Classical Physics
Multibranched parametric resonance and swallowtail catastrophe in electromechanical oscillators with nonlinear friction
P. Y. Chan, L. Huang, X. Dong et al. (+2 more)
Parametric resonance underpins the operation of a wide range of physical systems, from nanomechanical resonators to
quantum-information systems and Ising machines. As an archetypal class of driven-dissipative systems, parametric oscillators are generally expected to exhibit a single pair of stable period-two states with opposite phases. This bistable behavior enables both the simulation of
spin Hamiltonians and the preparation of superconducting cat states. Whether multiple pairs of such states can coexist in a single oscillator, however, remains an open question. Here, we show experimentally and theoretically that conventional controlled nonlinear friction can induce the coexistence of two distinct pairs of period-two states in a micromechanical oscillator. The friction is implemented via a canonical approach, utilizing a drive-induced resonant coupling that transfers two vibrational quanta from the oscillatory mode to a faster decaying mode. We demonstrate that the onset of multistability is governed by a swallowtail catastrophe and quantitatively map the associated bifurcation structure. Our results broaden the understanding of parametric resonance and establish micro- and nano-mechanical oscillators as a versatile platform for studying catastrophe theory and multistable nonequilibrium dynamics.
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All authors P. Y. Chan, L. Huang, X. Dong, M. I. Dykman, H. B. Chan
Physics and Society
The Evolutionary Dynamics of AI, Politicization, Contestation, and Trust in Science Funding
Animesh Ray
Economic stability and progress in modern technological societies depend on vigorous and independent public funding of science and engineering research. When peer review or funding decisions are perceived as politically directed, scientists, funding agencies, and the public react in coupled and conflicting ways. We an evolutionary game-theoretic model to analyze how perceived political interference in science funding affects the interrelated behaviors of scientists, funding agencies, and the public. The model simulates scientists choosing to refuse peer reviews and retaliate, agencies responding by adopting AI-assisted review and altering reviewer pay, and the public accepting or rejecting these AI systems. Through numerical simulations, five principal findings are identified: (1) Operational capacity and institutional legitimacy are governed by separate conditions and can fail independently. (2) Legitimacy of the process is bistable, meaning final states are determined by the public's acceptance of AI. (3) Since the career cost for researchers refusing to review is generally low, resistance/retaliation cascades can readily ignite, leading identical institutions to entirely opposite fates. (4) Increasing reviewer pay only stabilizes participation within a strict budget-solvency frontier, and emergency pay can paradoxically erode the legitimacy it aims to protect. (5) Finally, finite-population simulations reveal that baseline scenarios partition into either legitimacy recovery without capacity or joint failure, confirming that the fundamental separation of capacity and legitimacy outcomes is a dominant structural feature driven primarily by initial scientific resistance and politicization levels. This theoretical work quantifies issues for future work in science policy.
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General Relativity and Quantum Cosmology
Phantom-Divide Crossing in Barrow-Tsallis Holographic Dark Energy with a Scale-Dependent Barrow Exponent
D. A. Yerokhin
Phantom-divide crossing is studied in spatially flat cosmologies with standard Friedmann equations, separately conserved
holographic dark energy and a barotropic fluid, and the future event horizon as the infrared cutoff. The horizon
entropy and dark-energy density are prescribed by $ S_h=S_{\mathrm{BH}}F(L) $ and $ \rho_X\propto F(L)/L^2 $, where $ F(L) $ is smooth, positive and single-valued, with $ \chi=\mathrm{d}\ln F/\mathrm{d}\ln L $. For $ w_b>-1 $, $ 0<\Omega_X<1 $ and $ \chi<2 $ along the trajectory, at most one phantom-divide crossing is possible. If a crossing occurs, dark energy passes from the quintessence regime into the phantom regime at a maximum of the horizon radius. The crossing kinematics determines the local
entropy-scaling dimension and the sign of the local Chevallier-Polarski-Linder coefficient. Integrating the locally prescribed scale-dependent Barrow exponent reconstructs the Barrow-Tsallis
entropy function. A necessary and sufficient event-horizon consistency criterion selects admissible solutions, whose late-time asymptotics include de Sitter states, Type III and Big Rip singularities, and accelerated power-law expansion under the corresponding parameter conditions. A numerical comparison with a constant Barrow exponent distinguishes the occurrence of a crossing from the effect of exponent variation on late-time
evolution. With an adiabatic barotropic fluid, additive total
entropy and an
equilibrium Gibbs relation for dark energy, the generalized second law fails at the kinematic crossing for positive barotropic-fluid
entropy and finite nonzero dark-energy temperature. The divergence of $ c_a^2 $ shows that the purely barotropic adiabatic description of perturbations breaks down. This divergence alone does not establish physical instability.
