Accelerator Physics
Emissivity measurements of CuCrZr alloy
J. Song, N. Bultman, M. Reaume et al. (+6 more)
The FRIB heavy-ion accelerator, in user operation since 2022, produces rare isotope beams (RIBs) via interactions of high-intensity stable ion beams with a graphite production target. Approximately 20-40$\%$ of the primary beam power is deposited in the target, while the remaining 60-80$\%$ is absorbed by the beam dump. The minichannel beam dump (MCBD), currently operated at 20 kW and designed for operation up to 50 kW, uses CuCrZr
alloy absorber plates. Thermal validation and thermal cycling tests of the MCBD were conducted at the Applied Research Laboratory (ARL) at Pennsylvania State University. Temperature measurements were obtained from an infrared (IR) camera. Since accurate temperature determination requires reliable emissivity values, the emissivity of CuCrZr was measured using the IR camera validated against thermocouple reference temperatures up to $\approx$ 650 $^{o}$C. The measurements were conducted under a
vacuum level of $\approx$10$^{-5}$ torr to minimize emissivity variations due to surface oxidation. The emissivity of CuCrZr was determined to be 0.056 $\pm$ 0.009 using a constant fit to the measured data over the surface temperature range from 100-650 $^{o}$C.
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All authors J. Song, N. Bultman, M. Reaume, S. I. Eom, W. Franklin, M. Patil, R. Quispe-Abad, E. Wakai, M. Vargas Vallejo
Medical Physics
Agentic MR sequence development: leveraging LLMs with MR skills for automatic physics-informed sequence development
Moritz Zaiss, Amr Aly, Jonathan Endres et al. (+3 more)
Purpose: Novel MR sequence developments still today allow generation of new diagnostic tools or novel imaging biomarkers. Programming MRI pulse sequences, however, is time-consuming and requires deep expertise in sequence design, restrictions by hardware constraints and MRI physics; even small modifications often require substantial debugging and validation. LLMs can assist when given structured
prompts and error feedback, but many generated sequences still exhibit physical inconsistencies. We present
Agent4MR, an
agent-based framework that automatically generates and refines PyPulseq sequences using a structured, physics-aware validation report. These
agents can perform also autonomous research. Methods: We evaluated
Agent4MR on a
spin-echo EPI task across three state-of-the-art LLMs and compared it to a context-only baseline (LLM4MR) and to a human developer with the same tools. We tested an MR autoresearch on a fluid-suppressed
spin-echo EPI challenge for three different model generations. Results: Across all models,
Agent4MR consistently produced artifact-free, physically valid sequences in a single user interaction, reducing the number of required interactions below the human baseline while maintaining correct timing and k-space coverage. Autonomous
agents could then improve a sequence to match a given target contrast in an autoresearch approach. Conclusion: An appropriate agentic harness with physics-based validation can turn general-purpose LLMs into reliable MRI sequence developers and may ultimately enable non-experts to refine or innovate MR sequences guided by biological or clinical questions, or let swarms of
agents realize sequence programming for them. Keywords: MRI; pulse sequence; PyPulseq; large
language models;
agents; autoresearch, sequence development.
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All authors Moritz Zaiss, Amr Aly, Jonathan Endres, Tobias Dornstetter, Simon Weinmüller, Andreas Maier
Chemical Physics
Free energy differences and coexistence of clathrate structures II and H via lattice-switch Monte Carlo
Olivia S. Moro, Nigel B. Wilding and Vincent Ballenegger
We introduce a simulation technique to compute the free energy difference between two hydrate structures of different stoichiometry connected to a reservoir of gas molecules at a prescribed pressure. The method permits the determination of coexistence parameters for the system when the two hydrate structures have the same number of water molecules $N_w$. The approach is based on performing isobaric
Lattice Switch Monte Carlo simulations to measure free energy differences between the hydrate structures when they are either fully occupied by gas molecules, or fully empty. This measurement is combined with thermodynamic integration within an ensemble in which the number of guest molecules $N_g$ can fluctuate under the control of a chemical potential $\mu_g$. We analyze the properties of the resulting constant-$N_w,\mu_g,P,T$ ensemble and show how it can be used to calculate coexistence points via a thermodynamic cycle. Applying the method to argon and methane structures, we find coexistence pressures that are in good agreement overall with the available experimental data.
