abstract stringlengths 3 192k | title stringlengths 4 857 |
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in the recent proposal [s. w. wei et al., black hole solutions as topological thermodynamic defects, phys. rev. lett. 129, 191101 (2022)., 10.1103/physrevlett.129.191101], the black holes were viewed as topological thermodynamic defects by using the generalized off shell free energy. in this paper, we follow such proposal to study the local and global topological natures of the gauss-bonnet black holes in anti-de sitter (ads) space. the local topological natures are reflected by the winding numbers, where the positive and negative winding numbers correspond to the stable and unstable black hole branches. the global topological natures are reflected by the topological numbers, which are defined as the sum of the winding numbers for all black hole branches and can be used to classify the black holes into different classes. when the charge is present, we find that the topological number is independent on the values of the parameters, and the charged gauss-bonnet ads black holes can be divided into the same class of the reissner-nordström anti-de sitter black hole black holes with the same topological number 1. however, when the charge is absent, we find that the topological number has certain dimensional dependence. this is different from the previous studies, where the topological number is found to be a universal number independent of the black hole parameters. furthermore, the asymptotic behaviors of curve τ (rh) in small and large radii limit can be a simple criterion to distinguish the different topological number. we find a new asymptotic behavior as τ (rh→0 )=0 and τ (rh→∞ )=0 in the black hole system, which shows topological equivalency with the asymptotic behaviors τ (rh→0 )=∞ and τ (rh→∞ )=∞ . we also give an intuitional proof of why there are only three topological classes in the black hole system under the condition (∂rhs )p>0 . | topological natures of the gauss-bonnet black hole in ads space |
in recent times there is a surge of interest in constructing einstein-gauss-bonnet (egb) gravity, in the limit d → 4, of the d-dimensional egb gravity. interestingly, the static spherically symmetric solutions in the various proposed d → 4 regularized egb gravities coincide, and incidentally some other theories also admit the same solution. we prove a theorem that characterizes a large family of nonstatic or radiating spherically symmetric solutions to the 4d egb gravity, representing, in general, spherically symmetric type ii fluid. an extension of the theorem, given without proof as being similar to the original theorem, generates static spherically symmetric black hole solutions of the theory. it not only enables us to identify available known black hole solutions as particular cases but also to generate several new solutions of the 4d egb gravity. | generating black holes in 4d einstein-gauss-bonnet gravity |
we show that extremal kerr black holes are sensitive probes of new physics. stringy or quantum corrections to general relativity are expected to generate higher-curvature terms in the gravitational action. we show that in the presence of these terms, asymptotically flat extremal rotating black holes have curvature singularities on their horizon. furthermore, near-extremal black holes can have large yet finite tidal forces for infalling observers. in addition, we consider five-dimensional extremal charged black holes and show that higher-curvature terms can have a large effect on the horizon geometry. | extremal kerr black holes as amplifiers of new physics |
we construct an infinite family of microstates for black holes in minkowski spacetime which have effective semiclassical descriptions in terms of collapsing dust shells in the black hole interior. quantum mechanical wormholes cause these states to have exponentially small, but universal, overlaps. we show that these overlaps imply that the microstates span a hilbert space of log dimension equal to the event horizon area divided by four times the newton constant, explaining the statistical origin of the bekenstein-hawking entropy. | microscopic origin of the entropy of astrophysical black holes |
we consider the low temperature quantum theory of a charged black hole of zero temperature horizon radius $r_h$, in a spacetime which is asymptotically ads$_{d}$ ($d > 3$) far from the horizon. at temperatures $t \ll 1/r_h$, the near-horizon geometry is ads$_2$, and the black hole is described by a universal 0+1 dimensional effective quantum theory of time diffeomorphisms with a schwarzian action, and a phase mode conjugate to the u(1) charge. we obtain this universal 0+1 dimensional effective theory starting from the full $d$-dimensional einstein-maxwell theory, while keeping quantitative track of the couplings. the couplings of the effective theory are found to be in agreement with those expected from the thermodynamics of the $d$-dimensional black hole. | universal low temperature theory of charged black holes with ads2 horizons |
primordial black holes (pbhs) might be formed in the early universe and could comprise at least a fraction of the dark matter. using the recently released gwtc-2 dataset from the third observing run of the ligo-virgo collaboration, we investigate whether current observations are compatible with the hypothesis that all black hole mergers detected so far are of primordial origin. we constrain pbh formation models within a hierarchical bayesian inference framework based on deep learning techniques, finding best-fit values for distinctive features of these models, including the pbh initial mass function, the fraction of pbhs in dark matter, and the accretion efficiency. the presence of several spinning binaries in the gwtc-2 dataset favors a scenario in which pbhs accrete and spin up. our results indicate that pbhs may comprise only a fraction smaller than 0.3% of the total dark matter, and that the predicted pbh abundance is still compatible with other constraints. | constraining the primordial black hole scenario with bayesian inference and machine learning: the gwtc-2 gravitational wave catalog |
we present the first surrogate model for gravitational waveforms from the coalescence of precessing binary black holes. we call this surrogate model nrsur4d2s. our methodology significantly extends recently introduced reduced-order and surrogate modeling techniques, and is capable of directly modeling numerical relativity waveforms without introducing phenomenological assumptions or approximations to general relativity. motivated by gw150914, ligo's first detection of gravitational waves from merging black holes, the model is built from a set of 276 numerical relativity (nr) simulations with mass ratios q ≤2 , dimensionless spin magnitudes up to 0.8, and the restriction that the initial spin of the smaller black hole lies along the axis of orbital angular momentum. it produces waveforms which begin ∼30 gravitational wave cycles before merger and continue through ringdown, and which contain the effects of precession as well as all ℓ∈{2 ,3 } spin-weighted spherical-harmonic modes. we perform cross-validation studies to compare the model to nr waveforms not used to build the model and find a better agreement within the parameter range of the model than other, state-of-the-art precessing waveform models, with typical mismatches of 10-3. we also construct a frequency domain surrogate model (called nrsur4d2s_fdrom) which can be evaluated in 50 ms and is suitable for performing parameter estimation studies on gravitational wave detections similar to gw150914. | a surrogate model of gravitational waveforms from numerical relativity simulations of precessing binary black hole mergers |
in this paper, we construct an effective rotating loop quantum black hole (lqbh) solution, starting from the spherical symmetric lqbh by applying the newman-janis algorithm modified by azreg-aïnou's noncomplexification procedure, and study the effects of loop quantum gravity (lqg) on its shadow. given the rotating lqbh, we discuss its horizon, ergosurface, and regularity as r →0 . depending on the values of the specific angular momentum a and the polymeric function p arising from lqg, we find that the rotating solution we obtained can represent a regular black hole, a regular extreme black hole, or a regular spacetime without horizon (a non-black-hole solution). we also study the effects of lqg and rotation, and show that, in addition to the specific angular momentum, the polymeric function also causes deformations in the size and shape of the black hole shadow. interestingly, for a given value of a and inclination angle θ0, the apparent size of the shadow monotonically decreases, and the shadow gets more distorted with increasing p . we also consider the effects of p on the deviations from the circularity of the shadow, and find that the deviation from circularity increases with increasing p for fixed values of a and θ0. additionally, we explore the observational implications of p in comparing with the latest event horizon telescope observation of the supermassive black hole, m87*. the connection between the shadow radius and quasinormal modes in the eikonal limit as well as the deflection of massive particles are also considered. | shadow and quasinormal modes of a rotating loop quantum black hole |
combining intervals of ekpyrotic (ultra-slow) contraction with a (non-singular) classical bounce naturally leads to a novel cyclic theory of the universe in which the hubble parameter, energy density and temperature oscillate periodically, but the scale factor grows by an exponential factor from one cycle to the next. the resulting cosmology not only resolves the homogeneity, isotropy, flatness and monopole problems and generates a nearly scale invariant spectrum of density perturbations, but it also addresses a number of age-old cosmological issues that big bang inflationary cosmology does not. there may also be wider-ranging implications for fundamental physics, black holes and quantum measurement. | a new kind of cyclic universe |
the formation and abundance of primordial black holes (pbhs) arising from the curvature perturbation ζ is studied. the non-linear relation between ζ and the density contrast δ means that, even when ζ has an exactly gaussian distribution, significant non-gaussianities affecting pbh formation must be considered. numerical simulations are used to investigate the critical value and the mass of pbhs which form, and peaks theory is used to calculate the mass fraction of the universe collapsing to form pbhs at the time of formation. a formalism to calculate the total present day pbh abundance and mass function is also derived. it is found that the abundance of pbhs is very sensitive to the non-linear effects, and that the power spectrum script pζ must be a factor of script o (2) larger to produce the same number of pbhs as if using the linear relation between ζ and δ (where the exact value depends on the critical value for a region to collapse and form a pbh). this also means that the derived constraints on the small-scale power spectrum from constraints on the abundance of pbhs are weaker by the same factor. | primordial black hole formation and abundance: contribution from the non-linear relation between the density and curvature perturbation |
recently, a novel formula for computing entropy in theories coupled to semi-classical gravity has been devised. using this so-called island formula the entropy of semi-classical black holes follows a page curve. here, we study the relation between this novel entropy and semi-classical entropy in the context of doubly-holographic models. double holography allows for two different d-dimensional descriptions of a black hole coupled to a non-gravitational bath, both of which allow a holographic computation of von neumann entropy in bath subregions. we argue that the correct homology constraint for ryu-takayanagi surfaces depends on which of those d-dimensional perspectives is taken. as a consequence the von neumann entropies of a fixed subregion in both descriptions can disagree. we discuss how the von neumann entropies in both descriptions are related to the entropy computed by the island formula and coarse grained entropy. moreover, we argue that the way operators transform between the two descriptions depends on their complexity. a simple toy model is introduced to demonstrate that a sufficiently complicated map between two descriptions of the system can give rise to an island formula and wormholes. lastly, we speculate about the relation between double-holography and black hole complementarity. | homology conditions for rt surfaces in double holography |
we present an automated method for finding hidden symmetries, defined as symmetries that become manifest only in a new coordinate system that must be discovered. its core idea is to quantify asymmetry as violation of certain partial differential equations, and to numerically minimize such violation over the space of all invertible transformations, parametrized as invertible neural networks. for example, our method rediscovers the famous gullstrand-painlevé metric that manifests hidden translational symmetry in the schwarzschild metric of nonrotating black holes, as well as hamiltonicity, modularity, and other simplifying traits not traditionally viewed as symmetries. | machine learning hidden symmetries |
