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gravitational waves emitted by black hole binary inspiral and mergers enable unprecedented strong-field tests of gravity, requiring accurate theoretical modeling of the expected signals in extensions of general relativity. in this paper we model the gravitational wave emission of inspiralling binaries in scalar gauss-bonnet gravity theories. going beyond the weak-coupling approximation, we derive the gravitational waveform to relative first post-newtonian order beyond the quadrupole approximation and calculate new contributions from nonlinear curvature terms. we also compute the scalar waveform to relative 0.5pn order beyond the leading -0.5pn order terms. we quantify the effect of these terms and provide ready-to-implement gravitational wave and scalar waveforms as well as the fourier domain phase for quasi-circular binaries. we also perform a parameter space study, which indicates that the values of black hole scalar charges play a crucial role in the detectability of deviation from general relativity. we also compare the scalar waveforms to numerical relativity simulations to assess the impact of the relativistic corrections to the scalar radiation. our results provide important foundations for future precision tests of gravity. | post-newtonian gravitational and scalar waves in scalar-gauss-bonnet gravity |
in this paper, we investigate the topological numbers for the singly rotating kerr black holes in all dimensions and the four-dimensional kerr-newman black hole. we show that for uncharged black holes, the rotation parameter has a significant effect on the topological number, and for rotating black holes, the dimension of spacetimes has a remarkable effect on the topological number too. in addition, we find that the topological numbers of the four-dimensional kerr and kerr-newman black holes are the same, which seems to indicate that the electric charge parameter has no effect on the topological number of rotating black holes. our current research provides more evidence that the conjecture put forward in wei et al. [phys. rev. lett., 129, 191101 (2022), 10.1103/physrevlett.129.191101], according to which all black hole solutions should be separated into three different topological classes, is accurate, at least in the pure einstein-maxwell gravity theory. | topological classes of rotating black holes |
the complexity of quantum states has become a key quantity of interest across various subfields of physics, from quantum computing to the theory of black holes. the evolution of generic quantum systems can be modelled by considering a collection of qubits subjected to sequences of random unitary gates. here we investigate how the complexity of these random quantum circuits increases by considering how to construct a unitary operation from haar-random two-qubit quantum gates. implementing the unitary operation exactly requires a minimal number of gates—this is the operation's exact circuit complexity. we prove a conjecture that this complexity grows linearly, before saturating when the number of applied gates reaches a threshold that grows exponentially with the number of qubits. our proof overcomes difficulties in establishing lower bounds for the exact circuit complexity by combining differential topology and elementary algebraic geometry with an inductive construction of clifford circuits. | linear growth of quantum circuit complexity |
in this paper we study the two-body gravitational scattering of massive scalars with different masses in general spacetime dimensions. we focus on the regge limit (eikonal regime) of the resulting scattering amplitudes and discuss how to extract the classical information representing the scattering of two black holes. we derive the leading eikonal and explicitly show the resummation of the first leading energy contribution up to second order in newton's gravitational constant. we also calculate the subleading eikonal showing that in general spacetime dimensions it receives a nontrivial contribution from the box integral. from the eikonal we extract the two-body classical scattering angle between the two black holes up to the second post-minkowskian order. taking various probe-limits of the two-body scattering angles we are able to show agreement between our results and various results in the literature. we highlight that the box integral also has a log-divergent (in energy) contribution at subsubleading order which violates perturbative unitarity in the ultrarelativistic limit. we expect this term to play a role in the calculation of the eikonal at the third post-minkowskian order. | revisiting the second post-minkowskian eikonal and the dynamics of binary black holes |
recently there has been a surge of interest in regularizing, a d → 4 limit of, the einstein-gauss-bonnet (egb) gravity, and the resulting regularized 4d egb gravity has nontrivial dynamics. the theory admits spherically symmetric black holes generalizing the schwarzschild black holes. we consider the rotating black hole in regularized 4d egb gravity and discuss their horizon properties and shadow cast. the effects of the gb coupling parameter on the shape and size of shadows are investigated in the context of recent m87* observations from the eht . interestingly, for a given spin parameter, the apparent size of the shadow decreases and gets more distorted due to the gb coupling parameter. we find that within the finite parameter space, e.g. for a=0.1m, α<= 0.00394m2, and within the current observational uncertainties, the rotating black holes of the 4d egb gravity are consistent with the inferred features of m87* black hole shadow. | rotating black holes in 4d einstein-gauss-bonnet gravity and its shadow |
we present a novel study of kerr compton amplitudes in a partial wave basis in terms of the nekrasov-shatashvili (ns) function of the \textit{confluent heun equation} (che). remarkably, ns-functions enjoy analytic properties and symmetries that are naturally inherited by the compton amplitudes. based on this, we characterize the analytic dependence of the compton phase-shift in the kerr spin parameter and provide a direct comparison to the standard post-minkowskian (pm) perturbative approach within general relativity (gr). we also analyze the universal large frequency behavior of the relevant characteristic exponent of the che -- also known as the renormalized angular momentum -- and find agreement with numerical computations. moreover, we discuss the analytic continuation in the harmonics quantum number $\ell$ of the partial wave, and show that the limit to the physical integer values commutes with the pm expansion of the observables. finally, we obtain the contributions to the tree level, point-particle, gravitational compton amplitude in a covariant basis through $\mathcal{o}(a_{\text{bh}}^8)$, without the need to take the super-extremal limit for kerr spin. | black hole perturbation theory meets cft$_2$: kerr compton amplitudes from nekrasov-shatashvili functions |
chaos and complexity entail an entropic and computational obstruction to describing a system, and thus are intrinsically difficult to characterize. in this paper, we consider time evolution by gaussian unitary ensemble (gue) hamiltonians and analytically compute out-of-time-ordered correlation functions (otocs) and frame potentials to quantify scrambling, haar-randomness, and circuit complexity. while our random matrix analysis gives a qualitatively correct prediction of the late-time behavior of chaotic systems, we find unphysical behavior at early times including an o(1) scrambling time and the apparent breakdown of spatial and temporal locality. the salient feature of gue hamiltonians which gives us computational traction is the haar-invariance of the ensemble, meaning that the ensemble-averaged dynamics look the same in any basis. motivated by this property of the gue, we introduce k-invariance as a precise definition of what it means for the dynamics of a quantum system to be described by random matrix theory. we envision that the dynamical onset of approximate k-invariance will be a useful tool for capturing the transition from early-time chaos, as seen by otocs, to late-time chaos, as seen by random matrix theory. | chaos, complexity, and random matrices |
the effect of a cft shockwave on the entanglement structure of an eternal black hole in jackiw-teitelboim gravity, that is in thermal equilibrium with a thermal bath, is considered. the shockwave carries energy and entropy into the black hole and heats the black hole up leading to evaporation and the eventual recovery of equilibrium. we find an analytical description of the entire relaxational process within the semiclassical high temperature regime. if the shockwave is inserted around the page time then several scenarios are possible depending on the parameters. the page time can be delayed or hastened and there can be more than one transition. the final entropy saddle has a quantum extremal surface that generically starts inside the horizon but at some later time moves outside. in general, increased shockwave energy and slow evaporation rate favour the extremal surface to be inside the horizon. the shockwave also disrupts the scrambling properties of the black hole. the same analysis is then applied to a shockwave inserted into the extremal black hole with similar conclusions. | islands and page curves for evaporating black holes in jt gravity |
for black hole evaporation to be unitary, the naive density matrix of hawking radiation needs to be corrected with a sprinkling of pseudorandom "noise." using wormholes, semiclassical gravity appears to describe an averaged "true random" theory of this noise. we discuss the wormholes in dilaton gravity theories with matter. they are classical solutions that depend on a small amount of backreaction from matter fields, and they are closely related to the wormholes that give the page curve. | more quantum noise from wormholes |
it was shown recently that the static tidal response coefficients, called love numbers, vanish identically for kerr black holes in four dimensions. in this work, we confirm this result and extend it to the case of spin-0 and spin-1 perturbations. we compute the static response of kerr black holes to scalar, electromagnetic, and gravitational fields at all orders in black hole spin. we use the unambiguous and gauge-invariant definition of love numbers and their spin-0 and spin-1 analogs as wilson coefficients of the point particle effective field theory. this definition also allows one to clearly distinguish between conservative and dissipative response contributions. we demonstrate that the behavior of kerr black hole responses to spin-0 and spin-1 fields is very similar to that of the spin-2 perturbations. in particular, static conservative responses vanish identically for spinning black holes. this implies that vanishing love numbers are a generic property of black holes in four-dimensional general relativity. we also show that the dissipative part of the response does not vanish even for static perturbations due to frame-dragging. | on the vanishing of love numbers for kerr black holes |
for ultra compact objects, light rings and fundamental photon orbits (fpos) play a pivotal role in the theoretical analysis of strong gravitational lensing effects, and of bh shadows in particular. in this short review, specific models are considered to illustrate how fpos can be useful in order to understand some non-trivial gravitational lensing effects. this paper aims at briefly overviewing the theoretical foundations of these effects, touching also some of the related phenomenology, both in general relativity and alternative theories of gravity, hopefully providing some intuition and new insights for the underlying physics, which might be critical when testing the kerr black hole hypothesis. | shadows and strong gravitational lensing: a brief review |
a novel 4d einstein-gauss-bonnet gravity was recently formulated by glavan and lin [phys. rev. lett. 124, 081301 (2020)]. although this theory may run into trouble at the level of action or equations of motion, the spherically symmetric black hole solution, which can be successfully reproduced in those consistent theories of 4d egb gravity, is still meaningful and worthy of study. in this paper, we investigate hawking radiation in the spacetime containing such a de sitter black hole. both the greybody factor and the power spectra of the hawking radiation of the massless scalar are studied numerically for the full range of various parameters, including the gb coupling constant α , the cosmological constant λ and the coupling constant related to the scalar filed ξ . in particular, we find a negative α leads to a larger greybody factor than that of a α ≥0 . while, for the power spectra of the hawking radiation the situation is quite the opposite. the reason is that the temperature of the black hole would be very high when α <0 . actually, we observe that the temperature would be arbitrarily high when α approaches to the lower bound. | greybody factor and power spectra of the hawking radiation in the 4d einstein-gauss-bonnet de-sitter gravity |
asymptotic causal diamonds (acds) are a natural flat space analogue of ads causal wedges, and it has been argued previously that they may be useful for understanding bulk locality in flat space holography. in this paper, we use acd-inspired ideas to argue that there exist natural candidates for quantum extremal surfaces (qes) and entanglement wedges in flat space, anchored to the conformal boundary. when there is a holographic screen at finite radius, we can also associate entanglement wedges and entropies to screen sub-regions, with the system naturally coupled to a sink. the screen and the boundary provide two complementary ways of formulating the information paradox. we explain how they are related and show that in both formulations, the flat space entanglement wedge undergoes a phase transition at the page time in the background of an evaporating schwarzschild black hole. our results closely parallel recent observations in ads, and reproduce the page curve. that there is a variation of the argument that can be phrased directly in flat space without reliance on ads, is a strong indication that entanglement wedge phase transitions may be key to the information paradox in flat space as well. along the way, we give evidence that the entanglement entropy of an acd is a well-defined, and likely instructive, quantity. we further note that the picture of the sink we present here may have an understanding in terms of sub-matrix deconfinement in a large-$n$ setting. | page curve and the information paradox in flat space |
