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Physics Physics

physics Watch Physics

Tuesday 21 July

Chemical Physics · Cross-listed from cond-mat.supr-con

Self-consistent GW theory for superconductivity in SrTiO3 models

Zhi-Hao Cui, John Sous, Andrew J. Millis et al. (+1 more)

Superconductivity in doped SrTiO$_3$ occurs over a wide range of carrier densities, including those for which the Fermi energy is below the polar longitudinal optical phonon scale. In this regime, the assumptions underpinning conventional implementations of Migdal-Eliashberg theory, including frequency cutoffs at the phonon scale and a Coulomb pseudopotential $\mu^\ast$, are not valid. We solve the finite-temperature $GW$ equations with full momentum and frequency dependence, without cutoffs or $\mu^\ast$, for polar one-band models of SrTiO$_3$, using effective masses and three-phonon dielectric functions parameterized from ab initio calculations. Comparing different self-consistency levels, namely $G_0W_0$, $GW_0$, and fully self-consistent $GW$, we find that the one-shot ($G_0W_0$) kernel overestimates the pairing-onset temperature by one to two orders of magnitude. The dominant suppression comes from replacing $G_0$ by $G$, thereby incorporating the phonon renormalization factor in the electron Green function. Using the self-consistently computed interaction $W$ further lowers and narrows the pairing-onset dome. In the dilute limit, our calculations identify the pairing channel as the Fröhlich phonon interaction screened by the incipient ferroelectricity of the material, with plasmonic and electronic screening effects negligible. The numerical solution of the full equations reveals a pairing-onset scale that remains non-zero as the density tends to zero, whereas Fermi-surface projection or Fermi-energy frequency truncation removes it. This work highlights the relevance of incipient ferroelectricity, the importance of self-consistency, and the need for a full momentum- and frequency-dependent treatment in modeling superconductivity in SrTiO$_3$-like doped polar semiconductors.
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All authors Zhi-Hao Cui, John Sous, Andrew J. Millis, David R. Reichman

Atomic Physics · Cross-listed from quant-ph

Quantum sensing of low-frequency electric signal enabled by modulated auxiliary field in Rydberg atoms

Xiayang Fan, Shenchao Jin, Jiatian Liu et al. (+3 more)

Rydberg atoms have emerged as a versatile and efficient platform for high-sensitivity quantum sensing of free-space electric fields, with remarkable progress in detecting low-frequency signals. To date, low-frequency Rydberg receivers have relied on a constant bias field, typically realized via intra-cell electrodes or Rydberg plasmas generated by photoelectric effects or inter-atomic interactions. While these approaches improve sensitivity, they suffer from inherent challenges in calibration, long-term stability, and robustness, hindering practical deployment. Here, we propose, design, and experimentally demonstrate a quantum sensing scheme for low-frequency electric signals using modulated auxiliary fields in Rydberg atoms. Unlike conventional methods that employ external DC electric fields that are often fully shielded by adsorbed atom layers on the cell walls, we introduce an AC-field modulation strategy. The incoming low-frequency signal mixes with the auxiliary field, and together they induce Stark shifts of the Rydberg level. These shifts are mapped onto the probe laser via electromagnetically induced transparency (EIT), in a manner analogous to heterodyne detection. We demonstrate a sensitivity of $7.5 \pm 2.6~\mathrm{\mu V/(cm\cdot Hz^{1/2})}$ at 5 kHz and a minimal detectable field of $0.26 \pm 0.04~\mathrm{\mu V/cm}$ with an integration time of 1000 s. Furthermore, we extend this approach to systematically analyze the performance of generalized auxiliary fields containing multiple frequency components. By virtue of modulated auxiliary field and quantum frequency mixing, our results establish a robust and systematic framework for quantum sensing of low-frequency electric fields with Rydberg atoms, offering improved sensitivity, stability, and immunity to environmental drifts.
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All authors Xiayang Fan, Shenchao Jin, Jiatian Liu, Jialiang Zhang, Qichao Qi, Yuan Sun

Computational Physics

Uncertainty quantification in mechanics: A unified Bayesian perspective

Sascha Ranftl, Malte Rolf, Gerhard A. Holzapfel et al. (+1 more)

Uncertainty quantification (UQ) is essential to experimental mechanics, but has become particularly relevant in computational mechanics, manifesting in two fundamental problem types: forward and inverse problems. The former addresses how input uncertainties propagate to the quantities of interest, whereas the latter aims to infer unknown parameters from experimental observations or simulations. Since efficient propagation typically requires a prohibitive number of evaluations to compute marginal output distributions, the development of fast, data-driven surrogate models becomes necessary. Thus, we can distinguish between two inverse tasks: (i) the identification and calibration of input uncertainties, and (ii) the construction of surrogates, a methodology collectively referred to as surrogate-based UQ. Building on probabilistic reasoning and the concept of partial belief, we demonstrate that Bayesian probability theory provides a unified theoretical framework for addressing both problem types. We further show that Bayesian inference allows for the seamless incorporation of essential subproblems, including model selection for identifying the most probable model specifications and experimental design for optimizing data collection by identifying experiments or simulations that maximize expected information gain about parameters, among others such as connections to sensitivity analysis or the use of special priors like random fields. While this theoretical framework is presented for general mechanical problems, particular emphasis is placed on biomechanics, where variability and uncertainty is especially pronounced due to inherent biological heterogeneity, patient-specific variability, and noisy data.
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All authors Sascha Ranftl, Malte Rolf, Gerhard A. Holzapfel, Ellen Kuhl

