Sodium iodide (NaI) is a widely used scintillator in direct dark matter searches. In particular, NaI-based cryogenic scintillating calorimeters have emerged as promising candidates, like in the COSINUS experiment, for testing the annually modulating signal reported by DAMA/LIBRA. In this study, we investigate defect formation within NaI crystals and its impact on the dark matter detection signal. Using molecular dynamics simulations and density functional theory techniques, we simulate a DM particle collision on an NaI crystal, focusing on the possible defects formation and their structural and electronic properties. Our analysis includes a detailed study of the electronic states associated with the interstitial atoms and vacancies, the energetic cost of defect formation, and the anisotropic threshold displacement energy. Finally, we highlight the potential to exploit dark matter-induced defects as a novel detection channel, enabled by the introduction of new states within the electronic band gap.

The rich phenomenology of binary neutron star mergers offers a unique opportunity to test general relativity, investigate matter at supranuclear densities, and learn more about the origin of heavy elements. As multimessenger sources, they emit both gravitational waves and electromagnetic radiation across several frequency bands. The interpretation of these signals relies heavily on accurate numerical-relativity simulations that incorporate the relevant microphysical processes. Using the latest updates of the bam code, we perform general-relativistic radiation magnetohydrodynamic simulations of binary neutron star mergers with two different spin configurations. We adopt a state-of-the-art equation of state based on relativistic mean-field theory developed for dense matter in neutron star mergers. To capture both dynamical ejecta and secular outflows from magnetic and neutrino-driven winds, we evolve the systems up to $\sim 100\mathrm{ms}$ after the merger with a resolution of 93 m across the neutron stars. Our results show that the nonspinning configuration undergoes a more violent merger, producing more ejecta with lower electron fraction and higher velocities, while the spinning configuration forms a larger disk due to its higher angular momentum. Although the initial magnetic field amplification within $\lesssim 10\mathrm{ms}$ after merger is similar in both systems, the nonspinning system reaches stronger magnetic fields and higher energies at later times. For a detailed view of the multimessenger observables, we extract the gravitational-wave signal and compute nucleosynthesis yields, the expected kilonova and afterglow light curves from our ejecta profiles.

When primordial black holes (PBHs) evaporate, they deposit energy in the surrounding plasma, leading to temperature gradients, or hot spots, which evolve during the evaporation process. Motivated by recent studies suggesting that a memory burden may slow down PBH evaporation, we explore how a suppression of the evaporation rate affects the morphology of such hot spots. We include such a suppression in the form of transfer functions and derive general formulas for the hot-spot core temperature and radius. Applying our results to illustrative scenarios, we find that, in the vanilla memory burden scenario in which the evaporation rate and Hawking temperature are exactly constant, the hot-spot temperature is substantially lowered. Nonetheless, we show that alternative scenarios may lead to sizable hot spots with morphologies that differ significantly from the semiclassical case.

The hot quark matter created in heavy-ion collision experiments can exhibit strong temperature and chemical-potential gradients, which in turn can generate electric fields through thermoelectric effects. In this work, we investigate two relevant thermoelectric coefficients—the thermopower (Seebeck coefficient) and the Thomson coefficient—of two-flavor quark matter using the Kubo formalism and the Nambu–Jona-Lasinio model as an effective description of dense, finite-temperature QCD. The required two-point equilibrium correlation functions are evaluated using the Matsubara formalism of thermal field theory, applying a $1/N_c$ expansion to the relevant multiloop Feynman diagrams. We employ previously derived quark spectral functions obtained from one-meson-exchange diagrams above the Mott transition temperature. Our numerical results show that both thermoelectric coefficients increase approximately linearly with temperature and decrease with increasing chemical potential. We also estimate the magnitude of the electric fields that can be generated in heavy-ion collisions by thermal gradients via the Seebeck effect.

