Quantum Physics · Cross-listed from cs.LG
Quantum Feature Engineering for Credit Default Prediction: When and Why IQP Circuits Help Linear Classifiers
Menachem Finkelstein, Diana Legziel Levy, Zohar Yakhini et al. (+1 more)
Credit default prediction is a tabular classification problem in which modest gains in F1 translate directly into reduced financial exposure. We ask whether Instantaneous
Quantum Polynomial-time (IQP)
circuits can produce features that improve a classifier over both its raw classical baseline and Kernel PCA - the strongest unsupervised classical non-linear alternative - at an equal feature budget. The
dataset provides 23 financial attributes per client; for an n-
qubit circuit we select n of them, encode each as a rotation angle, and read 2n expectation values back out as new features. The motivation for using a
quantum circuit is computational: an n-
qubit IQP
circuit runs in constant depth and encodes feature correlations in a 2^n-dimensional
Hilbert space, whereas classical simulation of its exact output statistics scales exponentially in n. Using the UCI Default of Credit Card Clients
dataset and five-fold cross-validation, we find that appending 16 IQP features (n = 8
qubits) to a Logistic Regression model raises F1 from 0.462 to 0.517 (+0.055, p < 0.0001). Kernel PCA, the next-best method, reaches only 0.493 at the same feature count; the gap survives Benjamini-Hochberg correction across 12 tests (p = 0.00007). No other classifier - Random Forest, SVM, XGBoost, or k-NN - benefits, which points to a linear-expressivity mechanism rather than a generic improvement. We also show that how the 8 input features are chosen matters: Random Forest importance-guided selection reaches F1 = 0.523, while encoding maximally uncorrelated features drops it to 0.496, demonstrating that the
circuit amplifies informative structure rather than creating it from scratch.
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All authors Menachem Finkelstein, Diana Legziel Levy, Zohar Yakhini, Sarel Cohen
High Energy Physics (Phenomenology)
Can Elastic Neutrino Scattering Account for the LZ230616 Event?
Ayan Chattaraj, Anirban Majumdar, Dimitrios K. Papoulias et al. (+1 more)
Recently, the LUX-ZEPLIN (LZ) Collaboration reported an isolated
nuclear-
recoil event at $248\pm 23_\mathrm{stat}\pm 23_\mathrm{syst}~\mathrm{keV_{nr}}$, in a region where the expected background is very small and conventional elastic dark matter (DM)-
nucleus scattering cannot readily account for such a localized feature. We investigate whether LZ230616 could instead originate from coherent elastic
neutrino-
nucleus scattering (CE$\nu$NS). We consider
neutrino-
nucleus interactions within and beyond the Standard Model, together with exotic
neutrino fluxes from DM annihilation ($\chi \chi \to \nu \bar{\nu}$) or decay ($\chi \to \nu \bar{\nu}$) into
neutrino pairs and from
primordial black hole (PBH) evaporation. We show that kinematic considerations, the accompanying low energy
recoil spectrum, and existing constraints exclude a viable interpretation of LZ230616 in terms of elastic
neutrino-
nucleus scattering for all scenarios considered.
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All authors Ayan Chattaraj, Anirban Majumdar, Dimitrios K. Papoulias, Rahul Srivastava
Mesoscale and Nanoscale Physics
Phonon-Bottleneck-Governed Ultrafast Hot-Carrier Super-Diffusion in Transition Metal Dichalcogenides
Yuwei Zhang, Dongyang Wan, Tao Zhou et al. (+3 more)
Two-dimensional transition metal dichalcogenides (TMDCs) are promising for low-power optoelectronics, yet their operational speed is widely considered constrained by low room-temperature mobilities and carrier transit delays. Here, by combining on-chip terahertz optoelectronic sampling with thermally evaporated Ohmic contacts, we eliminate external parasitic delays and directly capture the intrinsic interfacial photoresponse in unencapsulated TMDCs under zero bias. The devices achieve ultrafast relaxation lifetimes of 48.5 ps in MoS2/Au and 14.2 ps in MoSe2/Ag, translating to intrinsic 3-dB bandwidths of 4.4 GHz and 7.5 GHz, respectively. Spatial scanning and bias-dependent measurements show that this response is position-independent and bias-immune, ruling out conventional drift-limited transport and identifying hot-carrier super-
diffusion driven by an interfacial electron temperature gradient as the operative mechanism. Furthermore, ultrafast pump-probe spectroscopy reveals that the macroscopic response time is quantitatively synchronized with the microscopic optical-to-acoustic
phonon scattering lifetime governed by the intrinsic
phonon bottleneck. Our findings establish
phonon engineering as a viable paradigm to tailor non-
equilibrium optoelectronic dynamics, offering a blueprint for zero-bias, ultrafast, self-powered devices.