the er = epr correspondence relates a superposition of entangled, disconnected spacetimes to a connected spacetime with an einstein-rosen bridge. we construct examples in which both sides may be described by weakly-coupled string theory. the relation between them is given by a lorentzian continuation of the fzz duality of the two-dimensional euclidean black hole cft in one example, and in another example by continuation of a similar duality that we propose for the asymptotic euclidean ads3 black hole. this gives a microscopic understanding of er = epr: one has a worldsheet duality between string theory in a connected, eternal black hole, and in a superposition of disconnected geometries in an entangled state. the disconnected description includes a condensate of entangled folded strings emanating from a strong-coupling region in place of a bifurcation point. our construction relies on a lorentzian interpretation of euclidean time winding operators via angular quantization, as well as some lesser known worldsheet string theories, such as perturbation theory around a thermofield-double state, which we define using schwinger-keldysh contours in target space. | stringy er = epr |
we conduct a thorough bayesian analysis of the possibility that the black hole merger events seen in gravitational waves are primordial black hole (pbh) mergers. using the latest merger rate models for pbh binaries drawn from a log-normal mass function, we compute posterior parameter constraints and bayesian evidences using data from the first two observing runs of ligo-virgo. we account for theoretical uncertainty due to possible disruption of the binary by surrounding pbhs, which can suppress the merger rate significantly. we also consider simple astrophysically motivated models and find that these are favored decisively over the pbh scenario, quantified by the bayesian evidence ratio. paying careful attention to the influence of the parameter priors and the quality of the model fits, we show that the evidence ratios can be understood by comparing the predicted chirp mass distribution to that of the data. we identify the posterior predictive distribution of chirp mass as a vital tool for discriminating between models. a model in which all mergers are pbh binaries is strongly disfavored compared with astrophysical models, in part due to the overprediction of heavy systems having mchirp≳40 m⊙ and positive skewness over the range of observed masses which does not match the observations. we find that the fit is not significantly improved by adding a maximum mass cutoff or a bimodal mass function or imposing that pbh binaries form at late times. we argue that a successful pbh model must either modify the log-normal shape of the initial mass function significantly or abandon the hypothesis that all observed merging binaries are primordial. we develop and apply techniques for analyzing pbh models with gravitational wave data, which will be necessary for robust statistical inference as the gravitational wave source sample size increases. | bayesian analysis of ligo-virgo mergers: primordial versus astrophysical black hole populations |
we study two-dimensional eternal black holes with non-zero mass, where each asymptotic boundary is in contact with a cft on a circle, following the doubly holographic braneworld models constructed in [1-3]. we compute the page curve of the black hole (or the bath cfts), which amounts to finding different geodesics in the bulk btz geometry with a randall-sundrum brane falling into the black hole. we also explore the possibility of including an intrinsic jt gravity action on the brane. as expected, the generalized entropy rises linearly at early times. however, there is a transition to a late-time phase in which the entropy remains constant. the value of the late-time entropy depends on the size of the thermal baths. for a small size, it corresponds to the thermal entropy of the baths, while for large size, it corresponds to twice the horizon entropy of the black hole. the critical size and the page time are proportional to ratio of the central charges of the conformal defect and the bath cft. | quantum extremal islands made easy. part iv. massive black holes on the brane |
matrix quantum mechanics plays various important roles in theoretical physics, such as a holographic description of quantum black holes, and it underpins the only practical numerical approach to the study of complex high-dimensional supergravity theories. understanding quantum black holes and the role of entanglement in a holographic setup is of paramount importance for the realization of a quantum theory of gravity. moreover, a complete numerical understanding of the holographic duality and the emergence of geometric space-time features from microscopic degrees of freedom could pave the way for new discoveries in quantum information science. euclidean lattice monte carlo simulations are the de facto numerical tool for understanding the spectrum of large matrix models and have been used to test the holographic duality. however, they are not tailored to extract dynamical properties or even the quantum wave function of the ground state of matrix models. quantum computing and deep learning provide potentially useful approaches to study the dynamics of matrix quantum mechanics. if successful in the context of matrix models, these rapidly improving numerical techniques could become the new swiss army knife of quantum gravity practitioners. in this paper, we perform the first systematic survey for quantum computing and deep-learning approaches to matrix quantum mechanics, comparing them to lattice monte carlo simulations. these provide baseline benchmarks before addressing more complicated problems. in particular, we test the performance of each method by calculating the low-energy spectrum. | matrix-model simulations using quantum computing, deep learning, and lattice monte carlo |
we investigate structural aspects of jt gravity through its bf description. in particular, we provide evidence that jt gravity should be thought of as (a coset of) the noncompact subsemigroup sl +(2 , &r;) bf theory. we highlight physical implications, including the famous plancherel measure sinh 2π √{e} . exploiting this perspective, we investigate jt gravity on more generic manifolds with emphasis on the edge degrees of freedom on entangling surfaces and factorization. it is found that the one-sided jt gravity degrees of freedom are described not just by a schwarzian on the asymptotic boundary, but also include frozen sl + (2 , &r;) degrees of freedom on the horizon, identifiable as jt gravity black hole states. configurations with two asymptotic boundaries are linked to 2d liouville cft on the torus surface. | fine structure of jackiw-teitelboim quantum gravity |
we revisit the covariant phase space formalism applied to gravitational theories with null boundaries, utilizing the most general boundary conditions consistent with a fixed null normal. to fix the ambiguity inherent in the wald-zoupas definition of quasilocal charges, we propose a new principle, based on holographic reasoning, that the flux be of dirichlet form. this also produces an expression for the analog of the brown-york stress tensor on the null surface. defining the algebra of charges using the barnich-troessaert bracket for open subsystems, we give a general formula for the central — or more generally, abelian — extensions that appear in terms of the anomalous transformation of the boundary term in the gravitational action. this anomaly arises from having fixed a frame for the null normal, and we draw parallels between it and the holographic weyl anomaly that occurs in ads/cft. as an application of this formalism, we analyze the near-horizon virasoro symmetry considered by haco, hawking, perry, and strominger, and perform a systematic derivation of the fluxes and central charges. applying the cardy formula to the result yields an entropy that is twice the bekenstein-hawking entropy of the horizon. motivated by the extended hilbert space construction, we interpret this in terms of a pair of entangled cfts associated with edge modes on either side of the bifurcation surface. | anomalies in gravitational charge algebras of null boundaries and black hole entropy |
a wide variety of astrophysical and cosmological sources are expected to contribute to a stochastic gravitational-wave background. following the observations of gw150914 and gw151226, the rate and mass of coalescing binary black holes appear to be greater than many previous expectations. as a result, the stochastic background from unresolved compact binary coalescences is expected to be particularly loud. we perform a search for the isotropic stochastic gravitational-wave background using data from advanced laser interferometer gravitational wave observatory's (aligo) first observing run. the data display no evidence of a stochastic gravitational-wave signal. we constrain the dimensionless energy density of gravitational waves to be ω0<1.7 ×10-7 with 95% confidence, assuming a flat energy density spectrum in the most sensitive part of the ligo band (20-86 hz). this is a factor of ∼33 times more sensitive than previous measurements. we also constrain arbitrary power-law spectra. finally, we investigate the implications of this search for the background of binary black holes using an astrophysical model for the background. | upper limits on the stochastic gravitational-wave background from advanced ligo's first observing run |
gravitational-wave observations of binary black holes currently rely on theoretical models that predict the dominant multipoles (ℓ=2 ,|m |=2 ) of the radiation during inspiral, merger, and ringdown. we introduce a simple method to include the subdominant multipoles to binary black hole gravitational waveforms, given a frequency-domain model for the dominant multipoles. the amplitude and phase of the original model are appropriately stretched and rescaled using post-newtonian results (for the inspiral), perturbation theory (for the ringdown), and a smooth transition between the two. no additional tuning to numerical-relativity simulations is required. we apply a variant of this method to the nonprecessing phenomd model. the result, phenomhm, constitutes the first higher-multipole model of spinning and coalescing black-hole binaries, and currently includes the (ℓ,|m |)=(2 ,2 ),(3 ,3 ),(4 ,4 ),(2 ,1 ),(3 ,2 ),(4 ,3 ) radiative moments. comparisons with numerical-relativity waveforms demonstrate that phenomhm is more accurate than dominant-multipole-only models for all binary configurations, and typically improves the measurement of binary properties. | first higher-multipole model of gravitational waves from spinning and coalescing black-hole binaries |
effects of massive object's spin on massive-massless 2 → 2 classical scattering is studied. focus is set on the less-considered dimensionless expansion parameter λ/b, where λ is the massless particle's wavelength and b is the impact parameter. corrections in λ/b start to appear from o (g2), with leading correction terms tied to the gravitational faraday effect, which is a special case of the lense-thirring effect. we compute the eikonal phase up to o (g2) and extract spin effect on the scattering angle and time delay up to 14th order in spin. the gravitational faraday effect at linear order in spin [1] is reproduced by λ/b correction terms, which we compute to higher orders in spin. we find that the equivalence principle, or universality, holds up to nlo for general spinning bodies, i.e. away from geometric optics limit. furthermore, in the black hole limit, we confirm the absence of particular spin structure observed [2-8], along with the associated shift symmetry [7], and argue that it holds to arbitrary spin order at o (g2) in the massless probe limit. | gravitational faraday effect from on-shell amplitudes |
the material surrounding accreting supermassive black holes connects the active galactic nucleus with its host galaxy and, besides being responsible for feeding the black hole, provides important information on the feedback that nuclear activity produces on the galaxy. in this review, we summarize our current understanding of the close environment of accreting supermassive black holes obtained from studies of local active galactic nuclei carried out in the infrared and x-ray regimes. the structure of this circumnuclear material is complex, clumpy and dynamic, and its covering factor depends on the accretion properties of the active galactic nucleus. in the infrared, this obscuring material is a transition zone between the broad- and narrow-line regions, and, at least in some galaxies, it consists of two structures: an equatorial disk/torus and a polar component. in the x-ray regime, the obscuration is produced by multiple absorbers across various spatial scales, mostly associated with the torus and the broad-line region. in the coming decade, the new generation of infrared and x-ray facilities will greatly contribute to our understanding of the structure and physical properties of nuclear obscuration in active galactic nuclei. | nuclear obscuration in active galactic nuclei |
the counting of bps states in four-dimensional ${\cal n}=1$ theories has attracted a lot of attention in recent years. for superconformal theories, these states are in one-to-one correspondence with local operators in various short representations. the generating function for this counting problem has branch cuts and hence several cardy-like limits, which are analogous to high-temperature limits. particularly interesting is the second sheet, which has been shown to capture the microstates and phases of supersymmetric black holes in ads$_5$. here we present a 3d effective field theory (eft) approach to the high-temperature limit on the second sheet. we use the eft to derive the behavior of the index at orders $\beta^{-2},\beta^{-1},\beta^0$. we also make a conjecture for $o(\beta)$, where we argue that the expansion truncates up to exponentially small corrections. an important point is the existence of vector multiplet zero modes, unaccompanied by massless matter fields. the runaway of affleck-harvey-witten is however avoided by a non-perturbative confinement mechanism. this confinement mechanism guarantees that our results are robust. | eft and the susy index on the 2nd sheet |
