高能暂现源 · 每日文献综述

High-energy neutrinos provide a potentially powerful and distinctive probe for dark matter (DM)─neutrino interactions, particularly in environments with enhanced DM densities, such as the DM spikes predicted to form around supermassive black holes at the center of active galactic nuclei (AGN). Recent results by the IceCube Neutrino Observatory, which reported four significant AGNs, namely TXS <inline-formula><mml:math><mml:mrow><mml:mn>0506</mml:mn><mml:mo>+</mml:mo><mml:mn>056</mml:mn></mml:mrow></mml:math></inline-formula>, NGC 1068, PKS <inline-formula><mml:math><mml:mrow><mml:mn>1424</mml:mn><mml:mo>+</mml:mo><mml:mn>240</mml:mn></mml:mrow></mml:math></inline-formula>, and NGC 4151 as candidate neutrino sources, provide a valuable opportunity to search for signatures of these interactions. In this study, we use IceCube data to derive the most stringent constraints to date on both the energy-dependent and energy-independent DM-neutrino scattering cross sections. We perform a statistical analysis using data from individual sources as well as a combined (stacked) analysis of all four sources. Our strongest limits arise from the stacking analysis, yielding an upper bound of <inline-formula><mml:math><mml:msub><mml:mi>σ</mml:mi><mml:mn>0</mml:mn></mml:msub><mml:mo>≲</mml:mo><mml:mn>8</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>39</mml:mn></mml:mrow></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>cm</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for an energy-independent cross section and <inline-formula><mml:math><mml:msub><mml:mi>σ</mml:mi><mml:mn>0</mml:mn></mml:msub><mml:mo>≲</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>39</mml:mn></mml:mrow></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:msup><mml:mrow><mml:mi>cm</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> for a linearly energy-dependent cross section, both at 90% confidence level, particularly in scenarios involving the adiabatic growth of black holes.

The postmerger phase of binary neutron star (BNS) mergers encodes valuable information about the equation of state (EOS) of supranuclear matter. Extracting this information from the analysis of the postmerger waveforms remains challenging due to the high-frequency limitations of current detectors. Future third-generation observatories, such as the Einstein Telescope (ET) and NEMO, will have the sensitivity required to resolve post-merger signals with high fidelity. In this work, we apply CLAWDIA, our recently developed sparse dictionary learning (SDL) framework, to classify different EOS models using the merger and postmerger gravitational-wave emission of simulated BNS mergers available in the CORE database. Our dataset comprises five EOS models representative of a broad range of neutron star properties. The SDL framework is optimized under realistic detection conditions by injecting signals into simulated noise matching the sensitivity curves of ET and NEMO. Our results show that classification is primarily driven by the dominant postmerger frequency, <inline-formula><mml:math><mml:msub><mml:mi>f</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math></inline-formula>, which encodes EOS-dependent information. At a modest signal-to-noise ratio of 5, our method achieves <inline-formula><mml:math><mml:msub><mml:mi>F</mml:mi><mml:mn>1</mml:mn></mml:msub></mml:math></inline-formula> scores of 0.76 for ET and 0.70 for NEMO, with performance improving for higher signal-to-noise ratios. The reliability and generalization capabilities of the model are assessed with additional tests, including the classification of an EOS not included in the training dataset and the analysis of detector-specific biases.

As the LIGO-Virgo-KAGRA Collaboration's (LVK's) gravitational-wave transient catalog grows, we are learning a wealth of information from the population properties of binary black hole mergers. Events in the catalog are represented with posterior samples describing the astrophysical parameters for each event. Population studies combine these samples to measure the distribution of astrophysical parameters such as black hole masses and spins. However, the posterior-sample representation of each event is only approximate. We construct a mock population with masses drawn from an astrophysically motivated distribution with sharp features. Using this, we demonstrate that when <inline-formula><mml:math><mml:mrow><mml:mo>≳</mml:mo><mml:mn>300</mml:mn></mml:mrow></mml:math></inline-formula> events are combined, even with each event's posterior represented by <inline-formula><mml:math><mml:mn>1</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>4</mml:mn></mml:msup><mml:mo>-</mml:mo><mml:mn>2</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>4</mml:mn></mml:msup></mml:math></inline-formula> samples, the numerical error can become large enough that the resulting population inference is unreliable. We consider two solutions. In the short term, we show that nested samples (already produced by LVK analyses) can be used to more accurately describe each event in population studies. But this will only grant a temporary reprieve until the nested-sample representation becomes inadequate. In the longer term, we propose to represent each event with a normalizing flow. In order to represent each event with sufficient accuracy, each normalizing flow can be used to generate an arbitrarily large number of new posterior samples with a significantly reduced computational cost relative to traditional sampling methods. When compared to nested sampling, our normalizing flows produce posterior draws with a median of <inline-formula><mml:math><mml:mo>≍</mml:mo><mml:mn>80</mml:mn><mml:mo>%</mml:mo></mml:math></inline-formula> fewer likelihood evaluations per sample, while also providing greater opportunity for parallelization. We believe refinement of normalizing flow architectures and training techniques in future works could further reduce this per-sample cost significantly.

