abstract stringlengths 3 192k | title stringlengths 4 857 |
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we study the page curve for asymptotically flat eternal schwarzschild black holes in four and higher spacetime dimensions. before the page time, the entanglement entropy grows linearly in time. after the page time, the entanglement entropy of a given region outside the black hole is largely modified by the emergence of an island, which extends to the outer vicinity of the event horizon. as a result, it remains a constant value which reproduces the bekenstein-hawking entropy, consistent with the finiteness of the von neumann entropy for an eternal black hole. | islands in schwarzschild black holes |
in this note, following [1-3], we introduce and study various holographic systems which can describe evaporating black holes. the systems we consider are boundary conformal field theories for which the number of local degrees of freedom on the boundary (cbdy) is large compared to the number of local degrees of freedom in the bulk cft (cbulk). we consider states where the boundary degrees of freedom on their own would describe an equilibrium black hole, but the coupling to the bulk cft degrees of freedom allows this black hole to evaporate. the page time for the black hole is controlled by the ratio cbdy/cbulk. using both holographic calculations and direct cft calculations, we study the evolution of the entanglement entropy for the subset of the radiation system (i.e. the bulk cft) at a distance d > a from the boundary. we find that the entanglement entropy for this subsystem increases until time a + tpage and then undergoes a phase transition after which the entanglement wedge of the radiation system includes the black hole interior. remarkably, this occurs even if the radiation system is initially at the same temperature as the black hole so that the two are in thermal equilibrium. in this case, even though the black hole does not lose energy, it "radiates" information through interaction with the radiation system until the radiation system contains enough information to reconstruct the black hole interior. | information radiation in bcft models of black holes |
celestial amplitudes represent 4d scattering of particles in boost, rather than the usual energy-momentum, eigenstates and hence are sensitive to both uv and ir physics. we show that known uv and ir properties of quantum gravity translate into powerful constraints on the analytic structure of celestial amplitudes. for example the soft uv behavior of quantum gravity is shown to imply that the exact four-particle scattering amplitude is meromorphic in the complex boost weight plane with poles confined to even integers on the negative real axis. would-be poles on the positive real axis from uv asymptotics are shown to be erased by a flat space analog of the ads resolution of the bulk point singularity. the residues of the poles on the negative axis are identified with operator coefficients in the ir effective action. far along the real positive axis, the scattering is argued to grow exponentially according to the black hole area law. exclusive amplitudes are shown to simply factorize into conformally hard and conformally soft factors. the soft factor contains all ir divergences and is given by a celestial current algebra correlator of goldstone bosons from spontaneously broken asymptotic symmetries. the hard factor describes the scattering of hard particles together with the boost-eigenstate clouds of soft photons or gravitons required by asymptotic symmetries. these provide an ir safe s -matrix for the scattering of hard particles. | celestial amplitudes from uv to ir |
in holographic duality an eternal anti-de sitter black hole is described by two copies of the boundary conformal field theory in the thermal field double state. this identification has many puzzles, including the boundary descriptions of the event horizons, the interiors of the black hole, and the singularities. compounding these mysteries is the fact that, while there is no interaction between the conformal field theories, observers from them can fall into the black hole and interact. we address these issues in this paper. in particular, we (i) present a boundary formulation of a class of in-falling bulk observers; (ii) present an argument that a sharp bulk event horizon can only emerge in the infinite n limit of the boundary theory; (iii) give an explicit construction in the boundary theory of an evolution operator for a bulk in-falling observer, making manifest the boundary emergence of the black hole horizons, the interiors, and the associated causal structure. a byproduct is a concept called causal connectability, which is a criterion for any two quantum systems (which do not need to have a known gravity dual) to have an emergent sharp horizon structure. | causal connectability between quantum systems and the black hole interior in holographic duality |
in this paper we use the ads/cft correspondence to refine and then establish a set of old conjectures about symmetries in quantum gravity. we first show that any global symmetry, discrete or continuous, in a bulk quantum gravity theory with a cft dual would lead to an inconsistency in that cft, and thus that there are no bulk global symmetries in ads/cft. we then argue that any "long-range" bulk gauge symmetry leads to a global symmetry in the boundary cft, whose consistency requires the existence of bulk dynamical objects which transform in all finite-dimensional irreducible representations of the bulk gauge group. we mostly assume that all internal symmetry groups are compact, but we also give a general condition on cfts, which we expect to be true quite broadly, which implies this. we extend all of these results to the case of higher-form symmetries. finally we extend a recently proposed new motivation for the weak gravity conjecture to more general gauge groups, reproducing the "convex hull condition" of cheung and remmen. an essential point, which we dwell on at length, is precisely defining what we mean by gauge and global symmetries in the bulk and boundary. quantum field theory results we meet while assembling the necessary tools include continuous global symmetries without noether currents, new perspectives on spontaneous symmetry-breaking and 't hooft anomalies, a new order parameter for confinement which works in the presence of fundamental quarks, a hamiltonian lattice formulation of gauge theories with arbitrary discrete gauge groups, an extension of the coleman-mandula theorem to discrete symmetries, and an improved explanation of the decay $\pi^0\to\gamma \gamma$ in the standard model of particle physics. we also describe new black hole solutions of the einstein equation in $d+1$ dimensions with horizon topology $\mathbb{t}^p\times \mathbb{s}^{d-p-1}$. | symmetries in quantum field theory and quantum gravity |
we recently introduced in [9] a boundary-to-bound dictionary between gravitational scattering data and observables for bound states of non-spinning bodies. in this paper, we elaborate further on this holographic map. we start by deriving the following — remarkably simple — formula relating the periastron advance to the scattering angle: δφ (" separators=",j e )=χ (" separators=",j e )+χ (" separators=",-j e ), via analytic continuation in angular momentum and binding energy. using explicit expressions from [9], we confirm its validity to all orders in the post-minkowskian (pm) expansion. furthermore, we reconstruct the radial action for the bound state directly from the knowledge of the scattering angle. the radial action enables us to write compact expressions for dynamical invariants in terms of the deflection angle to all pm orders, which can also be written as a function of the pm-expanded amplitude. as an example, we reproduce our result in [9] for the periastron advance, and compute the radial and azimuthal frequencies and redshift variable to two-loops. agreement is found in the overlap between pm and post-newtonian (pn) schemes. last but not least, we initiate the study of our dictionary including spin. we demonstrate that the same relation between deflection angle and periastron advance applies for aligned-spin contributions, with j the (canonical) total angular momentum. explicit checks are performed to display perfect agreement using state-of-the-art pn results in the literature. using the map between test- and two-body dynamics, we also compute the periastron advance up to quadratic order in spin, to one-loop and to all orders in velocity. we conclude with a discussion on the generalized `impetus formula' for spinning bodies and black holes as `elementary particles'. our findings here and in [9] imply that the deflection angle already encodes vast amount of physical information for bound orbits, encouraging independent derivations using numerical and/or self-force methodologies. | from boundary data to bound states. part ii. scattering angle to dynamical invariants (with twist) |
we consider black holes in 2d de sitter jt gravity coupled to a cft, and entangled with matter in a disjoint non-gravitating universe. tracing out the entangling matter leaves the cft in a density matrix whose stress tensor backreacts on the de sitter geometry, lengthening the wormhole behind the black hole horizon. naively, the entropy of the entangling matter increases without bound as the strength of the entanglement increases, but the monogamy property predicts that this growth must level off. we compute the entropy via the replica trick, including wormholes between the replica copies of the de sitter geometry, and find a competition between conventional field theory entanglement entropy and the surface area of extremal "islands" in the de sitter geometry. the black hole and cosmological horizons both play a role in generating such islands in the backreacted geometry, and have the effect of stabilizing the entropy growth as required by monogamy. we first show this in a scenario in which the de sitter spatial section has been decompactified to an interval. then we consider the compact geometry, and argue for a novel interpretation of the island formula in the context of closed universes that recovers the page curve. finally, we comment on the application of our construction to the cosmological horizon in empty de sitter space. | islands in de sitter space |
the gravitational wave observations gw150914 and gw151226 by advanced ligo provide the first opportunity to learn about physics in the extreme gravity environment of coalescing binary black holes. the ligo scientific collaboration and the virgo collaboration have verified that this observation is consistent with einstein's theory of general relativity, constraining the presence of certain parametric anomalies in the signal. this paper expands their analysis to a larger class of anomalies, highlighting the inferences that can be drawn on nonstandard theoretical physics mechanisms that could otherwise have affected the observed signals. we find that these gravitational wave events constrain a plethora of mechanisms associated with the generation and propagation of gravitational waves, including the activation of scalar fields, gravitational leakage into large extra dimensions, the variability of newton's constant, the speed of gravity, a modified dispersion relation, gravitational lorentz violation and the strong equivalence principle. though other observations limit many of these mechanisms already, gw150914 and gw151226 are unique in that they are direct probes of dynamical strong-field gravity and of gravitational wave propagation. we also show that gw150914 constrains inferred properties of exotic compact object alternatives to kerr black holes. we argue, however, that the true potential for gw150914 to both rule out exotic objects and constrain physics beyond general relativity is severely limited by the lack of understanding of the coalescence regime in almost all relevant modified gravity theories. this event thus significantly raises the bar that these theories have to pass, both in terms of having a sound theoretical underpinning and reaching the minimal level of being able to solve the equations of motion for binary merger events. we conclude with a discussion of the additional inferences that can be drawn if the lower-confidence observation of an electromagnetic counterpart to gw150914 holds true, or such a coincidence is observed with future events; this would provide dramatic constraints on the speed of gravity and gravitational lorentz violation. | theoretical physics implications of the binary black-hole mergers gw150914 and gw151226 |
for the first time, we construct an inspiral-merger-ringdown waveform model within the effective-one-body formalism for spinning, nonprecessing binary black holes that includes gravitational modes beyond the dominant (ℓ,|m |)=(2 ,2 ) mode, specifically (ℓ,|m |)=(2 ,1 ),(3 ,3 ),(4 ,4 ),(5 ,5 ). our multipolar waveform model incorporates recent (resummed) post-newtonian results for the inspiral and information from 157 numerical-relativity simulations, and 13 waveforms from black-hole perturbation theory for the (plunge-)merger and ringdown. we quantify the improvement in accuracy when including higher-order modes by computing the faithfulness of the waveform model against the numerical-relativity waveforms used to construct the model. we define the faithfulness as the match maximized over time, phase of arrival, gravitational-wave polarization and sky position of the waveform model, and averaged over binary orientation, gravitational-wave polarization and sky position of the numerical-relativity waveform. when the waveform model contains only the (2,2) mode, we find that the averaged faithfulness to numerical-relativity waveforms containing all modes with ℓ≤5 ranges from 90% to 99.9% for binaries with total mass 20 - 200 m⊙ (using the advanced ligo's design noise curve). by contrast, when the (2,1), (3,3), (4,4), (5,5) modes are also included in the model, the faithfulness improves to 99% for all but four configurations in the numerical-relativity catalog, for which the faithfulness is greater than 98.5%. starting from the complete inspiral-merger-ringdown model, we develop also a (stand-alone) waveform model for the merger-ringdown signal, calibrated to numerical-relativity waveforms, which can be used to measure multiple quasi-normal modes. the multipolar waveform model can be extended to include spin-precessional effects, and will be employed in upcoming observing runs of advanced ligo and virgo. | enriching the symphony of gravitational waves from binary black holes by tuning higher harmonics |
