Papers

We propose using H$_{2}$ emission lines as a novel diagnostic to identify dwarf AGN by running photoionization models incorporating active intermediate-mass black holes and using an observed WISE dwarf AGN as a template. Though many dwarf AGN would be incorrectly classified as star-forming if the H$_{2}$~2.12~$\mu$m/Br$\gamma$ ratio is used, ratios between H$_{2}$ emission lines can reveal active IMBHs in cases where log $n_{\text{H}} \gtrsim 4.0$. This includes the case where $M_{\text{BH}} = 10^3~M_{\odot}$, even though the optical strong lines and NIR coronal lines would likely go undetected. We conclude that H$_{2}$ emission lines show promise in detecting the most elusive IMBHs.

We investigate the dynamics of harmonically confined quantum droplets in a binary Bose Einstein condensate within the one dimensional extended Gross Pitaevskii framework, including LHY corrections, under a constant linear (gravitational like) potential. By analyzing the COM and width dynamics, we show that the monopole (breathing) mode remains governed by the harmonic confinement, with a frequency asymptotically insensitive to the linear perturbation, demonstrating the robustness of internal collective excitations against uniform external forcing. In contrast, the COM exhibits interaction-dependent transport, with weak confinement producing large susceptibility and rapid displacement, whereas strong confinement suppresses transport even under large forcing. The COM response decreases monotonically with increasing trap frequency. We further characterize the evolving quantum state through the quantum Fisher information and Wigner quasi-probability distributions, showing that the linear potential enables controlled generation of states with enhanced metrological sensitivity over finite times, while stronger confinement shifts the onset of the high-sensitivity regime to larger forcing strengths. Numerical simulations based on the split-step Fourier method confirm the dynamical stability of the obtained solutions. These results illustrate the impact of linear gravitational like trap on the collective excitations, transport, and quantum metrological properties of 1D ultradilute quantum fluids.

We study exclusive electroproduction of heavy quark-antiquark pairs off nucleons in the framework of generalized transverse momentum dependent parton distributions (GTMDs) for gluons. The short-distance part of the process is treated at leading order in perturbative Quantum Chromodynamics and in first order in a collinear expansion, which allows identification with the description in terms of Generalized Parton Distributions (GPDs). For the results for the structure functions in terms of GTMDs and GPDs we consider only unpolarized (spin-averaged) nucleons, but include all possible azimuthal modulations that can arise. The presented results extend known expressions in the literature and are relevant for experimental studies of this exclusive process at the future Electron Ion Collider. Furthermore, we introduce a convenient decomposition of the gluon-gluon correlation matrix in terms of GTMDs, expanded in a Lorentz basis of symmetric traceless tensors obtained from the partonic momentum $k_T$ and the momentum transfer $\Delta_T$. The adopted notation for the GTMDs relates to the nucleon helicity states at the amplitude level, rather than to polarization states of the incoming nucleon or of the gluons, which makes it more transparent which contributions from helicity difference and helicity flip matrix elements can be accessed with unpolarized nucleon beams.

Precise control over the rotational dynamics of structured lights has become a defining objective in contemporary photonics. It plays a central role in governing the functional distribution of optical energy. Particularly, orbital angular momentum driven intensity rotation and azimuthal energy flow in vortex beams have emerged as crucial degrees of freedom in light-matter interactions. Leveraging this foundation, we establish a discrete optical vortex (DOV) platform comprising concentric rings of phase-locked lasers that enable precise control over vortex-beam rotation. By engineering the spatial distribution of topological charges (TCs) across the concentric rings of DOVs, we realize shape-invariant asymmetric vortex beams with controllable reversal of intensity rotation, without altering the sign of constituent TCs. This result establishes a new framework for controlling energy flow in vortex beams, beyond the conventional paradigm that links vortex rotation solely to the sign of the TC. Such controllable rotational dynamics opens new avenues for programmable beam steering, advanced optical micromanipulation, information multiplexing, and adaptive structured-light systems.

