arXiv subjects

Matteo Beccaria

Publications and source records attributed to Matteo Beccaria.

At least 37 records · Page 2Linked to original sources

arXiv2024

Large N expansion of superconformal index of k=1 ABJM theory and semiclassical M5 brane partition function

It was shown in arXiv:2309.10786 that the leading non-perturbative contribution to the large $N$ expansion of superconformal index of (2,0) 6d theory (which describes low-energy dynamics of $N$ coincident M5 branes) is reproduced by the semiclassical partition function of quantum M2 brane wrapped on $S^{1}\times S^{2}$ in a twisted version of AdS$_{7}\times S^{4}$ background. Here we demonstrate an analogous relation for the leading non-perturbative contribution to the large $N$ expansion of the superconformal index of the ${n}=8$ supersymmetric level-one $U(N) \times U(N)$ ABJM theory (which describes low-energy dynamics of $N$ coincident M2 branes). The roles of M2 and M5 branes get effectively interchanged. Namely, the large $N$ correction to the ABJM index is found to be given by the semiclassical partition function of quantum M5 brane wrapped on $S^1 \times S^5$ in a twisted version of AdS$_{4}\times S^{7}$ background. This effectively confirms the suggestion for the "M5 brane index" made in arXiv:2007.05213 on the basis of indirect superconformal algebra considerations.

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arXiv2024

Large $N$ Schur index of $\mathcal N=4$ SYM from semiclassical D3 brane

We consider the refined Schur superconformal index of 4d $\mathcal N=4$ $U(N)$ SYM and the first term of its giant-graviton expansion, first predicted in arXiv:2001.11667 using indirect superconformal algebra considerations and analytic continuation of fugacities. This correction is the leading non-perturbative correction to the index at large $N$ and we reproduce it from the semiclassical partition function of quantum D3 brane wrapped on $S^{1}\times S^{3}$ in a twisted modification of the $AdS_{5}\times S^{5}$ string background, depending on the index R-symmetry fugacity. Our calculation does not exploit directly supersymmetry. It is based on the determination of the partition function of the various bosonic and fermionic fluctuations on the wrapped brane whose action is conformal with specific constant holonomies along thermal cycle. We show how those partition functions may be obtained by adapting the operator counting method of Cardy to the twisted background.

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arXiv2023

(2,0) theory on $S^5 \times S^1$ and quantum M2 branes

The superconformal index $Z$ of the 6d (2,0) theory on $S^5 \times S^1$ (which is related to the localization partition function of 5d SYM on $S^5$) should be captured at large $N$ by the quantum M2 brane theory in the dual M-theory background. Generalizing the type IIA string theory limit of this relation discussed in arXiv:2111.15493 and arXiv:2304.12340, we consider semiclassically quantized M2 branes in a half-supersymmetric 11d background which is a twisted product of thermal AdS$_7$ and $S^4$. We show that the leading non-perturbative term at large $N$ is reproduced precisely by the 1-loop partition function of an "instanton" M2 brane wrapped on $S^1\times S^2$ with $S^2\subset S^4$. Similarly, the (2,0) theory analog of the BPS Wilson loop expectation value is reproduced by the partition function of a "defect" M2 brane wrapped on thermal AdS$_3\subset$ AdS$_7$. We comment on a curious analogy of these results with similar computations in arXiv:2303.15207 and arXiv:2307.14112 of the partition function of quantum M2 branes in AdS$_4 \times S^7/\mathbb Z_k$ which reproduced the corresponding localization expressions in the ABJM 3d gauge theory.

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arXiv2023

Instanton contributions to the ABJM free energy from quantum M2 branes

We present a quantum M2 brane computation of the instanton prefactor in the leading non-perturbative contribution to the ABJM 3-sphere free energy at large $N$ and fixed level $k$. Using supersymmetric localization, such instanton contribution was found earlier to take the form $F^{\rm inst}(N,k) = - ({\sin^{2} \frac{2π}{k}} )^{-1} \, \exp (-2π\sqrt\frac{2N}{k}) + \cdots$ . The exponent comes from the action of an M2 brane instanton wrapped on $S^3/{\mathbb Z}_k$, which represents the M-theory uplift of the $\mathbb{C}P^1$ instanton in type IIA string theory on AdS$_4 \times \mathbb{C}P^3$. The IIA string computation of the leading large $k$ term in the instanton prefactor was recently performed in arXiv:2304.12340. Here we find that the exact value of the prefactor $({\sin^{2} \frac{2π}{k}})^{-1} $ is reproduced by the 1-loop term in the M2 brane partition function expanded near the $S^3/\mathbb{Z}_k$ instanton configuration. As in the Wilson loop example in arXiv:2303.15207, the quantum M2 brane computation is well defined and produces a finite result in exact agreement with localization.

