2D Black Hole Research Articles

Finite-size spectrum of the staggered six-vertex model with antidiagonal boundary conditions

The finite-size spectrum of the critical staggered six-vertex model with antidiagonal boundary conditions is studied. Similar to the case of periodic boundary conditions, we identify three different phases. In two of those, the underlying conformal field theory can be identified to be related to the twisted U(1) Kac-Moody algebra. In contrast, the finite size scaling in the third regime, whose critical behaviour with the (quasi-)periodic BCs is related to the 2d black hole CFTs possessing a non-compact degree of freedom, is more subtle. Here with antidiagonal BCs imposed, the corrections to the scaling of the ground state grow logarithmically with the system size, while the energy gaps appear to close logarithmically. Moreover, we obtain an explicit formula for the Q-operator which is useful for numerical implementation.

Dark dimension, the swampland, and the dark matter fraction composed of primordial near-extremal black holes

In a recent publication we studied the decay rate of primordial black holes perceiving the dark dimension, an innovative five-dimensional (5D) scenario that has a compact space with characteristic length scale in the micron range. We demonstrated that the rate of Hawking radiation of 5D black holes slows down compared to 4D black holes of the same mass. Armed with our findings we showed that for a species scale of O(1010 GeV), an all-dark-matter interpretation in terms of primordial black holes should be feasible for black hole masses in the range 1014≲M/g≲1021. As a natural outgrowth of our recent study, herein we calculate the Hawking evaporation of near-extremal 5D black holes. Using generic entropy arguments we demonstrate that Hawking evaporation of higher-dimensional near-extremal black holes proceeds at a slower rate than the corresponding Schwarzschild black holes of the same mass. Assisted by this result we show that if there were 5D primordial near-extremal black holes in nature, then a primordial black hole all-dark-matter interpretation would be possible in the mass range 105β≲M/g≲1021, where β is a parameter that controls the difference between mass and charge of the associated near-extremal black hole. Published by the American Physical Society 2024

Gravitational repulsive effects in 3D regular black holes

Gravitational repulsive effects in 3D regular black holes

Boundary description of microstates of the two-dimensional black hole

We identify the microstates of the non-supersymmetric, asymptotically flat 2d black hole in the dual c=1 matrix quantum mechanics (MQM). We calculate the partition function of the theory using Hamiltonian methods and reproduce one of two conflicting results found by Kazakov and Tseytlin. We find the entropy by counting states and the energy by approximately solving the Schrödinger equation. The dominant contribution to the partition function in the double-scaling limit is a novel bound state that can be considered an explicit dual of the black hole microstates. This bound state is long-lived and evaporates slowly, exactly like a black hole in asymptotically flat space.

Singularities in 2D and 3D quantum black holes

We study black holes in two and three dimensions that have spacelike curvature singularities behind horizons. The 2D solutions are obtained by dimensionally reducing certain 3D black holes, known as quantum BTZ solutions. Furthermore, we identify the corresponding dilaton potential and show how it can arise from a higher-dimensional theory. Finally, we show that the rotating BTZ black hole develops a singular inner horizon once quantum effects are properly accounted for, thereby solidifying strong cosmic censorship for all known cases.

Horizon strings as 3D black hole microstates

We propose that 3d black holes are an ensemble of tensionless null string states. These microstates typically have non-zero winding. We evaluate their partition function in the limit of large excitation numbers and show that their combinatorics reproduces the Bekenstein-Hawking entropy and its semiclassical logarithmic corrections.

