We discuss graviton dark radiation produced by the decay of a secluded scalar field that couples to the Standard Model (SM) only through gravity. Such scalar fields are long lived, and their decay channels generically include gravitons. If such particles existed and dominated the early Universe, a sizable branching ratio into gravitons would yield non-negligible dark radiation that significantly alters the subsequent thermal history of the Universe. In this work, we focus on the dark glueball as a representative secluded hidden scalar and compare the decay rates into SM particles via a nonminimal coupling to gravity with those into gravitons, paying attention to how the breaking of conformal invariance affects the amount of graviton dark radiation. We find that decays into the SM are dominated by two-body decay channels into Higgs bosons and gluons. In particular, when the Higgs field has a large nonminimal coupling to gravity, the production of graviton dark radiation is naturally suppressed in the metric formalism, and the SM sector is preferentially reheated and energy transfer to other hidden sectors is suppressed. Finally, we present the expected gravitational-wave spectrum resulting from dark glueball domination.

First-order phase transitions in the early Universe are a well-motivated source of gravitational waves (GWs). In this paper, we identify a previously overlooked GW production mechanism: gravitational transition radiation, arising from graviton emission by particles whose mass changes as they pass through expanding bubble walls. Unlike conventional sources, such as bubble collisions or sound waves, this mechanism operates at the microscopic scale set by the Lorentz-contracted wall thickness, leading to GW emission at significantly higher frequencies. The resulting spectrum features a distinctive shape with a peak frequency redshifting to $f_{\mathrm{peak}}\sim T_0\sim {10}^{10}\mathrm{Hz}$, where $T_0$ is the current temperature of the Universe. This mechanism is generic and is expected to operate similarly for domain walls and other relativistic interfaces.

We investigate the sensitivity of a future high-luminosity $e^{-}{e}^{+}$ collider operating at $\sqrt{s}=250\mathrm{GeV}$ to $CP$-violating and $CP$-conserving anomalous $hVV$ interactions via the Higgsstrahlung process. The effects of new physics are parametrized in the Standard Model effective field theory (SMEFT) framework through six dimension-6 operators modifying the $hVV$ vertices. Using polarized beams and exploiting polarization and spin correlation asymmetries reconstructed from Higgs decay products, we perform a comprehensive analysis across the three dominant decay modes, $h\to b\overline{b}$, $W{W}^{\star }$, and $Z{Z}^{\star }$. The $h\to W{W}^{\star }$ channel exhibits the highest sensitivity to ${\mathcal{O}}_{HW}$ and ${\mathcal{O}}_{H\tilde{W}}$, while the $b\overline{b}$ mode constrains the remaining operators with high statistical precision. Sensitivity studies incorporating luminosity scaling and systematic uncertainties show that the projected bounds improve significantly with increasing integrated luminosity, but saturate once experimental systematics exceed the few-percent level. These results highlight the crucial role of spin-based observables and beam polarization in achieving subpercent precision on SMEFT coefficients at future lepton colliders.

In this work, we use neutrino masses as a probe of the neutrino-light-quark effective scalar interactions. It is found that neutrinos can acquire masses not only from the usual light quark loop corrections, but also from the light quark condensates. The latter contribution has been overlooked in the literature. We show that both contributions are comparable for operators involving $u$ and $d$ quarks, while quark loop corrections dominate for operators involving the $s$ quark. Using the low-energy effective field theory extended with light right-handed neutrinos and matching to chiral perturbation theory, we systematically analyze these contributions, deriving constraints on the corresponding Wilson coefficients from neutrino mass bounds, coherent elastic neutrino-nucleus scattering, and light pseudoscalar meson invisible decays. Our analysis shows that electron neutrino mass measurements provide the most stringent constraints on these scalar couplings, significantly improving upon limits from other observables. The results highlight the importance of including both perturbative and nonperturbative contributions in complete phenomenological analyses of neutrino mass generation mechanisms.

We propose a three-zero texture for the down-quark mass matrix within a $SU(5)$ grand unified theory (GUT)-inspired Standard Model, enforced by a noninvertible selection rule originating from ${\mathbb{Z}}_2$ gauging of ${\mathbb{Z}}_N$ symmetries. Assuming $CP$ invariance at the high-energy scale, our framework solves the strong $CP$ problem while reproducing a realistic quark mass matrix. The $CP$ symmetry is spontaneously broken down at an intermediate scale via complex vacuum expectation values of new scalar fields ${\eta }_i$, which generate the $CP$ phase in the Cabibbo-Kobayashi-Maskawa matrix without inducing the quantum chromodynamics (QCD) $\overline{\theta }$ term. The present model incorporates three generations of matter, Higgs, and additional scalars with a common structure under the noninvertible symmetry, which may be naturally embedded into $SO(10)$ GUTs at high energies.

