Quantum Physics · Cross-listed from cs.GR
General purpose graphical rendering on quantum devices with composable function systems
James Schloss and Ayaka Usui
The controlled creation of specific
quantum states is a highly challenging field of research that is also in high demand with applications in various
quantum technologies. Due to its difficulty, it has been historically impossible to use
quantum states as a rendering target for complex scenes and visualizations, especially in the Noisy Intermediate-Scale
Quantum (NISQ) era where operations are noisy and only a few
qubits are available. Even so, in this paper we propose a new,
quantum compatible method for general purpose rendering by extending Composable Function Systems (CFSs) to
quantum architectures. We discuss limitations in the classical implementation of CFSs and the physical maps necessary for adapting the classical method to
quantum by showing the generation of object primitives and transformations of such objects, including duplications and smears, some of which are topologically non-trivial. Our results reveal the possibility of a speed-up for this, specific method on
quantum hardware and our method has been used to create the first
video rendered on
quantum architectures.
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Physics and Society
Risk-mediated transmission dynamics govern epidemic trajectories beyond physical mobility
Ryosuke Omori, Koichi Ito, Laith J Abu-Raddad et al. (+1 more)
Standard epidemiological models rely on physical mobility and policy indicators, which fail when physical movement decouples from actual transmission risk. To address this, we establish a unified theoretical framework governed by risk-mediated transmission dynamics. Rather than treating societal responses as independent phenomenological proxies, we embed the underlying risk-avoidance tendency directly into the transmission mechanism. This is parsimoniously formulated via the Weber-Fechner law as a logarithmically scaled response to disease incidence, alongside behavioral fatigue. Analyzing multi-regional COVID-19 data, our risk-mediated model significantly outperforms traditional frameworks. While mobility metrics merely track movement volume, our approach directly captures unobserved qualitative contact changes, such as mask-wearing. By integrating this intrinsic behavioral principle, our framework provides a robust, mobility-independent baseline for predicting future epidemic trajectories.
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All authors Ryosuke Omori, Koichi Ito, Laith J Abu-Raddad, Yoh Iwasa
Statistical Mechanics
Brownian Bridge for Coherent State Path Integral Monte Carlo
Riccardo Fantoni
We propose a new Brownian bridge construction for our newly devised Coherent States Path Integral Monte Carlo
algorithm. We apply it to the numerically exact calculation of the thermodynamic properties of the Helium fluid on a plane at low non zero temperature. We find very good agreement with the conventional plane waves path integral Monte Carlo results.
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Physics Education
Medical Physics and Biomedical Engineering Education, Training and Professional Development
Emily Simpson-Page, Naasiha Cassim, Dominika Firth et al. (+2 more)
Supporting and nurturing early career members is a vital component of succession planning for any profession or associations. Ensuring the thoughts and needs of newly-joined and early-career members of the Australasian College of Physical Sciences and Engineering in Medicine (ACPSEM) were represented and optimally met were key drivers in the creation of the New and Early career Special Interest Group (NESIG) in 2021. NESIG was incepted through the networking and collaboration of early career ACPSEM members who felt there was a need for such a group. The formation of this group was also motivated by data acquired from recent surveys highlighting motivation for initiatives that supported early career ACPSEM members. For example, the 2021 ACPSEM Radiation Oncology Medical Physics workforce survey showed overwhelming desire of early career members to be involved in student supervision, academic work and research. Similar themes have been identified in a Better Healthcare Technology survey on actions that would reduce barriers to ACPSEM members research and development work, and within other ACPSEM groups. Through consultation and guided by the findings of these surveys and discussions, NESIG will identify opportunities and initiatives for early career ACPSEM members that complement the existing ACPSEM training and mentoring programs. The development of this special interest group has been supported not only by the college but also other established groups, senior members of the field in both Australia and New Zealand and existing international early career groups. NESIG aims to provide stronger networking and collaboration amongst newly joined and early career members and on-going support and encouragement of activities tailored to NESIG members, to further support and nurture early career members for the benefit of individuals and the wider profession.
