abstract stringlengths 3 192k | title stringlengths 4 857 |
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preface; 1. introduction; 2. condensed matter: the charted territory; 3. condensed matter: the challenges; 4. large n field theories for holography and condensed matter; 5. the ads/cft correspondence as computational device: the dictionary; 6. finite temperature magic: black holes and holographic thermodynamics; 7. holographic hydrodynamics; 8. finite density: the reissner-nordström black hole and strange metals; 9. holographic photoemission and the rn metal: the fermions as probes; 10. holographic superconductivity; 11. holographic fermi liquids; 12. breaking translational invariance; 13. ads/cmt from the top down; 14. outlook: holography and quantum matter; references; index. | holographic duality in condensed matter physics |
we study the complexity of gaussian mixed states in a free scalar field theory using the `purification complexity'. the latter is defined as the lowest value of the circuit complexity, optimized over all possible purifications of a given mixed state. we argue that the optimal purifications only contain the essential number of ancillary degrees of freedom necessary in order to purify the mixed state. we also introduce the concept of `mode-by- mode purifications' where each mode in the mixed state is purified separately and examine the extent to which such purifications are optimal. we explore the purification complexity for thermal states of a free scalar qft in any number of dimensions, and for subregions of the vacuum state in two dimensions. we compare our results to those found using the various holographic proposals for the complexity of subregions. we find a number of qualitative similarities between the two in terms of the structure of divergences and the presence of a volume law. we also examine the `mutual complexity' in the various cases studied in this paper. | complexity of mixed states in qft and holography |
we study scalar fields in a black hole background and show that, when the scalar is suitably coupled to curvature, rapid rotation can induce a tachyonic instability. this instability, which is the hallmark of spontaneous scalarization in the linearized regime, is expected to be quenched by nonlinearities and endow the black hole with scalar hair. hence, our results demonstrate the existence of a broad class of theories that share the same stationary black hole solutions with general relativity at low spins, but which exhibit black hole hair at sufficiently high spins (a /m ≳0.5 ). this result has clear implications for tests of general relativity and the nature of black holes with gravitational and electromagnetic observations. | spin-induced black hole spontaneous scalarization |
we present a counting of microstates of a class of dyonic bps black holes in ads4 which precisely reproduces their bekenstein-hawking entropy. the counting is performed in the dual boundary description, that provides a non-perturbative definition of quantum gravity, in terms of a twisted and mass-deformed abjm theory. we evaluate its twisted index and propose an extremization principle to extract the entropy, which reproduces the attractor mechanism in gauged supergravity. | exact microstate counting for dyonic black holes in ads4 |
in this paper, via employing the uniformly modified form of the generalized off-shell helmholtz free energy, we investigate the topological numbers for the four-dimensional neutral lorentzian taub-nut, taub-nut-ads and kerr-nut spacetimes, and find that these solutions can also be classified into one of three types of those well-known black hole solutions, which implies that these spacetimes should be viewed as generic black holes from the viewpoint of the thermodynamic topological approach. | classifying topology of consistent thermodynamics of the four-dimensional neutral lorentzian nut-charged spacetimes |
recently a non-trivial 4-dimensional theory of gravity that claims to circumvent lovelock's theorem and avoid ostrogradsky instability was formulated in glavan and lin (2020) [1]. this theory, named "4d einstein gauss-bonnet gravity", presents several novel predictions for cosmology and black hole physics. in this paper, we generalize the vacuum black hole solution of glavan & lin to include electric charge in an anti-de sitter space and explore some properties of this solution such as the asymptotics, properties of the horizons, the general relativity limit and thermodynamics. | charged black holes in ads spaces in 4d einstein gauss-bonnet gravity |
we study the doubly holographic model of [1] in the situation where a black hole in two-dimensional jt gravity theory is coupled to an auxiliary bath system at arbitrary finite temperature. depending on the initial temperature of the black hole relative to the bath temperature, the black hole can lose mass by emitting hawking radiation, stay in equilibrium with the bath or gain mass by absorbing thermal radiation from the bath. in all of these scenarios, a unitary page curve is obtained by applying the usual prescription for holographic entanglement entropy and identifying the quantum extremal surface for the generalized entropy, using both analytical and numeric calculations. as the application of the entanglement wedge reconstruction, we further investigate the reconstruction of the black hole interior from a subsystem containing the hawking radiation. we examine the roles of the hawking radiation and also the purification of the thermal bath in this reconstruction. | evaporating black holes coupled to a thermal bath |
we construct black hole solutions with spin-induced scalarization in a class of models where a scalar field is quadratically coupled to the topological gauss-bonnet term. starting from the tachyonically unstable kerr solutions, we obtain families of scalarized black holes such that the scalar field has either even or odd parity, and we investigate their domain of existence. the scalarized black holes can violate the kerr rotation bound. we identify "critical" families of scalarized black hole solutions such that the expansion of the metric functions and of the scalar field at the horizon no longer allows for real coefficients. for the quadratic coupling considered here, solutions with spin-induced scalarization are entropically favored over kerr solutions with the same mass and angular momentum. | spin-induced black hole scalarization in einstein-scalar-gauss-bonnet theory |
superradiant instabilities may create clouds of ultralight bosons around rotating black holes, forming so-called "gravitational atoms". it was recently shown that the presence of a binary companion can induce resonant transitions between bound states of these clouds, whose backreaction on the binary's orbit leads to characteristic signatures in the emitted gravitational waves. in this work, we show that the interaction with the companion can also trigger transitions from bound to unbound states of the cloud—a process that we refer to as "ionization" in analogy with the photoelectric effect in atomic physics. the orbital energy lost in the process overwhelms the losses due to gravitational wave emission and contains sharp features carrying information about the energy spectrum of the cloud. moreover, we also show that if the companion is a black hole, then the part of the cloud impinging on the event horizon will be absorbed. this "accretion" leads to a significant increase of the companion's mass, which alters the dynamical evolution and ensuing waveform of the binary. we argue that a combined treatment of resonances, ionization, and accretion is crucial to discover and characterize gravitational atoms with upcoming gravitational-wave detectors. | ionization of gravitational atoms |
we study the link between classical scattering of spinning black holes and quantum amplitudes for massive spin-s particles. generic spin orientations of the black holes are considered, allowing their spins to be deflected on par with their momenta. we rederive the spin-exponentiated structure of the relevant tree-level amplitude from minimal coupling to einstein's gravity, which in the s →∞ limit generates the black holes' complete series of spin-induced multipoles. the resulting scattering function is seen to encode in a simple way the known net changes in the black-hole momenta and spins at first post-minkowskian order. we connect our findings to a rigorous framework developed elsewhere for computing such observables from amplitudes. | black-hole scattering with general spin directions from minimal-coupling amplitudes |
we find models of two dimensional gravity that resolve the factorization puzzle and have a discrete spectrum, whilst retaining a semiclassical description. a novelty of these models is that they contain non-trivially correlated spacetime branes or, equivalently, nonlocal interactions in their action. such nonlocal correlations are motivated in the low-energy gravity theory by integrating out uv degrees of freedom. demanding factorization fixes almost all brane correlators, and the exact geometric expansion of the partition function collapses to only two terms: the black hole saddle and a subleading "half-wormhole" geometry, whose sum yields the desired discrete spectrum. by mapping the insertion of correlated branes to a certain double-trace deformation in the dual matrix integral, we show that factorization and discreteness also persist non-perturbatively. while in our model all wormholes completely cancel, they are still computationally relevant: self-averaging quantities, like the page curve, computed in the original theory with wormholes, accurately approximate observables in our theory, which accounts for uv corrections. our models emphasize the importance of correlations between different disconnected components of spacetime, providing a possible resolution to the factorization puzzle in any number of dimensions. | gravity factorized |
under semiclassical evolution, black holes retain a smooth horizon but fail to return information. yet, the ryu-takayanagi (rt) prescription computes the boundary entropy expected from unitary conformal field theory (cft) evolution. we demonstrate this in a novel setting with an asymptotic bulk detector, eliminating an assumption about the entanglement wedge of auxiliary systems. we consider three interpretations of this result. (i) at face value, information is lost in the bulk but not in the cft. this conflicts with the ads /cft dictionary. (ii) no unique quantum field theory state (pure or mixed) governs all detector responses to the bulk hawking radiation. this conflicts with the existence of an s matrix. (iii) nonlocal couplings to the black hole interior cause asymptotic detectors to respond as though the radiation was pure, even though it is naively thermal. this invalidates the standard interpretation of the semiclassical state, including its smoothness at the horizon. we conclude that unitary boundary evolution requires asymptotic bulk detectors to become unambiguously pure at late times. we ask whether the rt prescription can still reproduce the boundary entropy in this bulk scenario. we find that this requires a substantial failure of semiclassical gravity in a low-curvature region, such as a firewall that purifies the hawking radiation. finally, we allow that the dual to semiclassical gravity may be an ensemble of unitary theories. this appears to relax the tensions we find: the ensemble average of out states would be mixed, but the ensemble average of final entropies would vanish. | unitarity from a smooth horizon? |
the detection of gravitational waves resulting by the ligo-virgo-kagra collaboration has inaugurated a new era in gravitational physics, providing an opportunity to test general relativity and its modifications in the strong gravity regime. one such test involves the study of the ringdown phase of gravitational waves from binary black-hole coalescence, which can be decomposed into a superposition of quasinormal modes. in general relativity, the spectra of quasinormal modes depend on the mass, spin, and charge of the final black hole, but they can be influenced by additional properties of the black hole, as well as corrections to general relativity. in this work, we employ the modified teukolsky formalism developed in a previous study to investigate perturbations of slowly rotating black holes in a modified theory known as dynamical chern-simons gravity. specifically, we derive the master equations for the $\psi_0$ and $\psi_4$ weyl scalar perturbations that characterize the radiative part of gravitational perturbations, as well as for the scalar field perturbations. we employ metric reconstruction techniques to obtain explicit expressions for all relevant quantities. finally, by leveraging the properties of spin-weighted spheroidal harmonics to eliminate the angular dependence from the evolution equations, we derive two, radial, second-order, ordinary differential equations for $\psi_0$ and $\psi_4$, respectively. these equations are coupled to another radial, second-order, ordinary differential equation for the scalar field perturbations. this work is the first attempt to derive a master equation for black holes in dynamical chern-simons gravity using curvature perturbations. the master equations can be numerically integrated to obtain the quasinormal mode spectrum of slowly rotating black holes in this theory, making progress in the study of ringdown in dynamical chern-simons gravity. | perturbations of spinning black holes in dynamical chern-simons gravity i. slow rotation equations |
volume complexity in ds2 remains o(1) up to a critical time, after which it suddenly diverges. on the other hand, for the ds2 solution in jt gravity, there is a linear dilaton which smoothly grows towards the future infinity. from the dimensional reduction viewpoint, the growth of the dilaton is due to the expansion of the orthogonal sphere in higher-dimensional dsd (d ≥ 3). since in higher dimensions complexity becomes very large even before the critical time, by properly taking into account the dilaton, the same behavior is expected for complexity in ds2 jt gravity. we show that this expectation is met by the complexity = action (ca) conjecture. for this purpose, we obtain an appropriate action for ds2 in jt gravity, by dimensional reduction from ds3. in addition, we discuss complexity = "refined volume" where we choose an appropriate weyl field-redefinition such that refined volume avoids the discontinuous jump in time evolution. | is action complexity better for de sitter space in jackiw-teitelboim gravity? |
we study correlation functions for extremal supersymmetric black holes. it is necessary to take into account the strongly coupled nature of the boundary supergraviton mode. we consider the case with {\cal n}=2 supercharges which is the minimal amount of supersymmetry needed to give a large ground state degeneracy, separated from the continuum. using the exact solution for this theory we derive formulas for the two point function and we also give integral expressions for any nn-point correlator. these correlators are time independent at large times and approach constant values that depend on the masses and couplings of the bulk theory. we also explain that in the non-supersymmetric case, the correlators develop a universal time dependence at long times. this paper is the longer companion paper of arxiv:2207.00407. | looking at supersymmetric black holes for a very long time |