We employ a recently proposed form-invariant algebraic model for the quark propagator and the Bethe-Salpeter amplitude of pseudoscalar mesons to study the internal structure of $\eta$ and ${\eta }^{\prime }$ mesons. This model facilitates the construction of the Bethe-Salpeter wave function, whose projection onto an appropriate flavor basis leads to the light-front wave function for convenient linear combinations of the $s\overline{s}$ and $l\overline{l}\sim (u\overline{u}+d\overline{d})$ states. Using an overlap representation, we compute the valence-quark generalized parton distributions (GPDs). The construction of the model ensures that this multidimensional quantity is determined entirely by the corresponding valence-quark distribution amplitudes. Once the GPDs are constructed, we carry out a straightforward derivation of other desired physical observables, such as the distribution functions and the electromagnetic form factors. We also provide explicit comparisons with available results, demonstrating that the present model offers a consistent physical picture for all ground-state pseudoscalar mesons.

Ninety years after their prediction, quantum vacuum nonlinearities in macroscopic electromagnetic fields still await a direct experimental verification in the laboratory. A particularly promising route towards their first measurement is the collision of counterpropagating laser beams in a pump-probe type experiment. Here, the key challenge is to separate the small quantum vacuum signal at the oscillation frequency of the probe that is mainly emitted in the vicinity of its forward cone from the large probe background. While quantitatively accurate predictions of the associated quantum vacuum signals are available, to date there is no framework that combines these predictions with a diffractive beam propagation code. Such codes are designed to holistically model optical experiments and can reliably account for diffraction and absorption losses of optical devices, such as lenses and apertures. The latter inevitably influence and modify both the induced signal and background components prior to their detection in experiment. The present work addresses this topical issue and reports on the first implementation of a quantum vacuum signals emission module in an established diffractive beam propagation toolkit designed for the realistic modeling of optical experiments.

Radon and its progeny constitute a major source of background in rare-event physics experiments, such as those searching for dark matter, neutrinos, and neutrinoless double $\beta$ decay, due to their origin as unavoidable decay products of natural uranium. In particular, ${}^{222}\mathrm{Rn}$ and its long-lived daughter ${}^{210}\mathrm{Pb}$ can diffuse from detector material surfaces, resulting in sustained background contributions. To investigate this process, a system was developed using a controlled radon source, a vacuum chamber with a high electric field, and a thin nylon-6 film to enable deposition of radon progeny onto the film surface. Nylon-6 was selected for the initial measurement given its history in low-background experiments. We intend to systematically study diffusion in various polymers in the future. Our setup allowed for controlled study of the diffusion behavior of ${}^{210}\mathrm{Pb}$ and its daughter ${}^{210}\mathrm{Po}$ under varying humidity conditions. Our results show that both ${}^{210}\mathrm{Pb}$ and ${}^{210}\mathrm{Po}$ diffuse significantly in nylon under high relative humidity, which can potentially lead to internal contamination and increased background in low-background detectors. The diffusivity of ${}^{210}\mathrm{Pb}$ was found to be lower than $1.14\times {10}^{-15}{\mathrm{cm}}^2/\mathrm{s}$ at 40% relative humidity (RH) and to be $(4.03\pm 1.01)\times {10}^{-13}{\mathrm{cm}}^2/\mathrm{s}$ at 95% RH. The diffusivity of ${}^{210}\mathrm{Po}$ at 95% RH was measured to be $(3.94\pm 0.98)\times {10}^{-13}{\mathrm{cm}}^2/\mathrm{s}$. These findings underscore the importance of controlling environmental humidity and material exposure to radon in the design of ultralow-background experiments.

Utilizing data samples of electron-positron collisions recorded with the BESIII detector at the center of mass energy of 3.773 GeV, corresponding to an integrated luminosity of $20.28{\mathrm{fb}}^{-1}$, we report the first search for the $CP$ forbidden process $e^{+}{e}^{-}\to \psi (3773)\to D^0{\overline{D}}^0\to (K_S^0{\pi }^0)(K_S^0{\pi }^0)$. No significant signal is observed. We set the upper limit on the observed cross section to be 7.37 fb, and the upper limit on the joint branching fraction of the C-odd correlated neutral $D$ pair $\mathcal{B}[(D^0{\overline{D}}^0{)}_{\mathrm{C}\text{−}\text{odd}}\to (K_S^0{\pi }^0)(K_S^0{\pi }^0)]<2.04\times {10}^{-6}$ at the 90% confidence level.