we present the derivation of the third subleading order (n3lo) spin-orbit interaction at the state of the art of post-newtonian (pn) gravity via the eft of spinning objects. the present sector contains the largest and most elaborate collection of feynman graphs ever tackled to date in sectors with spin, and in all pn sectors up to third subleading order. our computations are carried out via advanced multi-loop methods. their most demanding aspect is the imperative transition to a generic dimension across the whole derivation, due to the emergence of dimensional-regularization poles across all loop orders as of the n3lo sectors. at this high order of sectors with spin, it is also critical to extend the formal procedure for the reduction of higher-order time derivatives of spin variables beyond linear order for the first time. this gives rise to a new unique contribution at the present sector. the full interaction potential in lagrangian form and the general hamiltonian are provided here for the first time. the consequent gravitational-wave (gw) gauge-invariant observables are also derived, including relations among the binding energy, angular momentum, and emitted frequency. complete agreement is found between our results, and the binding energy of gw sources, and also with the extrapolated scattering angle in the scattering problem, derived via traditional gr. in contrast with the latter derivation, our framework is free-standing and generic, and has provided theory and results, which have been critical to establish the state of the art, and to push the precision frontier for the measurement of gws. | n3lo spin-orbit interaction via the eft of spinning gravitating objects |
we extend the semianalytic technique of iyer and will for computing the complex quasinormal frequencies of black holes, ω , by constructing the padé approximants of the (formal) series for ω2. it is shown that for the (so-far best documented) quasinormal frequencies of the schwarzschild and reissner-nordström black holes the padé transforms p66 and p76 are, within the domain of applicability, always in excellent agreement with the numerical results. we argue that the method may serve as a black box with the "potential" q (x ) as an input and the accurate quasinormal modes as the output. the generalizations and modifications of the method are briefly discussed as well as the preliminary results for other classes of black holes. | quasinormal modes of black holes: the improved semianalytic approach |
we rewrite the chern-simons description of pure gravity on global ads3 and on euclidean btz black holes as a quantum field theory on the ads boundary. the resulting theory is (two copies of) the path integral quantization of a certain coadjoint orbit of the virasoro group, and it should be regarded as the quantum field theory of the boundary gravitons. this theory respects all of the conformal field theory axioms except one: it is not modular invariant. the coupling constant is 1 /c with c the central charge, and perturbation theory in 1 /c encodes loop contributions in the gravity dual. the qft is a theory of reparametrizations analogous to the schwarzian description of nearly ads2 gravity, and has several features including: (i) it is ultraviolet-complete; (ii) the torus partition function is the vacuum virasoro character, which is one-loop exact by a localization argument; (iii) it reduces to the schwarzian theory upon compactification; (iv) it provides a powerful new tool for computing virasoro blocks at large c via a diagrammatic expansion. we use the theory to compute several observables to one-loop order in the bulk, including the "heavy-light" limit of the identity block. we also work out some generalizations of this theory, including the boundary theory which describes fluctuations around two-sided eternal black holes. | a theory of reparameterizations for ads3 gravity |
we discuss static spherically symmetric metrics which represent nonsingular black holes in four- and higher-dimensional spacetime. we impose a set of restrictions, such as a regularity of the metric at the center r =0 and schwarzschild asymptotic behavior at large r . we assume that the metric besides mass m contains an additional parameter ℓ, which determines the scale where modification of the solution of the einstein equations becomes significant. we require that the modified metric obeys the limiting curvature condition; that is, its curvature is uniformly restricted by the value ∼ℓ-2. we also make a "more technical" assumption that the metric coefficients are rational functions of r . in particular, the invariant (∇r )2 has the form pn(r )/p∼n(r ), where pn and p∼n are polynomials of the order of n . we discuss first the case of four dimensions. we show that when n ≤2 such a metric cannot describe a nonsingular black hole. for n =3 we find a suitable metric, which besides m and ℓ contains a dimensionless numerical parameter. when this parameter vanishes, the obtained metric coincides with hayward's one. the characteristic property of such spacetimes is -ξ2=(∇r )2, where ξ2 is a timelike at infinity killing vector. we describe a possible generalization of a nonsingular black-hole metric to the case when this equality is violated. we also obtain a metric for a charged nonsingular black hole obeying similar restrictions as the neutral one and construct higher dimensional models of neutral and charged black holes. | notes on nonsingular models of black holes |
the weak gravity conjecture postulates the existence of superextremal charged particles, i.e. those with mass smaller than or equal to their charge in planck units. we present further evidence for our recent observation that in known examples a much stronger statement is true: an infinite tower of superextremal particles of different charges exists. we show that effective kaluza-klein field theories and perturbative string vacua respect the sublattice weak gravity conjecture, namely that a finite index sublattice of the full charge lattice exists with a superextremal particle at each site. in perturbative string theory we show that this follows from modular invariance. however, we present counterexamples to the stronger possibility that a superextremal particle exists at every lattice site, including an example in which the lightest charged particle is subextremal. the sublattice weak gravity conjecture has many implications both for abstract theories of quantum gravity and for real-world physics. for instance, it implies that if a gauge group with very small coupling e exists, then the fundamental gravitational cutoff energy of the theory is no higher than ∼ e 1/3 m pl. | evidence for a sublattice weak gravity conjecture |
could it be that the matter from the electrons in high tc superconductors is of a radically new kind that may be called "many body entangled compressible quantum matter"? much of this text is intended as an easy to read tutorial, explaining recent theoretical advances that have been unfolding at the cross roads of condensed matter- and string theory, black hole physics as well as quantum information theory. these developments suggest that the physics of such matter may be governed by surprisingly simple principles. my real objective is to present an experimental strategy to test critically whether these principles are actually at work, revolving around the famous linear resistivity characterizing the strange metal phase. the theory suggests a very simple explanation of this "unreasonably simple" behavior that is actually directly linked to remarkable results from the study of the quark gluon plasma formed at the heavy ion colliders: the "fast hydrodynamization" and the "minimal viscosity". this leads to high quality predictions for experiment: the momentum relaxation rate governing the resistivity relates directly to the electronic entropy, while at low temperatures the electron fluid should become unviscous to a degree that turbulent flows can develop even on the nanometre scale. | planckian dissipation, minimal viscosity and the transport in cuprate strange metals |
we show that the asymptotic symmetries close to nonextremal black hole horizons are generated by an extension of supertranslations. this group is generated by a semidirect sum of virasoro and abelian currents. the charges associated with the asymptotic killing symmetries satisfy the same algebra. when considering the special case of a stationary black hole, the zero mode charges correspond to the angular momentum and the entropy at the horizon. | supertranslations and superrotations at the black hole horizon |
we formulate an effective field theory describing large mass scalars and fermions minimally coupled to gravity. the operators of this effective field theory are organized in powers of the transfer momentum divided by the mass of the matter field, an expansion which lends itself to the efficient extraction of classical contributions from loop amplitudes in both the post-newtonian and post-minkowskian regimes. we use this effective field theory to calculate the classical and leading quantum gravitational scattering amplitude of two heavy spin-1/2 particles at the second post-minkowskian order. | heavy black hole effective theory |
we prove the following theorem: axisymmetric, stationary solutions of the einstein field equations formed from classical gravitational collapse of matter obeying the null energy condition, that are everywhere smooth and ultracompact (i.e., they have a light ring) must have at least two light rings, and one of them is stable. it has been argued that stable light rings generally lead to nonlinear spacetime instabilities. our result implies that smooth, physically and dynamically reasonable ultracompact objects are not viable as observational alternatives to black holes whenever these instabilities occur on astrophysically short time scales. the proof of the theorem has two parts: (i) we show that light rings always come in pairs, one being a saddle point and the other a local extremum of an effective potential. this result follows from a topological argument based on the brouwer degree of a continuous map, with no assumptions on the spacetime dynamics, and, hence, it is applicable to any metric gravity theory where photons follow null geodesics. (ii) assuming einstein's equations, we show that the extremum is a local minimum of the potential (i.e., a stable light ring) if the energy-momentum tensor satisfies the null energy condition. | light-ring stability for ultracompact objects |
we study the entanglement islands and subsystem volume complexity corresponding to the left/ right entanglement of a conformal defect in d-dimensions in randall-sundrum (rs) braneworld model with subcritical tension brane. the left and right modes of the defect mimic the eternal black hole and radiation system respectively. hence the entanglement entropy between the two follows an eternal black hole page curve which is unitarity compatible. we compute the volumes corresponding to the left and right branes with preferred ryu-takanayagi (rt) surfaces at different times, which provide a probe of the subregion complexity of the black hole and the radiation states respectively. an interesting jump in volume is found at page time, where the entanglement curve is saturated due to the inclusion of the island surfaces. we explain various possibilities of this phase transition in complexity at page time and argue how these results match with a covariant proposal qualitatively. | islands and complexity of eternal black hole and radiation subsystems for a doubly holographic model |
we explain how the lowest-order classical gravitational radiation produced during the inelastic scattering of two schwarzschild black holes in general relativity can be obtained from a tree scattering amplitude in gauge theory coupled to scalar fields. the gauge calculation is related to gravity through the double copy. we remove unwanted scalar forces which can occur in the double copy by introducing a massless scalar in the gauge theory, which is treated as a ghost in the link to gravity. we hope these methods are a step towards a direct application of the double copy at higher orders in classical perturbation theory, with the potential to greatly streamline gravity calculations for phenomenological applications. | inelastic black hole scattering from charged scalar amplitudes |
we introduce deep learning models to estimate the masses of the binary components of black hole mergers, $(m_1,m_2)$ (m1,m2) , and three astrophysical properties of the post-merger compact remnant, namely, the final spin, $a_\mathrm f$ af , and the frequency and damping time of the ringdown oscillations of the fundamental $\ell = m = 2$ ℓ=m=2 bar mode, $(\omega_\mathrm r, \omega_\mathrm i)$ (ωr,ωi) . our neural networks combine a modified wavenet architecture with contrastive learning and normalizing flow. we validate these models against a gaussian conjugate prior family whose posterior distribution is described by a closed analytical expression. upon confirming that our models produce statistically consistent results, we used them to estimate the astrophysical parameters $(m_1,m_2, a_\mathrm f, \omega_\mathrm r, \omega_\mathrm i)$ (m1,m2,af,ωr,ωi) of five binary black holes: gw150914, gw170104, gw170814, gw190521 and gw190630. we use pycbc inference to directly compare traditional bayesian methodologies for parameter estimation with our deep learning based posterior distributions. our results show that our neural network models predict posterior distributions that encode physical correlations, and that our data-driven median results and 90% confidence intervals are similar to those produced with gravitational wave bayesian analyses. this methodology requires a single v100 nvidia gpu to produce median values and posterior distributions within two milliseconds for each event. this neural network, and a tutorial for its use, are available at the data and learning hub for science. | statistically-informed deep learning for gravitational wave parameter estimation |
