In this paper, we study the recently proposed Schwarzschild acoustic black hole spacetime, in which we investigate some physical phenomena related to the effective geometry of this background, including the analogous Hawking radiation and the quasibound states. We calculate the spectrum of quasibound state frequencies and the wave functions on the Schwarzschild acoustic background by using the polynomial condition of the general Heun function, and then we discuss the stability of the system. We also compare the resonant frequencies of the Schwarzschild acoustic black hole with the ones by the standard Schwarzschild black hole. Our results may shed some light on the physics of black holes and their analog models in condensed matter. Moreover, these studies could provide the possibility, in principle, for laboratory testing of effects whose nature is unquestionably associated with purely quantum effects in gravity.

Nonlinear electrodynamic (NLED) theories are well motivated for their extensions to classical electrodynamics in the strong field regime, and have been extensively investigated in the search for regular black hole solutions. In this paper, we focus on two spherically symmetric and static black hole solutions based on two types of NLED—the Euler-Heisenberg NLED model and the Bronnikov NLED model—and calculate the weak deflection angle of light and charged particles by these two black holes with the help of the Gauss-Bonnet theorem. We investigate the effects of the one-loop corrections to quantum electrodynamics on the deflection angle and analyze the behavior of the deflection angle by a regular magnetically charged black hole. It is found that both the electric and magnetic charges of the black hole reduce the weak deflection angle, and the one-loop corrections make a positive contribution to the deflection angle, but their influence is deeply suppressed by the impact parameter. For the charged particles, due to electrostatic interaction, the weak deflection angle changes noticeably and the influence of the one-loop corrections is enhanced. We find that the regular magnetically charged black hole based on the Bronnikov NLED model has a smaller deflection angle than the singular one. We also calculate the deflection angle of light by the geodesic method for verification. In addition, we discuss the effects of a cold nonmagnetized plasma on the deflection angle and find that the deflection angle increases with the plasma parameter.

Time-dependent spherically symmetric perturbations of Schwarzschild black holes are studied within torsion bigravity, i.e., within generalized Einstein-Cartan theories where the dynamical torsion carries massive spin-2 excitation. We reduce linearized perturbations to a Zerilli-like equation. The structure of the potential entering the latter Zerilli-like equation has two important consequences. First, in order to avoid the presence of singularities in generic perturbations, one must restrict the range (or inverse mass) of the spin-2 excitation to be (essentially) smaller than the radius of the considered black hole. Second, we then show that the Schwarzschild black hole is linearly stable against spherically symmetric perturbations.

In the context of black hole chemistry (BHC), holographic phase transitions of asymptotically anti–de Sitter (AdS) charged topological black holes (TBHs) in massive gravity coupled to power Maxwell invariant (PMI) electrodynamics are discussed in the grand canonical (fixed $U(1)$ potential, $\mathrm{\Phi }$) ensemble. Considering the higher-order of graviton’s self-interactions of (dRGT) massive gravitational field theory in arbitrary dimensions, we derive exact TBH solutions. We also calculate the explicit form of the on-shell action and the associated thermodynamic quantities in the grand canonical ensemble (GCE). Besides, we examine the validity of the first law of thermodynamics and Smarr relation in the extended phase space thermodynamics. Regarding this model, we show that (a) a van der Waals (vdW) behavior takes place in $d\ge 4$ dimensions, (b) a typical reentrant phase transition can happen in $d\ge 5$, and (c) both anomalous vdW and triple point phenomena are recognized in $d\ge 6$. Accordingly, we find that the obtained results are quite different from their counterparts in the GCE of Maxwell-massive gravity. Furthermore, we briefly study the critical behaviors of higher-dimensional TBHs with a conformally invariant Maxwell source as a specific subclass of our solutions for Einstein’s theory and the massive gravity in various ensembles.

