abstract stringlengths 3 192k | title stringlengths 4 857 |
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the reissner-nordström black hole solution in a generic cosmological constant background in the the context of rastall gravity is obtained. it is shown that the cosmological constant arises naturally from the consistency of the non-vacuum field equations of the rastall theory for a spherical symmetric spacetime, rather than its {\it ad-hoc} introduction in the usual einstein and einstein-maxwell field equations. the usual reissner-nordström, schwarzschild and schwarzschild-(anti)de sitter black hole solutions in the framework of this theory are also addressed as the special independent subclasses of the obtained general solution. | black hole solutions in rastall theory |
the study of quasi-periodic oscillations (qpos) of x-ray flux observed in the stellar-mass black hole binaries can provide a powerful tool for testing of the phenomena occurring in the strong gravity regime. magnetized versions of the standard geodesic models of qpos can explain the observationally fixed data from the three microquasars. we perform a successful fitting of the hf qpos observed for three microquasars, grs 1915+105, xte 1550-564 and gro 1655-40, containing black holes, for magnetized versions of both epicyclic resonance and relativistic precession models and discuss the corresponding constraints of parameters of the model, which are the mass and spin of the black hole and the parameter related to the external magnetic field. the estimated magnetic field intensity strongly depends on the type of objects giving the observed hf qpos. it can be as small as 10^{-5} g if electron oscillatory motion is relevant, but it can be by many orders higher for protons or ions (0.02-1 g), or even higher for charged dust or such exotic objects as lighting balls, etc. on the other hand, if we know by any means the magnetic field intensity, our model implies strong limit on the character of the oscillating matter, namely its specific charge. | possible signature of the magnetic fields related to quasi-periodic oscillations observed in microquasars |
we demonstrate the separability of the massive vector (proca) field equation in general kerr-nut-ads black-hole spacetimes in any number of dimensions, filling a long-standing gap in the literature. the obtained separated equations are studied in more detail for the four-dimensional kerr geometry and the corresponding quasinormal modes are calculated. two of the three independent polarizations of the proca field are shown to emerge from the separation ansatz and the results are found in an excellent agreement with those of the recent numerical study where the full coupled partial differential equations were tackled without using the separability property. | massive vector fields in rotating black-hole spacetimes: separability and quasinormal modes |
taking a thermodynamic perspective, we study the weak gravity conjecture in the context of four-dimensional einstein-maxwell-dilaton theory. we find closed-form expressions for the corrected thermodynamic quantities in the presence of four-derivative terms in the action, and in particular the charge-to-mass ratio and entropy, for several families of solutions of special magnetic-to-electric charge ratio or dilaton coupling constant. assuming that dyonic black holes themselves are the conjectured charged states, this places constraints on the wilson coefficients of the theory which we show are satisfied for several generic uv completions. | thermodynamics of 4d dilatonic black holes and the weak gravity conjecture |
this article is devoted to the study of new exact analytical solutions in the background of reissner-nordström space-time by using gravitational decoupling via minimal geometric deformation approach. to do so, we impose the most general equation of state, relating the components of the θ -sector in order to obtain the new material contributions and the decoupler function f(r). besides, we obtain the bounds on the free parameters of the extended solution to avoid new singularities. furthermore, we show the finitude of all thermodynamic parameters of the solution such as the effective density ρ ~, radial p~r and tangential p~t pressure for different values of parameter α and the total electric charge q. finally, the behavior of some scalar invariants, namely the ricci r and kretshmann rμ ν ω ɛrμ ν ω ɛ scalars are analyzed. it is also remarkable that, after an appropriate limit, the deformed schwarzschild black hole solution always can be recovered. | minimal geometric deformation in a reissner-nordström background |
we study a spherical gravitational collapse of a small mass in higher-derivative and ghost-free theories of gravity. by boosting a solution of linearized equations for a static point mass in such theories we obtain in the penrose limit the gravitational field of an ultrarelativistic particle. taking a superposition of such solutions we construct a metric of a collapsing null shell in the linearized higher-derivative and ghost-free gravity. the latter allows one to find the gravitational field of a thick null shell. by analyzing these solutions we demonstrate that in a wide class of the higher dimensional theories of gravity as well as for the ghost-free gravity there exists a mass gap for mini-black-hole production. we also found conditions when the curvature invariants remain finite at r =0 for the collapse of the thick null shell. | mass gap for black-hole formation in higher-derivative and ghost-free gravity |
we study the capability of the space-based gravitational wave observatory tianqin to test the no-hair theorem of general relativity, using the ringdown signal from the coalescence of massive black hole binaries. we parametrize the ringdown signal by the four strongest quasinormal modes and estimate the signal to noise ratio for various source parameters. we consider constraints both from single detections and from all the events combined throughout the lifetime of the observatory, for different astrophysical models. we find that at the end of the mission, tianqin will have constrained deviations of the frequency and decay time of the dominant 22 mode from the general relativistic predictions to within 0.2% and 1.5% respectively, the frequencies of the subleading modes can be also constrained within 0.3%. we also find that tianqin and lisa are highly complementary, by virtue of their different frequency windows. indeed, lisa can best perform ringdown tests for black hole masses in excess of ∼3×106m</mml:mrow>, while tianqin is best suited for lower masses. | science with the tianqin observatory: preliminary results on testing the no-hair theorem with ringdown signals |
we consider inhomogeneous, periodic, holographic lattices of d = 4 einstein-maxwell theory. we show that the dc thermoelectric conductivity matrix can be expressed analytically in terms of the horizon data of the corresponding black hole solution. we numerically construct such black hole solutions for lattices consisting of one, two and ten wave-numbers. we numerically determine the ac electric conductivity which reveals drude physics as well as resonances associated with sound modes. no evidence for an intermediate frequency scaling regime is found. all of the monochromatic lattice black holes that we have constructed exhibit scaling behaviour at low temperatures which is consistent with the appearance of in the far ir at t = 0. | the thermoelectric properties of inhomogeneous holographic lattices |
scalar-tensor theories of gravity where a new scalar degree of freedom couples to the gauss-bonnet invariant can exhibit the phenomenon of spontaneous black hole scalarization. these theories admit both the classic black hole solutions predicted by general relativity as well as novel hairy black hole solutions. the stability of hairy black holes is strongly dependent on the precise form of the scalar-gravity coupling. a radial stability investigation revealed that all scalarized black hole solutions are unstable when the coupling between the scalar field and the gauss-bonnet invariant is quadratic in the scalar, whereas stable solutions exist for exponential couplings. here, we elucidate this behavior. we demonstrate that, while the quadratic term controls the onset of the tachyonic instability that gives rise to the black hole hair, the higher-order coupling terms control the nonlinearities that quench that instability and, hence, also control the stability of the hairy black hole solutions. | stability of scalarized black hole solutions in scalar-gauss-bonnet gravity |
we specify bulk coordinates in jackiw-teitelboim (jt) gravity using a boundary-intrinsic radar definition. this allows us to study and calculate exactly diff-invariant bulk correlation functions of matter-coupled jt gravity, which are found to satisfy microcausality. we observe that quantum gravity effects dominate near-horizon matter correlation functions. this shows that quantum matter in classical curved spacetime is not a sensible model for near-horizon matter-coupled jt gravity. this is how jt gravity, given our choice of bulk frame, evades an information paradox. this echoes into the quantum expectation value of the near-horizon metric, whose analysis is extended from the disk model to the recently proposed topological completion of jt gravity [1]. due to quantum effects, at distances of order the planck length to the horizon, a dramatic breakdown of rindler geometry is observed. | clocks and rods in jackiw-teitelboim quantum gravity |
light primordial black holes (pbhs) with masses smaller than 109 g (10−24m⊙) evaporate before the onset of big-bang nucleosynthesis, rendering their detection rather challenging. if efficiently produced, they may have dominated the universe energy density. we study how such an early matter-dominated era can be probed successfully using gravitational waves (gw) emitted by local and global cosmic strings. while previous studies showed that a matter era generates a single-step suppression of the gw spectrum, we instead find a double-step suppression for local-string gw whose spectral shape provides information on the duration of the matter era. the presence of the two steps in the gw spectrum originates from gw being produced through two events separated in time: loop formation and loop decay, taking place either before or after the matter era. the second step — called the knee — is a novel feature which is universal to any early matter-dominated era and is not only specific to pbhs. detecting gws from cosmic strings with lisa, et, or bbo would set constraints on pbhs with masses between 106 and 109 g for local strings with tension gμ = 10−11, and pbhs masses between 104 and 109 g for global strings with symmetry-breaking scale η = 1015 gev. effects from the spin of pbhs are discussed. | primordial black hole archaeology with gravitational waves from cosmic strings |
motivated by recent work suggesting observably large spacetime fluctuations in the causal development of an empty region of flat space, we conjecture that these metric fluctuations can be quantitatively described in terms of a conformal field theory of near-horizon vacuum states. one consequence of this conjecture is that fluctuations in the modular hamiltonian δ k of a causal diamond are equal to the entanglement entropy: ⟨δ k2⟩=⟨k ⟩=a/(σd -2) 4 gd , where a (σd -2) is the area of the entangling surface in d dimensions. our conjecture applies to flat space, the cosmological horizon of ds, and ads ryu-takayanagi diamonds, but not to large finite area diamonds in the bulk of ads. we focus on three pieces of quantitative evidence, from a randall-sundrum ii braneworld, from the conformal description of black hole horizons, and from the fluid-gravity correspondence. our hypothesis also suggests that a broader range of formal results can be brought to bear on observables in flat and ds spaces. | conformal description of near-horizon vacuum states |
in this work, we have studied the quasinormal modes of a black hole in a model of the type f (q ) =∑n an(q-q0)n in f(q) gravity by using a recently introduced method known as bernstein spectral method and confirmed the validity of the method with the help of well known padé averaged higher order wkb approximation method. here we have considered scalar perturbation and electromagnetic perturbation in the black hole spacetime and obtained the corresponding quasinormal modes. we see that for a non-vanishing nonmetricity scalar q0, quasinormal frequencies in scalar perturbation are greater than those in electromagnetic perturbation scenarios. on the other hand, the damping rate of gravitational waves is higher for electromagnetic perturbation. to confirm the quasinormal mode behaviour, we have also investigated the time domain profiles for both types of perturbations. | quasinormal modes of black holes in f(q) gravity |
recent observations with jwst have identified several bright galaxy candidates at z ≳ 10, some of which appear unusually massive (up to ~1011 m ⊙). such early formation of massive galaxies is difficult to reconcile with standard λcdm predictions, demanding a very high star formation efficiency (sfe), possibly even in excess of the cosmic baryon mass budget in collapsed structures. with an idealized analysis based on linear perturbation theory and the press-schechter formalism, we show that the observed massive galaxy candidates can be explained with lower sfe than required in λcdm if structure formation is accelerated/seeded by massive (≳109 m ⊙) primordial black holes (pbhs) that make a up a small fraction (~10-6-10-3) of dark matter, considering existing empirical constraints on pbh parameters. we also discuss the potential observational signatures of pbh cosmologies in the jwst era. more work needs to be done to fully evaluate the viability of such pbh models to explain observations of the high-z universe. | accelerating early massive galaxy formation with primordial black holes |
