Papers

We introduce a general mechanism for engineering moment-selective temporal designs with hierarchically structured aperiodic drives. At special control settings where the driven dynamics is constrained by a finite symmetry group, lower-order moments can already reproduce Haar statistics while a selected higher-order deviation remains nonzero. A small static detuning from such a setting generically produces an exponentially long lifetime whose exponent scales inversely with the square of the detuning. We illustrate this mechanism in qubit systems through exact Fibonacci and silver-mean constructions with tetrahedral and icosahedral resonances, for which the first retained non-Haar moments occur at orders $3$ and $6$, respectively. We further show that stochastic control fluctuations produce a qualitatively different cutoff from coherent detuning. Finally, we propose a finite-time signature of the long-lived moment that can be measured without requiring observations over exponentially long times.

We perform a numerical conformal bootstrap study of the mixed system of correlation functions involving a spin-1 $\mathrm{U}(1)$ current $J$ and the stress-energy tensor $T$ in parity-preserving 3d CFTs. We find universal bounds on the stress-tensor two-point function $c_T$, which numerically reproduce the conformal collider bounds on $\langle JJT\rangle$ and $\langle TTT\rangle$, as well as bounds on the leading parity-even and parity-odd scalar operator dimensions. Under mild assumptions, we determine the values of the $\langle JJT\rangle$ and $\langle TTT\rangle$ three-point functions in the $\mathrm{O}(2)$ vector model. The $\langle TTT\rangle$ result is new and $\langle JJT\rangle$ is consistent with a previous result in the literature.

Multireference electronic-structure calculations remain difficult to automate because critical workflow decisions, including active-space selection, state averaging, convergence recovery, and state identification, traditionally rely on expert judgment. Here, we investigate whether an autonomous large language model (LLM) agent can perform these tasks without human intervention. The agent selects active spaces using literature-grounded analogies or explicitly documented chemical reasoning, generates and submits ORCA calculations, analyzes outputs, and records all decisions in an auditable reasoning log. Benchmarking against 558 vertical transition energies (VTEs) from QUESTDB shows that an unguided baseline agent achieves 24.9% coverage with a mean absolute error (MAE) of 0.373 eV. Introducing a structured decision ladder increases coverage to 44.1% while reducing the MAE to 0.339 eV. The largest gains are observed for double and Rydberg excitations, demonstrating that expert-informed procedural guidance substantially improves active-space construction and state identification. When provided with complete workflow information, the agent successfully reproduces published QUEST calculations with an MAE of only 23 meV, resolving 75% of target configurations within seven attempts. These results demonstrate that contemporary LLM agents can autonomously execute and reproduce complex multireference quantum-chemical workflows, while highlighting the importance of structured reasoning frameworks for achieving reliable high-throughput and high-fidelity electronic-structure calculations.

Understanding interparticle radiation forces between spherical and nonspherical particles is crucial for the trapping of micro- and nano-objects in acoustophoresis. Most theoretical and numerical models treat spherical particles as identical to estimate interparticle forces, owing to their symmetry. Here, we elucidated interparticle radiation forces between three particles with different shapes and material contrast using experimentally validated numerical models. We performed a frequency sweep of the full acoustic device, accounting for viscous effects in a two-dimensional model, to predict the system's resonance. The pressure field obtained at the resonant frequency was then fitted to a 1D sinusoidal wave and used in a three-dimensional model based on the perturbation technique and tensor integral method to calculate the interparticle forces on the particles due to scattering and re-scattering of the acoustic field. Our results revealed a shape-dependent reversal of interparticle forces, even for positive-contrast materials. We found that for spherical particles, the interparticle forces are independent of material properties when the particles are positioned on the nodal plane. However, material contrast and particle asymmetry significantly affect interparticle forces when particles are placed outside the nodal plane. Finally, we studied the effects of the orientation of the asymmetric particle placed outside the nodal plane on the interparticle radiation forces. Interestingly, for the orientation angle of 0 degrees, the interparticle force is maximum for the asymmetrical particle and then gradually decreases to zero as we increase the orientation angle to 90 degrees. The detailed analysis presented in the paper will facilitate a better understanding of shape-based acoustic manipulation of microparticles.

