Inelastic dark matter (iDM) is an interesting thermal DM scenario that can pose challenges for conventional detection methods. However, recent studies demonstrated that iDM coupled to a photon by electric or magnetic dipole moments can be effectively constrained by intensity frontier experiments using the displaced single-photon decay signature. In this work, we show that, by utilizing additional signatures for such models, the sensitivity reach can be increased towards the short-lived regime, $\gamma c\tau \sim O(1)\mathrm{m}$, which can occur in the region of the parameter space relevant to successful thermal freeze-out. These processes are secondary iDM production taking place by upscattering in front of the decay vessel and electron scattering. Additionally, we consider dimension-six scenarios of photon-coupled iDM—the anapole moment and the charge radius operator—where the leading decay of the heavier iDM state is ${\chi }_1\to {\chi }_0{e}^{+}{e}^{-}$, resulting in a naturally long-lived ${\chi }_1$. We find that the decays of ${\chi }_1$ at FASER2, MATHUSLA, and SHiP will constrain these models more effectively than the scattering signature considered for the elastic coupling case, while secondary production yields similar constraints as the scattering.

The nucleon isovector electromagnetic form factors are calculated up to next-to-next-to-leading order by combining relativistic chiral perturbation theory (ChPT) of pion, nucleon, and $\mathrm{\Delta }(1232)$ with dispersion theory. We specifically address the light-quark mass dependence of the form factors, achieving a good description of recent lattice QCD results over a range of $Q^2\lesssim 0.6{\mathrm{GeV}}^2$ and $M_{\pi }\lesssim 350\mathrm{MeV}$. For the Dirac form factor, the combination of ChPT and dispersion theory outperforms the pure dispersive and pure ChPT descriptions. For the Pauli form factor, the combined calculation leads to results comparable to the purely dispersive ones. The anomalous magnetic moment and the Dirac and Pauli radii are extracted.

We investigate the renormalization group flow of projectable Hořava gravity in ($3+1$) dimensions generated by marginal operators with respect to the Lifshitz scaling. The flow possesses a number of asymptotically free fixed points. We find a family of trajectories connecting one of these fixed points in the ultraviolet to the region of the parameter space where the kinetic term of the theory acquires the general relativistic form. The gravitational coupling exhibits nonmonotonic behavior along the flow, vanishing both in the ultraviolet and the infrared.

In the past two decades, one of the most puzzling phenomena discovered in hadron physics is that a nominal hadronic state can actually correspond to two poles on the complex energy plane. This phenomenon was first noticed for the $\mathrm{\Lambda }(1405)$, then for $K_1(1270)$, and to a lesser extent for $D_0^{*}(2300)$. In this Letter, we show explicitly how the two-pole structures emerge from the underlying universal chiral dynamics describing the coupled-channel interactions between heavy matter particles and pseudo-Nambu-Goldstone bosons. In particular, the fact that two poles appear in between the two dominant coupled channels can be attributed to the particular form of the leading order chiral potentials of the Weinberg-Tomozawa form. Their line shapes overlap with each other because the degeneracy of the two coupled channels is only broken by explicit chiral symmetry breaking of higher order. We predict that for light-quark (pion) masses heavier than their physical values (e.g., about 200 MeV in the $\mathrm{\Lambda }(1405)$ case studied), the lower pole becomes a virtual state, which can be easily verified by future lattice QCD simulations. Furthermore, we anticipate similar two-pole structures in other systems, such as the isopin $1/2$ $\overline{K}{\mathrm{\Sigma }}_c-\pi {\mathrm{\Xi }}_c^{\prime }$ coupled channel, which await for experimental discoveries.

We investigate the transport properties within a holographic model characterized by a novel gauge-axion coupling. A key innovation is the introduction of the direct coupling between axion fields, the antisymmetric tensor, and the gauge field in our bulk theory. This novel coupling term leads to the emergence of nondiagonal components in the conductivity tensor. An important characteristic is that the off-diagonal elements manifest antisymmetry. Remarkably, the conductivity behavior in this model akin to that of Hall conductivity. Additionally, this model can also achieve metal-insulator transition.