we explore the implications of stable gravitational orbits around an ads black hole for the boundary conformal field theory. the orbits are long-lived states that eventually decay due to gravitational radiation and tunneling. they appear as narrow resonances in the heavy-light ope when the spectrum becomes effectively continuous due to the presence of the black hole horizon. alternatively, they can be identified with quasi-normal modes with small imaginary part in the thermal two-point function. the two pictures are related via the eigenstate thermalisation hypothesis. when the decay effects can be neglected the orbits appear as a discrete family of double-twist operators. we investigate the connection between orbits, quasi-normal modes, and double-twist operators in detail. using the corrected bohr-sommerfeld formula for quasi-normal modes, we compute the anomalous dimension of double-twist operators. we compare our results to the prediction of the light-cone bootstrap, finding perfect agreement where the results overlap. we also compute the orbit decay time due to scalar radiation and compare it to the tunneling rate. perturbatively in spin, in the light-cone bootstrap framework double-twist operators appear as a small fraction of the hilbert space which violate the eigenstate thermalization hypothesis, a phenomenon known as many-body scars. nonperturbatively in spin, the double-twist operators become long-lived states that eventually thermalize. we briefly discuss the connection between perturbative scars in holographic theories and known examples of scars in the condensed matter literature. | gravitational orbits, double-twist mirage, and many-body scars |
we consider the scattering of lightlike matter in the presence of a heavy scalar object (such as the sun or a schwarzschild black hole). by treating general relativity as an effective field theory we directly compute the nonanalytic components of the one-loop gravitational amplitude for the scattering of massless scalars or photons from an external massive scalar field. these results allow a semiclassical computation of the bending angle for light rays grazing the sun, including long-range ℏ contributions. we discuss implications of this computation, in particular, the violation of some classical formulations of the equivalence principle. | bending of light in quantum gravity |
we re-analyse current single-field inflationary models related to primordial black holes formation. we do so by taking into account recent developments on the estimations of their abundances and the influence of non-gaussianities. we show that, for all of them, the gaussian approximation, which is typically used to estimate the primordial black holes abundances, fails. however, in the case in which the inflaton potential has an inflection point, the contribution of non-gaussianities is only perturbative. finally, we infer that only models featuring an inflection point in the inflationary potential, might predict, with a very good approximation, the desired abundances by the sole use of the gaussian statistics. | the role of non-gaussianities in primordial black hole formation |
in this paper, we consider a dyonic charged anti-de sitter black hole, which is a holographic dual of a van der waals fluid. we use logarithm-corrected entropy and study thermodynamics of the black hole and show that holographic picture is still valid. critical behaviors and stability are also discussed. logarithmic corrections arises due to thermal fluctuations, which are important when the size of black hole is small. so, thermal fluctuations are interpreted as a quantum effect. it means that we can see the quantum effect of a black hole, which is a gravitational system. | p -v criticality of logarithm-corrected dyonic charged ads black holes |
the laser interferometer gravitational-wave observatory (ligo)/virgo collaboration reported the detection of the most massive black hole-black hole (bh-bh) merger to date with component masses of 85m⊙ and 66m⊙ (gw190521). motivated by recent observations of massive stars in the 30 doradus cluster in the large magellanic cloud (m⋆ ≳ 200m⊙; e.g., r136a) and employing newly estimated uncertainties on pulsational pair-instability mass loss (that allow for the possibility of forming bhs with mass up to mbh ∼ 90m⊙), we show that it is trivial to form such massive bh-bh mergers through the classical isolated binary evolution (with no assistance from either dynamical interactions or exotica). a binary consisting of two massive (180m⊙ + 150m⊙) population ii stars (metallicity: z ≈ 0.0001) evolves through a stable roche lobe overflow and common envelope episode. both exposed stellar cores undergo direct core collapse and form massive bhs while avoiding pair-instability pulsation mass loss or total disruption. ligo/virgo observations show that the merger rate density of light bh-bh mergers (both components: mbh < 50m⊙) is of the order of 10-100gpc-3yr-1, while gw190521 indicates that the rate of heavier mergers is 0.02-0.43gpc-3yr-1. our model (with standard assumptions about input physics), but extended to include 200m⊙ stars and allowing for the possibility of stellar cores collapsing to 90m⊙ bhs, produces the following rates: 63gpc-3yr-1 for light bh-bh mergers and 0.04gpc-3yr-1 for heavy bh-bh mergers. we do not claim that gw190521 was formed by an isolated binary, but it appears that such a possibility cannot be excluded. | the most ordinary formation of the most unusual double black hole merger |
we study the schwinger-dyson equations of a fermionic planar matrix quantum mechanics [or tensor and sachdev-ye-kitaev (syk) models] at leading melonic order. we find two solutions describing a high entropy, syk black-hole-like phase and a low entropy one with trivial ir behavior. there is a line of first order phase transitions that terminates at a new critical point. critical exponents are nonmean field and differ on the two sides of the transition. interesting phenomena are also found in unstable and stable bosonic models, including kazakov critical points and inconsistency of syk-like solutions of the ir limit. | phase diagram of planar matrix quantum mechanics, tensor, and sachdev-ye-kitaev models |
for black-hole binaries whose spins are (anti-) aligned with respect to the orbital angular momentum of the binary, we compute the frequency-domain phasing coefficients including the quadratic-in-spin terms up to the third post-newtonian (3pn) order, the cubic-in-spin terms at the leading order, 3.5pn, and the spin-orbit effects up to the 4pn order. in addition, we obtain the 2pn spin contributions to the amplitude of the frequency-domain gravitational waveforms for nonprecessing binaries, using recently derived expressions for the time-domain polarization amplitudes of binaries with generic spins, complete at that accuracy level. these two results are updates to [k. g. arun, a. buonanno, g. faye, and e. ochsner, phys. rev. d 79, 104023 (2009).] for amplitude and [m. wade, j. d. e. creighton, e. ochsner, and a. b. nielsen, phys. rev. d 88, 083002 (2013).] for phasing. they should be useful for constructing banks of templates that accurately model nonprecessing inspiraling binaries, for parameter estimation studies, and for constructing analytical template families that account for the inspiral-merger-ringdown phases of the binary. | ready-to-use post-newtonian gravitational waveforms for binary black holes with nonprecessing spins: an update |
we revisit the "state-dependence" of the map that we proposed recently between bulk operators in the interior of a large anti-de sitter black hole and operators in the boundary cft. by refining recent versions of the information paradox, we show that this feature is necessary for the cft to successfully describe local physics behind the horizon—not only for single-sided black holes but even in the eternal black hole. we show that state-dependence is invisible to an infalling observer who cannot differentiate these operators from those of ordinary quantum effective field theory. therefore the infalling observer does not observe any violations of quantum mechanics. we successfully resolve a large class of potential ambiguities in our construction. we analyze states where the cft is entangled with another system and show that the er =epr conjecture emerges from our construction in a natural and precise form. we comment on the possible semiclassical origins of state-dependence. | remarks on the necessity and implications of state-dependence in the black hole interior |
the relaxation of a distorted black hole to its final state provides important tests of general relativity within the reach of current and upcoming gravitational wave facilities. in black hole perturbation theory, this phase consists of a simple linear superposition of exponentially damped sinusoids (the quasinormal modes) and of a power-law tail. how many quasinormal modes are necessary to describe waveforms with a prescribed precision? what error do we incur by only including quasinormal modes, and not tails? what other systematic effects are present in current state-of-the-art numerical waveforms? these issues, which are basic to testing fundamental physics with distorted black holes, have hardly been addressed in the literature. we use numerical relativity waveforms and accurate evolutions within black hole perturbation theory to provide some answers. we show that (i) a determination of the fundamental l =m =2 quasinormal frequencies and damping times to within 1% or better requires the inclusion of at least the first overtone, and preferably of the first two or three overtones; (ii) a determination of the black hole mass and spin with precision better than 1% requires the inclusion of at least two quasinormal modes for any given angular harmonic mode (ℓ , m ). we also improve on previous estimates and fits for the ringdown energy radiated in the various multipoles. these results are important to quantify theoretical (as opposed to instrumental) limits in parameter estimation accuracy and tests of general relativity allowed by ringdown measurements with high signal-to-noise ratio gravitational wave detectors. | black hole spectroscopy: systematic errors and ringdown energy estimates |
a characteristic value formulation of the weyl double copy leads to an asymptotic formulation. we find that the weyl double copy holds asymptotically in cases where the full solution is algebraically general, using rotating stu supergravity black holes as an example. the asymptotic formulation provides clues regarding the relation between asymptotic symmetries that follows from the double copy. using the c-metric as an example, we show that a previous interpretation of this gravity solution as a superrotation has a single copy analogue relating the appropriate liénard-wiechert potential to a large gauge transformation. | asymptotic weyl double copy |
recent work by shenker, stanford, and kitaev has related the black hole horizon geometry to chaotic behavior. we extend this from eternal black holes to black holes that form and then evaporate. this leads to an identity for the change in the black hole s-matrix (over times shorter than the scrambling time) due an addition infalling particle, elaborating an idea of 't hooft. | chaos in the black hole s-matrix |
de sitter black holes and other non-perturbative configurations can be used to probe the holographic degrees of freedom of de sitter space. for small black holes, evidence was first provided in the seminal work of banks, fiol, and morrise and follow-ups by banks and fischler, showing that ds is described by a form of matrix theory. for large black holes, the evidence provided here is new: gravitational calculations and matrix theory calculations of the rates of exponentially rare fluctuations match one another in surprising detail. the occurrences of nariai geometry and the "inside-out" transition are particularly interesting examples, which i explain in this paper. | black holes hint towards de sitter matrix theory |
the general-relativistic phenomenon of spin-induced orbital precession has not yet been observed in strong-field gravity. gravitational-wave observations of binary black holes (bbhs) are prime candidates, as we expect the astrophysical binary population to contain precessing binaries1,2. imprints of precession have been investigated in several signals3-5, but no definitive identification of orbital precession has been reported in any of the 84 bbh observations so far5-7 by the advanced ligo and virgo detectors8,9. here we report the measurement of strong-field precession in the ligo-virgo-kagra gravitational-wave signal gw200129. the binary's orbit precesses at a rate ten orders of magnitude faster than previous weak-field measurements from binary pulsars10-13. we also find that the primary black hole is probably highly spinning. according to current binary population estimates, a gw200129-like signal is extremely unlikely, and therefore presents a direct challenge to many current binary-formation models. | general-relativistic precession in a black-hole binary |
nonlinear electrodynamics is known as the generalizations of maxwell electrodynamics at strong fields and presents interesting features such as curing the classical divergences present in the linear theory when coupled to general relativity. in this paper, we consider the asymptotically flat reissner–nordström black hole solution with higher-order magnetic correction in einstein-nonlinear-maxwell fields. we study the effect of the magnetic charge parameters on the black hole, viz., weak deflection angle of photons and massive particles using the gauss–bonnet theorem. moreover, we apply keeton–petters formalism to confirm our results concerning the weak deflection angle. apart from a vacuum, their influence in the presence of different media such as plasma and dark matter are probed as well. finally, we examine the black hole shadow cast using the null-geodesics method and investigate its spherically in-falling thin accretion disk. our inferences show how the magnetic charge parameter p affects the other physical quantities; so, we impose some constraints on this parameter using observations from the event horizon telescope. | deflection angle and shadow of the reissner–nordström black hole with higher-order magnetic correction in einstein-nonlinear-maxwell fields |
