We study gravitational perturbations of Schwarzschild-AdS black holes in $\textit{d}$ = 5 and identify a regime of late-time power-law decay for smooth initial data. Based on an analysis of the quasinormal mode spectrum, we predict and characterise this decay behaviour. We perform fully nonlinear numerical evolutions with long integration times that support the prediction and exhibit no signs of instability. Remarkably, the decay is modulated by a universal oscillatory pattern, consistent with subleading corrections from a large-angular-momentum (eikonal) analysis of the quasinormal mode spectrum.

United Kingdom

John Crump

Jorge Santos

Tails from the bulk: gravitational decay in AdS 5

We analyze the recently discovered localized and non-uniform phases of the Banks-Fischler-Shenker-Susskind (BFSS) matrix quantum mechanics. Building on [1], we provide first-principles derivations of their properties and extend the results with new analytic and numerical insights. We show that strongly coupled BFSS dynamics emerge from a specific Carrollian transformation of 11-dimensional supergravity, which we justify in detail. In this framework, the uniform BFSS phase corresponds to a black string in a $\textit{pp}$-wave background. We demonstrate that this background is unstable to a Gregory-Laflamme instability and, for the first time, compute the associated growth rate. The instability gives rise to non-uniform and localized phases that dominate the microcanonical ensemble in certain low-energy regimes, with the localized phase also prevailing in the canonical ensemble at low temperatures. We identify the corresponding first- and second-order phase transitions and derive analytic formulas for the thermodynamics of the localized phase, accurate to better than 0$\textit{.}$3% against numerical results.

Óscar Dias

Localized states of BFSS super quantum mechanics

We construct a new class of smooth, horizonless, non-supersymmetric solutions in five-dimensional minimal supergravity, which we call $\textit{rotating topological stars}$. Built from a Kerr-Taub-bolt geometry embedded in five dimensions, they constitute the first rotating generalization of the topological star compatible with both smoothness in the interior and standard Kaluza-Klein asymptotics, S × ℝ . The solutions carry angular momentum, magnetic and electric charges, and form a discrete tower of states labeled by a primary quantum number controlling the spin. Remarkably, despite lying outside the black-hole extremality bound, they can approach arbitrarily closely (in conserved charges) the Kerr black string with a large boost along the fifth dimension, making them relevant prototypes for rotating and astrophysical black-hole microstates. We analyze their geometry in detail, including their gravitational multipoles that can significantly deviate from those of black holes and the presence of an ergoregion, and show that both geodesics and scalar perturbations separate, paving the way for analyzing their dynamics in future work.

United States

Pierre Heidmann

Italy

Paolo Pani

Asymptotically flat rotating topological stars

It is known that linearized perturbations of extremal black holes result in growing curvature on the horizon. However, nonlinear perturbations typically do not evolve to extremal black holes and do not have growing curvature at late times. We show that a large class of nonlinear perturbations of an extremal planar anti-de Sitter black hole does have horizon curvature that grows unbounded in time. The late time behavior of the nonlinear evolution is found to be captured by a linearized analysis. We argue that the generic nonlinear perturbation behaves similarly.

Gary Horowitz

Maciej Kolanowski

Frozen firewall: generic singularity formation on an extremal horizon

We study the impact of higher-derivative corrections from Effective Field Theory on the quasinormal mode spectrum of Reissner-Nordström black holes. While previous work has explored corrections to Schwarzschild and Kerr black holes — typically using small-rotation approximations — a comprehensive analysis near extremality remains lacking. We focus on Reissner-Nordström black holes as a tractable model admitting an extremal limit, enabling investigation of the effect of these corrections on the so-called zero-damped modes, which dominate in this regime. Specifically, we derive a corrected Moncrief equation governing quasinormal modes and present both analytic and numerical results for the corrected frequencies. This work also offers the first explicit test of the recently proposed “Quasinormal Mode Causality” bound $\textit{Eur. Phys. J. Plus}$ (2024) 725, which constrains Effective Field Theory coefficients by requiring that quasinormal mode lifetimes do not increase measurably under ultraviolet — complete Effective Field Theory corrections. Using Standard Model contributions — particularly those arising from integrating out the electron — we verify that this bound holds. Our results provide new insights into the interplay between Effective Field Theory, extremal black hole dynamics, and causality in gravitational theories.

