abstract stringlengths 3 192k | title stringlengths 4 857 |
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we show that the free energy at low temperatures for near-extremal black holes is correctly obtained from the jackiw-teitelboim (jt) model of gravity. our arguments apply to all black holes, including rotating ones, whose metric has a near-horizon ads2 factor and the associated sl (2, &r;) symmetry. we verify these arguments by explicit calculations for rotating black holes in 4 and 5 dimensions. our results suggest that the jt model could prove useful in analysing the dynamics of near-extremal kerr black holes found in nature. | jackiw-teitelboim gravity and rotating black holes |
we measured the power spectrum and two-point correlation function for the randomly fluctuating free surface on the downstream side of a stationary flow with a maximum froude number fmax≈0.85 reached above a localized obstacle. on such a flow the scattering of incident long wavelength modes is analogous to that responsible for black hole radiation (the hawking effect). our measurements of the noise show a clear correlation between pairs of modes of opposite energies. we also measure the scattering coefficients by applying the same analysis of correlations to waves produced by a wave maker. | observation of noise correlated by the hawking effect in a water tank |
we present the results of nine simulations of radiatively inefficient magnetically arrested discs (mads) across different values of the black hole spin parameter a*: -0.9, -0.7, -0.5, -0.3, 0, 0.3, 0.5, 0.7, and 0.9. each simulation was run up to $t \gtrsim 100\, 000\, gm/c^3$ to ensure disc inflow equilibrium out to large radii. we find that the saturated magnetic flux level, and consequently also jet power, of mad discs depends strongly on the black hole spin, confirming previous results. prograde discs saturate at a much higher relative magnetic flux and have more powerful jets than their retrograde counterparts. mads with spinning black holes naturally launch jets with generalized parabolic profiles whose widths vary as a power of distance from the black hole. for distances up to 100gm/c2, the power-law index is k ≈ 0.27-0.42. there is a strong correlation between the disc-jet geometry and the dimensionless magnetic flux, resulting in prograde systems displaying thinner equatorial accretion flows near the black hole and wider jets, compared to retrograde systems. prograde and retrograde mads also exhibit different trends in disc variability: accretion rate variability increases with increasing spin for a* > 0 and remains almost constant for a* ≲ 0, while magnetic flux variability shows the opposite trend. jets in the mad state remove more angular momentum from black holes than is accreted, effectively spinning down the black hole. if powerful jets from mad systems in nature are persistent, this loss of angular momentum will notably reduce the black hole spin over cosmic time. | jets in magnetically arrested hot accretion flows: geometry, power, and black hole spin-down |
the ruppeiner geometry of thermodynamic fluctuations provides a powerful diagnostic of black hole microstructures. we investigate this for charged anti-de sitter black holes and find that, while an attractive microstructure interaction dominates for most parameter ranges, a weak repulsive interaction dominates for small black holes of high temperature. this unique property distinguishes the black hole system from that of a van der waals fluid, where only attractive microstructure interactions are found. we also find two other novel universal properties for charged black holes. one is that the repulsive interaction is independent of the black hole charge and temperature. the other is that the behavior of the ruppeiner curvature scalar near criticality is characterized by a dimensionless constant that is identical to that for a van der waals fluid, providing us with new insight into black hole microstructures. | repulsive interactions and universal properties of charged anti-de sitter black hole microstructures |
recent works have suggested that the entanglement wedge of hawking radiation coming from an ads black hole will include an island inside the black hole interior after the page time. in this paper, we propose a concrete way to extract the information from the island by acting only on the radiation degrees of freedom, building on the equivalence between the boundary and bulk modular flow. we consider examples with black holes in jt gravity coupled to baths. in the case that the bulk conformal fields contain free massless fermion field, we provide explicit bulk picture of the information extraction process, where we find that one can almost pull out an operator from the island to the bath with modular flow. | pulling out the island with modular flow |
we extract the relativistic classical radial action from scattering amplitudes, to all orders in perturbation theory, in the probe limit. our sources include point charges and monopoles, as well as the schwarzschild and pure-nut gravitational backgrounds. a characteristic relativistic effect, that scattering trajectories may wind around these sources any number of times, can be recovered when all-order amplitudes are available. we show that the amplitude for scattering a probe off a pure nut is given by the solution of a transcendental equation involving continued fractions, and explain how to solve this equation to any desired loop order. | the radial action from probe amplitudes to all orders |
in this paper, we study the fine structure of entanglement in holographic two-dimensional boundary conformal field theories (bcft) in terms of the spatially resolved quasilocal extension of entanglement entropy — entanglement contour. we find that the boundary induces discontinuities in the contour revealing hidden localization-delocalization patterns of the entanglement degrees of freedom. moreover, we observe the formation of "islands" where the entanglement contour vanishes identically implying that these regions do not contribute to the entanglement at all. we argue that these phenomena are the manifestation of the entanglement islands recently discussed in the literature. we apply the entanglement contour proposal to the recently discussed bcft black hole models reproducing the page curve — moving mirror model and the pair of bcft in the thermofield double state. from the viewpoint of entanglement contour, the page curve also carries the imprint of strong delocalization caused by dynamical entanglement islands. | shaping contours of entanglement islands in bcft |
we present a public catalogue of numerical-relativity binary-black-hole simulations. the catalogue contains datasets from 80 distinct configurations of precessing binary-black-hole systems, with mass ratios up to $m_2/m_1 = 8$, dimensionless spin magnitudes on the larger black hole up to $|\vec{s}_2|/m_2^2 = 0.8$ (the small black hole is non-spinning), and a range of five values of spin misalignment for each mass-ratio/spin combination. we discuss the physical properties of the configurations in our catalogue, and assess the accuracy of the initial configuration of each simulation and of the gravitational waveforms. we perform a careful analysis of the errors due to the finite resolution of our simulations and the finite distance from the source at which we extract the waveform data and provide a conservative estimate of the mismatch accuracy. we find that the upper limit on the mismatch uncertainty of our waveforms is $0.4\%$. in doing this we present a consistent approach to combining mismatch uncertainties from multiple error sources. we compare this release to previous catalogues and discuss how these new simulations complement the existing public datasets. in particular, this is the first catalogue to uniformly cover this parameter space of single-spin binaries and there was previously only sparse coverage of the precessing-binary parameter space for mass ratios $\gtrsim 5$. we discuss applications of these new data, and the most urgent directions for future simulation work. the public dataset can be accessed online at https://data.cardiffgravity.org/bam-catalogue/. | a catalogue of precessing black-hole-binary numerical-relativity simulations |
it is believed that curvature singularities are a creation of general relativity and, hence, in the absence of a quantum gravity, models of nonsingular black holes have received significant attention. we study the shadow (apparent shape), an optical appearance because of its strong gravitational field, cast by a nonsingular black hole which is characterized by three parameters, i.e., mass (m ), spin (a ), and a deviation parameter (k ). the nonsingular black hole under consideration is a generalization of the kerr black hole that can be recognized asymptotically (r ≫k ,k >0 ) explicitly as the kerr-newman black hole, and in the limit k →0 as the kerr black hole. it turns out that the shadow of a nonsingular black hole is a dark zone covered by a deformed circle. interestingly, it is seen that the shadow of a black hole is affected due to the parameter k . indeed, for a given a , the size of a shadow reduces as the parameter k increases, and the shadow becomes more distorted as we increase the value of the parameter k when compared with the analogous kerr black hole shadow. we also investigate, in detail, how the ergoregion of a black hole is changed due to the deviation parameter k . | shapes of rotating nonsingular black hole shadows |
the well-known correspondence between quasinormal modes of any stationary, spherically symmetric and asymptotically flat or de sitter black hole and parameters of the circular null geodesic was initially claimed for gravitational and test field perturbations. according to this correspondence the real and imaginary parts of the ℓ ≫ n quasinormal mode (where ℓ and n are multipole and overtone numbers respectively) are multiples of the frequency and instability timescale of the circular null geodesics respectively. later it was shown that the correspondence is guaranteed only for test fields and may be broken for gravitational and other non-minimally coupled fields. here, we further specify the correspondence and prove that even when it is guaranteed, it may not represent the full spectrum of the ℓ ≫ nmodes, missing the quasinormal frequencies which cannot be found by the standard wkb method. in particular we show that this always happens for an arbitrary asymptotically de sitter black holes and further argue that, in general, this might be related to sensitivity of the quasinormal spectrum to geometry deformations near the boundaries. | further clarification on quasinormal modes/circular null geodesics correspondence |
the recent opening of gravitational wave astronomy has shifted the debate about black hole mimickers from a purely theoretical arena to a phenomenological one. in this respect, missing a definitive quantum gravity theory, the possibility to have simple, meta-geometries describing in a compact way alternative phenomenologically viable scenarios is potentially very appealing. a recently proposed metric by simpson and visser is exactly an example of such meta-geometry describing, for different values of a single parameter, different non-rotating black hole mimickers. here, we employ the newman-janis procedure to construct a rotating generalisation of such geometry. we obtain a stationary, axially symmetric metric that depends on mass, spin and an additional real parameter ℓ. according to the value of such parameter, the metric may represent a rotating traversable wormhole, a rotating regular black hole with one or two horizons, or three more limiting cases. by studying the internal and external rich structure of such solutions, we show that the obtained metric describes a family of interesting and simple regular geometries providing viable kerr black hole mimickers for future phenomenological studies. | a novel family of rotating black hole mimickers |
we calculate the vacuum entanglement entropy of maxwell theory in a class of curved spacetimes by kaluza-klein reduction of the theory onto a two-dimensional base manifold. using two-dimensional duality, we express the geometric entropy of the electromagnetic field as the entropy of a tower of scalar fields, constant electric and magnetic fluxes, and a contact term, whose leading-order divergence was discovered by kabat. the complete contact term takes the form of one negative scalar degree of freedom confined to the entangling surface. we show that the geometric entropy agrees with a statistical definition of entanglement entropy that includes edge modes: classical solutions determined by their boundary values on the entangling surface. this resolves a long-standing puzzle about the statistical interpretation of the contact term in the entanglement entropy. we discuss the implications of this negative term for black hole thermodynamics and the renormalization of newton's constant. | geometric entropy and edge modes of the electromagnetic field |
the classical double copy relates solutions to the equations of motion in gauge theory and in gravity. in this paper, we present two double-copy formalisms for relating the coulomb solution in gauge theory to the two-parameter janis-newman-winicour solution in gravity. the latter is a static, spherically symmetric, asymptotically fiat solution that generically includes a dilaton field, but also admits the schwarzschild solution as a special case. we first present the classical double copy as a perturbative construction, similar to its formulation for scattering amplitudes, and then present it as an exact map, with a novel generalisation of the kerr-schild double copy motivated by double field theory. the latter formalism exhibits the relation between the kerr-schild classical double copy and the string theory origin of the double copy for scattering amplitudes. | the classical double copy of a point charge |
