There has been a recent revival in understanding the spontaneous scalarization phenomenon in scalar-tensor gravity as a phase transition. Using the tools of the Landau theory, we now know that first-order transitions where scalarization occurs in a discontinuous manner are more prominent than what had been considered in the literature, and this might lead to novel observation channels. However, the examples so far have been restricted to specific quadratic scalar coupling terms and spherically symmetric stars. Here we explore the phase transition structure of scalarization for more general couplings, considering linear as well as quadratic terms in the conformal scaling factor of the theory. Moreover, we also investigate the effect of rotation on the scalarization phase transition. Both of these considerations are natural choices since the coupling in a scalar-tensor theory can appear at all orders, and astrophysical neutron stars commonly have angular momentum. The introduction of linear coupling leads to a complex solution space which is harder to explore. However, we demonstrate that the Landau model of scalarization enables us to systematically find the branches of scalarized solutions that are commonly overlooked in numerical searches, providing a novel tool. On the other hand, the main effect of stellar rotation is shifting the stellar masses at which the phase transition occurs to higher values, but the qualitative picture remains similar to what happens under spherical symmetry.

We explore the ability of normalizing flow (NF) generative models to reproduce weak-lensing summary statistics when trained on a set of cosmological simulations. Our analysis focuses on how accurately NF models recover the mean, standard deviation, and covariance of key statistics derived from convergence ($\kappa$) maps; the angular power spectrum $C_{\ell }$, probability density function, and Minkowski functionals of weak lensing convergence $\kappa$-maps. We test two scenarios for training; (1) on the data vectors and (2) on the full $\kappa$-maps. In both cases, the NF models reproduce the mean and variance of the target statistics within percent-level accuracy. However, the accuracy of the off-diagonal elements of the covariance matrix is underestimated by up to $\sim 25\%$. We study several mitigation strategies and find that data augmentation and training with noisy fields help improve covariance recovery to $\mathcal{O}(5\%)$ on power spectrum statistics. Our study demonstrates that while the means and variances of weak lensing statistics can be well-modeled by NF, covariances can be significantly underestimated if mitigation strategies are not applied. We present this test as a rigorous diagnostic of generative-model fidelity.

In gravitational-wave astronomy, as in other scientific disciplines, “exceptional” sources attract considerable interest because they challenge our current understanding of the underlying (astro)physical processes. Crucially, “exceptionality” is defined only relative to the rest of the detected population. For instance, among all gravitational-wave events detected so far, GW231123 is the binary black hole with the largest total mass, while GW241110 is the binary black hole with the most strongly misaligned spin relative to the orbital angular momentum. Mandel [Astrophys. J. Lett. 996, L4 (2026)] argued that apparent “exceptionality” may reflect measurement error rather than an extreme true value, and suggested that the total mass of GW231123 may be significantly overestimated. Here we present a quantitative analysis that supports this conceptual point. We find that claims of “exceptionality” obtained under population-agnostic priors should be critically questioned whenever measurement uncertainties are comparable to the width of the underlying population. Specifically, we find that the total mass of GW231123 is unlikely to be meaningfully affected by this effect while the spin of GW241110 is far less likely to be antialigned than initially claimed: about 70% of realizations that appear to yield an “exceptionally antialigned” spin are in fact consistent with either nonspinning or aligned configurations.

We compute the excitation function of the global $\mathrm{\Lambda }$ polarization in semicentral heavy-ion collisions within a core-corona framework, where the interaction region is described as a dense core and a dilute corona separated by a critical value of the participant density. An important ingredient in the model is the intrinsic polarization functions in each of the two regions. These are computed from a field-theoretical approach where the vortical motion of the medium is included in an effective fermion propagator, which we derive explicitly. The interactions in the core and the corona are transmitted by suitable mediators at finite temperature and baryon chemical potential; gluons for the former and $\sigma$-mesons for the latter. The temperatures and baryon chemical potentials are related to the collision energies along the chemical freezeout curve. By allowing the cross section for $\mathrm{\Lambda }$ production in the nuclear environment to take on values below the nucleon–nucleon threshold cross section, the calculation describes the lowest energy polarization data point. For the centralities corresponding to the experimental data, we find that the contribution from the corona is the dominant one and that a lifetime, and correspondingly a volume of this region which becomes larger for the smaller energies due to stopping, is an essential ingredient in the calculation. Overall, the model provides a good description of the excitation function across the full experimental range and predicts a robust maximum near $\sqrt{s_{NN}}\sim 3\mathrm{GeV}$ that remains stable under reasonable variations of the freezeout curve and the proton–proton $\mathrm{\Lambda }$ production threshold to account for subthreshold production in a nuclear environment.