In this work, we investigate a cross-section-ratio-based inversion method for extracting distribution functions at the Electron–Ion Collider (EIC). Starting from the general factorization formula $d\sigma = H \otimes f$, we show that, for an appropriate bremsstrahlung process and suitably chosen differential observables, the convolution structure can be reduced to a multiplicative form. On this basis, we define the ratio $R = \frac{d\sigma_{\mathrm{exp}}}{d\sigma_{\mathrm{hard}}},$ where $d\sigma_{\mathrm{exp}}$ is the experimentally measured differential cross section and $d\sigma_{\mathrm{hard}}$ is a perturbatively calculable theoretical input. We then establish the relation between $R$ and the target distribution function $f$. Finally, we investigate how the theoretical input $d\sigma_{\mathrm{hard}}$ should be constructed when soft-photon radiation, finite-bin-width effects, and experimental acceptance are taken into account.

The transverse shape of the proton's small-$x$ gluon distribution is determined from exclusive $J/\psi$ photoproduction at HERA. We derive analytic expressions for the coherent and incoherent diffractive cross sections in the hotspot model at leading twist, enabling a global fit to all 104 available H1 and ZEUS data points, with $|t|<30~{\rm GeV}^2$ and $40\leq W\leq 251~{\rm GeV}$, with $\chi^2/{\rm ndf}=0.72$. The gluonic hotspots are resolved into a core of size 0.088(10) fm surrounded by an exponential halo of range 0.20(2) fm, matching the penetration depth of lattice flux tubes. This shape is stable over $\xpom$ and over the assumed number of hotspots in the range $5\leq N_{hs}\leq 12$. We find the Ginzburg-Landau parameter of the QCD vacuum to be $\kappa=2.7(7)$, which corresponds to fluxtube geometry in a type-II dual superconductor. The calculated QCD string-tension from the extracted parameter values is in agreement with theoretical calculations on the lattice. The gluonic geometry evolves only through a slow transverse diffusion of the hotspot centers with $\alpha'_{\rm eff.}=0.060(19)~{\rm GeV}^{-2}$, while the incoherent cross section at small $|t|$ is dominated by shot-noise fluctuations at the order of a few gluons per hotspot.

The stochastic process model of rough surface contact, widely known as Persson's theory of contact, serves as a representative multi-scale model that has been extensively applied across various fields of tribology. In this chapter, we briefly introduce the background of the development of Persson's theory of contact. We thoroughly discuss Persson's theory for purely normal elastic contact, with a special focus on solving the probability density of the contact pressure and the interfacial gap using partial differential equations. Subsequent applications of these fundamental results in addressing more complex interfacial properties in other fields of tribology are also examined. Finally, several recommendations regarding future studies of Persson's theory are proposed. This review article is expected to assist researchers in quickly familiarizing themselves with the current state of the art of Persson's theory and to attract more attention from tribologists and solid mechanicians, thereby contributing to the development and application of Persson's theory of contact.

Sulfur vacancy migration has a crucial impact on electronic transport and the functional behavior of MoS$_2$-based devices such as memristors and memtransistors. According to recent atomistic simulations, vacancy migration proceeds via cooperative, vacancy-assisted sulfur jumps, implying strongly correlated defect dynamics. Here, we investigate the collective behavior of sulfur-vacancy clusters in MoS$_2$ using kinetic Monte-Carlo simulations with transition rates derived from machine learning interatomic potential molecular dynamics simulations. We identify three transport regimes: At low concentrations, vacancies are immobile or confined within small clusters, whereas at high concentrations, classical diffusive transport with a constant diffusion coefficient is observed, and vacancies aggregate into anisotropically extended clusters. A well defined intermediate regime is characterized by clusters merging into a connected, fluctuating network with a concentration-dependent diffusion coefficient. This regime is characterized by a broad distribution of cluster sizes. The strong dependence of the vacancy diffusion coefficient on the average defect concentration provides new insights into the origin of memristive behavior observed in MoS$_2$.

