We study the thermodynamics of a class of four-dimensional black hole solutions arising from the compactification of a higher-curvature gravity theory featuring an infinite tower of Lovelock-type invariants. For planar horizons, we identify two distinct branches: a regular black hole supported by a nontrivial scalar field and a non-regular general relativity (GR) solution with a trivial scalar profile. Despite their differing geometries, both branches share the same free energy at fixed temperature, revealing a thermodynamic degeneracy naturally linked to the enhanced symmetry and scale invariance of the planar base manifold. In the case of a spherical horizon, even if the scalarized branch is not obtained in closed form, one can see that the degeneracy persists in the absence of the quadratic curvature contribution. On the other hand, if this quadratic term is taken into account, the regular solution may be thermodynamically favored (or not) over the Schwarzschild-anti–de Sitter solution depending on the values of the coupling constants of the theory.

Separating a stochastic gravitational wave background (SGWB) from noise is a challenging statistical task. One approach to establishing a detection criterion for the SGWB is using Bayesian evidence. If the evidence ratio (Bayes factor) between models with and without the signal exceeds a certain threshold, the signal is considered detected. We present a formalism to compute the averaged Bayes factor, incorporating instrumental-noise and SGWB uncertainties. As an example, we consider the case of power-law-shaped SGWB in LISA and generate the corresponding Bayesian sensitivity curve. Unlike existing methods in the literature, which typically neglect uncertainties in both the signal and noise, our approach provides a reliable and realistic alternative. This flexible framework opens avenues for more robust stochastic gravitational wave background detection across gravitational-wave experiments.

We present the first exact and analytical solution in general relativity describing an equilibrium configuration for two stationary black holes. The metric models two collinear extremal Kerr black holes immersed in an external and back-reacting rotating tidal drag. The gravitational attraction is balanced by the repulsive gravitational spin-spin interaction generated by the interplay between the black holes’ angular momenta and the rotational background. The new solution is built by embedding the double Kerr metric into a swirling universe by means of the Ehlers transformation. The geometry is completely regular outside the event horizons. Thermodynamic properties of the binary black hole system are studied; the Smarr law, the first law, and the Christodoulou-Ruffini formulas are verified. The microscopic degrees of freedom of the entropy are computed from the dual conformal field theories living on the boundary of the near horizon geometries.

We consider a novel bounce universe model constructed within the framework of Horndeski gravity. We have analyzed the bispectrum of primordial scalar perturbations and evaluated the corresponding non-Gaussianities for this specific model. The nonlinear parameter $f_{\mathrm{NL}}$ was computed for various wave vector configurations, including: (i) the local configuration, (ii) the equilateral configuration, and (iii) the enfolded configuration, which is a linear combination of the equilateral and orthogonal shapes. We demonstrate that the observational constraints on the scalar spectrum index tilt and the scalar-to-tensor ratio, together with the unitarity bounds, ensure that the bounds from non-Gaussianities are trivially satisfied. Therefore, this particular bounce universe scenario is fully viable in light of modern observational data.

Given that black holes are ubiquitous in the Universe and axionlike scalar fields are potential candidates for dark energy and/or dark matter, it is natural to consider cosmological black holes endowed with axions. We investigate the photon quasinormal modes of a Schwarzschild black hole with axions where the electromagnetic field is coupled to the axion field via a Chern-Simons interaction. We derive the master equations for the electromagnetic field as a set of coupled equations for parity-even and parity-odd modes and numerically compute quasinormal modes by using Leaver’s continued fraction method. We find parity violation in the polarization of photons within the quasinormal mode spectrum. This parity violation in electromagnetic signals could serve as a new probe to explore the nature of the dark sector.

