arXiv subjects

Nikolay Bobev

Publications and source records attributed to Nikolay Bobev.

At least 37 records · Page 2Linked to original sources

arXiv2023

Large $N$ Partition Functions of the ABJM Theory

We study the large $N$ limit of some supersymmetric partition functions of the $\mathrm{U}(N)_{k}\times \mathrm{U}(N)_{-k}$ ABJM theory computed by supersymmetric localization. We conjecture an explicit expression, valid to all orders in the large $N$ limit, for the partition function on the $\mathrm{U}(1)\times \mathrm{U}(1)$ invariant squashed sphere in the presence of real masses in terms of an Airy function. Several non-trivial tests of this conjecture are presented. In addition, we derive an explicit compact expression for the topologically twisted index of the ABJM theory valid at fixed $k$ to all orders in the $1/N$ expansion. We use these results to derive the topologically twisted index and the sphere partition function in the 't Hooft limit which correspond to genus $\tt g$ type IIA string theory free energies to all orders in the $α'$ expansion. We discuss the implications of our results for holography and the physics of AdS$_4$ black holes.

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arXiv2023

The planar limit of the $\mathcal{N} = 2$ $\mathbf{E}$-theory: numerical calculations and the large $λ$ expansion

We study correlation functions of local operators and Wilson loop expectation values in the planar limit of a 4d $\mathcal{N}=2$ superconformal ${\rm SU}(N)$ YM theory with hypermultiplets in the symmetric and antisymmetric representations of the gauge group. This so-called $\mathbf{E}$ theory is closely related to $\mathcal{N}=4$ SYM and has a holographic description in terms of a $\mathbb{Z}_2$ orientifold of AdS$_5\times S^5$. Using recent matrix model results based on supersymmetric localization we develop efficient numerical methods to calculate two- and three-point functions of certain single trace operators as well as 1/2-BPS Wilson loop expectation values as a function of the 't Hooft coupling $λ$. We use our numerical results to arrive at simple analytic expressions for these correlators valid up to the sixth order in the $λ^{-1/2}$ strong coupling expansion. These results provide explicit field theory predictions for the $α'$ corrections to the supergravity approximation of type IIB string theory on the AdS$_5\times S^5/\mathbb{Z}_2$ orientifold.

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arXiv2023

AdS$_7$ Black Holes from Rotating M5-branes

We construct a general asymptotically locally AdS$_7$ stationary black hole solution of 7d maximal gauged supergravity with three angular momenta and two electric charges. When embedded in 11d supergravity the black hole describes the backreaction of $N$ coincident rotating M5-branes. We study the thermodynamic properties of the black hole and present explicit expressions for its entropy, energy, electric charges, and angular momenta. We show that in the supersymmetric limit of the solution its entropy and on-shell action precisely agree with the result for the path integral of the holographically dual 6d $\mathcal{N}=(2,0)$ SCFT on $S^1\times S^5$ to leading order in the large $N$ limit.

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arXiv2023

Large $N$ Superconformal Indices for 3d Holographic SCFTs

We study a limit of the superconformal index of the ABJM theory on $S^1\times S^2$ in which the size of the circle is much smaller than the radius of the two-sphere. We derive closed form expressions for the two leading terms in this Cardy-like limit which are valid to all orders in the $1/N$ expansion. These results are facilitated by a judicious rewriting of the superconformal index which establishes a connection with the Bethe Ansatz Equations that control the topologically twisted index. Using the same technique we extend these results to the superconformal index of another holographic theory: 3d $\mathcal{N}=4$ SYM coupled to one adjoint and $N_f$ fundamental hypermultiplets. We discuss the implications of our results for holography and the physics of charged rotating black holes in AdS$_4$.

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arXiv2023

Large $N$ Topologically Twisted Indices, Holography, and Black Holes

We present a simple closed form expression for the topologically twisted index of the ABJM theory as a function of the magnetic fluxes and complex chemical potentials valid at fixed $k$ and to all orders in the $1/N$ expansion. This in turn leads to analytic expressions for the topologically twisted index at fixed genus in the 't Hooft limit to all orders in the $1/\sqrtλ$ expansion. These results have important implications for holography and the microscopic entropy counting of supersymmetric static AdS$_4$ black holes. Generalizations to other SCFTs arising from M2-branes are also briefly discussed.

