Studies of quasinormal modes (QNMs) of black holes have a long and well-established history. Predominantly, much research in this area has customarily focused on the equations given by Regge, Wheeler, and Zerilli. In this work, we study linearized perturbations of a Schwarzschild black hole using the characteristic formulation of numerical relativity, with an emphasis on the computation of QNMs. Within this formalism, the master equation describing gravitational perturbations is known to satisfy a fourth-order differential equation. We analyze the singular points of this master equation, and obtain series solutions whose coefficients are given by three term recurrence relations, from which Leaver’s continued fraction method can be applied. Using this technique, we recover the standard Schwarzschild quasinormal modes. In addition, we find that imposing purely outgoing boundary conditions, a natural feature of the Bondi-Sachs framework, leads to the recovery of the algebraically special mode.

Geometric optics effectively describes the propagation of electromagnetic waves when the wavelength is much smaller than the characteristic length scale of the medium, making wave phenomena like diffraction negligible. As a result, light propagation in a vacuum is typically modeled by rays that follow null geodesics. However, general relativity predicts that polarization-dependent deviations from these geodesics occur in an inhomogeneous gravitational field. In this article, we evaluate the corrections for the deflection and emission of light by a massive gravitating body. Additionally, we derive the scaling behavior of the physical parameters characterizing the trajectories. The calculations are performed at leading order in frequency. We use these results to assess the significance of the birefringence effect in various astrophysical observations. We find that the effect cannot be measured with current instruments but may be detectable in the near future.

Primordial black holes (PBHs) would induce non-Gaussianity in the cosmic microwave background (CMB) by sourcing recombination perturbations spatially modulated by relative velocities between PBHs and the baryons they accrete. The leading non-Gaussian signatures are nonvanishing connected 4-point correlation functions, or trispectra. Earlier, we computed the CMB temperature trispectrum, and forecasted Planck to be more sensitive to it than to changes in the CMB temperature power spectrum for light enough PBHs. Excitingly, accreting PBHs would also induce non-Gaussianity in CMB polarization, and source both $E$ and $B$ modes, which we compute in this paper. We first calculate linear-response perturbations to the tensor-valued photon distribution function sourced by a general spatially varying ionization history, and apply our results to accreting PBHs. We then compute linear-order perturbations to the temperature and polarization 2-point functions sourced by inhomogeneities in recombination due to accreting PBHs; we find them to be negligible relative to their counterparts sourced by homogeneous perturbations to the ionization history. Lastly, we compute all CMB trispectra including temperature, $E$- and $B$-mode polarization at linear order in the PBH abundance. We forecast that including polarization data in a 4-point-function analysis would only increase Planck’s sensitivity to accreting PBHs by a factor $\sim 2$ relative to using temperature alone. As a consequence, we find that a search for PBHs using all temperature and polarization trispectra with Planck data would mostly not be competitive with current bounds from temperature and polarization power spectra. In contrast, we forecast that a CMB Stage-4 experiment would gain significant sensitivity to accreting PBHs through a 4-point-function search, in particular through the contributions of parity-odd trispectra including one $B$-mode field.

Recent searches for parity breaking in the galaxy four-point correlation function, as well as the prospects for greatly improved sensitivity to parity breaking in forthcoming surveys, motivate the search for physical mechanisms that could produce such a signal. Here we show that a parity-violating galaxy four-point correlation function may be induced by lensing by a chiral gravitational-wave background. We estimate the amplitude of a signal that would be detectable with a current galaxy survey, taking into account constraints to the primordial gravitational-wave-background amplitude. We find that this mechanism is unlikely to produce a signal large enough to be seen with a galaxy survey but note that it may come within reach with future 21 cm observations.

The Lambda cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model, while pivotal in cosmological studies, has faced significant challenges due to emerging observational and theoretical inconsistencies. In this work, we analyze constraints on dynamic dark energy models—Chevallier-Polarski-Linder (CPL), Barboza-Alcaniz (BA), Jassal-Bagla-Padmanabhan (JBP), Scaled CPL (SCPL), and Generalized Chaplygin Gas (GCG)—using current datasets, including PantheonPlus, Union, the Dark Energy Survey 5-Year (DESY5) supernova compilations, and baryon acoustic oscillation (BAO) measurements. Our findings reveal that, except for PantheonPlus, these datasets exhibit consistent deviations from the $\mathrm{\Lambda }\mathrm{CDM}$ model, with significance exceeding $2\sigma$ across all considered dynamic dark energy models. We further forecast the constraining power of three years of simulated photometric Supernova Ia data from the Legacy Survey of Space and Time (LSST). Our analysis shows that LSST’s high-precision data can significantly tighten constraints on dark energy parameters, surpassing the precision of current datasets. Additionally, the inclusion of BAO measurements alongside LSST data further improves parameter constraints for all models. These results underscore the necessity of exploring dynamic dark energy frameworks as a potential resolution to the tensions within the $\mathrm{\Lambda }\mathrm{CDM}$ paradigm and highlight LSST’s crucial role in advancing our understanding of alternative cosmologies.

