The superposition of many astrophysical gravitational wave (GW) signals below typical detection thresholds baths detectors in a stochastic gravitational wave background (SGWB). In this work, we present a Fourier space approach to compute the frequency-domain distribution of stochastic gravitational wave backgrounds produced by discrete sources. Expressions for the moment-generating function and the distribution of observed (discrete) Fourier modes are provided. The results are first applied to the signal originating from all the mergers of compact stellar remnants (black holes and neutron stars) in the Universe, which is found to exhibit a $-4$ power-law tail. This tail is verified in the signal-to-noise ratio distribution of Gravitational-Wave Transient Catalogue (GWTC) events. The extent to which the subtraction of bright (loud) mergers gaussianizes the resulting confusion noise of unresolved sources is then illustrated. The power-law asymptotic tail for the unsubtracted signal, and an exponentially decaying tail in the case of the SGWB, are also derived analytically. Our results generalize to any background of gravitational waves emanating from discrete, individually coherent, sources.

We present a measurement of neutrino oscillation parameters with the Super-Kamiokande detector using atmospheric neutrinos from the complete pure-water SK I–V (April 1996–July 2020) dataset, including events from an expanded fiducial volume. The dataset corresponds to 6511.3 live days and an exposure of 484.2 kiloton-years. Measurements of the neutrino oscillation parameters $\mathrm{\Delta }{m}_{32}^2$, ${\sin }^2{\theta }_{23}$, ${\sin }^2{\theta }_{13}$, ${\delta }_{\mathrm{CP}}$, and the preference for the neutrino mass ordering are presented with atmospheric neutrino data alone, and with constraints on ${\sin }^2{\theta }_{13}$ from reactor neutrino experiments. Our analysis including constraints on ${\sin }^2{\theta }_{13}$ favors the normal mass ordering at the 92.3% level.

We search for the $e^{+}{e}^{-}\to {\eta }_b(1S)\omega$ and $e^{+}{e}^{-}\to {\chi }_{b0}(1P)\omega$ processes at a center-of-mass energy of 10.745 GeV, which is close to the peak of the $\mathrm{\Upsilon }(10753)$ state. We use data collected by the Belle II experiment during a special run, corresponding to an integrated luminosity of $9.8{\mathrm{fb}}^{-1}$. We reconstruct $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays and use the $\omega$ meson’s recoil mass to search for the signals. We do not find evidence for either process, and set upper limits on the corresponding Born-level cross sections of 2.5 pb and 7.8 pb, respectively, at the 90% confidence level. The ${\chi }_{b0}(1P)\omega$ limit is the result of a combination of this analysis and a previous search using full reconstruction.

We perform an updated analysis of long-baseline accelerator data in the framework of neutrino oscillations in presence of invisible neutrino decay. We analyze data from T2K, NOvA and $\mathrm{MINOS}/\mathrm{MINOS}+$ and show that the combined analysis of all experiments improves the previous bound from long-baseline data by approximately one order of magnitude.

This paper compares features, challenges, and puzzles of different models for a unitary black hole $S$-matrix, focusing on both recent nonisometric models, as well as “nonviolent unitarization,” which is based on new quantum interactions of a black hole. As a foundation for comparison, the description of real-time Hawking evolution is first overviewed, including leading effects of gravitational dressing and backreaction. Connection is then made to qubit models for evolution, and some technology is outlined to facilitate their description. Important features of both nonisometric models and nonviolent unitarization are investigated in qubit models, which illustrate essential differences between the respective approaches. The nonisometric models present puzzles for understanding evolution of internal outgoing excitations, which can be excited by interactions such as particle decay. Qubit models for nonviolent unitarization are further developed, and nicely illustrate aspects of that approach. Some remaining questions in generalizing to more complete models for evolution are discussed.

The detection of extreme-mass-ratio inspirals (EMRIs) is intricate due to their complex waveforms, extended duration, and low signal-to-noise ratio (SNR), making them more challenging to be identified compared to compact binary coalescences. While matched filtering-based techniques are known for their computational demands, existing deep learning-based methods primarily handle time-domain data and are often constrained by data duration and SNR. In addition, most existing work ignores time delay interferometry (TDI) and applies the long-wavelength approximation in detector response calculations, thus limiting their ability to handle laser frequency noise. In this study, we introduce dilated convolutional neural network for detecting extreme-mass-ratio inspirals (DECODE), an end-to-end model focusing on EMRI signal detection by sequence modeling in the frequency domain. Centered around a dilated causal convolutional neural network, trained on synthetic data considering TDI-1.5 detector response, DECODE can efficiently process a year’s worth of multichannel TDI data with an SNR of around 50. We evaluate our model on one-year data with accumulated SNR ranging from 50 to 120 and achieve a true positive rate of 96.3% at a false positive rate of 1%, keeping an inference time of less than 0.01 seconds. With the visualization of three showcased EMRI signals for interpretability and generalization, DECODE exhibits strong potential for future space-based gravitational wave data analyses.