We explore the sensitivity of the $e^{+}{e}^{-}\to K^{+}{K}^{-}2{\pi }^0$ cross section to the magnetic dipole moment (MDM) of the $K^{*}$ vector meson. We describe the ${\gamma }^{*}\to 2K2\pi$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant for energies below 2.4 GeV. Using $BABAR$ data for this process, we show that this observable is indeed sensitive to the MDM of the $K^{*}$; we obtain a central value for the MDM of ${\mu }_{K^{*}}=4.5$ and an upper bound of ${\overline{\mu }}_{K^{*}}=6.3$, in units of $e/2m_{K^{*}}$. We emphasize the need for higher precision data to provide a first data-driven determination of this parameter to confront it with theoretical predictions.

Strong magnetic fields modify the force that confines quarks inside hadrons and make it direction-dependent. Using quark-antiquark potentials obtained from lattice simulations as inputs to a quark potential model, we investigate how the anisotropic confinement affects the mass spectrum of quarkonium. In the strong-field regime, we find downward mass shifts induced by a softening of the confining potential along the field direction. In particular, the mass shifts of radially excited states are more significant than that of the ground state. For the longitudinal spin eigenstates, the excited-state spectrum strongly depends on the magnetic-field strength, in contrast to the spectrum with conventional isotropic confinement, which is insensitive to the field strength. This provides a clean probe of magnetically induced confinement anisotropy that can be confirmed in future lattice simulations.

With the growth of statistics in the future experiments at the LHC, the number of events with charm production will increase substantially. It may become possible to measure the multiplicity distribution of charm particles. Using pythia-8, we generated charm multiplicity distributions in $pp$ collisions for different pseudorapidity ranges ($|\eta |<0.5$, 1.0, 2.0, 3.0) and center-of-mass energies ($\sqrt{s}=0.9$, 2.36, 2.76, 7.0, 8.0, 13.0 TeV). We investigated the role played by multiple parton interactions and color reconnection. We compared the multiplicity distribution of D mesons with the charm quark multiplicity distribution. We observe that the “quark-hadron” duality hypothesis is satisfied. With the obtained distributions, we tested the validity of the Koba-Nielsen-Olesen scaling. We also parametrized the charm distributions considering the Poisson distribution and negative binomial distributions.

It is widely repeated in the popular literature and elsewhere that the singularity at the center of a black hole is a point. It is not true. Two observers who free fall into a spherical black hole along two different angular trajectories at the same time $t$ do not encounter each other at the central singularity; rather, they lose causal contact with each other already well away from the singularity. Counterintuitively, in general relativity two points can be spatially close yet causally distant. The singularity is a surface not a point. The story for rotating black holes is more complicated, but the same conclusion holds. For a rotating black hole, the singular surface almost certainly resides at its inner horizon, where even the tiniest classical or quantum perturbations ignite the exponential mass inflation instability, precipitating collapse to a spacelike singular surface. There are implications for quantum gravity. We argue that, whatever the ultimate theory of quantum gravity may be, the quantum states of a black hole probably reside at its effectively two-dimensional singular surface, which coevolves unitarily with, and in thermodynamic equilibrium with, the hot atmosphere of trapped Hawking radiation that the black hole generates within its event horizon.

