We investigate the absorption and scattering of a charged massive scalar field by a charged Horndeski black hole using both the approximation or classical geometric method and the partial wave method and compare the numerical and analytical results, which are found to agree with each other very well. We observe that an increase in either the black hole (BH) charge $Q$ or the field charge $q$ when $qQ>0$ leads to a smaller absorption cross section and a widening of the interference fringes in the scattering cross section, while the increase in the field mass enlarges the absorption cross section and the width of the interference fringes. Compared to the Reissner-Nordström BH with the same charge and other parameter settings, the absorption and scattering cross sections of the charged Horndeski BH are higher, and its interference fringes are narrower. We also investigate the effect of the field charge $q$ on the absorption and scattering cross sections when superradiance is triggered. It is shown that the total absorption cross section can be negative, and the scattering intensity can be significantly enhanced by superradiance.

We study the null geodesics in the extremal Kerr-Newman exterior. We clarify the roots of the radial potential and obtain the parameter space of the azimuthal angular momentum and the Carter constant of the light rays for varieties of the orbits. It is known that one of the unique features of extremal black holes for the null geodesics is the existence of the stable double root at the horizon, giving rise to the stable spherical motion. For the black hole’s spin $a<M/2$, the stable double root is isolated from the unstable one. However, for $a\ge M/2$, the unstable and stable double roots merge at the triple root so that the unstable double root in some parameter region can lie at the horizon, giving a very different shape to the light ring. We then find the analytical expressions of light orbits, which can reach spatial infinity for both nonequatorial and equatorial motions. In particular, for the orbits starting from the near horizon of the extremal Kerr-Newman black holes with the parameters for the unstable double and triple roots, the solutions are remarkably simple in terms of elementary functions. It is also found that the analytical solutions of the equatorial motion can shed light on the deflection of the light by black holes. Varying the azimuthal angular momentum, as either the double or triple root at the horizon is approached from the turning point, the stronger power-law divergence in the deflection angle is found in comparison with the typical logarithmic divergence in nonextremal black holes in the strong deflection limit. This could be another interesting effect of light deflection by extremal black holes.

Owing to our work in part I of this series of papers, it is understood that the analytically known black hole solutions in the theory of ghost-free multimetric gravity can be split into three distinct classes and that one of these classes—the proportional branch—exhibits the Gregory-Laflamme instability at linear level in the metric perturbations, whenever the black hole horizon size is smaller than (roughly) the Compton wavelength of the theory’s lightest massive graviton. In this first of two sequels, we determine the linear stability of the two remaining classes of black hole solutions—the nonproportional and partially proportional branches—and discuss how our results likely differ at nonlinear level. We also give a general prescription to construct multimetric solutions describing black holes endowed with massive graviton hair, which may constitute the end state of the instability in the proportional branch. We utilize a tractable example model involving three metrics to see how this works in practice and determine the asymptotic form of its corresponding hairy solutions at infinity, where one can clearly see the individual contributions from each of the graviton mass modes.

It has recently been noted that deformations of extremal anti–de Sitter (AdS) black holes in four and higher dimensions are generically nonsmooth or singular on the horizon. Further, it was found that certain deformations of asymptotically flat extremal black holes are marginal, causing the nature of the horizon to be strongly sensitive to UV corrections—in particular, Wilson coefficients associated with consistent UV completions generically lead to worse behavior on the horizon. In this work, we extend the discussion of deformed horizons in the presence of UV corrections to extremal charged black holes in AdS, where we find a tower of marginal perturbations for different black hole masses. We argue that the apparent UV sensitivity of marginal modes is, in fact, a feature of the UV theory, which is correctly reproduced by the effective field theory (EFT), and illustrate this with explicit UV completions confirming the validity of the EFT. We demonstrate that the same holds for a scalar-Maxwell EFT with known UV completion. In the gravitational case, the sign of EFT corrections to marginal perturbations is generally connected with the signs implied by positivity bounds, with UV completions generically leading to worse behavior on the horizon. We conjecture that this result is more generic and use this to derive more general positivity bounds motivated by the weak gravity conjecture, which we illustrate with further evidence.