Reconnection-driven flares in 3D black hole magnetospheres

Context. Low-luminosity supermassive and stellar-mass black holes (BHs) may be embedded in a collisionless and highly magnetized plasma. They show nonthermal flares indicative of particles being accelerated up to relativistic speeds by dissipative processes in the vicinity of the BH. During near-infrared flares from the supermassive BH Sagittarius A* (Sgr A*), the GRAVITY Collaboration detected circular motion and polarization evolution, which suggest the presence of transient synchrotron-emitting hot spots moving around the BH. Aims. We study 3D reconnecting current layers in the magnetosphere of spinning BHs to determine whether plasma-loaded flux ropes which are formed near the event horizon could reproduce the hot spot observations and help constrain the BH spin. Methods. We performed global 3D particle-in-cell simulations in Kerr spacetime of a pair plasma embedded in a strong and large-scale magnetic field originating in a perfectly conducting disk in prograde Keplerian rotation. Results. A cone-shaped current layer develops which surrounds the twisted open magnetic field lines threading the event horizon. Spinning magnetic field lines coupling the disk to the BH inflate and reconnect a few gravitational radii above the disk. This quasi-periodic cycle accelerates particles, which accumulate in a few macroscopic flux ropes rotating with the outermost coupling magnetic field line. Once flux ropes detach, they propagate in the current layer following what appears as a rapidly opening spiral when seen face-on. A single flux rope carries enough relativistic electrons and positrons to emit synchrotron radiation at levels suitable to reproduce the peak-luminosity of the flares of Sgr A* but it quickly fades away as it flows away. Conclusions. Our kinematic analysis of the flux ropes motion favors a BH spin of 0.65 to 0.8 for Sgr A*. The duration of the flares of Sgr A* can only be explained provided the underlying magnetic loop seeded in the disk mid-plane has a finite lifetime and azimuthal extension. In this scenario, the hot spot corresponds to a spinning arc along which multiple reconnection sites power the net emission as flux ropes episodically detach.

Quasinormal modes and optical properties of 4-D black holes in Einstein Power-Yang–Mills gravity

This paper explores the impact of the Yang–Mills charge parameter and the exponent term on a 4D black hole solution in the Einstein Power-Yang–Mills theory. Through an investigation of the massless scalar quasinormal mode spectrum, black hole shadow, and emission rate, we have determined that the effects of these two parameters are opposite. Specifically, the Yang–Mills charge parameter causes an increase in the real quasinormal frequencies with a correspondingly smaller damping rate. It also results in a smaller black hole shadow and a lower evaporation rate.

AdS2 holography and ModMax

We present a JT gravity set up in the presence of projected ModMax corrections in two dimensions. Our starting point is the Einstein’s gravity in four dimensions accompanied by the ModMax Lagrangian. The 2D gravity action is obtained following a suitable dimensional reduction which contains a 2D image of the 4D ModMax Lagrangian. We carry out a perturbative analysis to find out the vacuum structure of the theory which asymptotes to AdS2 in the absence of U(1) gauge fields. We estimate the holographic central charge and obtain corrections perturbatively upto quadratic order in the ModMax and the U(1) coupling. We also find out ModMax corrected 2D black hole solutions and discuss their extremal limits.

Non-perturbative correction to thermodynamics of conformally dressed [formula omitted] black hole

We extend the study of corrected thermodynamics for the 3D black holes conformally coupled to scalar field up to non-perturbative level. We calculate the exponential correction to entropy arises due to the microstate counting for quantum states on the boundary. This exponential correction in entropy attributes to the other thermodynamical quantities also. We study the stability and phase transition for this system of black hole under the influence of non-perturbative correction. We also discuss the quantum work associated with exponential corrected entropy. Finally, we justify the results from the view point of thermodynamic geometry.

Ladder symmetries of black holes and de Sitter space: love numbers and quasinormal modes

In this note, we present a synopsis of geometric symmetries for (spin 0) perturbations around (4D) black holes and de Sitter space. For black holes, we focus on static perturbations, for which the (exact) geometric symmetries have the group structure of SO(1,3). The generators consist of three spatial rotations, and three conformal Killing vectors obeying a special melodic condition. The static perturbation solutions form a unitary (principal series) representation of the group. The recently uncovered ladder symmetries follow from this representation structure; they explain the well-known vanishing of the black hole Love numbers. For dynamical perturbations around de Sitter space, the geometric symmetries are less surprising, following from the SO(1,4) isometry. As is known, the quasinormal solutions form a non-unitary representation of the isometry group. We provide explicit expressions for the ladder operators associated with this representation. In both cases, the ladder structures help connect the boundary condition at the horizon with that at infinity (black hole) or origin (de Sitter space), and they manifest as contiguous relations of the hypergeometric solutions.

