We investigate the properties of fermion-boson stars (FBSs), which can be viewed as neutron stars with a bosonic dark matter (DM) admixture. A challenge in studying the impact of DM on neutron stars is the absence of a universally accepted nuclear-matter equation of state (EOS), making it difficult to distinguish between the effects of DM and various EOS models. To address this issue, we extend the study of the I-Love-Q universal relations of neutron stars to FBSs with a nonrotating bosonic component by solving the Einstein-Klein-Gordon system. We study how DM parameters, such as the boson particle mass and self-interaction strength, would affect the structure of FBSs and explore the parameter space that leads to deviations from the I-Love-Q relations. The properties of FBSs and the level of deviations in general depend sensitively on the DM parameters. For boson particle mass within the range of $\mathcal{O}({10}^{-10}\mathrm{eV})$, where the Compton wavelength is comparable to the Schwarzschild radius of a $1M_{\odot }$ star, the deviation is up to about 5% level if the star contains a few percent of DM admixture. The deviation increases significantly with a higher amount of DM. We also find that the universal relations are still valid to within a 1% deviation level for boson particle mass $m_b\ge 26.8\times {10}^{-10}\mathrm{eV}$. This effectively sets an upper bound on the boson particle mass, beyond which it becomes not feasible to probe the properties of FBSs by investigating the I-Love-Q relation violations.

We demonstrate that the orbital eccentricity in compact binary mergers can be used to improve their sky localization using gravitational wave observations. Existing algorithms that conduct the localizations are not optimized for eccentric sources. We use a semi-Bayesian technique to carry out localizations of simulated sources recovered using a matched-filter search. Through these simulations, we find that if a non-negligible eccentricity is obtained during the detection, an eccentricity-optimized algorithm can significantly improve the localization areas compared to the existing methods. We also lay out the foundation for an eccentric early warning system using the matched-filter search. The potential impact on the early warning localization is investigated. We indicate a few possible cases of improvements while accounting for eccentricity toward any detectable eccentric neutron star binaries in the forthcoming observing scenarios of ground-based detectors. Improved localizations can be useful in effectually utilizing the capabilities of the follow-up facilities.

In a recent investigation, the initial value problem of light propagation in the gravitational field of a body at rest with monopole and quadrupole structure has been determined in the second post-Newtonian (2PN) approximation. In reality, the light source as well as the observer are located at finite distances from the solar system bodies. This fact requires solving the boundary value problem of light propagation. In this investigation, the solution of the boundary value problem is deduced from the initial value problem of light propagation in 2PN approximation. These results are a basic requirement for subsequent investigations aiming at ultra-highly precise tests of light deflection and time delay in the solar system.

The main challenge of 21-cm cosmology experiments is astrophysical foregrounds that are difficult to separate from the signal due to telescope systematics. An earlier study has shown that foreground residuals induced by antenna gain errors can be estimated and subtracted using the hybrid foreground residual subtraction (HyFoReS) technique, which relies on cross-correlating linearly filtered data. In this paper, we apply a similar technique to the CHIME stacking analysis to subtract beam-induced foreground contamination. Using a linear high-pass delay filter for foreground suppression, the CHIME collaboration reported a $11.1\sigma$ detection in the 21-cm signal stacked on eBOSS quasar locations, despite foreground residual contamination mainly due to the instrument chromatic transfer function. Following the HyFoReS formalism, we cross-correlate the foreground-dominated data at low delay with the contaminated signal at high delay to estimate residual foregrounds and subtract them from the signal. We find that HyFoReS can improve the signal-to-noise ratio of the stacked 21-cm signal by 10%–20% after the delay foreground filter, although some of the improvement can also be achieved with an alternative flagging technique. We have shown that it is possible to use HyFoReS to reduce beam-induced foreground contamination, benefiting the analysis of the HI auto power spectrum with CHIME and enabling the recovery of large-scale modes.

We study the interaction between dark matter (DM) and highly magnetized neutron stars (NSs), focusing on how DM particle mass, mass fraction, and magnetic field (MF) strength affect NS structure and stability. We consider self-interacting nonannihilating asymmetric fermionic DM that couples to NSs only through gravitational interaction. Using the quantum Monte Carlo relativistic mean-field model with density-dependent magnetic fields, we investigate the magnetized equation of state (EOS) and examine the accumulation of DM under various conditions. Our results show that as the DM fraction increases, the maximum gravitational mass of the NS decreases, especially for heavier DM particles, while lighter DM particles can induce a transition from a dark core to a halo structure, increasing the maximum mass. Strong MFs soften the EOS and reduce the dark mass a NS core can retain before transitioning to a halo. By comparing our results with observations from the Neutron Star Interior Composition Explorer and GW170817, we identify the possible range of DM parameters for these objects. We find that the magnetic field slightly changes these limits, mainly affecting the maximum NS mass and tidal deformability. These findings provide key insights into how DM and MF jointly shape the mass-radius relation and the stability of DM-admixed magnetized NSs.

