In our previous papers [Phys. Rev. D 104, 064025 (2021); 105, 064074 (2022); 106, 084007 (2022)], we analyzed the asymptotic behavior of future directed null geodesics near future null infinity, and then we showed a proposition on the accessibility of the null geodesics to future null infinity in a specific class of asymptotically flat spacetimes. In this paper, we adopt the retarded time of the Bondi coordinate as the parameter for the null geodesics and then see that one can relax the assumptions imposed in our previous studies. As a consequence, we obtain a new null-access theorem for generic asymptotically flat spacetimes.

Nonlinear gravitational instability is a crucial way to comprehend the clustering of matter and the formation of nonlinear structures in both the Universe and stellar systems. However, with the exception of a few exact particular solutions for pressureless matter, there are only some approximations and numerical and phenomenological approaches to study the nonlinear gravitational instability instead of mathematically rigorous analysis. We construct a family of particular solutions of the Euler-Poisson system that exhibits the nonlinear gravitational instability of matter with inhomogeneous pressure and entropy (i.e., the cold center and hot rim) in the expanding Newtonian universe. Despite the density perturbations being homogeneous, the pressure is not, resulting in significant nonlinear effects. By making use of our prior work on nonlinear analysis of a class of differential equations, we estimate that the growth rate of the density contrast is approximately $\sim \exp (t^{\frac{2}{3}})$, much faster than the growth rate anticipated by classical linear Jeans instability ($\sim t^{\frac{2}{3}}$). Our main motivation for constructing this family of solutions is to provide a family of reference solutions for conducting a fully nonlinear analysis of inhomogeneous perturbations of density contrast. We will present the general results in a mathematical article separately. Additionally, we emphasize that our model does not feature any shell-crossing singularities before mass accretion singularities since we are specifically interested in analyzing the mathematical mechanics of a pure mass accretion model, which poses limitations on the applicability of our model for understanding the realistic nonlinear structure formation.

In this work, we consider polar perturbations, and we calculate the frequency and damping time of the quadrupolar fundamental $f$-mode of compact objects, constructed using a wide range of model-independent hybrid equations of state that include quark matter. We give special attention to the impact of the hadron-quark conversion speed that, in the slow case, gives rise to a branch of slow stable hybrid stars. Moreover, we study the validity of universal relationships proposed in the literature and find out that none of them remains valid when slow stable hybrid stars are taken into account. This fact could constrain the applicability of asteroseismology methods with fundamental modes designed to estimate the properties of pulsating compact objects. We hope that this result could be tested with the start up of the third-generation gravitational wave observatories, which might shed some light on the $f$-mode emission from compact objects.

This article summarizes our study to develop an intracavity parametric signal amplification system for improving the sensitivity of a gravitational-wave detector at high frequencies to aim at an observation of a postmerger remnant of a binary neutron star collision. The detector configuration is based on a dual recycling interferometer and an optical parametric amplifier crystal is inserted into the signal recycling cavity. The cavity is detuned and an optical spring is generated for the differential motion of the two end mirrors. The amplifier converts the energy of the pump beam to the optical spring and the spring frequency can be enhanced to a few kilohertz. The system is contrasting to the squeeze injection technique commonly used in second-generation gravitational-wave detectors. Although both techniques use an optical parametric amplifier crystal, the squeeze injection reduces noise while signal amplification increases the signal to modify the optomechanical dynamics of the system.

Nonrelativistic quantum chromodynamics (NRQCD) factorization formulism is an important approach to investigate the production of the heavy quarkonium. In this paper, we study the production of the ${\mathrm{\Omega }}_{ccc}$ and ${\mathrm{\Omega }}_{bbb}$ at the $e^{+}{e}^{-}$ collider, using the NRQCD factorization formulism. We do the full calculation of the total and differential cross sections of the processes $e^{+}{e}^{-}\to {\gamma }^{*}/Z^{*}\to {\mathrm{\Omega }}_{QQQ}+\overline{Q}+\overline{Q}+\overline{Q}$, in the leading order at the $e^{+}{e}^{-}$ colliders with different energies. In this paper, ${\mathrm{\Omega }}_{QQQ}$ means the triply heavy baryon ${\mathrm{\Omega }}_{ccc}$ or ${\mathrm{\Omega }}_{bbb}$. And $Q$ denotes the $c$ or $b$ quark. The results show that it is hard to observe them at the $e^{+}{e}^{-}$ colliders directly.