Optics

Raman-Assisted Multiband Nonlinear Frequency-Conversion Network in a High-Q LTOI Microdisk

Zhifan Fang, Yuxuan He, Zhangning Pan et al. (+2 more)

On-chip nonlinear frequency conversion offers a key route to broadband coherent light sources, but spanning telecom, visible, and ultraviolet wavelengths within a single resonator remains challenging. Lithium tantalate-on-insulator (LTOI), which has recently emerged as a promising material platform for integrated photonics, combines strong Raman activity, a large second-order nonlinearity, broad optical transparency and high resistance to photorefractive damage, thereby attracting increasing attention for on-chip nonlinear frequency conversion. Here, we experimentally demonstrate a Raman-assisted multiband frequency-conversion network in a high-Q LTOI microdisk with a loaded quality factor of 2.48x10^6. The resonant pumping produced high-purity single-mode Raman lasing with a 3.14 mW threshold, 32.44% slope efficiency, and an excellent side-mode suppression ratio (SMSR) of 29.5 dB. Under a nearby pump condition, we also observe multiple Stokes components together with an anti-Stokes line on the short-wavelength side of the pump. The resulting multiple intracavity Stokes fields subsequently acted as frequency seeds for cascaded chi^(2) processes, producing near-infrared and visible signals and extending the emission to 312.6 nm in the ultraviolet. These findings establish the cooperative action of Raman gain and second-order nonlinearity across widely separated spectral bands within a single microcavity. The device therefore offers a route toward integrated multiband light sources and a platform for studying coupled nonlinear dynamics.
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All authors Zhifan Fang, Yuxuan He, Zhangning Pan, Xianfeng Chen, Yuping Chen

Optics · Cross-listed from eess.SP

Cyclic-Prefix-Free OFDM With Tail-Reuse Reconstruction for Distributed Acoustic Sensing

Ziang Chen, Zhiyang Xue, Zhongxing Tian et al. (+4 more)

Orthogonal frequency-division multiplexing (OFDM) enables frequency-domain reconstruction of the distributed Rayleigh backscatter channel in coherent distributed acoustic sensing (DAS), but an explicitly transmitted cyclic prefix (CP) lengthens the probing period and reduces the slow-time Nyquist limit of each range cell. We investigate a repeated cyclic-prefix-free OFDM waveform for DAS, in which the tail of the preceding useful block serves as a virtual cyclic extension. A finite-memory range condition for tail-reuse reconstruction is derived, and circular folding is identified when the useful period is shorter than the channel memory. For fixed useful-block length and fiber memory, removing the explicit CP increases the period-limited highest unaliased vibration frequency without changing the occupied-bandwidth-limited spatial resolution. In a 5.2-km numerical configuration, a 75-MSa/s processing rate and a 4096-sample useful block give a 54.61-us probing period and a 9.16-kHz slow-time Nyquist limit. Simulations verify tail reuse, the predicted folding boundary, and recovery of 100 vibration events from 800 Hz to 8800 Hz. Bandwidth-scaling simulations further show that joint processing of fine spatial observations improves differential-phase reliability and reconstruction SNR at a fixed reporting interval. Experiments on a 5.2-km coherent DAS link with 111.984-MHz occupied OFDM bandwidth blindly localize 500-Hz and 3-kHz PZT-induced vibrations at 5063.7 m and 5070.1 m, respectively, and recover their waveforms and spectra. The results demonstrate feasible tail-reuse channel reconstruction and quantify the extension of the unaliased vibration bandwidth.
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All authors Ziang Chen, Zhiyang Xue, Zhongxing Tian, Zeyu Feng, Dongdong Zou, Yi Cai, Huan Huang

Plasma Physics

Current-Sheet Formation in Electron Magnetohydrodynamics with Split Fractional Dissipation

Ruimeng Hu, Qirui Peng and Xu Yang

Thin current sheets are central small-scale structures in electron magnetohydrodynamics (EMHD), closely associated with energy dissipation and fast magnetic reconnection at electron scales. We study their formation numerically in a $2\frac{1}{2}$-dimensional EMHD system on a periodic domain with split fractional dissipation, where the magnetic potential and the vertical magnetic component are damped separately. The local theory is governed by a symmetric combined damping balance, but the numerical onset of small-scale growth need not follow this symmetry. A scaling analysis identifies the out-of-plane current as the primary concentration observable, since it is regularized only through the magnetic-potential equation. Using a validated Fourier pseudospectral exponential time-differencing solver with resolution-controlled diagnostics, we find a clear decay/concentration dichotomy. The onset boundary is markedly asymmetric: current-sheet formation appears to be controlled mainly by damping of the magnetic potential, rather than by the combined damping strength. The analyticity strip collapses to the grid scale, the concentration sharpens under grid refinement, and the observed growth is consistent with an energy-critical self-similar rate, with exponent near three. These experiments indicate that magnetic-potential damping is the apparent binding constraint for current-sheet concentration, refining the symmetric sum picture.
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Computational Physics · Cross-listed from gr-qc