There has been recent progress in extending the zeroth and second laws of black hole mechanics to gravitational effective field theories (EFTs). We generalize these results to a much larger class of EFTs describing gravity coupled to electromagnetism and a real scalar field. We also show that the zeroth law holds for the EFT of gravity coupled to electromagnetism and a charged scalar field.

Astrometry holds the potential for testing fundamental physics through the effects of the stochastic gravitational wave background (SGWB) in the $\sim 1–100\mathrm{nHz}$ frequency band on precision measurements of stellar positions. Such measurements are complementary to tests made possible by the detection of the SGWB using pulsar timing arrays. Here, the feasibility of using astrometry for the identification of parity-violating signals within the SGWB is investigated. This is achieved by defining and quantifying a nonvanishing $EB$ correlation function within astrometric correlation functions and investigating how one might estimate the detectability of such signals.

The temperature gradient effect (TGE) is an important disturbance source in the inertial sensor, the core payload of space gravitational wave detectors. The inertial sensor electrode, made of copper alloy with high thermal conductivity, is expected to achieve lower temperature gradient, but its outgassing characteristics need to be verified experimentally. In this work, we have developed a torsion pendulum and measured the TGE of the copper alloy electrode. The measurement results show that the upper limit of the outgassing effect of this copper alloy gravitational reference sensor is about $18.0\mathrm{pN}/\mathrm{K}$, and the total TGE is less than $30.2\mathrm{pN}/\mathrm{K}$ at 293 K, which can be ignored in the application of gravitational wave detection. Our work reveals key physical properties associated with TGE and provides a viable alternative for specialized equipment applications in spaceborne gravitational wave detection missions and beyond.

We investigate the small-mass asymptotics of a class of massive $d$-dimensional angular integrals. These integrals arise in a wide range of perturbative quantum field theory calculations. We derive expressions characterizing their behavior in the vicinity of the massless limit for all cases with up to two denominators. The results established in this work are applicable to phase-space calculations where an integration over virtuality including the massless limit is required.

We ask whether Krylov complexity is mutually compatible with the circuit and Nielsen definitions of complexity. We show that the Krylov complexities between three states fail to satisfy the triangle inequality and so cannot be a measure of distance: there is no possible metric for which Krylov complexity is the length of the shortest path to the target state or operator. We show this explicitly in the simplest example, a single qubit, and in general.

We investigate chiral phase transitions and the screening masses, pole masses, and thermal widths of neutral pion mesons with finite temperature $T$ and magnetic field $B$ in a lattice-improved $\mathrm{AdS}/\mathrm{QCD}$ model, which is constructed by fitting the lattice results of the pseudocritical temperatures $T_{\mathrm{pc}}(B)$. Specifically, we find that the chiral condensate $\sigma$ undergoes a crossover phase transition demonstrating distinct magnetic catalysis and inverse magnetic catalysis effects in very low- and high-temperature regions with fixed finite $B$, respectively. For the screening masses, we find that the longitudinal component decreases with $B$ at very low and high temperatures and increases with $B$ near $T_{\mathrm{pc}}$. The transverse component always increases with $B$ at fixed $T$. However, both the longitudinal and transverse screening masses increase with $T$ at fixed $B$. Furthermore, we find that the pole mass decreases with the increase of $B$ or $T$. It is interesting to note that the thermal width shows similar behavior to the longitudinal screening masses in the very-high-temperature region.

By using the gauge-gravity duality, we investigate the correlation function of flavored fermion in the ${\mathrm{D}}_p/{\mathrm{D}}_{p+4}$ model as top-down approaches of holographic QCD for $p=4,3$. The bulk spinor, as the source of the flavored fermion in QCD, is identified to the worldvolume fermion on the flavor ${\mathrm{D}}_{p+4}$-branes and the standard form of its action can be therefore obtained by the T-duality rules in string theory. Keeping this in hand, we afterwards generalize the prescription for two-point correlation function in the $\mathrm{AdS}/\mathrm{CFT}$ dictionary into general D-brane backgrounds and apply it to the case of $p=4,3$, i.e., the $\mathrm{D}4/\mathrm{D}8$ and $\mathrm{D}3/\mathrm{D}7$ approaches, respectively. Resultantly, our numerical calculation with the bubble background always displays discrete peaks in the correlation functions which imply the bound states created by the flavored fermions as the confinement in QCD. With the black brane background, the on-shell condition illustrated by the correlation function covers basically the dispersion curves of fermion obtained by the hard thermal loop approximation in the hot medium. Finally, we interpret the flavored fermions in the bubble background as baryons by taking into account a baryon vertex, then find the two-point correlation function is able to fit the lowest baryon spectrum. In this sense, we conclude remarkably that our top-down approach in this work could reveal the fundamental properties of QCD both in the confined and deconfined phases.