With the advent of current and future high-resolution cosmic microwave background (CMB) experiments, the kinematic Sunyaev-Zel’dovich (kSZ) effect has become a unique observational probe of the distribution of baryons and velocities in the Universe. In this work, we propose a novel binned bispectrum of the form temperature-temperature-density to extract the late-time kSZ effect from cleaned CMB maps. Unlike “kSZ tomography” methods, this estimator can use any tracer of the large-scale structure density field projected along the line-of-sight and does not require individual redshifts. With our method, we forecast signal-to-noise ratios (SNR) of $\sim 100–200$ for the upcoming Simons Observatory (SO) and CMB-S4 correlated with a galaxy sample from WISE that is restricted to the linear regime. We also extend galaxy modes into the nonlinear regime and explore this harmonic space to show that the SNR peaks for squeezed triangles that have a short (linear) density mode and long temperature modes in harmonic space. The existing ${\mathrm{kSZ}}^2$-density projected-fields estimator compresses the rich information contained in this bispectrum across various scales and triangle shapes. Moreover, we find that the lensing correction to this estimator’s signal is relatively small for high-SNR squeezed triangle configurations. We study the dependence of this kSZ signal on $\mathrm{\Lambda }\mathrm{CDM}$ parameters for SO and CMB-S4 and forecast initial constraints on the sum of neutrino masses while restricting to the linear galaxy bias regime. Our work illustrates the potential of the projected-fields kSZ bispectrum as a novel probe of baryonic abundance and beyond-$\mathrm{\Lambda }\mathrm{CDM}$ cosmology with upcoming precision measurements.

We apply an internal robustness (iR) analysis to the recently released Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillations Data Release 1 (DR1) dataset. This approach examines combinations of data subsets through a fully Bayesian model comparison, aiming to identify potential outliers, subsets possibly influenced by systematic errors, or hints of new physics. Using this approach, we statistically confirm the existence of three data points at $z=0.295$, 0.51, 0.71 as potential outliers. Excluding these points improves the internal robustness of the dataset by minimizing statistical anomalies and enables the recovery of $\mathrm{\Lambda }\mathrm{cold}$ dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) predictions with a best-fit value of $w_0=-1.050\pm 0.128$ and $w_a=0.208\pm 0.546$. These results raise the intriguing question of whether the identified outliers signal the presence of systematics or point toward new physics.

We consider the 21-cm brightness temperature as a probe of the Hubble tension in the framework of an inhomogeneous cosmological model. Employing Buchert’s averaging formalism to study the effect of inhomogeneities on the background evolution, we consider scaling laws for the backreaction and curvature consistent with structure formation simulations. We calibrate the effective matter density using Markov chain Monte Carlo analysis using Union 2.1 Supernova Ia data. Our results show that a higher Hubble constant ($\sim 73\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$) leads to a shallower absorption feature in the brightness temperature versus redshift curve. On the other hand, a lower value ($\sim 67\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$) produces a remarkable dip in the brightness temperature $T_{21}$. Such a substantial difference is absent in the standard $\mathrm{\Lambda }\mathrm{CDM}$ model. Our findings indicate that inhomogeneities could significantly affect the 21-cm signal, and may shed further light on the different measurements of the Hubble constant.

We perform numerical relativity simulations of black hole-neutron star (BH-NS) mergers with a fixed mass ratio of $q=3$, varying the BH spin to produce a wide range of postmerger accretion disk masses. Our high-order numerical scheme, fine resolution, and large eddy simulation techniques enable us to achieve likely one of the most resolved BH-NS merger simulations to date, capturing the postmerger magnetic field amplification driven by turbulent dynamo processes. Following tidal disruption and during disk formation, the Kelvin-Helmholtz instability in the spiral arm drives a turbulent state in which the magnetic field, initialized to a realistic average value of ${10}^{11}\mathrm{G}$, grows to an average of approximately ${10}^{14}\mathrm{G}$ in the first $\approx 20\mathrm{ms}$ postmerger. Notably, the dimensionless magnetic flux on the BH, $\varphi$, evolves similarly across nearly 2 orders of magnitude in disk mass. This similarity, along with estimates from longer numerical simulations of the decay of the mass accretion rate, suggests a universal timescale (at least for this equation of state) at which the dimensionless flux saturates at a magnetically arrested state (MAD) such that $\varphi \approx 50$ at $t_{\mathrm{MAD}}\gtrsim 10\mathrm{s}$. The unified framework of Gottlieb et al. [Astrophys. J. Lett. 958, L33 (2023)] established that the MAD timescale sets the duration of the resulting compact binary gamma-ray burst (cbGRB), implying that all BH-NS mergers contribute to the recently detected new class of long-duration cbGRBs.

