Papers

Variational inference is a flexible tool for modeling experimental data and has proven useful in crystallography. Pathwise gradient estimators provide low-variance gradients for reparameterized variational inference, but are not readily available for some distributions central to crystallography. This work derives and implements implicit and explicit reparameterized gradient estimators for the folded Normal and Rice distributions in \prog{PyTorch}, and compares their variance analytically and empirically. In each case the implicit estimator achieves lower variance for the location derivative, particularly at small location-to-scale ratios, while the scale-derivative variances are nearly equal. For both distributions, implicit estimator is proved to be the conditional expectation of the explicit estimator given the sampled magnitude, so its variance is never larger. As a practical application, French-Wilson scaling is formulated as a variational inference problem, using the folded Normal and Rice distributions as variational families for centric and acentric reflections, respectively. Both estimators recover the exact posterior to better than $1\%$ on the amplitude, and converge at the same rate. The implementations are available in the open-source package \prog{rs-distributions}.

The Boltzmann equation is the fundamental kinetic bridge between molecular mechanics and fluid behaviour. It converts binary encounters into the evolution of a velocity distribution, underlies rigorous routes from hard-sphere dynamics to Euler and Navier–Stokes–Fourier equations, and remains indispensable when continuum descriptions fail, from hypersonic shock layers and atmospheric re-entry to rarefied multiscale flows. Yet its nonlinear collision term is conventionally represented by an infinite three-index tensor of collisional brackets, with apparently new coefficients at every polynomial order. Here we prove that this entire hard-sphere tensor contains only one primitive collision law: the exact rank-two stress-production vertex $S$. Every polynomial collision vertex is obtained from $S$ by a finite sequence of universal differential and tensor operations, and every conventional bracket follows by differentiation. Thus the interaction physics and its representation separate exactly: all hard-sphere-specific information is concentrated in $S$, whereas the hierarchy above it is universal algebra. A blind eighth-order test in a Mach-5 shock agrees with independent collision sampling and strongly amplifies a weak kinetic precursor. The hard-sphere hierarchy is infinite in dimension, but its primitive collision content consists of a single scalar law.

Molecular chiral discrimination is vital across chemistry and life sciences, yet optical approaches remain highly inefficient for small organic molecules. Here we turn vector beams, whose polarization carries a topological charge, into an efficient probe of molecular handedness. We show that the combination of a tightly focused radially polarized beam at the fundamental frequency {\omega} and an azimuthally polarized beam at 2{\omega} creates chiral vector beams, a locally chiral field with structured handedness. Using state-of-the-art computational modeling in the chiral molecule carvone, we show that the nonlinear response (notably sum-frequency generation) of randomly oriented chiral molecules to this chiral vector beam captures the fields' local handedness and is highly enantio-sensitive. The two enantiomers emit light at frequency 3{\omega} with topological ring structures of different divergence, and thus the molecular handedness can be read out directly from the ring radius. The signal inherits the Poincaré index of the driving field, opening up new ways to robust, ultrafast, and and all-optical chiral discrimination.

We present DeboRheo v2.0, an unstructured, geometrically unsplit Volume-of-Fluid framework implemented in OpenFOAM for viscoelastic two-phase flows. Version 2.0 improves numerical robustness when large viscosity contrasts coincide with strongly deformed interfaces and thin viscoelastic lamellae or filaments. The revised interfacial viscosity treatment retains a sharp geometric interface while regularizing the viscous contribution to the momentum equation. The solver combines mass-momentum-consistent phase advection, optional SIMPLEC pressure-velocity coupling, and a modular rheological framework with conformation-tensor stabilization. We assess the method using two-dimensional, axisymmetric, and three-dimensional benchmarks governed by the Oldroyd-B and exponential Phan-Thien-Tanner models. The results agree well with published numerical and experimental data and demonstrate improved robustness for demanding viscoelastic free-surface configurations on unstructured meshes.