we investigate how a spherically symmetric fluid modifies the schwarzschild vacuum solution when there is no exchange of energy-momentum between the fluid and the central source of the schwarzschild metric. this system is described by means of the gravitational decoupling realised via the minimal geometric deformation approach, which allows us to prove that the fluid must be anisotropic. several cases are then explicitly shown. | black holes by gravitational decoupling |
quantitative tools for measuring the propagation of information through quantum many-body systems, originally developed to study quantum chaos, have recently found many new applications from black holes to disordered spin systems. | unscrambling the physics of out-of-time-order correlators |
we prove that higher-dimension operators contribute positively to the entropy of a thermodynamically stable black hole at fixed mass and charge. our results apply whenever the dominant corrections originate at tree level from quantum field theoretic dynamics. more generally, positivity of the entropy shift is equivalent to a certain inequality relating the free energies of black holes. these entropy inequalities mandate new positivity bounds on the coefficients of higher-dimension operators. one of these conditions implies that the charge-to-mass ratio of an extremal black hole asymptotes to unity from above for increasing mass. consequently, large extremal black holes are unstable to decay to smaller extremal black holes and the weak gravity conjecture is automatically satisfied. our findings generalize to arbitrary spacetime dimension and to the case of multiple gauge fields. the assumptions of this proof are valid across a range of scenarios, including string theory constructions with a dilaton stabilized below the string scale. | proof of the weak gravity conjecture from black hole entropy |
structure at the horizon scale of black holes would give rise to echoes of the gravitational wave signal associated with the postmerger ringdown phase in binary coalescences. we study the waveform of echoes in static and stationary, traversable wormholes in which perturbations are governed by a symmetric effective potential. we argue that echoes are dominated by the wormhole quasinormal frequency nearest to the fundamental black hole frequency that controls the primary signal. we put forward an accurate method to construct the echoes' waveform(s) from the primary signal and the quasinormal frequencies of the wormhole, which we characterize. we illustrate this in the static damour-solodukhin wormhole and in a new, rotating generalization that approximates a kerr black hole outside the throat. rotation gives rise to a potential with an intermediate plateau region that breaks the degeneracy of the quasinormal frequencies. rotation also leads to late-time instabilities that, however, fade away for small angular momentum. | echoes of kerr-like wormholes |
we prove a version of the weak gravity conjecture for 6d f-theory or heterotic string compactifications with 8 supercharges. this sharpens our previous analysis by including massless scalar fields. the latter are known to modify the weak gravity conjecture bound in two a priori independent ways: first, the extremality condition of a charged black hole is modified, and second, the test particles required to satisfy the weak gravity conjecture are subject to additional yukawa type interactions. we argue on general grounds that at weak coupling, the two types of effects are equivalent for a tower of asymptotically massless charged test particles predicted by the swampland distance conjecture. we then specialize to f-theory compactified on elliptic calabi-yau three-folds and prove that the precise numerical bound on the charge-to-mass ratio is satisfied at weak coupling. this amounts to an intriguing coincidence of two a priori different notions of extremality, namely one based on the balance of gauge, gravitational and scalar forces for extremal (non-bps) black holes, and the other encoded in the modular properties of certain jacobi forms. in the presence of multiple abelian gauge group factors, the elliptic genus counting these states is a lattice quasi-jacobi form of higher rank, and we exemplify this in a model with two abelian gauge group factors. | a stringy test of the scalar weak gravity conjecture |
the eikonal approximation is an ideal tool to extract classical observables in gauge theory and gravity directly from scattering amplitudes. here we consider effective theories of gravity where in addition to the einstein-hilbert term we include nonminimal couplings of the type r3, r4 and ffr. in particular, we study the scattering of gravitons and photons of frequency ω off heavy scalars of mass m in the limit m ≫ω ≫|q →|, where q → is the momentum transfer. the presence of nonminimal couplings induces helicity-flip processes which survive the eikonal limit, thereby promoting the eikonal phase to an eikonal phase matrix. we obtain the latter from the relevant two-to-two helicity amplitudes that we compute up to one-loop order, and confirm that the leading-order terms in ω exponentiate à la amati, ciafaloni and veneziano. from the eigenvalues of the eikonal phase matrix we then extract two physical observables, to 2pm order: the classical deflection angle and shapiro time delay/advance. whenever the classical expectation of helicity conservation of the massless scattered particle is violated, i.e., the eigenvalues of the eikonal matrix are nondegenerate, causality violation due to time advance is a generic possibility for small impact parameter. we show that for graviton scattering in the r4 and ffr theories, time advance is circumvented if the couplings of these interactions satisfy certain positivity conditions, while it is unavoidable for graviton scattering in the r3 theory and photon scattering in the ffr theory. the scattering processes we consider mimic the deflection of photons and gravitons off spinless heavy objects such as black holes. | eikonal phase matrix, deflection angle, and time delay in effective field theories of gravity |
our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the event horizon telescope (eht). we use here the m87* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. for example, we show that the quality of the measurements is already sufficient to rule out that m87* is a highly charged dilaton black hole. similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for the doubly-charged dilaton and the sen black holes. | constraints on black-hole charges with the 2017 eht observations of m87* |
we advance two alternative proposals for the island contributions to the entanglement negativity of various pure and mixed state configurations in quantum field theories coupled to semiclassical gravity. the first construction involves the extremization of an algebraic sum of the generalized renyi entropies of order half. the second proposal involves the extremization of the sum of the effective entanglement negativity of quantum matter fields and the backreacted area of a cosmic brane spanning the entanglement wedge cross section which also extremizes the generalized renyi reflected entropy of order half. these proposals are utilized to obtain the island contributions to the entanglement negativity of various pure and mixed state configurations involving the bath systems coupled to extremal and non-extremal black holes in jt gravity demonstrating an exact match with each other. furthermore, the results from both the proposals match precisely with the island contribution to half the renyi reflected entropy of order half providing a strong consistency check. we then allude to a possible doubly holographic picture of our island proposals and provide a derivation of the first proposal by determining the corresponding replica wormhole contributions. | islands for entanglement negativity |
we apply the recently proposed quantum extremal surface construction to calculate the page curve of the eternal reissner-nordström black holes in four dimensions ignoring the backreaction and the greybody factor. without the island, the entropy of hawking radiation grows linearly with time, which results in the information paradox for the eternal black holes. by extremizing the generalized entropy that allows the contributions from the island, we find that the island extends to the outside the horizon of the reissner-nordström black hole. when taking the effect of the islands into account, it is shown that the entanglement entropy of hawking radiation at late times for a given region far from the black hole horizon reproduces the bekenstein-hawking entropy of the reissner-nordström black hole with an additional term representing the effect of the matter fields. the result is consistent with the finiteness of the entanglement entropy for the radiation from an eternal black hole. this facilitates to address the black hole information paradox issue in the current case under the above-mentioned approximations. | islands and page curves of reissner-nordström black holes |
we compute the conservative two-body hamiltonian of a compact binary system with a spinning black hole through o (g3) to all orders in velocity, including linear and quadratic spin terms. to obtain our results we calculate the classical limit of the two-loop amplitude for the scattering of a massive scalar particle with a massive spin-1 particle minimally coupled to gravity. we employ modern scattering amplitude and loop integration techniques, in particular numerical unitarity, integration-by-parts identities, and the method of regions. the conservative potential in terms of rest-frame spin vectors is extracted by matching to a nonrelativistic effective field theory. we also apply the kosower-maybee-o'connell (kmoc) formalism to calculate the impulse in the covariant spin formalism directly from the amplitude. we work systematically in conventional dimensional regularization and explicitly evaluate all divergent integrals that appear in full- and effective-theory amplitudes, as well as in the phase-space integrals that arise in the kmoc formalism. | conservative binary dynamics with a spinning black hole at o (g3) from scattering amplitudes |
observers in de sitter space can only access the space up to their cosmological horizon. assuming thermal equilibrium, we use the quantum ryu-takayanagi or island formula to compute the entanglement entropy between the states inside the cosmological horizon and states outside, as a function of time. we obtain a page curve that is bound at a value corresponding to the gibbons-hawking entropy. at this transition an 'island' forms, which is in a significantly different location as compared to when considering black hole horizons and even moves back in time. these differences turn out to be essential for non-violation of the no-cloning theorem in combination with entanglement wedge reconstruction. this consideration furthermore introduces the need for a scrambling time, the entropy dependence of which turns out to coincide with what is expected for black holes. the model we employ has classically pure three-dimensional de sitter space as a solution. we dimensionally reduce to two dimensions in order to take into account semi-classical effects. nevertheless, we expect the aforementioned qualitative features of the island to persist in higher dimensions. | pure de sitter space and the island moving back in time |
we define a new information theoretic quantity called odd entanglement entropy (oee) which enables us to compute the entanglement wedge cross section in holographic conformal field theories (cfts). the entanglement wedge cross section has been introduced as a minimal cross section of the entanglement wedge, a natural generalization of the ryu-takayanagi surface. by using the replica trick, we explicitly compute the oee for two-dimensional holographic cft (three-dimensional anti-de sitter space and planar bañados-teitelboim-zanelli black hole) and see agreement with the entanglement wedge cross section. we conjecture this relation will hold in general dimensions. | entanglement wedge cross section from the dual density matrix |
"do carroll particles move?" the answer depends on the characteristics of the particle such as its mass, spin, electric charge, and magnetic moment. a massive carroll particle (closely related to fractons) does not move; its immobility follows from carroll boost symmetry which implies dipole conservation, but not conversely. a massless carroll particle may propagate by following the hall law, consistently with the partial breaking of the carroll boost symmetry. the framework is extended to carroll field theory. in d = 2 space dimensions, the carroll group has a two-fold central extension which allows us to generalize the dynamics to massive and massless particles, including anyons. the anyonic spin and magnetic moment combine with the doubly-extended structure parametrized by two casimir invariants interpreted as intrinsic magnetization and non-commutativity parameter. the extended carroll particle subjected to an electromagnetic background field moves following a generalized hall law which includes a zeeman force. this theory is illustrated by massless, uncharged anyons with doubly-centrally extended structure we call exotic photons, which move on the horizon of a black hole, giving rise to an anyonic spin-hall effect. | hall motions in carroll dynamics |
we show that the presence of replica wormholes in the euclidean path integral of gravity leads to a non-perturbative violation of charge conservation for any global symmetry present in the low-energy description of quantum gravity. explicitly, we compute the scattering probability between different charged states in several two-dimensional models of quantum gravity and find a non-vanishing answer. this suggests that the set of all charged states is typically over-complete, which has drastic consequences for the fate of black hole remnants that could carry a global symmetry charge. in the holographic context, we argue that the presence of such a symmetry in the effective description of the bulk should appear on the boundary as an emergent global symmetry after ensemble averaging. | a violation of global symmetries from replica wormholes and the fate of black hole remnants |
