Applied Physics · Cross-listed from cond-mat.mtrl-sci
Polarons from first principles
Zhenbang Dai, Jon Lafuente-Bartolome and Feliciano Giustino
This article reviews recent theoretical developments in the ab initio study of polarons in materials. The polaron is an emergent quasiparticle that arises from the interaction between electrons and
phonons in solids, and consists of an electron or a hole accompanied by a distortion of the
crystal lattice. Recent advances in experiments, theory, and computation have made it possible to investigate these quasiparticles with unprecedented detail, reigniting the interest in this classic problem of condensed matter physics. Recent theoretical and computational advances include ab initio calculations of polaron spectral functions, wavefunctions,
lattice distortions, and transport and optical properties. These developments provide new insight into polaron physics, but they have evolved somewhat independently from the earlier effective
Hamiltonian approaches that laid the foundation of the field. This article aims to bridge these complementary perspectives by placing them within a single unified conceptual framework. To this end, we start by reviewing effective
Hamiltonians of historical significance in polaron theory, ab initio techniques based on density functional theory, and many-body first-principles approaches to polarons. After this survey, we outline a general field-theoretic framework that bridges between these diverse approaches to polaron physics. For completeness, we also review recent progress in the study of
exciton polarons and self-trapped
excitons and their relations to polarons. Beyond the methodology, we discuss recent applications to several classes of materials that attracted
attention in the context of polaron physics.
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Computational Physics
MaxwellLink: A unified framework for self-consistent light-matter simulations
Xinwei Ji, Andres Felipe Bocanegra Vargas, Gang Meng et al. (+1 more)
A major challenge in light-matter simulations is bridging the disparate time and length scales of electrodynamics and molecular dynamics. Current computational approaches often rely on heuristic approximations of either the electromagnetic (EM) or the material component, hindering the exploration of complex light-matter systems. Herein, MaxwellLink – a modular, open-source Python framework – is developed for the massively parallel, self-consistent propagation of classical EM fields interacting with a large heterogeneous molecular ensemble. The package utilizes a robust TCP/UNIX socket interface to couple EM solvers with a wide range of molecular drivers. In this initial release, MaxwellLink supports EM solvers spanning from single-mode cavities to full-feature three-dimensional finite-difference time-domain (FDTD) engines, and molecules described by multilevel open
quantum systems, force-field and first-principles molecular dynamics, and nonadiabatic real-time Ehrenfest dynamics. With the socket-based architecture, users can seamlessly switch between levels of theory of either the EM solver or molecules without modifying the counterpart. Moreover, the EM engine and molecular drivers scale independently across multiple high-performance computing (HPC) nodes, facilitating large-scale simulations previously inaccessible to existing numerical schemes. The versatility and accuracy of this code are further demonstrated through applications including superradiance, radiative energy transfer, vibrational strong coupling in Bragg resonators, and plasmonic heating of molecular gases. By providing a unified, extensible engine, MaxwellLink potentially offers a powerful platform for exploring emerging phenomena across the research fronts of spectroscopy,
quantum optics, plasmonics, and polaritonics.
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All authors Xinwei Ji, Andres Felipe Bocanegra Vargas, Gang Meng, Tao E. Li
Atmospheric and Oceanic Physics
Direct Radiative Impacts of Stratospheric Aerosols on the Tropical Troposphere: Clouds, Precipitation, and Circulation in Convection-Resolving and Global Simulations
Zachary McGraw and Lorenzo M. Polvani
A concern for stratospheric aerosol injection (SAI) is that stratospheric aerosols could inadvertently alter rain and winds through mechanisms independent of the intended surface cooling. We here use a multi-model framework to investigate how the tropical troposphere responds to SAI when sea surface temperatures are held fixed. By performing convection-resolving simulations in small-domains and in mock-Walker setups, and contrasting these with global
climate model simulations, we trace how stratospheric aerosols radiatively heat the troposphere, and in turn alter convection, clouds, and rainfall. Our simulations show an SAI-induced reduction in tropical mean precipitation, yet decreased cloud radiative heating moderates this effect and complicates its predictability. Regional rainfall anomalies within the tropics can be substantial. However, surface-temperature-independent effects on tropical circulation are found to be negligible, indicating that stratospheric aerosols do not inherently alter the tropical overturning circulation as previously suggested. These results clarify the mechanisms governing SAI hydroclimate impacts and show that key uncertainties arise from cloud processes that models are unable to constrain. Consequently, near-term SAI deployment would carry the risk of being implemented without the ability to reliably predict its hydroclimate impacts.
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Chemical Physics
Synergistic Computational Approaches for Accelerated Drug Discovery: Integrating Quantum Mechanics, Statistical Thermodynamics, and Quantum Computing
Farzad Molani and Art E. Cho
Accurately predicting
protein-ligand binding free energies (BFEs) remains a central challenge in drug discovery, particularly because the most reliable methods, such as free energy perturbation (FEP), are computationally intensive and difficult to scale. Here, we introduce a hybrid
quantum-classical framework that combines Mining Minima sampling with
quantum mechanically refined ligand partial charges, QM/MM interaction evaluation, and variational
quantum eigensolver (VQE)-based electronic energy correction. This design enables explicit treatment of polarization, charge redistribution, and electronic correlation effects that are often underestimated in purely classical scoring schemes, while retaining computational efficiency. Across 23
protein targets and 543 ligands, the method achieves a mean absolute error of about 1.10 kcal/mol with strong rank-order fidelity (Pearson R = 0.75, Spearman rho = 0.76, Kendall tau = 0.57), consistent with the performance of contemporary FEP protocols. Notably, the workflow requires only about 25 minutes per ligand on standard compute resources, resulting in an approximate 20-fold reduction in computational cost relative to alchemical free energy approaches. This level of accuracy and efficiency makes the method well-suited for high-throughput lead optimization and iterative design cycles in pharmaceutical discovery. The framework also provides a natural foundation for future integration with machine learning models to enable predictive, large-scale, and adaptive screening strategies.