We present the perturbative calculation of the leading-twist gluon transverse momentum dependent distribution functions (TMDPDFs) at one-loop level within large-momentum effective theory. By employing the basis of circular polarizations, we generalize the gluon-gluon correlator to a matrix ${\mathrm{\Phi }}_{\mathrm{\Lambda }{\mathrm{\Lambda }}^{\prime }}^{ij}(x,{\mathit{k}}_T^2;S)$ in the gluon $\otimes$ hadron spin space. Incorporating the transverse momentum of external states, we derive the leading-twist gluon TMDPDFs and quasi-TMDPDFs at one-loop level. Our calculations reveal nonzero distributions for the gluon TMDPDFs $f_{1T}^{\perp g}(x,{\mathit{k}}_T^2)$, $h_1^{\perp g}(x,{\mathit{k}}_T^2)$, $h_{1T}^g(x,{\mathit{k}}_T^2)$, and $h_{1T}^{\perp g}(x,{\mathit{k}}_T^2)$. These findings enable future lattice quantum chromodynamics simulations to extract these gluon TMDPDFs, which will facilitate a complete determination of nucleon tomography.

In this paper, we propose the analysis of the heavy quark photoproduction associated with a leading neutron in hadronic collisions at the LHC as an alternative to probe the pion gluon distribution in a kinematical range not covered by previous experiments. We perform an exploratory study of the charm and bottom photoproduction associated with a leading neutron in proton-proton ($pp$) and proton-lead ($pPb$) collisions, and present calculations for the rapidity distributions and cross sections. Our predictions indicate that experimental studies of these processes are feasible, and that a future measurement of this final state will be useful to constrain the pion gluon distribution at small values of the Bjorken $x$ variable and to improve our understanding of the pion structure.

We investigate a class of stationary, planar-symmetric solutions of relativistic hydrodynamics, in which a dissipative fluid is confined between two parallel plates that move relative to each other and/or are maintained at different temperatures. We find that neglecting the heat flux leads to qualitatively incorrect flow profiles, even in systems with temperature-independent viscosity. This arises from the fact that, in special relativity, the heat flux itself contributes to the momentum density (the so-called “inertia of heat”). This effect is most evident in the Landau frame, where the fluid removes the excess energy generated by viscous heating by streaming across the boundaries. The analysis is further extended to the limit of vanishing chemical potential.

In this work, we investigate the exclusive decays of the fully-heavy tetraquark states $T_{4c,b}$ into light mesons, specifically $\pi$ and $K$, using the framework of nonrelativistic quantum chromodynamics (NRQCD) and collinear QCD factorization for hard exclusive processes. We estimate the decay widths to be ${10}^{-9}\mathrm{GeV}$ and ${10}^{-14}\mathrm{GeV}$ for the decays $T_{4c}\to {\pi }^{+}{\pi }^{-}$ and $T_{4b}\to {\pi }^{+}{\pi }^{-}$ (and similarly for $K^{+}{K}^{-}$), respectively. The branching ratio for $T_{4c}\to {\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ is on the order of ${10}^{-8}$, making it currently unobservable in existing experiments. The factorization of $T_{4c,b}$ into light hadrons shares similarities with the decay $J/\psi \to p\overline{p}$. However, unlike the latter process, the decay $T_{4c,b}\to {\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ exhibits unique features that arise only in processes involving multiple incoming or outgoing particles. One such feature is the necessity of maintaining the $iϵ$-prescription for the denominators or propagators due to the divergences in the kinematic region of interest. Employing the sector decomposition method, along with the aid of the Cheng-Wu theorem and the qhull program, we present a systematic approach to handle the convolutions and phase-space integrations. This method can also be extended to similar processes, such as $T_{4c,b}\to p\overline{p}$, as well as to phase-space integrations where each denominator is a linear combination of integration variables.

In the experiment with the SND at the VEPP-$2000e^{+}{e}^{-}$ collider, the $e^{+}{e}^{-}\to \eta \gamma$ cross section is measured in the energy range $E=980–1060\mathrm{MeV}$. The measurement is carried out in the $\eta \to 2\gamma$ decay mode. Data with an integrated luminosity of $73{\mathrm{pb}}^{-1}$ collected in 2018 and 2024 are used in the analysis. The measured cross section is the most accurate to date and is higher compared to other measurements. From the fit to the cross section data with the vector meson dominance model, the value of the product of the branching fractions $B(\varphi \to e^{+}{e}^{-})B(\varphi \to \eta \gamma )$ has been obtained.

