefficients of the AdS curvature expansion of the EEC in terms of the world-sheet integral over a unit disk. To illustrate this idea, we explicitly compute the flat-space contribution and the first curvature correction to the EEC. Our results provide a rigorous description of the stringy energy flow, demonstrating how world-sheet correlators imprint themselves on collider observables and offering a potential template for effective string descriptions of energy correlators in general gauge theories.

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arXiv2025

Surprising one-loop finiteness of 6D half-maximal supergravities

In four dimensions, it has long been established that gravity coupled to matter exhibits ultraviolet divergences at one loop, irrespective of supersymmetry. Notably, the four-matter one-loop amplitudes of half-maximal supergravity coupled to Maxwell multiplets were shown in the 1970s to be divergent. Surprisingly, we demonstrate in this work that half-maximal theories can nevertheless become one-loop finite when uplifted to higher dimensions, contrary to naive expectations. Specifically, we study the ultraviolet properties of the four-matter and two-matter two-graviton amplitudes in six-dimensional $\mathcal{N}=(2,0)$ and $\mathcal{N}=(1,1)$ supergravities, coupled to $n_T$ tensor and $n_V$ vector multiplets, respectively. We find that the one-loop amplitudes are finite for $n_T=21$ and $n_V=20$. This finiteness is unexpected, as symmetry-preserving counterterms do exist. Interestingly, both values exactly correspond to low-energy limits of type II string theories compactified on K3, which hints at possible origins to the surprising cancellations.

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arXiv2025

Universality of giant graviton correlators

We study a class of heavy-heavy-light-light (HHLL) integrated correlators of superconformal primary operators in $SU(N)$ $\mathcal{N}=4$ super Yang-Mills theory involving two light operators from the stress-tensor multiplet and two heavy operators whose conformal dimensions are proportional to the number of colours $N$. In the large-$N$ limit these heavy operators are dual to sphere and AdS giant gravitons, realised holographically as D3-branes wrapping an $S^3$ inside either the $S^5$ or the $AdS_5$ factor of the $AdS_5 \times S^5$ background geometry. These HHLL correlators thus describe the scattering of two gravitons off D3-branes. In the planar limit we derive exact expressions for the HHLL integrated correlators as functions of both the 't Hooft coupling and the giant graviton dimension. Remarkably, despite exhibiting distinct perturbative expansions at weak coupling, these integrated correlators share the same universal asymptotic series at strong coupling. We also demonstrate that a seemingly unrelated integrated correlator in a $USp(2N)$ $\mathcal{N}=2$ gauge theory, holographically dual to gluon-graviton scattering off D7-branes, exhibits precisely the same strong coupling asymptotic series. This reveals a striking universality of D-brane scattering processes. Furthermore, we compute the exponentially suppressed corrections at strong coupling for all these observables, showing that they are precisely the non-perturbative effects that account for the differences between these integrated correlators beyond the universal asymptotic series. Finally, we comment on the resurgent properties and the holographic interpretation of these exponentially suppressed terms.

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arXiv2025

Large charge meets semiclassics in $\mathcal{N}=4$ super Yang-Mills

We study the large-charge sector of $\mathcal{N}=4$ super Yang-Mills theory (SYM) with $SU(N)$ gauge group by constructing a special class of half-BPS heavy operators, termed "canonical operators". Such operators exhibit remarkable simplicity in the large-charge 't Hooft limit, where the dimension of the operators $\Delta \to \infty$ with $\Delta\, g_{\text{YM}}^2$ held finite. Canonical operator insertions in this regime map $\mathcal{N}=4$ SYM onto the Coulomb branch, by assigning a classical profile to the scalar fields with non-vanishing values along the diagonals given by the roots of unity. We follow a semiclassical approach to study two-point, three-point and Heavy-Heavy-Light-Light (HHLL) correlators. In particular we show that HHLL correlators in the large-charge 't Hooft limit are computed as two-point functions in a background determined by the classical profiles. We provide consistent evidence of our findings by computing the same observables via supersymmetric localization.

