Binary systems of black holes emit gravitational waves as they move through their orbits. While most of the emitted radiation escapes to future null infinity, a small fraction is absorbed by the black holes themselves. This is known as horizon absorption or tidal heating/torquing and causes the black holes’ masses and spins to change as the system evolves. In this work, we quantify the effects of the horizon flux on binary black holes dynamics by computing them up to next-to-next-to-leading order on generic planar orbits, also exploring physically motivated factorizations of the results. We integrate these fluxes over unbound, hyperboliclike trajectories obtained with the effective-one-body model TEOBResumS-Dalí. We discuss the resulting phenomenology across a sizable slice of the relevant parameter space, finding a very small effect in most cases, except on highly energetic orbits. However, the predicted mass and spin variations are quantitatively and qualitatively very sensitive to the analytical representation chosen for the fluxes in that regime. We then perform comparisons with numerical relativity data of induced spins from hyperbolic encounters of initially nonrotating black holes, finding that the next-to-next-to-leading order factorized expressions we derive are crucial to reproduce the data. An optimization on the initial conditions (energy, angular momentum) is necessary for this, however, with differences of up to 9% between the numerical and optimal initial data. Finally, we use our analytical expressions to model possible astrophysical implications for black holes in globular clusters.

We compute the conservative scattering angle of two classical charged particles at the sixth order in electromagnetic coupling, and at the fourth order in velocity, thereby going beyond the current state of the art [fifth order in coupling, derived by Bern et al., Phys. Rev. Lett. 132, 251601 (2024)]. Our result is obtained by using the electromagnetic version of the effective one-body formalism to transfer information from the exact circular binary-charge solution of Schild [Phys. Rev. 131, 2762 (1963)] to the post-Lorentzian expansion of the scattering angle.

The Penrose process, a process that transfers energy from a black hole to infinity, together with the Bañados-Silk-West (BSW) mechanism, a mechanism that uses collisions of ingoing particles at the event horizon of a black hole to locally produce large amounts of energy, is studied in a combined description for a $d$ dimensional extremal Reissner-Nordström black hole spacetime with negative, zero, or positive cosmological constant, i.e., for an asymptotically anti-de Sitter (AdS), flat, or de Sitter (dS) spacetime. This blending of the Penrose process with BSW collisions is an instance of a collisional Penrose process. In an electrically charged extremal Reissner-Nordström black hole background, in the vicinity of the event horizon, several types of radial collisions between electrically charged particles can be considered, the most interesting one is between a critical particle, i.e., a particle that has its electric charge adjusted in a specific way to the other relevant parameters, and a usual particle, as it gives a divergent center of mass frame energy locally. A divergent center of mass frame energy at the point of collision is a favorable condition to extract energy from the black hole, but not sufficient, since, e.g., the product particles might go down the hole. So, to understand whether energy can be extracted or not in a Penrose process, we investigate in detail a collision between ingoing particles 1 and 2, from which particles 3 and 4 emerge, with the possibility that particle 3 can carry the energy extracted far out from the black hole horizon, i.e., there is a high Killing energy transported by particle 3. One finds that the mass, the energy, the electric charge, and the initial direction of motion of particle 3 can have different values, depending on the collision internal process itself. But, the different possible values of the parameters of the emitted particle 3 lie within some range, and moreover the energy of particle 3 can, in some cases, be arbitrarily high but not infinite, characterizing a super-Penrose process. It is also shown that particle 4 has negative energy, as required in a Penrose process, living in its own electric ergosphere while it exists, i.e., before being engulfed by the event horizon. For zero cosmological constant we find that the results do not depend on the number of dimensions, but they do for negative and positive cosmological constant. The value of the cosmological constant also introduces differences in the lower bound for the energy extracted.

This work develops a comprehensive algorithm and a Mathematica program to construct boundary data and compute real and complex critical points in spin foam amplitudes. Our approach covers both spacelike tetrahedra and triangles in the Engle-Pereira-Rovelli-Livine model and timelike tetrahedra and triangles in the Conrady-Hnybida extension, aiming at addressing a wide range of physical scenarios such as cosmology and black holes. Starting with a single 4-simplex, we explain how to numerically construct boundary data and corresponding real critical points from any nondegenerate 4-simplex geometry. Extending this to the simplicial complex, we demonstrate the algorithm for constructing boundary data and critical points using examples with two 4-simplices sharing an internal tetrahedron. By revisiting the ${\mathrm{\Delta }}_3$ triangulation with curved geometry, we demonstrate the numerical computation of the real critical point corresponding to the flat geometry and the deformation to the complex critical points. Additionally, the program evaluates the spin foam action at the critical points and compare to the Regge action.