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Optics
Ultrawide-angle diffraction-limited 2D beam steering via hybrid integrated metasurface-photonic circuit
Zhiping He, Luigi Ranno, Padraic Burns et al. (+12 more)
Two-dimensional (2D) wide field-of-view (FOV) beam steering is a key enabling capability for emerging free-space optical systems, including inter-satellite optical links, airborne
LiDAR, point-to-point optical wireless communications, and collaborative robotic platforms. These applications require rapid acquisition and tracking across both azimuth and elevation; architectures that offer wide scanning in only one dimension while maintaining limited coverage in the orthogonal direction constrain link availability, coverage uniformity, and system agility. Here, we demonstrate a chip-scale platform for ultrawide-angle, diffraction-limited 2D beam steering based on hybrid integration of a silicon photonic integrated
circuit (PIC) and an optical metasurface. A free-form micro-optical reflector efficiently transforms the guided waveguide mode into an expanded free-space beam that illuminates an analytically optimized ultrawide-FOV metasurface. The integrated system achieves a measured FOV exceeding 160{\deg} while maintaining diffraction-limited beam quality over a broad angular range at telecom wavelengths. This hybrid PIC-metasurface architecture provides a compact and scalable route to high-quality 2D beam steering and establishes a practical pathway toward integrated optical projectors for space-based optical communications and other applications requiring agile, wide-angle, high-fidelity beam control.
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All authors Zhiping He, Luigi Ranno, Padraic Burns, Fan Yang, Hung-I Lin, Maarten R. A. Peters, Hanyu Zheng, Rui Chen, Yi Ji Tan, Chuanyu Lian, Nathan Dostart, Hyun Jung Kim, Carlos Ríos, Tian Gu, Juejun Hu
Instrumentation and Detectors
MAS-CCD: New technique for measuring low-level charge content based on the multiple amplifier architecture
Miqueas E. Gamero, Guillermo Fernández Moroni, Fernando Chierchie et al. (+4 more)
Low-noise detectors are a key technology for the next generation of astronomical instruments aimed at spectroscopy of faint objects and the search for
exoplanets. In this context, the multiple-amplifier sensing charge-coupled device (MAS-CCD) emerges as a promising technology for future scientific instruments. A critical parameter affecting the performance of these devices is spurious charge, produced by the clocking of the gates. Its measurement is typically challenging with existing methods. In practice, the optimization of this parameter often relies on empirical procedures that require significant time and careful consideration of the trade-off with full-well capacity. In this work, we present a new technique to estimate spurious charge based on covariance analysis of the output amplifiers of the MAS-CCD, which measures the same charge packet in different amplifiers at different times. The method enables fast and precise measurements of spurious charge under operating conditions where conventional approaches are difficult to apply. We develop the theoretical framework of the method and validate the model through simulations. The results demonstrate the feasibility of this approach and suggest that it could serve as a basis for reliable large-scale characterization of sensor performance.
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All authors Miqueas E. Gamero, Guillermo Fernández Moroni, Fernando Chierchie, Agustin J. Lapi, Blas J. Irigoyen Gimenez, Juan Estrada, Javier Tiffenberg
Chemical Physics · Cross-listed from stat.ML
Rare Event Analysis via Stochastic Optimal Control
Yuanqi Du, Jiajun He, Dinghuai Zhang et al. (+2 more)
Rare events such as conformational changes in biomolecules, phase transitions, and chemical reactions are central to the behavior of many physical systems, yet they are extremely difficult to study computationally because unbiased simulations seldom produce them. Transition Path Theory (TPT) provides a rigorous statistical framework for analyzing such events: it characterizes the ensemble of reactive trajectories between two designated metastable states (reactant and product), and its central object–the committor function, which gives the probability that the system will next reach the product rather than the reactant–encodes all essential kinetic and thermodynamic information. We introduce a framework that casts committor estimation as a
stochastic optimal control (SOC) problem. In this formulation the committor defines a feedback control–proportional to the gradient of its logarithm–that actively steers trajectories toward the reactive region, thereby enabling efficient sampling of reactive paths. To solve the resulting hitting-time control problem we develop two complementary objectives: a direct backpropagation loss and a principled off-policy Value Matching loss, for which we establish first-order optimality guarantees. We further address metastability, which can trap controlled trajectories in intermediate basins, by introducing an alternative sampling process that preserves the reactive current while lowering effective energy barriers. On
benchmark systems, the framework yields markedly more accurate committor estimates, reaction rates, and
equilibrium constants than existing methods.
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All authors Yuanqi Du, Jiajun He, Dinghuai Zhang, Eric Vanden-Eijnden, Carles Domingo-Enrich
Computational Physics · Cross-listed from math-ph
Deferred Cyclotomic Representation for Stable and Exact Evaluation of q-Hypergeometric Series
Seth K. Asante
We introduce a cyclotomic representation for finite $q$-hypergeometric series and $q$-deformed amplitudes that separates algebraic structure from evaluation. By expressing each summand in a sparse exponent basis over irreducible cyclotomic
polynomials, all products and ratios of
quantum factorials reduce to integer vector arithmetic. This ensures that cancellations between numerator and denominator are resolved exactly prior to any evaluation. This formulation yields the deferred cyclotomic representation (DCR), a parameter-independent combinatorial object of the series, from which evaluation in any target field is realized as a ring homomorphism. For
quantum recoupling coefficients, we demonstrate that this framework achieves linear
memory scaling in the compilation phase, eliminates intermediate expression swell in exact arithmetic, and substantially extends the range of reliable double-precision computation by reducing cancellation-induced error amplification. Beyond its computational advantages, the DCR provides a unified perspective on $q$-deformed amplitudes. Structural properties like admissibility at roots of unity, and the classical limit all emerge as intrinsic properties of a single underlying combinatorial object.
