The recent observation of a diphoton excess around 95 GeV by the CMS and ATLAS Collaborations, along with the $b\overline{b}$ excess reported by the LEP Collaboration in the same mass region, has drawn significant interest in the possibility of new physics beyond the Standard Model (SM). The Georgi-Machacek (GM) model, which extends the Higgs sector of the SM by introducing additional triplet scalars while preserving custodial symmetry at tree level, provides a compelling framework to explain both excesses simultaneously via a light custodial singlet Higgs. In this work, we investigate whether the GM model can still accommodate these excesses when taking into account newly proposed vacuum stability constraints, particularly the positive definiteness conditions. Our numerical analysis not only confirms the existence of a viable parameter space capable of explaining the 95 GeV excesses, but also demonstrates that, compared to traditional tree-level constraints at the electroweak scale, the positive definiteness conditions further expand the allowed parameter space, thereby enhancing the viability of the GM model. Furthermore, we emphasize that future collider experiments will play a crucial role in testing this interpretation by refining Higgs coupling measurements and searching for additional Higgs bosons.

The dynamical diquark model describes multiquark exotic hadrons in terms of diquark components nucleated by heavy quarks and successfully explains multiple features of hidden-charm and hidden-bottom exotics. Here, we apply the model to the marginally heavy case of hidden-strange states to probe whether mesons near 2 GeV with peculiar properties, such as $\varphi (2170)$, $f_2(2340)$, and $X(2370)$, are possible tetraquark candidates. We calculate spin-multiplet average masses using potentials obtained through lattice simulations and quark models, and we also describe the detailed spectra of the expected multiplets as a diagnostic to discern the nature of future hadrons likely to be discovered in this mass region by experiments at facilities such as BESIII, JLab, and the EIC.

Inspired by the BESIII observation of exotic hadron $G(3900)$ in the $e^{+}{e}^{-}\to D\overline{D}$ process [M. Ablikim et al. (BESIII Collaboration), Phys. Rev. Lett. 133, 081901 (2024)], we use the parton and hadron cascade model PACIAE to simulate the productions of charmonium-like exotic hadrons, including $X(3872)$, $Z_c(3900{)}^0$, and $G(3900)$ in the $e^{+}{e}^{-}$ annihilations at $\sqrt{s}=4.95\mathrm{GeV}$. The charmonium-like candidates are recombined by the dynamically constrained phase-space coalescence model using component mesons $D\overline{D}$ [for $G(3900)$] or $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ [for $X(3872)$, $Z_c(3900{)}^0$, and $G(3900)$] in the PACIAE simulated final hadronic state. We then calculate, for the first time, the charmonium-like candidate’s orbital angular momentum quantum number in its rest frame and perform the spectral classification for each of the above candidates. For $G(3900)$, as its $J^{PC}$ is $1^{--}$, it is identified as the $P$-wave $D\overline{D}$ or $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ state. Meanwhile, for $X(3872)$ and $Z_c(3900{)}^0$, as their $J^{PC}\mathrm{s}$ are, respectively, $1^{++}$ and $1^{+-}$, they are identified as the $S$-wave $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ candidates. It is observed that the yield of the $P$-wave $G(3900)$ composed of $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ is significantly larger than that composed of $D\overline{D}$. Moreover, in the $D{\overline{D}}^{*}/\overline{D}{D}^{*}$ channel, the yield of the $P$-wave $G(3900)$ is around three times as large as the yield of the $S$-wave $Z_c(3900{)}^0$, and it is around two orders of magnitude as large as the yield of the $S$-wave $X(3872)$. Finally, significant discrepancies are observed in the transverse momentum spectra and the rapidity distributions among the $X(3872)$, $Z_c(3900{)}^0$, and $G(3900)$ states. These discrepancies are proposed as valuable criteria for identifying the different charmonium-like exotic hadrons from each other.