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Chemical Physics
Lewis-labeled graphs: curly arrows and fishhooks as executable electron transfers
Tieu-Long Phan
The curly-arrow formalism is the lingua franca of organic reaction mechanisms, but it is not executable. Molecular graphs used in rule-based modeling encode atomic connectivity while omitting lone pairs, radical electrons, and distinct sigma and pi components. Topological matching therefore cannot determine whether a reactive center holds the electrons a step consumes, while matching on derived formal charge can reject centers that do hold them. We introduce the Lewis-labeled graph (LLG), whose atom labels carry lone-pair and radical populations and whose bond labels separate sigma- and pi-bond occupancies. Bond order, formal charge, and valence electron inventory are derived from these fields. Chemical transformations become resource-constrained double-pushout rules, and curly arrows and coupled fishhooks become locus-sorted electron transfers committed atomically from a common pre-state. For a specified event group, we prove that its execution, application of its induced rule, and the corresponding integral occupancy update are equivalent. Every admissible event conserves valence electrons and net formal charge, and bond-centered fishhook coupling follows from integrality rather than drawing convention. Bidirectional replay recovers all 39,732 mapped reference endpoints, while LLG admits 96 fewer forward and 818 fewer inverse unique outcomes than conventional atom-bond rules. Ten radical records require manual annotation corrections. After review, transition construction succeeds for 101,313 of 101,314 records. The remaining case requires an endpoint atom-map correction rather than an arrow edit. Strict replay accepts all 160 reviewed steps and rejects all 1,120 controlled corruptions. These results establish a common executable state space for molecular graphs, reaction rules, and electron-flow annotations, prior to questions of kinetic or thermodynamic feasibility.
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Quantum Physics
Malleability of transformations on the ciphertext in noisy Quantum public key encryption
Pete Rigas
We characterize a noisy variant of a
Quantum public encryption protocol recently introduced by Malavolta and Walter which demonstrated that the notion of everlasting security can be rigorously formulated for
Quantum key distribution after two rounds of interaction between Alice and Bob. To address one possible direction of research that is related to injecting noise in the cryptographic protocol related to
Quantum key distribution we formulate arguments for further examining the notion of everlasting security through malleability assumptions on transformations of the ciphertext. Assumptions surrounding malleability were introduced by Maurer and Tackmann for the purposes of comparing how authenticate then encrypt, and encrypt then authenticate, protocols behave through a variety of expressions for the forwarding error, deleting error, and reconstruction probabilities. Such probabilities are put to further use for obtaining connections between the indistinguishability and security threshold for a cryptographic protocol of interests. To further build upon such associations we demonstrate, through an adaptation of the Gentle Measurement Lemma from
Quantum information theory, how upper bounds on the trace distance can be used to generalize the negligibility function obtained by Malavolta and Walter in the noiseless setting. Besides the fact that the negligibility function in the noisy setting is related to a higher security threshold it continues to remain of interest to determine whether computations provided in this work for upper bounding the trace distance can be related to other settings that are centered more on game-theoretic approaches.
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General Relativity and Quantum Cosmology
Dark Matter Deficient Galaxies as Probes of Dark Matter
Oem Trivedi and Abraham Loeb
Dark matter deficient
galaxies provide a direct way to test whether
baryons and dark matter can become sufficiently separated during
galaxy evolution. We formulate a Dark Matter-
Baryon Separability condition based on the relative incorporation efficiencies of the two components, requiring the final dark matter to
baryon ratio to fall below an observationally defined threshold. Applied to high speed collisions, this condition constrains dark matter
baryon momentum transfer cross section, interacting dark matter fraction and the efficiency of gravitational recapture. The same framework gives us bounds on the abundance and cooling time of dissipative dark matter, and on the integrated escape rate of ultralight fuzzy dark matter from shallow or tidally disturbed potentials. These results show how dark matter deficient
galaxies can complement cosmological and laboratory probes by constraining late time dark matter interactions, dissipation and
halo stability.
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Quantum Physics
Agentic AI for Scientific Reasoning in Autonomous Quantum Sensing Experiments
Takuya Isogawa, Ryotaro Okabe, Nutdech Phadetsuwannukun et al. (+2 more)
We implement an agentic AI workflow built around a large
language model (LLM)
agent for autonomous experiments with nitrogen-vacancy (NV) centers in diamond. NV centers are a widely used platform for
quantum sensing, and the ability to control many measurements from a computer makes NV experiments a natural setting for autonomous workflows. We make two main contributions. First, we demonstrate an autonomous NV experiment workflow that combines persistent project records, quantitative calculation and data analysis tools, and deterministic experiment control. In one autonomous experiment, the
agent selected a single NV center, calibrated its resonant frequency, measured \(T_2^\ast\) with Ramsey measurements, and added a Carr–Purcell–Meiboom–Gill (CPMG) measurement to check a weak feature that could be related to nearby \(^{13}\mathrm{C}\). Second, we introduce two offline
benchmarks that evaluate the
agent's
reasoning separately from laboratory execution. We evaluated both
benchmarks with GPT-5.4, GPT-5.5, and GPT-5.6 Sol. In the Ramsey checkpoint
benchmark, greater
reasoning effort generally improved recognition of a residual resonance calibration offset. By contrast, in the pulsed optically detected
magnetic resonance (pODMR) data evaluation
benchmark, pulse sequence information alone produced more false positive resonance judgments at higher
reasoning effort. Requiring an expected signal calculation kept false positive rates low across all three models and
reasoning settings. The results suggest a clear division of labor for autonomous experiments. The
agent forms scientific hypotheses and uses quantitative tools to evaluate data, while deterministic code controls the hardware and enforces safety constraints.