The axion, motivated as a solution to the strong $CP$ problem, is also a viable dark matter candidate. The axion field takes random values in causally disconnected regions if the symmetry breaking that establishes the particle occurs after inflation, leading to white-noise density fluctuations at low wave numbers and forming dense minihalos with sub-planetary masses subsequently. There have been two recent proposals that appear capable of testing this scenario, namely using pulsar timing arrays and studying cosmological microlensing caustics. Motivated by these proposals, we use N-body simulations to study the formation of substructures from white-noise density fluctuations. The density profiles of our relaxed axion minihalos can be described by the Navarro-Frenk-White profile, and the minihalos’ concentration number agrees well with a simple, physically-motivated model. We develop a semianalytic formula to fit the mass function from our simulation, which agrees broadly at different redshifts and only differs at factor of two level from classic halo mass functions. This analytic mass function allows us to consider uncertainties in the post-inflation axion scenario, as well as extrapolate our high-redshift simulations results to the present. Our work estimates the present-day abundance of axion substructures, as is necessary for predicting their effect on cosmological microlensing caustics and pulsar timing. Our calculations suggest that if pulsar timing and microlensing probes can reach recent sensitivity forecasts, they may be sensitive to the post-inflation axion dark matter scenario, even when accounting for uncertainties pertaining to axion strings. For pulsar timing, the most significant caveat is whether axion minihalos are disrupted by stars, which our estimates show is mildly important at the most relevant masses. Finally, as our gravitational simulations are scale invariant, the results can be extended to models where the dark matter is comprised of other axion-like particles and even clusters of primordial black holes.

Dark energy (DE) plays an important role in the expansion history of our Universe. But we only got limited knowledge about its nature and properties after decades of study. In most numerical researches, DE is usually considered as a dynamical whole. Actually, multicomponent DE models can also explain the accelerating expansion of our Universe, which is accepted theoretically but lack numerical researches. We try to study the multicomponent DE models from observation by constructing $w_n\mathrm{CDM}$ models. The total energy density of DE is separated into $n$ ($n=2$, 3, 5) parts equally and every part has a constant equation of state $w_i$ ($i=1,2...n$). We modify the Friedmann equation and the parametrized post-Friedmann description of DE, then put constraints on $w_i\mathrm{s}$ from Planck 2018 $\mathrm{TT},\mathrm{TE},\mathrm{EE}+\mathrm{lo}\mathrm{wE}+\mathrm{lensing}$, BAO data, and PANTHEON samples. The multicomponent DE models are favored if any $w_n\mathrm{CDM}$ model is preferred by observational data and there is no overlap between the highest and lowest values of $w_i\mathrm{s}$. We find the data combination supports the $w_n\mathrm{CDM}$ model when $n$ is small and the $w_2\mathrm{CDM}$ model is slightly preferred by $\mathrm{\Delta }{\chi }_{\min }^2=\mathrm{\Delta }\text{Akaike information criterion}(\text{AIC})=\mathrm{\Delta }\text{Bayesian information criterion}=-2.48$ over the Chevallier-Polarski-Linder (CPL) model, but the largest value of $w_i$ overlaps the smallest one. With larger $n$, the maximum and minimum of $w_i\mathrm{s}$ do not overlap with each other, but ${\chi }_{\min }^2$ and AIC also increase. In brief, we find no obvious evidence that DE is composed of different components.

We present the first numerical solutions of the causal, stable relativistic Navier-Stokes equations as formulated by Bemfica, Disconzi, Noronha, and Kovtun (BDNK). For this initial investigation we restrict to plane-symmetric configurations of a conformal fluid in Minkowski spacetime. We consider evolution of three classes of initial data: a smooth (initially) stationary concentration of energy, a standard shock tube setup, and a smooth shockwave setup. We compare these solutions to those obtained with a code based on the Müller-Israel-Stewart (MIS) formalism, variants of which are the common tools used today to model relativistic, viscous fluids. We find that for the two smooth initial data cases, simple finite difference methods are adequate to obtain stable, convergent solutions to the BDNK equations. For low viscosity, the MIS and BDNK evolutions show good agreement. At high viscosity the solutions begin to differ in regions with large gradients, and there the BDNK solutions can (as expected) exhibit violation of the weak energy condition. This behavior is transient, and the solutions evolve toward a hydrodynamic regime in a way reminiscent of an approach to a universal attractor. For the shockwave problem, we give evidence that if a hydrodynamic frame is chosen so that the maximum characteristic speed of the BDNK system is the speed of light (or larger), arbitrarily strong shockwaves are smoothly resolved. Regarding the shock tube problem, it is unclear whether discontinuous initial data is mathematically well-posed for the BDNK system, even in a weak sense. Nevertheless we attempt numerical solution, and then need to treat the perfect fluid terms using high-resolution shock-capturing (HRSC) methods. When such methods can successfully evolve the solution beyond the initial time, subsequent evolution agrees with corresponding MIS solutions, as well as the perfect fluid solution in the limit of zero viscosity.