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Optics
Tunable Narrowband Terahertz Radiation from van der Waals Ferroelectrics
Chun-Ying Huang, Taketo Handa, Daniel G. Chica et al. (+10 more)
The terahertz (THz) spectral range is central to high-speed communication, precision metrology, sensing technologies, and a range of fundamental scientific investigations. Achieving these capabilities in practical systems increasingly demands chip-scale integration of THz photonic components that are typically bulky. In this context, van der Waals (vdW) materials provide a unique platform for integrated nonlinear photonics in the visible and near-infrared regimes, and extending this framework into the THz domain would constitute a significant advance. Here, we report tunable, intense, and narrowband THz radiation from ferroelectric niobium oxyhalides. Through halogen substitution and alloying, we achieve continuous and precise control over the emission frequency from 3.1 to 5.8 THz. We show that the narrowband THz radiation is driven by
phonons associated with the ferroelectric polarization. We further demonstrate dynamic and nonvolatile control of the polarity of the coherent THz wave with external electric field. This work demonstrates efficient narrowband THz emission from vdW ferroeletrics and provides microscopic insight into its origin, paving the way for on-chip THz technology for a broad range of applications.
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All authors Chun-Ying Huang, Taketo Handa, Daniel G. Chica, Zhihao Cui, Ding Xu, Jeongheon Choe, Yiliu Li, Margalit L. Feuer, Milan E. Delor, Michael Fechner, David R. Reichman, Xavier Roy, Xiaoyang Zhu
Instrumentation and Detectors
Using Open Source EDA Tools in ASICs for HEP: A Mixed Comparison
Édney M. V. Freitas, Nicolas Guimarães, Rafael Maria et al. (+4 more)
This work compares open-source electronic design automation tools with a commercial environment using three representative integrated
circuit blocks in the IHP 130 nm open PDK: a common-mode noise filter, a finite-state machine, and a voltage-controlled oscillator. The study reports design effort and quality of results for digital logic, including area, power, and timing closure, and examines analog layout feasibility. For the finite-state machine at 50 MHz, the open-source flow reached 0.029 mm$^2$ (post-layout) and 4.37 mW (estimated) with 828 standard
cells, whereas the commercial flow achieved 0.019 mm$^2$ and 2.00 mW with 497
cells, corresponding to increases of 53% in area and 118% in power. The common-mode noise filter totals 1.879 mm$^2$ with 1703 flip-flops at 50 MHz. The voltage-controlled oscillator occupies 0.0025 mm$^2$ and achieves a simulated maximum oscillation frequency of 2.65 GHz. The contribution is a side-by-side quantification of quality of results across digital and analog blocks in the IHP open PDK. The results indicate that open-source tools are viable for early prototyping, training, and collaboration, while commercial flows retain advantages in automation and quality of results when strict targets on power and area or precision analog layout are required.
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All authors Édney M. V. Freitas, Nicolas Guimarães, Rafael Maria, Felipe Costa, Guilherme Milani, Bruno Sanches, Wilhelmus Van Noije
Optics
Nonlinear phenomena in X-ray fluorescence from single nanoparticles under extreme conditions
Sebastian Cardoch, Tamme Wollweber, Sarodi Jonak Dutta et al. (+26 more)
Materials exposed to intense femtosecond X-ray pulses with energies above their K-shell absorption edge can enter an extremely ionized state, which could give rise to nonlinear phenomena, such as saturable absorption and reverse saturable absorption. In this work, we investigate these effects on single copper nanoparticles irradiated by an X-ray free-electron
laser pulse. We study the properties of the K$\alpha$ fluorescence for two different short pulse durations and three X-ray incident energies below and above the K-shell absorption edge, and correlate these with incident fluence estimates based on coherent diffraction. We observe that the incident fluence of the pulse and not its duration, is the main factor that modulates the nonlinear response, which leads to an effective shortening of the fluorescence emission. Our findings have implications for fluorescence-based methods for imaging single particles using transiently coherent fluorescence, or diffractive imaging through transient resonances.
