Chemical Physics · Cross-listed from quant-ph
Elucidating the Inter-system Crossing of the Nitrogen-Vacancy Center up to Megabar Pressures
Benchen Huang, Srinivas V. Mandyam, Weijie Wu et al. (+12 more)
The integration of Nitrogen-Vacancy color centers into diamond anvil
cells has opened the door to
quantum sensing at megabar pressures. Despite a multitude of experimental demonstrations and applications ranging from
quantum materials to geophysics, a detailed microscopic understanding of how stress affects the NV center remains lacking. In this work, using a combination of first principles calculations as well as high-pressure NV experiments, we develop a complete description of the NV's optical properties under general stress conditions. In particular, our ab initio calculations reveal the complex behavior of the NV's inter-system crossing rates under stresses that both preserve and break the defect's
symmetry. Crucially, our proposed framework immediately resolves a number of open questions in the field, including: (i) the microscopic origin of the observed contrast-enhancement in (111)-oriented anvils, and (ii) the surprising observation of NV contrast-inversion in certain high-pressure regimes. Our work lays the foundation for optimizing the performance of NV high-pressure sensors by controlling the local stress environment, and more generally, suggests that
symmetry-breaking stresses can be utilized as a novel tuning knob for generic solid-state
spin defects.
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All authors Benchen Huang, Srinivas V. Mandyam, Weijie Wu, Bryce Kobrin, Prabudhya Bhattacharyya, Yu Jin, Bijuan Chen, Max Block, Esther Wang, Zhipan Wang, Satcher Hsieh, Chong Zu, Christopher R. Laumann, Norman Y. Yao, Giulia Galli
Physics and Society
City-level energy and emission assessment based on 20+ million electric vehicle registrations in China
Yanqiao Deng, Minda Ma, Nan Zhou et al. (+3 more)
China, the world's largest electric vehicle (EV)
market, plays a pivotal role in global decarbonization of the transport sector. We present the first high-resolution assessment of EV adoption in 295 cities, utilizing more than 20 million registrations of 586 EV models tracked monthly from 2022 to 2024 and projecting transition pathways to 2035. Real-world data reveal that EVs are 30.9-212.8 megajoules per 100 km more energy efficient than internal combustion vehicles, yet their carbon intensities range from 18.2 to 270.4 gCO2/km among provinces. The limited electrification of hybrids means that gasoline still accounts for 44% of EV energy use. Scenario projections suggest that emissions will peak about 2030 at 21.1-30.9 megatonnes of CO2 and decline by 2035 under continued
market transition. The findings establish an empirical foundation for accurate emissions accounting, emphasize the need to reduce regional disparities in adoptability, and offer globally relevant insights for road-transport decarbonization.
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All authors Yanqiao Deng, Minda Ma, Nan Zhou, Hong Yuan, Zhili Ma, Xin Ma
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Towards superior van der Waals density functionals for molecular crystals
Dmitry V. Fedorov, Nikita E. Rybin, Mikhail A. Averyanov et al. (+3 more)
Ubiquitous van der Waals (vdW) interactions play a subtle yet crucial role in determining the precise atomic arrangements in solids, particularly in molecular
crystals where these weak forces are the primary link between constituent building blocks. Within density functional (DF) theory, the most natural approach for addressing vdW forces is the use of vdW-inclusive density functionals. Through a detailed analysis of the underlying formalism, we have developed a computational scheme that combines vdW functionals of type DF1 and DF2 and serves as a well optimizable tool to improve the theoretical description and prediction of molecular
crystals and other sparse materials. The proof of principle is demonstrated by our consideration of the molecular
crystals from the X23
dataset.
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All authors Dmitry V. Fedorov, Nikita E. Rybin, Mikhail A. Averyanov, Alexander V. Shapeev, Artem R. Oganov, Carlo Nervi
History and Philosophy of Physics · Cross-listed from quant-ph
Mikołaj Sienicki and Krzysztof Sienicki
A recent paper by Aziz and Howl (Nature 2025) argues that, once
quantum matter is described at the level of
quantum field theory and coupled to a classical gravitational field, higher order processes can generate
entanglement between two spatially separated masses. A contemporaneous critical note (Marletto, Oppenheim, Vedral, Wilson, arXiv:2511.07348v1) shows that, in the actual nonrelativistic limit employed there, the interaction becomes ultra local, the total
unitary factorizes, and no
entanglement is generated from a product input. In this comment we (i) restate the core point of that critique, (ii) give a channel theoretic reformulation that makes the conclusion model independent, and (iii) clarify the distinction between activation of
entanglement in already
quantum matter and genuine mediation of
entanglement by a classical field. Once these clarifications are in place, the standard BMV inference that observation of
gravity mediated
entanglement strongly indicates nonclassical gravitational degrees of freedom remains intact.