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Physics and Society
Simon's model does not produce Zipf's law: The fundamental rich-get-richer mechanism for any power-law size ranking
Pablo Rosillo-Rodes, Julia Witte Zimmerman, Laurent Hébert-Dufresne et al. (+1 more)
Many complex systems are composed of disparate, interacting types of varying sizes: Species abundances in ecosystems, firm sizes in
markets, city populations in countries, word counts in
language, etc. A longstanding mystery of complex systems is Zipf's law, which is the empirical observation that component size decreases as the inverse of component rank – $S \propto r^{-1}$ – and its generalization $S \propto r^{-\alpha}$ for $\alpha \ge 0$. Herbert Simon's 1955 theoretical rich-get-richer mechanism for system growth has prevailed as capturing the essential process. But Simon's analysis is in fact flawed: In the limit of zero innovation, the model leads to a winner-takes-all system with $\alpha \rightarrow \infty$, rather than $\alpha \rightarrow 1$. Here, for pure rich-get-richer systems, we derive the time-dependent innovation rate $\rho_t$ that correctly produces power-law size rankings across all $\alpha \ge 0$. To produce Zipf's law, we uncover that $\rho_t$ must decay as the inverse of the log of the number of types, $1/\ln N$. We then show that our time-dependent innovation rate governs type emergence in any system obeying a power-law size-ranking, independent of the underlying mechanism. We demonstrate agreement between our model's output and word rankings in a collection of famous novels, while Simon's model fails. Going forward, our dynamic innovation rate mechanism provides the fundamental, Drosophila-like model for all rich-get-richer systems.
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All authors Pablo Rosillo-Rodes, Julia Witte Zimmerman, Laurent Hébert-Dufresne, Peter Sheridan Dodds
Atomic Physics · Cross-listed from hep-ph
Searching for axions with quantum interferometry
Tanmay Kumar Poddar and Michael Spannowsky
Quantum phase measurements offer a complementary route to
axion searches. We show that
axion-
photon interactions can imprint both Aharonov-Bohm (AB) and Berry phases in experimentally motivated
quantum setups. For a coherently oscillating
axion dark matter background, the induced effective current generates a time dependent
magnetic flux in an rf-SQUID, leading to a measurable voltage signal through the Josephson phase. For representative
benchmarks, this AB phase search reaches the minimum
axion-
photon coupling $g_{a\gamma\gamma}^{\mathrm{min}}\sim 7.8\times10^{-14}~\mathrm{GeV}^{-1}$ at
axion mass $m_a\sim 10^{-10}~\mathrm{eV}$, with projected sensitivity that can improve on existing limits in that parameter space by roughly one to two orders of magnitude. We also identify a
geometric phase observable in a Mach-Zehnder interferometer with an adiabatically rotating
magnetic field, providing a proof-of-principle phase-based probe of meV-scale
axions even when they do not constitute the dark matter, although sensitivity on the coupling remains weaker than current bounds with conservative tabletop
benchmarks. Extending the analysis to a three level
photon-
axion quasiparticle (AQP)-
axion system, with the AQP realized in a topological
magnetic insulator, we find a potentially measurable THz Berry phase dominated by the AQP sector, furnishing a nontrivial validation of the formalism in a richer coupled system. These setups establish
quantum phase observables as a useful new framework for
axion searches, with immediate phenomenological promise in superconducting
circuits and longer term potential in
quantum enhanced interferometry.
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Instrumentation and Detectors · Cross-listed from quant-ph
Measuring quasiparticle dynamics for particle impact reconstruction in a superconducting qubit chip
E. Celi, R. Linehan, P. M. Harrington et al. (+7 more)
Quasiparticle poisoning following particle impacts poses a significant challenge to the development of fault-tolerant superconducting
quantum computers, as a sudden excess of quasiparticles can simultaneously degrade the coherence of multiple
qubits across large device arrays. In this work, we present a statistical analysis that models the time
evolution of radiation-induced
qubit energy relaxation through quasiparticle density dynamics. This study provides insight into quasiparticle loss processes by distinguishing between recombination and trapping decay channels and assessing their respective impact on
qubit performance. We precisely measure quasiparticle recombination in multiple transmon
qubits and uncover an unexpected dependence of
qubit relaxation dynamics on deposited energy. By linking correlated relaxation events across
qubits to ballistic
phonon propagation, we introduce a statistical localization approach to extract the energy deposited in the substrate, which is in good agreement with Monte Carlo simulation. This work establishes the quantitative framework for using an arbitrary subset of superconducting transmon
qubits in a QPU as energy-resolving witness particle detectors.