we study four-derivative corrections to five-dimensional minimal gauged supergravity. we evaluate the on-shell action of the ads5 black hole solution with two independent angular momenta and one electric charge at linear order in the corrections. after imposing supersymmetry, we are able to recast the action in terms of the supersymmetric chemical potentials and match the result obtained from the dual superconformal index on the second sheet. to achieve this, we exploit the freedom to implement field redefinitions to recast the action in a much simpler form, as well as the fact that the two-derivative solution is enough. we use the on-shell action to determine the corrections to the black hole thermodynamics, including those to the entropy and the charges. we then specialize to the supersymmetric and extremal case and find a simple expression for the microcanonical entropy. in particular, for the case with one independent angular momentum the corrections are entirely encoded in the dual superconformal anomaly coefficients. we corroborate this result for the entropy by constructing the corrected near-horizon solution and applying wald's formula. | corrections to ads5 black hole thermodynamics from higher-derivative supergravity |
in this note, we explore the possibility that certain high-energy holographic cft states correspond to black hole microstates with a geometrical behind-the-horizon region, modelled by a portion of a second asymptotic region terminating at an end-of-the-world (etw) brane. we study the time-dependent physics of this behind-the-horizon region, whose etw boundary geometry takes the form of a closed frw spacetime. we show that in many cases, this behind-the-horizon physics can be probed directly by looking at the time dependence of entanglement entropy for sufficiently large spatial cft subsystems. we study in particular states defined via euclidean evolution from conformal boundary states and give specific predictions for the behavior of the entanglement entropy in this case. we perform analogous calculations for the syk model and find qualitative agreement with our expectations. we also calculate holographic complexity for the d = 2 etw geometries, finding that complexity-action and complexity-volume proposals give the same linear growth at late times, but differ at early times.a fascinating possibility is that for certain states, we might have gravity localized to the etw brane as in the randall-sundrum ii scenario for cosmology. in this case, the effective description of physics beyond the horizon could be a big bang/big crunch cosmology of the same dimensionality as the cft. in this case, the d-dimensional cft describing the black hole microstate would give a precise, microscopic description of the d-dimensional cosmological physics. | black hole microstate cosmology |
we continue the analysis of the krylov complexity in the ip matrix model. in a previous paper, [1], for a fundamental operator, it was shown that at zero temperature, the krylov complexity oscillates and does not grow, but in the infinite temperature limit, the krylov complexity grows exponentially in time as ∼exp(o (√{t})). we study how the krylov complexity changes from a zero-temperature oscillation to an infinite-temperature exponential growth. at low temperatures, the spectral density is approximated as collections of infinite wigner semicircles. we showed that this infinite collection of branch cuts yields linear growth to the lanczos coefficients and gives exponential growth of the krylov complexity. thus the ip model for any nonzero temperature shows exponential growth for the krylov complexity even though the green function decays by a power law in time. we also study the lanczos coefficients and the krylov complexity in the iop matrix model taking into account the 1/n2 corrections. there, the lanczos coefficients are constants and the krylov complexity does not grow exponentially as expected. | krylov complexity in the ip matrix model. part ii |
we analyse the weak gravity conjecture for chiral four-dimensional f-theory compactifications with n = 1 supersymmetry. extending our previous work on nearly tensionless heterotic strings in six dimensions, we show that under certain assumptions a tower of asymptotically massless states arises in the limit of vanishing coupling of a u(1) gauge symmetry coupled to gravity. this tower contains super-extremal states whose charge-to-mass ratios are larger than those of certain extremal dilatonic reissner-nordström black holes, precisely as required by the weak gravity conjecture. unlike in six dimensions, the tower of super-extremal states does not always populate a charge sub-lattice. the main tool for our analysis is the elliptic genus of the emergent heterotic string in the chiral n = 1 supersymmetric effective theories. this also governs situations where the heterotic string is non-perturbative. we show how it can be computed in terms of bps invariants on elliptic four-folds, by making use of various dualities and mirror symmetry. compared to six dimensions, the geometry of the relevant elliptically fibered four-folds is substantially richer than that of the three-folds, and we classify the possibilities for obtaining critical, nearly tensionless heterotic strings. we find that the (quasi-)modular properties of the elliptic genus crucially depend on the choice of flux background. our general results are illustrated in a detailed example. | modular fluxes, elliptic genera, and weak gravity conjectures in four dimensions |
extensions of einstein gravity with higher-order derivative terms arise in string theory and other effective theories, as well as being of interest in their own right. in this letter we study static black-hole solutions in the example of einstein gravity with additional quadratic curvature terms. a lichnerowicz-type theorem simplifies the analysis by establishing that they must have vanishing ricci scalar curvature. by numerical methods we then demonstrate the existence of further black-hole solutions over and above the schwarzschild solution. we discuss some of their thermodynamic properties, and show that they obey the first law of thermodynamics. | black holes in higher derivative gravity |
recently, a non-trivial 4d einstein-gauss-bonnet (egb) theory of gravity, by rescaling the gb coupling parameter as α/(d-4), was formulated in [1], which bypasses lovelock's theorem and avoids ostrogradsky instability. the theory admits a static spherically symmetric black hole, unlike 5d egb or general relativity counterpart, which can have both cauchy and event horizons. we generalize previous work, on gravitational lensing by a schwarzschild black hole, in the strong and weak deflection limits to the 4d egb black holes to calculate the deflection coefficients ā and bar b, while former increases and later decrease with increasing α. we also find that the deflection angle αd, angular position θ∞ and um decreases, but angular separation s increases with α. the effect of the gb coupling parameter α on positions and magnification of the source relativistic images is discussed in the context of sgra* and m87* black holes. a brief description of the weak gravitational lensing using the gauss-bonnet theorem is presented. | gravitational lensing by black holes in the 4d einstein-gauss-bonnet gravity |
in this paper, we study rotating black holes in symmergent gravity, and use deviations from the kerr black hole to constrain the parameters of the symmergent gravity. symmergent gravity induces the gravitational constant g and quadratic curvature coefficient co from the flat spacetime matter loops. in the limit in which all fields are degenerate in mass, the vacuum energy vo can be wholly expressed in terms of g and co. we parametrize deviation from this degenerate limit by a parameter α ^ such that the black hole spacetime is ds for α ^<1 and ads for α ^>1 . in constraining the symmergent parameters co and α ^, we utilize the eht observations on the m87* and sgr. a* black holes. we investigate first the modifications in the photon sphere and shadow size, and find significant deviations in the photonsphere radius and the shadow radius with respect to the kerr solution. we also find that the geodesics of time-like particles are more sensitive to symmergent gravity effects than the null geodesics. finally, we analyze the weak field limit of the deflection angle, where we use the gauss-bonnet theorem for taking into account the finite distance of the source and the receiver to the lensing object. remarkably, the distance of the receiver (or source) from the lensing object greatly influences the deflection angle. moreover, co needs be negative for a consistent solution. in our analysis, the rotating black hole acts as a particle accelerator and possesses the sensitivity to probe the symmergent gravity. | testing symmergent gravity through the shadow image and weak field photon deflection by a rotating black hole using the m87∗ and sgr. a∗ results |
the entropy of a black hole1 and hawking radiation2 should have the same temperature given by the surface gravity, within a numerical factor of the order of unity. in addition, hawking radiation should have a thermal spectrum, which creates an information paradox3,4. however, the thermality should be limited by greybody factors5, at the very least6. it has been proposed that the physics of hawking radiation could be verified in an analogue system7, an idea that has been carefully studied and developed theoretically8-18. classical white-hole analogues have been investigated experimentally19-21, and other analogue systems have been presented22,23. the theoretical works and our long-term study of this subject15,24-27 enabled us to observe spontaneous hawking radiation in an analogue black hole28. the observed correlation spectrum showed thermality at the lowest and highest energies, but the overall spectrum was not of the thermal form, and no temperature could be ascribed to it. theoretical studies of our observation made predictions about the thermality and hawking temperature29-33. here we construct an analogue black hole with improvements compared with our previous setup, such as reduced magnetic field noise, enhanced mechanical and thermal stability and redesigned optics. we find that the correlation spectrum of hawking radiation agrees well with a thermal spectrum, and its temperature is given by the surface gravity, confirming the predictions of hawking's theory. the hawking radiation observed is in the regime of linear dispersion, in analogy with a real black hole, and the radiation inside the black hole is composed of negative-energy partner modes only, as predicted. | observation of thermal hawking radiation and its temperature in an analogue black hole |
we systematically study the field equations of f (q ) gravity for spherically symmetric and stationary metric-affine spacetimes. such spacetimes are described by a metric as well as a flat and torsionless affine connection. in the symmetric teleparallel equivalent of general relativity (stegr), the connection is pure gauge and hence unphysical. however, in the nonlinear extension f (q ), it is promoted to a dynamical field which changes the physics. starting from a general metric-affine geometry, we construct the most general static and spherically symmetric forms of the metric and the affine connection. we then use these symmetry reduced geometric objects to prove that the field equations of f (q ) gravity admit general relativity (gr) solutions as well as beyond-gr solutions, contrary to what has been claimed in the literature. we formulate precise criteria, under which conditions it is possible to obtain gr solutions and under which conditions it is possible to obtain beyond-gr solutions. we subsequently construct several perturbative corrections to the schwarzschild solution for different choices of f (q ), which in particular include a hair stemming from the now dynamical affine connection. we also present an exact beyond-gr vacuum solution. lastly, we apply this method of constructing spherically symmetric and stationary solutions to f (t ) gravity, which reproduces similar solutions but without a dynamical connection. | black holes in f (q ) gravity |
entanglement islands play an essential role in the recent breakthrough in resolving the black hole information paradox. however, whether entanglement islands can exist in massless gravity theories is controversial. it is found that entanglement islands disappear in the initial model of wedge holography with massless gravity on the brane. as a result, the entanglement entropy of hawking radiation becomes a time-independent constant, and there is no page curve. in this paper, we recover massless entanglement islands in wedge holography with suitable dgp gravity or higher derivative gravity on the branes. we study two typical cases. in the first case, we consider a black hole on the strong-gravity brane and a bath on the weak-gravity brane. it is similar to the usual double holography with non-gravitational baths. in the second case, we discuss two black holes on the two branes with the same gravitational strength. we recover massless entanglement islands and non-trivial page curves in both cases. we also argue that the entanglement island is consistent with massless gravity. our results strongly support that entanglement islands can exist in long-range theories of gravity. | entanglement island and page curve in wedge holography |
we consider the capacity of entanglement as a probe of the hawking radiation in a two-dimensional dilaton gravity coupled with conformal matter of large degrees of freedom. a formula calculating the capacity is derived using the gravitational path integral, from which we speculate that the capacity has a discontinuity at the page time in contrast to the continuous behavior of the generalized entropy. we apply the formula to a replica wormhole solution in an eternal ads black hole coupled to a flat non-gravitating bath and show that the capacity of entanglement is saturated by the thermal capacity of the black hole in the high temperature limit. | replica wormholes and capacity of entanglement |