Evidence of a gravitational wave (GW) signal has emerged in pulsar timing array (PTA) data, opening a new window into the nanohertz GW Universe. We explore the physics of GW signals that may explain the data, with a focus on GW backgrounds (GWBs) considering both astrophysical and cosmological origins. We describe how: ▪ An astrophysical nanohertz GWB emerges as the superposition of individual signals from inspiraling massive black hole binaries. ▪ Environment coupling, eccentricity, and sparse sampling cause great uncertainty in the theoretical prediction of the supermassive black hole signal but also offer a way to determine the origin of the signal. ▪ PTA data offer unprecedented opportunities to constrain high-energy physics beyond the Standard Model by probing early Universe GWBs that originated during or after inflation. ▪ Different early Universe GWBs, typically created by nonlinear and out-of-equilibrium dynamics, can explain the PTA data (e.g., those from inflation scenarios, first-order phase transitions, or topological defects). ▪ The PTA detection of GWs opens a new window to explore the Universe, with profound implications for astrophysics and particle physics (probing, e.g., the equation of state of the early Universe, the origin of cosmological perturbations, the nature of dark matter, or whether exotic objects like primordial black holes or cosmic strings exist). An astrophysical nanohertz GWB emerges as the superposition of individual signals from inspiraling massive black hole binaries. Environment coupling, eccentricity, and sparse sampling cause great uncertainty in the theoretical prediction of the supermassive black hole signal but also offer a way to determine the origin of the signal. PTA data offer unprecedented opportunities to constrain high-energy physics beyond the Standard Model by probing early Universe GWBs that originated during or after inflation. Different early Universe GWBs, typically created by nonlinear and out-of-equilibrium dynamics, can explain the PTA data (e.g., those from inflation scenarios, first-order phase transitions, or topological defects). The PTA detection of GWs opens a new window to explore the Universe, with profound implications for astrophysics and particle physics (probing, e.g., the equation of state of the early Universe, the origin of cosmological perturbations, the nature of dark matter, or whether exotic objects like primordial black holes or cosmic strings exist).

We simulate a self-interacting three-flavor neutrino system within a core-collapse supernova using a hybrid classical-quantum algorithm on a qutrit computer. Based on the Dirac-Frenkel evolution equations, we employ a variation of the quantum-assisted simulator to calculate the system's time evolution operator by performing qutrit Hadamard tests to find expectation values of unitary operators in the Hamiltonian. The time evolution simulation is then done classically. We find that the hybrid algorithm produces results comparable to an exact numerical integration out to times of <inline-formula><mml:math><mml:mrow><mml:mi>t</mml:mi><mml:mo>≍</mml:mo><mml:mn>30</mml:mn><mml:msubsup><mml:mrow><mml:mi>ω</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math></inline-formula> with time step <inline-formula><mml:math><mml:mrow><mml:mi>δ</mml:mi><mml:mi>t</mml:mi><mml:mo>=</mml:mo><mml:mn>0.005</mml:mn><mml:msubsup><mml:mrow><mml:mi>ω</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math></inline-formula>, where <inline-formula><mml:math><mml:msub><mml:mi>ω</mml:mi><mml:mn>0</mml:mn></mml:msub></mml:math></inline-formula> is the energy scale of the single neutrino vacuum oscillations. We discuss the lessons learned in simulating neutrino systems using this hybrid quantum-classical algorithm, along with the advantages it offers over quantum Trotterization.