we show how to decoupling two spherically symmetric and static gravitational sources through the most general possible extension of the so-called minimal geometric deformation-decoupling. as a test, we decouple the einstein-maxwell system and reproduce the reissner-nordstrom solution. we show the potential of this method to study i) the consequences of modified gravity on general relativity, ii) to investigate the conjectured dark matter, and iii) to study hairy black holes. | decoupling gravitational sources in general relativity: the extended case |
quantum computational complexity estimates the difficulty of constructing quantum states from elementary operations, a problem of prime importance for quantum computation. surprisingly, this quantity can also serve to study a completely different physical problem - that of information processing inside black holes. quantum computational complexity was suggested as a new entry in the holographic dictionary, which extends the connection between geometry and information and resolves the puzzle of why black hole interiors keep growing for a very long time. in this pedagogical review, we present the geometric approach to complexity advocated by nielsen and show how it can be used to define complexity for generic quantum systems; in particular, we focus on gaussian states in qft, both pure and mixed, and on certain classes of cft states. we then present the conjectured relation to gravitational quantities within the holographic correspondence and discuss several examples in which different versions of the conjectures have been tested. we highlight the relation between complexity, chaos and scrambling in chaotic systems. we conclude with a discussion of open problems and future directions. this article was written for the special issue of epj-c frontiers in holographic duality. | quantum computational complexity from quantum information to black holes and back |
we use a previously developed scattering-amplitudes-based framework for determining two-body hamiltonians for generic binary systems with arbitrary spin s . by construction this formalism bypasses difficulties with unphysical singularities or higher-time derivatives. this framework has been previously used to obtain the exact velocity dependence of the o (g2) quadratic-in-spin two-body hamiltonian. we first evaluate the s3 scattering angle and two-body hamiltonian at this order in g , including not only all operators corresponding to the usual worldline operators, but also an additional set due to an interesting subtlety. we then evaluate s4 and s5 contributions at o (g2) which we confirm by comparing against aligned-spin results. we conjecture that a certain shift symmetry together with a constraint on the high-energy growth of the scattering amplitude specify the wilson coefficients for the kerr black hole to all orders in the spin and confirm that they reproduce the previously obtained results through s4. | binary dynamics through the fifth power of spin at o (g2) |
the large-n limit of asymptotically flat two-dimensional dilaton gravity coupled to n free matter fields provides a useful toy model for semiclassical black holes and the information paradox. analyses of the asymptotic information flux as given by the entanglement entropy show that it follows the hawking curve, indicating that information is destroyed in these models. recently, motivated by developments in ads/cft, a semiclassical island rule for entropy has been proposed. we define and compute the island rule entropy for black hole formation and evaporation in the large-n rst model of dilaton gravity and show that, in contrast, it follows the unitary page curve. the relation of these two observations, and interesting properties of the dilaton gravity island rule, are discussed. | islands in asymptotically flat 2d gravity |
we provide a moduli-dependent definition of species scale in quantum gravity based on black hole arguments. concretely, it is derived from a lower bound on the entropy of extremal black holes with higher curvature corrections, which ensures that the black hole can be reliably described within the effective theory. by demanding that our definition coincides with a recent proposal for a moduli-dependent species scale motivated from the topological string, we conclude that the conjecture zbh = |ztop|2 relating the black hole to the topological string partition functions should hold, at least within the regime of validity of our analysis. | black hole entropy and moduli-dependent species scale |
we provide the analytic waveform in time domain for the scattering of two kerr black holes at leading order in the post-minkowskian expansion and up to fourth order in both spins. the result is obtained by the generalization of the kmoc formalism to radiative observables, combined with the analytic continuation of the five-point scattering amplitude to complex kinematics. we use analyticity arguments to express the waveform directly in terms of the three-point coupling of the graviton to the spinning particles and the gravitational compton amplitudes, completely bypassing the need to compute and integrate the five-point amplitude. in particular, this allows to easily include higher-order spin contributions for any spinning compact body. finally, in the spinless case we find a new compact and gauge-invariant representation of the kovacs-thorne waveform. | spinning waveforms from kmoc at leading order |
there are various definitions of the concept of complexity in quantum field theory as well as for finite quantum systems. for several of them there are conjectured holographic bulk duals. in this work we establish an entry in the ads/cft dictionary for one such class of complexity, namely krylov or k-complexity. for this purpose we work in the double-scaled syk model which is dual in a certain limit to jt gravity, a theory of gravity in ads2. in particular, states on the boundary have a clear geometrical definition in the bulk. we use this result to show that krylov complexity of the infinite-temperature thermofield double state on the boundary of ads2 has a precise bulk description in jt gravity, namely the length of the two-sided wormhole. we do this by showing that the krylov basis elements, which are eigenstates of the krylov complexity operator, are mapped to length eigenstates in the bulk theory by subjecting k-complexity to the bulk-boundary map identifying the bulk/boundary hilbert spaces. our result makes extensive use of chord diagram techniques and identifies the krylov basis of the boundary quantum system with fixed chord number states building the bulk gravitational hilbert space. | a bulk manifestation of krylov complexity |
motivated by holographic complexity proposals as novel probes of black hole spacetimes, we explore circuit complexity for thermofield double (tfd) states in free scalar quantum field theories using the nielsen approach. for tfd states at t = 0, we show that the complexity of formation is proportional to the thermodynamic entropy, in qualitative agreement with holographic complexity proposals. for tfd states at t > 0, we demonstrate that the complexity evolves in time and saturates after a time of the order of the inverse temperature. the latter feature, which is in contrast with the results of holographic proposals, is due to the gaussian nature of the tfd state of the free bosonic qft. a novel technical aspect of our work is framing complexity calculations in the language of covariance matrices and the associated symplectic transformations, which provide a natural language for dealing with gaussian states. furthermore, for free qfts in 1+1 dimension, we compare the dynamics of circuit complexity with the time dependence of the entanglement entropy for simple bipartitions of tfds. we relate our results for the entanglement entropy to previous studies on non-equilibrium entanglement evolution following quenches. we also present a new analytic derivation of a logarithmic contribution due to the zero momentum mode in the limit of vanishing mass for a subsystem containing a single degree of freedom on each side of the tfd and argue why a similar logarithmic growth should be present for larger subsystems. | complexity and entanglement for thermofield double states |
we introduce on-shell variables for heavy particle effective theories (hpets) with the goal of extending heavy black hole effective theory to higher spins and of facilitating its application to higher post-minkowskian orders. these variables inherit the separation of spinless and spin-inclusive effects from the hpet fields, resulting in an explicit spin-multipole expansion of the three-point amplitude for any spin. by matching amplitudes expressed using the on-shell hpet variables to those derived from the one-particle effective action, we find that the spin-multipole expansion of a heavy spin-s particle corresponds exactly to the multipole expansion (up to order 2s) of a kerr black hole, that is, without needing to take the infinite spin limit. finally, we show that tree-level radiative processes with same-helicity bosons emitted from a heavy spin-s particle exhibit a spin-multipole universality. | on-shell heavy particle effective theories |
in the 1980's, work by coleman and by giddings and strominger linked the physics of spacetime wormholes to `baby universes' and an ensemble of theories. we revisit such ideas, using features associated with a negative cosmological constant and asymptotically ads boundaries to strengthen the results, introduce a change in perspective, and connect with recent replica wormhole discussions of the page curve. a key new feature is an emphasis on the role of null states. we explore this structure in detail in simple topological models of the bulk that allow us to compute the full spectrum of associated boundary theories. the dimension of the asymptotically ads hilbert space turns out to become a random variable z , whose value can be less than the naive number k of independent states in the theory. for k > z , consistency arises from an exact degeneracy in the inner product defined by the gravitational path integral, so that many a priori independent states differ only by a null state. we argue that a similar property must hold in any consistent gravitational path integral. we also comment on other aspects of extrapolations to more complicated models, and on possible implications for the black hole information problem in the individual members of the above ensemble. | transcending the ensemble: baby universes, spacetime wormholes, and the order and disorder of black hole information |
we study the ads/bcft duality between two-dimensional conformal field theories with two boundaries and three-dimensional anti-de sitter space with two karch-randall branes. we compute the entanglement entropy of a bipartition of the bcft, on both the gravity side and the field theory side. at finite temperature this entanglement entropy characterizes the communication between two braneworld black holes, coupled to each other through a common bath. we find a page curve consistent with unitarity. the gravitational result, computed using double-holographically realized quantum extremal surfaces, matches the conformal field theory calculation.at zero temperature, we obtain an interesting extension of the ads3/bcft2 correspondence. for a central charge c, we find a gap ,c/16 c/12 ) in the spectrum of the scaling dimension ∆bcc of the boundary condition changing operator (which interpolates mismatched boundary conditions on the two boundaries of the bcft). depending on the value of ∆bcc, the gravitational dual is either a defect global ads3 geometry or a single sided black hole, and in both cases there are two karch-randall branes. | holographic bcfts and communicating black holes |
we explore various tree-level double copy constructions for amplitudes including massive particles with spin. by working in general dimensions, we use that particles with spins s ≤ 2 are fundamental to argue that the corresponding double copy relations partially follow from compactification of their massless counterparts. this massless origin fixes the coupling of gluons, dilatons and axions to matter in a characteristic way (for instance fixing the gyromagnetic ratio), whereas the graviton couples universally reflecting the equivalence principle. for spin-1 matter we conjecture all-order lagrangians reproducing the interactions with up to two massive lines and we test them in a classical setup, where the massive lines represent spinning compact objects such as black holes. we also test the amplitudes via chy formulae for both bosonic and fermionic integrands. at five points, we show that by applying generalized gauge transformations one can obtain a smooth transition from quantum to classical bcj double copy relations for radiation, thereby providing a qft derivation for the latter. as an application, we show how the theory arising in the classical double copy of goldberger and ridgway can be naturally identified with a certain compactification of n = 4 supergravity. | on the double copy for spinning matter |
we present a general procedure for constructing exact black hole solutions with electric or magnetic charges in general relativity coupled to a nonlinear electrodynamics. we obtain a variety of two-parameter family spherically symmetric black hole solutions. in particular, the singularity at the center of the space-time can be canceled in the parameter space and the black hole solutions become regular everywhere in space-time. we study the global properties of the solutions and derive the first law of thermodynamics. we also generalize the procedure to include a cosmological constant and construct regular black hole solutions that are asymptotic to anti-de sitter space-time. | construction of regular black holes in general relativity |
using extended island formula we compute entanglement entropy of hawking radiation for black hole solutions of certain gravitational models containing higher derivative terms. to be concrete we consider two different four dimensional models to compute entropy for both asymptotically flat and ads black holes. one observes that the resultant entropy follows the page curve, thanks to the contribution of the island, despite the fact that the corresponding gravitational models might be non-unitary. | island in the presence of higher derivative terms |