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All authors Emily Simpson-Page, Naasiha Cassim, Dominika Firth, Emma Spelleken, Suzanne Lydiard
Physics and Society · Cross-listed from cs.RO
Locker-based Truck-Drone Routing with Integrated Considerations of Pickups, Deliveries, and No-Fly Zones
Xuanyu Liu, Hui Hu, Jiao Zhao et al. (+2 more)
Truck-drone delivery is an emerging last-mile logistics mode combining the long-haul capacity of trucks with the flexible service capability of drones. In locker-based operations, smart lockers serve not only as temporary parcel storage facilities but also as automated drone docking and service nodes. These automated nodes support drone takeoff, landing, parcel handover, and battery replacement, thereby significantly extending the service range and operational flexibility of drone-assisted delivery networks. However, practical locker-based delivery systems face complex real-world challenges, requiring the integrated coordination of not only parcel delivery, return pickup, battery-constrained and load-dependent drone flights, but also necessary detours around restricted airspace. To address this practical and multifaceted challenge, this paper introduces a locker-based truck-drone routing problem with integrated considerations of pickups, deliveries, and no-fly zones (LTDRP-PDNF), with the objective of minimizing the total operational cost of a fleet of drone-equipped trucks. We formulate the route construction process as a Markov Decision Process and develop a two-stage deep reinforcement learning-based neural heuristic. The first stage utilizes an
attention-based encoder and a Bidirectional Gated Recurrent Unit decoder to solve the truck-only routing problem, formulated as a capacitated vehicle routing problem. The second stage combines a policy-transfer strategy with a hybrid dispatch assignment heuristic to construct fully coordinated truck and drone routes for LTDRP-PDNF. Experiments on instances of different scales demonstrate that the proposed method outperforms metaheuristic and neural heuristic baselines in most cases while maintaining exceptionally short computation times, offering an effective, scalable solution framework under practical operational constraints.
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All authors Xuanyu Liu, Hui Hu, Jiao Zhao, Ziliang Wang, Zhengbing He
Classical Physics
The structure of the new SI
B. C. Regan
The "new" Système international d'unités (SI), which became effective May 20, 2019, defines and is defined by a set of constants. These include the speed of light, the Planck constant, the Boltzmann constant, and the constant relating the elementary electric charge to the coulomb. Interpreting such constants as conversion factors organizes the units they relate into a unifying
geometric framework. In this framework, units appear (perhaps raised to some power) either as rows/columns in a single conversion table or as entries in a list of dimensionless numbers. This organization clarifies the distinction between "fundamental" physical constants with values that are set by people, like those defined in the SI, and those with values that are set by nature. It also reveals geometry permeating our theories of physics that is normally hidden by a surplus of units.
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Chemical Physics
NanoVer: An open-source framework for interactive molecular dynamics in extended reality (iMD-XR) on commodity hardware
Mark D. Wonnacott, Luis Ernesto Toledo Castro, Harry J. Stroud et al. (+6 more)
This article outlines 'NanoVer', an open-source software framework which enables groups of people to co-habit the same virtual space and manipulate real-time MD (Molecular Dynamics) simulations of flexible 3D molecular structures with atomic-level precision as if they were tangible objects, an approach that we call 'interactive Molecular Dynamics in eXtended Reality' (iMD-XR). Distinct from our earlier iMD work that relied on tethered PC-VR systems with large graphics cards, NanoVer represents a change in philosophy, emphasizing compatibility with standalone mobile consumer XR hardware and corresponding software APIs. The NanoVer architecture enables multiple XR clients and/or Python clients to simultaneously communicate with a flexible server architecture that can carry out a range of tasks, including for example: recording iMD-XR sessions, static structure visualization, and MD trajectory visualization. NanoVer allows researchers, educators, and students to fluidly move between AR and VR environments, to explore creative new approaches to molecular research and education, including for example: molecular conformational sampling,
protein-ligand binding, molecular psychophysics, training AI
agents to sample molecular transitions, and a new interface which allows iMD-XR participants to sketch 3D conformational paths which automated
agents can then follow. As an immersive platform that offers new ways to understand, engineer, communicate, and interact with dynamical behaviour at the nanoscale, NanoVer invites us to imagine new ways for combining human intelligence (e.g., spatial cognition and design
reasoning) with machine intelligence. To expand NanoVer's accessibility, we have published a version to the Meta Horizon Store, for easy download by those with a Meta Quest 3/3S headset, to explore pre-recorded iMD-XR trajectory visualizations and set up their own multi-user system.