we revisit the spectrum of pure quantum gravity in ads3. the computation of the torus partition function will — if computed using a gravitational path integral that includes only smooth saddle points — lead to a density of states which is not physically sensible, as it has a negative degeneracy of states for some energies and spins. we consider a minimal cure for this non-unitarity of the pure gravity partition function, which involves the inclusion of additional states below the black hole threshold. we propose a geometric interpretation for these extra states: they are conical defects with deficit angle 2π(1 - 1/n), where n is a positive integer. that only integer values of n should be included can be seen from a modular bootstrap argument, and leads us to propose a modest extension of the set of saddle-point configurations that contribute to the gravitational path integral: one should sum over orbifolds in addition to smooth manifolds. these orbifold states are below the black hole threshold and are regarded as massive particles in ads, but they are not perturbative states: they are too heavy to form multi-particle bound states. we compute the one-loop determinant for gravitons in these orbifold backgrounds, which confirms that the orbifold states are virasoro primaries. we compute the gravitational partition function including the sum over these orbifolds and find a finite, modular invariant result; this finiteness involves a delicate cancellation between the infinite tower of orbifold states and an infinite number of instantons associated with psl(2, &z;) images. | pure gravity and conical defects |
holographic braneworlds are used to present a higher-dimensional origin of extended black hole thermodynamics. in this framework, classical, asymptotically anti-de sitter black holes map to quantum black holes in one dimension less, with a conformal matter sector that backreacts on the brane geometry. varying the brane tension alone leads to a dynamical cosmological constant on the brane, and, correspondingly, a variable pressure attributed to the brane black hole. thus, standard thermodynamics in the bulk, including a work term coming from the brane, induces extended thermodynamics on the brane, exactly, to all orders in the backreaction. a microsopic interpretation of the extended thermodynamics of specific quantum black holes is given via double holography. | higher-dimensional origin of extended black hole thermodynamics |
making use of the recently derived, all-spin, opposite-helicity compton amplitude, we calculate the classical gravitational scattering amplitude for one spinning and one spinless object at o (g2) and all orders in spin. by construction, this amplitude exhibits the spin structure that has been conjectured to describe kerr black holes. this spin structure alone is not enough to fix all deformations of the compton amplitude by contact terms, but when combined with considerations of the ultrarelativistic limit we can uniquely assign values to the parameters remaining in the even-in-spin sector. once these parameters are determined, much of the spin dependence of the amplitude resums into hypergeometric functions. finally, we derive the eikonal phase for aligned-angular-momentum scattering. | classical gravitational spinning-spinless scattering at o (g2s∞) |
in this paper, we study the weak gravitational lensing in the spacetime of rotating regular black hole geometries such as ayon-beato-garcía (abg), bardeen, and hayward black holes. we calculate the deflection angle of light using the gauss-bonnet theorem (gbt) and show that the deflection of light can be viewed as a partially topological effect in which the deflection angle can be calculated by considering a domain outside of the light ray applied to the black hole optical geometries. then, we demonstrate also the deflection angle via the geodesics formalism for these black holes to verify our results and explore the differences with the kerr solution. these black holes have, in addition to the total mass and rotation parameter, different parameters of electric charge, magnetic charge, and deviation parameter. we find that the deflection of light has correction terms coming from these parameters, which generalizes the kerr deflection angle. | deflection of light by rotating regular black holes using the gauss-bonnet theorem |
we derive new positivity bounds for scattering amplitudes in theories with a massless graviton in the spectrum in four spacetime dimensions, of relevance for the weak gravity conjecture and modified gravity theories. the bounds imply that extremal black holes are self-repulsive, m /|q |<1 in suitable units, and that they are unstable to decay to smaller extremal black holes, providing an s -matrix proof of the weak gravity conjecture. we also present other applications of our bounds to the effective field theory of weakly broken galileons, axions, and p (x ) theories. | positivity of amplitudes, weak gravity conjecture, and modified gravity |
thermodynamic quantities associated with black holes in anti-de sitter space obey an interesting identity when the cosmological constant is included as one of the dynamical variables, the generalized smarr relation. we show that this relation can easily be understood from the point of view of the dual holographic field theory. it amounts to the simple statement that the extensive thermodynamic quantities of a large n gauge theory only depend on the number of colors, n , via an overall factor of n 2. | holographic black hole chemistry |
we sharpen swampland constraints on 8d supergravity theories by studying consistency conditions on worldvolume theory of 3-brane probes. combined with a stronger form of the cobordism conjecture, this leads to the reconstruction of the compact internal geometry and implies strong restrictions on the gauge algebra and on some higher derivative terms (related to the level of the current algebra on the 1-brane). in particular we argue that 8d supergravity theories with g2 gauge symmetry are in the swampland. these results provide further evidence for the string lamppost principle in 8d with 16 supercharges. | 8d supergravity, reconstruction of internal geometry and the swampland |
we report on the polarized light curves of the galactic center supermassive black hole sagittarius a*, obtained at millimeter wavelength with the atacama large millimeter/submillimeter array (alma). the observations took place as a part of the event horizon telescope campaign. we compare the observations taken during the low variability source state on 2017 apr. 6 and 7 with those taken immediately after the x-ray flare on 2017 apr. 11. for the latter case, we observe rotation of the electric vector position angle with a timescale of ∼70 min. we interpret this rotation as a signature of the equatorial clockwise orbital motion of a hot spot embedded in a magnetic field dominated by a dynamically important vertical component, observed at a low inclination ∼20°. the hot spot radiates strongly polarized synchrotron emission, briefly dominating the linear polarization measured by alma in the unresolved source. our simple emission model captures the overall features of the polarized light curves remarkably well. assuming a keplerian orbit, we find the hot spot orbital radius to be ∼5 schwarzschild radii. we observe hints of a positive black hole spin, that is, a prograde hot spot motion. accounting for the rapidly varying rotation measure, we estimate the projected on-sky axis of the angular momentum of the hot spot to be ∼60° east of north, with a 180° ambiguity. these results suggest that the accretion structure in sgr a* is a magnetically arrested disk rotating clockwise. | orbital motion near sagittarius a* . constraints from polarimetric alma observations |
we conduct a preliminary investigation into the phenomenological implications of einsteinian cubic gravity (ecg), a four-dimensional theory of gravity cubic in curvature of interest for its unique formulation and properties. we find an analytic approximation for a spherically symmetric black hole solution to this theory using a continued fraction ansatz. this approximate solution is valid everywhere outside of the horizon and we use it to study the orbit of massive test bodies near a black hole, specifically computing the innermost stable circular orbit. we compute constraints on the ecg coupling parameter imposed by shapiro time delay. we then compute the shadow of an ecg black hole and find it to be larger than its einsteinian counterpart in general relativity for the same value of the mass. applying our results to sgr a*, we find that departures from general relativity are small but in principle distinguishable. | shadows, signals, and stability in einsteinian cubic gravity |
in a recent note [1] i argued that the holographic origin of ordinary gravitational attraction is the quantum mechanical tendency for operators to grow under time evolution. in a follow-up [2] the claim was tested in the context of the syk theory and its bulk dual—the theory of near-extremal black holes. in this paper i give an improved version of the size-momentum correspondence of [2], and show that newton's laws of motion are a consequence. operator size is closely related to complexity. therefore one may say that gravitational attraction is a manifestation of the tendency for complexity to increase. the improved version of the size-momentum correspondence can be justified by the arguments of lin, maldacena, and zhao [3] constructing symmetry generators for the approximate symmetries of the syk model. | complexity and newton's laws |
we construct regular rotating black hole and no-horizon spacetimes based on the recently introduced spherically symmetric generic regular black hole spacetimes related to electric or magnetic charge under nonlinear electrodynamics coupled to general relativity that for special values of the spacetime parameters reduce to the bardeen and hayward spacetimes. we show that the weak and strong energy conditions are violated inside the cauchy horizons of these generic rotating black holes. we give the boundary between the rotating black hole and no-horizon spacetimes and determine the black hole horizons and the boundary of the ergosphere. we introduce the separated carter equations for the geodesic motion in these rotating spacetimes. for the most interesting new class of the regular spacetimes, corresponding for magnetic charges to the maxwell field in the weak field limit of the nonlinear electrodynamics, we determine the structure of the circular geodesics and discuss their properties. we study the epicyclic motion of a neutral particle moving along the stable circular orbits around the "maxwellian" rotating regular black holes. we show that epicyclic frequencies measured by the distant observers and related to the oscillatory motion of the neutral test particle along the stable circular orbits around the rotating singular and regular maxwellian black holes are always smaller than ones in the kerr spacetime. | generic rotating regular black holes in general relativity coupled to nonlinear electrodynamics |
we study a holographic construction of quantum rotating btz black holes that incorporates the exact backreaction from strongly coupled quantum conformal fields. it is based on an exact four-dimensional solution for a black hole localized on a brane in ads4, first discussed some years ago but never fully investigated in this manner. besides quantum cft effects and their backreaction, we also investigate the role of higher-curvature corrections in the effective three-dimensional theory. we obtain the quantum-corrected geometry and the renormalized stress tensor. we show that the quantum black hole entropy, which includes the entanglement of the fields outside the horizon, satisfies the first law of thermodynamics exactly, even in the presence of backreaction and with higher-curvature corrections, while the bekenstein-hawking-wald entropy does not. this result, which involves a rather non-trivial bulk calculation, shows the consistency of the holographic interpretation of braneworlds. we compare our renormalized stress tensor to results derived for free conformal fields, and for a previous holographic construction without backreaction effects, which is shown to be a limit of the solutions in this article. | quantum btz black hole |
we consider black holes generically sourced by quantum matter described by regular wavefunctions. this allows for integrable effective energy densities and the removal of cauchy horizons in spherically symmetric configurations. moreover, we identify the ultrarigid rotation of the kerr spacetime as causing the existence of an inner horizon in rotating systems, and describe general properties for quantum matter cores at the centre of rotating black holes with integrable singularities and no cauchy horizon. | quantum rotating black holes |