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All authors Takuya Isogawa, Ryotaro Okabe, Nutdech Phadetsuwannukun, Mingda Li, Paola Cappellaro
Mathematical Physics · Cross-listed from math.NA
An adaptive phase field framework for large-scale interface evolution problems using a strong-form gradient smoothing approach
Zirui Mao, Alice Xu, Shenyang Hu et al. (+4 more)
Multiscale problems with evolving interfaces are ubiquitous in science and engineering. Phase-field models are a powerful tool for simulating interface-dominated phenomena in computational mechanics and materials modeling, but their application to large-scale problems is often constrained by the high computational cost of resolving thin diffuse interfaces over the entire domain. This paper presents an efficient strong-form phase-field solver that couples the Gradient Smoothing Method (GSM) with a hierarchical adaptive and moving structured mesh, enabling automatic localization of resolution within a narrow interfacial region while retaining coarse discretization in bulk domains. A layered refinement design is introduced to preserve locally uniform resolution across the interface, allowing the GSM discretization to maintain overall second-order accuracy despite strong mesh non-uniformity away from the interface. Although GSM incurs a higher per-degree-of-freedom cost than standard finite-difference schemes, the adaptive framework substantially reduces the total number of degrees of freedom, resulting in near-linear computational scaling compared with the quadratic scaling of uniform-grid approaches. Numerical examples based on the Allen-Cahn and Cahn-Hilliard equations demonstrate that the proposed adaptive GSM solver delivers desired accuracy for interface
evolution while attaining more favorable computational complexity, O(N), than existing weak-form and strong-form solvers, becoming significantly more efficient for large-scale problems with thin interfaces or a small interfacial area fraction relative to the whole domain.
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All authors Zirui Mao, Alice Xu, Shenyang Hu, Panos Stinis, Yuyan Shao, Ang Li, Yulan Li
Physics and Society
Emergent contagion complexity: Disentangling mechanistic complexity from correlated heterogeneity
Katerina Tang, Daniel Kaiser, William Thompson et al. (+3 more)
Simple and complex contagions differ mechanistically; multiple exposures act synergistically in the latter but independently in the former. Yet correlated mixtures of simple contagions may appear complex when inferring global contagion rules, a phenomenon we call "emergent complexity." We present a measure of contagion complexity and an inferential framework for estimating mixtures of nonparametric contagion rules from time-series data. Our work reframes past studies on complex contagion by offering heterogeneous mixtures of simple contagions as an alternative explanation.
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All authors Katerina Tang, Daniel Kaiser, William Thompson, Jean-Gabriel Young, Laurent Hébert-Dufresne, Nicholas W. Landry
Nuclear Theory
Analytic and Approximate Solutions to Color Glass Condensate in the Classical Weak-Field Limit
S. Robicheaux and R. J. Fries
We discuss two-point functions and the energy momentum tensor of the classical
gluon field after the collision of sheets of color charges on the light cone in the weak-field limit. The classical fields created by such a setup is thought to approximate the behavior of the
gluon matter created right after the collision of heavy
nuclei at large energies. Our discussion is based on a general expression for the
gluon distribution in a
nucleus, which contains the McLerran-Venugopalan (MV) Model as a special case. We derive the time-dependence of the energy momentum tensor in this general scenario. We show that the large-time behavior is universal, i.e.\ independent of the specific model for the
gluon distribution, e.g.\ for energy density, transverse pressure and longitudinal pressure $\epsilon, P_T \sim 1/\tau$ and $P_L \sim 1/\tau^3$, where $\tau$ is longitudinal proper time. Subsequently, we focus on two special cases, the MV model and a proposed improved Gaussian (iG) model with improved ultraviolet (UV) and infrared (IR) behavior, the latter inspired by earlier work by Lam and Mahlon. We explicitly discuss the time dependence of the energy momentum tensor in both models. In the case of the MV-model, for infinite colliding
nuclei, it is possible to give closed-formed analytic solutions for the energy momentum tensor in terms of special functions. Components of the energy momentum tensor take the form $\sim C (m\tau)^{-n} H(m\tau)$, where $n$ is an integer power, $m$ is the infrared cutoff, $H$ is a linear combination of Meijer-G functions with constant asymptotic value, and $C$ is a known constant. For the iG-model, we obtain reliable series expansions for both small and large times and show that the MV-model is recovered qualitatively in the UV limit. We briefly comment on implications for the angular momentum carried by the
gluon field.
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Optics
A geometric approach to QNMs in optics: application to pseudospectrum and structural stability
Lamis Al Sheikh and José Luis Jaramillo
We develop a
geometric–spectral framework for the computation and stability analysis of quasi-normal modes (QNMs) in open optical cavities of compact support. The hyperboloidal approach, transferred from gravitational physics to electromagnetism [1], incorporates outgoing boundary conditions directly into the formulation of the optical resonance problem. Dispersive and absorbing media are described by a Lorentz-model permittivity through an auxiliary-field formulation, and the resulting non-Hermitian spectral problem is solved using Chebyshev spectral discretization.Pseudospectrum analysis is then extended to the optical setting following [2] and used to study the stability of optical resonances under perturbations. The pseudospectrum provides information on the sensitivity of the resonances that is not contained in the QNM spectrum alone. Particular
attention is given to the role of the norm used to define the pseudospectrum, by comparing the stability properties obtained with different choices of scalar product. The results show that the assessment of spectral stability is closely related to the functional setting in which perturbations are measured. Combining the hyperboloidal formulation with pseudospectrum analysis therefore makes it possible to compute optical QNMs while also studying their spectral stability. The approach extends techniques developed for resonance problems in gravitational physics to dispersive electromagnetism and provides a basis for studying stability and sensitivity in open optical systems.