the fate of cauchy horizons, such as those found inside charged black holes, is intrinsically connected to the decay of small perturbations exterior to the event horizon. as such, the validity of the strong cosmic censorship (scc) conjecture is tied to how effectively the exterior damps fluctuations. here, we study massless scalar fields in the exterior of reissner-nordström-de sitter black holes. their decay rates are governed by quasinormal modes of the black hole. we identify three families of modes in these spacetimes: one directly linked to the photon sphere, well described by standard wkb-type tools; another family whose existence and time scale is closely related to the de sitter horizon; finally, a third family which dominates for near-extremally charged black holes and which is also present in asymptotically flat spacetimes. the last two families of modes seem to have gone unnoticed in the literature. we give a detailed description of linear scalar perturbations of such black holes, and conjecture that scc is violated in the near extremal regime. | quasinormal modes and strong cosmic censorship |
we study the shadows cast by the different types of rotating regular black holes viz. ayón-beato-garcía (abg), hayward, and bardeen. these black holes have in addition to the total mass (m ) and rotation parameter (a ), different parameters as electric charge (q ), deviation parameter (g ), and magnetic charge (g*). interestingly, the size of the shadow is affected by these parameters in addition to the rotation parameter. we found that the radius of the shadow in each case decreases monotonically, and the distortion parameter increases when the values of these parameters increase. a comparison with the standard kerr case is also investigated. we have also studied the influence of the plasma environment around regular black holes to discuss its shadow. the presence of the plasma affects the apparent size of the regular black hole's shadow to be increased due to two effects: (i) gravitational redshift of the photons and (ii) radial dependence of plasma density. | shadow of rotating regular black holes |
a remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. this area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. in this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. however, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires rényi entropies. here we show that all rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. this geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. applying this we provide the first holographic calculation of mutual rényi information between two disks of arbitrary dimension. our results provide a framework for efficiently studying rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity. | the gravity dual of rényi entropy |
we review potential low-frequency gravitational-wave sources, which are expected to be detected by taiji, a chinese space-based gravitational-wave detector, estimate the detection rates of these gravitational-wave sources and present the parameter estimation of massive black hole binaries. | taiji program: gravitational-wave sources |
quantum black holes are described by a large number of macroscopically indistinguishable microstates. correlation functions of fields outside the horizon at long time separation probe this indistinguishability. the simplest of these, the thermal two-point function, oscillates erratically around a nonperturbatively small average "ramp" and "plateau" after an initial period of decay; these non-decaying averaged features are signatures of the discreteness of the black hole spectrum. for a theory described by an ensemble of hamiltonians, the two-point function follows this averaged behavior. in this paper we study certain correlation functions in jackiw-teitelboim (jt) gravity and find precise agreement with the behavior expected for a theory described by an ensemble of hamiltonians with random matrix statistics -- the eigenstates obey the eigenstate thermalization hypothesis (eth) and the energy levels have random matrix level statistics. a central aspect of our analysis is an averaged bulk hilbert space description of the relevant behavior. the mechanism behind this behavior is topology change due the the emission and absorption of closed "baby universes". these baby universe effects give two complementary pictures of the non-decaying behavior, related by different continuations of a euclidean geometry. a long einstein-rosen bridge can become short by emitting a large baby universe, and baby universes emitted and reabsorbed at points widely separated in space and time creates a "shortcut", allowing particles to leave the interior of the black hole. | late time correlation functions, baby universes, and eth in jt gravity |
scrambling, a process in which quantum information spreads over a complex quantum system, becoming inaccessible to simple probes, occurs in generic chaotic quantum many-body systems, ranging from spin chains to metals and even to black holes. scrambling can be measured using out-of-time-ordered correlators (otocs), which are closely tied to the growth of heisenberg operators. we present a general method to calculate otocs of local operators in one-dimensional systems based on approximating heisenberg operators as matrix product operators (mpos). contrary to the common belief that such tensor network methods work only at early times, we show that the entire early growth region of the otoc can be captured using an mpo approximation with modest bond dimension. we analytically establish the goodness of the approximation by showing that, if an appropriate otoc is close to its initial value, then the associated heisenberg operator has low entanglement across a given cut. we use the method to study scrambling in a chaotic spin chain with 201 ? sites. on the basis of these data and previous results, we conjecture a universal form for the dynamics of the otoc near the wavefront. we show that this form collapses the chaotic spin chain data over more than 15 orders of magnitude. | accessing scrambling using matrix product operators |
we study the stability of quasinormal modes (qnm) in asymptotically flat black hole spacetimes by means of a pseudospectrum analysis. the construction of the schwarzschild qnm pseudospectrum reveals the following: (i) the stability of the slowest-decaying qnm under perturbations respecting the asymptotic structure, reassessing the instability of the fundamental qnm discussed by nollert [h. p. nollert, about the significance of quasinormal modes of black holes, phys. rev. d 53, 4397 (1996), 10.1103/physrevd.53.4397] as an "infrared" effect; (ii) the instability of all overtones under small-scale ("ultraviolet") perturbations of sufficiently high frequency, which migrate towards universal qnm branches along pseudospectra boundaries, shedding light on nollert's pioneer work and nollert and price's analysis [h. p. nollert and r. h. price, quantifying excitations of quasinormal mode systems, j. math. phys. (n.y.) 40, 980 (1999), 10.1063/1.532698]. methodologically, a compactified hyperboloidal approach to qnms is adopted to cast qnms in terms of the spectral problem of a non-self-adjoint operator. in this setting, spectral (in)stability is naturally addressed through the pseudospectrum notion that we construct numerically via chebyshev spectral methods and foster in gravitational physics. after illustrating the approach with the pöschl-teller potential, we address the schwarzschild black hole case, where qnm (in)stabilities are physically relevant in the context of black hole spectroscopy in gravitational-wave physics and, conceivably, as probes into fundamental high-frequency spacetime fluctuations at the planck scale. | pseudospectrum and black hole quasinormal mode instability |
recent progress in our understanding of the black hole information paradox has lead to a new prescription for calculating entanglement entropies, which involves special subsystems in regions where gravity is dynamical, called \textit{quantum extremal islands}. we present a simple holographic framework where the emergence of quantum extremal islands can be understood in terms of the standard ryu-takayanagi prescription, used for calculating entanglement entropies in the boundary theory. our setup describes a $d$-dimensional boundary cft coupled to a ($d$-1)-dimensional defect, which are dual to global ads${}_{d+1}$ containing a codimension-one brane. through the randall-sundrum mechanism, graviton modes become localized at the brane, and in a certain parameter regime, an effective description of the brane is given by einstein gravity on an ads${}_d$ background coupled to two copies of the boundary cft. within this effective description, the standard rt formula implies the existence of quantum extremal islands in the gravitating region, whenever the rt surface crosses the brane. this indicates that islands are a universal feature of effective theories of gravity and need not be tied to the presence of black holes. | quantum extremal islands made easy, part i: entanglement on the brane |
the presence of a bright "photon ring" surrounding a dark "black hole shadow" has been discussed as an important feature of the observational appearance of emission originating near a black hole. we clarify the meaning and relevance of these heuristics with analytic calculations and numerical toy models. the standard usage of the term "shadow" describes the appearance of a black hole illuminated from all directions, including from behind the observer. a backlit black hole casts a somewhat larger shadow. neither "shadow" heuristic is particularly relevant to understanding the appearance of emission originating near the black hole, where the emission profile and gravitational redshift play the dominant roles in determining the observed size of the central dark area. a photon ring results from light rays that orbit around the black hole in the near-field region before escaping to infinity, where they arrive near a ring-shaped "critical curve" on the image plane. although the brightness can become arbitrarily large near this critical curve in the case of optically thin emitting matter near the black hole, we show that the enhancement is only logarithmic, and hence is of no relevance to present observations. for optically thin emission from a geometrically thin or thick disk, photons that make only a fraction of an orbit will generically give rise to a much wider "lensing ring," which is a demagnified image of the back of the disk, superimposed on top of the direct emission. for nearly face-on viewing, the lensing ring is centered at a radius ∼5 % larger than the photon ring and, depending on the details of the emission, its width is ∼0.5 - 1 m (where m is the mass of the black hole). it can be relatively brighter by a factor of 2-3, as compared to the surrounding parts of the image, and thus could provide a significant feature in high-resolution images. nevertheless, the characteristic features of the observed image are dominated by the location and properties of the emitting matter near the black hole. we comment on the recent m87* event horizon telescope observations and mass measurement. | black hole shadows, photon rings, and lensing rings |
the exactly solvable sachdev-ye-kitaev (syk) model has recently received considerable attention in both condensed matter and high energy physics because it describes quantum matter without quasiparticles, while being at the same time the holographic dual of a quantum black hole. in this letter, we examine syk-based charging protocols of quantum batteries with n quantum cells. extensive numerical calculations based on exact diagonalization for n up to 16 strongly suggest that the optimal charging power of our syk quantum batteries displays a superextensive scaling with n that stems from genuine quantum mechanical effects. while the complexity of the nonequilibrium syk problem involved in the charging dynamics prevents us from an analytical proof, we believe that this letter offers the first (to the best of our knowledge) strong numerical evidence of a quantum advantage occurring due to the maximally entangling underlying quantum dynamics. | quantum advantage in the charging process of sachdev-ye-kitaev batteries |
in this note, we consider entanglement and renyi entropies for spatial subsystems of a boundary conformal field theory (bcft) or of a cft in a state constructed using a euclidean bcft path integral. holographic calculations suggest that these entropies undergo phase transitions as a function of time or parameters describing the subsystem; these arise from a change in topology of the rt surface. in recent applications to black hole physics, such transitions have been seen to govern whether or not the bulk entanglement wedge of a (b)cft region includes a portion of the black hole interior and have played a crucial role in understanding the semiclassical origin of the page curve for evaporating black holes.in this paper, we reproduce these holographic results via direct (b)cft calculations. using the replica method, the entropies are related to correlation functions of twist operators in a euclidean bcft. these correlations functions can be expanded in various channels involving intermediate bulk or boundary operators. under certain sparseness conditions on the spectrum and ope coefficients of bulk and boundary operators, we show that the twist correlators are dominated by the vacuum block in a single channel, with the relevant channel depending on the position of the twists. these transitions between channels lead to the holographically observed phase transitions in entropies. | bcft entanglement entropy at large central charge and the black hole interior |
we formulate a version of the information paradox in de sitter spacetime and show that it is solved by the emergence of entanglement islands in the context of the de sitter/de sitter correspondence; in particular, the entanglement entropy of a subregion obeys a time-dependent page curve. our construction works in general spacetime dimensions and keeps the graviton massless. we interpret the resulting behavior of the entanglement entropy using double holography. it suggests that the spatial distribution of microscopic degrees of freedom depends on descriptions, as in the case of a black hole. in the static (distant) description of de sitter (black hole) spacetime, these degrees of freedom represent microstates associated with the gibbons-hawking (bekenstein-hawking) entropy and are localized toward the horizon. on the other hand, in a global (effective two-sided) description, which is obtained by the quantum analog of analytic extension and is intrinsically semiclassical, they are distributed uniformly and in a unique semiclassical de sitter (black hole) vacuum state. | information paradox and its resolution in de sitter holography |
