The local Universe is highly inhomogeneous and anisotropic. We live in a relatively sparse region of the Laniakea supercluster at the edge of a large 80 Mpc-wide void. We study the effect of these inhomogeneities on the measured gravitational wave event rates. In particular, we estimate how the measured merger rate of compact binaries is biased by the local matter distribution. The effect of the inhomogeneities on the merger rate is suppressed by the low angular resolution of gravitational wave detectors coupled with their smoothly decreasing population-averaged sensitivity with distance. We estimate the effect on the compact binary coalescence event rate to be at most 6% depending on the chirp mass of the target binary system and the sensitivity and orientation of the detectors.

The composition of the core of neutron stars (NSs) is still under debate. One possibility is that because of the high densities reached in their cores, matter could be deconfined into quark matter. In this work, we investigate the possible existence of hybrid stars, using microscopic models to describe the different phases of matter. Within the adopted microscopic models we aim at calculating both the properties of NSs and the properties of matter. In particular, we want to probe the influence of perturbative quantum chromodynamics (pQCD) calculations and analyze the properties that identify a transition to deconfined matter. A Bayesian approach using a Markov-Chain Monte Carlo sampling process is applied to generate eight sets of equations of state. A Maxwell construction is adopted to describe the deconfinement transition. For the hadronic phase, we consider a stiff and a soft equations of state (EOS) obtained from the relativistic mean field model with nonlinear meson terms. For the quark phase, we use two different models: the Nambu-Jona-Lasinio model with multiquark interactions and the mean field theory of QCD, a model similar to the MIT bag model with a vector term. Bayesian inference was applied to determine the model parameters that satisfy the x-ray observations from NICER and have phase transition at densities between 0.15 and $0.40{\mathrm{fm}}^{-3}$. We have also applied restrictions from the pQCD calculations to half of the sets. Hybrid stars are compatible with current observational data. The restrictions of pQCD reduce the value of the maximum mass. However, even when applying this restriction, the models were able to reach values of $M_{\max }=2.1–2.3M_{\odot }$. The conformal limit was still not attained at the center of the most massive stars. The vector interactions are essential to describe hybrid stars with a mass above $2M_{\odot }$. The multiquark interactions introduced may affect the limits of some quantities considered as indicators of the presence of a deconfined phase. It is possible to find a set of EOS, that predict that inside NSs the renormalized matter trace anomaly is always positive.

An accreting neutron star is potentially the gravitational wave source. In this study, we examine the gravitational wave frequencies from such an object in the steady state, adopting the Cowling approximation. We can derive the empirical relations independently of the mass accretion rate for the frequencies of the fundamental and first pressure modes multiplied by the stellar mass as a function of the stellar compactness, together with those for the first and second gravity mode frequencies. So, once one simultaneously observes the fundamental (or first pressure) and gravity mode frequencies, one could constrain the neutron star mass and radius. In addition, we find that the luminosity can be well characterized by the mass accretion rate independently of the stellar mass and equation of state, if the direct Urca does not work inside the star. Since the luminosity from the neutron star with the direct Urca can deviate from this characterization, one could identify whether the direct Urca process works or not inside the star by observing the luminosity. Both information obtained from the gravitational waves and luminosity help us to understand the equation of state for neutron star matter.

We calculate the extent to which collisionless dark matter impacts the stability of supermassive stars $(M\gtrsim {10}^4{M}_{\odot })$. We find that, depending on the star’s mass, a dark matter content in excess of $\sim 1\%$ by mass throughout the entire star can raise the critical central density for the onset of general relativistic instability, in some cases by orders of magnitude. We consider implications of this effect for the onset of nuclear burning and significant neutrino energy losses.

We put forward a novel method for generating ultrarelativistic vortex positrons and electrons with intrinsic orbital angular momenta (OAM) through nonlinear Breit-Wheeler (NBW) scattering of vortex $\gamma$ photons. A complete angular momentum-resolved scattering theory has been formulated, introducing angular momenta of laser photons and vortex particles into the conventional NBW scattering framework. We find that vortex positron (electron) can be produced when the outgoing electron (positron) is generated along the collision axis. By unveiling the angular momentum transfer mechanism, we clarify that the OAM of the $\gamma$ photon and the large angular momenta due to multiple laser photons are entirely transferred to the generated vortex leptons. Furthermore, the cone opening angle and superposition state of the vortex $\gamma$ photon can be determined via the angular distribution of created pairs in NBW processes.