Identifying Majorana zero modes in semiconductor–superconductor nanowires requires ultra-low temperature transport measurements in dilution refrigerators, making device screening slow and resource-intensive. Here, we investigate whether high-temperature conductance data can be used to infer low-temperature Majorana nanowire properties before committing devices to dilution-refrigerator characterization. We generate paired high- and low-temperature conductance simulations for disordered Majorana nanowires and train neural networks to perform two related tasks. First, we use a Shifted Window U-Net Transformer diffusion-inspired architecture to reconstruct low-temperature conductance from thermally broadened high-temperature measurements, achieving high-fidelity recovery with $R^2 \approx {0.95}$ for local conductance and $R^2 \approx {0.91}$ for nonlocal conductance. Second, we train a Video Vision Transformer-based network to predict the low-temperature topological visibility directly from high-temperature conductance, obtaining $R^2 \approx {0.80}$. These results demonstrate that machine-learning models can recover and infer low-temperature Majorana features from experimentally easier high-temperature data, providing a practical route for rejecting poor devices early thus avoiding slow and resource-intensive dilution refrigeration for non-promising devices. This high-temperature screening approach could substantially accelerate the experimental feedback loop for Majorana nanowire device development.

Recent advances in data-driven modelling have highlighted the potential of hybrid approaches which combine Tensor Basis Neural Networks (TBNN) with Universal Differential Equations (UDE) to discover frame-invariant, non-linear viscoelastic constitutive models. These hybrid models enable the creation of digital twins for complex viscoelastic fluids, offering direct transferability to computational fluid dynamics simulations. In this work, we introduce a reduced dimensional tensor basis formulation that enhances both the physical consistency of the learned representations with respect to the training data and the numerical stability of subsequent simulations. The UDE architecture is embedded into an open-source finite volume solver in which the constitutive response is generated dynamically at runtime based on local fluid flow conditions. Training on synthetic datasets generated using a range of well established viscoelastic models in oscillatory shear flows alone, the performance of the resulting UDEs is evaluated under extrapolation to unseen conditions and flow-types. These include deploying the UDEs in viscometric extensional flows as well as 2D and 3D benchmark flows, such as the 4:1 sudden contraction and cross-slot, providing a quantitative analysis of their capabilities, limitations and failure modes. The proposed reduced-basis framework enables data-efficient discovery of frame-invariant constitutive models that generalise beyond their training regime, capturing key flow features such as the onset and growth of flow-induced elastic instabilities in strong extensional flows even though trained solely on shear data. Quantitative accuracy decreases as extrapolation increases, but incorporating first normal stress difference information further improves quantitative accuracy and extends predictive fidelity to higher Deborah numbers.

Two-nucleon emission is a leading uncertainty in neutrino–nucleus interaction modeling, and no neutrino measurement constrains its short-range-correlation (SRC) component. We propose such a measurement: the ratio of neutral-current to charged-current two-proton production in neutrino–argon interactions as a function of the proton-pair relative momentum. Charged-current interactions convert the abundant neutron–proton SRC pairs into visible proton pairs, whereas neutral-current interactions lack an analogous SRC contribution because proton–proton pairs are about twenty times less abundant. The ratio is therefore predicted to decrease at large relative momentum, where the charged-current SRC contribution dominates, while the neutral-current sample provides a smooth reference determined mainly by final-state interactions and multinucleon processes. Simulations predict a suppression whose magnitude scales with the SRC fraction. Flux normalization and correlated detector systematics largely cancel in the ratio, making the measurement feasible with existing liquid-argon time projection chambers. Independently of the precise SRC contribution, this observable provides the first direct experimental probe of the isospin structure of weak two-nucleon emission.