Phase retrieval recovers complex-valued objects from intensity-only measurements. In its classical Fourier form, reconstruction suffers from twin-image stagnation. Coded diffraction imaging, which adds a random phase mask before the Fourier transform, has so far required several masks. We show that an image prior makes single-shot coded diffraction imaging possible, with a single random mask followed by a Fourier transform. We validate this claim in simulation and in an optical experiment, in which a spatial light modulator displays the phase object together with the random mask. Our experimental validation covers five test signals and 530 images from the public Brno quantitative phase microscopy dataset of five adherent cell lines. With no image prior or with Fourier-only measurements, reconstruction of complex-valued objects from a single diffraction pattern consistently fails. An out-of-the-box pretrained image denoiser enables accurate reconstruction, in simulation even with fewer measurements than unknowns. Five regularization frameworks built on the same denoiser and one learned weakly convex regularizer all reconstruct the experimental images with peak signal-to-noise ratios within one decibel of each other. A single random phase mask and image priors thus turn coded diffraction imaging into a practical single-shot modality for quantitative phase imaging.

Molecular systems with optically addressable electron spins are emerging as versatile quantum sensing platforms, offering tunable qubit properties and molecular-scale spatial control. Owing to their longer lifetimes, coupled nuclear spins provide an attractive resource for enhancing sensing performance. For molecular spin systems, the ability to initialise, coherently control and readout nuclear spins at room temperature is crucial for realising such benefits. Here, we present the first optical detection of nuclear magnetic resonance and coherent nuclear spin control with a molecular system at room temperature. Specifically, we demonstrate optically detected Rabi oscillations of $^{14}$N nuclear spins in the photoexcited triplet state of the organic chromophore 6,13-diazapentacene. The strong hyperfine coupling between the electronic spin and $^{14}$N nuclei enhances the nuclear Rabi frequency, enabling fast coherent nuclear-spin rotations. This work lays the foundation for leveraging nuclear spins as memories for enhanced molecular-based quantum sensing.

We present and analyze a spatially and temporally adaptive high-order method for the one-dimensional Richards equation describing vertical water transport in unsaturated soil, with an emphasis on resolving sharp wetting fronts while satisfying a fully discrete water mass balance. The spatial discretization uses an arbitrary-order local discontinuous Galerkin spectral-element formulation with collocated Legendre-Gauss-Lobatto quadrature, and the time integration is based on a high-order Rosenbrock-Wanner method. We focus primarily on the mixed formulation of the Richards equation, which advances water content as the conserved variable while evaluating the nonlinear diffusion operator in terms of pressure head; the resulting fully discrete scheme satisfies the water mass balance in exact arithmetic, independent of spatial resolution and time step size, including under spatial and temporal adaptivity. In contrast, the pressure-head formulation advances pressure head through a nonlinear capacity function and satisfies the corresponding conservation identity only at the semi-discrete level. Numerical experiments examine convergence through spatial and temporal refinement studies, with mass conservation assessed under spatial and temporal adaptivity using the solver flux output method (SFOM). The SFOM results confirm machine-precision mass conservation for the mixed formulation, whereas the pressure-head formulation exhibits mass balance errors above roundoff. Moreover, in the temporal refinement studies, the mixed formulation yields more accurate solutions than the pressure-head formulation for a prescribed time step size. The combination of high-order accuracy, spatial and temporal adaptivity, and fully discrete mass conservation makes the proposed mixed-form discontinuous spectral-element method a promising approach for simulating unsaturated flow in next-generation land models.

A two-dimensional electron gas in a uniform neutralizing background forms a triangular Wigner crystal at low density. In a strongly mass-asymmetric electron-hole bilayer, localized heavy holes instead provide a nonuniform positive background that supports an electron crystal at densities two orders of magnitude higher than for a homogeneous electron gas in the same material. Here we show that correlated mobile electrons can overturn the preference for triangular order, stabilizing a honeycomb electron-hole crystal. Using the powerful real-space neural-network variational Monte Carlo in the Born-Oppenheimer limit with fixed holes, we find that increasing the density drives a transition from a triangular electron-hole crystal to a honeycomb crystal, which eventually melts into itinerant electrons coexisting with the honeycomb or the triangular hole lattice at fixed interlayer separation. Relative to triangular order, honeycomb order emerges when gains in electronic kinetic energy and electron-hole attraction outweigh its higher intralayer Coulomb repulsion, a threshold never reached in the rigid point-dipole model. Moreover, the honeycomb hole lattice supports paramagnetic, antiferromagnetic, and stripe-ordered spin states. Complex polarization indicates a metal-insulator transition, while the states on the honeycomb hole lattice are consistent with a stripe-ordered Dirac semimetal and paramagnetic or antiferromagnetic Mott insulators via mapping to the half-filled Hubbard model. We further propose a BLG/hBN/WS$_2$-WSe$_2$ heterostructure as a platform for the predicted honeycomb crystal, at an experimentally feasible density $n\sim10^{11}~\text{cm}^{-2}$.

