For twisted particles in arbitrary gravitational fields, the problems of the rotation of intrinsic orbital angular momentum and the orbital Hall effect are solved in the general case. We need not use the Maxwell equations in curved spacetimes for a description of twisted photons. The exact general equation rigorously defining the orbital-angular-momentum dynamics in any Riemannian spacetimes is derived. The general description of different manifestations of the orbital Hall effect for any twisted particles is also presented. Our short analysis shows that the results obtained can find important practical applications.

We develop an analytic action principle in $\mathcal{N}=2$ ${\mathrm{AdS}}_4$ harmonic superspace and apply it to study the component structure of the free $q$-hypermultiplet model.

We analyze the renormalized stress-energy tensor (RSET) of a massless quantum scalar field in time-dependent gravitational backgrounds. Starting from its formal expression obtained within the covariant perturbative expansion to lowest order in the curvature, we evaluate the RSET in an arbitrary number of dimensions in terms of coordinate-space distributions. For time-dependent spherically symmetric spacetimes, we derive a multipole expansion and determine its asymptotic behavior. We find that the RSET is locally nonvanishing at null infinity and depends on the detailed dynamics of the collapsing body. However, the total emitted energy vanishes at this order, meaning that the leading contribution does not account for the energy density of the created particles. Nevertheless, by enforcing stress-tensor conservation up to second order in the curvature, we show that the total radiated energy can be extracted from the first-order RSET. Finally, we compute the induced quantum corrections to the metric at large distances, which display several interesting features.

Stability of circular orbits of the dust particles within a charged rotating disc of dust with respect to perturbations in the equatorial plane is analyzed. Within Einstein-Maxwell theory, the charged rotating disc of dust is an axisymmetric, stationary solution given in terms of a post-Newtonian expansion. The disc solution is characterized by a rigid rotation around the axis of symmetry and a constant specific charge $\epsilon$. It is found that for $\epsilon <1$ all realized dust particle orbits are stable and for $\epsilon =1$ all dust particles are in marginally stable states.

The ringdown signal following a black hole (BH) merger can be modeled as a superposition of BH quasinormal modes (QNMs), offering a clean setup for testing gravitational theories. In particular, detecting multiple QNMs enables consistency checks of their frequencies and damping times, serving as a test of general relativity—a technique known as black hole spectroscopy. However, incorporating additional QNMs introduces challenges such as increased parameter correlations and higher computational costs in data analysis. To address this, we propose an efficient Bayesian analysis method that applies the Gram-Schmidt algorithm to the QNMs. This reduces the correlation between the modes and enables analytic marginalization over the mode amplitudes. We validate our approach using damped sinusoids and numerical waveforms from the Simulating eXtreme Spacetimes catalog.

We study gravitational wave production at strong first order phase transitions, with large-scale, long-running simulations of a system with a scalar order parameter and a relativistic fluid. One transition proceeds by detonations with asymptotic wall speed $v_{\mathrm{w}}=0.92$ and transition strength ${\alpha }_{\mathrm{n}}=0.67$, and the other by deflagrations, with a nominal asymptotic wall speed $v_{\mathrm{w}}=0.44$ and transition strength ${\alpha }_{\mathrm{n}}=0.5$. We investigate in detail the power spectra of velocity and shear stress and—for the first time (to the best of our knowledge) in a phase transition simulation—their time decorrelation, which is essential for the understanding of gravitational wave production. In the detonation, the decorrelation speed is larger than the sound speed over a wide range of wave numbers in the inertial range, supporting a visual impression of a flow dominated by supersonic shocks. Vortical modes do not contribute greatly to the produced gravitational wave power spectra even in the deflagration, where they dominate over a range of wave numbers. In both cases, we observe dissipation of kinetic energy by acoustic turbulence and, in the case of the detonation, an accompanying growth in the integral scale of the flow. The gravitational wave power approaches a constant with a power law in time, from which can be derived a gravitational wave production efficiency. For both cases, this is approximately ${\tilde{\mathrm{\Omega }}}_{\mathrm{gw}}^{\infty }\simeq 0.017$, even though they have quite different kinetic energy densities. The corresponding fractional density in gravitational radiation today, normalized by the square of the mean bubble spacing in Hubble units, for flows which decay in much less than a Hubble time, is ${\mathrm{\Omega }}_{\mathrm{gw},0}/(H_{\mathrm{n}}{R}_{*}{)}^2=(4.8\pm 1.1)\times {10}^{-8}$ for the detonation and ${\mathrm{\Omega }}_{\mathrm{gw},0}/(H_{\mathrm{n}}{R}_{*}{)}^2=(1.3\pm 0.2)\times {10}^{-8}$ for the deflagration.

