Narrow Results

We review the recent developements in the stability problem and phase diagram for asymptotically locally AdS black strings. First, we quickly review the case of locally flat black string before turning to the case of locally AdS spacetimes.

In this work, we reconsider the study of 5D black branes in M-theory compactifications by means of ${𝒩}=2$ supergravity formalism. Precisely, we provide a model relaying on a three-parameter Calabi–Yau (CY) manifold in the ${\mathbb{P}}^1\times {\mathbb{P}}^1\times {\mathbb{P}}^2$ projective space factorization, referred to as economical model. First, we investigate the stability of 5D BPS and non-BPS black holes obtained from wrapped M2-branes on nonholomorphic two-cycles in such a CY manifold. Then, we approach the stability of 5D black strings derived from wrapped M5-branes on nonholomorphic four-cycles. Among others, we find various stable and unstable black brane solutions depending on the charge regions of the involved moduli space.

We discuss simple vacuum solutions to the Einstein Equations in five-dimensional space–times compactified in two different ways. In such spaces, one black hole phase and more than one black string phase may exist. Several old metrics are adapted to new background topologies to yield new solutions to the Einstein Equations. We then briefly talk about the angular momentum they may carry, the horizon topology and phase transitions that may occur.

We discuss the explicit dictionary between general stationary four- and five-dimensional supersymmetric solutions in N = 2 supergravity theories with cubic prepotentials. All these solutions are completely determined in terms of the same set of harmonic functions and attractor equations. We discuss various examples like black holes and black rings in Taub-NUT space–time. Then we consider corrections to the four-dimensional solutions associated with more general prepotentials and comment on analogous corrections on the 5D side.

Cosmic censorship is known to fail in some well-controlled phenomena, calling into question the predictive power of General Relativity and opening up the possibility of observing Planck-scale physics. We propose that the cosmic censorship conjecture can be amended so that its spirit prevails. Naked singularities that, classically, have zero mass are allowed. Physically, these are Planck-sized “black holes”, which evaporate in a few Planck times. General Relativity fails only for a tiny interval in time, to then quickly regain control in a Miltonian evolution that returns us to the predictive paradise of Einstein’s equations. If this refinement of the conjecture is correct, then, even though Nature does allow to expose breakdowns in the smooth fabric of spacetime, it limits them to a mostly harmless minimum.

In this work, we reconsider the study of black holes and black strings in the compactification of M-theory on a Calabi–Yau three-fold, considered as a complete intersection of hypersurfaces in a product of weighted projective spaces given by ${𝕎\mathbb{P}}^4(\omega ,1,1,1,1)\times {\mathbb{P}}^1$. Using the $N=2$ supergravity formalism in five dimensions, we examine the BPS and non-BPSsolutions by wrapping M-branes on appropriate cycles in such a Calabi–Yau geometry. For the black hole case, we compute certain thermodynamical quantities. In particular, we calculate the entropy taking a maximal value corresponding to the ordinary projective space ${\mathbb{P}}^4$ with $\omega =1$. Using extended black hole entropies, we evaluate the temperature involving a minimal value for ${\mathbb{P}}^4$. Then, we approach the stability of the non-BPS black holes via the recombination factor. In the allowed electric charge regions, we show that such states are unstable. For the black string solutions, we calculate the tension taking a minimal value corresponding to ${\mathbb{P}}^4$. Computing the recombination factor, we show that the associated non-BPS black string states are stable in the allowed magnetic charge regions of the moduli space.

The last three years have again seen new exciting developments in the area of higher dimensional black objects. For black objects with noncompact higher dimensions, the solution space was exlored further within the blackfold approach and with numerical schemes, yielding a large variety of new families of solutions, while limiting procedures created so-called super-entropic black holes. Concerning compact extra dimensions, the sequences of static nonuniform black strings in five and six dimensions were extended to impressively large values of the nonuniformity parameter with extreme numerical precision, showing that an oscillating pattern arises for the mass, the area or the temperature, while approaching the conjectured double-cone merger solution. Besides the presentation of interesting new types of higherdimensional solutions, also their physical properties were addressed in this session. While the main focus was on Einstein gravity, a significant number of talks also covered Lovelock theories.

We propose to compute the action and global charges of the asymptotically anti-de Sitter solutions in Einstein-Gauss-Bonnet theory by adding boundary counterterms to the gravitational action. As an application, we consider Einstein-Gauss-Bonnet black string solutions with negative cosmological constant.

The main focus of this session was the presentation of new higher-dimensional black hole solutions, including black rings, black strings, and multi black holes, and the study of their properties. Besides new asymptotically flat and locally asymptotically flat black objects also new black holes with anti-de Sitter asymptotics were reported. The studies of their properties included the investigation of their stability, their thermodynamics, their analyticity and their existence. Furthermore, the geodesics in such higher-dimensional space-times were investigated.