Nitrite photochemistry in atmospheric aerosols and natural waters is a major source of hydroxyl radicals and reactive nitrogen oxides. Contrary to the prevailing view that in the environment aqueous nitrite photochemistry proceeds exclusively through photoexcitation followed by homolytic bond cleavage, we show that visible light directly ionizes aqueous nitrite in individual micron-sized droplets. Although the photoionization cross section is exceptionally small, this pathway is observable at the high photon flux densities accessible in single-droplet experiments. Molecular simulations reveal that this is because photoionization absorption has an exceptionally long wavelength tail due to the large solvent reorganization energy in aqueous solutions. Kinetic modeling of an aqueous-phase reaction mechanism quantitatively accounts for the observed chemistry and predicts the formation of nitrate, hydroxyl radicals, and solvated electrons. The overlap of the predicted broad photoionization continuum with the visible solar spectrum further suggests that visible-light photoionization is an overlooked source of nitrogen oxides, solvated electrons, and oxidants in atmospheric aerosols, snowpack, and natural waters. Under dilute conditions, where dissolved oxygen is the main sink for solvated electrons, photoionization is expected to be the dominant photochemical loss pathway for nitrite.

Observables in complex biological systems are often reduced in their inherent complexity, resulting in abstract, a priori mathematical representations based on simple concepts such as points in spaces or interconnected nodes in lattices or networks. This reduction is relevant not only for the formulation of multiscale mathematical models and field theories but also for experimental planning and data collection to gain systematic evidence for the nature of such systems, thus extracting robust causal relationships that would lead to better control of the system. However, mathematical abstraction remains challenging and problematic, especially given the tightly intertwined elements between objects and their environment, the system's affordance, and the fact that all these aspects limit fundamental mathematical concepts such as set theory, thus hindering the definition of phase spaces in extreme cases. In this work, I introduce a potential axiomatic representing a nonreducible representation of high order structures representing entanglement between observables in complex systems and their environment, considering not only their coupling but also their affordance in relation to the overall system and context, and thus intend to formalize concepts already used in complex systems such as Kantian wholes. In light of this axiomatic, I identify states that are rather less elastic with respect to their environment, discuss how low elasticity enables the application of set theory, while high elasticity limits the mathematical representation of complex systems, and present an exemplary Ising model with a network of elastic states with respect to different contexts as a limiting case for mathematical modelling in this context.

Wireless energy transfer (WET) decouples energy generation from energy use, offering strategic advantages for distributed spacecraft, lunar surface networks, mobile assets, and high-power remote loads. This review organizes the field along four axes: physical mechanism, energy reference plane, mission architecture, and evidence maturity. It examines near field inductive and resonant transfer, microwave and millimeter wave power beaming, optical and laser-based transfer, space-based solar power, lunar and cislunar energy delivery, inter-spacecraft power sharing, intraspacecraft contactless interfaces, and reconfigurable or relay assisted routing within a common R0,R7 energy-accounting framework. Three conclusions emerge. First, WET is most valuable when spatial or temporal mismatches separate energy generation from load demand; it does not universally replace local generation or onboard storage. Second, dominant losses vary across system architectures. Beam collection, rectification, receiver output, and useful load efficiencies are therefore not directly comparable without explicitly defined energy reference planes. Third, technological maturity is uneven. High power ground demonstrations and short range flight applications are relatively well established, whereas long-range radiative inter spacecraft transfer, spaceborne routing hardware, lunar energy networks, and deep space applications remain supported primarily by models, simulations, and mission studies rather than hardware demonstrations. Progress requires validated end to end energy budgets under mission realistic constraints, including pointing and tracking, thermal management, environmental exposure, reliability, energy storage, and regulatory compliance.