We calculate the <inline-formula><mml:math><mml:mrow><mml:mi>f</mml:mi></mml:mrow></mml:math></inline-formula>-mode frequency of quark stars using the full general relativity method, and evaluate the tidal overlap with an analogy method incorporating effective general relativistic corrections. We verify the universal relations obtained from conventional neutron stars in the case of quark stars, including the <inline-formula><mml:math><mml:mrow><mml:mi>f</mml:mi><mml:msub><mml:mrow><mml:mi>M</mml:mi></mml:mrow><mml:mrow><mml:mn>1.4</mml:mn></mml:mrow></mml:msub><mml:mi>─</mml:mi><mml:mi>Λ</mml:mi></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math><mml:mrow><mml:msub><mml:mrow><mml:mi>Q</mml:mi></mml:mrow><mml:mrow><mml:mi>f</mml:mi></mml:mrow></mml:msub><mml:mi>R</mml:mi><mml:mo>/</mml:mo><mml:mi>M</mml:mi><mml:mi>─</mml:mi><mml:mi>Λ</mml:mi></mml:mrow></mml:math></inline-formula> relations, and explore the cases with different values of parameters of the quark star equation of state. Since quark stars have significantly smaller radii compared to neutron stars in the low-mass range, the <inline-formula><mml:math><mml:msub><mml:mi>ω</mml:mi><mml:mi>f</mml:mi></mml:msub><mml:mi>R</mml:mi><mml:mi>─</mml:mi><mml:mi>Λ</mml:mi></mml:math></inline-formula> relation differs between neutron stars and quark stars. This difference has an impact on the dynamical tide, which is the lowest-order effect we know of that can distinguish quark stars and neutron stars from the gravitational wave during the inspiral phase. We calculate the tidal dephasing caused by this effect using the post-Newtonian method and estimate that <inline-formula><mml:math><mml:mrow><mml:msubsup><mml:mrow><mml:mn>34</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>16</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>12</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math></inline-formula> events for the Einstein Telescope and <inline-formula><mml:math><mml:msubsup><mml:mn>10</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>6</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula> events for Cosmic Explorer are required to distinguish between quark stars and neutron stars at the population level.

We present a framework to study the orientation distribution of nearby double white dwarf binaries with LISA, explicitly accounting for the fourfold degeneracy in the polarization angle. Exploiting the beltlike sky distribution of the nearby sample along the Galactic plane, we show that the low-multipole extraction can be recast as an effectively one-dimensional Fourier analysis along Galactic longitude, within a spherical-harmonic expansion based on the Wigner-<inline-formula><mml:math><mml:mi>D</mml:mi></mml:math></inline-formula> formalism. The symmetry with respect to the Galactic plane governs the sensitivity: modes even under reflection across the plane remain accessible, while odd modes are strongly suppressed. For a fiducial sample of about 500 binaries within <inline-formula><mml:math><mml:mo>≲</mml:mo><mml:mn>4</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>kpc</mml:mi></mml:math></inline-formula>, corresponding to roughly 5% of the resolved Galactic population, the method yields an uncertainty of order 0.02 for the reflection-even coefficients with <inline-formula><mml:math><mml:mo>ℓ</mml:mo><mml:mo>≤</mml:mo><mml:mn>3</mml:mn></mml:math></inline-formula>, and is readily applicable to the forthcoming LISA catalog.

By monitoring the times of arrival of radio pulses from millisecond pulsars, pulsar timing arrays (PTAs) serve as unique gravitational wave (GW) laboratories in the nanohertz band. To date, the primary astrophysical sources of GWs targeted in this frequency range have been inspiraling supermassive black hole binaries (SMBHBs) on circular and eccentric orbits. In this work, we demonstrate that, thanks to the so-called pulsar term in the timing residual waveform of GW signals, PTAs can probe individual SMBHBs that merged before timing observations began. We refer to the latter as zombie binaries. Using SMBHB population models consistent with current PTA constraints, we find that while the probability of detecting such systems in existing PTA datasets remains low, the Square Kilometer Array observatory is expected to achieve sufficient sensitivity to have a few zombie binaries with optimal matched filter signal-to-noise ratios exceeding 3 in its data. Although their confident identification might be challenging, this new class of PTA sources opens a novel window for studying the most massive SMBHBs in our local universe.