superradiance is a radiation enhancement process that involves dissipative systems. with a 60 year-old history, superradiance has played a prominent role in optics, quantum mechanics and especially in relativity and astrophysics. in general relativity, black-hole superradiance is permitted by the ergoregion, that allows for energy, charge and angular momentum extraction from the vacuum, even at the classical level. stability of the spacetime is enforced by the event horizon, where negative energy-states are dumped. black-hole superradiance is intimately connected to the black-hole area theorem, penrose process, tidal forces, and even hawking radiation, which can be interpreted as a quantum version of black-hole superradiance. various mechanisms (as diverse as massive fields, magnetic fields, anti-de sitter boundaries, nonlinear interactions, etc...) can confine the amplified radiation and give rise to strong instabilities. these "black-hole bombs" have applications in searches of dark matter and of physics beyond the standard model, are associated to the threshold of formation of new black hole solutions that evade the no-hair theorems, can be studied in the laboratory by devising analog models of gravity, and might even provide a holographic description of spontaneous symmetry breaking and superfluidity through the gauge-gravity duality. this work is meant to provide a unified picture of this multifaceted subject. we focus on the recent developments in the field, and work out a number of novel examples and applications, ranging from fundamental physics to astrophysics. | superradiance |
we describe an efficient method for extracting the parts of d -dimensional loop integrals that are needed to derive observables in classical general relativity from scattering amplitudes. our approach simplifies the soft-region method of integration by judiciously combining terms before the final integrations. we demonstrate the method by computing the required integrals for black-hole scattering to the second post-minkowskian order in einstein gravity coupled to scalars. we also confirm recent results at the third post-minkowskian order regarding universality and high-energy behavior of gravitational interactions in maximal supergravity. | classical gravity from loop amplitudes |
we compute holographic entanglement entropy for subregions of a bcft thermal state living on a nongravitating black hole background. the system we consider is doubly holographic and dual to an eternal black string with an embedded karch-randall brane that is parameterized by its angle. entanglement islands are conventionally expected to emerge at late times to preserve unitarity at finite temperature, but recent calculations at zero temperature have shown such islands do not exist when the brane lies below a critical angle. when working at finite temperature in the context of a black string, we find that islands exist even when the brane lies below the critical angle. we note that although these islands exist when they are needed to preserve unitarity, they are restricted to a finite connected region on the brane which we call the atoll. depending on two parameters — the size of the subregion and the brane angle — the entanglement entropy either remains constant in time or follows a page curve. we discuss this rich phase structure in the context of bulk reconstruction. | entanglement phase structure of a holographic bcft in a black hole background |
we study the islands and the page curve in the 1+1-dimensional eternal dilaton black hole models. without islands, the entanglement entropy of the radiation grows linearly at late time. however with an island, its growth stops at the value of almost twice of the black hole entropy. therefore an island emerges at the late time, and the entanglement entropy of the radiation shows the page curve. | notes on islands in asymptotically flat 2d dilaton black holes |
an important open question in black hole thermodynamics is about the existence of a "mass gap" between an extremal black hole and the lightest near-extremal state within a sector of fixed charge. in this paper, we reliably compute the partition function of reissner-nordström near-extremal black holes at temperature scales comparable to the conjectured gap. we find that the density of states at fixed charge does not exhibit a gap; rather, at the expected gap energy scale, we see a continuum of states. we compute the partition function in the canonical and grand canonical ensembles, keeping track of all the fields appearing through a dimensional reduction on s2 in the near-horizon region. our calculation shows that the relevant degrees of freedom at low temperatures are those of 2d jackiw-teitelboim gravity coupled to the electromagnetic u(1) gauge field and to an so(3) gauge field generated by the dimensional reduction. | the statistical mechanics of near-extremal black holes |
forty years after the discovery of hawking radiation, its exact nature remains elusive. if hawking radiation does not carry any information out from the ever shrinking black hole, it seems that unitarity is violated once the black hole completely evaporates. on the other hand, attempts to recover information via quantum entanglement lead to the firewall controversy. amid the confusions, the possibility that black hole evaporation stops with a "remnant" has remained unpopular and is often dismissed due to some "undesired properties" of such an object. nevertheless, as in any scientific debate, the pros and cons of any proposal must be carefully scrutinized. we fill in the void of the literature by providing a timely review of various types of black hole remnants, and provide some new thoughts regarding the challenges that black hole remnants face in the context of the information loss paradox and its latest incarnation, namely the firewall controversy. the importance of understanding the role of curvature singularity is also emphasized, after all there remains a possibility that the singularity cannot be cured even by quantum gravity. in this context a black hole remnant conveniently serves as a cosmic censor. we conclude that a remnant remains a possible end state of hawking evaporation, and if it contains large interior geometry, may help to ameliorate the information loss paradox and the firewall controversy. we hope that this will raise some interests in the community to investigate remnants more critically but also more thoroughly. | black hole remnants and the information loss paradox |
the thermodynamic euler equation for high-energy states of large-n gauge theories is derived from the dependence of the extensive quantities on the number of colors n . this euler equation relates the energy of the state to the temperature, entropy, number of degrees of freedom and its chemical potential, but not to the volume or pressure. in the context of the gauge/gravity duality we show that the euler equation is dual to the generalized smarr formula for black holes in the presence of a negative cosmological constant. we also match the fundamental variational equation of thermodynamics to the first law of black hole mechanics, when extended to include variations of the cosmological constant and newton's constant. | holographic thermodynamics requires a chemical potential for color |
we study the index of $\mathcal{n}=4$ yang-mills theory on $s^3\times\mathbb{r}$ at large angular momenta. a generalized cardy limit exhibits macroscopic entropy at large $n$. our result is derived using free qft analysis, and also a background field method on $s^3$. the index sets a lower bound on the entropy. it saturates the bekenstein-hawking entropy of known supersymmetric ads$_5$ black holes, thus accounting for their microstates. we further analyze the so-called macdonald index, exploring small black holes and possibly new black holes reminiscent of hairy black holes. finally, we study aspects of large supersymmetric ads$_7$ black holes, using background field method on $s^5$ and 't hooft anomalies. | large ads black holes from qft |
we revisit the amplitude-based derivation of gravitational waveform for the scattering of two scalar black holes at subleading post-minkowskian (pm) order. we take an eikonal-inspired approach to the two-massive-particle cut needed in the kmoc framework, as highlighted in arxiv:2308.02125, and show that its effect is to implement a simple change of frame. this clarifies one of the points raised in arxiv:2309.14925 when comparing with the post-newtonian (pn) results. we then provide an explicit pm expression for the waveform in the soft limit, $\omega\to0$, including the first non-universal, $\omega\log\omega$, contribution. focusing on this regime, we show that the small-velocity limit of our result agrees with the soft limit of the pn waveform of arxiv:2309.14925, provided that the two quantities are written in the same asymptotic frame. performing the bms supertranslation that, as discussed in arxiv:2201.11607, is responsible for the $\mathcal o(g)$ static contribution to the asymptotic field employed in the pn literature, we find agreement between the amplitude-based and the pn soft waveform up to and including $g^3/c^5$ order. | an eikonal-inspired approach to the gravitational scattering waveform |
we analyse particle species and the species scale in quantum gravity from a thermodynamic perspective. in close analogy to black hole thermodynamics, we propose that particle species have an entropy and a temperature, which is determined by the species scale. this is identical to the bekenstein-hawking entropy of a corresponding minimal black hole and agrees with the number of species in a given tower of states. through the species entropy, we find that certain entropy bounds are connected to recent swampland constraints. moreover, the concept of species entropy and temperature allow us to formulate the laws of species thermodynamics, which are argued to govern the variations of moduli in string theory. they can be viewed as general rules that imply certain swampland conjectures, and vice versa. | species entropy and thermodynamics |
the origin of black hole mergers discovered by the ligo and virgo gravitational-wave observatories is currently unknown. gw190521 is the heaviest black hole merger detected so far. its observed high mass and possible spin-induced orbital precession could arise from the binary having formed following a close encounter. an observational signature of close encounters is eccentric binary orbit; however, this feature is currently difficult to identify due to the lack of suitable gravitational waveforms. no eccentric merger has been previously found. here we report 611 numerical relativity simulations covering the full eccentricity range and an estimation approach to probe the eccentricity of mergers. our set of simulations corresponds to $\sim 10^5$ waveforms, comparable to the number used in gravitational wave searches, albeit with coarser mass-ratio and spin resolution. we applied our approach to gw190521 and found that it is the most consistent with a highly eccentric ($e=0.69^{+0.17}_{-0.22}$; 90% credible level) merger within our set of waveforms. this interpretation is supported over a non-eccentric merger with $>10$ odds ratio if $\gtrsim10\%$ of gw190521-like mergers are highly eccentric. detectable orbital eccentricity would be evidence against an isolated binary origin, which is otherwise difficult to rule out based on observed mass and spin. | eccentricity estimate for black hole mergers with numerical relativity simulations |
we propose that the dynamics of kerr black holes is strongly constrained by the principle of gauge symmetry. we initiate the construction of effective field theories for kerr black holes of any integer quantum spin s using stückelberg fields, and show that the known three-point kerr amplitudes are uniquely predicted using massive higher-spin gauge symmetry. this symmetry is argued to be connected to an enhanced range of validity for the kerr effective field theories. we consider the closely related root-kerr electromagnetic solution in parallel, for which the dynamical interactions with photons are also constrained by massive higher-spin gauge symmetry. finally, the spin-s compton amplitudes are analyzed, and we discuss contact-term constraints at s =2 from ward identities. | kerr black holes from massive higher-spin gauge symmetry |
we study the topology of the thermodynamic space of four dimensional dyonic anti-de sitter (ads) black hole in three different ensembles: canonical, mixed, and grand canonical ensemble. while canonical ensemble refers to the ensemble with fixed electric and magnetic charges, mixed ensemble is an ensemble where we fix magnetic charge and electric potential. in the grand canonical ensemble, potentials corresponding to both electric and magnetic charges are kept fixed. in each of these ensembles, we first compute the topological charges associated with critical points. we find that while in both canonical and mixed ensembles, there exists one conventional critical point with topological charge -1 , in the grand canonical ensemble, we find no critical point. then, we consider the dyonic ads black hole as topological defects in thermodynamic space and study its local and global topology by computing the winding numbers at the defects. we observe that while the topologies of the black hole in canonical and mixed ensembles are identical with total topological charge equaling 1, in the grand canonical ensemble, depending on the values of potentials, the total topological charge is either equal to 0 or 1. in canonical and mixed ensembles, either one generation and one annihilation points or no generation/annihilation points are found. in the grand canonical ensemble, depending on the values of potentials, we find either one generation point or no generation/annihilation point. thus, we infer that the topological class of 4d dyonic ads black hole is ensemble dependent. | thermodynamic topology of 4d dyonic ads black holes in different ensembles |