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arXiv2023

Comments on ABJM free energy on $S^{3}$ at large $N$ and perturbative expansions in M-theory and string theory

We compare large $N$ expansion of the localization result for the free energy $F$ in the 3d $\mathcal{N}=6$ superconformal $U(N)_k \times U(N)_{-k}$ Chern-Simons-matter theory to its AdS/CFT counterpart, i.e. to the perturbative expansion of M-theory partition function on AdS$_{4}\times S^{7}/\mathbb{Z}_{k}$ and to the weak string coupling expansion of type IIA effective action on AdS$_{4}\times {\rm CP}^3$. We show that the general form of the perturbative expansions of $F$ on the two sides of the AdS/CFT duality is indeed the same. Moreover, the transcendentality properties of the coefficients in the large $N$, large $k$ expansion of $F$ match those in the corresponding M-theory or string theory expansions. To shed light on the structure of the 1-loop M-theory partition function on AdS$_{4}\times S^{7}/\mathbb{Z}_{k}$ we use the expression for the 1-loop 4-graviton scattering amplitude in the 11d supergravity. We also use the known information about the transcendental coefficients of the leading curvature invariants in the low-energy effective action of type II string theory. Matching of the remaining rational factors in the coefficients requires a precise information about currently unknown RR field strength terms in the corresponding superinvariants.

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arXiv2023

On the brane expansion of the Schur index

We consider the Schur index of $\mathcal N=4$ $U(N)$ SYM theory in 4d and its holographic giant graviton-type expansion at finite $N$. We compute the world-volume brane superconformal index by a recently proposed definition of the gauge holonomy integral as a multivariate residue. This is evaluated by a novel deformation algorithm that avoids Gröbner basis methods. Various terms of the brane expansion are computed and shown to be free of wall-crossing singularities to the order we explored. The relation between the brane expansion and previous giant graviton-type represenations of the Schur index is clarified.

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arXiv2023

On the structure of non-planar strong coupling corrections to correlators of BPS Wilson loops and chiral primary operators

Starting with some known localization (matrix model) representations for correlators involving 1/2 BPS circular Wilson loop $\cal W$ in ${\cal N}=4$ SYM theory we work out their $1/N$ expansions in the limit of large 't Hooft coupling $λ$. Motivated by a possibility of eventual matching to higher genus corrections in dual string theory we follow arXiv:2007.08512 and express the result in terms of the string coupling $g_{\rm s} \sim g^2_{\rm YM} \sim λ/N$ and string tension $T\sim \sqrt λ$. Keeping only the leading in $1/T$ term at each order in $g_{\rm s} $ we observe that while the expansion of $\langle {\cal W} \rangle$ is a series in $g^2_{\rm s} /T$, the correlator of the Wilson loop with chiral primary operators ${\cal O}_J $ has expansion in powers of $g^2_{\rm s}/T^2$. Like in the case of $\langle {\cal W} \rangle$ where these leading terms are known to resum into an exponential of a "one-handle" contribution $\sim g^2_{\rm s} /T$, the leading strong coupling terms in $\langle {\cal W}\, {\cal O}_J \rangle$ sum up to a simple square root function of $g^2_{\rm s}/T^2$. Analogous expansions in powers of $g^2_{\rm s}/T$ are found for correlators of several coincident Wilson loops and they again have a simple resummed form. We also find similar expansions for correlators of coincident 1/2 BPS Wilson loops in the ABJM theory.

