Papers

Score-based generative models generate new samples by integrating a time-dependent drift that carries Gaussian noise onto the target distribution. In practice this drift is modeled by a neural network, trained on a loss integrated over time $t$ with a weighting schedule $w(t)$. Along the backward dynamics, and for multi-modal distributions, trajectories commit to modes of the target within a narrow time window, the speciation time. In this work, focusing on high-dimensional data, we decompose the integrated loss into its single-time contributions and analyze each at fixed signal-to-noise ratio $\Lambda(t)$: we show that $\Lambda(t)$ sets the rate at which each feature of a multimodal target - the mode directions and their relative weights - is acquired during training. Crucially, at high $\Lambda(t)$ all mode directions are acquired together, on a single timescale insensitive to their amplitudes, while the relative weights are not learned at all. Only near the speciation time, where $\Lambda(t)$ becomes of order one, do all features become learnable, each on its own timescale: the weights are acquired jointly with the directions, and the directions at rates set by their relative amplitudes. For models trained on time-integrated objectives, the learning dynamics is then governed by how much of the weighting effectively sits near the speciation time, which provides insights on $w(t)$ design choices. These results follow from an exact high-dimensional analysis of the training dynamics of unbalanced and hierarchical Gaussian mixtures. Numerical experiments on image and human genome haplotype generation recover the predicted hierarchy of learning timescales in more complex settings.

In this study, we numerically investigate how interparticle attraction affects stress transmission, torque organization, and particle rotation in a two-dimensional frictional granular material. Although the attraction is a central force and exerts no direct torque on the particles, it strongly modifies the contact network and particle rotation. Attraction produces a low-rate stress state and selects the high-stress state near the shear-thickening regime of the dry system, while leaving the high-rate thickened state almost unchanged. By decomposing the shear stress, we find that the direct attractive contribution accounts for only a fraction of the total stress, while the repulsive contribution is strongly enhanced. Attraction increases the coordination number and torque amplitude and can reverse the local torque-sign correlation. At low packing fractions and intermediate shear rates, a stress-collapse state emerges with strongly suppressed torque and rotation despite a finite contact network. These results show that attraction controls macroscopic rheology through reorganization of the frictional contact network.

The complex spacing ratio is the complex displacement from a reference eigenvalue to its nearest neighbor divided by the corresponding displacement to its next-to-nearest neighbor. Its statistics provide a useful diagnostic of spectral correlations and nonintegrability in open quantum systems. Here, starting from the exact joint eigenvalue probability densities, we derive finite-$N$ complex-spacing-ratio distributions for the Gaussian ensembles of non-Hermitian random matrices in classes AI$^{\dag}$ and AII$^{\dag}$, realized by complex symmetric and complex self-dual random matrices, respectively. In class AII$^{\dag}$, we obtain an exact algebraic expression for arbitrary $N$ and explicitly evaluate the distributions and representative moments for $N=3, 4, 5, 6$. In class AI$^{\dag}$, although the joint density retains a noncompact integral over nonunitary eigenvector degrees of freedom, we analytically derive a normalized one-dimensional integral representation for $N=3$ and determine the asymptotic behavior, including a logarithmic correction to the cubic level repulsion and a nonanalytic contribution to the angular density. We further confirm these analytical results through direct numerical diagonalization of non-Hermitian random matrices.

I briefly overview the original formulation of the t-J model starting from Hubbard model, as well as stress its unique features, i.e., advantages and shortcomings when discussing its physical properties. Particular emphasis is put on a brief characterization of connection between magnetism, unconventional superconductivity, and the Mott-Hubbard localization of the correlated carriers in a narrow band. In the second part I summarize the model generalization to the three–orbital situation. The main purpose is to list some basic features of the physics associated with t–J model.