Heavy axions that couple to both quantum electrodynamics and quantum chromodynamics with masses on the order of MeV–GeV and high-scale decay constants in excess of $\sim {10}^8\mathrm{GeV}$ may arise generically in, e.g., axiverse constructions. In this work we provide the most sensitive search to date for the existence of such heavy axions using Fermi-LAT data toward four recent supernovae (SN): Cassiopea A, SN1987A, SN2023ixf, and SN2024ggi. We account for heavy axion production in the proto-neutron-star cores through nuclear and electromagnetic processes and then the subsequent decay of the axions into photons. While previous works have searched for gamma rays from SN1987A using the Solar Maximum Mission that observed SN1987A during the SN itself, we show that using Fermi Large Area Telescope data provides an approximately 5 orders of magnitude improvement in flux sensitivity for axions with lifetimes larger than around 10 yrs. We find no evidence for heavy axions and exclude large regions of previously unexplored parameter space.

Recent studies suggest that global fits of parton distribution functions (PDFs) might inadvertently “fit away” signs of new physics in the high-energy tails of the distributions measured at the high luminosity program of the LHC (HL-LHC). This could lead to spurious effects that might conceal key beyond the Standard Model (BSM) signatures and hinder the success of indirect searches for new physics. In this paper, we demonstrate that future deep-inelastic scattering (DIS) measurements at the Electron-Ion Collider (EIC), and at CERN via $\mathrm{FASER}\nu$ and SND@LHC at LHC Run III, and the future neutrino experiments to be hosted at the proposed Forward Physics Facility (FPF) at the HL-LHC, provide complementary constraints on large-$x$ sea quarks. These constraints are crucial to mitigate the risk of missing key BSM signals, by enabling precise constraints on large-$x$ PDFs through a “BSM-safe” integration of both high- and low-energy data, which is essential for a robust interpretation of the high-energy measurements.

Based on an analysis that considers the isotropic $CPT$-odd standard model extension (SME) coefficients, we find new constraints for them coming from a combined DUNE and ESSnuSB fit. Furthermore, we investigate the correlations of the standard oscillation parameters, the leptonic $CP$-violating phase, ${\delta }_{CP}$, and the atmospheric mixing angle, ${\sin }^2{\theta }_{23}$, with respect to the SME coefficients $(a_L{)}^T$. The combination of DUNE and ESSnuSB may establish the strongest limit on the diagonal coefficient $(a_L{)}_{\mu \mu }^T$ compared to the existing limits in the literature. We also consider the possible effect of the SME coefficient $(a_L{)}^Z$ on neutrino propagation and discuss how this can affect DUNE limits on the coefficient $(a_L{)}^T$ found elsewhere.

We investigate the discovery prospects for a vectorlike top partner (VLT) in the type-II two-Higgs-doublet model (2HDM-II) extended by a vectorlike quark doublet ($TB$) at the 14 TeV LHC. The study focuses on the pair production process $pp\to T\overline{T}\to b{H}^{+}\overline{b}{H}^{-}\to b(tb)\overline{b}(\overline{t}b)$, yielding fully hadronic final states characterized by high $b$-jet multiplicity. Two analysis strategies are employed, requiring at least four or five $b$-tagged jets ($4b$ and $5b$), to exploit the signal topology. Assuming a charged Higgs mass of $m_{H^{\pm }}\sim 600\mathrm{GeV}$ and a systematic uncertainty of $\delta =5\%$, the $4b$ channel enables discovery up to $m_T\sim 1200\mathrm{GeV}$ at $\mathcal{L}=300{\mathrm{fb}}^{-1}$, while the $5b$ analysis extends the reach to $m_T\sim 1300\mathrm{GeV}$. At higher luminosities of $1000–3000{\mathrm{fb}}^{-1}$, the $5b$ strategy achieves discovery sensitivity up to $m_T\sim 1400\mathrm{GeV}$. The reach is significantly reduced as $m_{H^{\pm }}$ increases, due to the suppression of the $\mathrm{BR}(T\to H^{+}b)$: for $m_{H^{\pm }}\sim 1000\mathrm{GeV}$, discovery becomes unattainable across all luminosity and systematic uncertainty configurations. Sensitivity is also strongly impacted by systematic uncertainties: for $\delta =10\%$ and $m_{H^{\pm }}<1000\mathrm{GeV}$, discovery remains viable up to $m_T\sim 1200\mathrm{GeV}$ in the $5b$ analysis, while for $\delta =20\%$, no discovery is achievable for $m_T\ge 1000\mathrm{GeV}$.

