The dark photon is a promising candidate for the dark matter which comprises most of the matter in our visible Universe. Via kinetic mixing with the Standard Model it can also be resonantly converted to photons in an electromagnetic cavity, offering novel experimental possibilities for the discovery and study of dark matter. We report the results of a pathfinder dark photon dark matter cavity search experiment performed at Hunan Normal University and the Institute of Physics, Chinese Academy of Sciences, representing the first stage of the Axion and dark Photon EXperiment program. Finding no statistically significant excess, we place an upper limit on the kinetic mixing parameter $|\chi |<3.7\times {10}^{-13}$ around $m_A\simeq 29.5\mathrm{\mu }\mathrm{eV}$ at 90% confidence level. This result exceeds other constraints on dark photon dark matter in this frequency range by roughly an order of magnitude.

This paper sets up a perturbative treatment of the evolving quantum state of a gravitational system, in a Schrödinger-like picture, working about a general background. This connects gauge symmetry, the constraints, gravitational dressing, and evolution. Starting with a general time slicing, we give a simple derivation of the relation between the constraints, the Hamiltonian, and its well-known boundary term. Among different approaches to quantization with constraints, we focus on a “gauge-invariant canonical quantization,” which is developed perturbatively in the gravitational coupling. The leading-order solution of the constraints (including the Wheeler-DeWitt equation) for perturbations about the background is given in terms of an explicit construction of gravitational dressings built using certain generalized Green’s functions; different such dressings corresponding to adding propagating gravitational waves to a particular solution of the constraints. Dressed operators commute with the constraints, expressing their gauge invariance, and have an algebraic structure differing significantly from the undressed operators of the underlying field theory. These operators can act on the vacuum to create dressed states, and evolution of general such states is then generated by the boundary Hamiltonian, and alternately may be characterized using other relational observables. This provides a concrete approach to studying perturbative time evolution, including the leading gravitational backreaction, of quantum states of black holes with flat or anti–de-Sitter asymptotics, for example on horizon-crossing slices. This description of evolution in turn provides a starting point for investigating possibly important corrections to quantum evolution, that go beyond quantized general relativity.

Feynman diagrams (notably the triangle diagram) involving heavy enough particles contain branch cuts on the physical sheet—anomalous thresholds—which, unlike normal thresholds and bound-state poles, do not correspond to any asymptotic $n$-particle state. “Who ordered that?” We show that anomalous thresholds arise as a consequence of established S-matrix principles and two reasonable assumptions: unitarity below the physical region and analyticity in the mass. We find explicit nonperturbative formulas for the anomalous threshold singularity and test them against the Coleman-Thun poles of the $E_8$ integrable model.

Remnants of binary black-hole mergers can gain significant recoil or kick velocities when the binaries are asymmetric. The kick is the consequence of the anisotropic emission of gravitational waves, which may leave a characteristic imprint in the observed signal. So far, only one gravitational-wave event supports a nonzero kick velocity: GW200129_065458. This signal is also the first to show evidence for spin precession. For most other gravitational-wave observations, spin orientations are poorly constrained as this would require large signal-to-noise ratios, unequal mass ratios, or inclined systems. Here we investigate whether the imprint of the kick can help to extract more information about the spins. We perform an injection and recovery study comparing binary black-hole signals with significantly different kick magnitudes, but the same spin magnitudes and spin tilts. To exclude the impact of higher signal harmonics in parameter estimation, we focus on equal-mass binaries that are oriented face-on. This is also motivated by the fact that equal-mass binaries produce the largest kicks and many observed gravitational-wave events are expected to be close to this configuration. We generate signals with imrphenomxo4a, which includes mode asymmetries. These asymmetries are the main cause for the kick in precessing binaries. For comparison with an equivalent model without asymmetries, we repeat the same injections with imrphenomxphm. We find that signals with large kicks necessarily include large asymmetries, and these give more structure to the signal, leading to more informative measurements of the spins and mass ratio. Our results also complement previous findings that argued precession in equal-mass, face-on, or face-away binaries is nearly impossible to identify. In contrast, we find that in the presence of a remnant kick, even those signals become more informative and allow determining precession with signal-to-noise ratios observable already by current gravitational-wave detectors.