All-sky searches for generic short-duration astrophysical gravitational-wave (GW) signals are often challenging because of noise transients. Developing novel signal-noise discriminators is crucial for GW transient searches with LIGO, Virgo, and KAGRA detectors. In this work, we demonstrate the sensitivity improvement of a weakly modeled GW transient search by leveraging the recently developed Jensen-Shannon divergence (JSD)-based cross-detector parameter consistency measure. We first extend a two-detector JSD-based measure developed in an earlier work [Ghosh et al., Phys. Rev. D 109, 064015 (2024)] to a three-detector network. We leverage this to modify the test statistic of the existing coherent WaveBurst (cWB)–Gaussian mixture modeling (GMM) algorithm for short-duration transients toward improving the search sensitivity to ad hoc waveforms like sine Gaussians, Gaussian pulses, and white noise bursts. We find that with the new method, which we term cWB-GMM-JSD, the sensitivity to the ad hoc waveforms, given by $h_{\mathrm{rss}50}$ (the signal amplitude at which 50% of the injected signals can be detected), improves by $\sim 10\%–20\%$ at an inverse false alarm rate (IFAR) of 10 yr for the two-detector network consisting of the LIGO-Hanford (LHO) and LIGO-Livingston (LLO) detectors, and by $\sim 5\%–10\%$ at the same IFAR for the three-detector network consisting of the LHO, LLO, and Virgo detectors. Finally, we apply the modified statistic in the revised data analysis pipeline on the publicly available data from the third observing run (O3) of the LIGO and Virgo detectors. Although we do not find any new event in the O3 data, we see a notable rise in the statistical significance of most of the known GW events, which further testifies to the enhancement in sensitivity.

Two notable anomalies in radio observations—the excess radiation in the Rayleigh-Jeans tail of the cosmic microwave background, revealed by ARCADE-2, and the twice-deeper absorption trough of the global 21-cm line, identified by EDGES—remain unresolved. These phenomena may have a shared origin, as the enhancement of the 21-cm absorption trough could arise from excess heating. We investigate this scenario through the framework of axionlike particles (ALPs), showing that the resonant conversion of ALPs into photons can produce a photon abundance sufficient to resolve both anomalies simultaneously. Our model naturally explains the observed radio excess between 0.4 and 10 GHz while also enhances the 21-cm absorption feature at 78 MHz. Furthermore, it predicts a novel power-law scaling of the radio spectrum above 0.5 GHz and an additional absorption trough below 30 MHz, which could be verified through cross-detection in upcoming experiments.

Core-collapse supernovae undergoing a first-order quantum chromodynamics (QCD) phase transition experience the collapse of the central protoneutron star that leads to a second bounce. This event is accompanied by the release of a second neutrino burst. Unlike the first stellar core bounce neutrino burst, which consists exclusively of electron neutrinos, the second burst is dominated by electron antineutrinos. Such a condition makes QCD supernovae an ideal site for the occurrence of fast neutrino flavor conversion (FFC), which can lead to rapid flavor equilibration and significantly impact the related neutrino signal. In this work, we perform a detailed analysis of the conditions for fast flavor instability around and after the second neutrino burst in QCD phase-transition supernova models launched from $25M_{\odot }$ and $40M_{\odot }$ progenitor models. We evaluate the relevant instability criteria and find two major phases of FFC. The first phase is closely associated with the collapse and the rapidly expanding shock wave, which is a direct consequence of the protoneutron star collapse due to the phase transition. The second phase takes place a few milliseconds later when electron degeneracy is restored near the protoneutron star surface. We also characterize the growth rate of fast flavor instability and estimate its impact on the evolution of the neutrino flavor content. The potential observational consequences on neutrino signals are evaluated by comparing a scenario assuming complete flavor equipartition with other scenarios without FFC. Finally, we investigate how FFC may influences $r$-process nucleosynthesis associated with QCD phase-transition-driven supernova explosions.

