abstract stringlengths 3 192k | title stringlengths 4 857 |
|---|---|
following the selection of the gravitational universe by esa, and the successful flight of lisa pathfinder, the lisa consortium now proposes a 4 year mission in response to esa's call for missions for l3. the observatory will be based on three arms with six active laser links, between three identical spacecraft in a triangular formation separated by 2.5 million km. lisa is an all-sky monitor and will offer a wide view of a dynamic cosmos using gravitational waves as new and unique messengers to unveil the gravitational universe. it provides the closest ever view of the infant universe at tev energy scales, has known sources in the form of verification binaries in the milky way, and can probe the entire universe, from its smallest scales near the horizons of black holes, all the way to cosmological scales. the lisa mission will scan the entire sky as it follows behind the earth in its orbit, obtaining both polarisations of the gravitational waves simultaneously, and will measure source parameters with astrophysically relevant sensitivity in a band from below $10^{-4}\,$hz to above $10^{-1}\,$hz. | laser interferometer space antenna |
we conjecture a sharp bound on the rate of growth of chaos in thermal quantum systems with a large number of degrees of freedom. chaos can be diagnosed using an out-of-time-order correlation function closely related to the commutator of operators separated in time. we conjecture that the influence of chaos on this correlator can develop no faster than exponentially, with lyapunov exponent λ l≤ 2π kbt/ℏ. we give a precise mathematical argument, based on plausible physical assumptions, establishing this conjecture. | a bound on chaos |
when absorbing boundary conditions are used to evaporate a black hole in ads/cft, we show that there is a phase transition in the location of the quantum ryu-takayanagi surface, at precisely the page time. the new rt surface lies slightly inside the event horizon, at an infalling time approximately the scrambling time β/2πlogsbh into the past. we can immediately derive the page curve, using the ryu-takayanagi formula, and the hayden-preskill decoding criterion, using entanglement wedge reconstruction. because part of the interior is now encoded in the early hawking radiation, the decreasing entanglement entropy of the black hole is exactly consistent with the semiclassical bulk entanglement of the late-time hawking modes, despite the absence of a firewall.by studying the entanglement wedge of highly mixed states, we can understand the state dependence of the interior reconstructions. a crucial role is played by the existence of tiny, non-perturbative errors in entanglement wedge reconstruction. directly after the page time, interior operators can only be reconstructed from the hawking radiation if the initial state of the black hole is known. as the black hole continues to evaporate, reconstructions become possible that simultaneously work for a large class of initial states. using similar techniques, we generalise hayden-preskill to show how the amount of hawking radiation required to reconstruct a large diary, thrown into the black hole, depends on both the energy and the entropy of the diary. finally we argue that, before the evaporation begins, a single, state-independent interior reconstruction exists for any code space of microstates with entropy strictly less than the bekenstein-hawking entropy, and show that this is sufficient state dependence to avoid the ampss typical-state firewall paradox. | entanglement wedge reconstruction and the information paradox |
in this review, recent progress on the black hole information problem that involves a new understanding of how to calculate the entropy of hawking radiation is described. the review shows how the method for computing gravitational fine-grained entropy, developed over the past 15 years, can be extended to capture the entropy of hawking radiation. this technique reveals large corrections needed for the entropy to be consistent with unitary black hole evaporation. | the entropy of hawking radiation |
the information paradox can be realized in anti-de sitter spacetime joined to a minkowski region. in this setting, we show that the large discrepancy between the von neumann entropy as calculated by hawking and the requirements of unitarity is fixed by including new saddles in the gravitational path integral. these saddles arise in the replica method as complexified wormholes connecting different copies of the black hole. as the replica number n → 1, the presence of these wormholes leads to the island rule for the computation of the fine-grained gravitational entropy. we discuss these replica wormholes explicitly in two-dimensional jackiw-teitelboim gravity coupled to matter. | replica wormholes and the entropy of hawking radiation |
bulk quantum fields are often said to contribute to the generalized entropy a/4 gn +sbulk only at o(1). nonetheless, in the context of evaporating black holes, o(1/gn ) gradients in sbulk can arise due to large boosts, introducing a quantum extremal surface far from any classical extremal surface. we examine the effect of such bulk quantum effects on quantum extremal surfaces (qess) and the resulting entanglement wedge in a simple two-boundary 2d bulk system defined by jackiw-teitelboim gravity coupled to a 1+1 cft. turning on a coupling between one boundary and a further external auxiliary system which functions as a heat sink allows a two-sided otherwise-eternal black hole to evaporate on one side. we find the generalized entropy of the qes to behave as expected from general considerations of unitarity, and in particular that ingoing information disappears from the entanglement wedge after a scambling time β/2 π logδs +o (1 ) in accord with expectations for holographic implementations of the hayden-preskill protocol. we also find an interesting qes phase transition at what one might call the page time for our process. | the entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole |
we consider a gravity theory coupled to matter, where the matter has a higher-dimensional holographic dual. in such a theory, finding quantum extremal surfaces becomes equivalent to finding the rt/hrt surfaces in the higher-dimensional theory. using this we compute the entropy of hawking radiation and argue that it follows the page curve, as suggested by recent computations of the entropy and entanglement wedges for old black holes. the higher-dimensional geometry connects the radiation to the black hole interior in the spirit of er=epr. the black hole interior then becomes part of the entanglement wedge of the radiation. inspired by this, we propose a new rule for computing the entropy of quantum systems entangled with gravitational systems which involves searching for "islands" in determining the entanglement wedge. | the page curve of hawking radiation from semiclassical geometry |
horizon-scale images of black holes (bhs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. we consider a wide range of well-motivated deviations from classical general relativity (gr) bh solutions, and constrain them using the event horizon telescope (eht) observations of sagittarius a $^*$ (sgr a $^*$ ), connecting the size of the bright ring of emission to that of the underlying bh shadow and exploiting high-precision measurements of sgr a $^*$ 's mass-to-distance ratio. the scenarios we consider, and whose fundamental parameters we constrain, include various regular bhs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and bh mimickers including well-motivated wormhole and naked singularity space-times. we demonstrate that the eht image of sgr a $^*$ places particularly stringent constraints on models predicting a shadow size larger than that of a schwarzschild bh of a given mass, with the resulting limits in some cases surpassing cosmological ones. our results are among the first tests of fundamental physics from the shadow of sgr a $^*$ and, while the latter appears to be in excellent agreement with the predictions of gr, we have shown that a number of well-motivated alternative scenarios, including bh mimickers, are far from being ruled out at present. | horizon-scale tests of gravity theories and fundamental physics from the event horizon telescope image of sagittarius a (*) |
recent work has shown how to obtain the page curve of an evaporating black hole from holographic computations of entanglement entropy. we show how these computations can be justified using the replica trick, from geometries with a spacetime wormhole connecting the different replicas. in a simple model, we study the page transition in detail by summing replica geometries with different topologies. we compute related quantities in less detail in more complicated models, including jt gravity coupled to conformal matter and the syk model. separately, we give a direct gravitational argument for entanglement wedge reconstruction using an explicit formula known as the petz map; again, a spacetime wormhole plays an important role. we discuss an interpretation of the wormhole geometries as part of some ensemble average implicit in the gravity description. | replica wormholes and the black hole interior |
this is a redacted transcript of a course given by the author at harvard in spring semester 2016. it contains a pedagogical overview of recent developments connecting the subjects of soft theorems, the memory effect and asymptotic symmetries in four-dimensional qed, nonabelian gauge theory and gravity with applications to black holes. the lectures may be viewed online at https://goo.gl/3djdor. please send typos or corrections to strominger@physics.harvard.edu. | lectures on the infrared structure of gravity and gauge theory |
in this article, we provide a review of the current state of the research of the black hole shadow, focusing on analytical (as opposed to numerical and observational) studies. we start with particular attention to the definition of the shadow and its relation to the often used concepts of escape cone, critical impact parameter and particle cross-section. for methodological purposes, we present the derivation of the angular size of the shadow for an arbitrary spherically symmetric and static space-time, which allows one to calculate the shadow for an observer at arbitrary distance from the center. then we discuss the calculation of the shadow of a kerr black hole, for an observer anywhere outside of the black hole. for observers at large distances we present and compare two methods used in the literature. special attention is given to calculating the shadow in space-times which are not asymptotically flat. shadows of wormholes and other black-hole impostors are reviewed. then we discuss the calculation of the black hole shadow in an expanding universe as seen by a comoving observer. the influence of a plasma on the shadow of a black hole is also considered. | calculating black hole shadows: review of analytical studies |
we argue that the late time behavior of horizon fluctuations in large anti-de sitter (ads) black holes is governed by the random matrix dynamics characteristic of quantum chaotic systems. our main tool is the sachdev-ye-kitaev (syk) model, which we use as a simple model of a black hole. we use an analytically continued partition function | z( β + it)|2 as well as correlation functions as diagnostics. using numerical techniques we establish random matrix behavior at late times. we determine the early time behavior exactly in a double scaling limit, giving us a plausible estimate for the crossover time to random matrix behavior. we use these ideas to formulate a conjecture about general large ads black holes, like those dual to 4d super-yang-mills theory, giving a provisional estimate of the crossover time. we make some preliminary comments about challenges to understanding the late time dynamics from a bulk point of view. | black holes and random matrices |
gravitational waves enable tests of general relativity in the highly dynamical and strong-field regime. using events detected by ligo-virgo up to 1 october 2019, we evaluate the consistency of the data with predictions from the theory. we first establish that residuals from the best-fit waveform are consistent with detector noise, and that the low- and high-frequency parts of the signals are in agreement. we then consider parametrized modifications to the waveform by varying post-newtonian and phenomenological coefficients, improving past constraints by factors of ∼2 ; we also find consistency with kerr black holes when we specifically target signatures of the spin-induced quadrupole moment. looking for gravitational-wave dispersion, we tighten constraints on lorentz-violating coefficients by a factor of ∼2.6 and bound the mass of the graviton to mg≤1.76 ×10-23 ev /c2 with 90% credibility. we also analyze the properties of the merger remnants by measuring ringdown frequencies and damping times, constraining fractional deviations away from the kerr frequency to δ f^220=0.0 3-0.35+0.38 for the fundamental quadrupolar mode, and δ f^221=0.0 4-0.32+0.27 for the first overtone; additionally, we find no evidence for postmerger echoes. finally, we determine that our data are consistent with tensorial polarizations through a template-independent method. when possible, we assess the validity of general relativity based on collections of events analyzed jointly. we find no evidence for new physics beyond general relativity, for black hole mimickers, or for any unaccounted systematics. | tests of general relativity with binary black holes from the second ligo-virgo gravitational-wave transient catalog |