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All authors E. Celi, R. Linehan, P. M. Harrington, M. Li, H. D. Pinckney, K. Serniak, W. D. Oliver, J. A. Formaggio, E. Figueroa-Feliciano, D. Baxter
Space Physics · Cross-listed from astro-ph.SR
Chromospheric dynamics and turbulence regulate the solar FIP effect
Andy S.H. To, J. Martin Laming, Jeffrey Reep et al. (+1 more)
Elemental abundance variations in the
solar corona, commonly characterised by First Ionisation Potential (FIP) bias, provide crucial diagnostics of chromospheric processes. The ponderomotive force model, which attributes fractionation to Alfvén wave propagation, has successfully reproduced the observed fractionation patterns in various
solar features. However, existing theoretical implementations rely on a static quiet Sun chromosphere, leaving the influence of chromospheric dynamics largely unexplored. We address this limitation by combining hydrodynamic simulations from HYDRAD with ponderomotive force calculations through FIPpy, a new open-source code. Comparing predictions between an initial VAL-C chromosphere and a heated chromosphere following impulsive nanoflare-like events, we show that the ponderomotive force model remains consistent under dynamic chromospheric conditions, while stronger changes in fractionation behaviour arise from variations in acoustic flux and
turbulence. Most significantly, when acoustic wave flux drops below $\sim5\times10^6$ erg cm$^{-2}$ s$^{-1}$, mass-dependent thermal velocities dominate the fractionation process, producing counterintuitive patterns where Fe exceeds Ca in FIP bias, while high-FIP Ar shows fractionation. We demonstrate that any source of chromospheric
turbulence will act to suppress fractionation. For
flares, our results predict that the increased
turbulence will suppress FIP bias, potentially explaining the observed abundance variations during
flares. These findings suggest that coronal abundances and composition encode a sensitive balance between dominant mechanisms, determined by the ratio of ponderomotive acceleration to turbulent velocity.
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All authors Andy S.H. To, J. Martin Laming, Jeffrey Reep, Adam J. Finley
Atomic Physics · Cross-listed from quant-ph
Programmable Fermionic Quantum Processors with Globally Controlled Lattices
Gabriele Calliari, Charles Fromonteil, Francesco Cesa et al. (+4 more)
We introduce a framework for realizing universal fermionic
quantum processing with globally controlled itinerant fermionic particles. Our approach is tailored to the example of neutral atoms in optical
lattices, but transposes to other setups with similar capabilities. We give constructive protocols to realize arbitrary fermionic processes, with time-dependent control over global parameters of the experimental setup, such as tunneling and interaction in a
Fermi-Hubbard type model. We first prove the universality of our framework and then discuss implementation variants, such as hybrid analog-digital simulation of extended
Fermi-Hubbard models, e.g., with long-range couplings.
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All authors Gabriele Calliari, Charles Fromonteil, Francesco Cesa, Torsten V. Zache, Philipp M. Preiss, Robert Ott, Hannes Pichler
General Physics
Finite Orbital Angular momentum Bessel beams propagating along light-cone coordinates
Felipe A. Asenjo and Swadesh M. Mahajan
New solutions for Bessel electromagnetic beams, propagating along the light cones, are investigated. Of the variety of structures possible in the light cone variables, the one involving a product of Airy functions is discussed in detail. This class of solutions, representing an asymmetry on the light-cone coordinates dependence, is a non-trivial extension to the usual plane wave solutions. We also explore the conditions under which these solutions will carry finite orbital angular momentum density.
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Physics Education
Building an Affordable Self-Driving Lab: Practical Machine Learning Experiments for Physics Education Using Internet-of-Things
Yang Liu, Qianjie Lei, Xiaolong He et al. (+9 more)
Machine learning (ML) is transforming modern physics research, but practical, hands-on experience with ML techniques remains limited due to cost and complexity barriers. To address this gap, we introduce an affordable, autonomous, Internet-of-Things (IoT)-enabled experimental platform designed specifically for applied physics education. Utilizing an Arduino microcontroller, a customizable multi-wavelength light emitting diode (LED) array, and photosensors, our setup generates diverse, real-time optical
datasets ideal for training and evaluating foundational ML
algorithms, including traversal methods,
Bayesian inference, and deep learning. The platform facilitates a closed-loop, self-driving experimental workflow, encompassing automated data collection, preprocessing, model training, and validation. Through systematic performance comparisons, we demonstrate the superior ability of deep learning to capture complex nonlinear relationships compared to traversal and
Bayesian methods. At approximately $60, this open-source IoT platform provides an accessible, practical pathway for students to master advanced ML concepts, promoting deeper conceptual insights and essential technical skills required for the next generation of physicists and engineers.