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All authors Yuwei Zhang, Dongyang Wan, Tao Zhou, Hao Wu, Junpeng Lu, Zhenhua Ni
Fluid Dynamics
Dynamic Reduced-Order Data Assimilation from Sparse Velocity Measurements
Mauricio Portilla, Felipe Galarce, Ernesto Castillo et al. (+1 more)
We present a novel reduced-order data assimilation framework, termed Reduced-Order Dynamical Assimilation (RODAS), for reconstructing high-resolution, time-resolved flow fields from sparse velocity measurements. The method combines low-dimensional experimental observations with a physics-based parametric reduced-order model, enabling both spatial extrapolation beyond the measurement region and temporal super-resolution. The approach first identifies the dominant dynamics from sparse measurements through Dynamic Mode Decomposition (DMD), and subsequently reconstructs the corresponding full-order flow
evolution by projecting the identified dynamics onto a parametric Proper Orthogonal Decomposition (POD)
manifold generated from high-fidelity numerical simulations. Unlike conventional reduced-order data assimilation methods that estimate independent snapshots or treat time as an additional parameter, RODAS reconstructs an entire dynamical trajectory in a single inference step while naturally incorporating parametric variability. We assess the proposed methodology on
vortex shedding behind a circular cylinder for both Newtonian and non-Newtonian (Carreau-Yasuda) fluids. Numerical experiments demonstrate accurate reconstruction of high-resolution velocity fields from localized, low-resolution measurements, achieving sub-percent reconstruction errors with sufficiently rich reduced bases, robust performance under severe temporal undersampling, and accurate prediction of engineering quantities of interest such as the drag coefficient. These results demonstrate that RODAS provides an efficient framework for real-time, physics-informed reconstruction of unsteady flows from sparse experimental data.
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All authors Mauricio Portilla, Felipe Galarce, Ernesto Castillo, Benjamin Herrmann
High Energy Physics (Phenomenology)
Inelastic Dark Matter and High-Energy Recoil Signatures in LZ
Zi-Tong Fan, Hong-Jian He, Yu-Chen Wang et al. (+1 more)
We study the inelastic dark matter (iDM) that consists of two-component dark matter particles $(\chi_1,\chi_2)$ and serves as a minimal extension beyond the commonly used one-component DM models. A distinctive feature of such iDM scattering with the target
nuclei is to favorably produce signals at high
nuclear recoil (NR) energy region in both exothermic and endothermic processes. In particular, for the exothermic dark matter scenario, the signal does not rely on the tail of the Boltzmann velocity distribution. As a result, the required DM-
nucleus scattering cross section is significantly reduced, which in turn helps to substantially relax the stringent constraints imposed by IceCube
neutrino searches. Using the inelastic DM-
nucleus scattering, we naturally explain the newly reported event excess at high
recoil energy with the LUX-ZEPLIN (LZ) experiment.
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All authors Zi-Tong Fan, Hong-Jian He, Yu-Chen Wang, Yue Zhao
Quantum Physics
Faster Quantum Monte Carlo Simulation by Random Compilation
John M. Martyn, Joshua Lin, Neill C. Warrington et al. (+2 more)
Quantum Monte Carlo (QMC)
algorithms are among the most powerful classical methods for simulating
quantum systems, yet their accuracy is often limited by the systematic errors in the approximations used, such as Trotterization. Here we introduce randomly compiled
quantum Monte Carlo (RC-QMC) as a general framework that suppresses these systematic errors by averaging over a family of approximations rather than relying on a single fixed one. This strategy is grounded in the concept of randomized compiling from
quantum computing, which suppresses errors by sampling over
quantum gates, at essentially no additional computational cost. Consequently, our framework achieves a computational advantage over standard QMC methods when estimating a target state to a desired level of accuracy. We illustrate this advantage on two key Monte Carlo
algorithms: (1) path integral
quantum Monte Carlo for estimating thermal states, and (2) the
quantum trajectories method for simulating open system dynamics. In aggregate, these results represent a cross-fertilization of
quantum and classical
algorithms, are readily generalizable to other QMC methods, and suggest wider applications in classical simulation.
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All authors John M. Martyn, Joshua Lin, Neill C. Warrington, Isaac L. Chuang, Andrew J. Daley
Mathematical Physics · Cross-listed from math.AP
Open Inextensible Filaments in Planar Stokes Flow: Well-Posedness, Endpoint Asymptotics, and Straightening
Han Zhou
We study an inextensible open filament with free ends in a planar Stokes fluid. The system reduces to a third-order nonlocal
curvature equation coupled to an
elliptic equation for the tension. We prove local well-posedness for nearly critical initial data in supported Sobolev spaces $\widetilde H^s$, $-1/2<s\le0$, satisfying the arc-chord condition. For positive times, we prove improved Sobolev regularity and derive a $d^{3/2}$-type expansion at each free end using Wiener–
Hopf factorization, where $d$ denotes the distance to that endpoint. We further prove global existence and exponential convergence to a straight filament for sufficiently small initial data and for finite-energy initial data satisfying $E(0)<\pi^2/4$. The finite-energy result follows from an energy identity and a
geometric estimate relating the bending energy to the arc-chord constant. More generally, any finite-time breakdown must be accompanied by loss of the arc-chord condition, while every global solution either converges exponentially to a straight filament or has arc-chord constants tending to zero along a sequence of times tending to infinity.