Stochastic template banks for GW searches using low-discrepancy sequences

Tarun Kumar and Anand S. Sengupta

Matched filtering remains the most sensitive method for detecting gravitational waves from compact binary coalescences. The efficiency of such searches depends on how well a discrete template bank covers the underlying parameter space. Conventional geometric, stochastic, and hybrid placement methods can lead to uneven coverage and redundant templates in higher dimensions. Hybrid methods are generally the most efficient among these, while stochastic methods are simpler to implement, particularly when the parameter-space metric is difficult to compute. In practice, both approaches rely on uniform random sampling, which often requires a large number of proposal points to achieve adequate coverage. We find that stochastic template banks constructed using low-discrepancy sequences achieve comparable recovery fractions while requiring 27.5% fewer proposal points in two dimensions, about 12% fewer in three dimensions and 17% fewer in a four-dimensional eccentric equal-spin toy bank. The final template count is much less sensitive to the proposal sampling, consistent with the metric-volume constraints of the covering problem. We introduce a slab-wise coarse prefilter to accelerate candidate rejection for strongly anisotropic metrics. Applied to the 4D toy bank, it gives a total bank-construction speed-up of about $1.28\times$. The primary benefit of low-discrepancy sampling is therefore a reduction in the size of the initial proposal set, leading to lower memory usage and reduced bookkeeping during bank generation. These results show that low-discrepancy sampling provides a simple improvement to stochastic template-bank generation for current and future gravitational-wave searches.
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Physics and Society

Temporal-Causal Unity as an Operational Framework for Collective Dynamics: Causal-Progress Clocks, Synchronization, and Polarization

Jian Liu and Dong Sun

This paper develops temporal-causal unity (TCU), a framework connecting a process-philosophical thesis – time is the ordered unfolding of causal change – to an operational model of cognitive and social dynamics. The framework deliberately separates three claims: an interpretive thesis about becoming, a measurable causal-progress coordinate, and a stochastic network model. Causal progress is defined by $\tau(t)=\int_0^t\lambda(s\mid\mathcal H_s)\,{\rm d}s$, where the nonnegative event intensity $\lambda$ must be specified independently of the outcome. Agents carry an orientation phase and an activation amplitude; weighted interaction, heterogeneous drift, external input, anchoring, and diffusion govern their evolution in $\tau$. First- and second-harmonic order parameters separate consensus from bipolar polarization. For the all-to-all noisy Kuramoto special case with Lorentzian drift width $\Delta$, synchronization begins at the conditional threshold $K_c = 2(\Delta + D)$, not at a universal constant. Reproducible numerical illustrations illustrate (not empirically demonstrate) this threshold, causal-clock curve collapse, and the consensus-polarization distinction. Six historical episodes are treated as scope probes rather than validation data. The paper derives falsifiable hypotheses and an out-of-sample protocol for comparing causal-progress and chronological-time models. TCU is therefore offered as a disciplined bridge between process ontology and complex-systems modeling, not as a replacement for spacetime physics or as an empirically established identity between time and causation.
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Chemical Physics · Cross-listed from quant-ph

Spontaneous optical emission of a randomly oriented chiral quantum source

Mikael P. Backlund

We derive the form of the one-photon state of the electromagnetic field resulting from spontaneous optical emission of a randomly oriented chiral quantum source, including electric dipole, magnetic dipole, and electric quadrupole contributions to the radiation. We describe how spatial coherence in the emission can be exploited to reveal hidden information about the emitter. This work serves as a prelude and companion piece to our concurrently submitted work \cite{Backlund2026Letter} in which we present the classical and quantum error bounds associated with assigning the handedness of such an emitter.
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Optics

High-Energy Microresonator Soliton Generation

Zhenhua Guo, Sushant Kumar, Xue Dong et al. (+7 more)

Kerr resonators generate stable frequency combs in a compact platform with applications in coherent communications, sensing, quantum information processing, and astrophysics. Ultrashort pulses can be generated, moreover, with a wavelength and repetition rate flexibility inaccessible by traditional mode-locked lasers, which is desirable for high peak-power applications including in biomedicine and materials processing. However, for these applications, single-pulse energies will need to be significantly improved beyond the fJ level characteristic of sources today. Here we describe and demonstrate a simple approach for increasing the pulse energy in anomalous dispersion Kerr microresonators. Through scaling laws based on a mean-field cavity model and supported by experimentally-accurate numerical simulations, we show that pulse energy scales strongly with output coupling if supported by sufficient drive power. In strongly over-coupled cavities, femtosecond pulses can be stabilized with pulse energy beyond the pJ level. With this theoretical framework, by pumping a 12 GHz Si3N4 cavity with 30% output coupling with 2.6-ps time-lens generated pulses, we observe stable 74-fs pulses with a record output pulse energy of 6 pJ. High energy Kerr resonators are anticipated to improve performance for current applications and compliment mode locked lasers for high peak power applications.
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All authors Zhenhua Guo, Sushant Kumar, Xue Dong, Yi Zhang, Jiewei Xiang, Arunima Nauriyal, Junchi Zhang, Elias Veilleux, Jaime Cardenas, William H. Renninger

Computational Physics

Isochoric thermodynamic preconditioning for resolving mechanically induced phase change in fractured porous media

Veljko Lipovac, Eirik Keilegavlen and Inga Berre

Rapid pore-volume changes can trigger phase change on timescales shorter than characteristic transport times and may therefore be skipped by conventional nonlinear solves and adaptive time stepping. We present a persistent-variable framework for transport in fractured porous media, introducing specific volume as an independent variable. Starting from a fully coupled system, we derive volume-based models and recover classical pressure-based formulations by eliminating local thermodynamic variables. To resolve abrupt fracture opening, we introduce a nonlinear preconditioner that assumes instantaneous free expansion and resolves the fluid state through an isochoric equilibrium calculation before advancing the transport problem. The preconditioner applies to both volume- and pressure-based models. In the studied fracture-opening cases, unpreconditioned simulations miss transient vaporization, whereas the preconditioned models do not. Across the investigated aperture range, larger openings produce monotonic increases in gas content, expansion-induced cooling, and durations of transients. Thermal effects alter the phase evolution but have otherwise minor influence on the overall transient duration. Within the proof-of-concept setting, fracture opening generates substantial transient pressure reductions, indicating that geomechanical feedback may become important in fully coupled applications. Pressure-enthalpy and volume-temperature formulations recover identical physical solutions but exhibit different nonlinear robustness, with the pressure-enthalpy formulation proving more robust in some recompression-dominated cases. These results show that equilibrium specifications control the numerical properties of the nonlinear problem rather than recovered physical responses, while isochoric preconditioning connects the nonlinear initialization directly to the underlying thermodynamics.
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Computational Physics · Cross-listed from quant-ph

