Papers

Self-sustained oscillators produce stable periodic motion robust to dissipation. Such motion is usually achieved by work fed back into the oscillator, but its performance is often limited by frequency-dependent operation. Here we propose a scheme for self-sustained vibrations without external feedback. We consider a movable Cooper-pair box attached to the free end of a voltage-biased normal-metal pillar. The Cooper-pair box carries an Andreev current subject to an electric field applied perpendicular to the current. In the adiabatic limit, where the Cooper-pair box state follows its motion, vibrational instability occurs, pumped by inelastic Andreev tunneling. Nonlinearity of the Josephson coupling saturates the vibrational amplitude, resulting in two-dimensional self-vibrations. We discuss the advantage of this adiabatic scheme in comparison with feedback-induced self-oscillation.

We investigate the structural, electronic, and superconducting properties of a hexagonal BP3 monolayer using first-principles calculations combined with anisotropic Migdal-Eliashberg theory. The optimized structure exhibits a stable, slightly buckled configuration, as confirmed by phonon dispersion analysis and ab initio molecular dynamics simulations. The phonon spectrum indicates high-frequency vibrational modes associated with B-P bonding. Electronic band structure calculations reveal a multiband metallic state, with states near the Fermi level predominantly derived from pz orbitals of both boron and phosphorus atoms, forming two distinct Fermi surface sheets. The electron-phonon coupling is relatively strong, with a total coupling constant of lambda = 1.59, dominated by low- and intermediate-frequency phonon modes. Solving the anisotropic Migdal-Eliashberg equations yields a superconducting transition temperature of Tc = 9.7 K. The superconducting state is characterized by a nodeless but anisotropic gap structure, exhibiting two distinct gap values of approximately 2.25 and 1.74 meV associated with different Fermi surface sheets. These results identify the BP3 monolayer as a strongly coupled, multiband two-dimensional superconductor and provide insight into the role of orbital hybridization in electron-phonon-mediated superconductivity in low-dimensional systems.

Magnetism in transition-metal systems emerges from exchange interactions that depend sensitively on carrier density. Yet leveraging this sensitivity to deliberately engineer exchange frustration and associated topological spin textures remains largely unexplored. Here, combining first-principles calculations with atomistic Monte Carlo simulations, we demonstrate that ferroelectric polarization enables electrostatic control of exchange frustration in the itinerant ferromagnet SrRuO3. We show that electrostatic hole doping renormalizes competing exchange interactions, driving SrRuO3 away from its bulk ferromagnetic ground state toward frustrated regimes, whereas electron doping largely preserves ferromagnetism. At BaTiO3/SrRuO3 interfaces, polarization-induced charge depletion modulates layer dependent exchange couplings, enhancing competition among J1, J2 and J3. The resulting exchange frustration stabilizes a sequence of magnetic phases as a function of thickness and applied magnetic field, including stripe and spiral states, topological meron and bimeron textures, and diverse skyrmionic objects. A minimal spin model identifies exchange frustration as the primary control parameter governing these crossovers, with magnetic anisotropy, Dzyaloshinskii-Moriya interaction, and external field selecting the emergent topology. Our results establish electrostatic doping as a route to engineer frustrated and topological magnetism in itinerant oxide metals.

Many biophysical processes begin when the fastest searcher finds a target out of many random searchers, which is called an extreme or fastest first passage time (fFPT). In some models, (i) the fFPT vanishes logarithmically as the number of searchers grows, and (ii) the fFPT can be faster for subdiffusive search compared to normal diffusion. Though mathematically rigorous, the relevance of (i) and (ii) to actual physical systems is suspect since their derivations involve searchers which move with unbounded speed. Indeed, we previously proved that the fFPT for searchers with bounded speed converges exponentially to a strictly positive minimal search time as the number of searchers grows. In this paper, we study fFPTs for a broad class of anomalous and normal diffusion models with bounded or unbounded speed. These models include scaled Brownian motion, Riemann-Liouville fractional Brownian motion, and fractional Brownian motion. For all of these models, we show that the fFPT decays logarithmically in the number of searchers and that subdiffusion can be faster than normal diffusion (we further show that superdiffusion can be slower than normal diffusion). In this sense, features (i) and (ii) are rather universal. On the other hand, we show that the parameter regimes in which (i) and (ii) are valid depend on the particulars of the individual model, and thus ambiguities remain in the relevance of these features to specific physical systems.