recent work has shown how to obtain the page curve of an evaporating black hole from holographic computations of entanglement entropy. we show how these computations can be justified using the replica trick, from geometries with a spacetime wormhole connecting the different replicas. in a simple model, we study the page transition in detail by summing replica geometries with different topologies. we compute related quantities in less detail in more complicated models, including jt gravity coupled to conformal matter and the syk model. separately, we give a direct gravitational argument for entanglement wedge reconstruction using an explicit formula known as the petz map; again, a spacetime wormhole plays an important role. we discuss an interpretation of the wormhole geometries as part of some ensemble average implicit in the gravity description. | replica wormholes and the black hole interior |
the ligo detection of gw150914 provides an unprecedented opportunity to study the two-body motion of a compact-object binary in the large-velocity, highly nonlinear regime, and to witness the final merger of the binary and the excitation of uniquely relativistic modes of the gravitational field. we carry out several investigations to determine whether gw150914 is consistent with a binary black-hole merger in general relativity. we find that the final remnant's mass and spin, as determined from the low-frequency (inspiral) and high-frequency (postinspiral) phases of the signal, are mutually consistent with the binary black-hole solution in general relativity. furthermore, the data following the peak of gw150914 are consistent with the least-damped quasinormal mode inferred from the mass and spin of the remnant black hole. by using waveform models that allow for parametrized general-relativity violations during the inspiral and merger phases, we perform quantitative tests on the gravitational-wave phase in the dynamical regime and we determine the first empirical bounds on several high-order post-newtonian coefficients. we constrain the graviton compton wavelength, assuming that gravitons are dispersed in vacuum in the same way as particles with mass, obtaining a 90%-confidence lower bound of 1013 km . in conclusion, within our statistical uncertainties, we find no evidence for violations of general relativity in the genuinely strong-field regime of gravity. | tests of general relativity with gw150914 |
we study a two dimensional dilaton gravity system, recently examined by almheiri and polchinski, which describes near extremal black holes, or more generally, nearly $ads_2$ spacetimes. the asymptotic symmetries of $ads_2$ are all the time reparametrizations of the boundary. these symmetries are spontaneously broken by the $ads_2$ geometry and they are explicitly broken by the small deformation away from $ads_2$. this pattern of spontaneous plus explicit symmetry breaking governs the gravitational backreaction of the system. it determines several gravitational properties such as the linear in temperature dependence of the near extremal entropy as well as the gravitational corrections to correlation functions. these corrections include the ones determining the growth of out of time order correlators that is indicative of chaos. these gravitational aspects can be described in terms of a schwarzian derivative effective action for a reparametrization. | conformal symmetry and its breaking in two dimensional nearly anti-de-sitter space |
it has recently been shown that bondi-van der burg-metzner-sachs supertranslation symmetries imply an infinite number of conservation laws for all gravitational theories in asymptotically minkowskian spacetimes. these laws require black holes to carry a large amount of soft (i.e., zero-energy) supertranslation hair. the presence of a maxwell field similarly implies soft electric hair. this letter gives an explicit description of soft hair in terms of soft gravitons or photons on the black hole horizon, and shows that complete information about their quantum state is stored on a holographic plate at the future boundary of the horizon. charge conservation is used to give an infinite number of exact relations between the evaporation products of black holes which have different soft hair but are otherwise identical. it is further argued that soft hair which is spatially localized to much less than a planck length cannot be excited in a physically realizable process, giving an effective number of soft degrees of freedom proportional to the horizon area in planck units. | soft hair on black holes |
we describe a systematic framework for finding the conservative potential of compact binary systems with spin based on scattering amplitudes of particles of arbitrary spin and effective field theory. an arbitrary-spin formalism is generally required in the classical limit. by matching the tree and one-loop amplitudes of four spinning particles with those of a suitably chosen effective field theory, we obtain the spin1 -spin2 terms of a two-body effective hamiltonian through o (g2) and valid to all orders in velocity. solving hamilton's equations yields the impulse and spin changes of the individual bodies. we write them in a surprisingly compact form as appropriate derivatives of the eikonal phase obtained from the amplitude. it seems likely this structure persists to higher orders. we also point out various double-copy relations for general spin. | spinning black hole binary dynamics, scattering amplitudes, and effective field theory |
we give an exposition of the syk model with several new results. a non-local correction to the schwarzian effective action is found. the same action is obtained by integrating out the bulk degrees of freedom in a certain variant of dilaton gravity. we also discuss general properties of out-of-time-order correlators. | the soft mode in the sachdev-ye-kitaev model and its gravity dual |
we describe a systematic framework for computing the conservative potential of a compact binary system using modern tools from scattering amplitudes and effective field theory. our approach combines methods for integration and matching adapted from effective field theory, generalized unitarity, and the double-copy construction, which relates gravity integrands to simpler gauge-theory expressions. with these methods we derive the third post-minkowskian correction to the conservative two-body hamiltonian for spinless black holes. we describe in some detail various checks of our integration methods and the resulting hamiltonian. | black hole binary dynamics from the double copy and effective theory |
in this paper we discuss the anatomy of frequency-domain gravitational-wave signals from nonprecessing black-hole coalescences with the goal of constructing accurate phenomenological waveform models. we first present new numerical-relativity simulations for mass ratios up to 18, including spins. from a comparison of different post-newtonian approximants with numerical-relativity data we select the uncalibrated seobnrv2 model as the most appropriate for the purpose of constructing hybrid post-newtonian/numerical-relativity waveforms, and we discuss how we prepare time-domain and frequency-domain hybrid data sets. we then use our data together with results in the literature to calibrate simple explicit expressions for the final spin and radiated energy. equipped with our prediction for the final state we then develop a simple and accurate merger-ringdown model based on modified lorentzians in the gravitational-wave amplitude and phase, and we discuss a simple method to represent the low frequency signal augmenting the taylorf2 post-newtonian approximant with terms corresponding to higher orders in the post-newtonian expansion. we finally discuss different options for modelling the small intermediate frequency regime between inspiral and merger ringdown. a complete phenomenological model based on the present work is presented in a companion paper [s. khan et al., following paper, phys. rev. d 93 044007 (2016)]. | frequency-domain gravitational waves from nonprecessing black-hole binaries. i. new numerical waveforms and anatomy of the signal |
our earlier paper "complexity equals action" conjectured that the quantum computational complexity of a holographic state is given by the classical action of a region in the bulk (the "wheeler-dewitt" patch). we provide calculations for the results quoted in that paper, explain how it fits into a broader (tensor) network of ideas, and elaborate on the hypothesis that black holes are the fastest computers in nature. | complexity, action, and black holes |
the detection of gravitational waves by advanced ligo and advanced virgo provides an opportunity to test general relativity in a regime that is inaccessible to traditional astronomical observations and laboratory tests. we present four tests of the consistency of the data with binary black hole gravitational waveforms predicted by general relativity. one test subtracts the best-fit waveform from the data and checks the consistency of the residual with detector noise. the second test checks the consistency of the low- and high-frequency parts of the observed signals. the third test checks that phenomenological deviations introduced in the waveform model (including in the post-newtonian coefficients) are consistent with 0. the fourth test constrains modifications to the propagation of gravitational waves due to a modified dispersion relation, including that from a massive graviton. we present results both for individual events and also results obtained by combining together particularly strong events from the first and second observing runs of advanced ligo and advanced virgo, as collected in the catalog gwtc-1. we do not find any inconsistency of the data with the predictions of general relativity and improve our previously presented combined constraints by factors of 1.1 to 2.5. in particular, we bound the mass of the graviton to be mg≤4.7 ×10-23 ev /c2 (90% credible level), an improvement of a factor of 1.6 over our previously presented results. additionally, we check that the four gravitational-wave events published for the first time in gwtc-1 do not lead to stronger constraints on alternative polarizations than those published previously. | tests of general relativity with the binary black hole signals from the ligo-virgo catalog gwtc-1 |
it is commonly believed that the ringdown signal from a binary coalescence provides a conclusive proof for the formation of an event horizon after the merger. this expectation is based on the assumption that the ringdown waveform at intermediate times is dominated by the quasinormal modes of the final object. we point out that this assumption should be taken with great care, and that very compact objects with a light ring will display a similar ringdown stage, even when their quasinormal-mode spectrum is completely different from that of a black hole. in other words, universal ringdown waveforms indicate the presence of light rings, rather than of horizons. only precision observations of the late-time ringdown signal, where the differences in the quasinormal-mode spectrum eventually show up, can be used to rule out exotic alternatives to black holes and to test quantum effects at the horizon scale. | is the gravitational-wave ringdown a probe of the event horizon? |
a variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp2 hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a ag(111) substrate. two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. the boron sheets are quite inert to oxidization and interact only weakly with their substrate. we envisage that such boron sheets may find applications in electronic devices in the future. | experimental realization of two-dimensional boron sheets |
we consider an ads$_2$ black hole in equilibrium with a bath, which we take to have a dual description as (0+1)-dimensional quantum mechanical system coupled to a (1+1)-dimensional field theory serving as the bath. we compute the entropies of both the quantum mechanical degrees of freedom and of the bath separately, while allowing contributions from entanglement wedge "islands". we find situations where the island extends {\it outside} the black hole horizon. this suggests possible causality paradoxes which we show are avoided because of the quantum focusing conjecture. finally, we formulate a version of the information paradox for a black hole in contact with a bath in the hartle-hawking state, and demonstrate the role of islands in resolving this paradox. | islands outside the horizon |
the grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. and of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of general relativity: event horizons, singularities and ergoregions. the hitherto invisible landscape of the gravitational universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the ligo-virgo collaboration marks the dawn of a new era of scientific exploration. gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. it will provide evidence for event horizons and ergoregions, test the theory of general relativity itself, and may reveal the existence of new fundamental fields. the synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of nature. the purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. this write-up is an initiative taken within the framework of the european action on ‘black holes, gravitational waves and fundamental physics’. | black holes, gravitational waves and fundamental physics: a roadmap |
