arXiv subjects

Alessandra Gnecchi

Publications and source records attributed to Alessandra Gnecchi.

18 recordsLinked to original sources

arXiv2026

A 1/4-BPS chiral algebra in D1D5: from charge concentration to BPS chaos

The D1D5 CFT exhibits a charge concentration puzzle for BPS states, similar to, but simpler than, that of $\mathcal{N}=4$ SYM. We consider the chiral algebra of 1/4-BPS operators in the D1D5 CFT arising from a supercharge cohomology, and the resulting rational correlators. Using crossing symmetry and this chiral algebra, we establish a non-perturbative proof of the existence of a family of 1/4-BPS states away from the charge concentration locus for general coupling and finite central charge. We further discuss possible implications for BPS chaos in the D1D5 CFT and compute a late-time BPS plateau at the orbifold point.

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arXiv2025

Entanglement surfaces for rotating cylindrical black holes

We construct entanglement surfaces for rotating cylindrical black holes in a double holographic setup, extending previous results to the case of stationary backgrounds. We analyze both the 5d braneworld construction as well as the embedding in 10d type IIB string theory. We couple the rotating cylindrical black hole to a non-gravitating bath, and study island and Hartman-Maldacena surfaces. Properties of island surfaces are characterized by three regimes, bounded by two critical parameters. In addition to the critical value known for the static case, we find that a new one emerges, related to the extremal limit of the rotating black hole. This behaviour is present both for the bottom-up as well as the top-down models, for which we find qualitative agreement.

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arXiv2025

Visions in Quantum Gravity

To deepen our understanding of Quantum Gravity and its connections with black holes and cosmology, building a common language and exchanging ideas across different approaches is crucial. The Nordita Program "Quantum Gravity: from gravitational effective field theories to ultraviolet complete approaches" created a platform for extensive discussions, aimed at pinpointing both common grounds and sources of disagreements, with the hope of generating ideas and driving progress in the field. This contribution summarizes the twelve topical discussions held during the program and collects individual thoughts of speakers and panelists on the future of the field in light of these discussions.

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arXiv2023

On the correspondence between black holes, domain walls and fluxes

We revisit and extend the correspondence between black holes, domain walls and fluxes in type IIA compactifications. We argue that these three systems can be described by the same supergravity effective action, modulo proper identifications and adjustments. Then, we apply the correspondence to investigate swampland conjectures on de Sitter and anti-de Sitter vacua, as well as on the black hole entropy. We show that, in certain cases, swampland conjectures can be motivated from properties of black hole solutions, such as positiveness of the entropy. This provides a bottom-up rationale which is complementary to the usual tests in string theory. When asking for an agreement between the anti-de Sitter and the black hole entropy distance conjectures, we are led to an extension of the correspondence which includes geometric fluxes and the associated Kaluza-Klein monopoles domain walls. Finally, we point out that the anti-de Sitter distance conjecture is naturally implemented in certain asymptotically anti-de Sitter black holes as a consequence of a constraint involving black hole charges and supergravity gauge couplings.

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arXiv2022

Large and Small Non-extremal Black Holes, Thermodynamic Dualities, and the Swampland

In this paper we discuss black hole solutions parametrized by their entropy $\mathcal{S}$ and temperature $\mathcal{T}$ in gravitational effective theories. We are especially interested in the analysis of the boundary regions in the $\mathcal{T}-\mathcal{S}$ diagram, i.e. large/small values of entropy and temperature, and their relation to Swampland constraints. To explore this correlation, we couple the gravitational theories to scalar fields and connect limits of thermodynamic quantities of black holes to scalar field excursions in the corresponding solutions. Whenever the scalar fields traverse an infinite field distance, the Swampland Distance Conjecture allows for a reformulation in terms of {\it entropy-} or {\it temperature-distance}. The effective theories with scalars we investigate are Einstein-Maxwell-dilaton theory as well as $\mathcal{N} = 2$ supergravity in four dimensions. The relation of the latter to type II string theory compactified on Calabi-Yau 3-folds often allows for a direct identification of the corresponding light tower of states. These setups also point towards various dualities between asymptotic regions of the black hole solution. In the context of $\mathcal{N} = 2$ supergravity black holes, these {\it thermodynamic dualities} have an interpretation in terms of T- and S-dualities along the internal directions and their natural action on Kaluza-Klein and winding states.

