Magnetars are potential energy sources or central engines for numerous transient phenomena in the Universe. How newborn magnetars evolve in different environments remains an open question. The majority of previous studies on the evolution of newborn magnetars considered either the spin evolution, inclination evolution, or magnetic field evolution in vacuum or in a plasma-filled magnetosphere. Based on both observed and candidate magnetars, it is found that the periods of all magnetars or candidates appear as a bimodal distribution, and are defined as the “long-$P$” and “short-$P$” magnetar subclasses, respectively. We find that for the short-$P$ subclass of magnetars, the $\dot{P}$ values also appear as a bimodal distribution, and therefore can be classified as “high-$\dot{P}$ short-$P$” and “low-$\dot{P}$ short-$P$” magnetar subclasses. In this paper, we use Monte Carlo simulations to generate synthetic magnetar populations and investigate the evolution of the high-$\dot{P}$ short-$P$ and low-$\dot{P}$ short-$P$ magnetar subclasses by considering both the magnetar spin and inclination, as well as the decay of their magnetic field within their evolution in both vacuum and plasma-filled magnetospheres. We find that the magnetar evolution is dependent on both spin and magnetic field, but seems to be insensitive to inclination evolution and magnetospheric environment for the high-$\dot{P}$ short-$P$ subclass. In comparison for the case of high-$\dot{P}$ short-$P$, the magnetar evolution is dependent on spin, magnetic field, and inclination evolution, as well as the magnetospheric environment. The best evolution model should be the case of inclination evolution in vacuum with a small value of $\overline{\mathrm{FOM}}$. The differences in the best-fit parameters also suggest that the high-$\dot{P}$ short-$P$ and low-$\dot{P}$ short-$P$ magnetar subclasses may be tracking with different evolution channels.

We argue that the axionic domain-wall with a QCD bias may be incompatible with the NANOGrav 15-year data on a stochastic gravitational wave (GW) background, when the domain wall network collapses in the hot-quantum chromodynamics (QCD) induced local $CP$-odd domain. This is due to the drastic suppression of the QCD bias set by the QCD topological susceptibility in the presence of the $CP$-odd domain with nonzero $\theta$ parameter of order one which the QCD sphaleron could generate. We quantify the effect on the GW signals by working on a low-energy effective model of Nambu-Jona-Lasinio type in the mean field approximation. We find that only at $\theta =\pi$, the QCD bias tends to get significantly large enough due to the criticality of the thermal $CP$ restoration, which would, however, give too big signal strengths to be consistent with the NANOGrav 15-year data and would also be subject to the strength of the phase transition at the criticality.

In the framework of the low-energy effective theory containing, in addition to the Standard-Model fields, heavy neutral leptons (HNLs), we compute the decay rates of neutral and charged kaons into HNLs. We consider both lepton-number-conserving and lepton-number-violating four-fermion operators, taking into account also the contribution of active-heavy neutrino mixing. Assuming that the produced HNLs are long-lived, we perform simulations and calculate the sensitivities of future long-lived-particle (LLP) detectors at the high-luminosity LHC as well as the near detector of the Deep Underground Neutrino Experiment (DUNE-ND) to the considered scenario. When applicable, we also recast the existing bounds on the minimal mixing case obtained by NA62, T2K, and PS191. Our findings show that, while the future LHC LLP detectors can probe currently allowed parameter space only in certain benchmark scenarios, DUNE-ND should be sensitive to parameter space beyond the current bounds in almost all the benchmark scenarios, and, for some of the effective operators considered, it can even probe new-physics scales in excess of 3000 TeV.

