We study the chaotic behavior of a phenomenological system of rotating black holes (BHs) surrounded by radiation, dust, and dark matter as effective matter fluids. We show that the chaos bound is saturated—but never violated—when the density parameter $k\to 1$, which corresponds to a high dark matter concentration in the halo. This saturation is independent of radiation and dust density, occurring in the low-temperature regime where the BH’s surface gravity and Hawking temperature decrease. Our results suggest that rotating BHs subjected to a phenomenological representation of a more realistic matter environment can scramble information as efficiently as allowed by physical laws in this limit. This work links quantum chaos research with phenomenological BH-matter configurations, providing a motivation for studies of chaos in astrophysical BHs.

A theory of quantum gravity consists of a gravitational framework, which, unlike general relativity, takes into account the quantum character of matter. In spite of impressive advances, no fully satisfactory, self-consistent, and empirically viable theory with those characteristics has ever been constructed. A successful semiclassical gravity model, in which the classical Einstein tensor couples to the expectation value of the energy-momentum tensor of quantum matter fields, would, at the very least, constitute a useful stepping stone toward quantum gravity. However, not only has no empirically viable semiclassical theory ever been proposed, but the self-consistency of semiclassical gravity itself has been called into question repeatedly over the years. Here, we put forward a fully self-consistent, empirically viable semiclassical gravity framework, in which the expectation value of the energy-momentum tensor of a quantum field, evolving via a relativistic objective collapse dynamics, couples to a fully classical Einstein tensor. We present the general framework, a concrete example, and briefly explore possible empirical consequences of our model.

Taking into account the mass transfer effect, we derive the equations of motion of a compact binary system at the second-half post-Newtonian order. Applying such equations of motion to quasicircular orbits, we obtain the time derivative of the orbital frequency, which is consistent with the angular momentum balance equation. Numerical estimates of the phase of gravitational waves are provided for typical mass transfer rates. Our result can be used to improve the waveforms of gravitational waves emitted by compact binaries with mass transfer.

We test the $n=3$ ultralight axionlike model of early dark energy (EDE) with the observations of the EB mode of the cosmic microwave background (CMB) radiation and local expansion rate measurements. Our results show that the shape of the CMB EB angular power spectrum is sensitive to the background cosmological parameters. We run Markov chain Monte Carlo simulations to fit the $\mathrm{\Lambda }\mathrm{CDM}+\mathrm{EDE}$ parameters simultaneously and find that the EDE model with $n=3$ can provide a good fit to the observed CMB EB spectra, consistent with the locally measured value of the Hubble constant. To the best of our knowledge, these results are the first to show that axionlike EDE can provide a unified explanation for the observed cosmic birefringence and the Hubble tension. In this work, we do not consider the contribution from the polarization miscalibration angle since current Planck CMB observations lack the precision required to distinguish the effects of the polarization miscalibration angle from that of EDE induced cosmic birefringence.

The advent of multimessenger cosmology, marked by the detection of GW170817, demonstrated that standard sirens are a valuable cosmological probe. In the absence of an electromagnetic counterpart identification, gravitational waves (GWs) carry valuable information through the dark siren (DS) approach, where the source redshift is estimated using galaxy catalogs of potential hosts within the localization volume. However, the DS analysis can be affected by galaxy catalog incompleteness at the limits of gravitational-wave detectability, potentially introducing biases in the constraints on cosmological parameters. Focusing on GWs from binary black holes (BBH) detected by the LIGO, Virgo, and KAGRA (LVK) collaboration, we explore the possible systematic biases in the measurement of the Hubble constant ($H_0$). These biases may arise from (1) the incompleteness of catalogs due to the apparent magnitude thresholds of optical telescope sensitivity, and (2) the use of incorrect weighting schemes (e.g., using star formation or stellar mass as tracers of the host galaxy) for each potential host. We found that an unbiased estimate of $H_0$ can be obtained when the corrected weighting scheme is applied to a complete or volume-limited catalog. We use a complete galaxy catalog covering 90% of the localization probability ($A_{90\%}$) for each GW detection, employing stellar mass as a tracer. Our results show that a sample of 100 binary black hole events with $A_{90\%}<10{\mathrm{deg}}^2$ and measured luminosity distances below 1600(2500) Mpc, detected by the LVK at O4(O5) sensitivity, can provide a percent-level measurement of $H_0$, with a precision of approximately 3%(1%). This number of detections is expected to be accumulated after approximately 8 and 3 years of observations with the LVK at O4 and O5 sensitivity, respectively. The O5 run provides a reduction in the $H_0$ uncertainty by $1.34\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ compared to the O4-like configuration. The $H_0$ precision increases to approximately 6% when it is assumed that every galaxy has an equal probability of being the host.