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All authors Yang Liu, Qianjie Lei, Xiaolong He, Yizhe Xue, Kexin He, Haitao Yang, Yong Wang, Xian Zhang, Li Yang, Yichun Zhou, Ruiqi Hu, Yong Xie
History and Philosophy of Physics · Cross-listed from quant-ph
Comment on arXiv:2604.09826: Discovery of the Solution to the "Einstein–Podolsky–Rosen Paradox"
Mikołaj Sienicki and Krzysztof Sienicki
Roman Schnabel's article argues that the Einstein-Podolsky-Rosen (EPR) paradox can be resolved by identifying a flaw in what the author calls the "EPR implication" and by using radioactive alpha decay as an example showing that predictability does not exclude genuine randomness. The paper is clearly written and addresses an important foundational question. In our view, however, its main conclusion does not follow. The article narrows the original EPR argument, attributes too much to Bell-inequality violations, and replaces the central EPR structure - which involves incompatible observables and locality-based
reasoning - with a simpler case of correlated random events. The result is an interesting interpretive remark, but not, we think, a satisfactory scientific resolution of the EPR problem.
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Chemical Physics
EOM-fpCCSD: An Accurate Alternative to EOM-CCSD for Doubly Excited and Charge-Transfer States
Katharina Boguslawski and Paweł Tecmer
We introduce a new equation-of-motion coupled-cluster method based on a pair coupled-cluster doubles (pCCD) reference, termed frozen-pair EOM-CCSD (EOM-fpCCSD). This approach combines the computational efficiency of the pCCD ansatz with a dynamical correlation correction, enabling a reliable description of electronically excited states within the EOM framework. The method has been implemented in the open-source PyBEST software package. Its performance is systematically benchmarked against standard EOM-CCSD and its pair-tailored variant (EOM-ptCCSD), using both canonical Hartree-Fock and pCCD natural orbitals. For charge-transfer (CT) excitations taken from the QUEST database, EOM-fpCCSD yields excitation energies very close to those of EOM-CCSD, outperforming EOM-ptCCSD, as well as to the theoretical best estimates (TBEs). Working within the localized pCCD natural orbital basis allows us to determine the directed CT character, which quantifies the directed charge flow from one molecular domain to another. Numerical results show that EOM-fpCCSD, EOM-CCSD, and EOM-ptCCSD provide nearly identical descriptions of the directed CT character, despite changes in excitation energies. The true advantage of EOM-fpCCSD becomes evident for the challenging QUEST subset of doubly excited states. While EOM-ptCCSD performs similarly to standard EOM-CCSD, EOM-fpCCSD significantly outperforms both methods for these problematic states compared to TBEs. In addition to improving the accuracy of excitation energies, EOM-fpCCSD also converges for several states that standard EOM-CCSD and EOM-ptCCSD fail to converge. These results demonstrate that EOM-fpCCSD offers a promising and computationally efficient route toward a more accurate description of complex electronic excitations.
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Accelerator Physics · Cross-listed from cond-mat.mtrl-sci
Evidence for Umklapp electron scattering emission from metal photocathodes
I-J. Shan, L.A. Angeloni and W. Andreas Schroeder
Comparison of the measured spectral emission properties of single-
crystal Cu(001) and W(111) photocathodes to established photoemission theories reveal evidence for an additional one
photon emission process predominantly affecting electron emission near and below the photoemission threshold. This additional photoemission process is postulated to be due to a momentum-resonant Franck-Condon mechanism mediated by inelastic Umklapp electron scattering. An initial first-principles simulation of this emission process (involving the electron thermal effective mass, the inelastic electron mean free path at the
vacuum level, and the number of
Fermi surfaces in the metal), when combined with a direct one-step band emission model, is consistent with the measured spectral dependencies of both the
quantum efficiency and mean transverse energy of electron photoemission from the two single-
crystal metal photocathodes.
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Classical Physics · Cross-listed from quant-ph
Steven Tomsovic
Through semiclassical methods the subject of
quantum chaos motivates and depends on
Hamiltonian chaos research. Presented here is a selection of some of the most important
Hamiltonian chaos topics that in this way get directly related to any of a variety of
quantum chaos research problems. The overall emphasis is on intuitive explanations and illustrations of various ideas with the references containing more mathematically rigorous expositions. The chapter begins with a description of various useful theoretical and computational tools of chaos research, e.g.~surfaces of section, paradigms of chaos, stability analysis, and symbolic dynamics... This is followed by discussions regarding the geometry of chaos, how chaotic systems respond to perturbations, and the complexification of
Hamiltonian dynamics. Most of the contents concern topics that are long established and well known by now. The exceptions involve complications that arise from the complexification of phase space variables and time. There are relatively recent results summarized regarding the appropriate branches of determinant phases and how to distinguish complex trajectories that are associated with classically allowed processes versus those associated with non-allowed ones.
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Accelerator Physics
Investigations and Considerations of Oxygen Diffusion Profiles in Superconducting Mid-T RF Cavities Utilizing EXAFS Spectroscopy
Niels Eckert, Marc Wenskat and Wolfgang Hillert
A screening of oxygen profiles in mid-T treated SRF cavities is crucial, in order to infer physical correlations between the microscopic cavity
lattice and cavity performance - a problem concerning acceleration physicists for years. This thesis provides an analysis of oxygen
diffusion profiles for three differently treated samples: Two mid-T baked and the third with the standard EuXFEL recipe. The measurement method utilizes EXAFS spectroscopy and was carried out at the DELTA facility in Dortmund. The result suffers heavily under noise, making the quantity of the result barely useable. Qualitatively, no deviations of current models regarding the profiles, could be proven, and no results of previous studies were contradicted. The experimental analysis is described in precision, interpretations of the possible are undertaken and theoretical considerations regarding error estimation and possible EXAFS simulations for future attempts are provided. A repetition at the PETRA III facility is indicated.