We study the cosmology of the complete quadratic (in torsion and nonmetricity) metric-affine gravity. Namely, we add to the scalar-curvature gravitational Lagrangian, the 17 independent quadratic (parity-even and parity-odd) torsion and nonmetricity invariants. Sticking to a homogeneous and isotropic Friedmann-Robertson-Walker spacetime and assuming a perfect hyperfluid source, we explore the new effects that torsion and nonmetricity bring into play. It is shown that the inclusion of these invariants offers rich phenomenology. In particular, some well-known examples of exotic matter like cosmic strings, domain walls, stiff matter, etc., emerge quite naturally as manifestations of the fluid’s intrinsic structure (hypermomentum). By studying the extended Friedmann equations in the complete quadratic theory and isolating the various parts of the hypermomentum, we find a plethora of solutions with interesting features.

Quantum gravity has long remained elusive from an observational standpoint. Developing effective cosmological models motivated by the fundamental aspects of quantum gravity is crucial for bridging theory with observations. One key aspect is the granularity of spacetime, which suggests that free particles would deviate from classical geodesics by following a covariant Brownian motion. This notion is further supported by swerves models in causal set theory, a discrete approach to quantum gravity. At an effective level, such deviations are described by a stochastic correction to the geodesic equation. We show that the form of this correction is strictly restricted by covariance and the mass-shell condition. Under minimal coupling to curvature, the resulting covariant Brownian motion is unique. The process is equivalently described by a covariant diffusion equation for the distribution of massive particles in their relativistic phase space. When applied to dark matter particles, covariant Brownian motion results in spontaneous warming at late times, suppressing the matter power spectrum at small scales in a time-dependent manner. Using bounds on the diffusion rate from CMB and growth history measurements of $f{\sigma }_8$, we show that the model offers a resolution to the $S_8$ tension. Future studies on the model’s behavior at nonlinear cosmological scales will provide further constraints and, therefore, critical tests for the viability of stochastic dark matter.

We investigate the effect of a dark matter caustic passing through the Solar System. We find, confirming a previous result, that the Sun tracks the caustic surface for some time. We integrate numerically the equations of motion of the Sun and a comet for a large number of initial conditions and of caustic passage properties. We calculate the probability for the comet to escape the Solar System and the probability for it to fall within 50 A.U. of the Sun, given the initial semimajor axis and eccentricity of its orbit. We find that the average probability for a comet to fall within 50 A.U. of the Sun is of order $3\times {10}^{-4}$ and that comets which are initially at a distance larger than about ${10}^5\mathrm{A}.\mathrm{U}.$ have a probability of order one to be ejected from the Solar System.

We develop a machine learning method for mapping data originating from both Standard Model processes and various theories beyond the Standard Model into a unified representation (latent) space while conserving information about the relationship between the underlying theories. We apply our method to three examples of new physics at the LHC of increasing complexity, showing that models can be clustered according to their LHC phenomenology: different models are mapped to distinct regions in latent space, while indistinguishable models are mapped to the same region. This opens interesting new avenues on several fronts, such as model discrimination, selection of representative benchmark scenarios, and identifying gaps in the coverage of model space.

We aim at insights about how localization of the background field impacts nonlinear quantum vacuum signatures probed by photons in purely magnetic, electric and crossed fields. The starting point of our study are the one-loop results for the Heisenberg-Euler effective Lagrangian and the photon polarization tensor in quantum electrodynamics (QED) evaluated in a uniform constant electromagnetic field. As is well known and often employed, especially in the weak-field limit, within certain restrictions these results also allow for the reliable analysis of vacuum polarization effects in slowly varying background fields. Here, our main interest is in manifestly nonperturbative effects. To this end, we make use of the fact that for the particular case of background field inhomogeneities of Lorentzian shape with $0\le d\le 3$ inhomogeneous directions analytical insights are possible. We study the scaling of conventional nonlinear QED signatures, such as probe-photon polarization flip and probe-photon induced electron-positron pair production, with relevant parameters. Special attention is put on the $d$ dependence of the considered effects.