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All authors Mark D. Wonnacott, Luis Ernesto Toledo Castro, Harry J. Stroud, Ludovica Aisa, Mohamed Dhouioui, Rhoslyn Roebuck Williams, Denis Protopopov, Sila Sobrado, David R. Glowacki
Statistical Mechanics
Phase Time Crystals and Pairing in Binary Active Chiral Systems
C. Reichhardt and C.J.O. Reichhardt
We introduce a class of dynamic systems we call phase time
crystals consisting of a binary assembly of particles with intermediate or long-range repulsive interactions that are subjected to a circular drive of uniform chirality in which each particle species is out of phase from the other by 180 degrees. As a function of the particle density and orbit radius, this system can organize into a rich variety of dynamical crystalline states, including one in which the out of phase particles form bound pairs that assemble into a triangular
lattice. We also find stripe phases, overlapping packed
crystals, disordered or phase glass states with no
diffusion, mixed fluids, and different types of phase-separated states. We show that these states are robust against the addition of thermal fluctuations, and that the paired
crystal can melt into a paired fluid. If the drive on each particle species is of opposite chirality, the system forms stripes and packed
lattices, but no paired
crystal is present. We demonstrate that by modifying the nature of the
chiral driving, it is possible to realize numerous kinds of active molecular
lattices, including dynamic square
spin ice geometries and higher-order complex structures.
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Mathematical Physics · Cross-listed from math.SP
The cost rate of nonlinear remote stabilization on the Aubry–André lattice: a reflected off-spectral exponent and the sharp identity for almost every phase
Nassim Athmouni, Nejib Brahmia and Ahmed Hachani
We study the exponential rate $r(\alpha,\lambda)$ of the energy $\mathcal{E}_N$ needed to steer a far site, at distance $N$, of an Aubry–André chain $H_\lambda$ via one boundary actuator with closed-loop margin $\alpha$. An exact eigenbasis reduction writes $\mathcal{E}_N$ as a Cauchy quadratic form $\tilde b^\top C^{-1}\tilde b$ in the boundary-amplitude ratios, whose rate is the off-spectral Lyapunov exponent of the transfer cocycle at the reflected band edge $z^\star=2E_{\min}-2\alpha-E_{\max}$, giving $r(\alpha,\lambda)=\gamma_\lambda(z^\star)$. The rate lies in a bracket of width $\log_+(\lambda/2)$ whose ends coincide for $\lambda\le2$, the spectrum having logarithmic capacity $\max(1,\lambda/2)$. We prove the identity unconditionally, for every phase, on the whole metallic–critical range $0<\lambda\le2$: for $\lambda<2$ through subcritical almost reducibility as the sole external input, and at $\lambda=2$ because the Green's function there equals the Lyapunov exponent. For $\lambda>2$ the upper bound is unconditional, and the lower bound takes localization as its only external input: an inverse-free cocycle form makes $\mathcal{E}_N$ a cancellation-free positive sum, and a Christoffel–Darboux identity collapses its coefficients to $|c_k|=Q(\delta_k)(\hat\psi^{(k)}_N)^2$, where band-edge near-degeneracies cancel. With a three-distance lemma this yields $r=\gamma_\lambda(z^\star)$ at every Diophantine frequency and almost every phase, with gap $O(N^{-2/(2+\tau)})$ for type $\tau$ ($N^{-2/3}$ at bounded type), unconditionally for $\lambda\ge\lambda_1$ and under a
polynomial-prefactor localization hypothesis for $2<\lambda<\lambda_1$. The relative gap $1-r/\gamma_\lambda(z^\star)$ vanishes at both ends of the localized phase, with $g_{\mathbb{C}\setminus\Sigma_\lambda}(z^\star)\to\operatorname{arccosh}3$ as $\lambda\to\infty$.