We develop a nonlocal minimal-coupling theory of structured-light dichroism. Optical absorption is written as a bilinear functional of the incident vector potential and the nonlocal current-response kernel, retaining the spatial structure of optical vortex beams and other inhomogeneous fields. Circular dichroism, helical dichroism, and helical circular dichroism are treated as distinct reversal channels that project different reversal-odd components of the same microscopic response. The resulting signal is resolved into symmetry, tensor, and angular-mode sectors. Single azimuthal-mode fields probe diagonal OAM-channel components, whereas mixed modes access off-diagonal mode-space coherence through interference between different OAM channels. The relative polarization of the mixed field further selects scalar, axial-vector, or rank-2 tensor sectors of the response. This decomposition gives selection rules for high-symmetry systems and a diagnostic scheme for low-symmetry nanophotonic structures, finite systems, and extended materials, where several angular-channel responses may coexist. It also connects the nonlocal current-response formulation to local-gradient descriptions based on spatial dispersion, optical chirality, and tensorial anisotropy.

Self-supervised representation learning is central to modern machine learning because it extracts structured latent features from unlabeled data and enables robust transfer across tasks and domains. However, it can suffer from representation collapse, a widely observed failure mode in which embeddings lose discriminative structure and distinct inputs become indistinguishable. To understand the mechanisms that drive collapse and the ingredients that prevent it, we introduce a minimal embedding-only model whose gradient-flow dynamics and fixed points can be analyzed in closed form, using a classification-representation setting as a concrete playground where collapse is directly quantified through the contraction of label-embedding geometry. We illustrate that the model does not collapse when the data are perfectly classifiable, while a small fraction of frustrated samples that cannot be classified consistently induces collapse through an additional slow time scale that follows the early performance gain. Within the same framework, we examine collapse prevention by adding a shared projection head and applying stop-gradient at the level of the training dynamics. We analyze the resulting fixed points and develop a dynamical mean-field style self-consistency description, showing that stop-gradient enables non-collapsed solutions and stabilizes finite class separation under frustration. We further verify empirically that the same qualitative dynamics and collapse-prevention effects appear in a linear teacher-student model, indicating that the minimal theory captures features that persist beyond the pure embedding setting.

Zero-vorticity contours in the collective flows of living cells obey Schramm-Loewner evolution with diffusivity $\kappa = 6$ and thus fall in the universality class of critical percolation. This observation is surprising because the underlying vorticity field has long-range correlations that, according to the Weinrib-Halperin criterion, should alter the universality class. Here we propose a spectral explanation for this apparent paradox in two-dimensional active nematic turbulence. The universal energy spectrum $E(q) \sim q^{-1}$ implies sign-field correlations whose decay exponent $a = 3/2$ matches the Weinrib-Halperin marginal threshold $2/\nu_0 = 3/2$ for two-dimensional percolation. At this marginal point the long-range correlations are irrelevant under renormalization, so the system flows to the uncorrelated percolation fixed point. Gaussian surrogate fields with the same spectrum confirm $a = 3/2$ to three significant figures, and left-passage analysis of their zero-vorticity interfaces yields $\kappa = 5.98 \pm 0.08$, consistent with SLE_6.

Distinguishing different subphases in the supercritical region is an important issue in statistical physics and condensed matter physics. Traditional approaches rely mainly on static thermodynamic response functions or equilibrium correlation functions, which are essentially limited to quasistatic processes. In this paper, we investigate the evolution behavior of a system after a rapid quench from the perspective of nonequilibrium dynamics within a holographic model. We find that, using the time at which inhomogeneous structures appear most rapidly, we can define a supercritical crossover curve based on the pure phase separation process. In addition, the uniform invasion phenomenon induced by topological defects persists in the supercritical region, and the invasion velocity exhibits a clear turning point as a function of the quench endpoint. This turning point can define another new nonequilibrium supercritical crossover line that simultaneously incorporates the effects of both symmetry breaking and phase separation. Unlike the classical Widom line or Frenkel line, these two new crossover lines contain both thermodynamic information and dynamical information, reflecting the dynamical nature of the supercritical region under nonequilibrium conditions. This work provides a novel nonequilibrium dynamical approach for characterizing supercritical subphases.