We construct light cone sum rules (LCSR) for the $B\to K^{*}$ form factors in the large recoil region using vacuum-to-$B$-meson correlation functions, and systematically calculate subleading-power corrections to these form factors at tree level, including next-to-leading power contributions from the hard-collinear propagator, the subleading effective current $\overline{q}\mathrm{\Gamma }[i{\cancel{D}}_{\perp }/(2m_b)]h_v$, and twist-five/six four-particle higher-twist effects. By incorporating the available leading-power results at $\mathcal{O}({\alpha }_s)$ and the corrections to higher-twist $B$-meson light cone distribution amplitudes from our previous work, we improve the precision of theoretical predictions for $B\to K^{*}$ form factors and find that the subleading-power contributions amount to 30% of the corresponding leading-power results. Employing the Bourrely-Caprini-Lellouch parametrization, we determine the numerical results for $B\to K^{*}$ form factors across the full kinematic range through a combined fit of LCSR predictions in the large recoil region and lattice QCD results in the small recoil region. Using the newly obtained $B\to K^{*}$ form factors, we compute the branching fractions for the rare decays $B\to K^{*}{\nu }_{\ell }{\overline{\nu }}_{\ell }$ in the Standard Model, obtaining $\mathcal{B}\mathcal{R}({\overline{B}}^0\to {\overline{K}}^{*0}{\nu }_{\ell }{\overline{\nu }}_{\ell })=8.09(96)\times {10}^{-6}$ and $\mathcal{B}\mathcal{R}({\overline{B}}^{+}\to {\overline{K}}^{*+}{\nu }_{\ell }{\overline{\nu }}_{\ell })=9.95(1.05)\times {10}^{-6}$. Additionally, we predict that the longitudinal $K^{*}$ polarization fraction is $F_L=0.44(4)$.

We measure the time-integrated $CP$ asymmetry in $D^0\to K_{\mathrm{S}}^0{K}_{\mathrm{S}}^0$ decays reconstructed in $e^{+}{e}^{-}\to c\overline{c}$ events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and $428{\mathrm{fb}}^{-1}$, respectively. To infer the flavor of the $D^0$ meson, we exploit the correlation between the flavor of the reconstructed decay and the electric charges of particles reconstructed in the rest of the $e^{+}{e}^{-}\to c\overline{c}$ event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, $A_{CP}(D^0\to K_{\mathrm{S}}^0{K}_{\mathrm{S}}^0)=(1.3\pm 2.0\pm 0.2)\%$, where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with $CP$ symmetry.

We develop the pole-skipping structure in de Sitter (dS) spacetime and find that their leading frequencies satisfy the relation ${\omega }_{dS}=i2\pi T_{dS}(1-s)$, where $T_{dS}=1/2\pi L$ and $s$ denotes spin. In the two-dimensional dS spacetime, the pole-skipping points near the cosmic horizon $r=L$ for the scalar field of spin 0 and the fermionic field of spin $\frac{1}{2}$ correspond one to one with those in the classical limit as $\lambda \to 0$ in double-scaled Sachdev-Ye-Kitaev model when the temperature is infinite (${\mathrm{DSSYK}}_{\infty }$). This provides a numerical correspondence between quantum gravity in the static patch of two-dimensional dS spacetime and a one-dimensional quantum system, which we consider as a realization of the DS/dS correspondence.

We use Ising-like models to probe the thermal nature of Euclidean spacetime backgrounds. We determine which properties of the background—curvature, the presence of a horizon, or temperature—play a role in phase transitions. The geometries we use are Euclidean Schwarzschild, Rindler, extremal Reissner-Nördstrom (ERN), anti–de Sitter (AdS), and de Sitter. Among these, Rindler is flat, AdS does not have a horizon, and both AdS and ERN have zero temperatures. We find second-order phase transitions as the metric parameter is varied in all cases except for Rindler. Specifically, we find that the transition from order to disorder occurs as the curvature—or Euclidean gravity—increases. This supports our conjecture that Euclidean gravity is an essential ingredient for these phase transitions, as opposed to the presence of a horizon or temperature. Separately, since the selected geometries are position-dependent, the Ising-like models constructed on them are inhomogeneous, whereby they generalize the standard Ising model. We find that a consequence of this is that criticality does not correspond to maximal correlation lengths and scale invariance.