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Biological Physics
Engineering Collective Microbial Dynamics for Sustainable Thermal Management
Nilanjan Mondal, Soumitree Mishra and Anupam Sengupta
The rapid growth of energy-intensive technologies, including artificial intelligence, large-scale computing, and thermal management systems, has intensified global energy demand amid accelerating
climate change. Meeting these demands requires innovative, low-carbon thermal management strategies that improve energy efficiency while minimizing environmental impact. This review revisits the underexplored phenomenon of bioconvection, a self-organized fluid motion generated by motile microorganisms, as a bio-inspired approach to sustainable heat transfer. Drawing on studies from natural ecosystems and laboratory experiments, we synthesize current knowledge of microorganism-induced hydrodynamics, pattern formation, and thermofluidic transport to assess the feasibility of harnessing bioconvection for thermal management. We further support this assessment through quantitative analyses of the thermal performance of bioconvective systems and discuss this in the framework of relevant non-dimensional numbers. By generating spontaneous convective plumes through density stratification, motile microorganisms enhance heat and mass transfer without external mechanical forcing. These self-organized flows provide a promising route toward hybrid bio-engineered cooling systems that reduce pumping energy, disrupt thermal boundary layers, and improve heat transfer efficiency. We conclude the review with the key challenges on the way to practical implementation, including microbial stability, material compatibility, controllability, scalability, as well as integration with existing cooling technologies. Finally, we identify critical research directions spanning heat transfer, microbiology, and nonlinear fluid mechanics within the broad context of sustainability, positioning bioconvection as a promising strategy for environmentally responsible thermal management in an era of rapidly increasing energy demand.
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Instrumentation and Methods for Astrophysics
GOATS: The next generation software infrastructure for time-domain astronomy at Gemini/NOIRLab. Application to alerts from Vera C. Rubin Observatory's Legacy Survey of Space and Time
Monika Soraisam, Louis Avner, Miguel Gómez et al. (+38 more)
Time-domain and multimessenger astronomy (MMA/TDA) targets demand rapid-response follow-up observations. In many cases, it is the only way to make discoveries and advance our understanding of the astrophysical phenomena, for example, kilonovae accompanying gravitational waves from compact object mergers, shock breakout in
supernovae,
prompt emission from GRBs, etc. Presently the MMA/TDA follow-up workflow requires wrangling disparate software packages and user interfaces. We present an end-to-end software tool for the community, the Gemini Observation and Analysis of Targets System (GOATS), which unifies and simplifies the workflow, particularly for Gemini follow-up observations. GOATS achieves this by integrating services from Gemini Observatory and its parent organization, NSF NOIRLab. From a single platform, GOATS enables enhanced target selection via NOIRLab's ANTARES alert broker, triggering of Gemini (and other facilities within the Astronomical Event Observatory Network), automated data
retrieval from the Gemini Observatory Archive, and interactive data reduction and analysis through Gemini's DRAGONS software and NOIRLab's Astro Data Lab science platform. GOATS was successfully deployed in an end-to-end demonstration of real-time follow-up of Rubin/LSST alerts with NOIRLab facilities. As part of this demonstration, we selected targets from the Rubin alert stream and triggered follow-up observations within minutes of the Rubin detections. We obtained spectra for several targets and classified them as
supernova of various types (Ia, IIP, Ib/c) with
redshifts ranging from 0.05 to 0.35. By eliminating the need to manually connect tools and automating repetitive tasks, GOATS lowers the entry barrier and allows users to focus on the scientific interpretation of the observation results.