the quantum field-theoretic approach to classical observables due to kosower, maybee and o'connell provides a rigorous pathway from on-shell scattering amplitudes to classical perturbation theory. in this paper, we promote this formalism to describe general classical spinning objects by using coherent spin states. our approach is fully covariant with respect to the massive little group su(2) and is therefore completely synergistic with the massive spinor-helicity formalism. we apply this approach to classical two-body scattering due gravitational interaction. starting from the coherent-spin elastic-scattering amplitude, we derive the classical impulse and spin kick observables to first post-minkowskian order but to all orders in the angular momenta of the massive spinning objects. from the same amplitude, we also extract an effective two-body hamiltonian, which can be used beyond the scattering setting. as a cross-check, we rederive the classical observables in the center-of-mass frame by integrating the hamiltonian equations of motion to the leading order in newton's constant. | classical observables from coherent-spin amplitudes |
the dynamics of a nearly-ads2 spacetime with boundaries is reduced to that of two particles in the anti-de sitter space. we determine the class of physically meaningful wavefunctions, and prescribe the statistical mechanics of a black hole. we demonstrate how wavefunctions for a two-sided black hole and a regularized notion of trace can be used to construct thermal partition functions, and more generally, arbitrary density matrices. we also obtain correlation functions of external operators. | statistical mechanics of a two-dimensional black hole |
we investigated the superradiance and stability of the regularized 4d charged einstein-gauss-bonnet black hole which is recently inspired by glavan and lin [phys. rev. lett. 124, 081301 (2020)]. we found that the positive gauss-bonnet coupling constant α enhances the superradiance, while the negative α suppresses it. the condition for superradiant instability is proved. we also worked out the quasinormal modes (qnms) of the charged einstein-gauss-bonnet black hole and found that the real part of all the qnms does not satisfy the superradiance condition and the imaginary parts are all negative. therefore this black hole is stable. when α makes the black hole extremal, there are normal modes. | superradiance and stability of the regularized 4d charged einstein-gauss-bonnet black hole |
recently a new class of scalarized black holes in einstein-gauss-bonnet (egb) theories was discovered. what is special for these black hole solutions is that the scalarization is not due to the presence of matter, but it is induced by the curvature of spacetime itself. moreover, more than one branch of scalarized solutions can bifurcate from the schwarzschild branch, and these scalarized branches are characterized by the number of nodes of the scalar field. the next step is to consider the linear stability of these solutions, which is particularly important due to the fact that the schwarzschild black holes lose stability at the first point of bifurcation. therefore we here study in detail the radial perturbations of the scalarized egb black holes. the results show that all branches with a nontrivial scalar field with one or more nodes are unstable. the stability of the solutions on the fundamental branch, whose scalar field has no radial nodes, depends on the particular choice of the coupling function between the scalar field and the gauss-bonnet invariant. we consider two particular cases based on the previous studies of the background solutions. if this coupling has the form used in [d. d. doneva and s. s. yazadjiev, phys. rev. lett. 120, 131103 (2018)] the fundamental branch of solutions is stable, except for very small masses. in the case of a coupling function quadratic in the scalar field [h. o. silva, j. sakstein, l. gualtieri, t. p. sotiriou, and e. berti, phys. rev. lett. 120, 131104 (2018)], though, the whole fundamental branch is unstable. | radial perturbations of the scalarized einstein-gauss-bonnet black holes |
it has long been conjectured that the large n deconfinement phase transition of n = 4 su(n) super-yang-mills corresponds via ads/cft to the hawking-page transition in which black holes dominate the thermal ensemble, and quantitative evidence of this has come through the recent matching of the superconformal index of 1/16 -bps states to the supersymmetric black hole entropy. we introduce the half-bps gukov-witten surface defect as a probe of the superconformal index, which also serves as an order parameter for the deconfinement transition. this can be studied directly in field theory as a modification of the usual unitary matrix model or in the dual description as a d3-brane probe in the background of a (complex) supersymmetric black hole. using a saddle point approximation, we determine our defect index in the large n limit as a simple function of the chemical potentials and show independently that it is reproduced by the renormalized action of the brane in the black hole background. along the way, we also comment on the cardy limit and the thermodynamics of the d3-brane in the generalized ensemble. the defect index sharply distinguishes between the confining and the deconfining phases of the gauge theory and thus is a supersymmetric non-perturbative order parameter for these large n phase transitions which deserves further investigation. finally, our work provides an example where the properties of a black hole coupled to an external system can be analyzed precisely. | probing supersymmetric black holes with surface defects |
we continue to investigate correspondences between, on the one hand, scattering amplitudes for massive higher-spin particles and gravitons in appropriate quantum-to-classical limits, and on the other hand, classical gravitational interactions of spinning black holes according to general relativity. we first construct an ansatz for a gravitational compton amplitude, at tree level, constrained only by locality, crossing symmetry, unitarity and consistency with the linearized-kerr 3-point amplitude, to all orders in the black hole's spin. we then explore the extent to which a unique classical compton amplitude can be identified by comparing with the results of the classical process of scattering long-wavelength gravitational waves off an exact kerr black hole, determined by appropriate solutions of the teukolsky equation. up to fourth order in spin, we find complete agreement with a previously conjectured exponential form of the tree-level compton amplitude. at higher orders, we extract tree-level contributions from the teukolsky amplitude by an analytic continuation from a physical ($a/gm<1$) to a particle-like ($a/gm>1$) regime. up to the sixth order in spin, we identify a unique \textit{conservative} part of the amplitude which is insensitive both to the choice of boundary conditions at the black hole horizon and to branch choices in the analytic continuation. the remainder of the amplitude is determined modulo an overall sign from a branch choice, with the sign flipping under exchanging purely ingoing and purely outgoing boundary conditions at the horizon. along the way, we make contact with novel applications of massive spinor-helicity variables pertaining to their relation to eft operators and (spinning) partial amplitudes. | scattering in black hole backgrounds and higher-spin amplitudes: part ii |
we construct an infinite family of microstates with geometric interiors for eternal black holes in general relativity with negative cosmological constant in any dimension. wormholes in the euclidean path integral for gravity cause these states to have small, but non-zero, quantum mechanical overlaps that have a universal form. the overlaps have a dramatic consequence: the microstates span a hilbert space of log dimension equal to the bekenstein-hawking entropy. the semiclassical microstates we construct contain einstein-rosen bridges of arbitrary size behind their horizons. our results imply that all these bridges can be interpreted as quantum superpositions of wormholes of size at most exponential in the entropy. | microscopic origin of the entropy of black holes in general relativity |
a perturbed black hole rings down by emitting gravitational waves in tones with specific frequencies and durations. such tones encode prized information about the geometry of the source spacetime and the fundamental nature of gravity, making the measurement of black hole ringdowns a key goal of gravitational wave astronomy. however, this task is plagued by technical challenges that invalidate the naive application of standard data analysis methods and complicate sensitivity projections. in this paper, we provide a comprehensive account of the formalism required to properly carry out ringdown analyses, examining in detail the foundations of recent observational results, and providing a framework for future measurements. we build on those insights to clarify the concepts of ringdown detectability and resolvability -- touching on the drawbacks of both bayes factors and naive fisher matrix approaches -- and find that overly pessimistic heuristics have led previous works to underestimate the role of ringdown overtones for black hole spectroscopy. we put our framework to work on the analysis of a variety of simulated signals in colored noise, including analytic injections and a numerical relativity simulation consistent with gw150914. we demonstrate that we can use tones of the quadrupolar angular harmonic to test the no-hair theorem at current sensitivity, with precision comparable to published constraints from real data. finally, we assess the role of modeling systematics, and project measurements for future, louder signals. we release ringdown, a python library for analyzing black hole ringdowns using the the methods discussed in this paper, under a permissive open-source license at https://github.com/maxisi/ringdown | analyzing black-hole ringdowns |
searching for violations of the no-hair theorem (nht) is a powerful way to test gravity, and more generally fundamental physics, particularly with regards to the existence of additional scalar fields. the first observation of a black hole (bh) shadow by the event horizon telescope (eht) has opened a new direct window onto tests of gravity in the strong-field regime, including probes of violations of the nht. we consider two scenarios described by the einstein-maxwell equations of general relativity and electromagnetism, to which we add a scalar field. in the first case we consider a minimally-coupled scalar field with a potential, whereas in the second case the field is conformally-coupled to curvature. in both scenarios we construct charged bh solutions, which are found to carry primary scalar hair. we then compute the shadows cast by these two bhs as a function of their electric charge and scalar hair parameter. comparing these shadows to the shadow of m87* recently imaged by the eht collaboration, we set constraints on the amount of scalar hair carried by these two bhs. the conformally-coupled case admits a regime for the hair parameter, compatible with eht constraints, describing a so-called mutated reissner-nordström bh: this solution was recently found to effectively mimic a wormhole. our work provides novel constraints on fundamental physics, and in particular on violations of the no-hair theorem and the existence of additional scalar fields, from the shadow of m87*. | black holes with scalar hair in light of the event horizon telescope |
in this paper, we discuss the effects of nonlinear electrodynamics (ned) on non-rotating black holes, parametrized by the field coupling parameter β and magnetic charge parameter p in detail. particularly, we survey a large range of observables and physical properties of the magnetically charged black hole, including the thermodynamic properties, observational appearance, quasinormal modes and absorption cross sections. initially, we show that the ned black hole is always surrounded by an event horizon and any magnetic charge is permissible. we then show that the black hole gets colder with increasing charge. investigating the heat capacity, we see that the black hole is thermally stable between points of phase transition. introducing a generalized uncertainty principle (gup) with a quantum gravity parameter λ extends the range of the stable region, but the effect on temperature is negligible. then we compute the deflection angle at the weak field limit, by the gauss-bonnet theorem and the geodesic equation, and find that even at the first order, the magnetic charge has a contribution due to the "field mass" term. small changes of the charge contributes greatly to the paths of null geodesics due to the p 2 dependence of the horizon radius. using a ray-tracing code, we simulate the observational appearance of a ned black hole under different emission profiles, thin disk and spherical accretion. we find that the parameter p has a very strong effect on the observed shadow radius, in agreement with the deflection angle calculations. we finally consider quasinormal modes under massless scalar perturbations of the black hole and the greybody factor. we find that the charge introduces a slight difference in the fundamental frequency of the emitted waveform. we find that the greybody factor of the ned black hole is strongly steepened by the introduction of increasing charge. to present observational constrains, we show that the magnetic charge of the m87* black hole is between 0 ≤ p ≤ 0.024 in units of m, in agreement with the idea that real astrophysical black holes are mostly neutral. we also find that ligo/virgo and lisa could detect ned black hole perturbations from bhs with masses between 5 m ⊙ and 8.0 · 108 m ⊙. we finally show that for black holes with masses detected with ligo so far, charged ned black holes would deviate from schwarzschild by 5~10 hz in their fundamental frequencies. | nonlinear electrodynamics effects on the black hole shadow, deflection angle, quasinormal modes and greybody factors |