we study the topology of black hole thermodynamics in four-, five-, and seven-dimensional r -charged black holes. while the 4d r -charged black hole possesses four charges, the 5d and 7d r -charged black holes have three and two charges, respectively. in our study, we investigate the influence of charge configuration of the r -charged black holes on the topology of their thermodynamics. in each of these black holes, we consider a number of different charge configurations and compute the topological charges associated with the critical points. based on the values of the topological charges, we classify the critical points into conventional and novel critical points. we find that the number of critical points and their nature depends on the charge configuration of the r -charged black holes irrespective of their dimensionality. however, the total topological charge for all the charge configurations in 4d, 5d, and 7d remains the same, q =-1 . this indicates that the r -charged black holes in 4d, 5d, and 7d are thermodynamically in the same topological class. we also conclude that the variation of charge configurations does not have any impact on the topological class of thermodynamics for r -charged black holes. | topology of thermodynamics in r -charged black holes |
we calculate the scattering amplitude of two rotating objects with the linear-in-curvature spin-induced multipoles of kerr black holes at o (g2) and all orders in the spins of both objects. this is done including the complete set of contact terms potentially relevant to kerr-black-hole scattering at o (g2). as such, kerr black holes should be described by this scattering amplitude for a specific choice of values for the contact-term coefficients. the inclusion of all potential contact terms means this amplitude allows for a comprehensive search for structures emerging for certain values of the coefficients, and hence special properties that might be exhibited by kerr-black-hole scattering. our result can also act as a template for comparison for future computations of classical gravitational high-spin scattering. | classical gravitational scattering amplitude at o (g2s1∞s2∞) |
dijet events are studied in the proton-proton collision data set recorded at √{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 data set 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 p p collision data collected at √{s }=13 tev with the atlas detector |
electrons in clean macroscopic samples of graphene exhibit an astonishing variety of quantum phases when strong perpendicular magnetic field is applied. these include integer and fractional quantum hall states as well as symmetry broken phases and quantum hall ferromagnetism. here we show that mesoscopic graphene flakes in the regime of strong disorder and magnetic field can exhibit another remarkable quantum phase described by holographic duality to an extremal black hole in two-dimensional anti-de sitter space. this phase of matter can be characterized as a maximally chaotic non-fermi liquid since it is described by a complex fermion version of the sachdev-ye-kitaev model known to possess these remarkable properties. | quantum holography in a graphene flake with an irregular boundary |
we show that bulk operators lying between the outermost extremal surface and the asymptotic boundary admit a simple boundary reconstruction in the classical limit. this is the converse of the python's lunch conjecture, which proposes that operators with support between the minimal and outermost (quantum) extremal surfaces-e.g. the interior hawking partners-are highly complex. our procedure for reconstructing this 'simple wedge' is based on the hkll construction, but uses causal bulk propagation of perturbed boundary conditions on lorentzian timefolds to expand the causal wedge as far as the outermost extremal surface. as a corollary, we establish the simple entropy proposal for the holographic dual of the area of a marginally trapped surface as well as a similar holographic dual for the outermost extremal surface. we find that the simple wedge is dual to a particular coarse-grained cft state, obtained via averaging over all possible python's lunches. an efficient quantum circuit converts this coarse-grained state into a 'simple state' that is indistinguishable in finite time from a state with a local modular hamiltonian. under certain circumstances, the simple state modular hamiltonian generates an exactly local flow; we interpret this result as a holographic dual of black hole uniqueness. | a world without pythons would be so simple |
we examine the question how string theory achieves a sum over bulk geometries with fixed asymptotic boundary conditions. we discuss this problem with the help of the tensionless string on ℳ3×s3×t4 (with one unit of ns-ns flux) that was recently understood to be dual to the symmetric orbifold symn (t4). we strengthen the analysis of [1] and show that the perturbative string partition function around a fixed bulk background already includes a sum over semi-classical geometries and large stringy corrections can be interpreted as various semi-classical geometries. we argue in particular that the string partition function on a euclidean wormhole geometry factorizes completely into factors associated to the two boundaries of spacetime. central to this is the remarkable property of the moduli space integral of string theory to localize on covering spaces of the conformal boundary of ℳ3. we also emphasize the fact that string perturbation theory computes the grand canonical partition function of the family of theories ⊕n symn (t4). the boundary partition function is naturally expressed as a sum over winding worldsheets, each of which we interpret as a `stringy geometry'. we argue that the semi-classical bulk geometry can be understood as a condensate of such stringy geometries. we also briefly discuss the effect of ensemble averaging over the narain moduli space of t4 and of deforming away from the orbifold by the marginal deformation. | summing over geometries in string theory |
the majority of the accreting supermassive black holes in the universe are obscured by large columns of gas and dust. the location and evolution of this obscuring material have been the subject of intense research in the past decades, and are still debated. a decrease in the covering factor of the circumnuclear material with increasing accretion rates has been found by studies across the electromagnetic spectrum. the origin of this trend may be driven by the increase in the inner radius of the obscuring material with incident luminosity, which arises from the sublimation of dust; by the gravitational potential of the black hole; by radiative feedback; or by the interplay between outflows and inflows. however, the lack of a large, unbiased and complete sample of accreting black holes, with reliable information on gas column density, luminosity and mass, has left the main physical mechanism that regulates obscuration unclear. here we report a systematic multi-wavelength survey of hard-x-ray-selected black holes that reveals that radiative feedback on dusty gas is the main physical mechanism that regulates the distribution of the circumnuclear material. our results imply that the bulk of the obscuring dust and gas is located within a few to tens of parsecs of the accreting supermassive black hole (within the sphere of influence of the black hole), and that it can be swept away even at low radiative output rates. the main physical driver of the differences between obscured and unobscured accreting black holes is therefore their mass-normalized accretion rate. | the close environments of accreting massive black holes are shaped by radiative feedback |
we extract the black hole (bh) static tidal deformability coefficients (love numbers) and their spin-0 and spin-1 analogs by comparing on-shell amplitudes for fields to scatter off a spinning bh in the worldline effective field theory and in general relativity. we point out that the general relativity amplitudes due to tidal effects originate entirely from the bh potential region. thus, they can be separated from gravitational nonlinearities in the wave region, whose proper treatment requires higher order effective field theory loop calculations. in particular, the elastic scattering in the near field approximation is produced exclusively by tidal effects. we find this contribution to vanish identically, which implies that the static love numbers of kerr bhs are zero for all types of perturbations. we also reproduce the known behavior of scalar love numbers for higher-dimensional bhs. our results are manifestly gauge invariant and coordinate independent, thereby providing a valuable consistency check for the commonly used off-shell methods. | vanishing of black hole tidal love numbers from scattering amplitudes |
the rate of complexification of a quantum state is conjectured to be bounded from above by the average energy of the state. a different conjecture relates the complexity of a holographic cft state to the on-shell gravitational action of a certain bulk region. we use `complexity equals action' conjecture to study the time evolution of the complexity of the cft state after a global quench. we find that the rate of growth of complexity is not only consistent with the conjectured bound, but it also saturates the bound soon after the system has achieved local equilibrium. | evolution of complexity following a global quench |
effective gravity and gauge fields are emergent properties intrinsic for low-energy quasiparticles in topological semimetals. here, taking two dirac semimetals as examples, we demonstrate that applied lattice strain can generate warped spacetime, with fascinating analogues in astrophysics. particularly, we study the possibility of simulating black-hole/white-hole event horizons and gravitational lensing effect. furthermore, we discover strain-induced topological phase transitions, both in the bulk materials and in their thin films. especially in thin films, the transition between the quantum spin hall and the trivial insulating phases can be achieved by a small strain, naturally leading to the proposition of a novel piezo-topological transistor device. possible experimental realizations and analogue of hawking radiation effect are discussed. our result bridges multiple disciplines, revealing topological semimetals as a unique table-top platform for exploring interesting phenomena in astrophysics and general relativity; it also suggests realistic materials and methods to achieve controlled topological phase transitions with great potential for device applications. | artificial gravity field, astrophysical analogues, and topological phase transitions in strained topological semimetals |
modular covariance of torus one-point functions constrains the three point function coefficients of a two dimensional cft. this leads to an asymptotic formula for the average value of light-heavy-heavy three point coefficients, generalizing cardy's formula for the high energy density of states. the derivation uses certain asymptotic properties of one-point conformal blocks on the torus. our asymptotic formula matches a dual ads3 computation of one point functions in a black hole background. this is evidence that the btz black hole geometry emerges upon course-graining over a suitable family of heavy microstates. | a cardy formula for three-point coefficients or how the black hole got its spots |
we study two disjoint universes in an entangled pure state. when only one universe contains gravity, the path integral for the nth rényi entropy includes a wormhole between the n copies of the gravitating universe, leading to a standard 'island formula' for entanglement entropy consistent with unitarity of quantum information. when both universes contain gravity, gravitational corrections to this configuration lead to a violation of unitarity. however, the path integral is now dominated by a novel wormhole with 2n boundaries connecting replica copies of both universes. the analytic continuation of this contribution involves a quotient by ${\mathbb{z}}_{n}$ replica symmetry, giving a cylinder connecting the two universes. when entanglement is large, this configuration has an effective description as a 'swap wormhole', a geometry in which the boundaries of the two universes are glued together by a 'swaperator'. this description allows precise computation of a generalized entropy-like formula for entanglement entropy. the quantum extremal surface computing the entropy lives on the lorentzian continuation of the cylinder/swap wormhole, which has a connected cauchy slice stretching between the universes-a realization of the er = epr idea. the new wormhole restores unitarity of quantum information. | entanglement between two gravitating universes |
we study the near-zone symmetries of a massless scalar field on four-dimensional black hole backgrounds. we provide a geometric understanding that unifies various recently discovered symmetries as part of an so(4, 2) group. of these, a subset are exact symmetries of the static sector and give rise to the ladder symmetries responsible for the vanishing of love numbers. in the kerr case, we compare different near-zone approximations in the literature, and focus on the implementation that retains the symmetries of the static limit. we also describe the relation to spin-1 and 2 perturbations. | near-zone symmetries of kerr black holes |
in this paper, we study joule-thomson expansion for kerr-ads black holes in the extended phase space. a joule-thomson expansion formula of kerr-ads black holes is derived. we investigate both isenthalpic and numerical inversion curves in the t- p plane and demonstrate the cooling-heating regions for kerr-ads black holes. we also calculate the ratio between minimum inversion and critical temperatures for kerr-ads black holes. | joule-thomson expansion of kerr-ads black holes |