the aim of the present research is the analysis of the photon motion in the regular spacetimes arising as solutions of the einstein gravity coupled with a non-linear electrodynamics (ned). the photons no longer follow the null geodesic of the background spacetime, but the null geodesics of an effective geometry where the electromagnetic non-linearity is directly reflected in addition to the spacetime geometry. motion of photons is compared to the motion of neutrinos that are not directly affected by the non-linearities of a non-maxwellian electromagnetic field, and follow null geodesics of the background spacetime. we determine shadows of the regular bardeen black holes, representing a special solution of the general relativity coupled with ned related to a magnetic charge, both for photons and neutrinos, and compare them to the shadow of the related reissner-nordstrom black holes. we demonstrate that the direct ned effects give clear signature of the presence of the regular black holes, on the level going up to 20% that is detectable by recent observational techniques. we also demonstrate strong influence of the ned effects on deflection angle of photons moving in the bardeen spacetimes, and on the time delay of the motion of photons and neutrinos in vicinity of the black hole horizon. | shadow of the regular bardeen black holes and comparison of the motion of photons and neutrinos |
we study four-derivative corrections to four-dimensional n =2 minimal gauged supergravity 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 ads4 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. | unreasonable effectiveness of higher derivative supergravity in ads4 holography |
we examine the thermodynamics of a near-extremal kerr black hole, and demonstrate that the geometry behaves as an ordinary quantum system with a vanishingly small degeneracy at low temperatures. this is in contrast with the classical analysis, which instead predicts a macroscopic entropy for the extremal kerr black hole. our results follow from a careful analysis of the gravitational path integral. specifically, the low temperature canonical partition function behaves as $z \sim \, t^\frac{3}{2}\, e^{s_0+ c \log s_0}$, with $s_0$ the classical degeneracy and $c$ a numerical coefficient we compute. this is in line with the general expectations for non-supersymmetric near-extremal black hole thermodynamics, as has been clarified in the recent past, although cases without spherical symmetry have not yet been fully analyzed until now. we also point out some curious features relating to the rotational zero modes of the near-extremal kerr black hole background that affects the coefficient $c$. this raises a puzzle when considering similar black holes in string theory. our results generalize to other rotating black holes, as we briefly exemplify. | thermodynamics of the near-extremal kerr spacetime |
in this paper, we investigate the topological numbers of the four-dimensional schwarzschild black hole, $d$-dimensional reissner-nordström (rn) black hole, $d$-dimensional singly rotating kerr black hole and five-dimensional gauss-bonnet black hole via the rényi statistics. we find that the topological number calculated via the rényi statistics is different from that obtained from the gibbs-boltzmann (gb) statistics. however, what is interesting is that the topological classifications of different black holes are consistent in both the rényi and gb statistics: the four-dimensional rn black hole, four-dimensional and five-dimensional singly rotating kerr black holes, five-dimensional charged and uncharged gauss-bonnet black holes belong to the same kind of topological class, and the four-dimensional schwarzschild black hole and $d(>5)$-dimensional singly rotating kerr black holes belong to another kind of topological class. in addition, our results suggest that the topological numbers calculated via the rényi statistics in asymptotically flat spacetime background are equal to those calculated from the standard gb statistics in asymptotically ads spacetime background, which provides more evidence for the connection between the nonextensivity of the rényi parameter $\lambda$ and the cosmological constant $\lambda$. | topology of black hole thermodynamics via rényi statistics |
primordial black holes (pbhs) can be both candidates of dark matter and progenitors of binary black holes (bbhs) detected by the ligo-virgo-kagra collaboration. since pbhs could form in the very early universe through the gravitational collapse of primordial density perturbations, the population of bbhs detected by gravitational waves encodes much information on primordial curvature perturbation. in this work, we take a reliable and systematic approach to reconstruct the power spectrum of the primordial curvature perturbation from gwtc-3, under the hierarchical bayesian inference framework, by accounting for the measurement uncertainties and selection effects. in addition to just considering the single pbh population model, we also report the results considering the multi-population model, i.e., the mixed pbh and astrophysical black hole binaries model. we find that the maximum amplitude of the reconstructed power spectrum of primordial curvature perturbation can be ∼ 2.5 ×10-2 at o (105) mpc-1 scales, which is consistent with the pbh formation scenario from inflation at small scales. | towards a reliable reconstruction of the power spectrum of primordial curvature perturbation on small scales from gwtc-3 |
we study the analytic structure of the heavy-heavy-light-light holographic correlators in the supergravity approximation of the ads3 × s3/cft2 duality. as an explicit example, we derive the correlator where the heavy operator is a classical microstate of the 5d supersymmetric black hole and its dual geometry interpolates as a function of a continuous parameter between global ads3 and the extremal btz black hole. the simplest perturbation of this interpolating geometry by a light field is described by the heun equation and we exploit the relation of its connection coefficients to the liouville cft to analytically compute the correlator in the two limits, focusing in particular on the black hole regime. in this limit we find that the real poles of the correlator become dense and can be approximated by a cut. we show that, when the charges of the heavy state are in the black hole regime, the discontinuity across the cut has complex poles corresponding to the quasi-normal modes of btz. this behaviour is qualitatively similar to what is expected for the large central charge limit of a typical black hole microstate. | the black hole behind the cut |
holographic entanglement entropy was recently recast in terms of riemannian flows or `bit threads'. we consider the lorentzian analog to reformulate the `complexity=volume' conjecture using lorentzian flows — timelike vector fields whose minimum flux through a boundary subregion is equal to the volume of the homologous maximal bulk cauchy slice. by the nesting of lorentzian flows, holographic complexity is shown to obey a number of properties. particularly, the rate of complexity is bounded below by conditional complexity, describing a multi-step optimization with intermediate and final target states. we provide multiple explicit geometric realizations of lorentzian flows in ads backgrounds, including their time-dependence and behavior near the singularity in a black hole interior. conceptually, discretized flows are interpreted as lorentzian threads or `gatelines'. upon selecting a reference state, complexity thence counts the minimum number of gatelines needed to prepare a target state described by a tensor network discretizing the maximal volume slice, matching its quantum information theoretic definition. we point out that suboptimal tensor networks are important to fully characterize the state, leading us to propose a refined notion of complexity as an ensemble average. the bulk symplectic potential provides a specific `canonical' thread configuration characterizing perturbations around arbitrary cft states. consistency of this solution requires the bulk satisfy the linearized einstein's equations, which are shown to be equivalent to the holographic first law of complexity, thereby advocating for a principle of `spacetime complexity'. lastly, we argue lorentzian threads provide a notion of emergent time. this article is an expanded and detailed version of [1], including several new results. | sewing spacetime with lorentzian threads: complexity and the emergence of time in quantum gravity |
we propose seven criteria to single out physically reasonable non-singular black-hole models and adopt them to four different spherically symmetric models with a regular center and their rotating counterparts. in general relativity, all such non-singular black holes are non-generic with a certain matter field including a class of nonlinear electromagnetic fields. according to a criterion that the effective energy-momentum tensor should satisfy all the standard energy conditions in asymptotically flat regions, the well- known bardeen and hayward black holes are discarded. in contrast, the dymnikova and fan-wang black holes respect the dominant energy condition everywhere. although the rotating fan-wang black hole contains a curvature singularity, the rotating dymnikova black hole is free from scalar polynomial curvature singularities and closed timelike curves. in addition, the dominant energy condition is respected on and outside the event horizons in the latter case. the absence of parallelly propagated curvature singularities remains an open question. | quest for realistic non-singular black-hole geometries: regular-center type |
we show how geometric phases may be used to fully describe quantum systems, with or without gravity, by providing knowledge about the geometry and topology of its hilbert space. we find a direct relation between geometric phases and von neumann algebras. in particular, we show that a vanishing geometric phase implies the existence of a well-defined trace functional on the algebra. we discuss how this is realised within the ads/cft correspondence for the eternal black hole. on the other hand, a non-vanishing geometric phase indicates missing information for a local observer, associated to reference frames covering only parts of the quantum system considered. we illustrate this with several examples, ranging from a single spin in a magnetic field to virasoro berry phases and the geometric phase associated to the eternal black hole in ads spacetime. for the latter, a non-vanishing geometric phase is tied to the presence of a centre in the associated von neumann algebra. | geometric phases characterise operator algebras and missing information |
in the swampland philosophy of constraining efts from black hole mechanics we study charged black hole evaporation in de sitter space. we establish how the black hole mass and charge change over time due to both hawking radiation and schwinger pair production as a function of the masses and charges of the elementary particles in the theory. we find a lower bound on the mass of charged particles by demanding that large charged black holes evaporate back to empty de sitter space, in accordance with the thermal picture of the de sitter static patch. this bound is satisfied by the charged spectrum of the standard model. we discuss phenomenological implications for the cosmological hierarchy problem and inflation. enforcing the thermal picture also leads to a heuristic remnant argument for the weak gravity conjecture in de sitter space, where the usual kinematic arguments do not work. we also comment on a possible relation between wgc and universal bounds on equilibration times. all in all, charged black holes in de sitter should make haste to evaporate, but they should not rush it.2 | festina lente:1 eft constraints from charged black hole evaporation in de sitter |
in light of our previous study [chin. phys. c 44(8), 085103 (2020)], we investigate the possibility of the formation of a primordial black hole in the second inflationary process induced by the oscillation of the curvaton. by adopting the instability of the mathieu equation, one can utilize the δ function to fully describe the power spectrum. owing to the running of the curvaton mass, we can simulate the value of the abundance of primordial black holes covering almost all of the mass ranges. three special cases are given. one case may account for dark matter because the abundance of a primordial black hole is approximately 75% . as late times, the relic of exponential potential may be approximated to a constant of the order of a cosmological constant, which is dubbed as the role of dark energy. thus, our model could unify dark energy and dark matter from the perspective of phenomenology. finally, it sheds new light on exploring higgs physics. *supported by the hunan provincial department of education (19b464), and the national natural science foundation of china (nsfc, 12165009). | primordial black hole from the running curvaton |
we use numerical simulations of scalar field dark matter evolving on a moving black hole background to confirm the regime of validity of (semi)analytic expressions derived from first principles for both dynamical friction and momentum accretion in the relativistic regime. we cover both small and large clouds (relative to the de broglie wavelength of the scalars), and light and heavy particle masses (relative to the black hole size). in the case of a small dark matter cloud, the effect of accretion is a non-negligible contribution to the total force on the black hole, even for small scalar masses. we confirm that this momentum accretion transitions between two regimes (wave and particlelike) and we identify the mass of the scalar at which the transition between regimes occurs. | relativistic drag forces on black holes from scalar dark matter clouds of all sizes |