Screened hybrid functionals such as HSE06 improve the description of band gaps, charge localization, and redox energetics relative to semilocal approximations, but their explicit Hartree-Fock exchange term is computationally costly for large, periodic systems, especially in plane-wave basis set calculations. Here we present RS-CIDER, a machine-learned non-local exchange functional that approximates the short-range Hartree-Fock exchange term in HSE06 by explicitly fitting both ground-state energies and single-particle energy levels. RS-CIDER combines scale-invariant semilocal and non-local density descriptors and can be evaluated self-consistently without explicitly applying the short-range Hartree-Fock exchange operator. RS-CIDER shows close agreement with HSE06 for molecular reaction energies and solid-state band gaps. Further tests across distinct materials show agreement between RS-CIDER and HSE06 for local magnetism, Cu-O phase competition, polaron localization, and neutral-defect energetics. For an Fe olivine, chemistry-specific fine-tuning recovers the HSE06 Li intercalation voltage. A timing benchmark shows that RS-CIDER reduces the measured per-SCF-step wall time by more than an order of magnitude relative to HSE06. Together, these molecular and solid-state results establish RS-CIDER as an efficient self-consistent machine-learned surrogate for HSE06.

Excitons in magnetic semiconductors have energies and spin structures that are sensitive to the underlying magnetic order. We study this coupling in a minimal one-dimensional lattice model of a conduction electron and a valence hole moving in a ferromagnetic background of localized quantum spins, treating the electron, the hole, and the magnon(s) as explicitly resolved degrees of freedom. At zero temperature, spin conservation closes the relevant Hilbert subspaces at the one- or two-magnon level, so the model can be solved essentially exactly with a real-space Green's function method. Comparison against a frozen-spin approximation in which the local moments are replaced by their ordered values identifies which effects are due to emission and absorption of quantum magnons. A frozen background already lifts the spin degeneracy of the exciton and, if the two carriers couple with different strengths to the local moments, it mixes the singlet with the spin-zero triplet exciton. The emission and absorption of quantum magnons goes qualitatively further: it splits and shifts the exciton energies nonlinearly in the exchange coupling even when all frozen-spin effects vanish; for carriers with unequal hopping integrals, it hybridizes the singlet and spin-zero triplet excitons, thereby brightening the dark triplet; and it increases the exciton radius, which in turn enhances the magnon dressing by removing an on-site cancellation. These quantum effects are therefore strongest for extended, Wannier-like excitons, which is precisely the regime that is commonly modeled assuming a static (frozen-spin) magnetic order.

Active disordered solids including dense human crowds and epithelial cells under confinement exhibit striking system-scale oscillatory spatiotemporal patterns. These are linked to a local feedback mechanism, self-alignment, that aligns the direction of a particle's motility vector to the total force. Simulations and experiments of solids made of such agents show these spontaneous oscillation patterns. Theoretically, they have been linked to both a nonlinear bifurcation and to selection of long-wavelength normal modes. Here we derive a closed nonlinear equation for the displacement field of active self-aligning 2d solids subject to angular noise. Along the normal modes of the solid, the dynamics of the mode amplitudes correspond to nonlinearly damped and stochastically driven harmonic oscillators. To linear order, we show that the system transitions from Active Brownian type correlated motion to oscillatory motion that increasingly condenses onto the lowest modes of the solid. We compare the analytical predictions for the mode spectra with simulations, finding excellent agreement approaching the transition from the disordered side. Strong nonlinearities manifest deep in the oscillating phase at strong alignment and small noise, consistent with the previous observations. At the continuum level, we derive a closed-form nonlinear wave equation for self-aligning solids. The transition to undamped oscillations is a second order dynamical phase transition driven by the competition between noise and alignment. At the linear level, we predict travelling acto-elastic waves, together with the emergence of system-scale oscillations for confined systems, consistent with observations in tissues and crowds. Our framework extends the understanding of self-aligning solids, which are pervasive among artificial and biological systems across multiple scales.