We present first-principles calculations of the electron-hole-pair creation energy in semiconductors and dielectrics, focusing in particular on AlN, 3C-SiC, 4H-SiC, Si, and SiO2. We have employed density functional theory (DFT) to calculate the band structure, density-functional perturbation theory to obtain the phonon dispersion, and time-dependent DFT (TDDFT) to calculate the electron energy loss function (via the dielectric function). We performed full-band Monte Carlo simulations of electron thermalization for energies up to ~100 eV and calculated the average energy required to excite an electron-hole pair. We calculated pair-creation energies of approximately 12.2, 6.5, 7.3, 3.10, and 16.7 eV/pair for AlN, 3C-SiC, 4H-SiC, Si, and SiO2, respectively. These values are in good agreement with measured data, with the largest discrepancy being that of Si (about 14.9% lower than the accepted experimental value of ~3.6 eV/pair). To improve the agreement for Si, we used the GW approach and the Bethe-Salpeter equation (BSE) to calculate the quasiparticle shifts of the electronic band structure and the dielectric function, respectively. Finally, using the GW/BSE data, we calculated a creation energy of ~3.50 eV/pair. We find that the marked improvement in the accuracy of the calculated creation energy, when using the GW/BSE approach, is primarily attributable to the slight decrease in the magnitude of the electron energy-loss function when using the GW/BSE approach for energies below ~10-15 eV. Overall, it is clear that the competition between phonon emission and ionization near the intersection of the phonon scattering and ionization rates is largely responsible for determining the value of the creation energy, with the other major factor being the location and shape of the plasmon peak in the energy-loss function.

The nearly collinear configuration of highly stretched polymer chains before fracture motivates one-dimensional models. At fixed extension, stretching one bond redistributes length among the others, coupling rupture to the whole chain. In this work, I develop a framework for fracture-healing rates in periodic Morse chains, combining deterministic theories, equilibrium simulations and a quasi-deterministic approach using equilibrium fluxes and barrier-top trajectories. Constrained-partition calculations closely reproduce simulated populations and intact-state tensions. An intact-reservoir potential of mean force (PMF) supplies the first-fracture surface probability, while recrossing corrects the attempt flux without a rate-fitted prefactor. Independent rate tests identify an operational chain-length boundary for accurate two-state kinetics; failed-return durations decrease relative to population relaxation as chains grow. Kramers-Grote-Hynes (KGH), nonlinear reactive-flux and equilibrium rates show excellent agreement in this regime. KGH predicts rates away from coexistence and a chain-dependent local activation length dominated by the barrier response. Rates decrease approximately exponentially before declining more gently for longer chains: barrier growth dominates, additional fracture sites partly compensate, and transmission varies more weakly. Beyond coexistence, long chains can fracture practically irreversibly because healing becomes too rare to observe. Projected committor crossings, where the configuration-averaged probability of reaching the fractured core first is one half, lie near site-PMF maxima, although configurations at equal bond length retain different fracture probabilities. Multiple fractures remain negligible near coexistence through at least $N=50$. The framework could supply state-dependent rates to mesoscopic fracture models of polymer networks.

The second quantum revolution is a revolution of information. Advances in quantum computation, communication, and sensing offer new capabilities while raising questions about how quantum infrastructures will be organised, accessed, and governed. We argue that their significance for governance lies not in transforming political principles, but in how their technical and infrastructural requirements may affect existing relationships of authority, responsibility, legitimacy, and power. This paper develops a quantum governance lens that connects governance scholarship with quantum information science, examining interactions between technical design, institutional arrangements, and infrastructural dependencies. We apply this lens to five areas: quantum computation, quantum key distribution, Quantum Byzantine Agreement, blind quantum computation, and dual-use quantum sensing. These applications illustrate how technical capabilities may influence access, trust, privacy, oversight, and accountability, while demonstrating that technical guarantees cannot resolve institutional questions independently. We conclude that quantum technologies do not necessarily introduce unique governance challenges or require entirely new governance frameworks. Rather, they provide a context in which established questions of legitimacy, accountability, and equity must be reconsidered in relation to emerging technological capabilities and institutional choices.

We generalize the second-order fluid constitutive model to accommodate a range of possible frame indifferent time derivatives. Using the Gordon–Schowalter derivative, which contains the upper-convected, lower-convected, and corotational (Jaumann-Zaremba) derivatives as subsets, we show how the subjective choice of derivative may change model predictions and we identify features that remain universal independent of this choice. Writing these models in terms of generic coefficients is non-universal and may lead to misinterpretations of flow predictions. However, writing the models in terms of zero-shear material functions or terminal relaxation time reveals universal and robust representations.