we study the page curve and the island rule for black holes evaporating into gravitating baths, with an eye towards establishing a connection with the er=epr proposal. we consider several models of two entangled 2d black holes in jackiw-teitelboim (jt) gravity with negative cosmological constant. the first, "doubled pssy," model is one in which the black holes have end-of-the-world (etw) branes with a flavour degree of freedom. we study highly entangled states of this flavour degree of freedom and find an entanglement-induced hawking-page-like transition from a geometry with two disconnected black holes to one with a pair of black holes connected by a wormhole, thus realising the er = epr proposal. the second model is a dynamical one in which the etw branes do not have internal degrees of freedom but the jt gravity is coupled to a 2d cft, and we entangle the black holes by coupling the two cfts at the ads boundary and evolving for a long time. we study the entanglement entropy between the two black holes and find that the story is substantially similar to that with a non-gravitating thermal bath. in the third model, we couple the two ends of a two-sided eternal black hole and evolve for a long time. finally, we discuss the possibility of a hawking-page-like transition induced by real-time evolution that realises the er = epr proposal in this dynamical setting. | islands with gravitating baths: towards er = epr |
we investigate the shadows and photon spheres of the four-dimensional gauss-bonnet black hole with the static and infalling spherical accretions. we show that, for both cases, there always exist shadows and photon spheres. the radii of the shadows and photon spheres are independent of the profiles of accretion for a fixed gauss-bonnet constant, implying that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion. because of the doppler effect, the shadows of the infalling accretion are found to be darker than in the static case. we also investigate the effect of the gauss-bonnet constant on the shadow and photon spheres, and we find that the larger the gauss-bonnet constant is, the smaller the radii of the shadow and photon spheres will be. in particular, the observed specific intensity increases as the gauss-bonnet constant grows. | shadows and photon spheres with spherical accretions in the four-dimensional gauss-bonnet black hole |
we comprehensively study galilean and carrollian hydrodynamics on arbitrary backgrounds, in the presence of a matter/charge conserved current. for this purpose, we follow two distinct and complementary paths. the first is based on local invariance, be it galilean or carrollian diffeomorphism invariance, possibly accompanied by weyl invariance. the second consists in analyzing the relativistic fluid equations at large or small speed of light, after choosing an adapted gauge, arnowitt-deser-misner-zermelo for the former and papapetrou-randers for the latter. unsurprisingly, the results agree, but the second approach is superior as it effortlessly captures more elaborate situations with multiple degrees of freedom. it furthermore allows to investigate the fate of hydrodynamic-frame invariance in the two limits at hand, and conclude that its breaking (in the galilean) or its preservation (in the carrollian) are fragile consequences of the behaviour of transport attributes at large or small c. both methods do also agree on the doom of nœtherian currents generated in the relativistic theory by isometries: conserved currents are not always guaranteed in newton-cartan or carroll spacetimes as a consequence of galilean or carrollian isometries. comparison of galilean and carrollian fluid equations exhibits a striking but often superficial resemblance, which we comment in relation to black-hole horizon dynamics, awkwardly akin to navier-stokes equations. this congruity is authentic in one instance though and turns out then to describe aristotelian dynamics, which is the last item in our agenda. | relativistic fluids, hydrodynamic frames and their galilean versus carrollian avatars |
we construct a family of multidyonically charged and rotating supersymmetric ads2×σ solutions of d =4 , n =4 gauged supergravity, where σ is a sphere with two conical singularities known as a spindle. we argue that these arise as near horizon limits of extremal dyonically charged rotating and accelerating supersymmetric black holes in ads4 that we conjecture to exist. we demonstrate this in the nonrotating limit, constructing the accelerating black hole solutions and showing that the nonspinning spindle solutions arise as the near horizon limit of the supersymmetric and extremal subclass of these black holes. from the near horizon solutions we compute the bekenstein-hawking entropy of the black holes as a function of the conserved charges, and show that this may equivalently be obtained by extremizing a simple entropy function. for appropriately quantized magnetic fluxes, the solutions uplift on s7, or its n =4 orbifolds s7/γ , to smooth supersymmetric solutions to d =11 supergravity, where the entropy is expected to count microstates of the theory on n m2-branes wrapped on a spinning spindle, in the large n limit. | multicharge accelerating black holes and spinning spindles |
we represent the first investigation of pole-skipping on both the gravity and field theory sides. in contrast to the higher dimensional models, there is no momentum degree of freedom in (1 + 1)−dimensional bulk theory. thus, we then consider a scalar field mass as our degree of freedom for the pole-skipping phenomenon instead of momentum. the pole-skipping frequencies of the scalar field in 2d gravity are the same as higher dimensional cases: ω = −i2πtn for positive integers n. at each of these frequencies, there is a corresponding pole-skipping mass, so the pole-skipping points exist in (ω, m) space. we also compute the pole-skipping points of the syk model in (ω, h) space where h is the dimension of the bilinear primary operator. we find that there is a one-to-one correspondence of the pole-skipping points between the jt gravity and the syk model. to obtain the pole-skipping points, we need to consider the parameter ϵ related to the chemical potential on the horizon of charged jt gravity and the particle-hole asymmetric parameter e of the complex syk model as shift parameters. this highlights the ϵ − e correspondence in relation to pole-skipping phenomenon. | pole-skipping points in 2d gravity and syk model |
many-body chaos has emerged as a powerful framework for understanding thermalization in strongly interacting quantum systems. while recent analytic advances have sharpened our intuition for many-body chaos in certain large n theories, it has proven challenging to develop precise numerical tools capable of exploring this phenomenon in generic hamiltonians. to this end, we utilize massively parallel, matrix-free krylov subspace methods to calculate dynamical correlators in the sachdev-ye-kitaev model for up to n =60 majorana fermions. we begin by showing that numerical results for two-point correlation functions agree at high temperatures with dynamical mean field solutions, while at low temperatures finite-size corrections are quantitatively reproduced by the exactly solvable dynamics of near extremal black holes. motivated by these results, we develop a novel finite-size rescaling procedure for analyzing the growth of out-of-time-order correlators. our procedure accurately determines the lyapunov exponent, λ , across a wide range in temperatures, including in the regime where λ approaches the universal bound, λ =2 π /β . | many-body chaos in the sachdev-ye-kitaev model |
a key issue in both the field of quantum chaos and quantum gravity is an effective description of chaotic conformal field theories (cfts), that is cfts that have a quantum ergodic limit. we develop a framework incorporating the constraints of conformal symmetry and locality, allowing the definition of ensembles of `cft data'. these ensembles take on the same role as the ensembles of random hamiltonians in more conventional quantum ergodic phases of many-body quantum systems. to describe individual members of the ensembles, we introduce the notion of approximate cft, defined as a collection of `cft data' satisfying the usual cft constraints approximately, i.e. up to small deviations. we show that they generically exist by providing concrete examples. ensembles of approximate cfts are very natural in holography, as every member of the ensemble is indistinguishable from a true cft for low-energy probes that only have access to information from semi-classical gravity. to specify these ensembles, we impose successively higher moments of the cft constraints. lastly, we propose a theory of pure gravity in ads$_3$ as a random matrix/tensor model implementing approximate cft constraints. this tensor model is the maximum ignorance ensemble compatible with conformal symmetry, crossing invariance, and a primary gap to the black-hole threshold. the resulting theory is a random matrix/tensor model governed by the virasoro 6j-symbol. | approximate cfts and random tensor models |
a class of tensor models were recently outlined as potentially calculable examples of holography: their perturbative large- n behavior is similar to the sachdev-ye-kitaev (syk) model, but they are fully quantum mechanical (in the sense that there is no quenched disorder averaging). these facts make them intriguing tentative models for quantum black holes. in this note, we explicitly diagonalize the simplest non-trivial gurau-witten tensor model and study its spectral and late-time properties. we find parallels to (a single sample of) syk where some of these features were recently attributed to random matrix behavior and quantum chaos. in particular, the spectral form factor exhibits a dip-ramp-plateau structure after a running time average, in qualitative agreement with syk. but we also observe that even though the spectrum has a unique ground state, it has a huge (quasi-?)degeneracy of intermediate energy states, not seen in syk. if one ignores the delta function due to the degeneracies however, there is level repulsion in the unfolded spacing distribution hinting chaos. furthermore, there are gaps in the spectrum. the system also has a spectral mirror symmetry which we trace back to the presence of a unitary operator with which the hamiltonian anticommutes. we use it to argue that to the extent that the model exhibits random matrix behavior, it is controlled not by the dyson ensembles, but by the bdi (chiral orthogonal) class in the altland-zirnbauer classification. | quantum chaos and holographic tensor models |
recent works have revealed that quantum extremal islands can contribute to the fine-grained entropy of black hole radiation reproducing the unitary page curve. in this paper, we use these results to assess if an observer in de sitter space can decode information hidden behind their cosmological horizon. by computing the fine-grained entropy of the gibbons-hawking radiation in a region where gravity is weak we find that this is possible, but the observer's curiosity comes at a price. at the same time the island appears, which happens much earlier than the page time, a singularity forms which the observer will eventually hit. we arrive at this conclusion by studying de sitter space in jackiw-teitelboim gravity. we emphasize the role of the observer collecting radiation, breaking the thermal equilibrium studied so far in the literature. by analytically solving for the backreacted geometry we show how an island appears in this out-of-equilibrium state. | the price of curiosity: information recovery in de sitter space |
numerical relativity is an essential tool in studying the coalescence of binary black holes (bbhs). it is still computationally prohibitive to cover the bbh parameter space exhaustively, making phenomenological fitting formulas for bbh waveforms and final-state properties important for practical applications. we describe a general hierarchical bottom-up fitting methodology to design and calibrate fits to numerical relativity simulations for the three-dimensional parameter space of quasicircular nonprecessing merging bbhs, spanned by mass ratio and by the individual spin components orthogonal to the orbital plane. particular attention is paid to incorporating the extreme-mass-ratio limit and to the subdominant unequal-spin effects. as an illustration of the method, we provide two applications, to the final spin and final mass (or equivalently: radiated energy) of the remnant black hole. fitting to 427 numerical relativity simulations, we obtain results broadly consistent with previously published fits, but improving in overall accuracy and particularly in the approach to extremal limits and for unequal-spin configurations. we also discuss the importance of data quality studies when combining simulations from diverse sources, how detailed error budgets will be necessary for further improvements of these already highly accurate fits, and how this first detailed study of unequal-spin effects helps in choosing the most informative parameters for future numerical relativity runs. | hierarchical data-driven approach to fitting numerical relativity data for nonprecessing binary black holes with an application to final spin and radiated energy |
we revisit the complexity = action proposal for charged black holes. we investigate the complexity for a dyonic black hole, and we find the surprising feature that the late-time growth is sensitive to the ratio between electric and magnetic charges. in particular, the late-time growth rate vanishes when the black hole carries only a magnetic charge. if the dyonic black hole is perturbed by a light shock wave, a similar feature appears for the switchback effect, e.g. it is absent for purely magnetic black holes. we then show how the inclusion of a surface term to the action can put the electric and magnetic charges on an equal footing, or more generally change the value of the late-time growt rate. next, we investigate how the causal structure influences the late-time growth with and without the surface term for charged black holes in a family of einstein-maxwell-dilaton theories. finally, we connect the previous discussion to the complexity=action proposal for the two-dimensional jackiw-teitelboim theory. since the two-dimensional theory is obtained by a dimensional reduction from einstein-maxwell theory in higher dimensions in a near-extremal and near-horizon limit, the choices of parent action and parent background solution determine the behaviour of holographic complexity in two dimensions. | holographic complexity equals which action? |
within general relativity, the unique stationary solution of an isolated black hole is the kerr spacetime, which has a peculiar multipolar structure depending only on its mass and spin. we develop a general method to extract the multipole moments of arbitrary stationary spacetimes and apply it to a large family of horizonless microstate geometries. the latter can break the axial and equatorial symmetry of the kerr metric and have a much richer multipolar structure, which provides a portal to constrain fuzzball models phenomenologically. we find numerical evidence that all multipole moments are typically larger (in absolute value) than those of a kerr black hole with the same mass and spin. current measurements of the quadrupole moment of black-hole candidates could place only mild constraints on fuzzballs, while future gravitational-wave detections of extreme mass-ratio inspirals with the space mission lisa will improve these bounds by orders of magnitude. | distinguishing fuzzballs from black holes through their multipolar structure |