Based on a contact Lagrangian that incorporates the SU(3) flavor and SU(2) spin symmetries, we discuss the symmetry properties of the interactions among the heavy flavor meson-baryon $P_{\psi }^N$, $P_{\psi s}^{\mathrm{\Lambda }}$ (with quark components $[n\overline{c}][nnc]$, $[s\overline{c}][nnc]$, or $[n\overline{c}][nsc]$) systems and dibaryon $H_{{\mathrm{\Omega }}_{ccc}}^N$, $H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$ (with quark components $[nnc][ncc]$, $[nnc][scc]$, or $[nsc][ncc]$) systems ($n=u$, $d$). The light quark components of the $P_{\psi }^N$ ($P_{\psi s}^{\mathrm{\Lambda }}$) and $H_{{\mathrm{\Omega }}_{ccc}}^N$ ($H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$) systems have identical flavors, the interactions generated from the exchanges of light mesons in the $P_{\psi }^N$ ($P_{\psi s}^{\mathrm{\Lambda }}$) systems should be very similar to that of the $H_{{\mathrm{\Omega }}_{ccc}}^N$ ($H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$) systems. We perform the single-channel and multichannel calculations on the $P_{\psi }^N/P_{\psi s}^{\mathrm{\Lambda }}/H_{{\mathrm{\Omega }}_{ccc}}^N/H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$ systems and introduce the SU(3) breaking effect to identify the different mass spectra among the $P_{\psi }^N$ ($H_{{\mathrm{\Omega }}_{ccc}}^N$) and $P_{\psi s}^{\mathrm{\Lambda }}$ ($H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$) systems. We suggest two kinds of evidences for the existence of the flavor-spin symmetry among the heavy flavor $P_{\psi }^N/H_{{\mathrm{\Omega }}_{ccc}}^N/P_{\psi s}^{\mathrm{\Lambda }}/H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$ molecule community, i.e., the mass arrangements of the $P_{\psi }^N/H_{{\mathrm{\Omega }}_{ccc}}^N/P_{\psi s}^{\mathrm{\Lambda }}/H_{{\mathrm{\Omega }}_{ccc}s}^{\mathrm{\Lambda }}$ mass spectra and the binding energies of the heavy flavor meson-baryon (dibaryon) systems attributed to the same contact potentials.

We perform a global fit to the experimental data of two-body charmed baryon decays based on the topological diagrammatic approach (TDA) and take into account the phase shifts between $S$- and $P$-wave amplitudes as inspired by the recent BESIII measurement of the decay asymmetry in the decay ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Xi }}^0{K}^{+}$. The TDA has the advantage that it is more intuitive, graphic, and easier to implement model calculations. The measured branching fractions and decay asymmetries are well accommodated in the TDA except for a few modes, in particular, the predicted $\mathcal{B}({\mathrm{\Xi }}_c^0\to {\mathrm{\Xi }}^{-}{\pi }^{+})=(2.83\pm 0.10)\%$ is larger than its current value. The equivalence of the TDA and the irreducible SU(3) approach (IRA) is established. We show that the number of the minimum set of tensor invariants in the IRA and the topological amplitudes in the TDA is the same and present their relations. The predicted magnitudes of $S$- and $P$-wave amplitudes and their phase shifts are presented for measured and yet-to-be-measured modes in both the TDA and IRA which can be tested in the near future. Besides the decay ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Xi }}^0{K}^{+}$, there exist several modes which proceed only through $W$-exchange. In particular, the observed channel ${\mathrm{\Xi }}_c^0\to {\mathrm{\Sigma }}^{+}{K}^{-}$ should have phase shifts similar to that in ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Xi }}^0{K}^{+}$ and its decay asymmetry is predicted to be $-0.21\pm 0.17$ which can be used to test our theoretical framework. In contrast, the TDA leads to a large $\alpha$ of order $-0.93$ for the decay ${\mathrm{\Xi }}_c^{+}\to {\mathrm{\Xi }}^0{\pi }^{+}$ even after the phase-shift effect is incorporated in the fit.

We evaluate the vacuum entanglement entropy across a cut of future null infinity for free Maxwell theory in four-dimensional Minkowski spacetime. The Weyl invariance of 4D Maxwell theory allows us to embed the Minkowski spacetime inside the Einstein static universe. The Minkowski vacuum can then be described as a thermofield double state on the (future) Milne wedges of the original and inverted Minkowski patches. We show that the soft mode contribution to entanglement entropy is due to correlations between asymptotic charges of these Milne wedges or, equivalently, nontrivial conformally soft (or edge) mode configurations at the entangling surface.

