The exact solution to the Dirac equation corresponding to a bound state in the spherical Rindler metric is derived and its relation to the near-horizon Schwarzschild metric is investigated. It is shown how to represent these solutions with a specially chirped free-electron wave packet. The spherical Rindler frame stands out as being invariant under Lorentz transformations, in contrast with the $1+1\mathrm{D}$ Rindler coordinates, and has been used in the description of the so-called expanding bubble spacetime. With heuristic modification of the wave function of the chirped free-electron wave packet quantitative predictions for the quantum properties of the electron crossing the black hole horizon are obtained.

It has only recently become possible to simulate the full nonlinear dynamics of binary black holes in scalar-Gauss-Bonnet theories of gravity. The simulations remain technically challenging and evolutions of unequal mass binaries in particular have been difficult to follow through the merger. Even when the merger is successful, accurately quantifying the physical dephasing, as opposed to contributions from transients in the initial data and gauge adjustments, remains difficult. We show the first full simulations of $2:1$ and $3:1$ binaries through merger, and we discuss how specific choices in the setup affect the dephasing observed and our ability to obtain reliable results. In cases with weaker couplings, we match the expected PN value for the dephasing, whereas for larger couplings, eccentricity introduced by the initial data transients can lead to artificial deviations. Our work highlights the need for improvements in the initial data methods used, to ensure reliable waveforms are obtained for data analysis in beyond-GR models.

We recently presented an efficient and accurate waveform model for the (2, 0) spherical harmonic mode including both the displacement memory contribution and the ringdown oscillations for aligned-spin binary black holes in quasicircular orbits. The model we developed is constructed in a time domain and implemented within the computationally efficient imrphenomthm waveform model. In this article, we employ it to perform in-depth parameter estimation studies for future ground-based detectors, specifically considering LIGO ${\mathrm{A}}^{\#}$, Cosmic Explorer, and the Einstein Telescope, combining them in different detector networks. While previous studies have reviewed the impact of the memory contribution in parameter estimation, we assess the effect of incorporating the complete mode in the analysis on the posterior estimation of source parameters, performing zero-noise injections of high signal-to-noise ratio signals. We investigate the impact of this mode on the distance-inclination degeneracy and compare its impact in edge-on and face-on configurations. We find that including this mode helps mitigate biases in the estimation of individual spin components, which may otherwise arise when the mode is neglected.

Hierarchical three-body systems offer a compelling framework to explore the subtle interplay between Newtonian and relativistic gravitational effects in astrophysical environments. In this work, we investigate post-Newtonian corrections to the periastron shift within such systems, focusing on the impact of orbital eccentricity. Modeling the secondary body’s influence as a quadrupolar perturbation, we compare Newtonian, Schwarzschild, and post-Newtonian quadrupolar contributions to orbital precession. Our analysis demonstrates that Newtonian quadrupolar effects could be observable, for a long monitoring time, in the orbit of the S87 star around Sagittarius A* if an intermediate-mass black hole is present, under the assumptions of our model. Additionally, post-Newtonian quadrupolar corrections may influence the dynamics of small Solar System bodies in the presence of massive companions. Although the predicted effects are minute and require long monitoring periods to be measurable, our analysis clarifies how relativistic corrections enter the dynamics of the third body and outlines the conditions under which future observations could reveal them.