The critical current density ($J_c$) of V-Ti alloy superconductors is strongly influenced by the size and distribution of microstructural defects that pin magnetic flux lines. In this work, the effect of successive cold working and annealing (SCA) at 550{\deg}C on the microstructure, superconducting properties, and flux-pinning behaviour of the V$_{0.59}$Ti$_{0.40}$Ce$_{0.01}$ alloy is investigated and compared with the previously reported SCA at 450 and 650{\deg}C. During SCA at 550{\deg}C, the superconducting transition temperature increases gradually with successive processing steps. The first annealing after cold rolling to 50% thickness produces a significant enhancement in $J_c$ over the measured field range, whereas subsequent SCA cycles result in only marginal changes. The $J_c$ remains relatively weakly dependent on magnetic field over wide magnetic-field range, and the final cold-worked sample exhibits a finite $J_c$ up to 8.5 T. Pinning force density analysis shows that grain boundaries dominate flux pinning in low magnetic fields, whereas dislocations and $\beta$-$\alpha'$ interfaces become the dominant pinning centres in higher fields. Comparison of the different SCA temperatures shows that 650{\deg}C provides the highest low-field $J_c$, whereas 450{\deg}C gives the best high-field performance. In contrast, SCA at 550{\deg}C provides most balanced field dependence and the largest enhancement in $J_c$ relative to the corresponding as-cast alloy. Although the highest absolute $J_c$ in the high-field regime is achieved after the third SCA cycle at 450{\deg}C, a comparable value is obtained after only the first annealing at 550{\deg}C. These results demonstrate that the intermediate annealing temperature of 550{\deg}C provides an effective balance between defect generation, phase evolution, and recovery, resulting in enhanced flux pinning over a wide magnetic-field range.

An asymptotic analysis of the Landau–de Gennes framework is performed to compute higher-order corrections to the Oseen–Frank limit in a bounded three-dimensional domain under appropriately scaled surface anchoring energy. A systematic decomposition of the $\mathbf{Q}$-tensor into three mutually orthogonal subspaces-the uniaxial scalar, geometric tilt vector, and transverse anisotropy tensor-reveals that the leading $\mathcal{O}(\varepsilon)$ correction to the Oseen–Frank director field $\mathbf{n}_0(\mathbf{x})$ is dominated by a non-vanishing tilt field $\mathbf{p}_1(\mathbf{x})$, where $\varepsilon$ represents the ratio of the nematic coherence length to the characteristic domain size. This macroscopic variation constitutes a soft mode released from the boundary once the surface anchoring energy is retained at its physical scaling rather than driven to an infinite strength. We show that this tilt field is governed by the linear Jacobi equation, $\mathcal{J}_{\mathbf{n}_0}(\mathbf{p}_1)=\mathbf{0}$, subject to a non-trivial, anchoring-driven Dirichlet boundary condition, where $\mathcal{J}_{\mathbf{n}_0}$ is the on-shell Jacobi operator of the harmonic map $\mathbf{n}_0$ on $\mathbb{S}^2$. The two fields are accompanied at $\mathcal{O}(\varepsilon^2)$ by an off-shell correction to both the uniaxial scalar and the transverse anisotropy tensor, passively induced by the elastic non-uniformity $(\nabla\mathbf{n}_0\neq\mathbf{0})$ and the boundary-driven tilt $(\mathbf{p}_1\neq\mathbf{0})$. Through $\mathcal{O}(\varepsilon^2)$, the tilt enters the energy only through surface terms, not the bulk, providing a pathway for the system to lower its energy . Under the conventional benchmark of rigid Dirichlet conditions, this response is annihilated outright, demonstrating that corrections built upon infinite energy barriers obscure the underlying physics of anchoring-driven tilt modes.

In the search for topological states in bilayer graphene, capacitance measurement methods are widely utilized in bridge type readouts or source-drain reflectometry setups. In this paper we demonstrate an alternative readout method based on gate reflectometry. We probe the capacitance of a BLG flake encapsulated between hBN and WSe$_2$ through a lumped-element LC resonator coupled to the top gate electrode of the heterostructure. The microwave readout reliably tracks the opening of a displacement field-induced band gap in the device. Compared to simultaneous DC transport measurements, the RF signal proves to be less affected by the percolating transport channels caused by sample disorder. Furthermore, we use the gate based readout to identify a small-angle alignment between the hBN and BLG flake. From the fixed frequency microwave readout, we extract the device capacitance change between the insulating and metallic state of the bilayer and utilize a comprehensive capacitance network model to explain its origin. Finally, we propose an advanced, multiplexed double-resonator readout scheme capable of simultaneously measuring top and bottom gate capacitances to extract the layer polarizability of the system. This work establishes gate reflectometry as a highly scalable and powerful methodology for exploring topological phases and internal charge dynamics in van der Waals heterostructures.