Surface modification is an important strategy for tailoring the physical and chemical properties of materials for advanced technological applications. In thin films, changes in surface structure, roughness, and composition can strongly influence their functional behavior. In this work, we studied the effect of N+-ion irradiation at 20 keV energy on Ru thin films of two different thicknesses, 100 Å and 1000 Å, over a fluence range of ~1014 to 1017 ions/cm2. The main objective of this study is to investigate the evolution of the structural and wettability properties of Ru thin films of different thicknesses under increasing ion fluence. Overall, the results reveal that increasing ion fluence promotes surface roughening in both film thicknesses, which is correlated with an increase in contact angle. This indicates a clear transition from hydrophilic to hydrophobic behaviour, with the highest contact angle of ~95.54{\deg} observed at a fluence of 1017 ions/cm2. TRIM simulations reveal that for the 100 Å film, the projected ion range exceeds the film thickness, allowing interaction with the bottom substrate, whereas in the 1000 Å film, ion penetration remains largely confined within the Ru layer. GIXRD confirms fluence-dependent structural modification, including peak broadening with preferred orientation changes from Ru (101) to (002). Overall, this study demonstrates that N+-ion irradiation serves as an effective route for tuning both the surface morphology and wettability of Ru thin films, enabling controlled enhancement of hydrophobicity.

Ultrafast creation and manipulation of topologically non-trivial spin objects promises significant potential for spintronic applications. Here, we demonstrate laser-induced nucleation of skyrmions and antiskyrmions with topological charge up to $|Q|=3$ from the saturated magnetization state of a Co/Ni-multilayer which does not intrinsically host a skyrmionic ground state. The resulting configuration of spin objects thus constitutes a metastable, thermodynamically hidden magnetic state. We control the number and type of spin objects by the excitation fluence and the external out-of-plane magnetic field.

We introduce an on-lattice minimal model of two-dimensional melting, a clock model with vacancies with control parameters temperature, chemical potential and external field. We study the full phase diagram using cluster Monte Carlo, Tensor Network Renormalisation Group and selfconsistent mean field methods. A non-universal ensemble of melting scenarios is observed including the KTHNY scenario of two Berezinskii-Kosterlitz-Thouless phase transitions delimiting a quasilong-range ordered phase. The upper transition evolves into first-order transition in analogy with simulations on hard and soft discs and at low chemical potential there is a single transition between ordered high density and disordered low density phases. The evolution is via a special tricritical point that is accessed in detail. This work therefore provides a framework for understanding the crossover between 2D melting scenarios and offers insights into the behavior of realistic systems.

Magic, or nonstabilizerness, is the resource that promotes stabilizer operations to universal quantum computation. For bipartite pure states, its component intrinsic to the correlations between the subsystems, the nonlocal magic, is obtained by minimizing a magic measure over local unitaries. For the stabilizer Rényi entropy (SRE), the minimum is conjectured to be attained by the computational-basis (CB) representative, the state obtained by assigning the Schmidt coefficients in decreasing order to matching computational-basis labels. We prove this conjecture for two families of states at every system size and bipartition: states with dyadic-staircase Schmidt spectra and states of Schmidt rank at most six. For arbitrary bipartite pure states, we show that the CB value exceeds the nonlocal SRE by at most $4$, fixing the leading term of any divergent scaling of nonlocal SRE. We further show that the nonlocal SRE grows at most logarithmically with the entanglement entropy. Consequently, one-dimensional area-law states have bounded nonlocal SRE, while critical states with logarithmic entanglement entropy permit at most doubly logarithmic growth with system size. We apply these results to the transverse-field Ising chain, where we tightly bound the nonlocal SRE in the gapped phases and identify its double-logarithmic growth at criticality.

Recently, unconventional superconductivity hosted by twisted van der Waals (vdW) heterostructures has received immense interest due to the exotic pairing symmetry, electronic interactions and nontrivial topological nature that are naturally relevant to the fast-advancing quantum technologies. Here, we report scanning-probe quantum sensing of nanoscale electromagnetic behaviors of twisted vdW cuprate superconductors. Using single-spin relaxometry, we directly visualize edge modes spontaneously formed in twisted Bi2Sr2CaCu2O8+x (BSCCO). By investigating temperature dependent variations of edge-state-induced quantum spin relaxation, we experimentally evaluate the magnitude of nontrivial topological band gap opened at nodal points in twisted BSCCO and its critical temperature behaviors under different twist angles. We further observe alternating chiral domains defined by edge modes, exploring experimental signatures of in-plane magnetic field-induced topology in 45{\deg} twisted BSCCO. Our results advance the current understanding of twisted vdW nodal superconductors, presenting an appealing high-temperature topological superconducting material platform for cutting-edge quantum innovation.