we explore the entanglement evolution of boundary intervals in eternal janus black holes that can be embedded consistently into string theory in the low-energy limit. by studying the geodesics we show that there is a transition in the entanglement characteristic around the page time, which manifests the unitarity of the evolution. we reproduce and reinterpret these bulk results from two different lower-dimensional perspectives: first as an interface cft in the usual ads/cft correspondence and second as an effective gravity theory in one lower dimension coupled to a radiation background. in the limit where the number of interface degrees of freedom becomes large, we obtain an effective theory on appropriate branes that replace the deep interior region in the bulk, coined the shadow region. in this effective theory, we also identify the island of the radiation entanglement wedge and verify the newly proposed quantum extremization method. our model clarifies that double holography with gravity in two higher dimensions can be realized in a concrete and consistent way and that the occurrence of islands is natural in one higher dimension. furthermore, our model reveals that there can be a transitional behavior of the page curve before the page time, which is related to the emergence of new matter degrees of freedom on the branes. | unitarity of entanglement and islands in two-sided janus black holes |
in this work we derive for the first time the complete gravitational cubic-in-spin effective action at the next-to-leading order in the post-newtonian (pn) expansion for the interaction of generic compact binaries via the effective field theory for gravitating spinning objects, which we extend in this work. this sector, which enters at the fourth and a half pn (4.5pn) order for rapidly-rotating compact objects, completes finite-size effects up to this pn order, and is the first sector completed beyond the current state of the art for generic compact binary dynamics at the 4pn order. at this order in spins with gravitational nonlinearities we have to take into account additional terms, which arise from a new type of worldline couplings, due to the fact that at this order the tulczyjew gauge for the rotational degrees of freedom, which involves the linear momentum, can no longer be approximated only in terms of the four-velocity. one of the main motivations for us to tackle this sector is also to see what happens when we go to a sector, which corresponds to the gravitational compton scattering with quantum spins larger than one, and maybe possibly also get an insight on the inability to uniquely fix its amplitude from factorization when spins larger than two are involved. a general observation that we can clearly make already is that even-parity sectors in the order of the spin are easier to handle than odd ones. in the quantum context this corresponds to the greater ease of dealing with bosons compared to fermions. | gravitational cubic-in-spin interaction at the next-to-leading post-newtonian order |
the central engines of active galactic nuclei (agns) are powered by accreting supermassive black holes, and while agns are known to play an important role in galaxy evolution, the key physical processes occur on scales that are too small to be resolved spatially (aside from a few exceptional cases). reverberation mapping is a powerful technique that overcomes this limitation by using echoes of light to determine the geometry and kinematics of the central regions. variable ionizing radiation from close to the black hole drives correlated variability in surrounding gas/dust, but with a time delay due to the light travel time between the regions, allowing reverberation mapping to effectively replace spatial resolution with time resolution. reverberation mapping is used to measure black hole masses and to probe the innermost x-ray emitting region, the uv/optical accretion disk, the broad emission line region and the dusty torus. in this article we provide an overview of the technique and its varied applications. | reverberation mapping of active galactic nuclei: from x-ray corona to dusty torus |
detection of a gravitational-wave signal of non-astrophysical origin would be a landmark discovery, potentially providing a significant clue to some of our most basic, big-picture scientific questions about the universe. in this white paper, we survey the leading early-universe mechanisms that may produce a detectable signal—including inflation, phase transitions, topological defects, as well as primordial black holes—and highlight the connections to fundamental physics. we review the complementarity with collider searches for new physics, and multimessenger probes of the large-scale structure of the universe. | detection of early-universe gravitational-wave signatures and fundamental physics |
we explore a simple spherical model of optically thin accretion on a schwarzschild black hole, and study the properties of the image as seen by a distant observer. we show that a dark circular region in the center—a shadow—is always present. the outer edge of the shadow is located at the photon ring radius {b}ph}\equiv \sqrt{27}{r}g, where {r}g={gm}/{c}2 is the gravitational radius of the accreting mass m. the location of the shadow edge is independent of the inner radius at which the accreting gas stops radiating. the size of the observed shadow is thus a signature of the spacetime geometry and it is hardly influenced by accretion details. we briefly discuss the relevance of these results for the event horizon telescope image of the supermassive black hole in m87. | the shadow of a spherically accreting black hole |
we study supersymmetric ads2 × y9 solutions of 11d supergravity where y9 is an s7 fibration over a riemann surface equipped with a metric of non-constant curvature. we consider two classes of riemann surface: the first is a spindle and the second is a topological disc. these solutions are interpreted as the near-horizon limit of m2 branes wrapped on the riemann surface and describe the near-horizon of a 4d black hole. in the case of the topological disc there are additional flavour m2 branes smeared on a five-sphere embedded in the transverse s7. we perform a full global analysis of both classes of solutions, both from a 4d and an 11d viewpoint. finally we compute the two-dimensional newton's constant from which we obtain a prediction for the entropy of the black hole. | m2-branes on discs and multi-charged spindles |
we study the p- v criticality and phase transition in the extended phase space of anti-de sitter (ads) black holes in higher-dimensional de rham, gabadadze and tolley (drgt) massive gravity, treating the cosmological constant as pressure and the corresponding conjugate quantity is interpreted as thermodynamic volume. besides the usual small/large black hole phase transitions, the interesting thermodynamic phenomena of reentrant phase transitions (rpts) are observed for black holes in all d≥6-dimensional spacetime when the coupling coefficients c_i m^2 of massive potential satisfy some certain conditions. | reentrant phase transitions of higher-dimensional ads black holes in drgt massive gravity |
we study superstring theory in three dimensional anti-de sitter spacetime with ns-ns flux, focusing on the case where the radius of curvature is equal to the string length. this corresponds to the critical level k = 1 in the formulation as a wess-zumino-witten model. previously, it was argued that a transition takes place at this special radius, from a phase dominated by black holes at larger radius to one dominated by long strings at smaller radius. we argue that the infinite tower of modes that become massless at k = 1 is a signal of this transition. we propose a simple two-dimensional conformal field theory as the holographic dual to superstring theory at k = 1. as evidence for our conjecture, we demonstrate that our putative dual exactly reproduces the full spectrum of the long strings of the weakly coupled string theory, including states unprotected by supersymmetry. | superstrings on ads3 at k = 1 |
using the holographic correspondence as a tool, we determine the steady-state velocity of expanding vacuum bubbles nucleated within chiral finite temperature first-order phase transitions occurring in strongly coupled large n qcd-like models. we provide general formulae for the friction force exerted by the plasma on the bubbles and for the steady-state velocity. in the top-down holographic description, the phase transitions are related to changes in the embedding of dq -d ¯q flavor branes probing the black hole background sourced by a stack of n dp-branes. we first consider the witten-sakai-sugimoto d 4 -d 8 -d ¯8 setup, compute the friction force and deduce the equilibrium velocity. then we extend our analysis to more general setups and to different dimensions. finally, we briefly compare our results, obtained within a fully non-perturbative framework, to other estimates of the bubble velocity in the literature. | bubble wall velocity at strong coupling |
we describe the computation of post-minkowskian hamiltonians in general relativity from scattering amplitudes. using a relativistic lippmann-schwinger equation, we relate perturbative amplitudes of massive scalars coupled to gravity to the post-minkowskian hamiltonians of classical general relativity to any order in newton's constant. we illustrate this by deriving a hamiltonian for binary black holes without spin up to second order in the post-minkowskian expansion and explicitly demonstrate the equivalence with the recently proposed method based on an effective field theory matching. | post-minkowskian hamiltonians in general relativity |
our galactic centre, sagittarius a*, is believed to harbour a supermassive black hole, as suggested by observations tracking individual orbiting stars1,2. upcoming submillimetre very-long baseline interferometry images of sagittarius a* carried out by the event horizon telescope collaboration (ehtc)3,4 are expected to provide critical evidence for the existence of this supermassive black hole5,6. we assess our present ability to use ehtc images to determine whether they correspond to a kerr black hole as predicted by einstein's theory of general relativity or to a black hole in alternative theories of gravity. to this end, we perform general-relativistic magnetohydrodynamical simulations and use general-relativistic radiative-transfer calculations to generate synthetic shadow images of a magnetized accretion flow onto a kerr black hole. in addition, we perform these simulations and calculations for a dilaton black hole, which we take as a representative solution of an alternative theory of gravity. adopting the very-long baseline interferometry configuration from the 2017 ehtc campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting black hole images as tests of general relativity. | the current ability to test theories of gravity with black hole shadows |
we study the page curve for eternal garfinkle-horowitz-strominger dilaton black holes in four dimensional asymptotically flat spacetime by using the island paradigm. the results demonstrate that without the island, the entanglement entropy of hawking radiation is proportional to time and becomes divergent at late times. while taking account of the existence of the island outside the event horizon, the entanglement entropy stops growing at late times and eventually reaches a saturation value. this value is twice of the bekenstein-hawking entropy and consistent with the finiteness of the von neumann entropy of eternal black holes. moreover, we discuss the impact of the stringy coefficient n and charge q on the page time and the scrambling time respectively. for the non-extremal case, the influence of the coefficient n on them is small compared to the influence of the charge q. however, for the extremal case, the page time and the scrambling time become divergent or near vanishing. this implies the island paradigm needs further investigation. | islands and page curves in charged dilaton black holes |
recently, several methods have been proposed to regularize a $d \to 4$ limit of einstein-gauss-bonnet (egb), leading to nontrivial gravitational dynamics in $4d$. we present an exact nonsingular black hole solution in the $4d$ egb gravity coupled to non-linear electrodynamics and analyze their thermodynamic properties to calculate precise expressions for the black hole mass, temperature, and entropy. because of the magnetic charge, the thermodynamic quantities are corrected, and the hawking--page phase transition is achievable with diverges of the heat capacity at a larger critical radius $r=r_{+}^{c}$ in comparison to the $5d$ counterpart where the temperature is maximum. thus, we have a black hole with cauchy and event horizons, and its evaporation leads to a thermodynamically stable extremal black hole remnant with vanishing temperature, and its size is larger than the $5d$ counterpart. the entropy does not satisfy the usual exact horizon bekenstein--hawking area law of general relativity with a logarithmic area correction term. | nonsingular black holes in $4d$ einstein--gauss--bonnet gravity |
strongly interacting matter undergoes a crossover phase transition at high temperatures t ∼1012 k and zero net-baryon density. a fundamental question in the theory of strong interactions, qcd, is whether a hot and dense system of quarks and gluons displays critical phenomena when doped with more quarks than antiquarks, where net-baryon number fluctuations diverge. recent lattice qcd work indicates that such a critical point can only occur in the baryon dense regime of the theory, which defies a description from first principles calculations. here we use the holographic gauge/gravity correspondence to map the fluctuations of baryon charge in the dense quark-gluon liquid onto a numerically tractable gravitational problem involving the charge fluctuations of holographic black holes. this approach quantitatively reproduces ab initio results for the lowest order moments of the baryon fluctuations and makes predictions for the higher-order baryon susceptibilities and also for the location of the critical point, which is found to be within the reach of heavy-ion collision experiments. | critical point in the phase diagram of primordial quark-gluon matter from black hole physics |
we initiate a systematic enumeration and classification of entropy inequalities satisfied by the ryu-takayanagi formula for conformal field theory states with smooth holographic dual geometries. for 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. this is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. we also find an infinite new family of inequalities applicable to 5 or more regions. the set of all holographic entropy inequalities bounds the phase space of ryu-takayanagi entropies, defining the holographic entropy cone. we characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. we find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. to establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in riemannian geometry and graph theory. | the holographic entropy cone |