Recently, Ruffini et al. [Phys. Rev. Lett. 134, 081403 (2025).] pointed out that the repetitive Penrose process cannot drain the entire extractable energy of a Kerr black hole. In this Letter, we alternatively point out the charge of a Reissner-Nordström black hole cannot drop down to exactly zero via the repetitive electric Penrose process that is terminated after a finite number of iterative steps, indicating a new thermodynamical third-law analog for the repetitive electric Penrose process.

We study the continuum limit of branched polymers (BPs) with loops coupled to Ising spins at the zero-temperature critical point. It is known that the continuum partition function can be represented by a Hermitian two-matrix model, and we propose a string field theory whose Dyson-Schwinger equation coincides with the loop equation of this continuum matrix model. By setting the matrix size to one, we analyze a convergent nonperturbative partition function expressed as a two-dimensional integral, and show that it satisfies a third-order linear differential equation. In contrast, in the absence of coupling to the critical Ising model, the continuum partition function of pure BPs with loops is known to satisfy the Airy equation. From the viewpoint of two-dimensional quantum gravity, we introduce a nonperturbative loop amplitude that serves as a solution to the Wheeler-DeWitt equation incorporating contributions from all genera. Furthermore, we demonstrate that the same Wheeler-DeWitt equation can also be derived through the stochastic quantization.

We present a detailed evaluation of constrained minisuperspace path integrals in Jackiw-Teitelboim (JT) gravity and in biaxial Bianchi IX quantum cosmology, employing the Gelfand-Yaglom theorem to compute the relevant functional determinants. In both settings, integrating out the dilaton or a minisuperspace variable produces a functional delta that enforces the classical constraint equation, thereby localizing the remaining path integral onto classical configurations. The associated Jacobian, equivalently, the functional determinant of the operator obtained by linearizing the constraint about the classical solution, fixes the semiclassical prefactor and the correct measure. We evaluate this determinant exactly via the Gelfand-Yaglom method and obtain the fully normalized fixed-lapse propagators. We further extend the JT analysis to a quadratic dilaton potential $U(\varphi )=m^2{\varphi }^2$ and comment on the corresponding saddle-point structure of the lapse integral. Finally, we apply the same approach to Bianchi IX quantum cosmology and derive the fixed-lapse propagator, including its prefactor. Our results provide a systematic and broadly applicable prescription for treating constraint structures in gravitational path integrals using functional determinant techniques, with potential applications to a wider class of minisuperspace quantum cosmology and quantum gravity.

Black holes with sufficiently large initial charge and mass will Hawking evaporate toward the extremal limit. The emission slows as the temperature approaches zero, but still reaches the point where a single Hawking quantum would make the object superextremal, removing the horizon. We take this semiclassical prediction at face value and ask: When the emission occurs, what is revealed? Using a model of thin-shell collapse with subsequent accretion/evaporation by a null flux of ingoing positive/negative energy (charged Vaidya spacetime glued to a flat interior), we find two possible outcomes: (i) For shells that are initially very tightly bound, a timelike singularity forms and later appears; or (ii) for unbound or modestly bound shells, the matter reemerges as a null shell that expands to infinity. This expanding remnant has been bathed in the ingoing Hawking quanta during evaporation and presumably carries correlations with the outgoing quanta, offering the attractive possibility of studying information paradox issues in a setup where spacetime curvatures are globally small, so that quantum gravity is not required. Even for ordinary black holes that evaporate down to the Planck size, we propose a radical new scenario for the interior: rather than forming a singularity, the collapsing matter settles onto an outgoing null trajectory inside the horizon for the entirety of evaporation.

In this paper, we present a deep-learning approach to generate synthetic cosmological images by training a convolutional variational autoencoder on two-dimensional dark matter density slices projected from $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) $N$-body simulations. The model learns a compact latent representation that enables accurate reconstructions and fast generation of new synthetic realizations through a single forward pass through the decoder. We validate the generated fields using cosmology-based summary statistics, focusing on the matter power spectrum and related Fourier space diagnostics, and found good agreement with the reference simulation across the range of scales where the maps exhibit good resolution. Thanks to its low inference cost and stable training target, this variational-autoencoder approach provides a lightweight and reproducible basis for generative modeling of large-scale projected structures and can support downstream tasks such as fast simulation generation and data augmentation.