We describe how strong vorticity fluctuations appear in three-dimensional incompressible turbulence driven by a large-scale random force. By combining analytical and numerical methods, we construct a vorticity instanton: the most probable force history driving the flow to a prescribed large vorticity at a given point and time. We show how the smooth, large-scale force produces a long vortex filament with a thin, viscous-scale core. Our main finding is that the standard mechanism of amplifying a vortex tube through radial compression and axial stretching is only effective up to a threshold value. Producing vorticity above the threshold requires an additional ingredient: vorticity waves propagating along the tube. The final vorticity is the result of two colliding waves. This mechanism has striking similarities to the one recently suggested by OpenAI for creating infinite vorticity in finite-time Navier–Stokes blow-up.

Ruddlesden-Popper (RP) nickelates superconduct when pressure suppresses intertwined charge- and spin-density waves. Here, we employ measurements of quantum corrections to magnetoconductivity as a probe of the dimensionality, phase coherence, and scattering mechanisms of the underlying single crystal trilayer RP nickelate Pr4Ni3O10 and La4Ni3O10. We observe signatures of 2D Weak Localization (WL), implying that the in-plane electron transport is in the quantum diffusive regime, while the out-of-plane transport is incoherent, and the electronic ground state is a quasi-2D disordered Fermi liquid. Application of pressure up to 3 GPa continuously suppresses signatures of WL, potentially signaling a 2D/3D dimensional crossover and an eventual pressure-driven transition into a superconductor.

Helical order can facilitate symmetry breaking and emergent physical responses in crystalline materials, yet how intrinsic chirality manifests beyond atomic length scales remains poorly understood. Here, the direct observation and quantitative characterization of long-range crystallographic helicity in template-grown tellurium (Te) quantum wires on amorphous substrates are reported. Four-dimensional scanning transmission electron microscopy (4D-STEM) enables quantitative mapping of crystallographic orientation with nanometer-scale spatial resolution. The resulting orientation maps establish continuous mesoscale lattice twisting, providing direct evidence of long-range crystallographic helicity. Correlated orientation and strain mapping reveal pronounced lateral strain heterogeneity, with compressive strain concentrated within the wire interior. Systematic analysis across multiple wires suggests that higher twist rates are generally associated with weaker lateral compressive strain, narrower wires, and better atomic chain - template axis alignment. Complementary first-principles calculations on finite Te nanorods further suggest that twisting is intrinsically accessible in nucleus-scale Te clusters and strain can bias the preferred torsional state. Together, these results support a growth-incorporated, strain-biased picture in which nanoscale confinement and anisotropic strain facilitate torsional relaxation and stabilize mesoscale helicity in Te nanostructures highlighting strain and confinement as potential routes for engineering chiral lattice states in van der Waals nanostructures.

Urban street networks are modeled as spatial graphs whose geometry reflects planning, history, and physical constraints. Global orientation measures describe the overall order of a city but do not reveal how street directions form coherent neighborhoods. Here we introduce bearings communities—spatially connected domains whose streets share a common orientation—and analyze them using concepts from the physics of polycrystalline materials. Across $1025$ large cities worldwide, these domains are almost perfectly ordered: their mean coherence is $0.964$ and varies by only $1.4\%$ from one city to the next, far above the value expected for randomly oriented streets. Every city is therefore a mosaic of well-ordered orientational grains, differing only in their number, size, and mutual alignment. Because the grains are equally regular everywhere, a city's global order is set mainly by how many of them it averages over: a city appears ordered because it is built from a few large grains, not because its fabric is locally more regular. A null model in which grain orientations are randomized confirms this grain-counting mechanism. Finally, the interface fraction $\gamma$ measures how strongly domains interlock, yielding a morphology diagram that organizes cities continuously between grid-like, polycrystalline, and fragmented limits.