Achieving high-quality superconducting thin films at low temperatures is a central challenge for scalable quantum device integration and Complementary Metal-Oxide-Semiconductor (CMOS)-compatible fabrication. Here, we demonstrate a room-temperature magnetron sputtering approach for synthesizing niobium nitride (NbN) thin films using a novel energy-selective ion source that enables independent control of ion energy and ion flux. This capability provides a powerful route to precisely tailor surface kinetics and crystallization pathways, overcoming longstanding limitations in stabilizing high-quality NbN at reduced temperatures. The resulting films were characterized by superconducting transport measurements, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Compared with conventional reactive sputtering, ion beam-assisted growth yields a substantial narrowing of the transition width at the superconducting temperature, indicating improved phase purity and electronic homogeneity. Furthermore, this work introduces energy-selective ion control as a general, non-equilibrium route to stabilize metastable superconducting phases at low temperatures, offering a new design paradigm for thin-film quantum materials.

Motivated by biological systems and my previous studies of quorum sensing with density-enhanced motility, I study a model of density-enhanced size and motility, in which both particle size and motility increase when the local density (over a distance larger than particle diameter) exceeds the global density. The emergent structures along different size ratios are spots, holes, bands and labyrinths controlled by several distinct observations. First, the characteristic pattern length scale is controlled by the sensing radius and remains approximately independent of the size ratio. Second, the total area occupied by the particles decreases with increasing size ratio. Third, the active fraction barely depends on the size ratio. These results demonstrate how both particle size and motility can couple microscopic regulation to large-scale pattern formation. I conclude by discussing possible extensions of the model.

A fundamental issue with first principles electronic structure calculation is the requirement for magnetic initialisations, which are usually derived from experimental results. In this paper, we present a new and computationally inexpensive method to predict magnetic structures from first principles, based upon symmetry analysis and a non-magnetic band structure only. We demonstrate that this method of creating initialisations successfully reproduces the known magnetic ground state for a wide class of magnetic materials, including ferromagnetic BCC Fe, antiferromagnetic L1$_0$ PtMn, and frustrated antiferromagnetic L1$_2$ IrMn$_3$, while also predicting non-magnetic materials to remain non-magnetic.

Confined aqueous electrolytes exhibit strong deviations from bulk behaviour, but it remains unclear which changes arise from genuine confinement-induced modification and which merely reflect the influence of interfaces. Here, we introduce an interfacial deficit-length framework, capable of decomposing density, diffusivity, and conductivity of confined electrolyte solutions into interfacial and confinement contributions. By applying the framework to molecular dynamics simulations of aqueous alkali halides in planar graphene nanoslits coupled to bulk reservoirs at variable electrolyte concentration, we show that genuine confinement effects emerge only for slit heights $H \lesssim 1$ nm; for larger H, deviations from bulk behaviour are quantitatively captured by interfacial deficit lengths. These deficit lengths are strongly ion-specific and generally positive for water and salt densities as well as for conductivities, meaning that graphene interfaces reduce the values of these observables, while diffusivity deficit lengths tend to be negative, corresponding to larger slit self-diffusivities relative to the corresponding bulk reference. Our deficit-length framework is applicable to any observable from experiments or simulations on nanoconfined electrolytes and predicts confined electrolyte properties for variable slit height H and reservoir electrolyte concentrations.

Testing the ergodicity hypothesis through experimentation in real systems is of crucial importance as it challenges a fundamental assumption underlying a wide range of theoretical models of physical and complex systems. High-calibre experiments can demonstrate whether, when and how a real system explores all of its possible states, and serve as a crucial conduit between abstract theoretical frameworks and tangible real-world applications. This approach is intended to guarantee that our descriptions of complex systems remain both physically meaningful and technologically relevant, thereby facilitating a more nuanced and comprehensive understanding. The development of a novel light scattering experiment has enabled us the direct measurement of the full distribution of fluctuations in the particle concentration in colloidal model systems and thus the direct determination of the probability distribution. This, in turn, facilitates the experimental verification of the ergodic hypothesis and the quantification of ergodicity breaking as a function of metastability.