Rare Poisson processes (PP) during cosmic inflation can lead to signatures that are localized in position space and are not well-captured by the standard two- or higher-point correlation functions of primordial density perturbations. As an example, PP can lead to localized overdense regions that are far denser than the ones produced through standard inflationary fluctuations. As a result, such overdense regions collapse earlier than expected based on the standard $\mathrm{\Lambda }\mathrm{CDM}$ model and would host anomalously high-redshift galaxies. We describe some general aspects of such PP and consider a particular realization in the context of inflationary particle production. We then show that the masses and redshifts of the resulting galaxies can lie in a range discoverable by the James Webb Space Telescope and future surveys, while being consistent with existing constraints on the matter power spectrum and UV luminosity functions at lower redshifts.

Inspired by the well-studied ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ model, we propose and investigate a class of dynamical dark energy models that evolve from a negative cosmological constant, transitioning to a positive value at low redshifts. Specifically, we introduce a dark energy framework based on a generalized ladder-step function for the cosmological constant. Furthermore, we present two additional models in which the cosmological constant undergoes a smooth sign change at a specified redshift. We provide a detailed discussion of the construction and theoretical properties of these models, analyzing their background cosmological evolution using a cosmographic approach and the statefinder hierarchy parameters. Our results are compared with those obtained for the standard $\mathrm{\Lambda }\mathrm{CDM}$ and ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ models. We also perform a careful analysis of the types of singularities that may arise in these models due to a sign change in the cosmological constant. Notably, we show that a continuous sign change removes the sudden singularity present in the ${\mathrm{\Lambda }}_{\mathrm{s}}\mathrm{CDM}$ model, replacing it with a milder $w$-singularity.

We show that the consistent application of the rules of quantum mechanics to cosmological systems inevitably results in the so-called multiverse states in which neither the background spacetime nor the inhomogeneous perturbation are in definite states. We study the multiverse states as perturbations to the usually employed so-called Born-Oppenheimer states that are products of a wave function of the background and a wave function of the perturbation. The obtained corrections involve integrals over virtual backgrounds that represent the effect of quantum background fluctuations on the perturbation state. They resemble loop corrections in quantum field theory. This approach demonstrates the inevitable existence of very specific non-Gaussian features in primordial fluctuations. We express the resulting non-Gaussian perturbation as a nonlinear function of the Gaussian perturbation obtained within the Born-Oppenheimer approximation, and compute its trispectrum, to show that the multiverse scenario leads to testable and distinct signatures in cosmological perturbations. Our approach applies both to inflationary and alternative cosmologies.

The 21-cm forest—narrow absorption features in the spectra of high-redshift radio sources caused by intervening neutral hydrogen—offers a unique probe of the intergalactic medium and small-scale structures during reionization. While traditional power spectrum methods have been widely used for analyzing the 21-cm forest, these techniques are limited in capturing the non-Gaussian nature of the signal. In this work, we introduce the wavelet scattering transform (WST) as a novel diagnostic tool for the 21-cm forest, which allows for the extraction of higher-order statistical features that power spectrum methods cannot easily capture. By decomposing simulated brightness temperature spectra into a hierarchy of scattering coefficients, the WST isolates both local intensity fluctuations (first-order coefficients) and scale-scale correlations (second-order coefficients), revealing the complex, multiscale non-Gaussian interactions inherent in the 21-cm forest. This approach enhances the power of 21-cm forest in distinguishing between different cosmological models, such as cold dark matter and warm dark matter (WDM), as well as scenarios with enhanced x-ray heating. Unlike traditional methods, which focus primarily on Gaussian statistics, the WST captures richer astrophysical and cosmological information. Our analysis shows that the WST can significantly improve constraints on key parameters, such as the x-ray heating efficiency and the WDM particle mass, providing deeper insights into the early stages of cosmic structure formation.