The 3D digital reconstruction of multi-scale, heterogeneous porous media is traditionally limited by the resolution boundaries and artifacts of X-ray computed tomography (XCT). This paper introduces a physically consistent 2D to 3D pore space synthesis framework that supersedes conventional geometric shuffling with dynamic Newtonian gravitational deposition using a high-performance rigid-body mechanics engine. To honor strict physical contact mechanics, statistical 2D targets, and morphological constraints, we develop a two-stage dynamic packing pipeline that combines realistic 3D grain shapes with a virtual sub-particle insertion engine. The framework is validated against synthetic and natural core benchmarks. First, we show that our stereological integral equation systematically converts size distributions; bypassing this inversion step induces a systematic 50% deviation in permeability predictions despite identical total porosities, independently altering flow channel topology. Second, temporary virtual spheres serve as architectural placeholders to stabilize large non-equilibrium dissolution voids, ensuring the reconstructed model satisfies target flow metrics within the prescribed tolerance. Finally, when applied to a fine-grained, weakly consolidated sandstone, the workflow exposes and suppresses systematic XCT artifacts, including phantom internal porosity. Ensembles of two-point correlation functions demonstrate that the hydrodynamically and structurally synthesized digital twins quantitatively exhibit closer structural proximity to the uncorrupted rock geometry than the reference XCT dataset itself. This methodology establishes a scalable foundation for high-fidelity multi-phase rock reconstruction, with potential extensions toward complex amorphous cement phases.

We present a systematic investigation of the robustness and limitations of equilibrium gap-based calibrations for hyperelastic physics-augmented neural networks (PANNs), where we consider the special case of isotropic and polyconvex PANNs. In full-field parameterizations, it is commonly assumed that the displacement field is captured with sufficient spatial resolution for an accurate evaluation of the deformation field, and that the specimen is thin enough for plane stress to hold to a good approximation. Since these assumptions are never ideally satisfied in real experiments, we investigate, using synthetically generated data, how severely an under-resolved surface measurement and a non-negligible specimen thickness can affect the model parameterization. Furthermore, we perform calibration on real experimental data for a set of inhomogeneous specimen geometries. We show that the coverage of the admissible deformation states during calibration governs the ability of a model to generalize to unseen geometries and load cases; this ability can be improved further by appropriate combinations of specimens. Accurately depicting the material behavior underlying this rich data, however, requires a sufficiently flexible constitutive model, for which PANNs are well suited. Yet a rich coverage of deformation states alone is not sufficient: unless the calibration data comprise biaxial-tension-like states, models that include the second deformation invariant extrapolate unphysically towards equi-biaxial tension, whereas restricting the PANN to the first invariant remains reliable.

Li$_x$CoO$_2$ is a prototypical layered cathode material for Li-ion batteries, yet its accurate description from first principles remains challenging because of self-interaction errors, weak interlayer interactions, and a complex magnetic energy landscape. Here, we present a systematic investigation of the structural, electronic, magnetic, and electrochemical properties of Li$_x$CoO$_2$ ($x=0,1$) using density-functional theory augmented with self-consistent Hubbard corrections and long-range van der Waals interactions, together with a systematic exploration of possible magnetic states. The on-site interactions on Co-$3d$ and O-$2p$ states, as well as inter-site Co-O interactions, are determined from first principles using linear-response theory in the framework of density-functional perturbation theory, with Löwdin-orthogonalized atomic orbitals employed as Hubbard projectors. For LiCoO$_2$, the inclusion of Hubbard corrections provides an accurate description of the structural properties, while the electronic structure is very sensitive to the choice of Hubbard projectors. In particular, frontier Wannier-function projectors substantially improve the description of the occupied electronic states compared with localized atomic orbitals. For CoO$_2$, we demonstrate that a systematic exploration of the magnetic energy landscape is essential to identify the lowest-energy low-spin ground state. However, the resulting Hubbard-corrected electronic structure is insulating, consistent with the prediction of the HSE06 hybrid functional, but in contrast to the experimentally observed metallic behavior. Structural relaxation further drives the system toward a different metallic solution with an electronic configuration inconsistent with low-spin Co$^{4+}$ character. Despite these limitations, the calculated intercalation voltages agree well with experiment, with deviations as small as 2%.