The Rezzolla-Zhidenko (RZ) and Konoplya-Rezzolla-Zhidenko (KRZ) frameworks provide an efficient approach to characterize agnostically spherically symmetric or stationary black-hole spacetimes in arbitrary metric theories. In their original construction, these metrics were defined only in the spacetime region outside of the event horizon, where they can reproduce any black-hole metric with percent precision and a few parameters only. At the same time, numerical simulations of accreting black holes often require metric functions that are regular across the horizon, so that the inner boundary of the computational domain can be placed in a region that is causally disconnected from the exterior. We present a novel formulation of the RZ/KRZ parametrized metrics in coordinate systems that are regular at the horizon and defined everywhere in the interior. We compare the horizon-penetrating form of the KRZ and RZ metrics with the corresponding forms of the Kerr metric in Kerr-Schild coordinates and of the Schwarzschild metric in Eddington-Finkelstein coordinates, noting the similarities and differences. We expect the horizon-penetrating formulations of the RZ/KRZ metrics to represent new tools to study via simulations the physical processes that occur near the horizon of an arbitrary black hole.

Complete waveform models able to account for arbitrary nonplanar orbits represent a holy grail in current gravitational-wave astronomy. Here, we take a step toward this direction and present a simple yet efficient prescription to obtain the evolution of the spin vectors and of the orbital angular momentum along noncircularized orbits, that can be applied to any eccentric aligned-spins waveform model. The scheme employed is motivated by insights gained from the post-Newtonian (PN) regime. We investigate the phenomenology of the Euler angles characterizing the time-dependent rotation that connects the coprecessing frame to the inertial one, gauging the importance of noncircular terms in the evolution of the spins of a precessing binary. We demonstrate that such terms are largely negligible, irrespectively of the details of the orbit. Such insights are confirmed by studying the radiation-frame of a few eccentric, precessing numerical relativity (NR) simulations. Our investigations confirm that the usual “twisting” technique employed for quasispherical systems can be safely applied to noncircularized binaries. By then augmenting a state-of-the-art effective-one-body (EOB) model for noncircular planar orbits with the prescription discussed, we obtain an inspiral-merger-ringdown (IMR) model for eccentric, precessing binary black holes (BBHs). We validate the model in the quasispherical limit via mismatches and present one phasing comparison against a precessing, eccentric simulation from the RIT catalog.

We present several high-accuracy surrogate models for gravitational-wave signals from equal-mass head-on mergers of Proca stars, computed through the Newman-Penrose scalar ${\psi }_4$. We also discuss the current state of the model extensions to mergers of Proca stars with different masses, and the particular challenges that these present. The models are divided in two main categories: two-stage and monolithic. In the two-stage models, a dimensional reduction algorithm is applied to embed the data in a reduced feature space, which is then interpolated in terms of the physical parameters. For the monolithic models, a single neural network is trained to predict the waveform from the input physical parameter. Our model displays mismatches below ${10}^{-3}$ with respect to the original numerical waveforms. Finally, we demonstrate the usage of our model in full Bayesian parameter inference through the accurate recovery of numerical relativity signals injected in zero noise, together with the analysis of GW190521. For the latter, we observe excellent agreement with existing results that make use of full numerical relativity.

We explore the asymptotic future evolution of holographic dark energy (HDE) models, in which the density of the dark energy is a function of a cutoff scale $L$. We develop a general methodology to determine which models correspond to future big rip, little rip, and pseudo rip (de Sitter) evolution, and we apply this methodology to a variety of well-studied HDE models. None of these HDE models display little rip evolution, and we are able to show, under very general assumptions, that HDE models with a Granda-Oliveros cutoff almost never evolve toward a future little rip. We extend these results to HDE models with nonstandard Friedman equations and show that a similar conclusion applies: little rip evolution is a very special case that is almost never realized in such models.

A model of baryogenesis is introduced where our usual visible Universe is a 3-brane coevolving with a hidden 3-brane in a multidimensional bulk. The visible matter and antimatter sectors are naturally coupled with the hidden matter and antimatter sectors, breaking the C/CP invariance and leading to baryogenesis occurring after the quark-gluon era. The issue of leptogenesis is also discussed. The symmetry breaking spontaneously occurs due to the presence of an extra scalar field supported by the $U(1)\otimes U(1)$ gauge group, which extends the conventional electromagnetic gauge field in the two-brane universe. Observational consequences are discussed.

In this work, we investigate the physical aspects of the inflection-point inflation scenario and assess its observational viability in light of current cosmic microwave background (CMB) data. The model we consider encapsulates the inflaton with a pseudoscalar (the dark matter candidate) in a complex neutral scalar singlet. The cosmological constraints on the parameters of inflation derived at a high-energy scale are translated to a low-energy scale by running these parameters. Ensuring the entire Lagrangian to be invariant under a $Z_3$ symmetry with the adequate transformation of the fields, the imaginary part of the singlet decouples from the other scalars of the model. We then investigate if the observational viability of inflation is also compatible with this pseudoscalar being the dark matter component. We show that the CMB constraints on the inflationary parameters assure that the pseudoscalar is stable and provides the correct relic dark matter abundance only when the pseudoscalar is thermally produced.