We develop a Melnikov framework for the Kuramoto Sivashinsky (KS) equation under weak deterministic and stochastic forcing. By treating KS as an infinite dimensional dynamical system, we derive a Melnikov functional that measures splitting of stable and unstable manifolds of a homoclinic orbit. Periodic forcing leads to phase dependent transverse intersections, while stochastic forcing produces random manifold splitting characterized by a variance determined by the adjoint solution. This provides a geometric mechanism linking invariant manifold theory to spatiotemporal chaos in dissipative partial differential equations.

Quantum mechanics owes much of its extraordinary success to a Hilbertian program of mathematical formalization. Yet, the formalism remains poorly aligned with the practical limitations of computations in finite dimensions and under finite accuracy. In this perspective, we argue that this mismatch points to the need for a new mathematical program: a rigorous constructive theory for effective descriptions to identify essential degrees of freedom. We propose an observation-centered point of view in which signals are treated as the primary objects of analysis, while wave functions and Hamiltonians are reconstructed as auxiliary structures to rationalize the observed data. Our starting point is a signal-based spectral equation that reformulates frequency analysis as an operator problem. We connect this point of view to results on prolate Fourier theory, spectral analysis with finite observation time, and short-time quantum simulation. We highlight a sharp accuracy transition relating necessary observation time to the effective spectral density of a signal for achieving accurate resolution. The resulting framework integrates approximation as a fundamental necessity more directly into the foundations of quantum mechanics and points toward a broader program for the effective description of complex quantum systems, such as those found in the molecular sciences.

Vapor-liquid-solid (VLS) growth has delivered a level of synthetic control in group IV and III-V semiconductor nanowires that remains unmatched in any other class of one-dimensional materials. For Si, Ge, and GaAs, decades of mechanistic study have made diameter, growth direction, crystal phase, and axial composition into design parameters. For oxides, carbides, and chalcogenides, including emerging van der Waals materials, which we refer to collectively as non-conventional nanowires, one-dimensional structures have been reported in abundance, but comparable deterministic control has not been achieved despite their predicted functional properties and broad application potential. This review examines where and why the two groups diverge. We survey and categorize the literature on VLS and VLS-related synthesis of non-conventional nanowires, following the sequence of the growth process itself, namely precursor creation and delivery, seed particle formation and evolution, and nucleation and growth of one-dimensional structures. Each step is compared against the group IV and III-V baseline to locate shared behavior and genuine differences. From this comparison we identify seed particles, spanning the choice of seed material, the chemical composition of the seed during and after growth, and its dynamics, as the principal bottleneck restricting deterministic synthesis, with precursor creation and delivery acting as an upstream constraint that narrows the accessible seed design space. We discuss potential solutions, including new precursor chemistries, improved reactor designs, and in situ characterization of growth, that would deepen mechanistic understanding of nanowires already demonstrated by VLS and extend seeded growth to emerging quantum and functional materials, ultimately paving the way for deterministic synthesis and integration of complex one-dimensional nanomaterials.

Our goal in this paper is twofold. First, we characterize the class of pairwise interactions for which the Seidl conjecture on the structure of optimal plans for the symmetric multimarginal optimal transport problem with one-dimensional marginal holds. This extends previous results by Colombo, De Pascale, and Di Marino [Can. Jou. Math., 67 (2015), https://doi.org/10.4153/CJM-2014-011-x], which treated the case of translation-invariant, convex and decreasing interactions. In particular, our results apply to physically relevant interactions for electrons living on a quantum ring. The second main goal of the paper is to rigorously derive the leading order asymptotics of the adiabatic connection potential for strongly interacting systems. More precisely, we show that for electrons in a quantum ring (or one-dimensional interval), not only the Lieb density functional converges to the optimal transport (or strictly correlated) functional in the semiclassical limit, but also the representing potential converges to a regular Kantorovich potential. As an intermediate step, we also extend previous results on the strongly interacting limit of the Lieb functional to periodic systems in arbitrary dimensions.

Exceptional points (EPs) represent non-Hermitian degeneracies where eigenvalues and eigenvectors coalesce, giving rise to enhanced sensitivity and critically damped dynamics. We demonstrate that when an EP coincides with a dissipative phase transition in an extended open Dicke model of two cavities coupled to a collective spin, the critical fluctuations are strongly amplified and governed by modified critical exponents. Numerical results reveal enhanced critical scaling in both the normal and superradiant phases, in agreement with an analytical theory based on the Jordan-block structure of the linearized dynamical matrix at the EP. Our results establish EPs as a mechanism to engineer critical scaling in open quantum systems, with potential applications to critical quantum sensing.