We present a quasi-static particle-in-cell scheme for beam-driven plasma wakefields in cylindrical geometry that works on an arbitrary non-uniform radial grid. The field equations are discretized with hat-function finite elements and conservative finite volumes on any monotone set of radial nodes, and the transverse magnetic field is obtained explicitly, without iterations, following Baxevanis and Stupakov. An optional azimuthal mode $m=1$ describes beam offsets, tilts and hosing. The discretization keeps the discrete Gauss law exact, deposits a uniform plasma exactly on every node including the axis, and remains second-order accurate on smoothly stretched grids. Resolution can therefore be placed where the physics needs it. For a tightly focused witness beam that pulls the plasma ions onto the axis, a grid that is fine only near the axis gives the same near-axis fields as a uniform grid with the same axis resolution, with thirty times fewer cells and in thirty times less computing time. Such a grid also resolves the singular closure of a cold-plasma bubble, which a uniform grid hides by smoothing it over one cell; smoothing the plasma sources over a fixed length, chosen independently of the grid, regularizes the closure and makes the wake behind it converge. The scheme is implemented in the open-source C++/Kokkos code QUARZ (Quasistatic Arbitrary-resolution RZ), which runs on CPUs and GPUs and uses MPI with a pipelined decomposition along the co-moving coordinate. Simulations of the self-modulation of the AWAKE proton bunch agree with the three-dimensional code HiPACE++. QUARZ is, to our knowledge, the first production-grade simulation code in plasma physics that is zero-touch: all of its source code, tests and documentation were written by an AI agent directed by a physicist who did not write a single line of the code.

Can collective quantum-noise measurements distinguish different mode temperatures from one common temperature when the coupling spectrum is unknown? For stationary Gaussian oscillator environments, we derive a sharp bandwidth threshold for an exact thermal alias on the integer-time sampling lattice. The threshold depends on temperature order through the quantum response. For frequencies within the first alias period, fixing sufficient integer-time correlations makes one additional fractional-time fluctuation observation enough to exclude every common-temperature fit. A calibrated second pulse width provides another route through the same collective port: both widths must probe one spectrum and retain their measured variance scales. For a specified two-mode example, continuous-frequency certificates cover all common temperatures and uncertainty in a shared pulse ramp. A binary-readout protocol combines randomly interleaved matched references with collective-variance and coherence checks to handle Gaussian oscillator loss and predictable readout drift. The selected fractional-clock and two-width designs require approximately $3.8\times10^7$ and $1.6\times10^8$ outcomes for at most 5% type-I error and at least 95% power on the stated alternative class. These theoretical and numerical acquisition guarantees assume independently validated preparation, spectral support and control specifications; validation costs are additional. The result identifies which new observation makes thermal-model testing informative when mode-resolved access is unavailable.

Weak measurements are used to amplify small signals, to address foundational questions, and to characterise quantum states without tomography. In direct state reconstruction each amplitude of the state vector is proportional to a single complex weak value, which for a temporal pointer is read from the mean arrival time and the mean frequency of the postselected pulse. Such an experiment requires three quantities to be fixed, the coupling, the angular resolution demanded of the reconstruction, and the set of states over which the method remains usable, and these are commonly set by the available apparatus rather than derived. We derive all three for a Gaussian temporal pointer and an arbitrary postselection state. The states that cannot be reconstructed form a spherical cap centred on the state orthogonal to the postselection, whose geodesic half-angle follows from the largest of three independent thresholds and involves no adjustable parameter. Two states are distinguishable only if they differ by more than a minimal step fixed by the coupling, by the number of incident photons and by the sensitivity of the weak value along the path followed. For an inversion at first order in the coupling the systematic and statistical errors are opposed and fix an optimal coupling that varies as the inverse sixth root of the number of incident photons, whereas an exact inversion at finite coupling removes the systematic error, the remaining bound being one on the two-centroid readout rather than on the inversion, since below an amplitude equal to a quarter of the coupling two states give the same pair of centroids while their profiles differ. These results allow a direct reconstruction experiment to be dimensioned before the apparatus is assembled.

Liouville equation contains an excess coupling term in addition to the Poisson bracket. Neglecting this term yields the Poisson bracket mapping equation (PBME). We expand the mapping dependence of the density in Hermite functions about the Gaussian factor common to all physical mapping densities. In this basis, the excess coupling term acts purely as a raising operator and exactly cancels the raising contribution generated by the back–reaction force. Consequently, the exact dynamics does not generate higher Hermite orders and closes on a finite, sparse system of equations for the coefficient fields. Within the physical sector, these equations reduce to the subsystem quantum–classical Liouville equation. In contrast, the PBME retains the raising contribution of the force, modifying the back reaction within the physical sector while continuously generating higher Hermite orders. For Tully's dual avoided crossing model, direct propagation of the coefficient equations confirms this finite closure and agrees with independent solutions of the subsystem equation. Comparison with converged full quantum dynamics further shows that, across all regimes examined, the PBME is less accurate than the quantum–classical description for populations, coherences, and momentum distributions.

