Rotations of axion fields in the early Universe can produce dark matter and the matter-antimatter asymmetry of the Universe. We point out that the rotation can generate an observable amount of a stochastic gravitational wave (GW) background. It can be doubly enhanced in a class of models in which the equation of state of the rotations rapidly changes from a nonrelativistic matterlike one to a kinationlike one by (1) the so-called poltergeist mechanism and (2) slower redshift of GWs compared to the axion-kination fluid. In supersymmetric UV completion, future GW observations can probe the supersymmetry-breaking scale up to ${10}^7\mathrm{GeV}$ even if the axion does not directly couple to the Standard Model fields.

The thermodynamics of rigidly rotating systems experience divergences when the system dimensions transverse to the rotation axis exceed the critical size imposed by the causality constraint. The rotation with imaginary angular frequency, suitable for numerical lattice simulations in Euclidean imaginary-time formalism, experiences fractalization of thermodynamics in the thermodynamic limit, when the system’s pressure becomes a fractal function of the rotation frequency. Our work connects these two phenomena by studying how thermodynamics fractalizes as the system size grows. We examine an analytically accessible system of rotating massless scalar matter on a one-dimensional ring and the numerically treatable case of rotation in the cylindrical geometry and show how the ninionic deformation of statistics emerges in these systems. We discuss a no-go theorem on analytical continuation between real and imaginary rotating theories. Finally, we compute the moment of inertia and shape deformation coefficients caused by the rotation of the relativistic bosonic gas. In all cases, we show that finite-mass effects are quantitative, leaving our conclusions qualitatively unchanged.

Gravitational lensing properties of supermassive astrophysical objects, such as black holes and wormholes, provide a realistic way for their discovering and investigating. Various lensing effects in a wormhole spacetime have been widely studied in the literature. One of the most popular objects for investigation is the Ellis wormhole which represents the simplest wormhole geometry. The Ellis solution represents only a special case of a general wormhole solution found independently by Ellis and Bronnikov. Surprisingly but gravitational lensing properties of general Ellis-Bronnikov wormholes are practically not investigated. In this paper we explore in detail the propagation of light, forming a shadow and silhouette, and forming an image of an accretion disk in the spacetime of the Ellis-Bronnikov wormhole. As well we compare characteristics of images obtained for the Ellis-Bronnikov wormhole with those for the Schwarzschild black hole. This comparison could be useful for future observations of supermassive astrophysical objects.

This work deals with the tail and “failed” tail sectors of the conservative dynamics for compact binary systems at the 5PN order. We employ the Fokker Lagrangian method with dimensional regularization, and our results for the tail sector are perfectly consistent with the previous effective field theory computations. As for the failed tail sector, we have good hopes that this new computation will help solving the current discrepancy in the literature.

The “ugly duckling” of the Segré-Plebański-Hawking-Ellis classification of stress-energy tensors is believed to be either impossible or extremely difficult to realise in Einstein gravity. Effective stress-energy tensors in alternative gravity offer a wider range of possibilities. We report a class of type-III realizations in “first-generation” scalar-tensor and in Horndeski gravity, and their physical interpretation. The ugly duckling may be a freak of nature of limited importance but it is not physically impossible.

Black holes can be electromagnetically charged or carry vector charge from new fundamental fields. Their response to small fluctuations is of paramount importance to study gravitational wave generation. However, the usual even and odd sectors of gravitoelectromagnetic waves couple if the black hole is magnetically charged, a fact that complicates significantly the perturbative approach. In this paper, perturbation theory based on harmonic expansion is extended to have manifest invariance under electric-magnetic duality. As a result, the equations decouple into two generalized even and odd sectors, each governed by master wave equations that include the most general coupling to a dyonic source. These can be used to compute, in a simple manner, the gravitational and electromagnetic radiation emitted in the interaction of the most general spherically symmetric black holes of the Einstein-Maxwell theory with electromagnetically charged matter.

Extreme mass-ratio inspirals (EMRIs) are expected to have considerable eccentricity when emitting gravitational waves (GWs) in the LISA band. Developing GW templates that remain phase accurate over these long inspirals requires the use of second-order self-force theory and practical second-order self-force calculations are now emerging for quasicircular EMRIs. These calculations rely on effective-source regularization techniques in the frequency domain that presently are specialized to circular orbits. Here we make a first step toward more generic second-order calculations by extending the frequency domain effective-source approach to eccentric orbits. In order to overcome the slow convergence of the Fourier sum over radial modes, we develop a new extended effective-sources approach which builds upon the method of extended particular solutions. To demonstrate our new computational technique we apply it a toy scalar-field problem which is conceptually similar to the gravitational case.