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arXiv2025

Modular Features of Superstring Scattering Amplitudes: Generalised Eisenstein Series and Theta Lifts

In previous papers it has been shown that the coefficients of terms in the large-$N$ expansion of a certain integrated four-point correlator of superconformal primary operators in $\mathcal{N}=4$ supersymmetric Yang-Mills theory are rational sums of real-analytic Eisenstein series and "generalised Eisenstein series''. The latter are novel modular functions first encountered in the context of graviton amplitudes in type IIB superstring theory. Similar modular functions, known as two-loop modular graph functions, are also encountered in the low-energy expansion of the integrand of genus-one closed superstring amplitudes. In this paper we further develop the mathematical structure of such generalised Eisenstein series emphasising, in particular, the occurrence of $L$-values of holomorphic cusp forms in their Fourier mode decomposition. We show that both the coefficients in the large-$N$ expansion of the integrated correlator and two-loop modular graph functions admit a unifying description in terms of four-dimensional lattice sums generated by theta lifts of local Maass functions, which generalise the structure of real-analytic Eisenstein series. Through the theta lift representation, we demonstrate that elements belonging to these two families of non-holomorphic modular functions can be expressed as rational linear combinations of generalised Eisenstein series for which all the $L$-values of holomorphic cusp forms precisely cancel.

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arXiv2024

Electromagnetic Duality for Line Defect Correlators in $\mathcal{N}=4$ Super Yang-Mills Theory

We study particular integrated correlation functions of two superconformal primary operators of the stress tensor multiplet in the presence of a half-BPS line defect labelled by electromagnetic charges $(p,q)$ in $\mathcal{N}=4$ supersymmetric Yang-Mills theory (SYM) with gauge group $SU(N)$. An important consequence of ${\rm SL}(2,\mathbb{Z})$ electromagnetic duality in $\mathcal{N}=4$ SYM is that correlators of line defect operators with different charges $(p,q)$ must be related in a non-trivial manner when the complex coupling $\tau=\theta/(2\pi)+4\pi i /g_{_{\rm YM}}^2$ is transformed appropriately. In this work we introduce a novel class of real-analytic functions whose automorphic properties with respect to ${\rm SL}(2,\mathbb{Z})$ match the expected transformations of line defect operators in $\mathcal{N}=4$ SYM under electromagnetic duality. At large $N$ and fixed $\tau$, the correlation functions we consider are related to scattering amplitudes of two gravitons from extended $(p,q)$-strings in the holographic dual type IIB superstring theory. We show that the large-$N$ expansion coefficients of the integrated two-point line defect correlators are given by finite linear combinations with rational coefficients of elements belonging to this class of automorphic functions. On the other hand, for any fixed value of $N$ we conjecture that the line defect integrated correlators can be expressed as formal infinite series over such automorphic functions. The resummation of this series produces a simple lattice sum representation for the integrated line defect correlator that manifests its automorphic properties. We explicitly demonstrate this construction for the cases with gauge group $SU(2)$ and $SU(3)$. Our results give direct access to non-perturbative integrated correlators in the presence of an 't Hooft-line defect, observables otherwise very difficult to compute by other means.

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arXiv2024

All-loop heavy-heavy-light-light correlators in $\mathcal{N}=4$ super Yang-Mills theory

We study Heavy-Heavy-Light-Light (HHLL) correlators $\langle \mathcal{H} \mathcal{H} \mathcal{O}_2 \mathcal{O}_2 \rangle$ in $\mathcal{N}=4$ super Yang-Mills theory with $SU(N)$ gauge group at generic $N$. The light operator $\mathcal{O}_2$ is the dimension two superconformal primary in the stress tensor multiplet and $\mathcal{H}$ is a general half-BPS superconformal primary operator with dimension (or $R$-charge) $\Delta_{\mathcal{H}}$. We consider the large-charge 't Hooft limit, where $\Delta_{\mathcal{H}} \rightarrow \infty$ with fixed 't Hooft-like coupling $\lambda:=\Delta_{\mathcal{H}}\, g_{_{\rm YM}}^2$. We show that the $L$-loop contribution to the HHLL correlators in the leading large-charge limit is universal for any choice of the heavy operator $\mathcal{H}$, given as $\lambda^L \sum_{\ell=0}^{L} \Phi^{(\ell)} \Phi^{(L-\ell)}$ with an $SU(N)$ colour factor coefficient, where $\Phi^{(\ell)}$ is the ladder Feynman integral, which is known to all loops. The dependence on the explicit form of the heavy operator lies only in the colour factor coefficients. We determine such colour factors for several classes of heavy operators, and show that the large charge limit leads to minimal powers of $N$. For the special class of "canonical heavy operators", one can even resum the all-loop ladder integrals and determine the correlators at finite $\lambda$. Furthermore, upon integrating over the spacetime dependence, the resulting integrated HHLL correlators agree with the existing results derived from supersymmetric localisation. Finally, as an application of the all-loop analytic results, we derive exact expressions for the structure constants of two heavy operators and the Konishi operator, finding intriguing connections with the integrated HHLL correlators.