We study the amplification and concentration of wave energy in smooth, periodic space-time media through the dynamics of the characteristic curves of the associated wave equation. In an impedance-matched setting, we show that stable limit cycles attract neighbouring characteristics, focusing the wave energy density. The exponential attraction rate is estimated analytically from the system's Lyapunov exponent. We further show that the attraction of characteristics and energy accumulation persist under a range of nonperiodic perturbations. Finally, we present a Floquet-Fourier numerical method for computing stable and unstable limit cycles and their attraction rates. Throughout, we exemplify the results using the example of modulation given by a superposition of travelling waves, revealing saddle–node bifurcations where limit cycles may appear depending on the relative wave speeds. Full-wave simulations confirm that the characteristic mechanism continues to describe energy accumulation beyond the impedance-matched case.

Global reanalyses are too coarse to resolve the convective systems that produce most West African monsoon rainfall. In this work, we use U-Net based architectures to downscale daily ERA5 fields (0.25{\deg}) to IMERG V07 satellite precipitation (0.1{\deg}) over West Africa for the June to October seasons of 2000 to 2024, using geopotential, temperature, humidity and wind at three pressure levels together with elevation and land fraction. Adding ERA5 precipitation as input slightly improves performance for this particular challenging region. We find that all the deterministic networks investigated for this work are too dry and lose almost all observed variance below a few hundred kilometers, which motivated our use of a GAN-based alternative. We also investigated permutation importance for the U-Net that ranks 500 hPa specific humidity first, consistent with the sensitivity of deep convection to mid-tropospheric moisture.

Static dipole polarizabilities of H$_2$, LiH, and helium confined in a single-mode optical cavity are computed using quantum-electrodynamical full configuration interaction (QED-FCI). Response properties are obtained as finite-field derivatives of the coupled electron-photon energy. The cavity-induced modification is found to arise from the competition of two contributions of opposite sign, the dipole self-energy and photon exchange, whose relative strength depends on both the cavity frequency and the number of photons involved in the exchange. The residual change suppresses the response of the molecular ground electronic states. For the metastable states of helium atom this balance changes qualitatively, and the differential response of the $2\,^3S_1 \to 2\,^1S_0$ clock transition, which governs its sensitivity to static electric fields and to thermal radiation, is strongly enhanced instead. Cavity confinement can therefore either reduce or increase the dc Stark and blackbody-radiation shifts of a frequency standard, depending on the electronic structure of the states involved. The reported data serve as a reference for cavity-modified response and underscore the need for an exact treatment of light-matter correlation in cavity-QED predictions.

How spatial structure is transferred through a forward-scattering medium depends jointly on pattern scale and propagation distance. Starting from photon exit displacements, we derive modulation transfer while retaining the number, depths, and projected angles of individual deflections, with event occurrences described by a homogeneous Poisson process along the propagation path. The second angular moment yields a leading low-frequency loss proportional to $k^2z^3$, where $k$ is angular spatial frequency and $z$ is thickness. At finite frequency, the model predicts two coupled departures: loss bends below its low-frequency quadratic extrapolation at fixed thickness, and transfer curves separate by thickness at fixed $k^2z^3$. The leading corrections to both effects arise from the same fourth angular moment. For symmetric, nondegenerate projected-angle distributions, the full response further establishes increasing loss with thickness in the same medium at fixed joint variable. Binary-pattern measurements through TiO$_2$ suspensions span five nominal loadings, seven thicknesses, and 20 spatial frequencies, supporting the approximate low-frequency scaling and showing both departures. A Gaussian effective-angle response calibrated only on lower-frequency data predicts the held-out higher-frequency band without refitting, with a logarithmic root-mean-square error of 0.0181 compared with 0.1021 for quadratic extrapolation. The results show that finite-event statistics provide a common physical origin for spectral bending and thickness-dependent departure from low-frequency scaling, linking coarse-pattern transport to finer spatial structure.

