We compute the light axial-vector and tensor meson two-photon transition form factors in the soft-wall holographic model of quantum chromodynamics (QCD) in the flavor-symmetric case. They are used to evaluate the axial-vector and tensor meson contributions to the anomalous magnetic moment of the muon via the hadronic light-by-light scattering process. As expected, these contributions are smaller than the one from pseudoscalar mesons. The result for axial-vector mesons is higher than the value found in other approaches.

The impact of the nonlinear effects in the QCD on the observables is directly related to the magnitude of the saturation scale $Q_s$, which is predicted to increase with the energy, rapidity, and multiplicity. In this paper, we investigate the $D^0$ meson production in $pp$ collisions at forward rapidities and/or high multiplicities considering the color glass condensate (CGC) formalism and the solutions of the running coupling Balitsky-Kovchegov equation. The contributions of gluon- and charm-initiated processes are taken into account, and a comparison with the current LHCb data is performed. The impact of an intrinsic charm component in the proton’s wave function is also estimated. Predictions for the self-normalized yields of $D^0$ mesons as a function of the multiplicity of coproduced charged hadrons are presented, considering $pp$ collisions at $\sqrt{s}=13\mathrm{TeV}$ and different values of the meson rapidity. A comparison with the predictions for the kaon and isolated photon production is performed. Our results indicate that a future experimental analysis of the $D^0$ meson production at forward rapidities and high multiplicities can be useful to probe the CGC formalism and to disentangle the contribution of initial—and final—state effects.

Heavy-flavor hadron production, in particular bottom hadron production, is difficult to study in deep-inelastic scattering (DIS) experiments due to small production rates and branching fractions. To overcome these limitations, a method for identifying heavy-flavor DIS events based on event topology is proposed. Based on a heavy-flavor jet tagging strategy developed for the LHCb experiment, this algorithm uses displaced vertices to identify decays of heavy-flavor hadrons. The algorithm’s performance at the Electron-Ion Collider is demonstrated using simulation, and it is shown to provide discovery potential for nonperturbative intrinsic bottom quarks in the proton.

We determine the corrections to the Schwarzschild geometry arising from including the Goroff-Sagnotti counterterm in the gravitational dynamics. We find that static, asymptotically flat, and spherically symmetric geometries are completely characterized by their asymptotic mass and the coupling associated with the counterterm. The latter induces distinct corrections at sixth order of the parametrized post-Newtonian expansion. The resulting spacetime geometries still exhibit an event horizon. In the parameter space accessible to numerical integration, the horizon area is smaller than its Schwarzschild counterpart, leading to an increase in the Hawking temperature. Corrections to the shadow size can be determined analytically and are used to give a first bound on the new coupling. While it is difficult to access the geometry inside of the event horizon, our analysis also provides evidence that the counterterm could resolve the curvature singularity appearing in the Schwarzschild geometry.

The Johannsen-Psaltis black hole is a phenomenologically viable metric obtained by judiciously deforming the Kerr black hole such that the metric is asymptotically flat and causal and is consistent with the weak field, post-Newtonian tests of gravity; however, it has additional hairs besides its mass and angular momentum. As it deviates from the Kerr black hole in the strong coupling regime, it is a useful metric to test the Kerr hypothesis that states that all astrophysical black holes are of the Kerr type. Here we give a membrane description of this black hole that effectively amounts to replacing the observable part of the black hole with a fluid with thermal properties. A timelike membrane, a stretched horizon local in time is assumed to exist. This membrane is expected to approximate the null event horizon that is highly nonlocal in time. We derive the energy-momentum tensor of the fluid and all the transport coefficients using the action formulation to the membrane as advocated by Parikh and Wilczek. In the fluid description, one observes that the finiteness of the transport coefficients constrains the additional hairs of the Johannsen-Psaltis black hole. Analytically continuing the pressure of the fluid to all values of the radial coordinate $r$, one obtains interesting Van der Waals–type behavior of the pressure of the fluid which diverges at the radius of the outer ergosphere, lending support, from the membrane paradigm’s perspective to the claim that relativistic astrophysical jets are produced by the ergoregion of the black hole.