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Optics
Topological edge states in curved zigzag superlattices in nonlinear exciton-polaritons
Jing Wang, Tobias Schneider, Wei Hu et al. (+2 more)
Zigzag chains allow for the formation of topological edge states. Several distinct chain architectures have been developed for this purpose. Here, we report a zigzag superlattice, containing two staggered sub-
lattices, that supports multiple edge states, including higher-order modes. In such
lattices, the intra- and intercell coupling is imbalanced by the tunneling effect of the eigenstates or deformation of the higher-order modes. We demonstrate that by arranging the zigzag superlattice into a curved shape, some of the edge states transition into bulk states as the
curvature of the
lattice increases, while some bulk states become more localized towards edge states. The reason is that a curved superlattice strengthens the intra-
lattice coupling of the inner sub-
lattice due to the separation reduction of the potential wells. %which, on the one hand, hinders the tunneling of the eigenstate to the outer sub-
lattice and hence weakens the edge states formed in the inner sub-
lattice. On the other hand, it can isolate more edge states formed in the outer sub-
lattice, because of the induced more intensive deformation of the higher-order modes in the inner sub-
lattice. We also show that some bulk states at larger
curvatures can be transformed into edge states by a repulsive nonlinearity, which also enables the coexistence of different edge states. As a specific and ideal platform for realizing such topological superlattices we explore
exciton-polaritons in
semiconductor microcavities with their strong nonlinearity and possibility for optical excitation and control. Our work introduces an additional dimension for the design of complex topological
lattices and functional photonic devices.
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All authors Jing Wang, Tobias Schneider, Wei Hu, Stefan Schumacher, Xuekai Ma
Atomic Physics
atomSmltr: a modular Python package to simulate laser cooling setups
Mateo Weill, Andrea Bertoldi and Alexandre Dareau
We introduce atomSmltr, a Python package for simulating
laser cooling in complex
magnetic field and
laser beams geometries. The package features a modular design that enables users to easily construct experimental setups, including
magnetic fields,
laser beams and other environment components, and to perform a range of simulations within these configurations. We present the overall architecture of atomSmltr and illustrate its capabilities through a series of examples, including
benchmarks against standard textbook cases in
laser cooling.
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Computational Physics
Active learning with physics-informed neural networks for optimal sensor placement in deep tunneling through transversely isotropic elastic rocks
Alec Tristani and Chloé Arson
This paper presents a deep learning strategy to simultaneously solve Partial Differential Equations (PDEs) and back-calculate their parameters in the context of deep tunnel excavation. A Physics-Informed Neural Network (PINN) model is trained with synthetic data that emulates in situ displacement measurements in the host rock and at the cavity wall, obtained from extensometers and convergence monitoring. As acquiring field observations can be costly, a sequential training approach based on active learning is implemented to determine the most informative locations for new sensors. In particular, Monte Carlo dropout is used to quantify epistemic uncertainty and query measurements in regions where the model is least confident. This approach reduces the amount of required field data and optimizes sensor placement. The PINN is tested to reconstruct the displacement field around a deep tunnel of circular section excavated in transversely isotropic elastic rock and to determine rock constitutive and stress-field parameters. Results demonstrate excellent performance on small, scattered, and noisy
datasets, achieving high precision for the Young's
moduli, shear modulus, horizontal-to-vertical far-field stress ratio, and the orientation of the bedding planes. The proposed framework shall ultimately support decision-making for optimal subsurface monitoring and for adaptive tunnel design and control.
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Optics
Complete inelastic transparency of time-modulated resonant photonic circuits
M. Sumetsky
Photonic
circuits modulated in time can convert the input light frequency $\omega_0$ shifting it by multiples of the modulation frequency $\omega_p$ and, in certain cases, amplify the total input light power. Of special interest are photonic
circuits employing microwave capacitors, which instantaneously modulate photonic waveguides with frequency $\omega_p \ll \omega_0$. While the amplification of light is negligible in such
circuits, ideally, frequency conversion can be completed with the conservation of the light amplitude. Therefore, similar to the elastically transparent photonic structures (i.e., structures conserving both the light amplitude and frequency), we can say that a photonic
circuit parametrically modulated in time exhibits complete inelastic transparency if a wave enters the structure with frequency $\omega_0$ and exits it with a different frequency and the same amplitude. Here, we develop an approach that allows us to introduce and investigate a broad class of time-modulated photonic
circuits exhibiting complete inelastic transparency. Light enters these
circuits with a resonant frequency $\omega_0$, cascades between their $N$ eigenstates separated by the modulation frequency $\omega_p$, and exits with frequency $\omega_0 + (N-1)\omega_p$ and the output amplitude close to the input amplitude. As examples, we consider
circuits of ring microresonators and SNAP microresonators.