The standard model (SM) one-loop contributions to the most general $H^{*}{Z}^{*}{Z}^{*}$ coupling are obtained via the background field method in terms of Passarino-Veltman scalar functions, from which the contributions to the $H^{*}ZZ$ and $HZ{Z}^{*}$ couplings are obtained in terms of two $CP$-conserving $h_{1,2}^V$ and one $CP$-violating $h_3^V$ form factors ($V=H$, $Z$). The current CMS constraints on the $HZZ$ coupling ratios are then used to obtain bounds on the real and absorptive parts of the anomalous $HZZ$ couplings. The former are up to two orders of magnitude tighter than previous results, whereas the latter are the first one of this kind. The effects of the absorptive parts of the $HZZ$ anomalous couplings, which have been overlooked in the past, are analyzed via the partial decay width ${\mathrm{\Gamma }}_{H^{*}\to ZZ}$, and a significant deviation from the SM tree-level contribution is observed at low energies, though it becomes negligible at high energies. We also explore the possibility that polarized $Z$ gauge bosons are used for the study of non-SM $HZZ$ contributions via a new left-right asymmetry ${\mathcal{A}}_{LR}$, which is sensitive to $CP$-violating complex form factors and can be as large as the unity at most, though in a more conservative scenario it is four to five orders of magnitude larger than the SM prediction arising up to the three-loop level. The partial decay widths ${\mathrm{\Gamma }}_{H^{*}\to Z_L{Z}_L}$ and ${\mathrm{\Gamma }}_{H^{*}\to Z_R{Z}_R}$ are also studied in several scenarios and it is observed that the deviations from the SM can be large at high energies and increases as the energy increases. Thus, the use of polarized $Z$ gauge bosons could give hints of $CP$ violation. The Mathematica code for our analytical results and the numerical evaluation is available in our GitLab site.

The interior of Earth’s core can be explored using weak interactions of atmospheric neutrinos. This would complement gravitational and seismic measurements, paving the way for multimessenger tomography of Earth. Oscillations of atmospheric neutrinos passing through Earth are affected by the ambient electron density. We demonstrate that atmospheric neutrinos can probe the possible existence of dark matter inside Earth’s core in a unique way—by measuring the amount of baryonic matter using neutrino oscillations. We find that a detector like ICAL at INO with muon charge identification capability can be sensitive to dark matter with $\sim 5\%–6\%$ mass of Earth, at $1\sigma$ level with 500 kt yr exposure. We show that, while it will not be possible to identify the dark matter profile using neutrino oscillation experiments, the baryonic matter profile inside the core can be probed with atmospheric neutrinos.

Using general properties of the $Q=0$ topological sector, we previously argued that a vectorlike theory, with chiral $U(1{)}_A$ anomaly, and exact non-Abelian chiral symmetry, should exhibit divergent susceptibilities in the chiral limit, the two-flavor Schwinger model being a paradigmatic example of the realization of this scenario. Two flavor QCD at $T>T_c$ satisfies all the above conditions, and it is also expected that the $U(1{)}_A$ axial symmetry remains effectively broken in its high temperature phase. Therefore, we would expect a nonanalyticity in the quark mass dependence of the free energy density, in contrast with the dilute instanton gas approximation (DIGA) prediction. We investigate in this work whether the aforementioned results can also be reproduced making only use of standard properties of the spectral density of the Dirac operator, without having to resort to general properties of the $Q=0$ topological sector. We show that the only way to derive a nontrivial $\theta$-dependence, and an analytical free energy density in QCD with two degenerate flavors is that the spectral density, $\rho (\lambda ,m)$, of the absolute value of the nonzero modes of the Dirac-Ginsparg-Wilson operator develops a $m^2\delta (\lambda )$ function in the thermodynamic limit. This is the expected result in the DIGA, where interactions between instantons in the dilute gas are fully neglected. However, at temperatures close to $T_c$ the interaction between instantons should become non-negligible, and the splitting from zero of the near-zero modes, which has been neglected in the DIGA, should be taken into account. Therefore we expect that the $m^2\delta (\lambda )$ contribution to the spectral density is no longer correct at these temperatures, and that the free energy density becomes a nonanalytic function of the quark mass.