We study the effect of temperature on the ability of a qubit probe to distinguish between different phases in strongly correlated systems. Now to this end, we investigate a spin-1/2 Heisenberg XXZ chain coupled to a qubit probe via a pure dephasing interaction. At zero temperature, as reported previously, the decoherence dynamics exhibit different behavior in the gapped and gapless phases of the chain, with characteristic strong oscillations in the gapped phase and monotonic decay in the gapless phase. These oscillations decay much more slowly than expected with rising temperature in the gapped phase and their remnants are still visible at infinite temperature. In the gapless phase at low temperatures, using Luttinger liquid theory, we predict that the coherence exhibits asymptotic exponential decay in time, with the decay rate sensitive to the sign of the anisotropy parameter. We conclude that probe dynamics continue to carry information about the chain even at finite, reasonably small temperatures, positioning qubit probes as sensitive and robust detectors for quantum phases of correlated spin systems.

Altermagnets combine compensated antiferromagnetic order with ferromagnet-like signatures such as spin-polarized bands and, under appropriate conditions, an anomalous Hall response. Their characteristic momentum-dependent spin splitting originates from the interplay of magnetic order and crystal structure and therefore does not require spin-orbit coupling (SOC), whereas the anomalous Hall effect relies on SOC. This raises the question whether the ferromagnet-like transport character of altermagnets can manifest already in the nonrelativistic limit. Here, we investigate the transport of orbital angular momentum in magnetic Lieb lattices. We show that a collinear antiferromagnetic texture realizes a d-wave altermagnetic state and simultaneously generates an orbital Hall effect, both in the complete absence of SOC. In this nonrelativistic limit, the orbital Hall response closely resembles that of the corresponding ferromagnet. When SOC is included, the orbital Hall effect is accompanied by a spin Hall response, while the altermagnetic spin texture acquires a corresponding orbital texture, realizing orbital altermagnetism. In contrast, an anomalous, or crystal, Hall effect requires SOC and is additionally subject to crystal-symmetry constraints. We extend the analysis from d-wave altermagnetism to odd-parity p-wave magnetism, where the orbital Hall effect becomes anisotropic and the orbital conductivity tensor develops a symmetric transverse component analogous to the planar Hall response in charge transport. Our results establish the orbital Hall effect as a nonrelativistic transport manifestation of the close relation between altermagnets and ferromagnets and extend this connection to unconventional magnetic orders beyond altermagnetism.

Slender elastic objects constrained to curved surfaces are ubiquitous in soft systems, with examples ranging from DNA wrapping around histones to actin filaments forming contractile rings on the cell membrane during cytokinesis. In the continuum limit, the conformation of these effectively one-dimensional (1D) objects is governed by both the geometry and mechanics of the embedding surface, and the elasticity of the object. Existing phenomenological typically describe such behavior through elastic energy minimization that incorporates bending and twisting, but neglect stretching that may be important for filaments with finite cross-section or are highly incompatible with the underlying surface. Here we present a coarse-grained geometric theory of 1D elastic curves constrained on rigid surfaces, derived from the first principles. For an isotropic material, our model emerges naturally in terms of the Young's modulus, Poisson's ratio, and area moments of inertia. The resulting effective energy functional explicitly includes stretching in addition to bending and twisting. We minimize it to determine the equilibrium curve conformations on different zero, positive, or negative Gaussian rigid surfaces. Our theory provides a general framework for analyzing the equilibrium configurations of surface-bound elastic curves in biologically and physically relevant settings.