We performed a post-Newtonian analysis of the regularized four-dimensional Einstein-Gauss-Bonnet gravitational theory. The resulting metric differs from the classical parametrized post-Newtonian (PPN) formalism in that a new gravitational potential arises from the integration of the approximate field equations. We also investigated the conserved quantities and equations of motion for massive bodies and light rays to a certain degree. By computing the predicted periastron advance rate in a binary system, we obtained an observational constraint that is stronger than those of previous analyses. Although the usual 10 PPN parameters can still be derived within the PPN framework, an extra parameter is needed to account for the full post-Newtonian tests.

Weak magnetic fields must have existed in the early Universe, as they were sourced by the cross product of electron density and temperature gradients through the Biermann-battery mechanism. In this paper we calculate the magnetic fields generated at cosmic dawn by a variety of small-scale primordial perturbations, carefully computing the evolution of electron density and temperature fluctuations, and consistently accounting for relative velocities between baryons and dark matter. We first compute the magnetic field resulting from standard, nearly scale-invariant primordial adiabatic perturbations, making significant improvements to previous calculations. This “standard” primordial field has a root mean square (rms) of a few times ${10}^{-15}\mathrm{nG}$ at $20\lesssim z\lesssim 100$, with fluctuations on $\sim \mathrm{kpc}$ comoving scales, and could serve as the seed of present-day magnetic fields observed in galaxies and galaxy clusters. In addition, we consider early Universe magnetic fields as a possible probe of nonstandard initial conditions of the Universe on small scales $k\sim 1-{10}^3{\mathrm{Mpc}}^{-1}$. To this end, we compute the maximally allowed magnetic fields within current upper limits on small-scale adiabatic and isocurvature perturbations. Enhanced small-scale adiabatic fluctuations below current cosmic microwave background spectral-distortion constraints could produce magnetic fields as large as $\sim 5\times {10}^{-11}\mathrm{nG}$ at $z=20$. Uncorrelated small-scale isocurvature perturbations within current big bang nucleosynthesis bounds could potentially enhance the rms magnetic field to $\sim {10}^{-14}-{10}^{-10}\mathrm{nG}$ at $z=20$, depending on the specific isocurvature mode considered. While these very weak fields remain well below current observational capabilities, our work points out that magnetic fields could potentially provide an interesting window into the poorly constrained small-scale initial conditions of the Universe.

One of the most exciting targets of current and future gravitational-wave observations is the angular power spectrum of the astrophysical GW background. This cumulative signal encodes information about the large-scale structure of the Universe, as well as the formation and evolution of compact binaries throughout cosmic time. However, the finite rate of compact binary mergers gives rise to temporal shot noise, which introduces a significant bias in measurements of the angular power spectrum if not explicitly accounted for. Previous work showed that this bias can be removed by cross-correlating GW sky maps constructed from different observing times. However, this work considered an idealized measurement scenario, ignoring detector specifics and in particular noise contributions. Here we extend this temporal cross-correlation method to account for these difficulties, allowing us to implement the first unbiased anisotropic search pipeline for LIGO-Virgo-KAGRA data. In doing so, we show that the existing pipeline is biased even in the absence of shot noise, due to previously neglected subleading contributions to the noise covariance. We apply our pipeline to mock LIGO data, and find that our improved analysis will be crucial for stochastic searches from the current observing run (O4) onwards.