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Optics
Modal response sensitivity to polarization across photonic lantern architectures
Rodrigo Itzamná Becerra-Deana, Joseph Lamarre, Raphaël Maltais-Tariant et al. (+4 more)
This paper examines the polarization-dependent output of various types of 3-mode photonic lanterns fabricated using double-clad fibers. We explore the sensitivity of the modal response across several types of photonic lanterns, from the fully symmetric and strongly coupled structure of regular photonic lanterns to the fully asymmetric structure of mode-selective photonic lanterns. We demonstrate the high sensitivity of the output of photonic lanterns with strong coupling between their ports to the polarization of the input state. In contrast, ports with high isolation or low coupling, such as in mode-selective photonic lanterns, exhibit responses that are almost polarization independent.
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All authors Rodrigo Itzamná Becerra-Deana, Joseph Lamarre, Raphaël Maltais-Tariant, Adam Zolnai, Nicolas Godbout, Stéphane Virally, Caroline Boudoux
Fluid Dynamics
Turbulent pair dispersion with Stochastic Generative Diffusion Models
Andrei Pantea, Luca Biferale, Michele Buzzicotti et al. (+3 more)
Recent advances in data-driven modeling have shown that
diffusion models can successfully generate synthetic Lagrangian trajectories in turbulent flows. Building on this progress, we extend the method to the joint generation of pairs of Lagrangian velocity trajectories, enabling a fully data-driven representation of turbulent pair dispersion, a long-standing fundamental problem with broad relevance in fluid dynamics. We demonstrate that
diffusion models accurately reproduce the
evolution of particle-pair separation, including deviations from Richardson's classical scaling law, while simultaneously preserving all key single-particle statistical properties reported in previous studies. These findings underscore the potential of
diffusion-based generative models to emulate high-dimensional, multi-scale turbulent dynamics, further establishing them as a powerful tool for scientific modeling and for future geophysical and astrophysical applications.
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All authors Andrei Pantea, Luca Biferale, Michele Buzzicotti, Guillaume Charpiat, Sergio Chibbaro, Tianyi Li
Biological Physics · Cross-listed from cond-mat.soft
Building and maintaining a System of Intracellular Compartments
Amit Kumar and Madan Rao
Organelle patterning and its heritability remain central mysteries in
cell biology, highlighting the fundamental tension between genetic inheritance and self-assembly. Here, we explore the nonequilibrium assembly and emdedded size control of the Golgi cisternae and endosomes, amid a continuous flux of membrane traffic, within a
stochastic framework of mechanochemical fusion-fission cycles that violate detailed balance. Using a dynamical systems approach, we identify distinct, robust regimes, ranging from fixed points to limit cycles with definite phase relations between cisternae. We identify these dynamical regimes with diverse phenotypes, from stable cisternae to periodic,
cell-cycle-dependent dissolution/reassembly of cisternae to cisternal progression. We analyse its dynamic response to systematic perturbations or driving protocols and make definite predictions that may be tested experimentally. Our analysis reveals that the two competing models of Golgi organization - vesicular transport and cisternal progression - are, in fact, two phases of the same underlying nonequilibrium process. We see that cisternal size homeostasis is brought about by a size-dependent embedded control system driven by fusion-fission kernels. Finally, our framework offers a strategy for controlling cisternal number and chemical identity by modulating the interplay between glycosylation enzymes and membrane fission-fusion dynamics.
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Chemical Physics
Efficient Implementation of Relativistic Coupled Cluster Linear Response Theory in Combination with Perturbation Sensitive Natural Spinors and Cholesky Decomposition Treatment of Two-electron Integrals
Sudipta Chakraborty, Muskan Begom, Xubo Wang et al. (+1 more)
We present an efficient implementation of the low-cost linear-response coupled-cluster singles and doubles (LR-CCSD) method for computing static and frequency-dependent polarizabilities in systems with significant relativistic and electron-correlation effects. The implementation combines X2C-based
Hamiltonians (X2CAMF and X2CMP), perturbation-sensitive natural spinors (FNS++), and Cholesky decomposition (CD)- based treatment of two-electron integrals to reduce both the computational and
memory demands of relativistic LR-CCSD calculations.
Benchmark calculations reveal that X2CMP exhibits more robust behavior than X2CAMF in the presence of highly augmented basis sets. The proposed FNS++CD-X2CMP-LR-CCSD approach reproduces four-component reference values with excellent accuracy across a diverse set of atomic and molecular systems. Additionally, different strategies for constructing the FNS++ basis were assessed, and the averaged-density approach was found to offer a favorable balance between accuracy and computational cost. Across the
benchmark systems considered in this work, approximately 70% of the virtual spinor space can be removed with the FNS++ approach. The present implementation enables accurate and scalable relativistic response calculations for large molecular systems, as demonstrated by the computation of the static and dynamic polarizabilities of uranium hexafluoride using a triple-
zeta basis comprising more than 1,400 basis functions.