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Mesoscale and Nanoscale Physics
Field-Induced Dissociation Reveals Excitonic Long-Range Photocarrier Transport in Bulk-Insulating Bi2Se3 Nanoribbons
Rodrigo Becerra Silva, Xiang Yi, Ziyi Song et al. (+1 more)
Photoexcited charge carriers in topological
insulators display anomalously long-range transport at cryogenic temperatures, but the underlying mechanism remains under debate. Here we use a transverse electric field as a discriminating probe of photocarrier dynamics in bulk-insulating Sb-doped Bi2Se3 nanoribbons, combining scanning photocurrent microscopy (SPCM) with ultrafast transient photovoltage (TPV) measurements. SPCM shows that suppression of the photocurrent requires a transverse electric field nearly 50 times larger than that needed to deflect free carriers, yet comparable to the expected
exciton dissociation field. TPV measurements at 12 K and low excitation fluence reveal that the photocarrier diffusivity exceeds the value implied by the Einstein relation and the measured drift mobility by more than an order of magnitude, a bound that holds even at the lower end of the fitting uncertainty. Together, these observations indicate that the long-range photoresponse is not carried by free charge carriers but by a charge-neutral correlated state.
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All authors Rodrigo Becerra Silva, Xiang Yi, Ziyi Song, Dong Yu
High Energy Physics (Theory)
Derivation of the NS5-brane limit of the plane wave matrix model
Yuhma Asano, Goro Ishiki and Shinji Shimasaki
From the gauge/
gravity duality, it was predicted that there exists a nontrivial double scaling limit of the plane wave
matrix model (the BMN
matrix model), which describes the type IIA little string theory (LST) on $R\times S^5$. We show on the gauge theory side that such a limit indeed exists for the partition function and in a certain 1/4 BPS sector of the
matrix model, and consequently derive an
eigenvalue integral, which is expected to describe the 1/4 BPS sector of LST.
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Plasma Physics
Emergence and Detection of Electron-Scale Current Sheets in Turbulence with MMS Observations and fully kinetic 3D simulations
Zachary Davis, Alexandros Chasepis, Colby Haggerty et al. (+2 more)
The
solar wind is characterized by
turbulence, where a cascade produces intermittent current structures called current sheets (CS) that efficiently dissipate energy into the
plasma. These have been studied with in situ spacecraft observations, but single-spacecraft techniques such as the partial variance of increments (PVI) are inherently limited since they lack spatial context. A combined analysis of in situ observations and numerical simulations can provide significant insight into the properties of intermittent structures forming in heliospheric
turbulence. Understanding the size and distribution of these structures is crucial in tracing the pathways of energy dissipation and particle energization in space
plasma. Using 3D fully kinetic simulations of magnetized
turbulence, we identify CS via machine learning and find a complex broken-power-law distribution for the CS widths, where the power-law breaks separate ion-scale CS from electron-scale CS. Electron-scale CS dominate, with widths peaking near $2d_e$. Comparing simulations with MMS data, we test PVI as a CS detector and show it can infer CS scale, though oblique crossings inflate inferred sizes. The prevalence of electron-scale sheets suggests they may contribute to
plasma heating in aggregate.
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All authors Zachary Davis, Alexandros Chasepis, Colby Haggerty, Luca Comisso, Derek Sikorski
Mathematical Physics · Cross-listed from math.AP
No Gelation and Global Existence for a Boltzmann Equation with Regularly Varying Mass-Exchange Rates
Siwei Luo and Jian-Guo Liu
We develop a no-gelation mechanism that yields global solutions to the spatially homogeneous Boltzmann equation with mass exchange for Grad-cutoff hard potentials $B=E^\gamma b(\xi), 0<\gamma<1$ and regularly varying mass-exchange rates. Without assuming any higher mass moment, we construct a convex superlinear weight assembled from dyadic hinges. Production of the weighted moment by collisions between large particles of comparable mass is absorbed by dissipation through collisions with a uniformly populated reservoir of bounded-mass particles. Regular variation makes the signed increments in these two collision configurations comparable, while mass conservation and $\gamma<1$ yield the vanishing factor $L^{\gamma-1}$. This yields a uniform moment bound of the mass-cutoff approximations on every finite time interval and rules out finite-time mass escape to infinity. Consequently, for every nonnegative initial density with finite physical moments, we obtain a global integral weak solution.