The number of gravitons emitted during binary inspiral is found to be remarkably close to (though slightly larger than) the radiated angular momentum in units of $2\hslash$. This ($\sim 1\%$) closeness holds both for an infinitesimal change in the eccentricity, and for the total graviton number emitted during inspiral from a large eccentricity initial orbit down to negligible final eccentricity.

Soft hairs are an intrinsic infrared feature of a black hole, which may also affect near-horizon physics. In this work, we study some of the subtleties surrounding one of the primary observables with which we can study their effects in the context of Einstein’s gravity: the black hole shadow. First, we clarify the singular pathology associated with black holes with soft hairs and demonstrate that the metrics of linearly superrotated black holes are free of near-zone pathologies due to appropriate asymptotic falloff conditions being imposed on the event horizon. We then analytically construct the photon orbits around such black holes, derive the shadow equation for near-zone observers, and find that the linear superrotation hairs deform the circular shadow of a bald Schwarzchild black hole into an ellipse. This is in sharp contrast to their supertranslated counterparts, which only shift the position of the center of the circular shadow but do not change its shape. Our results suggest a richness to the observable effects due to the infrared structures of Einstein’s gravity.

We study spherical evolution in scalar-Gauss-Bonnet gravity with additional Ricci coupling and use the gauge-invariant approach introduced recently by Reall to track well-posedness. Our results show that loss of hyperbolicity when it occurs, is due to the behavior of physical degrees of freedom. They provide further support to the idea that this behavior can be tamed by additional interactions of the scalar. We also point out a limitation of this gauge-invariant approach: the fact that field redefinitions can change the character of the evolution equations.

The first observation of a gravitational wave (GW) and a short gamma-ray burst (sGRB) emitted by the same binary neutron star (BNS) merger officially opened the field of GW multimessenger astronomy. In this paper, we define and address lagging sirens, a new class of multimessenger BNSs for which associated GWs and sGRBs are observed without the identification of their host galaxy. We propose a new methodology to use the observed time delay of these sources to constrain the speed of gravity that is, the propagation speed of gravitational waves, the Hubble constant and the prompt time delay distribution between GWs and sGRBs, even though a direct redshift estimation from the host galaxy is unavailable. Our method exploits the intrinsic relation between GWs and sGRBs observed and prompt time delays to obtain a statistical redshift measure for the cosmological sources. We show that this technique can be used to infer the Hubble constant at the 10% level of precision with future-generation GW detectors such as the Einstein Telescope and only 100 observations of this kind. The novel procedure that we propose has systematics that differ completely from the ones of previous GW methods for cosmology. Additionally, we demonstrate for the first time that the speed of gravity and the distribution of the prompt time delays between GWs and sGRBs can be inferred conjointly with less than 10 sources even with current GW detector sensitivities.

We propose symbolic regression as a powerful tool for the numerical studies of proposed models of physics beyond the Standard Model. In this paper we demonstrate the efficacy of the method on a benchmark model, namely the constrained minimal supersymmetric Standard Model, which has a four-dimensional parameter space. We provide a set of analytical expressions that reproduce three low-energy observables of interest in terms of the parameters of the theory: the Higgs mass, the contribution to the anomalous magnetic moment of the muon, and the cold dark matter relic density. To demonstrate the power of the approach, we employ the symbolic expressions in a global fits analysis to derive the posterior probability densities of the parameters, which are obtained two orders of magnitude more rapidly than is possible using conventional methods.

This work investigates the capability of future lepton colliders to determine the sign of the gauge-Higgs coupling through the vector boson fusion $Zh$ process. This channel offers a model-independent way to probe the sign of the gauge-Higgs coupling. Its sensitivity to interference effects and universal coupling with new physics makes it particularly effective. We show that a high-energy lepton collider such as CLIC can fully determine the sign of the gauge-Higgs coupling in a model-independent way and with high confidence.