Recent years have seen intense research on heavy fermion superconductivity, inspired by the discovery of multiple superconducting phases in UTe$_\text{2}$ and CeRh$_\text{2}$As$_\text{2}$. In the latter material, two superconducting phases observed under applied magnetic field oriented along the crystallographic $\textit{c}$ direction are associated with local inversion symmetry breaking. To advance understanding of these phenomena, it is highly desirable to find further examples of heavy fermion superconductivity in materials with locally non-centrosymmetric structure. We have succeeded in this quest, by growing single crystals of the CaBe$_\text{2}$Ge$_\text{2}$ isomorph of CeNi$_\text{2}$As$_\text{2}$. The resulting superconductivity brings more than we had foreseen. In addition to providing the opportunity to compare and contrast with that of CeRh$_\text{2}$As$_\text{2}$, the condensation occurs from an incoherent normal state quantitatively similar to that of UBe$_\text{13}$. Our findings therefore raise profound questions not just about superconductivity in the locally non-centrosymmetric structures, but about unconventional superconductivity itself.

Even-layer topological antiferromagnetic thin films such as MnBi$_2$Te$_4$ exhibit an unconventional layer Hall effect (LHE) arising from a layer-locked Berry curvature. This effect manifests as a layer-polarized anomalous Hall effect that can be controlled by a vertical displacement field. However, achieving a quantized version of the LHE remains experimentally challenging. In this work, we propose that moiré engineering, using an electrostatic superlattice potential from control layers, can realize the quantum layer Hall effect (QLHE). Specifically, by placing moiré control layers in close proximity to the surfaces of a MnBi$_2$Te$_4$ thin film without breaking $PT$ symmetry, the resulting system exhibits a vanishing net Hall conductance but a quantized layer Hall conductance of $e^2/h$. A weak gate electric field then breaks $PT$ symmetry and drives the system into a layer-polarized quantum anomalous Hall (QAH) phase. Furthermore, when a single control layer is introduced on only one surface, the layer-polarized QAH emerges even in the absence of an external electric field. We identify the microscopic origin of the QLHE as an emergent layer-$U(1)$ gauge field generated by the scalar moiré potential, which in turn produces opposite periodic pseudomagnetic fields on the top and bottom layers. Our work provides a feasible pathway toward realizing the QLHE in antiferromagnetic thin films.

The Efimov effect manifests discrete scale invariance through a geometric series of three-body bound states. Analogous discrete scale symmetry has been observed in the Efimovian expansion of scale-invariant strongly interacting Fermi gases. However, it is unclear whether strong correlation is necessary. Here we investigate the spontaneous breaking of continuous scale invariance in a simple driven-dissipative harmonic oscillator whose driving and dissipation parameters scale as $1/t$. By transforming to logarithmic time, we show that the dynamics is governed by a non-Hermitian superoperator whose spectral decomposition reveals the emergence of a pair of eigenmodes with opposite real parts and equal imaginary parts. This signals the spontaneous breaking of continuous scale invariance and gives rise to Efimovian-like oscillations: log-periodic decay oscillations obeying discrete scaling laws. The onset of oscillations coincides with a PT-symmetry breaking transition in logarithmic time. The Efimovian-like oscillations are robust against weak nonlinear interactions and perturbations. Our work implies that the spontaneous breaking of continuous temporal scale symmetry and the emergence of Efimovian-like dynamics can even be observed in a simple driven-dissipative system without many-body interactions.