We present a probabilistic model for the QCD critical endpoint (CEP) and the equation of state (EOS) at $\beta$-equilibrium, constrained by neutron-star (NS) observations. Using a hybrid framework that combines the holographic V-QCD model with an effective van der Waals description of nuclear matter, we generate a large ensemble of EOS incorporating nuclear theory uncertainties. Constraining this ensemble with NS mass-radius data and tidal deformability measurements from gravitational waves, we identify a strong first-order deconfinement transition at zero temperature, with a transition strength $\mathrm{\Delta }{n}_{\mathrm{PT}}/n_0=3.89_{-0.60}^{+0.77}$ and onset density $n_{\mathrm{PT}}/n_0={5.4}_{-1.25}^{+1.41}$. The resulting posterior yields 95% credible intervals for the CEP location: ${\mu }_{\mathrm{crit}}=626_{-176}^{+91}\mathrm{MeV}$, $T_{\mathrm{crit}}=119_{-6}^{+14}\mathrm{MeV}$.

Flux compactifications that give three- or four-dimensional anti–de Sitter vacua with a parametrically small negative cosmological constant are claimed to be ubiquitous in string theory. However, the $1+1$ and $2+1$ dimensional conformal-field-theory (CFT) duals to such vacua should have very large central charges and rather unusual properties. We construct brane configurations that source these would-be anti-de Sitter (AdS) flux compactifications, and identify certain UV AdS geometries that these branes source. The central charge of the CFT duals to these UV AdS geometries place lower bounds on the absolute values of the cosmological constants of the AdS vacua. These bounds are incompatible with the scale separation needed to construct realistic cosmological models.

We determine the maximal gauge groups arising in $E_8$ heterotic string theory on $T^2$. Our analysis proceeds along two approaches. First, we start the moduli space of the supersymmetric heterotic string theory on $T^2$ focusing on points of maximal gauge enhancement. At these special points, the charge lattice can exhibit a ${\mathbb{Z}}_2$ outer automorphism corresponding to the bulk gauge symmetry. By orbifolding the worldsheet theory by it with the fermion parity, we obtain the maximal gauge group of the $E_8$ theory. Second, we directly study the toroidal compactification of 10D $E_8$ heterotic string. Both approaches agree, yielding a classification of 22 maximal gauge groups. For each case, we present the corresponding massless spectrum. In light of the no global symmetry/cobordism conjecture in quantum gravity, our result also offers a classification of nonsupersymmetric branes in 8D supersymmetric heterotic string theories.

We investigate quantum corrections to the Randall-Sundrum (RS) model in the near-extremal black brane background with quantum corrections in the near horizon. The near-horizon geometry is described by Jackiw-Teitelboim gravity, and the quantum fluctuations are governed by the Schwarzian action. We introduce the Schwarzian modes into the RS metric, derive the quantum-corrected equation for the Kaluza-Klein (KK) modes via the Schwinger-Dyson equation, calculate the correction to the KK mass spectrum, and discuss the impact of quantum corrections on the Goldberger-Wise mechanism. Our work introduces both quantum corrections and temperature into the RS model, providing insights into cosmology and phase transitions within it.