we test various conjectures about quantum gravity for six-dimensional string compactifications in the framework of f-theory. starting with a gauge theory coupled to gravity, we analyze the limit in kähler moduli space where the gauge coupling tends to zero while gravity is kept dynamical. we show that such a limit must be located at infinite distance in the moduli space. as expected, the low-energy effective theory breaks down in this limit due to a tower of charged particles becoming massless. these are the excitations of an asymptotically tensionless string, which is shown to coincide with a critical heterotic string compactified to six dimensions. for a more quantitative analysis, we focus on a u(1) gauge symmetry and use a chain of dualities and mirror symmetry to determine the elliptic genus of the nearly tensionless string, which is given in terms of certain meromorphic weak jacobi forms. their modular properties in turn allow us to determine the charge-to-mass ratios of certain string excitations near the tensionless limit. we then provide evidence that the tower of asymptotically massless charged states satisfies the (sub-)lattice weak gravity conjecture, the completeness conjecture, and the swampland distance conjecture. quite remarkably, we find that the number theoretic properties of the elliptic genus conspire with the balance of gravitational and scalar forces of extremal black holes, such as to produce a narrowly tuned charge spectrum of superextremal states. as a byproduct, we show how to compute elliptic genera of both critical and non-critical strings, when refined by mordell-weil u(1) symmetries in f-theory. | tensionless strings and the weak gravity conjecture |
we provide universal expressions for the classical piece of the amplitude given by the graviton/photon exchange between massive particles of arbitrary spin, at both tree and one loop level. in the gravitational case this leads to higher order terms in the post-newtonian expansion, which have been previously used in the binary inspiral problem. the expressions are obtained in terms of a contour integral that computes the leading singularity, which was recently shown to encode the relevant information up to one loop. the classical limit is performed along a holomorphic trajectory in the space of kinematics, such that the leading order is enough to extract arbitrarily high multipole corrections. these multipole interactions are given in terms of a recently proposed representation for massive particles of any spin by arkani-hamed et al. this explicitly shows universality of the multipole interactions in the effective potential with respect to the spin of the scattered particles. we perform the explicit match to standard eft operators for s = 1/2 and s = 1. as a natural byproduct we obtain the classical pieces up to one loop for the bending of light. | holomorphic classical limit for spin effects in gravitational and electromagnetic scattering |
as gravitational-wave detectors become more sensitive and broaden their frequency bandwidth, we will access a greater variety of signals emitted by compact binary systems, shedding light on their astrophysical origin and environment. a key physical effect that can distinguish among different formation scenarios is the misalignment of the spins with the orbital angular momentum, causing the spins and the binary's orbital plane to precess. to accurately model such precessing signals, especially when masses and spins vary in the wide astrophysical range, it is crucial to include multipoles beyond the dominant quadrupole. here, we develop the first multipolar precessing waveform model in the effective-one-body (eob) formalism for the entire coalescence stage (i.e., inspiral, merger and ringdown) of binary black holes: seobnrv4phm. in the nonprecessing limit, the model reduces to seobnrv4hm, which was calibrated to numerical-relativity (nr) simulations, and waveforms from black-hole perturbation theory. we validate seobnrv4phm by comparing it to the public catalog of 1405 precessing nr waveforms of the simulating extreme spacetimes (sxs) collaboration, and also to 118 sxs precessing nr waveforms, produced as part of this project, which span mass ratios 1-4 and (dimensionless) black-hole's spins up to 0.9. we stress that seobnrv4phm is not calibrated to nr simulations in the precessing sector. we compute the unfaithfulness against the 1523 sxs precessing nr waveforms, and find that, for 94% (57%) of the cases, the maximum value, in the total mass range 20 -200 m⊙, is below 3% (1%). those numbers change to 83% (20%) when using the inspiral-merger-ringdown, multipolar, precessing phenomenological model imrphenompv3hm. we investigate the impact of such unfaithfulness values with two bayesian, parameter-estimation studies on synthetic signals. we also compute the unfaithfulness between those waveform models as a function of the mass and spin parameters to identify in which part of the parameter space they differ the most. we validate them also against the multipolar, precessing nr surrogate model nrsur7dq4, and find that the seobnrv4phm model outperforms imrphenompv3hm. | multipolar effective-one-body waveforms for precessing binary black holes: construction and validation |
in this paper we compute the spin-dependent terms of the gravitational potential for general spinning bodies at the leading newton's constant g and to all orders in spin. we utilize the on-shell approach, which extracts the classical potential directly from the scattering amplitude. for spinning particles, extra care is required due to the fact that the spin space of each particle is independent. once the appropriate matching procedures are applied, taking the classical-spin limit we obtain the potential for general spinning bodies. when the wilson coefficients are set to unity, we successfully reproduced the potential for the kerr black hole. interestingly, for finite spins, we find that the finite-spin deviations from kerr wilson coefficients cancel with that in the matching procedure, reproducing the kerr potential without the need for taking the classical-spin limit. finally, we find that when cast into the chiral basis, the spin-dependence of minimal coupling exhibits factorization, allowing us to take the classical-spin limit straight forwardly. | classical potential for general spinning bodies |
we consider a black hole in three dimensional ads space entangled with an auxiliary radiation system. we model the microstates of the black hole in terms of a field theory living on an end of the world brane behind the horizon, and allow this field theory to itself have a holographic dual geometry. this geometry is also a black hole since entanglement of the microstates with the radiation leaves them in a mixed state. this "inception black hole" can be purified by entanglement through a wormhole with an auxiliary system which is naturally identified with the external radiation, giving a realization of the er=epr scenario. in this context, we propose an extension of the ryu-takayanagi (rt) formula, in which extremal surfaces computing entanglement entropy are allowed to pass through the brane into its dual geometry. this new rule reproduces the page curve for evaporating black holes, consistently with the recently proposed "island formula". we then separate the radiation system into pieces. our extended rt rule shows that the entanglement wedge of the union of radiation subsystems covers the black hole interior at late times, but the union of entanglement wedges of the subsystems may not. this result points to a secret sharing scheme in hawking radiation wherein reconstruction of certain regions in the interior is impossible with any subsystem of the radiation, but possible with all of it. | geometric secret sharing in a model of hawking radiation |
we improve the accuracy of the effective-one-body (eob) waveforms that were employed during the first observing run of advanced ligo for binaries of spinning, nonprecessing black holes by calibrating them to a set of 141 numerical-relativity (nr) waveforms. the nr simulations expand the domain of calibration toward larger mass ratios and spins, as compared to the previous eobnr model. merger-ringdown waveforms computed in black-hole perturbation theory for kerr spins close to extremal provide additional inputs to the calibration. for the inspiral-plunge phase, we use a markov-chain monte carlo algorithm to efficiently explore the calibration space. for the merger-ringdown phase, we fit the nr signals with phenomenological formulae. after extrapolation of the calibrated model to arbitrary mass ratios and spins, the (dominant-mode) eobnr waveforms have faithfulness—at design advanced-ligo sensitivity—above 99% against all the nr waveforms, including 16 additional waveforms used for validation, when maximizing only on initial phase and time. this implies a negligible loss in event rate due to modeling for these binary configurations. we find that future nr simulations at mass ratios ≳4 and double spin ≳0.8 will be crucial to resolving discrepancies between different ways of extrapolating waveform models. we also find that some of the nr simulations that already exist in such region of parameter space are too short to constrain the low-frequency portion of the models. finally, we build a reduced-order version of the eobnr model to speed up waveform generation by orders of magnitude, thus enabling intensive data-analysis applications during the upcoming observation runs of advanced ligo. | improved effective-one-body model of spinning, nonprecessing binary black holes for the era of gravitational-wave astrophysics with advanced detectors |
recently, new holographic models of black hole evaporation have given fresh insights into the information paradox [1-3]. in these models, the black hole evaporates into an auxiliary bath space after a quantum quench, wherein the holographic theory and the bath are joined. one particularly exciting development is the appearance of `er=epr'-like wormholes in the (doubly) holographic model of [3]. at late times, the entanglement wedge of the bath includes the interior of the black hole. in this paper, we employ both numerical and analytic methods to study how information about the black hole interior is encoded in the hawking radiation. in particular, we systematically excise intervals from the bath from the system and study the corresponding page transition. repeating this process ad infinitum, we end up with a fractal structure on which the black hole interior is encoded, implementing the überholography protocol of [4]. | information flow in black hole evaporation |
in the context of the einstein-scalar-gauss-bonnet theory, with a general coupling function between the scalar field and the quadratic gauss-bonnet term, we investigate the existence of regular black-hole solutions with scalar hair. based on a previous theoretical analysis, which studied the evasion of the old and novel no-hair theorems, we consider a variety of forms for the coupling function (exponential, even and odd polynomial, inverse polynomial, and logarithmic) that, in conjunction with the profile of the scalar field, satisfy a basic constraint. our numerical analysis then always leads to families of regular, asymptotically flat black-hole solutions with nontrivial scalar hair. the solution for the scalar field and the profile of the corresponding energy-momentum tensor, depending on the value of the coupling constant, may exhibit a nonmonotonic behavior, an unusual feature that highlights the limitations of the existing no-hair theorems. we also determine and study in detail the scalar charge, horizon area, and entropy of our solutions. | black-hole solutions with scalar hair in einstein-scalar-gauss-bonnet theories |
we discuss a doubly-holographic prescription for black holes in braneworlds with a vanishing cosmological constant. it involves calculating ryu-takayanagi surfaces in ads black funnel spacetimes attached to braneworld black holes in the critical randall- sundrum ii model. critical braneworlds have the virtue of having massless gravitons. our approach should be useful when the braneworld is a cosmological black hole interacting with deconfined, large-n matter. in higher dimensions, explicit funnel metrics will have to be constructed numerically — but based on the general structure of the geometry, we present a natural guess for where one might find the semi-classical island. in a 3-dimensional example where a toy analytic black funnel is known, we can check our guess by direct calculation. we argue that this resolves a version of the information paradox in these braneworld systems, by finding strong evidence for "cosmological islands". comoving ryu-takayanagi surfaces and associated uv cut-offs on the brane, play natural roles. | critical islands |
in a quantum theory of gravity, the species scale $\lambda_s$ can be defined as the scale at which corrections to the einstein action become important or alternatively as codifying the "number of light degrees of freedom", due to the fact that $\lambda_s^{-1}$ is the smallest size black hole described by the eft involving only the einstein term. in this paper, we check the validity of this picture in diverse dimensions and with different amounts of supersymmetry and verify the expected behavior of the species scale at the boundary of the moduli space. this also leads to the evaluation of the species scale in the interior of the moduli space as well as to the computation of the diameter of the moduli space. we also find evidence that the species scale satisfies the bound $\big|{\nabla \lambda_s \over \lambda_s} \big|^2\leq {1\over d-2}$ all over moduli space including the interior. | species scale in diverse dimensions |
the ip matrix model is a simple large n quantum mechanical model made up of an adjoint harmonic oscillator plus a fundamental harmonic oscillator. it is a model introduced previously as a toy model of the gauge theory dual of an ads black hole. in the large n limit, one can solve the schwinger-dyson equation for the fundamental correlator, and at sufficiently high temperature, this model shows key signatures of thermalization and information loss; the correlator decay exponentially in time, and the spectral density becomes continuous and gapless. we study the lanczos coefficients bn in this model and at sufficiently high temperature, it grows linearly in n with logarithmic corrections, which is one of the fastest growth under certain conditions. as a result, the krylov complexity grows exponentially in time as ∼exp(o (√{t}). these results indicate that the ip model at sufficiently high temperature is chaotic. | krylov complexity in the ip matrix model |