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Computational Physics · Cross-listed from math.NA
Invariant domain preservation for hybrid point-value and cell-average discretizations of hyperbolic equations on general meshes
Shengrong Ding, Shumo Cui, Remi Abgrall et al. (+1 more)
This paper presents a unified invariant-domain-preserving (IDP) framework for hybrid discretizations of
hyperbolic conservation laws, including active flux and PAMPA methods, in which
cell averages are updated conservatively while
cell-boundary point values evolve under a possibly non-conservative operator. The main challenge is to preserve admissibility for these two coupled sets of states under a single local stability condition, without adding evolved degrees of freedom or relying on post-update repairs. For the point-value update, we introduce an admissibility transform based on a barrier–Legendre map for convex admissible interiors described by concave constraints, and prove that the inverse map is globally defined and Lipschitz continuous on the relevant sets. For the conservative
cell-average update, we establish a structural obstruction
theorem: the single-state continuous physical flux built from admissible boundary traces alone cannot provide a conservative IDP guarantee, for any prescribed CFL number, when internal reconstruction values are uncontrolled. This identifies the missing local control that must be supplied by an additional IDP flux mechanism. To realize this mechanism explicitly, we combine
cell average decompositions (CAD),
geometric quasilinearization, and local a priori scaling to construct admissible, generally discontinuous trace states before flux evaluation. Under an explicit trace-based CFL condition, with constants determined by local CAD weights and trace-state wave-speed bounds, the coupled hybrid update preserves the prescribed invariant domain. Concrete third-order schemes are developed on triangular, Cartesian, convex quadrilateral, and general convex polygonal meshes. Numerical results demonstrate the designed order of accuracy for smooth solutions and the strict preservation of physical admissibility.
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All authors Shengrong Ding, Shumo Cui, Remi Abgrall, Kailiang Wu
Instrumentation and Methods for Astrophysics
Beyond the BLUE I: the advantage ceiling - how much can any estimator beat the matched filter in mm/submm survey data?
Kaustuv Basu
Papers claiming that convolutional neural networks outperform the matched filter are now common in astronomy. Since that filter is the best linear unbiased
estimator (BLUE) for any noise of given covariance, and the minimum-variance unbiased
estimator under Gaussian noise, such a claim requires that the noise covariance varies from image to image or the noise is non-Gaussian. We introduce the advantage ceiling eta >= 1, which quantifies both cases: the Fisher information for the amplitude in units of the matched filter's, computable from noise-only simulations before any network is trained, and a bound on the variance of any
estimator unbiased at each true amplitude. We compute eta for a suite of millimeter/submillimeter survey noise models and for compact and extended source templates, using a variational score-matching ladder whose rungs are
estimator classes of increasing statistical order, from linear to convolutional. With an instrumental white-noise floor, Gaussian noise returns eta = 0.94-1.06 (+-0.04); covariance mixtures give exact ceilings of 10.2 (spectral tilt, extended source), 2.1 (leaked components) and 1.1-1.8 otherwise; residual artifacts give eta <= 1.09. Source confusion gives the largest advantage, eta >= 3.8 (extended) and >= 2.4 (compact). Three unmodelled channels - a zeroed DC mode, a missing white floor and floating-point rounding - can manufacture spurious advantages of up to two orders of magnitude. A ResNet regressor is 6-15% less efficient than the matched filter on Gaussian noise once prior shrinkage is divided out, and realizes a factor 1.8 of the 10.2 available on the spectral-tilt mixture; a companion paper tests such regressors against these ceilings.
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Physics and Society
Assessing flood-conditioned power dependency of urban rail transit and its effects on resilience under climate change
Wei Bi, Bryan T. Adey and Jürgen Hackl
Urban rail transit (URT) faces increasing flood risk while relying on traction power systems whose failures can trigger cascading disruption. Existing studies on URT flood resilience often oversimplify power dependency by overlooking traction power redundancy and rarely consider flood-conditioned cascading impacts, providing limited insight into how flood-induced traction power failures propagate through operations and affect system resilience. This study marks the first quantitative assessment of flood-conditioned power dependency of URT and its effects on system resilience. The methodology integrates a double-layer URT network model, spatial flood exposure assessment, service disruption simulation, a flood-conditioned power dependency index, and a journey-based performance metric that captures resilience properties of robustness and redundancy. It is applied to the London rail transit network under surface water flood scenarios across current and RCP8.5
climate conditions, two traction power feeding mechanisms, and four substation flood-failure thresholds. Results show that traction power redundancy fundamentally shapes the severity of cascading impacts. Under double-end feeding, power-attributable performance loss remains minimal, whereas single-end feeding leads to substantially greater loss and is highly sensitive to substation failure thresholds. The proposed dependency index is strongly correlated with dependency-related performance loss, supporting its use as a proxy for dependency-induced additional consequences in strategic planning.
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Astrophysics of Galaxies
ACES VIII: A Survey of Compact, High-Velocity Features Observed in CS(2-1)
Dani R. Lipman, Jakub Poznanski, Savannah R. Gramze et al. (+46 more)
The extreme kinematics of the Milky Way's Central Molecular Zone (CMZ) are influenced by processes such as dynamical shearing, cloud collisions, and
stellar feedback. These events are visible in molecular data as vertically spiked features in position-velocity (PV) diagrams referred to as high velocity dispersion compact clouds (HVCCs). Using ALMA CMZ Exploration Survey (ACES) CS (2-1) molecular data, we identify a total of 235 HVCC candidates, 163 of which are visually identified, and an additional 72 identified via automated dendrogram methods. For each HVCC we catalog and report the physical and kinematic properties, explore line ratios of the cold dense gas tracer \HNCO with C-shock tracers, classify the morphology of their PV diagrams, and view their position-position-velocity distribution. The sample includes structures which are compact (d<5 pc) and have large velocity extents (20 km/s $<\Delta \mathrm{V} <$ 140 km/s), with most structures showing thin, `spiked' PV morphologies. We highlight areas of high ratios between HNCO and C-shock tracers along the edge of known orbital streams, implying a buildup of bar lane gas accreting onto the CMZ. We also find a collection of HVCCs overlapping with the 50 km/s cloud and known circumnuclear disk features. This catalog will be used for future investigation of
nuclear inflow and determining dominant mechanisms disrupting average CMZ gas flows.