Decades of analytic and computational work have demonstrated that a charge immersed in a hot plasma is screened. For both Abelian and non-Abelian interactions, the characteristic screening length $1/m_D$ is set by the so-called Debye mass $m_D\sim g_{s}T$, proportional to the plasma temperature $T$ and the dimensionless gauge coupling $g_s$. One of the most interesting naturally occurring examples is the quark-gluon plasma (QGP) that filled the early universe prior to the QCD confinement phase transition at $t_{\mathrm{QCD}}\sim {10}^{-5}\mathrm{s}$. During this early epoch, regimes of strong spacetime curvature are of significant cosmological interest, such as near primordial black holes (PBHs). However, the typical description of Debye screening only applies within Minkowski spacetime and is therefore insufficient to describe the dynamics of charged plasmas near PBHs or other primordial features. We construct an effective field theory for soft modes of the gauge field $A_{\mu }^a$ to give a full description of Debye screening in non-Abelian plasmas within arbitrary curved spacetimes, recovering a temperature-dependent Debye mass that exhibits gravitational redshift. We then apply our results to some scenarios of cosmological interest: an expanding Friedmann-Lemaître-Robertson-Walker universe and the vicinity of a PBH immersed in a hot QGP.

Fifth forces are ubiquitous in modified theories of gravity. In this paper, we analyze their effect on the Cepheid-calibrated cosmic distance ladder, specifically with respect to the inferred value of the Hubble constant ($H_0$). We consider a variety of effective models where the strength, or amount of screening, of the fifth force is estimated using proxy fields related to the large-scale structure of the Universe. To quantify the level of tension between the local distance ladder and the Planck value for $H_0$, we calculate the probability of obtaining a test result at least as extreme as the observed one, assuming that the model is correct (the $p$-value). For all models considered, the level of agreement is $\gtrsim 20\%$, relieving the tension compared to the concordance model, exhibiting an agreement of only 1%. The alleviated discrepancy comes partially at the cost of an increased tension between distance estimates from Cepheids and the tip of the red-giant branch (TRGB). Demanding also that the consistency between Cepheid and TRGB distance estimates is not impaired, some fifth force models can still accommodate the data with a probability $\gtrsim 20\%$. This provides incentive for more detailed investigations of fundamental theories on which the effective models are based and their effect on the Hubble tension.

In this paper, we construct models that admit the traversable wormhole geometries in the framework of Einstein’s gravity with two scalar fields. As is well known, the energy conditions are broken, and we show that a ghost appears. The ghost can be, however, eliminated by imposing a constraint on the ghost field, which is a scalar. The constraint is similar to the mimetic one proposed by Chamseddine and Mukhanov to construct an alternative description of cold dark matter. We explicitly show that there does not appear to be any unstable mode although the energy conditions are broken. Therefore, we obtain a model that realizes the traversable and stable wormhole.

A massive spin-2 field can grow unstably around a black hole, giving rise to a potential probe of the existence of such fields. In this work, we use time-domain evolutions to study such instabilities. Considering the linear regime by solving the equations generically governing a massive tensor field on the background of a Kerr black hole, we find that black hole spin increases the growth rate and, most significantly, the mass range of the axisymmetric (azimuthal number $m=0$) instability, which takes the form of the Gregory-Laflamme black string instability for zero spin. We also consider the superradiant unstable modes with $1\le m\le 3$, extending previous results to higher spin-2 masses, black hole spins, and azimuthal numbers. We find that the superradiant modes grow slower than the $m=0$ modes, except for a narrow range of high spins and masses, with $m=1$ and 2 requiring a dimensionless black hole spin of $a_{\mathrm{BH}}\gtrsim 0.95$ to be dominant. Thus, in most of the parameter space, the backreaction of the $m=0$ instability must be taken into account when using black holes to constrain massive spin-2 fields. As a simple model of this, we consider nonlinear evolutions in quadratic gravity, in particular Einstein-Weyl gravity. We find that, depending on the initial perturbation, the black hole may approach zero mass with the curvature blowing up in finite time, or can saturate at a larger mass with a surrounding cloud of the ghost spin-2 field.

There are tens of millions of compact binary systems in the Milky Way, called galactic binaries (GBs), most of which are unresolved, and the gravitational waves (GWs) emitted overlap to form confusion foreground. By simulating such a confusion foreground, we have studied how LISA, Taiji and TianQin, including their alternative orbital configurations, subtract resolvable GBs when they combine as some networks. The results of our research indicate that the order of the detected number for a single detector from high to low is Taiji-m, Taiji-p (c), LISA, TianQin I, and TianQin II. For detector combinations on the network, the confusion foreground is effectively reduced as the number of detectors grows, and the optimal combinations with different numbers are Taiji-m, $\mathrm{LISA}+\mathrm{Taiji}\text{−}\mathrm{m}$, $\mathrm{LISA}+\mathrm{Taiji}\text{−}\mathrm{m}+\mathrm{TianQin}\mathrm{I}$, and $\mathrm{LISA}+\mathrm{Taiji}\text{−}\mathrm{m}+\mathrm{TianQin}\mathrm{I}+\text{II}$. The sensitivity curve is optimized as the number of detectors increases, which renders it possible to detect other gravitational-wave sources more precisely and decrease the resolvable GB parameter uncertainty. Based on this, we discuss the parameter uncertainty of resolvable GBs detected by the combinations above and find that GW detection can promote electromagnetic (EM) detection. On the contrary, we discovered that by utilizing EM detection, determining the inclination angle can reduce the uncertainty of GW strain amplitude by $\sim 93\%$, and determining the sky position can reduce the uncertainty of the phase by $\sim 30\%$, further strengthening the connection between GW detection and EM detection, and contributing to the research of multimessenger astronomy.