we study the growth and saturation of the superradiant instability of a complex, massive vector (proca) field as it extracts energy and angular momentum from a spinning black hole, using numerical solutions of the full einstein-proca equations. we concentrate on a rapidly spinning black hole (a =0.99 ) and the dominant m =1 azimuthal mode of the proca field, with real and imaginary components of the field chosen to yield an axisymmetric stress-energy tensor and, hence, spacetime. we find that in excess of 9% of the black hole's mass can be transferred into the field. in all cases studied, the superradiant instability smoothly saturates when the black hole's horizon frequency decreases to match the frequency of the proca cloud that spontaneously forms around the black hole. | superradiant instability and backreaction of massive vector fields around kerr black holes |
it was recently conjectured that the quantum complexity of a holographic boundary state can be computed by evaluating the gravitational action on a bulk region known as the wheeler-dewitt patch. we apply this complexity=action duality to evaluate the `complexity of formation' [1, 2], i.e. the additional complexity arising in preparing the entangled thermofield double state with two copies of the boundary cft compared to preparing the individual vacuum states of the two copies. we find that for boundary dimensions d > 2, the difference in the complexities grows linearly with the thermal entropy at high temperatures. for the special case d = 2, the complexity of formation is a fixed constant, independent of the temperature. we compare these results to those found using the complexity=volume duality. | complexity of formation in holography |
motivated by recent work on the modified maxwell (modmax) black holes [phys lett b 10.1016/j.physletb.2020.136011], which are invariant in duality rotations and conformal transformations founded in [phys rev d 10.1103/physrevd.102.121703], we probe its effects on the shadow cast, weak field gravitational lensing, and neutrino propagation in its vicinity. using the eht data for the shadow diameter of sgr. a* and m87*, and ligo/virgo experiments for the dyonic modmax black hole perturbations, we find constraints for modmax parameters such as qm and the screening factor γ . we also analyze how the shadow radius behaves as perceived by a static observer and one that is comoving with the cosmic expansion. the effect of the modmax parameters is constant for a static observer, and we found that it varies when the observer is comoving with cosmic expansion. we also analyzed its effect on the weak deflection angle by exploiting the gauss-bonnet theorem and its application to einstein ring formation. we also consider the finite distance effect and massive particle deflection. our results indicate that the far approximation of massive particle gives the largest deflection angle and amplifies the effect of qm and γ . then we also calculate the quasinormal modes and greybody bounds which encode unique characteristic features of the dyonic modmax black hole. with the advent of improving space technology, we reported that it is possible to detect the deviation caused through the shadow cast, einstein rings, quasinormal modes, and neutrino oscillations. | shadow, lensing, quasinormal modes, greybody bounds and neutrino propagation by dyonic modmax black holes |
we analyze gravitational-wave data from the first ligo detection of a binary black-hole merger (gw150914) in search of the ringdown of the remnant black hole. using observations beginning at the peak of the signal, we find evidence of the fundamental quasinormal mode and at least one overtone, both associated with the dominant angular mode (ℓ=m =2 ), with 3.6 σ confidence. a ringdown model including overtones allows us to measure the final mass and spin magnitude of the remnant exclusively from postinspiral data, obtaining an estimate in agreement with the values inferred from the full signal. the mass and spin values we measure from the ringdown agree with those obtained using solely the fundamental mode at a later time, but have smaller uncertainties. agreement between the postinspiral measurements of mass and spin and those using the full waveform supports the hypothesis that the gw150914 merger produced a kerr black hole, as predicted by general relativity, and provides a test of the no-hair theorem at the ∼10 % level. an independent measurement of the frequency of the first overtone yields agreement with the no-hair hypothesis at the ∼20 % level. as the detector sensitivity improves and the detected population of black-hole mergers grows, we can expect that using overtones will provide even stronger tests. | testing the no-hair theorem with gw150914 |
we consider the status of black hole (bh) solutions with nontrivial scalar fields but no gauge fields, in four-dimensional asymptotically flat spacetimes, reviewing both classical results and recent developments. we start by providing a simple illustration on the physical difference between bhs in electro-vacuum and scalar-vacuum. next, we review no-scalar-hair theorems. in particular, we detail an influential theorem by bekenstein and stress three key assumptions: (1) the type of scalar field equation; (2) the spacetime symmetry inheritance by the scalar field and (3) an energy condition. then, we list regular (on and outside the horizon), asymptotically flat bh solutions with scalar hair, organizing them by the assumption which is violated in each case and distinguishing primary from secondary hair. we provide a table summary of the state-of-the-art. | asymptotically flat black holes with scalar hair: a review |
following a major upgrade, the two advanced detectors of the laser interferometer gravitational-wave observatory (ligo) held their first observation run between september 2015 and january 2016. with a strain sensitivity of 10-23/√{hz } at 100 hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. on september 14, 2015, the advanced ligo detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [b. p. abbott et al., phys. rev. lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. the event, gw150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. here, we present the main features of the detectors that enabled this observation. at full sensitivity, the advanced ligo detectors are designed to deliver another factor of 3 improvement in the signal-to-noise ratio for binary black hole systems similar in mass to gw150914. | gw150914: the advanced ligo detectors in the era of first discoveries |
the recent discovery of the novel four-dimensional static and spherically symmetric gauss-bonnet black hole provides a promising bed to test gauss-bonnet gravity by using astronomical observations (glavan et al. in prl 124:081301, 2020). in this paper, we first obtain the rotating gauss-bonnet black hole solution by using the newman-janis algorithm and then study the shadow cast by the nonrotating and rotating candidate gauss-bonnet black holes. the result indicates that positive metric parameter α shrinks the shadow, while negative one enlarges it. meanwhile, both the distortion and ratio of two diameters of the shadow are found to increase with the metric parameter for certain spin. comparing with the kerr black hole, the shadow gets more distorted for α and less distorted for negative one. furthermore, we calculate the angular diameter of the shadow by making use of the observation of m87*. the result indicates that negative metric parameter α in (−4.5, 0) is more favored. since the negative energy appears for negative α , our results extends the study of gauss-bonnet gravity. we believe further study on the four-dimensional rotating black hole may shed new light on gauss-bonnet gravity. | testing the nature of gauss-bonnet gravity by four-dimensional rotating black hole shadow |
we discuss holographic models of extremal and non-extremal black holes in contact with a bath in d dimensions, based on a brane world model introduced in arxiv:2006.04851. the main benefit of our setup is that it allows for a high degree of analytic control as compared to previous work in higher dimensions. we show that the appearance of quantum extremal islands in those models is a consequence of the well-understood phase transition of rt surfaces, and does not make any direct reference to ensemble averaging. for non-extremal black holes the appearance of quantum extremal islands has the right behaviour to avoid the information paradox in any dimension. we further show that for these models the calculation of the full page curve is possible in any dimension. the calculation reduces to numerically solving two odes. in the case of extremal black holes in higher dimensions, we find no quantum extremal islands for a wide range of parameters. in two dimensions, our results agree with arxiv:1910.11077 at leading order; however a finite uv cutoff introduced by the brane results in subleading corrections. for example, these corrections result in the quantum extremal surfaces moving further outward from the horizon, and shifting the page transition to a slightly earlier time. | quantum extremal islands made easy, part ii: black holes on the brane |
a page curve for an evaporating black hole in asymptotically flat spacetime is computed by adapting the quantum ryu-takayanagi (qrt) proposal to an analytically solvable semi-classical two-dimensional dilaton gravity theory. the page time is found to be one third of the black hole lifetime, at leading order in semi-classical corrections. a page curve is also obtained for a semi-classical eternal black hole, where energy loss due to hawking evaporation is balanced by an incoming energy flux. | page curve for an evaporating black hole |
in this paper, we study the physical significance of the thermodynamic volumes of ads black holes using the noether charge formalism of iyer and wald. after applying this formalism to study the extended thermodynamics of a few examples, we discuss how the extended thermodynamics interacts with the recent complexity = action proposal of brown et al. (ca-duality). we, in particular, discover that their proposal for the late time rate of change of complexity has a nice decomposition in terms of thermodynamic quantities reminiscent of the smarr relation. this decomposition strongly suggests a geometric, and via ca-duality holographic, interpretation for the thermodynamic volume of an ads black hole. we go on to discuss the role of thermodynamics in complexity = action for a number of black hole solutions, and then point out the possibility of an alternate proposal, which we dub "complexity = volume 2.0". in this alternate proposal the complexity would be thought of as the spacetime volume of the wheeler-dewitt patch. finally, we provide evidence that, in certain cases, our proposal for complexity is consistent with the lloyd bound whereas ca-duality is not. | noether charge, black hole volume, and complexity |
we review recent progress on the information paradox. we explain why exponentially small correlations in the radiation emitted by a black hole are sufficient to resolve the original paradox put forward by hawking. we then describe a refinement of the paradox that makes essential reference to the black-hole interior. this analysis leads to a broadly-applicable physical principle: in a theory of quantum gravity, a copy of all the information on a cauchy slice is also available near the boundary of the slice. this principle can be made precise and established - under weak assumptions, and using only low-energy techniques - in asymptotically global ads and in four dimensional asymptotically flat spacetime. when applied to black holes, this principle tells us that the exterior of the black hole always retains a complete copy of the information in the interior. we show that accounting for this redundancy provides a resolution of the information paradox for evaporating black holes and, conversely, that ignoring this redundancy leads to paradoxes even in the absence of black holes. we relate this perspective to recent computations of the page curve for holographic cfts coupled to nongravitational baths. but we argue that such models may provide an inaccurate picture of the rate at which information can be extracted from evaporating black holes in asymptotically flat space. we discuss large black holes dual to typical states in ads/cft and the new paradoxes that arise in this setting. these paradoxes also extend to the eternal black hole. they can be resolved by assuming that the map between the boundary cft and the black-hole interior is state dependent. we discuss the consistency of state-dependent bulk reconstructions. we conclude by examining the viability of arguments for firewalls, fuzzballs and other kinds of structure at the horizon. | lessons from the information paradox |
we study the information paradox for the eternal black hole with charges on a doubly-holographic model in general dimensions, where the charged black hole on a planck brane is coupled to the baths on the conformal boundaries. in the case of weak tension, the brane can be treated as a probe such that its backreaction to the bulk is negligible. we analytically calculate the entanglement entropy of the radiation and obtain the page curve with the presence of an island on the brane. for the near-extremal black holes, the growth rate is linear in the temperature. taking both dvali-gabadadze-porrati term and nonzero tension into account, we obtain the numerical solution with backreaction in four-dimensional spacetime and find the quantum extremal surface at t = 0. to guarantee that a page curve can be obtained in general cases, we propose two strategies to impose enough degrees of freedom on the brane such that the black hole information paradox can be properly described by the doubly-holographic setup. | island in charged black holes |
we investigate the page curve for a nonstandard black hole which is asymptotically nonflat/ads/ds. for this purpose, we apply the island prescription to the charged linear dilaton black holes and analyze, in detail, the entanglement entropy of hawking radiation for both the nonextremal case and the extremal case. in the nonextremal case, we find the page curve consistent with the unitarity principle: at early times the entanglement entropy grows linearly in time without the island and at late times it saturates to double of the bekenstein-hawking entropy in the presence of the island. we observe the page time is universal for all different models studied by our method: tpage=3/π c s/bhth. for the extremal case, the island prescription provides the well-defined entanglement entropy only with the island, which cannot be obtained from the continuous limit of the nonextremal case. this implies that the page curve may not be reproduced for the extremal case and further investigation is needed. | islands in charged linear dilaton black holes |