This study presents a first-principles study at the level of hybrid-level density functional theory of the sodium intercalation process in a layered potassium birnessite (a layered manganese dioxide, {\delta}-MnO2). Understanding the intercalation processes of {\delta}-MnO2 is a vital step in advancing its potential innovative applications. Through a formation energy formalism, we analyze the stability of the structure as sodium ions (Na+) are intercalated between layers. Simulated Raman spectra allow us to find relationships between the vibrational and structural properties of the material, i.e. we identify the most important vibrational modes and related them to the structural/geometrical change. The diffusion of Na+ and K+ ions in birnessite is studied by transition state theory, determining the energy barriers to ion displacement in the interlayer. The symmetry and planar density of the system are characterized by simulated X-ray diffraction and geometrical analysis of the optimized structures. Through binding energy analysis, we also find that the Na+ ions are more loosely bound to the lattice as they reach the saturation limit. Finally, the electronic properties are studied via spin-polarized densities of states. As intercalants are added, the electronic properties are profoundly modified, resulting from modification of Mn oxidation states, lattice distortions, and symmetry effects. Moreover, some of the intercalated structures behave as bipolar magnetic semiconductors with potential applications in spintronics devices. In other words, the band gaps and magnetic behavior of the system can be controlled by intercalation. This work provides an overarching analysis of intercalated birnessite and describes the essential properties of potassium birnessite and co-intercalation with Sodium as a next-generation energy, electronic, and spintronic material.

Advances in next-generation hypersonic hot structures, high heat-flux fusion or fission components, and laser based additive manufacturing depend on reliable solid state thermal conductivity data at high and ultrahigh temperatures, where conventional measurements become increasingly sensitive to contact resistances, uncertain boundary conditions, and nonlinear radiative losses. Building on our initial demonstration of ultrahigh temperature steady-state temperature differential radiometry (SSTDR), we present a substantially more robust platform aimed at making high temperature thermal and radiative property measurements more routine. The method integrates lock-in infrared thermography with a spatially localized, modulated perturbation laser to form a conduction dominant differential observable along with hyperspectral pyrometry and a validated 2D axisymmetric steady state heat transfer model. Using high purity molybdenum as a benchmark, we report solid state thermal conductivity k(T) from 1500 - 3000 K (to the onset of melting) with uncertainties of 7.9-11 % enabled by comprehensive uncertainty propagation, sensitivity analysis, and bounding studies. We additionally provide normal spectral emittance of molybdenum in both solid and liquid states over 500-1000 nm. These advances establish SSTDR as an accurate, non-contact route for closing the high temperature k(T) data gap while simultaneously producing much needed phase dependent radiative property data for melt adjacent and extreme heat-flux applications. Note: This is a shortened abstract; full version in manuscript.

The elastic behavior of materials is of critical importance for the design, fabrication, and testing of industrial and structural components. The ease with which the wave angle of incidence can be varied makes ultrasonic techniques well suited for the characterization of anisotropic materials, whose properties are direction-dependent. This work aims to develop an ultrasonic goniometry method in which a wave is transmitted through a sample while scanning over spherical coordinates. A plane-wave model is formulated that accounts for fluid-solid interfaces and is applicable to a wide range of sample thicknesses. The model assumes general anisotropy, enabling the characterization of materials with symmetries up to triclinic, and does not require precise sample alignment. Specially designed transducers support the plane-wave approximation, thereby avoiding the need for more computationally expensive finite-beam models. Furthermore, implementation of the forward model on GPU architectures significantly reduces the computational cost associated with the numerous evaluations required during the waveform fitting inversion. The introduction of optimal zeroth-order bounds is used to tightly delimit the search space, and an isotropic self-consistent solution is shown to provide an effective initial guess. Finally, measurements on plate-like samples are compared with the literature and diffraction-based methods.