Reconstructing the galaxy peculiar velocity field from the distribution of large-scale structure plays an important role in cosmology. On one hand, it gives us an insight into structure formation and gravity; on the other, it allows us to selectively extract the kinetic Sunyaev-Zel’dovich (kSZ) effect from cosmic microwave background maps. In this work, we employ high-accuracy synthetic galaxy catalogs on the light cone to investigate how well we can recover the velocity field when utilizing the three-dimensional spatial distribution of the galaxies in a modern large-scale structure experiment such as the Dark Energy Spectroscopic Instrument (DESI) and the Rubin Observatory Legacy Survey of Space and Time. In particular, we adopt the standard technique used in baryon acoustic oscillation analysis for reconstructing the Zel’dovich displacements of galaxies through the continuity equation, which yields a first-order approximation to their large-scale velocities. We investigate variations in the number density, bias, mask, area, redshift noise, and survey depth, as well as modifications to the settings of the standard reconstruction algorithm. Since our main goal is to provide guidance for planned kSZ analysis between DESI and the Atacama Cosmology Telescope, we apply velocity reconstruction to a faithful representation of DESI spectroscopic and photometric targets. We report the cross-correlation coefficient between the reconstructed and the true velocities along the line of sight. For the DESI Y1 spectroscopic survey, we expect the correlation coefficient to be $r\approx 0.64$, while for a photometric survey with ${\sigma }_z/(1+z)=0.02$, as is approximately the case for the Legacy Survey used in the target selection of DESI galaxies, $r$ shrinks by half to $r\approx 0.31$. We hope the results in this paper can be used to inform future kSZ stacking studies and other velocity reconstruction analyses planned with the next generation of cosmology experiments.

Peculiar velocities of galaxies and halos can be reconstructed from their spatial distribution alone. This technique is analogous to the baryon acoustic oscillations reconstruction, using the continuity equation to connect density and velocity fields. The resulting reconstructed velocities can be used to measure imprints of galaxy velocities on the cosmic microwave background like the kinematic Sunyaev-Zel’dovich effect or the moving lens effect. As the precision of these measurements increases, characterizing the performance of the velocity reconstruction becomes crucial to allow unbiased and statistically optimal inference. In this paper, we quantify the relevant performance metrics: the variance of the reconstructed velocities and their correlation coefficient with the true velocities. We show that the relevant velocities to reconstruct for kSZ and moving lens are actually the halo—rather than galaxy—velocities. We quantify the impact of redshift-space distortions, photometric redshift errors, satellite galaxy fraction, incorrect cosmological parameter assumptions and smoothing scale on the reconstruction performance. We also investigate hybrid reconstruction methods, where velocities inferred from spectroscopic samples are evaluated at the positions of denser photometric samples. We find that using exclusively the photometric sample is better than performing a hybrid analysis. The $2\mathrm{Gpc}/h$ length simulations from abacussummit with realistic galaxy samples for DESI and Rubin LSST allow us to perform this analysis in a controlled setting. In the companion paper [B. Hadzhiyska, S. Ferraro, B. Ried Guachalla, and E. Schaan, companion paper, Phys. Rev. D 109, 103534 (2024).], we further include the effects of evolution along the light cone and give realistic performance estimates for DESI luminous red galaxies, emission line galaxies, and Rubin LSST-like samples.

It has been discussed whether viscous processes in neutron star matter during a binary inspiral can damp out the tidal energy induced by the companion and heat up the star. Earlier investigations concluded that this tidal heating is negligible for normal neutron star matter. In this work, we suggest a novel effect of tidal heating involving strange matter in the neutron star interior that can significantly heat up the star, and is potentially observable by current and future gravitational wave detectors. We propose that this could serve as a direct probe of strangeness in neutron stars.

In this paper, we explore the prospect for improving the measurement accuracy of masses and radii of neutron stars. We consider imminent and long-term upgrades of the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo, as well as next-generation observatories—the Cosmic Explorer and Einstein Telescope. We find that neutron star radius with single events will be constrained to within roughly 500 m with the current generation of detectors and their upgrades. This will improve to 200, 100 and 50 m with a network of observatories that contain one, two or three next-generation observatories, respectively. Combining events in bins of $0.05M_{\odot }$ we find that for stiffer (softer) equations-of-state like ALF2 (APR4), a network of three XG observatories will determine the radius to within 30 m (100 m) over the entire mass range of neutron stars from $1M_{\odot }$ to $2.0M_{\odot }$ ($2.2M_{\odot }$), allowed by the respective equations-of-state. Neutron star masses will be measured to within 0.5% with three XG observatories irrespective of the actual equation-of-state. Measurement accuracies will be a factor of 4 or 2 worse if the network contains only one or two XG observatories, respectively, and a factor of 10 worse in the case of networks consisting of Advanced LIGO, Virgo KAGRA and their upgrades. Tens to hundreds of high-fidelity events detected by future observatories will allow us to accurately measure the mass-radius curve and hence determine the dense matter equation-of-state to exquisite precision.