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arXiv2024

Exact results for giant graviton four-point correlators

We study the four-point correlator $\langle \mathcal{O}_2 \mathcal{O}_2 \mathcal{D} \mathcal{D} \rangle$ in $\mathcal{N}=4$ super Yang-Mills theory (SYM) with $SU(N)$ gauge group, where $\mathcal{O}_2$ represents the superconformal primary operator with dimension two, while $\mathcal{D}$ denotes a determinant operator of dimension $N$, which is holographically dual to a giant graviton D3-brane extending along $S^5$. We analyse the integrated correlator associated with this observable, obtained after integrating out the spacetime dependence over a supersymmetric invariant measure. Similarly to other classes of integrated correlators in $\mathcal{N}=4$ SYM, this integrated correlator can be computed through supersymmetric localisation on the four-sphere. Employing matrix-model recursive techniques, we demonstrate that the integrated correlator can be reformulated as an infinite sum of protected three-point functions with known coefficients. This insight allows us to circumvent the complexity associated with the dimension-$N$ determinant operator, significantly streamlining the large-$N$ expansion of the integrated correlator. In the planar limit and beyond, we derive exact results for the integrated correlator valid for all values of the 't Hooft coupling, and investigate the resurgent properties of their strong coupling expansion. Additionally, in the large-$N$ expansion with fixed (complexified) Yang-Mills coupling, we deduce the $SL(2, \mathbb{Z})$ completion of these results in terms of the non-holomorphic Eisenstein series. The proposed modular functions are confirmed by explicit instanton calculations from the matrix model, and agree with expectations from the holographic dual picture of known results in type IIB string theory.

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arXiv2024

Kinematic Hopf algebra for amplitudes from higher-derivative operators

Recently it has been shown that Bern-Carrasco-Johansson (BCJ) numerators of colour-kinematic duality for tree-level scattering amplitudes in Yang-Mills theory (coupled with scalars) can be determined using a quasi-shuffle Hopf algebra. In this paper we consider the same theory, but with higher-derivative corrections of the forms $α' F^3$ and $α'^2 F^4$, where $F$ is the field strength. In the heavy mass limit of the scalars, we show that the BCJ numerators of these higher-derivative theories are governed by the same Hopf algebra. In particular, the kinematic algebraic structure is unaltered and the derivative corrections only arise when mapping the abstract algebraic generators to physical BCJ numerators. The underlying kinematic Hopf algebra enables us to obtain a compact expression for the BCJ numerators of any number of gluons and two heavy scalars for amplitudes with higher-derivative operators. The pure gluon BCJ numerators can also be obtained from our results by a simple factorisation limit where the massive particles decouple.

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arXiv2024

Kinematic Hopf algebra and BCJ numerators at finite $α'$

In this letter, starting from a kinematic Hopf algebra, we first construct a closed-form formula for all Bern-Carrasco-Johansson (BCJ) numerators in Yang-Mills (YM) theory with infinite orders of $α'$ corrections, known as $\rm DF^2+YM$ theory, when coupled to two heavy particles which can be removed through a simple factorization limit. The full $α'$ dependence appears simply in massive physical propagator factors, with factorization strongly constraining the construction. The intricate structure induced by the massive poles also naturally leads us to find a novel closed-form and local expression for BCJ numerators in usual pure YM theory, based directly on the kinematic Hopf algebra.