The supertranslation ambiguity of angular momentum is a long-standing problem in general relativity, which raises the puzzle of the angular momentum loss in the post-Minkowskian (PM) expansion. The angular momentum loss in gravitational scattering is of order $G^2$ in the linear response theory but of order $G^3$ in the amplitudes-based methods. In this paper, we propose a generic prescription to fix the supertranslation ambiguity in the PM expansion which will uniquely determine the angular momentum loss. The proposal is self-contained and involves only the null infinity data.

In the bottomonium sector, the hindered magnetic dipole transitions between P-wave states $h_b(2P)\to {\chi }_{bJ}(1P)\gamma$, $J=0$, 1, 2, are expected to be severely suppressed according to the relativized quark model, due to the spin flip of the $b$ quark. Nevertheless, a recent model following the coupled-channel approach predicts the corresponding branching fractions to be enhanced by orders of magnitude. In this Letter, we report the first search for such transitions. We find no significant signals and set upper limits at 90% confidence level on the corresponding branching fractions: $\mathcal{B}[h_b(2P)\to \gamma {\chi }_{b0}(1P)]<2.7\times {10}^{-1}$, $\mathcal{B}[h_b(2P)\to \gamma {\chi }_{b1}(1P)]<5.4\times {10}^{-3}$ and $\mathcal{B}[h_b(2P)\to \gamma {\chi }_{b2}(1P)]<1.3\times {10}^{-2}$. These values help to constrain the parameters of the coupled-channel models. The results are obtained using a $121.4{\mathrm{fb}}^{-1}$ data sample taken around $\sqrt{s}=10.860\mathrm{GeV}$ with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider.

We measure the Born cross section for the reaction $e^{+}{e}^{-}\to \eta h_c$ from $\sqrt{s}=4.129$ to 4.600 GeV using datasets collected by the BESIII detector running at the BEPCII collider. A resonant structure in the cross-section line shape near 4.200 GeV is observed with a statistical significance of $7\sigma$. The parameters of this resonance are measured to be $M=4188.8\pm 4.7\pm 8.0\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=49\pm 16\pm 19\mathrm{MeV}$, where the first uncertainties are statistical and the second systematic.

We consider spherically symmetric gravity coupled to a spherically symmetric scalar field with a specific coupling which depends on the areal radius. Appropriate to spherical collapse, we require the existence of an axis of symmetry and consequently a single asymptotic past and future (rather than a pair of “left” and “right” ones). The scalar field stress energy takes the form of null dust. Its classical collapse is described by the Vaidya solution. From a two dimensional “$(r,t)$” perspective, the scalar field is conformally coupled so that its quantum stress energy expectation value is well defined. Quantum backreaction is then incorporated through an explicit formulation of the 4D semiclassical Einstein equations. The semiclassical solution describes black hole formation together with its subsequent evaporation along a timelike dynamical horizon (i.e. a timelike outer marginally trapped “tube”). A balance law at future null infinity relates the rate of change of a backreaction-corrected Bondi mass to a manifestly positive flux. The detailed form of this balance law together with a proposal for the dynamics of the true degrees of freedom underlying the putative nonperturbative quantum gravity theory is supportive of the paradigm of singularity resolution and information recovery proposed by Ashtekar and Bojowald. In particular all the information including that in the collapsing matter is expected, in our proposed scenario, to emerge along a single “quantum extended” future null infinity. Our analysis is on the one hand supported and informed by earlier numerical work of Lowe [Phys. Rev. D 47, 2446 (1993)] and Parentani and Piran [Phys. Rev. Lett. 73, 2805 (1994)] and on the other, serves to clarify certain aspects of their work through our explicit requirement of the existence of an axis of symmetry.

In the framework of the AdS/CFT correspondence, we find a neutral complex scalar field dynamics in a $2+1$-dimensional black hole background which can provide a scheme for studying the pattern formation process in $1+1$-dimensional reaction-diffusion systems. The patterns include plane wave, defect turbulence, phase turbulence, spatiotemporal intermittency where defect chaos coexists with a stable plane wave, and coherent structures. A phase diagram is obtained by studying the linear instability of the plane wave solutions to determine the onset of the holographic version of the Benjamin-Feir-Newell instability. Near the critical temperature, the holographic model is dual to the one-dimensional complex Ginzburg-Landau equation (CGLE), which has been studied extensively in reaction-diffusion systems, while at low temperature the holographic theory is different from CGLE.