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Quantum Physics
Exceptional-point braiding with native controls
Vishnu Chavva, Nero Osmancevic and Hugo Ribeiro
Exceptional points define branch-exchange state transfers through holomorphic continuation of non-Hermitian eigenmodes, but realizing these transfers dynamically remains difficult. Slow encircling does not generally transport the full set of instantaneous eigenstates, while shortcuts to adiabaticity can require controls outside the native experimental
manifold. Here, we introduce a constrained shortcut-to-adiabaticity principle for exceptional-point braiding using native controls. In a dressed instantaneous-eigenstate frame, the available controls cancel the accessible transition channels locally, while the residual channels remain active during the
evolution but are constrained to have no net accumulated effect over the closed loop. The protocol therefore targets the endpoint state transfer selected by ideal adiabatic branch exchange, rather than enforcing complete local cancellation or adiabatic following throughout the trajectory. We demonstrate the construction in a minimal two-mode non-Hermitian model equivalent, up to a trace shift and a basis convention, to the effective
Hamiltonian used in dissipative-transmon exceptional-point experiments, where detuning and drive amplitude provide real controls and the relative loss imbalance fixes the non-Hermitian scale. Smooth real waveforms reshape only these controls, reproduce the branch-exchange transfer, and remain accurate under calibration errors, exceptional-point uncertainty and finite-bandwidth filtering with modest overhead.
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Solar and Stellar Astrophysics
Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effects
Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves et al. (+2 more)
Strong
magnetic fields modify the thermodynamics of white
dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the
magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb
lattice contributions, electron capture thresholds,
neutron drip limits, and
nuclear composition are treated consistently in the equation of state (EoS). The
stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman–Oppenheimer–Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the
stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass–radius plane alone, since the corresponding $M(\rho_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong
magnetic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White
Dwarf Database and suggesting that future high-precision observations of massive
magnetic WDs could help assess the role of
magnetic pressure anisotropy in determining their masses and radii.
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All authors Edson Otoniel, Juan M. Z. Pretel, Victor B. T. Alves, César O. V. Flores, Clésio E. Mota
Materials Science
Identifying Contact Barrier Types in Few-Layer MoS2 Devices Using Correlative IV, LBIC, and Bias-Dependent KPFM
Ariane Ufer, Zeinab Eftekhari, Benjamin Mayer et al. (+4 more)
Electrical contacts between metals and two-dimensional (2D)
semiconductors such as molybdenum disulfide (MoS2) critically govern device performance, yet their microscopic nature remains difficult to disentangle using any single characterization technique. Here we present an integrated experimental framework that combines current-voltage (IV) characterization,
laser beam induced current (LBIC) mapping, and bias-dependent Kelvin probe force microscopy (KPFM) to comprehensively resolve the contact properties of few-layer MoS2-based two-terminal devices under ambient conditions. IV measurements deliver macroscopic transport characteristics as a function of bias voltage and illumination conditions. LBIC maps the local photocurrent response with micrometer spatial resolution, revealing the position and nature of internal electric fields at MoS2-metal interfaces. KPFM, operated under an applied static bias rather than in the conventional work-function mode, provides nanoscale-resolved potential distributions that quantify the relative magnitudes and spatial locations of contact barriers. We apply this framework to three representative devices - one exhibiting ohmic-like and two exhibiting diode-like contact behavior - and demonstrate that the combined analysis can unambiguously identify whether the dominant barrier is of Schottky or tunnel type and determine the asymmetry between the two contacts. We further demonstrate that thermal annealing significantly reduces the total resistance, while contact barriers remain the dominant source of resistance. The methodology is directly transferable to other 2D
semiconductor-metal systems and provides a practical yet comprehensive route toward a quantitative microscopic understanding of 2D device contacts.
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All authors Ariane Ufer, Zeinab Eftekhari, Benjamin Mayer, Hendrik Lambers, Hubert J. Krenner, Rebecca Saive, Ursula Wurstbauer
Quantum Physics
Covariant Quantum Measurements and Stochastic Dynamics on Representation Space
Naeem Shahid
We develop a framework for group-covariant
quantum measurements in which measurement-induced transitions between irreducible representation sectors are described by a
stochastic process on representation space. Starting from the Peter-Weyl decomposition, we construct covariant measurement operators from irreducible tensor operators and show that, for
symmetry-invariant states, the measurement channel reduces to a Markov process on the representation graph. We further show that analyticity of the measurement operator constrains the detector spectrum through Sugiura's
theorem, motivating a class of exponentially decaying detector models. Specializing to SU(2), we obtain the transition kernel in closed form, establish reversibility and the associated invariant measure, and derive a continuum Fokker-Planck description of the induced dynamics. Analytical predictions for the drift and
diffusion coefficients are found to agree with numerical simulations. Our results provide a
stochastic description of repeated covariant
quantum measurements on representation space.
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High Energy Physics (Phenomenology)
Spin resummation of heavy quarkonium photoproduction: from the gluonic gravitational form factors to the holographic pomeron
Kiminad A. Mamo, Kemal Tezgin and Christian Weiss
Exclusive heavy quarkonium photoproduction probes the
proton's gluonic structure from near-threshold (fixed-
spin exchanges, gravitational form factors) to high energies (reggeized dynamics). We construct a
holographic QCD amplitude that resums the even
spin-$j$ gluonic exchanges, with the
spin-2 input fixed by
lattice QCD GFFs. The new framework describes the $J/\psi$ cross section from JLab to HERA energies in a unified manner. It explains why the
spin-2 exchange model for GFF extraction near threshold is not a controlled approximation and suggests how to improve it.