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All authors Dani R. Lipman, Jakub Poznanski, Savannah R. Gramze, Claire E. Cook, Cara Battersby, Jennifer Wallace, Pablo García, Samantha Adams, Xinyu Mai, Kai Smith, Natalie Butterfield, Sophia Kempe, Adam Ginsburg, Rojita Buddhacharya, Tomoharu Oka, Danya Alboslani, Jairo Armijos-Abendaño, John Bally, Ashley T. Barnes, Nazar Budaiev, Alyssa Bulatek, Laura Colzi, Christoph Federrath, Zi-Xuan Feng, Jonathan D. Henshaw, Paul Ho, Pei-Ying Hsieh, Katharina Immer, Izaskun Jiménez-Serra, Ralf S. Klessen, Steven N. Longmore, Xing Lu, Elisabeth A.C. Mills, N. Bijas, Francisco Nogueras-Lara, Dylan M. Paré, Maya A. Petkova, Jaime E. Pineda, Marc W. Pound, Víctor M. Rivilla, Álvaro Sánchez-Monge, Miriam G. Santa-Maria, Anika Schmiedeke, Yoshiaki Sofue, Mattia C. Sormani, Howard A. Smith, Robin G. Tress, Daniel Walker, Qizhou Zhang
Quantum Physics
Symmetry structure dependent diagnostic of the Quantum Mpemba Effect
Tamizhselvan S, Manju C, Bijay Kumar Agarwalla et al. (+1 more)
Understanding
symmetry restoration in isolated
quantum many-body systems is an important problem in nonequilibrium many-body
quantum physics. Recent studies have shown that the
quantum Mpemba effect can be characterized through
entanglement asymmetry, where states with stronger initial
symmetry breaking restore
symmetry faster. However, it remains unclear whether conventional energy-based measures, such as the trace distance, capture the same phenomenon. We investigate this question in closed
spin-$1/2$
quantum systems with different
symmetries by analyzing the dynamics of
symmetry-breaking initial states. Combining numerical simulations with an analytical decomposition of the trace distance into
symmetry-coherence and residual contributions, we identify the conditions under which trace distance tracks
entanglement asymmetry and reproduces the Mpemba–like behavior observed in it. For charge
symmetry, the residual contribution is negligible, making the trace distance effectively governed by
symmetry-sector coherences. In contrast, for permutation
symmetry, a significant residual contribution leads to qualitatively different relaxation dynamics. Our results establish when conventional energy-based diagnostics reliably capture
symmetry-restoration dynamics and clarify the distinct physical information encoded by
entanglement asymmetry and trace distance.
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All authors Tamizhselvan S, Manju C, Bijay Kumar Agarwalla, Uma Divakaran
Statistical Mechanics
Protected domains and cooperative invasion on weighted networks
Abhishek Chowdhury
Reciprocal contacts can favor cooperation by protecting a lineage until its descendants compete as a group. An individual is chosen to reproduce from the whole population, with a probability increasing with its averaged cooperation payoff. Its offspring replaces a neighbor through contacts weighted equally in both directions. We compare a single cooperator taking over defectors with the reverse invasion, using the same distribution of introduction sites. When payoffs weakly affect reproduction, every network with at least six sites and a path visiting them all admits weights favoring cooperation at any benefit-cost ratio $b/c>1$. This holds for mutants placed uniformly or arising in newborn offspring. Unequal contacts sustain aligned domains around two protected sites, converting individual reproduction into collective competition. Cooperation cannot have an advantage when its benefit does not exceed its cost, at any positive selection strength with positive reproduction rates. Where mutants arise changes which contact patterns can use this mechanism. On a five-site path, the weak-selection threshold has the sharp lower bound seven under uniform placement; newborn introduction never favors cooperation at this order. We classify the contact patterns with at most five sites that can favor cooperation under either rule; newborn introduction requires a four- or five-site cycle. Tracing copies backward to their ancestors separates domain competition from the probability of reaching it. Exact
polynomial inequalities prove sharp threshold bounds for paths and the four- and five-site cycles. The same ancestry reconstructs
evolution without selection on weighted paths and cycles and fixes the slowest relaxation rate on every connected reciprocal network. Cooperation thus depends on both the collective competitors created by contacts and the route by which a new lineage enters them.
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High Energy Physics (Phenomenology)
Anomalies at the End of the Universe?
Jay Hubisz, Hanieh Moradipasha and Prakriti Singh
The spatial distribution of anomalies in extra dimensional theories on a slice of AdS leads to a puzzle where anomalies may not match across different geometries that are dual to various states of the same CFT. We argue that consistency of the anomaly across such geometries necessitates the addition of topological terms or other bulk
fermions to the theory that flow any IR localized consistent anomaly into the “UV" region of these geometries if one wishes to have such a dual interpretation.