We investigate the impact of beam chromaticity, i.e., the frequency dependence of the beam window function, on cosmological and astrophysical parameter constraints from CMB power spectrum observations. We show that for future high-resolution CMB measurements it is necessary to include a color-corrected beam for each sky component with a distinct spectral energy distribution. We introduce a formalism able to easily implement the beam chromaticity in CMB power spectrum likelihood analyses and run a case study using a Simons Observatory Large Aperture Telescope-like experimental setup and within the public SO software stack. To quantify the impact, we assume that beam chromaticity is present in simulated spectra but omitted in the likelihood analysis. We find that, for passbands of fractional width $\mathrm{\Delta }\nu /\nu \sim 0.2$, neglecting this effect leads to significant biases, with astrophysical foreground parameters shifting by more than $2\sigma$ and cosmological parameters by significant fractions of the error.

This paper investigates Bianchi I spacetimes within the Jordan frame of Brans-Dicke theory, incorporating the framework of effective loop quantum gravity. After developing general formulas, we analyze the robustness of classical singularity resolution due to quantum geometric effects using two common quantization schemes. We then compare the resulting physical properties. We find that both schemes replace classical singularities with regular quantum bounces. Notably, in contrast to similar studies based on general relativity, we find that all three directional scale factors of the Bianchi I spacetimes increase and after the quantum bounce they reach values similar to their initial values, leading to a merging with classical spacetimes in both schemes.

We calculate the $\mu$ and $y$-type spectral distortions of cosmic microwave background (CMB), taking a nonstandard interaction between baryons and viscous dark matter. Using the CMB spectral distortion observations, we can constrain any exotic mechanism that may change the energy of the CMB photon, leading to a CMB spectrum distortion. Depending on the viscosity of dark matter, the energy transfer between dark matter and baryons may modify, leading to a modification in CMB distortion. The existing Cosmic Background Explorer/Far Infrared Absolute Spectrophotometer and the Primordial Inflation Explorer (PIXIE) set limits on $y$ and $\mu$ types of distortions to $y=1.5\times {10}^{-5}$, $\mu =9.0\times {10}^{-5}$ and $y={10}^{-8}$, $\mu =5.0\times {10}^{-8}$, respectively. In this paper, we discuss the prerecombination contributions to $\mu$ and $y$-type distortions by viscous dark matter and constrain the parameter space using PIXIE bounds on spectral distortion.

We present a realizability-preserving numerical method for solving a spectral two-moment model to simulate the transport of massless, neutral particles interacting with a steady background material moving with relativistic velocities. The model is obtained as the special relativistic limit of a four-momentum-conservative general relativistic two-moment model. Using a maximum-entropy closure, we solve for the Eulerian-frame energy and momentum. The proposed numerical method is designed to preserve moment realizability, which corresponds to moments defined by a nonnegative phase-space density. The realizability-preserving method is achieved with the following key components: (i) a discontinuous Galerkin phase-space discretization with specially constructed numerical fluxes in the spatial and energy dimensions; (ii) a strong stability-preserving implicit-explicit time-integration method; (iii) a realizability-preserving conserved to primitive moment solver; (iv) a realizability-preserving implicit collision solver; and (v) a realizability-enforcing limiter. Component (iii) is necessitated by the closure procedure, which closes higher order moments nonlinearly in terms of primitive moments. The nonlinear conserved to primitive and the implicit collision solves are formulated as fixed-point problems, which are solved with custom iterative solvers designed to preserve the realizability of each iterate. With a series of numerical tests, we demonstrate the accuracy and robustness of this discontinuous-Galerkin-implicit-explicit method.