we investigate the thermodynamic behaviour of ads quasitopological black hole solutions in the context of extended thermodynamic phase space, in which the cosmological constant induces a pressure with a conjugate volume. we find that the third order exact quasitopological solution exhibits features consistent with the third order lovelock solutions for positive quasitopological coupling, including multiple reentrant phase transitions and isolated critical points. for negative coupling we find the first instances of both reentrant phase transitions and thermodynamic singularities in five dimensions, along with other modified thermodynamic behaviour compared to einstein-ads-gauss bonnet gravity. | p - v criticality in quasitopological gravity |
we obtain constraints from black hole superradiance in an ensemble of compactifications of type iib string theory. the constraints require knowing only the axion masses and self-interactions, and are insensitive to the cosmological model. we study more than $2 \cdot 10^5$ calabi-yau manifolds with hodge numbers $1\leq h^{1,1}\leq 491$ and compute the axion spectrum at two reference points in moduli space for each geometry. our computation of the classical theory is explicit, while for the instanton-generated axion potential we use a conservative model. the measured properties of astrophysical black holes exclude parts of our dataset. at the point in moduli space corresponding to the tip of the stretched kähler cone, we exclude $\approx 50\%$ of manifolds in our sample at 95% c.l., while further inside the kähler cone, at an extremal point for realising the standard model, we exclude a maximum of $\approx 7\%$ of manifolds at $h^{1,1}=11$, falling to nearly zero by $h^{1,1}=100$. | superradiance exclusions in the landscape of type iib string theory |
collective behavior strongly influences the charging dynamics of quantum batteries (qbs). here, we study the impact of nonlocal correlations on the energy stored in a system of n qbs. a unitary charging protocol based on a sachdev-ye-kitaev (syk) quench hamiltonian is thus introduced and analyzed. syk models describe strongly interacting systems with nonlocal correlations and fast thermalization properties. here, we demonstrate that, once charged, the average energy stored in the qb is very stable, realizing an ultraprecise charging protocol. by studying fluctuations of the average energy stored, we show that temporal fluctuations are strongly suppressed by the presence of nonlocal correlations at all time scales. a comparison with other paradigmatic examples of many-body qbs shows that this is linked to the collective dynamics of the syk model and its high level of entanglement. we argue that such feature relies on the fast scrambling property of the syk hamiltonian, and on its fast thermalization properties, promoting this as an ideal model for the ultimate temporal stability of a generic qb. finally, we show that the temporal evolution of the ergotropy, a quantity that characterizes the amount of extractable work from a qb, can be a useful probe to infer the thermalization properties of a many-body quantum system. | ultra-stable charging of fast-scrambling syk quantum batteries |
recent progress in ads/cft has provided a good understanding of how the bulk spacetime is encoded in the entanglement structure of the boundary cft. however, little is known about how spacetime emerges directly from the bulk quantum theory. we address this question in an effective 3d quantum theory of pure gravity, which describes the high temperature regime of a holographic cft. this theory can be viewed as a q-deformation and dimensional uplift of jt gravity. using this model, we show that the bekenstein-hawking entropy of a two-sided black hole equals the bulk entanglement entropy of gravitational edge modes. in the conventional chern-simons description, these black holes correspond to wilson lines in representations of psl(2, &r;) ⨂ psl(2, &r;). we show that the correct calculation of gravitational entropy suggests we should interpret the bulk theory as an extended topological quantum field theory associated to the quantum semi-group slq+(" separators=",2 &r; )⨂slq+(" separators=",2 &r; ). our calculation suggests an effective description of bulk microstates in terms of collective, anyonic degrees of freedom whose entanglement leads to the emergence of the bulk spacetime. | a proposal for 3d quantum gravity and its bulk factorization |
we demonstrate equivalences, under simple mappings, between the dynamics of three distinct systems—(i) an arbitrary-mass-ratio two-spinning-black-hole system, (ii) a spinning test black hole in a background kerr spacetime, and (iii) geodesic motion in kerr—when each is considered in the first post-minkowskian (1pm) approximation to general relativity, i.e. to linear order g but to all orders in 1/c, and to all orders in the black holes’ spins, with all orders in the multipole expansions of their linearized gravitational fields. this is accomplished via computations of the net results of weak gravitational scattering encounters between two spinning black holes, namely the net o(g) changes in the holes’ momenta and spins as functions of the incoming state. the results are given in remarkably simple closed forms, found by solving effective mathisson-papapetrou-dixon-type equations of motion for a spinning black hole in conjunction with the linearized einstein equation, with appropriate matching to the kerr solution. the scattering results fully encode the gauge-invariant content of a canonical hamiltonian governing binary-black-hole dynamics at 1pm order, for generic (unbound and bound) orbits and spin orientations. we deduce one such hamiltonian, which reproduces and resums the 1pm parts of all such previous post-newtonian results, and which directly manifests the equivalences with the test-body limits via simple effective-one-body mappings. | scattering of two spinning black holes in post-minkowskian gravity, to all orders in spin, and effective-one-body mappings |
building upon recent work, we present an improved effective-one-body (eob) model for spin-aligned, coalescing, black hole binaries with generic orbital configurations, i.e., quasicircular, eccentric, or hyperbolic orbits. the model, called teobresumsgeneral, relies on the idea of incorporating general newtonian prefactors, instead of the usual quasicircular ones, in both radiation reaction and waveform. the major advance with respect to previous work is that the quasicircular limit of the model is now correctly informed by numerical relativity (nr) quasicircular simulation. this provides eob/nr unfaithfulness for the dominant quadrupolar waveform, calculated with advanced ligo noise, at most of the order of 1% over a meaningful portion of the quasicircular nr simulations computed by the simulating extreme spacetime (sxs) collaboration. in the presence of eccentricity, the model is similarly nr-faithful, ≲1 %, all over the 28 public sxs nr datasets, with initial eccentricity up to ≃0.2 , mass ratio up to q =3 and dimensionless spin magnitudes as large as +0.7 . higher multipoles, up to ℓ=5 are also reliably modeled through the eccentric inspiral, plunge, merger and ringdown. for hyperbolic-like configurations, we also show that the eob computed scattering angle is in excellent agreement with all currently available nr results. | effective one-body multipolar waveform model for spin-aligned, quasicircular, eccentric, hyperbolic black hole binaries |
black holes in scalar-gauss-bonnet gravity are prone to scalarization, that is a spontaneous development of scalar hair for strong enough spacetime curvature. since large spacetime curvature is associated with smaller black hole masses, the merging of black holes can lead to dynamical descalarization. this is a spontaneous release of the scalar hair of the newly formed black hole in case its mass is above the scalarization threshold. depending on the exact form of the gauss-bonnet coupling function, the stable scalarized solutions can be either continuously connected to the schwarzschild black hole, or the transitions between the two can happen with a jump. by performing simulations of black hole head-on collisions in scalar-gauss-bonnet gravity prone to dynamical descalization we have demonstrated that such a jump can be clearly observed in the accumulated gravitational wave data of multiple merger events with different masses. the simulations were performed in the decoupling limit approximation, where the backreaction of the scalar field on the metric is neglected. this is a reasonable assumption for weak enough scalar fields. the distinct signature in the gravitational wave signal will share similarities with the effects expected from first order matter phase transitions happening during neutron star binary mergers. | dynamical descalarization with a jump during a black hole merger |
the complete gravitational collapse of a body in general relativity will result in the formation of a black hole. although the black hole is classically stable, quantum particle creation processes will result in the emission of hawking radiation to infinity and corresponding mass loss of the black hole, eventually resulting in the complete evaporation of the black hole. semiclassical arguments strongly suggest that, in the process of black hole formation and evaporation, a pure quantum state will evolve to a mixed state, i.e. there will be ‘information loss’. there has been considerable controversy over this issue for more than 40 years. in this review, we present the arguments in favor of information loss, and analyze some of the counter-arguments and alternative possibilities. | information loss |
the black hole information problem has been a challenge since hawking's original 1975 paper. it led to the discovery of ads/cft, which gave a partial resolution of the paradox. however, recent developments, in particular the firewall puzzle, show that there is much that we do not understand. i review the black hole, hawking radiation, and the page curve, and the classic form of the paradox. i discuss ads/cft as a partial resolution. i then discuss black hole complementarity and its limitations, leading to many proposals for different kinds of `drama.' i conclude with some recent ideas. presented at the 2014-15 jerusalem winter school and the 2015 tasi. | the black hole information problem |
primordial black holes (pbhs) are a viable candidate for dark matter if the pbh masses are in the currently unconstrained "sublunar" mass range. we revisit the possibility that pbhs were produced by nucleation of false vacuum bubbles during inflation. we show that this scenario can produce a population of pbhs that simultaneously accounts for all dark matter, explains the candidate event in the subaru hyper suprime-cam (hsc) data, and contains both heavy black holes as observed by ligo and very heavy seeds of supermassive black holes. we demonstrate with numerical studies that future observations of hsc, as well as other optical surveys, such as lsst, will be able to provide a definitive test for this generic pbh formation mechanism if it is the dominant source of dark matter. | exploring primordial black holes from the multiverse with optical telescopes |
as a charged fermion drops into a btz black hole, the laws of thermodynamics and the weak cosmic censorship conjecture are investigated in both the normal and extended phase space, where the cosmological parameter and renormalization length are regarded as extensive quantities. in the normal phase space, the first and second law of thermodynamics, and the weak cosmic censorship are found to be valid. in the extended phase space, although the first law and weak cosmic censorship conjecture remain valid, the second law is dependent on the variation of the renormalization energy dk. moreover, in the extended phase space, the configurations of extremal and near-extremal black holes are not changed, as they are stable, while in the normal phase space, the extremal and near-extremal black holes evolve into non-extremal black holes. | thermodynamics and weak cosmic censorship conjecture of btz black holes in extended phase space |
the high rate of black hole (bh) mergers detected by ligo/virgo opened questions on their astrophysical origin. one possibility is the dynamical channel, in which binary formation and hardening is catalyzed by dynamical encounters in globular clusters (gcs). previous studies have shown that the bh merger rate from the present day gc density in the universe is lower than the observed rate. in this letter, we study the bh merger rate by accounting for the first time for the evolution of gcs within their host galaxies. the mass in gcs was initially ∼8 ×higher , which decreased to its present value due to evaporation and tidal disruption. many bh binaries that were ejected long before their merger originated in gcs that no longer exist. we find that the comoving merger rate in the dynamical channel from gcs varies between 18 to 35 gpc-3 yr-1 between redshift z =0.5 to 2, and the total rate is 1, 5, 24 events per day within z =0.5 , 1, and 2, respectively. the cosmic evolution and disruption of gcs systematically increases the present-day merger rate by a factor ∼2 relative to isolated clusters. gravitational wave detector networks offer an unique observational probe of the initial number of gc populations and their subsequent evolution across cosmic time. | black hole mergers from an evolving population of globular clusters |