we compare shadows cast by schwarzschild black holes with those produced by two classes of naked singularities that result from gravitational collapse of spherically symmetric matter. the latter models consist of an interior naked singularity space-time restricted to radii r ≤ rb, matched to schwarzschild space-time outside the boundary radius rb. while a black hole always has a photon sphere and always casts a shadow, we find that the naked singularity models have photon spheres only if a certain parameter m0 that characterizes these models satisfies m0 ≥ 2/3, or equivalently, if rb ≤ 3m, where m is the total mass of the object. such models do produce shadows. however, models with m0 < 2/3 (or rb > 3m) have no photon sphere and do not produce a shadow. instead, they produce an interesting `full-moon' image. these results imply that the presence of a shadow does not by itself prove that a compact object is necessarily a black hole. the object could be a naked singularity with m0 ≥ 2/3, and we will need other observational clues to distinguish the two possibilities. on the other hand, the presence of a full-moon image would certainly rule out a black hole and might suggest a naked singularity with m0 < 2/3. it would be worthwhile to generalize the present study, which is restricted to spherically symmetric models, to rotating black holes and naked singularities. | shadows of spherically symmetric black holes and naked singularities |
two-dimensional materials provide opportunities for developing semiconductor applications at atomistic thickness to break the limits of silicon technology. black phosphorus (bp), as a layered semiconductor with controllable bandgap and high carrier mobility, is one of the most promising candidates for transistor devices at atomistic thickness1-4. however, the lack of large-scale growth greatly hinders its development in devices. here, we report the growth of ultrathin bp on the centimetre scale through pulsed laser deposition. the unique plasma-activated region induced by laser ablation provides highly desirable conditions for bp cluster formation and transportation5,6, facilitating growth. furthermore, we fabricated large-scale field-effect transistor arrays on bp films, yielding appealing hole mobility of up to 213 and 617 cm2 v−1 s−1 at 295 and 250 k, respectively. our results pave the way for further developing bp-based wafer-scale devices with potential applications in the information industry. | large-scale growth of few-layer two-dimensional black phosphorus |
we establish a generic, fully relativistic formalism to study gravitational-wave emission by extreme-mass-ratio systems in spherically symmetric, nonvacuum black hole spacetimes. the potential applications to astrophysical setups range from black holes accreting baryonic matter to those within axionic clouds and dark matter environments, allowing one to assess the impact of the galactic potential, of accretion, gravitational drag, and halo feedback on the generation and propagation of gravitational waves. we apply our methods to a black hole within a halo of matter. we find fluid modes imparted to the gravitational-wave signal (a clear evidence of the black hole fundamental mode instability) and the tantalizing possibility to infer galactic properties from gravitational-wave measurements by sensitive, low-frequency detectors. | gravitational waves from extreme-mass-ratio systems in astrophysical environments |
we compute the most general leading-order correction to kerr solution when the einstein-hilbert action is supplemented with higher-derivative terms, including the possibility of dynamical couplings controlled by scalars. the model we present depends on five parameters and it contains, as particular cases, einstein-dilaton-gauss-bonnet gravity, dynamical chern-simons gravity and the effective action coming from heterotic superstring theory. by solving the corrected field equations, we find the modified kerr metric that describes rotating black holes in these theories. we express the solution as a series in the spin parameter χ, and we show that including enough terms in the expansion we are able to describe black holes with large spin. for the computations in the text we use an expansion up to order χ 14, which is accurate for χ < 0 .7, but we provide as well a mathematica notebook that computes the solution at any given order. we study several properties of the corrected black holes, such as geometry of the horizon, ergosphere, light rings and scalar hair. some of the corrections violate parity, and we highlight in those cases plots of horizons and ergospheres without &z;2 symmetry. | leading higher-derivative corrections to kerr geometry |
the weak gravity conjecture is a nontrivial conjecture about quantum gravity that makes sharp, falsifiable predictions which can be checked in a broad range of string theory examples. however, in the presence of massless scalar fields (moduli), there are (at least) two inequivalent forms of the conjecture, one based on charge-to-mass ratios and the other based on long-range forces. we discuss the precise formulations of these two conjectures and the evidence for them, as well as the implications for black holes and for "strong forms" of the conjectures. based on the available evidence, it seems likely that both conjectures are true, suggesting that there is a stronger criterion which encompasses both. we discuss one possibility. | repulsive forces and the weak gravity conjecture |
the ligo/virgo collaboration has by now observed or constrained the gravitational merger rates of different classes of compact objects. we consider the possibility that the bulk of these mergers are primordial black hole (pbh) mergers of pbhs formed during the qcd epoch making up the entirety of the dark matter. having shown in a companion paper that mergers due to the initial binary population formed in the early universe are likely negligible, we compute current merger rates in pbh clusters in which the typical pbh resides. we consider two scenarios: (i) the pbh mass function dictated by the qcd equation of state and (ii) the pbh mass function dictated by the existence of a peak in the inflationary perturbation spectrum. in the first scenario, which is essentially parameter-free, we reproduce very well the merger rates for heavy bhs, the merger rate of mass-asymmetric bhs such as gw190814, a recently discovered merger of a 23 m⊙ black hole with a 2.6 m⊙ object, and can naturally explain why ligo/virgo has not yet observed mergers of two light pbhs from the dominant ∼1 m⊙ pbh population. in the second scenario, which has some parameter freedom, we match well the observed rate of heavy pbhs but can currently not explain the rate for mass-asymmetric events. in either case, it is tantalizing that in both scenarios pbh merger rates made with a minimum of assumptions match most ligo/virgo observed rates very well. | consistency of primordial black hole dark matter with ligo/virgo merger rates |
the purpose of this work is to investigate the formation and evaporation of the primordial black holes in the inflationary scenarios. thermodynamic parameters such as mass, temperature and entropy are expressed in terms of nanograv frequency. by numerical calculations we show that the constraint on the mass range $10^{-5}kg-10^{50}kg$ is well confirmed. we discuss the relation between the redshift and the probability for gravitational wave source populations. a new parameter associated with the frequency and hubble rate is presented, by which for the spectral index $n_{s}\approx 0.996$ and the hubble constant $h_{0}\approx 67.27km.s^{-1}.mpc^{-1}$, the effective hubble constant is calculated to be $h_{eff,0}\approx 73.24km.s^{-1}.mpc^{-1} $ which is compatible with the observational data. we make a comparison between the hubble tension and the primordial perturbations and the expression of the mass loss rate, chemical potential and central charge needed to describe the hawking evaporation will be established. | implications of the nanograv results for primordial black holes and hubble tension |
collaborative international efforts under the name of the event horizon telescope project, using sub-mm very long baseline interferometry, are soon expected to provide the first images of the shadow cast by the candidate supermassive black hole in our galactic center, sagittarius a*. observations of this shadow would provide direct evidence of the existence of astrophysical black holes. although it is expected that astrophysical black holes are described by the axisymmetric kerr solution, there also exist many other black hole solutions, both in general relativity and in other theories of gravity, which cannot presently be ruled out. to this end, we present calculations of black hole shadow images from various metric theories of gravity as described by our recent work on a general parametrization of axisymmetric black holes [r. konoplya, l. rezzolla, and a. zhidenko, phys. rev. d 93, 064015 (2016).]. an algorithm to perform general ray-tracing calculations for any metric theory of gravity is first outlined and then employed to demonstrate that even for extremal metric deformation parameters of various black hole spacetimes, this parametrization is both robust and rapidly convergent to the correct solution. | new method for shadow calculations: application to parametrized axisymmetric black holes |
we put forward a broader picture of the effective theory of a spinning particle within the eft of spinning gravitating objects, through which we derive and establish the new precision frontier at the fifth pn (5pn) order. this frontier includes higher-spin sectors, quadratic and quartic in the spin, which both display novel physical features, due to the extension of the effective theory beyond linear order in the curvature. the quadratic-in-spin sectors give rise to a new tidal effect, and the quartic-in-spin sectors exhibit a new multipolar deformation. we then generalize the concept of tidal operators and of spin-induced multipolar operators, and make conjectures on the numerical values of their wilson coefficients, and on the effective point-particle action of kerr black holes. we confirm the generalized actions for generic compact binaries of the nlo quartic-in-spin sectors which were derived via the extension of the eft of gravitating spinning objects. we first present the corresponding interaction potentials and general hamiltonians, which consist of 12 distinct sectors, with a new one due to the new multipolar deformation. these hamiltonians give the full physical information on the binary system, which mostly gets lost in higher-spin sectors, when going to the aligned-spins configuration. moreover these general hamiltonians uniquely allow us to find the complete poincaré algebra at the 5pn order with spins, including the third subleading quadratic-in-spin sectors. we derive consequent observables for gw applications. finally, to make contact with the scattering problem, we also derive the extrapolated scattering angles for aligned spins. our completion of the poincaré algebra provides the strongest validation of our most comprehensive new results, and thus that the 5pn order has now been established as the new precision frontier. | completing the fifth pn precision frontier via the eft of spinning gravitating objects |
hierarchical analysis of binary black hole (bbh) detections by the advanced ligo and virgo detectors has offered an increasingly clear picture of their mass, spin, and redshift distributions. fully understanding the formation and evolution of bbh mergers will require not just the characterization of these marginal distributions, but the discovery of any correlations that exist between the properties of bbhs. here, we hierarchically analyze the ensemble of bbhs discovered by ligo and virgo with a model that allows for intrinsic correlations between their mass ratios q and effective inspiral spins χ eff. at 98.7% credibility, we find that the mean of the χ eff distribution varies as a function of q, such that more unequal-mass bbhs exhibit systematically larger χ eff. we find a bayesian odds ratio of 10.5 in favor of a model that allows for such a correlation over one that does not. finally, we use simulated signals to verify that our results are robust against degeneracies in the measurements of q and χ eff for individual events. while many proposed astrophysical formation channels predict some degree correlation between spins and mass ratio, these predicted correlations typically act in an opposite sense to the trend we observationally identify in the data. | who ordered that? unequal-mass binary black hole mergers have larger effective spins |
we study the formation of primordial black hole (pbh) dark matter and the generation of scalar induced secondary gravitational waves (sigws) in a non-supersymmetric model of hybrid inflation with chaotic (polynomial-like) potential, including one-loop radiative corrections. a radiatively corrected version of these models is entirely consistent with planck's data. by adding non-canonical kinetic energy term in the lagrangian, the inflation experiences a period of ultra-slow-roll, and the amplitude of primordial power spectrum is enhanced to o (10-2). the enhanced power spectra of primordial curvature perturbations can have both sharp and broad peaks. a wide mass range of pbhs is realized in our model with the frequencies of scalar induced gravitational waves ranged from nhz to khz. we present several benchmark points where the pbh mass generated during inflation is around (1 - 100)m⊙, (10-9 -10-7)m⊙ and (10-16 -10-11)m⊙. the pbhs can make up most of the dark matter with masses around (10-16 -10-11)m⊙ and (1 - 100)m⊙, and their associated sigws can be probed by the upcoming ground and space-based gravitational wave (gw) observatories. the evidence of stochastic process recently reported by nanograv may be interpreted as sigws associated with the formation of pbhs. these sigws may also be tested by future interferometer-type gw observations of ska, decigo, lisa, bbo, taiji, tianqin, ce and et. | primordial black holes and gravitational waves in hybrid inflation with chaotic potentials |