We construct a new type of holographic correspondence between nonrelativistic string theory in string Newton-Cartan ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ and Galilean electrodynamics supplemented with five uncharged massless free scalar fields living on the $3+1$ dimensional Penrose conformal boundary. In our derivation, we start with Maldacena’s setting of a stack of $N$ coincident D3-branes, and we show that the near-horizon/decoupling limit commutes with the nonrelativistic limit, giving a unique answer both from the gravity and gauge theory perspectives. As a first evidence, we systematically compute the Killing vectors on the string theory side, and find that they match the symmetries of the dual gauge theory.

We apply the Hamiltonian formalism to investigate the massless sector of scalar field theory coupled with Maxwell electrodynamics through the Pontryagin term. To this end, we generalize the Dirac procedure to include radially independent zero modes of the symplectic matrix associated with the asymptotic symmetries. Specifically, we analyze asymptotic symmetries at the null infinity of this theory, conserved charges, and their algebra. We find that the theory possesses asymptotic shift symmetries of the fields not present in the bulk manifold coming from the zero modes of the symplectic matrix of constraints. Consequently, we conclude that the real scalar field also contains asymptotic symmetries previously found in the literature by a different approach. We show that these symmetries can be seen as the electric-magnetic duality in electromagnetism with the topological Pontryagin term, and obtain a nontrivial central extension between the electric and magnetic conserved charges. Finally, we examine the full interacting theory and find that, due to the interaction, the symmetry generators are more difficult to identify among the constraints, such that we obtain them in the weak-coupling limit. We find that the asymptotic structure of the theory simplifies due to a fast fall-off of the scalar field, leading to decoupled scalar and Maxwell asymptotic sectors, and losing the electric-magnetic duality.

We propose a stochastic interpretation of spacetime noncommutativity starting from the path integral formulation of quantum mechanical commutation relations. We discuss how the (non)commutativity of spacetime is inherently related to the continuity or discontinuity of paths in the path integral formulation. Utilizing Wiener processes, we demonstrate that continuous paths lead to commutative spacetime, whereas discontinuous paths correspond to noncommutative spacetime structures. As an example we introduce discontinuous paths from which the $\kappa$-Minkowski spacetime commutators can be obtained. Moreover we focus on modifications of the Leibniz rule for differentials acting on discontinuous trajectories. We show how these can be related to the deformed action of translation generators focusing, as a working example, on the $\kappa$-Poincaré algebra. Our findings suggest that spacetime noncommutativity can be understood as a result of fundamental discreteness in temporal and/or spatial evolution.

We study the time evolution of a state of a relativistic quantum field theory restricted to a spatial subregion $\mathrm{\Omega }$. More precisely, we use the Feynman-Vernon influence functional formalism to describe the dynamics of the field theory in the interior of $\mathrm{\Omega }$ arising after integrating out the degrees of freedom in the exterior. We show how the influence of the environment gets encoded in a boundary term. Furthermore, we derive a stochastic equation of motion for the field expectation value in the interior. We find that the boundary conditions obtained in this way are energy nonconserving and nonlocal in space and time. Our results find applications in understanding the emergence of local thermalization in relativistic quantum field theories and the relationship between quantum field theory and relativistic fluid dynamics.

We analyze the excitations and deexcitations of an inertial Unruh-DeWitt detector in the ($1+1$)-dimensional expanding Milne cosmology with compact spatial sections, coupled to a real massless scalar field with either untwisted or twisted boundary conditions, prepared in the conformal vacuum. We find the detector’s response as a function of the energy gap, the Milne spatial circumference parameter, the interaction duration, the age of the Universe at the switch-on moment, the detector’s peculiar velocity at the switch-on moment, and, for the untwisted field, the state of the zero mode. Asymptotic analytic results are obtained at large energy gap and at large circumference parameter, in each case recovering the Minkowski vacuum response in the leading order, and in the double limit of small circumference parameter and late cosmological time, recovering the response in a static Minkowski cylinder. Numerical results are given in the interpolating regimes. The results confirm the detector’s sensitivity to both classical and quantum properties of its environment.