The use of quasicircular waveforms in matched-filter analyses of signals from eccentric binary neutron star (BNS) mergers can lead to biases in the source’s parameter estimation. We demonstrate that significant biases can be present already for moderate eccentricities $e_0\gtrsim 0.05$ and signals detected by LIGO-Virgo-KAGRA with signal-to-noise ratio (SNR) $\gtrsim 12$. We perform systematic Bayesian mock analyses of unequal-mass nonspinning BNS signals up to eccentricities $e_0\sim 0.1$ using quasicircular effective-one-body (EOB) waveforms with spins. We find fractional SNR losses up to tens of percent and up to $16\sigma$ deviations in the inference of the chirp mass. The latter effect is sufficiently large to lead to an incorrect (and ambiguous) source identification. The inclusion of spin precession in the quasicircular waveform does not capture eccentricity effects. We conclude that high-precision observations with advanced (and next generation) detectors are likely to require standardized, accurate, and fast eccentric waveforms.

The population of unresolved stellar-mass black hole binaries (sBBHs) is expected to produce a stochastic gravitational-wave background (SGWB) potentially detectable by the Laser Interferometer Space Antenna (LISA). In this work, we compute the imprint of astrophysical environmental effects—such as gas dynamical friction and accretion—on this background. Using the sBBH population constraints obtained by the LIGO-Virgo-KAGRA Collaboration, we compute the expected SGWB and develop a phenomenological parametric model that can accurately capture the effect of dynamical friction and accretion. Using our model, we perform Bayesian inference on simulated signals to assess the detectability of these environmental effects. We find that, even for large injected values of the Eddington ratio, the effect of accretion in the SGWB is undetectable by LISA. However, LISA will be able to constrain the effect of dynamical friction with an upper bound on the gas density of $\rho \lesssim 7.6\times {10}^{-10}\mathrm{g}{\mathrm{cm}}^{-3}$, thus probing the sBBH environment forming in typical thin accretion disks around active galactic nuclei. For injected densities of $\rho \sim {10}^{-10}–{10}^{-9}\mathrm{g}{\mathrm{cm}}^{-3}$, dynamical friction effects can be well measured and clearly distinguished from vacuum, with Bayes factors reaching up to $\sim 60$, even when the Galactic foreground is included.

We investigate the degrees of freedom of new general relativity (NGR). This theory is a three-parameter theory and is classified into nine irreducible types according to the rotation symmetry of $SO(3)$ on each leaf of Arnowitt-Deser-Misner (ADM) foliation. In this work, we focus on unveiling the degrees of freedom of the physically interesting types of NGR: Type 2, Type 3, Type 5, and Type 8, which contain the gravitational propagating degrees of freedom. First, we revisit the theory based on the gauge approach to gravity and reformulate the Lagrangian of the theory. Second, we review the irreducible decomposition of the theory while focusing on the Hamiltonian and the primary constraints in each type. Third, we perform the Dirac-Bergmann analysis to unveil the degrees of freedom of the theory in the cases of Type 2, Type 3, Type 5, and Type 8. We find a novel behavior of constraints in Type 8, which is classified as second-class, but not to determine any Lagrange multipliers and to provide the gauge invariance of the theory under the satisfaction of a specific condition of the multipliers. The number of degrees of freedom of Type 2, Type 3, and Type 5 are unveiled as six, five, and seven, respectively. The number of degrees of freedom of Type 8 is either four, under a specific condition to the Lagrange multipliers, or six, in the generic case. Finally, we conclude this work with five future perspectives.

We quantize a Bianchi IX universe in Hořava-Lifshitz theory. For analytical tractability, we consider the small anisotropy limit of the Bianchi IX, that is, a perturbative anisotropic deformation of a closed, homogeneous, and isotropic universe. In the case of the projectable theory we further set the “dark matter as integration constant” to zero by assuming that the space consists of only one connected piece. In that limit and under the assumption, we first study the semiclassical Wentzel-Kramers-Brillouin (WKB) solutions to the Wheeler-DeWitt equation. We find the wave function of the universe, up to an overall normalization, and estimate the semiclassical tunneling probability for the emergence of an expanding universe. We establish a dictionary of correspondence between the WKB wave functions in general relativity and Hořava-Lifshitz theory in the large-scale factor (or IR) limit. For a small universe (UV limit), on the other hand, due to contributions from higher-dimensional operators, the anisotropies decouple from the scale factor, a behavior significantly different from general relativity, and analytic solutions to the Wheeler-DeWitt equation beyond the WKB approximation can be found. The wave function of the scale factor satisfies the DeWitt criterion, whereas the wave functions of anisotropies resemble those of quantum harmonic oscillators. The quantum prediction for the initial condition of anisotropies is obtained in terms of the coupling parameters of Hořava-Lifshitz theory. We find a bound on the coupling parameters from the normalizability of the wave functions of anisotropies. Further, we calculate the expectation values for squared anisotropic shear and squared anisotropies in both the large universe and the small universe limits.