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Medical Physics
Understanding Search and Decision Errors in Liver Metastasis Detection and the Effects of Lower Radiation Dose
Parmita Mondal, Rickey Carter, Andrew D Missert et al. (+7 more)
The detection performance of liver metastases decreases with the reduction of radiation dose, but misses are heterogeneous. Previous eye tracking work has characterized missed metastases into two categories: search errors i.e., the eyes never land on the lesion, and decision errors i.e., the lesion is seen but not recognized as malignant. We integrated three prior reader studies to answer this question. In all studies, radiologists interpreted the same set of 40 contrast enhanced abdominal CT exams containing 91 liver metastases whose locations had been previously marked. In two studies, the workstation recorded their gaze and eye movements. Using eye dwell times, metastases were classified as search-error-dominant (majority of misses had <2 sec gaze time) or decision-error-dominant (>2 sec gaze time). In the third study, exams were interpreted both at 120 and 200 quality reference mAs (QRM) by ten radiologists. The third study did not include eye tracking. Out of 91 liver metastases, we excluded 16 that were never missed in the eye tracking studies and used 75 liver metastases for the present study.
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All authors Parmita Mondal, Rickey Carter, Andrew D Missert, Akitoshi Inoue, Joel G. Fletcher, Hao Gong, Shuai Leng, Lifeng Yu, Cynthia H. McCollough, Scott S. Hsieh
High Energy Physics (Phenomenology)
Transition magnetic-dipole dark matter and the LZ230616 high-recoil candidate
Yuxuan He
A transition
magnetic dipole connects an endothermic
nuclear recoil to a delayed
photon. We study this interpretation of LZ230616, the 248-keV candidate in LZ's extended-energy search. Imposing the thermal abundance in a point hypercharge theory fixes a moment near $2.4 \times 10^{-4} \mathrm{TeV}^{-1}$ at the preferred masses, leaving a mass–splitting fit. The excited state travels about 0.6 m, making its decay relevant to the isolated-
recoil selection. A position-dependent TPC-exit response gives conditional maxima at $(1.07 \,\mathrm{TeV} ,346 \,\mathrm{keV} )$ without the high-energy sideband and $(0.44 \,\mathrm{TeV} ,321 \,\mathrm{keV})$ with its zero-count proxy. Their line rates exceed the H.E.S.S. Einasto bound by factors of about 11 and 5.5. We examine
halo dependence, other direct and indirect probes, and charged-messenger matching. Allowing a smaller moment and additional annihilation preserves the low-mass maxima while admitting heavier fits over 0.1–100 TeV. Delayed
recoil–
photon data can measure the splitting and moment, testing both the detector response and the assumed connection to thermal annihilation.
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Mathematical Physics · Cross-listed from math.PR
Aldous' spectral gap phenomena in stochastic exchange models
Pietro Caputo, Matteo Quattropani and Federico Sau
We consider a broad class of exchange dynamics with arbitrary weighted graph or hypergraph update structures, which includes the Kipnis–Marchioro–Presutti (KMP) model and the energies of Kac's walk on the sphere. These are conservative continuous-
spin systems whose reversible measures are Dirichlet distributions. We prove that their spectral gap is always attained by a
polynomial of degree at most two in the energy variables. Equivalently, through an intertwining with the associated discrete particle systems, the dominant mode is always represented by either a one-particle or a two-particle observable. We interpret this as a manifestation of an Aldous-type spectral gap phenomenon. In particular, the resulting two-particle spectral gap identity settles a recent
conjecture of Alon and Puder. We also characterize sharply when one particle suffices and when a genuinely two-particle mode dominates. Under a common rescaling of the Dirichlet parameters, segment-like geometries are precisely those for which the gap is always of one-particle type, mean-field geometries are precisely those for which it is always of two-particle type, and all other geometries exhibit a nontrivial transition. The proof relies on the analysis of the so-called hidden model, a dual representation of the original process. The mechanism underlying the degree-two reduction is remarkably robust and extends to a much broader class of
stochastic exchange models and their associated particle systems, including the harmonic process, the immediate exchange model, averaging-type processes, and nonreversible variants. Finally, we analyze boundary-driven versions of the KMP model, in which the bulk exchange dynamics interacts with reservoirs, generally resulting in nonreversible processes. In contrast to the conservative setting, we prove that the spectral gap of a boundary-driven model is always of one-particle type.
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Quantum Physics
Coherent advantage in the computational expressivity of excitonic networks
Matthew Du, Carlos Floyd, Dipti Jasrasaria et al. (+1 more)
The rising energy consumption of AI has generated interest in physical systems as alternative substrates for trainable computation. Recent experimental advances have enabled precise control over the couplings between molecular chromophores, which give rise to coherent excitation dynamics. Here, we study driven-dissipative excitonic networks as a computational platform, where the intersite couplings define the input and the steady state defines the output. We show that coherence enables computational expressivity to scale with network size, analogous to artificial neural networks. Both this scaling and the overall expressivity are suppressed by strong dephasing. Our work establishes coherence as a resource for expressive computation in nonequilibrium
quantum systems.