We employ the nuclear lattice effective field theory (NLEFT), an efficient tool for nuclear ab initio calculations, to solve the asymmetric multihadron systems. We take the $D{D}^{*}K$ three-body system as an illustration to demonstrate the capability of the method. Here the two-body chiral interactions between $D$, $D^{*}$, and $K$ are regulated with a soft lattice regulator and calibrated with the binding energies of the $T_{cc}^{+}$, $D_{s0}^{*}(2317)$, and $D_{s1}(2460)$ molecular states. We then calculate the three-body binding energy using the NLEFT and analyze the systematic uncertainties due to the finite volume effects, the sliding cutoff, and the leading-order three-body forces. Even when the three-body interaction is repulsive (even as large as the infinite repulsive interaction), the three-body system has a bound state unambiguously with binding energy no larger than the $D_{s1}(2460)D$ threshold. To check the renormalization group invariance of our framework, we extract the first excited state. We find that when the ground state is fixed, the first excited states with various cutoffs coincide with each other when the cubic size goes larger. In addition, the standard angular momentum and parity projection technique is implemented for the quantum numbers of the ground and excited states. We find that both of them are $S$-wave states with quantum number $J^P=1^{-}$. Because the three-body state contains two charm quarks, it is easier to be detected in the Large Hadron Collider.

We derive the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c$ form factors for the Standard Model and beyond at second order in heavy quark effective theory, applying the recently proposed residual chiral expansion to reduce the set of unknown subsubleading hadronic functions to a single, highly constrained function, that is fully determined by hadron mass parameters at zero recoil. We fit a form factor parametrization based on these results to all available lattice QCD predictions and experimental data. We find that the constrained and predictive structure of the form factors under the residual chiral expansion is in excellent agreement with lattice QCD predictions and experimental data, as well as prior heavy-quark-effective-theory-based fits.

We investigate constraints on neutrino nonstandard interactions (NSIs) in the effective field theory framework, using data from the first measurement of solar ${}^8\mathrm{B}$ neutrinos via coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$) in the PandaX-4T and XENONnT experiments and data from the COHERENT experiment. The impacts of neutrino NSIs on the $\mathrm{CE}\nu \mathrm{NS}$ cross section and the matter effect in the propagation of solar neutrinos are included, while we obtain that the expected number of $\mathrm{CE}\nu \mathrm{NS}$ events is more sensitive to neutrino NSIs appearing in the cross section. Due to relatively large statistical uncertainties, the sensitivities of the PandaX-4T and XENONnT experiments to the neutrino NSIs are currently limited, compared to the COHERENT experiment. Besides, we find that since the central value of the measured $\mathrm{CE}\nu \mathrm{NS}$ counts significantly differs from the Standard Model prediction, the sensitivity of PandaX-4T experiment is even more restricted compared to XENONnT. However, the measurements of PandaX-4T and XENONnT are uniquely sensitive to the neutrino NSIs for the $\tau$ flavor due to oscillation feature of the solar ${}^8\mathrm{B}$ neutrinos. We also assess how the experimental central value, exposure, and systematic uncertainties will affect the constraints on neutrino NSIs from various $\mathrm{CE}\nu \mathrm{NS}$ measurements in the future.

Extracting constraints on the kinetic mixing of a new $U(1{)}^{\prime }$ gauge boson hiding under the Standard Model $Z$ boson resonance requires the formalism of non-Hermitian two-point correlation functions at 1-loop order. We derive self-consistent collider constraints on $Z^{\prime }$ bosons with kinetic mixing in a narrow mass window around the $Z$ boson, considering both model-independent and model-dependent bounds. Our treatment elucidates the importance of both avoided level crossing and the dispersive seesaw effect in interpreting the existing constraints. We also discuss the implications for future measurements on the $Z$-pole.

A recent analysis of the LHCb data [Esposito et al., Phys. Rev. D 105 L031503 (2022)] obtained a sizable negative effective range for the $X(3872)$. This has attracted intensive discussions on whether $X(3872)$ can be deemed as a $D{\overline{D}}^{*}$ molecular state. This work explicitly demonstrates that the negative effective range of the $X(3872)$ does not contradict the molecular picture, adopting an effective field theory formulation of the $D{\overline{D}}^{*}$ interaction that can simultaneously reproduce the binding energy and effective range of the $X(3872)$. We elaborate on the implications of the large negative effective range of $X(3872)$ and the small binding energy on the underlying $D{\overline{D}}^{*}$ interaction. Such results are relevant for a better understanding of hadronic molecules and their binding mechanism.