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arXiv2023

$1/N$ expansion of the D3-D5 defect CFT

We consider four dimensional $U(N)$ $\mathcal N=4$ SYM theory interacting with a 3d $\mathcal N=4$ theory living on a codimension-one interface and holographically dual to the D3-D5 system without flux. Localization captures several observables in this dCFT, including its free energy, related to the defect expectation value, and single trace $\frac{1}{2}$-BPS composite scalars. These quantities may be computed in a hermitian one-matrix model with non-polynomial single-trace potential. We exploit the integrable Volterra hierarchy underlying the matrix model and systematically study its $1/N$ expansion at any value of the 't Hooft coupling. In particular, the strong coupling regime is determined -- up to non-perturbative exponentially suppressed corrections -- by differential relations that constrain higher order terms in the $1/N$ expansion. The analysis is extended to the model with $SU(N)$ gauge symmetry by resorting to the more general Toda lattice equations.

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arXiv2022

Did Maxwell dream of electrical bacteria?

We propose a model for bacterial Quorum Sensing based on an auxiliary electrostatic-like interac-tion originating from a fictitious electrical charge that represents bacteria activity. A cooperative mechanism for charge/activity exchange is introduced to implement chemotaxis and replication. The bacteria system is thus represented by means of a complex resistor network where link re-sistances take into account the allowed activity-flow among individuals. By explicit spatial sto-chastic simulations, we show that the model exhibits different quasi-realistic behaviors from colo-ny formation to biofilm aggregation. The electrical signal associated with Quorum Sensing is ana-lyzed in space and time and provides useful information about the colony dynamics. In particular, we analyze the transition between the planktonic and the colony phases as the intensity of Quorum Sensing is varied.

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arXiv2022

BPS Wilson loop in $\mathcal N=2$ superconformal $SU(N)$ "orientifold" gauge theory and weak-strong coupling interpolation

We consider the expectation value $\langle \cal W \rangle$ of the circular BPS Wilson loop in ${\cal N}=2$ superconformal $SU(N)$ gauge theory containing a vector multiplet coupled to two hypermultiplets in rank-2 symmetric and antisymmetric representations. This model admits a regular large $N$ expansion, is planar-equivalent to ${\cal N}=4$ SYM theory and is expected to be dual to a certain orbifold/orientifold projection of AdS$_5\times S^5$ superstring theory. On the string theory side $\langle\cal W \rangle $ is represented by the path integral expanded near the same AdS$_2$ minimal surface as in the maximally supersymmetric case. Following the string theory argument in arXiv:2007.08512, we suggest that as in the ${\cal N}=4$ SYM case and in the ${\cal N}=2$ $SU(N) \times SU(N)$ superconformal quiver theory discussed in arXiv:2102.07696, the coefficient of the leading non-planar $1/N^2$ correction in $\langle\cal W \rangle $ should have the universal $λ^{3/2}$ scaling at large 't Hooft coupling. We confirm this prediction by starting with the localization matrix model representation for $\langle\cal W \rangle $. We complement the analytic derivation of the $λ^{3/2}$ scaling by a numerical high-precision resummation and extrapolation of the weak-coupling expansion using conformal mapping improved Padé analysis.

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arXiv2022

$1/N$ expansion of circular Wilson loop in $\mathcal N=2$ superconformal $SU(N)\times SU(N)$ quiver

Localization approach to $\mathcal N=2$ superconformal $SU(N) \times SU(N)$ quiver theory leads to a non-Gaussian two-matrix model representation for the expectation value of BPS circular $SU(N)$ Wilson loop $\langle\mathcal W\rangle$. We study the subleading $1/N^2$ term in the large $N$ expansion of $\langle\mathcal W\rangle$ at weak and strong coupling. We concentrate on the case of the symmetric quiver with equal gauge couplings which is equivalent to the $\mathbb Z_{2}$ orbifold of the $SU(2N)$ $\mathcal N=4$ SYM theory. This orbifold gauge theory should be dual to type IIB superstring in ${\rm AdS}_5\times (S^{5}/\mathbb Z_{2})$. We present a string theory argument suggesting that the $1/N^2$ term in $\langle\mathcal W\rangle$ in the orbifold theory should have the same strong-coupling asymptotics $ λ^{3/2}$ as in the $\mathcal N=4$ SYM case. We support this prediction by a numerical study of the localization matrix model on the gauge theory side. We also find a relation between the $1/N^2$ term in the Wilson loop expectation value and the derivative of the free energy of the orbifold gauge theory on 4-sphere.