simulating a binary black hole coalescence by solving einstein's equations is computationally expensive, requiring days to months of supercomputing time. using reduced order modeling techniques, we construct an accurate surrogate model, which is evaluated in a millisecond to a second, for numerical relativity (nr) waveforms from nonspinning binary black hole coalescences with mass ratios in [1, 10] and durations corresponding to about 15 orbits before merger. we assess the model's uncertainty and show that our modeling strategy predicts nr waveforms not used for the surrogate's training with errors nearly as small as the numerical error of the nr code. our model includes all spherical-harmonic -2yℓm waveform modes resolved by the nr code up to ℓ=8 . we compare our surrogate model to effective one body waveforms from 50 m⊙ to 300 m⊙ for advanced ligo detectors and find that the surrogate is always more faithful (by at least an order of magnitude in most cases). | fast and accurate prediction of numerical relativity waveforms from binary black hole coalescences using surrogate models |
we study charge and energy diffusion in simple holographic theories with broken translational symmetry. we find that when the effects of momentum relaxation are very strong the diffusion constants take universal values dc∼de∼ℏvb2/(kbt ) . here vb is the velocity of the butterfly effect and the coefficients of proportionality depend only on the scaling exponents of the infra-red fixed point. our results suggest that diffusion in these incoherent black holes is controlled by τ ∼ℏ/(kbt ) independently of the mechanism of momentum relaxation. | universal diffusion in incoherent black holes |
we formulate a quantum generalization of maximin surfaces and show that a quantum maximin surface is identical to the minimal quantum extremal surface, introduced in the ew prescription. we discuss various subtleties and complications associated to a maximinimization of the bulk von neumann entropy due to corners and unboundedness and present arguments that nonetheless a maximinimization of the uv-finite generalized entropy should be well-defined. we give the first general proof that the ew prescription satisfies entanglement wedge nesting and the strong subadditivity inequality. in addition, we apply the quantum maximin technology to prove that recently proposed generalizations of the ew prescription to nonholographic subsystems (including the so-called "quantum extremal islands") also satisfy entanglement wedge nesting and strong subadditivity. our results hold in the regime where backreaction of bulk quantum fields can be treated perturbatively in gnħ, but we emphasize that they are valid even when gradients of the bulk entropy are of the same order as variations in the area, a regime recently investigated in new models of black hole evaporation in ads/cft. | quantum maximin surfaces |
using numerical and perturbative methods, we construct the first examples of black hole solutions in einsteinian cubic gravity and study their thermodynamics. focusing first on four-dimensional solutions, we show that these black holes have a novel equation of state in which the pressure is a quadratic function of the temperature. despite this, they undergo a first order phase transition with associated van der waals behavior. we then construct perturbative solutions for general d ≥5 and study the properties of these solutions for d =5 and d =6 in particular. we note that for d >4 the solutions are described by two independent metric functions. we find novel examples of super-entropic behavior over a large portion of the parameter space. we analyze the specific heat, determining that the black holes are thermodynamically stable over large regions of parameter space. | black holes in einsteinian cubic gravity |
due to a well-known, but curious, minus sign in the gibbons-hawking first law for the static patch of de sitter space, the entropy of the cosmological horizon is reduced by the addition of killing energy. this minus sign raises the puzzling question how the thermodynamics of the static patch should be understood. we argue the confusion arises because of a mistaken interpretation of the matter killing energy as the total internal energy, and resolve the puzzle by introducing a system boundary at which a proper thermodynamic ensemble can be specified. when this boundary shrinks to zero size the total internal energy of the ensemble (the brown-york energy) vanishes, as does its variation. part of this vanishing variation is thermalized, captured by the horizon entropy variation, and part is the matter contribution, which may or may not be thermalized. if the matter is in global equilibrium at the de sitter temperature, the first law becomes the statement that the generalized entropy is stationary. | the minus sign in the first law of de sitter horizons |
we construct a black-hole spacetime which includes the running of the gravitational coupling in a self-consistent way. starting from a classical schwarzschild black hole, the backreaction effects produced by the running newton's coupling are taken into account iteratively. the sequence, described by a simple recurrence relation, flows towards a self-consistent solution that can be derived analytically. as a key result, if the gravitational renormalization group flow attains a non-trivial fixed point at high energies, the sequence converges to a "renormalized" black-hole spacetime of the dymnikova-type, which is free of singularities. | dynamical renormalization of black-hole spacetimes |
because of coherent superradiant amplification, massive bosonic fields can trigger an instability in spinning black holes, tapping their energy and angular momentum and forming macroscopic bose-einstein condensates around them. this phenomenon produces gaps in the mass-spin distribution of astrophysical black holes, a continuous gravitational-wave signal emitted by the condensate, and several environmental effects relevant for gravitational-wave astronomy and radio images of black holes. while the spectrum of superradiantly unstable mode is known in great detail for massive scalar (spin-0) and vector (spin-1) perturbations, so far only approximated results were derived for the case of massive tensor (spin-2) fields, due to the nonseparability of the field equations. here, solving a system of ten elliptic partial differential equations, we close this program and compute the spectrum of the most unstable modes of a massive spin-2 field for generic black-hole spin and boson mass, beyond the hydrogenic approximation and including the unique dipole mode that dominates the instability in the spin-2 case. we find that the instability timescale for this mode is orders of magnitude shorter than for any other superradiant mode, yielding much stronger constraints on massive spin-2 fields. these results pave the way for phenomenological studies aimed at constraining beyond standard model scenarios, ultralight dark matter candidates, and extensions to general relativity using gravitational-wave and electromagnetic observations, and have implications for the phase diagram of vacuum solutions of higher-dimensional gravity. | black hole superradiant instability for massive spin-2 fields |
we present a review of the influence of cosmic repulsion and external magnetic fields on accretion disks rotating around rotating black holes and on jets associated with these rotating configurations. we consider both geometrically thin and thick disks. we show that the vacuum energy represented by the relic cosmological constant strongly limits extension of the accretion disks that is for supermassive black holes comparable to extension of largest galaxies, and supports collimation of jets at large distances from the black hole. we further demonstrate that an external magnetic field crucially influences the fate of ionized keplerian disks causing creation of winds and jets, enabling simultaneously acceleration of ultra-high energy particles with energy up to 1021 ev around supermassive black holes with m∼1010m⊙ surrounded by sufficiently strong magnetic field with b∼104 g. we also show that the external magnetic fields enable existence of "levitating" off-equatorial clouds or tori, along with the standard equatorial toroidal structures, if these carry a non-vanishing, appropriately distributed electric charge. | influence of cosmic repulsion and magnetic fields on accretion disks rotating around kerr black holes |
we investigate the consequences for the black hole area of introducing fractal structure for the horizon geometry. we create a three-dimensional spherical analogue of a 'koch snowflake' using a infinite diminishing hierarchy of touching spheres around the schwarzschild event horizon. we can create a fractal structure for the horizon with finite volume and infinite (or finite) area. this is a toy model for the possible effects of quantum gravitational spacetime foam, with significant implications for assessments of the entropy of black holes and the universe, which is generally larger than in standard picture of black hole structure and thermodynamics, potentially by very considerable factors. the entropy of the observable universe today becomes s ≈10 120 (1 + δ / 2), where 0 ≤ δ ≤ 1, with δ = 0 for a smooth spacetime structure and δ = 1 for the most intricate. the hawking lifetime of black holes is also reduced. | the area of a rough black hole |
primordial black holes form in the early universe and constitute one of the most viable candidates for dark matter. the study of their formation process requires the determination of a critical energy density perturbation threshold $\delta_\mathrm{c}$ , which in general depends on the underlying gravity theory. up to now, the majority of analytic and numerical techniques calculate $\delta_\mathrm{c}$ within the framework of general relativity. in this work, using simple physical arguments we estimate semi-analytically the pbh formation threshold within the framework of quantum gravity, working for concreteness within loop quantum cosmology (lqc). in particular, for low mass pbhs formed close to the quantum bounce, we find a reduction in the value of $\delta_\mathrm{c}$ up to $50\%$ compared to the general relativistic regime quantifying for the first time to the best of our knowledge how quantum effects can influence pbh formation within a quantum gravity framework. finally, by varying the barbero-immirzi parameter γ of loop quantum gravity (lqg) we show its effect on the value of $\delta_\mathrm{c}$ while using the observational/phenomenological signatures associated to ultra-light pbhs, namely the ones affected by lqg effects, we propose the pbh portal as a novel probe to constrain the potential quantum nature of gravity. | primordial black holes in loop quantum cosmology: the effect on the threshold |
the newly proposed island formula for entanglement entropy of hawking radiation is applied to spherically symmetric 4-dimensional eternal kaluza-klein (kk) black holes. the "charge" q of kk black holes quantifies its deviation from schwarzschild black holes. the impact of q on the island is studied at late times. the late-time island, whose boundary is located outside but within a planckian distance of the horizon, is slightly extended by q. while the no-island entropy grows linearly, the late-time entanglement entropy is given by island configuration with twice the bekenstein-hawking entropy. thus we reproduce the page curve for the eternal kk black holes. compared with schwarzschild results, the page time is delayed by a factor (1 +q /rh) and the scrambling time is prolonged by a factor (1+q /rh) 1 /2. moreover, the higher-dimensional generalization is presented. skeptically, there are planck length scales involved, in which a semi-classical description may break down. | islands in kaluza-klein black holes |
by considering the quantum oppenheimer-snyder model in loop quantum cosmology, a new quantum black hole model whose metric tensor is a suitably deformed schwarzschild one is derived. the quantum effects imply a lower bound on the mass of the black hole produced by the collapsing dust ball. for the case of larger masses where the event horizon does form, the maximal extension of the spacetime and its properties are investigated. by discussing the opposite scenario to the quantum oppenheimer-snyder, a quantum swiss cheese model is obtained with a bubble surrounded by the quantum universe. this model is analogous to black hole cosmology or fecund universes where the big bang is related to a white hole. thus our models open a new window to cosmological phenomenology. | quantum oppenheimer-snyder and swiss cheese models |
the observational data of primordial black holes and scalar-induced gravitational waves can constrain the primordial curvature perturbation at small scales. we parameterize the primordial curvature perturbation by a broken power law form and find that it is consistent with many inflation models that can produce primordial black holes, such as nonminimal derivative coupling inflation, scalar-tensor inflation, gauss-bonnet inflation, and k/g inflation. the constraints from primordial black holes on the primordial curvature power spectrum with the broken power law form are obtained, where the fraction of primordial black holes in dark matter is calculated by the peak theory. both the real-space top-hat and the gaussian window functions are considered. the constraints on the amplitude of primordial curvature perturbation with gaussian window function are around three times larger than those with real-space top-hat window function. the constraints on the primordial curvature perturbation from the nanograv 12.5 years data sets are displayed, where the nanograv signals are assumed as the scalar-induced gravitational waves, and only the first five frequency bins are used. | constraints on primordial curvature spectrum from primordial black holes and scalar-induced gravitational waves |