The interaction potential between a pair of heavy quarks is calculated with the resummed perturbation method in Gribov-Zwanziger (GZ) approach around the deconfinement phase transition. The resummed loop correction makes the potential complex. While the real part is suppressed by color screening and becomes short-ranged at high temperatures, the imaginary part is enhanced through decay processes in a hot medium and becomes comparable with the real part around the phase transition. The strong imaginary potential comes from the magnetic scale in the GZ approach and shows that both the color screening and decay processes play important roles in quarkonium dissociation in high-energy nuclear collisions.

We investigate various properties of extremal dyonic static black holes in Einstein-Maxwell-dilaton theory. Using the fact that the long-range force between two identical extremal black holes always vanishes, we obtain a simple first-order ordinary differential equation for the black hole mass in terms of its electric and magnetic charges. Although this equation appears not to be solvable explicitly for general values of the strength $a$ of the dilatonic coupling to the Maxwell field, it nevertheless provides a powerful way of characterizing the black hole mass and the scalar charge. We make use of these expressions to derive general results about the long-range force between two nonidentical extremal black holes. In particular, we argue that the force is repulsive whenever $a>1$ and attractive whenever $a<1$ (it vanishes in the intermediate BPS case $a=1$). The sign of the force is also correlated with the sign of the binding energy between extremal black holes, as well as with the convexity or concavity of the surface characterizing the extremal mass as a function of the charges. Our work is motivated in part by the repulsive force conjecture and the question of whether long range forces between nonidentical states can shed new light on the swampland.

We determine the impact of the $\theta$ angle and axion physics on the near conformal dynamics of the large-charge baryon sector of $SU(2)$ gauge theories with $N_f$ fermions in the fundamental representation. We employ an effective approach featuring Goldstone and dilaton degrees of freedom augmented by the topological terms in the theory. We investigate how different dilaton potentials, including the ones for which a systematic counting scheme can be established, affect the results. Via state-operator correspondence we compute the corrections to the would-be conformal dimensions of the lowest large-charge operators as a function of the $\theta$ term and dilaton potential.

We use the Klein-Gordon equation in a curved spacetime to construct the relativistic analog of the Schrödinger-Newton problem, where a scalar particle lives in a gravitational potential well generated by its own probability distribution. A static, spherically symmetric metric is computed from the field equations of general relativity, both directly and as modeled by a perfect-fluid assumption that uses the Tolman-Oppenheimer-Volkov equation for hydrostatic equilibrium of the mass density. The latter is appropriate for a Hartree approximation to the many-body problem of a bosonic star. The simultaneous self-consistent solution of the Klein-Gordon equation in this curved spacetime then yields solitons with a range of radial excitations. We compare results with the nonrelativistic case.