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arXiv2022

Wilson loop in general representation and RG flow in 1d defect QFT

The generalized Wilson loop operator interpolating between the supersymmetric and the ordinary Wilson loop in ${\cal N}=4$ SYM theory provides an interesting example of renormalization group flow on a line defect: the scalar coupling parameter $ζ$ has a non-trivial beta function and may be viewed as a running coupling constant in a 1d defect QFT. In this paper we continue the study of this operator, generalizing previous results for the beta function and Wilson loop expectation value to the case of an arbitrary representation of the gauge group and beyond the planar limit. Focusing on the scalar ladder limit where the generalized Wilson loop reduces to a purely scalar line operator in a free adjoint theory, and specializing to the case of the rank $k$ symmetric representation of $SU(N)$, we also consider a certain semiclassical limit where $k$ is taken to infinity with the product $k\, ζ^2$ fixed. This limit can be conveniently studied using a 1d defect QFT representation in terms of $N$ commuting bosons. Using this representation, we compute the beta function and the circular loop expectation value in the large $k$ limit, and use it to derive constraints on the structure of the beta function for general representation. We discuss the corresponding 1d RG flow and comment on the consistency of the results with the 1d defect version of the F-theorem.

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arXiv2021

Higher order RG flow on the Wilson line in $\mathcal{N}=4$ SYM

Extending earlier work, we find the two-loop term in the beta-function for the scalar coupling $ζ$ in a generalized Wilson loop operator of the $\mathcal{N}=4$ SYM theory, working in the planar weak-coupling expansion. The beta-function for $ζ$ has fixed points at $ζ=\pm 1$ and $ζ=0$, corresponding respectively to the supersymmetric Wilson-Maldacena loop and to the standard Wilson loop without scalar coupling. As a consequence of our result for the beta-function, we obtain a prediction for the two-loop term in the anomalous dimension of the scalar field inserted on the standard Wilson loop. We also find a subset of higher-loop contributions (with highest powers of $ζ$ at each order in `t Hooft coupling) coming from the scalar ladder graphs determining the corresponding terms in the five-loop beta-function. We discuss the related structure of the circular Wilson loop expectation value commenting, in particular, on consistency with a 1d defect version of the F-theorem. We also compute (to two loops in the planar ladder approximation) the two-point correlators of scalars inserted on the Wilson line.

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arXiv2021

Non-supersymmetric Wilson loop in N=4 SYM and defect 1d CFT

Following Polchinski and Sully (arXiv:1104.5077), we consider a generalized Wilson loop operator containing a constant parameter $ζ$ in front of the scalar coupling term, so that $ζ=0$ corresponds to the standard Wilson loop, while $ζ=1$ to the locally supersymmetric one. We compute the expectation value of this operator for circular loop as a function of $ζ$ to second order in the planar weak coupling expansion in N=4 SYM theory. We then explain the relation of the expansion near the two conformal points $ζ=0$ and $ζ=1$ to the correlators of scalar operators inserted on the loop. We also discuss the $AdS_5\times S^5$ string 1-loop correction to the strong-coupling expansion of the standard circular Wilson loop, as well as its generalization to the case of mixed boundary conditions on the five-sphere coordinates, corresponding to general $ζ$. From the point of view of the defect 1d CFT defined on the Wilson line, the $ζ$-dependent term can be seen as a perturbation driving a RG flow from the standard Wilson loop in the UV to the supersymmetric Wilson loop in the IR. Both at weak and strong coupling we find that the logarithm of the expectation value of the standard Wilson loop for the circular contour is larger than that of the supersymmetric one, which appears to be in agreement with the 1d analog of the F-theorem.