Recent foundation models (FMs) for zero-shot reconstruction of dynamical systems (DS) achieve strong out-of-domain generalization but provide little insight into the mechanisms that underlie their forecasts. Such an understanding could help to strip down overladen FM architectures to their bare essence and expose the minimal requirements for in-context learning in the DS domain. Toward this goal, here we iteratively reduce a recent powerful SOTA model for DS reconstruction, DynaMix (Hemmer & Durstewitz, 2025), to a minimal interpretable two-parameter form, which we call DynaBase. DynaBase produces forecasts through a linear blend of the current latent state and the nearest in-context neighbor and its temporal successor. Surprisingly, despite its extreme simplicity, DynaBase produces highly competitive zero-shot DS reconstructions across chaotic and cyclic systems, with a negligible parameter load, many orders of magnitude below that of other FMs. Even more, this extreme simplicity permits direct model optimization on DS reconstruction measures, as well as closed-form one-step analytical solutions on prediction MSE. Theoretical and empirical analysis of DynaBase further leads to a 1-parameter family of maps, with the context-parroting algorithm of (Zhang & Gilpin, 2026) recovered at one end, and chaotic (divergent but bounded) behavior at the other. We further show how different training strategies lead to models either optimal for short-term prediction or for DS reconstruction. Thus, DynaBase not only exposes the minimal mechanisms required for producing zero-shot DS reconstruction, but also reconciles within an accessible mathematical frame divergent observations in the literature.

Gleason's theorem identifies the Born rule via non-contextuality over an infinite continuous lattice of projectors, while its corollary the Kochen-Specker (KS) theorem rules out the specific class of deterministic ($\{0,1\}$-valued) noncontextual models using finite sets of projectors. Gleason's theorem also indicates the existence of KS-type finite vector constructions to rule out other discrete nondeterministic alternatives to quantum theory beyond the $\{0, 1\}$ case. Here, we construct finite measurement configurations to rule out noncontextual empirical models with outcome probabilities drawn from an arbitrary finite subset $O \subset [0,1]$. We do this by two means: (i) constructing a family of experimentally feasible state-dependent Hardy-type tests, and (ii) proving a generalized KS theorem for a broad class of $O$ that includes prior results as special cases. In the sheaf-theoretic framework of Abramsky and Brandenburger, a hierarchy of probabilistic-possibilistic-strong contextuality has been established quantifying contextuality as a resource. We extend this framework by introducing strong $O$-valued contextuality, showing that quantum theory evades global sections of all finite-valued presheaves. We also discuss the implications of the result on finite many-valued logics as viable ontological models for quantum theory and for contextuality-based (semi)-device-independent protocols.

In two dimensions, the geometric constraints due to Pauli blocking and conservation laws lead to the even-odd effect exhibited by the electron-electron scattering lengths: electron-electron collisions are more efficient at relaxing the even angular harmonics of the distribution function than the odd ones. Inspired by a recent experiment on the magnetotransport in the Corbino disk geometry, we numerically analyze the electron flows in this geometry across all the regimes. We predict a clear signature of the even-odd effect - enhancement of the resistance sensitivity $\partial R/\partial(B^2)$ at small magnetic fields $B\rightarrow 0$. This enhancement is most prominent at the crossover from the ballistic to the tomographic regime, and gradually disappears when the temperature is further increased. Our estimates suggest that in the temperature range of the experiment, the effect should be small. This implies that the attribution of the anomalous scaling of the kinematic viscosity, that was observed in the experiment, to the even-odd effect might need more careful consideration. As a side note, we show how the method of characteristics can be extended to treat the long-lived odd harmonics, which allows one to recast the linearized Boltzmann equation as a system of integral ones.

In 2019, the first image of a black hole's shadow based on observation was released by the Event Horizon Telescope Collaboration (EHT). This paper shows that despite the EHT's emphasis on a single image as its final result, there were countless plausible ways of rendering the data, among which researchers could not easily choose. To obtain a single image from the extremely noisy and sparse data, it was necessary to select one of multiple plausible approaches, or to average the results from different approaches, at each stage of data processing. We examine the epistemic and aesthetic choices involved at various stages, and explore what the images would have looked like if the EHT had made different choices. We suggest that the most valuable evidence produced by the EHT comes not from the single image it ultimately advertised as its central result, but from the demonstration of the limited variability that emerged from the specific choices made.