Dismantling the Stoquastic Dichotomy

Armen Karakashian and Itay Hen

We challenge the notion that a stoquastic binary governs fundamental computational boundaries in quantum computing and classical simulation of quantum systems. We argue that vanishing geometric phase (VGP), a geometric condition on the Hamiltonian's transition graph, more adequately captures these boundaries. To distinguish VGP from stoquasticity, we construct VGP 3-local Hamiltonians that are formally hard to stoquastize, yet belong to a family admitting polynomial-time recognition of the VGP property. Without constructing a stoquastizing unitary, we prove that the local Hamiltonian problem is $\mathsf{StoqMA}$-complete under the promise that the input Hamiltonian has VGP, and that a frustration-free variant is in $\mathsf{MA}$ under the same promise. We use this result to argue that non-VGP is necessary for any claimed adiabatic advantage justified by escaping the $\mathsf{StoqMA}$ regime. Further, we identify natural settings where the VGP property can be recognized in polynomial time. In contrast, we show that recognition of VGP is $\mathsf{PSPACE}$-complete in general for geometrically local Hamiltonians. Our results show that the computational boundaries $\mathsf{MA} \subseteq \mathsf{StoqMA} \subseteq \mathsf{QMA}$ traditionally attributed to stoquasticity are better understood as boundaries between vanishing and non-vanishing geometric phase structure.
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Monday 20 July

Computational Physics

LSR-Net: Learning the Forward Evolution Operator for Nonlinear Fluid Dynamics

Qian Hou, Sutrisno, Yuqing Li et al. (+1 more)

We introduce the Long-Short-Range Neural Network (LSR-Net), a novel neural operator architecture designed for data-driven forward evolution modeling, and extends it to the prediction of nonlinear fluid dynamics. LSR-Net learns the evolution operator of a dynamical system solely from pairs of initial and future state snapshots, which splits the learnable integral kernel into long-range (LR) and short-range (SR) components within stacked network blocks. While the SR component uses standard convolutions to capture local dynamics, the LR component employs a sum-of-exponentials (SOE) representation. This allows for the efficient computation of global interactions as a trainable Fourier multiplier, reducing computational complexity to $O(n \log n)$ where $n$ is the number of pixels in an input snapshot and requiring only a few parameters per channel. LSR-Net is evaluated on three challenging 2D benchmarks: the coupled Burgers equation, the wave equation with a spatially varying coefficient, and the nonlinear shallow water equation {(SWE)}. Results demonstrate that LSR-Net significantly outperforms the baseline short-range network (SR-Net) as well as FNO and DeepONets in predictive accuracy, achieving substantially lower relative errors by effectively capturing both local fine-scale structures and crucial global pattern interactions.
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All authors Qian Hou, Sutrisno, Yuqing Li, Zecheng Gan

Physics and Society

Exact solutions for models of evolving clustered networks with addition and deletion via age-resolved message passing

Peter Mann, Lei Fang and Simon Dobson

Evolving networks experience vertex addition and deletion over time via processes which shape their structure and function. In many empirical networks, vertices do not arrive or depart in isolation but instead within groups or cohorts: for example, coauthorship networks grow by the addition of cliques whenever a new paper with multiple authors is published. In this paper, we propose a stochastic network evolution model based on block graphs that evolve through the addition of fully connected subgraphs ($m$-cliques) and the deletion of individual vertices. We derive a master equation governing the time evolution of the joint degree distribution and obtain an exact closed-form solution, valid for an arbitrary vertex deletion rate under uniform attachment, that describes both growing and constant-size networks. From this solution we obtain the marginal degree distributions and the clustering coefficient in closed form and the size of the giant connected component and percolation threshold governing robustness to random vertex failure using age-resolved message passing. Our results generalise existing single-vertex addition-deletion models to clique-based dynamics at arbitrary rates of turnover, and are confirmed by Monte Carlo simulation.
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Physics Education

P-A.I.R.: A Structured AI-Replication Framework for Active Learning in Introductory Physics

Bilas Paul

The growing use of generative AI tools among students raises an important pedagogical question: how can AI be structured to promote active learning rather than passive answer-seeking? This study introduces the Physics AI-Replication (P-A.I.R.) framework, in which students identify challenging problems, use AI to explain underlying concepts and solutions, generate similar problems, and practice independently before reviewing answers. Survey data from 39 undergraduate students in algebra-based physics indicate that nearly all participants reported improved conceptual understanding following engagement with P-A.I.R. across the semester, and self-confidence scores were consistently above the scale midpoint (mean = 7.03; range 5-9). A strong association between conceptual clarity and replication helpfulness (Spearman r = 0.582, p < 0.001) supports the framework's design. Qualitative findings highlight conceptual clarification and structured problem-solving. These results suggest that P-A.I.R. offers a practical approach for integrating AI into physics learning.
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Atomic Physics · Cross-listed from quant-ph