Accurate prediction of avalanche motion is essential for hazard assessment in mountainous terrain. This study develops and evaluates a physics-informed neural network (PINN) framework for the Savage-Hutter model of depth-averaged granular flow, progressing from 1D analytical verification to 2D experimental validation. First, three 1D problems of increasing complexity were verified against the analytical solution: height prediction with prescribed velocity, velocity prediction with prescribed height, and coupled prediction of both fields using the conservative formulation. The decoupled tests accurately reconstructed the spatio-temporal evolution of each field when the other was prescribed. The coupled formulation learned both fields without prescribed data, achieving mean height and velocity RMSEs of 0.043 and 0.079 in non-dimensional units. A hyperparameter sensitivity study evaluated the effects of network depth, width, collocation density, learning rate, and epochs. The framework was then extended to 2D and validated against laboratory experiments of a cylindrical granular pile collapsing on an inclined plane, with TITAN2D providing numerical comparisons. Purely physics-based training converged to the trivial zero solution; augmenting the loss with 10 sparse training points from final deposit profiles produced a physics-informed, data-assisted hybrid framework. Peak flow depth, depth-averaged velocity, RMSE, and wetted-area IoU evaluated global and local agreement. Global height RMSE ranged from 2.7 to 6.7 mm across four experimental cases, while mean wetted-area IoU ranged from 69 to 81 %, demonstrating consistent performance across variations in pile mass and slope angle.

We develop a rational-function approximation for the structural properties of multicomponent fluids with narrow square-well and square-shoulder interactions, together with weakly nonadditive hard-sphere mixtures. The theory is obtained by reformulating the analytical Percus–Yevick solution for additive sticky hard-sphere mixtures so as to account for finite interaction widths, leading to a unified semianalytical framework for these classes of fluids. The approximation satisfies the exact low-density limit and preserves the continuity of the cavity functions; a simple local correction restores the continuity of their first derivatives. Comparison with Monte Carlo simulations for binary mixtures shows that the theory accurately describes both the radial distribution functions and their Fourier transforms for narrow wells and shoulders and for weak nonadditivity. The proposed formulation extends previous sticky-hard-sphere-based approaches while retaining their analytical simplicity.

We employ a projection operator technique to study the equilibrium phases and the non-equilibrium quench and ramp dynamics of ultracold bosons described by a two-dimensional (2D) Bose-Hubbard model coupled to a high-finesse cavity with competing local short-range and cavity-mediated long-range interactions. Our analysis relies on a systematic elimination of high-energy virtual hopping processes; this enables us to capture the effects of short-range quantum fluctuations on the phase diagram of the model while treating the cavity-induced long-range interaction within mean-field theory. We find that the phase boundaries between the superfluid (SF), supersolid (SS), charge-density-wave (CDW) and Mott insulating (MI) phases are significantly modified by the presence of these fluctuations. We use this approach to study the dynamics of bosons following a quench/ramp from the CDW to the SS and SF phases; our analysis indicates the presence of oscillatory dynamics characterized by a single frequency due to a quench which takes the system near the critical point. In contrast, for a quench deep inside the SF phase, the dynamics involves multiple frequencies. An explicit comparison with Gutzwiller mean-field theory shows the importance of quantum fluctuations in shaping such post-quench dynamics; this feature may be tested experimentally as we discuss. We also study the ramp dynamics of these bosons and identify a bound on the ramp rate above which the present method is expected to produce accurate results.

The O-band telecommunication spectral range combines minimal chromatic dispersion with low transmission loss, making it highly suitable for optical communications. Semiconductor telecom lasers utilizing low-dimensional active regions, such as quantum dots, offer low threshold power and high thermal stability. However, long-wavelength quantum dot emitters often suffer from thermal carrier escape through excited states when the energy separation between the ground and excited states is insufficient. Here we demonstrate the optimization of InAs quantum dot emitters grown on InP by molecular-beam epitaxy for O-band laser active regions. By optimizing the design for better carrier capture efficiency and tuning the emission wavelength to the O-band, we show ways of improving the carrier confinement. Absorption spectroscopy on the finalized structure confirms substantial energy separation between the quantum dot ground and excited states, effectively suppressing thermal carrier escape even at elevated temperatures. These results highlight critical design for improving carrier capture and retention in long-wavelength quantum dot lasers.