This study presents DD4AO progress towards its implementation in the RISTRETTO instrument. DD4AO is a novel frequency-domain, data-driven controller for adaptive optics that leverages power spectral density estimation for optimization while enforcing stability criteria. It addresses disturbance rejection, command amplitude constraints, and system transfer functions through convex optimization, yielding an optimal controller in Infinite Impulse Response (IIR) filter form. We present the on-sky validation of DD4AO conducted using the PAPYRUS instrument at the Observatoire de Haute-Provence (OHP). The observations were performed on two stars over the night of 24-25 March 2026: the bright star Arcturus, and the faint binary HD137909. DD4AO successfully maintained a closed and stable loop over hour-long exposures while continuously adapting to evolving atmospheric conditions. The pipeline enabled instantaneous switching between DD4AO and standard controllers, namely the Integrator and OMGI, allowing direct statistical comparisons throughout each observation. On Arcturus, DD4AO achieved a 5% Strehl ratio improvement over the integrator at lambda = 1310 nm, from 28.8% to 33.9%. On HD137909, performance differences were smaller due to the low-SNR regime, though DD4AO consistently used less deformable mirror stroke and suppressed vibration peaks present in the residuals of the standard controllers. These results validate DD4AO as a robust on-sky control solution and represent an important milestone towards its deployment in RISTRETTO and SAXO+ at the VLT.

We demonstrate the use of high-resolution spot-profile analysis low-energy electron diffraction to determine the mean grain size of plasma-enhanced chemical vapor deposition grown few-layer graphene on sapphire (Al$_2$O$_3$). The diffraction patterns exhibit broadened graphene spots, pronounced diffuse scattering, and azimuthally extended features, indicating finite crystallite size and rotational disorder. By analyzing the finite-size broadening of the specular (00) spot with an Airy-type diffraction profile, we determine a mean grain diameter of 3.7$\,$nm for the as-grown graphene layer. Post-growth annealing under ultrahigh-vacuum conditions increases the mean grain size to about 5.7$\,$nm and 6.8$\,$nm, respectively. These results establish SPA-LEED as a sensitive reciprocal-space method for quantifying the structural coherence of directly grown graphene on insulating substrates.

We construct the three-point continuous-variable (CV) quantum MacWilliams identity, extending the two-point framework of Burchards, and give its closed-form integral kernel. Its configuration space carries a symplectic invariant with no classical counterpart, which encodes the GKP quantization condition and a three-point sign phase. Using the identity, we derive the semidefinite-programming bounds it supports on the dimension of CV quantum error-correcting codes, and we prove, in two collapse theorems, that the three-point apparatus does not improve on the two-point bound. For GKP lattice codes the three-point optimum equals the Burchards two-point linear-programming optimum identically. This is an exact determination of the lattice three-point optimum, so the $E_8$ and Leech magic functions saturate it rather than beat it. For general bosonic codes a completely-positive reformulation bypasses the positivity obstruction that rules out the natural factored-form constructions; the phase-sign condition together with Choi positivity then force the three-point term to vanish. We certify this collapse for radial Choi forms on the first eight Laguerre levels at one mode, and leave the full trace-class cone open. Both collapses have a single cause with no classical analogue, the code projector: it orients the bound correctly but also removes the full positivity that powers the classical three-point improvement.