We analyze $B^0\to K^0\overline{\ell }\ell$ long-distance contributions induced by the rescattering of a pair of charmed and charmed-strange mesons. We present an explicit estimate of these contributions using an effective description in terms of hadronic degrees of freedom, supplemented by data on the $B^0\to D^{*}{D}_s(D_s^{*}D)$ transition in order to reproduce the corresponding discontinuity in the $B^0\to K^0\overline{\ell }\ell$ amplitude. The $D^{*}{D}_s(D_s^{*}D)K$ vertex is estimated using heavy-hadron chiral perturbation theory, obtaining an accurate description of the whole rescattering process in the low-recoil (or high-$q^2$) limit. We also present an extrapolation to the whole kinematical region introducing hadronic form factors. The explicit estimate of the leading $D^{*}{D}_s(D_s^{*}D)$ intermediate state leads to a long-distance amplitude which does not exceed a few percent relative to the short-distance one. The consequences of this result for the extraction of the short-distance coefficient $C_9$ are discussed.

We present a general class of nonsingular black holes in semiclassical, two-dimensional dilaton gravity, with a focus on a Bardeen-like model. The equations of motion for an evaporating black hole including backreaction are solved numerically. The apparent horizons evaporate smoothly in finite time to form a compact trapped region. Backreaction effects lead to the formation of additional trapped and antitrapped regions after the primary black hole evaporates. Numerical simulations of microscopic black holes yield a final spacetime that is free of apparent horizons and Cauchy horizons, suggesting that the evaporation of regular 2D black holes is a unitary process.

Validating the results of Abrahams and Evans [Phys. Rev. Lett. 70, 2980–2983 (1993)] poses a numerical challenge and has been inspiring a lot of research. We join these efforts and present our first steps to achieve this goal: we discuss a formulation of the Einstein equations for a vacuum axisymmetric spacetime with a vanishing twist in spherical-polar coordinates and its linearized approximation, and identify some problems in achieving numerically stable evolution at the threshold of a black hole formation.

The standard cosmological model involves the assumption of isotropy and homogeneity, a principle that is generally well motivated but is now in conflict with various anisotropies found using independent astrophysical probes. These anisotropies tend to take the form of dipoles; while some can be explained by simple kinematic effects, many others are not fully understood. Thus, generic phenomenological models are being considered, such as a dipole in the luminosity distance. We demonstrate how such a dipole could be measured using gravitational waves from binary neutron star mergers observed by six different networks of gravitational-wave detectors, ranging from upgraded LIGO detectors to anticipated next-generation ground-based observatories. We find that, for example, a network of three next-generation detectors would produce strong constraints on a dipole’s amplitude ($\sim 20\%$) and location ($\sim 220{\mathrm{deg}}^2$) after just one year of observing. We demonstrate that the constraints scale with the number of detections, enabling projections for multiple years of observing. Our findings indicate that future observations of binary neutron star mergers would improve upon existing dipole constraints, provided that at least one next-generation detector is built. We also assess directional sensitivity of the dipole measurements by varying the dipole’s location on a grid across the sky. We find that for a network of three next-generation detectors, the variation in the constraints is only $\sim 1\%$ for the amplitude and $\lesssim 1.6\%$ for the location, indicating that the location of the dipole will not greatly impact our ability to measure its effects.

Extreme mass-ratio inspirals (EMRIs), consisting of a secondary (stellar mass) black hole (BH) orbiting around a supermassive BH, are one of the primary targets for future spaceborne gravitational wave (GW) detectors. The spin of the secondary BH encodes the formation history of the stellar mass BH and the formation process of the EMRI. In this work, we construct a kludge EMRI waveform model taking the secondary spin into account and preliminarily forecast the measurement precision of the secondary spin by future spaceborne GW detectors with the Fisher information matrix. We find the secondary spin might be measured with reasonably good precision for generic eccentric and inclined EMRIs, with the caveat that the predictive precision may be constrained by the model’s inherent simplifications. As an example of its astrophysical applications, we propose that the secondary spin can be used for distinguishing dry (loss cone) EMRIs (where the secondary BHs were born in the collapse of individual massive stars and are of low spin) and Hills EMRIs (where the secondary BHs are remnants of massive star binaries and the secondary spins follow a bimodal distribution).