we present a new effective description of macroscopic kruskal black holes that incorporates corrections due to quantum geometry effects of loop quantum gravity. it encompasses both the "interior" region that contains classical singularities and the "exterior" asymptotic region. singularities are naturally resolved by the quantum geometry effects of loop quantum gravity, and the resulting quantum extension of the full kruskal space-time is free of all the known limitations of previous investigations of the schwarzschild interior. we compare and contrast our results with these investigations and also with the expectations based on the ads /cft duality. | quantum transfiguration of kruskal black holes |
we study aspects of black holes and quantum chaos through the behavior of computational costs, which are distance notions in the manifold of unitaries of the theory. to this end, we enlarge nielsen geometric approach to quantum computation and provide metrics for finite temperature/energy scenarios and cft's. from the framework, it is clear that costs can grow in two different ways: operator vs `simple' growths. the first type mixes operators associated to different penalties, while the second does not. important examples of simple growths are those related to symmetry transformations, and we describe the costs of rotations, translations, and boosts. for black holes, this analysis shows how infalling particle costs are controlled by the maximal lyapunov exponent, and motivates a further bound on the growth of chaos. the analysis also suggests a correspondence between proper energies in the bulk and average `local' scaling dimensions in the boundary. finally, we describe these complexity features from a dual perspective. using recent results on syk we compute a lower bound to the computational cost growth in syk at infinite temperature. at intermediate times it is controlled by the lyapunov exponent, while at long times it saturates to a linear growth, as expected from the gravity description. | black holes, complexity and quantum chaos |
the eigenstate thermalization hypothesis (eth) explains how closed unitary quantum systems can exhibit thermal behavior in pure states. in this work we examine a recently proposed microscopic model of a black hole in ads2, the so-called sachdev-ye-kitaev (syk) model. we show that this model satisfies the eigenstate thermalization hypothesis by solving the system in exact diagonalization. using these results we also study the behavior, in eigenstates, of various measures of thermalization and scrambling of information. we establish that two-point functions in finite-energy eigenstates approximate closely their thermal counterparts and that information is scrambled in individual eigenstates. we study both the eigenstates of a single random realization of the model, as well as the model obtained after averaging of the random disordered couplings. we use our results to comment on the implications for thermal states of a putative dual theory, i.e. the ads2 black hole. | eigenstate thermalization in the sachdev-ye-kitaev model |
in this paper, we study the thermodynamic geometry of charged gauss-bonnet black holes (and reissner-nordström black holes, for the sake of comparison) in anti-de sitter spacetimes in both (t , v ) and (s , p ) planes. the thermodynamic phase space is known to have an underlying contact and metric structure; ruppeiner geometry then naturally arises in this framework. sign of ruppeiner curvature can be used to probe the nature of interactions between the black hole microstructures. it is found that there are both attraction and repulsion dominated regions which are in general determined by the electric charge, gauss-bonnet coupling, and horizon radius of the black hole. the results are physically explained by considering that these black hole systems consist of charged as well as neutral microstructures much like a binary mixture of fluids. | thermodynamic geometry for charged gauss-bonnet black holes in ads spacetimes |
quantum scrambling describes the spreading of information into many degrees of freedom in quantum systems, such that the information is no longer accessible locally but becomes distributed throughout the system. this idea can explain how quantum systems become classical and acquire a finite temperature, or how in black holes the information about the matter falling in is seemingly erased. we probe the exponential scrambling of a multiparticle system near a bistable point in phase space and utilize it for entanglement-enhanced metrology. a time-reversal protocol is used to observe a simultaneous exponential growth of both the metrological gain and the out-of-time-order correlator, thereby experimentally verifying the relation between quantum metrology and quantum information scrambling. our results show that rapid scrambling dynamics capable of exponentially fast entanglement generation are useful for practical metrology, resulting in a 6.8(4)-decibel gain beyond the standard quantum limit. | improving metrology with quantum scrambling |
we study the holographic complexity in de sitter spacetime, especially how the hyperfast growth of holographic complexity in de sitter spacetime is affected under a small and early perturbation. the perturbed geometry is de sitter spacetime with shock waves. we find that the critical time, at which de sitter holographic complexity diverges, becomes always greater in the presence of the shock waves, which satisfies the averaged null energy conditions. this means that the hyperfast property of de sitter complexity is delayed by small perturbations. | shock waves and delay of hyperfast growth in de sitter complexity |
we present new analytic results on black hole perturbation theory. our results are based on a novel relation to four-dimensional$${\mathcal {n}}=2$$n=2supersymmetric gauge theories. we propose an exact version of bohr-sommerfeld quantization conditions on quasinormal mode frequencies in terms of the nekrasov partition function in a particular phase of the$$\omega $$ω-background. our quantization conditions also enable us to find exact expressions of eigenvalues of spin-weighted spheroidal harmonics. we test the validity of our conjecture by comparing against known numerical results for kerr black holes as well as for schwarzschild black holes. some extensions are also discussed. | black hole quasinormal modes and seiberg–witten theory |
we argue that, in a theory of quantum gravity in a four dimensional asymptotically flat spacetime, all information about massless excitations can be obtained from an infinitesimal neighbourhood of the past boundary of future null infinity and does not require observations over all of future null infinity. moreover, all information about the state that can be obtained through observations near a cut of future null infinity can also be obtained from observations near any earlier cut although the converse is not true. we provide independent arguments for these two assertions. similar statements hold for past null infinity. these statements have immediate implications for the information paradox since they suggest that the fine-grained von neumann entropy of the state defined on a segment $(-\infty,u)$ of future null infinity is independent of u. this is very different from the oft-discussed page curve that this entropy is sometimes expected to obey. we contrast our results with recent discussions of the page curve in the context of black hole evaporation, and also discuss the relation of our results to other proposals for holography in flat space. | the holographic nature of null infinity |
the novel data analysis challenges posed by the laser interferometer space antenna (lisa) arise from the overwhelmingly large number of astrophysical sources in the measurement band and the density with which they are found in the data. robust detection and characterization of the numerous gravitational wave sources in lisa data can not be done sequentially, but rather through a simultaneous global fit of a data model containing the full suite of astrophysical and instrumental features present in the data. while previous analyses have focused on individual source types in isolation, here we present the first demonstration of a lisa global fit analysis containing combined astrophysical populations. the prototype pipeline uses a blocked metropolis hastings algorithm to alternatingly fit to a population of ultracompact galactic binaries, known "verification binaries" already identified by electromagnetic observations, a population of massive black hole mergers, and an instrument noise model. the global lisa analysis software suite (glass) is assembled from independently developed samplers for the different model components. the modular design enables flexibility to future development by defining standard interfaces for adding new, or updating additional, components to the global fit without being overly prescriptive for how those modules must be internally designed. the glass pipeline is demonstrated on data simulated for the lisa data challenge 2b. results of the analysis and a road-map for continued development are described in detail. | prototype global analysis of lisa data with multiple source types |
topological lifshitz transitions involve many types of topological structures in momentum and frequency-momentum spaces, such as fermi surfaces, dirac lines, dirac and weyl points, etc., each of which has its own stability-supporting topological invariant ( n_1, n_2, n_3, {\tilde n}_3, etc.). the topology of the shape of fermi surfaces and dirac lines and the interconnection of objects of different dimensionalities produce a variety of lifshitz transition classes. lifshitz transitions have important implications for many areas of physics. to give examples, transition-related singularities can increase the superconducting transition temperature; lifshitz transitions are the possible origin of the small masses of elementary particles in our universe, and a black hole horizon serves as the surface of the lifshitz transition between vacua with type-i and type-ii weyl points. | exotic lifshitz transitions in topological materials |
scalar fields coupled to the gauss-bonnet invariant can undergo a tachyonic instability, leading to spontaneous scalarization of black holes. studies of this effect have so far been restricted to single black hole spacetimes. we present the first results on dynamical scalarization in head-on collisions and quasicircular inspirals of black hole binaries with numerical relativity simulations. we show that black hole binaries can either form a scalarized remnant or dynamically descalarize by shedding off its initial scalar hair. the observational implications of these findings are discussed. | dynamical descalarization in binary black hole mergers |
the acoustic black hole (abh) is a technique for passive vibration control that was recently developed within the structural dynamics and vibroacoustics communities. from a general perspective, the abh effect is achieved by embedding a local inhomogeneity in a thin-walled structure, typically a beam or a plate. this inhomogeneity is characterized by a variation of the geometric properties (although material variations are also possible) according to a spatial power law profile. the combination of a local stiffness reduction, due to the power law variation of the wall thickness, and of a local increase in damping, provided by the concurrent application of viscoelastic layers, gives rise to a significant reduction of the wave speed and to a remarkable enhancement of the attenuation properties. as an elastic wave travels within an abh, its speed experiences a smooth and continuous decrease. in the ideal case, that is when the wall thickness vanishes at the abh center, the wave speed decreases to zero. in the non-ideal case, that is when the abh has a non-zero residual thickness at its center, the wave speed still decreases smoothly but it never vanishes. in this latter case, which is of great importance for practical applications, the abh is typically combined with lossy media (e.g. viscoelastic layers) in order to achieve significantly enhanced structural loss factors. if the speed of an incoming wave can vanish inside the abh, it follows that this object behaves as a wave trap that extracts elastic energy from the host medium without, in principle, ever releasing it. several characteristic properties are generally observed in structures with embedded abhs: significant reduction in vibration and acoustic radiation levels, low reflection coefficient at the abh location, localized vibration and trapped modes, and existence of cut-on frequencies. contrarily to passive vibration methods based on viscoelastic materials, the abh was developed and applied to reduce vibrations and structure-radiated noise without increasing the total mass of the system. more recently, applications to other areas including elastic metastructures, energy harvesting, vibro-impact systems, and cochlear systems were also investigated. this review is intended to provide a comprehensive summary of the state-of-the-art of abh technology, spanning from theoretical and numerical contributions to practical applications. | the acoustic black hole: a review of theory and applications |
we introduce a systematic and direct procedure to generate hairy rotating black holes by deforming a spherically symmetric seed solution. we develop our analysis in the context of the gravitational decoupling approach, without resorting to the newman-janis algorithm. as examples of possible applications, we investigate how the kerr black hole solution is modified by a surrounding fluid with conserved energy-momentum tensor. we find nontrivial extensions of the kerr and kerr-newman black holes with primary hair. we prove that a rotating and charged black hole can have the same horizon as kerr's, schwarzschild's, or reissner-nordström's, thus showing possible observational effects of matter around black holes. | gravitational decoupling for axially symmetric systems and rotating black holes |