We present a joint cosmological analysis of the two-point correlation function and the aperture-mass skewness measured from the Year 3 data of the Hyper Suprime-Cam Subaru Strategic Program. The aperture-mass skewness is a compressed representation of three-point shear information, designed to capture non-Gaussian features while keeping the data vector computationally tractable. We find that including the aperture-mass skewness improves the $S_8\text{−}{\mathrm{\Omega }}_m$ figure of merit by 80% compared to the two-point-correlation-function-only case, primarily due to the breaking of degeneracies. Our joint analysis yields a constraint of $S_8=0.736\pm 0.020$, which is slightly lower than the two-point-only result and increases the tension with Planck 2018 to $3.2\sigma$ in the $S_8\text{−}{\mathrm{\Omega }}_m$ plane. The two- and three-point statistics are found to be internally consistent across redshift bins and angular scales, and we detect no significant intrinsic alignment signal. We also explore extensions to the $w$ cold dark matter model and find no evidence for deviations from a cosmological constant. This work demonstrates the feasibility and scientific value of incorporating third-order shear statistics into weak lensing cosmology and provides a practical pathway for similar analyses in future Stage-IV surveys such as LSST, Euclid, and Roman.

We implement a novel formalism to constrain primordial non-Gaussianity of the local type from the large-scale modulation of the small-scale power spectrum. Our approach combines information about primordial non-Gaussianity contained in the squeezed bispectrum and the collapsed trispectrum of large-scale structure together in a computationally amenable and consistent way, while avoiding the need to model complicated covariances of higher $N$-point functions. This work generalizes our recent work, which used a neural network estimate of local power, to the more conventional local power spectrum statistics and explores using both matter field and halo catalogs from the Quijote simulations. We find that higher $N$-point functions of the matter field can provide strong constraints on $f_{NL}$, but higher $N$-point functions of the halo field, at the halo density of Quijote, only marginally improve constraints from the two-point function.

Wide-parameter-space searches for continuous gravitational waves using semicoherent matched-filter methods require enormous computing power, which limits their achievable sensitivity. Here we explore an alternative search method based on training neural networks as classifiers on detector strain data with minimal preprocessing. Contrary to previous studies using convolutional neural networks (CNNs), we investigate the suitability of the transformer architecture, specifically the vision transformer (ViT). We establish sensitivity benchmarks using the matched-filter $\mathcal{F}$-statistic for ten targeted searches over a ten day timespan, and ten directed and six all-sky searches over a one day timespan. We train ViTs on each of these benchmark cases. The trained ViTs achieve essentially matched-filter sensitivity on the targeted benchmarks, and approach the $\mathcal{F}$-statistic detection probability of $p_{\det }=90\%$ on the directed ($p_{\det }\approx 85–89\%$) and all-sky benchmarks ($p_{\det }\approx 78–88\%$). Unlike the CNNs in our previous studies, which required extensive manual design and hyperparameter tuning, the ViT achieves better performance with a standard architecture and minimal tuning.

We present a precise measurement of the westward rigidity-dependent shift of the Moon’s shadow using three and a half years of cosmic ray data collected by the kilometer square array (KM2A) of the Large High Altitude Air Shower Observatory (LHAASO) experiment. These measurements enable us to calibrate the detector energy response in the range of 20 to 260 TeV, with results showing excellent agreement with the energy response derived from Monte Carlo (MC) simulations of the KM2A detector. We also measure a best-fit parameter $\epsilon =0.015\pm 0.08$, corresponding to a 95% CI of $[-14\%,+17\%]$ for the energy scale estimation. This result establishes the exceptional accuracy of the KM2A-MC in simulating the detector’s response within this energy range.

A finite axion-nucleon coupling enables the production of axions in stellar environments via the thermal excitation and subsequent deexcitation of the ${}^{57}\mathrm{Fe}$ isotope. Given its low-lying excited state at 14.4 keV, ${}^{57}\mathrm{Fe}$ can be efficiently excited in the hot cores of supergiant stars, possibly leading to axion emission. The conversion of these axions into photons in the Galactic magnetic field results in a characteristic 14.4 keV line, potentially detectable by hard x-ray telescopes such as NASA’s Nuclear Spectroscopic Telescope Array (nustar). In this work, we present the first constraints on axion-nucleon couplings derived from nustar observations of Betelgeuse and discuss the potential insights that could be gained from detecting this line in other nearby supergiants. Our results establish significantly more stringent bounds than those obtained from solar observations, setting a limit of $|g_{a\gamma }{g}_{aN}^{\mathrm{eff}}|<(1.2–2.7)\times {10}^{-20}{\mathrm{GeV}}^{-1}$ for $m_a\lesssim {10}^{-10}\mathrm{eV}$.