we consider a general einstein-scalar-gauss-bonnet theory with a coupling function f (ϕ ) . we demonstrate that black-hole solutions appear as a generic feature of this theory since a regular horizon and an asymptotically flat solution may be easily constructed under mild assumptions for f (ϕ ). we show that the existing no-hair theorems are easily evaded, and a large number of regular black-hole solutions with scalar hair are then presented for a plethora of coupling functions f (ϕ ). | evasion of no-hair theorems and novel black-hole solutions in gauss-bonnet theories |
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 anti-de sitter spacetime, 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. | holographic complexity equals bulk action? |
we develop models of 1+1 dimensional dilaton gravity describing flows to ads2 from higher dimensional ads and other spaces. we use these to study the effects of backreaction on holographic correlators. we show that this scales as a relevant effect at low energies, for compact transverse spaces. we also discuss effects of matter loops, as in the cghs model. | models of ads2 backreaction and holography |
we present a method to construct the extended kähler cone of any calabi-yau threefold by using gopakumar-vafa invariants to identify all geometric phases that are related by flops or weyl reflections. in this way we obtain the kähler moduli spaces of all favorable calabi-yau threefold hypersurfaces with h1,1 ≤ 4, including toric and non-toric phases. in this setting we perform an explicit test of the weak gravity conjecture by using the gopakumar-vafa invariants to count bps states. all of our examples satisfy the tower/sublattice wgc, and in fact they even satisfy the stronger lattice wgc. | moduli space reconstruction and weak gravity |
late-time dominance of entanglement islands plays a critical role in addressing the information paradox for black holes in ads coupled to an asymptotic non-gravitational bath. a natural question is how this observation can be extended to gravitational systems. to gain insight into this question, we explore how this story is modified within the context of karch-randall braneworlds when we allow the asymptotic bath to couple to dynamical gravity. we find that because of the inability to separate degrees of freedom by spatial location when defining the radiation region, the entanglement entropy of radiation emitted into the bath is a time-independent constant, consistent with recent work on black hole information in asymptotically flat space. if we instead consider an entanglement entropy between two sectors of a specific division of the hilbert space, we then find non-trivial time-dependence, with the page time a monotonically decreasing function of the brane angle -- provided both branes are below a particular angle. however, the properties of the entropy depend discontinuously on this angle, which is the first example of such discontinuous behavior for an ads brane in ads space. | information transfer with a gravitating bath |
we point out a connection between the emergence of bulk locality in ads/cft and the theory of quantum error correction. bulk notions such as bogoliubov transformations, location in the radial direction, and the holographic entropy bound all have natural cft interpretations in the language of quantum error correction. we also show that the question of whether bulk operator reconstruction works only in the causal wedge or all the way to the extremal surface is related to the question of whether or not the quantum error correcting code realized by ads/cft is also a "quantum secret sharing scheme", and suggest a tensor network calculation that may settle the issue. interestingly, the version of quantum error correction which is best suited to our analysis is the somewhat nonstandard "operator algebra quantum error correction" of beny, kempf, and kribs. our proposal gives a precise formulation of the idea of "subregion-subregion" duality in ads/cft, and clarifies the limits of its validity. | bulk locality and quantum error correction in ads/cft |
we investigate a dilaton gravity model in ads2 proposed by almheiri and polchinski [1] and develop a 1d effective description in terms of a dynamical boundary time with a schwarzian derivative action. we show that the effective model is equivalent to a 1d version of liouville theory, and investigate its dynamics and symmetries via a standard canonical framework. we include the coupling to arbitrary conformal matter and analyze the effective action in the presence of possible sources. we compute commutators of local operators at large time separation, and match the result with the time shift due to a gravitational shockwave interaction. we study a black hole evaporation process and comment on the role of entropy in this model. | an investigation of ads2 backreaction and holography |
recently a d-dimensional regularization approach leading to the non-trivial (3 +1 ) -dimensional einstein-gauss-bonnet (egb) effective description of gravity was formulated which was claimed to bypass the lovelock's theorem and avoid ostrogradsky instability. later it was shown that the regularization is possible only for some broad, but limited, class of metrics and aoki et al. (arxiv:2005.03859) formulated a well-defined four-dimensional egb theory, which breaks the lorentz invariance in a theoretically consistent and observationally viable way. the black-hole solution of the first naive approach proved out to be also the exact solution of the well-defined theory. here we calculate quasinormal modes of scalar, electromagnetic and gravitational perturbations and find the radius of shadow for spherically symmetric and asymptotically flat black holes with gauss-bonnet corrections. we show that the black hole is gravitationally stable when (-16 m2<α ⪅0.6 m2 ). the instability in the outer range is the eikonal one and it develops at high multipole numbers. the radius of the shadow rsh obeys the linear law with a remarkable accuracy. | quasinormal modes, stability and shadows of a black hole in the 4d einstein-gauss-bonnet gravity |
we comment on the recently introduced gauss-bonnet gravity in four dimensions. we argue that it does not make sense to consider this theory to be defined by a set of d → 4 solutions of the higher-dimensional gauss-bonnet gravity. we show that a well-defined d → 4 limit of gauss-bonnet gravity is obtained generalizing a method employed by mann and ross to obtain a limit of the einstein gravity in d = 2 dimensions. this is a scalar-tensor theory of the horndeski type obtained by dimensional reduction methods. by considering simple spacetimes beyond spherical symmetry (taub-nut spaces) we show that the naive limit of the higher-dimensional theory to d = 4 is not well defined and contrast the resultant metrics with the actual solutions of the new theory. | on taking the d → 4 limit of gauss-bonnet gravity: theory and solutions |
we construct a nearly-$ads_2$ solution describing an eternal traversable wormhole. the solution contains negative null energy generated by quantum fields under the influence of an external coupling between the two boundaries. in parallel, we discuss two syk systems coupled by a relevant interaction. the physics of the two cases is very similar. they both share a "gravitational" subsector which is identical. the solution within this subsector sets the stage for dynamics which is almost conformal invariant. we study this system in detail, both in gravity and in the syk model. the coupled syk models have an interesting phase diagram at finite temperature, displaying the usual hawking-page transition between the thermal ads phase at low temperature and the black hole phase at high temperature. interestingly, these two phases are continuously connected in the microcannonical ensemble. | eternal traversable wormhole |
very compact objects probe extreme gravitational fields and may be the key to understand outstanding puzzles in fundamental physics. these include the nature of dark matter, the fate of spacetime singularities, or the loss of unitarity in hawking evaporation. the standard astrophysical description of collapsing objects tells us that massive, dark and compact objects are black holes. any observation suggesting otherwise would be an indication of beyond-the-standard-model physics. null results strengthen and quantify the kerr black hole paradigm. the advent of gravitational-wave astronomy and precise measurements with very long baseline interferometry allow one to finally probe into such foundational issues. we overview the physics of exotic dark compact objects and their observational status, including the observational evidence for black holes with current and future experiments. | testing the nature of dark compact objects: a status report |
motivated by recent studies of holographic complexity, we examine the question of circuit complexity in quantum field theory. we provide a quantum circuit model for the preparation of gaussian states, in particular the ground state, in a free scalar field theory for general dimensions. applying the geometric approach of nielsen to this quantum circuit model, the complexity of the state becomes the length of the shortest geodesic in the space of circuits. we compare the complexity of the ground state of the free scalar field to the analogous results from holographic complexity, and find some surprising similarities. | circuit complexity in quantum field theory |
in finite entropy systems, real-time partition functions do not decay to zero at late time. instead, assuming random matrix universality, suitable averages exhibit a growing "ramp" and "plateau" structure. deriving this non-decaying behavior in a large $n$ collective field description is a challenge related to one version of the black hole information problem. we describe a candidate semiclassical explanation of the ramp for the syk model and for black holes. in syk, this is a two-replica nonperturbative saddle point for the large $n$ collective fields, with zero action and a compact zero mode that leads to a linearly growing ramp. in the black hole context, the solution is a two-sided black hole that is periodically identified under a killing time translation. we discuss but do not resolve some puzzles that arise. | a semiclassical ramp in syk and in gravity |
in ordinary gravitational theories, any local bulk operator in an entanglement wedge is accompanied by a long-range gravitational dressing that extends to the asymptotic part of the wedge. islands are the only known examples of entanglement wedges that are disconnected from the asymptotic region of spacetime. in this paper, we show that the lack of an asymptotic region in islands creates a potential puzzle that involves the gravitational gauss law, independently of whether or not there is a non-gravitational bath. in a theory with long-range gravity, the energy of an excitation localized to the island can be detected from outside the island, in contradiction with the principle that operators in an entanglement wedge should commute with operators from its complement. in several known examples, we show that this tension is resolved because islands appear in conjunction with a massive graviton. we also derive some additional consistency conditions that must be obeyed by islands in decoupled systems. our arguments suggest that islands might not constitute consistent entanglement wedges in standard theories of massless gravity where the gauss law applies. | inconsistency of islands in theories with long-range gravity |
we propose a procedure for the d → 4 limit of einstein-gauss-bonnet (egb) gravity that leads to a well defined action principle in four dimensions. our construction is based on compactifying d-dimensional egb gravity on a (d - 4)-dimensional maximally symmetric space followed by redefining the gauss-bonnet coupling α →α/d-4. the resulting model is a special scalar-tensor theory that belongs to the family of horndeski gravity. static black hole solutions in the scalar-tensor theory are investigated. interestingly, the metric profile is independent of the curvature of the internal space and coincides with the d → 4 limit of the usual egb black hole with the unusual gauss-bonnet coupling α/d-4. the curvature information of the internal space is instead encoded in the profile of the extra scalar field. our procedure can also be generalized to define further limits of the gauss-bonnet combination by compactifying the d-dimensional theory on a (d - p)-dimensional maximally symmetric space with p ≤ 3. these lead to different d → 4 limits of egb gravity as well as its d → 2 , 3 limits. | horndeski gravity as d → 4 limit of gauss-bonnet |