Interatomic potentials are central tools in the atomistic modeling of materials. The atomic cluster expansion (ACE) parameterizes such potentials from ab initio data, conventionally encoding the chemical degrees of freedom with a one-hot representation that yields chemically stratified models. The alternative chemical representations used in on-lattice configurational cluster expansions have not been assessed for interatomic potentials. Here we revisit the multicomponent ACE for an arbitrary chemical site basis. We then establish an exact analytical mapping between a fitted linear ACE and the average-atom potential that describes a perfectly random alloy. We benchmark potentials built on the occupational, Chebyshev, and conventional ACE bases against solute binding and vacancy formation energies in Mg-Nd, and against the mixing enthalpies of the Mo-Nb and Cr-W solid solutions. When training data are scarce, the occupational basis converges fastest and offers the best control over targeted material properties, while the conventional and Chebyshev bases face challenges in reproducing these properties. The occupational basis likewise yields the most reliable average-atom description of disordered alloy thermodynamics. In the large-data limit the three bases perform identically. The chemical basis is therefore a design choice that governs data efficiency. Its explicit treatment opens a route to average-atom potentials for the thermodynamic, mechanical, and kinetic properties of concentrated alloys.

A measure of correlations for statistical systems is advanced, called correlation index. The measure is general, being applicable to quantum and classical, equilibrium and nonequilibrium statistical systems. After formulating the general notion of correlation indices for arbitrary trace-class operators, the calculation of the correlation indices are illustrated by several examples of density operators and reduced density matrices. The computation of the correlation indices for equilibrium systems is exemplified for bosonic systems with the Bose-Einstein condensate, superconducting systems, and for spin systems. Correlation indices for nonequilibrium systems are considered for nonlinear dynamics of spin and pseudospin systems.

In this work, a comprehensive thermodynamic description of the formation of phases in amorphous SiOxNy (0 <= x <= 2, 0 <= y <= 4/3) films as a function of the film chemical composition and fabrication temperature is presented. Two possible phase states, namely homogeneous single-phase Si oxynitride and two-phase mixture of Si oxide and Si nitride phases, are analyzed in terms of the lowest values of the Gibbs free energy. The characters of the modification of the phase composition upon changing the SiOxNy stoichiometry indices and fabrication temperature are determined. Moreover, characteristic features of the chemical composition of the Si oxide and Si nitride phases in two-phase Si oxynitrides are revealed. Particular attention is given to the thermodynamic origin of the boundaries between different phase states of the SiOxNy films and to determining the critical stoichiometry values separating them. A comprehensive phase diagram indicating single- and two-phase SiOxNy regions as functions of the fabrication temperature is constructed. The peculiarities of the transitions between different SiOxNy phase states, along with underlying mechanisms, are discussed with reference to this phase diagram. The obtained results extend our understanding of the fundamental properties of Si oxynitride films and their dependence on the film fabrication conditions, and may be used for tailoring SiOxNy characteristics for practical applications.

We study the localization properties of 1D and 2D tight-binding models with power-law distributed couplings by comparing the spectrum and the localization properties of the eigenmodes of the Laplacian and the adjacency matrix, using numerical diagonalization of these matrices for different system sizes and connectivities. These two matrices are relevant for different types of dynamical processes. While all eigenmodes of the adjacency matrix are localized for sufficiently large system sizes, the Laplacian matrix always leads to a small proportion of system-spanning modes due to a conservation law, and therefore to power-law tails in the probability distribution of the participation ratio and its relation to the eigenvalues. In one dimension, the exponent of these power laws change continuously with the exponent that characterizes the distribution of couplings. In two dimensions, the modes with the largest relaxation times change from system-spanning to localized when the exponent of the distribution of couplings becomes larger than 0.75. We provide phenomenological explanations for all these findings.