Motional Kerr-Cat States of an Atom in an Optical Tweezer

Steven K. Pampel, Gur Lubin, Dawson P. Hewatt et al. (+6 more)

Schrödinger cat states - quantum superpositions of classically or macroscopically distinct states - constitute a powerful resource for quantum computing, enhanced metrology, and probing coherence on large scales. Encoding such states in the phase space of an oscillator requires a nonlinearity, typically inherited from an auxiliary degree of freedom such as atomic spin or a Josephson junction. Neutral atoms trapped in reconfigurable optical tweezer arrays - a leading platform for quantum science and computing - provide an intrinsic nonlinearity via the motion of a single atom in a tightly focused trap. However, this self-Kerr mechanism has not previously been exploited for cat-state generation, and remains largely unexplored as a resource for motional-state control. Here we realize Schrödinger cat states in the quantized motion of a single neutral atom trapped in an optical tweezer. By modulating the depth and position, we demonstrate parity control of both Kerr-cat and Fock states alongside tunable nonlinearity, establishing a spin- and species-independent framework for controlling motion. We further show that the cat-state encoding is intrinsically robust against trap-frequency fluctuations that otherwise limit the fidelity of direct Fock-state transitions. These results establish Kerr-based control of neutral-atom motion as a new paradigm for cat-state and bosonic-state engineering in optical tweezers, providing a route toward quantum-error-correcting codes such as grid states, and toward quantum-enhanced sensing with arrays of non-Gaussian states.
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All authors Steven K. Pampel, Gur Lubin, Dawson P. Hewatt, Conall McCabe, Jaeyong Hwang, Sean R. Muleady, Tianrui Xu, Ana Maria Rey, Cindy A. Regal

Plasma Physics

The power exhaust constrained SPARC separatrix operational space

B. Lomanowski, T. Eich, J.D. Lore et al. (+3 more)

In this work we extrapolate the separatrix operational space (SepOS) projections to SPARC and introduce detachment access criteria, thus formulating the combined power exhaust constrained SepOS (i.e., PE-SepOS) to evaluate integrated power exhaust solutions at scale. Through the interpretation of SPARC SOLPS-ITER datasets and foundational work already demonstrated in experiments we formulate an as simple as possible description of the SOL net power and momentum losses in dissipative regimes to link the main power exhaust quantities with the SepOS parameters. Through this framework, we demonstrate the utility of a normalized PE-SepOS framework in identifying accessible operational points for given exhaustible Psep requirements. In applying the PE-SepOS framework to project the SPARC operational space, we find inherent trade-offs, namely: i) accessing high impurity radiation scenarios leads to pronounced reductions in ne,sep (e.g., 50% reductions at 2% Ne concentration) as a consequence of power limitation, and ii) given present understanding of access criteria to the quasi-continuous exhaust regime (QCE), a compromise between high radiative fraction and high density/neutral pressure is required for QCE access at sufficiently high density, high alpha_t conditions, with the divertor dissipative regime transitioning to pronounced detachment. Taking advantage of universal trends enabling projections of density and impurity seeding scans, the PE-SepOS thus provides a framework for mapping out the edge plasma operational space in a scalable manner, subject to validation during early SPARC operations with suitable divertor and edge plasma observables.
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All authors B. Lomanowski, T. Eich, J.D. Lore, J.-S. Park, T. Body, P. Stangeby

Geophysics

AGENTS4GEOS: agentic platform for open-source multi-physics simulation

Adriano M. A. Côrtes, Roberto M. Velho, Fernando A. Rochinha et al. (+3 more)

Multi-physics simulations are essential for understanding and monitoring intricate subsurface processes such as CO2 storage. Their computational demands call for surrogate models and, for unstructured meshes, Graph Neural Networks (GNNs) are natural candidates. The main bottleneck in developing them is generating and managing the large, physically consistent simulation datasets required for training. To address this challenge, we present Agents4GEOS, an AI-agent framework built on the Model Context Protocol (MCP) that provides 52 domain-aware tools for natural-language-driven workflows with GEOS, an open-source multi-physics simulator. The agent facilitates input-file creation, mesh inspection, fluid-property computation, and result post-processing. Through human-curated skills and fresh-context subagents coordinated by an orchestrator, the system executes complex workflows, evaluates simulation outputs, diagnoses issues, and suggests improvements, grounding every quantity in actual computation. By automating routine tasks, Agents4GEOS allows domain experts to focus on the most challenging aspects of their work.
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All authors Adriano M. A. Côrtes, Roberto M. Velho, Fernando A. Rochinha, Alvaro L. G. A. Coutinho, Mauricio Araya-Polo, Hervé Gross

Atomic Physics · Cross-listed from quant-ph

Simulating the Dicke Model on Qubit-Based and hybrid Qubit-Boson-Based Quantum Computers

Aravind P. Babu, Seongjin Ahn, Jing Sun et al. (+3 more)

The Dicke model provides a fundamental description of collective light-matter interactions and has long served as a testbed for exploring a wide range of physical phenomena in quantum optics and condensed matter physics. In this work, we develop a variational framework for investigating the finite-size Dicke model on both fully qubit-based (digital) and hybrid qubit boson based (digital-analogue) quantum computing platforms. We show that the resulting model reproduces the characteristic critical behavior of the Dicke model in the appropriate large-spin limit while remaining suitable for implementation on both classical emulators of quantum computers and actual trapped ion quantum computers, albeit in the case of latter somewhat limited by noise. Finally, we introduce a complementary hybrid qubit-bosonic variational ansatz that directly exploits the bosonic degree of freedom to reduce quantum resources and discuss its potential implementation on hybrid quantum hardware. Our results establish a scalable, symmetry-aware framework for variational quantum simulations of collective light-matter systems and provide a pathway toward efficient simulations of more general spin-boson models on near-term quantum devices.
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All authors Aravind P. Babu, Seongjin Ahn, Jing Sun, Augustas G. Landsbergis, Andrey S. Moskalenko, Marko J. Rančić