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Materials Science
First-Principles Origins of Charge Transport in Molecular Semiconductors
Tong Jiang and Joonho Lee
Charge transport governs organic transistors and photovoltaics, yet predicting it from atomic structure remains challenging. Electron–
phonon interactions span disparate frequencies, strengths and spatial ranges, and collectively generate nonperturbative carrier dynamics. Existing methods regain tractability only by assuming a mechanism or reducing electron–
phonon coupling to a few modes. We introduce a parameter-free framework that instead computes transport from ab initio electron–
phonon Hamiltonians, propagating carriers across hundreds-of-molecule domains with the full
phonon spectrum and letting transport regimes and bottlenecks emerge from nonperturbative Green–Kubo dynamics. Across five representative
crystals, it captures measured mobilities, temperature exponents, and optical-conductivity fingerprints. Our results overturn the prevailing microscopic mechanism for DNTT, tracing its transient localization to correlated on-site disorder from acoustic
phonons rather than independent hopping fluctuations. The resulting two-axis transport map provides design principles and highlights the underexplored phenacene family, exemplified by the high-mobility picene, as a promising direction.
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Soft Condensed Matter
The effect of side chain length on the mesomorphic properties of ferroelectric nematogens
Natalia Podoliak, Martin Cigl, Pavlo Golub et al. (+8 more)
The discovery of ferroelectric nematic phase opened new directions in the field of soft matter chemistry and physics. In this paper, we have modified a previously reported ferroelectric nematogen based on molecular structure with dimethylamino-terminated part. We have prepared two new homologues by prolonging a side chain and investigated the effect of its length on the mesomorphic properties. While previously reported homologues exhibited a direct phase transition from the isotropic (Iso) to the ferroelectric nematic phase (NF), for prolonged alkyl chain there is a narrow nematic phase (N) in between. For new compounds, we have established their mesomorphic and material properties. We have confirmed ferroelectricity of the NF phase by the polarization, SHG signal and permittivity. Finally, we have compared these parameters with respect to the side-chain length and discussed new effects, discovered for prolonged homologues due to the presence of an additional N phase.
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All authors Natalia Podoliak, Martin Cigl, Pavlo Golub, Anej Sterle, Marta Lavrič, Nerea Sebastian, Aitor Erkoreka, Josu Martinez-Perdiguero, Alenka Mertelj, George Cordoyiannis, Vladimíra Novotná
Astrophysics of Galaxies
Radiation-Driven Evolution and Gas Kinematics of the Bright-Rimmed Cloud SFO 25
Puja Porel, Archana Soam, William D. Vacca et al. (+1 more)
Bright-rimmed clouds (BRCs) are valuable laboratories for investigating how ionizing radiation from massive
stars reshapes molecular clouds and influences
star formation. We present a kinematic and dynamical study of the BRC SFO 25 using archival JCMT-HARP observations of the $^{12}$CO, $^{13}$CO, and C$^{18}$O ($J = 3-2$) transitions at an angular resolution of about 14-15 arcsec (0.051-0.054 pc).
Gaia parallaxes of young
stellar objects associated with the cloud yield a revised distance placing SFO 25 behind the ionizing O7V
star HD 47839, implying that ultraviolet radiation can directly affect both the head and tail. The molecular gas exhibits a pronounced head-tail velocity gradient, with the tail systematically redshifted relative to the head, inconsistent with the expectations of classical radiation-driven implosion (RDI) and suggestive of an evolved phase dominated by radiative dispersal and photoevaporation. The head is moderately denser than the tail, while a compact C$^{18}$O clump associated with IRAS 06382+1017 reaches densities of $10^4~\mathrm{cm}^{-3}$. Virial and energy analyses indicate that the head, tail, and dense clump are gravitationally unbound, with kinetic energy exceeding both the gravitational binding energy and the external ionized gas pressure. Class II young
stellar object candidates identified in the tail demonstrate that
star formation is not confined to the dense head. Although RDI may have triggered earlier
star formation in the head, it cannot readily explain the activity observed in the tail, pointing to a more complex evolutionary history than predicted by the classical RDI scenario.
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All authors Puja Porel, Archana Soam, William D. Vacca, Janik Karoly
Physics and Society
Economic Complexity as a Determinant of Regional Human Development in Brazil: Evidence across Aggregation Scales
Eduardo Moura Zampirolli and Ruben Interian
This study investigates the predictive capacity of models based on Economic Complexity and Complex Network Theory when applied to Brazil's Municipal Human Development Index (IDHM). For this purpose, the Economic Complexity Index was adapted to the Brazilian context. The main objective is to assess the extent to which different approaches to regional development analysis, such as local productive sophistication and structural integration into the national transportation network, determine socioeconomic development. The methodology compares linear regression models (Ridge, LASSO, and Elastic Net) and nonlinear models (Decision Trees and the Explainable Boosting Machine), evaluated through 5-fold cross-validation with grid search. The analyses were conducted at two levels of spatial aggregation: municipalities and Immediate Geographic Regions. The results show that regionally aggregated models exhibit less statistical noise and greater stability, achieving substantially higher coefficients of determination and greater explanatory power for ICE relative to the other variables. Notably, at the Immediate Region level, ICE alone emerges as the main structural determinant of IDHM, suggesting that regional productive sophistication by itself explains a large share of the variation in human development at this territorial scale. In addition, the inclusion of topological metrics from the road infrastructure network generally improved performance. The Explainable Boosting Machine achieved the best predictive performance, reaching R^2 = 0.8196 at the Immediate Region level when network metrics were included.
