We analyze DAMPE and H.E.S.S. measurements of the total cosmic-ray electron-positron spectrum, together with the AMS-02 positron fraction, using an anisotropic, spatially varying diffusion framework. The diffusion-tensor components are computed via numerical integration of test-particle trajectories in a prescribed Galactic magnetic-field model. We show that simultaneously accounting for the spatial dependence and anisotropy of the diffusion tensor yields an accurate description of the local electron and positron data up to TeV energies. The inferred injection spectral index, $\gamma =2.169$, is fully consistent with expectations from diffusive shock-acceleration theory. In this approach, the observed spectral softening arises naturally from enhanced energy losses experienced by leptons propagating over larger effective distances along the large-scale magnetic field.

GW231123 is an exceptional gravitational-wave event consistent with the merger of two massive, highly spinning black holes. Reliable inference of the source properties is crucial for accurate interpretation of its astrophysical implications. However, characterization of GW231123 is challenging: only few signal cycles are observed and different signal models result in systematically different parameters. We investigate whether the interpretation of GW231123 is robust against model systematics and Gaussian detector noise. We show that the model systematics observed in GW231123 can be reproduced for a simulated signal based on the numerical-relativity surrogate model nrsur7dq4. Simulating data using the maximum-likelihood nrsur7dq4 waveform for GW231123 and no noise realization, we closely recover the systematics observed for the real signal. We then explore how the headline properties of GW231123 are impacted by Gaussian detector noise. Using the nrsur7dq4 maximum-likelihood waveform and different noise realizations, we consistently find support for large masses, high spin magnitudes (median ${\chi }_1\ge 0.7$), and high spin precession (median ${\chi }_{\mathrm{p}}\ge 0.68$). The spin in the direction of the angular momentum (${\chi }_{\mathrm{eff}}$) fluctuates more. Finally, again comparing to simulated signals, we show that any differences in the GW231123 inference based on each separate detector are not statistically significant. These results show that the properties of GW231123, and most importantly the high mass and high spin magnitudes inferred by nrsur7dq4, are robust.

Current data on ultrahigh-energy (UHE) cosmic rays suggest they are predominantly made of heavy nuclei. This indicates that, in the absence of a subdominant proton component, the flux of neutrinos produced from cosmic ray collisions on the cosmic microwave background is small and hard to observe. Motivated by the recent extremely high-energy muon event reported by KM3NeT, we explore the possibility of enhancing the energy-flux of cosmogenic neutrinos through nuclear photodisintegration in the presence of new physics. Specifically, we speculate that UHE neutrons may oscillate into a new state, dark (or mirror) neutron $n^{\prime }$ that in turn decays injecting large amount of energy to neutrinos, $n\to n^{\prime }\to {\nu }_{\mathrm{UHE}}$. While this mechanism does not explain the tension between the KM3NeT event and null results from IceCube, it reconciles the experimental preference for a heavier cosmic ray composition with a large diffuse cosmogenic flux of UHE neutrinos.

We analyze the excesses at 95 GeV in the light Higgs-boson searches in the diphoton decay channel reported by CMS and ATLAS, which combined are at the level of three standard deviations and are compatible with the excess in the $b\overline{b}$ final state observed at Large Electron-Positron Collider, together with an excess in the diphoton channel at around 152 GeV reported based on a sideband analysis. We demonstrate that these excesses can be well described in a minimally extended Georgi-Machacek (meGM) model. This is enabled by four key features of the meGM model: (1) a natural prediction for scalar boson masses of $\lesssim 200\mathrm{GeV}$ arising from the condition to describe both the Higgs boson signal at 125 GeV and the excesses at 95 GeV, (2) the prediction for a doubly charged Higgs boson that can potentially enhance the diphoton decay rates, (3) asymmetric $WW$ and $ZZ$ couplings to neutral scalar bosons that are induced by mild custodial symmetry breaking, and (4) the approximate preservation of the electroweak $\rho$ parameter to be 1 at tree level. We show in our numerical analysis that the meGM model naturally improves the fit to the LHC data around 152 GeV when describing the excesses at 95 GeV. At the same time, the model also predicts additional light $CP$-odd and charged scalar bosons that can be potentially probed in future experiments, which motivates dedicated searches in the upcoming LHC runs. We also present the results of sensitivity studies for the 95 and 125 GeV Higgs-boson couplings at the HL-LHC and future $e^{+}{e}^{-}$ colliders, which demonstrate very interesting prospects for probing the meGM model at future colliders.