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All authors Sebastian Cardoch, Tamme Wollweber, Sarodi Jonak Dutta, Zhou Shen, Johan Bielecki, Fabian Trost, Armando D. Estillore, Lukas V. Haas, Sebastian Karl, Faisal H.M. Koua, Abhishek Mall, Parichita Mazumder, Diogo Melo, Mauro Prasciolu, Omkar V. Rambadey, Amit Kumar Samanta, Abhisakh Sarma, Tokushi Sato, Egor Sobolev, Saša Bajt, Richard Bean, Carl Caleman, Jochen Küpper, Ralf Röhlsberger, Joachim von Zanthier, Florian Schulz, Henry N. Chapman, Kartik Ayyer, Nicusor Timneanu
Optics · Cross-listed from quant-ph
High-Performance Labyrinth Circular Bragg Grating Design for Charge and Stark-Tunable Quantum Light Sources Spanning Visible to Telecom Wavelengths
Rohit Prasad, Quirin Buchinger, Fei Chi Kristy Yuen et al. (+3 more)
Semiconductor quantum dots embedded in circular Bragg gratings (CBGs) are among the most efficient integrated single-
photon sources. However, the fully etched rings of conventional CBGs restrict the implementation of charge and Stark tuning via electrical contacts. To overcome this limitation, a labyrinth CBG geometry with four bridges has been proposed, yet the added bridges significantly degraded optical performance. In this work, we numerically demonstrate that a periodic labyrinth CBG design preserves both high coupling efficiency and strong Purcell enhancement while enabling electrical integration if optimized after introducing the bridges. We show three optimized designs at emission wavelengths of 780 nm, 930 nm, and 1550 nm, because these wavelengths are among the most relevant for
quantum dots and show the general applicability of our approach. At all three wavelengths collection efficiencies exceeding 90% into a numerical aperture of 0.7 and Purcell factors greater than 25 are achieved. Furthermore, we propose a device layout incorporating a barrier layer that separates p- and n-doped
semiconductor regions, which is incorporated to prevent tunneling of one of the charge carriers for selective charging. Also this design can be reoptimized to retain the performance of a device without tunnel barrier. These results establish labyrinth CBGs as a platform for electrically tunable
quantum dot single-
photon sources with high efficiency and scalability.
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All authors Rohit Prasad, Quirin Buchinger, Fei Chi Kristy Yuen, Yorick Reum, Sven Höfling, Tobias Huber-Loyola
Plasma Physics
A Method for Solving Linearized Vlasov Equation for Low-Frequency Long-Wavelength Electromagnetic Modes in Inhomogeneous Plasmas
Bamandas Basu
A method for solving linearized Vlasov equation for low-frequency, long-wavelength electromagnetic modes in magnetically confined inhomogeneous
plasmas is described. The relevant non-local solution that includes the lowest-significant-order effects of inhomogeneities is obtained from the solutions of three simple equations by means of elementary
algebra. The method appears to be more convenient than the commonly used method of integration along the unperturbed particle orbits and should be of interest to students of theoretical
plasma physics.
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Optics
Single-particle incoherent diffractive imaging and amplified spontaneous emission in copper nanocubes
Tamme Wollweber, Sarodi Jonak Dutta, Zhou Shen et al. (+26 more)
We demonstrate element-specific incoherent diffractive imaging (IDI) of single copper nanocubes using intensity correlations of K$\alpha$ fluorescence at a hard X-ray free-electron
laser. Combining single particle diffraction classification with IDI, we retrieve the form factor of 88 nm cubes with 20 nm resolution, extending IDI to the destructive single-particle regime with a large gain in resolution. IDI visibility drops sharply above a fluence of $10^2$ J/cm$^2$, consistent with the assumption of amplified spontaneous emission. Our results reveal fundamental limits for high-fluence nanoimaging towards future single-particle X-ray imaging.
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All authors Tamme Wollweber, Sarodi Jonak Dutta, Zhou Shen, Johan Bielecki, Carl Caleman, Sebastian Cardoch, Armando D. Estillore, Lukas V. Haas, Sebastian Karl, Faisal H.M. Koua, Abhishek Mall, Parichita Mazumder, Diogo Melo, Mauro Prasciolu, Omkar V. Rambadey, Amit Kumar Samanta, Abhisakh Sarma, Tokushi Sato, Egor Sobolev, Fabian Trost, Saša Bajt, Richard Bean, Jochen Küpper, Nicusor Timneanu, Ralf Röhlsberger, Joachim von Zanthier, Florian Schulz, Henry N. Chapman, Kartik Ayyer
Data Analysis and Statistics · Cross-listed from astro-ph.CO
Generalized tension metrics for multiple cosmological datasets
Matías Leizerovich, Susana J. Landau and Claudia G. Scóccola
We introduce a novel
estimator to quantify statistical tensions among multiple cosmological
datasets simultaneously. This
estimator generalizes the Difference-in-Means statistic, $Q_{\rm DM}$, to the multi-
dataset regime. Our framework enables the detection of dominant tension directions in the shared parameter space. It further provides a
geometric interpretation of the tension for the two- and three-
dataset cases in two dimensions. According to this approach, the previously reported increase in tension between DESI and Planck from $1.9\sigma$ (DR1) to $2.3\sigma$(DR2) is reinterpreted as a more modest shift from $1.18\sigma^{\rm eff}$ (DR1) to $1.45\sigma^{\rm eff}$ (DR2). These new tools may also prove valuable across research fields where
dataset discrepancies arise.