To clarify spin relaxation and precession across the weak-to-strong SOC crossover in chiral conductors, we formulate a density-matrix quantum kinetic theory for a three-dimensional isotropic chiral metal with hedgehog SOC and nonmagnetic impurity scattering. The formulation retains interband coherence, and its collision integral conserves charge, energy, and spin during impurity scattering. We identify three spin modes that evolve continuously from a long-lived D'yakonov–Perel' relaxation mode and two strongly damped precessional modes at weak SOC to one relaxational and two coherent precessional modes at strong SOC. A closed multipole decomposition maps the spin dynamics onto an effective Bloch equation, providing a unified interpretation of relaxation and precession across the crossover. We further derive the ac Edelstein susceptibility and the reciprocal current response to a time-dependent Zeeman field, show that their poles coincide with the spin modes, and verify Onsager reciprocity. The theory thus provides a unified analytic description of spin relaxation, precession, and spin–charge conversion across the weak-to-strong SOC crossover.

The spin splitting of collinear altermagnets is usually attributed to the crystal symmetry relating the opposite-spin sublattices — a rotation or mirror in place of the translation or inversion of a conventional antiferromagnet. We show that this symmetry organizes the splitting but does not produce it; its origin is the anisotropic arrangement of the magnetic orbitals and their ligands, which also fixes the symmetry itself. Two results establish this. A triclinic ($P1$) \ce{Mn} oxide, a fully compensated ferrimagnet whose two inequivalent sublattices are related by no symmetry, is spin split throughout the Brillouin zone; repositioning the same ligands, atom for atom, to restore an inversion centre relating the two metal sites collapses the splitting to a residual two orders of magnitude smaller, so the splitting follows from the arrangement rather than the symmetry. Symmetry, we show formally, can only ever reverse or forbid a splitting that already exists: it cannot create one between sublattices an arrangement has left electronically identical, nor where the underlying orbitals carry no anisotropy to arrange in the first place. Organizing the analysis through an operation-resolved symmetry hierarchy and reading the crystal classes as a single axis, the enforced nodal planes fall from two to one to zero across the orthorhombic, monoclinic, and triclinic classes while the arrangement-generated splitting persists to the base. The altermagnet and the fully compensated ferrimagnet are thus the two ends of one axis — the same splitting, organized by symmetry at one end and unorganized at the other — and the search for compensated spin-split magnets is a search over orbital arrangements rather than symmetry labels.

Artificial spin ices built on quasiperiodic geometries remain under-explored. Here we investigate an ASI based on the octagonal Ammann-Beenker tiling, whose six vertex types present local environments inaccessible in periodic lattices. Combining Monte Carlo simulations of dipolar-coupled macrospins with micromagnetic calculations of individual vertex energies, we find that vertex types freeze in an order set not by coordination number, but by quasi-degenerate levels at five-island vertices and their local environment. Excitations in the low energy state are correspondingly localised to specific, geometrically determined sites. Using twice-inflated substitution rules as an energetic backbone, we propose an analytical ground state combining a long-range ordered fixed spin network with a sparse set of degenerate regions.

Across biological scales, from cytoskeletal networks to whole tissues, orientational order and topological defects arise within complex three-dimensional geometries. However, quantifying nematic order orientational order with head-to-tail symmetry remains challenging: 2D projections introduce geometric distortions, while current 3D methods often struggle to resolve distinct nematic fields within curved or multilayer structures. Here, we introduce NEMO, a modular Python framework for the depth-resolved quantification of tangential nematic order and surface morphology. By reconstructing biological surfaces as triangulated meshes, NEMO projects curved intensity layers, extracts local nematic directors, and computes locally averaged nematic tensors within the tangent plane. The pipeline identifies topological defects and computes their topological charge by accounting for the Gaussian curvature of the underlying surface. Furthermore, NEMO quantifies tissue morphology through inter-surface distance and surface-fitted estimates of Gaussian and mean curvatures. We show the capacities of this framework using a synthetic nematic film on a vesicle and experimental actin organisation in Hydra. By combining customisable projections with surface-constrained analysis, NEMO provides a unified framework for quantifying the interplay between orientational order and geometry across scales.