A first-order, confinement/deconfinement phase transition appears in the finite temperature behavior of many non-Abelian gauge theories. These theories play an important role in proposals for completion of the Standard Model of particle physics, hence the phase transition might have occurred in the early stages of evolution of our Universe, leaving behind a detectable relic stochastic background of gravitational waves. Lattice field theory studies implementing the density of states method have the potential to provide detailed information about the phase transition, and measure the parameters determining the gravitational-wave power spectrum, by overcoming some of the challenges faced by importance-sampling methods. We assess this potential for a representative choice of Yang-Mills theory with $Sp(4)$ gauge group. We characterize its finite-temperature, first-order phase transition, in the thermodynamic (infinite volume) limit, for two different choices of number of sites in the compact time direction, hence taking the first steps toward the continuum limit extrapolation. We demonstrate the persistence of nonperturbative phenomena associated to the first-order phase transition: coexistence of states, metastability, latent heat, surface tension. We find consistency between several different strategies for the extraction of the volume-dependent critical coupling, hence assessing the size of systematic effects. We also determine the minimum choice of ratio between spatial and time extent of the lattice that allows one to identify the contribution of the surface tension to the free energy. We observe that this ratio scales nontrivially with the time extent of the lattice, and comment on the implications for future high-precision numerical studies.

We study the Dalitz decays of heavy quarkonia, which result from the internal virtual photon conversion into an ${\ell }^{+}{\ell }^{-}$ lepton pair. Heavy-quark symmetries allow us to establish systematic relations between transitions of different quarkonium states and to precisely determine the branching fractions for several charmonium and bottomonium decay modes. For charmonium, existing data on ${\chi }_{cJ}(1P)\to J/\psi {\ell }^{+}{\ell }^{-}$ and $\psi (2S)\to {\chi }_{cJ}(1P){\ell }^{+}{\ell }^{-}$ enable us to determine the parameters of the transition form factors and to predict the rates of yet-unobserved modes. The Dalitz transitions of ${\chi }_{c1}(3872)$ are important, as they can help assessing the structure of this meson. For bottomonium, recent LHCb measurements allow us to predict the branching fractions of ${\chi }_{bJ}(nP)\to \mathrm{\Upsilon }(1S){\ell }^{+}{\ell }^{-}$ and $h_b(nP)\to {\eta }_b(1S){\ell }^{+}{\ell }^{-}$ ($n=1$, 2). We also investigate the sensitivity of heavy quarkonia Dalitz modes to the contribution of a new light vector mediator, such as the putative $X(17)$.

Monochromatic high-frequency gravitational waves (HFGWs) provide a distinctive probe of new physics scenarios, most notably axion clouds around rotating black holes formed via superradiance. We reanalyzed data from the CAPP-12T multicell axion haloscope experiment [Kim et al., Phys. Rev. Lett. 133, 051802 (2024)]. The study covers a continuous 2 MHz frequency span centered at 5.311 GHz. No rescan candidates were found, and we set 90% confidence-level exclusion limits on the gravitational-wave strain, reaching $h_0\approx 3.9\times {10}^{-21}$ in the most sensitive regions of the sky. Interpreted in the context of black hole superradiance from axion clouds, the results exclude black holes with mass $M_{\mathrm{BH}}\simeq 1.22\times {10}^{-6}{M}_{\odot }$ within distances of $\mathcal{O}({10}^{-2})$ AU from Earth, under benchmark assumptions. This work demonstrates the potential of electromagnetic resonant cavities as novel detectors of monochromatic HFGWs and motivates future searches for both long-lived and transient signals.