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Atomic Physics
Extreme Ultraviolet Spectroscopy of Highly Charged Lu and Yb Ions for Nuclear Charge Radius Determination
Hunter Staiger, Endre Takacs, Steven A. Blundell et al. (+16 more)
We report a high-precision determination of the natural-abundance-averaged
nuclear charge-radius difference between Yb and Lu using extreme ultraviolet (EUV) spectroscopy of highly charged ions (HCIs). By measuring the $D_1$ transition energies in Na- and Mg-like charge states of Lu and Yb confined in the Tokyo electron-beam ion trap, we extract meV-level energy shifts that are directly sensitive to
nuclear-size effects. Transition-energy differences obtained from these spectra are compared with state-of-the-art relativistic many-body perturbation theory, including a new treatment of Mg-like ions. We develop a generalized framework to propagate uncertainties arising from
nuclear deformation and surface diffuseness and evaluate corresponding
nuclear-sensitivity coefficients. Combining Na- and Mg-like results yields mutually consistent radius differences, demonstrating the robustness of both the experimental calibration and the theoretical predictions. To determine absolute isotopic radii, we perform a generalized least-squares optimization incorporating our HCI constraints together with optical-isotope-shift data and muonic-atom results. This analysis establishes that the $^{175}$Lu charge radius is smaller than that of $^{174}$Yb, restoring the expected odd-even staggering across the $N=94$ isotonic chain. Our recommended value, $R(^{175}\text{Lu}) = 5.291(11)$ fm, reduces the uncertainty of the Lu radius by a factor of three compared with the previous electron-scattering result and resolves a long-standing anomaly in rare-earth
nuclear systematics. This work demonstrates that EUV spectroscopy of HCIs provides a powerful and broadly applicable method for precision
nuclear-structure studies in heavy, deformed
nuclei. The techniques developed here enable future investigations of isotonic and isoelectronic sequences, including radioactive nuclides and higher-$Z$ systems.
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All authors Hunter Staiger, Endre Takacs, Steven A. Blundell, Naoki Kimura, Hiroyuki A. Sakaue, Ronald F. Garcia Ruiz, Witold Nazarewicz, Paul-Gerhard Reinhard, Chowdhury A. Faiyaz, Chihiro Suzuki, Dipti, István Angeli, Yuri Ralchenko, Izumi Murakami, Daiji Kato, Yuki Nagai, Ryuji Takaoka, Yoshiki Miya, Nobuyuki Nakamura
Optics · Cross-listed from quant-ph
Magnetic Control of the Non-Hermitian Skin Effect in Two-Dimensional Lattices
Stefano Longhi
The non-Hermitian skin effect (NHSE) – the anomalous boundary accumulation of an extensive number of bulk modes – has emerged as a hallmark of non-Hermitian physics, with broad implications for transport, sensing, and topological classification. A central open question is how
magnetic or synthetic gauge fields influence this boundary phenomenon. Here, we develop a theoretical framework for
magnetic control of the NHSE along line boundaries in two-dimensional single-band
lattices. Using a non-Hermitian extension of the anisotropic Harper–Hofstadter model as a representative example, we show that
magnetic fields suppress the
geometric skin effect in reciprocal models, whereas skin localization can persist in nonreciprocal systems. The analysis disentangles the interplay of flux, nonreciprocity, and boundary geometry, revealing that
magnetic fields mitigate or suppress the NHSE through distinct physical mechanisms – such as bulk localization via Landau or Anderson physics, or the restoration of effective reciprocity. In particular, the geometry-dependent skin effect in reciprocal systems is found to be fragile against even weak
magnetic fields.
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Medical Physics
Real-time 3D Ultrasonic Needle Tracking with a Photoacoustic Beacon
Christian Baker, Weidong Liang, Richard Colchester et al. (+7 more)
Many minimally invasive procedures, such as core needle biopsy of focal liver lesions, nerve blocks, and fetal and vascular interventions, are typically performed under ultrasound guidance, which provides real-time, high-resolution visualisation of tissue anatomy. Accurate and efficient localisation of the needle tip relative to patient anatomy is essential for guiding the needle towards the procedure target, avoiding adverse events and reducing the need for repeat procedures. However, the 3D nature of the procedure and poor image contrast of the needle in heterogeneous tissue or at steep insertion angles often lead to confusion over the true location of the tip within the 2D guidance images, and existing methods to enhance needle visibility largely remain limited to 2D. Here, we present a novel interventional ultrasound system capable of 2D B-mode imaging and 3D needle tracking. The tip location is determined from the time-of-flight of ultrasound generated by a photoacoustic beacon embedded in the needle bevel and received by a sparse receiver array distributed around the imaging system's curvilinear ultrasound probe. The measured tracking accuracy was better than 2 mm for depths up to 140 mm in water, and approximately 2 mm on average in an ex vivo tissue phantom, with referenced positions derived from X-ray computed
tomography. In a usability study involving 12 clinicians performing biopsy procedures in a ex vivo tissue phantom, the failure rate was reduced by 35%, from 15.8% to 10.3% after only a few minutes of training. These results demonstrate that the proposed system has strong potential to support a wide range of minimally invasive procedures by enabling clinicians to accurately target small anatomical structures, improving the efficiency and effectiveness of diagnostic sampling and therapeutic delivery or ablation, and reducing the risk of adverse events.