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arXiv2022

Islands and Light Gravitons in type IIB String Theory

We consider the setup of an evaporating black hole in AdS$_{4}$ coupled to an external bath, embedded in type IIB string theory. We study quantum extremal islands in these backgrounds, in relation to the existence of a massive graviton. Using explicit results of the microscopic embedding of AdS$_{4}$ massive gravity in string theory, we investigate whether it is possible to achieve backgrounds with extremal islands, in which the lowest lying graviton is only slightly massive. For certain regions of the microscopic parameters, the graviton mass can be computed explicitly, and we explain how it directly affects the existence and the properties of the islands. We also show that islands can in principle exist within the regime of validity of the massive gravity effective field theory. However we see via numerical computations that the existence of quantum extremal islands at zero temperature is highly constrained, also when the dilaton is allowed to vary, so that the mass of the graviton cannot be made arbitrarily light. At finite temperature, we also identify a critical parameter, above and below which islands still exist but exhibit a different behavior. Our work supports recent proposals that the unitary evolution of black holes in higher dimensions, and more precisely their Page curve, strongly relies on the presence of a massive graviton in the effective theory.

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arXiv2021

$τ_{RR}$ minimization in presence of hypermultiplets

We compute $τ_{RR}$ minimization in gauged supergravity for M-theory and String Theory truncations with both massless and massive vector multiplets. We explicitly compute, as anticipated in \cite{Amariti:2015ybz}, that massive vector fields at the vacuum require the introduction of a constraint through a Lagrange multiplier. We illustrate this explicitly in two examples, namely the $U(1)^2$-invariant truncation dual to the mABJM model and the ISO(7) truncation in massive IIA, the latter being a theory with both electric and magnetic gauging. We revisit the vacuum constraints at $AdS_4$ and show how the supergravity analysis matches the results of the field theory dual computation.

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arXiv2019

On AdS$_7$ stability

AdS$_7$ supersymmetric solutions in type IIA have been classified, and they are infinitely many. Moreover, every such solution has a non-supersymmetric sister. In this paper, we study the perturbative and non-perturbative stability of these non-supersymmetric solutions, focusing on cases without orientifolds. Perturbatively, we first look at the KK spectrum of spin-2 excitations. This does not exhibit instabilities, but it does show that there is no separation of scales for either the BPS and the non-BPS case, thus proving for supersymmetric AdS$_7$ a well-known recent conjecture. We then use 7d gauged supergravity and a brane polarization computation to access part of the spectrum of KK scalars. The result signals an instability for all non-supersymmetric solutions except those that have a single D8 on each side. We finally look at non-perturbative instabilities, and find that NS5 bubbles make these remaining solutions decay.

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arXiv2018

Holographic duals of 6d RG flows

A notable class of superconformal theories (SCFTs) in six dimensions is parameterized by an integer $N$, an ADE group $G$, and two nilpotent elements $μ_\mathrm{L,R}$ in $G$. Nilpotent elements have a natural partial ordering, which has been conjectured to coincide with the hierarchy of renormalization-group flows among the SCFTs. In this paper we test this conjecture for $G=\mathrm{SU}(k)$, where AdS$_7$ duals exist in IIA. We work with a seven-dimensional gauged supergravity, consisting of the gravity multiplet and two $\mathrm{SU}(k)$ non-Abelian vector multiplets. We show that this theory has many supersymmetric AdS$_7$ vacua, determined by two nilpotent elements, which are naturally interpreted as IIA AdS$_7$ solutions. The BPS equations for domain walls connecting two such vacua can be solved analytically, up to a Nahm equation with certain boundary conditions. The latter admit a solution connecting two vacua if and only if the corresponding nilpotent elements are related by the natural partial ordering, in agreement with the field theory conjecture.

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arXiv2018

Interactions resolve state-dependence in a toy-model of AdS black holes

We show that the holographic description of a class of AdS black holes with scalar hair involves dual field theories with a double well effective potential. Black hole microstates have significant support around both vacua in the dual, which correspond to perturbative degrees of freedom on opposite sides of the horizon. A solvable toy-model version of this dual is given by a quantum mechanical particle in a double well potential. In this we show explicitly that the interactions replace the state-dependence that is needed to describe black hole microstates in a low energy effective model involving the tensor product of two decoupled harmonic oscillators. A naive number operator signals the presence of a firewall but a careful construction of perturbative states and operators extinguishes this.