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Instrumentation and Detectors
Cracking under pressure — investigating mitigation approaches for silicon fractures on ATLAS strip tracker petals at cold temperatures
S.H. Abidi, J.-H. Arling, M.J. Basso et al. (+35 more)
For the High-Luminosity upgrade of the Large
Hadron Collider, the ATLAS experiment will replace its current Inner Detector with an all-silicon Inner Tracker (ITk), consisting of pixel and strip detectors. The strip detector will consist of a central region or "barrel" assembled with staves and forward regions or "end-caps" assembled with petals. The ITk will nominally operate with
liquid $\textrm{CO}^2$ cooling at $-35\,^\circ\textrm{C}$; however, in the event of cooling system failures, it is possible that sensors will experience temperatures below $-35\,^\circ\textrm{C}$. At these low temperatures, it has been observed that the silicon sensors within modules — the fundamental readout units of the detector — can physically crack, rendering the modules inoperable. Understanding and resolving the issue of sensor cracking was one of the most important and urgent issues for the ITk project. This paper presents part of the mitigation strategies developed for petals. These mitigation strategies are based on modifications to the choice of adhesive and its deposition pattern for module assembly and petal loading. The most promising mitigation strategy presented here prevents cracking to temperatures as low as $-45\,^\circ\textrm{C}$, which can be expected in case of cooling system problems, with a small percentage of cracks observed after being cycled to $-55\,^\circ\textrm{C}$, which can be expected in case of catastrophic cooling system failures.
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All authors S.H. Abidi, J.-H. Arling, M.J. Basso, S. Beaupre, I. Bloch, A.J. Blue, M. Caspar, J. Chen, S. Díez Cornell, U. Epstein, E.K. Filmer, A. Fournier, L. Franconi, A. Gabrielli, J.A. Hallford, S. Heim, C.M. Helling, N.P. Hessey, R.M. Jacobs, T. Kuhl, M. Licht, C.K. Mahajan, S. Manson, K. Mauer, S. Oerdek, V. Platero Montagut, L. Poley, C.O. Sander, K. Ran, S. Sinha, C. Solaz Contell, U. Soldevila Serrano, D. Sperlich, B. Stelzer, A.H. Tigchelaar, E. Torres Reoyo, G. Vallone, L.M. Veloce
Optics
Anisotropic optical chirality and Lipkin's zilch tensor
Ilia Smagin and Sergey Dyakov
Optical chirality density is widely used as a scalar measure for describing the
chiral properties of electromagnetic fields and their interaction with isotropic
chiral media. However, in anisotropic optically-active media, a single scalar quantity is generally insufficient to capture the full complexity of
chiral field-matter coupling. In this work, we go beyond the conventional optical chirality density and introduce a tensor of electromagnetic chirality based on the Lipkin formalism. This tensor provides a richer and more physically transparent description of
chiral electromagnetic fields, particularly in the context of their interaction with general magneto-electric media. We discuss the physical meaning of the individual tensor components and provide an expression for the excitation rate of small anisotropically
chiral molecules in the presence anisotropically
chiral fields.
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Chemical Physics
Electron-Stimulated Desorption of D Atoms from Gibbsite (Al(OD)3) and D2O Ice: Energy and Temperature Dependence of Translational Energy Distributions
William T. P. Denman, Brant M. Jones, Jacob Messner et al. (+5 more)
The electron-stimulated desorption (ESD) of neutral D atoms from gibbsite (\ce{Al(OD)3}) nanoplatelets and amorphous \ce{D2O} ice has been investigated using $2+1$ resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectroscopy in a high
vacuum chamber at temperatures 15 and 300\,K. Electron irradiation at 540, 250, and 150\,eV produces similar translational energy distributions at $\sim$300\,K, with a dominant intermediate-temperature component ($T \sim 1500$–$2100$\,K). Cooling to 15\,K suppresses the D atom yield by approximately 50% and removes the lowest-temperature (slowest) component. This decrease in yield is consistent with diminished hole mobility and restricted
diffusion at cryogenic temperatures. Under identical conditions, \ce{D2O} amorphous solid water ice films produce approximately 20 times greater D atom signal than bare gibbsite, with significantly hotter translational distributions, reflecting the higher deuterium surface density and distinct bonding environments of bulk ice relative to the terminal hydroxyl groups on gibbsite. These results identify hole transport to terminal hydroxyl sites as the rate-limiting step for nonthermal D atom production and provide a mechanistic framework for understanding atomic hydrogen release from aluminum hydroxide phases relevant to radioactive waste storage at the Hanford Site.