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All authors Christian Baker, Weidong Liang, Richard Colchester, Peng Lei, Francois Joubert, Sebastien Ourselin, Simeon West, Adrien Desjardins, Athanasios Diamantopoulos, Wenfeng Xia
Optics
Ultralow noise microwaves with free-running frequency combs and electrical feedforward
Takuma Nakamura, William Groman, Qing-Xin Ji et al. (+11 more)
Optically generated microwave signals exhibit some of the lowest phase noise and timing jitter of any microwave-generating technology to date. The success of octave-spanning optical frequency combs in down-converting ultrastable optical frequency references has motivated the development of compact, robust and highly manufacturable optical systems that maintain the ultralow microwave phase noise of their tabletop counterparts. Two-point optical frequency division using chip-scale components and ~1 THz-spanning microcombs has been quite successful, but with stringent requirements on the comb source's free-running noise and feedback control dynamics. Here we introduce a major simplification of this architecture that replaces feedback control of the frequency comb in favor of electronic feedforward noise cancelation that significantly relaxes the comb requirements. Demonstrated with both a high repetition rate solid-state mode-locked
laser and a microcomb, feedforward on a 10 GHz carrier results in more robust operation with phase noise as low as -153 dBc/Hz at offsets >10 kHz, femtosecond timing jitter, and elimination of the large "servo bump" noise increase at high offset frequency. The system's compatibility with a variety of highly manufacturable mode-locked
laser designs and its resilience and straightforward implementation represents an important step forward towards a fully chip-scale implementation of optically generated microwaves, with applications in radar, sensing, and position,
navigation and timing.
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All authors Takuma Nakamura, William Groman, Qing-Xin Ji, Oguzhan Kara, Benjamin Rudin, Anatoliy Savchenkov, Vladimir Iltchenko, Wei Zhang, Andrey Matsko, John E. Bowers, Florian Emaury, Kerry J. Vahala, Scott A. Diddams, Franklyn Quinlan
Chemical Physics
MLIPAudit: A benchmarking tool for Machine Learned Interatomic Potentials
Leon Wehrhan, Lucien Walewski, Marie Bluntzer et al. (+4 more)
Machine-learned interatomic potentials (MLIPs) promise to significantly advance atomistic simulations by delivering
quantum-level accuracy for large molecular systems at a fraction of the computational cost of traditional electronic structure methods. While model hubs and categorisation efforts have emerged in recent years, it remains difficult to consistently discover, compare, and apply these models across diverse scenarios. The field still lacks a standardised and comprehensive framework for evaluating MLIP performance. We introduce MLIPAudit, an open, curated and modular benchmarking suite designed to assess the accuracy of MLIP models across a variety of application tasks. MLIPAudit offers a diverse collection of
benchmark systems, including small organic compounds, molecular
liquids,
proteins and flexible peptides, along with pre-computed results for a range of pre-trained and published models. MLIPAudit also provides tools for users to evaluate their models using the same standardised pipeline. A continuously updated leaderboard tracks performance across
benchmarks, enabling direct comparison on downstream tasks. By providing a unified, transparent reference framework for model validation and comparison, MLIPAudit aims to foster reproducibility, transparency, and community-driven progress in the development of MLIPs for complex molecular systems. In order to illustrate the use of the library, we present some
benchmarks run on a series of internal models, along with publicly available ones (UMA-Small, MACE-OFF, MACE-MP). The library is available on GitHub at https://github.com/instadeepai/mlipaudit, on PyPI at https://pypi.org/project/mlipaudit/ under the Apache License 2.0, and the leaderboard can be accessed on HuggingFace at https://huggingface.co/spaces/InstaDeepAI/mlipaudit-leaderboard.
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All authors Leon Wehrhan, Lucien Walewski, Marie Bluntzer, Heloise Chomet, Jules Tilly, Christoph Brunken, Silvia Acosta-Gutiérrez
Physics and Society
Public opinion between rearmament and crisis of the nuclear taboo
Fabrizio Battistelli and Francesca Farruggia
This article examines the changing relationship between the public and
nuclear weapons in a context of increasing international insecurity. It discusses the erosion of the
nuclear taboo, understood as a normative aversion to
nuclear use. Standard surveys capture abstract and rational opinions, while experimental surveys place respondents in simulated strategic scenarios designed to evoke more emotional responses. The divergence between their results is explained by the fact that they measure two different objects: rational opinions and emotional attitudes. A nationally representative survey conducted in Italy in 2025 shows that 81 percent of respondents consider
nuclear weapons fundamentally different from conventional weapons and always wrong to use. Among opponents, a distinction is drawn between deontologists and consequentialists. The article concludes by highlighting the importance of integrating affective and cognitive dimensions in the study of public opinion, as a contribution to countering the normalization of
nuclear weapons in political discourse.