Electrostatic force actuation is a key component of the system of geodesic reference test masses (TM) for the LISA orbiting gravitational wave observatory and in particular for performance at low frequencies, below 1 mHz, where the observatory sensitivity is limited by stray force noise. The system needs to apply forces of order ${10}^{-9}\mathrm{N}$ while limiting fluctuations in the measurement band to levels approaching ${10}^{-15}\mathrm{N}/{\mathrm{Hz}}^{1/2}$. We present here the LISA actuation system design, based on audio-frequency voltage carrier signals, and results of its in-flight performance test with the LISA Pathfinder test mission. In LISA, TM force actuation is used to align the otherwise free-falling TM to the spacecraft-mounted optical metrology system, without any forcing along the critical gravitational wave-sensitive interferometry axes. In LISA Pathfinder, on the other hand, the actuation was used also to stabilize the TM along the critical $x$ axis joining the two TM, with the commanded actuation force entering directly into the mission’s main differential acceleration science observable. The mission allowed demonstration of the full compatibility of the electrostatic actuation system with the LISA observatory requirements, including dedicated measurement campaigns to amplify, isolate, and quantify the two main force noise contributions from the actuation system, from actuator gain noise and from low frequency “in band” voltage fluctuations. These campaigns have shown actuation force noise to be a relevant, but not dominant, noise source in LISA Pathfinder and have allowed performance projections for the conditions expected in the LISA mission.

At leading order in the QCD coupling constant, we compute the energy loss per traveling distance of a heavy quark $dE/dz$ from elastic scattering off thermal quarks and gluons at a temperature $T$, including the thermal perturbative description of soft scatterings ($-t<-t^{*}$) and a perturbative QCD-based calculation for hard collisions ($-t>-t^{*}$). Within this soft-hard factorization model, we find that the full results of $dE/dz$ behaves a mild sensitivity to the intermediate cutoff $t^{*}$, supporting the validity of the soft-hard approach within the temperature region of interest. We rederive the analytic formula for $dE/dz$ in the high-energy approximation, $E_1\gg m_1^2/T$, where $E_1$ is the injected heavy quark energy and $m_1$ is its mass. It is realized that the soft logarithmic contribution, $dE/dz\propto \ln (-t^{*}/m_D^2)$, arises from the $t$-channel scattering off thermal partons, while the hard logarithmic term, $dE/dz\propto \ln [E_{1}T/(-t^{*})]$, stems from the $t$-channel scattering off thermal partons, and the one $dE/dz\propto \ln (E_{1}T/m_1^2)$ comes from the $s$- and $u$-channel scattering off gluons. The sum of these contributions cancels the $t^{*}$-dependence as observed in the full result. The mass hierarchy is observed $dE/dz(\text{charm})>dE/dz(\text{bottom})$. Our full results are crucial for a better description of heavy quark transport in QCD medium, in particular at low and moderate energy. We also calculate the energy loss by imposing the Einstein’s relationship. The related results appear to be systematically larger than that without imposing the Einstein’s relationship.

The measurements of off-shell Higgs boson contributions in massive gauge boson pair production are known to probe its electroweak interactions across different energy scales. Often employed as an estimator of the Higgs boson width in restricted theories of beyond the Standard Model physics, we revisit this measurement and readvertise its potential to constrain aspects of Higgs boson nonlinearity. We show that this so-called off-shell measurement complements related analyses of multi-Higgs final states.

We study the effects of exceptionally light QCD axions on the stellar configuration of white dwarfs. At finite baryon density, the nonderivative coupling of the axion to nucleons displaces the axion from its in-vacuum minimum, which implies a reduction of the nucleon mass. This dramatically alters the composition of stellar remnants. In particular, the modifications of the mass-radius relationship of white dwarfs allow us to probe large regions of unexplored parameter space without requiring that axions are dark matter.