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All authors Monika Soraisam, Louis Avner, Miguel Gómez, William Vacca, Bryan Miller, Andrew Stephens, Arturo Núñez, Andrew Adamson, César Briceño, Hernán Chacana, Guillermo Damke, Nicolás Esquivel, Paul Hirst, Kathleen Labrie, Thomas Matheson, Chadd Myers, Robert Nikutta, Abhijit Saha, Chris Simpson, Olesja Smirnova, D. J. Teal, Sergio Troncoso, James Turner, Sebastián Vicencio, Hubert Condoretti, Scott Dahm, Tómas Ahumada, Eric Bellm, Robert Blum, Aleksandar Cikota, Hannah Crayton, Diego Gómez, Melissa Graham, Stephen Heathcote, Leanne Guy, Fredrik Rantakyrö, Kevin Reil, Rachel Street, Sandrine Thomas, Simón Torres, Kathy Vivas
Quantum Physics
The Schrödinger equation in the complex plane and quantum entanglement
Vassiliy Lubchenko
We formulate a continuity equation for the Schrödinger equation in the complex space. We define a complex momentum by normalizing the complex current by the particle density. This momentum is a
quantum analog of the classical, kinematic momentum analytically continued into the complex plane. The kinematic momentum and the gradient of the wavefunction's phase each represent a fluid-like flow in the complex plane; the phase-gradient flow is incompressible. The zeros of the wavefunction give rise to simple poles in the momentum. The poles manifest as irrotational vortexes in the phase-gradient flow, while critical points of the wavefunction present as rigid body-like rotational flows of the kinematic momentum. A discrete nature of elementary excitations comes about inherently because the quantity of the poles is automatically integer. An exact quantization condition is subsequently formulated, which reduces to the Bohr-Sommerfeld condition in the semiclassical limit. We establish a priori that the Bohr-Sommerfeld condition must be exact for the Harmonic Oscillator. We show that the kinetic energy is a sum of contributions of the average value and fluctuations, respectively, of the kinematic momentum. The zero-point vibrations within bound states are solely due to the fluctuations of the momentum and manifest as rigid-body flows at infinity. The momentum poles – and hence the wavefunction's zeros – can be viewed as emergent, consistent with the remarkable property of
quantum entanglement exhibited by standing wave solutions of the Schrödinger equation.
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Accelerator Physics
An extension of Lambertson method to horizontally asymmetric Beam Position Monitors
T. Luo, C. Sun, J. De Chant et al. (+1 more)
Lambertson method is a classical approach that can indirectly measure the electrical center offset in the beam position monitor (BPM) due to imperfections in the pickup buttons. It applies to BPMs that are symmetric in both the horizontal and vertical directions. In this paper, we present our extension of this method to BPMs that are asymmetric in the horizontal direction, and we apply it to such BPMs in ALS Upgrade project at Lawrence Berkeley National Laboratory.
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All authors T. Luo, C. Sun, J. De Chant, A. Zabala
Quantum Physics
The Prepare and Broadcast Scenario
Tailan S. Sarubi, Moisés Alves, Santiago Zamora et al. (+3 more)
We introduce the dimension-restricted prepare and broadcast (PAB) scenario, which generalizes standard prepare-and-measure frameworks. Here, the system prepared by a sender undergoes a broadcasting transformation before being locally measured by multiple receivers. We develop a hierarchy of classical,
quantum, and nonsignalling models describing this scenario, characterize their corresponding correlation sets, and derive new families of Bell-like inequalities together with linear and semidefinite programming methods for their certification. First, assuming shared randomness, we prove that the hierarchy collapses into a single set whenever we consider only one measurement per party. Then, considering multiple possible measurements, we show that PAB scenarios allow the activation of nonclassicality, revealing genuinely nonclassical features in resources that admit classical descriptions in standard prepare-and-measure or Bell settings.