The data release six of the Atacama Cosmology Telescope (ACT DR6) and the second data release from the Dark Energy Spectroscopic Instrument (DESI DR2) recently became available. In light of these data, we update constraints on the early dark energy (EDE) resolution to the Hubble tension. While ACT DR6 does not favor EDE over the core cosmological model, $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$), it allows for a significantly larger maximum contribution of EDE, $f_{\mathrm{EDE}}$, in the prerecombination era than the latest analysis of Planck NPIPE despite increased precision at small angular scales. Moreover, EDE rises the value of $H_0{r}_s$, improving consistency between cosmic microwave background and DESI DR2 data. We find a residual tension with SH0ES of $\sim 2\sigma$ for the combination of Planck at $\ell <1000+$ ACT DR6 + lensing + Pantheon-plus + DESI DR2, a significant decrease from $3.7\sigma$ for analyses that use NPIPE and SDSS baryonic acoustic oscillation data. A profile likelihood analysis reveals significant prior volume effects in Bayesian analyses which do not include SH0ES, with confidence intervals of $f_{\mathrm{EDE}}=0.09\pm 0.03$ and $H_0=71.0\pm 1.1\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. When including DESI data, the EDE model with $H_0=73\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ provides a better fit than the $\mathrm{\Lambda }\mathrm{CDM}$ model with $H_0=68.4\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$. The inclusion of SH0ES data rises the preference well above $5\sigma$, with $\mathrm{\Delta }{\chi }^2=-35.4$. Our work demonstrates that after ACT DR6 and DESI DR2, EDE remains a potential resolution to the Hubble tension.

We investigate the effects of dark scalar- and vector-mediated interactions on dark matter admixed neutron stars, employing the two-fluid formalism. We adopt three different nuclear equations of state—BSk22, MPA1 and APR4—to describe the baryonic sector, while the dark component consists of fermionic particles within a relativistic mean field framework. We consider both linear and quadratic scalar interactions with the dark fermion, including a quartic self-interaction in the latter case. The parameters of the dark matter (DM) models are inferred via a Bayesian analysis that incorporates data from NICER observations and binary neutron star merger detections. The neutron star configurations obtained from the selected model parameters develop dark matter cores, leading to more compact objects with smaller masses and radii. Our findings suggest that scalar interactions generally have a weaker impact on the stellar structure compared to vector-mediated ones, though quantitative differences arise. In particular, quadratic scalar couplings suppress the net attractive interaction, allowing for larger dark matter fractions to be accreted. We also compute the sound speed of DM, finding that the scalar and quadratic interactions modify the stiffness of the dark equation of state while respecting causality: vector repulsion enhances the sound speed, whereas scalar attraction tends to soften it. We compare our results with GW1708017, GW190425 and NICER data and constrain DM couplings and mass.

We study the matter power spectrum constraint on primordial black holes (PBHs) by the dark matter (DM) emitted through Hawking radiation. We particularly focus on the scenario where a PBH, with mass ranges between 1 g and ${10}^9\mathrm{g}$, evaporates before big bang nucleosynthesis. In addition to that, we consider the case where PBH abundance is scarce and there is no early PBH domination taking place. On the DM side, we assume a fraction of the population is produced from PBH evaporation, while the remaining part is the regular cold dark matter, which is produced by some genesis processes that decouples later on. Therefore, in the rest of the cosmological history, DM interacts solely through gravity. Under this condition, there is no thermal equilibrium ever established between DM and standard model plasma. An important feature in our analysis is that, for the light PBH we consider, its temperature is much larger than the mass of DM, which is consequently produced ultrarelativistically and requires a protracted time to become matterlike. In this context, even though a PBH evaporates in the very early Universe, PBH-produced DM could still be energetic and smooth out the small scale structure at a much later time. By the precision measurement on the matter power spectrum from cosmic surveys, we are able to set a joint constraint on light PBHs and the noncold DMs they produced.

We present a dedicated search for gravitational-wave backgrounds with nontrivial peak structures using data from the first three and the initial part of the fourth observing runs of the LIGO-Virgo-KAGRA network. The analysis is motivated by a variety of early-Universe models characterized by signals with multiple peaks. We introduce a model independent parametrization of double-peaked spectra based on the superposition of two normalized broken power laws and perform a Bayesian inference study using the LIGO-Virgo-KAGRA isotropic cross-correlation data. While no statistically significant evidence for a multipeak background is found, the analysis provides constraints on the interpeak slopes in correlation with the signal amplitude. These results exhibit LIGO-Virgo-KAGRA’s ability to probe signals beyond a single peak structure and establish a foundation for future targeted searches for nontrivial gravitational waves background spectral shapes in future observing runs and the advanced detector era.