We address two important questions in gravitational-wave astronomy. What is the astrophysical formation scenario leading to black-hole binary mergers? Did some of the merging black holes form hierarchically through previous generations of mergers? Leveraging fast-to-generate astrophysical simulations from the rapster code and a random forest algorithm, we develop a pipeline to accurately classify the most likely generation and formation scenario of dynamically formed black holes on an event-by-event basis. We test our framework on four merger events with features suggesting a dynamical origin: the large total mass event GW190521, GW190412 (with large mass asymmetry), and two events with effective spins antialigned with the orbital angular momentum (GW191109 and GW200225). Within the models we consider, and assuming these events to be formed dynamically, we find that one of the component black holes in GW190521 formed from a previous merger with high probability ($\gtrsim 85\%$). GW190521, GW191109, and GW200225 are compatible with formation through three-body interactions, while the most likely formation channel for GW190412 is two-body captures. We also rule out that GW191109 contains only first-generation black holes with a probability of 97%. Our pipeline could be useful to identify the evolutionary path of individual gravitational-wave observations once it is trained on more comprehensive sets of binary formation simulations.

A recent result from Fermilab suggests that the measured $W$-boson mass deviates from the prediction of the Standard Model (SM) with a significance of $>7\sigma$, and there may exist new physics beyond the SM. It is proposed that the inert two Higgs doublet model (i2HDM) can well explain the new $W$-boson mass. Meanwhile, the lightest neutral scalar $S$ in the i2HDM can be stable and play the role of dark matter with a preferred dark matter mass of $\sim 54–74\mathrm{GeV}$. It is also found that part of the parameter space of this model can explain both the Galactic Center GeV gamma-ray excess detected by Fermi-LAT and the GeV antiproton excess detected by AMS-02 through a $SS\to W{W}^{*}$ annihilation. In this paper, we aim to test the possible common i2HDM origin of the three anomaly/excesses using the Fermi-LAT observations of Milky Way dwarf spheroidal galaxies. We perform single and stacking analyses on 19 dwarf spheroidal galaxies that have $J$-factor measurements. We find that our upper limits are below the favored parameters and seems to be able to exclude the possibility of a common origin of the three anomaly/excesses. However, because the $J$-factor measurements include relatively large uncertainties, which come from the measurements of stellar kinematics, whether this model could be reliably excluded needs to be further confirmed by future observations.

Current gravitational-wave data from stellar-mass black-hole binary mergers suggest a correlation between the binary mass ratio $q$ and the effective spin ${\chi }_{\mathrm{eff}}$: more unequal-mass binaries consistently show larger and positive values of the effective spin. Multiple generations of black-hole mergers in dense astrophysical environments may provide a way to form unequal-mass systems, but they cannot explain the observed correlation on their own. We show that the symmetry of the astrophysical environment is a crucial feature to shed light on this otherwise puzzling piece of observational evidence. We present a toy model that reproduces, at least qualitatively, the observed correlation. The model relies on axisymmetric, disklike environments where binaries participating in hierarchical mergers share a preferential direction. Migration traps in AGN disks are a prime candidate for this setup, hinting at the exciting possibility of constraining their occurrence with gravitational-wave data.

In this work, we present a non–general relativity full waveform for general parametrization of axisymmetric black holes by extending our previous photon $\text{sphere}+\text{inspiral}$ model. Our model comprises two main components: an inspiral part obtained by using a phenomenological method in a frequency domain and a ringdown part derived from quasinormal modes associated with photon motion. For quantitatively revealing the influence of the deviation from Kerr black holes on the waveforms, we specify our model to the bumpy black holes, which are typical examples of non–general relativity black holes. The results show that the deviation from the Kerr quadrupole moment could be measured with a high accuracy. The new waveform model can be directly used to test black holes for the LIGO-Virgo-KAGRA observations, the third generation detectors, and space-borne interferometers.

The equation of state (EoS) governing high-density matter inside neutron stars can exhibit phase transitions (PTs), which have the potential to induce anomalous wave structures in hydrodynamics and alterations in star stability. However, existing analytic models that are employed to replace realistic tabulated EoS in simulations often fall short in accurately capturing the intricate thermodynamics associated with these PT. Modeling PTs poses a challenge as they occur in thin density regions yet significantly impact the description of matter, rendering the EoS nonconvex and leading to a distinct hydrodynamic behavior. In this paper, we present a new analytic model for tabulated EoS with special focus on the modeling of PTs by means of a thermodynamically adaptive slope piecewise polytropic (T-ASPP) approximation, able to replicate nonconvex EoS and therefore triggering anomalous wave dynamics. In addition, we present a comprehensive analysis of the stellar properties (mass, radius, and tidal deformability) obtained from our model and compare them with those derived from the tabulated EoS. The results demonstrate that our T-ASPP EoS model provides a fair approximation to the neutron star properties. Furthermore, we investigate the hydrodynamic discrepancies between including and excluding the proper thermodynamics of PTs by examining two Riemann problems. This analysis sheds light on the significant impact of incorporating the accurate thermodynamics of PTs on the hydrodynamic behavior.