In studies of binary black hole (BBH) mergers in eccentric orbits, the mean anomaly, traditionally regarded as less significant than eccentricity, has been thought to encode only the orbital phase, leading to the assumption that it exerts minimal influence on the dynamics of eccentric mergers. In a previous investigation, we identified consistent oscillations in dynamical quantities peak luminosity $L_{\mathrm{peak}}$, remnant mass $M_{\mathrm{rem}}$, spin ${\alpha }_{\mathrm{rem}}$, and recoil velocity $V_{\mathrm{rem}}$—in relation to the initial eccentricity $e_0$. These oscillations are associated with integer orbital cycles within a phenomenological framework. In this paper, we aim to explore the underlying physical nature of these oscillations through gravitational waveforms. Our examination of remnant mass and spin reveals that, while the initial Arnowitt, Deser, Misner (ADM) mass $M_{\mathrm{ADM}}$ and orbital angular momentum $L_0$ exhibit gradual variations with $e_0$, the radiated energy $E_{\mathrm{rad}}$ and angular momentum $L_{\mathrm{rad}}$ display oscillatory patterns akin to those observed in $M_{\mathrm{rem}}$ and ${\alpha }_{\mathrm{rem}}$. By decomposing the waveforms into three distinct phases—inspiral, late inspiral to merger, and ringdown—we demonstrate that these oscillations persist across all phases, suggesting a common origin. Through a comparative analysis of $E_{\mathrm{rad}}$ and $L_{\mathrm{rad}}$ derived from numerical relativity, post-Newtonian (PN) waveforms, and orbital-averaged PN fluxes during the inspiral phase, we identify the initial mean anomaly $l_0$ as the source of the observed oscillations. This effect, which is averaged out in orbital-averaged flux calculations, significantly influences $M_{\mathrm{rem}}$, ${\alpha }_{\mathrm{rem}}$, and $V_{\mathrm{rem}}$, with its impact increasing as $e_0$ rises. Further, we find that by continuously varying $l_0$ within the parameter space $[0,2\pi ]$, we can construct an envelope that encompasses the original oscillations of these radiative quantities, indicating that the oscillations originate from the specific initial condition $l_0$. We synthesize and analyze the relationships between dynamical quantities and mass ratio for orbital BBH mergers, integrating data from both eccentric and circular orbits. Our findings emphasize that eccentricity and mean anomalies induce oscillations and ranges in dynamical quantities relative to circular orbits. We interpolate the maximum and minimum values of the dynamical quantities to delineate the vicinities of these quantities for eccentric orbits compared to circular orbits. Notably, the vicinities intensify with higher mass ratios ($q=m_1/m_2\le 1$, $m_1$, and $m_2$ are component masses of the BBH) for $M_{\mathrm{rem}}$, ${\alpha }_{\mathrm{rem}}$, and $L_{\mathrm{peak}}$, reaching maximum effects for $q\approx 1/3$ on $V_{\mathrm{rem}}$. By quantifying the residual deviations relative to circular orbits, we highlight significant differences between the vicinities and the polynomial modeling of circular orbits, underscoring the importance of this effect, which cannot be overlooked and has a broad impact.

Cosmic strings are predicted in many extensions of the Standard Model and constitute a plausible source of gravitational waves (GWs) from the early Universe. In a previous article [K. Schmitz and T. Schröder, Phys. Rev. D 110, 063549 (2024)], we pointed out that the GW spectrum from a population of string loops in the scaling regime can exhibit a sharp cutoff frequency associated with the fundamental oscillation mode of string loops. In this paper, we study the effect of particle decay due to kink-kink collisions and cusps on the GW spectrum in the nonscaling scenario introduced in P. Auclair et al., [Phys. Rev. D 101, 083511 (2020)]. We find analytical conditions for the existence of a cutoff frequency in the fundamental spectrum and provide expressions for this frequency. In large regions of parameter space, our results in the nonscaling model turn out to be identical to those in the scaling model. Finally, we demonstrate how the spectrum changes when transitioning from the regime with a cutoff frequency to the regime without a cutoff frequency. Our analytical estimates are validated at qualitatively different benchmark points by comparing them with numerical spectra.