The G-Scheme is an explicit, adaptive integration framework for stiff systems of ordinary differential equations that exploits a local time-scale decomposition provided by the eigensystem of the Jacobian (the kernel set). Its computational cost is dominated by the evaluation of a new kernel set at each time step. In a recent paper [R.Malpica Galassi and M.Valorani, Combust. Theory Model. 2025], we introduced a multi-resolution sparse hash-table strategy that replaces online kernel computation with retrieval from a precomputed lookup table, demonstrated in Python. Here we present cpp-gscheme, a production-grade C++ implementation of both the G-Scheme and the multi-resolution hash table, together with the porting methodology that guarantees behavioural equivalence with the Python reference: identical scaling, binning and hashing semantics, a bitwise-inert retrieval hook in the integrator, and a fully native evaluation path for the chemical source terms. On 33 n-heptane autoignition mechanisms spanning 56-459 species plus the detailed 654-species mechanism, the hash-tabulated C++ G-Scheme retrieves 100 percent of the kernel sets, performs zero online eigen decompositions, and outperforms the natively compiled CVODE solver by a factor increasing from 2.7x (56 species) to 9.3x (654 species), with observed cost scaling of approximately N power 1.4 versus CVODE's N power 1.9. A three-metric accuracy assessment (ignition delay, equilibrium state, and accumulated entropy-progress error) shows that the solver contributes negligibly to the overall error budget, which is dominated by skeletal reduction. Consequently, a 5 percent ignition-delay target is achieved by the 80-species skeletal mechanism with a 225x speed-up over CVODE on the detailed mechanism. The software, training-set builders, and benchmark drivers are released as open source.

We study a duality analysis in conjunction with the star-triangle transformation for symmetric-group permutation models on the triangular and honeycomb lattices. The calculation is motivated by the permutation-model description of random tensor networks and by earlier duality analyses of replicated spin glasses. The essential point is that the finite-basis unit is not a bare bond but a star-triangle block. Our analysis estimates the critical bond dimension for the honeycomb lattice to be 2.634929344884, and the associated single-bond duality relation yields the triangular-lattice estimate 1.475661534848.

The integrability of the Kudryashov-Sinelshchikov equation in (1+3) dimension is detected using its point symmetries and the Singularity analysis method. The symmetries mostly points to the existence of infinite-dimensional Lie algebra with the presence of mostly arbitrary functions. The reduction process is initiated by considering these arbitrary functions in the general symmetry vectors. For certain functions, trivial solutions for the general parent equation is obtained whereas for some of the functions, the reductions does not yield an unmitigated result. Finally, a positive result is listed for one of the arbitrary function, for which the singularity analysis method is employed to study the Painleve property. The resultant PDE happens to be a fourth-order equation and its approval of the Painleve property hints at the integrability of the Kudryashov- Sinelshchikov equation in the general case.

The p-type point-contact germanium detectors have emerged as the ideal detection technology for rare-event experiments such as direct dark matter searches and neutrinoless double beta decay, and have been verified to be capable of single-site spatial position resolution. Accurately characterizing the position-dependent pulse shape responses of the detector is a crucial prerequisite for deepening background understanding and achieving background reduction. Relying on an optimized cross-scanning localization method and a full-chain physical framework, this study extracted the pulse shape responses in critical regions of the CDEX detector, quantitatively evaluated its intrinsic spatial position resolution for the first time, and ultimately achieved the position tracing of real environmental backgrounds using the constructed pulse shape database. This study completely establishes a physical analysis closed-loop for spatial position resolution, providing critical theoretical and technical support for background analysis in future ton-scale arrays.

Resource scarcity can fundamentally encourage antisocial behaviour, whereas resource abundance can promote fair behaviour. Experimental evidence indeed suggests that scarcity induces spiteful behaviour, while repeated interactions enhance fairness. However, existing studies of game–environment feedback systems are largely confined to the evolution of cooperation and they overlook the interplay between resources, spite, and fairness. To address this lacuna, we develop a stochastic ultimatum game framework in which an offerer and an accepter repeatedly interact to negotiate exploitation of a self-renewable resource under the ownership of the offerer. Successful agreements deplete the resource, whereas unsuccessful agreements inhibit exploitation and facilitate replenishment. The mutation–selection driven two-species stochastic evolutionary dynamics reveal that the emergence of spite and fairness strongly depends on the resource growth rate. Fairness predominantly prevails for resources with high growth rates. Intriguingly, low resource growth rates give rise to a resource feedback loop driven by spite: spiteful behaviour dominates in the depleted state, facilitating transition of the resource state to replete state which, in turn, promotes fairness through repeated interactions.