To elucidate the physical mechanism of turbulence attenuation by polymers at each scale, we conduct direct numerical simulations of homogeneous isotropic turbulence in dilute polymer solutions. We model polymers as FENE dumbbells and simulate them using Brownian dynamics. By visualising the hierarchical structures of coherent vortices, we demonstrate that as the Weissenberg number increases, polymers progressively suppress vortices from smaller to larger scales, attenuating their turbulent energy. While inspired by Lumley's theory, we propose a novel timescale-based framework for analysing this attenuation process using the scale decomposition. We define a scale-dependent Weissenberg number, $\mathrm{Wi}_{\mathrm{sd}}(k)$, as the ratio of the polymer relaxation time to the turnover time of multiscale vortices at each wave-number. We reveal that when expressed in terms of $\mathrm{Wi}_{\mathrm{sd}}(k)$, the energy attenuation rate at each scale collapses onto a single curve that rises at $\mathrm{Wi}_{\mathrm{sd}}(k) \gtrsim 1$, proving that $\mathrm{Wi}_{\mathrm{sd}}(k)$ successfully describes both the onset and the degree of turbulence attenuation at any given scale $k^{-1}$. Furthermore, the scale decomposition uncovers that polymers preferentially align with the turbulent stretching direction at the scale satisfying $\mathrm{Wi}_{\mathrm{sd}}(k) \approx 1$. Based on these results, we establish a physical picture of the polymer–turbulence interaction and explicitly link it to the statistics in turbulence attenuated by polymers.

Pressure and concentration profiles from non-equilibrium molecular dynamics (NEMD) simulations are often used to infer water transport mechanisms in dense and swollen polymer membranes. However, the mechanical restraints needed to stabilize simulated membranes can alter these profiles and their interpretation. Here, we test whether restraint-induced differences in pressure and water concentration profiles are accompanied by changes in molecular water dynamics. Crosslinked poly(ethylene glycol) diacrylate (PEGDA) membranes were simulated using three support strategies: a graphene support lattice, frozen membrane atoms near the permeate interface, and homogeneously distributed frozen membrane atoms. The restraints produced markedly different profiles, ranging from solution-diffusion-like to pore-flow-like, while overall water fluxes remained comparable. Molecular water dynamics, however, changed little. Interfacial exchange was strongly bidirectional and far exceeded the net permeation flux, membrane water diffusivities were similar, and complete crossings occurred in both directions. Local water associations were short-lived, and directional velocity correlations decayed rapidly with time and distance. Thus, substantially different pressure and concentration profiles can arise despite similar molecular water dynamics. Such profiles alone are therefore insufficient to identify transport mechanisms in mechanically restrained NEMD simulations. In PEGDA, water motion is dominated by stochastic diffusion with a small net directional bias.

As a simple model of interacting systems of excitable degrees of freedom, we consider a threshold contact process on various lattices and networks, in which a successful activation event requires the presence of more than one active neighbors. We show by combining numerical simulations and a phenomenological theory that, in the two-phase coexistence region and for a sufficiently low initial activity, a slower-than-exponential temporal decay of the global density emerges, caused by the spontaneous formation of slowly vanishing and non-communicating clusters of activity. This slow-decay phenomenon is found to appear generally for regular lattices and also for finite-dimensional random lattices such as the Voronoi-Delaunay network. However, the slow-decay is impeded by small-world property, as demonstrated by simulations on random-regular networks. In the case of a power-law decay of the order parameter, which is valid among others on two-dimensional regular lattices, our phenomenological theory points out that the decaying state is stable against unbounded nucleation only if the decay exponent exceeds $1/2$. Besides the well-known Griffiths effects of quenched random systems, this slow-decay phenomenon rooted in the threshold condition provides an alternative mechanism of off-critical but scale-free dynamics, occurring also in the absence of disorder.

We propose a chiral valence-bond solid (VBS) in which spin-singlet bond order itself spontaneously acquires handedness without magnetic order. Using a spin-lattice model on the diamond lattice, we demonstrate two enantiomorphic VBS states. In the presence of anisotropic spin interactions, this emergent handedness is inherited by chiral triplons with spin-split bands and spin textures that reverse between the two enantiomers. These textures generate a temperature-gradient-induced net spin response whose sign is set by the VBS handedness. The imaginary off-diagonal components of the dynamical spin structure factor encode the triplon polarization and change sign between the two enantiomers, enabling direct detection of chiral triplons and the selected handedness by polarized inelastic neutron scattering. Our results establish a direct connection between spontaneous chirality and magnetic excitations, opening avenues for exploring the interplay between quantum magnetism and chiral physics.