Scalar-tensor gravity models are among the prime candidates to explain cosmic acceleration, and compact stars provide unique laboratories for testing such theories. Predictions of scalar-tensor gravity in compact stars can be examined during the evolution of neutron stars. Spontaneous scalarization in relativistic stars is influenced by different properties of stellar matter in various evolution regimes. In the present study, we investigate the scalarization of neutron stars in different stages of the evolvement. For this aim, we apply the isentropic equations of state for the neutron star matter including nucleons, hyperons, and $\mathrm{\Delta }$-resonances in neutrino-trapped, neutrino diffusion, and neutrino-transparent stages as well as cold-catalyzed neutron star. Our equations of state are based on the relativistic model within the mean-field approximation. To emphasize the role of scalar-tensor theories in exploring the properties and structure of compact stars, we calculate the structure of neutron stars with hyperons and $\mathrm{\Delta }$-resonances in different snapshots of the neutron star evolution in the scalar-tensor gravity. Our calculations confirm that the neutron star scalarization is affected by the hyperons as well as the $\mathrm{\Delta }$-resonances. Moreover, the properties of scalarized neutron stars depend on the stage of the star evolution.

The intense magnetic fields inferred from magnetars suggest they may be strong gravitational-wave emitters. Although emissions due to hydromagnetic deformations are more promising from a detection standpoint, exterior fields also contribute a strain. However, numerical evidence suggests that the free energy of stable magnetospheric solutions cannot exceed a few tens of percent relative to the potential state, implying that the magnetospheric contribution to the gravitational-wave luminosity cannot differ significantly between models. This prompts “universality,” in the sense that the strain provides a direct probe of the near-surface field without being muddied by magnetospheric currents. Using a suite of three-dimensional, force-free, general-relativistic solutions for dipole and dipole-plus-quadrupole fields, we find that space-based interferometers may enable marginal detections out to $\lesssim \mathrm{kpc}$ distances for slowly rotating magnetars with fields of $\gtrsim {10}^{15}\mathrm{G}$ independently of internal deformations.

We study low angular momentum, advective accretion flows around a Kerr black hole within the framework of general relativistic magnetohydrodynamics (GRMHD) in the steady state. By solving the full set of GRMHD equations, we aim to provide a comprehensive understanding of the behavior of magnetized plasma in the strong gravity regime near a rotating black hole. The accretion solutions are obtained for a set of input parameters, namely energy ($\mathcal{E}$), angular momentum ($\mathcal{L}$), magnetic flux ($\mathrm{\Phi }$), and isorotation parameter ($I$). By systematically varying these parameters, we generate a family of global GRMHD accretion solutions that characterize the physical environment around the black hole. Using this approach, we investigate whether the inferred magnetic field strengths reported by the Event Horizon Telescope (EHT) for Sagittarius ${\mathrm{A}}^{*}$ at various radii can be reproduced. We find that, for a broad range of parameter values, our model successfully recovers the EHT inferred magnetic field strengths with an accuracy of approximately 10%, offering a self-consistent framework for interpreting near-horizon accretion physics.

The low-lying light tetraquark states are investigated in the nonrelativistic quark model including the pseudoscalar meson exchange, where two different confinement potential schemes, the Cornell potential and the linear potential, are employed, along with the instanton-induced interaction serving as the residual spin-dependent interaction. The numerical results show agreement with masses of $f_0(500)$, $f_0(1370)$, $f_0(1500)$, $f_0(2020)$, $f_0(2200)$, $h_1(1170)$, $h_1(1595)$, $h_1(1900)$, $h_1(1965)$, $h_1(2215)$, $f_2(1430)$, $f_2(1640)$, $f_2(1810)$, $f_2(2010)$, $f_2(2150)$, $a_0(980)$, $a_0(1450)$, $a_0(1950)$, $a_1(1260)$, $a_1(1640)$, $a_2(1700)$, $K_0^{*}(1430)$, $K_0^{*}(1950)$, $K_1(1270)$, $K_1(1440)$, $K_1(1650)$, and $K_2^{*}(1980)$. The results shed light on the spectrum of these mesons and offer guidance to search for the tetraquarks in the future.