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All authors Tailan S. Sarubi, Moisés Alves, Santiago Zamora, Vinícius F. Alves, A. de Oliveira Junior, Rafael Chaves
Optics
Automated Vector-Scanning Spectroscopy for Large-Scale Characterization of Single Quantum Emitters
William Eshbaugh, Ashish Chanana, Edgar Perez et al. (+13 more)
The inherent spatial randomness and broad spectral heterogeneity of epitaxial
quantum dots (QDs) – one of the most mature classes of solid-state
quantum emitters – remains a major obstacle to their scalable deployment in integrated photonic
quantum technologies. Overcoming this challenge requires deterministic fabrication strategies capable of precisely aligning nanophotonic structures with high-quality emitters, which in turn demands efficient and automated single-QD characterization. Despite substantial progress in optical measurement techniques, a platform capable of autonomous, data-efficient, and sufficiently versatile characterization of single
quantum dots at the chip scale remains lacking. Here, we introduce an automated cryogenic measurement platform that combines wide-field photoluminescence imaging with vector-stage-scanning confocal spectroscopy to enable high-throughput, chip-scale targeted optical characterization of individual QDs. Using this platform, we automatically acquire photoluminescence data from thousands of GaAs/AlGaAs QDs on a single chip. We demonstrate how this extensive
dataset enables identification of high-performance emitters for future deterministic device fabrication, while simultaneously revealing statistical trends across the QD ensemble. By uniting data-efficient targeted measurements with scalable automation, our platform establishes a foundation for large-scale
quantum photonic integration and the high throughput characterization framework needed to accelerate materials optimization.
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All authors William Eshbaugh, Ashish Chanana, Edgar Perez, Junyeob Song, Craig R. Copeland, Sulaiman Al Ghadani, Daniel McBride, Prasiddha Siwakoti, Maria Carolina Volpato, Armando Rastelli, Saimon Filipe Covre da Silva, Ignacio Segovia-Dominguez, Sadhvikas Addamane, Kartik Srinivasan, Edward B. Flagg, Marcelo Davanco
Space Physics
Wave Activity at MHD-ion Scales Associated with Switchbacks
Kyung-Eun Choi, Oleksiy V. Agapitov, Forrest Mozer et al. (+9 more)
Magnetic switchbacks (SB) – the localized
magnetic structures with
magnetic field direction inclined at an angle $\theta$ relative to the background $B_0$ – in the young
solar wind have been associated with enhanced ion-scale wave activity and local
plasma heating. It remains debated whether the apparent wave-power increase is intrinsic or mainly caused by sampling geometry. In this work, we analyze
magnetic and electric field fluctuations measured by Parker
Solar Probe, focusing on the 0.1–3~\(f_{cp}\) frequency band that spans the transition from the MHD inertial range to ion-kinetic scales. By decomposing
magnetic fluctuations into field-aligned and transverse components and comparing SB and non-SB intervals at the same local
magnetic field angle, we test whether SBs sample an anisotropic cascade from different viewing angles or host intrinsically amplified wave activity. We find that the transverse
magnetic power $\delta B_{\perp}$ is systematically enhanced inside switchbacks across a wide range of
magnetic field rotation angles $\theta$. The enhancement persists even at small and intermediate deflections, where
geometric projection alone predicts weak power, indicating an intrinsic origin beyond sampling geometry. The inertial-range spectral indices also remain similar between SB and non-SB intervals despite the enhanced wave power inside SBs, suggesting that the underlying
turbulence cascade is largely preserved. This excess $\delta B_{\perp}$ coincides with elevated
proton temperatures and enhanced electric-field fluctuations, supporting the interpretation that SBs act as localized sites of cross-scale energy transfer and ion-scale dissipation in the near-Sun
solar wind.