magnetic reconnection can power bright, rapid flares originating from the inner magnetosphere of accreting black holes. we conduct extremely high-resolution (5376 × 2304 × 2304 cells) general-relativistic magnetohydrodynamics simulations, capturing plasmoid-mediated reconnection in a 3d magnetically arrested disk for the first time. we show that an equatorial, plasmoid-unstable current sheet forms in a transient, nonaxisymmetric, low-density magnetosphere within the inner few schwarzschild radii. magnetic flux bundles escape from the event horizon through reconnection at the universal plasmoid-mediated rate in this current sheet. the reconnection feeds on the highly magnetized plasma in the jets and heats the plasma that ends up trapped in flux bundles to temperatures proportional to the jet's magnetization. the escaped flux bundles can complete a full orbit as low-density hot spots, consistent with sgr a* observations by the gravity interferometer. reconnection near the horizon produces sufficiently energetic plasma to explain flares from accreting black holes, such as the tev emission observed from m87. the drop in the mass accretion rate during the flare and the resulting low-density magnetosphere make it easier for very-high-energy photons produced by reconnection-accelerated particles to escape. the extreme-resolution results in a converged plasmoid-mediated reconnection rate that directly determines the timescales and properties of the flare. | black hole flares: ejection of accreted magnetic flux through 3d plasmoid-mediated reconnection |
we explore conformal primary wave functions for all half integer spins up to the graviton. half steps are related by supersymmetry, integer steps by the classical double copy. the main results are as follows: we 1) introduce a convenient spin frame and null tetrad to organize all radiative modes of varying spin; 2) identify the massless spin-3/2 conformal primary wave function as well as the conformally soft goldstone mode corresponding to large supersymmetry transformations; 3) indicate how to express a conformal primary of arbitrary spin in terms of differential operators acting on a scalar primary; 4) demonstrate that conformal primary metrics satisfy the double copy in a variety of forms—operator, weyl, and kerr-schild—and are exact, albeit complex, solutions to the fully nonlinear einstein equations of petrov type n ; 5) propose a novel generalization of conformal primary wave functions; and 6) show that this generalization includes a large class of physically interesting metrics corresponding to ultra-boosted black holes, shockwaves and more. | shifting spin on the celestial sphere |
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 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 adsd+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 adsd 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 |
a charged rotating black hole in f(r) gravity is characterized by mass, m, spin, a, electric charge, q, and r0 which is proportional to cosmological constant. we analyze the image of the black hole shadow in four types (1) at r →∞ , (2) at r →ro in vacuum, (3) at r →∞ and (4) at r →ro for an observer at the presence of plasma. moreover, we investigate the effect of spin, charge, and modification of gravity on the shape of the shadow. in addition, we use two observable parameters, the radius rs and the distortion parameter δs, characterizing the apparent shape. we show that the shadow becomes smaller with increasing electric charge for all cases. also, by increasing the rotation parameters, the circular symmetry of the black hole's shadow image will change. furthermore, in the presence of plasma, the plasma parameter also affects the size of the shadow. | shadow of a charged rotating black hole in f(r) gravity |
we study shadows cast by a certain class of rotating wormholes and point out the crucial role of a rotating wormhole throat in the formation of a shadow. overlooking this crucial role of a wormhole throat has resulted in incomplete results in the previous studies on shadows of the same class of rotating wormholes. we explore the dependence of the shadows on the spin of the wormholes. we compare our results with that of the kerr black hole. with increasing values of the spin, the shapes of the wormhole shadows start deviating considerably from that of the black hole. such considerable deviation, if detected in future observations, may possibly indicate the presence of a wormhole. in other words, the results obtained here indicate that, through the observations of their shadows, the wormholes which are considered in this work and have reasonable spin can be distinguished from a black hole. | shadows of rotating wormholes |
we reformulate the scattering amplitudes of 4d flat space gauge theory and gravity in the language of a 2d cft on the celestial sphere. the resulting cft structure exhibits an ope constructed from 4d collinear singularities, as well as infinite-dimensional kac-moody and virasoro algebras encoding the asymptotic symmetries of 4d flat space. we derive these results by recasting 4d dynamics in terms of a convenient foliation of flat space into 3d euclidean ads and lorentzian ds geometries. tree-level scattering amplitudes take the form of witten diagrams for a continuum of (a)ds modes, which are in turn equivalent to cft correlators via the (a)ds/cft dictionary. the ward identities for the 2d conserved currents are dual to 4d soft theorems, while the bulk-boundary propagators of massless (a)ds modes are superpositions of the leading and subleading weinberg soft factors of gauge theory and gravity. in general, the massless (a)ds modes are 3d chern-simons gauge fields describing the soft, single helicity sectors of 4d gauge theory and gravity. consistent with the topological nature of chern-simons theory, aharonov-bohm effects record the "tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. soft particle exchanges between hard processes define the kac-moody level and virasoro central charge, which are thereby related to the 4d gauge coupling and gravitational strength in units of an infrared cutoff. finally, we discuss a toy model for black hole horizons via a restriction to the rindler region. | 4d scattering amplitudes and asymptotic symmetries from 2d cft |
we consider the shift of charge-to-mass ratio for extremal black holes in the context of effective field theory, motivated by the weak gravity conjecture. we constrain extremality corrections in different regimes subject to unitarity and causality constraints. in the asymptotic ir, we demonstrate that for any supersymmetric theory in flat space, and for all minimally coupled theories, logarithmic running at one loop pushes the wilson coefficient of certain four-derivative operators to be larger at lower energies, guaranteeing the existence of sufficiently large black holes with q > m. we identify two exceptional cases of nonsupersymmetric theories involving large numbers of light states and planck-scale nonminimal couplings, in which the sign of the running is reversed, leading to black holes with negative corrections to q/m in the deep ir, but argue that these do not rule out extremal black holes as the requisite charged states for the wgc. we separately show that causality and unitarity imply that the leading threshold corrections to the effective action from integrating out massive states, in any weakly coupled theory, can be written as a sum of squares and is manifestly positive for black hole backgrounds. quite beautifully, the shift in the extremal q/m ratio is directly proportional to the shift in the on-shell action, guaranteeing that these threshold corrections push q > m in compliance with the wgc. our results apply for black holes with or without dilatonic coupling and charged under any number of u(1)s. | causality, unitarity, and the weak gravity conjecture |
this paper addresses a long standing problem, the counting of the microstates of supersymmetric asymptotically ads black holes in terms of a holographically dual field theory. we focus on a class of asymptotically ads4 static black holes preserving two real supercharges which are dual to a topologically twisted deformation of the abjm theory. we evaluate in the large n limit the topologically twisted index of the abjm theory and we show that it correctly reproduces the entropy of the ads4 black holes. an extremization of the index with respect to a set of chemical potentials is required. we interpret it as the selection of the exact r-symmetry of the superconformal quantum mechanics describing the horizon of the black hole. | black hole microstates in ads4 from supersymmetric localization |
we investigate the thermodynamic behaviour of the four dimension gauss bonnet black hole, proposed in [phys. rev. lett. 124, 081301 (2020)], in the ads background . we study the thermodynamics in extended phase space, where the cosmological constant is taken as the thermodynamic pressure. the black hole exhibits a phase transition similar to that of van der waals system. the phase transition is investigated via isotherms in $p-v$ diagram, gibbs free energy and specific heat plots. the charged and neutral cases are considered separately to observe the effect of charge on critical behaviour. in both cases the van der waals like behaviour is exhibited. we also study the throttling process of the black hole analytically using isenthalpic and inversion curves. | thermodynamics, phase transition and joule thomson expansion of novel 4-d gauss bonnet ads black hole |
we examine holographic complexity in time-dependent vaidya spacetimes with both the complexity=volume (cv) and complexity=action (ca) proposals. we focus on the evolution of the holographic complexity for a thin shell of null fluid, which collapses into empty ads space and forms a (one-sided) black hole. in order to apply the ca approach, we introduce an action principle for the null fluid which sources the vaidya geometries, and we carefully examine the contribution of the null shell to the action. further, we find that adding a particular counterterm on the null boundaries of the wheeler-dewitt patch is essential if the gravitational action is to properly describe the complexity of the boundary state. for both the cv proposal and the ca proposal (with the extra boundary counterterm), the late time limit of the growth rate of the holographic complexity for the one-sided black hole is precisely the same as that found for an eternal black hole. | holographic complexity in vaidya spacetimes. part i |
a set of infinitesimal virasoro l ⊗ virasoro r diffeomorphisms are presented which act non-trivially on the horizon of a generic kerr black hole with spin j. the covariant phase space formalism provides a formula for the virasoro charges as surface integrals on the horizon. integrability and associativity of the charge algebra are shown to require the inclusion of `wald-zoupas' counterterms. a counterterm satisfying the known consistency requirement is constructed and yields central charges cl= cr= 12 j. assuming the existence of a quantum hilbert space on which these charges generate the symmetries, as well as the applicability of the cardy formula, the central charges reproduce the macroscopic area-entropy law for generic kerr black holes. | black hole entropy and soft hair |
we consider gedanken experiments to destroy an extremal or nearly extremal kerr-newman black hole by causing it to absorb matter with sufficient charge and/or angular momentum as compared with energy that it cannot remain a black hole. it was previously shown by one of us that such gedanken experiments cannot succeed for test particle matter entering an extremal kerr-newman black hole. we generalize this result here to arbitrary matter entering an extremal kerr-newman black hole, provided only that the nonelectromagnetic contribution to the stress-energy tensor of the matter satisfies the null energy condition. we then analyze the gedanken experiments proposed by hubeny and others to overcharge and/or overspin an initially slightly nonextremal kerr-newman black hole. analysis of such gedanken experiments requires that we calculate all effects on the final mass of the black hole that are second-order in the charge and angular momentum carried into the black hole, including all self-force effects. we obtain a general formula for the full second order correction to mass, δ2m , which allows us to prove that no gedanken experiments of the generalized hubeny type can ever succeed in overcharging and/or overspinning a kerr-newman black hole, provided only that the nonelectromagnetic stress-energy tensor satisfies the null energy condition. our analysis is based upon lagrangian methods, and our formula for the second-order correction to mass is obtained by generalizing the canonical energy analysis of hollands and wald to the einstein-maxwell case. remarkably, we obtain our formula for δ2m without having to explicitly compute self-force or finite size effects. indeed, in an appendix, we show explicitly that our formula incorporates both the self-force and finite size effects for the special case of a charged body slowly lowered into an uncharged black hole. | gedanken experiments to destroy a black hole. ii. kerr-newman black holes cannot be overcharged or overspun |
in holographic duality, a higher dimensional quantum gravity system emerges from a lower dimensional conformal field theory (cft) with a large number of degrees of freedom. we propose a formulation of duality for a general causally complete bulk spacetime region, called subalgebra-subregion duality, which provides a framework to describe how geometric notions in the gravity system, such as spacetime subregions, different notions of times, and causal structure, emerge from the dual cft. subalgebra-subregion duality generalizes and brings new insights into subregion-subregion duality (or equivalently entanglement wedge reconstruction). it provides a mathematically precise definition of subregion-subregion duality and gives an independent definition of entanglement wedges without using entropy. geometric properties of entanglement wedges, including those that play a crucial role in interpreting the bulk as a quantum error correcting code, can be understood from the duality as the geometrization of the additivity anomaly of certain algebras. using general boundary subalgebras rather than those associated with geometric subregions makes it possible to find duals for general bulk spacetime regions, including those not touching the boundary. applying subalgebra-subregion duality to a boundary state describing a single-sided black hole also provides a precise way to define mirror operators. | subalgebra-subregion duality: emergence of space and time in holography |