dijet events produced in lhc proton-proton collisions at a center-of-mass energy √{s }=8 tev are studied with the atlas detector using the full 2012 data set, with an integrated luminosity of 20.3 fb-1 . dijet masses up to about 4.5 tev are probed. no resonancelike features are observed in the dijet mass spectrum. limits on the cross section times acceptance are set at the 95% credibility level for various hypotheses of new phenomena in terms of mass or energy scale, as appropriate. this analysis excludes excited quarks with a mass below 4.06 tev, color-octet scalars with a mass below 2.70 tev, heavy w' bosons with a mass below 2.45 tev, chiral w* bosons with a mass below 1.75 tev, and quantum black holes with six extra space-time dimensions with threshold mass below 5.66 tev. | search for new phenomena in the dijet mass distribution using p p collision data at √{s }=8 tev with the atlas detector |
understanding the fate of semi-classical black hole solutions at very late times is one of the most important open questions in quantum gravity. in this paper, we provide a path integral definition of the volume of the black hole interior and study it at arbitrarily late times for black holes in various models of two-dimensional gravity. because of a novel universal cancellation between the contributions of the semi-classical black hole spectrum and some of its non-perturbative corrections, we find that, after a linear growth at early times, the length of the interior saturates at a time, and towards a value, that is exponentially large in the entropy of the black hole. this provides a non-perturbative test of the complexity equals volume proposal since complexity is also expected to plateau at the same value and at the same time. | the volume of the black hole interior at late times |
in this paper, we study the deflection of light by a class of phantom black hole and wormhole solutions in the weak limit approximation. more specifically, in the first part of this work we study the deflection of light by garfinkle-horowitz-ströminger black hole and einstein-maxwell anti-dilaton black hole using the optical geometry and the gauss-bonnet theorem. our calculation shows that gravitational lensing is affected by the phantom scalar field (phantom dilaton). in the second part of this work, we explore the deflection of light by a class of asymptotically flat phantom wormholes. in particular we have used three types of wormholes: wormhole with a bounded/unbounded mass function, and a wormhole with a vanishing redshift function. we show that the particular choice of the shape function and mass function plays a crucial role in the final expression for the deflection angle of light. in the third part of the paper we verify our findings with the help of standard geodesics equations. finally, in the fourth part of this paper we consider the problem for the observational relevance of our results studying the creation of the weak field einstein rings. | weak gravitational lensing by phantom black holes and phantom wormholes using the gauss-bonnet theorem |
we study the dynamics of black holes in scalar einstein-gauss-bonnet theories that exhibit spontaneous black hole scalarization using recently introduced methods for solving the full, nonperturbative equations of motion. for one sign of the coupling parameter, nonspinning vacuum black holes are unstable to developing scalar hair, while for the other, instability only sets in for black holes with sufficiently large spin. we study scalarization in both cases, demonstrating that there is a range of parameter space where the theory maintains hyperbolic evolution and for which the instability saturates in a scalarized black hole that is stable without symmetry assumptions. however, this parameter space range is significantly smaller than the range for which stationary scalarized black hole solutions exist. we show how different choices for the subleading behavior of the gauss-bonnet coupling affect the dynamics of the instability and the final state, or lack thereof. finally, we present mergers of binary black holes and demonstrate the imprint of the scalar hair in the gravitational radiation. | dynamics of spontaneous black hole scalarization and mergers in einstein-scalar-gauss-bonnet gravity |
this paper presents updated estimates of source parameters for gw150914, a binary black-hole coalescence event detected by the laser interferometer gravitational-wave observatory (ligo) in 2015 [abbott et al. phys. rev. lett. 116, 061102 (2016).]. abbott et al. [phys. rev. lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing imrphenom) and an 11-dimensional nonprecessing effective-one-body (eob) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing eobnr). here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing eobnr) developed within the eob formalism. we find good agreement with the parameters estimated previously [abbott et al. phys. rev. lett. 116, 241102 (2016).], and we quote updated component masses of 35-3+5 m⊙ and 3 0-4+3 m⊙ (where errors correspond to 90% symmetric credible intervals). we also present slightly tighter constraints on the dimensionless spin magnitudes of the two black holes, with a primary spin estimate <0.65 and a secondary spin estimate <0.75 at 90% probability. abbott et al. [phys. rev. lett. 116, 241102 (2016).] estimated the systematic parameter-extraction errors due to waveform-model uncertainty by combining the posterior probability densities of precessing imrphenom and nonprecessing eobnr. here, we find that the two precessing-spin models are in closer agreement, suggesting that these systematic errors are smaller than previously quoted. | improved analysis of gw150914 using a fully spin-precessing waveform model |
we prove price's law with an explicit leading order term for solutions ϕ (t ,x ) of the scalar wave equation on a class of stationary asymptotically flat (3 +1 ) -dimensional spacetimes including subextremal kerr black holes. our precise asymptotics in the full forward causal cone imply in particular that ϕ (t ,x ) =c t-3+o (t-4 +) for bounded |x|, where c ∈c is an explicit constant. this decay also holds along the event horizon on kerr spacetimes and thus renders a result by luk-sbierski on the linear scalar instability of the cauchy horizon unconditional. we moreover prove inverse quadratic decay of the radiation field, with explicit leading order term. we establish analogous results for scattering by stationary potentials with inverse cubic spatial decay. on the schwarzschild spacetime, we prove pointwise t-2 l -3 decay for waves with angular frequency at least l, and t-2 l -4 decay for waves which are in addition initially static. this definitively settles price's law for linear scalar waves in full generality. the heart of the proof is the analysis of the resolvent at low energies. rather than constructing its schwartz kernel explicitly, we proceed more directly using the geometric microlocal approach to the limiting absorption principle pioneered by melrose and recently extended to the zero energy limit by vasy. | a sharp version of price's law for wave decay on asymptotically flat spacetimes |
generalized dilaton gravity in 2d is the most general consistent deformation of the jackiw-teitelboim model that maintains local lorentz invariance. the action is generically not power-counting renormalizable, thus going beyond the class of models typically studied. nevertheless, all these models are exactly soluble. we focus on a subclass of dilaton scale invariant models. within this subclass, we identify a 3-parameter family of models that describe black holes asymptoting to ads2 in the uv and to ds2 in the ir. since these models could be interesting for holography, we address thermodynamics and boundary issues, including boundary charges, asymptotic symmetries and holographic renormalization. | generalized dilaton gravity in 2d |
the accretion around the black hole plays a pivotal role in the theoretical analysis of black hole shadow, and of the black hole observation in particular. we mainly study the shadow and observation characteristics of noncommutative schwarzschild black holes wrapped by three accretion models, and then explore the influence of noncommutative parameters on the observation appearance and spacetime geometry of black holes. when the black hole is surrounded by an optically and geometrically thin accretion disk, it shows that the direct emissions always dominate the total observed intensity, while the lensing ring superimposed upon the direct emission produces a thin ring, which improves the observation intensity of the black hole image. however, the photon rings makes negligible contributions to the total observed brightness due to its exponential narrowness, although the photon ring intersects the thin plane more than three times to pick up larger intensity. more importantly, when the noncommutative parameters changed, the corresponding regions and observation intensities of photon ring, lensing ring and direct emission all change correspondingly. for optical thin spherically symmetric accretion, we consider the static and infalling matters, respectively. we find that the observation intensity of the two spherical accretion models increase with the increase of noncommutative parameters. in addition, due to the doppler effect of the infalling movement, the shadow image of infalling accretion is darker than that of static accretion. in a word, the different accretion models and noncommutative parameters will lead to different shadow images and optical appearances of noncommutative schwarzschild black holes. | the shadows and observational appearance of a noncommutative black hole surrounded by various profiles of accretions |
we expand our recent work on the outer entropy, a holographic coarse-grained entropy defined by maximizing the boundary entropy while fixing the classical bulk data outside some surface. when the surface is marginally trapped and satisfies certain "minimar" conditions, we prove that the outer entropy is exactly equal to a quarter the area (while for other classes of surfaces, the area gives an upper or lower bound). we explicitly construct the entropy-maximizing interior of a minimar surface, and show that it satisfies the appropriate junction conditions. this provides a statistical explanation for the area-increase law for spacelike holographic screens foliated by minimar surfaces. our construction also provides an interpretation of the area for a class of non-minimal extremal surfaces. on the boundary side, we define an increasing simple entropy by maximizing the entropy subject to a set of "simple experiments" performed after some time. we show (to all orders in perturbation theory around equilibrium) that the simple entropy is the boundary dual to our bulk construction. | coarse graining holographic black holes |
we study the behaviour of extremal and near-extremal black holes at low energies and low temperatures and find that it can be understood from the near-horizon ads2 region. our analysis includes charged matter and also goes beyond the s-wave approximation. we find that the leading behaviour at low energies arises from a mode linked to time reparametrisations and from phase modes arising from gauge fields. at somewhat higher energies, additional modes arising from higher partial waves can also be cumulatively significant. these results can be applied quite generally to cases where an ads2 × sd near-horizon geometry arises, including black holes in asymptotically ads and flat space-times. | extremal and near-extremal black holes and near-cft1 |
the black-hole information paradox provides a stringent test of would-be theories of quantum gravity. string theory has made significant progress toward a resolution of this paradox, and has led to the fuzzball and microstate geometry programs. the central thesis of these programs is that only string theory has sufficiently many degrees of freedom to resolve black-hole microstructure, and that horizons and singularities are artifacts of attempting to describe gravity using a theory that has too few degrees of freedom to resolve the physics. fuzzballs and microstate geometries recast black holes within string theory as horizonless and singularity-free objects that not only resolve the paradox but provide new insight into the underlying microstructure. we give an overview of this approach, summarize its current status and describe future prospects and insights that are now within reach. | snowmass white paper: micro- and macro-structure of black holes |
a fundamental question in qcd is the existence of a phase transition at large doping of quarks over antiquarks. we present the first prediction of a qcd critical point (cp) from a bayesian analysis constrained by first principle results at zero doping. we employ the gauge/gravity duality to map qcd onto a theory of dual black holes. predictions for the cp location in different realizations of the model overlap at one sigma. even if many prior samples do not include a cp, one is found in nearly 100% of posterior samples, indicating a strong preference for a cp. | bayesian location of the qcd critical point from a holographic perspective |
black holes in anti-de sitter spacetime provide an important testing ground for both gravitational and field-theoretic phenomena. in particular, the study of perturbations can be useful to further our understanding regarding certain physical processes, such as superradiance, or the dynamics of strongly coupled conformal field theories through the holographic principle. in this work we continue our systematic study of the ultraviolet instabilities of black-hole quasinormal modes, built on the characterization of the latter as eigenvalues of a (spectrally unstable) non-selfadjoint operator and using the pseudospectrum as a main analysis tool, extending our previous studies in the asymptotically flat setting to anti-de sitter asymptotics. very importantly, this step provides a singularly well-suited probe into some of the key structural aspects of the pseudospectrum. this is a consequence of the specific features of the schwarzschild-anti-de sitter geometry, together with the existence of a sound characterization by warnick of quasinormal modes as eigenvalues, that is still absent in asymptotic flatness. this work focuses on such structural aspects, with an emphasis on the convergence issues of the pseudospectrum and, in particular, the comparison between the hyperboloidal and null slicing cases. as a physical by-product of this structural analysis we assess, in particular, the spectral stability of purely imaginary ``hydrodynamic" modes, which appear for axial gravitational perturbations, that become dominant when the black-hole horizon is larger than the anti-de sitter radius. we find that their spectral stability, under perturbations, depends on how close they are to the real axis, or conversely how distant they are from the first oscillatory overtone. | structural aspects of the anti-de sitter black hole pseudospectrum |