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Medical Physics
Wide Area Surface Dosimetry with Conformal Scintillator Array for External Beam Radiotherapy
Roman Vasyltsiv, Allison L. Matous, Natasha Mulenga et al. (+5 more)
Background: In vivo dosimetry is essential for treatment verification in modern radiotherapy, but existing techniques are limited by spatiotemporal resolution and performance on non-uniform anatomy. Scintillation imaging dosimetry shows potential to address several of these limitations. Here, translation to conventional
photon external beam radiotherapy was examined using a novel wide-area imaging and sensing technique. Methods: A modular scintillator array was combined with a dual-camera stereovision system for 3D localization and a clinical Cherenkov imaging system for optical scintillation detection. Water equivalent thickness, dose linearity, repetition rate stability, and angular dependence were characterized. Field edge detection was evaluated against radiochromic film using gamma analysis. System reproducibility was tested with consecutive deliveries simulating contralateral breast monitoring during whole-breast tangential radiotherapy. Results: The array showed high dose linearity across the tested range, minimal beam perturbation, and consistent response within 5% across all available LINAC repetition rates. Dose-normalized scintillation varied within 5% over clinically relevant gantry angles, and camera angle corrections compensated for non-Lambertian emission. Field edge detection agreed closely with film, with a 99.98% gamma pass rate (3%/3 mm). Inter-delivery reproducibility of +/-1 cGy demonstrated robust system performance. Conclusion: The conformable scintillator array imaging system provides spatially resolved, dynamic surface dosimetry with minimal workflow impact. Its ability to generate continuous dose maps across complex anatomical surfaces, while maintaining angular correction, addresses key limitations of current in vivo dosimetry and shows strong potential for clinical integration where wide-area surface dosimetry is required.
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All authors Roman Vasyltsiv, Allison L. Matous, Natasha Mulenga, Megan A. Clark, Brian W. Pogue, David J. Gladstone, Lesley A. Jarvis, Petr Bruza
Fluid Dynamics
Fluid Intelligence: A Forward Look on AI Foundation Models in Computational Fluid Dynamics
Neil Ashton, Johannes Brandstetter and Siddhartha Mishra
Driven by the advancement of GPUs and AI, the field of Computational Fluid Dynamics (CFD) is undergoing significant transformations. This paper bridges the gap between the machine learning and CFD communities by deconstructing industrial-scale CFD simulations into their core components. Our main contribution is to propose the first scaling law that incorporates CFD inputs for both data generation and model training to outline the unique challenges of developing and deploying these next-generation AI models for complex fluid dynamics problems. Using our new scaling law, we establish quantitative estimates for the large-scale limit, distinguishing between regimes where the cost of data generation is the dominant factor in total compute versus where the cost of model training prevails. We conclude that the incorporation of high-fidelity transient data provides the optimum route to a foundation model. We constrain our theory with concrete numbers, providing the first public estimates on the computational cost and time to build a foundation model for CFD.
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Optics
Vehicle-Mounted Mid-Infrared Dual-Comb Spectroscopy for On-Road Trace Gas Detection
Xutian Jing, Kaiwen Wei, Chenglin Gu et al. (+12 more)
Advances in mid-infrared (MIR) dual-comb spectroscopy (DCS) have significantly enhanced molecular detection in recent years. The capability of DCS to precisely identify and quantify atmospheric trace gases makes it attractive for field applications across the environmental, agricultural, energy, and industrial sectors. In particular, there is a growing demand for mobile and continuous gas monitoring in outdoor environments where emission sources and sinks are often episodic and spatially heterogeneous. However, the practical field-deployment of DCS on mobile platforms under realistic field conditions has remained limited. This study demonstrates for the first time a vehicle-mounted MIR DCS system that enables continuous mobile atmospheric sampling across multiple outdoor sites and road environments. The system exhibited a stable signal-to-noise performance during on-road operation, including expressway driving at speeds up to 100 km/h. Furthermore, natural-gas leakage sources were successfully located and a two-dimensional methane concentration field was reconstructed around a controlled release source. In the future, the system can be integrated into more mobile platforms, such as unmanned aerial vehicles, enabling flexible trace gas detection over urban-scale regions.
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All authors Xutian Jing, Kaiwen Wei, Chenglin Gu, Xiong Qin, Junwei Li, Xingyin Yang, Zhaoting Huang, Jianping Zhang, Chenhao Sun, Chenyu Liu, Zejiang Deng, Zhiwei Zhu, Daping Luo, Wenxue Li, Heping Zeng
Fluid Dynamics
A meshless data-tailored approach to compute statistics from scattered data with adaptive radial basis functions
Damien Rigutto, Manuel Ratz and Miguel A. Mendez
Constrained radial basis function (RBF) regression has recently emerged as a powerful meshless tool for reconstructing continuous velocity fields from scattered flow measurements, particularly in image-based velocimetry. However, existing formulations based on isotropic kernels often suffer from spurious oscillations in regions with sharp gradients or strong flow anisotropy. This work introduces an anisotropic, gradient-informed, and adaptively sampled extension of the constrained RBF framework for regression of scattered data. Gradient information is estimated via local
polynomial regression at collocation points, smoothed, and used to (1) re-sample data, maximizing sampling density near steep gradients while downsampling in smooth regions, and (2) construct a local anisotropic metric that shapes each basis function according to the flow directionality. In addition, a gradient-informed regularization is introduced by
embedding observed gradients into the least-squares system as weighted soft constraints. The resulting formulation is fully meshless, linear, and computationally efficient, while significantly improving reconstruction quality in challenging regions. The method is evaluated on both synthetic and experimental
datasets, including direct numerical simulation (DNS) data of a turbulent channel and time-resolved particle tracking velocimetry of a turbulent jet. Results show that the proposed approach outperforms isotropic and gradient-free RBF formulations in accuracy, smoothness, and physical consistency – particularly near shear layers and boundaries – while reducing the number of bases by an order of magnitude. To support the application, we have created a repository (https://github.com/mendezVKI/SPICY_VKI) that provides access to the investigated
datasets.