It has been three decades since the ground-breaking work by Choptuik on critical phenomena in gravitational collapse involving a real massless scalar field minimally coupled to general relativity in spherical symmetry. These phenomena are characterized by the emergence of surprising structure in solution space, namely, the appearance of universal power laws and periodicities near the threshold of collapse and a universal discretely self-similar solution at the threshold itself. This seminal work spurred a comprehensive investigation of extreme spherical spacetimes in numerical relativity, with analogous results for numerous matter models. Recent research suggests that the generalization to less symmetric scenarios is subtle. In twist-free axisymmetric vacuum collapse, for instance, numerical evidence suggests a breakdown of universality of solutions at the threshold of collapse. In this study, we explore gravitational collapse involving a massless complex scalar field minimally coupled to general relativity. We employ the pseudospectral code bamps to investigate a neighborhood of the spherically symmetric critical solution in phase space, focusing on aspherical departures from it. First, working in explicit spherical symmetry, we find strong evidence that the spacetime metric of the spherical critical solution of the complex scalar field agrees with that of the Choptuik solution. We then examine universality of the behavior of solutions near the threshold of collapse as the departure from spherical symmetry increases, comparing with recent investigations of the real scalar field. We present a series of well-tuned numerical results and document shifts of the power-law exponent and periods as a function of the degree of asphericity of the initial data. At sufficiently high asphericities, we find that the center of collapse bifurcates, on the symmetry axis, but away from the origin. Finally, we look for and evaluate evidence that in the highly aspherical setting the collapse is driven by gravitational waves.

If two particles moving toward a black hole collide in the vicinity of the horizon, the energy $E_{\mathrm{c}.\mathrm{m}.}$ in the center-of-mass frame can grow indefinitely if one of the particles is fine-tuned. This is the Bañados-Silk-West (BSW) effect. One of the objections against this effect is that, for some types of horizon, fine-tuned particles cannot reach the horizon. However, this difficulty can be overcome if, instead of exact fine-tuning, one particle is nearly fine-tuned, with the value of small detuning being adjusted to the distance to the horizon. Such particles are called near-fine-tuned. We give classification of such particles and describe possible high-energy scenarios of collision in which they participate. We analyze the ranges of possible motion for each type of particle and determine under which condition such particles can reach the horizon. We analyze collision energy $E_{\mathrm{c}.\mathrm{m}.}$ and determine under which conditions it may grow indefinitely. We also take into consideration the forces acting on particles and find when the BSW effect with nearly fine-tuned particles is possible with finite forces. We demonstrate that the BSW effect with particles under discussion is consistent with the principle of kinematic censorship. According to this principle, $E_{\mathrm{c}.\mathrm{m}.}$ cannot be literally infinite in any event of collision (if no singularity is present), although it can be made as large as one likes.

We show that backreaction of quantum fields on black hole geometries can trigger new thermal phase transitions. Specifically, we study the phase behavior of the three-dimensional quantum-corrected static Bañados-Teitelboim-Zanelli black hole, an exact solution to specific semiclassical gravitational equations due to quantum conformal matter, discovered through braneworld holography. Focusing on the canonical ensemble, for large backreaction, we find novel reentrant phase transitions as the temperature monotonically increases, namely, from thermal anti–de Sitter space to the black hole and back to thermal anti–de Sitter. The former phase transition is first-order, a quantum analog of the classical Hawking-Page phase transition, while the latter is zeroth order and has no classical counterpart.

We construct and discuss new solutions of primary hair charged black holes in asymptotically anti–de Sitter space that have well-defined Coulomb-like potential in three dimensions. The gauge field source to the Einstein equation is a power-Maxwell nonlinear electrodynamics with traceless energy-momentum tensor. The coupled Einstein-power-Maxwell-scalar gravity system, which carries the coupling $f(\varphi )$ between the gauge and scalar fields, is analyzed, and hairy-charged black hole solutions are found analytically. We consider three different profiles of the coupling functions: (i) $f(\varphi )=1$, corresponding to no direct coupling between the gauge and scalar fields, (ii) $f(\varphi )=e^{\varphi }$, and (iii) $f(\varphi )=e^{{\varphi }^2/2}$, corresponding to their nonminimal coupling. For all these cases, the scalar field, gauge fields, and curvature scalars are regular and well behaved everywhere outside the horizon. We further study the thermodynamics of the obtained hairy black hole in the canonical and grand-canonical ensembles and find significant changes in its thermodynamic structure due to the scalar field. In particular, for all considered coupling functions, the hairy parameter has a critical value above which the hairy black hole undergoes the Hawking/Page phase transition, whereas below which no such phase transition appears.