using hydrodynamical simulations for a large set of high-density matter equations of state (eoss), we systematically determine the threshold mass mthres for prompt black-hole formation in equal-mass and asymmetric neutron star (ns) mergers. we devise the so far most direct, general, and accurate method to determine the unknown maximum mass of nonrotating nss from merger observations revealing mthres. considering hybrid eoss with hadron-quark phase transition, we identify a new, observable signature of quark matter in ns mergers. furthermore, our findings have direct applications in gravitational wave searches, kilonova interpretations, and multimessenger constraints on ns properties. | equation of state constraints from the threshold binary mass for prompt collapse of neutron star mergers |
we show how to obtain a consistent thermodynamic description of accelerating asymptotically ads black holes, extending our previous results by including charge and rotation. we find that the key ingredient of consistent thermodynamics is to ensure that the system is not over-constrained by including the possibility of varying the `string' tensions that are responsible for the acceleration of the black hole, yielding a first law of full cohomogeneity. the first law assumes the standard form, with the entropy given by one quarter of the horizon area and other quantities identified by standard methods. in particular we compute the mass in two independent ways: through a euclidean action calculation and by the method of conformal completion. the ambiguity in the choice of the normalization of the timelike killing vector can be fixed by explicit coordinate transformation (in the case of rotation) to the standard ads form or by holographic methods (in the case of charge). this resolves a long-standing problem of formulating the thermodynamics of accelerating black holes, opening the way to detailed studies of their phase behaviour. | thermodynamics of charged, rotating, and accelerating black holes |
in this paper, we investigate the motion of a classical spinning test particle in a background of a spherically symmetric black hole based on the novel four-dimensional einstein–gauss–bonnet gravity [d. glavan and c. lin, phys. rev. lett. 124, 081301 (2020)]. we find that the effective potential of a spinning test particle in this background could have two minima when the gauss–bonnet coupling parameter α is nearly in a special range ‑8<α/m2<‑2 (m is the mass of the black hole), which means a particle can be in two separate orbits with the same spin-angular momentum and orbital angular momentum, and the accretion disc could have discrete structures. we also investigate the innermost stable circular orbits of the spinning test particle and find that the corresponding radius could be smaller than the cases in general relativity. | spinning test particle in four-dimensional einstein–gauss–bonnet black holes |
spherical black hole (bh) solutions in einstein-maxwell-scalar (ems) models wherein the scalar field is non-minimally coupled to the maxwell invariant by some coupling function are discussed. we suggest a classification for these models into two classes, based on the properties of the coupling function, which, in particular, allow, or not, the reissner- nordström (rn) bh solution of electrovacuum to solve a given model. then, a comparative analysis of two illustrative families of solutions, one belonging to each class is performed: dilatonic versus scalarised bhs. by including magnetic charge, that is considering dyons, we show that scalarised bhs can have a smooth extremal limit, unlike purely electric or magnetic solutions. in particular, we study this extremal limit using the entropy function formalism, which provides insight on why both charges are necessary for extremal solutions to exist. | einstein-maxwell-scalar black holes: classes of solutions, dyons and extremality |
we find new asymptotically locally ads4 euclidean supersymmetric solutions of the stu model in four-dimensional gauged supergravity. these "black saddles" have an s1×σg boundary at asymptotic infinity and cap off smoothly in the interior. the solutions can be uplifted to eleven dimensions and are holographically dual to the topologically twisted abjm theory on s1×σg. we show explicitly that the on-shell action of the black saddle solutions agrees exactly with the topologically twisted index of the abjm theory in the planar limit for general values of the magnetic fluxes, flavor fugacities, and real masses. this agreement relies on a careful holographic renormalization analysis combined with a novel uv/ir holographic relation between supergravity parameters and field theory sources. the euclidean black saddle solution space contains special points that can be wick-rotated to regular lorentzian supergravity backgrounds that correspond to the well-known supersymmetric dyonic ads4 black holes in the stu model. | euclidean black saddles and ads4 black holes |
context. various binary black hole formation channels have been proposed since the first gravitational event gw150914 was discovered by the advanced laser interferometer gravitational-wave observatory (adligo). the immediate progenitor of the binary black hole is a close binary system composed of a black hole and a helium star, which can be the outcome of the classical isolated binary evolution through the common envelope, or alternatively of the massive close evolution through chemically homogeneous channel.aims: we study the spin angular momentum evolution of the helium star in order to constrain the spin of the second-born black hole. this work focuses on the common envelope formation channel, however, some of our conclusions are also relevant for the chemically homogeneous evolution channel.methods: we perform detailed stellar structure and binary evolution calculations that take into account, mass-loss, internal differential rotation, and tidal interactions between the helium star and the black hole companion, where we also calculate the strength of the tidal interactions from first principles based on the structure of the helium stars. we systematically explore the parameter space of initial binary properties, including initial black hole and helium star masses, initial rotation of the helium star as well as metallicity.results: we argue that the natal spin of the first-born black hole through the common envelope scenario is negligible (≲0.1), and therefore the second-born black hole's spin dominates the measured effective spin, χeff, from gravitational wave events of double black hole mergers. we find that tides can be only important when orbital periods are shorter than 2 days. upon core collapse, the helium star produces a black hole (the second-born black hole in the system) with a spin that can span the entire range from zero to maximally spinning. we show that the bimodal distribution of the spin of the second-born black hole obtained in recent papers is mainly due to oversimplifying assumptions. we find an anti-correlation between the merging timescale of the two black holes, tmerger, and the effective spin χeff. finally, we provide new prescriptions for the tidal coefficient e2 for both h-rich and the he-rich stars.conclusions: to understand the spin of the second-born black hole, careful treatment of both tides and stellar winds is needed. we predict that, with future improvements to adligo's sensitivity, the sample of merging binary black hole systems will show an overdensity of sources with positive but small χeff originating from lower-mass black hole mergers born at low redshift. | the spin of the second-born black hole in coalescing binary black holes |
we construct the most general, to cubic order in curvature, theory of gravity whose (most general) static spherically symmetric vacuum solutions are fully described by a single field equation. the theory possesses the following remarkable properties: (i) it has a well-defined einstein gravity limit, (ii) it admits "schwarzschild-like" solutions characterized by a single metric function, (iii) on maximally symmetric backgrounds it propagates the same degrees of freedom as einstein's gravity, and (iv) lovelock and quasitopological gravities, as well as the recently developed einsteinian cubic gravity [bueno and cano phys. rev. d 94, 104005 (2016)., 10.1103/physrevd.94.104005] in four dimensions, are recovered as special cases. we perform a brief analysis of asymptotically flat black holes in this theory and study their thermodynamics. | generalized quasitopological gravity |
this paper studies the holographic description of 2 + 1-dimensional accelerating black holes. we start by using an adm decomposition of the coordinates suitable to identify boundary data. as a consequence, the holographic cft lies in a fixed curved background which is described by the holographic stress tensor of a perfect fluid. we compute the euclidean action ensuring that the variational principle is satisfied in the presence of the domain wall. this requires including the gibbons-hawking-york term associated with internal boundaries on top of the standard renormalised ads3 action. finally, we compute the entanglement entropy by firstly mapping the solution to the rindler-ads spacetime in which the ryu-takayanagi surface is easily identifiable. we found that as the acceleration increases the accessible region of the conformal boundary decreases and also the entanglement entropy, indicating a loss of information in the dual theory due to acceleration. | accelerating black holes in 2 + 1 dimensions: holography revisited |
we perform a detailed study of the covariance properties of the symplectic potential of general relativity on a null hypersurface, and of the different polarizations that can be used to study conservative as well as leaky boundary conditions. this allows us to identify a one-parameter family of covariant symplectic potentials. we compute the charges and fluxes for the most general phase space with arbitrary variations. we study five symmetry groups that arise when different restrictions on the variations are included. requiring stationarity as in the original wald-zoupas prescription selects a unique member of the family of symplectic potentials, the one of chandrasekaran, flanagan and prabhu. the associated charges are all conserved on non-expanding horizons, but not on flat spacetime. we show that it is possible to require a weaker notion of stationarity which selects another symplectic potential, again in a unique way, and whose charges are conserved on both non-expanding horizons and flat light-cones. furthermore, the flux of future-pointing diffeomorphisms at leading-order around an outgoing flat light-cone is positive and reproduces a tidal heating plus a memory term. we also study the conformal conservative boundary conditions suggested by the alternative polarization and identify under which conditions they define a non-ambiguous variational principle. our results have applications for dynamical notions of entropy, and are useful to clarify the interplay between different boundary conditions, charge prescriptions, and symmetry groups that can be associated with a null boundary. | general gravitational charges on null hypersurfaces |
we compute the first-order \alpha'α′ corrections to well-known families of heterotic multi-center black-hole solutions in five and four dimensions. the solutions can be either supersymmetric or non-supersymmetric, depending on the relative sign between two of the black-hole charges. for both cases, we find that the equilibrium of forces persists after including the \alpha'α′ corrections, as the existence of multi-center solutions free of unphysical singularities shows. we analyze the possibility of black-hole fragmentation. | extremal stringy black holes in equilibrium at first order in \\alpha' |
the black hole (bh) binaries in active galactic nuclei (agn) are expected to form mainly through scattering encounters in the ambient gaseous medium. recent simulations, including our own, have confirmed this formation pathway is highly efficient. we perform 3d smoothed particle hydrodynamics (sph) simulations of bh scattering encounters in agn disks. using a range of impact parameters, we probe the necessary conditions for binary capture and how different orbital trajectories affect the dissipative effects from the gas. we identify a single range of impact parameters, typically of width $\sim0.86-1.59$ binary hill radii depending on agn disk density, that reliably leads to binary formation. the periapsis of the first encounter is the primary variable that determines the outcome of the initial scattering. we find an associated power-law between the energy dissipated and the periapsis depth to be $\delta e\propto r^{-b}$ with $b=0.42\pm0.16$, where deeper encounters dissipate more energy. excluding accretion physics does not significantly alter these results. we identify the region of parameter space in initial energy vs impact parameter where a scattering leads to binary formation. based on our findings, we provide a ready-to-use analytic criterion that utilises these two pre-encounter parameters to determine the outcome of an encounter, with a reliability rate of >90\%. as the criterion is based directly on our simulations, it provides a reliable and highly physically motivated criterion for predicting binary scattering outcomes which can be used in population studies of bh binaries and mergers around agn. | black hole binaries in agn accretion discs ii: gas effects on black hole satellite scatterings |