we present a novel approach, $\textit{metric perturbations with spectral methods}$ (metrics), to calculate the gravitational metric perturbations and the quasinormal-mode frequencies of rotating black holes of any spin without decoupling the linearized field equations. we demonstrate the method by applying it to perturbations of kerr black holes of any spin, simultaneously solving all ten linearized einstein equations in the regge-wheeler gauge through purely algebraic methods and computing the fundamental (co-rotating) quadrupole mode frequency at various spins. we moreover show that the metrics approach is accurate and precise, yielding (i) quasinormal mode frequencies that agree with leaver's, continuous-fraction solution with a relative fractional error smaller than $10^{-5}$ for all dimensionless spins below up to 0.95, and (ii) metric perturbations that lead to teukolsky functions that also agree with leaver's solution with mismatches below $1\%$ for all spins below 0.9. by not requiring the decoupling or the angular separation of the linearized field equations, the metrics approach has the potential to be straightforwardly adapted for the computation of the quasinormal-mode frequencies of rotating black holes of any spin beyond general relativity or in the presence of matter. | spectral method for metric perturbations of black holes: kerr background case in general relativity |
the bubbles that nucleated during slow-roll inflation can be supercritical, i.e. their radii are larger than the hubble horizon of de sitter spacetime inside the bubble (an inflating baby universe inside it), and thus naturally develop to the supermassive primordial black holes (smpbhs) with a multi-peaks mass function. in this paper, we further investigate relevant phenomenology. after slow-roll inflation ended, the bubbles may be not only supercritical, but also subcritical. it is showed that it seems unlikely for the subcritical bubbles to collapse to smpbhs. theoretically, however, before they collapsed such bubbles might have a probability of up-tunnelling to the supercritical ones and thus contribute to smpbhs. we present a mechanism for the origin of initial clustering of smpbhs, which can significantly magnify the merger rate of smpbh binaries, and show the possibility that the merging of such smpbh binaries explains recent nanograv signal. | towards supermassive primordial black holes from inflationary bubbles |
it has been argued by iliesiu, kologlu and turiaci in arxiv:2107.09062 that one can compute the supersymmetric index of black holes using black hole geometry carrying finite temperature but a specific complex angular velocity. we follow their prescription to compute the logarithmic correction to the entropy of bps states in four dimensions, defined as the log of the index of supersymmetric black holes, and find perfect agreement with the previous results for the same quantity computed using the near horizon $ads_2 \times s^2$ geometry of zero temperature black holes. besides giving an independent computation of supersymmetric black hole entropy, this analysis also provides a test of the procedure used previously for computing logarithmic corrections to schwarzschild and other non-extremal black hole entropy. | logarithmic correction to bps black hole entropy from supersymmetric index at finite temperature |
we describe an approach to incorporating the physical effects of the absorption of energy by the event horizon of black holes in the scattering amplitudes based post-minkowskian, point-particle effective description. absorptive dynamics are incorporated in a model-independent way by coupling the usual point-particle description to an invisible sector of gapless internal degrees-of-freedom. the leading order dynamics of this sector are encoded in the low-energy expansion of a spectral density function obtained by matching an absorption cross section in the ultraviolet description. this information is then recycled using the scattering amplitudes based kosower-maybee-o'connell in-in formalism to calculate the leading absorptive contribution to the impulse and change in rest mass of a schwarzschild black hole scattering with a second compact body sourcing a massless scalar, electromagnetic or gravitational field. the results obtained are in complete agreement with previous worldline schwinger-keldysh calculations and provide an alternative on-shell scattering amplitudes approach to incorporating horizon absorption effects in the gravitational two-body problem. | absorptive effects and classical black hole scattering |
we propose a new test of strong-field general relativity (gr) based on the universal interferometric signature of the black hole photon ring. the photon ring is a narrow ring-shaped feature, predicted by gr but not yet observed, that appears on images of sources near a black hole. it is caused by extreme bending of light within a few schwarzschild radii of the event horizon and provides a direct probe of the unstable bound photon orbits of the kerr geometry. we show that the precise shape of the observable photon ring is remarkably insensitive to the astronomical source profile and can therefore be used as a stringent test of gr. we forecast that a tailored space-based interferometry experiment targeting m87* could test the kerr nature of the source to the sub-subpercent level. | the shape of the black hole photon ring: a precise test of strong-field general relativity |
we propose a new link between entropy and area: an eternal black hole with an er bridge with cross-section $a$ can carry a macroscopic amount of quantum information, or be in a mixed state, with entropy bounded by $s \leq a/4g_n$. we substantiate our proposal in the context of ads3 and jt gravity, by using the island prescription and replica wormhole method for computing the black hole entropy. we argue that the typical mixed state of a two sided black hole takes the form of an entangled `thermo-mixed double' state with only classical correlations between the two sides. our result for the von neumann entropy of a post-page time two-sided black hole is smaller by a factor of two from previous answers. our reasoning implies that black hole quantum information is topologically protected, similar to the information stored inside a topological quantum memory. | er = epr revisited: on the entropy of an einstein-rosen bridge |
logarithmic corrections to the entropy of extremal black holes have been successfully used to accurately match degeneracies from microscopic constructions to calculations of the gravitational path integral. in this paper, we revisit the problem of deriving such corrections for the case of extremal black holes, either non-supersymmetric or supersymmetric, and for near-extremal black holes. the zero-modes that are present at extremality are crucial, since their path integral cannot be treated quadratically and needs to be regulated. we show how the regulated result can be obtained by taking the zero-temperature limit of either the $4d$ einstein-maxwell or $4d$ supergravity path integral to find the schwarzian or super-schwarzian theories. this leads to drastically different estimates for the degeneracy of non-supersymmetric and supersymmetric extremal black holes. in a companion paper, we discuss how such zero-modes affect the calculation of bps black holes degeneracies, using supersymmetric localization for an exact computation of the gravitational path integral. | revisiting the logarithmic corrections to the black hole entropy |
the island paradigm for the fine-grained entropy of hawking radiation is applied to eternal charged accelerating black holes. in the absence of the island, the entanglement entropy grows linearly and divergent at late times, while once the island outside the event horizon is taken into account, the unitary page curve is reproduced naturally. the impact of the charge and the acceleration on page curves is investigated at late times. for the page time and the scrambling time, they both increase as the acceleration increases, while decreasing as the charge increases. in particular, neutral black holes have the largest page time and scrambling time. it is worth noting that the page time and the scrambling time is divergent at the extremal case, which implies that islands may be related to the causal structure of spacetime. | page curves for accelerating black holes |
we discuss aspects of the possible transition between small black holes and highly excited fundamental strings. we focus on the connection between black holes and the self gravitating string solution of horowitz and polchinski. this solution is interesting because it has non-zero entropy at the classical level and it is natural to suspect that it might be continuously connected to the black hole. surprisingly, we find a different behavior for heterotic and type ii cases. for the type ii case we find an obstruction to the idea that the two are connected as classical solutions of string theory, while no such obstruction exists for the heterotic case. we further provide a linear sigma model analysis that suggests a continuous connection for the heterotic case. we also describe a solution generating transformation that produces a charged version of the self gravitating string. this provides a fuzzball-like construction of near extremal configurations carrying fundamental string momentum and winding charges. we provide formulas which are exact in $\alpha'$ relating the thermodynamic properties of the charged and the uncharged solutions. | on the black hole/string transition |
we present a holographic construction of solutions to the gravitational wave equation starting from qft scattering amplitudes. the construction amounts to a change of basis from momentum to $(2,2)$ twistor space, together with a recently introduced analytic continuation between $(2,2)$ and $(1,3)$ spacetimes. we test the transform for three and four-point amplitudes in a classical limit, recovering both stationary and dynamical solutions in gr as parametrized by their tower of multipole moments, including the kerr black hole. as a corollary, this provides a link between the kerr-schild classical double copy and the qft double copy. | reconstructing classical spacetimes from the s-matrix in twistor space |
understanding the dynamic process of the thermodynamic phase transition can provide the deep insight into the black hole microscopic properties and structures. we in this paper study the dynamic properties of the stable small-large black hole phase transition for the five-dimensional neutral gauss-bonnet ads black hole. firstly, by using the first law of black holes, we prove that the extremal points of the free energy on the landscape denote the real black hole solutions satisfying the field equations. the local maximal and minimal points correspond to local unstable and stable black hole states, respectively. especially, on the free energy landscape, the wells of the coexistence small and large black holes have the same depth. then we investigate the probability evolution governed by the fokker-planck equation. due to the thermal fluctuation, we find that the small (large) black hole state can transit to the large (small) black hole state. furthermore, the first passage time is calculated. for each temperature, a single peak is presented, which suggests that there is a considerable fraction of the first passage events taking place at short time. and the higher the temperature is, the faster decrease of the probability is. these results will uncover some intriguing dynamic properties of the stable small-large black hole phase transition in modified gravity. | dynamic properties of thermodynamic phase transition for five-dimensional neutral gauss-bonnet ads black hole on free energy landscape |
in this paper, by exploring photon motion in the region near a bardeen black hole, we studied the shadow and observed properties of the black hole surrounded by various accretion models. we analyzed the changes in shadow imaging and observed luminosity when the relevant physical parameters are changed. for the different spherical accretion backgrounds, we find that the radius of shadow and the position of the photon sphere do not change, but the observed intensity of shadow in the infalling accretion model is significantly lower than that in the static case. we also studied the contribution of the photon rings, lensing rings and direct emission to the total observed flux when the black hole is surrounded by an optically thin disk accretion. under the different forms of the emission modes, the results show that the observed brightness is mainly determined by direct emission, while the lensing rings will provide a small part of the observed flux, and the flux provided by the photon ring is negligible. by comparing our results with the schwarzschild spacetime, we find that the existence or change of relevant status parameters will greatly affect the shape and observed intensity of the black hole shadow. these results support the theory that the change of state parameter will affect the spacetime structure, thus affecting the observed features of black hole shadows. *supported by the national natural science foundation of china (11875095, 11903025), the sichuan youth science and technology innovation research team (21cxtd0038) and basic research project of science and technology committee of chongqing (cstc2018jcyja2480) | shadow images and observed luminosity of the bardeen black hole surrounded by different accretions |