The thermodynamical properties of magnetized nuclear matter at finite temperature and baryon chemical potential are studied within an effective model incorporating the QCD trace anomaly effect. The presence of magnetic field induces anisotropic structure in the energy momentum tensor due to the broken rotational invariance. The study exhibits a phase transition through the sudden change of the effective nucleon mass in a certain range of baryon chemical potential and temperature. The addition of nucleonic vacuum contribution at finite magnetic field leads to the magnetic catalysis effect. The change in squared speed of sound with chemical potential at various temperatures is closely connected to the nature of phase transition in nuclear matter. The pressure anisotropy results in different values of sound speed and isothermal compressibility in the parallel and perpendicular directions with respect to the magnetic field. The smaller values of isothermal compressibility in the parallel direction compared to the perpendicular one indicate that the equation of state is stiffer along the magnetic field direction. The studies of these thermodynamic observables can have significant importance in analyzing the properties of some compact astrophysical objects as well as in the context of noncentral heavy-ion collision experiments.

The calculation of particle decay widths and scattering cross sections naturally decomposes into a quantum mechanical amplitude and a relativistic phase space (PS). This PS can be formulated in terms of parallelotopes providing frame independent invariants. We demonstrate how these invariants are related to frame dependent observables such as momenta, energies, and angles between particles. Furthermore, we derive expressions for $n$-dimensional PSs featuring simple integration limits that are particularly well suited for an analytical treatment. To that end we develop a pictorial description using PS diagrams that allow one to straightforwardly identify the optimal set of integration variables for arbitrary $n$.

Thermal dark matter is a compelling setup that has been probed by a multitude of experiments, mostly in the GeV–TeV mass range. The thermal paradigm in the sub-GeV range is about to experience the same experimental test with the next generation of low-energy accelerators and light dark matter detectors. Motivated by this, we investigate thermal dark matter in the $L_{\mu }-L_{\tau }$ and assess how the introduction of a matter-dominated era impacts the parameter that yields the correct relic density. Interestingly, we show that the projected experiments, such as the Muon (Synchrotron) Ion Collider, Future Circular Collider-ee, and Light Dark Matter eXperiment, will probe a large region of the viable parameter space that yields the correct relic density. In the GeV–TeV mass regime, the usual large-scale detectors push the sensitivity. Our work highlights the rich interplay between early-Universe dynamics, dark matter phenomenology, and the discovery potential of next-generation experiments.

The Higgs field is conventionally treated as a small local perturbation atop a large, constant vacuum value that uniformly permeates the Universe. I propose instead that in regions of extreme gravitational intensity—such as near gravitational singularities—the Higgs field behaves in a profoundly nonperturbative manner. In such environments, spacetime and the Higgs field engage in a dynamic interplay that extends spacetime beyond the singularity, achieving geodesic completeness. The continuation beyond the singularity is dominated by antigravity effects, reshaping the causal structure of spacetime and enabling novel flows of matter and information, including traversal through singularities. In its standard form, the combined framework of the Standard Model (SM) and general relativity (GR), as well as most of its extensions, fails to capture these phenomena due to its geodesic incompleteness. By contrast, a refined, locally conformal-symmetric formulation—denoted i($\mathrm{SM}+\mathrm{GR}$)—naturally incorporates these effects. GR is not an optional component of i($\mathrm{SM}+\mathrm{GR}$) but an essential ingredient. This framework preserves the empirical success of $\mathrm{SM}+\mathrm{GR}$ in the low-energy regime while predicting striking new phenomena in extreme gravitational settings, including within black holes (on both sides of the singularity) and in pre–big bang cosmology. At the classical field theory level, i($\mathrm{SM}+\mathrm{GR}$) offers fresh perspectives on the black hole information puzzle and provides a platform for locally scale-invariant generalizations, such as geodesically complete quantum field theory, string theory, and unified models of fundamental interactions. This paper presents the detailed derivations and explanations that underlie a condensed letter version recently published in Itzhak Bars, Higgs field as architect of a geodesically complete universe and agent for new physics in interiors of black holes, arXiv:2509.07346.

Recent developments in mapping lattice gauge theories relevant to the Standard Model onto digital quantum computers identify scalable paths with well-defined quantum compilation challenges toward the continuum. As an entry point to these challenges, we address the simulation of SU(2) lattice gauge theory. Using qudit registers to encode the digitized gauge field, we provide quantum resource estimates, in terms of elementary qudit gates, for arbitrarily high local gauge field truncations. We then demonstrate an end-to-end simulation of real-time, qutrit-digitized SU(2) dynamics on a cube. Through optimizing the simulation, we improved circuit decompositions for uniformly controlled qudit rotations, an algorithmic primitive for general applications of quantum computing. The decompositions also apply to mixed-dimensional qudit systems, which we found advantageous for compiling lattice gauge theory simulations. Furthermore, we parallelize the evolution of opposite faces in anticipation of similar opportunities arising in three-dimensional lattice volumes. This work details an ambitious executable for future qudit hardware and attests to the value of codesign strategies between lattice gauge theory simulation and quantum compilation.