This paper presents a novel approach for directly generating full events at detector-level from parton-level information, leveraging cutting-edge machine learning techniques. To address the challenge of multiplicity variations between parton and reconstructed object spaces, we employ transformers, score-based models and normalizing flows. Our method tackles the inherent complexities of the stochastic transition between these two spaces and achieves remarkably accurate results. The combination of innovative techniques and the achieved accuracy demonstrates the potential of our approach in advancing the field and opens avenues for further exploration. This research contributes to the ongoing efforts in high-energy physics and generative modeling, providing a promising direction for enhanced precision in fast detector simulation.

We estimate the nuclear saturation density and the binding energy in a nuclear liquid from precision data on the coupling of the four-quark scattering vertex in the vector channel, computed within functional QCD. We show that this coupling is directly related to the density-density potential and the latter is used for the estimates. In a first qualitative computation we find a saturation density of $0.2{\mathrm{fm}}^{-3}$ and an upper bound for the binding energy of 21.5 MeV, in agreement with the empirical values of $0.16{\mathrm{fm}}^{-3}$ and 16 MeV, respectively. We also use the scattering vertex for constructing an emergent low-energy effective theory for the liquid gas transition from QCD correlation function, whose coupling parameters can be determined within QCD. As a first consistency check of this construction we estimate the in-medium reduction of the nucleon pole mass.

We demonstrate that it is not necessary to substantially break the mass degeneracy between the Standard Model Higgs boson doublet and the corresponding scalar leptoquark, where these two fields comprise a single five-dimensional $SU(5)$ representation. More precisely, we show that the experimental data on partial proton decay lifetimes cannot place any meaningful bound on the mass of the scalar leptoquark, also known as the color triplet, if one includes effects of higher-dimensional operators. We use the Georgi-Glashow model for our demonstration and point out that the complete suppression of proton decay via the scalar leptoquark mediation is not in conflict with the partial suppression of the gauge mediated two-body proton decay signatures. Finally, we derive a proper limit on the cutoff scale of the aforementioned higher-dimensional operators and outline how this scenario could be tested.

Current discrepancy between the measurement and the prediction of the muon anomalous magnetic moment can be resolved in the presence of a long-range force created by ordinary atoms acting on the muon spin via axial-vector and/or pseudoscalar coupling, and requiring a tiny $\mathcal{O}({10}^{-13}\mathrm{eV})$ spin energy splitting between muon state polarized in the vertical direction. We suggest that an extension of the muon spin resonance ($\mathrm{\mu }\mathrm{SR}$) experiments can provide a definitive test of this class of models. We also derive indirect constraints on the strength of the muon spin force by considering the muon-loop-induced interactions between nuclear spin and external directions. The limits on the muon spin force extracted from the comparison of ${}^{199}\mathrm{Hg}/{}^{201}\mathrm{Hg}$ and ${}^{129}\mathrm{Xe}/{}^{131}\mathrm{Xe}$ spin precession are strong for the pseudoscalar coupling but are significantly relaxed for the axial-vector one. These limits suffer from significant model uncertainties, poorly known proton/neutron spin content of these nuclei, and therefore do not exclude the possibility of a muon spin force relevant for the muon $g-2$.

Recently, Soleti et al. [J. High Energy Phys. 03 (2024) 148] proposed a new experiment called SHiNESS at the upcoming European Spallation Source (ESS) facility, making use of the 2-GeV proton beam there impinging on a fixed target, in order to search for hidden sterile neutrinos that could lie in different mass ranges and arise with distinct signatures. Such signatures include excesses in electron-positron pairs that may originate from displaced decays of long-lived particles (LLPs). At the ESS, the dominant sources of such LLPs are decays at rest of ${\pi }^{+}$ mesons and ${\mu }^{+}$ leptons. We choose to investigate theoretical scenarios of long-lived light neutralinos in the $R$-parity-violating supersymmetry and long-lived weak-violating electrophilic axionlike particles, as these LLPs can be produced from decays of ${\pi }^{+}$ and ${\mu }^{+}$. Since the ${\pi }^{+}$’s and ${\mu }^{+}$’s decay at rest at the ESS, we compute the spectra of the therefrom produced LLPs and thus estimate the expected sensitivity reach of SHiNESS to the LLPs in these two scenarios. Our calculation shows that in multiple relevant benchmark scenarios, SHiNESS can probe large parameter regions of these models beyond the existing bounds, in just a couple of years of data-collection time.