Within the $f(Q)$-gravity framework we perform a phenomenological study of the cosmological observables in light of the degeneracy between neutrinos physics and the modified gravity parameter and we identify specific patterns which allow to break such degeneracy. We also provide separately constraints on the total mass of the neutrinos, $\mathrm{\Sigma }{m}_{\nu }$, and on the effective number of neutrino species, $N_{\mathrm{eff}}$, using cosmic microwave background (CMB), baryon acoustic oscillation (BAO), redshift space distortion (RSD), supernovae (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. The strongest upper bound on the total mass of the neutrinos is found for the combination of $\mathrm{CMB}+\mathrm{BAO}+\mathrm{RSD}+\mathrm{SNIa}$ and it is $\mathrm{\Sigma }{m}_{\nu }<0.277\mathrm{eV}$ at 95% C.L. For the same combination of data we find $N_{\mathrm{eff}}={2.93}_{-0.34}^{+0.31}$ at 95% C.L. We also find that all combinations of data we consider, prefer a stronger gravitational interaction than $\mathrm{\Lambda }\mathrm{CDM}$. Finally, we consider the ${\chi }^2$ and deviance information criterion statistics and find the $f(Q)+\mathrm{\Sigma }{m}_{\nu }$ model to be statistically supported by data over the standard scenario. On the contrary $f(Q)+N_{\mathrm{eff}}$ is supported by $\mathrm{CMB}+\mathrm{BAO}+\mathrm{RSD}+\mathrm{SNIa}$ but a moderate evidence against it is found with GC and WL data.

Three-dimensional static and spinning black hole solutions of the Einstein-Klein-Gordon system are obtained for a particular scalar field configuration. At large distances, and for a small scalar field, the solutions reduce to the Bañados Teitelboim Zanelli black hole. The scalar field dresses the black hole with secondary scalar hair, since the scalar charge is related to the conserved black hole mass. A self-interacting potential is included, containing a mass term that is above the Breitenlohner-Freedman bound in three dimensions. Independence of the scalar potential from the conserved black hole charges imposes fixed mass and angular momentum to scalar charge ratios. The thermodynamic properties as well as the energy conditions of the black hole are analyzed.

From the quantum point of view, singularity should not exist. Recently, Bah and Heidmann constructed a five-dimensional singularity free topology star/black hole [Phys. Rev. Lett. 126, 151101 (2021)]. By integrating the extra dimension, a four-dimensional static spherically symmetric black hole with a magnetic charge and scalar hair can be obtained. In this paper, we study the quasinormal modes (QNMs) of the magnetic field and gravitational field on the background of this four-dimensional charged black hole with scalar hair. The odd parity of the gravitational perturbations couples with the even parity of the magnetic field perturbations. Two coupled second-order derivative equations are obtained. Using the matrix-valued direct integration method and the matrix-valued continued fraction method, we obtain the fundamental QNM frequencies numerically. The effect of the magnetic charge on the QNMs is studied. The differences of the frequencies of the fundamental QNMs between the charged black hole with scalar hair and the Reissner-Nordström black hole are very small for the angular number $l=2$.

In recent years, modified gravity theories have gained significant attention as potential replacements for the general theory of relativity. Neutron stars, which are dense compact objects, provide ideal astrophysical laboratories for testing these theories. However, understanding the properties of neutron stars within the framework of modified gravity theories requires careful consideration of the presently known uncertainty of equations of state (EoS) that describe the behavior of matter at extreme densities. In this study, we investigate three realistic EoS generated using a relativistic mean field framework, which covers the currently known uncertainties in the stiffness of neutron star matter. We then employ a Bayesian approach to statistically analyze the posterior distribution of the free parameter $\alpha$ of the $f(R)$ gravity model, specifically $f(R)=R+\alpha R^2$. By using this approach, we are able to account for our limited understanding of the interiors of neutron stars as well as the uncertainties associated with the modified gravity theory. We impose observational constraints on our analysis, including the maximum mass, and the radius of a neutron star with a mass of $1.4M_{\odot }$ and $2.08M_{\odot }$, which are obtained from x-ray NICER observations. By considering these constraints, we are able to robustly investigate the relationship between the $f(R)$ gravity model parameter $\alpha$ and the maximum mass of neutron stars. Our results reveal a universality relationship between the $f(R)$ gravity model parameter $\alpha$ and the maximum mass of neutron stars. This relationship provides insights into the behavior of neutron stars in modified gravity theories and helps us understand the degeneracies arising from our current limited knowledge of the interiors of neutron stars and the free parameter $\alpha$ of the modified gravity theory.