Motivated by the ion-collision program at the Large Hadron Collider, plans for its high-luminosity upgrade, and ongoing discussions for multi-TeV future hadron colliders, we systematically investigate hard-scattering, Standard Model processes in many-TeV ion-ion collisions. We focus on the symmetric beam configurations ${}^{208}\mathrm{Pb}\text{−}{}^{208}\mathrm{Pb}$, ${}^{131}\mathrm{Xe}\text{−}{}^{131}\mathrm{Xe}$, ${}^{12}\mathrm{C}\text{−}{}^{12}\mathrm{C}$, and $pp$, and we catalog total and fiducial cross sections for dozens of processes, ranging from associated-Higgs and multiboson production to associated-top pair production, at next-to-leading order in QCD for nucleon-nucleon collision energies from $\sqrt{s_{NN}}=1$ to 100 TeV. We report the residual scale uncertainties at this order as well as the uncertainties originating from fits of nuclear parton densities. We also discuss the propagation of nuclear dynamics (as encoded in nuclear parton densities) into parton luminosities and ultimately into predictions for cross sections. Finally, we report on the emergence of trends and the reliability of extrapolating cross sections across different nuclei. For Pb-Pb collisions at a hypothetical Future Circular Collider with $\sqrt{s_{NN}}=39\mathrm{TeV}$, $\mathcal{O}({10}^8)$ weak bosons, $\mathcal{O}({10}^5)$ diboson pairs, $\mathcal{O}({10}^4)$ $WH$ and $ZH$ pairs, $\mathcal{O}({10}^3)$ triboson events, $\mathcal{O}({10}^5)$ high-$p_T$ photons events, and $\mathcal{O}({10}^7)$ $t\overline{t}$ pairs can be produced with $\mathcal{L}=33{\mathrm{nb}}^{-1}$ of data. At $\sqrt{s_{NN}}=5.52\mathrm{TeV}$, one can expect $\mathcal{O}(10–{10}^6)$ single, multiboson, and top events per $1{\mathrm{nb}}^{-1}$. Decay rates and experimental selection/acceptance rates will impact final event yields and merit further study; as an illustrative example, we focus on select diboson and triboson channels in lead-lead collisions and discuss their observability at the high-luminosity phase of the Large Hadron Collider and the Future Circulate Collider.

The $CP$-even fractions ($F_{+}$) of the decays $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ and $D^0\to K^{+}{K}^{-}{\pi }^0$ are measured with a quantum-correlated $\psi (3770)\to D\overline{D}$ data sample collected by the BESIII experiment corresponding to an integrated luminosity of $7.93{\mathrm{fb}}^{-1}$. The results are $F_{+}^{{\pi }^{+}{\pi }^{-}{\pi }^0}=0.9406\pm 0.0055\pm 0.0033$ and $F_{+}^{K^{+}{K}^{-}{\pi }^0}=0.631\pm 0.014\pm 0.011$, where the first uncertainties are statistical and the second systematic. These measurements are consistent with the previous determinations, and the uncertainties for $F_{+}^{{\pi }^{+}{\pi }^{-}{\pi }^0}$ and $F_{+}^{K^{+}{K}^{-}{\pi }^0}$ are reduced by factors of 2.6 and 2.6, respectively. The reported results provide important inputs for the precise measurement of the angle $\gamma$ of the Cabibbo-Kobayashi-Maskawa matrix and indirect $CP$ violation in charm mixing.

We argue there is an interesting triple-scaling limit of quantum gravity, namely when Planck’s constant scales to infinity while Newton’s constant and the speed of light tend to zero, keeping fixed the gravitational coupling $G_N{c}^{-4}$ and the combination $\hslash c$. We refer to this limiting theory as “tantum gravity” and describe in this Letter some of its main properties and prospects for physics. Most notably, the laws of black hole thermodynamics survive this limit, which means that puzzles related to black holes and their evaporation could be addressed more easily in tantum gravity than in fully fledged quantum gravity.