In this work, we perform a systematic investigation of the hidden-bottom molecular pentaquark states, encompassing both bound states and resonances, which originate from the $P$-wave interactions between ground-state bottom baryons ($\Lambda_b$, $\Sigma_b^{(*)}$) and ground-state antibottom mesons ($B^{(*)}$). Adopting the one-boson-exchange model and including the coupled-channel effects, we derive the effective potentials for all allowed quantum numbers $I(J^P) = 1/2(1/2^+)$, $1/2(3/2^+)$, $1/2(5/2^+)$, $1/2(7/2^+)$, $3/2(1/2^+)$, $3/2(3/2^+)$, $3/2(5/2^+)$, and $3/2(7/2^+)$. We then solve the coupled-channel Schrödinger equations to search for the bound-state solutions and perform the phase-shift analyses to identify resonance poles. Our results reveal a rich spectrum of positive-parity hidden-bottom molecular pentaquark candidates. In the isospin $I=1/2$ sector, we find several loosely bound states and associated resonances, particularly in the $\Sigma_b B^*$ and $\Sigma_b^* B^*$ channels, where the coupled-channel dynamics plays an essential role in their formation. In the isospin $I=3/2$ sector, the attraction is generally weaker because of the isospin factors. Nevertheless, we still obtain the loosely bound states and resonances, such as the $\Sigma_b^* B^*$ states with $J^P=3/2^+$, $5/2^+$, and $7/2^+$. The prominence of high-spin partial waves, for instance the $^6P_J$ components, underscores the importance of the spin-spin and tensor interactions. Our predictions provide a comprehensive and systematic spectrum of the $P$-wave hidden-bottom molecular pentaquark states and offer clear guidance for future experimental searches at LHCb and Belle~II.

We report non-Hermitian mode couplings in a photonic time crystal induced by the light within its momentum bandgap. When the relative phase between the light and the photonic time crystal compensates for the detuning, we observe a periodic suppression of exponentially growing Floquet modes. In contrast, the optical response in this regime cannot be reproduced by the conventional Floquet expansion of the Green's function, revealing that the light induces effective mode couplings beyond the quasinormal mode approximation. We further investigate the parity-time phase transition through the exceptional point and quantitatively explain the suppression dynamics based on the phase, detuning, and modulation amplitude. The nontrivial interaction with light and the controllable non-Hermiticity indicate the great potential of photonic time crystals in temporally modulated nanophotonics.

We present a class of regular axisymmetric black hole geometries fully characterized by the parameters $\{{\cal M},a\}$ and possessing the Kerr event horizon. This family interpolates between regular spacetimes, configurations with integrable singularities, and the Kerr solution as a limiting case. Its main features are: (i) the existence of quasi-extremal configurations without requiring $a \approx {\cal M}$; and (ii) a possible framework toward an analytical description of Kerr black hole formation from an initially regular configuration.

We present angular correlation and power spectral analyses of the clustering of VST ATLAS galaxies, LRGs and QSOs and their cross-correlations with the ACT DR6 CMB lensing map with its $\approx3\times$ higher resolution than Planck DR3. We first use $\Lambda$CDM Halofit models at linear scales to estimate galaxy, LRG and QSO bias, $b$, from the ratio of the 3-D power spectra, $b= P_{gg}/P_{gK}$ and hence the mass clustering amplitudes, $\sigma_8$. For galaxies we find $b_G(z=0.15)=1.22\pm0.07$, $\sigma_8(z=0)=0.71\pm0.06$ and for LRGs $b_{LRG}(z=0.26)=2.76\pm0.11$, $\sigma_8(z=0)=0.63\pm0.15$, both consistent with $\Lambda$CDM predictions. But for QSOs, we estimate a bias of $b_Q(z=1.7)=4.44\pm0.24$ and $\sigma_8(z=0)=0.49\pm0.06$, the latter significantly lower than expected for $\Lambda$CDM and leads to an observed $0.15<z<1.7$ gravitational growth rate faster than predicted for $\Lambda$CDM. At smaller non-linear scales, HOD model fits imply a broad halo mass distribution for $z\approx0.15$ galaxies but much narrower mass distributions for LRGs and QSOs. More surprisingly, the HOD fit for QSOs implies $M_{eff}=5\times10^{14}M_\odot$, $\approx10\times$ higher than expected. Finally, while the LRG and QSO HOD models fit $w_{gg}$ and $w_{gK}$ consistently, the same is not true for the $z\approx0.15$ galaxies unless we hypothesise anti-bias with $b_G\approx0.55$. This result supports previous QSO lensing analyses that also found anti-bias at $r<5$h$^{-1}$Mpc. We suggest that while HOD + NFW halo models may well describe LRG mass profiles and clustering, at intermediate scales the dominant galaxy population (and QSOs) may follow the alternative hierarchical clustering model of Peebles(1974) where galaxies trace the mass more closely than in a halo model.

