arXiv subjects

Nikolay Bobev

Publications and source records attributed to Nikolay Bobev.

At least 55 records · Page 3Linked to original sources

arXiv2020

The Unreasonable Effectiveness of Higher-Derivative Supergravity in AdS$_4$ Holography

We study four-derivative corrections to four-dimensional $\mathcal{N}=2$ minimal gauged supergravity and show that they are controlled by two real constants. The solutions of the equations of motion in the two-derivative theory are not modified by the higher-derivative corrections. We use this to derive a general formula for the regularized on-shell action for any asymptotically locally AdS$_4$ solution of the theory and show how the higher-derivative corrections affect black hole thermodynamic quantities in a universal way. We employ our results in the context of holography to derive explicit expressions for the subleading corrections in the large $N$ expansion of supersymmetric partition functions on various compact manifolds for a large class of three-dimensional SCFTs.

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arXiv2020

A Cornucopia of AdS$_5$ Vacua

We report on a systematic search for AdS$_5$ vacua corresponding to critical points of the potential in the five-dimensional $\mathcal{N}=8$ SO(6) gauged supergravity. By employing Google's TensorFlow Machine Learning library, we find the total of 32 critical points including 5 previously known ones. All 27 new critical points are non-supersymmetric. We compute the mass spectra of scalar fluctuatons for all points and find that the non-supersymmetric AdS$_5$ vacua are perturbatively unstable. Many of the new critical points can be found analytically within consistent truncations of the $\mathcal{N}=8$ supergravity with respect to discrete subgroups of the S(O(6)$\times$ GL(2,$\mathbb{R}$)) symmetry of the potential. In particular, we discuss in detail a $\mathbb{Z}_2^3$-invariant truncation with 10 scalar fields and 15 critical points. We also compute explicitly the scalar potential in a $\mathbb{Z}_2^2$-invariant extension of that truncation to 18 scalar fields and reproduce 17 of the 32 critical points from the numerical search. Finally, we show that the full potential as a function of 42 scalar fields can be studied analytically using the so-called solvable parametrization. In particular, we find that all critical points lie in a $\mathbb{Z}_2$-invariant subspace spanned by 22 scalar fields.

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arXiv2020

Holographic Uniformization and Black Hole Attractors

We establish an attractor mechanism for the horizon metric of asymptotically locally AdS4 supersymmetric black holes. The Kähler moduli of the metric are not fixed in the asymptotic region, however supersymmetry dictates that the near horizon metric must be the constant curvature one. We show how this mechanism is realized in detail for four-dimensional N=2 gauged supergravity coupled to vector multiplets by focusing on the STU model. A similar analysis is performed for gauged supergravity theories in five, six, and seven dimensions where we establish the same mechanism by extending previous results on holographic uniformization.

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arXiv2020

Holographic Interfaces in N=4 SYM: Janus and J-folds

We find the holographic dual to the three classes of superconformal Janus interfaces in $\mathcal{N}=4$ SYM that preserve three-dimensional $\mathcal{N}=4$, $\mathcal{N}=2$, and $\mathcal{N}=1$ supersymmetry. The solutions are constructed in five-dimensional SO(6) maximal gauged supergravity and are then uplifted to type IIB supergravity. Corresponding to each of the three classes of Janus solutions, there are also AdS$_4\times S^1\times S^5$ J-fold backgrounds. These J-folds have a non-trivial SL$(2,\mathbb{Z})$ monodromy for the axio-dilaton on the $S^1$ and are dual to three-dimensional superconformal field theories.

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arXiv2019

Wrapped Branes and Punctured Horizons

Large classes of AdS$_p$ supergravity backgrounds describing the IR dynamics of $p$-branes wrapped on a Riemann surface are determined by a solution to the Liouville equation. The regular solutions of this equation lead to the well-known wrapped brane supergravity solutions associated with the constant curvature metric on a compact Riemann surface. We show that some singular solutions of the Liouville equation have a physical interpretation as explicit point-like brane sources on the Riemann surface. We uncover the details of this picture by focusing on $\mathcal{N}=1$ theories of class $\mathcal{S}$ arising from M5-branes on a punctured Riemann surface. We present explicit AdS$_5$ solutions dual to these SCFTs and check the holographic duality by showing the non-trivial agreement of 't Hooft anomalies.

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arXiv2019

Universal Spinning Black Holes and Theories of Class $\mathcal R$

We study a supersymmetric, rotating, electrically charged black hole in AdS$_{4}$ which is a solution of four-dimensional minimal gauged supergravity. Using holography we show that the free energy on $S^3$ and the superconformal index of the dual three-dimensional $\mathcal N=2$ SCFT, in the planar limit, are related in a simple universal way. This result applies to large classes of SCFTs constructed from branes in string and M-theory which we discuss in some detail. For theories of class $\mathcal R$, which arise from $N$ M5-branes wrapped on hyperbolic three-manifolds, we show that the superconformal index agrees with the black hole entropy in the large $N$ limit.