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All authors Matthew Du, Carlos Floyd, Dipti Jasrasaria, Suriyanarayanan Vaikuntanathan
Strongly Correlated Electrons
Gauge mean-field theories of the underscreened Kondo lattice
Ewan Scott and Michal Kwasigroch
Various mean-field decoupling schemes have been introduced thus far to study the important and challenging problem of the
spin-$1$ underscreened Kondo
lattice where
magnetic order can coexist with Kondo hybridization. We use a single control parameter $N$ and an unbiased variational ansatz to unify and connect the previously proposed decouplings to standard Read-Newns theory, where fluctuations are small in $1/N$. We compute the corrections around the large-$N$ limit. In particular, we make contact with Nozières strong-coupling theory by finding the residual
ferromagnetic Hund interaction that decays logarithmically in the case of a heavy-
fermion metal. We map out the ground state phase diagram as a function of $N$ and the Kondo coupling. We find crucial differences between the previously proposed mean-field theories in the strength of the hybridization and total magnetization of the coexistent phase. We show that, within our unifying variational theory, the previously proposed decouplings correspond to either taking $N=2$ from the start, or performing a $1/N$ expansion and then extrapolating to $N=2$. Finally, we summarize the generalization of our theory to $S>1$.
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Materials Science
Overcoming Transport Layer Bottlenecks to Quantify Ionic Parameters from Transient Ion Current Measurements of Perovskite Solar Cells
Shudi Jiao, Miguel Torre Cachafeiro, Huagui Lai et al. (+7 more)
In perovskite
solar cells (PSCs), voltage step-induced transient ion current (TIC) measurements, commonly referred to as bias-assisted charge extraction (BACE), are frequently used to quantify ion density. Drift-
diffusion simulations predict that the ion density computed from TIC saturates once mobile ions screen the electric field in the perovskite. However, experimental studies often report ion densities orders of magnitude above this limit, whose physical origin remains incompletely explained in terms of transport layer (TL) properties. In this work, the capacitance of the TLs is identified to be the fundamental bottleneck: the maximum quantifiable ion density is limited to the charge that can accumulate at the perovskite/TL interfaces, so that TIC most often depends more strongly on TL properties than on the ionic properties of the perovskite. Experiments with systematically varied C$_{\rm 60}$ electron-TL thickness (p-i-n) and Spiro-OMeTAD hole-TL doping (n-i-p) confirm this dependence across architectures. To overcome this limitation, the importance of a correction based on the average ionic displacement is discussed, and it is shown how extrapolating the TL-thickness trend towards the TL-free situation yields the actual ionic conductivity of the absorber, alongside density and mobility, depending on the assumed ionic model. Simulations are also examined in which ion penetration into the TLs or initial accumulation under forward bias raise the capacitive limit and extend TIC sensitivity to higher ion densities. The slow release of trapped carriers is also discussed as a potential source of current which can inflate the TIC signal. Overall, the presented analysis provides important practical considerations for interpreting TIC and quantifying ionic properties in PSCs.
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All authors Shudi Jiao, Miguel Torre Cachafeiro, Huagui Lai, Fuxiang Ji, Tristan Sachsenweger Ballantyne, Sharun Parayil Shaji, Matthias Diethelm, Fan Fu, Wei E.I. Sha, Wolfgang Tress
Physics and Society
Assessing extreme flood impacts on urban rail transit: A passenger-oriented, resilience-informed framework
Wei Bi
Urban rail transit systems (URTSs) are increasingly exposed to extreme floods following heavy precipitation, yet passenger travel impacts are often assessed through delay-based indicators that overlook infeasible journeys under large-scale disruptions. This study develops a passenger-oriented, resilience-informed framework for assessing flood impacts on URTS journeys from disruption onset to recovery completion. The framework presents a novel six-category classification of journey impacts, explicitly considering rerouting, alternative station use, and a delay threshold. It is demonstrated through hourly dynamic simulations of 15 London URTS lines under 30-year, 100-year, and 1,000-year flood risk scenarios. Results indicate that severe flood disruptions lead to substantial unsatisfied demand, driven primarily by unavailable routes rather than unacceptable delays. Compared with finer behaviour adjustments, rerouting dominates travel impacts. These findings highlight the significance of moving beyond delay-based assessment and provide valuable evidence on essential behavioural mechanisms for strategic-level stress testing intended to inform URTS flood resilience intervention planning.
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High Energy Physics (Theory)
Null String Holography, Null Strings Probe Projective Boundary of Their Target Spaces
M.M. Sheikh-Jabbari and H. Yavartanoo
We prove that the minimal null string theory on a background
manifold ${\mathcal M}$ is classically equivalent to the ILST theory on the projective boundary of $\mathcal M$, ${{\cal B}_{_{\text{P}}}}={\partial_{_{\text{P}}}\mathcal{M}}$. We
conjecture that this equivalence also holds at
quantum level, we dub this correspondence null string holography. In particular, we show the minimal null string theory on the Poincaré patch of a $D$ dimensional Anti de Sitter (AdS$_D$) background is described by the ILST theory on $(D-1)$-dimensional Minkowski background, paralleling the celebrated AdS/CFT. The minimal null string theory on the cosmological patch of dS$_D$ is governed by the ILST theory on $(D-1)$-dimensional flat Euclidean space. For null strings on a $D$-dimensional Minkowski space $\mathbb{M}_D$, depending on the coordinate patches used to span $\mathbb{M}_D$, the projective boundary includes a dS$_{D-1}$, asymptotic null infinities ${\mathcal I}^\pm$ and the hyperboloid $\mathbb{H}^{D-1}$ patches. The ILST theory dual to the minimal null strings on each patch, then resides on the piece of the projective boundary spanned by the coordinates adopted in the patch. We comment on possible applications of null string holography to black hole horizons.