We collect evidence that the notion of path-ordered non-Abelian integration admits an extension to two dimensions. We propose the corresponding notion of non-Abelian 2-form along the lines of Lie algebroid theory and argue it is an appropriate one. The processes of parallel transport and integration turn out to be subtly different in the two-dimensional case; we discuss parallel transport along surfaces and present an indirect definition of a non-Abelian integral. This integral includes, for specific choices of 2-forms, both Abelian integrals and the continuous limit of the Baker-Campbell-Hausdorff formula as special cases; it interpolates between those cases and broadly generalizes them, allowing, for example, an analog of path exponential with local, point-depending commutators to be spoken about. We comment on all these objects, their relations, gauge symmetries, and geometrical meaning and roughly sketch a plausible order-by-order procedure for obtaining formulas for non-Abelian integrals. The exposition is reasonably concrete, relying on no notions more abstract than sections of vector bundles and homotopies.

In this paper, we construct the rotating multistate Proca stars (RMPSs) composed of two coexisting Proca fields including the ground state and first excited state. We discuss the multistate solutions in synchronized frequency and nonsynchronized frequency scenarios for RMPSs. In the synchronized frequency case, we calculate the multistate solutions for several values of the first excited state mass ${\mu }_1$, and we calculate the multistate solutions under several values of the ground state frequencies ${\omega }_0$ in the nonsynchronized frequency case. Based on these solutions, we analyze the characteristics of the Arnowitt–Deser–Misner mass $M$, angular momentum $J$ of RMPSs. Furthermore, we also calculate the binding energy of these solutions. Finally, we discuss the ergosphere of RMPSs.

As we move into an era of more sensitive pulsar timing array datasets, we may be able to resolve individual gravitational wave sources from the stochastic gravitational wave background. While some of these sources, like orbiting massive black hole binaries, have well-defined waveform models, there could also be signals present with unknown morphology. This motivates the search for generic gravitational-wave bursts in a signal-agnostic way. However, these searches are computationally prohibitive due to the expansive parameter space. In this paper we present QuickBurst, an algorithm with a redefined likelihood that lets us expedite Markov chain Monte Carlo sampling for a subset of the signal parameters by avoiding repeated calculations of costly inner products. This results in an overall speedup factor of $\sim 200$ on realistic simulated datasets, which is sufficient to make generic gravitational-wave burst searches feasible on current and growing pulsar timing array datasets.

An accurate description of the photon spectrum line shape is essential for extracting resonance parameters of the ${\eta }_c$ meson through the radiative transition $J/\psi \to \gamma {\eta }_c$. However, a persistent challenge remains in the form of a divergent tail at high photon energies, arising from the $E_{\gamma }^3$ factor in theoretical calculations. Various damping functions have been proposed to mitigate this effect in practical experiments, but their empirical nature lacks a rigorous theoretical basis. In this study, we introduce two key considerations: incorporating full-order contributions of the Bessel function in the overlap integral of charmonium wave functions and the phase space factor neglected in previous experimental studies. By accounting for these factors, we demonstrate a more rational and effective damping function of the divergent tail associated with the $E_{\gamma }^3$ term. We present the implications of these findings on experimental measurements and provide further insights through toy Monte Carlo simulations.

We show that, in the Nelson-Barr solution to the strong $CP$-problem, a naturally light scalar can arise. It gives rise to a completely new phenomenology beyond that of the celebrated QCD axion, if this field constitutes dark matter, as the elements of the Cabibbo–Kobayashi–Maskawa matrix vary periodically in time. We also discuss how the model can be tested using quantum sensors, in particular using nuclear clocks, which leads to an interesting synergy between different frontiers of physics.

Lattice QCD studies have shown the attractive character of the ${}^1{S}_0$ ${\mathrm{\Omega }}_{QQQ}{\mathrm{\Omega }}_{QQQ}$, $Q=s$, $c$, $b$, interaction, predicting deeply bound states as the mass of the heavy quark increases. This has led to the question of the possible existence of bound states of more than two ${\mathrm{\Omega }}_{QQQ}$ baryons, in particular ${\mathrm{\Omega }}_{QQQ}{\mathrm{\Omega }}_{QQQ}{\mathrm{\Omega }}_{QQQ}$ bound states. We discuss how these states might not exist in nature in any flavor sector. The reason would be due to the simultaneous action of two consequences of the Pauli principle in the different partial waves: one at the baryon level, affecting the ${}^1{S}_0$ partial wave, and the other due to the quark substructure, affecting the ${}^5{S}_2$ partial wave.