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arXiv2019

A new N=1 AdS4 Vacuum of Maximal Supergravity

The recent comprehensive numerical study of critical points of the scalar potential of four-dimensional N=8, SO(8) gauged supergravity using Machine Learning software has led to a discovery of a new N=1 vacuum with a triality-invariant SO(3) symmetry. Guided by the numerical data for that point, we obtain a consistent SO(3)xZ2-invariant truncation of the N=8 theory to an N=1 supergravity with three chiral multiplets. Critical points of the truncated scalar potential include both the N=1 point as well as two new non-supersymmetric and perturbatively unstable points not found by previous searches. Studying the structure of the submanifold of SO(3)xZ2-invariant supergravity scalars, we find that it has a simple interpretation as a submanifold of the 14-dimensional Z2^3-invariant scalar manifold (SU(1,1)/U(1))^7, for which we find a rather remarkable superpotential whose structure matches the single bit error correcting (7, 4) Hamming code. This 14-dimensional scalar manifold contains approximately one quarter of the known critical points. We also show that there exists a smooth supersymmetric domain wall which interpolates between the new N=1 AdS4 solution and the maximally supersymmetric AdS4 vacuum. Using holography, this result indicates the existence of an N=1 RG flow from the ABJM SCFT to a new strongly interacting conformal fixed point in the IR.

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arXiv2019

Supersymmetric Yang-Mills, Spherical Branes, and Precision Holography

Using supersymmetric localization we compute the free energy and BPS Wilson loop vacuum expectation values for planar maximally supersymmetric Yang-Mills theory on $S^d$ in the strong coupling limit for $2\leq d<6$. The same calculation can also be performed in supergravity using the recently found spherical brane solutions. We find excellent agreement between the two sets of results. This constitutes a non-trivial precision test of holography in a non-conformal setting. The free energy of maximal SYM on $S^6$ diverges in the strong coupling limit which might signify the onset of little string theory. We show how this divergence can be regularized both in QFT and in supergravity. We also consider $d=7$ with a small negative 't Hooft coupling and show that the free energy and Wilson loop vacuum expectation value agree with the results from supergravity after addressing some subtleties.

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arXiv2019

The Holographic Dual of the $Ω$-background

We find an explicit supergravity background dual to the $Ω$-deformation of a four-dimensional $\mathcal{N}=2$ SCFT on $\mathbb{R}^4$. The solution can be constructed in the five-dimensional ${\cal N}=4^+$ gauged supergravity and has a nontrivial self-dual 2-form. When uplifted to type IIB supergravity the background is a deformation of AdS$_5\times S^5$ which preserves 16 supercharges. We also discuss generalizations of this solution corresponding to turning on a vacuum expectation value for a scalar operator in the dual SCFT.

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arXiv2019

Janus and J-fold Solutions from Sasaki-Einstein Manifolds

We show that for every Sasaki-Einstein manifold, $M_5$, the AdS$_5\times M_5$ background of type IIB supergravity admits two universal deformations leading to supersymmetric AdS$_4$ solutions. One class of solutions describes an AdS$_4$ domain wall in AdS$_5$ and is dual to a Janus configuration with $\mathcal{N}=1$ supersymmetry. The other class of backgrounds is of the form AdS$_4\times S^1\times M_5$ with a non-trivial SL$(2,\mathbb{Z})$ monodromy for the IIB axio-dilaton along the $S^1$. These AdS$_4$ solutions are dual to three-dimensional $\mathcal{N}=1$ SCFTs. Using holography we express the $S^3$ free energy of these theories in terms of the conformal anomaly of the four-dimensional $\mathcal{N}=1$ SCFT arising from D3-branes on the Calabi-Yau cone over $M_5$.

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arXiv2019

A Holographic Kaleidoscope for $\mathcal{N}=1^*$

We study in detail the recently-found family of asymptotically AdS$_5\times S^5$ type IIB supergravity solutions dual to the $\mathcal{N}=1^*$ SYM theory with equal masses. The backgrounds exhibit a naked singularity and are labelled by a dimensionless parameter, $λ$, which is interpreted as the ratio of the gaugino condensate and the mass in the dual field theory. When $|λ|<1$ we show that the naked singularity is due to a smeared distribution of polarized $(p,q)$ five-branes. For this range of parameters we study the nature of the singularity using probe strings and show that the dual line operators exhibit screening behavior. These features are in line with the physics anticipated in the work of Polchinski-Strassler. For $|λ|=1$ the naked singularity has qualitatively different behavior which has no clear brane interpretation. We show that when $λ=1$ the singularity can be excised and replaced by a smooth Euclidean supergravity solution with an $S^4$ boundary.