recently, a novel 4d einstein-gauss-bonnet gravity was formulated by glavan and lin (phys rev lett 124(8):081301, 2020). although whether the theory is well defined is currently debatable, the spherically symmetric black hole solution is still meaningful and worthy of study. in this paper, we study the geodesic motions in the spacetime of the spherically symmetric black hole solution. first of all, we find that a negative gb coupling constant is allowable, as in which case the singular behavior of the black hole can be hidden inside the event horizon. then we calculate the innermost stable circular orbits for massive particles, which turn out to be monotonic decreasing functions of the gb coupling constant. furthermore, we study the unstable photon sphere and shadow of the black hole. it is interesting to find that the proposed universal bounds on black hole size in lu and lyu (phys rev d 101(4):044059, 2020) recently can be broken when the gb coupling constant takes a negative value. | innermost stable circular orbit and shadow of the 4d einstein-gauss-bonnet black hole |
tensor networks provide a natural framework for exploring holographic duality because they obey entanglement area laws. they have been used to construct explicit toy models realizing many of the interesting structural features of the ads/cft correspondence, including the non-uniqueness of bulk operator reconstruction in the boundary theory. in this article, we explore the holographic properties of networks of random tensors. we find that our models naturally incorporate many features that are analogous to those of the ads/cft correspondence. when the bond dimension of the tensors is large, we show that the entanglement entropy of all boundary regions, whether connected or not, obey the ryu-takayanagi entropy formula, a fact closely related to known properties of the multipartite entanglement of assistance. we also discuss the behavior of rényi entropies in our models and contrast it with ads/cft. moreover, we find that each boundary region faithfully encodes the physics of the entire bulk entanglement wedge, i.e., the bulk region enclosed by the boundary region and the minimal surface. our method is to interpret the average over random tensors as the partition function of a classical ferromagnetic ising model, so that the minimal surfaces of ryu-takayanagi appear as domain walls. upon including the analog of a bulk field, we find that our model reproduces the expected corrections to the ryu-takayanagi formula: the bulk minimal surface is displaced and the entropy is augmented by the entanglement of the bulk field. increasing the entanglement of the bulk field ultimately changes the minimal surface behavior topologically, in a way similar to the effect of creating a black hole. extrapolating bulk correlation functions to the boundary permits the calculation of the scaling dimensions of boundary operators, which exhibit a large gap between a small number of low-dimension operators and the rest. while we are primarily motivated by the ads/cft duality, the main results of the article define a more general form of bulk-boundary correspondence which could be useful for extending holography to other spacetimes. | holographic duality from random tensor networks |
we study products of precursors of spatially local operators, , where wx ( t) = e - ihtwxeiht . using chaotic spin-chain numerics and gauge/gravity duality, we show that a single precursor fills a spatial region that grows linearly in t. in a lattice system, products of such operators can be represented using tensor networks. in gauge/gravity duality, they are related to einstein-rosen bridges supported by localized shock waves. we find a geometrical correspondence between these two descriptions, generalizing earlier work in the spatially homogeneous case. | localized shocks |
we introduce a framework for quantifying random matrix behavior of 2d cfts and ads3 quantum gravity. we present a 2d cft trace formula, precisely analogous to the gutzwiller trace formula for chaotic quantum systems, which originates from the sl(2, &z;) spectral decomposition of the virasoro primary density of states. an analogy to berry's diagonal approximation allows us to extract spectral statistics of individual 2d cfts by coarse-graining, and to identify signatures of chaos and random matrix universality. this leads to a necessary and sufficient condition for a 2d cft to display a linear ramp in its coarse-grained spectral form factor.turning to gravity, ads3 torus wormholes are cleanly interpreted as diagonal projections of squared partition functions of microscopic 2d cfts. the projection makes use of hecke operators. the cotler-jensen wormhole of ads3 pure gravity is shown to be extremal among wormhole amplitudes: it is the minimal completion of the random matrix theory correlator compatible with virasoro symmetry and sl(2, &z;)-invariance. we call this maxrmt: the maximal realization of random matrix universality consistent with the necessary symmetries. completeness of the sl(2, &z;) spectral decomposition as a trace formula allows us to factorize the cotler-jensen wormhole, extracting the microscopic object zrmt(τ) from the coarse-grained product. this captures details of the spectrum of btz black hole microstates. zrmt(τ) may be interpreted as an ads3 half-wormhole. we discuss its implications for the dual cft and modular bootstrap at large central charge. | ads3/rmt2 duality |
we comment on the role of the graviton mass in recent calculations of the page curve using holographic ideas. all reliable calculations of the page curve in more than 2+1 spacetime dimensions have been performed in systems with massive gravitons. a crucial ingredient in these calculations is the formation of islands, regions that contribute to the entropy of degrees of freedom located elsewhere. while most often simply ignored, it is indeed true that mass of the graviton does not appear to significantly affect the calculations that appeared in the literature. we use the freedom to change the graviton mass to give an extremely simple model of analytically tractable island formation in general dimensions. we do however note that if one attempts to take the limit of zero graviton mass, any contribution from the islands disappears. this raises the question to what extent entanglement islands can play a role in standard massless gravity. | massive islands |
only numerical relativity simulations can capture the full complexities of binary black hole mergers. these simulations, however, are prohibitively expensive for direct data analysis applications such as parameter estimation. we present two fast and accurate surrogate models for the outputs of these simulations: the first model, nrsur7dq4, predicts the gravitational waveform and the second model, nrsur7dq4remnant, predicts the properties of the remnant black hole. these models extend previous seven-dimensional, noneccentric precessing models to higher mass ratios and have been trained against 1528 simulations with mass ratios q ≤4 and spin magnitudes χ1,χ2≤0.8 , with generic spin directions. the waveform model, nrsur7dq4, which begins about 20 orbits before merger, includes all ℓ ≤4 spin-weighted spherical harmonic modes, as well as the precession frame dynamics and spin evolution of the black holes. the final black hole model, nrsur7dq4remnant, models the mass, spin, and recoil kick velocity of the remnant black hole. in their training parameter range, both models are shown to be more accurate than existing models by at least an order of magnitude, with errors comparable to the estimated errors in the numerical relativity simulations. we also show that the surrogate models work well even when extrapolated outside their training parameter space range, up to mass ratios q =6 . | surrogate models for precessing binary black hole simulations with unequal masses |
we provide evidence that the classical scattering of two spinning black holes is controlled by the soft expansion of exchanged gravitons. we show how an exponentiation of cachazo-strominger soft factors, acting on massive higher-spin amplitudes, can be used to find spin contributions to the aligned-spin scattering angle, conjecturally extending previously known results to higher orders in spin at one-loop order. the extraction of the classical limit is accomplished via the on-shell leading-singularity method and using massive spinor-helicity variables. the three-point amplitude for arbitrary-spin massive particles minimally coupled to gravity is expressed in an exponential form, and in the infinite-spin limit it matches the effective stress-energy tensor of the linearized kerr solution. a four-point gravitational compton amplitude is obtained from an extrapolated soft theorem, equivalent to gluing two exponential three-point amplitudes, and becomes itself an exponential operator. the construction uses these amplitudes to: 1) recover the known tree-level scattering angle at all orders in spin, 2) recover the known one-loop linear-in-spin interaction, 3) match a previous conjectural expression for the one-loop scattering angle at quadratic order in spin, 4) propose new one-loop results through quartic order in spin. these connections link the computation of higher-multipole interactions to the study of deeper orders in the soft expansion. | scattering of spinning black holes from exponentiated soft factors |
in [1] we gave a precise holographic calculation of chaos at the scrambling time scale. we studied the influence of a small perturbation, long in the past, on a two-sided correlation function in the thermofield double state. a similar analysis applies to squared commutators and other out-of-time-order one-sided correlators [2-6]. the essential bulk physics is a high energy scattering problem near the horizon of an ads black hole. the above papers used einstein gravity to study this problem; in the present paper we consider stringy and planckian corrections. elastic stringy corrections play an important role, effectively weakening and smearing out the development of chaos. we discuss their signature in the boundary field theory, commenting on the extension to weak coupling. inelastic effects, although important for the evolution of the state, leave a parametrically small imprint on the correlators that we study. we briefly discuss ways to diagnose these small corrections, and we propose another correlator where inelastic effects are order one. | stringy effects in scrambling |
we propose a method to compute the scattering angle for classical black hole scattering directly from two massive particle irreducible diagrams in a heavy-mass effective field theory approach to general relativity, without the need of subtracting iteration terms. the amplitudes in this effective theory are constructed using a recently proposed novel colour-kinematic/double copy for tree-level two-scalar, multi-graviton amplitudes, where the bcj numerators are gauge invariant and local with respect to the massless gravitons. these tree amplitudes, together with graviton tree amplitudes, enter the construction of the required d-dimensional loop integrands and allow for a direct extraction of contributions relevant for classical physics. in particular the soft/heavy-mass expansions of full integrands is circumvented, and all iterating contributions can be dropped from the get go. we use this method to compute the scattering angle up to third post-minkowskian order in four dimensions, including radiation reaction contributions, also providing the expression of the corresponding integrand in d dimensions. | classical gravitational scattering from a gauge-invariant double copy |
after turning on an interaction that couples the two boundaries of an eternal btz black hole, we find a quantum matter stress tensor with negative average null energy, whose gravitational backreaction renders the einstein-rosen bridge traversable. such a traversable wormhole has an interesting interpretation in the context of er=epr, which we suggest might be related to quantum teleportation. however, it cannot be used to violate causality. we also discuss the implications for the energy and holographic entropy in the dual cft description. | traversable wormholes via a double trace deformation |
we propose that a class of new topologies, for which there is no classical solution, should be included in the path integral of three-dimensional pure gravity, and that their inclusion solves pathological negativities in the spectrum, replacing them with a nonperturbative shift of the btz extremality bound. we argue that a two dimensional calculation using a dimensionally reduced theory captures the leading effects in the near extremal limit. to make this argument, we study a closely related two-dimensional theory of jackiw-teitelboim gravity with dynamical defects. we show that this theory is equivalent to a matrix integral. | the path integral of 3d gravity near extremality; or, jt gravity with defects as a matrix integral |
this review article presents the progress made over the last decade, since the introduction of effective field theories (efts) into post-newtonian (pn) gravity. these have been put forward in the context of gravitational waves (gws) from the compact binary inspiral. the mature development of this interdisciplinary field has resulted in significant advances of wide interest to physics at several levels serving various purposes. the field has firmly demonstrated, that seemingly disparate physical domains, such as quantum field theory and classical gravity, are related, and that the eft framework is a universal one, where it has been proven to supply a robust methodology to boost progress in the development of pn theory. in this review emphasis was put on an accessible pedagogic presentation of the field theoretic aspects of the subject, with the view, that these are in fact common across the whole of theoretical physics, rather than in their original narrow quantum context. the review is aimed at a broad audience, from general readers new to the field, to specialists and experts in related subjects. *to my loving father, sister, and old friend, who is a brother to me. | effective field theories of post-newtonian gravity: a comprehensive review |