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All authors Sudipta Chakraborty, Muskan Begom, Xubo Wang, Achintya Kumar Dutta
Optics
Noise factor of Brillouin amplifiers
John H. Dallyn, Nils T. Otterstrom, Matt Eichenfield et al. (+2 more)
Stimulated Brillouin scattering (SBS), an optical nonlinearity arising from
photon-
phonon interactions, has formed the basis for a large class of optical signal processing devices, including Brillouin amplifiers. A limiting factor of such amplifiers is the noise due to thermal-mechanical fluctuations that the
phonons imprint on the optical signal. Prior work has either inferred or experimentally observed a noise factor ($F$) that depends only on the thermal occupation of the
phonons ($F\approx 1+n_{th}$). We show that this noise factor results naturally from a
Hamiltonian-based spatio-temporal coupled mode treatment in the limit of large Brillouin amplification and when
phonon propagation is neglected. Moreover, this theoretical framework allows us to extend our treatment to a much larger and more representative parameter space for emerging SBS systems; specifically, this analysis accounts for the forward or backward nature of the scattering process and the effects of
phonon propagation, optical loss, and small Brillouin gains. Our results demonstrate that the noise factor can deviate radically from $F\approx 1+n_{th}$ for a host of modern SBS devices, especially those in which
phonon propagation significantly changes the coupled mode dynamics.
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All authors John H. Dallyn, Nils T. Otterstrom, Matt Eichenfield, Peter T. Rakich, Ryan O. Behunin
History and Philosophy of Physics
Defining Absence: The Origin of "Neutrinoless" and How it Obscures the Physics of Matter Creation
Francesco Vissani
The term 'neutrinoless' is a cornerstone of modern particle physics, yet it defines a fundamental process by what is missing rather than what is created. We trace the origins of this privative neologism to a 1953 experimental claim and show how a 'sociology of suspicion' transformed Ettore Majorana's affirmative ontology into an agnostic shorthand. By examining this linguistic shift, we argue that our current terminology may obscure the profound physical meaning of the search. Reclaiming the
language of 'matter creation' is not merely a semantic choice, but a timely conceptual shift to bridge the gap between experimental caution and the radical character of the laws of nature we aim to uncover.
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Optics
Neuron Surface Emitting Laser (NeuronSEL): Spiking Regimes and Negative Differential Resistance in Solitary Multi-junction VCSELs
Maria Duque-Gijon, Joshua Robertson, Dafydd Owen-Newns et al. (+6 more)
Neuromorphic photonics is emerging as a powerful platform for fast and efficient optical information processing and sensing. However, future
brain-inspired photonic systems require compact and scalable light sources, capable of generating the neuro-mimetic optical signals needed for their operation. This work demonstrates a single-stack
laser that delivers optical and electrical neural-like spiking emission under solitary operation. Termed the
Neuron Surface-Emitting
Laser (NeuronSEL), this compact, multi-junction Vertical-Cavity Surface Emitting
Laser (VCSEL) exhibits non-linear Negative Differential Resistance (NDR), similar to that observed in memristive devices. Leveraging this NDR behaviour enables the novel demonstration of multiple neuronal features in the NeuronSEL including refractoriness and threshold-/integrate-and-fire dynamics. We demonstrate the NeuronSEL's behaviour as an optical spiking
neuron and its ability to perform processing functions, such as coincidence detection and exclusive OR operations. Its scalability is illustrated by proposing a network based on an array of NeuronSELs, able to perform classification tasks. The NeuronSEL emerges as a strong candidate for practical and scalable neuromorphic photonic hardware, with potential impact across a range of applications in optical sensing, communications and computing technologies, whilst benefitting from the inherent advantages of VCSEL technology -low manufacturing cost, compactness, efficiency, vertical emission, and straightforward integration into large arrayed-structures and networks.
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All authors Maria Duque-Gijon, Joshua Robertson, Dafydd Owen-Newns, Jack Baker, Craig P. Allford, Xavier Porte, Samuel Shutts, Peter M. Smowton, Antonio Hurtado
Optics
Building reliable 3D photonic integrated circuits and cavities at the wafer scale
Yuhao Huang, Yunqi Fu, Yu Xia et al. (+6 more)
Three-dimensional (3D) photonic integrated
circuits (PIC) are emerging as an indispensable scheme for high density and multifunctional photonic systems. However, the wafer-scale scaling of PICs towards a 3D configuration is constrained by two key factors: (i) the trade-off between inter-layer taper efficiency and footprint, and (ii) wafer-scale uniformity of inter-layer transition loss. In this work, we introduce etch-back assisted chemical mechanical polishing (E-CMP) to achieve high wafer-scale uniformity of the spacer layer. Moreover, we break the efficiency-footprint trade-off by demonstrating a novel $\kappa$-engineered taper, achieving a reliability metric that is 75% higher than the traditional linearly tapered structure. Building on these design and fabrication developments, we enable reliable 3D PICs with typical loss of 0.077 and 0.068 dB/cm on two silicon nitride (SiN) waveguide layers and typical 3D transition loss as low as 6 mdB. Furthermore, the low 3D transition loss enables the first class of 3D high-Q optical cavities occupying two distinct device layers, providing new design space for high-Q optical cavities. The scalable fabrication process and design methodology provide routes for wafer-scale reliable 3D PICs that are promising in a series of applications ranging from photonic interconnects and computing networks to high-density photonic sensors and nonlinear photonics.