Exponential quintessence models motivated by string compactifications naturally involve both a dilatonic scalar and its axionic partner evolving on a curved field space, while spatial curvature enlarges the cosmological phase space and may affect late-time dynamics. We perform a systematic analysis of the minimal two-field exponential system in a curved FLRW background including radiation and matter components, combining a complete dynamical systems classification with analytical approximations and numerical integration. In the scalar-dominated limit, nongeodesic trajectories can sustain accelerated expansion on steep potentials, and in curved universes, a scaling-curvature fixed point can in principle soften the requirements for acceleration. However, we show that these mechanisms arise in distinct invariant manifolds and cannot be simultaneously realized in the presence of a background fluid: no nongeodesic scaling fixed point exists within an open region of parameter space. As a consequence, in the observationally viable thawing regime, the axion does not track the background fluid and spatial curvature becomes dynamically subdominant, leading to an effectively single-field evolution. We further identify a degeneracy between curvature effects and scalar-field dynamics that limits their independent impact on late-time cosmology. Confronting the model with current cosmological background data (Planck 2018 distance priors, Pantheon+, BAO, and cosmic chronometers), we obtain an upper bound $\lambda \lesssim 0.75$ (95% C.L.) on the potential slope. Our results demonstrate that even in the minimal multifield setup with spatial curvature, sustained late-time acceleration requires a sufficiently flat potential, so that the tension between cosmic acceleration and quantum gravity expectations persists within this framework.

Numerical weather prediction requires initial estimates of the atmospheric state. Since the atmospheric density field is intricately woven into the atmosphere’s governing equations, advancing atmospheric density estimation will improve numerical weather prediction. However, current meteorological instrumentation cannot directly measure the atmospheric density field over large volumes. Existing techniques rely on sparse point measurements, limiting our ability to accurately estimate the three-dimensional atmospheric density field. One potential solution is to employ measurements of the atmospheric muon flux. Atmospheric muons are particles produced when energetic atomic nuclei (cosmic rays) collide with nuclei in the upper atmosphere, producing a shower of secondary particles (muons) that propagates to the Earth’s surface. The surface atmospheric muon flux is known to be proportional to the local atmospheric density field, implying that this technique can be used as a measurement of atmospheric density. This study examines the potential for using atmospheric muon flux measurements to improve atmospheric state estimation via a case study of simulated atmospheric muon observations in the path of tropical cyclone Freddy. We show that improvement in data assimilation performance can be achieved using data from a relatively small astroparticle detector, well within the capabilities of existing astroparticle technology. Our results also indicate the potential for muon flux measurements to be more effective than surface pressure measurements at state estimation.

The discovery of supermassive black holes (SMBHs) at redshifts $z\gtrsim 10$ by JWST challenges the standard Eddington-limited growth models. We propose a novel mechanism for the rapid assembly of primordial black hole (PBH) seeds through scalar-induced critical accretion during early universe phase transitions. By solving the generalized relativistic Euler equations with a non-minimal coupling between dark matter and a background scalar field $\varphi$, we demonstrate that a “scalar fifth force” significantly shifts the sonic point outward. This mechanism yields an accretion enhancement factor $\mathrm{\Upsilon }\approx (1+\beta {)}^2$, enabling a $10M_{\odot }$ seed to reach ${10}^6{M}_{\odot }$ by $z\approx 15$, far exceeding standard General Relativistic predictions. Furthermore, this rapid mass growth predicts a distinctive spectral redshift in the stochastic gravitational wave background (SGWB), shifting the peak from the LIGO/Virgo band toward the Einstein Telescope sensitivity window (1–10 Hz).

We perform a systematic study of invariant operators in the three-Higgs-doublet model (3HDM). We compute the closed-form multigraded Hilbert series associated with the global symmetry group of the theory. In addition, we construct explicit expressions for the corresponding invariant operators up to cubic order in the couplings. As a phenomenological application, we further organize the invariants up to quadratic order in the field content into $CP$-even and $CP$-odd combinations. For the special case of invariants involving no $\mathbf{27}$ representations, our results are complete to all orders.

We discuss the HL-LHC sensitivity to probe new invisible particles including scalars and fermions using semivisible Higgs decays in the $pp\to \mathrm{ZH},Z\to jj({\ell }^{+}{\ell }^{-}),H\to {\ell }^{+}{\ell }^{-}(jj)+{\cancel{\mathrm{E}}}_{\mathrm{T}}$ production mode. The kinematics of these decays allow new particle masses below $m\lesssim 50\mathrm{GeV}$. We carry out our analysis using both a cut-based approach and a multivariate method based on a boosted decision tree. We work within the dark Standard Model effective field theory framework with operators up to dimension six and a discrete ${\mathbb{Z}}_2$ symmetry under which the new particles are odd and the SM particles are even. We compare our results to those obtained from considering the invisible $Z$ width, as well as perturbative unitarity arguments. Finally, we outline kinematic strategies at the LHC to distinguish different operator structures of the postulated invisible particles.