Supernova explosions are expected as one of the promising candidates for gravitational wave sources. In this study, we examine the supernova gravitational waves, focusing on the multidimensional treatment of gravity in the simulation. For this purpose, we newly performed two-dimensional relativistic simulations with a nonmonopole (two-dimensional) potential and compared the resultant gravitational wave signals in the simulations with the frequencies of the proto-neutron stars with and without the Cowling approximation. Then, we find that the proto-neutron star frequencies with the Cowling approximation overestimates the gravitational wave frequencies. On the other hand, the frequencies of the proto-neutron star oscillations with metric perturbations agree well with the gravitational wave signals in the simulations. Employing the new data, we derive a new fitting formula for the supernova gravitational wave frequencies with the two-dimensional gravitational potential, independently of the progenitor mass. Combining this new formula with the previous one derived from the Cowling approximation, we also derive the formula to predict the gravitational wave frequencies with a two-dimensional potential, using those with a monopole potential.

Motivated by the recent observations of $T_{cs0}^{*}(2870{)}^0$, $T_{c\overline{s}0}^{*}(2900{)}^0$, and $T_{c\overline{s}0}^{*}(2900{)}^{++}$ open-charmed tetraquark states by LHCb, we study the decays of heavy mesons to these open-charmed tetraquark states ($T$) using a topological amplitude approach. We first obtain the $T\to DP$ and $DS$ strong decay amplitudes by decomposing them into several topological amplitudes, where $P$ is a light pseudoscalar particle and $S$ is a low-lying scalar particle. Subsequently, weak decay amplitudes of $\overline{B}\to D\overline{T}$, $\overline{D}T$, $\overline{B}\to TP$, and $TS$ decays are decomposed topologically. In addition, $B_c^{-}\to T\overline{T}$ decays are also discussed. Using these results, modes with an unambiguous exotic interpretation in flavor are highlighted.

We calculate the threshold $T$ matrices of the meson and baryon processes that have no annihilation diagrams: ${\pi }^{+}{\mathrm{\Sigma }}^{+}$, ${\pi }^{+}{\mathrm{\Xi }}^0$, $K^{+}p$, $K^{+}n$, and ${\overline{K}}^0{\mathrm{\Xi }}^0$ to the fourth order in heavy baryon chiral perturbation theory. By performing least-squares and Bayesian fits to the nonphysical lattice QCD data, we determine the low-energy constants through both perturbative and nonperturbative iterative methods. By using these low-energy constants, we obtain the physical scattering lengths in these fits. The convergence behavior is not good across all channels in the perturbative method. The scattering lengths for the five channels, obtained by taking the median values from four different fitting approaches, are $a_{{\pi }^{+}{\mathrm{\Sigma }}^{+}}=-0.16\pm 0.07\mathrm{fm}$, $a_{{\pi }^{+}{\mathrm{\Xi }}^0}=-0.04\pm 0.04\mathrm{fm}$, $a_{K^{+}p}=-0.41\pm 0.11\mathrm{fm}$, $a_{K^{+}n}=-0.19\pm 0.10\mathrm{fm}$, and $a_{{\overline{K}}^0{\mathrm{\Xi }}^0}=-0.30\pm 0.07\mathrm{fm}$, where the uncertainties are conservatively estimated by taking the maximum deviation between the median and extreme values of the statistical errors.

We focus on a novel baryon number ($\mathcal{B}$)-violating process within neutron stars, where two neutrons convert into two dark photons ($nn\to VV$) via new Higgs-like scalar bosons. This process is believed to be greatly suppressed at low energies but could be highly amplified in a dense neutron environment like neutron stars. The $nn\to VV$ process could give rise to nontrivial effects that are distinct from similar processes in previous studies and could alter the properties of neutron stars, such as orbital periods, collapse thresholds, stability conditions, cooling rates, gravitational-wave emissions, etc. The emitted dark photons may serve as dark-matter candidates and exhibit special redshifted energy spectra mainly linked to the compactness of the neutron star. We point out that the dark photons emitted from neutron stars may yield detectable signals in future experiments. We also show that the precision pulsar-timing data provide a powerful tool to constrain the parameter space of new-physics models. The study of the $nn\to VV$ process, which combines astronomical observations and particle physics models, may open new windows to the detection of the $\mathcal{B}$-violating effects and provide new insights on the study of dark matter.