This study investigates polarized images of an equatorial synchrotron-emitting ring surrounding hairy black holes within the Einstein-Maxwell-scalar theory. Our analysis demonstrates qualitative similarities between the polarization patterns of hairy black holes and Schwarzschild black holes. However, due to the nonminimal coupling between the scalar and electromagnetic fields, an increase in black hole charge and coupling constant can substantially amplify polarization intensity and induce deviations in the electric vector position angle. These effects may offer observational signatures to distinguish hairy black holes from Schwarzschild black holes.

The regularity of black-hole solutions, embedded in an expanding universe, is studied in a subclass of Horndeski theories, namely the sum of the simplest quadratic, cubic, and quintic actions. We find that in the presence of a time derivative of the scalar field, driven by the cosmological expansion, this regularity generically imposes large scalar charges for black holes, even when assuming strictly no direct coupling of matter to the scalar field. Such charges cause a significant accretion of the scalar field by the black holes, driving its local time derivative to a small value. This phenomenon, together with the Vainshtein screening typical of these theories, strongly suppresses observable scalar effects. We show that this full class of models is consistent with LIGO/Virgo detections of gravitational waves, but that the LISA mission should be able to constrain the coefficient of the quintic term at the ${10}^{-30}$ level in a self-acceleration scenario, an improvement by 16 orders of magnitude with respect to what is imposed by the speed of gravitational waves.

We investigate the gravitational wave emission from extreme mass ratio inspirals, key targets for the upcoming space-based detector LISA, considering the scenario where the lighter black hole in the binary is endowed by a long-lived, time-dependent scalar field configuration, known as a scalar wig. We develop a formalism to compute scalar perturbations for extreme mass ratio inspirals on circular orbits around Schwarzschild and Kerr black holes, and apply this framework to compute additional fluxes induced by the scalar wig as well as their dependence on the scalar field properties. Our computation provides strong indications that in this scenario the presence of the scalar field does not significantly affect the orbital motion and the gravitational waveform.

We present a new framework for modeling gravitational wave diffraction near fold caustics using the uniform approximation (UA), focusing on binary mass lenses—axially asymmetric systems with complex caustic structures. Full-wave methods based on the Kirchhoff integral become impractical in this regime due to highly oscillatory integrands. The UA provides a robust and accurate description of the wave field near folds, resolving the breakdown of geometrical optics at caustics and improving upon transitional asymptotics—based on Airy function approximations—which lack global validity. Central to our approach is the concept of the caustic width, $d_c$, a characteristic length scale defining the region where diffraction significantly alters wave propagation. We find that $d_c$ scales universally with the gravitational wavelength as $\sim {\lambda }^{2/3}$ and inversely with the redshifted lens mass as $\sim M_{Lz}^{-2/3}$. The wave amplification near the fold grows as $\sim d_c^{-1/4}$, substantially enhancing the signal and potentially playing a key role in the detection of gravitational waves lensed near caustics. Notably, for lens masses below the galactic scale, the caustic width for gravitational waves is not negligible compared to the Einstein radius—as it is in electromagnetic lensing—making the UA essential for accurately capturing wave effects.

During the coalescence of binary black holes (BBHs), asymmetric gravitational wave (GW) emission imparts a kick velocity to the remnant black hole, affecting observed waveforms and parameter estimation. In this study, we investigate the impact of this effect on GW observations using space- and ground-based detectors. By applying Lorentz transformations, we analyze waveform modifications due to kick velocities. For space-based detectors, nearly 50% of detected signals require corrections, while for ground-based detectors, this fraction is below one-third. For the q3d population model, space-based detectors could observe kick effects in over 60% of massive BBH mergers, while in pop3 model, this fraction could drop to $3\sim 4\%$. Third-generation ground-based detectors may detect kick effects in up to 16% of stellar-mass BBH mergers. Our findings highlight the importance of incorporating kick velocity effects into waveform modeling, enhancing GW signal interpretation and our understanding of BBH dynamics and astrophysical implications.