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Plasma Physics · Cross-listed from cs.LG
Diffusion for Fusion: Designing Stellarators with Generative AI
Misha Padidar, Teresa Huang, Andrew Giuliani et al. (+1 more)
Stellarators are a prospective class of fusion-based power plants that confine a hot
plasma with three-dimensional
magnetic fields. Typically framed as a PDE-constrained optimization problem, stellarator design is a time-consuming process that can take hours to solve on a computing cluster. Developing fast methods for designing stellarators is crucial for advancing fusion research. Given the recent development of large
datasets of optimized stellarators, machine learning approaches have emerged as a potential candidate. Motivated by this, we present an open inverse problem to the machine learning community: to rapidly generate high-quality stellarator designs which have a set of desirable characteristics. As a case study in the problem space, we train a conditional
diffusion model on data from the QUASR database to generate quasisymmetric stellarator designs with desirable characteristics (aspect ratio and mean rotational transform). The
diffusion model is applied to design stellarators with characteristics not seen during training. We provide evaluation protocols and show that many of the generated stellarators exhibit solid performance: less than 5% deviation from quasisymmetry and the target characteristics. The modest deviation from quasisymmetry highlights an opportunity to reach the sub 1% target. Beyond the case study, we share multiple promising avenues for generative modeling to advance stellarator design.
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All authors Misha Padidar, Teresa Huang, Andrew Giuliani, Marina Spivak
Accelerator Physics
Benchmarking the Use of BPM Quadrupole Moments to Measure Emittance
M.A. Balcewicz and C.Y. Tan
For the PIP-II program, transverse emittance in the Fermilab Booster must remain well controlled at higher bunch intensities. 4-plate beam position monitors (BPMs) have a small but measurable quadrupole moment, making it possible to infer transverse emittance. By compositing many BPMs together, it becomes possible to improve the quality of the quadrupole signal. The Fermilab Booster BPM system has been used to measure these quadrupole moments in the past year and derive emittances from them. Recent
benchmarks show that the derived BPM emittances show similar emittance
evolution and value to IPM and Multiwire data. This approach can both supplement and complement existing non-intercepting emittance monitors in accelerators.
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Chemical Physics
A Vibronic Coupling Model to Study the Nonadiabatic Dynamics of Polyenes
Timothy N. Georges, Louis Summerley, Johan E. Runeson et al. (+1 more)
We develop a linear vibronic coupling (LVC) model for polyenes described by the extended Hubbard-Peierls
Hamiltonian. This model is applied to trans-hexatriene to
benchmark quantum-classical dynamics methods against fully
quantum simulations. We find that surface-hopping methods describe short times more accurately than multi-trajectory Ehrenfest. None of the
quantum-classical methods studied obtain the long-time population oscillations found in fully
quantum simulations. Varying the parameters of the LVC
Hamiltonian, we find that surface hopping reproduces the correct trends in the long-time dynamics across a wide range of parameters, but generally overestimates the degree of internal conversion. On the other hand, multi-trajectory Ehrenfest gives more accurate long-time populations in proximity to the hexatriene parameter set.
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All authors Timothy N. Georges, Louis Summerley, Johan E. Runeson, William Barford
Applied Physics · Cross-listed from cond-mat.supr-con
Planar Josephson junctions for sensors and electronics:Different geometry, new functionality
Vladimir M. Krasnov
Josephson junctions are key elements in superconducting electronics. The most common type is the overlap (sandwich-type) junction, formed by vertically stacking two superconducting layers. In contrast, planar junctions are fabricated without overlap, at the edge of two superconducting films within a single plane. This
geometric distinction has a significant impact on their physical properties. The planar geometry greatly enhances sensitivity to
magnetic fields and improves impedance matching for terahertz (THz) devices. Its two-dimensional structure allows for simple and flexible electronic component design, enabling drastic miniaturization. Here I highlight recent advances in the application of planar junctions for novel technologies, including junction-on-cantilever sensors for super-resolution
magnetic imaging,
vortex-based
memory cells, and programmable superconducting diodes. I will also discuss the general requirements, future perspectives, and key challenges in the evolving field of superconducting electronics.
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Accelerator Physics
Comparative evaluation of future collider options
G. Arduini, M. Benedikt, F. Gianotti et al. (+10 more)
In anticipation of the completion of the High-Luminosity Large
Hadron Collider (HL-LHC) programme by the end of 2041, CERN is preparing to launch a new major facility in the mid-2040s. According to the 2020 update of the European Strategy for Particle Physics (ESPP), the highest-priority next
collider is an electron-positron
Higgs factory, followed in the longer term by a
hadron-
hadron collider at the highest achievable energy. The CERN directorate established a Future
Colliders Comparative Evaluation working group in June 2023. This group brings together project leaders and domain experts to conduct a consistent evaluation of the Future Circular
Collider (FCC) and alternative scenarios based on shared assumptions and standardized criteria. This report presents a comparative evaluation of proposed future
collider projects submitted as input for the Update of the European Strategy for Particle Physics. These proposals are compared considering main performance parameters, environmental impact and sustainability, technical maturity, cost of construction and operation, required human resources, and realistic implementation timelines. An overview of the international
collider projects within a similar timeframe, notably the CEPC in China and the ILC in Japan is also presented, as well as a short review of the status and prospects of new accelerator techniques.