Collective neutrino oscillations exhibit instabilities that induce appreciable flavor conversion, with crucial astrophysical implications. While the importance of initial phase-space distributions is well established, a general instability criterion for distributions dependent on both energy and emission angle has been lacking. We identify and analyze the sufficient (and necessary) conditions for a generic collective neutrino flavor instability.

In the presence of an ultralight scalar or vector boson, a spinning black hole will be spun down through the superradiant instability. We use spin measurements from gravitational wave observations of binary black holes, in particular the heavy binary black hole merger event GW231123, along with the lower-mass GW190517 event, to constrain the existence of ultralight bosons. We disfavor scalars with masses in the range of $[0.55,11]\times {10}^{-13}\mathrm{eV}$ and vectors in the range of $[0.11,18]\times {10}^{-13}\mathrm{eV}$, making only a conservative assumption that the black hole lifetimes are greater than ${10}^5\mathrm{years}$. The lower ends of these ranges, where the exclusion confidence is the highest, were not previously excluded by spin measurements from electromagnetic or gravitational wave observations. We map these constraints to axion and dark photon models with interactions.

We investigate the neutrino and gravitational wave (GW) signals from accretion disks formed during the failed collapse of a rotating massive star (a collapsar). Following black hole formation, a neutrino-cooled, shocked accretion disk forms, which displays nonspherical oscillations for a period of seconds before becoming advective and exploding the star. We compute the neutrino and GW signals (matter quadrupole, frequencies $\lesssim 100\mathrm{Hz}$) from collapsar disks using global axisymmetric, viscous hydrodynamic simulations. The neutrino signal with typical energies of $\mathcal{O}(10)\mathrm{MeV}$ is maximal during the neutrino-cooled (NDAF) phase that follows shock formation. This phase lasts for a few seconds and is easily detectable within $\mathcal{O}(10–100)\mathrm{kpc}$ by the IceCube neutrino telescope. Additional neutrino signatures from a precursor equatorial shock and by stochastic accretion plumes during the advective phase are detectable within the Galaxy. The GW signal during the NDAF phase is detectable in the Galaxy by current and next-generation ground-based observatories. The explosion (memory) GW signal is similar to that of standard core-collapse supernovae and can be probed with a decihertz space-based detector. Shock oscillations during the NDAF phase impart time variations with frequency $\mathcal{O}(10–100)\mathrm{Hz}$ to the neutrino and GW signals, encoding information about the shock dynamics and inner disk. These time variations can be detectable in neutrinos by IceCube within $\mathcal{O}(1–10)\mathrm{kpc}$ depending on the progenitor model, flavor transformation scenario, and detailed properties of the angular momentum transport mechanism.

The future space-based gravitational wave observatory, the Laser Interferometer Space Antenna, is expected to observe between 1 and 1000s of extreme-mass-ratio inspirals (EMRIs) per year. Because of the simultaneous presence of other gravitational wave signals in the data, it can be challenging to detect EMRIs and accurately estimate their parameters. In this work, we investigate the interaction between a gravitational signal from an EMRI and millions of signals from inspiraling Galactic white dwarf binaries. We demonstrate that bright Galactic binaries can contaminate the detection and characterization of EMRIs. We perform Bayesian inference of EMRI parameters after removing resolvable Galactic binaries and confirm an accuracy comparable to that expected in Gaussian noise.

Neutrino flavor evolution in dense astrophysical environments is inherently nonlinear and sensitive to many-body (MB) quantum effects beyond the mean-field approximation. Existing MB studies are constrained by small system sizes, closed boundaries, and highly idealized symmetry assumptions. We present a unified tensor-network framework that enables simulations of inhomogeneous and anisotropic flavor evolution under conditions relevant to core-collapse supernovae and neutron-star mergers. Within this framework, we examine the effects of inhomogeneity, boundary conditions, and convergence with resolution for multiple neutrino distributions, allowing direct comparison of these setups under one consistent formulation. In our simulations, many-body systems equilibrate earlier than their mean-field counterparts while approaching similar final flavor states. Enlarging the interaction region allows open boundaries to reproduce closed-system behavior, but only when the beams begin superimposed and interact continuously. By contrast, initially separated configurations develop entanglement more slowly, interact over longer times, and equilibrate to a flavor content that differs from that obtained from initially superimposed calculations.