Quantum effects in general induce scale dependence in the coupling constants. We explore this possibility in gravity, with a scale-dependent Newton coupling. When applied to Kerr black holes with such a running coupling, the consistency of black hole thermodynamics requires that the Newton coupling have a specific dependence on the black hole parameters. In this work, we consider such a class of Newton couplings and look for the possible observational implications on the highly lensed images of the black holes. In addition to placing constraints on the parameter space of the model through the latest Sgr A* images, we find that the variations in the shape of shadows in a large portion of the parameter space can be qualitatively captured by a quantity solely defined by the event horizon. Most importantly, the consistency of thermodynamics suggests a lower bound on the shadow size, beyond which either horizon disappears, or the shadow cannot keep the standard D-shaped structure. The possibility that the black holes in this model could spin faster than the Kerr bound, and the physical implications of the resulting cuspy shadows, are also discussed.

Black holes in our Universe are rarely truly isolated, being instead embedded in astrophysical environments such as plasma or dark matter. A particularly intriguing possibility is that light scalar fields form bound states around black holes, producing extended “clouds” known as gravitational atoms. When these clouds become sufficiently compact, the spacetime can no longer be described by a vacuum solution of general relativity. In this regime, one can construct quasistationary, spherically symmetric, self-gravitating scalar gravitational atom configurations. Here, we explore an observationally relevant aspect of these systems by computing their fundamental quasinormal mode. We present a fully relativistic calculation of the axial modes in both the time and frequency domains, finding frequency shifts relative to the vacuum case that depend mostly on the compactness of the gravitational atom. For sufficiently compact configurations, these shifts may be detectable by current or future gravitational wave detectors.

In static, spherically symmetric spacetimes, the deflection angle of photons in the strong deflection limit exhibits a logarithmic divergence. We introduce an analytical framework that clarifies the physical origin of this divergence by employing local, coordinate-invariant geometric quantities alongside the properties of the matter distribution. In contrast to conventional formulations—where the divergence rate $\overline{a}$ is expressed via coordinate-dependent metric functions—our approach relates $\overline{a}$ to the components of the Einstein tensor in an orthonormal basis adapted to the spacetime symmetry. By applying the Einstein equations, we derive the expression $\overline{a}=\frac{1}{\sqrt{1-8\pi R_{\mathrm{m}}^2({\rho }_{\mathrm{m}}+{\mathrm{\Pi }}_{\mathrm{m}})}}$, where ${\rho }_{\mathrm{m}}$ and ${\mathrm{\Pi }}_{\mathrm{m}}$ denote the local energy density and tangential pressure evaluated at the photon sphere of areal radius $R_{\mathrm{m}}$. This result reveals that $\overline{a}$ is intrinsically governed by the local matter distribution, with the universal value $\overline{a}=1$ emerging when ${\rho }_{\mathrm{m}}+{\mathrm{\Pi }}_{\mathrm{m}}=0$. Notably, this finding resolves the long-standing puzzle of obtaining $\overline{a}=1$ in a class of spacetimes supported by a massless scalar field. Furthermore, these local properties are reflected in the frequencies of quasinormal modes, suggesting a profound connection between strong gravitational lensing and the dynamical response of gravitational wave signals.

Observations of gravitational waves (GWs) generated by binary black hole (BBH) mergers provide us with a powerful way to explore the strong and highly dynamical regime of gravity theories. The ringdown of the BBH merger, consisting of a series of quasinormal modes (QNMs), is of particular interest for both the black hole (BH) spectroscopy and the inspiral-merger-ringdown consistency check. Unlike the QNM frequencies that only depend on the properties of the remnant BH, the excitation amplitudes and phases of QNMs depend on the progenitor system, and calculating them is beyond the perturbative approach. In this paper, by performing self-consistent fully nonlinear simulations of a BBH merger in shift-symmetric scalar-Gauss-Bonnet (sGB) gravity as well as in sGB gravity allowing for scalarization, and extracting the QNM excitation, we explore the possible deviations from general relativity at the ringdown stage. We numerically verify that the mode frequencies are consistent with the theory prediction, and provide the fitting results of mode amplitudes and phases. We find relatively small changes in the mode excitation, considering that the largest coupling we used in the simulations is close to the limit of loss of hyperbolicity. To demonstrate that our results are robust against the eccentricity caused by the imperfect initial data, we also perform eccentricity reduction and estimate the effect caused by the initial eccentricity. These studies are useful for understanding the ringdown in sGB gravity.