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Instrumentation and Detectors
GPU acceleration of optical photon propagation in low photon yield applications: Opticks for the Electron Ion Collider
Gabor Galgoczi, Kolja Kauder, Maxim Potekhin et al. (+3 more)
The bulk of time spent in the simulation of Cherenkov and other scintillation detectors is spent on optical-
photon transport, i.e. ray tracing, a task that GPUs are uniquely qualified to perform. We present EIC-Opticks, a fork of Opticks, which uses event aggregation to drastically accelerate
photon transport simulation for low-to-moderate
photon yield experiments. During the full Geant4 Monte Carlo simulation of a given detector, optical
photon simulation is performed on GPU(s) using the NVIDIA OptiX framework. We validate this approach using the ePIC pfRICH detector. We find GPU and CPU simulations in excellent agreement. For $5\times 10^4$ electrons with a momentum of $p=5~\mathrm{MeV}/c$ in the test case of the pfRICH detector, EIC-Opticks shows an order-of-magnitude speedup over multi-threaded Geant4, and a factor of up to 161$\pm$3 over single-threaded execution. In the case of low-to-moderate applications event aggregation reduces the per-
photon simulation time from $\sim60\,\mu\mathrm{s}$ for single events to $\sim20\,\mathrm{ns}$ with batching, a factor of $\sim3000$. In order to make EIC-Opticks easily installable, we authored a Spack package that makes it possible to install it with a single command. Additionally, a Docker container is provided for users with EIC-Opticks installed. EIC-Opticks provides guardrails for common pitfalls (e.g. nested volume conversion, ray tracing setting optimization).
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All authors Gabor Galgoczi, Kolja Kauder, Maxim Potekhin, Sakib Rahman, Dmitri Smirnov, Torre Wenaus
Applied Physics · Cross-listed from cs.LG
Deep learning recognition and analysis of Volatile Organic Compounds based on experimental and synthetic infrared absorption spectra
Andrea Della Valle, Annalisa D'Arco, Tiziana Mancini et al. (+5 more)
Volatile Organic Compounds (VOCs) are organic molecules that have low boiling points and therefore easily evaporate into the air. They pose significant risks to human health, making their accurate detection the crux of efforts to monitor and minimize exposure. Infrared (IR) spectroscopy enables the ultrasensitive detection at low-concentrations of VOCs in the atmosphere by measuring their IR absorption spectra. However, the complexity of the IR spectra limits the possibility to implement VOC recognition and quantification in real-time. While deep neural networks (NNs) are increasingly used for the recognition of complex data structures, they typically require massive
datasets for the training phase. Here, we create an experimental VOC
dataset for nine different classes of compounds at various concentrations, using their IR absorption spectra. To further increase the amount of spectra and their diversity in term of VOC concentration, we augment the experimental
dataset with synthetic spectra created via conditional generative NNs. This allows us to train robust discriminative NNs, able to reliably identify the nine VOCs, as well as to precisely predict their concentrations. The trained NN is suitable to be incorporated into sensing devices for VOCs recognition and analysis.
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All authors Andrea Della Valle, Annalisa D'Arco, Tiziana Mancini, Rosanna Mosetti, Maria Chiara Paolozzi, Stefano Lupi, Sebastiano Pilati, Andrea Perali
Physics and Society · Cross-listed from cs.DL
Measuring the Potential of Scientific Literature: A Network-Based Approach to Identifying Paradigm-Shifting Research
Sarah James
This study introduces the Disruption Index as a superior citation-based metric. This index quantitatively assesses the degree to which a publication redirects subsequent scholarly
attention away from its preceding literature, thus measuring its novelty and disruptive impact. We tested the D metric's efficacy using a rigorous
dataset comprising seminal publications by Nobel Prize winners across Physics, Chemistry, and Physiology or Medicine, benchmarked against control papers with comparable citation counts but non-transformative influence. Our analysis conclusively demonstrates that the D metric effectively distinguishes these prize-worthy, field-redefining works from highly cited but merely incremental research. Furthermore, we explore two contextual variables associated with high disruptive potential: (i) the scale of collaboration (author team size) and (ii) the linguistic structure of the article's title and summary text. The results reveal a strong positive correlation between larger collaborative teams and elevated average D scores, suggesting that extensive collaboration may be a facilitator for generating paradigm shifts. Additionally, publications with high D values tend to feature more expansive titles and greater density of specialized, technical jargon in their abstracts. These findings validate the D metric as a reliable and scalable instrument for both historical and predictive identification of transformative research. They also furnish empirical evidence concerning the team structures and communication patterns that optimize for the production of groundbreaking scientific knowledge.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Ferromagnetic Phase Transition of DPPH Induced by a Helical Magnetic Field
Emmanouil Markoulakis, John Chatzakis, Antonios Konstantaras et al. (+2 more)
We report the results and unique instrument configuration of a novel experiment in which we successfully transitioned a DPPH sample from its natural paramagnetic state and essentially a non-
magnetic material to a
ferromagnetic state at room temperature. This was achieved using a specifically applied helical flux
magnetic field. The DPPH sample (2,2-diphenyl-1-picrylhydrazyl) remained
ferromagnetic for at least one hour after the experiment, indicating that a transformation in the material was induced by the external field rather than being merely a temporary
magnetic phase transition observed only during the experiment. The external
magnetic field used had a helical pitch angle of approximately $54.7{\deg}$, known mathematically as the Magic Angle, relative to the +z-axis, which is aligned with the normal S to N external field's
magnetic moment vector. Based on the phenomenology of the experiment and results, we suggest that this specific magic angle corresponding to the known quantization precession
spin angle of free electrons under a homogeneous straight flux
magnetic field potentially enhances the percentage of unpaired valence electrons within the DPPH material, allowing them to align in parallel with the applied external field. Typically, in paramagnetic materials, the distribution of unpaired electrons'
quantum spins relative to an external field is nearly random, showing roughly a 50% chance of either parallel or antiparallel
alignment. Only a slight majority preference exists in one
alignment direction due to the Boltzmann thermal distribution, which contributes to the paramagnetic nature of these materials. In our measurements, we found that the induced ferromagnetism of the DPPH sample resulted in an abnormal thousand-fold decimal value increase in relative
magnetic permeability at ${\mu}{\approx}1.4$, compared to its typical paramagnetic value of $1.0001$ for this material.