The Laser Interferometer Space Antenna (LISA) will play a vital role in constraining the origin and evolution of massive black holes throughout the Universe. In this study we use a waveform model (IMRPhenomXPHM) that includes both precession and higher multipoles, and full Bayesian inference to explore the accuracy to which LISA can constrain the binary parameters. We demonstrate that LISA will be able to track the evolution of the spins—magnitude and orientation—to percent accuracy, providing crucial information on the dynamics and evolution of massive black hole binaries and the galactic environment in which the merger takes place. Such accurate spin-tracking further allows LISA to measure the recoil velocity of the remnant black hole to better than $100\mathrm{km}{\mathrm{s}}^{-1}$ (90% credibility) and its direction to a few degrees, which provides additional important astrophysical information on the postmerger association. Using a suite of binaries at $z=3$ broadly consistent with astrophysical predictions, we showcase that the component masses will be measurable at the subpercent level, the sky area can be constrained to within $\mathrm{\Delta }{\mathrm{\Omega }}_{90}\approx 0.01{\mathrm{deg}}^2$, and the binary redshift to less than 0.01.

When an extreme-mass-ratio inspiral involving a nonintegrable gravitational field, such as a deformed Kerr black hole, undergoes a prolonged resonance, the frequencies that engage in resonance retain a fixed rational ratio, despite experiencing gradual changes due to radiation reaction. In the past this plateau effect in the evolution of the ratio of frequencies has been investigated by studying the orbital evolution through kludge models, which provide approximate average losses of energy and angular momentum experienced by a test particle in this field. By employing a Newtonian gravitational field that closely resembles a pure Kerr or a perturbed Kerr relativistic field, we demonstrate that the actual evolution of an orbit driven by artificial “self-force” results in more prolonged periods of resonance crossings compared to those obtained by imposing a predetermined rate of energy and angular momentum change throughout the orbital progression.

We perform general relativistic simulations of magnetized, accreting disks onto spinning black hole binaries with mass ratio $q\equiv M_{1,\mathrm{irr}}/M_{2,\mathrm{irr}}=1,2$ and 4. The magnitude of the individual dimensionless black hole spins are all $\chi =0.26$ and lie either along the initial orbital plane or 45° above it. We evolve these systems throughout the late inspiral, merger and postmerger phases to identify the impact of the black hole spins and the binary mass ratio on any jet and their electromagnetic (Poynting) signatures. We find that incipient jets are launched from both black holes regardless of the binary mass ratio and along the spin directions as long as the force-free parameter $B^2/(8\pi {\rho }_0)$ in the funnel and above their poles is larger than one. At large distances the two jets merge into a single one. This effect may prevent the electromagnetic detection of individual jets. As the accretion rate reaches a quasistationary state during the late predecoupling phase, we observe a sudden amplification of the outgoing Poynting luminosity that depends on the binary mass ratio. Following the merger, the sudden change in the direction of the spin of the black hole remnant with respect to the spins of its progenitors causes a reorientation of the jet. The remnant jet drives a single, high-velocity, outward narrow beam collimated by a tightly wound, helical magnetic field which, in turn, boosts the Poynting luminosity. This effect is nearly mass-ratio independent. During this process, a kink is produced in the magnetic field lines, confining the jet. The kink propagates along the jet but rapidly decays, leaving no memory of the spin shift. These results suggest that the merger of misaligned, low-spinning, black hole binary mergers in low-mass disks does not necessarily provide a viable scenario to explain x-shaped radio galaxies if other features are not taken into account. However, the sudden changes in the outgoing luminosity at the merger may help to identify mergers of black holes in active galactic nuclei, shedding light on black hole growth mechanisms and the observed co-evolution of their host galaxies.

Pulsar timing arrays (PTAs) are expected to be able to detect gravitational waves (GWs) from individual supermassive black hole binaries in the near future. In order to identify the host galaxy of a gravitational wave source, the angular resolution of PTAs should be much better than that expected from the conventional methodology of PTAs. We study the potential usefulness of precise pulsar-distance measurements in the determination of the sky location of a single GW source. Precise distance information from external observations such as astrometry by very long baseline interferometry is incorporated as priors in the PTA analysis and we evaluate the precision of the sky location of a GW source by simulating PTA data of 12 milli-second pulsars with only the GW signal and the Gaussian white noise in the timing residuals. We show that only a few pulsars with a distance precision of 1 pc will improve the precision of the source location by more than 1 order in the presence of white noise of 10 ns.