a precise link is derived between scalar-graviton s-matrix elements and expectation values of operators in a worldline quantum field theory (wqft), both used to describe classical scattering of black holes. the link is formally provided by a worldline path integral representation of the graviton-dressed scalar propagator, which may be inserted into a traditional definition of the s-matrix in terms of time-ordered correlators. to calculate expectation values in the wqft a new set of feynman rules is introduced which treats the gravitational field hμν(x) and position xiμ(τi) of each black hole on equal footing. using these both the 3pm three-body gravitational radiation <hμv(k)> and 2pm two-body deflection δ piμ from classical black hole scattering events are obtained. the latter can also be obtained from the eikonal phase of a 2 → 2 scalar s-matrix, which we show corresponds to the free energy of the wqft. | classical black hole scattering from a worldline quantum field theory |
we present imrphenomxphm, a phenomenological frequency-domain model for the gravitational-wave signal emitted by quasicircular precessing binary black holes, which incorporates multipoles beyond the dominant quadrupole in the precessing frame. the model is a precessing extension of imrphenomxhm, [c. garcía-quirós et al., phys. rev. d 102, 064002 (2020), 10.1103/physrevd.102.064002] based on approximate maps between aligned-spin waveform modes in the coprecessing frame and precessing waveform modes in the inertial frame, which is commonly referred to as "twisting up" the nonprecessing waveforms. imrphenomxhxphmncludes imrphenomxp as a special case, the restriction to the dominant quadrupole contribution in the coprecessing frame. we implement two alternative mappings, one based on a single-spin post-newtonian approximation, as used in imrphenompv2 [m. hannam et al., phys. rev. lett. 113, 151101 (2014)., 10.1103/physrevlett.113.151101], and one based on the double-spin multiple scale analysis approach of [k. chatziioannou et al., phys. rev. d 95, 104004 (2017)., 10.1103/physrevd.95.104004]. we include a detailed discussion of conventions used in the description of precessing binaries and of all choices made in constructing the model. the computational cost of imrphenomxphm is further reduced by extending the interpolation technique of [c. garcía-quirós et al., classical quant. grav. 38, 015006 (2021)., 10.1088/1361-6382/abc36e] to the euler angles. the accuracy, speed, robustness, and modularity of the imrphenomx family will make these models productive tools for gravitational wave astronomy in the current era of greatly increased number and diversity of detected events. | computationally efficient models for the dominant and subdominant harmonic modes of precessing binary black holes |
we compute the path integral of three-dimensional gravity with negative cosmological constant on spaces which are topologically a torus times an interval. these are euclidean wormholes, which smoothly interpolate between two asymptotically euclidean ads3 regions with torus boundary. from our results we obtain the spectral correlations between btz black hole microstates near threshold, as well as extract the spectral form factor at fixed momentum, which has linear growth in time with small fluctuations around it. the low-energy limit of these correlations is precisely that of a double-scaled random matrix ensemble with virasoro symmetry. our findings suggest that if pure three-dimensional gravity has a holographic dual, then the dual is an ensemble which generalizes random matrix theory. | ads3 gravity and random cft |
the syk model is a quantum mechanical model that has been proposed to be holographically dual to a 1 + 1-dimensional model of a quantum black hole. an emergent "gravitational" mode of this model is governed by an unusual action that has been called the schwarzian action. it governs a reparametrization of a circle. we show that the path integral of the schwarzian theory is one-loop exact. the argument uses a method of fermionic localization, even though the model itself is purely bosonic. | fermionic localization of the schwarzian theory |
we develop a general formalism for computing classical observables for relativistic scattering of spinning particles, directly from on-shell amplitudes. we then apply this formalism to minimally coupled einstein-gravity amplitudes for the scattering of massive spin 1/2 and spin 1 particles with a massive scalar, constructed using the double copy. in doing so we reproduce recent results at first post-minkowskian order for the scattering of spinning black holes, through quadrupolar order in the spin-multipole expansion. | observables and amplitudes for spinning particles and black holes |
in this paper we use the ads/cft correspondence to refine and then establish a set of old conjectures about symmetries in quantum gravity. we first show that any global symmetry, discrete or continuous, in a bulk quantum gravity theory with a cft dual would lead to an inconsistency in that cft, and thus that there are no bulk global symmetries in ads/cft. we then argue that any "long-range" bulk gauge symmetry leads to a global symmetry in the boundary cft, whose consistency requires the existence of bulk dynamical objects which transform in all finite-dimensional irreducible representations of the bulk gauge group. we mostly assume that all internal symmetry groups are compact, but we also give a general condition on cfts, which we expect to be true quite broadly, which implies this. we extend all of these results to the case of higher-form symmetries. finally we extend a recently proposed new motivation for the weak gravity conjecture to more general gauge groups, reproducing the "convex hull condition" of cheung and remmen. an essential point, which we dwell on at length, is precisely defining what we mean by gauge and global symmetries in the bulk and boundary. quantum field theory results we meet while assembling the necessary tools include continuous global symmetries without noether currents, new perspectives on spontaneous symmetry-breaking and 't hooft anomalies, a new order parameter for confinement which works in the presence of fundamental quarks, a hamiltonian lattice formulation of gauge theories with arbitrary discrete gauge groups, an extension of the coleman-mandula theorem to discrete symmetries, and an improved explanation of the decay π0→γ γ in the standard model of particle physics. we also describe new black hole solutions of the einstein equation in d +1 dimensions with horizon topology tp×sd -p -1. | symmetries in quantum field theory and quantum gravity |
we present a new frequency-domain phenomenological model of the gravitational-wave signal from the inspiral, merger and ringdown of nonprecessing (aligned-spin) black-hole binaries. the model is calibrated to 19 hybrid effective-one-body-numerical-relativity waveforms up to mass ratios of 1 ∶18 and black-hole spins of |a /m |∼0.85 (0.98 for equal-mass systems). the inspiral part of the model consists of an extension of frequency-domain post-newtonian expressions, using higher-order terms fit to the hybrids. the merger ringdown is based on a phenomenological ansatz that has been significantly improved over previous models. the model exhibits mismatches of typically less than 1% against all 19 calibration hybrids and an additional 29 verification hybrids, which provide strong evidence that, over the calibration region, the model is sufficiently accurate for all relevant gravitational-wave astronomy applications with the advanced ligo and virgo detectors. beyond the calibration region the model produces physically reasonable results, although we recommend caution in assuming that any merger-ringdown waveform model is accurate outside its calibration region. as an example, we note that an alternative nonprecessing model, seobnrv2 (calibrated up to spins of only 0.5 for unequal-mass systems), exhibits mismatch errors of up to 10% for high spins outside its calibration region. we conclude that waveform models would benefit most from a larger number of numerical-relativity simulations of high-aligned-spin unequal-mass binaries. | frequency-domain gravitational waves from nonprecessing black-hole binaries. ii. a phenomenological model for the advanced detector era |
we provide a general protocol to measure out-of-time-order correlation functions. these correlation functions are of broad theoretical interest for diagnosing the scrambling of quantum information in interacting quantum systems and have recently received particular attention in the study of chaos and black holes within holographic duality. measuring them requires an echo-type sequence in which the sign of a many-body hamiltonian is reversed. we illustrate our protocol by detailing an implementation employing cold atoms and cavity quantum electrodynamics to probe spin models with nonlocal interactions. to verify the feasibility of the scheme with current technology, we analyze the effects of dissipation in a chaotic kicked-top model. finally, we propose a number of other experimental platforms where similar out-of-time-order correlation functions can be measured. | measuring the scrambling of quantum information |
the ability to detect light over a broad spectral range is central to practical optoelectronic applications and has been successfully demonstrated with photodetectors of two-dimensional layered crystals such as graphene and mos2. however, polarization sensitivity within such a photodetector remains elusive. here, we demonstrate a broadband photodetector using a layered black phosphorus transistor that is polarization-sensitive over a bandwidth from ∼400 nm to 3,750 nm. the polarization sensitivity is due to the strong intrinsic linear dichroism, which arises from the in-plane optical anisotropy of this material. in this transistor geometry, a perpendicular built-in electric field induced by gating can spatially separate the photogenerated electrons and holes in the channel, effectively reducing their recombination rate and thus enhancing the performance for linear dichroism photodetection. the use of anisotropic layered black phosphorus in polarization-sensitive photodetection might provide new functionalities in novel optical and optoelectronic device applications. | polarization-sensitive broadband photodetector using a black phosphorus vertical p-n junction |
recently leutheusser and liu [1, 2] identified an emergent algebra of type iii1 in the operator algebra of n = 4 super yang-mills theory for large n. here we describe some 1/n corrections to this picture and show that the emergent type iii1 algebra becomes an algebra of type ii∞. the type ii∞ algebra is the crossed product of the type iii1 algebra by its modular automorphism group. in the context of the emergent type ii∞ algebra, the entropy of a black hole state is well-defined up to an additive constant, independent of the state. this is somewhat analogous to entropy in classical physics. | gravity and the crossed product |
we examine models of fermions with infinite-range interactions that realize non-fermi liquids with a continuously variable u(1) charge density q and a nonzero entropy density s at vanishing temperature. real-time correlators of operators carrying u(1) charge q at a low temperature t are characterized by a q -dependent frequency ωs=(q t /ℏ)(∂s /∂q ) , which determines a spectral asymmetry. we show that the correlators match precisely with those of the two-dimensional anti-de sitter (ads2 ) horizons of extremal charged black holes. on the black hole side, the matching employs s as the bekenstein-hawking entropy density and the laws of black hole thermodynamics that relate (∂s /∂q )/(2 π ) to the electric field strength in ads2 . the fermion model entropy is computed using the microscopic degrees of freedom of a uv complete theory without supersymmetry. | bekenstein-hawking entropy and strange metals |
we compute classical gravitational observables for the scattering of two spinless black holes in general relativity and n =8 supergravity in the formalism of kosower, maybee, and o'connell (kmoc). we focus on the gravitational impulse with radiation reaction and the radiated momentum in black hole scattering at o (g3) to all orders in the velocity. these classical observables require the construction and evaluation of certain loop-level quantities which are greatly simplified by harnessing recent advances from scattering amplitudes and collider physics. in particular, we make use of generalized unitarity to construct the relevant loop integrands, employ reverse unitarity, the method of regions, integration-by-parts (ibp), and (canonical) differential equations to simplify and evaluate all loop and phase-space integrals to obtain the classical gravitational observables of interest to two-loop order. the kmoc formalism naturally incorporates radiation effects which enables us to explore these classical quantities beyond the conservative two-body dynamics. from the impulse and the radiated momentum, we extract the scattering angle and the radiated energy. finally, we discuss universality of the impulse in the high-energy limit and the relation to the eikonal phase. | radiative classical gravitational observables at o (g3) from scattering amplitudes |