we consider quantum diffusion in ultraslow-roll (usr) inflation. using the δ n formalism, we present the first stochastic calculation of the probability distribution p (r ) of the curvature perturbation during usr. we capture the nonlinearity of the system, solving the coupled evolution of the coarse-grained background with random kicks from the short wavelength modes, simultaneously with the mode evolution around the stochastic background. this leads to a non-markovian process from which we determine the highly non-gaussian tail of p (r ). studying the production of primordial black holes in a viable model, we find that stochastic effects during usr increase their abundance by a factor of ∼105 compared with the gaussian approximation. | non-gaussian tail of the curvature perturbation in stochastic ultraslow-roll inflation: implications for primordial black hole production |
simulated images of a black hole surrounded by optically thin emission typically display two main features: a central brightness depression and a narrow "photon ring" consisting of strongly lensed images superimposed over the direct emission. the photon ring closely tracks a theoretical curve on the image plane corresponding to light rays that asymptote to bound photon orbits. the size and shape of this critical curve are purely governed by the kerr geometry; in contrast, the size, shape, and depth of the observed brightness depression depend on the details of the emission region. for instance, images of spherical accretion models display a distinctive dark region-the "black hole shadow"-that completely fills the photon ring. by contrast, in models of equatorial disks extending to the event horizon, the darkest region in the image is restricted to a much smaller area-an inner shadow-whose edge lies near the direct lensed image of the equatorial horizon. using both general relativistic mhd simulations and semi-analytic models, we demonstrate that the photon ring and inner shadow may be simultaneously visible in submillimeter images of m87*, where magnetically arrested disk simulations predict that the emission arises in a thin region near the equatorial plane. we show that the relative size, shape, and centroid of the photon ring and inner shadow can be used to estimate the black hole mass and spin, breaking degeneracies in measurements of these quantities from the photon ring alone. both features may be accessible to direct observation via high-dynamic-range images with a next-generation event horizon telescope. | observing the inner shadow of a black hole: a direct view of the event horizon |
we consider primordial black hole (pbh) production in inflationary α-attractors. we discuss two classes of models, namely models with a minimal polynomial superpotential as well as modulated chaotic ones that admit pbhs. we find that a significant amplification of the curvature power spectrum script pr can be realized in this class of models with a moderate tuning of the potential parameters. we consistently examine the pbh formation during radiation and additionally during reheating eras where the background pressure is negligible. it is shown that basic features of the curvature power spectrum are explicitly related with the postinflationary cosmic evolution and that the pbh mass and abundance expressions are accordingly modified. pbhs in the mass range 10-16-10-14 msolar can form with a cosmologically relevant abundance for a power spectrum peak script pr ~ 10-2 and large reheating temperature and, furthermore, for a moderate peak script pr ~ 10-5 and reheating temperature trh~ 107 gev, characteristic of the position of the power spectrum peak. regarding the cmb observables, the α-attractor models utilized here to generate pbh in the low-mass region predict in general a smaller ns and larger r and αs parameter values compared to the conventional inflationary α-attractor models. | primordial black holes from α-attractors |
we propose a new entropy construct that generalizes the tsallis, rényi, sharma-mittal, barrow, kaniadakis, and loop quantum gravity entropies and reduces to the bekenstein-hawking entropy in a certain limit. this proposal is applied to the schwarzschild black hole and to spatially homogeneous and isotropic cosmology, where it is shown that it can potentially describe inflation and/or holographic dark energy. | from nonextensive statistics and black hole entropy to the holographic dark universe |
we derive the third subleading (n3lo) corrections of the quadratic-in-spin sectors via the eft of spinning objects in post-newtonian (pn) gravity. these corrections consist of contributions from 4 sectors for generic compact binaries, that enter at the fifth pn order. one of these contributions is due to a new tidal interaction, that is unique to the sectors with spin, and complements the first tidal interaction that also enters at this pn order in the simple point-mass sector. the evaluation of feynman graphs is carried out in a generic dimension via advanced multi-loop methods, and gives rise to dimensional-regularization poles in conjunction with logarithms. at these higher-spin sectors the reduction of generalized lagrangians entails redefinitions of the position beyond linear order. we provide here the most general lagrangians and hamiltonians. we then specify the latter to simplified configurations, and derive the consequent gauge-invariant relations among the binding energy, angular momentum, and frequency. we end with a derivation of all the scattering angles that correspond to an extension of our hamiltonians to the scattering problem in the simplified aligned-spins configuration, as a guide to scattering-amplitudes studies. | n3lo quadratic-in-spin interactions for generic compact binaries |
we argue that novel (highly nonclassical) quantum extremal surfaces (qess) play a crucial role in reconstructing the black hole interior even for isolated, single-sided, non-evaporating black holes (i.e. with no auxiliary reservoir). specifically, any code subspace where interior outgoing modes can be excited will have a qes in its maximally mixed state. we argue that as a result, reconstruction of interior outgoing modes is always exponentially complex. our construction provides evidence in favor of a strong python's lunch proposal: that nonminimal qess are the exclusive source of exponential complexity in the holographic dictionary. we also comment on the relevance of these qess to the geometrization of state dependence in the typicality arguments for firewalls. | finding pythons in unexpected places |
space-borne gravitational wave detectors like tianqin are expected to detect gravitational wave signals emitted by the mergers of massive black hole binaries. luminosity distance information can be obtained from gravitational wave observations, and one can perform cosmological inference if redshift information can also be extracted, which would be straightforward if an electromagnetic counterpart exists. in this paper, we concentrate on the conservative scenario where the electromagnetic counterparts are not available, and comprehensively study if cosmological parameters can be inferred through a statistical approach, utilizing the nonuniform distribution of galaxies as well as the black hole mass-host galaxy bulge luminosity relationship. by adopting different massive black hole binary merger models, and assuming different detector configurations, we conclude that the statistical inference of cosmological parameters is indeed possible. tianqin is expected to constrain the hubble constant to a relative error of about 4%-7%, depending on the underlying model. the multidetector network of tianqin and lisa can significantly improve the precision of cosmological parameters. in the most favorable model, it is possible to achieve a level of 1.7% with a network of tianqin and lisa. we find that without electromagnetic counterparts, constraints on all other parameters need a larger number of events or more precise sky localization of gravitational wave sources, which can be achieved by the multidetector network or under a favorable model for massive black hole mergers. however, in the optimistic case, where electromagnetic counterparts are available, one can obtain useful constraints on all cosmological parameters in the lambda cold dark matter cosmology, regardless of the population model. moreover, we can also constrain the equation of state of the dark energy without the electromagnetic counterparts, and it is even possible to study the evolution of equation of state of the dark energy when the electromagnetic counterparts are observed. | constraining the cosmological parameters using gravitational wave observations of massive black hole binaries and statistical redshift information |
in a semimetal, both electrons and holes contribute to the density of states at the fermi level. the small band overlaps and multiband effects engender novel electronic properties. we show that a moderate hydrostatic pressure effectively suppresses the band gap in the elemental semiconductor black phosphorus. an electronic topological transition takes place at approximately 1.2 gpa, above which black phosphorus evolves into a semimetal state that is characterized by a colossal positive magnetoresistance and a nonlinear field dependence of hall resistivity. the shubnikov-de haas oscillations detected in magnetic field reveal the complex fermi surface topology of the semimetallic phase. in particular, we find a nontrivial berry phase in one fermi surface that emerges in the semimetal state, as evidence of a dirac-like dispersion. the observed semimetallic behavior greatly enriches the material property of black phosphorus and sets the stage for the exploration of novel electronic states in this material. | pressure-induced electronic transition in black phosphorus |
a (3 +1 )-dimensional einstein-gauss-bonnet theory of gravity has been recently formulated by glavan and lin [d. glavan and c. lin, phys. rev. lett. 124, 081301 (2020), 10.1103/physrevlett.124.081301] which is different from the pure einstein theory, i.e., bypasses the lovelock's theorem and avoids ostrogradsky instability. the theory was formulated in d >4 dimensions and its action consists of the einstein-hilbert term with a cosmological constant, while the gauss-bonnet term multiplied by a factor 1 /(d -4 ). then, the four-dimensional theory is defined as the limit d →4 . here we generalize this approach to the four-dimensional einstein-lovelock theory and formulate the most general static 4 d black-hole solution allowing for a λ term (either positive or negative) and the electric charge q . as metric functions cannot be found in a closed form in the general case, we develop and share publicly the code which constructs the metric functions for every given set of parameters. | black holes in the four-dimensional einstein-lovelock gravity |
the paper at hand studies the heat engine provided by black holes in the presence of massive gravity. the main motivation is to investigate the effects of massive gravity on different properties of the heat engine. it will be shown that massive gravity parameters modify the efficiency of engine on a significant level. furthermore, it will be pointed out that it is possible to have a heat engine for non-spherical black holes in massive gravity, and therefore, we will study the effects of horizon topology on the properties of heat engine. surprisingly, it will be shown that the highest efficiency for the heat engine belongs to black holes with the hyperbolic horizon, while the lowest one belongs to the spherical black holes. | black holes in massive gravity as heat engines |
making use of definitive new lattice computations of the standard model thermodynamics during the quantum chromodynamic (qcd) phase transition, we calculate the enhancement in the mass distribution of primordial black holes (pbhs) due to the softening of the equation of state. we find that the enhancement peaks at approximately 0.7msolar, with the formation rate increasing by at least two orders of magnitude due to the softening of the equation of state at this time, with a range of approximately 0.3msolar<m<1.4msolar at full width half-maximum. pbh formation is increased by a smaller amount for pbhs with masses spanning a large range, 10-3msolar<mpbh<103msolar, which includes the masses of the bhs that ligo detected. the most significant source of uncertainty in the number of pbhs formed is now due to unknowns in the formation process, rather than from the phase transition. a near scale-invariant density power spectrum tuned to generate a population with mass and merger rate consistent with that detected by ligo should also produce a much larger energy density of pbhs with solar mass. the existence of bhs below the chandresekhar mass limit would be a smoking gun for a primordial origin and they could arguably constitute a significant fraction of the cold dark matter density. they also pose a challenge to inflationary model building which seek to produce the ligo bhs without overproducing lighter pbhs. | primordial black holes with an accurate qcd equation of state |