The coherent WaveBurst (cWB) search algorithm identifies generic gravitational wave (GW) signals in the LIGO-Virgo strain data. We propose a machine learning (ML) method to optimize the pipeline sensitivity to the special class of GW signals known as binary black hole (BBH) mergers. Here, we test the ML-enhanced cWB search on strain data from the first and second observing runs of Advanced LIGO and successfully recover all BBH events previously reported by cWB, with higher significance. For simulated events found with a false alarm rate less than $1{\mathrm{yr}}^{-1}$, we demonstrate the improvement in the detection efficiency of 26% for stellar-mass BBH mergers and 16% for intermediate mass black hole binary mergers. To demonstrate the robustness of the ML-enhanced search for the detection of generic BBH signals, we show that it has the increased sensitivity to the spin precessing or eccentric BBH events, even when trained on simulated quasicircular BBH events with aligned spins.

Galactic cosmic rays (CRs) inside the heliosphere are affected by solar modulation. To investigate this phenomenon and its underlying physical mechanisms, we have performed a data-driven analysis of the temporal dependence of the CR proton flux over the solar cycle. The modulation effect was modeled by means of stochastic simulations of cosmic particles in the heliosphere. The model was constrained using measurements of CR protons made by AMS-02 and PAMELA experiments on a monthly basis from 2006 to 2017. With a global statistical analysis of these data, we have determined the key model parameters governing CR diffusion, its dependence on the particle rigidity, and its evolution over the solar cycle. Our results span over epochs of solar minimum and solar maximum, as well as epochs with magnetic reversal and opposite polarities. Along with the evolution of the CR transport parameters, we study their relationship with solar activity proxies and interplanetary parameters. We find that the rigidity dependence of the parallel mean free path of CR diffusion shows a remarkable time dependence, indicating a long-term variability in the interplanetary turbulence that interchanges across different regimes over the solar cycle. The evolution of the diffusion parameters shows a delayed correlation with solar activity proxies, reflecting the dynamics of the heliospheric plasma, and distinct dependencies for opposite states of magnetic polarity, reflecting the influence of charge-sign-dependent drift in the CR modulation.

We present measurements of the $E$-mode ($EE$) polarization power spectrum and temperature-$E$-mode ($TE$) cross-power spectrum of the cosmic microwave background using data collected by SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a $1500{\mathrm{deg}}^2$ region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the $EE$ and $TE$ power spectra over the angular multipole range $300\le \ell <3000$, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges $300\le \ell \le 1400$ for $EE$ and $300\le \ell \le 1700$ for $TE$, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G data set is well fit by a $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find $H_0=68.8\pm 1.5\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ and ${\sigma }_8=0.789\pm 0.016$, with a gravitational lensing amplitude consistent with the $\mathrm{\Lambda }\mathrm{CDM}$ prediction ($A_L=0.98\pm 0.12$). We combine the SPT-3G and the Planck data sets and obtain joint constraints on the $\mathrm{\Lambda }\mathrm{CDM}$ model. The volume of the 68% confidence region in six-dimensional $\mathrm{\Lambda }\mathrm{CDM}$ parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with no significant shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.