we establish that unitarity of scattering amplitudes imposes universal entropy bounds. the maximal entropy of a self-sustained quantum field object of radius r is equal to its surface area and at the same time to the inverse running coupling α evaluated at the scale r. the saturation of these entropy bounds is in one-to-one correspondence with the non-perturbative saturation of unitarity by 2 → n particle scattering amplitudes at the point of optimal truncation. these bounds are more stringent than bekenstein's bound and in a consistent theory all three get saturated simultaneously. this is true for all known entropy-saturating objects such as solitons, instantons, baryons, oscillons, black holes or simply lumps of classical fields. we refer to these collectively as saturons and show that in renormalizable theories they behave in all other respects like black holes. finally, it is argued that the confinement in su(n) gauge theory can be understood as a direct consequence of the entropy bounds and unitarity. | entropy bound and unitarity of scattering amplitudes |
recently, there has been a surge of interest in the 4d einstein-gauss-bonnet (4d egb) gravity theory which bypasses the lovelock theorem and avoids ostrogradsky's instability. such a novel theory has nontrivial dynamics and presents several predictions for cosmology and black hole physics. motivated by recent astrophysical observations and the importance of anti-de sitter spacetime (ads), we investigate shadow geometrical shapes and deflection angle of light from the charged ads black holes in 4d egb gravity theory. we explore the shadow behaviors and photon sphere around such black holes, and inspect the effect of different parameters on them. then, we present a study regarding the energy emission rate of such black holes and analyze the significant role of the gauss-bonnet (gb) coupling constant in the radiation process. then, we perform a discussion of holographic heat engines of charged 4d egb-ads black holes by obtaining the efficiency of a rectangular engine cycle. finally, by comparing heat engine efficiency with the carnot efficiency, we indicate that the ratio η/ηc is always less than one which is consistent with the thermodynamic second law. | charged 4d einstein-gauss-bonnet-ads black holes: shadow, energy emission, deflection angle and heat engine |
we present the result of the spin-orbit interaction hamiltonian for binary systems of rotating compact objects with generic spins, up to n3lo corrections within the post-newtonian expansion. the calculation is performed by employing the effective field theory diagrammatic approach, and it involves feynman integrals up to three loops, evaluated within the dimensional regularization scheme. we apply canonical transformations to eliminate the non-physical divergences and spurious logarithmic behaviours of the hamiltonian, and use the latter to derive the gauge-invariant binding energy and the scattering angle, in special kinematic regimes. | gravitational spin-orbit hamiltonian at nnnlo in the post-newtonian framework |
we introduce a new paradigm for constructing accurate analytic waveforms (and fluxes) for eccentric compact binaries. our recipe builds on the standard post-newtonian (pn) approach but (i) retains implicit time-derivatives of the phase space variables in the instantaneous part of the noncircular waveform, and then (ii) suitably factorizes and resums this partly pn-implicit waveform using effective-one-body (eob) procedures. we test our prescription against the exact results obtained by solving the teukolsky equation with a test-mass source orbiting a kerr black hole, and compare the use of the exact vs pn equations of motion for the time derivatives computation. focusing only on the quadrupole contribution, we find that the use of the exact equations of motion yields an analytical/numerical agreement of the (averaged) angular momentum fluxes that is improved by 40% with respect to previous work, with 4.5% fractional difference for eccentricity e =0.9 and black hole dimensionless spin -0.9 ≤a ^≤+0.9 . we also find a remarkable convergence trend between newtonian, 1pn and 2pn results. our approach carries over to the comparable mass case using the resummed eob equations of motion and paves the way to faithful eob-based waveform model for long-inspiral eccentric binaries for current and future gravitational wave detectors. | new avenue for accurate analytical waveforms and fluxes for eccentric compact binaries |
in this paper, we explore the effect of non-linear electrodynamics (nled) parameters and magnetic charges on various aspects of black holes, like how they bend light, how they emit radiation, and how they appear as a shadow by considering a thin accretion disk model. we initially examine the overall behavior of the photonsphere and the corresponding shadow silhouette under the effects of these parameters. using the eht data for sgr. a* and m87*, we aim to find constraints for $q_m$. our results indicate that m87* gives better constraints, and as the value of $\beta$ is varied to increase, the constrained range for $q_m$ widens. at lower values of $q_m$, we find that the shadow radius is close to the observed value. then, we study different things like how much energy the black hole emits, the temperature of the disk around it, and the kind of light it gives off. we also look at how the black hole shadow appears in different situations. we also study how matter falls onto the black hole from all directions. finally, we investigate how the magnetic charge affects all these things when we take into account a theory called nled along with gravity. this study helps us understand the complex relationship between magnetic charge and black holes. | nonlinearly charged black holes: shadow and thin-accretion disk |
using first-principle numerical simulations of the lattice su(3) gauge theory, we calculate the isothermal moment of inertia of the rigidly rotating gluon plasma. we find that the moment of inertia unexpectedly takes a negative value below the "supervortical temperature" $t_s = 1.50(10) t_c$, vanishes at $t = t_s$, and becomes a positive quantity at higher temperatures. the negative moment of inertia indicates a thermodynamic instability of rigid rotation. we derive the condition of thermodynamic stability of the vortical plasma and show how it relates to the scale anomaly and the magnetic gluon condensate. the rotational instability of gluon plasma shares a striking similarity with the rotational instabilities of spinning kerr and myers-perry black holes. | negative moment of inertia and rotational instability of gluon plasma |
we analyze a class of topological static spherically symmetric vacuum solutions in f(q)-gravity. we considered an ansatz ensuring that those solutions trivially satisfy the field equations of the theory when the non-metricity scalar is constant. in the specific, we provide and discuss local solutions in the form of black holes and traversable wormholes. | a class of static spherically symmetric solutions in f(q)-gravity |
the third gravitational-wave transient catalog (gwtc-3) contains 90 binary coalescence candidates detected by the ligo-virgo-kagra collaboration (lvk). we provide a re-analysis of binary black hole (bbh) events using a recently developed numerical relativity (nr) waveform surrogate model, nrsur7dq4, that includes all $\ell \leq 4$ spin-weighted spherical harmonic modes as well as the complete physical effects of precession. properties of the remnant black holes' (bh's) mass, spin vector, and kick vector are found using an associated remnant surrogate model nrsur7dq4remnant. both nrsur7dq4 and nrsur7dq4remnant models have errors comparable to numerical relativity simulations and allow for high-accuracy parameter estimates. we restrict our analysis to 47 bbh events that fall within the regime of validity of nrsur7dq4 (mass ratios greater than 1/6 and total masses greater than $60 m_{\odot}$). while for most of these events our results match the lvk analyses that were obtained using the semi-analytical models such as imrphenomxphm and seobnrv4phm, we find that for more than 20\% of events the nrsur7dq4 model recovers noticeably different measurements of black hole properties like the masses and spins, as well as extrinsic properties like the binary inclination and distance. for instance, gw150914_095045 exhibits noticeable differences in spin precession and spin magnitude measurements. other notable findings include one event (gw191109_010717) that constrains the effective spin $\chi_{eff}$ to be negative at a 99.3\% credible level and two events (gw191109_010717 and gw200129_065458) with well-constrained kick velocities. furthermore, compared to the models used in the lvk analyses, nrsur7dq4 recovers a larger signal-to-noise ratio and/or bayes factors for several events. | analysis of gwtc-3 with fully precessing numerical relativity surrogate models |
the scattering of massless waves of helicity ∣h ∣=0 ,1/2 ,1 in schwarzschild and kerr backgrounds is revisited in the long-wavelength regime. using a novel description of such backgrounds in terms of gravitating massive particles, we compute classical wave scattering in terms of 2 → 2 qft amplitudes in flat space, to all orders in spin. the results are newman-penrose amplitudes which are in direct correspondence with solutions of the regge-wheeler/teukolsky equation. by introducing a precise prescription for the point-particle limit, in part i of this work we show how both agree for h = 0 at finite values of the scattering angle and arbitrary spin orientation.associated classical observables such as the scattering cross sections, wave polarizations and time delay are studied at all orders in spin. the effect of the spin of the black hole on the polarization and helicity of the waves is found in agreement with previous analysis at linear order in spin. in the particular limit of small scattering angle, we argue that wave scattering admits a universal, point-particle description determined by the eikonal approximation. we show how our results recover the scattering eikonal phase with spin up to second post-minkowskian order, and match it to the effective action of null geodesics in a kerr background. using this correspondence we derive classical observables such as polar and equatorial scattering angles.this study serves as a preceding analysis to part ii, where the gravitational wave (h = 2) case will be studied in detail. | scattering in black hole backgrounds and higher-spin amplitudes. part i |
we consider tree-level off-shell currents of two massive particles and n massless bosons in the classical limit, which can be fused into the classical limit of n + 2 scattering amplitudes. we show that dressing up the current with coherent wave-functions associated with the massive particles leads to the recently proposed worldline quantum field theory (wqft) path integral. the currents thus constructed encode solutions of classical equations of motion so they can be applied to contexts where the classical limit is relevant, including hard thermal loops. we give several examples of these currents in scalar, gauge and gravitational theories. | classical off-shell currents |
based on the rate of gravitational-wave (gw) detections by advanced ligo and virgo, we expect these detectors to observe hundreds of binary black hole mergers as they achieve their design sensitivities (within a few years). a small fraction of them can undergo strong gravitational lensing by intervening galaxies, resulting in multiple images of the same signal. to a very good approximation, the lensing magnifies/de-magnifies these gw signals without affecting their frequency profiles. we develop a bayesian inference technique to identify pairs of strongly lensed images among hundreds of binary black hole events and demonstrate its performance using simulated gw observations. | identifying strongly lensed gravitational wave signals from binary black hole mergers |
for a variety of ongoing and planned gravitational-wave (gw) experiments, we study expected constraints on the fraction (fpbh) of primordial black holes (pbhs) in dark matter by evaluating the energy-density spectra of two kinds of stochastic gw backgrounds. the first one is produced from an incoherent superposition of gws emitted from coalescences of all of the binary pbhs. the second one is induced through nonlinear mode couplings of large primordial curvature perturbations inevitably associated with the generation of pbhs in the early universe. in this paper, we focus on pbhs with masses 10-8 m⊙≤mpbh<1 m⊙ , since they are not expected to be of stellar origin. in almost all mass ranges, we show that the experiments are sensitive enough to constrain the fraction for 10-5≲fpbh≲1 by considering the gws from coalescing events and 10-10≲fpbh≲1 by considering the gws from curvature perturbations. exceptionally, the fraction cannot be constrained for fpbh≲3 ×10-3 by these two gw backgrounds only in the narrow mass range 2 ×10-5 m⊙≲mpbh≲4 ×10-5 m⊙ . | prospective constraints on the primordial black hole abundance from the stochastic gravitational-wave backgrounds produced by coalescing events and curvature perturbations |
we consider applications of the curvature radius of a kerr black hole shadow and propose three new approaches to simultaneously determine the black hole spin and inclination angle of the observer. the first one uses only two symmetric characteristic points, i.e., the top and the bottom points of the shadow, and is the smallest amount of data employed to extract information about spin and inclination angle amongst all current treatments. the second approach shows that only measuring the curvature radius at the characteristic points can also yield the black hole spin and the inclination angle. the observables used in the third approach have large changes to the spin and the inclination angle, which may give us a more accurate way to determine these parameters. moreover, by modeling the supermassive black hole m87* with a kerr black hole, we calculate the angular size for these curvature radii of the shadow. some novel properties are found and analyzed. the results may shine new light on the relationship between the curvature radius and the black hole shadow, and provide several different approaches to test the nature of the black hole through the shadow. | curvature radius and kerr black hole shadow |