We investigate the impact of spatial curvature <inline-formula><mml:math><mml:msub><mml:mi>Ω</mml:mi><mml:mi>k</mml:mi></mml:msub></mml:math></inline-formula> and dynamical dark energy on the cosmological constraints of the neutrino mass sum, <inline-formula><mml:math><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mi>ν</mml:mi></mml:msub></mml:math></inline-formula>. Using a joint analysis of the latest cosmic microwave background (Planck and ACT DR6), baryon acoustic oscillation (DESI Data Release 2), and Type Ia supernovae (DESY5 and DES-Dovekie) datasets, we perform a systematic exploration of the neutrino mass parameter space. To mitigate prior-driven biases near the physical boundary, we implement a symmetric extension wrapper that allows for effective negative masses. We find that the inclusion of spatial curvature modifies the posterior distributions, exhibiting a smooth transition across the <inline-formula><mml:math><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mi>ν</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>0</mml:mn></mml:math></inline-formula> threshold. In the <inline-formula><mml:math><mml:mi>Λ</mml:mi><mml:mi>CDM</mml:mi><mml:mo>+</mml:mo><mml:msub><mml:mi>Ω</mml:mi><mml:mi>k</mml:mi></mml:msub><mml:mo>+</mml:mo><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mrow><mml:mi>ν</mml:mi><mml:mo>,</mml:mo><mml:mi>eff</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> framework, we obtain <inline-formula><mml:math><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mrow><mml:mi>ν</mml:mi><mml:mo>,</mml:mo><mml:mi>eff</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mo>−</mml:mo><mml:mn>0.01</mml:mn><mml:msubsup><mml:mn>1</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.050</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.052</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula>, reducing the tension with the terrestrial lower limit of 0.06 eV from <inline-formula><mml:math><mml:mn>2.59</mml:mn><mml:mi>σ</mml:mi></mml:math></inline-formula> for the <inline-formula><mml:math><mml:mi>Λ</mml:mi><mml:mi>CDM</mml:mi><mml:mo>+</mml:mo><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mrow><mml:mi>ν</mml:mi><mml:mo>,</mml:mo><mml:mi>eff</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> model to <inline-formula><mml:math><mml:mn>1.17</mml:mn><mml:mi>σ</mml:mi></mml:math></inline-formula>. For the most flexible scenario <inline-formula><mml:math><mml:msub><mml:mi>ω</mml:mi><mml:mn>0</mml:mn></mml:msub><mml:msub><mml:mi>ω</mml:mi><mml:mi>a</mml:mi></mml:msub><mml:mi>CDM</mml:mi><mml:mo>+</mml:mo><mml:msub><mml:mi>Ω</mml:mi><mml:mi>k</mml:mi></mml:msub><mml:mo>+</mml:mo><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mrow><mml:mi>ν</mml:mi><mml:mo>,</mml:mo><mml:mi>eff</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula>, we find <inline-formula><mml:math><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mrow><mml:mi>ν</mml:mi><mml:mo>,</mml:mo><mml:mi>eff</mml:mi></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mo>-</mml:mo><mml:mn>0.07</mml:mn><mml:mo>±</mml:mo><mml:mn>0.11</mml:mn></mml:math></inline-formula> with a tension of <inline-formula><mml:math><mml:mn>1.13</mml:mn><mml:mi>σ</mml:mi></mml:math></inline-formula>, illustrating how the increased parameter freedom notably degrades the precision of the mass estimate compared to simpler extensions. Our results demonstrate that current cosmological bounds on <inline-formula><mml:math><mml:mo>∑</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mi>ν</mml:mi></mml:msub></mml:math></inline-formula> are influenced by boundary effects and geometric degeneracies.