We calculate diffractive $D^0$ photoproduction in ultraperipheral lead-lead (Pb-Pb) collisions at the Large Hadron Collider (LHC) within the recently developed generalized photon-nucleus fixed-order next-to-leading logarithm ($\mathrm{G}\gamma \mathrm{A}\text{−}\mathrm{FONLL}$) framework, where photon-lead diffraction is modeled using nuclear diffractive parton distributions obtained in the leading-twist shadowing approach and the photon fluxes include corrections for independent electromagnetic dissociation accompanying the hard photoproduction process. We then use the predicted diffractive cross section to quantify the coherent diffractive contribution rejected by the $Xn0n$ neutron-tagged event selection adopted in the first measurement of $D^0$ photoproduction in Pb-Pb collisions at the LHC, which requires neutron emission from only one of the two lead nuclei. In this work, we also extend the $\mathrm{G}\gamma \mathrm{A}\text{−}\mathrm{FONLL}$ framework to proton-lead ($p$-Pb) ultraperipheral collisions and present predictions for inclusive and diffractive $D^0$ photoproduction at the LHC. In this case, the dominant configuration is photon emission from the lead ion followed by photon-proton scattering, and the diffractive contribution is evaluated using proton diffractive parton distributions constrained by HERA data.

We study exclusive vector meson production in ultraperipheral collisions (UPCs) of a wide range of nuclei, and assess the potential of measurements to constrain the small-$x$ structure of oxygen and neon nuclei. We employ an impact-parameter-dependent color glass condensate framework incorporating Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov, Kovner evolution, with parameters constrained by a recent global Bayesian analysis of $\gamma +p$ and $\gamma +\mathrm{Pb}$ data. We present predictions for coherent and incoherent $\mathrm{J}/\psi$ production in $\mathrm{O}+\mathrm{O}$ and $\mathrm{Ne}+\mathrm{Ne}$ UPCs at LHC energies, and quantify theoretical uncertainties using posterior samples from the calibration. We employ several nuclear structure models and find that $t$-differential observables are sensitive to the chosen model. We further study the mass-number dependence of saturation effects through nuclear suppression factors for coherent and incoherent vector meson production. Saturation-induced suppression increases systematically with both nuclear mass number and energy. Our results provide a unified framework for the systematic study of the onset of gluon saturation and nuclear structure at high energy, accessible in future UPC measurements at the LHC and at the electron-ion collider.

To circumvent the severe numerical cancellations in the standard integrated $CP$ asymmetry ($A_{CP}$) near the $\omega$ mass $m_{\omega }$, we propose a modified $CP$-violating observable $A_{CP}^{\Re }$, which explicitly highlights the contribution of the real part of the interference term. Subsequently, we employ the three-body hadronic decay $B^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^{-}$ within the perturbative QCD approach as a primary case study to validate this theoretical framework. Furthermore, this method naturally eliminates the smooth, sign-preserving continuum background originating from broad scalar resonances like the $f_0(500)$. This generalized framework provides clean and robust theoretical guidance for recovering localized $CP$-violation signals that might otherwise be masked by coarse experimental binning at future high-luminosity colliders.