the emergence of statistical mechanics for isolated classical systems comes about through chaotic dynamics and ergodicity. here we review how similar questions can be answered in quantum systems. the crucial point is that individual energy eigenstates behave in many ways like a statistical ensemble. a more detailed statement of this is named the eigenstate thermalization hypothesis (eth). the reasons for why it works in so many cases are rooted in the early work of wigner on random matrix theory and our understanding of quantum chaos. the eth has now been studied extensively by both analytic and numerical means, and applied to a number of physical situations ranging from black hole physics to condensed matter systems. it has recently become the focus of a number of experiments in highly isolated systems. current theoretical work also focuses on where the eth breaks down leading to new interesting phenomena. this review of the eth takes a somewhat intuitive approach as to why it works and how this informs our understanding of many body quantum states. | eigenstate thermalization hypothesis |
we study the quantum effects of near-extremal black holes near their horizons. the gravitational dynamics in such backgrounds are closely connected to a particle in ads 2 with constant electric field. we use this picture to solve the theory exactly. we will give a formula to calculate all correlation functions with quantum gravity backreactions as well as the exact wheeler-dewitt wavefunction. using the wdw wavefunction, we investigate the complexity growth in quantum gravity. | the quantum gravity dynamics of near extremal black holes |
recent researches of the novel 4d einstein-gauss-bonnet (egb) gravity have attracted great attention. in this paper, we investigate the validity of the weak cosmic censorship conjecture for a novel 4d charged egb black hole with test charged scalar field and test charged particle respectively. for the test charged field scattering process, we find that both extremal and near-extremal black holes cannot be overcharged. for the test charged particle injection, to first order, an extremal black hole cannot be overcharged while a near-extremal 4d charged egb black hole can be destroyed. to second order, however, both extremal and near-extremal 4d charged egb black holes can be overcharged for positive gauss-bonnet coupling constant; for negative gauss-bonnet coupling constant, an extremal black hole cannot be overcharged and the validity of the weak cosmic censorship conjecture for a near-extremal black hole depends on the gauss-bonnet coupling constant. | weak cosmic censorship conjecture for the novel 4d charged einstein-gauss-bonnet black hole with test scalar field and particle |
we analyze the charge-to-mass structure of bps states in general infinite-distance limits of n = 2 compactifications of type iib string theory on calabi-yau three-folds, and use the results to sharpen the formulation of the swampland conjectures in the presence of multiple gauge and scalar fields. we show that the bps bound coincides with the black hole extremality bound in these infinite distance limits, and that the charge-to-mass vectors of the bps states lie on degenerate ellipsoids with only two non-degenerate directions, regardless of the number of moduli or gauge fields. we provide the numerical value of the principal radii of the ellipsoid in terms of the classification of the singularity that is being approached. we use these findings to inform the swampland distance conjecture, which states that a tower of states becomes exponentially light along geodesic trajectories towards infinite field distance. we place general bounds on the mass decay rate λ of this tower in terms of the black hole extremality bound, which in our setup implies λ ≥1 /√{6 }. we expect this framework to persist beyond n = 2 as long as a gauge coupling becomes small in the infinite field distance limit. | merging the weak gravity and distance conjectures using bps extremal black holes |
we show that in 2d cfts at large central charge, the coupling of the stress tensor to heavy operators can be re-absorbed by placing the cft in a non-trivial background metric. this leads to a more precise computation of the virasoro conformal blocks between heavy and light operators, which are shown to be equivalent to global conformal blocks evaluated in the new background. we also generalize to the case where the operators carry u(1) charges. the refined virasoro blocks can be used as the seed for a new virasoro block recursion relation expanded in the heavy-light limit. we comment on the implications of our results for the universality of black hole thermality in ads3, or equivalently, the eigenstate thermalization hypothesis for cft2 at large central charge. | virasoro conformal blocks and thermality from classical background fields |
the species scale serves as a uv cutoff in the gravitational sector of an eft and can depend on the moduli of the theory as the spectrum of the theory varies. it is argued that the dependence of the species scale on massless (or light) modes satisfies . this bound is true at all points in moduli space including also its interior. the argument is based on the idea that the short distance contribution of massless modes to gravitational terms in the eft cannot dramatically affect the black hole entropy. based on string theory arguments the constant in this bound is expected to be equal to as the boundary of the moduli space is approached. however, it turns out that along trajectories going from interior points to the boundaries of moduli space the slope of the species scale can approach its asymptotic value from above, thereby implying that the constant in the bound must be larger than . the bound on the variation of the species scale also implies that the mass of towers of light modes cannot go to zero faster than exponential in field distance in accordance with the distance conjecture.the species scale serves as a uv cutoff in the gravitational sector of an eft and can depend on the moduli of the theory as the spectrum of the theory varies. it is argued that the dependence of the species scale on massless (or light) modes satisfies . this bound is true at all points in moduli space including also its interior. the argument is based on the idea that the short distance contribution of massless modes to gravitational terms in the eft cannot dramatically affect the black hole entropy. based on string theory arguments the constant in this bound is expected to be equal to as the boundary of the moduli space is approached. however, it turns out that along trajectories going from interior points to the boundaries of moduli space the slope of the species scale can approach its asymptotic value from above, thereby implying that the constant in the bound must be larger than . the bound on the variation of the species scale also implies that the mass of towers of light modes cannot go to zero faster than exponential in field distance in accordance with the distance conjecture. | bounds on species scale and the distance conjecture |
we combine tools from effective field theory and generalized unitarity to construct a map between on-shell scattering amplitudes and the classical potential for interacting spinless particles. for general relativity, we obtain analytic expressions for the classical potential of a binary black hole system at second order in the gravitational constant and all orders in velocity. our results exactly match all known results up to fourth post-newtonian order, and offer a simple check of future higher order calculations. by design, these methods should extend to higher orders in perturbation theory. | from scattering amplitudes to classical potentials in the post-minkowskian expansion |
accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximum science. near the time of merger, the gravitational waves from merging black holes can be computed only using numerical relativity. in this paper, we present a major update of the simulating extreme spacetimes (sxs) collaboration catalog of numerical simulations for merging black holes. the catalog contains 2018 distinct configurations (a factor of 11 increase compared to the 2013 sxs catalog), including 1426 spin-precessing configurations, with mass ratios between 1 and 10, and spin magnitudes up to 0.998. the median length of a waveform in the catalog is 39 cycles of the dominant gravitational-wave mode, with the shortest waveform containing 7.0 cycles and the longest 351.3 cycles. we discuss improvements such as correcting for moving centers of mass and extended coverage of the parameter space. we also present a thorough analysis of numerical errors, finding typical truncation errors corresponding to a waveform mismatch of ∼10-4. the simulations provide remnant masses and spins with uncertainties of 0.03% and 0.1% (90th percentile), about an order of magnitude better than analytical models for remnant properties. the full catalog is publicly available at www.black-holes.org/waveforms. | the sxs collaboration catalog of binary black hole simulations |
the essential singularity in einstein's gravity can be avoidable if the preconditions of penrose's theorem can be bypassed, i.e., if the strong energy condition is broken in the vicinity of a black hole center. the singularity mentioned here includes two aspects: (i) the divergence of curvature invariants, and (ii) the incompleteness of geodesics. both aspects are now taken into account in order to determine whether a black hole contains essential singularities. in this sense, black holes without essential singularities are dubbed regular (non-singular) black holes. the regular black holes have some intriguing phenomena that are different from those of singular black holes, and such phenomena have inspired numerous studies. in this review, we summarize the current topics that are associated with regular black holes. | regular black holes: a short topic review |
the duality between color and kinematics was originally observed for purely adjoint massless gauge theories, and later found to hold even after introducing massive fermionic and scalar matter in arbitrary gauge-group representations. such a generalization was critical for obtaining both loop amplitudes in pure einstein gravity and realistic gravitational matter from the double copy. in this paper we elaborate on the double copy that yields amplitudes in gravitational theories coupled to flavored massive matter with spin, which is relevant to the problems of black-hole scattering and gravitational waves. our construction benefits from making the little group explicit for the massive particles, as shown on lower-point examples. for concreteness, we focus on the double copy of qcd with massive quarks, for which we work out the gravitational lagrangian up to quartic scalar and vector-scalar couplings. we find new gauge-invariant double-copy formulae for tree-level amplitudes with two distinct-flavor pairs of matter and any number of gravitons. these are similar to, but inherently different from, the well-known kawai-lewellen-tye formulae, since the latter only hold for the double copy of purely adjoint gauge theories. | double copy for massive quantum particles with spin |
we show that the newman-janis shift property of the exact kerr solution can be interpreted in terms of a worldsheet effective action. this holds both in gravity, and for the single-copy √{kerr} solution in electrodynamics. at the level of equations of motion, we show that the newman-janis shift holds also for the leading interactions of the kerr black hole. these leading interactions are conveniently described using chiral classical equations of motion with the help of the spinor-helicity method familiar from scattering amplitudes. | a worldsheet for kerr |
scrambling is the process by which information stored in local degrees of freedom spreads over the many-body degrees of freedom of a quantum system, becoming inaccessible to local probes and apparently lost. scrambling and entanglement can reconcile seemingly unrelated behaviors including thermalization of isolated quantum systems and information loss in black holes. here, we demonstrate that fidelity out-of-time-order correlators (fotocs) can elucidate connections between scrambling, entanglement, ergodicity and quantum chaos (butterfly effect). we compute fotocs for the paradigmatic dicke model, and show they can measure subsystem rényi entropies and inform about quantum thermalization. moreover, we illustrate why fotocs give access to a simple relation between quantum and classical lyapunov exponents in a chaotic system without finite-size effects. our results open a path to experimental use fotocs to explore scrambling, bounds on quantum information processing and investigation of black hole analogs in controllable quantum systems. | unifying scrambling, thermalization and entanglement through measurement of fidelity out-of-time-order correlators in the dicke model |
we analyse the dynamics of near-extremal reissner-nordström black holes in asymptotically four-dimensional anti de sitter space (ads4). we work in the spherically symmetric approximation and study the thermodynamics and the response to a probe scalar field. we find that the behaviour of the system, at low energies and to leading order in our approximations, is well described by the jackiw-teitelboim (jt) model of gravity. in fact, this behaviour can be understood from symmetry considerations and arises due to the breaking of time reparametrisation invariance. the jt model has been analysed in considerable detail recently and related to the behaviour of the syk model. our results indicate that features in these models which arise from symmetry considerations alone are more general and present quite universally in near-extremal black holes. | on the dynamics of near-extremal black holes |
these are lecture notes based on a series of lectures presented at the xiii modave summer school in mathematical physics aimed at phd students and young postdocs. the goal is to give an introduction to some of the recent developments in understanding holography in two bulk dimensions, and its connection to microscopics of near extremal black holes. the first part reviews the motivation to study, and the problems (and their interpretations) with holography for ads$_2$ spaces. the second part is about the jackiw-teitelboim theory and nearly-ads$_2$ spaces. the third part introduces the sachdev-ye-kitaev model, reviews some of the basic calculations and discusses what features make the model exciting. | ads_{2} holography and the syk model |