Gravitational-wave (GW) observations of compact binaries have the potential to unlock several remarkable applications in astrophysics, cosmology, and nuclear physics through accurate measurements of the source luminosity distance and inclination. However, these parameters are strongly correlated when performing parameter estimation, which may hamper the enormous potential of GW astronomy. We comprehensively explore this problem by performing Bayesian inference on synthetic data for a network of current and planned second-generation GW detectors and for the third-generation interferometer Einstein Telescope. We quantify the role of the network alignment factor, detector sensitivity, and waveform higher-order modes in breaking this degeneracy. We discuss the crucial role of the binary mass ratio: In particular, we find that the Einstein Telescope can efficiently remove the error in the distance as long as the compact binary is asymmetric in mass.

The Laser Interferometer Space Antenna (LISA) will enable direct observations of low-frequency gravitational waves, offering unprecedented insight into astrophysical and cosmological phenomena. LISA’s heterodyne interferometric measurement system requires phase-locking five of its six onboard lasers with tunable frequency offsets to ensure that all beatnotes remain within the metrology system’s operational range, despite Doppler-induced frequency shifts. The selection of these offset frequencies—collectively forming a frequency plan—is a complex optimization problem constrained by the spacecraft’s orbital dynamics and instrument limitations. While previous work established an algorithmic solution for deriving time-dependent frequency plans, this study takes a complementary approach by systematically analyzing and cataloging all possible laser locking configurations. We present an automated method to explore, validate, and classify viable locking schemes, identifying 36 unique non-frequency-swapping configurations and 72 additional frequency-swapping configurations for an arbitrary choice of primary laser. This exhaustive classification provides a foundation for frequency planning across the full range of operational scenarios.

We introduce a novel end-to-end framework for jet reconstruction in high-energy collider events, leveraging the efficiency and long-range modeling capabilities of the Mamba architecture. Our model unifies instance segmentation, classification, and kinematic regression into a single multitask learning system, enabling a sophisticated multilevel reconstruction that simultaneously identifies primary heavy jets ($t$, $H$, $W/Z$) and their constituent subjets. To facilitate supervised learning for this complex task, we develop a novel method for assigning final-state hadrons to their ancestor colored partons using a mixed-integer linear programming solver, which generates high-fidelity ground-truth labels. The model achieves high classification accuracy, with an average precision score of 0.569 for $W/Z$-jets and 0.568 for $b$-jets, and shows exceptional precision in kinematic reconstruction. Furthermore, we show that the model not only maintains stable performance in high-pileup environments but also successfully reconstructs the mass peaks of beyond the standard model particles. This work presents a powerful and versatile new tool for comprehensive event reconstruction at the LHC.

Fundamental principles of quantum field theory (QFT) such as Lorentz invariance, $CPT$ symmetry, and locality may be tested to extremely high precision in atomic and molecular spectroscopy. The narrow natural linewidth of rovibrational states in the hydrogen molecular ion ${\mathrm{H}}_2^{+}$ and its antimatter counterpart ${\overline{\mathrm{H}}}_2^{-}$ make these ideal candidates, and give $O(m_p/m_e)$ increased sensitivity to Lorentz and $CPT$ violation in the proton sector compared to $\mathrm{H}$ and $\overline{\mathrm{H}}$ atoms. In a previous paper, we presented a detailed analysis of the rovibrational spectrum of ${\mathrm{H}}_2^{+}$ and ${\overline{\mathrm{H}}}_2^{-}$ in an effective QFT encoding Lorentz and $CPT$ violation, focusing on spin-independent effects. Here, we extend this analysis to include the full hyperfine-Zeeman spectrum and include spin-dependent Lorentz and $CPT$ violating operators in the effective theory. The results demonstrate how constraints on these symmetry-violating couplings may be extracted from specific rovibrational transitions between hyperfine-Zeeman states in the presence of an applied magnetic field.