The cosmological 21-cm signal is sourced from hyperfine transitions in neutral hydrogen atoms. Yet, although the abundance of hydrogen atoms follows the baryon density field, seminumerical codes that simulate the 21-cm signal simplify their treatment as if all the matter in the Universe was in the form of collisionless cold dark matter (CDM). This is usually done by evolving the density field via a scale-independent growth factor. In this work, we separate the baryons from CDM and evolve the two species with a proper scale-dependent growth factor (SDGF). By incorporating the SDGF in the 21cmfirstclass code, we demonstrate the effect that baryons and CDM have on the 21-cm signal at the linear dark ages epoch and the subsequent nonlinear epochs of cosmic dawn and reionization. Our analysis shows that the baryonic nature of hydrogen cannot be ignored during the dark ages and that nonlinear effects in density-field evolution must be accounted for after stars have formed. Furthermore, we discuss how the 21-cm signal is modified at lower redshifts, where ground-based 21-cm interferometers are mostly sensitive, due to the choice of working with either the “linear” or “nonlinear” matter overdensity (that is, the overdensity as computed from linear perturbation theory and nonlinear perturbation theory, respectively) in the extended Press-Schechter formalism.

We present a follow-up study to the method recently proposed by Namikawa and Sherwin (2023) to probe gravitational waves using cross-correlations between two cosmic microwave background (CMB) $B$-modes and a large-scale structure tracer. We first improve on the previous forecast by including the impact of CMB component separation and find that, if the tensor-to-scalar ratio is $r=0$, we can achieve ${\sigma }_r\simeq 3.6\times {10}^{-3}$ by combining upcoming experiments, i.e., LiteBIRD, CMB-S4 and the Advanced Simons Observatory. With a more futuristic experiment, we can achieve even tighter constraints on $r$ if improved delensing can be realized. Using a simulated analysis pipeline, we also explore possible biases from higher-order terms in the lensing potential, which were previously not examined in detail. We find that these bias terms are negligible compared to a detectable signal from inflationary gravitational waves. Our simulated results confirm that this new method is capable of obtaining powerful constraints on $r$. The method is immune to Gaussian Galactic foregrounds and has a different response to non-Gaussian Galactic foregrounds than the $B$-mode power spectrum, offering an independent cross-check of $r$ constraints from the standard power spectrum analysis.

The charge-velocity-dependent one-scale model is an extension of the canonical velocity-dependent one-scale model that explicitly incorporates additional degrees of freedom on the string world sheet, such as arbitrary currents and charges, expected in physically realistic models. A previous paper [Phys. Rev. D 110, 023540 (2024)] started an in-depth classification of its possible asymptotic scaling solutions, with the goal of identifying distinguishing features which may be tested against numerical simulations or future observations. This earlier analysis restricted itself to unbiased solutions; in the present work we relax this assumption, allowing for the possibility of energy loss biases between the bare string and the charge/current or between the charge and the current themselves. We find additional scaling solutions, some of which are parametric extensions of the unbiased ones, while others are new scaling branches that do not exist in the unbiased case. Overall, it remains the case that there are three broad classes of solutions, mainly depending on the balance between the expansion rate and the available energy loss mechanisms. Our results enable a quantitative calibration of the model, using forthcoming high-resolution numerical simulations.

Motivated by observed discrepancies between the Atacama Cosmology Telescope Data Release 4 (ACT DR4) and Planck 2018 cosmic microwave background (CMB) anisotropy power spectra, particularly in the cross-correlation of temperature and E-mode polarization, we investigate challenges that may be encountered in the comparison of satellite and ground-based CMB data. In particular, we focus on the effects of Fourier-space filtering and masking involving bright point sources. We show that the filtering operation generates bright cross-shaped artifacts in the map, which stretch far outside typical point-source masks. If not corrected, these artifacts can add bias or additional variance to cross-spectra, skewing results. However we find that the effect of this systematic is not large enough to explain the ACT-Planck differences presented with ACT DR4.