The holographic superconductor phase transition and spontaneous scalarization are triggered by the instability of the underlying vacuum black hole spacetime. Although both hairy black hole solutions are closely associated with the tachyonic instability of the scalar degree of freedom, they are understood to be driven by distinct causes. Therefore, it is interesting to explore the interplay between the two phenomena in the context of a scenario where both mechanisms are present. To this end, we investigate the Einstein-scalar-Gauss-Bonnet theory in asymptotically anti–de Sitter spacetime with the presence of a Maxwell field. Even though different origins for the tachyonic mass behave independently and can be recognized by the distinctive natures of their effective potentials, it is shown that near the transition curve, the holographic superconductor, and spontaneous scalarization are found to be largely indistinguishable. This raises the question of whether the hairy black holes triggered by different mechanisms are smoothly joined by a phase transition or whether these are actually identical solutions. To assess the transition more closely, we evaluate the phase diagram in terms of temperature and chemical potential and discover a smooth but first-order transition between the two hairy solutions by explicitly evaluating the Gibbs free energy and its derivatives. In particular, one can elaborate a thermodynamic process through which a superconducting black hole transits into a scalarized one by raising or decreasing the temperature. Exhausting the underlying phase space, we analyze the properties and the interplay between the two hairy solutions.

We show that a charged, massive scalar field in the vicinity of an electrically charged Ayón-Beato–García (ABG) regular black hole has a spectrum of quasibound states that (in a certain parameter regime) grow exponentially with time, due to black hole superradiance. Superradiant quasibound states are made possible by the enhancement of the electrostatic potential at the horizon in nonlinear electrodynamics; in contrast, the Reissner-Nordström black hole does not appear to possess such superradiant quasibound states. Here we compute the spectrum for a range of multipoles $\ell$ across the parameter space, and we find the fastest growth rate in the monopole mode. We find that a regular black hole with a small charge can still trigger a significant superradiant instability if the charge-to-mass ratio of the field is compensatingly large. We estimate the amount of black hole mass that can be deposited in the scalar field, finding an upper bound of circa 20% in the extreme charge scenario. Finally, we consider the stationary bound states at the superradiant threshold, and we conjecture that, due to this instability, the ABG black hole will evolve toward a configuration with charged scalar hair.

The Standard Model of particle physics predicts the speed of light to be a universal speed of propagation of massless carriers. However, other possibilities exist—including Lorentz-violating theories—where different fundamental fields travel at different speeds. Black holes are interesting probes of such physics, as distinct fields would probe different horizons. Here, we build an exact spacetime for two interacting scalar fields which have different propagation speeds. One of these fields is able to probe the black hole interior of the other, giving rise to energy extraction from the black hole and a characteristic late-time relaxation. Our results provide further stimulus to the search for extra degrees of freedom, black hole instability, and extra ringdown modes in gravitational-wave events.

We revisit the formation of a thermal population of hadronic axions in nonstandard cosmologies, in light of the recent developments in obtaining continuous and smooth interaction rates for both the gluon and photon couplings. For certain cosmological histories, such as low-temperature reheating (LTR) and kinationlike scenarios, the thermalization of the axion can be severely delayed to higher masses. In the case that thermal equilibrium is achieved, we improve the constraints on LTR for axion masses around the eV scale with respect to previous works and we constrain for the first time early matter-dominated cosmologies. We also point out the possibility of having the coexistence of cold and warm dark matter populations of axions in kinationlike scenarios in the eV mass range.