the scattering of massless waves of helicity $|h|=0,\frac{1}{2},1$ in schwarzschild and kerr backgrounds is revisited in the long-wavelenght regime. using a novel description of such backgrounds in terms of gravitating massive particles, we compute classical wave scattering in terms of $2\to 2$ qft amplitudes in flat space, to all orders in spin. the results are newman-penrose amplitudes which are in direct correspondence with solutions of the regge-wheeler/teukolsky equation. by introducing a precise prescription for the point-particle limit, in part i of this work we show how both agree for $h=0$ at finite values of the scattering angle and arbitrary spin orientation. associated classical observables such as the scattering cross sections, wave polarizations and time delay are studied at all orders in spin. the effect of the black hole spin on the polarization and helicity of the waves is found in agreement with previous analysis at linear order in spin. in the particular limit of small scattering angle, we argue that wave scattering admits a universal, point-particle description determined by the eikonal approximation. we show how our results recover the scattering eikonal phase with spin up to second post-minkowskian order, and match it to the effective action of null geodesics in a kerr background. using this correspondence we derive classical observables such as polar and equatorial scattering angles. this study serves as a preceding analysis to part ii, where the gravitational wave ($h=2$) case will be studied in detail. | scattering in black hole backgrounds and higher-spin amplitudes: part i |
we calculate the time evolution of entanglement entropy in two-dimensional conformal field theory with a moving mirror. for a setup modeling hawking radiation, we obtain a linear growth of entanglement entropy and show that this can be interpreted as the production of entangled pairs. for the setup, which mimics black hole formation and evaporation, we find that the evolution follows the ideal page curve. we perform these computations by constructing the gravity dual of the moving mirror model via holography. we also argue that our holographic setup provides a concrete model to derive the page curve for black hole radiation in the strong coupling regime of gravity. | entanglement entropy in a holographic moving mirror and the page curve |
entanglement, chaos, and complexity are as important for de sitter space as for ads and for black holes. there are similarities and great differences between ads and ds in how these concepts are manifested in the space-time geometry. in the first part of this paper the ryu-takayanagi prescription, the theory of fast scrambling, and the holographic complexity correspondence are reformulated for de sitter space. criteria are proposed for a holographic model to describe de sitter space. the criteria can be summarized by the requirement that scrambling and complexity growth must be "hyperfast." in the later part of the paper i show that a certain limit of syk is a concrete, computable, holographic model of de sitter space. calculations are described which support the conjecture. | entanglement and chaos in de sitter holography: an syk example |
we study scenarios where a scalar field has a spatially varying vacuum expectation value such that the total field variation is super-planckian. we focus on the case where the scalar field controls the coupling of a u(1) gauge field, which allows us to apply the weak gravity conjecture to such configurations. we show that this leads to evidence for a conjectured property of quantum gravity that as a scalar field variation in field space asymptotes to infinity there must exist an infinite tower of states whose mass decreases as an exponential function of the scalar field variation. we determine the rate at which the mass of the states reaches this exponential behaviour showing that it occurs quickly after the field variation passes the planck scale. | super-planckian spatial field variations and quantum gravity |
quantum extremal islands reproduce the unitary page curve of an evaporating black hole. this has been derived by including replica wormholes in the gravitational path integral, but for the transient, evaporating black holes most relevant to hawking's paradox, these wormholes have not been analyzed in any detail. in this paper we study replica wormholes for black holes formed by gravitational collapse in jackiw-teitelboim gravity, and confirm that they lead to the island rule for the entropy. the main technical challenge is that replica wormholes rely on a euclidean path integral, while the quantum extremal islands of an evaporating black hole exist only in lorentzian signature. furthermore, the euclidean equations for the schwarzian mode are non-local, so it is unclear how to connect to the local, lorentzian dynamics of an evaporating black hole. we address these issues with schwinger-keldysh techniques and show how the non-local equations reduce to the local `boundary particle' description in special cases. | replica wormholes for an evaporating 2d black hole |
we use n = 8 supergravity as a toy model for understanding the dynamics of black hole binary systems via the scattering amplitudes approach. we compute the conservative part of the classical scattering angle of two extremal (half-bps) black holes with minimal charge misalignment at o (g3) using the eikonal approximation and effective field theory, finding agreement between both methods. we construct the massive loop integrands by kaluza-klein reduction of the known d-dimensional massless integrands. to carry out integration we formulate a novel method for calculating the post-minkowskian expansion with exact velocity dependence, by solving velocity differential equations for the feynman integrals subject to modified boundary conditions that isolate conservative contributions from the potential region. motivated by a recent result for universality in massless scattering, we compare the scattering angle to the result found by bern et. al. in einstein gravity and find that they coincide in the high-energy limit, suggesting graviton dominance at this order. | extremal black hole scattering at o (g3): graviton dominance, eikonal exponentiation, and differential equations |
krylov complexity measures the spread of the wavefunction in the krylov basis, which is constructed using the hamiltonian and an initial state. we investigate the evolution of the maximally entangled state in the krylov basis for both chaotic and non-chaotic systems. for this purpose, we derive an ehrenfest theorem for the krylov complexity, which reveals its close relation to the spectrum. our findings suggest that neither the linear growth nor the saturation of krylov complexity is necessarily associated with chaos. however, for chaotic systems, we observe a universal rise-slope-ramp-plateau behavior in the transition probability from the initial state to one of the krylov basis states. moreover, a long ramp in the transition probability is a signal for spectral rigidity, characterizing quantum chaos. also, this ramp is directly responsible for the late-time peak of krylov complexity observed in the literature. on the other hand, for non-chaotic systems, this long ramp is absent. therefore, our results help to clarify which features of the wave function time evolution in krylov space characterize chaos. we exemplify this by considering the sachdev-ye-kitaev model with two-body or four-body interactions. | universal chaotic dynamics from krylov space |
a two-dimensional cft dual to a semiclassical theory of gravity in three dimensions must have a large central charge c and a sparse low energy spectrum. this constrains the ope coefficients and density of states of the cft via the conformal bootstrap. we define an ensemble of cft data by averaging over ope coefficients subject to these bootstrap constraints, and show that calculations in this ensemble reproduce semiclassical 3d gravity. we analyze a wide variety of gravitational solutions, both in pure einstein gravity and gravity coupled to massive point particles, including euclidean wormholes with multiple boundaries and higher topology spacetimes with a single boundary. in all cases we find that the on-shell action of gravity agrees with the ensemble-averaged cft at large c. the one-loop corrections also match in the cases where they have been computed. we also show that the bulk effective theory has random couplings induced by wormholes, providing a controlled, semiclassical realization of the mechanism of coleman, giddings, and strominger. | semiclassical 3d gravity as an average of large-c cfts |
comparing with an ordinary thermodynamic system, we investigate the possible microscopic structure of a charged anti-de sitter black hole completely from the thermodynamic viewpoint. the number density of the black hole molecules is introduced to measure the microscopic degrees of freedom of the black hole. we found that the number density suffers a sudden change accompanied by a latent heat when the black hole system crosses the small-large black hole coexistence curve, while when the system passes the critical point, it encounters a second-order phase transition with a vanishing latent heat due to the continuous change of the number density. moreover, the thermodynamic scalar curvature suggests that there is a weak attractive interaction between two black hole molecules. these phenomena might cast new insight into the underlying microscopic structure of a charged anti-de sitter black hole. | insight into the microscopic structure of an ads black hole from a thermodynamical phase transition |
in cardoso et al. [6] it was claimed that quasinormal modes which any stationary, spherically symmetric and asymptotically flat black hole emits in the eikonal regime are determined by the parameters of the circular null geodesic: the real and imaginary parts of the quasinormal mode are multiples of the frequency and instability timescale of the circular null geodesics respectively. we shall consider asymptotically flat black hole in the einstein-lovelock theory, find analytical expressions for gravitational quasinormal modes in the eikonal regime and analyze the null geodesics. comparison of the both phenomena shows that the expected link between the null geodesics and quasinormal modes is violated in the einstein-lovelock theory. nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits. | are eikonal quasinormal modes linked to the unstable circular null geodesics? |
we report evidence for nonlinear modes in the ringdown stage of the gravitational waveform produced by the merger of two comparable-mass black holes. we consider both the coalescence of black hole binaries in quasicircular orbits and high-energy, head-on black hole collisions. the presence of nonlinear modes in the numerical simulations confirms that general-relativistic nonlinearities are important and must be considered in gravitational-wave data analysis. | nonlinear effects in black hole ringdown |
poincaré gauge's theory of gravity is the most noteworthy alternative extension of general relativity that has a correspondence between spin and spacetime geometry. in this paper, we use reissner-nordstrom-de sitter and anti-de sitter solutions, where torsion τ is added as an independent field, to analyze the weak deflection angles α ˆ of massive and null particles in finite distance regime. we then apply α ˆ to determine the einstein ring formation in m87* and sgr. a* and determine that relative to earth's location from these black holes, massive torsion effects can provide considerable deviation, while the cosmological constant's effect remains negligible. furthermore, we also explore how the torsion parameter affects the shadow radius perceived by both static and co-moving (with cosmic expansion) observers in a universe dominated by dark energy, matter, and radiation. our findings indicate that torsion and cosmological constant parameters affect the shadow radius differently between observers in static and co-moving states. we also show how the torsion parameter affects the luminosity of the photonsphere by studying the shadow with infalling accretion. the calculation of the quasinormal modes, greybody bounds, and high-energy absorption cross-section are also affected by the torsion parameter considerably. | testing dynamical torsion effects on the charged black hole's shadow, deflection angle and greybody with m87* and sgr. a* from eht |
we propose a generalisation of the weak gravity conjecture in the presence of scalar fields. the proposal is guided by properties of extremal black holes in n=2 supergravity, but can be understood more generally in terms of forbidding towers of stable gravitationally bound states. it amounts to the statement that there must exist a particle on which the gauge force acts more strongly than gravity and the scalar forces combined. we also propose that the scalar force itself should act on this particle stronger than gravity. this implies that generically the mass of this particle decreases exponentially as a function of the scalar field expectation value for super-planckian variations, which is behaviour predicted by the refined swampland conjecture. in the context of n=2 supergravity the weak gravity conjecture bound can be tied to bounds on scalar field distances in field space. guided by this, we present a general proof that for any linear combination of moduli in any calabi-yau compactification of string theory the proper field distance grows at best logarithmically with the moduli values for super-planckian distances. | the weak gravity conjecture and scalar fields |
the weak gravity conjecture states that quantum gravity theories have to contain a charged state with a charge-to-mass ratio bigger than unity. by studying unitarity and causality constraints on higher derivative corrections to the charge-to-mass ratio of extremal back holes, we demonstrate that heavy extremal black holes can play the role of the required charged state under several assumptions. in particular, our argument is applicable when the higher-spin states reggeizing graviton exchange are subdominant in the photon scattering. it covers (1) theories with light neutral bosons such as dilaton and moduli, and (2) uv completion where the photon and the graviton are accompanied by different sets of regge states just like open string theory. our result provides an existence proof of the weak gravity conjecture in a wide class of theories, including generic string theory setups with the dilaton or other moduli stabilized below the string scale. | weak gravity conjecture from unitarity and causality |
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