We investigate the evolution of supermassive black hole (SMBH) binaries and the possibility that their merger is facilitated by ultralight dark matter (ULDM). When ULDM is the main dark matter (DM) constituent of a galaxy, its wave nature enables the formation of massive quasiparticles throughout the galactic halo. Here we show that individual encounters between quasiparticles and a SMBH binary can lead to the efficient extraction of energy and angular momentum from the binary. The relatively short coherence time of ULDM provides a steady-state population of massive quasiparticles, and consequently a potential solution to the final parsec problem. Furthermore, we demonstrate that, in the presence of stars, ULDM quasiparticles can also act as massive perturbers to enhance the stellar relaxation rate locally, replenish the stellar loss cone efficiently, and consequently resolve the final parsec problem.

We systematically study the observable properties of dark-matter admixed neutron stars with arbitrary dark-matter fraction, employing a realistic nuclear equation of state in combination with self-interacting fermionic dark matter respecting constraints on the self-interaction cross section. Deviations from universal relations valid for nucleonic neutron stars are analyzed over the whole parameter space of the model and unequivocal signals for the presence of dark matter in neutron stars are identified.

Analytical models of magnetized, geometrically thick disks are relevant to understand the physical conditions of plasma around compact objects and to explore its emitting properties. This has become increasingly important in recent years in the light of the Event Horizon Telescope observations of Sgr ${\mathrm{A}}^{*}$ and M87. Models of thick disks around black holes usually consider constant angular momentum distributions and do not take into account the magnetic response of the fluid to applied magnetic fields. We present a generalization of our previous work on stationary models of magnetized accretion disks with magnetic polarization [, Astron. Astrophys. 619, A57 (2018)]. This extension is achieved by accounting for nonconstant specific angular momentum profiles, done through a two-parameter ansatz for those distributions. We build a large number of new equilibrium solutions of thick disks with magnetic polarization around Kerr black holes, selecting suitable parameter values within the intrinsically substantial parameter space of the models. We study the morphology and the physical properties of those solutions, finding qualitative changes with respect to the constant angular momentum tori solutions [, Astron. Astrophys. 619, A57 (2018)]. However, the dependencies found on the angular momentum distribution or on the black hole spin do not seem to be strong. Some of the new solutions, however, exhibit a local maximum of the magnetization function, absent in standard magnetized tori. Due to the enhanced development of the magnetorotational instability as a result of magnetic susceptibility, those models might be particularly well-suited to investigate jet formation through general relativistic magnetohydronamical simulations. The new equilibrium solutions reported here can be used as initial data in numerical codes to assess the impact of magnetic susceptibility in the dynamics and observational properties of black hole–thick disk systems.

Bosonic fields (within suitable mass range) may be collectively generated by rotating black holes through the black hole superradiance process. The resulting black hole is surrounded by a “cloud” of particles whose wave function populates the superradiant energy level of the black hole. For comparable mass ratio binary black hole systems, it has been suggested that these clouds often deplete at large binary separations because of level mixing effects. As a result, these clouds may not be dynamically relevant for black hole and neutron star binaries that enter the LIGO-Virgo-KAGRA and LISA detection frequency band. In this work, we point out that the common envelope process during a compact binary evolution may bring the binary to $\sim 0.01\mathrm{AU}$ in hundreds to thousands of years, so that depletion caused by certain level mixings are no longer important. We derive a relevant regime of binary parameters where the clouds are still present for binary entering the LISA band, and show that common envelope process does enlarge such parameter regime. When the binary separation further decreases due to gravitational wave radiation, we discuss the impact of possible cloud mass transfer between the binary objects.

High-frequency gravitational waves (HFGWs) are predicted in various exotic scenarios involving both cosmological and astrophysical sources. These elusive signals have recently sparked the interest of a diverse community of researchers, due to the possibility of HFGW detection in the laboratory through graviton-photon conversion in strong magnetic fields. Notable examples include the redesign of the resonant cavities currently under development to detect the cosmic axion. In this work, we derive the sensitivities of some existing and planned resonant cavities to detect a HFGW background. As a concrete scenario, we consider the collective signals that originate from the merging of compact objects, such as two primordial black holes (PBHs) in the asteroid mass window. Our findings improve over existing work by explicitly discussing and quantifying the loss in the experimental reach due to the actual coherence of the source. We elucidate on the approach we adopt in relation with recent literature on the topic. Most notably, we give a recipe for the estimate of the stochastic background that focuses on the presence of the signal in the cavity at all times and showing that, in the relevant PBH mass region, the signal is dominated by coherent binary mergers.