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arXiv2019

Uplifting GPPZ: A Ten-dimensional Dual of $\mathcal{N}=1^{*}$

We find a new supersymmetric solution of type IIB supergravity which is the uplift of the GPPZ solution of maximal SO$(6)$ gauged supergravity in five dimensions. This background is expected to be holographically dual to an $\mathcal{N}=1^{*}$ supersymmetric mass deformation of four-dimensional $\mathcal{N}=4$ SYM. The ten-dimensional solution is singular in the region corresponding to the IR regime of the dual gauge theory and we discuss the physics of the singularity in some detail.

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arXiv2018

Mass Deformations of the ABJM Theory: The Holographic Free Energy

We find a class of new supersymmetric Euclidean solutions in four-dimensional maximal gauged supergravity. The holographic dual description of these backgrounds is given by a mass-deformation of the ABJM theory with general values for the R-charges. We calculate the $S^3$ free energy for the supergravity backgrounds and find agreement with the supersymmetric localization calculation of the free energy in the large $N$ limit.

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arXiv2018

Spherical Branes

We construct new solutions of ten-dimensional supergravity with sixteen supercharges which describe the backreaction of D$p$-branes with spherical worldvolume. These solutions are holographically dual to the $(p+1)$-dimensional maximally supersymmetric Yang-Mills theory on $S^{p+1}$. The finite size of the sphere provides an IR cut-off for the gauge theory which is manifested in the supergravity solution as a smooth cap-off of the geometry. In the UV the size of the sphere plays no role and the backgrounds asymptote to the well-known supergravity solutions that describe the near-horizon limit of flat D$p$-branes. We compute the on-shell action of our spherical brane solutions and show that it is in agreement with recent supersymmetric localization results for the free energy of maximal SYM theory on $S^{p+1}$.

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arXiv2018

Holographic RG Flows for Four-dimensional $\mathcal{N}=2$ SCFTs

We study holographic renormalization group flows from four-dimensional $\mathcal{N}=2$ SCFTs to either $\mathcal{N}=2$ or $\mathcal{N}=1$ SCFTs. Our approach is based on the framework of five-dimensional half-maximal supergravity with general gauging, which we use to study domain wall solutions interpolating between different supersymmetric AdS$_5$ vacua. We show that a holographic RG flow connecting two $\mathcal{N}=2$ SCFTs is only possible if the flavor symmetry of the UV theory admits an ${\rm SO}(3)$ subgroup. In this case the ratio of the IR and UV central charges satisfies a universal relation which we also establish in field theory. In addition we provide several general examples of holographic flows from $\mathcal{N}=2$ to $\mathcal{N}=1$ SCFTs and relate the ratio of the UV and IR central charges to the conformal dimension of the operator triggering the flow. Instrumental to our analysis is a derivation of the general conditions for AdS vacua preserving eight supercharges as well as for domain wall solutions preserving eight Poincare supercharges in half-maximal supergravity.

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arXiv2018

Precision Holography for $\mathcal{N}=2^{*}$ on $S^4$ from type IIB Supergravity

We find a new supersymmetric solution of type IIB supergravity which is holographically dual to the planar limit of the four-dimensional $\mathcal{N}=2^*$ supersymmetric Yang-Mills theory on $S^4$. We study a probe fundamental string in this background which is dual to a supersymmetric Wilson loop in the $\mathcal{N}=2^*$ theory. Using holography we calculate the expectation value of this line operator to leading order in the 't Hooft coupling. The result is a non-trivial function of the mass parameter of the $\mathcal{N}=2^*$ theory that precisely matches the result from supersymmetric localization.

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arXiv2018

Mass-deformed ABJM and Black Holes in AdS$_4$

We find a class of new supersymmetric dyonic black holes in four-dimensional maximal gauged supergravity which are asymptotic to the ${\rm SU(3)}\times {\rm U(1)}$ invariant AdS$_4$ Warner vacuum. These black holes can be embedded in eleven-dimensional supergravity where they describe the backreaction of M2-branes wrapped on a Riemann surface. The holographic dual description of these supergravity backgrounds is given by a partial topological twist on a Riemann surface of a three-dimensional $\mathcal{N}=2$ SCFT that is obtained by a mass-deformation of the ABJM theory. We compute explicitly the topologically twisted index of this SCFT and show that it accounts for the entropy of the black holes.

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arXiv2017

Decoding a Three-Dimensional Conformal Manifold

We study the one-dimensional complex conformal manifold that controls the infrared dynamics of a three-dimensional $\mathcal{N}=2$ supersymmetric theory of three chiral superfields with a cubic superpotential. Two special points on this conformal manifold are the well-known XYZ model and three decoupled copies of the critical Wess-Zumino model. The conformal manifold enjoys a discrete duality group isomorphic to $S_4$ and can be thought of as an orbifold of $\mathbf{CP}^1$. We use the $4-\varepsilon$ expansion and the numerical conformal bootstrap to calculate the spectrum of conformal dimensions of low-lying operators and their OPE coefficients, and find a very good quantitative agreement between the two approaches.

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