we compute the next-to-leading order term in the scattering waveform of uncharged black holes in classical general relativity and of half-bps black holes in n = 8 supergravity. we propose criteria, generalizing explicit calculations at next-to-leading order, for determining the terms in amplitudes that contribute to local observables. for general relativity, we construct the relevant classical integrand through generalized unitarity in two distinct ways, (1) in a heavy-particle effective theory and (2) in general relativity minimally-coupled to scalar fields. with a suitable prescription for the matter propagator in the former, we find agreement between the two methods, thus demonstrating the absence of interference of quantum and classically-singular contributions. the classical n = 8 integrand for massive scalar fields is constructed through dimensional reduction of the known five-point one-loop integrand. our calculation exhibits novel features compared to conservative calculations and inclusive observables, such as the appearance of master integrals with intersecting matter lines and the appearance of a classical infrared divergence whose absence from classical observables requires a suitable definition of the retarded time. | the sub-leading scattering waveform from amplitudes |
in holographic duality an eternal anti-de sitter black hole is described by two copies of the boundary conformal field theory in the thermal field double state. in this paper we provide explicit constructions in the boundary theory of infalling time evolutions which can take bulk observers behind the horizon. the constructions also help to illuminate the boundary emergence of the black hole horizons, the interiors, and the associated causal structure. a key element is the emergence, in the large n limit of the boundary theory, of a type iii1 von neumann algebraic structure from the type i boundary operator algebra and the half-sided modular translation structure associated with it. | emergent times in holographic duality |
the dynamics of quantum information in strongly interacting systems, known as quantum information scrambling, has recently become a common thread in our understanding of black holes, transport in exotic non-fermi liquids, and many-body analogs of quantum chaos. to date, verified experimental implementations of scrambling have focused on systems composed of two-level qubits. higher-dimensional quantum systems, however, may exhibit different scrambling modalities and are predicted to saturate conjectured speed limits on the rate of quantum information scrambling. we take the first steps toward accessing such phenomena, by realizing a quantum processor based on superconducting qutrits (three-level quantum systems). we demonstrate the implementation of universal two-qutrit scrambling operations and embed them in a five-qutrit quantum teleportation protocol. measured teleportation fidelities favg=0.568 ±0.001 confirm the presence of scrambling even in the presence of experimental imperfections and decoherence. our teleportation protocol, which connects to recent proposals for studying traversable wormholes in the laboratory, demonstrates how quantum technology that encodes information in higher-dimensional systems can exploit a larger and more connected state space to achieve the resource efficient encoding of complex quantum circuits. | quantum information scrambling on a superconducting qutrit processor |
we construct a type ii∞ von neumann algebra that describes the large n physics of single-trace operators in ads/cft in the microcanonical ensemble, where there is no need to include perturbative 1/n corrections. using only the extrapolate dictionary, we show that the entropy of semiclassical states on this algebra is holographically dual to the generalized entropy of the black hole bifurcation surface. from a boundary perspective, this constitutes a derivation of a special case of the qes prescription without any use of euclidean gravity or replicas; from a purely bulk perspective, it is a derivation of the quantum-corrected bekenstein-hawking formula as the entropy of an explicit algebra in the g → 0 limit of lorentzian effective field theory quantum gravity. in a limit where a black hole is first allowed to equilibrate and then is later potentially re-excited, we show that the generalized second law is a direct consequence of the monotonicity of the entropy of algebras under trace-preserving inclusions. finally, by considering excitations that are separated by more than a scrambling time we construct a "free product" von neumann algebra that describes the semiclassical physics of long wormholes supported by shocks. we compute rényi entropies for this algebra and show that they are equal to a sum over saddles associated to quantum extremal surfaces in the wormhole. surprisingly, however, the saddles associated to "bulge" quantum extremal surfaces contribute with a negative sign. | large n algebras and generalized entropy |
it has been shown that a special set of three-point amplitudes between two massive spinning states and a graviton reproduces the linearised stress-energy tensor for a kerr black hole in the classical limit. in this work we revisit this result and compare it to the analysis of the amplitudes describing the interaction of leading regge states of the open and closed superstring. we find an all-spin result for the classical limit of two massive spinning states interacting with a photon or graviton. this result differs from kerr and instead matches the current four-vector and the stress-energy tensor generated by a classical string coupled to electromagnetism and gravity respectively. for the superstring amplitudes, contrary to the black-hole case, we find that the spin to infinity limit is necessary to reproduce the classical spin multipoles. | classical limit of higher-spin string amplitudes |
we study various aspects of the carroll limit in which the speed of light is sent to zero. a large part of this paper is devoted to the quantization of carroll field theories. we show that these exhibit infinite degeneracies in the spectrum and may suffer from non-normalizable ground states. as a consequence, partition functions of carroll systems are ill-defined and do not lead to sensible thermodynamics. these seemingly pathological properties might actually be a virtue in the context of flat space holography.better defined is the carroll regime, in which we consider the leading order term in an expansion around vanishing speed of light without taking the strict carroll limit. such an expansion may lead to sensible notions of carroll thermodynamics. an interesting example is a gas of massless particles with an imaginary chemical potential conjugate to the momentum. in the carroll regime we show that the partition function of such a gas leads to an equation of state with w = −1.as a separate story, we study aspects of carroll gravity and couplings to carrollian energy-momentum tensors. we discuss many examples of solutions to carroll gravity, including wormholes, maxwell fields, solutions with a cosmological constant, and discuss the structure of geodesics in a carroll geometry. the coupling of matter to carroll gravity also allows us to derive energy-momentum tensors for hypothetical carroll fluids from expanding relativistic fluids as well as directly from hydrostatic partition functions. | carroll stories |
long ago, newman and janis showed that a complex deformation z → z + ia of the schwarzschild solution produces the kerr solution. the underlying explanation for this relationship has remained obscure. the complex deformation has an electromagnetic counterpart: by shifting the coloumb potential, we obtain the em field of a certain rotating charge distribution which we term √{kerr}. in this note, we identify the origin of this shift as arising from the exponentiation of spin operators for the recently defined "minimally coupled" three-particle amplitudes of spinning particles coupled to gravity, in the large- spin limit. we demonstrate this by studying the impulse imparted to a test particle in the background of the heavy spinning particle. we first consider the electromagnetic case, where the impulse due to √{kerr} is reproduced by a charged spinning particle; the shift of the coloumb potential is matched to the exponentiated spin-factor appearing in the amplitude. the known impulse due to the kerr black hole is then trivially derived from the gravitationally coupled spinning particle via the double copy. | kerr black holes as elementary particles |
we present a holographic derivation of the entropy of supersymmetric asymp-totically ads5 black holes. we define a bps limit of black hole thermodynamics by first focussing on a supersymmetric family of complexified solutions and then reaching extremality. we show that in this limit the black hole entropy is the legendre transform of the on-shell gravitational action with respect to three chemical potentials subject toa constraint. this constraint follows from supersymmetry and regularity in the euclidean bulk geometry. further, we calculate, using localization, the exact partition function of the dual n = 1 scft on a twisted s1 × s3 with complexified chemical potentials obeying this constraint. this defines a generalization of the supersymmetric casimir energy, whose legendre transform at large n exactly reproduces the bekenstein-hawking entropy of the black hole. | microscopic origin of the bekenstein-hawking entropy of supersymmetric ads5 black holes |
we observe spontaneous hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole in an atomic bose-einstein condensate. correlations are observed between the hawking particles outside the black hole and the partner particles inside. these correlations indicate an approximately thermal distribution of hawking radiation. we find that the high-energy pairs are entangled, while the low-energy pairs are not, within the reasonable assumption that excitations with different frequencies are not correlated. the entanglement verifies the quantum nature of the hawking radiation. the results are consistent with a driven oscillation experiment and a numerical simulation. | observation of quantum hawking radiation and its entanglement in an analogue black hole |
the gravitational wave strain emitted by a perturbed black hole (bh) ringing down is typically modeled analytically using first-order bh perturbation theory. in this letter, we show that second-order effects are necessary for modeling ringdowns from bh merger simulations. focusing on the strain's (ℓ,m )=(4 ,4 ) angular harmonic, we show the presence of a quadratic effect across a range of binary bh mass ratios that agrees with theoretical expectations. we find that the quadratic (4 ,4 ) mode's amplitude exhibits quadratic scaling with the fundamental (2 ,2 ) mode—its parent mode. the nonlinear mode's amplitude is comparable to or even larger than that of the linear (4 ,4 ) mode. therefore, correctly modeling the ringdown of higher harmonics—improving mode mismatches by up to 2 orders of magnitude—requires the inclusion of nonlinear effects. | nonlinearities in black hole ringdowns |
we compute the total radiated momentum carried by gravitational waves during the scattering of two spinless black holes at the lowest order in newton's constant, o (g3) , and all orders in velocity. by analytic continuation into the bound state regime, we obtain the o (g3) energy loss in elliptic orbits. this provides an essential step toward the complete understanding of the third-post-minkowskian binary dynamics. we employ the formalism of kosower, maybee, and o'connell (kmoc), which relates classical observables to quantum scattering amplitudes, and derive the relevant integrands using generalized unitarity. the subsequent phase-space integrations are performed via the reverse unitarity method familiar from collider physics, using differential equations to obtain the exact velocity dependence from near-static boundary conditions. | gravitational bremsstrahlung from reverse unitarity |
a quantum extremal island suggests that a region of spacetime is encoded in the quantum state of another system, like the encoding of the black hole interior in hawking radiation. we study conditions for islands to appear in general spacetimes, with or without black holes. they must violate bekenstein's area bound in a precise sense, and the boundary of an island must satisfy several other information-theoretic inequalities. these conditions combine to impose very strong restrictions, which we apply to cosmological models. we find several examples of islands in crunching universes. in particular, in the four-dimensional frw cosmology with radiation and a negative cosmological constant, there is an island near the turning point when the geometry begins to recollapse. in a two-dimensional model of jt gravity in de sitter spacetime, there are islands inside crunches that are encoded at future infinity or inside bubbles of minkowski spacetime. finally, we discuss simple tensor network toy models for islands in cosmology and black holes. | islands in cosmology |