Simulating realistic time-domain observations of gravitational waves (GWs) and other events of interest in GW detectors, such as transient noise bursts called glitches, can help in advancing GW data analysis. Simulated data can be used in downstream data analysis tasks by augmenting datasets for signal searches, balancing datasets for machine learning applications, validating detection schemes, and constructing mock data challenges. In this work, we present a conditional derivative GAN (cDVGAN), a novel conditional model in the generative adversarial network framework for simulating multiple classes of time-domain observations that represent gravitational waves (GWs) and detector glitches. cDVGAN can also generate generalized hybrid samples that span the variation between classes through class interpolation in the conditioned class vector. cDVGAN introduces an additional player into the typical 2-player adversarial game of GANs, where an auxiliary discriminator analyzes the first-order derivative time series. Our results show that this provides synthetic data that better capture the features of the original data. cDVGAN conditions on three classes in the time domain, two denoized from LIGO blip and tomte glitch events from its third observing run (O3), and the third representing binary black hole (BBH) mergers. Our proposed cDVGAN outperforms four different baseline GAN models in replicating the features of the three classes. Specifically, our experiments show that training convolutional neural networks (CNNs) with our cDVGAN-generated data improves the detection of samples embedded in detector noise beyond the synthetic data from other state-of-the-art GAN models. Our best synthetic dataset yields as much as a 4.2% increase in area-under-the-curve (AUC) performance, maintaining the same CNN architecture, compared to synthetic datasets from baseline GANs. Moreover, training the CNN with class-interpolated hybrid samples from our cDVGAN outperforms CNNs trained only on the standard classes, when identifying real samples embedded in LIGO detector background between signal-to-noise ratios ranging from 1 to 16 (4% AUC improvement for cDVGAN). We also illustrate an application of cDVGAN in a data augmentation example, showing that it is competitive with a traditional augmentation approach. Lastly, we test cDVGAN’s BBH signals in a fitting-factor study, showing that the synthetic signals are generally consistent with the semianalytical model used to generate the training signals and the corresponding parameter space.

We present first-order models for tilt-to-length (TTL) coupling in Laser Interferometer Space Antenna (LISA), both for the individual interferometers, as well as in the time-delay interferometry (TDI) Michelson observables. These models include the noise contributions from angular and lateral jitter coupling of the six test masses, six movable optical subassemblies, and three spacecraft. We briefly discuss which terms are considered to be dominant and reduce the TTL model for the second-generation TDI Michelson X observable to these primary noise contributions to estimate the resulting noise level. We show that the expected TTL noise will initially violate the entire mission displacement noise budget, resulting in the known necessity to fit and subtract TTL noise in data postprocessing. By comparing the noise levels for different assumptions prior to subtraction, we show why noise mitigation by realignment prior to subtraction is favorable. We then discuss that the TTL coupling in the individual interferometers will have noise contributions that will not be present in the TDI observables. Models for TTL coupling noise in TDI and in the individual interferometers are therefore different, and commonly made assumptions are valid as such only for TDI, but not for the individual interferometers. Finally, we analyze what implications can be drawn from the presented models for the subsequent fit-and-subtraction in postprocessing. We show that noise contributions from the test mass and intersatellite interferometers are indistinguishable, such that only the combined coefficients can be fit and used for subtraction. However, a distinction is considered not necessary. Additionally, we show a correlation between coefficients for transmitter and receiver jitter couplings in each individual TDI Michelson observable. This full correlation, however, can be resolved by using all three Michelson observables for fitting the TTL coefficients.

With the continuous accumulation of data from hadron collision experiments, efficient partial wave analysis tools are indispensable for constructing a clear hadron spectrum. Currently, automated computations of scattering amplitudes primarily use the helicity scheme and covariant effective Lagrangian method. The automated calculations under the covariant $L\text{−}S$ scheme, which is one of the commonly used partial wave analysis schemes, have not been fully realized. In this work, we provide a general algorithm for computing partial wave amplitudes under the covariant $L\text{−}S$ scheme. This will lay the foundation for automated computation of partial wave amplitudes under the covariant $L\text{−}S$ scheme.

We analyze the influence of a massive photon in the dispersive interaction between two atoms in their fundamental states. We work in the context of Proca quantum electrodynamics. The photon mass not only introduces a new length scale but also gives rise to a longitudinal polarization for the electromagnetic field. We obtain explicitly the interaction energy between the atoms for any distance regime and consider several particular cases. We show that, for a given interatomic distance, the greater the photon mass the better it is the nonretarded approximation.