Hybrid organic-inorganic materials enable systematic structural tuning through chemical modification of organic ligands. Predictive control, however, requires mechanistic understanding of how ligand chemistry and inorganic frameworks jointly determine structural motif selection. Metal-organic chalcogenides (MOCs), where metal-chalcogenide units are covalently bonded to organic ligands, offer an ideal platform in which ligand substitution directly alters crystal structure. Here, we investigate silver selenide-based MOCs with fluorinated phenyl ligands to elucidate governing interactions. Density functional theory with fragment-based energy analysis identifies ligand-ligand interactions as the primary energetic driver of motif selection. Symmetry-adapted perturbation theory further decomposes ligand-ligand interactions and shows that electrostatic interactions are decisive in selecting the preferred motif by selectively stabilizing specific packing arrangements. The results further show that ligand orientation controls the effectiveness of long-range electrostatic interactions, establishing a physically grounded design principle for directing structural motifs in MOCs through targeted control of ligand packing and electrostatics.

DX behavior limits $n$-type carrier concentrations in ultrawide-bandgap nitrides such as aluminum nitride (AlN) and cubic boron nitride ($c$-BN). Instead of acting as effective-mass donors, DX centers capture two electrons, stabilizing a negative charge state that leads to self compensation. Silicon is the most effective $n$-type dopant in this class of materials; in AlN, its DX level [(i.e., the (+/$-$) transition level] is $\sim$270 meV from the conduction-band minimum. This implies that many silicon impurities incorporated into AlN will be negatively charged and compensate the intended $n$-type doping. By combining density functional theory calculations of temperature-dependent band gaps and Si dopant transition levels, we show here that significant compensation occurs in silicon-doped AlN, even in the absence of any other defects. This compensation strongly limits free electron concentrations which become independent of doping concentration, and donor activation is only significant for light doping scenarios. Higher free carrier concentrations can be achieved in AlGaN alloys or in $c$-BN, where the DX level sits closer to the conduction-band minimum.

Recent experiments in rhombohedral graphene find evidence for a "self-doped" Wigner crystal (SDC) in which a slightly incommensurate Wigner crystal (WC) coexists with a small Fermi sea. We provide non-perturbative arguments that such SDCs generically arise from preempted band-inversion transitions between commensurate crystals, which motivates simple band-theory criteria for their appearance. Self-consistent Hartree-Fock calculations establish the existence of a SDC consistent with this mechanism in both the $\lambda$-jellium model and rhombohedral pentalayer graphene (R5G). In the $\lambda$-jellium model, we identify a SDC phase located between a "halo"-WC and an anomalous Hall crystal (AHC), which would otherwise be connected via a Dirac transition when pinned to commensuration; this contrasts with the WC-AHC transition, which we show cannot be connected by a continuous transition due to a mismatch of symmetry indices. In R5G, we predict a SDC phase located between a WC and a "disqualified" halo anomalous Hall crystal. We discuss in general how the Berry curvature distribution in the parent band affects the appearance of SDC, revealing a novel role of quantum geometry in inducing exotic quantum phases of matter.

The discovery of superconductivity in bulk Ruddlesden-Popper La$_3$Ni$_2$O$_7$(LNO327) under high hydrostatic pressure has redefined the recent experimental consensus that nickelate superconductivity is restricted to systems with a $3d^9$ electronic configuration and square-planar coordination. However, the structural and electronic prerequisites for stabilizing superconductivity, whether under pressure or at ambient conditions in the case of thin films, remain poorly understood, largely due to the metastable nature of the LNO327 phase. Here, we present a detailed structural study of epitaxial La$_3$Ni$_2$O$_{7-\delta}$ thin films by using scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). Grown via pulsed laser deposition onto SrLaAlO$_4$ substrates, those films exhibit distinct superconducting properties as a function of the different post-annealing conditions used. By correlating the rich landscape of stacking polymorphs with transport behavior, this work establishes a framework for understanding the metastable superconducting phase in bilayer nickelate thin films. Our findings underscore the critical role of homogeneity in oxygen stoichiometry, epitaxial strain and structural motif in stabilizing superconductivity, offering a clear pathway for designing ambient-pressure superconducting nickelates.