We conduct systematic calculations of the $S$-wave fully strange systems with “normal” $(J^{PC}=0^{++},1^{+-},2^{++})$ and “exotic” $(J^{PC}=0^{+-},1^{++},2^{+-})$ $C$-parities, which are the strange analog of the fully charmed tetraquark state $X(6900)$. Within a constituent quark potential model, we employ the Gaussian expansion method to solve the four-body Schrödinger equation and the complex scaling method to identify resonant states. We obtain a series of resonant states and zero-width states in the mass range of 2.7 to 3.3 GeV, with their widths ranging from less than 1 to about 50 MeV. Their rms radii strongly indicate that they are compact tetraquark states. Among these states, the $T_{4s,2^{++}}(2714)$ may be the most likely one to be observed experimentally. We urge the experimental exploration of the $2^{++}ss\overline{s}\overline{s}$ state around 2.7 GeV in the $\varphi \varphi$ channel. Since the lowest S-wave $ss\overline{s}\overline{s}$ state is around 2.7 GeV, the compact P-wave $ss\overline{s}\overline{s}$ states are expected to be heavier. Hence, $\varphi (2170)$ and $X(2370)$ are unlikely to be compact tetraquark states.

Using $10.1{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector with center-of-mass energies between 4.15 GeV and 4.30 GeV, we search for the decays $X(3872)\to {\pi }^0{\pi }^0{\chi }_{c1,2}$, where the $X(3872)$ is produced in $e^{+}{e}^{-}\to \gamma X(3872)$. No evidence above $3\sigma$ is found for either decay. Upper limits at the 90% CL on the branching fractions of $X(3872)\to {\pi }^0{\pi }^0{\chi }_{c1,2}$ normalized to the branching fraction of $X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi$ are set to be $\mathcal{B}(X(3872)\to {\pi }^0{\pi }^0{\chi }_{c1})/\mathcal{B}(X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi )<1.1$ and $\mathcal{B}(X(3872)\to {\pi }^0{\pi }^0{\chi }_{c2})/\mathcal{B}(X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi )<0.5$, taking into account both statistical and systematic uncertainties.

A search for the lepton-flavor violating decays $B_s^0\to \varphi {\mu }^{\pm }{\tau }^{\mp }$ is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$. The $\tau$ leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be $\mathcal{B}(B_s^0\to \varphi {\mu }^{\pm }{\tau }^{\mp })<1.0\times {10}^{-5}$ at 90% confidence level.

We report a methodology to determine the quality factor ($Q$) of wavy dark matter detectors equipped with multilayered resonators, including Fabry-Pérot interferometers and the so-called dielectric haloscope. An anechoic chamber enables the observation of the resonance frequency and its amplitude for an unlimited series of layers for the first time, which is conveniently filtered. The frequency-normalized power enhancement measured in a Dark Photons and Axionlike Particles Interferometer (DALI) prototype is a few hundred per layer over a sweep bandwidth of a few dozen of megahertz. In light of this result, this scaled-down prototype is sensitive to axions saturating the local dark matter density with a coupling to photons between $g_{a\gamma \gamma }\gtrsim {10}^{-12}$ and $g_{a\gamma \gamma }\gtrsim \mathrm{few}\times {10}^{-14}{\mathrm{GeV}}^{-1}$ at frequencies of several dozens of gigahertz once cooled down to the different working temperatures of the experiment and immersed in magnetic fields ranging from about 1 to 10 T; while the sensitivity of the full-scale DALI is projected at $g_{a\gamma \gamma }\gtrsim \mathrm{few}\times {10}^{-15}{\mathrm{GeV}}^{-1}$ over the entire $25–250\mathrm{\mu }\mathrm{eV}$ range since $Q\gtrsim {10}^4$ is expected.