The spin polarization for a baryon in a hydrodynamic medium has been extensively studied in the weakly coupled regime using quantum kinetic theory. As a first study of this problem in the strongly coupled regime, we investigate holographically the spectral function of a probe baryon in the fluid-gravity background. This is done by carefully performing gradient expansion of the Dirac equation in the fluid-gravity background. Different contributions in the expansion are understood in terms of density matrices of the probe baryon and the medium. The resulting spectral functions indicate that the holographic baryon is polarized as responses to fluid acceleration, shear stress, and vorticity. The structures of the responses are similar to those found in weakly coupled studies.

Nuclear modifications to collinear parton distribution functions are conventionally quantified by the ratios $r_i^{\mathrm{A}}(x,Q^2)=f_i^{\mathrm{A},\mathrm{proton}}(x,Q^2)/f_i^{\text{proton}}(x,Q^2)$. For a given nucleus $A$, these ratios generally depend on the parton momentum fraction $x$, the probing scale $Q^2$, and the parton species $i$. Determining these dependencies relies on a global analysis of diverse experimental data. However, in realistic observables, these dependencies are intricately intertwined, making their extraction challenging. In this paper, we propose a novel approach to effectively image the nuclear modification factors $r_i^{\mathrm{A}}(x,Q^2)$ at the observable level in proton-nucleus collisions at the Large Hadron Collider. Specifically, through a combined study of $Z$-boson production, $Z+\text{jet}$ production, and $Z+c$-jet production, we separately enhance signals arising from light-quark, gluon, and heavy-flavor (charm) distributions in nuclei. This enables us to effectively image the $r_i^{\mathrm{A}}(x,Q^2)$ for specific parton species. The feasibility of this method is validated through perturbative calculations at next-to-leading order in the strong coupling constant, employing three sets of nuclear PDF parametrizations: EPPS21, nCTEQ15, and TUJU19. Future measurements of these observables are expected to provide better-motivated parametrization forms of nuclear PDFs and yield new insights into the detailed partonic structures of nuclei.

We present a comprehensive study of triply heavy baryons (${\mathrm{\Omega }}_{ccc}$, ${\mathrm{\Omega }}_{bbb}$, ${\mathrm{\Omega }}_{bcc}$, and ${\mathrm{\Omega }}_{bbc}$) within the nonrelativistic quark model, employing the Gaussian expansion method to calculate mass spectra up to $D$-wave states. Our analysis represents the most complete treatment to date for this model, incorporating full angular momentum mixing effects. While our predictions for low-lying states agree well with lattice quantum chromodynamics (QCD) results, we find systematically lower masses for excited states compared to lattice calculations. Using the obtained wave functions, we estimate radiative decay widths up to $1D$ states, revealing significant differences from previous theoretical work. Additionally, we identify and resolve several misconceptions in prior treatments of triply heavy baryon spectroscopy, particularly symmetry constraint and wave function construction in three-quark systems. These results provide crucial information for future experimental searches and theoretical investigations of triply heavy baryon systems.

We present Fanto10, a Hessian ensemble of next-to-leading-order error parton distribution functions (PDFs) in a charged pion, constructed to enable precision comparisons with upcoming experimental data and ab initio QCD predictions. Fanto10 estimates several experimental, theoretical, and methodological uncertainties on pion PDFs. It follows a statistical procedure, grounded in de Finetti’s theorem, to systematically determine the component of the epistemic uncertainty associated with the choice of PDF functional forms. This uncertainty is estimated by fitting the data with multiple functional forms generated in a versatile format based on polynomial universal approximators (Bézier curves). The most distinct fits are converted into a joint Monte Carlo replica ensemble and then combined into one Hessian ensemble through a major update of the metapdf methodology, expanded in this article to combine PDFs for arbitrary hadrons and partonic flavor representations. This study also goes beyond the previous pion fits by estimating, for the first time, the uncertainty from nCTEQ15 nuclear PDFs for the tungsten target in the E615 pion-nucleus Drell-Yan data—a third-party input in our analysis, also included in the expanded metapdf combination. The upgraded metapdf framework, thus, altogether provides a principled algorithm to propagate parametrization dependence and other types of the epistemic uncertainty into conveniently represented PDFs. Notably, Fanto10 modifies the key physics conclusions from the earlier, more constrained analyses of the pion’s gluon and sea-quark content. It facilitates studies of PDF-induced correlations and comparisons to lattice QCD. We summarize the methodology, structure of the Fanto10 PDFs, and experimental implications.