Topology of thermodynamics in R -charged black holes

We study the topology of black hole thermodynamics in four-, five-, and seven-dimensional $R$-charged black holes. While the 4D $R$-charged black hole possesses four charges, the 5D and 7D $R$-charged black holes have three and two charges, respectively. In our study, we investigate the influence of charge configuration of the $R$-charged black holes on the topology of their thermodynamics. In each of these black holes, we consider a number of different charge configurations and compute the topological charges associated with the critical points. Based on the values of the topological charges, we classify the critical points into conventional and novel critical points. We find that the number of critical points and their nature depends on the charge configuration of the $R$-charged black holes irrespective of their dimensionality. However, the total topological charge for all the charge configurations in 4D, 5D, and 7D remains the same, $Q=\ensuremath{-}1$. This indicates that the $R$-charged black holes in 4D, 5D, and 7D are thermodynamically in the same topological class. We also conclude that the variation of charge configurations does not have any impact on the topological class of thermodynamics for $R$-charged black holes.

Microstates of a 2d Black Hole in string theory

We analyse models of Matrix Quantum Mechanics in the double scaling limit that contain non-singlet states. The finite temperature partition function of such systems contains non-trivial winding modes (vortices) and is expressed in terms of a group theoretic sum over representations. We then focus in the case when the first winding mode is dominant (model of Kazakov-Kostov-Kutasov). In the limit of large representations (continuous Young diagrams), and depending on the values of the parameters of the model such as the compactification radius and the string coupling, the dual geometric background corresponds to that of a long string (winding mode) condensate or a 2d (non-supersymmetric) Black Hole. In the matrix model we can tune these parameters and explore various phases and regimes. Our construction allows us to identify the origin of the microstates of these backgrounds, arising from non trivial representations, and paves the way for computing various observables on them.

Non-Holomorphic Cycles and Non-BPS Black Branes

We study extremal non-BPS black holes and strings arising in M-theory compactifications on Calabi–Yau threefolds, obtained by wrapping M2 branes on non-holomorphic 2-cycles and M5 branes on non-holomorphic 4-cycles. Using the attractor mechanism we compute the black hole mass and black string tension, leading to a conjectural formula for the asymptotic volumes of connected, locally volume-minimizing representatives of non-holomorphic, even-dimensional homology classes in the threefold, without knowledge of an explicit metric. In the case of divisors we find examples where the volume of the representative corresponding to the black string is less than the volume of the minimal piecewise-holomorphic representative, predicting recombination for those homology classes and leading to stable, non-BPS strings. We also compute the central charges of non-BPS strings in F-theory via a near-horizon $$AdS_3$$ limit in 6d which, upon compactification on a circle, account for the asymptotic entropy of extremal non-supersymmetric 5d black holes (i.e., the asymptotic count of non-holomorphic minimal 2-cycles).

Topology of Born-Infeld AdS black holes in 4D novel Einstein-Gauss-Bonnet gravity

The topological classification of critical points of black holes in 4D Einstein-Gauss-Bonnet gravity coupled to Born-Infeld theory is investigated. Considered independently, Born-infeld corrections to the Einstein action alter the topological charge of critical points of the charged AdS black hole system, whereas the Gauss-Bonnet corrections do not. For the combined system though, the topological charge of the Einstein-Gauss-Bonnet theory is unaltered in the presence of Born-Infeld coupling.