black-hole solutions to general relativity carry a thermodynamic entropy, discovered by bekenstein and hawking to be proportional to the area of the event horizon, at leading order in the semiclassical expansion. in a theory of quantum gravity, black holes must constitute ensembles of quantum microstates whose large number accounts for the entropy. we study this issue in the context of gravity with a negative cosmological constant. we exploit the most basic example of the holographic description of gravity (ads /cft ): type iib string theory on ads5×s5 , equivalent to maximally supersymmetric yang-mills theory in four dimensions. we thus resolve a long-standing question: does the four-dimensional n =4 su (n ) super-yang-mills theory on s3 at large n contain enough states to account for the entropy of rotating electrically charged supersymmetric black holes in 5d anti-de sitter space? our answer is positive. by reconsidering the large n limit of the superconformal index, using the so-called bethe-ansatz formulation, we find an exponentially large contribution which exactly reproduces the bekenstein-hawking entropy of the black holes. besides, the large n limit exhibits a complicated structure, with many competing exponential contributions and stokes lines, hinting at new physics. our method opens the way toward a quantitative study of quantum properties of black holes in anti-de sitter space. | black holes in 4d n =4 super-yang-mills field theory |
in the ads/cft correspondence, amplitudes associated to connected bulk manifolds with disconnected boundaries have presented a longstanding mystery. a possible interpretation is that they reflect the effects of averaging over an ensemble of boundary theories. but in examples in dimension d ≥ 3, an appropriate ensemble of boundary theories does not exist. here we sharpen the puzzle by identifying a class of "fixed energy" or "sub-threshold" observables that we claim do not show effects of ensemble averaging. these are amplitudes that involve states that are above the ground state by only a fixed amount in the large n limit, and in particular are far from being black hole states. to support our claim, we explore the example of d = 3, and show that connected solutions of einstein's equations with disconnected boundary never contribute to these observables. to demonstrate this requires some novel results about the renormalized volume of a hyperbolic three-manifold, which we prove using modern methods in hyperbolic geometry. why then do any observables show apparent ensemble averaging? we propose that this reflects the chaotic nature of black hole physics and the fact that the hilbert space describing a black hole does not have a large n limit. | no ensemble averaging below the black hole threshold |
in 1933-1934 born and infeld constructed the first non-linear generalization of maxwell's electrodynamics that turned out to be a remarkable theory in many respects. in 1935 heisenberg and euler computed a complete effective action describing non-linear corrections to maxwell's theory due to quantum electron-positron one-loop effects. since then, these and a variety of other models of non-linear electrodynamics proposed in the course of decades have been extensively studied and used in a wide range of areas of theoretical physics including string theory, gravity, cosmology and condensed matter (cmt). in these notes i will overview general properties of non-linear electrodynamics and particular models which are distinguished by their symmetries and physical properties, such as a recently discovered unique non-linear modification of maxwell's electrodynamics which is conformal and duality invariant. i will also sketch how non-linear electromagnetic effects may manifest themselves in physical phenomena (such as vacuum birefringence), in properties of gravitational objects (e.g. charged black holes) and in the evolution of the universe, and can be used, via gravity/cmt holography, for the description of properties of certain conducting and insulating materials.in 1933-1934 born and infeld constructed the first non-linear generalization of maxwell's electrodynamics that turned out to be a remarkable theory in many respects. in 1935 heisenberg and euler computed a complete effective action describing non-linear corrections to maxwell's theory due to quantum electron-positron one-loop effects. since then, these and a variety of other models of non-linear electrodynamics proposed in the course of decades have been extensively studied and used in a wide range of areas of theoretical physics including string theory, gravity, cosmology and condensed matter (cmt). in these notes the author will overview general properties of non-linear electrodynamics and particular models which are distinguished by their symmetries and physical properties, such as a recently discovered unique non-linear modification of maxwell's electrodynamics which is conformal and duality invariant. there will follow also also a sketch how non-linear electromagnetic effects may manifest themselves in physical phenomena (such as vacuum birefringence), in properties of gravitational objects (e.g. charged black holes) and in the evolution of the universe, and can be used, via gravity/cmt holography, for the description of properties of certain conducting and insulating materials. | introductory notes on non-linear electrodynamics and its applications |
we study analytic properties of the dispersion relations in classical hydrody- namics by treating them as puiseux series in complex momentum. the radii of convergence of the series are determined by the critical points of the associated complex spectral curves. for theories that admit a dual gravitational description through holography, the critical points correspond to level-crossings in the quasinormal spectrum of the dual black hole. we illustrate these methods in n = 4 supersymmetric yang-mills theory in 3+1 dimensions, in a holographic model with broken translation symmetry in 2+1 dimensions, and in con- formal field theory in 1+1 dimensions. we comment on the pole-skipping phenomenon in thermal correlation functions, and show that it is not specific to energy density correlations. | the complex life of hydrodynamic modes |
in this paper, we derive the consistent thermodynamics of the four-dimensional lorentzian reissner-nordström-nut (rn-nut), kerr-newman-nut (kn-nut), and rn-nut-ads spacetimes in the framework of the (ψ -n )-pair formalism, and then investigate their topological numbers by using the uniformly modified form of the generalized off-shell helmholtz free energy. we find that these solutions can be included into one of three categories of those well-known black hole solutions, which implies that these spacetimes should be viewed as generic black holes from the perspective of the topological thermodynamic defects. in addition, we demonstrate that although the existence of the nut charge parameter seems to have no impact on the topological number of the charged asymptotically locally flat spacetimes, it has a remarkable effect on the topological number of the charged asymptotically locally ads spacetime. | consistent thermodynamics and topological classes for the four-dimensional lorentzian charged taub-nut spacetimes |
we examine the circuit complexity of coherent states in a free scalar field theory, applying nielsen's geometric approach as in [1]. the complexity of the coherent states have the same uv divergences as the vacuum state complexity and so we consider the finite increase of the complexity of these states over the vacuum state. one observation is that generally, the optimal circuits introduce entanglement between the normal modes at intermediate stages even though our reference state and target states are not entangled in this basis. we also compare our results from nielsen's approach with those found using the fubini-study method of [2]. for general coherent states, we find that the complexities, as well as the optimal circuits, derived from these two approaches, are different. | circuit complexity for coherent states |
in this paper the deflection angle of light by a rotating teo wormhole spacetime is calculated in the weak limit approximation. we mainly focus on the weak deflection angle by revealing the gravitational lensing as a partially global topological effect. we apply the gauss-bonnet theorem (gbt) to the optical geometry osculating the teo-randers wormhole optical geometry to calculate the deflection angle. furthermore we find the same result using the standard geodesic method. we have found that the deflection angle can be written as a sum of two terms, namely the first term is proportional to the throat of the wormhole and depends entirely on the geometry, while the second term is proportional to the spin angular momentum parameter of the wormhole. a direct observation using lensing can shed light and potentially test the nature of rotating wormholes by comparing with the black holes systems. | gravitational lensing by rotating wormholes |
building upon recent progress in applying on-shell amplitude techniques to classical observables in general relativity, we propose a closed-form formula for the conservative hamiltonian of a spinning binary system at the 1st post-minkowskian (1pm) order. it is applicable for general compact spinning bodies with arbitrary spin multipole moments. the formula is linear in gravitational constant by definition, but exact to all orders in momentum and spin expansions. at each spin order, our formula implies that the spin-dependence and momentum dependence factorize almost completely. we expand our formula in momentum and compare the terms with 1pm parts of the post-newtonian computations in the literature. up to canonical transformations, our results agree perfectly with all previous ones. we also compare our formula for black hole to that derived from a spinning test-body near a kerr black hole via the effective one-body mapping, and find perfect agreement. | complete hamiltonian for spinning binary systems at first post-minkowskian order |
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 |
several recent papers have shown a close relationship between entanglement wedge reconstruction and the unitarity of black hole evaporation in ads/cft. the analysis of these papers however has a rather puzzling feature: all calculations are done using bulk dynamics which are essentially those hawking used to predict information loss, but applying ideas from entanglement wedge reconstruction seems to suggest a page curve which is consistent with information conservation. why should two different calculations in the same model give different answers for the page curve? in this note we present a new pair of models which clarify this situation. our first model gives a holographic illustration of unitary black hole evaporation, in which the analogue of the hawking radiation purifies itself as expected, and this purification is reproduced by the entanglement wedge analysis. moreover a smooth black hole interior persists until the last stages the evaporation process. our second model gives an alternative holographic interpretation of the situation where the bulk evolution leads to information loss: unlike in the models proposed so far, this bulk information loss is correctly reproduced by the entanglement wedge analysis. this serves as an illustration that quantum extremal surfaces are in some sense kinematic: the time-dependence of the entropy they compute depends on the choice of bulk dynamics. in both models no bulk quantum corrections need to be considered: classical extremal surfaces are enough to do the job. we argue that our first model is the one which gives the right analogy for what actually happens to evaporating black holes, but we also emphasize that any complete resolution of the information problem will require an understanding of non-perturbative bulk dynamics. | simple holographic models of black hole evaporation |
we consider the entanglement entropy in 2d conformal field theory in a class of excited states produced by the insertion of a heavy local operator. these include both high-energy eigenstates of the hamiltonian and time-dependent local quenches. we compute the universal contribution from the stress tensor to the single interval renyi entropies and entanglement entropy, and conjecture that this dominates the answer in theories with a large central charge and a sparse spectrum of low-dimension operators. the resulting entanglement entropies agree precisely with holographic calculations in three-dimensional gravity. high-energy eigenstates are dual to microstates of the btz black hole, so the corresponding holographic calculation is a geodesic length in the black hole geometry; agreement between these two answers demonstrates that these individual microstates of holographic cfts effectively thermalize at the level of the single-interval entanglement entropy. for local quenches, the dual geometry is a highly boosted black hole or conical defect. on the cft side, the rise in entanglement entropy after a quench is directly related to the monodromy of a virasoro conformal block. | holographic entanglement entropy from 2d cft: heavy states and local quenches |
we generalize the worldline eft formalism developed in [4-9] to calculate the non-conservative tidal effects on spinning black holes in a long wavelength approximation that is valid to all orders in the magnitude of the spin. we present results for the rate of change of mass and angular momentum in a background field and find agreement with previous calculations obtained by different techniques. we also present new results for both the non-conservative equations of motion and power loss/gain for a binary inspiral, which start at 5pn and 2.5pn order respectively and manifest the penrose process. | non-conservative effects on spinning black holes from world-line effective field theory |
starting from the leading soft term of the 5-point amplitude, involving a graviton and two kerr black holes, that factorises into the product of the elastic amplitude without the graviton and the leading soft factor, we compute the infrared divergent contribution to the imaginary part of the two-loop eikonal. then, using analyticity and crossing symmetry, we determine the radiative contribution to the real part of the two-loop eikonal and from it the radiative part of the deflection angle for spins aligned to the orbital angular momentum, the loss of angular momentum and the zero frequency limit of the energy spectrum for any spin and for any spin orientation. for spin one we find perfect agreement with recent results obtained with the supersymmetric worldline formalism. | radiation reaction for spinning black-hole scattering |