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All authors William T. P. Denman, Brant M. Jones, Jacob Messner, Xin Zhang, Micah P. Prange, Greg A. Kimmel, Jay A. LaVerne, Thomas M. Orlando
General Relativity and Quantum Cosmology
Fixing IR tail of gravitational waves from domain walls
Ivan Dankovsky and Dmitry Gorbunov
Numerical simulations of gravitational waves (GW) production during violent
evolution of matter inhomogeneities in the early Universe yield highly wiggle infrared parts of the spectra. Obtained directly from the two-point correlation function, these wiggles are nonphysical, corresponding to the parasitic, double frequency terms in naively averaged squared oscillation amplitudes of GW, and hence must be washed out. The deep infrared behavior can be predicted on general grounds, e.g. fixed by causality considerations. However, what matters for real observations, e.g. like that of NANOGrav, and what can be only inferred from numerical simulations, is the infrared slope near the maximum of the spectrum. It reflects the dynamics responsible for the GW production in its heyday, and hence must be accurately predicted. We illustrate the problem with numerical simulations of the Domain Wall network performed with the help of code CosmoLattice. We suggest a numerical procedure to smooth out these parasitic wiggles, which allows us to recover the true spectrum. Being quite generic, it may be applied to numerical simulations of other hypothetical sources of GW possibly operating in the early Universe. The procedure requires to extend the simulation by a few Hubble times after termination of the GW production. We checked with numerical simulations, that the technically natural long-time extension of simulations, which becomes available via artificial scaling of different parts in the scalar sector equations provided by PRS prescription, gives wrong GW spectra even if the source terms are properly rescaled.
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High Energy Physics (Theory)
A discrete series gauge field at the late-time boundary of $dS_4$
Manizheh Botshekananfard, Elif Büşra Güraks{\i}n, Vasileios A. Letsios et al. (+1 more)
We study the free Maxwell field on the planar patch of four-dimensional de Sitter spacetime ($dS_4$). We review its bulk canonical quantization in the Bunch-Davies
vacuum, and we give a representation-theoretic viewpoint by studying the transformation properties of single-particle states under infinitesimal dS transformations. By taking the late-time limit, we identify two late-time operators with scaling dimensions $\Delta=1$ (leading) and $\Delta=2$ (subleading). We introduce CFT-inspired inner products invariant under the dS group ($SO(4,1)$) for states created by late-time operators acting on the Bunch-Davies
vacuum. We explain how the
unitary discrete series representations of $SO(4,1)$ associated with the
photon are furnished by both operators, in contrast with the Maxwell field on $AdS$ where the $\Delta=1$ operator corresponds to a non-normalizable mode. We also explain how the corresponding discrete series representations of $SO(4,1)$ split into a direct sum of representations corresponding to two helicities $+1$ and $-1$. This is achieved by taking advantage of the dS invariance of the self-dual and anti-self-dual sectors of the
photon field strength. In our outlook, we draw inspiration from a recent proposal for the microscopic description of $dS_4$ higher-
spin gravity where conformal gauge fields in 3 dimensions play a central role, and we investigate a possible connection of the $\Delta=1$ late-time operator with a conformal
spin-1 gauge field in 3 dimensions.
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All authors Manizheh Botshekananfard, Elif Büşra Güraks{\i}n, Vasileios A. Letsios, Gizem Şengör
Quantum Physics
A broadband, individually addressing two- and three-dimensional photonic integrated circuit for trapped-ion qubit control
Daniel Klawson, Yiyang Zhi, Bingran You et al. (+21 more)
Trapped ions provide a high-fidelity platform for
quantum information processing, yet delivery of multiple, distinct wavelengths across large networks of interaction zones remains a bottleneck. Conventional free-space light delivery lacks scalability, while on-chip grating couplers suffer from narrow operational bandwidth that increases
circuit footprint and optical interfacing complexity. Here we show a broadband photonic integrated
circuit capable of addressing individual ions. The
circuit combines a planar waveguide lens with a micromirror fabricated using two-
photon polymerization at wafer scale. This implementation can address three individual ions from $\lambda$ = 405 - 880 nm with -27 dB average intensity crosstalk at $5\,\mu\mathrm{m}$ pitch. We trap $^{40}\mathrm{Ca}^{+}$ and $^{138}\mathrm{Ba}^{+}$ ions above such devices, characterize optical crosstalk with barium ions, and demonstrate individual repumping of calcium ions. This monolithic photonic architecture brings broadband addressing in an on-chip modality to trapped-ion technology. More generally, integrating additive manufacturing into
quantum devices is poised to unlock expanded design space for implementing novel
quantum architectures.
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All authors Daniel Klawson, Yiyang Zhi, Bingran You, Michael Bareian, Elijah Mossman, Chun-Yuan Fan, Arkadev Roy, Ke Sun, Jason Lee, Sung Cheol Yoon, Qiming Wu, Lai Jiang, Wenjun Ke, Weiwei Wu, Sirui Tang, Zachary Wall, Jiaxiang Wang, Louis Paul Romero, Sam Vizvary, Steven Diaz, Eric R. Hudson, Wesley C. Campbell, Hartmut Haeffner, Ming C. Wu