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All authors G. Arduini, M. Benedikt, F. Gianotti, K. Jakobs, M. Lamont, R. Losito, M. Meddahi, J. Mnich, N. Mounet, D. Schulte, F. Sonnemann, S. Stapnes, F. Zimmermann
Instrumentation and Detectors
Optimization of the X-Arapuca Photon Collection Efficiency for the DUNE Horizontal Drift Far Detector
E. Bertolini, C. Brizzolari, F. Bruni et al. (+19 more)
The Deep Underground
Neutrino Experiment (DUNE) Far Detector (FD)
Photon Detection System (PDS) employs the X-Arapuca concept, a
photon trapping system relying on reflective surfaces and dichroic filters. In this paper are reported measurements, performed at the University of Milano-Bicocca, aimed at increasing the FD Horizontal Drift (HD) PDS module efficiency. The baseline implementation of the X-Arapuca concept for the FD-HD PDS module is close to the DUNE requirements as demonstrated in the collaborations laboratory testing. However, an increased performance would provide a safety margin for a detector planned to be operated for 30 years, without possibility of performing maintenance. A higher detector performance would also benefit the DUNE low energy physics program. The already proven Milano-Bicocca setup has been utilized to test different PDS module configurations comparing them to the original baseline. Exploiting prior knowledge of the X-Arapuca components and Geant4 based optical simulations it has been possible to achieve up to an ~84% performance increase over the baseline design. In the following it is presented the testing procedure, the performed measurements and a brief discussion on the obtained results.
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All authors E. Bertolini, C. Brizzolari, F. Bruni, P. Carniti, C.M. Cattadori, S. Copello, E. Cristaldo, M. Delgado, F. Galizzi, C. Gotti, D. Guffanti, A. A. Machado, L. Malinverni, L. Meazza, F. Meinardi, G. Pessina, G. Raselli, M. Rossella, E. Segreto, H. Souza, F. Terranova, D. Warner
Optics
Unusual sign-changing Faraday effect in nanometer-thick magnetic films
A.V. Belkova, D.O. Ignatyeva, A.N. Kalish et al. (+3 more)
It is generally believed that the magneto-optical Faraday effect appears in the the bulk of a
magnetic material and its sign is fully determined by the sign of the non-diagonal permittivity element. Here we reveal an additional contribution to the Faraday effect from the film interfaces. It becomes notable for films with a thickness of a few tens of nanometers. As a result, in the absorption band of the film a novel feature of the Faraday effect is experimentally observed and numerically confirmed: sign of the Faraday rotation at a fixed wavelength becomes dependent on the film thickness and therefore is ambiguously related to the sign of the gyration and magnetization of the film. We elaborated an analytical model taking into account an interplay between the bulk and surface contributions which nicely describes the experimental data. Moreover, the Faraday rotation coming purely from interfaces without any bulk contribution is demonstrated. Possible applications of the observed unusual Faraday rotation behavior include hardware data encryption and other devices performing polarization control at nanoscale.
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All authors A.V. Belkova, D.O. Ignatyeva, A.N. Kalish, P.M. Vetoshko, A.L. Kudryashov, V.I. Belotelov
Optics
Near-field photon Nernst effect
Alireza Kalantari Dehaghi and Linxiao Zhu
We consider the consequence of having nonreciprocal
photon transfer between two surfaces with temperature gradient. We demonstrate that in a system consisting of
graphene and a magneto-optical substrate separated by a gap, a transverse electric field is generated in
graphene perpendicular to
magnetic field and temperature gradient, in analogy to the Nernst effect. Such
photon Nernst effect is driven by nonreciprocal Casimir force carried by
photons. We show that the thermal efficiency of near-field
photon Nernst effect is bounded by the Carnot limit, and nonreciprocal high-k modes are needed for approaching the limit. The near-field
photon Nernst effect enables electrical probing of nonreciprocal radiative transfer and provides a novel means of energy harvesting.