It is shown that a complex coordinate transformation maps the Taub-Newman-Unti-Tamburino instanton metric to a Kerr-Schild metric. This metric involves a semi-infinite line defect as the gravitational analog of the Dirac string, much like the original metric. Moreover, it facilitates three versions of classical double copy correspondence with the self-dual dyon in electromagnetism, one of which involves a nonlocal operator. The relevance to the Newman-Janis algorithm is briefly noted.

We derive the celestial optical theorem from the $S$-matrix unitarity, which provides nonperturbative bootstrap equations of conformal partial wave (CPW) coefficients. This theorem implies that the imaginary parts of CPW coefficients exhibit a positivity property. By making certain analyticity assumptions and using the celestial optical theorem, we derive nonperturbative constraints concerning the analytic structure of CPW coefficients. We discover that the CPW coefficients of four massless particles must and can only have simple poles located at specific positions. The CPW coefficients involving massive particles exhibit double-trace poles, indicating the existence of double-trace operators in nonperturbative celestial conformal field theory. It is worth noting that, in contrast to AdS/CFT, the conformal dimensions of double-trace operators do not have anomalous dimensions.

We propose a novel method to construct ghost-free multiple scalar-tensor theories. The key idea is to use the geometric quantities of hypersurfaces defined by the scalar fields, rather than the covariant derivatives of scalar fields or spacetime curvature, to build the theory. This approach has proven effective in developing ghost-free scalar-tensor theories in the single-field case. When multiple scalar fields are present, each field specifies a foliation of spacelike hypersurfaces, on which we can define the normal vector, induced metric, extrinsic and intrinsic curvatures, as well as extrinsic (Lie) and intrinsic (spatial) derivatives, respectively. By employing these hypersurface geometric quantities as foundational elements, we construct the Lagrangian for interacting hypersurfaces that describes a multiple scalar-tensor theory. Given that temporal (Lie) and spatial derivatives are separated, it becomes relatively easier to control the order of time derivatives, thus helping to avoid ghostlike or unwanted degrees of freedom. In this work, we use biscalar-field theory as an example, focusing on polynomial-type Lagrangians. We construct monomials of hypersurface geometric quantities up to $d=3$, where $d$ denotes the number of derivatives in each monomial. Additionally, we present the correspondence between expressions in terms of hypersurface quantities and those in covariant biscalar-tensor theory. Through a cosmological perturbation analysis of a simple model, we demonstrate that the theory propagates two tensor and two scalar degrees of freedom at the linear order in perturbations, thereby remaining free from any extra degrees of freedom.

We present cosmological constraints from a joint analysis including the power spectrum and bispectrum of Baryon Oscillation Spectroscopic Survey (BOSS) galaxies based on the effective field theory of large-scale structure predictions at one-loop order, in combination with cosmic microwave background (CMB) data from Planck, Supernovae from Pantheon+, and baryon acoustic oscillations (BAO) from Extended Baryon Oscillation Spectroscopic Survey (eBOSS) and 6-degree Field galaxy survey (6dF)/Main Galaxy Sample from the Sloan Digital Galaxy Survey I (MGS). Limits on $\mathrm{\Lambda }$ cold dark matter model ($\mathrm{\Lambda }\mathrm{CDM}$) parameters are in good agreement, and on average $\sim 5\%-10\%$ tighter, compared to former results including similar datasets but no bispectrum. Moreover, we find that galaxies at the three-point level with one-loop precision are decisive for the dark energy equation of state, constrained to be $w=-0.975\pm 0.019$ at 68% CL. This constraint, about 30% tighter than the former determination, is consistent at $\sim 1.3\sigma$ with a cosmological constant. Our analyses illustrate the importance of beyond-two-point statistics at the highest reachable scales in constraining cosmological parameters, and in particular departure from $\mathrm{\Lambda }\mathrm{CDM}$.