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arXiv2023

Holographic 3d $\mathcal N=1$ Conformal Manifolds

We construct and study several examples of continuous families of AdS$_4$ $\mathcal N = 1$ solutions of four-dimensional maximal gauged supergravity. These backgrounds provide the holographic descriptions of conformal manifolds of the dual 3d $\mathcal N = 1$ SCFTs. The solutions we study can be uplifted to type IIB supergravity where they arise from D3-branes wrapping an $S^1$ with an S-duality twist. We find the spectrum of low lying operators in the 3d $\mathcal N = 1$ SCFTs as a function of the exactly marginal coupling and discuss the structure of the corresponding superconformal multiplets. Using string theory techniques we also study additional examples of continuous families of $\mathcal N = 1$ AdS$_4$ vacua in type IIB and massive type IIA supergravity.

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arXiv2022

Wrapped M5-branes and AdS$_5$ Black Holes

We use consistent truncations in supergravity to show that the backreaction of $N$ rotating M5-branes wrapped on a Riemann surface leads to asymptotically AdS$_5$ black hole solutions of 11d supergravity. We discuss the thermodynamic properties of these black holes focusing on their supersymmetric limit. The Bekenstein-Hawking entropy of the supersymmetric black holes scales as $N^3$ and can be reproduced by the superconformal index of the holographically dual 4d $\mathcal{N}=1$ SCFTs of class $\mathcal{S}$.

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arXiv2022

Higher-Derivative Corrections and AdS$_5$ Black Holes

Using recent results in four-derivative 5d $\mathcal{N}=2$ minimal gauged supergravity, we evaluate the regularized on-shell action of the Euclidean solution in this theory that admits a Lorentzian continuation to an AdS$_5$ black hole with one electric charge and two angular momenta. We focus on the supersymmetric limit of this solution and employ holography to show that the result can be expressed purely in terms of angular momentum fugacities and the 't Hooft anomalies for the $\mathrm{U}(1)_{\mathrm R}$ R-symmetry of the dual 4d $\mathcal{N}=1$ SCFT. This holographic calculation is in perfect agreement with recent studies of the 4d $\mathcal{N}=1$ superconformal index ``on the second sheet''. We illustrate the utility of these results in two classes of 4d $\mathcal{N}=1$ holographic SCFTs that have 't Hooft anomalies with suitable large $N$ behavior that leads to non-trivial corrections at first subleading order in the $1/N$ expansion. We also explicitly calculate the Wald entropy of the black hole solution and delineate the leading four-derivative corrections to the Bekenstein-Hawking entropy.

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arXiv2022

AdS$_5$ Holography and Higher-Derivative Supergravity

We study four-derivative corrections to 5d $\mathcal{N}=2$ minimal gauged supergravity using tools from conformal supergravity. There are two supersymmetric invariants at the four-derivative order and we show explicitly how to write down the action in the Poincaré frame in terms of their coefficients. We apply our results in the context of holography where the four-derivative terms in the supergravity action translate into corrections to the conformal anomalies of the dual 4d $\mathcal{N}=1$ SCFT. We use these results to study corrections to the entropy of the supersymmetric black string solutions of minimal supergravity. We also discuss explicit embeddings of the 5d supergravity in string and M-theory and use them to fix the higher-derivative coefficients in terms of the microscopic parameters.