The polarization of the 21-cm radiation from the epoch of reionization arises from Thomson scattering of 21-cm photons from free electrons and provides information that complements that from the intensity fluctuation. Previous work showed that a direct detection of this signal will be difficult, and hinted that the signal might be enhanced via correlation with other tracers. Here, we discuss the cross-correlation between the cosmic microwave background polarization and the 21-cm polarization. We treat reionization using an analytical model with parameters calibrated by seminumerical simulations. We then derive the cross-correlation angular power spectrum using the total-angular-momentum formalism. We also provide a noise analysis to test against the null hypothesis of no 21-cm polarization. We find that, due to the smallness of the signal, it will be difficult to reject this null hypothesis even with a synergy of ambitious next-generation 21-cm and cosmic microwave background missions.

We present results from a search for solar bosonic dark matter using the annual modulation method with the COSINE-100 experiment. The results were interpreted considering three dark sector bosons models: solar dark photons, Dine-Fischler-Srednicki-Zhitnisky (DFSZ) and Kim-Shifman-Vainshtein-Zakharov (KSVZ) solar axions, and Kaluza-Klein solar axions. No modulation signal compatible with the expected from the models was found from a dataset of 2.82 yr, using 61.3 kg of NaI(Tl) crystals. Therefore, we set a 90% confidence level upper limits for each of the three models studied. For the solar dark photon model, the most stringent mixing parameter upper limit is $1.61\times {10}^{-14}$ for dark photons with a mass of 215 eV. For the DFSZ and KSVZ solar axion, and the Kaluza-Klein axion models, the upper limits exclude axion-electron couplings, $g_{ae}$, above $1.61\times {10}^{-11}$ for axion mass below 0.2 keV; and axion-photon couplings, $g_{a\gamma \gamma }$, above $1.83\times {10}^{-11}{\mathrm{GeV}}^{-1}$ for an axion number density of $4.07\times {10}^{13}{\mathrm{cm}}^{-3}$. This is the first experimental search for solar dark photons and DFSZ and KSVZ solar axions using the annual modulation method. The lower background, higher light yield and reduced threshold of NaI(Tl) crystals of the future COSINE-200 experiment are expected to enhance the sensitivity of the analysis shown in this paper. We show the sensitivities for the three models studied, considering the same search method with COSINE-200.

The generalized parton distributions (GPDs) for the spin-$3/2{\mathrm{\Delta }}^{+}$ resonance are studied numerically using a diquark spectator approach. Our results show that symmetric constraints from time reversal on GPDs are satisfied. The axial-vector form factors of the system are also provided and compared with the lattice QCD calculation. Furthermore, the structure functions are obtained from GPDs in the forward limit. The evolution of structure functions to the scales up to 4 GeV are carried out as predictions for the possible lattice QCD calculations.

With a goal toward explaining the observed baryon asymmetry of the Universe, we extend the standard model (SM) by adding a vector-vector dimension-six effective operator coupling a new Dirac fermion $\chi$, uncharged under the SM gauge symmetries but charged under baryon number, to a quarklike up-type fermion and two identical down-type fermions. We introduce baryon number violation by adding Majorana masses to $\chi$, which splits the Dirac fermion into two Majorana fermions with unequal masses. We speculate on the origin of the effective operator, the Majorana mass, and the new physics sector connection to the SM by considering some ultraviolet completion examples. In addition to the baryon number violation, we show that $C$ and $CP$ invariances can be violated in the theory, and the interference between tree and loop amplitudes with on-shell intermediate states can lead to a baryon asymmetry in $\chi$ decay and scattering processes. We provide numerical estimates for the baryon asymmetry generated, and for the neutron-antineutron oscillation rate.