In Guo [Toward extracting the scattering phase shift from integrated correlation functions. II. A relativistic lattice field theory model, Phys. Rev. D 110, 014504 (2024).] and associated studies, a relativistic finite-volume formalism in $1+1$ dimensions is proposed to extract infinite-volume scattering phaseshift. It is based on the difference of integrated correlation functions rather than energy spectrum in the finite volume, and can be regarded as complementary to the well-known Lüscher formalism. In the present work, the formalism is further extended into $3+1$ dimensional spacetime. The aim is to explore and demonstrate the challenges in applying the formalism to more practical settings. Specifically, Monte Carlo simulations of a complex ${\varphi }^4$ relativistic field model are carried out in both $2+1$ and $3+1$ dimensions on lattices of varying sizes, and phaseshifts for the contact interaction are extracted from the formalism using modest computing resources.

An anomaly detection search for narrow-width resonances beyond the Standard Model that decay into a pair of jets is presented. The search is based on $139{\mathrm{fb}}^{-1}$ of proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ recorded during 2015–2018 with the ATLAS detector at the Large Hadron Collider. The analysis is optimized without a particular signal model and aims to be sensitive to a broad range of new physics. It uses two different machine learning strategies to estimate the background in different signal regions. In each region, a weakly supervised classifier is trained to distinguish this background model from data. The analysis focuses on events with high transverse momentum jets reconstructed as large-radius jets. The mass and substructure of these jets are used as inputs to the classifiers. After a classifier-based selection, the distribution of the invariant mass of the two jets is used to search for potential local excesses. The model-independent results of both the anomaly detection methods show no signs of significant local excesses. In addition to model-independent results, a representative set of signal models is injected into the data, and the sensitivity of the methods to these scenarios is reported.

Algebraic noncovariant gauges are used often in string theory, Chern-Simons theory, and gravitation and gauge theories. Loop integrals, however, have spurious singularities that need to be regularized. The most popular and consistent regularization is the Mandelstam-Leibbrandt (ML) prescription. This paper extends the ML prescription outside the light cone. It shares all the properties of light cone ML regularization: it preserves naive power counting and gauge invariance. Moreover, using dimensional regularization, we get a closed form for the basic integrals, including divergent and finite pieces. These results simplify calculations in gauge theories and open new avenues for applications in nonlocal models.

We study graviton-photon conversion in the presence of stochastic magnetic fields. Assuming Gaussian magnetic fields that may possess nontrivial helicity, and unpolarized gravitational waves (GWs) as the initial state, we obtain expressions for the intensity and linear/circular polarizations of GWs after propagation over a finite distance. We calculate both the expectation values and variances of these observables and find their nontrivial dependence on the typical correlation length of the magnetic field, the propagation distance, and the photon plasma mass. Our analysis reveals that an observationally favorable frequency range with narrower variance can emerge for the intensity, while a peak structure appears in the expectation value of the circular polarization when the magnetic field has nonzero helicity. We also identify a consistency relation between the GW intensity and circular polarization.

Undoing the effect of gravitational lensing on the cosmic microwave background (CMB) (“delensing”) is essential in shaping constraints on weak signals limited by lensing effects on the CMB, for example on a background of primordial gravitational waves. Removing these anisotropies induced by large-scale structures from the CMB maps also generally helps our view of the primordial Universe by sharpening the acoustic peaks and the damping tail. However, practical implementations of delensing transfer parts of these anisotropies to the noise maps. This will induce a new large scale “mean-field” bias to any anisotropy estimator applied to the delensed CMB, and this bias directly traces large-scale structures. This paper analytically quantifies this delensed noise mean field and its impact on quadratic and likelihood-based lensing estimators. We show that for Simons-Observatory-like surveys, this mean-field bias can reach 15% in cross-correlation with large-scale structures if unaccounted for. We further demonstrate that this delensed noise mean field can be safely neglected in likelihood-based estimators without compromising the quality of lensing reconstruction or $B$-mode delensing, provided the resulting lensing map is properly renormalized.

We report a thunderstorm-induced muon event (TIME) observed on 20 March 2020 using the GRAPES-3 muon telescope in Ooty, India. This event was investigated using complementary data from the INSAT-3DR satellite, the Indian lightning location network, and ground-based electric field measurements. A 1.4% suppression in muon flux ($12.4\sigma$ significance) was detected in the southeast sector, coinciding with intense upward-directed electric fields ($-5\mathrm{kV}/\mathrm{m}$) and elevated lightning activity. These observations support the hypothesis that upward electric fields cause energy losses in positive muons, resulting in reduced ground-level flux. The event provides evidence for the directional sensitivity of cosmic-ray secondaries to storm-time electric fields and highlights the unique capability of muon telescopes in probing high-altitude atmospheric electrodynamics. This study illustrates the value of integrating particle physics with atmospheric science, leveraging ground- and space-based observations to deepen our understanding of energetic atmospheric processes and their connections to space weather phenomena.