advanced ligo's discovery of gravitational-wave events is stimulating extensive studies on the origin of binary black holes. assuming that the gravitational-wave events can be explained by binary primordial black hole mergers, we utilize the upper limits on the stochastic gravitational-wave background given by advanced ligo as a new observational window to independently constrain the abundance of primordial black holes in dark matter. we show that advanced ligo's first observation run gives the best constraint on the primordial black hole abundance in the mass range 1 m⊙≲mpbh≲100 m⊙, pushing the previous microlensing and dwarf galaxy dynamics constraints tighter by 1 order of magnitude. moreover, we discuss the possibility to detect the stochastic gravitational-wave background from primordial black holes, in particular from subsolar mass primordial black holes, by advanced ligo in the near future. | constraints on the primordial black hole abundance from the first advanced ligo observation run using the stochastic gravitational-wave background |
the sachdev-ye-kitaev (syk) model describes a collection of randomly interacting majorana fermions that exhibits profound connections to quantum chaos and black holes. we propose a solid-state implementation based on a quantum dot coupled to an array of topological superconducting wires hosting majorana zero modes. interactions and disorder intrinsic to the dot mediate the desired random majorana couplings, while an approximate symmetry suppresses additional unwanted terms. we use random-matrix theory and numerics to show that our setup emulates the syk model (up to corrections that we quantify) and discuss experimental signatures. | approximating the sachdev-ye-kitaev model with majorana wires |
we reformulate recent insights into black hole information in a manner emphasizing operationally-defined notions of entropy, lorentz-signature descriptions, and asymptotically flat spacetimes. with the help of replica wormholes, we find that experiments of asymptotic observers are consistent with black holes as unitary quantum systems, with density of states given by the bekenstein-hawking formula. however, this comes at the cost of superselection sectors associated with the state of baby universes. spacetimes studied by polchinski and strominger in 1994 provide a simple illustration of the associated concepts and techniques, and we argue them to be a natural late-time extrapolation of replica wormholes. the work aims to be self-contained and, in particular, to be accessible to readers who have not yet mastered earlier formulations of the ideas above. | observations of hawking radiation: the page curve and baby universes |
computation of topological charges of the schwarzschild and charged black holes in ads in canonical and grand canonical ensembles allows for a classification of the phase transition points via the bragg-williams off-shell free energy. we attempt a topological classification of the critical points and the equilibrium phases of the dual gauge theory via a phenomenological matrix model, which captures the features of the ${\cal{n}}=4$, $su(n)$ super yang-mills theory on $s^3$ at finite temperature at large $n$. with minimal modification of parameters, critical points of the matrix model at finite chemical potential can be classified as well. the topological charges of locally stable and unstable dynamical phases of the system turn out to be opposite to each other, totalling to zero, and this matches the analysis in the bulk. | topology of critical points in boundary matrix duals |
we investigate the hawking radiation of massive spin-1 vector particles, which are coupled to vacuum fluctuations of a quantum field, from a rindler modified schwarzschild black hole. rindler acceleration is used to produce the post-general relativistic theory of gravity for the distant field of a point mass. the gravitational lensing problem of the rindler modified schwarzschild black hole is also studied. we compute the deflection angle for the ir region (large distance limit as infrared) by using the gaussian curvature of the optical metric of this back hole. our investigations clarify how the rindler acceleration plays a role on the hawking radiation and gravitational lensing. | hawking radiation and deflection of light from rindler modified schwarzschild black hole |
an outstanding open issue in our quest for physics beyond einstein is the unification of general relativity (gr) and quantum physics. loop quantum gravity (lqg) is a leading approach toward this goal. at its heart is the central lesson of gr: gravity is a manifestation of spacetime geometry. thus, the approach emphasizes the quantum nature of geometry and focuses on its implications in extreme regimes—near the big bang and inside black holes—where einstein's smooth continuum breaks down. we present a brief overview of the main ideas underlying lqg and highlight a few recent advances. this report is addressed to non-experts. | a short review of loop quantum gravity |
the primordial scalar power spectrum is well constrained by the cosmological data on large scales, primarily from the observations of the anisotropies in the cosmic microwave background. over the last few years, it has been recognized that a sharp rise in power on small scales will lead to the enhanced formation of primordial black holes (pbhs) and also generate secondary gravitational waves (gws) of higher and, possibly, detectable amplitudes. it is well understood that scalar power spectra with cobe normalized amplitude on the cosmic microwave background scales and enhanced amplitudes on smaller scales can be generated due to deviations from slow roll in single, canonical scalar field models of inflation. in fact, an epoch of so-called ultraslow roll inflation can lead to the desired amplification. we find that scenarios that lead to ultraslow roll can be broadly classified into two types, one wherein there is a brief departure from inflation (a scenario referred to as punctuated inflation) and another wherein such a departure does not arise. in this work, we consider a set of single field inflationary models involving the canonical scalar field that lead to ultraslow roll and punctuated inflation and examine the formation of pbhs as well as the generation of secondary gws in these models. apart from considering specific models, we reconstruct potentials from certain functional choices of the first slow roll parameter leading to ultraslow roll and punctuated inflation and investigate their observational signatures. in addition to the secondary tensor power spectrum, we calculate the secondary tensor bispectrum in the equilateral limit in these scenarios. moreover, we calculate the inflationary scalar bispectrum that arises in all the cases and discuss the imprints of the scalar non-gaussianities on the extent of pbhs formed and the amplitude of the secondary gws generated. we conclude with a discussion on the wider implications of our results. | primordial black holes and secondary gravitational waves from ultraslow roll and punctuated inflation |
setting the cosmological constant to be dynamical, we study the bulk and boundary thermodynamics of charged anti-de sitter black holes. we develop mass/energy formulas in terms of thermodynamic state functions for the extended thermodynamics, mixed thermodynamics, and boundary conformal field theory thermodynamics. we employ the residue method to study the topological properties of the phase transitions. our analysis reveals that the bulk and boundary thermodynamics are topologically equivalent for both criticalities and first-order phase transitions in the canonical ensembles, as well as for the hawking-page(-like) phase transitions in the grand canonical ensembles. additionally, those three kinds of phase transitions are shown to be distinguished by their unique topological charges. our results exemplify the gravity-gauge duality in terms of topology. | bulk-boundary thermodynamic equivalence: a topology viewpoint |
the nearby radio galaxy m87 is a prime target for studying black hole accretion and jet formation1,2. event horizon telescope observations of m87 in 2017, at a wavelength of 1.3 mm, revealed a ring-like structure, which was interpreted as gravitationally lensed emission around a central black hole3. here we report images of m87 obtained in 2018, at a wavelength of 3.5 mm, showing that the compact radio core is spatially resolved. high-resolution imaging shows a ring-like structure of 8.4−1.1+0.5 schwarzschild radii in diameter, approximately 50% larger than that seen at 1.3 mm. the outer edge at 3.5 mm is also larger than that at 1.3 mm. this larger and thicker ring indicates a substantial contribution from the accretion flow with absorption effects, in addition to the gravitationally lensed ring-like emission. the images show that the edge-brightened jet connects to the accretion flow of the black hole. close to the black hole, the emission profile of the jet-launching region is wider than the expected profile of a black-hole-driven jet, suggesting the possible presence of a wind associated with the accretion flow. | a ring-like accretion structure in m87 connecting its black hole and jet |
to test the role of large-scale magnetic fields in accretion processes, we study the dynamics of the charged test particles in the vicinity of a black hole immersed into an asymptotically uniform magnetic field. using the hamiltonian formalism of the charged particle dynamics, we examine chaotic scattering in the effective potential related to the black hole gravitational field combined with the uniform magnetic field. energy interchange between the translational and oscillatory modes of the charged particle dynamics provides a mechanism for charged particle acceleration along the magnetic field lines. this energy transmutation is an attribute of the chaotic charged particle dynamics in the combined gravitational and magnetic fields only, the black hole rotation is not necessary for such charged particle acceleration. the chaotic scatter can cause a transition to the motion along the magnetic field lines with small radius of the larmor motion or vanishing larmor radius, when the speed of the particle translational motion is largest and it can be ultra-relativistic. we discuss the consequences of the model of ionization of test particles forming a neutral accretion disc, or heavy ions following off-equatorial circular orbits, and we explore the fate of heavy charged test particles after ionization where no kick of heavy ions is assumed and only the switch-on effect of the magnetic field is relevant. we demonstrate that acceleration and escape of the ionized particles can be efficient along the kerr black hole symmetry axis parallel to the magnetic field lines. we show that a strong acceleration of the ionized particles to ultra-relativistic velocities is preferred in the direction close to the magnetic field lines. therefore, the process of ionization of keplerian discs around the kerr black holes can serve as a model of relativistic jets. | acceleration of the charged particles due to chaotic scattering in the combined black hole gravitational field and asymptotically uniform magnetic field |
relativistic reflection features are commonly observed in the x-ray spectra of accreting black holes. in the presence of high quality data and with the correct astrophysical model, x-ray reflection spectroscopy can be quite a powerful tool to probe the strong gravity region, study the morphology of the accreting matter, measure black hole spins, and possibly test einstein's theory of general relativity in the strong field regime. in the last decade, there has been significant progress in the development of the analysis of these features, thanks to more sophisticated astrophysical models and new observational facilities. here we review the state-of-the-art in relativistic reflection modeling, listing assumptions and simplifications that may affect, at some level, the final measurements and may be investigated better in the future. we review black hole spin measurements and the most recent efforts to use x-ray reflection spectroscopy for testing fundamental physics. | towards precision measurements of accreting black holes using x-ray reflection spectroscopy |
we have studied the quasinormal modes (qnms) of a slowly rotating black hole with lorentz-violating parameter in einstein-bumblebee gravity. we analyse the slow rotation approximation of the rotating black hole in the einstein-bumblebee gravity, and obtain the master equations for scalar perturbation, vector perturbation and axial gravitational perturbation, respectively. using the matrix method and the continuous fraction method, we numerically calculate the qnm frequencies. in particular, for scalar field, it shows that the qnms up to the second order of rotation parameter have higher accuracy. the numerical results show that, for both scalar and vector fields, the lorentz-violating parameter has a significant effect on the imaginary part of the qnm frequencies, while having a relatively smaller impact on the real part of the qnm frequencies. but for axial gravitational perturbation, the effect of increasing the lorentz-violating parameter ℓ is similar to that of increasing the rotation parameter a ~. | qnms of slowly rotating einstein-bumblebee black hole |
we perform a hierarchical bayesian analysis of the gwtc-2 catalog to investigate the mixed scenario in which the merger events are explained by black holes of both astrophysical and primordial origin. for the astrophysical scenario we adopt the phenomenological model used by the ligo/virgo collaboration and we include the correlation between different parameters inferred from data, the role of the spins in both the primordial and astrophysical scenarios, and the impact of accretion in the primordial scenario. our best-fit mixed model has a strong statistical evidence relative to the single-population astrophysical model, thus supporting the coexistence of populations of black-hole mergers of two different origins. in particular, our results indicate that the astrophysical mergers account for roughly four times the number of primordial black hole events and predict that third-generation detectors, such as the einstein telescope and cosmic explorer, should detect up to hundreds of mergers from primordial black hole binaries at redshift z≳30. | bayesian evidence for both astrophysical and primordial black holes: mapping the gwtc-2 catalog to third-generation detectors |