We study the nonlinear effects of minimally coupled, massless, cosmological scalar fields on the cosmic microwave background (CMB). These fields can exhibit postrecombination parametric resonance and subsequent nonlinear evolution leading to novel contributions to the gravitational potential. We compute the resulting contributions to the CMB temperature anisotropies through the time variation of the gravitational potential (i.e., the integrated Sachs-Wolfe (ISW) effect). We find that fields that constitute 5% of the total energy density and become dynamical at $z_c\simeq {10}^4$ can produce marginally observable ISW signals at multipoles $\ell \simeq 2000$. Fields that become dynamical at earlier times and/or have initial displacements at a flatter part of their potential, produce ISW contributions that are significantly larger and at higher multipoles. We calculate these dynamics and the resulting evolution of gravitational perturbations using analytic estimates alongside detailed nonlinear lattice simulations, which couple scalar fields and cosmological fluids to a perturbed metric. Finally, we discuss the possibility of detecting these features with future high-resolution CMB observations.

We decompose $\mathrm{Pantheon}+$ Type Ia supernovae (SN) in hemispheres on the sky finding angular variations up to $4\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, corresponding to a statistical significance up to $1.9\sigma$, in the Hubble constant $H_0$ both in the SH0ES redshift range $0.0233<z<0.15$ and in extended redshift ranges. The variations are driven largely by variations in absolute magnitude from SN in Cepheid hosts but are reinforced by SN in the Hubble flow. $H_0$ is larger in a hemisphere encompassing the CMB dipole direction. The variations we see exceed the errors on the recent SH0ES determination, $H_0=73.04\pm 1.04\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, but are not large enough to explain early versus late Universe discrepancies in the Hubble constant. Nevertheless, the Cepheid-SN distance ladder is anisotropic at current precision. The anisotropy may be due to a breakdown in the cosmological principle, or mundanely due to a statistical fluctuation in a small sample of SN in Cepheid host galaxies.

Pulsar timing array collaborations have recently announced the discovery of a stochastic gravitational wave (GW) background at nanohertz frequencies. We analyze the GW signals from the domination of ultralow mass primordial black holes (PBHs) in the early Universe and show that they can explain this recent discovery. This scenario requires a relatively broad peak in the power spectrum of scalar perturbations from inflation with a spectral index in a narrow range of 1.45–1.6. The resulting PBH population would have mass around ${10}^8\mathrm{g}$, and the initial abundance ${\beta }_f$ lies between ${10}^{-10}$ and ${10}^{-9}$. We find that this explanation is preferred by the data over the generic model, assuming supermassive black holes as the source. These very light PBHs would decay before big bang nucleosynthesis; however, upcoming third-generation terrestrial laser interferometers would be able to test the model by observing the GW spectrum produced during the formation of the PBHs. Also, the scalar power spectra associated with our scenario will be within the reach of PIXIE probing cosmic microwave background spectral distortions.

The oscillating pressure of ultralight scalar dark matter (DM) can induce the oscillation of the local gravitational potential. Similarly to the time-dependent frequency shift for the pulse signals of pulsars, the oscillation of the local gravitational potential can induce a time-dependent frequency shift (or frequency modulation) for quasimonochromatic gravitational wave (GW) signals from Galactic white dwarf (WD) binaries. To make this effect detectable, we suppose that some Galactic WD binaries are located in DM clumps/subhalos where the energy density of DM is about 8 orders of magnitude higher than at the position of the Earth. Turning to the Fisher information matrix, we find that an amplified GW frequency modulation induced by ultralight scalar DM with a mass of $m=1.67\times {10}^{-23}–4.31\times {10}^{-23}\mathrm{eV}/c^2$ can be detected by LISA.

We consider the local physics of an open quantum system embedded in an expanding three-dimensional space $\mathbf{x}$, evolving in cosmological time $t$, weakly coupled to a massless quantum field. We derive the corresponding Markovian master equation for the system’s nonunitary evolution and show that, for a de Sitter space with Hubble parameter $h=\mathrm{const}$, the background fields act as a physical heat bath with temperature $T_{\mathrm{dS}}=h/2\pi$. The energy density of this bath obeys the Stefan-Boltzmann law ${\rho }_{\mathrm{dS}}\propto h^4$. We comment on how these results clarify the thermodynamics of de Sitter space and support previous arguments for its instability in the infrared. The cosmological implications are considered in an accompanying Letter.