A search for electroweak production of a single vectorlike $T$ quark in association with a bottom ($b$) quark in the all-hadronic decay channel is presented. This search uses proton-proton collision data at $\sqrt{s}=13\mathrm{TeV}$ collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. The $T$ quark is assumed to have charge $2/3$ and decay to a top ($t$) quark and a Higgs ($H$) or $Z$ boson. Hadronic decays of the $t$ quark and the $H$ or $Z$ boson are reconstructed from the kinematic properties of jets, including those containing $b$ hadrons. No deviation from the standard model prediction is observed in the reconstructed $tH$ and $tZ$ invariant mass distributions. The 95% confidence level upper limits on the product of the production cross section and branching fraction of a $T$ quark produced in association with a $b$ quark and decaying via $tH$ or $tZ$ range from 1260 to 68 fb for $T$ quark masses of 600–1200 GeV.

In this work we consider anomalous and linear holographic hard wall (HW) models for light unflavored mesons inspired by the AdS/CFT correspondence. The anomalous dimensions depend on the logarithm of the spin $S$ of the meson state and come from a semiclassical analysis of gauge/string duality. The anomalous HW model produces very good masses and good Regge trajectories for mesons compared with PDG data. Inspired by this anomalous HW model we also propose a phenomenological modification of the dimension of the boundary operators such that the model produces asymptotic linear Regge trajectories. Both anomalous HW models considered here present mass percentage deviations of less than 3%, when compared with PDG data.

In this paper, we investigated the motion of massive particles in the presence of scalar and gravitational fields, particularly focusing on the Janis-Newman-Winicour (JNW) naked singularity solution. It is shown that the innermost stable circular orbit radius strongly depends on scalar coupling parameter. Additionally, we explored the radiation reaction effects on particle dynamics, incorporating a reaction term into the motion equations. Numerical simulations indicated minimal impact on particle trajectories from radiation reaction. We also examined the oscillatory motion of particles around compact objects in the JNW spacetime, focusing on radial and vertical oscillations. Our analysis indicated that the scalar field’s coupling parameter and the spacetime deformation parameter $n$ significantly alter the fundamental frequencies of these oscillations. Furthermore, we studied quasiperiodic oscillations (QPOs) in x-ray binaries, using the relativistic precession model to analyze upper- and lower-frequency relationships. Our results indicated that increasing parameters ($n$ and $g_s$) shifts the frequency ratio of $3:2$ QPOs closer to the naked singularity, with $n$ decreasing and $g_s$ increasing both frequencies. Finally, we analyzed QPO data from four selected x-ray binary systems using Markov chain Monte Carlo analysis to constrain JNW parameters. Our findings provided insights into the mass, coupling, and deformation parameter for each system, enhancing our understanding of compact object dynamics in strong gravitational fields.

We discuss the Hamiltonian hybrid coupling between a classical and a quantum subsystem. If applicable to classical gravity coupled to quantized matter, this hybrid theory might realize a captivating “postquantum” alternative to full quantum gravity. We summarize the nonrelativistic hybrid dynamics in improved formalism adequate to Hamiltonian systems. The mandatory decoherence and diffusion terms become divergent in special and general relativistic extensions. It is not yet known if any renormalization method might reconcile Markovian decoherence and diffusion with relativity. Postquantum gravity could previously only be realized in the Newtonian approximation. We argue that pending problems of the recently proposed general relativistic postquantum theory will not be solved if Markovian diffusion/decoherence are truly incompatible with relativity.

Considering the so-called Ricci-based gravity theories, a family of extensions of general relativity whose action is given by a nonlinear function of contractions and products of the (symmetric part of the) Ricci tensor of an independent connection, the Hamiltonian formulation of the theory is obtained. To do so, the independent connection is decomposed in two parts, one compatible with a metric tensor and the other one given by a 3-rank tensor. Subsequently, the Riemann tensor is expressed in terms of its projected components onto a hypersurface, allowing one to construct the $3+1$ decomposition of the theory and the corresponding Gauss-Codazzi relations, where the boundary terms naturally arise in the gravitational action. Finally, the Arnowitt-Deser-Misner (ADM) decomposition is followed in order to construct the corresponding Hamiltonian and the ADM energy for any Ricci-based gravity theory. The formalism is applied to the simple case of Schwarzschild spacetime.