We present the first formulation of a homotopy algebra adapted to a $1/r$ expansion near future null infinity (${\mathcal{I}}^{+}$). Focusing on self-dual Yang-Mills theory in Bondi coordinates, we demonstrate that imposing the homotopy algebra relations naturally yields the physically consistent fall-off behavior of the fields near ${\mathcal{I}}^{+}$. Furthermore, we employ this framework to systematically construct kinematic algebras, uncovering novel infinite families of such algebras that satisfy the Jacobi identity on slices near ${\mathcal{I}}^{+}$.

We demonstrate that the isentropic absorption of a classical charged test particle is classically forbidden for all ($3+1$)-dimensional stationary, nonextremal, axisymmetric black holes in any diffeomorphism invariant theory of gravity. This result is derived purely from the near-horizon geometry and thermodynamic properties of the black hole spacetime, independent of the specific gravitational theory. We further consider the Kerr-Newman black hole in general relativity and analyse, using the quantum tunneling approach, the conditions under which isentropic absorption may be allowed. Broader implications for the second law and extremality bounds are discussed.

Gravitational waves from binary neutron star mergers provide insights into dense matter physics and strong-field gravity, but waveform modeling remains computationally challenging. We develop a deep generative model for gravitational waveforms from binary neutron star mergers, covering the late inspiral, merger, and ringdown, incorporating precession and tidal effects. Using the conditional autoencoder, our model efficiently generates waveforms with high precision across a broad parameter space, including component masses $(m_1,m_2)$, spin components $(S_{1x},S_{1y},S_{1z},S_{2x},S_{2y},S_{2z})$, and tidal deformability $({\mathrm{\Lambda }}_1,{\mathrm{\Lambda }}_2)$. Trained on $1\times {10}^6$ waveforms from the IMRPhenomXP_NRTidalv2 waveform model, our model achieves a mean mismatch of $2.13\times {10}^{-3}$. The model accelerates waveform generation. For a single sample, it requires 0.12 s (s), compared to 0.66 s for IMRPhenomXP_NRTidalv2 making it approximately 5 times faster. When generating 1000 waveforms, the network completes the task in 0.75 s, while IMRPhenomXP_NRTidalv2 requires 7.12 s, making it approximately 10 times faster. This speed advantage enables rapid parameter estimation and real-time gravitational wave searches. With higher precision, it will support low-latency detection and broader applications in multimessenger astrophysics.

Eccentric binaries are key targets for current and future gravitational wave (GW) detectors, offering unique insights into the formation and environments of compact binaries. However, accurately and efficiently modeling eccentric waveforms remains challenging, in part due to their complex harmonic structure. In this work, we develop a post-Newtonian (PN) framework to compute the Fourier amplitudes of GWs from the inspiral of eccentric binaries, deriving simple expressions at 1PN order for all relevant $(l,m)$ multipoles, valid for arbitrary eccentricities. We then characterize the GW emission by analyzing the contribution of each $(l,m)$ mode to the strain, its mean frequency, frequency spread, and asymptotic behavior at high frequencies. Additionally, we introduce a method to determine the minimal set of Fourier modes needed to reconstruct the waveform to a given accuracy. Finally, we discuss how our framework can be extended to higher PN orders, obtaining closed-form expressions for the leading-order tail and spin contributions and outlining the steps required to include higher-order corrections. Our results provide both a deeper theoretical understanding of eccentric GW emission and practical tools for developing more accurate and efficient waveform models.