In contrast to our understanding of density field tracers, the modeling of direct statistics pertaining to the cosmic velocity field remains open to significant opportunities for improvement. The lack of accurate modeling for the nonlinear domain of pairwise velocities restricts our capacity to fully exploit the information encoded in this observable. We present a robust approach for modeling the mean infall velocities, $v_{12}(r,a)$, with broad applicability spanning sub-megaparsec scales and cosmologies extending beyond the standard $\mathrm{\Lambda }\mathrm{CDM}$ paradigm. Our approach involves solving the full pair-conservation equation using accurate nonlinear power spectrum descriptions. To assess the robustness of our model, we extend it to cosmologies beyond the standard $\mathrm{\Lambda }\mathrm{CDM}$, in particular, the Hu-Sawicki $f(R)$-gravity and Dvali-Gabadadze-Porrati (DGP) modified gravity models. Remarkably, our predictions for pairwise velocities of dark matter particles at kiloparsec scales exhibit excellent agreement with $N$-body simulations throughout the entire dynamical range ($0.1\lesssim \xi \lesssim 1000$, or $r\ge 0.4h^{-1}\mathrm{Mpc}$). Furthermore we show that different gravity models leave distinct signatures in the shape and dynamics of the mean pairwise velocities, providing a potent test of cosmological gravity laws.

To determine whether or not H ii starburst galaxies (H iiG) are standardizable candles, we study the correlation between the $\mathrm{H}\beta$ luminosity ($L$) and the velocity dispersion ($\sigma$) of the ionized gas from H iiG measurements by simultaneously constraining the $L-\sigma$ relation parameters and the cosmological model parameters. We investigate six flat and nonflat relativistic dark energy cosmological models. We find that low-redshift and high-redshift H iiG data subsets are standardizable but obey different $L-\sigma$ relations. Current H iiG data are too sparse and too nonuniformly distributed in redshift to allow for a determination of why the samples follow different relations, but it could be caused by the high-redshift sample containing relatively fewer intrinsically dimmer sources (Malmquist bias) or it could be a consequence of H iiG evolution. Until this issue is better understood, H iiG data cosmological constraints must be treated with caution.

We investigate a cosmological model wherein a waterfall symmetry breaking occurs during the radiation-dominated era. The model comprises a complex waterfall field, an axion field, and the gauge field (dark photon) generated through a tachyonic instability due to the Chern-Simons interaction. Prior to symmetry breaking, the total energy density incorporates a vacuum energy from the waterfall field, establishing a novel scenario for the early dark energy. Subsequent to the symmetry breaking, the dark photon dynamically acquires mass via the Higgs mechanism, potentially contributing to the dark matter abundance. Hence, our model has the potential to simultaneously address the $H_0$ tension and the origin of dark matter.

We demonstrate that pairwise peculiar velocity correlations for galaxy clusters can be directly reconstructed from the kinematic Sunyaev-Zel’dovich (kSZ) signature imprinted in the cosmic microwave background (CMB) using a machine learning model with a gradient boosting algorithm trained on high-fidelity kSZ simulations. The machine learning model is trained using six to seven cluster features that are directly related to observables from CMB and large-scale structure surveys. We validate the capabilities of the approach in light of the presence of primary CMB, detector noise, and potential uncertainties in the cluster mass estimate and cluster center location. The pairwise velocity statistics extracted using the techniques developed here have the potential to elicit valuable cosmological constraints on dark energy, modified gravity models, and massive neutrinos with kSZ measurements from upcoming CMB surveys, including the Simons Observatory, CMB-S4 and CCAT, and the DESI and SDSS galaxy surveys.

By means of $N$-body simulations, we study early structure formation in the presence of a scaling distribution of cosmic string loops. Cosmic string loops dominate the high redshift halo mass function while the fluctuations seeded by the standard structure formation scenario dominate structure at low redshifts. In our study, the effects of the cosmic string loops are taken into account by displacing the dark matter particles and their velocities at the initial time of the simulation by amounts determined by the analytical analysis which makes use of the Zel’dovich approximation. We find that the resulting halo mass function is to a good approximation given by the sum of the analytically determined cosmic string halo mass function and the halo mass function obtained from the standard $\mathrm{\Lambda }\mathrm{CDM}$ model.