We establish a quantitative bulk-boundary correspondence in interacting topological insulators by relating many-body topological invariants to characteristic degeneracy structures in the entanglement spectrum. Focusing on generalized Su-Schrieffer-Heeger chains with higher winding number, we construct a gauge-invariant many-body winding invariant based on Pancharatnam geometric phases that remains well defined in the presence of interactions. We show that this invariant uniquely determines the low-lying entanglement-spectrum degeneracy, which exhibits a universal $4^\nu$ scaling with the winding number $\nu$, providing a concrete formulation of bulk-boundary correspondence beyond single-particle topology. Using exact diagonalization, we demonstrate the robustness of this correspondence under interactions and symmetry-preserving disorder, and identify inversion symmetry as a minimal protecting symmetry that stabilizes both the quantization of the invariant and the associated entanglement degeneracies. Our results unify geometric-phase invariants and entanglement diagnostics within a many-body framework and provide a route to identifying interacting topological phases beyond band theory.

We use segment DMRG on the infinite cylinder to compute energies of charged excitations in gate-screened fractional quantum Hall states. For the $\nu=1/3$ Laughlin, $\nu=2/5$ Jain, and $\nu=5/2$ anti-Pfaffian states, we find screening can bind like-charged anyons into molecules, with a strong dependence on filling-factor, gate distance, and fusion channel. In the Laughlin state, stable $\pm 2e/3$ molecules and larger clusters appear over a broad gate-distance window. The Jain state is molecular throughout the range we consider. In the anti-Pfaffian, binding is strongest on the hole side, where the charge-$e/2$ molecule is fused into the $\psi$ channel over a broad window of gate distances. In all three cases, screening suppresses long-range repulsion and exposes an intermediate-range attraction encoded in the oscillatory density tail of the fundamental anyon. We discuss consequences for addition spectra, interferometry, Wigner crystallization, anyon superconductivity, and entropy measurements.

The two-dimensional character of van der Waals magnets allows for efficient control of their properties via proximity effects and electrical stimuli, making them promising candidates for application in spin-electronics. We use spin-polarized low energy electron microscopy to directly image the magnetic texture of thin CrSBr on top of a Au film, uncovering a ferromagnetic ground state for CrSBr thicknesses smaller than 11 nm. We argue that the stabilization of the ferromagnetic ordering - as compared to the conventional antiferromagnetic one - is obtained via electron transfer from the Au film to the CrSBr flakes, in agreement with ab-initio density functional theory calculations. Reflected-electron spectroscopy shows clear differences in the unoccupied density of states between a few layers of CrSBr on Au and bulk CrSBr, pointing towards electronic band structure modification in thin CrSBr. This work sheds light on the possibility to tune magnetic properties of two-dimensional magnets via substrate engineering.

We prove that a violation of a Leggett-Garg inequality for bounded observables in stationary pure states and thermal states yields a rigorous lower bound on the quantum Fisher information. This turns a qualitative foundations test of realism in quantum systems into a quantitative witness of useful quantum sensitivity and, in the collective setting, into a lower bound on multipartite entanglement depth in many-body systems. We further demonstrate that Leggett-Garg violations are constrained by the same spectral moments, susceptibilities, and $f$-sum-rule bounds that organize many-body response. Our results show that temporal correlations of a single collective observable can serve as an experimentally accessible witness of many-body quantum coherence, without requiring full state reconstruction.

Rare events are central to the evolution of complex many-body systems, characterized as key transitional configurations on the free energy surface (FES). Conventional methods require adequate sampling of rare event transitions to obtain the FES, which is computationally very demanding. Here we introduce the variational free energy surface (VaFES), a dataset-free framework that directly models FESs using tractable-density generative models. Rare events can then be immediately identified from the FES with their configurations generated directly via one-shot sampling of generative models. By extending a coarse-grained collective variable (CV) into its reversible equivalent, VaFES constructs a latent space of intermediate representation in which the CVs explicitly occupy a subset of dimensions. This latent-space construction preserves the physical interpretability and transparent controllability of the CVs by design, while accommodating arbitrary CV formulations. The reversibility makes the system energy exactly accessible, enabling variational optimization of the FES without pre-generated simulation data. A single optimization yields a continuous, differentiable FES together with one-shot generation of rare-event configurations. Our method can reproduce the exact analytical solution for the bistable dimer potential and identify a chignolin native folded state in close alignment with the experimental NMR structure. Our approach thus establishes a scalable, systematic framework for advancing the study of complex statistical systems.