recent work paints a conflicting portrait of the distribution of black hole spins in merging binaries measured with gravitational waves. some analyses find that a significant fraction of merging binaries contain at least one black hole with a spin tilt >90° with respect to the orbital angular momentum vector, which has been interpreted as a signature for dynamical assembly. other analyses find that the data are consistent with a bimodal population in which some binaries contain black holes with negligible spin while the rest contain black holes with spin vectors preferentially aligned with the orbital angular momentum vector. in this work, we scrutinize models for the distribution of black hole spins to pinpoint possible failure modes in which the model yields a faulty conclusion. we reanalyze data from the second ligo-virgo gravitational-wave transient catalog (gwtc-2) using a revised spin model, which allows for a subpopulation of black holes with negligible spins. in agreement with recent results by roulet et al., we show that the gwtc-2 detections are consistent with two distinct subpopulations. we estimate that 69%-90% (90% credible interval) of merging binaries contain black holes with negligible spin χ ≈ 0. the remaining binaries are part of a second subpopulation in which the spin vectors are preferentially (but not exactly) aligned to the orbital angular momentum. the black holes in this second subpopulation are characterized by spins of χ ~ 0.5. we suggest that the inferred spin distribution is consistent with the hypothesis that all merging binaries form via the field formation scenario. | building better spin models for merging binary black holes: evidence for nonspinning and rapidly spinning nearly aligned subpopulations |
we show that the geometry of a black hole horizon can be described as a carrollian geometry emerging from an ultra-relativistic limit where the near-horizon radial coordinate plays the role of a virtual velocity of light tending to zero. we prove that the laws governing the dynamics of a black hole horizon, the null raychaudhuri and damour equations, are carrollian conservation laws obtained by taking the ultra-relativistic limit of the conservation of an energy-momentum tensor; we also discuss their physical interpretation. we show that the vector fields preserving the carrollian geometry of the horizon, dubbed carrollian killing vectors, include bms-like supertranslations and superrotations and that they have non-trivial associated conserved charges on the horizon. in particular, we build a generalization of the angular momentum to the case of non-stationary black holes. finally, we discuss the relation of these conserved quantities to the infinite tower of charges of the covariant phase space formalism. | carrollian physics at the black hole horizon |
in this paper, we have studied the particle dynamics, gravitational lensing and energy processes around the black hole (bh) in kalb-ramond (kr) gravity. the motion of particles is considered with parameters in kr bh and investigated for massive and massless particles. from this work, we have got the horizon structure, photon orbit of photon and isco (inner stable circular orbit) of a mass particle with parameters in kr gravity. the effective potential is also studied for the massless and mass particles. additionally, we tested energy extracted from bh using the bsw (banados-silk-west) method and derived the expression of center mass-energy in kr gravity. the impact of the model parameters γ and λ is checked to study the size of the bh shadow in the kr gravity. gravitational weak lensing has been explored using the general method and the derived deflection angle of light rays around the bh for the plasma of various concentration distributions. the magnification of brightness is obtained using the angle of deflection of the light rays. | particle dynamics and gravitational weak lensing around black hole in the kalb-ramond gravity |
in this paper we derive for the first time the complete gravitational quartic-in-spin interaction of generic compact binaries at the next-to-leading order in the post-newtonian (pn) expansion. the derivation builds on the effective field theory for gravitating spinning objects, and its recent extensions, in which new type of worldline couplings should be considered, as well as on the extension of the effective action of a spinning particle to quadratic order in the curvature. the latter extension entails a new wilson coefficient that appears in this sector. this work pushes the precision frontier with spins at the fifth pn (5pn) order for maximally-spinning compact objects, and at the same time informs us of the gravitational compton scattering with higher spins. | nlo gravitational quartic-in-spin interaction |
it has recently been demonstrated that the large n limit of a model of fermions charged under the global/gauge symmetry group o( n) q-1 agrees with the large n limit of the syk model. in these notes we investigate aspects of the dynamics of the o( n) q-1 theories that differ from their syk counterparts. we argue that the spectrum of fluctuations about the finite temperature saddle point in these theories has (q-1)n^2/2 new light modes in addition to the light schwarzian mode that exists even in the syk model, suggesting that the bulk dual description of theories differ significantly if they both exist. we also study the thermal partition function of a mass deformed version of the syk model. at large mass we show that the effective entropy of this theory grows with energy like e ln e (i.e. faster than hagedorn) up to energies of order n 2. the canonical partition function of the model displays a deconfinement or hawking page type phase transition at temperatures of order 1 /ln n. we derive these results in the large mass limit but argue that they are qualitatively robust to small corrections in j/m. | notes on melonic o( n) q-1 tensor models |
the basic unified model of active galactic nuclei (agns) invokes an anisotropic obscuring structure, usually referred to as a torus, to explain agn obscuration as an angle-dependent effect. we present a new grid of x-ray spectral templates based on radiative transfer calculations in neutral gas in an approximately toroidal geometry, appropriate for ccd-resolution x-ray spectra (fwhm ≥ 130 ev). fitting the templates to broadband x-ray spectra of agns provides constraints on two important geometrical parameters of the gas distribution around the supermassive black hole: the average column density and the covering factor. compared to the currently available spectral templates, our model is more flexible, and capable of providing constraints on the main torus parameters in a wider range of agns. we demonstrate the application of this model using hard x-ray spectra from nustar (3-79 kev) for four agns covering a variety of classifications: 3c 390.3, ngc 2110, ic 5063, and ngc 7582. this small set of examples was chosen to illustrate the range of possible torus configurations, from disk-like to sphere-like geometries with column densities below, as well as above, the compton-thick threshold. this diversity of torus properties challenges the simple assumption of a standard geometrically and optically thick toroidal structure commonly invoked in the basic form of the unified model of agns. finding broad consistency between our constraints and those from infrared modeling, we discuss how the approach from the x-ray band complements similar measurements of agn structures at other wavelengths. | new spectral model for constraining torus covering factors from broadband x-ray spectra of active galactic nuclei |
in this paper, we use the gauss-bonnet theorem to obtain the deflection angle by the photons coupled to weyl tensor in a schwarzschild black hole and schwarzschild-like black hole in bumblebee gravity in the weak limit approximation. to do so, we first calculate the corresponding optical metrics, and then we find the gaussian curvature to use in gauss-bonnet theorem, which is first done by gibbons and werner. hence, in the leading order terms we show the deflection angle, that is affected by the coupling between the photon and weyl tensor, and there is a deviation from the deflecting angle as compared with schwarzschild black hole with schwarzschild-like black hole in bumblebee gravity. moreover, we investigate the deflection angle by einstein-rosen type wormhole in weyl gravity and in bumblebee gravity. interestingly, the deflection angle by einstein-rosen type wormhole in bumblebee gravity is found as larger than the deflection angle by einstein-rosen type wormhole in weyl gravity. | gravitational lensing under the effect of weyl and bumblebee gravities: applications of gauss-bonnet theorem |
a tidal disruption event (tde) takes place when a star passes near enough to a massive black hole to be disrupted. about half the star’s matter is given elliptical trajectories with large apocenter distances, and the other half is unbound. to form an accretion flow, the bound matter must lose a significant amount of energy, with the actual amount depending on the characteristic scale of the flow measured in units of the black hole’s gravitational radius (∼ {{10}51}{{(r/1000{{r}g})}-1} erg). recent numerical simulations have revealed that the accretion flow scale is close to the scale of the most bound initial orbits, ∼ {{10}3}mbh,6.5-2/3{{r}g}∼ {{10}15}mbh,6.51/3 cm from the black hole, and the corresponding energy dissipation rate is ∼ {{10}44}mbh,6.5-1/6 erg s-1. we suggest that the energy liberated during the formation of the accretion disk, rather than the energy liberated by subsequent accretion onto the black hole, powers the observed optical tde candidates. the observed rise times, luminosities, temperatures, emission radii, and line widths seen in these tdes are all more readily explained in terms of heating associated with disk formation rather than in terms of accretion. | ‧disk formation versus disk accretion—what powers tidal disruption events? |
this paper describes the first all-sky search for long-duration, quasimonochromatic gravitational-wave signals emitted by ultralight scalar boson clouds around spinning black holes using data from the third observing run of advanced ligo. we analyze the frequency range from 20 to 610 hz, over a small frequency derivative range around zero, and use multiple frequency resolutions to be robust towards possible signal frequency wanderings. outliers from this search are followed up using two different methods, one more suitable for nearly monochromatic signals, and the other more robust towards frequency fluctuations. we do not find any evidence for such signals and set upper limits on the signal strain amplitude, the most stringent being ≈10-25 at around 130 hz. we interpret these upper limits as both an "exclusion region" in the boson mass/black hole mass plane and the maximum detectable distance for a given boson mass, based on an assumption of the age of the black hole/boson cloud system. | all-sky search for gravitational wave emission from scalar boson clouds around spinning black holes in ligo o3 data |
we carry out the first investigation of the entanglement and mutual information harvesting protocols for detectors freely falling into a black hole. working in (1 +1 )-dimensional schwarzschild black hole spacetime, we consider two pointlike unruh-dewitt detectors in different combinations of free-falling and static trajectories. employing a generalization of relative velocity suitable for curved spacetimes, we find that the amount of correlations extracted from the black hole vacuum, at least outside the near-horizon regime, is largely kinematic in origin (i.e., it is mostly due to the relative velocities of the detectors). second, correlations can be harvested purely from the black hole vacuum even when the detectors are causally disconnected by the event horizon. finally, we show that the previously known `entanglement shadow' near the horizon is indeed absent for the case of two free-falling-detectors, since their relative gravitational redshift remains finite as the horizon is crossed, in accordance with the equivalence principle. | harvesting entanglement with detectors freely falling into a black hole |
we study the non-gaussianity and secondary gravitational waves (gws) in the process of the primordial black holes (pbhs) production from inflation. in our work, we focus on the α -attractor inflation model in which a tiny bump in the inflaton potential enhances the amplitude of the curvature perturbations at some scales and consequently leads to the pbhs production with different mass scales. we implement the computational code bingo which calculates the non-gaussianity parameter in different triangle configurations. our examination implies that in this setup, the non-gaussianity gets amplified significantly in the equilateral shape around the scales in which the power spectrum of the scalar perturbations undergoes a sharp declination. the imprints of these non-gaussianities can be probed in the scales corresponding to the bbn and μ -distortion events, or in smaller scales, and detection of such signatures in the future observations may confirm the idea of our model for the generation of pbhs or rule it out. moreover, we investigate the secondary gws in this framework and show that in our model, the peak of the present fractional energy density is obtained as ωgw 0∼10-8 at different frequencies which depends on the model parameters. these results lie well within the sensitivity region of some gws detectors at some frequencies, and therefore the observational compatibility of our model can be evaluated by the forthcoming data from these detectors. we further provide some estimations for the tilts of the induced gws spectrum in the different intervals of frequency, and demonstrate that the spectrum obeys the power-law relation ωgw 0∼fn in those frequency bands. | non-gaussianity and secondary gravitational waves from primordial black holes production in α -attractor inflation |