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All authors Emmanouil Markoulakis, John Chatzakis, Antonios Konstantaras, Iraklis Rigakis, Emmanuel Antonidakis
Physics and Society
Quantum, Diplomacy, and Geopolitics
Axel Ferrazzini
Quantum technologies, spanning communication, sensing, computing, and cryptography, are rapidly emerging as critical paths of geopolitical competition and strategic defence innovation. Unlike traditional technological advances,
quantum introduces novel capabilities that fundamentally disrupt established norms of security, intelligence, and diplomatic engagement. This strategic analysis explores the evolving
quantum landscape through the dual lenses of diplomacy and geopolitics, with specific implications for defence leaders, policymakers, and industry stakeholders. The benefits and challenges of
quantum technologies are examined from a diplomatic and geopolitical perspective to help leaders make informed strategic decisions. Leading powers now recognise
quantum as a domain where technological leadership directly translates to geopolitical influence, compelling an intense race for dominance alongside new forms of multilateral diplomacy aimed at managing both risks and opportunities.
Quantum technologies do not all have the same operational maturity, but technological progress is accelerating. Post-
quantum cryptography demands immediate action, every encrypted communication created today may be harvested and decrypted within the decade by adversaries equipped with
quantum capabilities.
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General Physics
A formalism of Gravitation based on a Physical Field Strength
L. Horoto and F. G. Scholtz
We propose a reformulation of gravitation in which the gravitational interaction is treated as a genuine force rather than an inertial effect arising from spacetime geometry. Within this framework, the difference between the affine connection and a flat reference connection defines a tensor $\mathrm{K}^\mu{}_{\alpha\beta}$, identified as the gravitational field strength. This object cannot be eliminated by coordinate transformations, demonstrating that
gravity possesses true physical degrees of freedom. The formalism introduces vector fields $\xi_a{}^\mu$ that extend the notion of infinitesimal translations to curved spacetime and naturally yield a gauge-invariant field strength $\mathfrak{F}^{\xi a}{}_{\mu\nu}$. The dynamics of the gravitational field are governed by a Lagrangian of Yang–Mills type with an additional scalar degree of freedom $\phi^{2}$, corresponding to the Newtonian potential. In the limit of vanishing gravitational coupling $\mathfrak{g}\to0$, the theory reduces to General Relativity, while for nonzero $\mathfrak{g}$ it constitutes an $\mathrm{SU(2)\times U(1)}$ gauge theory of
gravity. The framework provides a unified description in which dark energy emerges as the self-interaction energy of the $\phi$ field, and dark-matter-like effects arise from the extended gravitational degrees of freedom. This formulation offers a consistent bridge between classical and
quantum descriptions of
gravity and clarifies the conceptual foundations of the gravitational interaction.
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Fluid Dynamics
From Time Series Expansion to Proper Generalized Decomposition via Graph-Theoretical Connection: Stabilized Simulation of Fluids Flow
Ahmad Deeb, Vladimir Parezanovic and Denys Dutykh
In this paper, we employ graph theory to establish a connection between the Time Series Expansion (TSE) and Proper Generalized Decomposition (PGD) methods. Using the concept of a directed graph, we demonstrate how one can transition from the computation of space modes in the TSE–first illustrated for the
diffusion equation–to those of space modes in PGD, in which an inhomogeneous Volterra-type convolution recurrence relation, weighted by time-dependent coefficients, appears. This recurrence relation is simplified through graph-based analysis into a compact form using a simple path traversal, reducing the computational complexity. Moreover, the compact formulation reveals a natural stabilization process in the computation of space modes, where stabilized coefficients are automatically derived and can be used in the Stabilized-TSE (STSE) framework. To explicitly construct these coefficients, we consider a Simplified PGD (SPGD) formulation in which the time modes are chosen to be the time
polynomial basis $t^n$. This choice yields a one-level Volterra-type recurrence relation that is similarly simplified using a simple path representation, demonstrating a connection in the computation of space modes from TSE, through STSE and SPGD, to PGD. This graph-based connection is exhibited in the case of inviscid flow to check how crucial the addition of an artificial
diffusion is in stabilizing the recurrence formula of TSE. Finally, we extend the approach to the incompressible, dimensionless Navier-Stokes (NS) equations and build stabilization coefficients that depend on the Reynolds number Re, the space mode rank, and the simulation time step. Both the STSE and SPGD approaches are tested to simulate the wake behind a bluff body at Re = 5 000.