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All authors Kyung-Eun Choi, Oleksiy V. Agapitov, Forrest Mozer, Seung-Ju Yang, Dae-Young Lee, Richard D. Sydora, Lucas Colomban, Liudmyla Kozak, Mingzhe Liu, Marc Pulupa, Jia Huang, Shaosui Xu
Plasma Physics
Semi-Implicit Stellarator Magnetohydrodynamics with Nodal Spectral Elements
C. R. Sovinec, S. A. Patil and J. V. Cauilan
Nonlinear time-dependent computation of macroscale dynamics in stellarators is motivated by laboratory results showing the possibility of robust operation in conditions where magnetohydrodynamic (MHD) modes are linearly unstable. A new formulation of semi-implicit MHD computation for toroidally shaped
magnetic confinement systems uses 2D nodal spectral elements over the poloidal plane and
Fourier representation over a generalized toroidal angle.
Geometric mappings and steady-state (
equilibrium) fields are expanded in the same 3D representation as the time-evolved fields to model non-axisymmetric configurations. For accuracy at large timestep, the semi-implicit operator is based on the ideal-MHD energy integral using 3D pressure and
magnetic fields. The nodal spectral elements allow numerical convergence through either h-refinement or p- refinement. Our implementation (NIMSTELL) with the continuous H1 expansion of
magnetic-field components and diUusive divergence control is a generalization of the NIMROD code [JCOMP 195, 355]. The NIMSTELL implementation is verified linearly and nonlinearly on resonant ideal interchange, where convergence from the stable side results from the stabilization method used in NIMROD [JCOMP 319, 61]. Optionally, NIMSTELL may use an H(curl) representation for vector potential, and both
magnetic representations are verified with respect to results from JOREK [Phys.
Plasmas 29, 063901] on linear and nonlinear
magnetic tearing in the W7-A rotating-ellipse configuration. Application of the existing vector-potential implementation to interchange shows that it needs a minimum level of electrical resistivity to avoid numerical noise for a given level of spatial resolution. Solving the algebraic systems from the implicit parts of the time advance is facilitated by including the
Fourier components of stellarator mode families in each preconditioning operation.
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Fluid Dynamics
Confinement-Induced Suppression of Jet Drop Size by Bubble Bursting in Shallow Liquids
Zhengyu Yang, Vatsal Sanjay, C. Ricardo Constante-Amores et al. (+1 more)
Bubble bursting is a major source of aerosol generation in a wide range of natural and industrial systems. While the resulting jet dynamics have been extensively studied in deep
liquid pools, bubble bursting often occurs in shallow
liquid layers where the influence of the nearby solid boundary remains poorly understood. Here, we show numerically that a shallow
liquid layer produces smaller and more numerous jet drops, even when the initial bubble shape is unchanged. We identify a wall-induced viscous sticking effect that suppresses the upward motion of the cavity bottom, leading to a steeper cavity geometry during capillary-wave focusing. We further develop a semi-empirical scaling law that predicts the jet drop radius as a function of the Ohnesorge number and the initial bubble-wall distance. Our results establish
geometric confinement as a governing factor in bubble bursting and provide a framework for predicting and controlling aerosol generation in shallow
liquid environments.