In this letter, we report a novel, somewhat analytical way to produce equations of state (EOSs) that generate particular values of neutron star mass, radius, and tidal deformability. This is possible because our description for the EoS of dense matter can produce recurring regions, small areas where several EoSs cross in the mass-radius and mass-tidal deformability diagrams. We can place recurring regions in desired locations of these diagrams, corresponding e.g., to a given observation. Our prescription is versatile, in the sense that different microscopic models can be used for the low density hadronic phase and high density quark phase, as long as they are connected by a percolation, a description that mimics quark deconfinement and is motivated by QCD. The several EoSs that pass by a recurring region can present different thresholds for the boundaries of the percolation region (different beginning and ending for the quark deconfinement region), as well as different orders for the phase transition at the boundaries. When combining all these features, our prescription allows one not only to produce an EoS that matches an observation, but also one that matches specific chosen criteria for the EoS. The EoSs produced by this new method will be specially suitable for the study of dense-matter properties in future gravitational-wave observations, when both the inspiral and postmerger phase signals will become available. Our numerical code that calculates recurring regions using CompOSE microscopic EoSs is open source and publicly available.

We develop a formalism, based on spinor-helicity techniques, to generalize the formulation of partial wave unitarity bounds. We discuss unitarity bounds for $N\to M$ (with $N,M\ge 2$) scattering processes—relevant for high-energy future colliders—and spin-2 or higher-spin theories—relevant for effective field theories of gravity—that are not approachable by standard methods. Moreover, we emphasize the power and complementarity of positivity and partial wave unitarity bounds to constrain the parameter space of effective field theories.

Using a $10.9{\mathrm{fb}}^{-1}$ data sample collected by the BESIII detector at center-of-mass energies from 4.16 to 4.34 GeV, we search for the charmless decays $X(3872)\to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $K^{*}(892)\overline{K}$, where the $X(3872)$ is produced via the radiative process $e^{+}{e}^{-}\to \gamma X(3872)$. No significant signal is observed. We set upper limits on the relative branching fractions $\mathcal{B}[X(3872)\to K_S^0{K}^{\pm }{\pi }^{\mp }]/\mathcal{B}[X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi ]<0.07$ and $\mathcal{B}[X(3872)\to K^{*}(892)\overline{K}]/\mathcal{B}[X(3872)\to {\pi }^{+}{\pi }^{-}J/\psi ]<0.10$ at the 90% confidence level. Additionally, upper limits on the product of the cross section $\sigma [e^{+}{e}^{-}\to \gamma X(3872)]$ and the branching fractions $\mathcal{B}[X(3872)\to K_S^0{K}^{\pm }{\pi }^{\mp }]$ and $\mathcal{B}[X(3872)\to K^{*}(892)\overline{K}]$ are reported at each energy point. In all cases, $K^{*}(892)\overline{K}$ refers to the sum of the modes $K^{*}(892{)}^{+}{K}^{-}+\mathrm{c}.\mathrm{c}.$ and $K^{*}(892{)}^0{\overline{K}}^0+\mathrm{c}.\mathrm{c}.$, where c.c. denotes the corresponding charge-conjugate modes.