given the recent development of rotating black-bounce-kerr spacetimes, for both theoretical and observational purposes it becomes interesting to see whether it might be possible to construct black-bounce variants of the entire kerr-newman family. specifically, herein we shall consider black-bounce-reissner-nordström and black-bounce-kerr-newman spacetimes as particularly simple and clean everywhere-regular black hole "mimickers" that deviate from the kerr-newman family in a precisely controlled and minimal manner, and smoothly interpolate between regular black holes and traversable wormholes. while observationally the electric charges on astrophysical black holes are likely to be extremely low, |q|/m ≪ 1, introducing any non-zero electric charge has a significant theoretical impact. in particular, we verify the existence of a killing tensor (and associated carter-like constant) but without the full killing tower of principal tensor and killing-yano tensor, also we discuss how, assuming general relativity, the black-bounce-kerr-newman solution requires an interesting, non-trivial matter/energy content. | charged black-bounce spacetimes |
we study the shadow cast or silhouette generated by a kerr-newman-kasuya (knk) spacetime (rotating dyon black hole). it is shown that in addition to the angular momentum of the black hole, the dyon charge also affects the shadow image of the knk black hole. moreover, we analyze the weak gravitational lensing by the knk black hole by using the gauss-bonnet theorem. finally, we find that extra dyon charge decreases both the deflection angle and shadow of the knk black hole. | shadow cast and deflection angle of kerr-newman-kasuya spacetime |
we propose a class of multidimensional higher derivative theories of gravity without extra real degrees of freedom besides the graviton field. the propagator shows up the usual real graviton pole in k2 = 0 and extra complex conjugates poles that do not contribute to the absorptive part of the physical scattering amplitudes. indeed, they may consistently be excluded from the asymptotic observable states of the theory making use of the lee-wick and cutkosky, landshoff, olive and polkinghorne prescription for the construction of a unitary s-matrix. therefore, the spectrum consists of the graviton and short lived elementary unstable particles that we named ;anti-gravitons; because of their repulsive contribution to the gravitational potential at short distance. however, another interpretation of the complex conjugate pairs is proposed based on the calmet's suggestion, i.e. they could be understood as black hole precursors long established in the classical theory. since the theory is cpt invariant, the conjugate complex of the micro black hole precursor can be interpreted as a white hole precursor consistently with the 't hooft complementarity principle. it is proved that the quantum theory is super-renormalizable in even dimension, i.e. only a finite number of divergent diagrams survive, and finite in odd dimension. furthermore, turning on a local potential of the riemann tensor we can make the theory finite in any dimension. the singularity-free newtonian gravitational potential is explicitly computed for a range of higher derivative theories. finally, we propose a new super-renormalizable or finite lee-wick standard model of particle physics. | super-renormalizable or finite lee-wick quantum gravity |
in this paper, we construct a deformed schwarzschild black hole from the de sitter gauge theory of gravity within dunkl generalization and we determine the metric coefficients versus dunkl parameter and parity operators. since the spacetime coordinates are not affected by the group transformations, only fields are allowed to change under the action of the symmetry group. a particular ansatz for the gauge fields is chosen and the components of the strength tensor are computed as well. additionally, we analyze the modifications on the thermodynamic properties to a spherically symmetric black hole due to dunkl parameters for even and odd parities. finally, we verify a novel remark highlighted from heat capacity: the appearance of a phase transition when the odd parity is taken into account. | thermodynamical properties of a deformed schwarzschild black hole via dunkl generalization |
accreting black holes (bhs) launch relativistic collimated jets, across many decades in luminosity and mass, suggesting the jet launching mechanism is universal, robust, and scale-free. theoretical models and general relativistic magnetohydrodynamic (grmhd) simulations indicate that the key jet-making ingredient is large-scale poloidal magnetic flux. however, its origin is uncertain, and it is unknown if it can be generated in situ or dragged inward from the ambient medium. here, we use the gpu-accelerated grmhd code h-amr to study global 3d bh accretion at unusually high resolutions more typical of local shearing box simulations. we demonstrate that turbulence in a radially extended accretion disc can generate large-scale poloidal magnetic flux in situ, even when starting from a purely toroidal magnetic field. the flux accumulates around the bh till it becomes dynamically important, leads to a magnetically arrested disc (mad), and launches relativistic jets that are more powerful than the accretion flow. the jet power exceeds that of previous grmhd toroidal field simulations by a factor of 10 000. the jets do not show significant kink or pinch instabilities, accelerate to γ ∼ 10 over three decades in distance, and follow a collimation profile similar to the observed m87 jet. | large-scale poloidal magnetic field dynamo leads to powerful jets in grmhd simulations of black hole accretion with toroidal field |
gravitational lensing by the light sphere of compact objects like black holes and wormholes will give us information on the compact objects. in this paper, we provide an improved strong deflection limit analysis in a general asymptotically flat, static, spherically symmetric spacetime. the strong deflection limit analysis also works in ultrastatic spacetimes. as an example of an ultrastatic spacetime, we reexamine the deflection angle in the strong deflection limit in an ellis wormhole spacetime. using the strong deflection limit, we obtain the deflection angle analytically for the reissner-nordström spacetime. the point of the improvement is the definition of a standard variable in the strong deflection limit analysis. we show that the choice of the variable is as important as the choice of the coordinates and we conclude that one should choose a proper variable for a given spacetime. | deflection angle in the strong deflection limit in a general asymptotically flat, static, spherically symmetric spacetime |
we perform radiative transfer simulations for kilonova in various situations, including the cases of prompt collapse to a black hole from neutron star mergers, high-velocity ejecta possibly accelerated by magnetars, and a black hole-neutron star merger. our calculations are done employing ejecta profiles predicted by numerical-relativity simulations and a new line list for all the r-process elements. we found that: (i) the optical emission for binary neutron stars promptly collapsing to a black hole would be fainter by ≳1-2 mag than that found in gw170817, while the infrared emission could be as bright as that in gw170817 if the post-merger ejecta is as massive as ≈0.01 m⊙; (ii) the kilonova would be brighter than that observed in gw170817 for the case that the ejecta is highly accelerated by the electromagnetic energy injection from the remnant, but within a few days it would decline rapidly and the magnitude would become fainter than in gw170817; and (iii) the optical emission from a black hole-neutron star merger ejecta could be as bright as that observed in gw170817 for the case that sufficiently large amount of matter is ejected (≳0.02 m⊙), while the infrared brightness would be brighter by 1-2 mag at the same time. we show that the difference in the ejecta properties would be imprinted in the differences in the peak brightness and time of peak. this indicates that we may be able to infer the type of the central engine for kilonovae by observation of the peak in the multiple band. | diversity of kilonova light curves |
defect extremal surface is defined by extremizing the ryu-takayanagi formula corrected by the quantum defect theory. this is interesting when the ads bulk contains a defect brane (or string). we introduce a defect extremal surface formula for reflected entropy, which is a mixed state generalization of entanglement entropy measure. based on a decomposition procedure of an ads bulk with a brane, we demonstrate the equivalence between defect extremal surface formula and island formula for reflected entropy in ads3/bcft2. we also compute the evolution of reflected entropy in evaporating black hole model and find that defect extremal surface formula agrees with island formula. | defect extremal surface for reflected entropy |
we study the entanglement entropy of a one-parameter family of exactly solvable gravities in the two-dimensional asymptotically flat space. the islands and page curves of eternal, evaporating, and bath-removed black holes are investigated. the different theories in this parameter class are identified through field redefinitions, which leave the island invariant. the page transition is found to occur at the first and third of the black hole lifetimes in the evaporating case for this family of solutions. in addition, we consider gluing the equilibrium black hole and the evaporating one along a null trajectory and study the effect of gluing on the islands and page curves. in the glued space, the island jumps across two different geometries at a certain retarded time. as a result, the page transition is stretched and split into two separate ones—the first transition happens when the net entropy generation stops, and the second one occurs as the early radiation effectively starts to become purified. finally, we discuss the issues concerning the inconsistent rates of purification and the paradox related to the state of the radiation. | page curves for a family of exactly solvable evaporating black holes |
we study the "complexity equals volume" (cv) and "complexity equals action" (ca) conjectures by examining moments of of time symmetry for ads3 wormholes having n asymptotic regions and arbitrary (orientable) internal topology. for either prescription, the complexity relative to n copies of the m = 0 btz black hole takes the form δ c = αcχ, where c is the central charge and χ is the euler character of the bulk time-symmetric surface. the coefficients αv= -4 π/3, αa= 1 /6 defined by cv and ca are independent of both temperature and any moduli controlling the geometry inside the black hole. comparing with the known structure of dual cft states in the hot wormhole limit, the temperature and moduli independence of αv, αaimplies that any cft gate set defining either complexity cannot be local. in particular, the complexity of an efficient quantum circuit building local thermofield-double-like entanglement of thermal-sized patches does not depend on the separation of the patches so entangled. we also comment on implications of the (positive) sign found for αa , which requires the associated complexity to decrease when handles are added to our wormhole. | holographic complexity is nonlocal |
a new description of macroscopic kruskal black holes that incorporates the quantum geometry corrections of loop quantum gravity is presented. 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. the resulting quantum extension of spacetime has the following features: (i) it admits an infinite number of trapped, anti-trapped and asymptotic regions; (ii) all curvature scalars have uniform (i.e., mass independent) upper bounds; (iii) in the large mass limit, all asymptotic regions of the extension have the same adm mass; (iv) in the low curvature region (e.g., near horizons) quantum effects are negligible, as one would physically expect; and (v) final results are insensitive to the fiducial structures that have to be introduced to construct the classical phase space description (as they must be). previous effective theories shared some but not all of these features. we compare and contrast our results with those of these effective theories and also with expectations based on the ads /cft conjecture. we conclude with a discussion of limitations of our framework, especially for the analysis of evaporating black holes. | quantum extension of the kruskal spacetime |
we present a novel generalization of the heisenberg uncertainty principle which introduces the existence of a maximal observable momentum and at the same time does not entail a minimal indeterminacy in position. the above result is an exact generalized uncertainty principle (gup), valid at all energy scales. for small values of the deformation parameter β, our ansatz is consistent with the usual expression for gup borrowed from string theory, doubly special relativity and other quantum gravity candidates that provide β with a negative sign. as a preliminary analysis, we study the implications of this new model on some quantum mechanical applications and on the black hole thermodynamics. | generalized uncertainty principle with maximal observable momentum and no minimal length indeterminacy |