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Medical Physics
Manganese-based macrocyclic chelates as novel MRI contrast agents: In vivo imaging in a porcine model
Pål B. Marthinsen, Tuva R. Hope, Wibeke Nordhøy et al. (+4 more)
Objectives: Mn-based MRI contrast
agents (MBCAs) have recently been proposed as alternatives to the currently used class of Gd-chelates. Unlike Gd, Mn is an endogenous paramagnetic metal with known biochemical pathways in the human body for excretion and metal regulation, which may alleviate the raised concerns about the safety of existing GBCAs. The aim of this study was to investigate the distribution, kinetics and image enhancement properties of a class of novel Mn-based macrocyclic chelates in a porcine model. Methods: Macrocyclic MBCAs, AH114608, GEH300017 and GEH200486, were tested and compared to gadoterate meglumine. Twelve female adult pigs were divided into four groups (n=3 for each CA). At 3 T MRI, T1 relaxometry analysis were measured longitudinally in multiple organs at five timepoints 30 minutes apart. CA kinetics was estimated from analysis of
plasma CA concentrations by ICP-OES. Results: All four CAs exhibited T1-enhancing properties in the blood pool with GEH200486 having the largest increase in T1 relaxation rate (R1), GEH300017 and gadoterate meglumine having similar R1 increase and AH114608 a lower peak R1 change. A persistent increase in liver, kidney and myocardium R1 was observed with AH114608. To a lesser extent, a persistent increase of liver enhancement was also observed in T1-weighted images for GEH300017 and GEH200486 compared to gadoterate meglumine. All four CAs had similar bi-exponential
plasma kinetics characterized by a rapid distribution phase and a slower elimination phase. Discussion: We have identified MBCA candidates with predominantly renal clearance and comparable efficacy in terms of vascular T1 relaxation, and comparable to the reference GBCA. The T1-enhancing properties of these novel Mn macrocyclic CAs can be used with routine clinical protocols and could be potentially utilised as an alternative to GBCAs for contrast-enhanced MRI procedures.
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All authors Pål B. Marthinsen, Tuva R. Hope, Wibeke Nordhøy, Deirdre B. Cassidy, Adrian P.L. Smith, Paul M. Evans, Atle Bjørnerud
Plasma Physics
Microphysical boundary condition for the electron kinetics of a plasma
Felix Willert, Clemens Hoyer, Gordon K. Grubert et al. (+1 more)
We derive and implement a suitable boundary condition for the kinetic description of the electrons inside a
plasma, which takes into account microphysical processes inside the wall. It is based on the surface scattering kernel, which describes the scattering cascade of the electron in the solid and the excitation of secondary electrons. The resulting boundary condition is inelastic, angle- and energy-dependent. The implementation for a Boltzmann equation solved by a Legendre
polynomial expansion method is presented, elucidating the modest additional computational cost of the new boundary condition. Results, indicating the influence of the inelasticity, are shown for the example of a silicon wall facing argon, helium and oxygen
plasmas, but the described construction is also valid for other materials. An effective reflection coefficient is defined to compare the results with previously used boundary conditions.
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All authors Felix Willert, Clemens Hoyer, Gordon K. Grubert, Franz X. Bronold
Fluid Dynamics
Morphology of mucus films in lung airways: secretion and ciliary evacuation
Swarnaditya Hazra and Jason R. Picardo
Lung airways are lined by a film of mucus which protects the epithelium from inhaled particles. To maintain a uniform coating, the mucus that is secreted into airways must be distributed into a film by wall-attached cilia, which constantly convey mucus along the airway. However, the film's natural tendency is to accumulate into humps and plugs, due to the Rayleigh-Plateau instability. To understand the behaviour of the film amidst these competing factors, we perform simulations of an idealized tubular airway using a reduced-order thin-film model. The axial boundaries are nonperiodic, allowing for cilia-driven inflow and
outflow; a tangential velocity along the tubular wall models ciliary transport, while a localized source at the wall accounts for secretion. On increasing the mucus input rate, we find three distinct film morphologies: (i) uniform flat films; (ii) nonuniform films that are composed of travelling unduloid-shaped humps, separated by mucus-depleted zones; and (iii) films that form an occluding plug. The flat-film regime, absent in closed periodic domains, emerges as a consequence of the convective nature of the Rayleigh-Plateau instability in the presence of ciliary transport. Higher secretion rates increase the mean film-thickness and induce a convective-to-absolute transition, which manifests in the appearance of travelling humps. In the plug-forming regime, capillary forces dominate and drive the incoming mucus into a single hump, which resists ciliary translation and remains near the mucus source. Our results show how low-level baseline secretion sustains a protective, uniform mucus film, and how hypersecretion – stimulated, for example, by inhaled allergens – produces mucus plugs.
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Plasma Physics
The PLUTO Code on GPUs: A First Look at Eulerian MHD Methods
Marco Rossazza, Andrea Mignone, Matteo Bugli et al. (+7 more)
We present preliminary performance results of gPLUTO, the new GPU-optimized implementation of the PLUTO code for computational
plasma astrophysics. Like its predecessor, gPLUTO employs a finite-volume formulation to numerically solve the equations of magnetohydrodynamics (MHD) in multiple spatial dimensions. Still, this new implementation is a complete rewrite in C++ and leverages the OpenACC programming model to achieve acceleration on NVIDIA GPUs. While a more comprehensive description of the code and its several other modules will be presented in a future paper, here we focus on some preparatory results that demonstrate the code potential and performance on pre exa-scale parallel architectures.
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All authors Marco Rossazza, Andrea Mignone, Matteo Bugli, Stefano Truzzi, Lubomir Riha, Tomas Panoc, Ondrej Vysocky, Nitin Shukla, Alessandro Romeo, Vittoria Berta