William Boyce

EFT corrections to charged black hole quasinormal modes

The Euclidean Einstein-Hilbert action is well-known to be unbounded below and thus to raise many questions regarding the definition of the gravitational path integral. A variety of works since the late 1980’s have suggested that this problem disappears when one fixes a foliation of the spacetime and imposes the corresponding gravitational constraints. However, we show here that this approach fails with various classes of boundary conditions imposed on the foliation: compact slices without boundary, asymptotically flat, or asymptotically locally anti-de Sitter slices. We also discuss the idea of fixing the scalar curvature and Wick-rotating the conformal factor, and show that it also fails to produce an action bounded from below.

Donald Marolf

Constraints are not enough

Using a mix of analytical and numerical methods, we construct new rotating, charged “hairy” black hole solutions of $\textit{D}$ = 5, $$ \mathcal{N} $$ $\textit{=}$ 8 gauged supergravity that are dual, via the AdS/CFT correspondence, to thermal states in $\textit{D}$ = 4, $$ \mathcal{N} $$ = 4 SYM at finite chemical and angular potential, thereby complementing and extending the results of [1–3]. These solutions uplift to asymptotically AdS × $\textit{S}$ solutions of Type IIB supergravity with equal angular momenta along AdS ($\textit{J}$ = $\textit{J}$ = $\textit{J}$ ) and $\textit{S}$ ($\textit{Q}$ = $\textit{Q}$ = $\textit{Q}$ = $\textit{Q}$ ). As we lower the mass $\textit{E}$ at fixed $\textit{Q}$ and $\textit{J}$, the known Cvetič-Lü-Pope (CLP) black holes are unstable to scalar condensation and the hairy black holes constructed here emerge as novel solutions associated to the instability. In the region of phase space where the CLP and hairy black holes coexist, the hairy black holes dominate the microcanonical ensemble and, therefore, describe a new thermodynamic phase of SYM. The hairy black holes extend beyond the CLP extremality surface all the way to the BPS surface, defined by $\textit{E}$ = 3$\textit{Q +}$ 2$\textit{J/L}$. Through a combination of analytical and numerical techniques, we argue that the BPS limit of the hairy black holes is a singular, horizonless solution, and $\textit{not}$ a new two-parameter family of BPS black holes that extend the known one-parameter Gutowski-Reall (GR) black hole solution, in contradiction with the conjectures of [1, 2]. To further support our conclusions, we perform a near-horizon analysis of the BPS equations and argue that they do not admit any regular solutions with an horizon.

Netherlands

Prahar Mitra

Charged rotating hairy black holes in AdS

We show that the general charged, rotating black hole in five-dimensional Einstein-Maxwell theory has a singular extremal limit. Only the known analytic solutions with exactly zero charge or zero angular momenta have smooth extremal horizons. We also consider general black holes in five-dimensional Einstein-Maxwell-Chern-Simons theory, and show that they also have singular extremal limits except for one special value of the coefficient of the Chern-Simons term (the one fixed by supergravity). Combining this with earlier results showing that extremal black holes have singular horizons in four-dimensional general relativity with small higher derivative corrections, and in anti-de Sitter space with perturbed boundary conditions, one sees that smooth extremal horizons are indeed the exception and not the rule.

Smooth extremal horizons are the exception, not the rule

In the context of the black hole/string transition, it is useful to produce Euclidean string backgrounds representing hot and self-gravitating strings. We utilise analytical and numerical methods to find a smooth, stationary rotating solution in the heterotic string theory at high temperatures. The solution describes a spinning winding-momentum condensate living in three non-compact dimensions, and its backreaction on the thermal cycle. At low temperatures, we expect a transition between our solution to an analytical continuation of an axionic Kerr black hole.

Yoav Zigdon

Self gravitating spinning string condensates

We derive gravitational backgrounds that are asymptotically Anti-de Sitter, have a regular black hole horizon and which deep in the interior exhibit mixmaster chaotic dynamics. The solutions are obtained by coupling gravity with a negative cosmological constant to three massive vector fields, within an Ansatz that reduces to ordinary differential equations. At late interior times the equations are identical to those analysed in depth by Misner and by Belinskii-Khalatnikov-Lifshitz fifty years ago. We review and extend known classical and semiclassical results on the interior chaos, formulated as both a dynamical system of ‘Kasner eras’ and as a hyperbolic billiards problem. The volume of the universe collapses doubly-exponentially over each Kasner era. A remarkable feature is the emergence of a conserved energy, and hence a ‘time-independent’ Hamiltonian, at asymptotically late interior times. A quantisation of this Hamiltonian exhibits arithmetic chaos associated with the principal congruence subgroup Γ(2) of the modular group. We compute a large number of eigenvalues numerically to obtain the spectral form factor. While the spectral statistics is anomalous for a chaotic system, the eigenfunctions themselves display random matrix behaviour.