The inspiral of a compact object into a black hole is a key source of low-frequency gravitational waves for future space-based detectors like LISA. While models of this process have advanced considerably, they typically focus on asymptotically flat spacetimes. In this paper, we investigate how departures from asymptotic flatness, whether driven by cosmic expansion or large-scale galactic environments, alter adiabatic orbital evolution. Using the Schwarzschild─de Sitter (SdS) metric, we parametrize these deviations via an"SdS parameter" (<inline-formula><mml:math><mml:mi>λ</mml:mi></mml:math></inline-formula>) and analyze its impact on bound orbits. We calculate how <inline-formula><mml:math><mml:mi>λ</mml:mi></mml:math></inline-formula> shifts the separatrix between bound and plunging states and modifies the relationship between a binary's energy, angular momentum, and orbital geometry. By applying a modified quadrupole formula in the weak-field limit, we investigate the effect of <inline-formula><mml:math><mml:mi>λ</mml:mi></mml:math></inline-formula> on circularization, plunge times, and orbital trajectories. We show that a positive SdS parameter accelerates eccentricity decay and shortens inspiral timescales. We also generate adiabatic waveforms from inspirals evolving under radiation reaction, exhibiting an increase in amplitude and a cumulative phase advance induced by <inline-formula><mml:math><mml:mi>λ</mml:mi></mml:math></inline-formula>. While these effects are negligible if <inline-formula><mml:math><mml:mi>λ</mml:mi></mml:math></inline-formula> is strictly cosmological, they become observationally relevant if the parameter serves as a proxy for astrophysical environments that induce <inline-formula><mml:math><mml:mo>∼</mml:mo><mml:msup><mml:mi>r</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math></inline-formula> potential corrections. Our results suggest that such environmental coupling could meaningfully bias event rate estimates and waveform templates for space-based gravitational wave astronomy.

We present a numerical-relativity study of comparable-mass boson star─black hole (BS-BH) head-on collisions, focusing on both initial-data construction and gravitational-wave (GW) phenomenology. We show that plain superposition can strongly perturb the BS core, leading to large constraint violations and unphysical radial oscillations. To remedy this problem, we introduce a one-body conformal-factor correction and find that it substantially suppresses these artifacts. Using the improved initial data, we analyze GW emission from equal- and unequal-mass BS-BH binaries and compare with matched BS-BS and BH-BH baselines. For equal masses, the BS-BH radiated energy increases with BS compactness and approaches the BH-BH limit for highly compact stars. For unequal masses, the <inline-formula><mml:math><mml:mi>q</mml:mi><mml:mo>=</mml:mo><mml:mn>2</mml:mn></mml:math></inline-formula> BS-BH configuration in our sample radiates slightly more GW energy than its matched BH-BH counterpart.

Precision observations of orbital systems have recently emerged as a promising new means of detecting gravitational waves and ultralight dark matter, offering sensitivity in new regimes with significant discovery potential. Such searches rely critically on precise modeling of the dynamical effects of these signals on the observed system, however, previous analyses have mainly only relied on the secularly averaged part of the response. We introduce here a fundamentally different approach that allows for a fully time-resolved description of the effects of oscillatory metric perturbations on orbital dynamics. We find that gravitational waves and ultralight dark matter can induce large oscillations in the orbital parameters of realistic binaries, enhancing the sensitivity to such signals by orders of magnitude compared to previous estimates.

In the past few decades, the waveform community has made advances in producing waveforms that span the inspiral-merger-ringdown of comparable-mass-ratio black hole binaries using advances in post-Newtonian and numerical relativity (NR) theory along with state-of-the-art gravitational wave models. Current methods in NR have shown progress toward producing stable simulations reaching mass ratios of <inline-formula><mml:math><mml:mrow><mml:mn>1</mml:mn><mml:mo>∶</mml:mo><mml:mn>100</mml:mn></mml:mrow></mml:math></inline-formula>; however, the computational cost becomes prohibitively expensive as the mass ratio and the length of the simulation increases. Meanwhile, the gravitational self-force (GSF) community has developed waveform models that not only generate extreme mass ratio inspiral waveforms, but also generate near-equal-mass-ratio waveforms with high fidelity. To assess the limits of both the GSF and NR waveforms and alleviate the computational costs of NR, we present hybridized GSF-NR waveforms for nonspinning binary black hole systems in which GSF provides the inspiral, and NR the merger and ringdown. The hybrid waveforms are generated from a set of 68 nonspinning NR waveforms from the SXS catalog with mass ratios spanning <inline-formula><mml:math><mml:mrow><mml:mn>1</mml:mn><mml:mo>∶</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math></inline-formula> to <inline-formula><mml:math><mml:mrow><mml:mn>1</mml:mn><mml:mo>∶</mml:mo><mml:mn>20</mml:mn></mml:mrow></mml:math></inline-formula> and include the (2, 2), (2, 1), (3, 3), (3, 2), (4, 4), (4, 3), and (5, 5) spin-weighted spherical harmonic modes. In this paper, we will highlight a selection of these hybrid waveforms and examine the error in the hybridization procedure. We will investigate the impact of subdominant modes on the accuracy of the hybrid waveforms by performing mismatch comparisons with surrogate models. To address the feasibility of hybridizing GSF inspirals with short-duration, high-mass ratio NR waveforms, thereby alleviating computational costs, we will discuss the relationship between mass ratio and the placement of the matching window, which can be used to predict the necessary and optimal number of NR cycles that contribute to the hybrid waveform.