Emergent de Sitter cosmology near black hole horizon

We propose an effective model for an exponentially expanding universe in the brane-world scenario. The setup consists of a 5D black hole and a brane close to the black hole horizon. In case the brane acquires a specific configuration, which we deduce from stability arguments, the induced metric outside the black hole horizon on the brane becomes de Sitter in static coordinates. Studying the Einstein equations perturbatively we find the effective gravity on the brane at this level and derive the 4D gravitational constant. Considering a homogeneous and isotropic fluid in the corresponding FLRW coordinates we find that the bulk fluid density inside the brane, which has the same equation of state as the fluid on the brane, contributes to the energy density in the Friedmann equation and therefore in late time may be attributed to dark matter. Studying the stability of the setup we observe that the brane becomes stabilized, in the presence of matter on the brane, with a de Sitter length that is qualitatively of the order of Schwarzschild radius of the universe due to matter. We briefly discuss effects that can bound the de Sitter lifetime. In particular this model can provide a lifetime compatible with Trans-Planckian Censorship conjecture for the current de Sitter phase.

2D quantum gravity partition function on the fluctuating sphere

Motivated by recent works on the connection between 2D quantum gravity and timelike Liouville theory, we revisit the latter and clarify some aspects of the computation of its partition function: we present a detailed computation of the Liouville partition function on the fluctuating sphere at finite values of the central charge. The results for both the spacelike theory and the timelike theory are given, and their properties analyzed. We discuss the derivation of the partition function from the DOZZ formula, its derivation using the Coulomb gas approach, a semiclassical computation of it using the fixed area saddle point, and, finally, we arrive to an exact expression for the timelike partition function whose expansion can be compared with the 3-loop perturbative calculations reported in the literature. We also discuss the connection to the 2D black hole and other related topics.

A tractroid realization of a 2d black hole vacuum

The two-dimensional black hole vacuum obtained from a spatial slice of the BTZ black hole is mapped explicitly to a tractroid surface minus a bounding circle.

On quasinormal modes in 4D black hole solutions in the model with anisotropic fluid

We consider a family of four-dimensional black hole solutions from Dehnen et al. (Grav Cosmol 9:153 arXiv:gr-qc/0211049, 2003) governed by natural number q= 1, 2, 3 , dots , which appear in the model with anisotropic fluid and the equations of state: p_r = -rho (2q-1)^{-1}, p_t = - p_r, where p_r and p_t are pressures in radial and transverse directions, respectively, and rho > 0 is the density. These equations of state obey weak, strong and dominant energy conditions. For q = 1 the metric of the solution coincides with that of the Reissner–Nordström one. The global structure of solutions is outlined, giving rise to Carter–Penrose diagram of Reissner–Nordström or Schwarzschild types for odd q = 2k + 1 or even q = 2k, respectively. Certain physical parameters corresponding to BH solutions (gravitational mass, PPN parameters, Hawking temperature and entropy) are calculated. We obtain and analyse the quasinormal modes for a test massless scalar field in the eikonal approximation. For limiting case q = + infty , they coincide with the well-known results for the Schwarzschild solution. We show that the Hod conjecture which connect the Hawking temperature and the damping rate is obeyed for all q ge 2 and all (allowed) values of parameters.

Analytic long-lived modes in charged critical plasma

Fluctuations around critical behavior of a holographic charged plasma are investigated by studying quasi-normal modes of the corresponding black branes in 5D Einstein-Maxwell-Dilaton gravity. The near horizon geometry of black branes approaches the well-known 2D charged string black hole in the critical limit, for which a world-sheet description is available, and the corresponding quasi-normal modes can be obtained analytically from the reflection amplitude of the 2D black hole geometry. We find two distinct set of modes: a purely imaginary “decoupled” set, directly following from the reflection amplitude, and a “non-decoupled” set that was already identified in the neutral holographic plasma in [1]. In the extremal limit, the former set of imaginary quasi-normal modes coalesce on a branch cut starting from the origin, signaling breakdown of hydrodynamic approximation. We further complete the black brane geometry with a slice of AdS near the boundary, to allow for a holographic construction, and find another set of modes localized in the UV. Finally, we develop an alternative WKB method to obtain the quasi-normal modes in the critical limit and apply this method to study the spectrum of hyperscaling-violating Lifshitz black branes. The critical limit of the plasma we consider in this paper is in one-to-one correspondence with the large D limit of Einstein’s gravity which allows for an alternative interesting interpretation of our findings.