We present for the first time an analysis of high-frequency gravitational wave emission from proto-neutron star (PNS) in core collapse supernovae (CCSNe) that combines spatial decomposition and modal decomposition to both source and characterize the emission using three-dimensional CCSN simulations. Our analysis is based on three-dimensional CCSN simulations initiated from a solar-metallicity $15\text{−}{M}_{\odot }$ progenitor and a zero-metallicity $25\text{−}{M}_{\odot }$ progenitor. We decompose the gravitational wave strains into five spatial regions, and find that strains are initially largest in the PNS surface layers from accretion and later largest from the Ledoux convective and convective overshoot regions deep within the PNS. We compute the fractional gravitational wave luminosity as a function of enclosed radius and observe that the majority of the luminosity moves from the PNS surface at $\sim 100$ ms after bounce to deep within the PNS at later times. Using a self-consistent perturbative analysis, we investigate the evolution of the quadrupolar, nonradial, quasinormal oscillation modes of the PNS. We find that the frequency of the evolving high-frequency component of the gravitational wave signal is well matched to the eigenfrequency evolution of the ${{}^{2}g}_2$ mode initially, then the ${{}^{2}g}_1$ mode, and finally the ${}^{2}f$ mode, as labeled by the Generalized Cowling Nomenclature. We show that the ${}^{2}g$ modes emit most of their power in gravitational waves initially from the PNS surface region, but within a few 100 ms after bounce, it is the convective overshoot region of the PNS, just above the region of sustained Ledoux convection, that emits the most gravitational wave power for the ${{}^{2}g}_1$ mode. Eventually, the ${}^{2}f$ mode is the dominant mode producing gravitational waves, and these waves are emitted primarily from the convective overshoot region. Thus, with three interconnected analyses, we show that, while the gravitational wave emission is global, stemming from multiple regions in and around the PNS, it nonetheless remains possible to source the dominant contributions to it. We find that the source of the high-frequency gravitational wave emission from the PNS in CCSNe is more complex than assessed by other methods, as well as time dependent, first emitted mainly by ${}^{2}g$ modes driven by accretion onto the PNS and later emitted by the ${}^{2}f$ mode driven by sustained Ledoux convection.

We report the identification of two statistically significant quasiperiodic oscillations in the weekly binned $\gamma$-ray light curve of the flat-spectrum radio quasar PKS 0805-07, observed by Fermi-LAT over the period MJD 59047.5-59740.5. By applying a suite of complementary time-series analysis techniques, we identify periodic signatures at $\sim 255$ and $\sim 112\mathrm{days}$. These techniques include the Lomb-Scargle periodogram, weighted wavelet Z-transform, REDFIT, date-compensated discrete Fourier transform , phase dispersion minimization, and the string-length method. The reliability of these signals is supported by high local significance ($\ge 99\%$) in all methods and reinforced through phase-folding. Model selection using the Akaike information criterion and Bayesian information criterion strongly supports a two-component periodic model. The detection of dual quasiperiodic oscillations is rare among blazars and suggests complex variability mechanisms. Although a binary supermassive black hole scenario could be considered given the source’s high redshift ($z=1.837$), the short periodicities are difficult to reconcile with orbital motion unless invoking extreme parameters. Double-sine model fitting reveals that the oscillatory components have comparable amplitudes but are out of phase, suggesting a potential beating phenomenon due to interference. This amplitude-modulated variability is consistent with a geometric origin, most plausibly jet precession driven by Lense-Thirring torques, superimposed with a secondary process such as polar jet oscillation. Doppler factor modulation arising from these effects can account for the observed flux variations without requiring an unrealistically compact binary.