Optics

Wave propagation and hybridization of plasmonic modes in Maxwell-Chern-Simons pseudo-electrodynamics

S. Duque Cesar and M. J. Neves

We investigate the propagation of classical plane waves and surface plasmon-polariton modes within the framework of pseudo-electrodynamics (PED) supplemented by a non-local Chern-Simons (CS) topological term. Starting from the dimensionally reduced action, we derive the decoupled second-order wave equations for the electromagnetic field, and for the gauge-potential. In vacuum, we show that the topological CS parameter works as a dynamical mass generator, modifying the strict transversality of plane waves, and introducing a distinct energy gap in the dispersion relation. Considering a planar conducting medium that satisfies the Ohm law, the topological mass induces a novel hybridization mechanism between the Transverse Electric (TE), and Transverse Magnetic (TM) modes, a feature entirely absent in the conventional planar plasmonics. We analyze the asymptotic limits of this system, obtaining the exact real solutions in the lossless reactive Drude regime, and deriving the complex refractive index through a quasi-local approximation in the dissipative regime.
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Data Analysis and Statistics · Cross-listed from hep-ph

D$e^+e^-$ffusion: Capturing the Beam-Beam Physics of $e^+e^-$ Collisions with Diffusion Models

Antonio Chahine, Mariarosaria D'Alfonso, Jan Eysermans et al. (+10 more)

Beam-induced backgrounds at high-luminosity $e^+e^-$ colliders, such as the FCC-ee, are dominated by incoherent pair creation (IPC), and require computationally expensive simulations with dedicated Monte Carlo (MC) event generators. Reliable detector and machine-detector interface studies necessitate event samples that are several orders of magnitude larger than what is practically attainable with existing MC. To alleviate this bottleneck, we present D$e^+e^-$ffusion, a denoising diffusion probabilistic model that operates as a permutation-equivariant, set-valued surrogate for fast IPC simulation. Trained on a small GuineaPig++ sample, D$e^+e^-$ffusion faithfully reproduces the marginal and joint kinematic, angular, and positional distributions of all three IPC production processes. In addition, we assess the fidelity at the detector level by propagating both Geant4 and D$e^+e^-$ffusion events through a Geant4 simulation of the CLD vertex detector and by training a transformer-based two-sample classifier; the classifier achieves an area under the ROC curve of $0.553 \pm 0.016$. The trained model generates events nearly four orders of magnitude faster than Geant4, paving the way for a fast-simulation surrogate for FCC-ee design studies.
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All authors Antonio Chahine, Mariarosaria D'Alfonso, Jan Eysermans, Emmett Forrestel, Loukas Gouskos, Lindsey Gray, Katie Kudela, Haoyun Liu, Benedikt Maier, Dimitrios Ntounis, Christoph Paus, Umar Sohail Qureshi, Caterina Vernieri

Applied Physics

Evaluation-Recording Contamination in Learned Nano-Quadrotor Dynamics: A Fresh-Seed Audit

David Shulman

Learned flight-dynamics models are often trained on short windows extracted from longer recordings. Randomly splitting these windows can place dependent samples from the same physical flight in both training and evaluation sets. We audit this issue using a fixed snapshot of the NanoBench Crazyflie 2.1 dataset. The experiment holds evaluation flights, rollout starts, training-window count, validation data, and optimization budget fixed. In the contaminated protocol, [LeakagePercent] percent of a recording-disjoint training set is replaced with windows from evaluation recordings, while both arms use the same clean validation set. We compare a world-coordinate delta multilayer perceptron with a relative-coordinate control across [NumSeeds] fresh training seeds and [NumEvalFlights] complete evaluation recordings. The primary endpoint is failure-aware position RMSE over 1-second rollouts, analyzed with paired crossed recording-by-seed inference. Contamination lowers apparent world-model error by 12.1 percent, from 0.299 m to 0.262 m, but the predeclared 95 percent confidence interval for contaminated minus disjoint error is -0.0735 to 0.0011 m. Because the interval crosses zero, the confirmatory result is negative. Secondary horizons and the relative-coordinate model show similar trends, but no coordinate-representation interaction is supported. Reliable leakage assessment therefore requires recording-level splits, failure-aware rollouts, replication across fresh seeds, and inference over both recordings and optimization seeds.
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Applied Physics

Sky-blue Solution-processed TADF and Hyperfluorescent OLEDs via a High-Work-Function PEDOT:PSS:PFI Hole Injection Layer

Džiugas Litvinas, Francisco Tenopala-Carmona, Mahni Fatahi et al. (+3 more)