the classical scattering of spinning objects is well described by the spinor-helicity formalism for heavy particles. using these variables, we derive spurious-pole-free, all-spin opposite-helicity compton amplitudes (factorizing on physical poles to the minimal, all-spin three-point amplitudes) in the classical limit for qed, qcd, and gravity. the cured amplitudes are subject to deformations by contact terms, the vast majority of whose contributions we can fix by imposing a relation between spin structures — motivated by lower spin multipoles of black hole scattering — at the second post-minkowskian (2pm) order. for qed and gravity, this leaves a modest number of unfixed coefficients parametrizing contact-term deformations, while the qcd amplitude is uniquely determined. our gravitational compton amplitude allows us to push the state-of-the-art of spinning-2pm scattering to any order in the spin vectors of both objects; we present results here and in the supplementary material file 2pmspin8aux.nb up to eighth order in the spin vectors. interestingly, despite leftover coefficients in the compton amplitude, imposing the aforementioned relation between spin structures uniquely fixes some higher-spin parts of the 2pm amplitude. | searching for kerr in the 2pm amplitude |
the ligo/virgo detections of binary black hole mergers marked a watershed moment in astronomy, ushering in the era of precision tests of kerr dynamics. we review theoretical and experimental challenges that must be overcome to carry out black hole spectroscopy with present and future gravitational wave detectors. among other topics, we discuss quasinormal mode excitation in binary mergers, astrophysical event rates, tests of black hole dynamics in modified theories of gravity, parameterized "post-kerr" ringdown tests, exotic compact objects, and proposed data analysis methods to improve spectroscopic tests of kerr dynamics by stacking multiple events. | extreme gravity tests with gravitational waves from compact binary coalescences: (ii) ringdown |
it was shown by tsallis and cirto that thermodynamical entropy of a gravitational system such as black hole must be generalized to the non-additive entropy, which is given by sh = γaβ, where a is the horizon area and β is the nonextensive parameter [1]. in this paper, by taking the entropy associated with the apparent horizon of the friedmann-robertson-walker (frw) universe in the form of tsallis entropy, and assuming the first law of thermodynamics, de =th dsh + wdv, holds on the apparent horizon, we are able to derive the corresponding friedmann equations describing the dynamics of the universe with any spatial curvature. we also examine the time evolution of the total entropy and show that the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. then, modifying the emergence proposal of gravity proposed by padmanabhan and calculating the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space, we again arrive at the modified friedmann equation of the frw universe with any spatial curvature which is the same as one obtained from the first law of thermodynamics. we also study the cosmological consequences of tsallis cosmology. interestingly enough, we find that this model can explain simultaneously the late time acceleration in the universe filled with pressureless matter without invoking dark energy, as well as the early deceleration. besides, the age problem can be circumvented automatically for an accelerated universe and is estimated larger than 3/2 age of the universe in standard cosmology. taking β = 2 / 5, we find the age of the universe ranges as 13.12 gyr <t0 < 16.32 gyr, which is consistent with recent observations. finally, using the jeans's analysis, we comment, in brief, on the density perturbation in the context of tsallis cosmology and found that the growth of energy differs compared to the standard cosmology. | modified friedmann equations from tsallis entropy |
we study the thermodynamics of ads4 black hole solutions of einstein-maxwell theory that are accelerating, rotating, and carry electric and magnetic charges. we focus on the class for which the black hole horizon is a spindle and can be uplifted on regular sasaki-einstein spaces to give solutions of d =11 supergravity that are free from conical singularities. we use holography to calculate the euclidean on-shell action and to define a set of conserved charges which give rise to a first law. we identify a complex locus of supersymmetric and nonextremal solutions, defined through an analytic continuation of the parameters, upon which we obtain a simple expression for the on-shell action. a legendre transform of this action combined with a reality constraint then leads to the bekenstein-hawking entropy for the class of supersymmetric and extremal black holes. | thermodynamics of accelerating and supersymmetric ads4 black holes |
ultrathin black phosphorus is a two-dimensional semiconductor with a sizeable band gap. its excellent electronic properties make it attractive for applications in transistor, logic and optoelectronic devices. however, it is also the first widely investigated two-dimensional material to undergo degradation upon exposure to ambient air. therefore a passivation method is required to study the intrinsic material properties, understand how oxidation affects the physical properties and enable applications of phosphorene. here we demonstrate that atomically thin graphene and hexagonal boron nitride can be used for passivation of ultrathin black phosphorus. we report that few-layer pristine black phosphorus channels passivated in an inert gas environment, without any prior exposure to air, exhibit greatly improved n-type charge transport resulting in symmetric electron and hole transconductance characteristics. | transport properties of pristine few-layer black phosphorus by van der waals passivation in an inert atmosphere |
we construct the first family of horizonless supergravity solutions that have the same mass, charges, and angular momenta as general supersymmetric rotating d 1 -d 5 -p black holes in five dimensions. this family includes solutions with arbitrarily small angular momenta, deep within the regime of quantum numbers and couplings for which a large classical black hole exists. these geometries are well approximated by the black-hole solution, and in particular exhibit the same near-horizon throat. deep in this throat, the black-hole singularity is resolved into a smooth cap. we also identify the holographically dual states in the n =(4 ,4 ) d 1 -d 5 orbifold conformal field theory (cft). our solutions are among the states counted by the cft elliptic genus, and provide examples of smooth microstate geometries within the ensemble of supersymmetric black-hole microstates. | smooth horizonless geometries deep inside the black-hole regime |
we construct a family of non-supersymmetric extremal black holes and their horizonless microstate geometries in four dimensions. the black holes can have finite angular momentum and an arbitrary charge-to-mass ratio, unlike their supersymmetric cousins. these features make them and their microstate geometries astrophysically relevant. thus, they provide interesting prototypes to study deviations from kerr solutions caused by new horizon-scale physics. in this paper, we compute the gravitational multipole structure of these solutions and compare them to kerr black holes. the multipoles of the black hole differ significantly from kerr as they depend non-trivially on the charge-to-mass ratio. the horizonless microstate geometries (that are comparable in size to a black hole) have a similar multipole structure as their corresponding black hole, with deviations to the black hole multipole values set by the scale of their microstructure. | gravitational footprints of black holes and their microstate geometries |
we establish a precise relation between the modular bootstrap, used to con- strain the spectrum of 2d cfts, and the sphere packing problem in euclidean geometry. the modular bootstrap bound for chiral algebra u(1)c maps exactly to the cohn-elkies linear programming bound on the sphere packing density in d = 2c dimensions. we also show that the analytic functionals developed earlier for the correlator conformal bootstrap can be adapted to this context. for c = 4 and c = 12, these functionals exactly repro- duce the "magic functions" used recently by viazovska [1] and cohn et al. [2] to solve the sphere packing problem in dimensions 8 and 24. the same functionals are also applied to general 2d cfts, with only virasoro symmetry. in the limit of large central charge, we relate sphere packing to bounds on the black hole spectrum in 3d quantum gravity, and prove analytically that any such theory must have a nontrivial primary state of dimension δ0<∼c /8.503. | sphere packing and quantum gravity |
these lecture notes are intended for starting phd students in theoretical physics who have a working knowledge of general relativity. the 4 topics covered are (1) surface charges as conserved quantities in theories of gravity; (2) classical and holographic features of three-dimensional einstein gravity; (3) asymptotically flat spacetimes in 4 dimensions: bms group and memory effects; (4) the kerr black hole: properties at extremality and quasi-normal mode ringing. each topic starts with historical foundations and points to a few modern research directions. | advanced lectures on general relativity |
in three-dimensional de sitter space classical black holes do not exist, and the schwarzschild-de sitter solution instead describes a conical defect with a single cosmological horizon. we argue that the quantum backreaction of conformal fields can generate a black hole horizon, leading to a three-dimensional quantum de sitter black hole. its size can be as large as the cosmological horizon in a nariai-type limit. we show explicitly how these solutions arise using braneworld holography, but also compare to a non-holographic, perturbative analysis of backreaction due to conformally coupled scalar fields in conical de sitter space. we analyze the thermodynamics of this quantum black hole, revealing it behaves similarly to its classical four-dimensional counterpart, where the generalized entropy replaces the classical bekenstein-hawking entropy. we compute entropy deficits due to nucleating the three-dimensional black hole and revisit arguments for a possible matrix model description of ds spacetimes. finally, we comment on the holographic dual description for ds spacetimes as seen from the braneworld perspective. | black holes in ds3 |
we prove that non-extremal black holes in four-dimensional general relativity exhibit an infinite-dimensional symmetry in their near horizon region. by prescribing a physically sensible set of boundary conditions at the horizon, we derive the algebra of asymptotic killing vectors, which is shown to be infinite-dimensional and includes, in particular, two sets of supertranslations and two mutually commuting copies of the witt algebra. we define the surface charges associated to the asymptotic diffeomorphisms that preserve the boundary conditions and discuss the subtleties of this definition, such as the integrability conditions and the correct definition of the dirac brackets. when evaluated on the stationary solutions, the only non-vanishing charges are the zero-modes. one of them reproduces the bekenstein-hawking entropy of kerr black holes. we also study the extremal limit, recovering the nhek geometry. in this singular case, where the algebra of charges and the integrability conditions get modified, we find that the computation of the zero-modes correctly reproduces the black hole entropy. furthermore, we analyze the case of three spacetime dimensions, in which the integrability conditions notably simplify and the field equations can be solved analytically to produce a family of exact solutions that realize the boundary conditions explicitly. we examine other features, such as the form of the algebra in the extremal limit and the relation to other works in the literature. | extended symmetries at the black hole horizon |
we study weakly coupled u(1) theories in ads3, their associated charged btz solutions, and their charged spectra. we find that modular invariance of the holographic dual two-dimensional cft and compactness of the gauge group together imply the existence of charged operators with conformal dimension significantly below the black hole threshold. we regard this as a form of the weak gravity conjecture (wgc) in three dimensions. we also explore the constraints posed by modular invariance on a particular discrete &z;nsymmetry which arises in our discussion. in this case, modular invariance does not guarantee the existence of light &z;n-charged states. we also highlight the differences between our discussion and the usual heuristic arguments for the wgc based on black hole remnants. | the weak gravity conjecture in three dimensions |
we study the boundary description of the volume of maximal cauchy slices using the recently derived equivalence between bulk and boundary symplectic forms. the volume of constant mean curvature slices is known to be canonically conjugate to "york time". we use this to construct the boundary deformation that is conjugate to the volume in a handful of examples, such as empty ads, a backreacting scalar condensate, or the thermofield double at infinite time. we propose a possible natural boundary interpretation for this deformation and use it to motivate a concrete version of the complexity=volume conjecture, where the boundary complexity is defined as the energy of geodesics in the kähler geometry of half sided sources. we check this conjecture for bañados geometries and a mini-superspace version of the thermofield double state. finally, we show that the precise dual of the quantum information metric for marginal scalars is given by a particularly simple symplectic flux, instead of the volume as previously conjectured. | complexity and the bulk volume, a new york time story |
we explore the construction and stability of asymptotically anti-de sitter euclidean wormholes in a variety of models. in simple ad hoc low-energy models, it is not hard to construct two-boundary euclidean wormholes that dominate over disconnected solutions and which are stable (lacking negative modes) in the usual sense of euclidean quantum gravity. indeed, the structure of such solutions turns out to strongly resemble that of the hawking-page phase transition for ads-schwarzschild black holes, in that for boundary sources above some threshold we find both a 'large' and a 'small' branch of wormhole solutions with the latter being stable and dominating over the disconnected solution for large enough sources. we are also able to construct two-boundary euclidean wormholes in a variety of string compactifications that dominate over the disconnected solutions we find and that are stable with respect to field-theoretic perturbations. however, as in classic examples investigated by maldacena and maoz, the wormholes in these uv-complete settings always suffer from brane-nucleation instabilities (even when sources that one might hope would stabilize such instabilities are tuned to large values). this indicates the existence of additional disconnected solutions with lower action. we discuss the significance of such results for the factorization problem of ads/cft. | ads euclidean wormholes |