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All authors Yuhao Huang, Yunqi Fu, Yu Xia, Yuemin Li, Zheng Li, Yaoran Huang, Zhaoting Geng, Mingfei Liu, Chao Xiang
Chemical Physics
Fidelity of Machine Learned Potentials: Quantitative Assessment for Protonated Oxalate
Chen Qu, Paul L. Houston, Qi Yu et al. (+5 more)
There has been a veritable explosion of methods and software to perform machine-learned regression on
datasets of electronic energies and forces to develop high-dimensional machine learned potential energy surfaces (ML-PESs). A major, but not deeply-studied aspect is how well different ML-PESs represent the same
dataset on which they are trained, beyond the standard fitting precision metrics. Here, this is examined in detail using several ”stress tests”, for two widely applied machine-learned potential approaches. One is based on permutationally invariant
polynomial (PIP) linear least square regression and the other is the message-passing neural network PhysNet approach. These potentials and dipole moment surfaces are used in VSCF/VCI calculations of vibrational energies and wavefunctions. The energies from the two PESs are directly compared as are the IR spectra. In addition, tunneling splittings for the hydrogen transfer between two equivalent structures are reported from using three methods: ring
polymer instanton theory,
diffusion Monte Carlo simulations, and the $Q_{im}$ path method. These calculations require the evaluation of on the order of one billion energies that are widely dispersed in the 15-dimensional configurational space. The two PESs yield results for these quantities in excellent agreement with each other.
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All authors Chen Qu, Paul L. Houston, Qi Yu, Apurba Nandi, Joel M. Bowman, Valerii Andreichev, Silvan Käser, Markus Meuwly
Fluid Dynamics · Cross-listed from nlin.CD
Precursors of extreme events and critical transitions
Riccardo Consonni and Luca Magri
We propose a theory based on dynamical systems to explain and predict the occurrence of extreme events, of which critical transitions form a subset. In fast-slow nonlinear systems, we identify a cascade of events preceding extreme events: (i) a slow regime, in which the fast covariant Lyapunov vectors (CLVs) are both tangent to the fast eigenvectors and remain transversal to the slow subspace; (ii) a transition regime, in which the fast
eigenvalues become neutrally stable while the fast CLVs are no longer tangent to the fast eigenvectors; and (iii) a critical regime, in which a strong spectral gap in the
eigenvalues causes both fast and slow CLVs to become tangent along the dominant fast direction, breaking the transversality between fast and slow subspaces. Building on this cascade, we propose two precursors to forewarn the occurrence of extreme events. We numerically test the theory and precursors on low- and higher-dimensional systems. The proposed precursors predict extreme events and critical transitions with 100% precision and recall. This work opens opportunities for time-
forecasting extreme events using theoretically grounded precursors.
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Chemical Physics
Atomistic Modeling of Methane and Carbon Dioxide Structure I Gas Hydrates Under Pressure: Guest Effects and Properties
Samuel Mathews, Xiaodan Zhu, Andr'e Guerra et al. (+2 more)
Gas hydrates are potential candidates in future energy sources while simultaneously providing structures with extensive applications in carbon capture and storage, gas transport, and important separation processes. Prior research in the field considers the dynamics of the water molecule backbone in particular. We investigated the pressure-enthalpy landscape and mechanical stability envelope of sI methane and carbon dioxide hydrates simulated using DFT. We investigated the effect of the revPBE + DFT-D2 and the SCAN + rVV10 and their treatment of the exchange correlation interactions. We examined the zero pressure material properties, finding that revPBE comparatively underbinds the interactions, causing more flexible structures with large
equilibrium volumes. Under pressure, the carbon dioxide molecule was found to align itself parallel to the hexagonal faces of the large cage despite the functional used. Additionally, the property differences are caused by the ability of the carbon dioxide molecule to rotate and disperse the changes in the energy landscape in ways that methane molecules cannot. This computational methodology describes the elastic stability of gas hydrate, marginal stability, and critical differences across important molecular interactions, confirming experimentally observed restrictions in guest molecule rotations and novel pressure behaviors under hydrostatic loads
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All authors Samuel Mathews, Xiaodan Zhu, Andr'e Guerra, Phillip Servio, Alejandro D. Rey