This paper is devoted to the study of quantum chromodynamics (QCD) equation of state in external magnetic field and nonzero baryon density. Our study is carried out by means of lattice simulation with $2+1$ dynamical staggered quarks at the physical masses. The simulation is conducted at imaginary baryon chemical potential what allowed us to overcome the sign problem. We expand the pressure in the baryon imaginary chemical potential and study three leading nonzero coefficients in this expansion. These coefficients were calculated for the following values of magnetic field: $eB=0.3$, 0.6, $1.2{\mathrm{GeV}}^2$ with the lattice sizes $8\times 32^3$, $10\times 40^3$, $12\times 48^3$. Using these data we take continuum limit for the coefficients. Our results indicate considerable enhancement of the expansion coefficients by the magnetic field.

There is a long-standing discrepancy between different measurements of the electric and magnetic radii of the proton. Lattice QCD calculations are a well-suited tool for theoretical investigations of the structure of the nucleon from first principles. However, all previous lattice studies of the proton’s electromagnetic radii have either neglected quark-disconnected contributions or were not extrapolated to the continuum and infinite-volume limit. Here, we present results for the electromagnetic form factors of the proton and neutron computed on the ($2+1$)-flavor coordinated lattice simulations (CLS) ensembles including both quark-connected and -disconnected contributions. From simultaneous fits to the $Q^2$-, pion-mass, lattice-spacing, and finite-volume dependence of the form factors, we determine the electric and magnetic radii and the magnetic moments of the proton and neutron. For the proton, we obtain as our final values $⟨r_E^2{⟩}^p=(0.672\pm 0.014(\mathrm{stat})\pm 0.018(\mathrm{syst})){\mathrm{fm}}^2$, $⟨r_M^2{⟩}^p=(0.658\pm 0.012(\mathrm{stat})\pm 0.008(\mathrm{syst})){\mathrm{fm}}^2$, and ${\mu }_M^p=(2.739\pm 0.063(\mathrm{stat})\pm 0.018(\mathrm{syst})$. The magnetic moment is in good agreement with the experimental value, as is the one of the neutron. On the one hand, our result for the electric (charge) radius of the proton clearly points towards a small value, as favored by muonic hydrogen spectroscopy and the recent $ep$-scattering experiment by PRad. Our estimate for the magnetic radius, on the other hand, is well compatible with that inferred from the A1 $ep$-scattering experiment.

We investigate the light quarkonium hybrid mesons of various spin parities in QCD. Considering different interpolating currents made of the valence light quarks and single gluon, we calculate the mass and current coupling of the strange and nonstrange members of light hybrid mesons by including into computations the nonperturbative quark and gluon condensates up to ten dimensions in order to increase the accuracy of the results. The obtained results may be useful for future experimental searches of these hypothetical states. They can also be used in the calculations of different parameters related to the decays/interactions of light hybrid mesons to/with other states.

We analyze the confinement/deconfinement transition of pure Yang-Mills theories within the framework of the center-symmetric Landau gauge supplemented by a Curci-Ferrari mass term that models the effect of the associated Gribov copies in the infrared. In addition to providing details for earlier one-loop calculations in that framework, we explore how the results depend on the renormalization scale and/or on the renormalization scheme. We find that the predicted values for the transition temperatures of SU(2) and SU(3) Yang-Mills theories are similar in both schemes and are little sensitive to the renormalization scale $\mu$ over a wide range of values including the standard range $\mu \in [\pi T,4\pi T]$. These values are also close both to those obtained from a minimal sensitivity principle and to those of lattice simulations, especially in the SU(3) case. These results further confirm the good behavior of perturbative calculations within the Curci-Ferrari model and support the adequacy of the latter as an effective description of Yang-Mills theories in the infrared. We perform a similar analysis for the spinodal temperatures in the SU(3) case and for the Polyakov loop, the order parameter associated with the breaking of center symmetry.