Physics Education
3D-printed experimental devices for teaching dynamical systems in physics
Mario Silva, Victoria López, Daniel Freire et al. (+1 more)
We present the design, construction and classroom use of 3D-printed experimental devices aimed at introducing dynamical systems in physics courses. Theoretical, technical and pedagogical criteria are proposed for producing low-cost, modifiable resources suitable for experimental work. Three devices are analysed as examples: a
magnetic pendulum, a wooden woodpecker toy and a double pendulum. The suggested activities are organised around prediction, observation, comparison between configurations, and the elaboration of physical explanations. The main contribution of this work is to show concrete implementation possibilities in secondary education, pre-service teacher training and introductory university courses, together with a discussion of the scope and limitations of 3D printing in experimental teaching.
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All authors Mario Silva, Victoria López, Daniel Freire, Arturo C. Marti
Instrumentation and Detectors
Cosmic-ray characterization of a timing detector based on extruded scintillators and wavelength-shifting fibers read-out through SiPMs
F.Anulli, A.Betti, C.Bini et al. (+8 more)
Timing detectors based on extruded scintillators of different dimensions with different kinds of wavelength-shifting fibers read-out through SiPMs have been extensively tested using a
cosmic ray
telescope. Results in terms of light-yield, time resolutions and longitudinal coordinate resolutions are presented.
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All authors F.Anulli, A.Betti, C.Bini, M.Corradi, C.Luci, L.Martinelli, A.Nisati, M.Pantalena, S.Rosati, R.Vari, S.Veneziano
Physics and Society · Cross-listed from q-bio.NC
Trophic structure predicts seizure propagation in brain network models
Peter Kissack, Catherine Drysdale and Samuel Johnson
Epilepsy is widely regarded as a disorder driven by connectivity in the
brain. We use a model of seizure dynamics on directed networks to investigate how structural properties affect seizure propensity. We find that properties such as trophic coherence, spectral radius, strong connectivity and non-normality are closely related to seizure propensity, and present a proof of a theoretical relationship between spectral radius and cycle structure. Our simulated results are robust to the kind of coupling used in the model and become stronger as network size is increased. They suggest that the overall directionality of information processing in the
brain may be related to a propensity for epileptic seizures.
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Atmospheric and Oceanic Physics
Rescene: stable century-long climate emulation from a frozen weather model
Minjong Cheon
Machine-learning weather models now match or exceed operational numerical prediction in the medium range, but when they are run freely for years they drift, blow up or lose their variability, and dedicated
climate emulators are expensive to train. Here we present Rescene, a 0.4 M-parameter wrapper that turns a frozen 1.5$^\circ$, 6-hourly, 69-variable weather model into a
stochastic climate emulator. A deterministic slow clock anchors the frozen model to a calendar climatology, and a band-limited AR(1) perturbation, whose spectral envelope is fixed to the observed anomaly spectrum, restores the weather that anchoring removes. A 100-year, 8-member Rescene run shows no detectable drift ($-0.004 \pm 0.014$ K per 100 years), and on the 2022 test year the 16-member ensemble is calibrated (spread/skill 0.89, 0.97 and 0.93 for Z500, T2m and MSLP) with an extratropical synoptic amplitude of 97% of ERA5 on the tuning year. The free run reproduces the geography of day-to-day variability (pattern correlation 0.83 for Z500) and 71% of the observed blocking frequency, where the deterministic wrapper alone has none. Interventions on the frozen operator show a scale-local, approximately linear response in which Z500 perturbations grow upscale 6–14 times more than downscale per 6 h. All constants are fitted on a training year against a rule declared beforehand, and we show that common evaluation shortcuts would have overstated variability and skill. Rescene makes an existing weather model usable for century-long ensembles at negligible training cost.