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arXiv2015

Rholography, Black Holes and Scherk-Schwarz

We present both the macroscopic and microscopic description of a class of near-extremal asymptotically flat black hole solutions in four (or five) dimensional gauged supergravity with R-symmetry gaugings obtained from Scherk-Schwarz reductions on a circle. The entropy of these black holes is counted holographically by the well known MSW (or D1/D5) system, with certain twisted boundary conditions labeled by a twist parameter ρ. We find that the corresponding (0,4) (or (4,4)) superconformal algebras are exactly those studied by Schwimmer and Seiberg, using a twist on the outer automorphism group. The interplay between R-symmetries, ρ-algebras and holography leads us to name our construction "Rholography".

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arXiv2015

3D $τ_{RR}$-minimization in AdS$_4$ gauged supergravity

In this paper we propose the identification in AdS4 N = 2 gauged supergravity of the coefficient $τ_{RR}$ of 3D N = 2 SCFTs. We constraint the structure of this function in supergravity by combining the results from unitarity, holography and localization. We show that our conjectured function is minimized by the exact R-charge, corresponding to a gravitational attractor for the scalars in the special geometry. We identify this mechanism with the supergravity dual of the $τ_{RR}$-minimization. We check this proposal in the ABJM model, comparing with the expectations from localization and the AdS/CFT duality. We comment also on some possible relations with the black hole microstate counting, recently obtained from the application of localization techniques.

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arXiv2013

Supersymmetric Black Holes in AdS4 from Very Special Geometry

Supersymmetric black holes in AdS spacetime are inherently interesting for the AdS/CFT correspondence. Within a four dimensional gauged supergravity theory coupled to vector multiplets, the only analytic solutions for regular, supersymmetric, static black holes in AdS4 are those in the STU-model due to Cacciatori and Klemm. We study a class of U(1)-gauged supergravity theories coupled to vector multiplets which have a cubic prepotential, the scalar manifold is then a very special Kahler manifold. When the resulting very special Kahler manifold is a homogeneous space, we find analytic solutions for static, supersymmetric AdS4 black holes with vanishing axions. The horizon geometries of our solutions are constant curvature Riemann surfaces of arbitrary genus.

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arXiv2013

Rotating black holes in 4d gauged supergravity

We present new results towards the construction of the most general black hole solutions in four-dimensional Fayet-Iliopoulos gauged supergravities. In these theories black holes can be asymptotically AdS and have arbitrary mass, angular momentum, electric and magnetic charges and NUT charge. Furthermore, a wide range of horizon topologies is allowed (compact and noncompact) and the complex scalar fields have a nontrivial radial and angular profile. We construct a large class of solutions in the simplest single scalar model with prepotential $F = -i X^0 X^1$ and discuss their thermodynamics. Moreover, various approaches and calculational tools for facing this problem with more general prepotentials are presented.

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arXiv2013

On the non-BPS first order flow in N=2 U(1)-gauged Supergravity

We consider theories of N=2 supergravity with Fayet-Iliopoulos gauging, and describe a procedure to obtain non-BPS extremal black hole solutions in asymptotically AdS_4 space, in a fully symplectic covariant framework. By considering both electric as well as magnetic gauging, we are able to find new extremal purely magnetic and dyonic solutions. We consistently impose the Dirac quantization condition as a constraint on the black hole and gravitinos charges. This additional requirement allows to parameterize the black hole entropy in terms of an integer and of the entropy of the corresponding black hole in the ungauged model. We also find the nonextremal generalization of the dyonic solution and we compute the product of the areas. For all the configurations with asymptotic supersymmetry we furthermore compute the mass.

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arXiv2012

d-Geometries Revisited

We analyze some properties of the four dimensional supergravity theories which originate from five dimensions upon reduction. They generalize to N>2 extended supersymmetries the d-geometries with cubic prepotentials, familiar from N=2 special Kähler geometry. We emphasize the role of a suitable parametrization of the scalar fields and the corresponding triangular symplectic basis. We also consider applications to the first order flow equations for non-BPS extremal black holes.

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arXiv2010

Flow equations and attractors for black holes in N = 2 U(1) gauged supergravity

We investigate the existence of supersymmetric static dyonic black holes with spherical horizon in the context of N= 2 U(1) gauged supergravity in four dimensions. We analyze the conditions for their existence and provide the general first-order flow equations driving the scalar fields and the metric warp factors from the asymptotic AdS4 geometry to the horizon. We work in a general duality-symmetric setup, which allows to describe both electric and magnetic gaugings. We also discuss the attractor mechanism and the issue of moduli (de-)stabilization.

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arXiv2010

5d/4d U-dualities and N=8 black holes

We use the connection between the U-duality groups in d=5 and d=4 to derive properties of the N=8 black hole potential and its critical points (attractors). This approach allows to study and compare the supersymmetry features of different solutions.

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