The gravitational-wave event GW231123_135430 is the heaviest binary black hole system observed by the LIGO–Virgo–KAGRA Collaboration to date, with the initial analysis indicating the individual black hole masses lie within or above the theorized pair-instability mass gap of roughly $60-130M_{\odot }$. The inference further suggests that both black holes possess high spins, measured to be ${0.90}_{-0.19}^{+0.10}$ and ${0.80}_{-0.51}^{+0.20}$. Therefore, the observation of this event suggests the formation of black holes from channels beyond the standard stellar collapse. However, different waveform models yield significantly different parameter estimates, possibly due to missing physics in the models used in inference. In this work, we carry out a reanalysis of GW231123 using a physically complete model, accounting for both spin precession and eccentricity. Our analysis shows that this event does not exhibit strong evidence for eccentricity, and the exclusion of eccentricity has minimal impact on inference. Furthermore, for GW231123-like systems, even eccentricities as large as 0.15 at 10 Hz do not yield a confident nonzero eccentricity measurement. Through a zero-noise injection recovery study, we show that the observed discrepancies in the parameter estimates can be explained by disagreement in the waveform models at strong spin precession, with the degree of parameter bias in the zero-noise runs being comparable to that observed for the real signal. We also show that inference performed with an eccentric, aligned-spin waveform model can yield a confident nonzero eccentricity measurement due to the degeneracy between eccentricity and spin precession. Bayesian model selection, however, rules out this interpretation in favor of the eccentric, spin precessing hypothesis, which supports zero eccentricity—a conclusion we confirm with additional zero-noise injection-recovery tests.

We have considered the problem of the influence of inhomogeneity of gravitational field on transport effects predicted by the field theory describing massless Dirac fermions in the Maxwell and dark matter background. As a model of dark sector one takes into account dark photon model, where the hidden sector is described by the auxiliary $U(1)$-gauge field coupled to the visible sector. Elaborating the model we restrict our considerations to the case when Weyl type conformal transformation slightly differs from the Minkowski spacetime. This assumption simplifies the calculations and enables us not to use complicated methods of the quantum field theory in the curved background. The resulting currents stemming both from visible and dark sectors are proportional to the adequate beta functions appearing in the elaborated systems. For charge-less dark sector we predict corrections to the scale conductivities in both sectors: linear in $\alpha$ in the dark sector and quadratic in the visible one.

Recent years have seen significant advances in models of gravitational waveforms emitted by quasicircular compact binaries in two regimes: the weak-field, post-Newtonian regime, in which the gravitational wave energy flux has now been calculated to fourth-and-a-half post-Newtonian order (4.5PN) [L. Blanchet et al., Phys. Rev. Lett. 131, 121402 (2023)] and the small-mass-ratio, gravitational self-force regime, in which the flux has now been calculated to second perturbative order in the mass ratio (2SF) [N. Warburton et al., Phys. Rev. Lett. 127, 151102 (2021)]. We compare these results and find evidence of mutual consistency between the two (very distinct though both first-principle) perturbative calculations.

We analyze gravitational lensing in a matched Kottler spacetime with cosmological constant $\mathrm{\Lambda }$, where a uniform-density fluid sphere described by the interior Kottler solution is smoothly joined to the exterior Kottler region. We derive an analytic expression for the deflection angle of light rays traversing both regions, isolating the corrections induced by the interior mass distribution relative to the vacuum Kottler case. The interior terms systematically reduce the bending angle and tangential magnification while enhancing the radial one, leading to a scale-dependent effect on the total magnification. Numerical evaluation shows a mild amplification for galaxy lenses and a demagnification for clusters, reflecting the contrast between compact and diffuse configurations. The induced $\mathrm{\Lambda }$ contribution from the interior corrections further reduces the bending, but only slightly, consistent with its role in the vacuum Kottler case. These results demonstrate that lensing observables retain a measurable imprint of interior structure in Schwarzschild–de Sitter-like lenses, crucial for refining realistic strong-lensing models.