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Computational Physics · Cross-listed from math.NA
Qualitative and Quantitative Analysis of Riemannian Optimization Methods for Ground States of Rotating Multicomponent Bose-Einstein Condensates
Martin Hermann, Tatjana Stykel and Mahima Yadav
We develop and analyze Riemannian optimization methods for computing ground states of rotating multicomponent Bose-Einstein condensates, defined as minimizers of the Gross-Pitaevskii energy functional. To resolve the non-uniqueness of ground states induced by phase invariance, we work on a quotient
manifold endowed with a general Riemannian metric. By introducing an auxiliary phase-aligned iteration and employing fixed-point convergence theory, we establish a unified local convergence framework for Riemannian gradient descent methods and derive explicit convergence rates. Specializing this framework to two metrics tailored to the energy landscape, we study the energy-adaptive and Lagrangian-based Riemannian gradient descent methods. While monotone energy decay and global convergence are established only for the former, a quantified local convergence analysis is provided for both methods. Numerical experiments confirm the theoretical results and demonstrate that the Lagrangian-based method, which incorporates second-order information on the energy functional and mass constraints, achieves faster local convergence than the energy-adaptive scheme.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Adsorption energies are necessary but not sufficient to identify good catalysts
Shahana Chatterjee, Alexander Davis, Lena Podina et al. (+7 more)
As a core technology for green chemical synthesis and electrochemical energy storage, electrocatalysis is central to decarbonization strategies aimed at combating
climate change. In this context, computational and machine learning driven catalyst discovery has emerged as a major research focus. These approaches frequently use the thermodynamic overpotential, calculated from adsorption free energies of reaction intermediates, as a key parameter in their analysis. In this paper, we explore the large-scale applicability of such overpotential estimates for identifying good catalyst candidates by using
datasets from the Open Catalyst Project (OC20 and OC22). We start by quantifying the uncertainty in predicting adsorption energies using ab initio methods and find that $\sim$0.3-0.5 eV is a conservative estimate for a single adsorption energy prediction. We then compute the overpotential of all materials in the OC20 and OC22
datasets for the hydrogen and oxygen
evolution reactions. We find that while the overpotential allows the identification of known good catalysts such as platinum and iridium
oxides, the uncertainty is large enough to misclassify a broad fraction of the
datasets as “good”, which limits its value as a screening criterion. These results question the reliance on overpotential estimation as a primary evaluation metric to sort through catalyst candidates and calls for a shift in focus in the computational catalysis and machine learning communities towards other metrics such as synthesizability, stability, lifetime or affordability.
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All authors Shahana Chatterjee, Alexander Davis, Lena Podina, Divya Sharma, Yoshua Bengio, Alexandre Duval, Oleksandr Voznyy, Alex Hernández-Garcia, David Rolnick, Félix Therrien
Plasma Physics
Thermodynamics of Shear Equilibration During Magnetic Reconnection Onset in Mixed-Equilibrium Current Sheets
Dominic Payne, Marc Swisdak, James Drake et al. (+1 more)
Magnetic shear across the polarity inversion line (PIL) plays an important role in the explosive nature of reconnection onset and in the equilibration of current sheets, acting as a source of free energy that can enhance or inhibit the onset process under certain conditions. In this study, we use a 2D PIC simulation to examine the local interaction between the reconnection guide field and thermodynamic variables during reconnection onset in a region of initially depleted thermal energy and enhanced
magnetic energy in a large guide field background. We identify critical stages of the equilibration process, characterize intervals based on whether the pressure
evolution is driven by changes in density or temperature, and discuss what these intervals imply about the
evolution of local heat and work density. Finally, we examine power densities associated with electromagnetic field time
evolution and electromagnetic energy transfer and compare to those related to thermodynamic changes.
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All authors Dominic Payne, Marc Swisdak, James Drake, Tak Chu Li
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Magnetic and moiré Proximity Effects in WSe2/WSe2/CrI3 Trilayers
Junyi Liu, Xu Zhang and Gang Lu
Integrating
magnetic order to moiré superlattices is of significant scientific and technological interest. Based on first-principles calculations, we study the interplay of
magnetic proximity and moiré proximity in WSe2/WSe2/CrI3 trilayers with different stackings and twist angles. Large valley splitting is observed due to redistribution of the
exciton charge density across layers via a super-exchange-like mechanism, and its electric-field dependence bears similarity to electrically tunable and valley-selective Feshbach resonances. The valley splitting can be magnified in moiré superlattices owing to the superposition of Umklapp
excitons folded from moiré minibands, yielding spatially modulated and enhanced
magnetic proximity. The moiré proximity effect is demonstrated via an imprinted moiré potential on CrI3 layer and its feedback to the direct moiré potential on WSe2
bilayers is observed. The cooperation between the direct and imprinted moiré potentials is shown to yield novel topological and correlated states.
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Plasma Physics
Transverse envelope dynamics of beam slices in a uniform charged ellipsoidal model of the plasma bubble regime
Abdul Mannan, Alessio Del Dotto and Massimo Ferrario
We consider a pair of driver/witness electron bunches propagating in an ionized gas background a configuration similar to the one produced in a capillary discharge where a
plasma oscillation has been excited by a driving pulse. We assume as in the
plasma nonlinear regime that the
plasma electrons behind the driver are completely expelled and an ellipsoidal cavity filled with ions only is formed. The fields are linear in both longitudinal and transverse directions, at least in the region of interest for particle acceleration, as the one produced by a uniform ion distribution within a uniformly charged ellipsoidal volume. The fields produced by the ions and experienced by a witness electron beam are purely electrostatic, being the ions at rest in the laboratory frame on the time scale of interest and it can be represented with the field distribution produced by a 3D charged ellipsoidal. The energy spread and emittance degradation has been studied by slicing the bunch in an array of cylinders and solving envelope equations for each bunch slice. The properties of transverse envelope and emittance oscillations and energy spread degradation have been analyzed together with the related matching conditions for optimal transport and acceleration.