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arXiv2021

On non-supersymmetric generalizations of the Wilson-Maldacena loops in N=4 SYM

Building on our previous work arXiv:1712.06874 we consider one-parameter Polchinski-Sully generalization of the Wilson-Maldacena (WM) loops in planar N=4 SYM theory. This breaks local supersymmetry of WM loop and leads to running of the deformation parameter $ζ$. We compute the three-loop ladder diagram contribution to the expectation value of the circular loop which gives the full answer for large $ζ$. The limit $ζ\gg 1$, $λζ^2=$ fixed in which the expectation value is determined by the Gaussian adjoint scalar path integral might be exactly solvable despite the lack of global supersymmetry. We study similar generalization of the 1/4-BPS "latitude" WM loop which depends on two parameters (in addition to the 't Hooft coupling $λ$). One may also introduce another supersymmetry-breaking parameter -- the winding number of the scalar coupling circle. We find the two-loop expression for the expectation value of the associated loop by combining the ladder diagram contribution with an indirect determination of the non-ladder contribution using 1d defect CFT perturbation theory.

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arXiv2021

On topological recursion for Wilson loops in $\mathcal N=4$ SYM at strong coupling

We consider $U(N)$ $\mathcal N=4$ super Yang-Mills theory and discuss how to extract the strong coupling limit of non-planar corrections to observables involving the $\frac{1}{2}$-BPS Wilson loop. Our approach is based on a suitable saddle point treatment of the Eynard-Orantin topological recursion in the Gaussian matrix model. Working directly at strong coupling we avoid the usual procedure of first computing observables at finite planar coupling $λ$, order by order in $1/N$, and then taking the $λ\gg 1$ limit. In the proposed approach, matrix model multi-point resolvents take a simplified form and some structures of the genus expansion, hardly visible at low order, may be identified and rigorously proved. As a sample application, we consider the expectation value of multiple coincident circular supersymmetric Wilson loops as well as their correlator with single trace chiral operators. For these quantities we provide novel results about the structure of their genus expansion at large tension, generalising recent results in arXiv:2011.02885.

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arXiv2020

Boundary correlators in WZW model on AdS$_2$

Boundary correlators of elementary fields in some 2d conformal field theories defined on AdS$_2$ have a particularly simple structure. For example, the correlators of the Liouville scalar happen to be the same as the correlators of the chiral component of the stress tensor on a plane restricted to the real line. Here we show that an analogous relation is true also in the WZW model: boundary correlators of the WZW scalars have the same structure as the correlators of chiral Kač-Moody currents. This is checked at the level of the tree and one-loop Witten diagrams in AdS$_2$. We also compute some tree-level correlators in a generic $σ$-model defined on AdS$_2$ and show that they simplify only in the WZW case where an extra Kač-Moody symmetry appears. In particular, the terms in 4-point correlators having logarithmic dependence on 1d cross-ratio cancel only at the WZW point. One motivation behind this work is to learn how to compute AdS$_2$ loop corrections in 2d models with derivative interactions related to the study of correlators of operators on Wilson loops in string theory in AdS.

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arXiv2020

Supersymmetric Liouville theory in AdS$_2$ and AdS/CFT

In a series of recent papers, a special kind of AdS$_2$/CFT$_1$ duality was observed: the boundary correlators of elementary fields that appear in the Lagrangian of a 2d conformal theory in rigid AdS$_2$ background are the same as the correlators of the corresponding primary operators in the chiral half of that 2d CFT in flat space restricted to the real line. The examples considered were: (i) the Liouville theory where the operator dual to the Liouville scalar in AdS$_2$ is the stress tensor; (ii) the abelian Toda theory where the operators dual to the Toda scalars are the $\mathcal W$-algebra generators; (iii) the non-abelian Toda theory where the Liouville field is dual to the stress tensor while the extra gauged WZW theory scalars are dual to non-abelian parafermionic operators. By direct Witten diagram computations in AdS$_2$ one can check that the structure of the boundary correlators is indeed consistent with the Virasoro (or higher) symmetry. Here we consider a supersymmetric generalization: the $\mathcal N=1$ superconformal Liouville theory in AdS$_2$. We start with the super Liouville theory coupled to 2d supergravity and show that a consistent restriction to rigid AdS$_2$ background requires a non-zero value of the supergravity auxiliary field and thus a modification of the Liouville potential from its familiar flat-space form. We show that the Liouville scalar and its fermionic partner are dual to the chiral half of the stress tensor and the supercurrent of the super Liouville theory on the plane. We perform tests supporting the duality by explicitly computing AdS$_2$ Witten diagrams with bosonic and fermionic loops.

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