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Nuclear Theory
Systematic study of E2 matrix elements in the framework of the Triaxial Projected Shell Model
Stefan Frauendorf, Syed Rouoof, Gowhar Bhat et al. (+5 more)
Nuclides for which extended sets of E2
matrix elements have been measured by means of COULEX experiments are studied in the framework of the triaxial projected shell model (TPSM). The studies encompass: 70,72,74,76Ge, 76,78,80,82Se, 100Mo, 104Ru, 110Pd, 168Er, 186,188,190Os, 184Pt. The experimental energies of the ground band, of the quasi gamma band and of some excited 0+ bands as well as their individual intra and inter band
matrix E2
matrix elements are systematically accounted for by the microscopic TPSM calculations.
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All authors Stefan Frauendorf, Syed Rouoof, Gowhar Bhat, Sheikh Jehangir, Nazira Nazir, Kouser Qureshie, Niyaz Rather, Javid Sheikh
Quantum Physics
Faster Computation with the Generalized Laplacian Quantum Walk
Jonas Duda and Thomas G. Wong
Quantum walks are the
quantum analogues of classical random walks or Markov chains. They are universal models of
quantum computing, and they underpin a variety of
quantum algorithms. We prove that a continuous-time
quantum walk effected by a generalized
Laplacian, which can arise in
spin chains, can solve a computational problem more quickly than typical
quantum walks governed by the standard
Laplacian or adjacency
matrix. This generalized
Laplacian consists of the standard
Laplacian plus a real-valued multiple of the degree
matrix, and we prove that as the magnitude of the multiple of the degree
matrix is increased, its corresponding
quantum walk can search the complete bipartite graph with multiple marked vertices in time that approaches the optimal. This raises the potential for the generalized
Laplacian quantum walk to be a useful method for developing additional faster
quantum algorithms.
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Applied Physics
Thermal Stability and Carrier Recombination Kinetics in InGaN/GaN Multiple Quantum Wells under High-Temperature Annealing
Quan-Shan Liu, Sadia Sheraz, Sabina Gurung et al. (+3 more)
The thermal stability and carrier recombination kinetics of an as-received InGaN/GaN multiple
quantum well (MQW) structure, capped with a protective AlN thin film, are studied following a series of thermal annealings at temperatures between 500 deg C and 1100 deg C. Under 325 nm focused
laser excitation at room temperature, the sample's photoluminescence (PL) spectrum exhibits three emission bands: an ultraviolet peak at 363 nm, a blue peak at 455 nm, and a yellow peak at 565 nm. We find that the MQW's 455 nm emission is preserved after annealing at 1100 deg C. Moreover, room-temperature PL excitation (PLE) and time-resolved PL (TRPL) have been investigated to shed light on the sample's energy-transfer mechanisms and emission decay characteristics. Power-dependent PL spectra analysis shows that the carrier recombination mechanism of the MQW's emission has not been affected by thermal treatment. Rate equation modelling and chromaticity coordinate analysis also show limited thermal impact on the calculated equivalent emission lifetime and emissive colour. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis has been performed, further evidencing the preservation of the MQW structure in the annealed sample.
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All authors Quan-Shan Liu, Sadia Sheraz, Sabina Gurung, Maddison Coke, Nicholas Lockyer, Richard J. Curry
Atomic Physics
Deterministic engineering of topological defects in two-dimensional single-species ion Coulomb crystals
Luca-Amadeus Rüffert, Hemanth Kalathur and Tanja E. Mehlstäubler
We propose and numerically demonstrate a deterministic protocol for preparing and tailoring topological defects in two-dimensional single-species Coulomb
crystals confined in
radio-frequency traps. In conventional finite-rate quenches through the linear-to-zigzag transition, defects form stochastically from independently chosen broken-
symmetry domains, and the quench rate controls the resulting domain structure. We instead use an initial three-dimensional helix structure and planarize it into a deterministic defected state. We demonstrate that the number and approximate axial positions of kinks are encoded by the projected nodes of the initial helix. We find that selected helices can remain on metastable finite-winding branches during planarization and yield reproducible single- or multi-kink states, even in the adiabatic limit. Using the quench rate as an additional control parameter substantially enlarges the set of precursor helices that result in defected states, as a fast planarization can prevent reordering during the quench and freeze in the pre-existing domain pattern. After planarization, the survival and mutual interaction of the defects are governed by their effective Peierls–Nabarro potential landscape. By numerically isolating the interaction energy for the two defect types, we find that the interaction of extended kinks is attractive over the investigated parameter range, while odd kinks exhibit a short-range repulsive barrier tunable by the anisotropy of the trapping potential $\alpha$. Finally, we introduce an experimentally motivated post-selection scheme in which $\alpha$ is used to selectively destabilize, annihilate, or convert targeted defects. Our results provide a route to deterministic single- and multi-kink preparation in single-species Coulomb
crystals, enabling controlled studies of defect interactions, transport, and nanofriction.