the rare case of changing-look (cl) active galactic nuclei (agns), with the appearance or disappearance of broad balmer emission lines within a few years, challenges our understanding of the agn unified model. we present a sample of 21 new cl agns at 0.08< z< 0.58, which doubles the number of such objects known to date. these new cl agns were discovered in various ways, from (1) repeat spectra in the sdss, (2) repeat spectra in the large sky area multi-object fiber spectroscopic telescope (lamost) and sdss, and (3) photometric variability and new spectroscopic observations. we use the photometric data from surveys, including the sdss imaging survey, the pan-starrs1, the desi legacy imaging survey, the wide-field infrared survey explorer (wise), the catalina real-time transient survey, and the palomar transient factory. the estimated upper limits of the transition timescale of the cl agns in this sample spans from 0.9 to 13 years in the rest-frame. the continuum flux in the optical and mid-infrared becomes brighter when the cl agns turn on, or vice versa. variations of more than 0.2 mag in the w1 band were detected in 15 cl agns during the transition. the optical and mid-infrared variability is not consistent with the scenario of variable obscuration in 10 cl agns at more than the 3σ confidence level. we confirm a bluer-when-brighter trend in the optical. however, the mid-infrared wise colors w1-w2 become redder when the objects become brighter in the w1 band, possibly due to a stronger hot dust contribution in the w2 band when the agn activity becomes stronger. the physical mechanism of type transition is important for understanding the evolution of agns. | discovery of 21 new changing-look agns in the northern sky |
expanding around null hypersurfaces, such as generic kerr black hole horizons, using co-rotating kruskal-israel-like coordinates we study the associated surface charges, their symmetries and the corresponding phase space within einstein gravity. our surface charges are not integrable in general. their integrable part generates an algebra including superrotations and a bms3-type algebra that we dub "t-witt algebra". the non-integrable part accounts for the flux passing through the null hypersurface. we put our results in the context of earlier constructions of near horizon symmetries, soft hair and of the program to semi-classically identify kerr black hole microstates. | t-witts from the horizon |
the large n limit of the four-dimensional superconformal index was computed and successfully compared to the entropy of a class of ads5 black holes only in the particular case of equal angular momenta. using the bethe ansatz formulation, we compute the index at large n with arbitrary chemical potentials for all charges and angular momenta, for general $\mathcal{n}=1$ four-dimensional conformal theories with a holographic dual. we conjecture and bring some evidence that a particular universal contribution to the sum over bethe vacua dominates the index at large n. for $\mathcal{n}=4$ sym, this contribution correctly leads to the entropy of bps kerr-newman black holes in ads5 × s5 for arbitrary values of the conserved charges, thus completing the microscopic derivation of their microstates. we also consider theories dual to ads5 × se5, where se5 is a sasaki-einstein manifold. we first check our results against the so-called universal black hole. we then explicitly construct the near-horizon geometry of bps kerr-newman black holes in ads5 × t1,1, charged under the baryonic symmetry of the conifold theory and with equal angular momenta. we compute the entropy of these black holes using the attractor mechanism and find complete agreement with the field theory predictions. | superconformal indices at large n and the entropy of ads5 × se5 black holes |
black holes are among the most extreme objects that can be found in the universe and an ideal laboratory for testing fundamental physics. this article will briefly review the basic properties of black holes as expected from general relativity, the main astronomical observations, and the leading astrophysical techniques to probe the strong gravity region of these objects. it is mainly intended to provide a compact introductory overview on astrophysical black holes to new students entering this research field, as well as to senior researchers working in general relativity and alternative theories of gravity and wishing to quickly learn the state of the art of astronomical observations of black holes. | astrophysical black holes: a compact pedagogical review |
we study the motion of charged particles in the field of a rotating black hole immersed into an external asymptotically uniform magnetic field, focusing on the epicyclic quasicircular orbits near the equatorial plane. separating the circular orbits into four qualitatively different classes according to the sign of the canonical angular momentum of the motion and the orientation of the lorentz force, we analyze the circular orbits using the so-called force formalism. we find the analytical solutions for the radial profiles of velocity, specific angular momentum, and specific energy of the circular orbits in dependence on the black-hole dimensionless spin and the magnetic field strength. the innermost stable circular orbits are determined for all four classes of the circular orbits. the stable circular orbits with an outward-oriented lorentz force can extend to radii lower than the radius of the corresponding photon circular geodesic. we calculate the frequencies of the harmonic oscillatory motion of the charged particles in the radial and vertical directions related to the equatorial circular orbits and study the radial profiles of the radial, ωr; vertical, ωθ; and orbital, ωϕ, frequencies, finding significant differences in comparison to the epicyclic geodesic circular motion. the most important new phenomenon is the existence of toroidal charged particle epicyclic motion with ωr∼ωθ≫ωϕ that could occur around retrograde circular orbits with an outward-oriented lorentz force. we demonstrate that for the rapidly rotating black holes the role of the "wald induced charge" can be relevant. | circular orbits and related quasiharmonic oscillatory motion of charged particles around weakly magnetized rotating black holes |
this review is an introduction to causal properties of general relativity. topics include the raychaudhuri equation, singularity theorems of penrose and hawking, the black hole area theorem, topological censorship, and the gao-wald theorem. the review is based on lectures at the 2018 summer program prospects in theoretical physics at the institute for advanced study, and also at the 2020 new zealand mathematical research institute summer school in nelson, new zealand. | light rays, singularities, and all that |
outflows from active galactic nuclei (agns) are one of the fundamental mechanisms by which the central supermassive black hole interacts with its host galaxy. detected in ≥50% of nearby agns, these outflows have been found to carry kinetic energy that is a large fraction of the agn power, and thereby give `negative' feedback to their host galaxies. to understand the physical processes that regulate them, it is important to have a robust estimate of their physical and dynamical parameters. in this review article, we summarize our current understanding of the physics of the ionized outflows detected via absorption in the ultraviolet and x-ray wavelength bands. we discuss the most relevant observations and our current knowledge and uncertainties in the measurements of the outflow parameters, as well as their origin and acceleration mechanisms. the commissioning and concept studies of large telescope missions with high-resolution spectrographs in ultraviolet/optical and x-rays along with rapid advancements in simulations offer great promise for discoveries in this field over the next decade. | ionized outflows from active galactic nuclei as the essential elements of feedback |
we discuss the footprint of evaporation of primordial black holes (pbhs) on stochastic gravitational waves (gws) induced by scalar perturbations. we consider the case where pbhs once dominated the universe but eventually evaporated before the big bang nucleosynthesis. the reheating through the pbh evaporation could end with a sudden change in the equation of state of the universe compared to the conventional reheating caused by particle decay. we show that this "sudden reheating" by the pbh evaporation enhances the induced gws, whose amount depends on the length of the pbh-dominated era and the width of the pbh mass function. we explore the possibility to constrain the primordial abundance of the evaporating pbhs by observing the induced gws. we find that the abundance parameter β ≳10-5-10-8 for 𝒪 (103-1 05) g pbhs can be constrained by future gw observations if the width of the mass function is smaller than about a hundredth of the mass. | gravitational wave production right after a primordial black hole evaporation |
primordial black holes may owe their origin to the small-scale enhancement of the comoving curvature perturbation generated during inflation. their mass fraction at formation is markedly sensitive to possible non-gaussianities in such large, but rare fluctuations. we discuss a path-integral formulation which provides the exact mass fraction of primordial black holes at formation in the presence of non-gaussianity. through a couple of classes of models, one based on single-field inflation and the other on spectator fields, we show that restricting to a gaussian statistics may lead to severe inaccuracies in the estimate of the mass fraction as well as on the clustering properties of the primordial black holes. | primordial black holes from inflation and non-gaussianity |
the nonminimal coupling of the nonzero vacuum expectation value of the self-interacting antisymmetric kalb-ramond field with gravity leads to a power-law hairy black hole having a parameter s , which encompasses the reissner-nordstrom black hole (s =1 ). we obtain the axially symmetric counterpart of this hairy solution, namely, the rotating kalb-ramond black hole, which encompasses, as special cases, kerr (s =0 ) and kerr-newman (s =1 ) black holes. interestingly, for a set of parameters (m , a , and γ ), there exists an extremal value of the kalb-ramond parameter (s =se), which corresponds to an extremal black hole with degenerate horizons, while for s <se, it describes a nonextremal black hole with cauchy and event horizons, and no black hole for s >se. we find that the extremal value se is also influenced by these parameters. the black hole shadow size decreases monotonically and the shape gets more distorted with an increasing s ; in turn, shadows of rotating kalb-ramond black holes are smaller and more distorted than the corresponding kerr black hole shadows. we investigate the effect of the kalb-ramond field on the rotating black hole spacetime geometry and analytically deduced corrections to the light deflection angle from the kerr and schwarzschild black hole values. the deflection angle for sgr a* and the shadow caused by the supermassive black hole m87* are included and compared with analogous results of kerr black holes. the inferred circularity deviation δ c ≤0.10 for the m87* black hole merely constrains the kalb-ramond field parameter, whereas shadow angular diameter θd=42 ±3 μ as , within the 1 σ region, places bounds γ ≤0.09205 for s =1 and γ ≤0.02178 for s =3 . | gravitational deflection of light and shadow cast by rotating kalb-ramond black holes |
the spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. however, it is a general belief that singularities do not exist in nature and that they are the limitations of the general relativity. in the absence of a well-defined quantum gravity, models of regular black holes have been studied. we employ a probability distribution inspired mass function m( r) to replace the kerr black hole mass m to represent a nonsingular rotating black hole that is identified asymptotically (r ≫ k, k>0 constant) exactly as the kerr-newman black hole, and as the kerr black hole when k=0. the radiating counterpart renders a nonsingular generalization of carmeli's spacetime as well as vaidya's spacetime, in the appropriate limits. the exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. the regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. | a nonsingular rotating black hole |
there is rich literature on regular black holes from loop quantum gravity (lqg), where quantum geometry effects resolve the singularity, leading to a quantum extension of the classical space-time. as we will see, the mechanism that resolves the singularity can also trigger conceptually undesirable features that can be subtle and are often uncovered only after a detailed examination. therefore, the quantization scheme has to be chosen rather astutely. we illustrate the new physics that emerges first in the context of the eternal black hole represented by the kruskal space-time in classical general relativity, then in dynamical situations involving gravitational collapse, and finally, during the hawking evaporation process. the emphasis is on novel conceptual features associated with the causal structure, trapping and anti-trapping horizons and boundedness of invariants associated with curvature and matter. this chapter is not intended to be an exhaustive account of all lqg results on non-singular black holes. rather, we have selected a few main-stream thrusts to anchor the discussion, and provided references where further details as well as discussions of related developments can be found. in the spirit of this volume, the goal is to present a bird's eye view that is accessible to a broad audience. | regular black holes from loop quantum gravity |
we introduce an entropy function for supersymmetric accelerating black holes in four-dimensional anti-de sitter space that uplift on general sasaki-einstein manifolds x7 to solutions of m theory. this allows one to compute the black hole entropy without knowing the explicit solutions. a dual holographic microstate counting would follow from computing certain supersymmetric partition functions of chern-simons-matter theories compactified on a spindle. we make a general prediction for a class of such partition functions in terms of "blocks," with each block being constructed from the partition function on a three-sphere. | entropy functions for accelerating black holes |
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