We establish a new no-go theorem for cosmology: spatially flat ($k=0$) and open ($k=-1$) Friedmann-Robertson-Walker (FRW) nonstatic spacetimes cannot be simultaneously nonsingular, geodesically complete, and consistent with the averaged null energy condition (ANEC). Equivalently, any dynamic flat or open universe that is complete must violate the ANEC. By contrast, closed universes ($k=+1$) uniquely admit nonsingular, geodesically complete, ANEC-consistent solutions, with global de Sitter space as the canonical realization that saturates the ANEC. Furthermore, we analytically demonstrate that positive spatial curvature naturally mimics the phenomenology of phantom dark energy ($w<-1$), biasing flat-model reconstructions of $w(z)$ at the $\sim 1\%$ level. These results sharpen the classical singularity theorems, establish a new classification of eternal cosmologies, and motivate renewed scrutiny of spatial curvature in both theory and observation.

The orbits of stars around Sgr A*, the Milky Way’s supermassive black hole, provide a unique laboratory for testing its environment with unprecedented precision. In this work, we compute the apsidal precession induced by extended matter distributions through Lagrange’s equations and compare it with the measured precession of S2, reproducing and extending GRAVITY’s constraints. In particular, we push bounds on boson clouds to larger gravitational couplings $\alpha$ and to the second-fastest superradiant mode. We also show that environments with mass of order 1% of Sgr A* drive stellar orbits to decay by dynamical friction within a few Myr. The inner star cluster is, however, efficiently replenished, masking this effect observationally. We also prove that orbital resonances from boson clouds have no impact on relevant timescales. While S2 currently provides the cleanest dataset, our framework is readily applicable to other stars that we identify as particularly promising, whose orbits will be measured with increasing accuracy, opening up new opportunities to probe the environment of Sgr A*.

Several observatories designed to detect ultrahigh-energy neutrinos are planned for the next decade. The most imminent of these is the Payload for Ultrahigh Energy Observations (PUEO), a long-duration balloon-based experiment that will provide unprecedented sensitivity to neutrinos with energies in the range of $\sim 1–1000\mathrm{EeV}$. In this work, we assess the scientific reach of PUEO. In particular, we evaluate the sensitivity of this observatory to cosmogenic neutrinos and, in turn, to the proton fraction of the ultrahigh-energy cosmic-ray spectrum. We also consider the potential of PUEO to probe scenarios in which neutrinos are produced through the decays of ultraheavy dark matter particles or are radiated from cosmic strings. We find that PUEO will be able to constrain the proton composition of ultrahigh-energy cosmic rays in scenarios that feature very strong source evolution and in which protons are accelerated to extremely high energies. Although $\gamma$-ray observations are generally more sensitive to decaying particles than neutrino observations, PUEO is expected to set the strongest neutrino-detector constraints above ${10}^{19}\mathrm{eV}$. PUEO will also provide the strongest constraints on some models of cosmic strings.

We present a study of the $\mathrm{\Omega }(2380)$ resonance and show that it is consistent with a dynamically generated state arising from the ${\overline{K}}^{*}{\mathrm{\Xi }}^{*}$, $\omega \mathrm{\Omega }$, and $\varphi \mathrm{\Omega }$ interactions. In this picture, the $\mathrm{\Omega }(2380)$ is analogous to the $\mathrm{\Omega }(2012)$, which is generated from the $\overline{K}{\mathrm{\Xi }}^{*}$ and $\eta \mathrm{\Omega }$ channels. The resulting mass, total width, and partial decay widths into the $\overline{K}{\mathrm{\Xi }}^{*}$ and ${\overline{K}}^{*}\mathrm{\Xi }$ channels are compatible with the available experimental data. We also discuss possible experimental observables that could provide further insight into the nature of this state.

In the quest to unravel the dark sector, feebly interacting freeze-in dark matter presents an intriguing possibility, plausibly explaining the consistent null results from various dark matter experiments. We propose a unique imprint in the form of gravitational waves generated during the freeze-in production of dark matter from heavy particle decay in the early Universe. This characteristic gravitational wave signature can serve as a powerful probe for freeze-in dark matter. Our study indicates that future high-frequency gravitational wave experiments can detect these waves, offering a novel avenue to critically test the underlying conditions and requirements of this dark matter paradigm, which typically lie beyond the reach of current and planned dark matter detection experiments.