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arXiv2021

Spin Structures and AdS$_4$ Holography

We study the importance of spin structures as defining data for 11d supergravity backgrounds of the form AdS$_4\times S^7/\mathbf{Z}_k$ with a free orbifold action. For a generic choice of the orbifold action, there is only one spin structure that preserves invariant Killing spinors. There are, however, orbifold actions that allow for more than one spin structure with preserved Killing spinors. In these cases the two different spin structures should lead to distinct holographically dual 3d SCFTs with different amounts of supersymmetry. We illustrate this phenomenon by studying the KK spectrum of 11d supergravity on AdS$_4\times S^7/\mathbf{Z}_4$. For one choice of spin structure this background is dual to the 3d $\mathcal{N}=6$ ABJM theory at level $k=4$. For the alternative choice of spin structure our results suggest that the holographic dual is a different 3d $\mathcal{N}=2$ SCFT and we discuss some of its properties.

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arXiv2021

Higher-Derivative Supergravity, AdS$_4$ Holography, and Black Holes

We use conformal supergravity techniques to study four-derivative corrections in four-dimensional gauged supergravity. We show that the four-derivative Lagrangian for the propagating degrees of freedom of the $\mathcal{N}=2$ gravity multiplet is determined by two real dimensionless constants. We demonstrate that all solutions of the two-derivative equations of motion in the supergravity theory also solve the four-derivative equations of motion. These results are then applied to explicitly calculate the regularized on-shell action for any asymptotically locally AdS$_4$ solution of the two-derivative equations of motion. The four-derivative terms in the supergravity Lagrangian modify the entropy and other thermodynamic observables for the black hole solutions of the theory. We calculate these corrections explicitly and demonstrate that the quantum statistical relation holds for general stationary black holes in the presence of the four-derivative corrections. Employing an embedding of this supergravity model in M-theory we show how to use supersymmetric localization results in the holographically dual three-dimensional SCFT to determine the unknown coefficients in the four-derivative supergravity action. This in turn leads to new detailed results for the first subleading $N^{\frac{1}{2}}$ correction to the large $N$ partition function of a class of three-dimensional SCFTs on compact Euclidean manifolds. In addition, we calculate explicitly the first subleading correction to the Bekenstein-Hawking entropy of asymptotically AdS$_4$ black holes in M-theory. We also discuss how to add matter multiplets to the supergravity theory in the presence of four-derivative terms and to generalize some of these results to six- and higher-derivative supergravity.

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arXiv2021

Kaluza-Klein Spectroscopy for the Leigh-Strassler SCFT

We apply recently developed tools from exceptional field theory to calculate the full Kaluza-Klein spectrum of the AdS$_5$ Pilch-Warner solution of type IIB supergravity. Through the AdS/CFT correspondence this yields detailed information about the spectrum of protected and unprotected operators of the four-dimensional $\mathcal{N}=1$ Leigh-Strassler SCFT, in the planar limit. We also calculate explicitly the superconformal index of the SCFT in this limit and show that it agrees precisely with the spectrum of protected operators in the supergravity calculation.

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arXiv2021

Comments on chiral algebras and $Ω$-deformations

Every six-dimensional $\mathcal{N}=(2,0)$ SCFT on $\mathbf{R}^6$ contains a set of protected operators whose correlation functions are controlled by a two-dimensional chiral algebra. We provide an alternative construction of this chiral algebra by performing an $Ω$-deformation~of a topological-holomorphic twist of the $\mathcal{N}=(2,0)$ theory on $\mathbf{R}^6$ and restricting to the cohomology of a specific supercharge. In addition, we show that the central charge of the chiral algebra can be obtained by performing equivariant integration of the anomaly polynomial of the six-dimensional theory. Furthermore, we generalize this construction to include orbifolds of the $\mathbf{R}^4$ transverse to the chiral algebra plane.

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arXiv2021

Marginal deformations from type IIA supergravity

We study marginal deformations of a class of three-dimensional $\mathcal{N}=2$ SCFTs that admit a holographic dual description in massive type IIA supergravity. We compute the dimension of the conformal manifold in these SCFTs and identify a special submanifold with enhanced flavor symmetry. We show how to apply the TsT transformation of Lunin-Maldacena to construct explicit supersymmetric AdS$_4$ solutions of massive type IIA supergravity with non-trivial internal fluxes that are the holographic dual of these marginal deformations. Finally, we also briefly comment on a class of RG flows between some of these SCFTs that also admit a holographic realization.