Three-dimensional conjugate heat-transfer simulations provide detailed predictions for microchannel heat sinks but can be computationally demanding when many geometries and operating conditions are evaluated. This study develops a versatile two-layer model (VTLM) that reduces the three-dimensional problem to two coupled two-dimensional fields while retaining the in-plane geometry of the flow passages and fins. Effects associated with the unresolved channel-height direction are incorporated through hydraulic and thermal closures that account for wall friction and the fluid- and fin-side contributions to interlayer heat transfer. The closures are evaluated from the representative channel geometry, flow-development condition, and fin configuration. The VTLM was assessed against three-dimensional reference models across broad ranges of channel aspect ratios and operating conditions, including uniform and nonuniform fin arrangements. Compared with the existing two-layer models, the VTLM showed improved overall agreement with the three-dimensional reference results. The results showed that prediction accuracy was governed mainly by the flow-development condition and channel aspect ratio, from which a conservative screening guideline was proposed for the examined straight-channel configurations. The assessment of finned expansion–contraction channels further supported the applicability of the VTLM to the investigated passages with abrupt width changes. Overall, the VTLM provides a reduced-dimensional framework for thermohydraulic analysis across the range of microchannel heat-sink configurations examined in this study without explicitly resolving the channel-height direction.

A potentially super El Niño is forecasted in 2026, raising the need to anticipate land carbon-cycle risks before its impacts unfold. We develop a prospective early-warning framework that uses dynamic global vegetation models driven by an ensemble of ECMWF seasonal climate forecasts and machine-learning burned area predictions. Forecasts indicate a $0.23 \pm 0.21$ PgC reduction in global net biome productivity in the second half of 2026, with hotspots of sink weakening in eastern South America and elevated fire risk in Southeast Asia.

The frequency noise of a resonant nanomechanical sensor is well understood down to its thermomechanical limit, but the longest useful averaging time is set by a flicker, or $1/f$, frequency-noise floor whose origin has remained unknown. We show that this floor is the thermal noise of the tension. By the fluctuation-dissipation theorem, the tension of a resonator with fixed ends fluctuates by an amount set by the loss angle of its material; for structural damping, these fluctuations produce $1/f$ frequency noise with a flicker coefficient $h_{-1}=E k_{\mathrm{B}} T/(2\pi V\sigma_0^2 Q_{\mathrm{el}})$, with $Q_{\mathrm{el}}$ the intrinsic loss under elongation, that contains no free parameter and is diluted by the tensile stress $\sigma_0$ in the same way as damping is in dissipation dilution. Silicon nitride strings and membranes from 30 to 340~nm thickness follow the predicted volume scaling, the predicted $\sigma_0^{-2}$ dilution across resonators and within stress-engineered strings, and the predicted thickness dependence, which places noise-active two-level systems in the volume and at the surfaces of the resonators, all at the absolute level set by the independently measured intrinsic loss. The same relation accounts for published data between 78 and 296~K; below 78~K, the loss measured at the resonance no longer represents the loss probed by the noise, marking the limit of the structural-damping assumption. Dissipation dilution therefore lowers the $1/f$ floor, and the longest useful integration time of a resonant sensor is set by its prestress, volume, temperature, and intrinsic loss angle.

Muons have fascinated physicists since their discovery in cosmic rays almost a century ago. Their large mass and relatively long lifetime allow relativistic muons to traverse large amounts of matter, a property that has been exploited to probe otherwise inaccessible structures, from volcanoes and archaeological monuments to shielded nuclear materials. Here, we experimentally demonstrate for the first time that muon scattering tomography can be extended to biological soft tissue. We image an anthropomorphic thorax phantom using a 2 GeV/c muon beam at the CERN Proton Synchrotron and reconstruct its three-dimensional scattering density from the measured deflections of individual muons. Despite the weak scattering produced by tissue-equivalent materials, the reconstructed density agrees with the expectation from simulation at the percent level. Our results extend muon imaging into a previously unexplored regime and open the possibility of using muons as a complementary probe for medical imaging.