Context. Three-dimensional dust radiative transfer provides a powerful framework to connect cosmological galaxy simulations to multiwavelength observations. Until recently, in large-volume simulations, the formation of a cold ISM phase was prevented and dust was not evolved self-consistently. This required calibration of dust-to-metal ratios and extra subgrid dust attenuation in birth clouds, thereby reducing the predictive power. Aims. We present the COLIBRE-SKIRT pipeline, a calibration-free dust radiative transfer framework for the novel COLIBRE suite of large-volume cosmological simulations, which include a live dust model and directly simulate the multiphase ISM. Our primary aim is to establish a reference pipeline for generating multiwavelength mock observables from these simulations. As a first application, we produce far-ultraviolet (FUV) to far-infrared (FIR) spatially integrated spectra and assess them by comparison with the observed low-redshift cosmic spectral energy distribution (CSED). Methods. We apply the SKIRT dust radiative transfer code to the COLIBRE simulations. Dust masses and species fractions are taken directly from the simulation, and no birth cloud model is added in postprocessing. We introduce a "split & scale" approach that maps the simulated two-size, multi-species dust distribution onto continuous grain size distributions without introducing free parameters. Results. We find that, for the first time, a large-volume cosmological simulation directly reproduces the local Universe CSED without calibrating the postprocessing routine a priori. Residual tensions in the mid-infrared (~0.2 dex) point towards insufficient heating of the hottest dust components and uncertainties in the modelling of the PAH-emission carriers. This framework can be readily applied at low and high redshift to create synthetic spectra and images from the FUV to the FIR.

The bond-dependent anisotropic Kitaev interactions are the key for the Kitaev model, which has attracted intense interest for its potential to host quantum-spin-liquid states and fractional excitations. However, experimental realizations of such interactions remain scarce. Here, we investigate the magnetic excitations of NiI$_2$, a van der Waals magnet with spin $S=1$. By combining inelastic neutron scattering, magnetization measurements, magnetic structure analysis, first-principles calculations, and linear-spin-wave simulations, we identify a minimal model that features substantial Kitaev and off-diagonal $\Gamma$ interactions, which together stabilize the canted magnetic ground state and open a gap in the spin-wave spectrum. Notably, these interactions arise from strong spin-orbit coupling on the ligand ions, despite the quenched orbital moment of the magnetic Ni$^{2+}$ ions. Our results provide compelling experimental evidence for the ligand-driven Kitaev mechanism. This demonstrates a concrete pathway to generating strong bond-dependent anisotropy in systems where the magnetic ions themselves have weak spin-orbit coupling, thereby substantially broadening the range of potential Kitaev materials.

We study four-wave kinetic equations in space dimension three with power-law dispersion $\omega(p)=|p|^a$ and collision kernels with high-frequency growth measured by $\beta$. In weighted $L^\infty$ spaces, we identify the sharp decay threshold $$ s_c=4\beta+3-\frac a2. $$ For $s>s_c$, we prove local well-posedness by establishing trilinear bounds for the full gain-loss collision operator. For $s<s_c$, we prove ill-posedness by constructing data concentrated near a high-low-low-high resonant configuration. This threshold captures the balance between the high-frequency strength of the kernel and the geometry of the resonant manifold. The proof also shows that gain-loss cancellations are essential in the most delicate regimes.