Pair production in inhomogeneous electric fields with symmetrical frequency chirp is studied numerically using the Dirac-Heisenberg-Wigner formalism. We investigate high- and low-frequency modes and consider two carrier envelope phases. Momentum spectrum is sensitive to chirp causing different interference effect for different spatial scales as well as the carrier phase of the external field. The reduced particle number is in general enhanced with increasing chirp. The effect of spatial scale of the field on the reduced particle number is also examined. It is found that it is enhanced at small spatial scale but is almost unchangeable at large spatial scales for the considered field parameters. On the other hand, at small spatial scale, the reduced particle number is enhanced by one or two orders when chirp is applied with the exception of cosine low-frequency field which is only a few times larger. Moreover it is found that the reduced particle number is further increased by symmetrical chirp at about two times by comparing to the usual asymmetrical chirp in high frequency field.

Singlino-dominated dark matter properties are investigated in the $Z_3$ next-to-minimal supersymmetric Standard Model, producing superweak interactions with nucleons involved in dark matter direct-detection experiments. Approximate analytical formulas describing the dark matter abundance and cross section in the scattering with nucleons are used to illustrate a dependence on theoretical parameters in the neutralino and Higgs sectors. It is shown that the measured abundance requires a sizable singlet-doublet Higgs coupling parameter $\lambda$, while the experimental detection results prefer a small $\lambda$. The parameter space is then surveyed using a nest sampling technique guided by a likelihood function containing various observables in dark matter, Higgs, and $B$ physics, such as the abundance and the scattering cross section. It is demonstrated that dark matter can achieve the correct abundance through ${\tilde{\chi }}_1^0{\tilde{\chi }}_1^0\to t\overline{t}$ or coannihilation with Higgsinos. The former process provides significantly larger Bayesian evidence than the latter, but this will be examined by the near-future PandaX-4T experiment. If the experiment shows no signs of dark matter, it will become highly disfavored. Furthermore, four cases are summarized to suppress dark matter scattering with nucleons, namely, a small $\lambda$ and three kinds of cancellation between different contributions.

We present the reweighting of two sets of nuclear parton distribution functions (PDFs), nCTEQ15 and EPPS16, using a selection of experimental data on heavy-flavor meson [$D^0$, $J/\psi$, $B\to J/\psi$ and $\mathrm{\Upsilon }(1S)$] production in proton-lead collisions at the LHC which were not used in the original determination of these nuclear PDFs. The reweighted PDFs exhibit significantly smaller uncertainties thanks to these new heavy-flavor constraints. We present a comparison with another selection of data from the LHC and relativistic heavy ion collider (RHIC) which were not included in our reweighting procedure. The comparison is overall very good and serves as a validation of these reweighted nuclear PDF sets, which we dub $\mathrm{nCTEQ}{15}_{\mathrm{rwHF}}$ and $\mathrm{EPPS}{16}_{\mathrm{rwHF}}$. This indicates that the LHC and forward RHIC heavy-flavor data can be described within the standard collinear factorization framework with the same (universal) small-$x$ gluon distribution. We discuss how we believe such reweighted PDFs should be used as well as the limitations of our procedure.

The assumption that the Standard Model is an effective field theory (SM EFT) of a more fundamental theory at a higher (than electroweak) energy scale implies a growth of cross sections for electroweak vector-boson scattering (VBS) processes signaling the appearance of a resonance (or resonances) near that scale. In this article, we investigate in detail SM EFT effects from dimension-six operators in VBS with like-sign-$W$ production in fully leptonic decay modes at the high-luminosity LHC (HL-LHC). We find that these effects are important for a handful of operators, most notably for the operator composed of three $SU(2)$ field-strength tensors responsible for strong transversely polarized vector-boson interactions. Current global fits on Wilson coefficients allow for an observable signal at the HL-LHC, if not accessible with the current LHC data set.

Saturation of the nuclear binding energy is one of the most important properties of atomic nuclei. We derive the saturation in holographic QCD, by building a shell-model-like mean-field nuclear potential from the nuclear density profile obtained in a holographic multibaryon effective theory. The numerically estimated binding energy is close to the experimental value.