Direct detections of gravitational waves provide a unique opportunity to probe the astrophysical origin of compact binary mergers. The formation channels of these systems remain highly debated, and a fraction may originate in dynamical environments or active galactic nuclei. Binaries formed in such environments are expected to experience line-of-sight acceleration from their surroundings, which can imprint characteristic signatures on the observed gravitational wave signal. Here, we rederive the line-of-sight acceleration effects and implement them in state-of-the-art quasicircular waveform models with precession and higher-order modes. We also implement the corrections in eccentric waveform models, applying them consistently to all contributing harmonics. Using this model, we investigate the impact of these effects on the inference of line-of-sight acceleration and analyze several selected events from the Gravitational-Wave Transient Catalog observed during the third observing run of LIGO and Virgo. We find no substantial evidence for line-of-sight acceleration in these events. We also show that an inconsistent treatment of line-of-sight acceleration between higher harmonics can lead to biased conclusions. Our model provides a robust framework for uncovering line-of-sight acceleration in current and future gravitational wave observations, enabling more accurate probes of environmental signatures in compact binary formation.

The flavor composition of cosmic neutrinos probes both the physical properties of their sources and oscillations over energies and distances unreachable by terrestrial experiments. Using 11.4 yr of IceCube data, we analyze the flavor composition of the all-sky neutrino flux from 5 TeV─10 PeV, significantly lowering the analysis threshold from a previous minimum of 35 TeV. The best-fit flavor fractions are <inline-formula><mml:math><mml:msub><mml:mi>f</mml:mi><mml:mi>e</mml:mi></mml:msub><mml:mo>,</mml:mo><mml:msub><mml:mi>f</mml:mi><mml:mi>μ</mml:mi></mml:msub><mml:mo>,</mml:mo><mml:msub><mml:mi>f</mml:mi><mml:mi>τ</mml:mi></mml:msub><mml:mo>=</mml:mo><mml:mn>0.3</mml:mn><mml:msubsup><mml:mn>0</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.15</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.20</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula>, <inline-formula><mml:math><mml:msubsup><mml:mn>0.37</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.16</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.14</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula>, <inline-formula><mml:math><mml:msubsup><mml:mn>0.33</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.25</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.24</mml:mn></mml:mrow></mml:msubsup></mml:math></inline-formula>. For the first time, we report that neutrinos of all three flavors are present in the observed cosmic neutrino flux at <inline-formula><mml:math><mml:mrow><mml:mo>&gt;</mml:mo><mml:mn>90</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math></inline-formula> confidence level. We infer the flavor composition at their sources, finding good agreement with pion decay while pure neutron decay is disfavored, with posterior probability <inline-formula><mml:math><mml:mn>2.7</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mrow><mml:mo>-</mml:mo><mml:mn>5</mml:mn></mml:mrow></mml:msup></mml:math></inline-formula> (<inline-formula><mml:math><mml:mo>∼</mml:mo><mml:mn>4</mml:mn><mml:mi>σ</mml:mi></mml:math></inline-formula>).