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arXiv2021

The Holographic Conformal Manifold of 3d $\mathcal{N}=2$ $S$-fold SCFTs

We employ a non-compact gauging of four-dimensional maximal supergravity to construct a two-parameter family of AdS$_4$ J-fold solutions preserving $\mathcal{N}=2$ supersymmetry. All solutions preserve $\mathfrak{u}(1)\times\mathfrak{u}(1)$ global symmetry and in special limits we recover the previously known $\mathfrak{su}(2)\times\mathfrak{u}(1)$ invariant $\mathcal{N}=2$ and $\mathfrak{su}(2)\times\mathfrak{su}(2)$ invariant $\mathcal{N}=4$ J-fold solutions. This family of AdS$_4$ backgrounds can be uplifted to type IIB string theory and is holographically dual to the conformal manifold of a class of three-dimensional $S$-fold SCFTs obtained from the $\mathcal{N}=4$ $T[\text{U}(N)]$ theory of Gaiotto-Witten. We find the spectrum of supergravity excitations of the AdS$_4$ solutions and use it to study how the operator spectrum of the three-dimensional SCFT depends on the exactly marginal couplings.

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arXiv2021

Euclidean Black Saddles and AdS$_4$ Black Holes

We find new asymptotically locally AdS$_4$ Euclidean supersymmetric solutions of the STU model in four-dimensional gauged supergravity. These "black saddles" have an $S^1\times Σ_{\mathfrak{g}}$ boundary at asymptotic infinity and cap off smoothly in the interior. The solutions can be uplifted to eleven dimensions and are holographically dual to the topologically twisted ABJM theory on $S^1\times Σ_{\mathfrak{g}}$. We show explicitly that the on-shell action of the black saddle solutions agrees exactly with the topologically twisted index of the ABJM theory in the planar limit for general values of the magnetic fluxes, flavor fugacities, and real masses. This agreement relies on a careful holographic renormalization analysis combined with a novel UV/IR holographic relation between supergravity parameters and field theory sources. The Euclidean black saddle solution space contains special points that can be Wick-rotated to regular Lorentzian supergravity backgrounds that correspond to the well-known supersymmetric dyonic AdS$_4$ black holes in the STU model.

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arXiv2020

New AdS$_4$ Vacua in Dyonic ISO(7) Gauged Supergravity

We identify 219 AdS$_4$ solutions in four-dimensional dyonically gauged ISO(7) $\mathcal{N}=8$ supergravity and present some of their properties. One of the new solutions preserves $\mathcal{N}=1$ supersymmetry and provides a rare explicit example of an AdS$_4$ vacuum dual to a 3d SCFT with no continuous global symmetry. There are also two new non-supersymmetric solutions for which all 70 scalar fields in the supergravity theory have masses above the BF bound. All of these AdS$_4$ solutions can be uplifted to massive type IIA supergravity. Motivated by this we present the low lying operator spectra of the dual 3d CFTs for all known supersymmetric AdS$_4$ solutions in the theory and organize them into superconformal multiplets.

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arXiv2020

Higher-Derivative Supergravity, Wrapped M5-branes, and Theories of Class $\mathcal{R}$

We study the interplay between four-derivative 4d gauged supergravity, holography, wrapped M5-branes, and theories of class $\mathcal{R}$. Using results from Chern-Simons theory on hyperbolic three-manifolds and the 3d-3d correspondence we are able to constrain the two independent coefficients in the four-derivative supergravity Lagrangian. This in turn allows us to calculate the subleading terms in the large-$N$ expansion of supersymmetric partition functions for an infinite class of three-dimensional $\mathcal{N}=2$ SCFTs of class $\mathcal{R}$. We also determine the leading correction to the Bekenstein-Hawking entropy of asymptotically AdS$_4$ black holes arising from wrapped M5-branes. In addition, we propose and test some conjectures about the perturbative partition function of Chern-Simons theory with complexified ADE gauge groups on closed hyperbolic three-manifolds.

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