we study the page curve and the information paradox for the bañados-teiteboim-zanelli black hole coupled to two thermal baths by applying the island paradigm. we prove that as the island locates outside the event horizon, the entanglement entropy of hawking radiation for finite temperature black holes obeys the page curve. however, for extremal rotating black holes, the page time and the scrambling time become divergent. to avoid the ill-defined nature of the page time, we consider the contribution of superradiance, which is a process that can extract rotational energy from black holes. the superradiance continues in a period much shorter than the page time when the central charge c is not too large. in this process, the page time, the scrambling time and the black hole thermal entropy all decrease. whenever the superradiance finishes, the black hole turns out to be a neutral black hole and the hawking radiation dominates. the page curve can then be well reproduced. | island, page curve, and superradiance of rotating btz black holes |
generalizing previous results for n = 0 and n = 1, we analyze n = 2 jt supergravity on asymptotically ads2 spaces with arbitrary topology and show that this theory of gravity is dual, in a holographic sense, to a certain random matrix ensemble in which supermultiplets of different r-charge are statistically independent and each is described by its own n = 2 random matrix ensemble. we also analyze the case with a time-reversal symmetry, either commuting or anticommuting with the r-charge. in order to compare supergravity to random matrix theory, we develop an n = 2 analog of the recursion relations for weil-petersson volumes originally discovered by mirzakhani in the bosonic case. | n = 2 jt supergravity and matrix models |
a search is reported for heavy resonances and quantum black holes decaying into eμ, eτ, and μτ final states in proton-proton collision data recorded by the cms experiment at the cern lhc during 2016-2018 at √{s } = 13 tev, corresponding to an integrated luminosity of 138 fb−1. the eμ, eτ, and μτ invariant mass spectra are reconstructed, and no evidence is found for physics beyond the standard model. upper limits are set at 95% confidence level on the product of the cross section and branching fraction for lepton flavor violating signals. three benchmark signals are studied: resonant τ sneutrino production in r parity violating supersymmetric models, heavy z' gauge bosons with lepton flavor violating decays, and nonresonant quantum black hole production in models with extra spatial dimensions. resonant τ sneutrinos are excluded for masses up to 4.2tev in the eμ channel, 3.7tev in the eτ channel, and 3.6tev in the μτ channel. a z' boson with lepton flavor violating couplings is excluded up to a mass of 5.0tev in the eμ channel, up to 4.3te v in the eτ channel, and up to 4.1tev in the μτ channel. quantum black holes in the benchmark model are excluded up to the threshold mass of 5.6tev in the eμ channel, 5.2tev in the eτ channel, and 5.0tev in the μτ channel. in addition, model-independent limits are extracted to allow comparisons with other models for the same final states and similar event selection requirements. the results of these searches provide the most stringent limits available from collider experiments for heavy particles that undergo lepton flavor violating decays. | search for heavy resonances and quantum black holes in eμ, eτ, and μτ final states in proton-proton collisions at √{s } = 13 tev |
the gravitational waves emitted by a perturbed black hole ringing down are well described by damped sinusoids, whose frequencies are those of quasinormal modes. typically, first-order black hole perturbation theory is used to calculate these frequencies. recently, it was shown that second-order effects are necessary in binary black hole merger simulations to model the gravitational-wave signal observed by a distant observer. here, we show that the horizon of a newly formed black hole after the head-on collision of two black holes also shows evidence of nonlinear modes. specifically, we identify one quadratic mode for the l =2 shear data, and two quadratic ones for the l =4 , 6 data in simulations with varying mass ratio and boost parameter. the quadratic mode amplitudes display a quadratic relationship with the amplitudes of the linear modes that generate them. | nonlinear ringdown at the black hole horizon |
recent works have suggested that nonlinear (quadratic) effects in black hole perturbation theory may be important for describing a black hole ringdown. we show that the technique of uniform approximations can be used to accurately compute 1) nonlinear amplitudes at large distances in terms of the linear ones, 2) linear (and nonlinear) quasi-normal mode frequencies, 3) the wavefunction for both linear and nonlinear modes. our method can be seen as a generalization of the wkb approximation, with the advantages of not losing accuracy at large overtone number and not requiring matching conditions. to illustrate the effectiveness of this method we consider a simplified source for the second-order zerilli equation, which we use to numerically compute the amplitude of nonlinear modes for a range of values of the angular momentum number. | nonlinear quasi-normal modes: uniform approximation |
we study the holographic correlators corresponding to scattering of fluctuations of an open string worldsheet with ads2 geometry. in the out-of-time-order configuration, the correlators display a lyapunov growth that saturates the chaos bound. we show that in a double-scaling limit interpolating between the lyapunov regime and the late time exponential decay, the out-of-time-order correlator (otoc) can be obtained exactly, and it has the same functional form found in the analogous calculation in jt gravity. the result can be understood as coming from high energy scattering near the horizon of a ads2 black hole, and is essentially controlled by the flat space worldsheet s-matrix. while previous works on the ads2 string employed mainly a static gauge approach, here we focus on conformal gauge and clarify the role of boundary reparametrizations in the calculation of the correlators. we find that the reparametrization mode is governed by a non-local action which is distinct from the schwarzian action arising in jt gravity, and in particular leads to sl(2, &r;) invariant boundary correlators. the otoc in the double-scaling limit, however, has the same functional form as that obtained from the schwarzian, and it can be computed using the reparametrization action and resumming a subset of diagrams that are expected to dominate in the limit. one application of our results is to the defect cft defined by the half-bps wilson loop in n = 4 sym. in this context, we show that the exact result for the otoc in the double-scaling limit is in precise agreement with a recent analytic bootstrap prediction to three-loop order at strong coupling. | chaos and the reparametrization mode on the ads2 string |
we compare gw150914 directly to simulations of coalescing binary black holes in full general relativity, including several performed specifically to reproduce this event. our calculations go beyond existing semianalytic models, because for all simulations—including sources with two independent, precessing spins—we perform comparisons which account for all the spin-weighted quadrupolar modes, and separately which account for all the quadrupolar and octopolar modes. consistent with the posterior distributions reported by abbott et al. [phys. rev. lett. 116, 241102 (2016)] (at the 90% credible level), we find the data are compatible with a wide range of nonprecessing and precessing simulations. follow-up simulations performed using previously estimated binary parameters most resemble the data, even when all quadrupolar and octopolar modes are included. comparisons including only the quadrupolar modes constrain the total redshifted mass mz∈[64 m⊙-82 m⊙] , mass ratio 1 /q =m2/m1∈[0.6 ,1 ], and effective aligned spin χeff∈[-0.3 ,0.2 ], where χeff=(s1/m1+s2/m2).l ^/m . including both quadrupolar and octopolar modes, we find the mass ratio is even more tightly constrained. even accounting for precession, simulations with extreme mass ratios and effective spins are highly inconsistent with the data, at any mass. several nonprecessing and precessing simulations with similar mass ratio and χeff are consistent with the data. though correlated, the components' spins (both in magnitude and directions) are not significantly constrained by the data: the data is consistent with simulations with component spin magnitudes a1 ,2 up to at least 0.8, with random orientations. further detailed follow-up calculations are needed to determine if the data contain a weak imprint from transverse (precessing) spins. for nonprecessing binaries, interpolating between simulations, we reconstruct a posterior distribution consistent with previous results. the final black hole's redshifted mass is consistent with mf ,z in the range 64.0 m⊙-73.5 m⊙ and the final black hole's dimensionless spin parameter is consistent with af=0.62 - 0.73 . as our approach invokes no intermediate approximations to general relativity and can strongly reject binaries whose radiation is inconsistent with the data, our analysis provides a valuable complement to abbott et al. [phys. rev. lett. 116, 241102 (2016)]. | directly comparing gw150914 with numerical solutions of einstein's equations for binary black hole coalescence |
we construct static and spherically symmetric generalizations of the schwarzschild- and reissner-nordström-(anti-)de sitter [rn-(a)ds] black-hole solutions in four-dimensional einsteinian cubic gravity (ecg). the solutions are characterized by a single function which satisfies a nonlinear second-order differential equation. interestingly, we are able to compute independently the hawking temperature t , the wald entropy s and the abbott-deser mass m of the solutions analytically as functions of the horizon radius and the ecg coupling constant λ . using these we show that the first law of black-hole mechanics is exactly satisfied. some of the solutions have positive specific heat, which makes them thermodynamically stable, even in the uncharged and asymptotically flat case. further, we claim that, up to cubic order in curvature, ecg is the most general four-dimensional theory of gravity which allows for nontrivial generalizations of schwarzschild- and rn-(a)ds characterized by a single function which reduce to the usual einstein gravity solutions when the corresponding higher-order couplings are set to zero. | four-dimensional black holes in einsteinian cubic gravity |
we study the reflected entropy sr in the west coast model, a toy model of black hole evaporation consisting of jt gravity coupled to end-of-the-world branes. we demonstrate the validity of the holographic duality relating it to the entanglement wedge cross section away from phase transitions. further, we analyze the important non-perturbative effects that smooth out the discontinuity in the sr phase transition. by performing the gravitational path integral, we obtain the reflected entanglement spectrum analytically. the spectrum takes a simple form consisting of superselection sectors, which we interpret as a direct sum of geometries, a disconnected one and a connected one involving a closed universe. we find that area fluctuations of o (√{gn}) spread out the sr phase transition in the canonical ensemble, analogous to the entanglement entropy phase transition. we also consider a renyi generalization of the reflected entropy and show that the location of the phase transition varies as a function of the renyi parameter. | the page curve for reflected entropy |
primordial black hole (pbh) formation during cosmic phase transitions and annihilation periods, such as the qcd transition or the $e^+e^-$-annihilation, is known to be particularly efficient due to a softening of the equation of state. we present a detailed numerical study of pbh formation during the qcd epoch in order to derive an accurate pbh mass function. we also briefly consider pbh formation during the $e^+e^-$-annihilation epoch. our investigation confirms that, for nearly scale-invariant spectra, pbh abundances on the qcd scale are enhanced by a factor $\sim 10^3$ compared to a purely radiation dominated universe. for a power spectrum producing an (almost) scale-invariant pbh mass function outside of the transition, we find a peak mass of $m_{\rm pbh}\approx 1.9 m_{\odot}$ of which a fraction $f\approx 1.5\times 10^{-2}$ of the pbhs have a mass of $m_{\rm pbh} > 10 m_{\odot}$, possibly contributing to the ligo-virgo black hole merger detections. we point out that the physics of pbh formation during the $e^+e^-$-annihilation epoch is more complex as it is very close to the epoch of neutrino decoupling. we argue that neutrinos free-streaming out of overdense regions may actually hinder pbh formation. | primordial black hole formation during the qcd phase transition: threshold, mass distribution and abundance |
perturbations of massless fields in the kerr-newman black hole background enjoy a ("love") sl(2, &r;) symmetry in the suitably defined near zone approximation. we present a detailed study of this symmetry and show how the intricate behavior of black hole responses in four and higher dimensions can be understood from the sl(2, &r;) representation theory. in particular, static perturbations of four-dimensional black holes belong to highest weight sl(2, &r;) representations. it is this highest weight properety that forces the static love numbers to vanish. we find that the love symmetry is tightly connected to the enhanced isometries of extremal black holes. this relation is simplest for extremal charged spherically symmetric (reissner-nordström) solutions, where the love symmetry exactly reduces to the isometry of the near horizon ads2 throat. for rotating (kerr-newman) black holes one is lead to consider an infinite-dimensional sl(2, &r;) ⋉ u ̂(1)v extension of the love symmetry. it contains three physically distinct subalgebras: the love algebra, the starobinsky near zone algebra, and the near horizon algebra that becomes the bardeen-horowitz isometry in the extremal limit. we also discuss other aspects of the love symmetry, such as the geometric meaning of its generators for spin weighted fields, connection to the no-hair theorems, non-renormalization of love numbers, its relation to (non-extremal) kerr/cft correspondence and prospects of its existence in modified theories of gravity. | love symmetry |
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