we present what we believe is the first example of a "λ -line" phase transition in black hole thermodynamics. this is a line of (continuous) second order phase transitions which in the case of liquid 4he marks the onset of superfluidity. the phase transition occurs for a class of asymptotically anti-de sitter hairy black holes in lovelock gravity where a real scalar field is conformally coupled to gravity. we discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur. | superfluid black holes |
we show that an extremely generic class of two-dimensional conformal field theories (cfts) contains a sector described by the schwarzian theory. this applies to theories with no additional symmetries and large central charge, but does not require a holographic dual. specifically, we use bootstrap methods to show that in the grand canonical ensemble, at low temperature with a chemical potential sourcing large angular momentum, the density of states and correlation functions are determined by the schwarzian theory, up to parametrically small corrections. in particular, we compute out-of-time-order correlators in a controlled approximation. for holographic theories, these results have a gravitational interpretation in terms of large, near-extremal rotating btz black holes, which have a near horizon throat with nearly ads2 × s1 geometry. the schwarzian describes strongly coupled gravitational dynamics in the throat, which can be reduced to jackiw-teitelboim (jt) gravity interacting with a u(1) field associated to transverse rotations, coupled to matter. we match the physics in the throat to observables at the ads3 boundary, reproducing the cft results. | a universal schwarzian sector in two-dimensional conformal field theories |
we obtain an exact vacuum solution from the gravity sector contained in the minimal standard-model extension. the theoretical model assumes a riemann spacetime coupled to the bumblebee field which is responsible for the spontaneous lorentz symmetry breaking. the solution achieved in a static and spherically symmetric scenario establishes a schwarzschild-like black hole. in order to study the effects of the spontaneous lorentz symmetry breaking we investigate some classic tests, including the advance of perihelion, the bending of light, and shapiro's time delay. furthermore, we compute some upper bounds, among which the most stringent associated with existing experimental data provides a sensitivity at the 10-15 level and that for future missions at the 10-19 level. | exact schwarzschild-like solution in a bumblebee gravity model |
we study the logarithmic corrections to various cft partition functions in the context of the ads$_4$/cft$_3$ correspondence for theories arising on the worldvolume of m2-branes. we utilize four-dimensional gauged supergravity and heat kernel methods and present general expressions for the logarithmic corrections to the gravitational on-shell action and black hole entropy for a number of different supergravity backgrounds. we outline several subtle features of these calculations and contrast them with a similar analysis of logarithmic corrections performed directly in the eleven-dimensional uplift of a given four-dimensional supergravity background. we find results consistent with ads/cft provided that the infinite sum over kk modes on the internal space is regularized in a specific manner. this analysis leads to an explicit expression for the logarithmic correction to the bekenstein-hawking entropy of large kerr-newmann and reissner-nordström black holes in ads$_4$. our results also have important implications for effective field theory coupled to gravity in ads$_4$ and for the existence of scale-separated ads$_4$ vacua in string theory, which come in the form of new constraints on the field content and mass spectrum of matter fields. | a compendium of logarithmic corrections in ads/cft |
in this work we complete the spin-dependent conservative dynamics of inspiralling compact binaries at the fourth post-newtonian order, and in particular the derivation of the next-to-next-to-leading order spin-squared interaction potential. we derive the physical equations of motion of the position and the spin from a direct variation of the action. further, we derive the quadratic-in-spin hamiltonians, as well as their expressions in the center-of-mass frame. we construct the conserved integrals of motion, which form the poincaré algebra. this construction provided a consistency check for the validity of our result, which is crucial in particular in the current absence of another independent derivation of the next-to-next-to-leading order spin-squared interaction. finally, we provide here the complete gauge-invariant relations among the binding energy, angular momentum, and orbital frequency of an inspiralling binary with generic compact spinning components to the fourth post-newtonian order. these high post-newtonian orders, in particular taking into account the spins of the binary constituents, will enable to gain more accurate information on the constituents from even more sensitive gravitational-wave detections to come. | complete conservative dynamics for inspiralling compact binaries with spins at the fourth post-newtonian order |
we investigate the entanglement between the eternal black hole and hawking radiation. for this purpose, we utilize the doubly holographic theories and study the entanglement entropy of the radiation to find the page curve consistent with the unitarity principle. doubly holographic theories introduce two types of boundaries in the ads bulk, namely the usual anti-de sitter boundary and the planck brane. in such a setup, we calculate the entanglement entropy by examining two extremal surfaces: the hartman-maldacena (hm) surface and the island surface. the latter surface emerges when the island appears on the planck brane. in this paper, we provide a detailed analysis of dyonic black holes with regard to the page curve in the context of the doubly holographic setup. to begin with, we ascertain that the pertinent topological terms must be included in the planck brane to describe the systems at finite density and magnetic field. furthermore, we also develop a general numerical method to compute the time-dependent hm surface and achieve excellent agreement between the numerical results and analytical expressions. utilizing numerical methodology, we find that the entanglement entropy of dyonic black holes exhibits unitary evolution over time, wherein it grows in early time and reaches saturation after the page time. the initial growth can be explained by the hm surface, while the saturation is attributed to the island surface. in addition, using the holographic entanglement density, we also show that, for the first time, the saturated value of the entanglement entropy is twice the bekenstein-hawking entropy with the tensionless brane in double holography. | entanglement entropy analysis of dyonic black holes using doubly holographic theory |
certain holographic states of matter with a global u(1) symmetry support a sound mode at zero temperature, caused neither by spontaneous symmetry breaking of the global u(1) nor by the emergence of a fermi surface in the infrared. in this work, we show that such a mode is also found in zero density holographic quantum critical states. we demonstrate that in these states, the appearance of a zero temperature sound mode is the consequence of a mixed `t hooft anomaly between the global u(1) symmetry and an emergent higher-form symmetry. at non-zero temperatures, the presence of a black hole horizon weakly breaks the emergent symmetry and gaps the collective mode, giving rise to a sharp drude-like peak in the electric conductivity. a similar gapped mode arises at low temperatures for non-zero densities when the state has an emergent lorentz symmetry, also originating from an approximate anomalous higher-form symmetry. however, in this case the collective excitation does not survive at zero temperature where, instead, it dissolves into a branch cut due to strong backreaction from the infrared, critical degrees of freedom. we comment on the relation between our results and the application of the luttinger theorem to compressible holographic states of matter. | zero sound and higher-form symmetries in compressible holographic phases |
we study the extended thermodynamics, obtained by considering the cosmological constant as a thermodynamic variable, of stu black holes in 4-dimensions in the fixed charge ensemble. the associated phase structure is conjectured to be dual to an rg-flow on the space of field theories. we find that for some charge configurations the phase structure resembles that of a van der waals gas: the system exhibits a family of first order phase transitions ending in a second order phase transition at a critical temperature. we calculate the holographic entanglement entropy for several charge configurations and show that for the cases where the gravity background exhibits van der waals behavior, the entanglement entropy presents a transition at the same critical temperature. to further characterize the phase transition we calculate appropriate critical exponents and show that they coincide. thus, the entanglement entropy successfully captures the information of the extended phase structure. finally, we discuss the physical interpretation of the extended space in terms of the boundary qft and construct various holographic heat engines dual to stu black holes. | holographic entanglement entropy and the extended phase structure of stu black holes |
the topological classification of critical points of black holes in 4d einstein-gauss-bonnet gravity coupled to born-infeld theory is investigated. considered independently, born-infeld corrections to the einstein action alter the topological charge of critical points of the charged ads black hole system, whereas the gauss-bonnet corrections do not. for the combined system though, the topological charge of the einstein-gauss-bonnet theory is unaltered in the presence of born-infeld coupling. | topology of born-infeld ads black holes in 4d novel einstein-gauss-bonnet gravity |
the entanglement properties of random pure states are relevant to a variety of problems ranging from chaotic quantum dynamics to black-hole physics. the averaged bipartite entanglement entropy of such states admits a volume law and upon increasing the subregion size follows the page curve. in this paper, we generalize this setup to random mixed states by coupling the system to a bath and use the partial transpose to study their entanglement properties. we develop a diagrammatic method to incorporate partial transpose within random matrix theory and formulate a perturbation theory in 1 /l , the inverse of the hilbert-space dimension. we compute several quantities including the spectral density of partial transpose (or entanglement negativity spectrum), two-point correlator of eigenvalues, and the logarithmic negativity. as long as the bath is smaller than the system, we find that upon sweeping the subregion size, the logarithmic negativity shows an initial increase and a final decrease similar to the page curve, while it admits a plateau in the intermediate regime where the logarithmic negativity depends only on the size of the system and of the bath but not on how the system is partitioned. this intermediate phase has no analog in random pure states, and is separated from the two other regimes by a critical point. we further show that when the bath is larger than the system by at least two extra qubits the logarithmic negativity is identically zero, which implies that there is no distillable entanglement. using the diagrammatic approach, we provide a simple derivation of the semicircle law of the entanglement negativity spectrum in the latter two regimes. we show that despite the appearance of a semicircle distribution, reminiscent of gaussian unitary ensemble (gue), the higher-order corrections to the negativity spectrum and two-point correlator deviate from those of gue. | entanglement negativity spectrum of random mixed states: a diagrammatic approach |
many three-dimensional n=2 scfts admit a universal partial topological twist when placed on hyperbolic riemann surfaces. we exploit this fact to derive a universal formula which relates the planar limit of the topologically twisted index of these scfts and their three-sphere partition function. we then utilize this to account for the entropy of a large class of supersymmetric asymptotically ads4 magnetically charged black holes in m-theory and massive type iia string theory. in this context we also discuss novel ads2 solutions of eleven-dimensional supergravity which describe the near horizon region of large new families of supersymmetric black holes arising from m2-branes wrapping riemann surfaces. | a universal counting of black hole microstates in ads4 |
by following closely weinberg's soft theorem, which captures the 1/ω pole contribution to the amplitude for soft graviton emissions (ω < λ) on top of an arbitrary background hard process, we calculate the expectation value of the graviton's angular momentum operator for arbitrary collisions dressed with soft radiation. we find that the result becomes independent of the cutoff λ on the graviton's frequency, effectively localizing at ω = 0. in this way, our result captures the contribution to the angular momentum that comes from the zero-frequency modes. like the soft theorem, our formula has an exact dependence on the kinematics of the hard particles and is only a function of their momenta. as an example, we discuss in some detail the case of the 2 → 2 scattering of spinless particles in general relativity and n = 8 supergravity. | angular momentum of zero-frequency gravitons |
we classify and study defects in 2d jackiw-teitelboim gravity. we show these are holographically described by a deformation of the schwarzian theory where the reparametrization mode is integrated over different coadjoint orbits of the virasoro group. we show that the quantization of each coadjoint orbit is connected to 2d liouville cft between branes with insertions of verlinde loop operators. we also propose an interpretation for the exceptional orbits. we use this perspective to solve these deformations of the schwarzian theory, computing their partition function and correlators. in the process, we define two geometric observables: the horizon area operator φ hand the geodesic length operator l( γ). we show this procedure is structurally related to the deformation of the particle-on-a-group quantum mechanics by the addition of a chemical potential. as an example, we solve the low-energy theory of complex syk with a u(1) symmetry and generalize to the non-abelian case. | defects in jackiw-teitelboim quantum gravity |