we study various aspects of wormholes that are made traversable by an interaction beween the two asymptotic boundaries. we concentrate on the case of nearly-$ads_2$ gravity and discuss a very simple mechanical picture for the gravitational dynamics. we derive a formula for the two sided correlators that includes the effect of gravitational backreaction, which limits the amount of information we can send through the wormhole. we emphasize that the process can be viewed as a teleportation protocol where the teleportee feels nothing special as he/she goes through the wormhole. we discuss some applications to the cloning paradox for old black holes. we point out that the same formula we derived for $ads_2$ gravity is also valid for the simple syk quantum mechanical theory, around the thermofield double state. we present a heuristic picture for this phenomenon in terms of an operator growth model. finally, we show that a similar effect is present in a completely classical chaotic system with a large number of degrees of freedom. | diving into traversable wormholes |
we present event horizon telescope (eht) 1.3 mm measurements of the radio source located at the position of the supermassive black hole sagittarius a* (sgr a*), collected during the 2017 april 5-11 campaign. the observations were carried out with eight facilities at six locations across the globe. novel calibration methods are employed to account for sgr a*'s flux variability. the majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. the effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. the calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of ~50 μas, as determined in later works in this series. contemporaneous multiwavelength monitoring of sgr a* was performed at 22, 43, and 86 ghz and at near-infrared and x-ray wavelengths. several x-ray flares from sgr a* are detected by chandra, one at low significance jointly with swift on 2017 april 7 and the other at higher significance jointly with nustar on 2017 april 11. the brighter april 11 flare is not observed simultaneously by the eht but is followed by a significant increase in millimeter flux variability immediately after the x-ray outburst, indicating a likely connection in the emission physics near the event horizon. we compare sgr a*'s broadband flux during the eht campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior. | first sagittarius a* event horizon telescope results. ii. eht and multiwavelength observations, data processing, and calibration |
it is possible to infer the mass and spin of the remnant black hole from binary black hole mergers by comparing the ringdown gravitational wave signal to results from studies of perturbed kerr spacetimes. typically, these studies are based on the fundamental quasinormal mode of the dominant ℓ=m =2 harmonic. by modeling the ringdown of accurate numerical relativity simulations, we find, in agreement with previous findings, that the fundamental mode alone is insufficient to recover the true underlying mass and spin, unless the analysis is started very late in the ringdown. including higher overtones associated with this ℓ=m =2 harmonic resolves this issue and provides an unbiased estimate of the true remnant parameters. further, including overtones allows for the modeling of the ringdown signal for all times beyond the peak strain amplitude, indicating that the linear quasinormal regime starts much sooner than previously expected. this result implies that the spacetime is well described as a linearly perturbed black hole with a fixed mass and spin as early as the peak. a model for the ringdown beginning at the peak strain amplitude can exploit the higher signal-to-noise ratio in detectors, reducing uncertainties in the extracted remnant quantities. these results should be taken into consideration when testing the no-hair theorem. | black hole ringdown: the importance of overtones |
using n = 8 supergravity as a theoretical laboratory, we extract the 3pm gravitational eikonal for two colliding massive scalars from the classical limit of the corresponding elastic two-loop amplitude. we employ the eikonal phase to obtain the physical deflection angle and to show how its non-relativistic (nr) and ultra-relativistic (ur) regimes are smoothly connected. such a smooth interpolation rests on keeping contributions to the loop integrals originating from the full soft region, rather than restricting it to its potential sub-region. this task is efficiently carried out by using the method of differential equations with complete near-static boundary conditions. in contrast to the potential-region result, the physical deflection angle includes radiation-reaction contributions that are essential for recovering the finite and universal ur limit implied by general analyticity and crossing arguments. we finally discuss the real emission of massless states, which accounts for the imaginary part of the 3pm eikonal and for the dissipation of energy-momentum. adopting a direct approach based on unitarity and on the classical limit of the inelastic tree-level amplitude, we are able to treat n = 8 and general relativity on the same footing, and to complete the conservative 3pm eikonal in einstein's gravity by the addition of the radiation-reaction contribution. we also show how this approach can be used to compute waveforms, as well as the differential and integrated spectra, for the different radiated massless fields. | the eikonal approach to gravitational scattering and radiation at o (g3) |
the covariant phase space method of iyer, lee, wald, and zoupas gives an elegant way to understand the hamiltonian dynamics of lagrangian field theories without breaking covariance. the original literature however does not systematically treat total derivatives and boundary terms, which has led to some confusion about how exactly to apply the formalism in the presence of boundaries. in particular the original construction of the canonical hamiltonian relies on the assumed existence of a certain boundary quantity "b", whose physical interpretation has not been clear. we here give an algorithmic procedure for applying the covariant phase space formalism to field theories with spatial boundaries, from which the term in the hamiltonian involving b emerges naturally. our procedure also produces an additional boundary term, which was not present in the original literature and which so far has only appeared implicitly in specific examples, and which is already nonvanishing even in general relativity with sufficiently permissive boundary conditions. the only requirement we impose is that at solutions of the equations of motion the action is stationary modulo future/past boundary terms under arbitrary variations obeying the spatial boundary conditions; from this the symplectic structure and the hamiltonian for any diffeomorphism that preserves the theory are unambiguously constructed. we show in examples that the hamiltonian so constructed agrees with previous results. we also show that the poisson bracket on covariant phase space directly coincides with the peierls bracket, without any need for non-covariant intermediate steps, and we discuss possible implications for the entropy of dynamical black hole horizons. | covariant phase space with boundaries |
when two black holes merge, the late stage of gravitational wave emission is a superposition of exponentially damped sinusoids. according to the black hole no-hair theorem, this ringdown spectrum depends only on the mass and angular momentum of the final black hole. an observation of more than one ringdown mode can test this fundamental prediction of general relativity. here, we provide strong observational evidence for a multimode black hole ringdown spectrum using the gravitational wave event gw190521, with a maximum bayes factor of 56 ±1 (1 σ uncertainty) preferring two fundamental modes over one. the dominant mode is the ℓ=m =2 harmonic, and the subdominant mode corresponds to the ℓ=m =3 harmonic. the amplitude of this mode relative to the dominant harmonic is estimated to be a330/a220=0.2-0.1+0.2 . we estimate the redshifted mass and dimensionless spin of the final black hole as 33 0-40+30 m⊙ and 0.86-0.11+0.06, respectively. we find that the final black hole is consistent with the no-hair theorem and constrain the fractional deviation from general relativity of the subdominant mode's frequency to be -0.0 1-0.09+0.08. | multimode quasinormal spectrum from a perturbed black hole |
motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal approach, inspired by its electromagnetic predecessor, has been successfully applied to the transplanckian energy collisions of elementary particles and strings since the late eighties, and to string-brane collisions in the past decade. after the direct detection of gravitational waves from black-hole mergers, most of the attention has shifted towards adapting these methods to the physics of black-hole encounters. for such systems, the eikonal exponentiation provides an amplitude-based approach to calculate classical gravitational observables, thus complementing more traditional analytic methods such as the post-newtonian expansion, the worldline formalism, or the effective-one-body approach. in this review we summarize the main ideas and techniques behind the gravitational eikonal formalism. we discuss how it can be applied in various different physical setups involving particles, strings and branes and then we mainly concentrate on the most recent developments, focusing on massive scalars minimally coupled to gravity, for which we aim at being as self-contained and comprehensive as possible. | the gravitational eikonal: from particle, string and brane collisions to black-hole encounters |
we calculate the inelastic 2 → 3 one-loop amplitude for the scattering of two point-like, spinless objects with generic masses involving the additional emission of a single graviton. we focus on the near-forward, or classical, limit. our results include the leading and subleading orders in the soft-region expansion, which captures all non-analytic contributions in the transferred momentum and in the graviton's frequency. this allows us to check the first constraint arising from the inelastic exponentiation put forward in refs. [1-3], and to calculate the 2 → 3 one-loop matrix element of the n-operator, linked to the s-matrix by s = ein, showing that it is real, classical and free of infrared divergences. we discuss how our results feature in the calculation of the o (g3) corrections to the asymptotic waveform. | inelastic exponentiation and classical gravitational scattering at one loop |
these lectures give an introduction to the quantum physics of black holes, including recent developments based on quantum information theory such as the firewall paradox and its various cousins. an introduction is also given to holography and the anti-de sitter/conformal field theory (ads/cft) correspondence, focusing on those aspects which are relevant for the black hole information problem. | jerusalem lectures on black holes and quantum information |
we evaluate the full time dependence of holographic complexity in various eternal black hole backgrounds using both the complexity=action (ca) and the complexity=volume (cv) conjectures. we conclude using the cv conjecture that the rate of change of complexity is a monotonically increasing function of time, which saturates from below to a positive constant in the late time limit. using the ca conjecture for uncharged black holes, the holographic complexity remains constant for an initial period, then briefly decreases but quickly begins to increase. as observed previously, at late times, the rate of growth of the complexity approaches a constant, which may be associated with lloyd's bound on the rate of computation. however, we find that this late time limit is approached from above, thus violating the bound. for either conjecture, we find that the late time limit for the rate of change of complexity is saturated at times of the order of the inverse temperature. adding a charge to the eternal black holes washes out the early time behaviour, i.e. complexity immediately begins increasing with sufficient charge, but the late time behaviour is essentially the same as in the neutral case. we also evaluate the complexity of formation for charged black holes and find that it is divergent for extremal black holes, implying that the states at finite chemical potential and zero temperature are infinitely more complex than their finite temperature counterparts. | on the time dependence of holographic complexity |
we present a complete discussion of the boundary term in the action functional of general relativity when the boundary includes null segments in addition to the more usual timelike and spacelike segments. we confirm that ambiguities appear in the contribution from a null segment, because it depends on an arbitrary choice of parametrization for the generators. we also show that similar ambiguities appear in the contribution from a codimension-two surface at which a null segment is joined to another (spacelike, timelike, or null) segment. the parametrization ambiguity can be tamed by insisting that the null generators be affinely parametrized; this forces each null contribution to the boundary action to vanish, but leaves intact the fredom to rescale the affine parameter by a constant factor on each generator. once a choice of parametrization is made, the ambiguity in the joint contributions can be eliminated by formulating well-motivated rules that ensure the additivity of the gravitational action. enforcing these rules, we calculate the time rate of change of the action when it is evaluated for a so-called "wheeler-dewitt patch" of a black hole in asymptotically anti de sitter space. we recover a number of results cited in the literature, obtained with a less complete analysis. | gravitational action with null boundaries |