The Cox-Merz rule is an empirical relation between the magnitude of the complex viscosity, $\lvert\eta^*(\omega)\rvert$, obtained from linear viscoelasticity, and the steady-shear viscosity, $\eta(\dot{\gamma})$. In this study, we performed molecular dynamics simulations of coarse-grained polymer melts using the Kremer-Grest model and systematically examined the validity of the Cox-Merz rule as a function of chain length and chain stiffness for linear and ring polymers. For short chains and, more generally, for flexible chains, $\lvert\eta^*(\omega)\rvert$ and $\eta(\dot{\gamma})$ show good agreement at corresponding values of angular frequency $\omega$ and shear rate $\dot{\gamma}$. For linear polymers, however, the discrepancy between the two viscosities becomes increasingly pronounced with increasing chain length and chain stiffness, with $\lvert\eta^*(\omega)\rvert$ exceeding $\eta(\dot{\gamma})$ at high corresponding values of $\omega$ and $\dot{\gamma}$. This deviation is associated with the pronounced nonlinear response under strong steady shear, where flow-induced chain extension and alignment can modify the entanglement constraints that govern relaxation near equilibrium. In contrast, ring polymers retain substantially better agreement between $\lvert\eta^*(\omega)\rvert$ and $\eta(\dot{\gamma})$ with increasing chain length and stiffness within the range examined here, indicating a weaker breakdown of the Cox-Merz rule. These results demonstrate that the applicability of the Cox-Merz rule depends strongly on chain length, chain stiffness, and molecular architecture. When the molecular response under steady shear deviates substantially from the relaxation behavior characterized by linear viscoelasticity near equilibrium, the complex viscosity can no longer accurately predict the steady-shear viscosity, resulting in a pronounced breakdown of the Cox-Merz rule.

Helium dimer in its metastable triplet electronic state, He$_2(a~^3\Sigma_u^+)$, is a promising candidate for direct laser cooling and precision measurements. Interactions and collisions involving He$_2(a~^3\Sigma_u^+)$ remain unexplored in ultracold and cold energy domains. Here, we present the first theoretical investigation of intermolecular interactions and collision dynamics of He$_2(a~^3\Sigma_u^+)$+Ne van der Waals complex. For the ground electronic state, $X~^3\mathrm{A}'$, we employ a spin-restricted coupled cluster method with single, double, and noniterative triple excitations. The resulting interaction potential exhibits an extremely shallow well with a depth of 4.612 cm$^{-1}$. We construct a three-dimensional vibrationally averaged potential energy surface. Using this surface, we perform full close-coupling calculations including fine-structure levels of He$_2(a~^3\Sigma_u^+)$ to investigate collisional excitation and quenching induced by Ne. We analyze the low-energy scattering dynamics and model resonant features associated with quasi-bound states supported by interaction potential. Propensity rule for fine-structure conserving transitions is established. We additionally consider He$_2$+Ar collisions and compare their energy dependence and resonance structure with those of He$_2$+Ne. The He$_2$+Ar system exhibits a richer resonance structure, highlighting the sensitivity of low-energy scattering to interaction potential and reduced mass. Calculated PES and scattering properties provide a reliable benchmark for description of He$_2$+Ne van der Waals complex and may be useful for interpretation of future experimental spectra and collision measurements.

Topological magnetization textures play a central role in modern magnetism. For many applications, spin textures with different topological charges $Q$ in the same system are particularly attractive. Although the coexistence of skyrmions and antiskyrmions ($|Q| = 1$) has been reported in inversion-symmetric magnets, extending this to high-$Q$ ($|Q| > 1$) textures with arbitrary charge remains elusive. Here, using an atomistic spin model parameterized from first-principles calculations, we predict the emergence of sub-20 nm high-$Q$ textures in Janus monolayers, van der Waals magnets of growing interest. We explore skyrmion and antiskyrmion rings as well as skyrmion bags with $|Q|$ up to 5, and characterize their nucleation mechanisms, thermal stability, and collapse pathways. We find that higher-order spin interactions (HOI), which extend the conventional bilinear-exchange Hamiltonian, are essential for stabilizing these high-$Q$ spin textures. The rings remain thermally stable at zero magnetic field. HOI substantially enhance their energy barriers while leaving their size nearly unchanged and stabilize them even in the absence of Dzyaloshinskii-Moriya interaction. Skyrmion bags, in contrast, nucleate only in the presence of HOI. In particular, the four-spin three-site interaction is the key ingredient preventing high-$Q$ textures from collapsing into the ferromagnetic state. Finally, we identify previously unreported parity-dependent collapse mechanisms for high-$Q$ textures. Our results establish HOI as an overlooked mechanism for high-$Q$ nucleation.