Solution-processed OLEDs offer a scalable route to large-area devices, but achieving competitive efficiency in multilayer stacks remains a challenge due to difficulties in hole injection as well as solvent orthogonality between layers. A hole injection layer (HIL) based on a blend of PEDOT:PSS and a perfluorinated ionomer (PFI) addresses both challenges simultaneously: surface segregation of PFI during film drying creates a high-work-function interface improving hole injection into high-ionisation potential host materials, while the insolubility of the blend in aromatic solvents prevents intermixing with subsequently deposited layers. Using this HIL with a solution-processed mCPCN:SpiroAC-TRZ emissive layer, sky-blue OLEDs with a peak external quantum efficiency (EQEmax) of 21.7%, an external quantum efficiency (EQE) of 20.2% at 100 cd m-2, a peak luminance of 29,000 cd m-2 and a full width at half maximum (FWHM) emission linewidth of 69 nm are demonstrated. The PFI-based HIL approach is extended to the photochemically stable TADF emitter 5TCzBN (EQEmax 18.4%, FWHM 73 nm) and to sensitized / hyperfluorescent OLEDs incorporating the multi-resonance TADF terminal emitters n-DABNA (EQEmax 22.8%, FWHM 26 nm) and the dendrimer TCzBN-BMes (EQEmax 20.4%, FWHM 29 nm). These results establish the PEDOT:PSS:PFI HIL as a broadly compatible platform for high-performance solution-processed TADF OLEDs.
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All authors Džiugas Litvinas, Francisco Tenopala-Carmona, Mahni Fatahi, Anna Popczyk, Eli Zysman-Colman, Malte C. Gather

Physics and Society · Cross-listed from cs.CY

The triumphs and tragedies of fandom: Emotional arcs in NFL tweets

Elisabeth Kollrack, Michael V. Arnold, Peter Sheridan Dodds et al. (+1 more)

Online fandom communities influence public opinion toward movies, musicians, and sports teams. Using a corpus of game-referencing tweets, we measure variation in sentiment toward National Football League (NFL) teams driven by geography, game outcomes, and team performance for the 2011–2014 NFL seasons. We estimate a fandom radius for each team, identifying regions where engagement exceeds background levels of discussion. We find sentiment for both winning and losing teams is positive immediately prior to games, drops at kickoff, and rebounds slightly during halftime. After halftime however, the trajectories diverge: Sentiment for winning teams increases toward the end of the game, while sentiment for losing teams remains low, though both end up below their start of game levels. Finally, a comparison between sentiment and win percentage reveals a weak positive relationship, suggesting that while team success contributes to fandom happiness, other factors also influence how fans discuss the NFL on social media. Our work contributes to a growing body of computational social science research that quantifies the many aspects of modern fandom.
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All authors Elisabeth Kollrack, Michael V. Arnold, Peter Sheridan Dodds, Christopher M. Danforth

Optics

Control of eigenmode localization and coupling anisotropy by multiscan femtosecond laser writing

S. A. Zhuravitskii, N. S. Kostyuchenko, N. N. Skryabin et al. (+5 more)

The multiscan method is widely used in femtosecond laser writing of waveguide systems to increase the refractive index contrast and to control the eigenmode shape. Here, we investigate multiscan writing with a constant effective writing speed and show that the displacement between adjacent scans provides an additional degree of freedom for controlling eigenmode confinement. By optimizing the multiscan parameters, the effective mode area can be reduced, enabling an up to eightfold increase in fabrication speed compared to conventional single-scan writing. We further demonstrate that careful tuning of the multiscan geometry substantially reduces the anisotropy of inter-waveguide coupling. These findings are applied to the fabrication of three-dimensional waveguide arrays operating at wavelengths of 808 nm and 1450 nm, where reduced coupling anisotropy is achieved. The proposed approach may be useful for three-dimensional waveguide arrays employed in topological photonics experiments, where low coupling anisotropy is desired.
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All authors S. A. Zhuravitskii, N. S. Kostyuchenko, N. N. Skryabin, I. V. Dyakonov, A. A. Korneev, A. A. Kalinkin, S. S. Straupe, S. P. Kulik

Instrumentation and Detectors

The RD50-MPW4: A Radiation Hard HV CMOS Sensor for Future Colliders

Jory Sonneveld, Thomas Bergauer, Raimon Casanova et al. (+17 more)

The former CERN RD50 collaboration develops monolithic active pixel high voltage (HV) CMOS sensors for future colliders with the aim of high radiation tolerance, good time resolution, and high granularity pixel detectors. The most recent prototype, the RD50-MPW4, was produced by LFoundry in December 2023 using a 150 nm CMOS process. It features a matrix of 64x64 pixels with a 62 $\mu$m pitch and employs a column-drain readout architecture. Compared to its predecessor, it now has separate analog and digital power domains and a new biasing scheme with a guard ring structure that supports bias voltages over 600 V. This contribution will discuss the design and latest results of the MPW4, where tests with unirradiated samples showed more than 99.9% efficiency, 16 $\mu$m spatial resolution and 10 ns timing resolution. Efficiencies of over 99% were achieved for samples irradiated to fluences of $1 \times 10^{15}$ 1 MeV n$_{\mathrm{eq}}/\mathrm{cm}^2$. A 3D map of the charge collection efficiency from a measurement with two-photon absorption laser is presented that nicely outlines the depletion depth of this radiation hard, high granularity monolithic active pixel sensor.
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All authors Jory Sonneveld, Thomas Bergauer, Raimon Casanova, Harald Handerkas, Christian Irmler, Jorge Jiménez-Sánchez, Uwe Krämer, Ricardo Marco-Hernandez, José Mazorra de Cose, Fernando Muñoz-Chavero, Rogelio Palomo, Bernhard Pilsl, Sebastian Portschy, Samuel Powell, Patrick Sieberer, Helmut Steininger, Eva Vilella, Benjamin Wade, Chenfan Zhang, Sinuo Zhang

Optics · Cross-listed from quant-ph

Bright Telecom Spin-Photon Interface in Silicon Photonics

Carolina Crosta, Amirehsan Alizadehherfati, Purbita Purkayastha et al. (+5 more)