Making use of the gauge/string duality, it is possible to study some aspects of the string breaking phenomenon in the three-quark system. Our results point out that the string breaking distance is not universal and depends on quark geometry. The estimates of the ratio of the string breaking distance in the three-quark system to that in the quark-antiquark system would range approximately from $\frac{2}{3}$ to 1. In addition, it is shown that there are special geometries which allow more than one breaking distance.

Noncommutative geometry provides both a unified description of the Standard Model of particle physics together with Einstein-Hilbert action (in Euclidean signature) and some tools to go beyond the Standard Model. In this paper, we extend to the full noncommutative geometry of the Standard Model the twist (in the sense of Connes-Moscovici) initially worked out for the electroweak sector and the free Dirac operator only. Namely, we apply the twist also to the strong interaction sector and the finite part of the Dirac operator. To do so, we are forced to take into account a violation of the twisted first-order condition. As a result, we still obtain the extra scalar field required to stabilize the electroweak vacuum and fit the Higgs mass, but it now has two chiral components. We also get the additive field of 1-forms already pointed out in the electroweak model, but with a richer structure. Finally, we obtain a pair of Higgs doublets, which are expected to combine into a single Higgs doublet in the action formula, as will be investigated in the second part of this work.

Mass generation of gauge fields can be universally described by topological couplings in gapped systems, such as the Abelian Higgs model in ($3+1$) dimensions and the Maxwell-Chern-Simons theory in ($2+1$) dimensions. These systems also exhibit the spontaneous breaking of higher-form ${\mathbb{Z}}_k$ symmetries and topological orders for level $k\ge 2$. In this paper, we consider topological mass generation in gapless systems. As a paradigmatic example, we study the axion electrodynamics with level $k$ in ($3+1$) dimensions in background fields that hosts both gapped and gapless modes. We argue that the gapped mode is related to those in fully gapped systems in lower dimensions via dimensional reduction. We show that this system exhibits the spontaneous breaking of a higher-form ${\mathbb{Z}}_k$ symmetry despite the absence of the conventional topological order. In the case of the background magnetic field, we also derive the low-energy effective theory of the gapless mode with the quadratic dispersion relation and show that it satisfies the chiral anomaly matching.

We investigate the particle content of parity-preserving Weyl gauge theories of gravity (${\mathrm{WGT}}^{+}$) about a Minkowski background. Within a subset of the full theory, we use a systematic method previously presented by Lin et al. [Phys. Rev. D 99, 064001 (2019)] to determine 862 critical cases for which the parameter values in the action lead to changes of particle contents or additional gauge invariances. We find that 168 of these cases are free of ghosts and tachyons, provided the parameters satisfy certain conditions that we also determine. We further identify 40 of these cases that are also propagating power-counting renormalizable and determine the corresponding conditions on the parameters. Of these theories, 11 have only massless tordion propagating particles, 23 have only a massive tordion propagating mode, and 6 have both. We also repeat our analysis for ${\mathrm{WGT}}^{+}$ with vanishing torsion or curvature, respectively. We compare our findings with the very few previous results in the literature.

We show that the no-hair theorem for scalar-tensor theories with bimetric structure can be evaded. We find that hairy black hole solutions in the presence of an electric charge admit anti-de Sitter (AdS), flat or de Sitter asymptotics with spherical, flat, or hyperbolic base manifolds. Spherically symmetric, asymptotically flat black holes and asymptotically AdS configurations with any horizon topology are compatible with a regular scalar field on and outside the event horizon. The latter presents a rich thermodynamic behavior induced by the disformal factor that enters as a coupling parameter in the theory. In the grand canonical ensemble, there is an interplay of stability and first-order phase transitions between thermal AdS, the hairy black hole, and the Reissner-Nordström-AdS black hole, whose thermodynamic phase space resembles a solid-liquid-gas system, with an electric potential playing the role of pressure. In close analogy, there is a triple point where the three phases coexist, being equally probable.