In the presence of a weak gravitational wave (GW) background, astrophysical binary systems act as high-quality resonators, with efficient transfer of energy and momentum between the orbit and a harmonic GW leading to potentially detectable orbital perturbations. In this Letter, we develop and apply a novel modeling and analysis framework that describes the imprints of GWs on binary systems in a fully time-resolved manner to study the sensitivity of lunar laser ranging, satellite laser ranging, and pulsar timing to both resonant and nonresonant GW backgrounds. We demonstrate that optimal data collection, modeling, and analysis lead to projected sensitivities that are orders of magnitude stronger than previously appreciated, opening up a new possibility for probing the physics-rich but notoriously challenging-to-access <inline-formula><mml:math><mml:mi>μ</mml:mi><mml:mi>Hz</mml:mi></mml:math></inline-formula> frequency band. This improvement arises from retaining accumulated orbital dephasing in the measured residual and scales quadratically with the ratio of the observing time to the unperturbed binary period, up to eccentricity-dependent factors. We also discuss improved prospects for the detection of the stochastic fluctuations of ultralight dark matter, which may analogously perturb the binary orbits.

Since the first gravitational-wave (GW) detection of September 14, 2015, and with hundreds of gravitational-wave sources identified by the LIGO-Virgo-KAGRA network, GW have produced many important results in astrophysics and fundamental physics. Along with planned new data takings, current detectors will be upgraded, and new projects, such as the Einstein Telescope and Cosmic Explorer, are under study. Among noises limiting low frequency sensitivity, vibroacoustic noises are particularly important. In this work, we focus on the gravity gradient noise (also called Newtonian noise) of acoustic origin, which refers to the small fluctuations in the gravity field resulting from the acoustic pressure field present in the experimental areas of the detector. The induced noise is quantified in an original way, using a detailed numerical acoustic model of the experimental room, when the pressure field is excited by the air conditioning system. The method is used for Virgo, but it can be easily extended for future detectors and used to guide the design of caverns and experimental areas.

While the potential of the Jiangmen Underground Neutrino Observatory (JUNO) to measure solar neutrinos is known, realizing this potential requires new techniques to reduce detector backgrounds. One of the most serious backgrounds is due to the beta decays of unstable nuclei produced through muon breakup (spallation) of nuclei. This background is much more significant in JUNO compared to Super-Kamiokande due to JUNO's shallower depth and its lack of directional information. We present the first detailed theoretical calculations of spallation backgrounds in JUNO, showing the underlying physical processes and new ways to cut backgrounds while preserving signals. A key point is showing the importance of neutron tagging to identify hadronic showers, which are rare but produce almost all of the dangerous isotopes. With our new techniques, JUNO will be able to reduce dead time (signal loss) by a factor of about 4.5 and to reduce the running time needed to meet sensitivity goals by a factor of 2. This will give JUNO greatly improved sensitivity to <inline-formula><mml:math><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>B</mml:mi></mml:mrow><mml:mrow><mml:mn>8</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math></inline-formula> and <inline-formula><mml:math><mml:mi>h</mml:mi><mml:mi>e</mml:mi><mml:mi>p</mml:mi></mml:math></inline-formula> solar neutrinos, as we will explore in a separate paper.

We study scalar field perturbations of a static and spherically symmetric spacetime describing a dyonic black bounce geometry. Depending on the electric and magnetic charges, the spacetime can represent either a regular black hole or a horizonless compact object. We derive the effective potential for massless scalar perturbations and analyze its structure for different parameter regimes. In the black hole phase, the quasinormal mode spectrum is calculated using the Wentzel-Kramers-Brillouin (WKB) approximation and compared with the eikonal formula derived from null geodesics. The two approaches show good agreement in the large multipole limit. When the charge parameters exceed a critical value, the event horizon disappears, and the spacetime becomes a horizonless compact object. In this case, the effective potential develops a characteristic double-barrier structure that forms a trapping cavity for perturbations. The time-domain evolution reveals the presence of the echoes produced by repeated reflections of waves inside this cavity. These results suggest that the dyonic black bounce geometry can naturally generate echo signals without introducing artificial boundary conditions, providing a possible observational probe to distinguish horizonless compact objects from classical regular black holes in gravitational-wave observations.

We report on numerical simulations of critical phenomena in the collapse of axisymmetric vacuum gravitational waves, adopting families of initial data that, to the best of our knowledge, have not been used in this context before. Like Teukolsky waves, the data are based on linear wave solutions to the Einstein equations. We follow Nakamura's construction and encode the wave content in the extrinsic curvature rather than the spatial curvature, which leads to several simplifications when the data are "dressed up" so that they satisfy the nonlinear constraint equations. We are able to fine-tune these data to the onset of black hole formation slightly better than in our previous simulations, allowing us to observe and examine one more echo in the approximately self-similar threshold solution. Our findings are consistent with earlier studies: while we find threshold solutions that are approximately discretely self-similar, the self-similarity is not exact, and we find no evidence for a unique critical solution. We discuss common features between the different threshold solutions, including the appearance of alternating maxima in the direction of the poles and the equator.