Ultraheavy dark matter candidates evade traditional direct detection experiments due to their low particle flux. We explore the potential of large underwater acoustic arrays, originally developed for ultrahigh energy neutrino detection, to detect ultraheavy dark matter interactions. These particles deposit energy via nuclear scattering while traversing seawater, generating thermoacoustic waves detectable by hydrophones. We present the first robust first-principles calculation of dark matter-induced acoustic waves, establishing a theoretical framework for signal modeling and sensitivity estimates. Our framework incorporates frequency-dependent attenuation effects, including viscous and chemical relaxation, not considered in previous calculations. A sensitivity analysis for a hypothetical $100{\mathrm{km}}^3$ hydrophone array in the Mediterranean Sea demonstrates that such an array could extend sensitivity to the previously unexplored mass range of $0.1-10\mathrm{\mu }\mathrm{g}$ ($\sim {10}^{20}–{10}^{23}\mathrm{GeV}$), with sensitivity to both spin-independent and spin-dependent interactions. Our results establish acoustic detection as a complementary dark matter search method, enabling searches in existing hydrophone data and informing future detector designs.

We obtain stringent bounds on neutrino quantum decoherence from the analysis of SN1987A data. We show that for the decoherence model considered here, which allows for neutrino loss along the trajectory, the bounds are many orders of magnitude stronger than the ones that can be obtained from the analysis of data from reactor neutrino oscillation experiments or neutrino telescopes.

Violent astrophysical events, including core-collapse supernovae and binary neutron star mergers, can result in rotating neutron stars with diverse degrees of differential rotation. Oscillation modes of these neutron stars could be excited and emit strong gravitational waves. Detecting these modes may provide information about neutron stars, including their structures and dynamics. Hence, dynamical simulations were employed to construct relations for quantifying the oscillation mode frequency in previous studies. Specifically, linear relations for the frequencies of fundamental $l=0$ quasiradial mode $f_F$ and fundamental $l=2$ quadrupolar mode $f_{{}^{2}f}$ were constructed by simulations with the Cowling approximation. Nevertheless, these relations can overestimate $f_F$ and underestimate $f_{{}^{2}f}$ up to $\sim 30\%$. Furthermore, it has yet to be fully studied how the degree of differential rotation affects $f_F$ and $f_{{}^{2}f}$. Here, for the first time, we consider both various degrees of differential rotation $\tilde{A}$ and dynamical spacetime to construct linear relations for quantifying $f_F$ and $f_{{}^{2}f}$. Through 2D axisymmetric simulations, we first show that both $f_F$ and $f_{{}^{2}f}$ scale almost linearly with the stellar compactness $M/R$ for different values of $\tilde{A}$. We also observe the quasilinear relations for both $f_F$ and $f_{{}^{2}f}$ with the kinetic-to-binding energy ratio $T/|W|$ for different $\tilde{A}$ values. Finally, we constructed linear fits that can quantify $f_F$ and $f_{{}^{2}f}$ by $T/|W|$. Consequently, this work updated the relations for the fundamental modes of rotating neutron stars with differential rotations in dynamical spacetime.

We consider a theory of fermions interacting with a (in general, non-Abelian) gauge field. The theory is assumed to be essentially inhomogeneous, which might be provided by nontrivial background fields interacting with both fermions and gauge bosons. For this theory, a version of Wigner-Weyl calculus is developed, in which the Wigner transformation of the fermion Green function belongs to a matrix representation of the gauge group. We demonstrate the power of the proposed formalism through the representation of responses of vector and axial currents to the gauge field strength through the topological invariants composed of the Wigner transformed two-point Green functions. This way, a new family of nondissipative transport phenomena is introduced. In particular, we discuss the non-Abelian versions of the chiral separation effect and of the quantum Hall effect.

In this paper, we investigate the helicity form factors (HFFs) of the $B_{(s)}$-meson decay into a scalar meson with a mass larger than 1 GeV, i.e., $B\to a_0(1450)$, $B_{(s)}\to K_0^{*}(1430)$, and $B_s\to f_0(1500)$ by using the light-cone sum rules approach. We take the standard currents for correlation functions. To enhance the precision of our calculations, we incorporate the next-to-leading order (NLO) corrections and retain the scalar meson twist-3 light-cone distribution amplitudes. Furthermore, we extend the HFFs to the entire physical $q^2$ region employing a simplified $z$-series expansion. At the point of $q^2=1{\mathrm{GeV}}^2$, all NLO contributions to the HFFs are negative, with the maximum contribution around 25%. Then, as applications of these HFFs, we analyze the differential decay widths, branching ratios, and lepton polarization asymmetries for the semileptonic $B_{(s)}\to S\ell {\overline{\nu }}_{\ell }$, FCNC $B_{(s)}\to S\ell \overline{\ell }$ and rare $B_{(s)}\to S\nu \overline{\nu }$ decays. Our results are consistent with existing studies within uncertainties. The current data still suffer from large uncertainties and need to be measured more precisely, which can lead to a better understanding of the fundamental properties of light scalar mesons.