The recent detection of nanohertz stochastic gravitational-wave backgrounds (SGWBs) by pulsar timing arrays (PTAs) promises unique insights into astrophysical and cosmological origins. However, traditional Markov Chain Monte Carlo (MCMC) approaches become prohibitively expensive for large datasets. We employ a normalizing flow (NF)-based machine learning framework to accelerate Bayesian inference in PTA analyses. For the first time, we perform Bayesian model comparison across SGWB source models in the framework of machine learning by training NF architectures on the PTA dataset (NANOGrav 15 year) and enabling direct evidence estimation via learned harmonic mean estimators. Our examples include 10 conventional SGWB source models such as supermassive black hole binaries, Power-Law spectrum, cosmic strings, domain walls, scalar-induced GWs, first-order phase transitions, and dual scenario/inflationary gravitational wave. Our approach jointly infers 20 red noise parameters (10 pulsars) and two SGWB parameters per model in $\sim 20$ hours (including training), compared to $\sim 10\mathrm{days}$ with MCMC (68 pulsars). Critically, the NF method preserves rigorous model selection accuracy, with small Hellinger distances ($\lesssim 0.3$) relative to MCMC posteriors, and reproduces MCMC-based Bayes factors across all tested scenarios. This scalable technique for SGWB source comparison will be essential for future PTA expansions, and next-generation arrays such as the SKA, may offer substantial efficiency gains without sacrificing physical interpretability.

Collisional flavor instabilities, driven by differing neutrino and antineutrino reaction rates, are expected to occur in dense astrophysical environments like supernovae and neutron star mergers, but have yet to be incorporated in large-scale simulations. We derive analytical expressions for the asymptotic state resulting from a homogeneous and isotropic instability, and apply these predictions to two representative conditions from a neutron star merger simulation. We emphasize the importance of using a collision term that allows for both damping of flavor coherence and relaxation back to the classical steady state. When this classical configuration is collisional unstable, the resulting asymptotic state reflects a compromise between classical relaxation and flavor conversion, defining a “quantum” equilibrium with nonzero coherence. This analysis highlights the possibility of a tradeoff between classical and quantum effects, an important feature with regard to the inclusion of flavor oscillation physics into global simulations.

We show that stars in the inner parsec of the Milky Way can be significantly affected by dark matter annihilation, producing population-level effects that are visible in a Hertzsprung-Russell (HR) diagram. We establish the dark HR diagram, where stars lie on a new stable dark main sequence with similar luminosities, but lower temperatures, than the standard main sequence. The dark matter density in these stars continuously replenishes, granting these stars immortality and solving multiple stellar anomalies. Upcoming telescopes could detect the dark main sequence, offering a new dark matter discovery avenue.

We present the psalter software for efficiently computing the mass and energy of the particle spectrum for any (e.g., higher-rank) tensor field theory in the wolfram language. The user must provide a Lagrangian density which is expanded quadratically in the fields around a Minkowski vacuum, is linear in the coupling coefficients, and otherwise built from the partial derivative and Minkowski metric. psalter automatically computes the spin-projection operators, saturated propagator, bare masses, residues of massive and massless poles, and overall unitarity conditions in terms of the coupling coefficients. The constraints on the source currents and total number of gauge symmetries are produced as a by-product. We provide examples from scalar, vector, tensor, and gauge theories of gravity. Each example, including spectra of higher-spin modified gravity theories, may be obtained on a personal computer in a matter of minutes. The software is also parallelized for use on high-performance computing resources. The initial release allows for parity-preserving operators constructed from fields of up to rank three: this functionality will be extended in future versions. psalter is a contribution to the xact project.