it has been argued that the strong cosmic censorship conjecture is violated by reissner-nordström-de sitter black holes: for near-extremal black holes, generic scalar field perturbations arising from smooth initial data have finite energy at the cauchy horizon even though they are not continuously differentiable there. in this paper, we consider the analogous problem for coupled gravitational and electromagnetic perturbations. we find that such perturbations exhibit a much worse violation of strong cosmic censorship: for a sufficiently large near-extremal black hole, perturbations arising from smooth initial data can be extended through the cauchy horizon in an arbitrarily smooth way. this is in apparent contradiction with an old argument in favour of strong cosmic censorship. we resolve this contradiction by showing that this old argument is valid only for initial data that is not smooth. this is in agreement with the recent proposal that, to recover strong cosmic censorship, one must allow rough initial data. | strong cosmic censorship: taking the rough with the smooth |
we construct the light escape cones of isotropic spot sources of radiation residing in special classes of reference frames in the kerr-de sitter (kds) black hole spacetimes, namely in the fundamental class of `non-geodesic' locally non-rotating reference frames (lnrfs), and two classes of `geodesic' frames, the radial geodesic frames (rgfs), both falling and escaping, and the frames related to the circular geodesic orbits (cgfs). we compare the cones constructed in a given position for the lnrfs, rgfs, and cgfs. we have shown that the photons locally counter-rotating relative to lnrfs with positive impact parameter and negative covariant energy are confined to the ergosphere region. finally, we demonstrate that the light escaping cones govern the shadows of black holes located in front of a radiating screen, as seen by the observers in the considered frames. for shadows related to distant static observers the lnrfs are relevant. | light escape cones in local reference frames of kerr-de sitter black hole spacetimes and related black hole shadows |
in this paper, we investigate the action growth in various backgrounds in einstein-maxwell-dilaton theory. we calculate the full time evolution of action growth in the anti-de sitter dilaton black hole and find it approaches the late time bound from above. we investigate the black hole which is asymptotically lifshitz and obtain its late time and full time behavior. we find the violation of lloyd bound in the late time limit and show the full time behavior approaching the late time bound from above and exhibiting some new features for z sufficiently large. | effect of the dilaton on holographic complexity growth |
black hole measurements have grown significantly in the new age of gravitation wave astronomy from ligo observations of binary black hole mergers. as yet unobserved massive ultralight bosonic fields represent one of the most exciting features of standard model extensions, capable of providing solutions to numerous paradigmatic issues in particle physics and cosmology. in this work we explore bounds from spinning astrophysical black holes and their angular momentum energy transfer to bosonic condensates which can form surrounding the black hole via superradiant instabilities. using recent analytical results we perform a simplified analysis with a generous ensemble of black hole parameter measurements where we find superradiance very generally excludes bosonic fields in the mass ranges; spin-0: ${\scriptsize \{ 3.8\times10^{-14}\ {\rm ev} \leq \mu_0 \leq 3.4\times10^{-11}\ {\rm ev}, 5.5\times10^{-20}\ {\rm ev} \leq \mu_0 \leq 1.3\times10^{-16}\ {\rm ev}, 2.5\times10^{-21}\ {\rm ev} \leq \mu_0 \leq 1.2\times10^{-20}\ {\rm ev}\}}$, spin-1: ${\scriptsize \{ 6.2\times10^{-15}\ {\rm ev} \leq \mu_1 \leq 3.9\times10^{-11}\ {\rm ev}, 2.8\times10^{-22}\ {\rm ev} \leq \mu_1 \leq 1.9\times10^{-16}\ {\rm ev} \}}$ and spin-2: ${\scriptsize \{ 2.2\times10^{-14}\ {\rm ev} \leq \mu_2 \leq 2.8\times10^{-11}\ {\rm ev}, 1.8\times10^{-20}\ {\rm ev} \leq \mu_2 \leq 1.8\times10^{-16}\ {\rm ev}, 6.4\times10^{-22}\ {\rm ev} \leq \mu_2 \leq 7.7\times10^{-21}\ {\rm ev} \}}$ respectively. we also explore these bounds in the context of specific phenomenological models, specifically the qcd axion, m-theory models and fuzzy dark matter sitting at the edges of current limits. in particular we include recent measurements of event gw190521 and m87* used to constrain both the masses and decay constants of axion like fields. finally we comment a simple example of a spectrum of fields for the spin-0 and spin-1 cases. | ultralight bosonic field mass bounds from astrophysical black hole spin |
the goal of these lectures is to present an informal but precise introduction to a body of concepts and methods of interest in number theory and string theory revolving around modular forms and their generalizations. modular invariance lies at the heart of conformal field theory, string perturbation theory, montonen-olive duality, seiberg-witten theory, and s-duality in type iib superstring theory. automorphic forms with respect to higher arithmetic groups as well as mock modular forms enter in toroidal string compactifications and the counting of black hole microstates. after introducing the basic mathematical concepts including elliptic functions, modular forms, maass forms, modular forms for congruence subgroups, vector-valued modular forms, and modular graph forms, we describe a small subset of the countless applications to problems in mathematics and physics, including those mentioned above. | lectures on modular forms and strings |
rotating black hole solutions in theories of modified gravity are important as they offer an arena to test these theories through astrophysical observation. the non-rotating black hole can be hardly tested since the black hole spin is very important in any astrophysical process. we present rotating counterpart of a recently obtained spherically symmetric exact black hole solution surrounded by perfect fluid in the context of rastall theory, viz, rotating rastall black hole that generalize the kerr-newman black hole solution. in turn, we analyze the specific cases of the kerr-newman black holes surrounded by matter like dust and quintessence fields. interestingly, for a set of parameters and a chosen surrounding field, there exists a critical rotation parameter (a=ae), which corresponds to an extremal black hole with degenerate horizons, while for a<ae, it describes a non-extremal black hole with cauchy and event horizons, and no black hole for a>ae with value a_e is also influenced by these parameters. we also discuss the thermodynamical quantities associated with rotating rastall black hole, and analyze the particle motion with the behavior of effective potential. | rotating black hole in rastall theory |
we study the nonlinear dynamics of black holes that carry scalar hair and binaries composed of such black holes. the scalar hair is due to a linear or exponential coupling between the scalar and the gauss-bonnet invariant. we work perturbatively in the coupling constant of that interaction but nonperturbatively in the fields. we first consider the dynamical formation of hair for isolated black holes of arbitrary spin and determine the final state. this also allows us to compute for the first time the scalar quasinormal modes of rotating black holes in the presence of this coupling. we then study the evolution of nonspinning black hole binaries with various mass ratios and produce the first scalar waveform for a coalescence. an estimate of the energy loss in scalar radiation and the effect this has on orbital dynamics and the phase of gravitational waves (gws) (entering at quadratic order in the coupling) shows that gw detections can set the most stringent constraint to date on theories that exhibit a coupling between a scalar field and the gauss-bonnet invariant. | black holes and binary mergers in scalar gauss-bonnet gravity: scalar field dynamics |
in this paper, we demonstrate that at leading order in post minkowskian (pm) expansion, the stress-energy tensor of kerr-newman black hole can be recovered to all orders in spin from three sets of minimal coupling: the electric and gravitational minimal coupling for higher-spin particles, and the "minimal coupling" for massive spin-2 decay. these couplings are uniquely defined from kinematic consideration alone. this is shown by extracting the classical piece of the one-loop stress-energy tensor form factor, which we provide a basis that is valid to all orders in spin. the 1 pm stress tensor, and the metric in the harmonic gauge, is then recovered from the classical spin limit of the form factor. | kerr-newman stress-tensor from minimal coupling |
in this paper, we report on the construction of a new and independent pipeline for analyzing the public data from the first observing run of advanced ligo for mergers of compact binary systems. the pipeline incorporates different techniques and makes independent implementation choices in all its stages including the search design, the method to construct template banks, the automatic routines to detect bad data segments ("glitches") and to insulate good data from them, the procedure to account for the nonstationary nature of the detector noise, the signal-quality vetoes at the single-detector level and the methods to combine results from multiple detectors. our pipeline enabled us to identify a new binary black hole merger gw151216 in the public ligo data. this paper serves as a bird's eye view of the pipeline's important stages. full details and derivations underlying the various stages will appear in accompanying papers. | new search pipeline for compact binary mergers: results for binary black holes in the first observing run of advanced ligo |
during its first four months of taking data, advanced ligo has detected gravitational waves from two binary black hole mergers, gw150914 and gw151226, along with the statistically less significant binary black hole merger candidate lvt151012. here we use the rapid binary population synthesis code compas to show that all three events can be explained by a single evolutionary channel--classical isolated binary evolution via mass transfer including a common envelope phase. we show all three events could have formed in low-metallicity environments (z=0.001) from progenitor binaries with typical total masses >~160m\xodot, >~60m\xodot and >~90m\xodot, for gw150914, gw151226 and lvt151012, respectively. | formation of the first three gravitational-wave observations through isolated binary evolution |
we give explicit expressions for the finite frequency greybody factor, quasinormal modes, and love numbers of kerr black holes by computing the exact connection coefficients of the radial and angular parts of the teukolsky equation. this is obtained by solving the connection problem of the confluent heun equation in terms of the explicit expression of irregular virasoro conformal blocks as sums over partitions via the alday, gaiotto, and tachikawa correspondence. in the relevant approximation limits our results are in agreement with existing literature. the method we use can be extended to solve the linearized einstein equation in other interesting gravitational backgrounds. | exact solution of kerr black hole perturbations via cft2 and instanton counting: greybody factor, quasinormal modes, and love numbers |
scalar metric fluctuations generically source a spectrum of gravitational waves at second order in perturbation theory, poising gravitational wave experiments as potentially powerful probes of the small-scale curvature power spectrum. we perform a detailed study of the imprint of primordial non-gaussianity on these induced gravitational waves, emphasizing the role of both the disconnected and connected components of the primoridal trispectrum. specializing to local-type non-gaussianity, we numerically compute all contributions and present results for a variety of enhanced primordial curvature power spectra. | non-gaussianity and the induced gravitational wave background |
several recent works [1-3] have claimed that the weak gravity conjecture (wgc) excludes super-planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. we argue that in theories with n ≫ 1 axions, super-planckian axion diameters d are readily allowed by the wgc. we clarify the non-trivial relationship between the kinetic matrix k — unambiguously defined by its form in a minkowski-reduced basis — and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues f 1 2 ≤ ṡ ṡ ṡ ≤ fn2 of k: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. in particular, even if one were to impose the condition fn< m pl, this would imply neither d < m pl nor d < √{n}{m}_{pl} . we then estimate the actions of instantons that fulfill the wgc. the leading instanton action is bounded from below by s≥ {s}{m}_{pl}/{f}_n , with {s} a fixed constant, but in the universal limit s≳ s√{n} {m}_{pl}/{f}_n . thus, having fn> m pl does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. finally, we argue that in effective axion-gravity theories, the zero-form version of the wgc can be satisfied by gravitational instantons that make negligible contributions to the potential. | planckian axions and the weak gravity conjecture |
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