we study the gravitational description of extremal supersymmetric black holes. we point out that the ads_2ads2 near horizon geometry can be used to compute interesting observables, such as correlation functions of operators. in this limit, the hamiltonian is zero and correlation functions are time independent. we discuss some possible implications for the gravity description of black hole microstates. we also compare with numerical results in a supersymmetric version of syk. these results can also be interpreted as providing a construction of wormholes joining two extremal black holes. this is the short version of a longer and more technical companion paper [scipost phys. 14, 128 (2023)]. | holography for people with no time |
in this work, we propose a testing procedure to distinguish between the different approaches for computing complexity. our test does not require a direct comparison between the approaches and thus avoids the issue of choice of gates, basis, etc. the proposed testing procedure employs the information-theoretic measures loschmidt echo and fidelity; the idea is to investigate the sensitivity of the complexity (derived from the different approaches) to the evolution of states. we discover that only circuit complexity obtained directly from the wave function is sensitive to time evolution, leaving us to claim that it surpasses the other approaches. we also demonstrate that circuit complexity displays a universal behaviour — the complexity is proportional to the number of distinct hamiltonian evolutions that act on a reference state. due to this fact, for a given number of hamiltonians, we can always find the combination of states that provides the maximum complexity; consequently, other combinations involving a smaller number of evolutions will have less than maximum complexity and, hence, will have resources. finally, we explore the evolution of complexity in non-local theories; we demonstrate the growth of complexity is sustained over a longer period of time as compared to a local theory. | time evolution of complexity: a critique of three methods |
we re-examine the black hole solutions in classical theories of dilaton gravity in two dimensions. we consider an arbitrary dilaton potential such that there are black hole solutions asymptotic at infinity to the nearly $\mathrm{ads}_2$ solutions of jt gravity, and such that the black hole energy and entropy are bounded below. we show that if there is a black hole solution with negative specific heat at some temperature $t$, then at the same temperature there is a black hole solution with lower free energy and positive specific heat. as the temperature is increased from 0 to infinity, the black hole energy and entropy increase monotonically but not necessarily continuously; there can be first order phase transitions, similar to the hawking-page transition. these theories can also have solutions corresponding to closed universes. | deformations of jt gravity and phase transitions |
we explore the celestial holography proposal for non-trivial asymptotically flat backgrounds including the coulomb field of a static and spinning point charge, their gravitational counterparts described by the schwarzschild and kerr metrics, as well as the aichelburg-sexl shockwave and spinning shockwave geometries and their electromagnetic cousins. we compute celestial two-point amplitudes on these kerr-schild type backgrounds which have the desirable feature, due to the presence of an external source, that they are non-vanishing for general operator positions and are not constrained by the kinematic delta functions of flat space celestial cft correlators. of particular interest is the case of shockwave backgrounds where the two-point scattering amplitude of massless scalars can be interpreted as a standard cft three-point correlator between two massless asymptotic states and a conformal primary shockwave operator. we furthermore show that the boundary on-shell action for general backgrounds becomes the generating functional for tree-level correlation functions in celestial cft. finally, we derive (conformal) faddeev-kulish dressings for particle-like backgrounds which remove all infrared divergent terms in the two-point functions to all orders in perturbation theory. | celestial holography on kerr-schild backgrounds |
given a solution to 4d einstein gravity with an isometry direction, it is known that the equations of motion are identical to those of a 3d σ model with target space geometry s u (1 ,1 )/u (1 ). thus, any transformation by s u (1 ,1 )≅s l (2 ,r ) is a symmetry for the action and allows one to generate new solutions in 4d. here we clarify and extend recent work on electromagnetic (em) duality in the context of the classical double copy. in particular, for pure gravity, we identify an explicit map between the maxwell field of the single copy and the scalars in the target space, allowing us to identify the u (1 )⊂s l (2 ,r ) symmetry dual to em duality in the single copy. moreover, we extend the analysis to einstein-maxwell theory, where we highlight the role of ehlers-harrison transformations and, for spherically symmetric charged black hole solutions, we interpret the equations of motion as a truncation of the putative single copy for einstein-yang-mills theory. | ehlers transformations as em duality in the double copy |
we compute the four-momentum radiated during the scattering of two spinless bodies, at leading order in the newton's contant g and at all orders in the velocities, using the effective field theory worldline approach. following [1], we derive the conserved stress-energy tensor linearly coupled to gravity generated by localized sources, at leading and next-to-leading order in g, and from that the classical probability amplitude of graviton emission. the total emitted momentum is obtained by phase-space integration of the graviton momentum weighted by the modulo squared of the radiation amplitude. we recast this as a two-loop integral that we solve using techniques borrowed from particle physics, such as reverse unitarity, reduction to master integrals by integration-by-parts identities and canonical differential equations. the emitted momentum agrees with recent results obtained by other methods. our approach provides an alternative way of directly computing radiated observables in the post-minkowskian expansion without going through the classical limit of scattering amplitudes. | radiated momentum in the post-minkowskian worldline approach via reverse unitarity |
dijet events are studied in the proton--proton collision dataset recorded at $\sqrt{s}=$13 tev with the atlas detector at the large hadron collider in 2015 and 2016, corresponding to integrated luminosities of 3.5 fb$^{-1}$ and 33.5 fb$^{-1}$ respectively. invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. for resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. the dataset is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. excited quarks with masses below 6.0 tev are excluded, and limits are set on quantum black holes, heavy w' bosons, w* bosons, and a range of masses and couplings in a z' dark matter mediator model. model-independent limits on signals with a gaussian shape are also set, using a new approach allowing factorization of physics and detector effects. from the angular distributions, a scale of new physics in contact interaction models is excluded for scenarios with either constructive or destructive interference. these results represent a substantial improvement over those obtained previously with lower integrated luminosity. | search for new phenomena in dijet events using 37 fb$^{-1}$ of $pp$ collision data collected at $\\sqrt{s}=$13 tev with the atlas detector |
we study the holographic dual of the extended thermodynamics of spherically symmetric, charged ads black holes in the context of the ads/cft correspondence. the gravitational thermodynamics of ads black holes can be extended by allowing for variations of the cosmological constant and newton's constant. in the dual cft this corresponds to including the central charge c and its chemical potential μ as a new pair of conjugate thermodynamic variables, in addition to the standard pairs: temperature vs. entropy (t, s), electric potential vs. charge (φ ~,q ~) and field theory pressure vs. volume (p,v ). for the (grand) canonical ensembles at fixed (q ~,v ,c ), (φ ~,v ,c ) and (q ~,v ,μ ), based on the holographic dictionary, we argue the cft description of charged ads black holes contains either critical phenomena or interesting phase behaviour. in the fixed (q ~,v ,μ ) we find a new zeroth-order phase transition between a high- and low-entropy phase at some μ-dependent temperature. finally, we point out there is no critical behaviour in the fixed p ensembles, i.e. there is no p − v criticality, and hence the cft state dual to a classical charged black hole cannot be a van der waals fluid. whether or not this phase structure is supported by cft computations remains an interesting open question. | holographic cft phase transitions and criticality for charged ads black holes |
we study the index of 4d n =4 yang-mills theory with u (n ) gauge group, focusing on the physics of the dual bogomolny-prasad-sommerfield black holes in ads5×s5. certain aspects of these black holes can be studied from finite n indices with reasonably large n2. we make numerical studies of the index for n ≤6 , by expanding it up to reasonably high orders in the fugacity. the entropy of the index agrees very well with the bekenstein-hawking entropy of the dual black holes, say at n2=25 or 36. our data clarifies and supports the recent ideas which allowed analytic studies of these black holes from the index, such as the complex saddle points of the legendre transformation and the oscillating signs in the index. in particular, the complex saddle points naturally explain the 1/n -subleading oscillating patterns of the index. we also illustrate the universality of our ideas by studying a model given by the inverse of the macmahon function. | ads black holes and finite n indices |
we introduce a formulation for spinning gravitating objects in the effective field theory in the post-newtonian scheme in the context of the binary inspiral problem. we aim at an effective action, where all field modes below the orbital scale are integrated out. we spell out the relevant degrees of freedom, in particular the rotational ones, and the associated symmetries. building on these symmetries, we introduce the minimal coupling part of the point particle action in terms of gauge rotational variables, and construct the spin-induced nonminimal couplings, where we obtain the leading order couplings to all orders in spin. we specify the gauge for the rotational variables, where the unphysical degrees of freedom are eliminated already from the feynman rules, and all the orbital field modes are integrated out. the equations of motion of the spin can be directly obtained via a proper variation of the action, and hamiltonians may be straightforwardly derived. we implement this effective field theory for spin to derive all spin dependent potentials up to next-to-leading order to quadratic level in spin, namely up to the third post-newtonian order for rapidly rotating compact objects. in particular, the proper next-to-leading order spin-squared potential and hamiltonian for generic compact objects are also derived. for the implementations we use the nonrelativistic gravitational field decomposition, which is found here to eliminate higher-loop feynman diagrams also in spin dependent sectors, and facilitates derivations. this formulation for spin is thus ideal for treatment of higher order spin dependent sectors. | spinning gravitating objects in the effective field theory in the post-newtonian scheme |
there has been recent progress in understanding chaotic features in many-body quantum systems. motivated by the scrambling of information in black holes, it has been suggested that the time dependence of out-of-time-ordered (oto) correlation functions such as <o2(t ) o1(0 ) o2(t ) o1(0 ) > is a faithful measure of quantum chaos. experimentally, these correlators are challenging to access since they apparently require access to both forward and backward time evolution with the system hamiltonian. here we propose a protocol to measure such oto correlators using an ancilla that controls the direction of time. specifically, by coupling the state of the ancilla to the system hamiltonian of interest, we can emulate the forward and backward time propagation, where the ancilla plays the role of a quantum clock. within this scheme, the continuous evolution of the entire system (the system of interest and the ancilla) is governed by a time-independent hamiltonian. we discuss the implementation of our protocol with current circuit-qed technology for a class of interacting hamiltonians. our protocol is immune to errors that could occur when the direction of time evolution is externally controlled by a classical switch. | measurement of many-body chaos using a quantum clock |
the membrane paradigm displays underlying connections between a timelike stretched horizon and a null boundary (such as a black hole horizon) and bridges the gravitational dynamics of the horizon with fluid dynamics. in this work, we revisit the membrane viewpoint of a finite distance null boundary and present a unified geometrical treatment to the stretched horizon and the null boundary based on the rigging technique of hypersurfaces. this allows us to provide a unified geometrical description of null and timelike hypersurfaces, which resolves the singularity of the null limit appearing in the conventional stretched horizon description. we also extend the carrollian fluid picture and the geometrical carrollian description of the null horizon, which have been recently argued to be the correct fluid picture of the null boundary, to the stretched horizon. to this end, we draw a dictionary between gravitational degrees of freedom on the stretched horizon and the carrollian fluid quantities and show that einstein's equations projected onto the horizon are the carrollian hydrodynamic conservation laws. lastly, we report that the gravitational pre-symplectic potential of the stretched horizon can be expressed in terms of conjugate variables of carrollian fluids and also derive the carrollian conservation laws and the corresponding noether charges from symmetries. | carrollian hydrodynamics and symplectic structure on stretched horizons |
we show that a holographic description of four-dimensional asymptotically locally flat spacetimes is reached smoothly from the zero-cosmological-constant limit of anti-de sitter holography. to this end, we use the derivative expansion of fluid/gravity correspondence. from the boundary perspective, the vanishing of the bulk cosmological constant appears as the zero velocity of light limit. this sets how carrollian geometry emerges in flat holography. the new boundary data are a two-dimensional spatial surface, identified with the null infinity of the bulk ricci-flat spacetime, accompanied with a carrollian time and equipped with a carrollian structure, plus the dynamical observables of a conformal carrollian fluid. these are the energy, the viscous stress tensors and the heat currents, whereas the carrollian geometry is gathered by a two-dimensional spatial metric, a frame connection and a scale factor. the reconstruction of ricci-flat spacetimes from carrollian boundary data is conducted with a flat derivative expansion, resummed in a closed form in eddington-finkelstein gauge under further integrability conditions inherited from the ancestor anti-de sitter set-up. these conditions are hinged on a duality relationship among fluid friction tensors and cotton-like geometric data. we illustrate these results in the case of conformal carrollian perfect fluids and robinson-trautman viscous hydrodynamics. the former are dual to the asymptotically flat kerr-taub-nut family, while the latter leads to the homonymous class of algebraically special ricci-flat spacetimes. | flat holography and carrollian fluids |