For the first time, we comprehensively examine the potential of a neutral-current interaction of reactor neutrino with ${}^{13}\mathrm{C}$ emitting a 3.685 MeV photon to identify the origin of the 5 MeV bump in reactor antineutrino spectra observed through the inverse beta decay process. This anomaly may be due to new physics, reactor antineutrino flux inaccuracies, or inverse beta decay systematics. The 3.685 MeV photon released during the deexcitation of ${}^{13}{\mathrm{C}}^{*}$ to its ground state is observable in liquid scintillator detectors. Remarkably, we confirm the powerfulness of our proposal by completely ruling out a new physics scenario explaining the bump from the existing NEOS data. We also explore the potential of current and forthcoming experiments, including solar neutrino studies at JUNO, pion and muon decay-at-rest experiments at OscSNS, and isotope decay-at-rest studies at Yemilab, to measure the cross section precisely enough to distinguish the expected bump and the theoretical flux models via our channel. Additionally, we propose a novel method to track the time evolution of reactor isotopes by analyzing the ${}^{13}\mathrm{C}$ signal, which yields critical insights into the contributions of ${}^{235}\mathrm{U}$ and ${}^{239}\mathrm{Pu}$ to the bump, acting as a robust tool.

The conservation of lepton flavor is a prediction of the Standard Model and is still an excellent approximate symmetry despite our observation of neutrino oscillations. Lepton flavor violation by one or two units has been discussed for decades, with several dedicated experiments exploring the vast model landscape but no discoveries so far. Here, we explore operators and processes that violate at least one lepton flavor by three units and identify testable signatures. In the Standard Model effective field theory, such operators already arise at mass dimension 7 and can be tested through their contributions to Michel parameters in leptonic decays. True neutrinoless charged-lepton flavor violation arises at mass dimension 10 and can realistically only be seen in the tau decay channels $\tau \to eee\overline{\mu }\overline{\mu }$ or $\tau \to \mu \mu \mu \overline{e}\overline{e}$, for example in Belle II. Testable rates for these tau decays require light new particles and subsequently predict an avalanche of remarkably clean but so-far unconstrained collider signatures.

While gluon fusion dominates Higgs pair production at the LHC, vector boson fusion (VBF) offers a unique window into beyond the Standard Model (BSM) physics through its distinctive kinematic features and direct sensitivity to Higgs-vector boson interactions. We perform a comprehensive analysis of double Higgs production via VBF in the Standard Model effective field theory (SMEFT), systematically investigating how dimension-6 and dimension-8 bosonic operators—particularly those involving field derivatives—can enhance the production rate. We identify the most relevant Wilson coefficients (WCs) affecting the trilinear Higgs coupling ($hhh$) and Higgs-vector boson interactions ($hVV$, $hhVV$). Using constraints from global fits and interpolating fit results for unconstrained WCs with naive dimensional analysis, we assess their effects on the $VV\to hh$ ($V=W,Z$) scattering amplitudes and cross sections. Our analysis includes a study of EFT convergence and validity in models with scalar extensions of the SM. Numerical simulations for the planned High-Luminosity LHC experiment (HL-LHC) in general reveal only a modest and challenging to detect enhancement of the VBF di-Higgs production rate over the SM prediction. However, we show that in optimistic scenarios, such a process could be observed at the HL-LHC. In certain cases, when the enhancement is dominated by the dimension-6 or dimension-8 operators containing field derivatives (and thus leading to stronger energy-dependent effects), this channel becomes competitive with di-Higgs production via gluon fusion. This work highlights the role of VBF di-Higgs production as a complementary channel for probing anomalous Higgs couplings and their impact on BSM physics.