Two-dimensional models assuming axisymmetry are an economical way to explore the long-term evolution of black hole accretion disks, but they are only realistic if the feedback of the nonaxisymmetric turbulence on the mean momentum and magnetic fields is incorporated. Dynamo terms added to the 2D induction equation should be calibrated to 3D magnetohydrodynamics simulations. For generality, the dynamo tensors should be calibrated as functions of local variables rather than explicit functions of spatial coordinates in a particular basis. In this paper, we study the feedback of nonaxisymmetric features on the 2D mean fields using a global 3D, relativistic, Cartesian simulation from the illinoisgrmhd code. We introduce new methods for estimating overall dynamo $\alpha$ and turbulent diffusivity effects, as well as measures of the dominance of nonaxisymmetric components of energies and fluxes within the disk interior. We attempt closure models of the dynamo electromotive force using least-squares fitting, considering both models where coefficient tensors are functions of space and more global, covariant models. None of these models are judged satisfactory, but we are able to draw conclusions on what sorts of generalizations are and are not promising.

This paper thoroughly analyzes the impact of various parameter changes on the estimation of parameters for massive black hole binaries (MBHBs) systems using a Bayesian inference technique with the upcoming TianQin and LISA gravitational wave detectors. Several designed MBHB systems were chosen to compare with a fiducial system and explore the influence of parameters such as sky localization, inclination angle, antialigned spin, large mass ratio, and low mass. Additionally, the two known MBHB candidates OJ287 and Tick-Tock are also considered in our study. Utilizing Bayesian inference, we explored the 11-dimensional parameter space and found that parameter relationships depend significantly on the source’s injected values and waveform phases. Our results indicate that while signal-to-noise ratio (SNR) is important, it does not solely determine parameter estimation accuracy. Joint detection by TianQin and LISA was particularly effective in breaking degeneracies and improving the precision of extrinsic parameters by approximately an order of magnitude. We also found about three orders of improvement for sky localization, partly due to the time delay between the two detectors. However, the primary contributor is the different configurations of the detectors that can help break down the parameter degeneracies. Moreover, when the source is near the surface of TianQin’s orbital plane, the Doppler effects from TianQin’s movement around the Earth play a significant role in determining sky localization. The study also demonstrates that our methodology is robust to noise, with most parameter estimates remaining within a $2\sigma$ confidence region even in the presence of noise.

The magnetic deformation of magnetars is affected by their internal magnetic fields, which are generally difficult to be measured directly through observations. In this work, the periodic pulse-phase modulations in the hard x-ray emissions of the magnetars 4U $0142+61$, 1E 1547.0-5408, SGR $1900+14$, and SGR 1806-20, and the periodicities of fast radio bursts (FRBs) 180916 and 121102 are interpreted as free precession of the (host) magnetars. Using these periodic signals, we investigate the magnetars’ internal magnetic fields. In order to simultaneously account for the modulation periods and surface thermal emissions of the former four magnetars, and require that their internal poloidal fields smoothly connect with the surface dipole fields, the parameter that characterizes the distribution of toroidal field in the magnetar interior should satisfy $\beta \gtrsim 1$. Moreover, their volume-averaged strengths of poloidal and toroidal fields are respectively ${\overline{B}}_{\mathrm{p}}\sim {10}^{14}–{10}^{15}\mathrm{G}$ and ${\overline{B}}_{\mathrm{t}}\sim {10}^{15}\mathrm{G}$ with the strength ratios ${\overline{B}}_{\mathrm{t}}/{\overline{B}}_{\mathrm{p}}$ generally distributing within $\sim 2–37$. We could also constrain the critical temperature for neutron superfluidity in the neutron-star core considering that the former four magnetars are probably precessing, and the most stringent constraint is $T_{c,\mathrm{core}}<6.4\times {10}^8\mathrm{K}$. Adopting a possible critical temperature $T_{c,\mathrm{core}}=5\times {10}^8\mathrm{K}$, we could obtain ${\overline{B}}_{\mathrm{p}}\gtrsim {10}^{14}–{10}^{15}\mathrm{G}$ and ${\overline{B}}_{\mathrm{t}}\gtrsim {10}^{14}–{10}^{15}\mathrm{G}$ for the host magnetars of FRBs 180916 and 121102, which indicates that the magnetars of our interest possibly have similar poloidal and toroidal fields.