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Quantum Physics · Cross-listed from math.FA
Noncommutative sharp Hausdorff-Young inequality
Hongsen Qiu and Xiao Xiong
We prove the sharp Hausdorff–Young inequality on
quantum euclidean spaces. Our result implies the sharp Hausdorff–Young constants for the Weyl transform. The key ingredients are a sharp Hessian comparison inequality and a novel flow related to the mixed- norm of noncommutative Gabor transform; the Hessian comparison leads to the monotonicity of the flow. We also apply the same flow technique to prove the sharp Hausdorff–Young inequalities on Heisenberg groups and the affine group.
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Solar and Stellar Astrophysics
Wave Emission and Absorption in a Near-Sun Proton-Cyclotron Wave Storm
Kristopher G Klein, Daniel Verscharen, Mihailo Martinovic et al. (+5 more)
Quantification of energy transport and dissipation in weakly collisional heliospheric
plasmas that are far from local thermodynamic
equilibrium is an outstanding scientific problem. A central challenge is determining how non-Maxwellian velocity-space structure affects damping and emission of coherent ion-scale waves, especially compared to simplified analytical models for background
plasma velocity distributions. In this work, we study the damping and emission of parallel-propagating
proton cyclotron waves for two models of
proton velocity distributions measured by the SPAN-I instrument on board Parker
Solar Probe during an extended storm of waves with left-hand polarization in the
solar wind at a heliocentric distance of 30.1
solar radii. Using the measured velocity distribution rather than a two-component bi-Maxwellian model predicts instabilities consistent with the observed coherent waves. For intervals in which both models predict net damping, the observed VDF model yields weaker damping in 90% of cases, with a reduction in the integrated heating rate of 0.44 relative to the bi-Maxwellian model. These results suggest that simplified analytical velocity distribution models may overestimate cyclotron damping and underestimate wave emission in the near-Sun
solar wind.
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All authors Kristopher G Klein, Daniel Verscharen, Mihailo Martinovic, Niranjana, Ali Rahmati, Roberto Livi, Davin Larson, Michael Stevens
Space Physics
Cascade models of anisotropic turbulence in magnetized plasma of solar wind
A. Bershadskii
The
solar wind
plasma is modeled as a collection of discrete domains, each possessing local rotational
symmetry about its domain-mean
magnetic field. Based on this partial
symmetry, we construct cascade models governed by the nonlinear and Alfvénic time scales. We introduce a
stochastic renewal process with a bimodal waiting-time distribution determined by these two time scales. This process yields a two-branch renormalization solution for the total energy: a statistically robust branch with an Iroshnikov-Kraichnan-like $k^{-3/2}$ spectrum and a statistically marginal branch with a Kolmogorov-like $k^{-5/3}$ spectrum. Whenever energy-flux fluctuations become supercritical, the system selects the faster of the two available cascade rates, thereby preventing flux accumulation. During
solar wind expansion, the system undergoes a dynamical first-order phase transition from the slow $k^{-3/2}$ cascade to the fast $k^{-5/3}$ cascade, with switchbacks accelerating the transition. The mixing of subcritical and supercritical domains in raw spacecraft measurements produces an apparent decoupling of the velocity and
magnetic-field spectral indices. Incorporating a
magnetic helicity cascade slaved to the energy cascade, we show that the large-scale spectra decouple into $k^{-3/4}$
magnetic and $k^{-3/2}$ kinetic spectra. For switchbacks inside the upper
solar corona, the corresponding large-scale spectra instead decouple into $k^{-2/3}$
magnetic and $k^{-5/3}$ kinetic spectra. Data from Voyager, Ulysses, Helios, Wind, and PSP confirm the spectral signatures across heliospheric regions spanning heliocentric distances from 0.056 to 140 AU.
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Mesoscale and Nanoscale Physics
WannierNLQG: A Julia package for nonlinear optical responses and quantum geometry from Wannier tight-binding models
Zhuocheng Lu, Zhichao Guo, Yuanyuan Xua et al. (+2 more)
Nonlinear optical responses and
quantum geometry are central to modern condensed matter physics and are deeply intertwined. We introduce WannierNLQG, an extensible Julia framework for computing nonlinear optical responses and
quantum geometric quantities from Wannier tight-binding models. Its gauge-consistent, degeneracy-aware architecture accommodates perturbative responses at arbitrary order and additional
quantum geometric quantities. The current release evaluates ordinary,
spin, and
photon-drag injection and shift currents, as Brillouin-zone integrals and on k slices. For shift current, a unified interface exposes four complementary formulations: the conventional method, projector trace, generalized Wilson loop, and a finite-momentum
geometric loop, with the last three explicitly accommodating degenerate subspaces. The framework also provides k-resolved Berry
curvature,
quantum metric, their multipoles, and additional
quantum geometric and mixed momentum-
spin quantities. Experimental
symmetry workflows additionally support
symmetry-adapted Wannier construction, symmetrization of tight-binding models and real-space operators, and reduction of spatially uniform response integrals to irreducible k-point orbits and invariant tensor components. The documentation covers formula conventions, the TaskConfig interface, and auditable output formats, with GeS and
bilayer MoS2 case studies illustrating method comparison, degeneracy handling,
quantum geometric analysis, and
photon-drag responses. Together, these capabilities enable first-principles calculations of nonlinear response and
quantum geometry in realistic multiband materials, connecting
quantum geometry with quantitative materials modeling for optoelectronic, spintronic, and photovoltaic applications.
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All authors Zhuocheng Lu, Zhichao Guo, Yuanyuan Xua, Jiacheng Yao, Hua Wang