Reducing orbital eccentricity in numerical relativity simulations of binary black holes is essential for producing astrophysically relevant gravitational wave models, as many of these systems are expected to be near circular in nature. Standard eccentricity-reduction procedures rely on iterative schemes, often requiring four or more trial simulations to achieve desired thresholds. This approach is computationally expensive because each trial simulation adds <inline-formula><mml:math><mml:mo>∼</mml:mo><mml:mn>10</mml:mn><mml:mo>%</mml:mo></mml:math></inline-formula> to the total simulation run-time of multiple weeks to months. We introduce a data-driven approach that accelerates this process by learning the values of the initial orbital frequency, <inline-formula><mml:math><mml:msub><mml:mi>Ω</mml:mi><mml:mn>0</mml:mn></mml:msub></mml:math></inline-formula>, and radial velocity, <inline-formula><mml:math><mml:msub><mml:mover><mml:mi>a</mml:mi><mml:mo>˙</mml:mo></mml:mover><mml:mn>0</mml:mn></mml:msub></mml:math></inline-formula>, that yield an evolution with small eccentricity. This is done using a Gaussian process regression model trained on an archive of previously eccentricity-reduced numerical relativity simulations. For all configurations tested, using the trained model consistently reduces the number of required eccentricity-reduction iterations to just zero or one, significantly lowering computational costs relative to post-Newtonian initial guesses. These results demonstrate the power of data-driven methods in accelerating expensive numerical relativity simulations.

We develop a unified framework for testing gravity beyond general relativity (GR) with continuous gravitational waves (CWs) from individual supermassive black hole binaries. These long-lived, nearly monochromatic nanohertz signals offer unique strengths for precision tests of gravity, since their coherent phase evolution and inter-pulsar correlations in pulsar timing arrays (PTAs) retain detailed information about departures from GR over cosmological propagation distances. We consider three representative classes of deviations from GR: additional polarization states, modified dispersion relations, and parity-violating birefringence. For each, we derive the interpulsar cross-correlation, the modified antenna response, and the propagation-induced pulsar-term phase delay. For nontensorial polarizations, the CW cross-correlation scales linearly in the alternative-polarization amplitude, compared to the quadratic scaling of the gravitational-wave background, provided the beyond-GR modes are subdominant. PTAs are also competitive for modified dispersion relations, where low frequencies enhance both the antenna-pattern modification and the pulsar-term phase delay. Birefringence, by contrast, is suppressed at nanohertz frequencies for most parity-violating theories. We validate the framework with injection-and-recovery simulations for breathing-mode and massive-graviton signals at current observational limits, recovering the injected beyond-GR parameters and distinguishing the CW signal from both correlated and uncorrelated background models. We further show that a pure-GR CW template recovers source parameters without significant bias when beyond-GR physics is present in the data, supporting a two-stage analysis strategy: identify candidates under GR, then test for deviations.

We present a systematic derivation of regular black hole solutions—and their horizonless counterparts—that achieve regularization via an anti─de Sitter core. These geometries emerge as polymerized vacuum solutions inspired by loop quantum gravity, constituting effective quantum gravity configurations that admit a Birkhoff-type theorem and are uniquely determined by their mass. Using an auxiliary relational dust clock, together with the absence of gravitational waves in spherical symmetry, we exploit the structural ultralocality of the system to decompose the dynamics into independent shell degrees of freedom. The dust field acts as a reference clock for deparametrization and does not source the vacuum geometries considered here. These assumptions tightly constrain the Lemaître-Tolman-Bondi shell Hamiltonian to a factorized form and the static vacuum metric function to a universal expression. We examine the possibility of a bounce and analyze how its presence is encoded, or missed, in finite-order effective truncations of the full model. The procedure for deriving the explicit physical Hamiltonian is described for a generic case before specializing to a specific model of interest. Finally, we construct a four-dimensional covariant completion of the spatially covariant Lagrangian, showing that it belongs to the class of generalized extended mimetic gravity models.