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arXiv2024

Integrated correlators in $\mathcal{N}=4$ SYM beyond localisation

We study integrated correlators of four superconformal primaries $\mathcal{O}_{p}$ with arbitrary charges $p$ in $\mathcal{N}{=}4$ super Yang-Mills theory (SYM). The $ \langle \mathcal{O}_{2} \mathcal{O}_{2} \mathcal{O}_{p} \mathcal{O}_{p} \rangle$ integrated correlators can be computed by supersymmetric localisation, whereas correlators with more general charges are currently not accessible from this method and in general contain complicated multi-zeta values. Nevertheless we observe that if one sums over the contributions from all different channels in a given correlator, then all the multi-zeta values (and products of zeta's) cancel leaving only $ζ(2\ell{+}1)$ at $\ell$-loops. We then propose an exact expression of such integrated correlators in the planar limit, valid for arbitrary 't Hooft coupling. The expression matches with the known exact localisation-based results for specific charges, as well as with all existing perturbative and strong-coupling results in the literature for more general charges. As an application, our result is used to determine certain $7$-loop Feynman integral periods and fix previously unknown coefficients in the correlators at strong coupling.

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arXiv2023

Relations between integrated correlators in $\mathcal{N}=4$ Supersymmetric Yang--Mills Theory

Integrated correlation functions in $\mathcal{N}=4$ supersymmetric Yang--Mills theory with gauge group $SU(N)$ can be expressed in terms of the localised $S^4$ partition function, $Z_N$, deformed by a mass $m$. Two such cases are $\mathcal{C}_N=(\text{Im} τ)^2 \partial_τ\partial_{\barτ} \partial_m^2\log Z_N\vert_{m=0}$ and $\mathcal{H}_N=\partial_m^4\log Z_N\vert_{m=0}$, which are modular invariant functions of the complex coupling $τ$. While $\mathcal{C}_N$ was recently written in terms of a two-dimensional lattice sum for any $N$ and $τ$, $\mathcal{H}_N$ has only been evaluated up to order $1/N^3$ in a large-$N$ expansion in terms of modular invariant functions with no known lattice sum realisation. Here we develop methods for evaluating $\mathcal{H}_N$ to any desired order in $1/N$ and finite $τ$. We use this new data to constrain higher loop corrections to the stress tensor correlator, and give evidence for several intriguing relations between $\mathcal{H}_N$ and $\mathcal{C}_N$ to all orders in $1/N$. We also give evidence that the coefficients of the $1/N$ expansion of $\mathcal{H}_N$ can be written as lattice sums to all orders. Lastly, these large $N$ and finite $τ$ results are used to accurately estimate the integrated correlators at finite $N$ and finite $τ$.

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arXiv2023

Generating functions and large-charge expansion of integrated correlators in $\mathcal{N}=4$ supersymmetric Yang-Mills theory

We recently proved that, when integrating out spacetime dependence with a certain measure, four-point correlators $\langle \mathcal{O}_2\mathcal{O}_2\mathcal{O}^{(i)}_p \mathcal{O}^{(j)}_p \rangle$ in $SU(N)$ $\mathcal{N}=4$ super Yang-Mills are governed by a universal Laplace-difference equation. Here $\mathcal{O}^{(i)}_p$ is a superconformal primary with charge $p$ and degeneracy $i$. These observables, called integrated correlators, are modular functions of coupling $τ$. The Laplace-difference equation relates integrated correlators of different charges recursively. In this paper, we introduce generating functions for the integrated correlators that sum over the charge. By utilising the Laplace-difference equation, we determine the generating functions given initial data. We show that the transseries of the integrated correlators in the large-$p$ (large-charge) expansion consists of three parts: 1) is independent of $τ$ as a power series in $1/p$, plus an additional $\log(p)$ term if $i=j$; 2) is a power series in $1/p$, with coefficients given by a sum of the non-holomorphic Eisenstein series; 3) is a sum of exponentially decayed modular functions in the large-$p$ limit, which can be viewed as a generalisation of the non-holomorphic Eisenstein series. When $i=j$, there is an additional modular function that is independent of $p$ and is determined by the integrated correlator with $p=2$. The Laplace-difference equation was obtained with a reorganisation of the operators that means the large-charge limit is taken in a particular way here. From the $SL(2,\mathbb{Z})$-invariant results, we also determine the generalised 't Hooft genus expansion and associated large-$p$ non-perturbative corrections of the integrated correlators by introducing $λ= pg^2_{YM}$. The generating functions have subtle differences between even and odd $N$ with important consequences in resurgence.

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