Silicon is an attractive host for scalable quantum photonics, but the absence of bright telecom-band emitters with optically addressable spin states has limited its use for spin-photon interfaces. Here we demonstrate the Al1-center, an aluminum–carbon defect in silicon, as a bright waveguide-integrated single-photon emitter with a ground-state spin. Using isotopically purified silicon-on-insulator nanophotonic devices, we isolate individual Al1-centers and observe high-purity single-photon emission with $g^{(2)}(0)=0.04$ without background subtraction. Time-resolved photoluminescence spectroscopy reveals a fast excited-state lifetime of 135 ns, nearly an order of magnitude shorter than the benchmark provided by the well-studied T-center. Resonant photoluminescence excitation measurements further resolve the zero-phonon transition and reveal a narrow homogeneous linewidth reaching 47 MHz, threefold narrower than the T-center under comparable temperature. Through magneto-optical spectroscopy, we resolve the spin-dependent transitions of the bound-exciton manifold and achieve spin-selective optical pumping, fulfilling the prerequisite for quantum state initialization and readout. These results establish the Al1-center as a bright telecom-band spin-photon interface in silicon photonics and introduce a promising platform for integrated quantum networks.
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All authors Carolina Crosta, Amirehsan Alizadehherfati, Purbita Purkayastha, Kyu-Young Kim, Jasvith Raj Basani, Chang-Min Lee, Fabio Pezzoli, Edo Waks

Physics and Society · Cross-listed from q-bio.PE

Gravity-Driven Eco-Epidemiological Dynamics in Tri-Trophic Food Chains

Yuvrajsingh Pravinsingh Patil, Eckehard Schöll, Fakhteh Ghanbarnejad et al. (+1 more)

Ecological communities are shaped by the interplay between trophic interactions and infectious disease, yet how spatially mediated interactions influence disease-driven ecosystem dynamics remains poorly understood. Here, we develop a gravity-based eco-epidemiological framework for a tri-trophic food chain in which trophic interaction depends on species abundances and effective interaction distance. The disease-free food chain system supports a stable coexistence equilibrium, providing a baseline for investigating disease-induced ecological transitions. Introducing infection at the intermediate trophic level destabilizes this equilibrium through a Hopf bifurcation, leading to sustained oscillations, whereas infection at the top predator level results in a qualitatively different transition from persistence to extinction. By systematically varying the gravity coupling strength, we show that gravity-mediated trophic interactions regulate the thresholds separating these ecological regimes, while the trophic position of infection determines the nature of the transition. Together, these findings establish a unified framework for understanding how spatially mediated trophic interactions and infectious disease jointly govern ecosystem stability, providing new insights into disease-driven dynamics in ecological communities.
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All authors Yuvrajsingh Pravinsingh Patil, Eckehard Schöll, Fakhteh Ghanbarnejad, Chandrakala Meena

Optics

Aromatic molecular emitters in a hexagonal boron nitride stack

Tianyu Fang, Ricardo Gioia Alvarez, Babak Behjati et al. (+8 more)

Single polycyclic aromatic hydrocarbon molecules embedded in organic matrices have proven to be an excellent family of narrow-linewidth quantum emitters. Extending this host-guest setting to van der Waals materials offers the opportunity to combine the preeminent properties of molecular emitters with the access to the versatility of two-dimensional hetero-structures and devices. In this work, we incorporate perylene molecules into multi-layered hexagonal boron nitride stacks and observe gigahertz-narrow zero-phonon-line transitions at cryogenic temperatures. We unambiguously verify the origins of photon emission through vibronic spectra analysis. By combining hyperspectral localization measurements with quantum chemistry calculations, we examine the insertion mechanisms of perylene molecules in the hexagonal boron nitride stacks, and conclude that pristine hBN layers tend to expel molecules from the sandwich, while extended morphological defects, hydroxyl groups and unpassivated boron and nitrogen atoms assist to stabilize molecular bindings to hBN. Our work provides valuable insight for future work to deterministically integrate narrow-linewidth molecular emitters into van der Waals devices.
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All authors Tianyu Fang, Ricardo Gioia Alvarez, Babak Behjati, Moritz Scharfstädt, Max Masuhr, Bo Deng, Noah Henseler, Andrea Bergschneider, Stefan Linden, Christian Schäfer, Daqing Wang

Optics · Cross-listed from cond-mat.mtrl-sci

Long lived localized defect states in monolayer WSe$_2$: Optical Lifetime distribution and thermal evolution

Immanuel Thekkooden, Susmitha Jana, Mrinal Deka et al. (+2 more)

We carefully investigate the recombination dynamics of localized defect emission in monolayer WSe$_2$ on SiO$_2$/Si substrate using time-resolved photoluminescence over the temperature range of 4 K to 120 K. We observe two long-lived optical lifetimes, one few nanosecond and one hundreds of nanoseconds. PL decay profile of these long lived states is fit well by a power-law, and based on laser fluence studies, the likely origin of the power-law is due to a distribution of life-times rather than many body interactions. Temperature-dependence of these rates shows that thermal detrapping governs these long-lived channels and we obtained a value of 60 meV for the characteristics energy in a Bose-Einstein model. We performed spin-resolved density functional calculations for selenium vacancies, the most likely source of native defects, to elucidate on spin- and momentum-forbidden pathways which are the likely origin of these long lifetimes. Such detailed understanding of long-lived defect states is crucial for quantum and optoelectronic applications.
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All authors Immanuel Thekkooden, Susmitha Jana, Mrinal Deka, B.R.K. Nanda, V Praveen Bhallamudi