The extremely narrow natural linewidths of rovibrational energy levels in the molecular hydrogen ion ${\mathrm{H}}_2^{+}$, and the prospect of synthesising its antimatter counterpart ${\overline{\mathrm{H}}}_2^{-}$, make it a promising candidate for high-precision tests of fundamental symmetries such as Lorentz and $CPT$ invariance. In this paper, we present a detailed analysis of the rovibrational spectrum of the (anti)hydrogen molecular ion in a low-energy effective theory incorporating Lorentz and $CPT$ violation. The focus is on the spin-independent couplings in this theory, and especially the $CPT$ odd couplings for which the best current bounds come from measurements of the $1S\text{−}2S$ transition in atomic hydrogen and antihydrogen. We show that in addition to the improvement in these bounds from the increased precision of the transition frequencies, potentially reaching 1 part in ${10}^{17}$, rovibrational transitions in the ${\mathrm{H}}_2^{+}$ and ${\overline{\mathrm{H}}}_2^{-}$ molecular ions have an enhanced sensitivity to Lorentz and $CPT$ violation of $O(m_p/m_e)$ in the proton (hadron) sector compared to $\mathrm{H}$ and $\overline{\mathrm{H}}$ atomic transitions.

Recently, $B\to PP$ decays ($B=\{B^0,B^{+},B_s^0\}$, $P=\{\pi ,K\}$) were analyzed under the assumption of flavor SU(3) symmetry (${\mathrm{SU}(3)}_F$). Although the individual fits to $\mathrm{\Delta }S=0$ or $\mathrm{\Delta }S=1$ decays are good, it was found that the combined fit is very poor: there is a $3.6\sigma$ disagreement with the ${\mathrm{SU}(3)}_F$ limit of the standard model (${\mathrm{SM}}_{{\mathrm{SU}(3)}_F}$). One can remove this discrepancy by adding ${\mathrm{SU}(3)}_F$-breaking effects, but 1000% ${\mathrm{SU}(3)}_F$ breaking is required. In this paper, we extend this analysis to include decays in which there is an $\eta$ and/or ${\eta }^{\prime }$ meson in the final state. We now find that the combined fit exhibits a $4.1\sigma$ discrepancy with the ${\mathrm{SM}}_{{\mathrm{SU}(3)}_F}$, and 1000% ${\mathrm{SU}(3)}_F$-breaking effects are still required to explain the data. These results are rigorous, group-theoretically—no theoretical assumptions have been made. But when one adds some theoretical input motivated by QCD factorization, the discrepancy with the ${\mathrm{SM}}_{{\mathrm{SU}(3)}_F}$ grows to $4.9\sigma$.

We study the potential collider discovery for right-handed neutrinos (RHNs) in the minimal left-right symmetric model (LRSM). In this model, the RHNs can be either produced from the right-handed gauge boson $W_R^{\pm }$, or the scalar triplet $\mathrm{\Delta }$ decays. The RHNs can subsequently decay via the heavy $W_R^{\pm }$, making them potentially long-lived. In looking for such long-lived RHNs, a search for displaced shower at the CMS muon system is reinterpreted for either the processes, $pp\to W_R^{\pm }\to {\ell }^{\pm }N$ or $pp\to \mathrm{\Delta }\to NN$. From the former process, we exclude $M_{W_R}\lesssim 3.6\mathrm{TeV}$ using current CMS data, or $\lesssim 8.0\mathrm{TeV}$ at the future HL-LHC. For the $pp\to \mathrm{\Delta }\to NN$ process, HL-LHC is able to probe much larger parameter space as long as the proper decay length of the RHNs, $0.01\mathrm{m}\lesssim L_0\lesssim 1\mathrm{m}$. This implies that the displaced shower searches are able to explore the parameter space of the LRSM which have not been excluded yet.

Dark matter (DM) could self-annihilate into neutrinos in dense regions of the Universe. We consider the resulting flux of neutrinos from the Milky Way DM halo and derive exclusion limits on the annihilation cross section using XENONnT electron recoil data. Assuming a $J$ factor independent of the annihilation cross section, we find leading limits for DM masses below $\mathcal{O}(\mathrm{MeV})$. Self-annihilating DM affects the DM halo via dissolution, introducing a cross-section dependency on the halo profile and thus the $J$ factor. We discuss such a situation in more detail, finding that the signal rate is below the experimental sensitivity of XENONnT, leaving the annihilation cross section unconstrained.