the optical appearance of a body compact enough to feature an unstable bound orbit, when surrounded by an accretion disk, is expected to be dominated by a luminous ring of radiation enclosing a central brightness depression typically known as the shadow. despite observational limitations, the rough details of this picture have been now confirmed by the results of the event horizon telescope (eht) collaboration on the imaging of the m87 and milky way supermassive central objects. however, the precise characterization of both features-ring and shadow-depends on the interaction between the background geometry and the accretion disk, thus being a fertile playground to test our theories on the nature of compact objects and the gravitational field itself in the strong-field regime. in this work we use both features in order to test a continuous family of solutions interpolating between regular black holes and horizonless compact objects, which arise within the eddington-inspired born-infeld theory of gravity, a viable extension of einstein's general relativity (gr). to this end we consider seven distinctive classes of such configurations (five black holes and two traversable wormholes) and study their optical appearances under illumination by a geometrically and optically thin accretion disk, emitting monochromatically with three analytic intensity profiles previously suggested in the literature. we build such images and consider the sub-ring structure created by light rays crossing the disk more than once and existing on top of the main ring of radiation. we discuss in detail the modifications as compared to their gr counterparts, the lyapunov exponents of unstable nearly-bound orbits, as well as the differences between black hole and traversable wormholes for the three intensity profiles. in addition we use the claim by the eht collaboration on the radius of the bright ring acting (under proper calibrations) as a proxy for the radius of the shadow itself to explore the parameter space of our solutions compatible with such a result. | shadows and photon rings of regular black holes and geonic horizonless compact objects |
black hole spectroscopy is the program to measure the complex gravitational wave frequencies of merger remnants, and to quantify their agreement with the characteristic frequencies of black holes computed at linear order in black hole perturbation theory. in a "weaker" (nonagnostic) version of this test, one assumes that the frequencies depend on the mass and spin of the final kerr black hole as predicted in perturbation theory. linear perturbation theory is expected to be a good approximation only at late times, when the remnant is close enough to a stationary kerr black hole. however, it has been claimed that a superposition of overtones with frequencies fixed at their asymptotic values in linear perturbation theory can reproduce the waveform strain even at the peak. is this overfitting, or are the overtones physically present in the signal? to answer this question, we fit toy models of increasing complexity, waveforms produced within linear perturbation theory, and full numerical relativity waveforms using both agnostic and nonagnostic ringdown models. we find that higher overtones are unphysical; their role is mainly to "fit away" features such as initial data effects, power-law tails, and (when present) nonlinearities. we then identify physical quasinormal modes by fitting numerical waveforms in the original, agnostic spirit of the no-hair test. we find that a physically meaningful ringdown model requires the inclusion of higher multipoles, quasinormal mode frequencies induced by spherical-spheroidal mode mixing, and nonlinear quasinormal modes. even in this "infinite signal-to-noise ratio" version of the original spectroscopy test, there is convincing evidence for the first overtone of the dominant multipole only well after the peak of the radiation. | agnostic black hole spectroscopy: quasinormal mode content of numerical relativity waveforms and limits of validity of linear perturbation theory |
we present the result of the quadratic-in-spin interaction hamiltonian for binary systems of rotating compact objects with generic spins, up to n3lo corrections within the post-newtonian expansion. the calculation is performed by employing the effective field theory diagrammatic approach, and it involves feynman integrals up to three loops, evaluated within the dimensional regularization scheme. the gauge-invariant binding energy and the scattering angle, in special kinematic regimes and spin configurations, are explicitly derived. the results extend our earlier study on the spin-orbit interaction effects. | gravitational quadratic-in-spin hamiltonian at nnnlo in the post-newtonian framework |
in this paper, we use the karch-randall braneworld to study theories of quantum gravity in two dimensional (nearly) anti-de sitter space (ads2). we focus on effective gravitational theories in the setup with two karch-randall branes embedded in an asymptotically ads3 bulk forming a wedge. we find the appearance of two-dimensional einstein-hilbert gravity (or the lorenzian version of the theory considered by marolf and maxfield) when the branes are rigid but the emergence of a class of dilaton gravity models parameterized by the tensions of the two branes when brane fluctuations are accounted for. a special case of our result is jackiw-teitelboim (jt) gravity, which has been proven useful to address many important problems in quantum gravity. an important implication of our work is that these models have holographic duals as one-dimensional quantum mechanics systems. at the end, we discuss a puzzle regarding the energy spectrum and its resolution. | aspects of ads2 quantum gravity and the karch-randall braneworld |
we demonstrate that the rotating four-dimensional gauss- bonnet black hole can act as a particle accelerator with arbitrarily high centre-of-mass (cm) energy, when collision of two general particles takes place near the event horizon. the particles are at rest initially at infinity, and by fine tuning their angular momenta within a finite range, they are released so that they follow the time-like geodesics in the black hole spacetime, and the collision taking place on the equatorial plane is observed. the gauss-bonnet coupling constant α, provides a deviation in the results, from that observed in the kerr black hole. the horizon structure, the range of allowed angular momentum and the critical angular momentum depend on the value of α. our results show that the cm energy depends on the coupling parameter α in addition to the black hole spin a. for extremal cases, the cm energy diverges at the horizon, suggesting that gauss-bonnet black hole can also act as a particle accelerator similar to a kerr black hole. for the non-extremal case, there exists a finite upper bound on the cm energy, the maximal value of which depends on the parameter α. | rotating 4d gauss-bonnet black hole as a particle accelerator |
recent work has shown that loop corrections from massless particles generate $\frac{3}{2}\log t_{\text{hawking}}$ corrections to black hole entropy which dominate the thermodynamics of cold near-extreme charged black holes. here we adapt this analysis to near-extreme kerr black holes. like ads$_2\times s^2$, the near-horizon extreme kerr (nhek) metric has a family of normalizable zero modes corresponding to reparametrizations of boundary time. the path integral over these zero modes leads to an infrared divergence in the one-loop approximation to the euclidean nhek partition function. we regulate this divergence by retaining the leading finite temperature correction in the nhek scaling limit. this "not-nhek" geometry lifts the eigenvalues of the zero modes, rendering the path integral infrared finite. the quantum-corrected near-extremal entropy exhibits $\frac{3}{2}\log t_{\text{hawking}}$ behavior characteristic of the schwarzian model and predicts a lifting of the ground state degeneracy for the extremal kerr black hole. | logarithmic corrections to kerr thermodynamics |
we develop an effective framework for the μ ¯ scheme of holonomy corrections motivated by loop quantum gravity for vacuum spherically symmetric space-times. this is done by imposing the areal gauge in the classical theory and then expressing the remaining components of the ashtekar-barbero connection in the hamiltonian constraint in terms of holonomies of physical length ℓpl. the stationary solutions to the effective hamiltonian constraint can be found exactly, and we give the explicit form of the effective metric in painlevé-gullstrand coordinates. this solution has the correct classical limit, the quantum gravity corrections decay rapidly at large distances, and curvature scalars are bounded by the planck scale, independently of the black hole mass m . in addition, the solution is valid for radii x ≥xmin∼(ℓpl2m )1/3 indicating the need for a matter field, with an energy density bounded by the planck scale, to provide a source for the curvature in the space-time. finally, for m ≫mpl, the space-time has an outer and also an inner horizon, within which the expansion for outgoing radial null geodesics becomes positive again. on the other hand, for sufficiently small m ∼mpl, there are no horizons at all in the effective metric. | effective loop quantum gravity framework for vacuum spherically symmetric spacetimes |
the standard black holes (bhs) in general relativity, as well as other ultracompact objects (with or without an event horizon) admit planar circular photon orbits. these light rings (lrs) determine several spacetime properties. for instance, stable lrs trigger instabilities and, in spherical symmetry, (unstable) lrs completely determine bh shadows. in generic stationary, axisymmetric spacetimes, nonplanar bound photon orbits may also exist, regardless of the integrability properties of the photon motion. we suggest a classification of these fundamental photon orbits (fpos) and, using poincaré maps, determine a criterion for their stability. for the kerr bh, all fpos are unstable (similar to its lrs) and completely determine the kerr shadow. but in non-kerr spacetimes, stable fpos may also exist, even when all lrs are unstable, triggering new instabilities. we illustrate this for the case of kerr bhs with proca hair, wherein, moreover, qualitatively novel shadows with a cuspy edge exist, a feature that can be understood from the interplay between stable and unstable fpos. fpos are the natural generalization of lrs beyond spherical symmetry and should generalize the lrs key role in different spacetime properties. | fundamental photon orbits: black hole shadows and spacetime instabilities |
much of the success of gravitational-wave astronomy rests on perturbation theory. historically, perturbative analysis of gravitational-wave sources has largely focused on post-newtonian theory. however, strong-field perturbation theory is essential in many cases such as the quasinormal ringdown following the merger of a binary system, tidally perturbed compact objects, and extreme-mass-ratio inspirals. in this review, motivated primarily by small-mass-ratio binaries but not limited to them, we provide an overview of essential methods in (i) black hole perturbation theory, (ii) orbital mechanics in kerr spacetime, and (iii) gravitational self-force theory. our treatment of black hole perturbation theory covers most common methods, including the teukolsky and regge-wheeler-zerilli equations, methods of metric reconstruction, and lorenz-gauge formulations, presenting them in a new consistent and self-contained form. our treatment of orbital mechanics covers quasi-keplerian and action-angle descriptions of bound geodesics and accelerated orbits, osculating geodesics, near-identity averaging transformations, multiscale expansions, and orbital resonances. our summary of self-force theory's foundations is brief, covering the main ideas and results of matched asymptotic expansions, local expansion methods, puncture schemes, and point particle descriptions. we conclude by combining the above methods in a multiscale expansion of the perturbative einstein equations, leading to adiabatic and post-adiabatic evolution schemes. our presentation is intended primarily as a reference for practitioners but includes a variety of new results. in particular, we present the first complete post-adiabatic waveform-generation framework for generic (nonresonant) orbits in kerr. | black hole perturbation theory and gravitational self-force |
in general relativity, when two black holes merge they produce a rotating (kerr) black hole remnant. according to perturbation theory, the remnant emits "ringdown" radiation: a superposition of exponentials with characteristic complex frequencies that depend only on the remnant's mass and spin. while the goal of the black hole spectroscopy program is to measure the quasinormal mode frequencies, a knowledge of their amplitudes and phases is equally important to determine which modes are detectable, and possibly to perform additional consistency checks. unlike the complex frequencies, the amplitudes and phases depend on the properties of the binary progenitors, such as the binary mass ratio and component spins. in this paper we develop a fitting algorithm designed to reliably identify the modes present in numerical simulations and to extract their amplitudes and phases. we apply the algorithm to over 500 binary black hole simulations from the public sxs numerical relativity simulation catalog, and we present fitting formulas for the resulting mode amplitudes and phases as functions of the properties of the progenitors. crucially, our algorithm allows for the extraction of not only prograde fundamental modes and overtones, but also retrograde modes and second-order modes. we unveil interesting relations for the amplitude ratios of different modes. the fitting code and interactive versions of some of the plots are publicly available. the results presented in this paper can be updated as more and better simulations become available. | extracting linear and nonlinear quasinormal modes from black hole merger simulations |