A few years ago it was shown that the superconformal index of the $\mathcal{N}=4$ supersymmetric $SU(N)$ Yang-Mills theory in the large $N$ limit matches with the entropy of $1/16$-supersymmetric black holes in type IIB string theory on ${\mathrm{AdS}}_5\times S^5$. In some cases, an even more detailed match between the two sides is possible. When the two angular momentum chemical potentials in the index are equal, the superconformal index can be written as a discrete sum of Bethe ansatz solutions, and it was shown that specific terms in this sum are in a one-to-one correspondence to stable black hole solutions, and that the matching can be extended to nonperturbative contributions from wrapped D3-branes. A Bethe ansatz approach to computing the superconformal index exists also when the ratio of the angular momentum chemical potentials is any rational number, but in those cases it involves a sum over a very large number of terms (growing exponentially with $N$). Benini et al. showed that a specific one of these terms matches with the black hole, but the role of the other terms is not clear. In this paper we analyze some of the additional contributions to the index in the Bethe ansatz approach, and we find that their matching to the gravity side is much more complicated than in the case of equal chemical potentials. In particular, we find some contributions that are larger than the one that was found to match the black holes, in which case they must cancel with other large contributions. We give some evidence that cancellations of this type are possible, but we leave a full understanding of how they work to the future.

We consider Einstein gravity extended with Riemann-squared term and construct the leading-order perturbative solution to the rotating black hole with all equal angular momenta in $D=7$. We find that in the extremal limit, the linear perturbation involves irrational powers in the near-horizon expansion. We argue that, despite that all curvature tensor invariants are regular on the horizon, the irrational power implies that the inside of the horizon is destroyed and the horizon becomes the natural boundary of the spacetime. We demonstrate that this vulnerability of the horizon regularity is an innate part of Einstein theory, and can arise in Einstein theory with minimally coupled matter. However, in fine-tuned theories such as supergravities, the black hole inside is preserved, which may be one of the criteria for a consistent theory of quantum gravity. We also show that the vulnerability occurs in general higher dimensions, which only a few sporadically distributed dimensions can evade.

Effective models of gravitational collapse in loop quantum gravity for the Lemaître-Tolman-Bondi spacetime predict that collapsing matter reaches a maximum finite density, bounces, and then expands outward. We show that in the marginally bound case, shell-crossing singularities commonly occur for inhomogeneous initial profiles of the dust energy density; this is the case in particular for all profiles that are continuous and of compact support, including configurations arbitrarily close to the Oppenheimer-Snyder model. When a shell-crossing singularity occurs, it is necessary to seek weak solutions to the dynamics; we argue that weak solutions typically contain shock waves.

We consider a quantum harmonic oscillator coupled with a graviton bath. We discuss the loss of coherence in the matter sector due to the matter-graviton vertex interaction, which leads to a loss of coherence provided that the matter-wave system is allowed to emit gravitons by the kinematics. Working in the quantum-field-theory framework, we obtain a master equation by tracing away the gravitational field at the leading order $\sim \mathcal{O}(G)$ and $\sim \mathcal{O}(c^{-2})$. We find that the decoherence rate is proportional to the cube of the harmonic trapping frequency and vanishes for a free particle, as expected for a system without a mass quadrupole. Furthermore, our quantum model of graviton emission recovers the known classical formula for gravitational radiation from a classical harmonic oscillator for coherent states with a large occupation number. In addition, we find that the quantum harmonic oscillator eventually settles in a steady state with a remnant coherence of the ground and first excited states. While classical emission of gravitational waves would make the harmonic system loose all of its energy, our quantum field theory model does not allow the number states $|1⟩$ and $|0⟩$ to decay via graviton emission. In particular, the superposition of number states $\frac{1}{\sqrt{2}}[|0⟩+|1⟩]$ is a steady state and never decoheres.

We first show that the master equations for massless perturbations of accelerating rotating black holes can be transformed into the Heun’s equation. The quasinormal modes of the black holes can be easily calculated in the framework of the Heun’s equation. We identify three modes for the tensor perturbations: the photon sphere modes, which reduce to the quasinormal modes of Kerr black holes when the acceleration parameter vanishes; the near-extremal modes, which branch from the first set and become dominant when the spin is near extremal; and the acceleration modes, which are closely related to the acceleration horizon. We calculate the frequency spectrum of the quasinormal modes in various spin and acceleration parameters. We choose an angular boundary condition that keeps the angular function regular at $\theta =0$ and $\pi$, which is consistent with the boundary condition of the Kerr black hole. The conical singularity caused by the acceleration influences this boundary condition. We find that the $m_0=1$ modes have an anomalous behavior at particular accelerations.

The aim of this work is twofold: (i) to properly define a wave-generation formalism for compact-supported sources embedded in Einstein-Maxwell theory, relying on matched post-Newtonian and multipolar-post-Minkowskian expansions; (ii) to apply this formalism (which is valid for any type of post-Newtonian sources) to the case of two stars with constant and aligned magnetic dipoles, by computing the fluxes of energy and angular momentum to the next-to-leading order, as well as the gravitational amplitude modes. Assuming eccentric orbits, we derive the evolution of orbital parameters, as well as the observables of the system, notably the gravitational phase for quasicircular orbits. Finally, we give some numerical estimates for the contribution of the magnetic dipoles for some realistic systems.