We develop a general formalism for introducing stochastic fluctuations around thermodynamic equilibrium which takes into account, for the first time, recent developments in the causality and stability properties of relativistic hydrodynamic theories. The method is valid for any covariantly stable theory of relativistic viscous fluid dynamics derived from a covariant maximum entropy principle. We illustrate the formalism with some applications, showing how it could be used to consistently introduce fluctuations in a model of relativistic heat diffusion and in conformally invariant Israel-Stewart theory in a general hydrodynamic frame. The latter example is used to study the hydrodynamic frame dependence of the symmetric two-point function of fluctuations of the energy-momentum tensor.

The amplitude of the pseudoscalar (axion) or scalar field fluctuates on a timescale of order of a million field oscillation periods which is a typical coherence time in the virialized axion galactic dark matter halo model. This causes fluctuations of frequencies of atomic clocks on the same timescale. We show that this effect may be employed to search for the axion and scalar field dark matter with atomic and nuclear clocks. We repurpose the results of the atomic clocks experiments comparing the variations of frequencies of hyperfine transitions in Rb and Cs atoms as well as in hydrogen atom vs cavity frequency fluctuations, and extract new limits on the axion coupling constant $f_a$ for masses in the range $2.4\times {10}^{-17}\mathrm{eV}\lesssim m\lesssim {10}^{-13}\mathrm{eV}$. We also show that similar energy shifts arise in the second-order perturbation theory with linear in the pseudoscalar field interaction. These shifts may be potentially measured with nuclear clocks based on the low-energy transition in ${}^{229}\mathrm{Th}$ nucleus. We propose a procedure which could, in principle, help determine the axion mass if the axion dark matter signal is present in experimental datasets.

When studied at finite temperature, Yang-Mills theories in $3+1$ dimensions display the presence of confinement/deconfinement phase transitions, which are known to be of first order—the $SU(2)$ gauge theory being the exception. Theoretical as well as phenomenological considerations indicate that it is essential to establish a precise characterization of these physical systems in proximity of such phase transitions. We present and test a new method to study the critical region of parameter space in non-Abelian quantum field theories on the lattice, based upon the logarithmic linear relaxation (LLR) algorithm. We apply this method to the $SU(3)$ Yang-Mills lattice gauge theory, and perform extensive calculations with one fixed choice of lattice size. We identify the critical temperature, and measure interesting physical quantities near the transition. Among them, we determine the free energy of the model in the critical region, exposing for the first time its multivalued nature with a numerical calculation from first principles, providing this novel evidence in support of a first-order phase transition. This study sets the stage for future high-precision measurements, by demonstrating the potential of the method.

We present a method for analytic continuation of retarded Green’s functions, including Euclidean Green’s functions computed using lattice QCD. The method is based on conformal maps and construction of an interpolation function which is analytic in the upper half-plane. A novel aspect of our treatment is rigorous bounding of systematic uncertainties, which are handled by constructing the full space of interpolating functions (at each point in the upper half-plane) consistent with the given Euclidean data and the constraints of analyticity. The resulting Green’s function in the upper half-plane has an appealing interpretation as a smeared spectral function. The bounding constraint applies to these smeared spectral functions.

We compute the sphaleron rate in quenched quantum chromodynamics (QCD) for a temperature $T\simeq 1.24T_c$ from the inversion of the Euclidean lattice time correlator of the topological charge density. We explore and compare two different strategies: one follows a new approach proposed in this study and consists in extracting the rate from finite lattice spacing correlators, and then in taking the continuum limit at fixed smoothing radius followed by a zero-smoothing extrapolation; the other follows the traditional approach of extracting the rate after performing such double extrapolation directly on the correlator. In both cases the rate is obtained from a recently proposed modification of the standard Backus–Gilbert procedure. The two strategies lead to compatible estimates within errors, which are then compared to previous results in the literature at the same or similar temperatures; the new strategy permits to obtain improved results, in terms of statistical and systematic uncertainties.

We compare recent MINERvA antineutrino-hydrogen charged-current measurements to phenomenological predictions of the axial-vector form factor based on fits to all available electron scattering and deuterium bubble-chamber data and to representative lattice-QCD (LQCD) determination by the PNDME Collaboration. While there is $1\sigma –2\sigma$ agreement in the cross section with MINERvA data for each bin in $Q^2$, we identify three regions with different relevance and opportunity for LQCD predictions. For $Q^2\lesssim 0.2{\mathrm{GeV}}^2$, the phenomenological extractions have large number of data points and LQCD is competitive, while MINERvA data have large errors. For $0.2{\mathrm{GeV}}^2\lesssim Q^2\lesssim 1{\mathrm{GeV}}^2$, LQCD is competitive with the MINERvA determination, and both give values larger than from phenomenological extraction. For $Q^2>1{\mathrm{GeV}}^2$, the MINERvA data are the most precise. Our analysis indicates that with improving precision of MINERvA-like experiments and LQCD data, the uncertainty in the nucleon axial-vector form factor will be steadily reduced.