Recent high-resolution (500 bp) Hi-C experiments reported contact maps with unusual patterns around highly expressed bacterial DNA loci. These patterns, described as arched stripes and bundled domains, extend over nearly 100 kbp. We performed Brownian Dynamics simulations with a specially designed coarse-grained model to rationalize these findings. The main feature of the model is that it takes explicitly into account the waves of positive (respectively, negative) supercoiling generated by the translocating polymerase downstream (respectively, upstream) of its position. Contact maps computed from the simulations also display the arched stripe and bundled domain patterns for above-threshold values of the rate of twist injection. Computed DNA conformations indicate that these patterns reflect an extraordinarily entangled DNA geometry, which involves both plectonemic and toroidal supercoiling, with some DNA segments experiencing both of them simultaneously. Moreover, DNA segments located on each side of the polymerase systematically wind around tracts located on the other side, which is a purely out-of-equilibrium effect driven by the continuous injection of twist. The present work therefore reveals that repeated transcription of a DNA locus systematically brings into contact DNA segments separated by several tens of kbp, which may eventually contribute to allosteric modulation and long-range communication.

Collective flows in epithelial tissues contain a geometric backbone of vortical interfaces whose statistics exhibit hallmarks of critical percolation and conformal invariance. Yet how fundamental cellular processes govern the breakdown of such symmetry-rich flow geometry remains unclear. Here we show that cell division plays a central physical role in regulating this universal flow organization by controlling both the geometric and mechanical flexibility of the cell-cell network. Using pharmacological perturbations, we find that when proliferation is suppressed through two independent interventions, coherent flows persist but neighbor exchanges decline and conformally invariant geometry is lost. Blocking apoptosis does not affect universality, isolating division as the key control. A vertex model with tunable division quantitatively reproduces these effects and restores conformal invariance when division is allowed. We further trace this effect to changes in both the geometric and mechanical organization of the cell layer: Divisions act as intermittent topological renewals that loosen constraints, preserving the network's flexibility and capacity to rearrange across scales. Thus, beyond its canonical role in growth, cell division acts as a structural and mechanical regulator of collective self-organization. These findings establish a direct connection between fundamental biological processes and emergent physical symmetries.

Digital quantum simulation (DQS) is one of the most promising applications of quantum computing. Trotterised DQS models quantum dynamics by decomposing the evolution into a sequence of gate-based Trotter steps. Using larger Trotter steps reduces the required gate count, but it is now understood that the Trotterisation step size cannot be increased beyond a certain threshold value, beyond which there is a sudden breakdown in simulation accuracy, due to the onset of quantum chaos. To date, this behaviour has only been studied for closed systems not subjected to the environmental noise and decoherence to which real-world quantum computers are highly sensitive. In this work, we study a range of experimentally relevant open-system quantum simulator models and show that Trotterisation thresholds persist even when open-system effects are included, even in the long-time, steady-state limit, once all coherence has been lost. We show that open DQS can accurately reproduce the dynamics of open target systems prior to the threshold, but still exhibits a sudden performance breakdown beyond it. We introduce new, statistical techniques to rigorously characterise the onset of quantum chaos beyond the Trotterisation threshold for both approximately unitary and genuine dissipative quantum chaos, based on random matrix theory (RMT), building on techniques developed for closed systems. Finally, we demonstrate that dissipative quantum chaos emerges when the dissipation is in balance with the presence of underlying unitary quantum chaos; the dissipation must be strong enough to induce genuinely dissipative behaviour, yet not so strong as to suppress the underlying chaotic structure.

Topological signals are dynamical variables supported on higher-order structures such as simplicial or cell complexes. In this work, we investigate the impact of time-delayed interactions on the emergence of global synchronization of topological oscillators, with application to the Stuart-Landau system. We first examine the case where signals are supported on simplexes, or cells, of a given dimension and coupled through the Hodge-Laplace matrix. We derive the Master Stability Function and we prove that for suitable discrete delay values, the stability of the synchronous solution becomes analytically tractable and can be solved by using the Lambert W-function. This analysis yields explicit spectral conditions for Global Topological Synchronization to emerge and shows that admissible delays may either promote or suppress synchronization. We then study delayed interactions between signals supported on simplexes, or cells, of different dimensions coupled by the Dirac operator. Under analogous admissible time delays the variational problem, still related to the Master Stability Function, can again be simplified, however in this case we prove that Global Topological Dirac Synchronization cannot emerge. Numerical simulations on simplicial and cell complexes corroborate and complement these findings.