Ordering at arbitrarily high temperature - entropic order - has been argued to take place in a class of generalized Ising models parameterised by a real interaction parameter $p$ when $p\ge 1$. We give a rigorous proof of this conjecture. We further show that on arbitrary graphs, these models solve graph packing problems - crucially, the Maximum Independent Set optimisation problem. Due to the NP-hardness of this packing problem on generic graphs, some lattice systems will exhibit glassy phases. We call this phenomenon $entropic$ $glass$.

Understanding how molecular structure gives rise to odor perception remains a long-standing challenge, with ongoing debate over whether olfaction is primarily governed by molecular shape, vibrational properties, or their interplay at the level of olfactory receptors. Here, we ask whether different odors rely on common molecular determinants or instead emerge from distinct physicochemical regimes. Using interpretable machine-learning models trained on molecular descriptors derived from first-principles calculations that span electronic, vibrational, and structural properties, we analyze feature contributions for odor categories and their associated receptors. We find that no single descriptor class universally dominates odor prediction; instead, different odors exhibit strongly odor-specific patterns of feature importance, with substantial variability across physicochemical domains. This heterogeneity is consistent across different models, suggesting that a universal encoding scheme does not capture odor perception but reflects receptor- and odor-dependent structure-odor relationships. Our results provide statistical constraints on competing olfactory theories and offer a data-driven framework for organizing odor space.

Porous media underpin absorption, filtration, separation, and high-area interfacial transport in chemical and diagnostic systems, yet sustained directional flow through them remains difficult because tortuous pore networks and strong acoustic losses promote bypassing, weak flow, and counterflow. Here, we show that floating-electrode unidirectional transducers (FEUDTs) convert porous materials into actively pumped transport platforms by generating predominantly unidirectional surface acoustic waves (SAWs) that couple more effectively than conventional interdigital transducers across wet multilayer interfaces. By varying pore size, permeability, sample thickness, and fluid viscosity, we find that transport is strongly enhanced when the SAW wavelength is comparable to the characteristic pore dimension, providing a practical design rule for acoustically activated porous media. Under these conditions, FEUDTs drive directional flow velocities up to 0.6 mm s$^{-1}$ at sub-watt input power, about 600 times faster than diffusion alone. FEUDTs also sustain pumping in prewetted porous media, where capillary contributions are removed, yielding velocities that exceed capillary-driven flow under matched conditions while remaining far above thermally induced transport. A reduced theoretical framework captures the main experimental trends and identifies transducer architecture, pore geometry, and actuation strength as the key parameters governing long-range, tunable transport in porous functional materials.

This article presents a numerical simulation of solvent diffusion in transition metal dichalcogenide based nanomaterials during solvothermal reaction, leading to layer exfoliation and, consequently, a reduction in the average nanoparticle size. By solving modified Ficks law of diffusion and utilizing the dynamic bond percolation model, this study examines the evolution of a system of nanoparticles. During the simulation, the effects of key parameters, such as the diffusivity variable that determines the diffusion rate, and the number of iterations needed to achieve enhanced nanoparticle size uniformity, have been analyzed. To gain more insight into the size evolution of the nanoparticles, avalanche statistics, and fluctuations in the average nanoparticle size by Shannon entropy has been utilized. The size distribution observed for different diffusivity variables and iterations has also been studied, which predicts the probability of finding the nanoparticles of specific sizes within the system. A correlation between the iteration for maximum entropy and the minimum of relative change in particle size with iteration has been established, indicating that an iteration exists that takes the system towards saturation in terms of the average size of the nanoparticles. The numerical findings indicate that the experimental parameters, such as solvent selectivity and diffusivity, as well as reaction time, play significant roles in determining nanoparticle size and uniformity, thereby enhancing potential material applications.

We construct effective $\mathrm{U}(2)$ Chern-Simons-Ginzburg-Landau theories for Abelian and non-Abelian fractional quantum Hall hierarchies for those which had previously been described only through categorical data or trial wavefunctions. Our framework captures both Abelian hierarchy states built on half-filled Pfaffian-type parents and non-Abelian hierarchies emerging from Abelian states. It reproduces all filling fractions obtained from wavefunction and categorical constructions and, moreover, uniquely determines the corresponding topological orders. We also identify an intriguing particle-hole symmetry relating two hierarchy sequences, one built on a trivial insulator and the other on the $\nu=1$ integer quantum Hall state, which respectively generate the Read-Rezayi sequences and their particle-hole conjugates under the same hierarchy construction.