Quantum aging transition has recently been reported, whereby the oscillatory dynamics of a network of globally coupled quantum self-sustained oscillators is degraded sharply when the fraction of inactive nodes exceeds a critical value. Here we explore the reverse process: the revival of rhythmic dynamics from an aged state in a quantum oscillator network by introducing a controlled incoherent single-boson pumping channel. Using a self-consistent quantum master equation in the Lindblad form for globally coupled active–inactive quantum Stuart–Landau oscillators, we show that increasing the pumping strength progressively suppresses the aging transition and eventually eliminates it, restoring rhythmicity even when all oscillators are inactive. Remarkably, complete compensation of the coupling-induced dissipative loss is not required; a substantially weaker pumping strength is sufficient to eliminate the aging transition. We show that the revival is governed by a redistribution of the Fock-state population of the inactive oscillators toward higher-occupation states. Our results establish controlled incoherent pumping as an effective mechanism for restoring dynamical robustness in quantum oscillator networks.

Halogen bonding in which a covalently bound fluorine acts as halogen-bond donor (F-bonding) is rare, and its open-shell variant with radical electron donors remains unexplored. We introduce SEFB-15 dataset (15 open-shell DF$\cdots$CH$_3$ complexes) exemplifying single-electron F-bonding (SEFB) and CSFB-14 dataset (14 closed-shell DF$\cdots$NH$_3$ complexes) representing closed-shell F-bonding (CSFB). Reference binding energies (BEs) at DF-RMP2-F12/CBS//DF-RMP2-F12/VDZ-F12 are validated against CCSD(T), CCSD(T)-F12b, W1-F12 and W2-F12 for selected systems (DF = F$_2$, NCF, CNF, NH$_3$F$^+$ and NH$_2$F$_2^+$), with MA%D of 4.5% (DF$\cdots$CH$_3$) and 3.4% (DF$\cdots$NH$_3$) against CCSD(T)-F12b/CBS//CCSD(T)-F12b/VDZ-F12. BEs from W1-F12 and W2-F12 are identical. Reference F-bond distances at DF-RMP2-F12/VDZ-F12 are validated against CCSD(T)-F12b, CCSD(T), CCSD, and DCSD for the same systems, with MA%D of 0.9% (SEFB) and 0.4% (CSFB) against CCSD(T)-F12b/VDZ-F12. M06-2X is recommended for closed-shell halogen bonding with heavier halogens but has never been assessed for open-shell F-bonding. M06-2X/AVTZ systematically overbinds all SEFB-15 complexes and underestimates their F-bond distances, with MA%Ds of 75.8% on BEs and 8.9% on F-bond distances. M06-2X predicts comparable BEs for F$_2\cdots$CH$_3$ and F$_2\cdots$NH$_3$, contrary to all ab initio results, an anomaly persisting across all 16 basis sets. Neither basis set nor BSSE correction resolves the overbinding. BSSE correction worsens BEs for DF$\cdots$NH$_3$ complexes. For CSFB-14, M06-2X/AVTZ yields MA%Ds of 16.0% for BEs and 3.3% for F-bond distances. M06-2X is reliable for CSFB but unreliable for SEFB regardless of basis set. Companion paper II reports performance of other Minnesota functionals and ab initio methods for these datasets.

To address non-uniqueness in geophysical inversions, Generative Neural Networks (GNNs) are often used to parameterise geological or other prior information in a lower-dimensional space (the so-called latent space), thereby reducing the number of inversion parameters. However, the training samples that represent this information are then always incorrect, because Earth structure is not intrinsically low-dimensional, and all GNNs are subject to training errors. Consequently, even when solutions are mapped back to the original higher-dimensional space, they inherit this imperfection and remain restricted to a low-dimensional manifold. From a mathematical point of view, latent space inversion thus fails fundamentally: generally, it can not even reproduce the best, higher-dimensional approximation to the true Earth. To overcome this limitation, we introduce an `escaping prior' distribution, which provides the necessary freedom to find solutions beyond the manifold of GNN-generated solutions, while still using the GNN as a guide. We use a hierarchical Bayesian approach to adapt the strength of prior information to the observed data and synthetic forward function $\textit{a posteriori}$. We illustrate our method on low-dimensional problems where the escaping prior is defined over a 1D manifold in 2D space. We then compare our approach with standard latent space and model space inversions using a uniform prior distribution in synthetic tomography problems, ranging from simple to more geologically realistic cases. Furthermore, we tested scenarios where the true solution is either far from or close to the manifold. In each case, our escaping prior shows significantly better results than the alternatives. It results in solutions beyond each GNN's generative capabilities, solutions which include the best possible model, and clearly demonstrates the limitations of latent space inversion.