Numerical simulations are essential to understand the complex physics accompanying the merger of binary systems of neutron stars. However, these simulations become computationally challenging when they have to model the merger remnants on timescales over which secular phenomena, such as the launching of magnetically driven outflows, develop. To tackle these challenges, we have recently developed a hybrid approach that combines, via a handoff transition, a fully general-relativistic code (fil) with a more efficient code making use of the conformally flat approximation (bhac+). We report here important additional developments of bhac+ consisting of the inclusion of gravitational-wave radiation-reaction contributions and of higher-order formulations of the equations of general-relativistic magnetohydrodynamics. Both improvements have allowed us to explore binary neutron-star merger remnants with high accuracy and over timescales that would have been computationally prohibitive otherwise. More specifically, we have investigated the impact of the magnetic-field strength on the long-term (i.e., $\sim 200\mathrm{ms}$) and high-resolution (i.e., 150 m) evolutions of the “magnetar” resulting from the merger of two neutron stars with a realistic equation of state. In this way, and for sufficiently large magnetic fields, we observe the weakening or suppression of differential rotation and the generation of magnetic flares in the outer layers of the remnant. These flares, driven mostly by the Parker instability, are responsible for intense and collimated Poynting flux outbursts and mass ejections. This novel phenomenology offers the possibility of seeking corresponding signatures from the observations of short gamma-ray bursts and hence revealing the existence of a long-lived strongly magnetized remnant.

We introduce the alaric parton shower for simulating quantum chromodynamics (QCD) radiation at hadron colliders and present numerical results from an implementation in the event generator sherpa. alaric provides a consistent framework to quantify certain systematic uncertainties which cannot be eliminated by comparing the parton shower with analytic resummation. In particular, it allows us to study recoil effects away from the soft and collinear limits without the need to change the evolution variable or the splitting functions. We assess the performance of alaric in Drell-Yan lepton pair and QCD jet production, and present the first multijet merging for the new algorithm.

The study of chaos and complexity in non-Hermitian quantum systems poses significant challenges due to the emergence of complex eigenvalues in their spectra. Recently, the singular value decomposition (SVD) method was proposed to address these challenges. In this work, we identify two critical shortcomings of the SVD approach when analyzing Krylov complexity and spectral statistics in non-Hermitian settings. First, we show that SVD fails to reproduce conventional eigenvalue statistics in the Hermitian limit for systems with nonpositive definite spectra, as exemplified by a variant of the Sachdev-Ye-Kitaev (SYK) model. Second, and more fundamentally, Krylov complexity and spectral statistics derived via SVD cannot distinguish chaotic from integrable non-Hermitian dynamics, leading to results that conflict with complex spacing ratio analysis. Our findings reveal that SVD is inadequate for probing quantum chaos in non-Hermitian systems, and we advocate employing more robust methods, such as the bi-Lanczos algorithm, for future research in this direction.

We investigate two salient chaotic features, namely Lyapunov exponent and butterfly velocity, for an asymptotically Lifshitz black hole background with arbitrary dynamical critical exponent. These features are computed using three methods: entanglement wedge method, out-of-time-ordered correlator computation, and pole skipping. We present a comparative study where all of these methods yield exactly similar results for the butterfly velocity and Lyapunov exponent. This establishes an equivalence between all three methods for probing chaos in the chosen gravity background. Furthermore, we evaluate the chaos at the classical level by computing the eikonal phase and Lyapunov exponent from the bulk gravity. In the classical approach, we comment on potential limitations while choosing the turning point of the null geodesic in our gravity background. All chaotic properties emerge as nontrivial functions of the anisotropy index. By examining the classical eikonal phase, we uncover different scattering scenarios in the near-horizon and near-boundary regimes. Finally, we remark on a possible classical/quantum correspondence from the analysis of classical eikonal phase shift and Lyapunov exponent.

We study the low-energy limit of general relativity in the presence of stationarity and axial symmetry, coupled to dust. Specifically, we demonstrate that differences between the dynamics of general relativity and those of Newtonian gravity persist even in the weak-field and slow-motion regime. Notably, these differences are driven by dragging terms that are not necessarily small, as is typically the case in the well-known gravitomagnetic limit. To highlight this distinction, we use the concept of strong gravitomagnetism that we introduced in previous works. We provide a pedagogical discussion of how these discrepancies arise and outline a systematic procedure to solve the equations of motion for such systems. Furthermore, we present analytical results for specific cases and also give the general solution for the vacuum case. A particularly notable result is our demonstration of how general relativity can naturally account for a Tully-Fisher-like relation.