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Plasma Physics
Computer simulations of the Stark effect in the helium-beta complex of krypton in ICF conditions
G. Pérez-Callejo, E. Stambulchik, R. Florido et al. (+1 more)
There is an ongoing interest in using spectroscopy in inertial confinement fusion (ICF) experiments, where dopants such as krypton can provide vital information about the temperature and density of the imploding
plasma. While the most advanced tools for calculating Stark profiles are computer simulation models (CSMs), their application to complex lineshapes under the extreme conditions of ICF experiments is computationally challenging. In this manuscript, we present results of several CSM realizations applied to the Stark shape of the krypton He-beta line and its satellites at ICF-relevant conditions (ne = 1e24 to 1e25 cm-3, Te = 3keV). We demonstrate that codes with the same underlying physics but different numerical approaches yield identical results and analyze the differences in the line profile caused by various physical effects.
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All authors G. Pérez-Callejo, E. Stambulchik, R. Florido, M. A. Gigosos
Fluid Dynamics
Quantitatively mapping the Eady model onto a two-layer quasi-geostrophic model
Julie Meunier and Basile Gallet
The two-layer quasigeostrophic model (2LQG) and the Eady model are two idealized systems illustrating the baroclinic instability of atmospheric jets and ocean currents. The two setups share many ingredients – background vertically sheared zonal flow of density-stratified fluid in a rapidly rotating frame – while differing in complexity and dimensionality. The Eady model has a continuous vertical direction, with baroclinic
turbulence induced by boundary potential vorticity (PV) gradients at top and bottom. By contrast, the 2LQG sytem typically models baroclinic instability induced by interior PV gradients. This distinction challenges our ability to clearly identify a couple of 'modes' through which the Eady dynamics could be inferred from a simpler 2LQG system. In the present study, we show that this difficulty can be circumvented in the turbulent regime arising for weak bottom drag. Namely, guided by the common organization of both systems into a gas of coherent
vortices, we identify a quantitative mapping between the Eady and the 2LQG models. The mapping allows for parameter-free predictions of the eddy diffusivity of the Eady model based on the knowledge of the 2LQG diffusivity. We illustrate these results using numerical simulations of the Eady and 2LQG models with linear or quadratic bottom drag.
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Optics
Deep-Space Optical Communication Receiver Based on Single Photon Coherent Beam Combination
Antoni Mikos-Nuszkiewicz, Karol Łukanowski, Konrad Banaszek et al. (+1 more)
We introduce an alternative receiver architecture for deep-space optical communication, in which a single large aperture is replaced by an array of smaller ones with outputs combined coherently, employing phase stabilization based on
photon counting events. We show that it allows to increase the signal to noise ratio, thus potentially attaining higher information transmission rates in the regime of large noise, typical for daytime communication. We analyze its practical performance by simulating pulse position modulation-based communication from the recently launched Psyche mission. Under nighttime conditions the achieved performance is comparable to that offered by a single large aperture, whereas in daytime conditions the single
photon coherent beam combination architecture provides an advantage in the information transmission rate.
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All authors Antoni Mikos-Nuszkiewicz, Karol Łukanowski, Konrad Banaszek, Marcin Jarzyna
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Relating the dynamics of photo de-mixing in mixed bromide-iodide perovskites to ionic and electronic transport
Ya-Ru Wang, Marko Mladenović, Eugene Kotomin et al. (+9 more)
The observation of reversible de-mixing phenomena in mixed-halide perovskites under illumination is one of the most challenging as well as intriguing aspects of this class of materials. On the one hand, it poses critical constraints to the compositional space that allows reliable design of absorbers for perovskite photovoltaics. On the other hand, it holds potential for the development of novel optoionic devices where an ionic response is triggered via optical stimuli. Funda-mental questions about the origin of such photo de-mixing process remain unanswered, both in terms of its mechanism as well as thermodynamic description. Here, we relate in-situ measurements of ionic and electronic transport of mixed bromide-iodide perovskite thin films performed during photo de-mixing with the
evolution of their optical and morpho-logical properties. The results point to the definition of different stages of the de-mixing process which, based on micros-copy and spectroscopic measurements, we assign to regimes of spinodal decomposition and nucleation of quasi-
equilibrium iodide- and bromide-rich phases. Combined with density functional theory calculations, we explore the role of dimensionality in the mechanism and reversibility of photo de-mixing and dark re-mixing processes, referring to elec-tronic and ionic contributions to the de-mixing driving force. Additionally, our data emphasizes the role of the surface, as significantly different de-mixing dynamics, in terms of extent and reversibility, are observed for films with or without encapsulation. Our comprehensive analysis of transport, phase and optical properties of mixed-halide perovskites pro-vides guidelines for future materials design as well as for the more general fundamental understanding of light-induced ionic phenomena.