We study the properties of massive fields extrapolated to the blowup of spatial infinity (${\widehat{i}}^0$), extending the program initiated by Laddha et al. [Squinting at massive fields from infinity, arXiv:2207.06406]. In the free theory, we find an explicit representation of boundary two-point functions and boundary to bulk two-point functions, and also present a Hamilton–Kabat–Lifschytz–Lowe (HKLL)-type reconstruction formula for local bulk operators in terms of smeared boundary operators. We study interacting Wightman correlators and find that, generically, interacting massive fields decay slower than free fields as one approaches ${\widehat{i}}^0$. We propose that meaningful correlators at ${\widehat{i}}^0$ can be obtained through a Lehmann–Symanzik–Zimmermann (LSZ)-like prescription that isolates the on-shell part of bulk Wightman correlators before extrapolating them to ${\widehat{i}}^0$. We show that a natural basis for operators at ${\widehat{i}}^0$, defined via this prescription, is given by the average of “in” and “out” operators defined at $i^{-}$ and $i^{+}$, respectively. Therefore, correlators at ${\widehat{i}}^0$ and cross-correlators between ${\widehat{i}}^0$, $i^{-}$, and $i^{+}$ can be represented within the class of asymptotic observables studied by Caron-Huot et al. [What can be measured asymptotically?, J. High Energy Phys. 01 (2024) 139]. We present several sample calculations.

The Bondi–van der Burg–Metzner–Sachs (BMS) frame of gravitational waves produced by numerical relativity simulations is crucial for building accurate waveform models. A proper comparison of numerical relativity waveforms with other models requires fixing the arbitrary BMS frame. In this work we improve the center-of-mass (c.m.) frame fixing for quasicircular, nonprecessing binary systems. Past work approximated the c.m. motion with just a linear fit. We compute a post-Newtonian result of the boosted c.m. charge to also capture its physical outspiraling oscillations. We show that using the analytical results improves the robustness of the fit parameters—translation and boost vectors—to the choice of duration and time of the fitting window. Our analysis demonstrates a maximum improvement in robustness when the window is placed at the center of the inspiral. We quantified this improvement by computing the ratio of variances of fit parameters when the fit window size is varied. The largest improvement in robustness of parameters is by a factor of $\sim 25$ for the boost vector and $\sim 20$ for the translation vector. Finally, we incorporate this method into the BMS frame-fixing routine of the python package scri for waveforms produced with Cauchy-characteristic evolution.

We study slowly rotating black hole solutions within degenerate higher order scalar tensor (DHOST) theories. Starting from a static, spherically symmetric metric solution of a DHOST theory, we employ the Hartle-Thorne Ansatz to model a slowly rotating spacetime. We show that the differential equation governing the frame-dragging function $\omega$ (which is supposed to depend on the radial coordinate only) is integrable for any DHOST theory allowing us to obtain its explicit form. We also consider angular dependence in $\omega$ and show that, for specific DHOST theories, regularity at the horizon and at infinity forbids it, as in general relativity. As an illustration of the formalism introduced here, we study the slowly rotating version of black hole solutions with primary hair obtained recently, examining the influence of the rotation on the innermost stable circular orbit (ISCO) and on the circular light trajectories in the equatorial plane.

We study the dynamics of spinning charged test particles orbiting a Schwarzschild black hole immersed in a test uniform magnetic field. This setup provides a simple but physically relevant framework for modeling particle motion in magnetized astrophysical environments near compact objects, where both spin-curvature coupling and electromagnetic interactions can play a significant role. The particle trajectories are obtained numerically in both equatorial and off-equatorial configurations, allowing us to examine the influence of spin-curvature and Lorentz forces on the motion. In the equatorial plane, assuming the particle’s spin vector is orthogonal to the orbital plane, we derive analytical expressions for the conserved energy and angular momentum, as well as for the radial and orbital frequencies as functions of spin parameter and magnetic parameter. We also construct the corresponding effective potential to determine the allowed regions of particle motion. The equatorial dynamics remain integrable due to the existence of conserved quantities associated with the spacetime symmetries and the alignment of the magnetic field. In contrast, the off-equatorial motion constitutes a nonintegrable dynamical system. While limiting subcases of the system, i.e., the spinning neutral and nonspinning charged cases, can be analyzed using two-dimensional Poincaré surface of sections, the combined system can be reduced only up to three degrees of freedom. Hence, to investigate the resulting complexity, we analyze the phase space using four-dimensional Poincaré surface of sections along with recurrence analysis, revealing the presence of chaotic behavior for particular choices of parameters and initial conditions. Finally, we compare the dynamics of spinning charged test particles with the limiting cases of nonspinning neutral, spinning neutral, and nonspinning charged particles, thereby distinguishing the respective contributions of spin-curvature and electromagnetic interactions.