from the s-matrix of spinning particles, we extract the 2 pm conservative potential for binary spinning black holes up to quartic order in spin operators. an important ingredient is the exponentiated gravitational compton amplitude in the classical spin-limit for all graviton helicity sectors. the validity of the resulting hamiltonian is verified by matching to known lower spin order results, as well as direct computation of the 2pm impulse and spin kicks from the eikonal phase and that from the test black hole scattering based on mathisson-papapetrou-dixon equations. | the 2pm hamiltonian for binary kerr to quartic in spin |
we give arguments for the existence of a thermodynamics of quantum complexity that includes a "second law of complexity." to guide us, we derive a correspondence between the computational (circuit) complexity of a quantum system of k qubits, and the positional entropy of a related classical system with 2k degrees of freedom. we also argue that the kinetic entropy of the classical system is equivalent to the kolmogorov complexity of the quantum hamiltonian. we observe that the expected pattern of growth of the complexity of the quantum system parallels the growth of entropy of the classical system. we argue that the property of having less-than-maximal complexity (uncomplexity) is a resource that can be expended to perform directed quantum computation. although this paper is not primarily about black holes, we find a surprising interpretation of the uncomplexity resource as the accessible volume of spacetime behind a black hole horizon. | second law of quantum complexity |
quantum scattering amplitudes for massive matter have received new attention in connection to classical calculations relevant to gravitational-wave physics. amplitude methods and insights are now employed for precision computations of observables needed for describing the gravitational dynamics of bound massive objects such as black holes. an important direction is the inclusion of spin effects needed to accurately describe rotating (kerr) black holes. higher-spin amplitudes introduced by arkani-hamed, huang and huang at three points have by now a firm connection to the effective description of kerr black-hole physics. the corresponding compton higher-spin amplitudes remain however an elusive open problem. here we draw from results of the higher-spin literature and show that physical insights can be used to uniquely fix the compton amplitudes up to spin 5/2, by imposing a constraint on a three-point higher-spin current that is a necessary condition for the existence of an underlying unitary theory. we give the unique effective lagrangians up to spin 5/2, and show that they reproduce the previously-known amplitudes. for the multi-graviton amplitudes analogous to the compton amplitude, no further corrections to our lagrangians are expected, and hence such amplitudes are uniquely predicted. as an essential tool, we introduce a modified version of the massive spinor-helicity formalism which allows us to conveniently obtain higher-spin states, propagators and compact expressions for the amplitudes. | compton black-hole scattering for s ≤ 5/2 |
it is shown that black hole spacetimes in classical einstein gravity are characterized by, in addition to their adm mass m, momentum \overrightarrow{p} , angular momentum \overrightarrow{j} and boost charge \overrightarrow{k} , an infinite head of supertranslation hair. the distinct black holes are distinguished by classical superrotation charges measured at infinity. solutions with super-translation hair are diffeomorphic to the schwarzschild spacetime, but the diffeomorphisms are part of the bms subgroup and act nontrivially on the physical phase space. it is shown that a black hole can be supertranslated by throwing in an asymmetric shock wave. a leading-order bondi-gauge expression is derived for the linearized horizon supertranslation charge and shown to generate, via the dirac bracket, supertranslations on the linearized phase space of gravitational excitations of the horizon. the considerations of this paper are largely classical augmented by comments on their implications for the quantum theory. | superrotation charge and supertranslation hair on black holes |
we obtain exact expressions for a general class of correlation functions in the 1d quantum mechanical model described by the schwarzian action, that arises as the low energy limit of the syk model. the answer takes the form of an integral of a momentum space amplitude obtained via a simple set of diagrammatic rules. the derivation relies on the precise equivalence between the 1d schwarzian theory and a suitable large c limit of 2d virasoro cft. the mapping from the 1d to the 2d theory is similar to the construction of kinematic space. we also compute the out-of-time ordered four point function. the momentum space amplitude in this case contains an extra factor in the form of a crossing kernel, or r-matrix, given by a 6j-symbol of su(1,1). we argue that the r-matrix describes the gravitational scattering amplitude near the horizon of an ads2 black hole. finally, we discuss the generalization of some of our results to n=1 and n=2 supersymmetric schwarzian qm. | solving the schwarzian via the conformal bootstrap |
we compute the classical tree-level five-point amplitude for the two-to-two scattering of spinning celestial objects with the emission of a graviton. using this five-point amplitude, we then turn to the computation of the leading-order time-domain gravitational waveform. the method we describe is suitable for arbitrary values of classical spin of kerr black holes and does not require any expansion in powers of the spin. in this paper we illustrate it in the simpler case of the scattering of one kerr and one schwarzschild black hole. an important ingredient of our calculation is a novel form of the compton amplitude with spinning particles including contact terms derived from matching to black-hole perturbation theory calculations. this ensures that our waveform is valid up to at least fourth order in the spin. our method can be applied immediately to generate improved waveforms once higher-order contact terms in the compton amplitude become available. finally, we show the formula for the gravitational memory to all orders in the spin, which is in agreement with our results. | resummed spinning waveforms from five-point amplitudes |
we review recent developments on the thermodynamics of black holes in extended phase space, where the cosmological constant is interpreted as thermodynamic pressure and treated as a thermodynamic variable in its own right. in this approach, the mass of the black hole is no longer regarded as internal energy, rather it is identified with the chemical enthalpy. this leads to an extended dictionary for black hole thermodynamic quantities; in particular a notion of thermodynamic volume emerges for a given black hole spacetime. this volume is conjectured to satisfy the reverse isoperimetric inequality—an inequality imposing a bound on the amount of entropy black hole can carry for a fixed thermodynamic volume. new thermodynamic phase transitions naturally emerge from these identifications. namely, we show that black holes can be understood from the viewpoint of chemistry, in terms of concepts such as van der waals fluids, reentrant phase transitions, and triple points. we also review the recent attempts at extending the ads/cft dictionary in this setting, discuss the connections with horizon thermodynamics, applications to lifshitz spacetimes, and outline possible future directions in this field. | black hole chemistry: thermodynamics with lambda |
in this paper we quantify the temporal variability and image morphology of the horizon-scale emission from sgr a*, as observed by the eht in 2017 april at a wavelength of 1.3 mm. we find that the sgr a* data exhibit variability that exceeds what can be explained by the uncertainties in the data or by the effects of interstellar scattering. the magnitude of this variability can be a substantial fraction of the correlated flux density, reaching ~100% on some baselines. through an exploration of simple geometric source models, we demonstrate that ring-like morphologies provide better fits to the sgr a* data than do other morphologies with comparable complexity. we develop two strategies for fitting static geometric ring models to the time-variable sgr a* data; one strategy fits models to short segments of data over which the source is static and averages these independent fits, while the other fits models to the full data set using a parametric model for the structural variability power spectrum around the average source structure. both geometric modeling and image-domain feature extraction techniques determine the ring diameter to be 51.8 ± 2.3 μas (68% credible intervals), with the ring thickness constrained to have an fwhm between ~30% and 50% of the ring diameter. to bring the diameter measurements to a common physical scale, we calibrate them using synthetic data generated from grmhd simulations. this calibration constrains the angular size of the gravitational radius to be ${4.8}_{-0.7}^{+1.4}$ 4.8-0.7+1.4 μas, which we combine with an independent distance measurement from maser parallaxes to determine the mass of sgr a* to be ${4.0}_{-0.6}^{+1.1}\times {10}^{6}$ 4.0-0.6+1.1×106 m ⊙. | first sagittarius a* event horizon telescope results. iv. variability, morphology, and black hole mass |
quantum error correction has given us a natural language for the emergence of spacetime, but the black hole interior poses a challenge for this framework: at late times the apparent number of interior degrees of freedom in effective field theory can vastly exceed the true number of fundamental degrees of freedom, so there can be no isometric (i.e. inner-product preserving) encoding of the former into the latter. in this paper we explain how quantum error correction nonetheless can be used to explain the emergence of the black hole interior, via the idea of "non-isometric codes protected by computational complexity". we show that many previous ideas, such as the existence of a large number of "null states", a breakdown of effective field theory for operations of exponential complexity, the quantum extremal surface calculation of the page curve, post-selection, "state-dependent/state-specific" operator reconstruction, and the "simple entropy" approach to complexity coarse-graining, all fit naturally into this framework, and we illustrate all of these phenomena simultaneously in a soluble model. | the black hole interior from non-isometric codes and complexity |
in this paper, we explore the physics of electromagnetically and gravitationally coupled massive higher spin states from the on-shell point of view. starting with the three-point amplitude, we focus on the simplest amplitude characterized by matching to minimal coupling in the uv. in the ir, for charged states this leads to g = 2 for arbitrary spin, and the leading deformation corresponds to the anomalous magnetic dipole moment. we proceed to construct the (gravitational) compton amplitude for generic spins via consistent factorization. we find that in gravitation couplings, the leading deformation leads to inconsistent factorization. this implies that for systems with gauge2 = gravity relations, such as perturbative string theory, all charged states must have g = 2. it is then natural to ask for generic spin, what is the theory that yields such minimal coupling. by matching to the one body effective action, we verify that for large spins the answer is kerr black holes. this identification is then an on-shell avatar of the no- hair theorem. finally using this identification as well as the newly constructed compton amplitudes, we proceed to compute the spin-dependent pieces for the classical potential at 2pm order up to degree four in spin operator of either black holes. | the simplest massive s-matrix: from minimal coupling to black holes |
i argue that a version of the quantum-corrected ryu-takayanagi formula holds in any quantum error-correcting code. i present this result as a series of theorems of increasing generality, with the final statement expressed in the language of operator-algebra quantum error correction. in ads/cft this gives a "purely boundary" interpretation of the formula. i also extend a recent theorem, which established entanglement-wedge reconstruction in ads/cft, when interpreted as a subsystem code, to the more general, and i argue more physical, case of subalgebra codes. for completeness, i include a self-contained presentation of the theory of von neumann algebras on finite-dimensional hilbert spaces, as well as the algebraic definition of entropy. the results confirm a close relationship between bulk gauge transformations, edge-modes/soft-hair on black holes, and the ryu-takayanagi formula. they also suggest a new perspective on the homology constraint, which basically is to get rid of it in a way that preserves the validity of the formula, but which removes any tension with the linearity of quantum mechanics. moreover, they suggest a boundary interpretation of the "bit threads" recently introduced by freedman and headrick. | the ryu-takayanagi formula from quantum error correction |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.