Extreme-mass-ratio inspirals, in which a stellar-mass object orbits a supermassive black hole, are prime sources of millihertz gravitational waves for upcoming space-based detectors. While most studies assume idealized vacuum backgrounds, realistic extreme-mass-ratio binaries are embedded in astrophysical environments such as accretion disks, stellar clusters, or dark matter spikes, disks, and halos, which can significantly alter the orbital dynamics. We explore bound geodesics around general-relativistic solutions describing rotating black holes surrounded by matter halos for the first time, mapping how environmental effects interfere with the spacetime symmetries of vacuum spinning (Kerr) black holes. In particular, we find that the loss of a Carter-like constant leads to geodesic nonintegrability and the onset of chaos. This manifests through the formation of resonant islands and chaotic layers around transient orbital resonances in phase space–features that are otherwise completely absent in integrable Kerr geodesics. Resonant islands, which are extended, non-zero volume regions in phase space, encapsulate periodic orbit points. Non-integrability dictates that all geodesics inside the resonant island share the periodicity of the resonance. Thus, the lifespan of resonances around non-Kerr objects can be significantly enhanced beyond the predicted lifetime of Kerr resonances. Consequently, these effects can leave distinct imprints on gravitational-wave signals, with significant implications for gravitational-wave modeling and parameter inference of astrophysical extreme-mass-ratio inspirals.

Quasinormal modes of rapidly rotating black holes were recently computed in a generic effective-field-theory extension of general relativity with higher-derivative corrections. We exploit this breakthrough to perform the most complete search for signatures of new physics in black hole spectra to date. We construct a template that describes the postmerger gravitational-wave emission in comparable-mass binary black hole mergers at current detector sensitivity, notably including isospectrality breaking. The analysis of all events with detectable quasinormal-driven ringdown signatures yields no evidence of higher-derivative corrections in the spectra, and we set an upper bound $\ell \lesssim 35\mathrm{km}$ on the length scale of new physics. Looking ahead, our scheme enables new studies on the capabilities of future detectors to robustly search for signatures of new gravitational physics.

We present that large numbers of light hidden-sector degrees of freedom can reverse the canonical evaporation hierarchy of Kerr–Newman black holes. When the effective number of uncharged species exceeds a critical value, the mass-loss rate outpaces the charge-loss rate, producing effective charge growth during evaporation and delaying neutralization. We investigate the evolution of black holes during the evaporation process, emphasizing how these quantities evolve relative to one another. Our study incorporates the effects of graybody factors, near-extremal conditions, and the introduction of additional particle species beyond the Standard Model. We demonstrate that the addition of particle degrees of freedom may significantly alter the evaporation hierarchy, potentially leading to scenarios in which the effective black hole charge increases during evaporation. Additionally, we examine the impact of Schwinger pair production and of superradiance on charged, spinning black hole evaporation. These findings offer new insights into the complex interplay between different black hole parameters during evaporation and highlight the importance of considering additional particle species in the process.

We investigate boson stars within the framework of the self-interacting Einstein-Friedberg-Lee-Sirlin (E-FLS) model, constituted by a complex scalar field with a quartic self-interaction and a real scalar field. Our analysis explores the family of static solutions across a broad range of parameters, including the self-interaction of the complex scalar field. We obtain that positive self-interaction terms increase the maximum mass and compactness of E-FLS stars, allowing them to reach masses comparable to the Chandrasekhar limit without the need of ultralight bosonic masses. Moreover, in the limit where the real scalar field becomes massless, the solutions present larger effective radii and allow a broader range of stable solutions. Astrophysical images, generated via backward ray tracing, show that these compact, self-interacting E-FLS stars produce strong gravitational lensing, yielding shadows that could visually mimic black holes, thus providing potential observational signatures detectable in ongoing electromagnetic surveys.