we present a closed formula for all bern-carrasco-johansson (bcj) numerators describing d -dimensional tree-level scattering amplitudes in a heavy-mass effective field theory with two massive particles and an arbitrary number of gluons. the corresponding gravitational amplitudes obtained via the double copy directly enter the computation of black-hole scattering and gravitational-wave emission. our construction is based on finding a kinematic algebra for the numerators, which we relate to a quasishuffle hopf algebra. the bcj numerators thus obtained have a compact form and intriguing features: gauge invariance is manifest, locality is respected for massless exchange, and they contain poles corresponding to massive exchange. counting the number of terms in a bcj numerator for n -2 gluons gives the fubini numbers fn -3, reflecting the underlying quasishuffle hopf algebra structure. finally, by considering an appropriate factorization limit, the massive particles decouple, and we thus obtain a kinematic algebra and all tree-level bcj numerators for d -dimensional pure yang-mills theory. | kinematic hopf algebra for bern-carrasco-johansson numerators in heavy-mass effective field theory and yang-mills theory |
we study reflected entropy as a mixed state correlation measure in black hole evaporation. as a measure for bipartite mixed states, reflected entropy can be computed between black hole and radiation, radiation and radiation, and even black hole and black hole. we compute reflected entropy curves in three different models: 3-side wormhole model, end-of-the-world (eow) brane model in three dimensions and two-dimensional eternal black hole plus cft model. for 3-side wormhole model, we find that reflected entropy is dual to island cross section. the reflected entropy between radiation and black hole increases at early time and then decreases to zero, similar to page curve, but with a later transition time. the reflected entropy between radiation and radiation first increases and then saturates. for the eow brane model, similar behaviors of reflected entropy are found.we propose a quantum extremal surface for reflected entropy, which we call quantum extremal cross section. in the eternal black hole plus cft model, we find a generalized formula for reflected entropy with island cross section as its area term by considering the right half as the canonical purification of the left. interestingly, the reflected entropy curve between the left black hole and the left radiation is nothing but the page curve. we also find that reflected entropy between the left black hole and the right black hole decreases and goes to zero at late time. the reflected entropy between radiation and radiation increases at early time and saturates at late time. | reflected entropy for an evaporating black hole |
a search for resonances and quantum black holes is performed using the dijet mass spectra measured in proton-proton collisions at √{s }=8 tev with the cms detector at the lhc. the data set corresponds to an integrated luminosity of 19.7 fb-1 . in a search for narrow resonances that couple to quark-quark, quark-gluon, or gluon-gluon pairs, model-independent upper limits, at 95% confidence level, are obtained on the production cross section of resonances, with masses above 1.2 tev. when interpreted in the context of specific models the limits exclude string resonances with masses below 5.0 tev; excited quarks below 3.5 tev; scalar diquarks below 4.7 tev; w' bosons below 1.9 tev or between 2.0 and 2.2 tev; z' bosons below 1.7 tev; and randall-sundrum gravitons below 1.6 tev. a separate search is conducted for narrow resonances that decay to final states including b quarks. the first exclusion limit is set for excited b quarks, with a lower mass limit between 1.2 and 1.6 tev depending on their decay properties. searches are also carried out for wide resonances, assuming for the first time width-to-mass ratios up to 30%, and for quantum black holes with a range of model parameters. the wide resonance search excludes axigluons and colorons with mass below 3.6 tev, and color-octet scalars with mass below 2.5 tev. lower bounds between 5.0 and 6.3 tev are set on the masses of quantum black holes. | search for resonances and quantum black holes using dijet mass spectra in proton-proton collisions at √{s }=8 tev |
our experiment prepares two types of nontrivial quantum states on a trapped ion quantum computer: the thermofield double state of the transverse-field ising model at arbitrary temperature and the quantum critical state of the zero-temperature model. we use techniques motivated by the quantum approximate optimization algorithm, and we implement a hybrid quantum-classical optimization loop to prepare the quantum critical state. our results pave the way for exploring strongly correlated models at finite temperature and teleportation protocols inspired by black hole physics. | generation of thermofield double states and critical ground states with a quantum computer |
the continued operation of the advanced ligo and advanced virgo gravitational-wave detectors is enabling the first detailed measurements of the mass, spin, and redshift distributions of the merging binary black hole population. our present knowledge of these distributions, however, is based largely on strongly parameteric models; such models typically assume the distributions of binary parameters to be superpositions of power laws, peaks, dips, and breaks, and then measure the parameters governing these "building block" features. although this approach has yielded great progress in initial characterization of the compact binary population, the strong assumptions entailed leave it often unclear which physical conclusions are driven by observation and which by the specific choice of model. in this paper, we instead model the merger rate of binary black holes as an unknown \textit{autoregressive process} over the space of binary parameters, allowing us to measure the distributions of binary black hole masses, redshifts, component spins, and effective spins with near-complete agnosticism. we find the primary mass spectrum of binary black holes to be doubly-peaked, with a fairly flat continuum that steepens at high masses. we identify signs of unexpected structure in the redshift distribution of binary black holes: a uniform-in-comoving volume merger rate at low redshift followed by a rise in the merger rate beyond redshift $z\approx 0.5$. finally, we find that the distribution of black hole spin magnitudes is unimodal and concentrated at small but non-zero values, and that spin orientations span a wide range of spin-orbit misalignment angles but are also moderately unlikely to be truly isotropic. | a parameter-free tour of the binary black hole population |
in many-body chaotic systems, the size of an operator generically grows in heisenberg evolution, which can be measured by certain out-of-time-ordered four-point functions. however, these only provide a coarse probe of the full underlying operator growth structure. in this article we develop a methodology to derive the full growth structure of fermionic systems, that also naturally introduces the effect of finite temperature. we then apply our methodology to the syk model, which features all-to-all q-body interactions. we derive the full operator growth structure in the large q limit at all temperatures. we see that its temperature dependence has a remarkably simple form consistent with the slowing down of scrambling as temperature is decreased. furthermore, our finite-temperature scrambling results can be modeled by a modified epidemic model, where the thermal state serves as a vaccinated population, thereby slowing the overall rate of infection. | quantum epidemiology: operator growth, thermal effects, and syk |
we study solutions in the plebański-demiański family which describe an accelerating, rotating, and dyonically charged black hole in ads4. these are solutions of d =4 einstein-maxwell theory with a negative cosmological constant and hence minimal d =4 gauged supergravity. it is well known that when the acceleration is nonvanishing the d =4 black hole metrics have conical singularities. by uplifting the solutions to d =11 supergravity using a regular sasaki-einstein seven-manifold, s e7, we show how the free parameters can be chosen to eliminate the conical singularities. topologically, the d =11 solutions incorporate an s e7 fibration over a two-dimensional weighted projective space, w c p[n−,n+] 1 , also known as a spindle, which is labeled by two integers that determine the conical singularities of the d =4 metrics. we also discuss the supersymmetric and extremal limit and show that the near horizon limit gives rise to a new family of regular supersymmetric ads2×y9 solutions of d =11 supergravity, which generalize a known family by the addition of a rotation parameter. we calculate the entropy of these black holes and argue that it should be possible to derive this from certain n =2 , d =3 quiver gauge theories compactified on a spinning spindle with the appropriate magnetic flux. | accelerating black holes and spinning spindles |
motivated by recent developments in black hole thermodynamics, we investigate van der waals phase transitions of charged black holes in massive gravity. we find that massive gravity theories can exhibit strikingly different thermodynamic behavior compared to that of einstein gravity, and that the mass of the graviton can generate a range of new phase transitions for topological black holes that are otherwise forbidden. | van der waals like behavior of topological ads black holes in massive gravity |
we conjecture that the quantum complexity of a holographic state is dual to the action of a certain spacetime region that we call a wheeler-dewitt patch. we illustrate and test the conjecture in the context of neutral, charged, and rotating black holes in ads, as well as black holes perturbed with static shells and with shock waves. this conjecture evolved from a previous conjecture that complexity is dual to spatial volume, but appears to be a major improvement over the original. in light of our results, we discuss the hypothesis that black holes are the fastest computers in nature. | complexity equals action |
we combine amortized neural posterior estimation with importance sampling for fast and accurate gravitational-wave inference. we first generate a rapid proposal for the bayesian posterior using neural networks, and then attach importance weights based on the underlying likelihood and prior. this provides (1) a corrected posterior free from network inaccuracies, (2) a performance diagnostic (the sample efficiency) for assessing the proposal and identifying failure cases, and (3) an unbiased estimate of the bayesian evidence. by establishing this independent verification and correction mechanism we address some of the most frequent criticisms against deep learning for scientific inference. we carry out a large study analyzing 42 binary black hole mergers observed by ligo and virgo with the seobnrv4phm and imrphenomxphm waveform models. this shows a median sample efficiency of ≈10 % (2 orders of magnitude better than standard samplers) as well as a tenfold reduction in the statistical uncertainty in the log evidence. given these advantages, we expect a significant impact on gravitational-wave inference, and for this approach to serve as a paradigm for harnessing deep learning methods in scientific applications. | neural importance sampling for rapid and reliable gravitational-wave inference |
motivated by m-theory/superstring inspired models, we investigate certain behaviors of the deflection angle and the shadow geometrical shapes of higher dimensional quintessential black holes associated with two values of the dark energy (de) state parameter, being $\omega =-\frac{1}{3}$ and $\omega =-\frac{2}{3}$ . concretely, we derive the geodesic equation of photons on such backgrounds. thanks to the gauss-bonnet theorem corresponding to the optical metric, we compute the leading terms of the deflection angle in the so-called weak-limit approximation. after that, we inspect the effect of de and the space-time dimension d on the calculated optical quantities. introducing de via the field intensity c and the state parameter ω, we find that the shadow size and the deflection angle increase by increasing values of the field intensity c. however, we observe that the high dimensions decrease such quantities for ω-models exhibiting similar behaviors. then, we consider the effect of the black hole charge, on these optical quantities, by discussing the associated behaviors. the present investigation recovers certain known results appearing in ordinary four dimensional models. | deflection angle and shadow behaviors of quintessential black holes in arbitrary dimensions |
the out-of-time-order correlator (otoc) is considered as a measure of quantum chaos. we formulate how to calculate the otoc for quantum mechanics with a general hamiltonian. we demonstrate explicit calculations of otocs for a harmonic oscillator, a particle in a one-dimensional box, a circle billiard and stadium billiards. for the first two cases, otocs are periodic in time because of their commensurable energy spectra. for the circle and stadium billiards, they are not recursive but saturate to constant values which are linear in temperature. although the stadium billiard is a typical example of the classical chaos, an expected exponential growth of the otoc is not found. we also discuss the classical limit of the otoc. analysis of a time evolution of a wavepacket in a box shows that the otoc can deviate from its classical value at a time much earlier than the ehrenfest time, which could be the reason of the difficulty for the numerical analyses to exhibit the exponential growth. | out-of-time-order correlators in quantum mechanics |
we show that there is a classical metric satisfying the einstein equations outside a finite spacetime region where matter collapses into a black hole and then emerges from a white hole. we compute this metric explicitly. we show how quantum theory determines the (long) time for the process to happen. a black hole can thus quantum tunnel into a white hole. for this to happen, quantum gravity should affect the metric also in a small region outside the horizon; we show that, contrary to what is commonly assumed, this is not forbidden by causality or by the semiclassical approximation, because quantum effects can pile up over a long time. this scenario alters radically the discussion on the black hole information puzzle. | quantum-gravity effects outside the horizon spark black to white hole tunneling |