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All authors Ya-Ru Wang, Marko Mladenović, Eugene Kotomin, Kersten Hahn, Jaehyun Lee, Wilfried Sigle, Jovana V. Milić, Peter A. van Aken, Ursula Rothlisberger, Michael Grätzel, Davide Moia, Joachim Maier
Medical Physics
Functional dual-slope frequency-domain near-infrared spectroscopy data interpreted with two- and three-layer models
Jodee Frias, Giles Blaney, Angelo Sassaroli et al. (+1 more)
Functional near-infrared spectroscopy (fNIRS) is impacted by signal contamination from superficial hemodynamics. It is important to develop methods that account for such contamination and provide accurate measurements of cerebral hemodynamics. This work aims to investigate whether simulated data with two-layer or three-layer tissue models are able to reproduce in vivo data collected with dual-slope (DS) frequency-domain (FD) near-infrared spectroscopy (NIRS) on human subjects during
brain activation. We performed Monte Carlo simulations to generate DS FD-NIRS data from two- and three-layer media with a range of layer thicknesses and optical properties. We collected in vivo data with DS FD-NIRS (source-detector distances: 25, 37 mm; wavelengths: 690, 830 nm; modulation frequency: 140 MHz) over the occipital lobe of human subjects during visual stimulation. Simulated and in vivo data were analyzed with
diffusion theory for a homogeneous medium and results were compared for each DS FD-NIRS data type. We found that the main qualitative features of in vivo data could be reproduced by simulated data from a three-layer medium, with a second layer (representing the cerebrospinal fluid in the subarachnoid space) that is less absorbing and less scattering than the other two layers, and with a top layer thickness that represents the combined scalp and skull thickness. A three-layer model is a viable improvement over a homogeneous model to analyze DS FD-NIRS data (or any other fNIRS data) to generate more accurate measurements of cerebral hemodynamic changes without a need for large data sets for tomographic reconstructions.
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All authors Jodee Frias, Giles Blaney, Angelo Sassaroli, Sergio Fantini
Atomic Physics
Nuclear spin quenching of the $^2S_{1/2}\rightarrow {^2}F_{7/2} $ electric octupole transition in $^{173}$Yb$^+$
Jialiang Yu, Anand Prakash, Clara Zyskind et al. (+4 more)
We report the coherent excitation of the highly forbidden $^2S_{1/2} \rightarrow {^2}F_{7/2}$ clock transition in the odd isotope $^{173}\mathrm{Yb}^+$ with
nuclear spin $I = 5/2$, and reveal the hyperfine-state-dependent,
nuclear spin induced quenching of this transition. The inferred lifetime of the $F_e = 4$ hyperfine state is one order of magnitude shorter than the unperturbed ${^2}F_{7/2}$ clock state of $^{171}\mathrm{Yb}^+$. This reduced lifetime lowers the required optical power for coherent excitation of the clock transition, thereby reducing the AC Stark shift caused by the clock
laser. Using a 3-ion Coulomb
crystal, we experimentally demonstrate an approximately 20-fold suppression of the AC Stark shift, a critical improvement for the scalability of future multi-ion $\mathrm{Yb}^+$ clocks. Furthermore, we report the $|^2S_{1/2},F_g=3\rangle~\rightarrow~|^2F_{7/2},F_e=6\rangle$ unquenched reference transition frequency as $642.11917656354(43)$ THz, along with the measured hyperfine splitting and calculated quadratic Zeeman sensitivities of the ${^2}F_{7/2}$ clock state. Our results pave the way toward multi-ion optical clocks and
quantum computers based on $^{173}\mathrm{Yb}^+$.
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All authors Jialiang Yu, Anand Prakash, Clara Zyskind, Ikbal A. Biswas, Rattakorn Kaewuam, Piyaphat Phoonthong, Tanja E. Mehlstäubler
Biological Physics · Cross-listed from q-bio.PE
Fluctuating Environments Favor Extreme Reproductive Delays and Penalize Intermediate Ones
Jorge Hidalgo, Lorenzo Fant, Rafael Rubio de Casas et al. (+1 more)
The timing of reproduction is crucial for biological fitness. Reproductive delays carry an inherent demographic cost: an individual that takes longer to reproduce contributes later to population growth, a priori, without any compensating benefit. However, natural selection favors delayed reproduction under certain environmental conditions, a phenomenon that remains poorly understood. Here, we investigate how the environment can determine the
evolution of particular life histories using a parsimonious delayed-logistic model. Individuals become reproductive only after a fixed lag whereas birth rates fluctuate under temporally correlated stochasticity. Numerical integration, analytical calculations and evolutionary simulations reveal that the joint effect of demographic
memory and colored multiplicative noise generate a strongly nonmonotonic dependence of fitness on life history, with three distinct regimes of population performance: rapid reproduction maximizes linear growth but amplifies fluctuations and extinction risk; delayed reproduction buffers environmental variability, substantially increasing mean extinction times despite slower growth; strikingly, and central to our results, there is a broad band of maladaptive intermediate life histories that simultaneously reduce both growth and persistence, an effect that arises generically from the mismatch between reproductive timing and environmental autocorrelation. Our results show that reproductive timing is not merely a life-history parameter but an adaptive mechanism tuned to environmental time scales, and that "dangerous middle" maturation times can be inherently disfavored, with implications for understanding reproductive strategies across the tree of life.
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All authors Jorge Hidalgo, Lorenzo Fant, Rafael Rubio de Casas, Miguel A. Muñoz