Assuming dark matter to be asymmetric as well as self-interacting and neutrinos to be Dirac fermions, we propose a framework to address the observed baryon imbalance of the Universe. We add three right-handed neutrinos ${\nu }_{R_i},i=1,2,3$, one singlet fermion $\chi$, a doublet fermion $\psi$, and heavy scalar doublets ${\eta }_i,i=1,2$ to the Standard Model. A global $B-L$ is imposed to protect the Dirac nature of neutrinos. Both $\chi$ and $\psi$ are fermions with nonzero charge under an extended $U(1{)}_{B-L}\times U(1{)}_D$ symmetry. Additionally, a ${\mathcal{Z}}_2$ symmetry is imposed, where the singlets $\chi$, ${\nu }_R$, and $\eta$ are negative and the doublet $\psi$ is positive. The $CP$-violating out-of-equilibrium decay of heavy scalar $\eta$ generates an equal and opposite $B-L$ asymmetry among the left-handed (${\nu }_L$) and right-handed (${\nu }_R$) neutrinos. The ${\nu }_L-{\nu }_R$ equilibration process does not take place until below the electroweak phase transition scale because of tiny Yukawa couplings. During this time, sphaleron processes, which are active at temperatures higher than 100 GeV, transform a portion of the $B-L$ asymmetry stored in left-handed neutrinos into baryon asymmetry. MeV scale gauge boson $Z^{\prime }$ of the $U(1{)}_D$ sector mediates both annihilation of symmetric dark matter component and self-interaction among dark matter particles. Moreover, $Z^{\prime }$ mixes with the Standard Model Z boson and provides a portal for dark matter direct detection.

Charged lepton flavor-violating (cLFV) processes, which are definite proof of new physics beyond the Standard Model, have remained experimentally elusive to date. Effective field theory (EFT) has been very useful in providing information about such new physics through the higher-dimensional operators. These operators respect SM gauge invariance, and they are suppressed by appropriate powers of the energy scale $\mathrm{\Lambda }$. In regard to lepton flavour violating (LFV) processes, the Standard Model effective field theory (SMEFT) is shown to be a useful tool for estimating any new physics effect at the scale $\mathrm{\Lambda }$. It is worth noting that a large class of cLFV processes involves both quarks and leptons. Thus, low-energy observables play a significant role in providing bounds on lepton-flavor-violating 2-quark-2-lepton ($2q2\ell$) operators. In this work, we explore several low-energy cLFV processes that can be addressed within the SMEFT framework, relating them to the specific operators of relevance. Keeping in mind the correlation that exists among the SMEFT operators, we want to extract the strongest constraints on these $2q2\ell$ operators.

The individual fermion generations of the standard model fit neatly into a representation of a simple grand unified theory gauge algebra. If grand unification is not realized in nature, this would appear to be a coincidence. We attempt to quantify how frequently this coincidence occurs among theories with group structure and fermion content similar to the standard model. While many of the completely chiral, anomaly-free fermion representations of the standard model gauge algebra that are no larger than the single-generation standard model are unifiable, we find that unifiability quickly becomes rare when the analysis is extended to include other gauge algebras or larger representations. This purely group-theoretical analysis may be taken as a bottom-up indication for grand unification, conceptually similar to a naturalness argument.

Light cone distribution amplitudes for a light baryon can be extracted through the simulation of the quasi-distribution amplitudes (quasi-DAs) on the lattice. We implement the hybrid renormalization for the quasi-DAs of light baryons. Lattice simulations are performed using $N_f=2+1$ stout-smeared clover fermions and a tree-level Symanzik-improved gauge action, with three lattice spacings of 0.105, 0.077, 0.052 fm. By analyzing zero-momentum matrix elements for different lattice spacings, we extract the linear divergence associated with the Wilson-line self-energy. Matching to perturbative matrix elements in the $\overline{\mathrm{MS}}$ scheme yields the residual self-renormalization factors. Using these factors, we renormalize the quasi-DAs within the hybrid scheme, which combines self-renormalization at large separations and the ratio scheme at short distances. The renormalized results demonstrate effective cancellation of linear divergences and yield smooth, continuumlike coordinate-space distributions suitable for subsequent Fourier transformation and perturbative matching. These results establish the viability of both self- and hybrid-renormalization frameworks for light baryon quasi-DAs, providing a robust foundation for LaMET-based determinations of light cone distribution amplitudes in future.