we study the small speed of light expansion of general relativity, utilizing the modern perspective on non-lorentzian geometry. this is an expansion around the ultra-local carroll limit, in which light cones close up. to this end, we first rewrite the einstein--hilbert action in pre-ultra-local variables, which is closely related to the 3+1 decomposition of general relativity. at leading order in the expansion, these pre-ultra-local variables yield carroll geometry and the resulting action describes the electric carroll limit of general relativity. we also obtain the next-to-leading order action in terms of carroll geometry and next-to-leading order geometric fields. the leading order theory yields constraint and evolution equations, and we can solve the evolution analytically. we furthermore construct a carroll version of bowen--york initial data, which has associated conserved boundary linear and angular momentum charges. the notion of mass is not present at leading order and only enters at next-to-leading order. this is illustrated by considering a particular truncation of the next-to-leading order action, corresponding to the magnetic carroll limit, where we find a solution that describes the carroll limit of a schwarzschild black hole. finally, we comment on how a cosmological constant can be incorporated in our analysis. | carroll expansion of general relativity |
quantum complexity, suitably defined, has been suggested as an important probe of late-time dynamics of black holes, particularly in the context of ads/cft. a notion of quantum complexity can be effectively captured by quantifying the spread of an operator in krylov space as a consequence of time evolution. complexity is expected to behave differently in chaotic many-body systems, as compared to integrable ones. in this paper we investigate krylov complexity for the case of interacting integrable models at finite size and find that complexity saturation is suppressed as compared to chaotic systems. we associate this behavior with a novel localization phenomenon on the krylov chain by mapping the theory of complexity growth and spread to an anderson localization hopping model with off-diagonal disorder, and find that localization is enhanced in the integrable case due to a stronger disorder in the hopping amplitudes, inducing an effective suppression of krylov complexity. we demonstrate this behavior for an interacting integrable model, the xxz spin chain, and show that the same behavior results from a phenomenological model that we define: this model captures the essential features of our analysis and is able to reproduce the behaviors we observe for chaotic and integrable systems via an adjustable disorder parameter. | krylov localization and suppression of complexity |
we study the bending of light in the space-time of black holes in the four-dimensional einstein-gauss-bonnet theory of gravity, recently proposed by glavan and lin in phys. rev. lett., 124 (2020) 081301. using the rindler-ishak method, the effect of gauss-bonnet coupling on the bending angle is studied. we show that a positive gauss-bonnet coupling gives a negative contribution to the schwarzschild-de sitter deflection angle, as one would expect. | bending of light in novel 4d gauss-bonnet-de sitter black holes by the rindler-ishak method |
this paper revisits the question of reconstructing bulk gauge fields as boundary operators in ads/cft. in the presence of the wormhole dual to the thermofield double state of two cfts, the existence of bulk gauge fields is in some tension with the microscopic tensor factorization of the hilbert space. i explain how this tension can be resolved by splitting the gauge field into charged constituents, and i argue that this leads to a new argument for the "principle of completeness", which states that the charge lattice of a gauge theory coupled to gravity must be fully populated. i also claim that it leads to a new motivation for (and a clarification of) the "weak gravity conjecture", which i interpret as a strengthening of this principle. this setup gives a simple example of a situation where describing low-energy bulk physics in cft language requires knowledge of high-energy bulk physics. this contradicts to some extent the notion of "effective conformal field theory", but in fact is an expected feature of the resolution of the black hole information problem. an analogous factorization issue exists also for the gravitational field, and i comment on several of its implications for reconstructing black hole interiors and the emergence of spacetime more generally. | wormholes, emergent gauge fields, and the weak gravity conjecture |
naively, resolving the black hole information paradox requires microscopic details about quantum gravity. recent work suggests that, instead, a unitary page curve can be recovered by adding disorder-averaged replica instantons to the path integral, though their origin is unclear. in this letter, we show how replica instantons and disorder averaging emerge naturally in an effective theory built from typical microscopic states. we relate replica instantons to a moment expansion of simple operators, and find a microcanonical description in terms of wormholes and euclidean black holes. | eigenstate thermalization and disorder averaging in gravity |
recently a complexity-action (ca) duality conjecture has been proposed, which relates the quantum complexity of a holographic boundary state to the action of a wheeler-dewitt (wdw) patch in the anti-de sitter (ads) bulk. in this paper we further investigate the duality conjecture for stationary ads black holes and derive some exact results for the growth rate of action within the wheeler-dewitt (wdw) patch at late time approximation, which is supposed to be dual to the growth rate of quantum complexity of holographic state. based on the results from the general d-dimensional reissner-nordström (rn)-ads black hole, rotating/charged bañados-teitelboim-zanelli (btz) black hole, kerr-ads black hole and charged gauss-bonnet-ads black hole, we present a universal formula for the action growth expressed in terms of some thermodynamical quantities associated with the outer and inner horizons of the ads black holes. and we leave the conjecture unchanged that the stationary ads black hole in einstein gravity is the fastest computer in nature. | action growth for ads black holes |
we investigate the behavior of the weak gravity conjecture (wgc) under toroidal compactification and rg flows, finding evidence that wgc bounds for single photons become weaker in the infrared. by contrast, we find that a photon satisfying the wgc will not necessarily satisfy it after toroidal compactification when black holes charged under the kaluza-klein photons are considered. doing so either requires an infinite number of states of different charges to satisfy the wgc in the original theory or a restriction on allowed compactification radii. these subtleties suggest that if the weak gravity conjecture is true, we must seek a stronger form of the conjecture that is robust under compactification. we propose a "lattice weak gravity conjecture" that meets this requirement: a superextremal particle should exist for every charge in the charge lattice. the perturbative heterotic string satisfies this conjecture. we also use compactification to explore the extent to which the wgc applies to axions. we argue that gravitational instanton solutions in theories of axions coupled to dilaton-like fields are analogous to extremal black holes, motivating a wgc for axions. this is further supported by a match between the instanton action and that of wrapped black branes in a higher-dimensional uv completion. | sharpening the weak gravity conjecture with dimensional reduction |
the three-point amplitude is the key building block in the on-shell approach to scattering amplitudes. we show that the classical objects computed by massive three-point amplitudes in gauge theory and gravity are newman-penrose scalars in a split-signature spacetime, where three-point amplitudes can be defined for real kinematics. in fact, the quantum state set up by the particle is a coherent state fully determined by the three-point amplitude due to an eikonal-type exponentiation. having identified this simplest classical solution from the perspective of scattering amplitudes, we explore the double copy of the newman-penrose scalars induced by the traditional double copy of amplitudes, and find that it coincides with the weyl version of the classical double copy. we also exploit the kerr-schild version of the classical double copy to determine the exact spacetime metric in the gravitational case. finally, we discuss the direct implication of these results for lorentzian signature via analytic continuation. | classical solutions and their double copy in split signature |
black holes provide a window into the microscopic structure of spacetime in quantum gravity. recently the quantum information contained in hawking radiation has been calculated, verifying a key aspect of the consistency of black hole evaporation with quantum mechanical unitarity. this calculation relied crucially on recent progress in understanding the emergence of bulk spacetime from a boundary holographic description. spacetime wormholes have played an important role in understanding the underpinnings of this result, and the precision study of such wormholes, in this and other contexts, has been enabled by the development of low-dimensional models of holography. in this white paper we review these developments and describe some of the deep open questions in this subject. these include the nature of the black hole interior, potential applications to quantum cosmology, the gravitational explanation of the fine structure of black holes, and the development of further connections to quantum information and laboratory quantum simulation. | snowmass white paper: quantum aspects of black holes and the emergence of spacetime |
as a probe of circuit complexity in holographic field theories, we study sub-system analogues based on the entanglement wedge of the bulk quantities appearing in the "complexity = volume" and "complexity = action" conjectures. we calculate these quantities for one exterior region of an eternal static neutral or charged black hole in general dimensions, dual to a thermal state on one boundary with or without chemical potential respectively, as well as for a shock wave geometry. we then define several analogues of circuit complexity for mixed states, and use tensor networks to gain intuition about them. in the action approach, we find two possible cases depending on an ambiguity in the definition of the action associated with a counterterm. in one case, there is a promising qualitative match between the holographic action and what we call the purification complexity, the minimum number of gates required to prepare an arbitrary purification of the given mixed state. in the other case, the match is to what we call the basis complexity, the minimum number of gates required to prepare the given mixed state starting from a minimal complexity state with the same eigenvalue spectrum. one way to fix this ambiguity is to choose an action definition such that uv divergent part is positive, in which case the best match to the action result is the basis complexity. in contrast, the holographic volume does not appear to match any of our definitions of mixed-state complexity. | subsystem complexity and holography |
moving mirrors have been known as tractable setups modeling hawking radiation from black holes. in this paper, motivated by recent developments regarding the black hole information problem, we present extensive studies of moving mirrors in conformal field theories by employing both field theoretic as well as holographic methods. reviewing first the usual field theoretic formulation of moving mirrors, we construct their gravity dual by resorting to the ads/bcft construction. based on our holographic formulation, we then calculate the time evolution of entanglement entropy in various moving mirror models. in doing so, we mainly focus on three different setups: escaping mirror, which models constant hawking radiation emanating from an eternal black hole; kink mirror, which models an evaporating black hole formed from collapse; and the double escaping mirror, which models two constantly radiating eternal black holes. in particular, by computing the holographic entanglement entropy, we show that the kink mirror gives rise to an ideal page curve. we also find that an interesting phase transition arises in the case of the double escaping mirror. furthermore, we argue and provide evidence for an interpretation of moving mirrors in terms of two dimensional liouville gravity. we also discuss the connection between quantum energy conditions and the time evolution of holographic entanglement entropy in moving mirror models. | holographic moving mirrors |
reproducing the integer count of black hole micro-states from the gravitational path integral is an important problem in quantum gravity. in this paper, we show that, by using supersymmetric localization, the gravitational path integral for $\frac{1}8$-bps black holes in $\mathcal{n}=8$ supergravity reproduces the index obtained in the string theory construction of such black holes, including all non-perturbatively suppressed geometries. a more refined argument then shows that, not only the black hole index, but also the total number of black hole microstates within an energy window above extremality that is polynomially suppressed in the charges, also matches this string theory index. to achieve such a match we compute the one-loop determinant arising in the localization calculation for all $\mathcal{n}=2$ supergravity supermultiplets in the $\mathcal{n}=8$ gravity supermultiplet. furthermore, we carefully account for the contribution of boundary zero-modes, that can be seen as arising from the zero-temperature limit of the $\mathcal{n}=4$ super-schwarzian, and show that performing the exact path integral over such modes provides a critical contribution needed for the match to be achieved. a discussion about the importance of such zero-modes in the wider context of all extremal black holes is presented in a companion paper. | black hole microstate counting from the gravitational path integral |
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