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All authors Zhengyu Yang, Vatsal Sanjay, C. Ricardo Constante-Amores, Jie Feng
High Energy Astrophysical Phenomena
Identifying Observational Signatures of Flux Eruption Events in Supermassive Black Hole Accretion Flows with Machine Learning
Angelo Ricarte, Erandi Chavez, Franc O et al. (+1 more)
Simulated black hole
accretion flows with strong
magnetic fields often exhibit "flux eruption events" (FEEs), transient and localized expulsions of matter near the event horizon due to
magnetic reconnection. It may now be possible to image them with the Event Horizon
Telescope (EHT), a global network of millimeter-wave observatories that images black holes. Here we use machine learning as an interpretable inference tool to identify observational signatures of FEEs that could be accessible to the EHT. First, we train a convolutional neural network to learn task-relevant representations of FEEs in uncorrupted simulated images. After using this network to label a larger set of images, we then train interpretable models (random forest and logistic regression) to determine observational signatures. We find that during a FEE, images in the millimeter tend toward more diffuse emission, higher linear polarization, and lower total fluxes, but these signatures are weak for most FEEs compared to the usual time variability of these features. Moreover, the Q-U loop rotation rate decreases during FEEs, contrary to a picture in which FEEs could jointly cause both millimeter Q-U loops and
flares. Our random forest trained on observable summary statistics achieves ~80% class-weighted accuracy, suggesting that the CNN learns FEE structure not fully mapped onto these traditional summary statistics. Our results imply that image size and polarization fraction can be used to flag candidate FEEs, but high-resolution, high-dynamic range images will still be important to confirm FEEs and test
accretion flows for this phenomenon.
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All authors Angelo Ricarte, Erandi Chavez, Franc O, Pavlos Protopapas
Optics
PT-symmetric time delay oscillator modelling beyond the weak coupling limit via a scattering matrix formulation
Abhijit Banerjee and Trevor J. Hall
Parity-time (PT)
symmetry in time-delay oscillators such as
lasers and optoelectronic oscillators provides a potential route to enhanced spectral purity, including reduced phase noise and improved sidemode suppression. Existing theoretical descriptions are typically based on coupled-mode formulations derived under slowly varying envelope and near-degeneracy assumptions, which restrict their validity to weak coupling, small gain/loss contrast, and small detuning. In this work, a non-perturbative formulation of PT symmetric time-delay oscillators is developed based on a delay-difference equation and a scattering
matrix representation of the coupling network. The approach treats propagation delay explicitly and does not rely on modal truncation, remaining valid for arbitrary coupling strength, gain/loss imbalance, and resonance detuning. The exact
eigenvalue structure of the system is obtained in closed form, yielding a complete characterization of the unbroken and broken PT symmetric regimes as well as the associated exceptional points. A dimensionless order parameter is introduced that governs the
symmetry transition over the full parameter space. It is further shown that conventional coupled-mode theory is recovered as an asymptotic limit of the exact formulation for small parameters. The results provide a unified and physically transparent framework for analysing PT symmetric delay systems beyond the weak-coupling limit, with direct implications for the design and optimisation of low-noise oscillators and photonic systems.
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Mesoscale and Nanoscale Physics
Graphene as a Tunable Nonradiative Bath for Moiré Excitons
Katsunori Wakabayashi
A minimal theory of nonradiative energy transfer from a two-dimensional (2D) moiré
exciton to a nearby
graphene layer is presented. From
Fermi's golden rule the transfer rate is the overlap of the
exciton near-field spectrum with the dissipative density response of
graphene, weighted by an
exciton form factor, and it reproduces the established $\GET\propto z^{-4}$ law in the point-dipole limit. A finite
exciton size filters out the high-momentum near field once the spacer thickness approaches the transition-polarization radius $R_X$, so the distance dependence of the rate—and of the photoluminescence (PL) quenching—probes the
exciton size. A low-momentum expansion shows that, relative to the calibrated point-dipole response of the same bath, this leading correction is set by $R_X$ alone. In the ideal coherent-envelope limit the accompanying
giant oscillator strength makes the rate non-monotonic in the
exciton size, with a peak near $\lX\approx z$. Treating
graphene as a gate-tunable bath, Pauli blocking suppresses the interband channel once $2|\muF|$ approaches $\hbar\omega$, partially restoring PL, and a full random-phase-approximation
benchmark confirms the normalized interband distance dependence to within a few percent away from the threshold. Mapping the PL observables across the transition-metal dichalcogenide/hexagonal boron nitride/
graphene parameter space, we find that a
graphene gate acts not as a passive electrostatic element but as a tunable 2D electronic reservoir probed through
exciton PL quenching.
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