we study general relativity at a null boundary using the covariant phase space formalism. we define a covariant phase space and compute the algebra of symmetries at the null boundary by considering the boundary-preserving diffeomorphisms that preserve this phase space. this algebra is the semi-direct sum of diffeomorphisms on the two sphere and a nonabelian algebra of supertranslations that has some similarities to supertranslations at null infinity. by using the general prescription developed by wald and zoupas, we derive the localized charges of this algebra at cross sections of the null surface as well as the associated fluxes. our analysis is covariant and applies to general non-stationary null surfaces. we also derive the global charges that generate the symmetries for event horizons, and show that these obey the same algebra as the linearized diffeomorphisms, without any central extension. our results show that supertranslations play an important role not just at null infinity but at all null boundaries, including non-stationary event horizons. they should facilitate further investigations of whether horizon symmetries and conservation laws in black hole spacetimes play a role in the information loss problem, as suggested by hawking, perry, and strominger. | symmetries and charges of general relativity at null boundaries |
we show that rotating black holes do not experience any tidal deformation when they are perturbed by a weak and adiabatic gravitational field. the tidal deformability of an object is quantified by the so-called "love numbers," which describe the object's linear response to its external tidal field. in this work, we compute the love numbers of kerr black holes and find that they vanish identically. we also compute the dissipative part of the black hole's tidal response, which is nonvanishing due to the absorptive nature of the event horizon. our results hold for arbitrary values of black hole spin, for both the electric-type and magnetic-type perturbations, and to all orders in the multipole expansion of the tidal field. the boundary conditions at the event horizon and at asymptotic infinity are incorporated in our study, as they are crucial for understanding the way in which these tidal effects are mapped onto gravitational-wave observables. in closing, we address the ambiguity issue of love numbers in general relativity, which we argue is resolved when those boundary conditions are taken into account. our findings provide essential inputs for current efforts to probe the nature of compact objects through the gravitational waves emitted by binary systems. | tidal deformation and dissipation of rotating black holes |
in the last few years, machine learning techniques, in particular convolutional neural networks, have been investigated as a method to replace or complement traditional matched filtering techniques that are used to detect the gravitational-wave signature of merging black holes. however, to date, these methods have not yet been successfully applied to the analysis of long stretches of data recorded by the advanced ligo and virgo gravitational-wave observatories. in this work, we critically examine the use of convolutional neural networks as a tool to search for merging black holes. we identify the strengths and limitations of this approach, highlight some common pitfalls in translating between machine learning and gravitational-wave astronomy, and discuss the interdisciplinary challenges. in particular, we explain in detail why convolutional neural networks alone cannot be used to claim a statistically significant gravitational-wave detection. however, we demonstrate how they can still be used to rapidly flag the times of potential signals in the data for a more detailed follow-up. our convolutional neural network architecture as well as the proposed performance metrics are better suited for this task than a standard binary classifications scheme. a detailed evaluation of our approach on advanced ligo data demonstrates the potential of such systems as trigger generators. finally, we sound a note of caution by constructing adversarial examples, which showcase interesting "failure modes" of our model, where inputs with no visible resemblance to real gravitational-wave signals are identified as such by the network with high confidence. | convolutional neural networks: a magic bullet for gravitational-wave detection? |
the kerr nature of a compact-object-coalescence remnant can be unveiled by observing multiple quasinormal modes in the post-merger signal. current methods to achieve this goal rely on matching the data with a superposition of exponentially damped sinusoids with amplitudes fitted to numerical-relativity (nr) simulations of binary black-hole mergers. these models presume the ability to correctly estimate the time at which the gravitational-wave signal starts to be dominated by the quasinormal modes of a perturbed black hole. here we show that this difficulty can be overcome by using multipolar inspiral-merger-ringdown waveforms, calibrated to nr simulations, as already developed within the effective-one-body formalism (eobnr). we build a parameterized (nonspinning) eobnr waveform model in which the quasinormal mode complex frequencies are free parameters (peobnr), and use bayesian analysis to study its effectiveness in measuring quasinormal modes in gw150914, and in synthetic gravitational-wave signals of binary black holes injected in gaussian noise. we find that using the peobnr model gives, in general, stronger constraints compared to the ones obtained when using a sum of damped sinusoids and using bayesian model selection, we also show that the peobnr model can successfully be employed to find evidence for deviations from general relativity in the ringdown signal. since the peobnr model properly includes time and phase shifts among quasinormal modes, it is also well suited to consistently combine information from several observations—e.g., we find on the order of ∼30 gw150914-like binary black-hole events would be needed for advanced ligo and virgo at design sensitivity to measure the fundamental frequencies of both the (2,2) and (3,3) modes, and the decay time of the (2,2) mode with an accuracy of ≲5 % at the 2 -σ level, thus allowing to test the black hole's no-hair conjecture. | black-hole spectroscopy by making full use of gravitational-wave modeling |
we carry out in full generality and without fixing specific boundary conditions, the symmetry and charge analysis near a generic null surface for two and three dimensional (2d and 3d) gravity theories. in 2d and 3d there are respectively two and three charges which are generic functions over the codimension one null surface. the integrability of charges and their algebra depend on the state-dependence of symmetry generators which is a priori not specified. we establish the existence of infinitely many choices that render the surface charges integrable. we show that there is a choice, the "fundamental basis", where the null boundary symmetry algebra is the heisenberg⊕diff(d - 2) algebra. we expect this result to be true for d > 3 when there is no bondi news through the null surface. | symmetries at null boundaries: two and three dimensional gravity cases |
we consider a nearly-ads2 gravity theory on the two-sided wormhole geometry. we construct three gauge-invariant operators in nads2 which move bulk matter relative to the dynamical boundaries. in a two-sided system, these operators satisfy an sl(2) algebra (up to non perturbative corrections). in a semiclassical limit, these generators act like sl(2) transformations of the boundary time, or conformal symmetries of the two sided boundary theory. these can be used to define an operator-state mapping. a particular large n and low temperature limit of the syk model has precisely the same structure, and this construction of the exact generators also applies. we also discuss approximate, but simpler, constructions of the generators in the syk model. these are closely related to the "size" operator and are connected to the maximal chaos behavior captured by out of time order correlators. | symmetries near the horizon |
we propose in this white paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of lisa and the terrestrial ligo/virgo/kagra/indigo experiments. this interdisciplinary experiment, called atomic experiment for dark matter and gravity exploration (aedge), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. we give examples of the extended range of sensitivity to ultra-light dark matter offered by aedge, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. aedge will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., lisa and cold atom experiments in microgravity. this paper is based on a submission (v1) in response to the call for white papers for the voyage 2050 long-term plan in the esa science programme. esa limited the number of white paper authors to 30. however, in this version (v2) we have welcomed as supporting authors participants in the workshop on atomic experiments for dark matter and gravity exploration held at cern: ({\tt https://indico.cern.ch/event/830432/}), as well as other interested scientists, and have incorporated additional material. | aedge: atomic experiment for dark matter and gravity exploration in space |
we discuss a remarkable correspondence between the description of black holes as highly occupied condensates of n weakly interacting gravitons and that of color glass condensates (cgcs) as highly occupied gluon states. in both cases, the dynamics of "wee partons" in regge asymptotics is controlled by emergent semihard scales that lead to perturbative unitarization and classicalization of 2 →n particle amplitudes at weak coupling. in particular, they attain a maximal entropy permitted by unitarity, bounded by the inverse coupling α of the respective constituents. strikingly, this entropy is equal to the area measured in units of the goldstone constant corresponding to the spontaneous breaking of poincaré symmetry by the corresponding graviton or gluon condensate. in gravity, the goldstone constant is the planck scale, and gives rise to the bekenstein-hawking entropy. likewise, in the cgc, the corresponding goldstone scale is determined by the onset of gluon screening. we point to further similarities in black hole formation, thermalization and decay, to that of the glasma matter formed from colliding cgcs in ultrarelativistic nuclear collisions, which decays into a quark-gluon plasma. | classicalization and unitarization of wee partons in qcd and gravity: the cgc-black hole correspondence |
we describe a class of holographic models that may describe the physics of certain four-dimensional big-bang/big-crunch cosmologies. the construction involves a pair of 3d euclidean holographic cfts each on a homogeneous and isotropic space m coupled at either end of an interval ℐ to a euclidean 4d cft on m × ℐ with many fewer local degrees of freedom. we argue that in some cases, when the size of m is much greater than the length of ℐ, the theory flows to a confining three-dimensional field theory on m in the infrared, and this is reflected in the dual description by the asymptotically ads spacetimes dual to the two 3d cfts joining up in the ir to give a euclidean wormhole. the euclidean construction can be reinterpreted as generating a state of the lorentzian 4d cft on m × time whose dual includes the physics of a big-bang/big-crunch cosmology. when m is &r;3, we can alternatively analytically continue one of the &r;3 directions to get an eternally traversable four-dimensional planar wormhole. we suggest explicit microscopic examples where the 4d cft is n = 4 sym theory and the 3d cfts are superconformal field theories with opposite orientation. in this case, the two geometries dual to the pair of 3d scfts can be understood as a geometrical version of a brane-antibrane pair, and the tendency of the geometries to connect up is related to the standard instability of brane-antibrane systems. | cosmology from confinement? |
extended scalar-tensor gauss-bonnet (estgb) gravity has been recently argued to exhibit spontaneous scalarization of vacuum black holes (bhs). a similar phenomenon can be expected in a larger class of models, which includes, e.g., einstein-maxwell scalar (ems) models, where spontaneous scalarization of electrovacuum bhs should occur. ems models have no higher curvature corrections, a technical simplification over estgb models that allows us to investigate, fully nonlinearly, bh scalarization in two novel directions. first, numerical simulations in spherical symmetry show, dynamically, that reissner-nordström (rn) bhs evolve into a perturbatively stable scalarized bh. second, we compute the nonspherical sector of static scalarized bh solutions bifurcating from the rn bh trunk. scalarized bhs form an infinite (countable) number of branches and possess a large freedom in their multipole structure. unlike the case of electrovacuum, the ems model admits static, asymptotically flat, regular on and outside the horizon bhs without spherical symmetry and even without any spatial isometries, which are thermodynamically preferred over the electrovacuum state. we speculate on a possible dynamical role of these nonspherical scalarized bhs. | spontaneous scalarization of charged black holes |
we present a package for mathematica that facilitates the numerical computation of the quasinormal mode (qnm) spectrum of a black hole/black brane. requiring as input only the qnm equation(s), the application of a single mathematica function will compute the spectrum efficiently, by discretizing the equation(s) and solving the resulting generalized eigenvalue equation. it is applicable to a large variety of black holes, independently of their asymptotics. the package comes fully documented and with several tutorials. here we present a self-contained review of the method and consider several applications. we illustrate the method in the simplest case of scalar qnms of a schwarzschild black brane in anti-de sitter. then we go on to look at the scalar qnms of the schwarzschild black hole in de sitter, in anti-de sitter and in asymptotically flat spacetimes, finding a novel infinite set of purely imaginary modes in the first case. we also derive the qnm equations for a generic einstein-maxwell-scalar background and use these to compute the qnms of the asymptotically anti-de sitter reissner-nordström black brane, as a further illustration and check of the method. | overdamped modes in schwarzschild-de sitter and a mathematica package for the numerical computation of quasinormal modes |
so-called "regular black holes" are a topic currently of considerable interest in the general relativity and astrophysics communities. herein we investigate a particularly interesting regular black hole spacetime described by the line element this spacetime neatly interpolates between the standard schwarzschild black hole and the morris-thorne traversable wormhole; at intermediate stages passing through a black-bounce (into a future incarnation of the universe), an extremal null-bounce (into a future incarnation of the universe), and a traversable wormhole. as long as the parameter a is non-zero the geometry is everywhere regular, so one has a somewhat unusual form of "regular black hole", where the "origin" r=0 can be either spacelike, null, or timelike. thus this spacetime generalizes and broadens the class of "regular black holes" beyond those usually considered. | black-bounce to traversable wormhole |
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