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Atmospheric and Oceanic Physics
Annually Modulated Pacific Subtropical Highs Pace the ENSO Cycle: A Hierarchical Framework from Earth Rotation to Atmosphere-Ocean Dynamics
Yafei Wang
The El Nino-Southern Oscillation drives Earth's dominant interannual
climate signal, yet what initiates an event and what ends it remain incompletely understood. Here we show that anomalies of the eastern Pacific subtropical high (EPSH) belts, marched through the year by the annual cycle, precede and govern the equatorial zonal wind near the dateline, which sets subsequent sea surface temperature
evolution. The Northern Hemisphere ridge triggers events in boreal spring, the Southern Hemisphere ridge sustains them in austral spring, and their synchrony decides ENSO diversity. Preceding the ridges lies a sub-annual oscillation in Earth's rotation rate (length of day, 0.5 to 1 yr band) that redistributes atmospheric mass poleward three times once its phase aligns with the annual cycle, in August, in December, and in the following May, each displacement carrying the response further east and poleward until the significant centers overlie the ridges themselves. Crucially, this band is deaf to ENSO: its cross-correlation with NINO3 never exceeds 0.05 at any lag, whereas the classical ENSO-driven rotation response resides in the 2 to 10 yr band at 0.40. The band therefore reads forward, and partial correlation identifies the EPSH as the conduit: the direct path from rotation to ocean vanishes once the ridges are held fixed. Complete by the July preceding the event year, the index fixes the phase of the coming event fourteen to seventeen months ahead, though not its amplitude. At maturity the event reorganizes the Hadley and Walker circulations into the Mirror-SIGMA pattern, disrupting the upstream chain and closing the cycle.
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Plasma Physics
Numerical modeling and simulation on nanosecond laser-target interactions
Jian Wu, Ying Zhou, Minxin Chen et al. (+1 more)
Nanosecond
lasers are widely used in industrial applications as they are relatively inexpensive, and their compactness and robustness are an advantage. Much experimental work has been carried out to understand deeper the interaction between the nanosecond
laser pulses and the targets, as these are complex, transient processes with spatial inhomogeneities. Beside the experiments, the modeling and numerical simulation on the
laser interaction with the target are also crucial for understanding the dynamics of
laser-material interactions and for optimizing
laser processing applications. In this review, the progress of numerical modeling and simulation on nanosecond
laser-target interactions are summarized from the aspects of
laser-target interactions and target-
plasma interface,
laser-
plasma interactions and
plasma radiation, and numerical models on different scales with artificial intelligence advancing. The
laser ablation, mass and energy transfer, and mechanical coupling are discussed in the aspect of the nanosecond
laser-target interactions and target-
plasma interface. The
plasma expansion,
plasma ionization and recombination, and
plasma radiation are discussed in the aspect of the nanosecond
laser-
plasma interactions and
plasma radiation. Then the numerical advances, including microscopic approaches based on molecular dynamics, mesoscopic approaches based on kinetic and statistical physics, macroscopic approaches based on fluid dynamics, and numerical simulations with machine learning are discussed. Finally, the challenges currently being encountered by numerical modeling and simulation on nanosecond
laser-target interactions and its potential development direction are considered.
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All authors Jian Wu, Ying Zhou, Minxin Chen, Xingwen Li
Geophysics
Seismic Properties of Coastal and Inland Sabkhas: Implications for Static Corrections
A. Eleslambouly, M. Y. Ali, A. El Husseiny et al. (+4 more)
Sabkha environments are a prevalent topographic feature in arid coastal areas. Along the Arabian Gulf, sabkhas overlie substantial hydrocarbon reservoirs and exhibit intricate lithological characteristics and an extremely shallow water table. These factors contribute to elevated seismic velocities and signal distortion. Static correction, a crucial initial step in seismic reflection processing, is employed to mitigate the impact of shallow surface layers. In this study, we investigate the variations in seismic properties along the uppermost part of mature and developing sabkhas. We employed high resolution seismic experiments with geophone spacing of 10 cm to explore the upper tens of centimeters. Conventional surveys with a 2m spacing complement this approach to investigate deeper layers. Both sabkhas exhibit a unique characteristic of a partially saturated zone, which affects the seismic velocity, leading to lower velocities and consequently influencing the accuracy of the static correction. The high resolution surveys demonstrated superior accuracy to conventional approaches in determining the top of the partial saturation zone and hardground layer, hence resulting in a more reliable velocity delineation. Moreover, velocities derived from conventional, replacement, and tomogram approaches resulted in unreliable static corrections in mature coastal sabkha compared with developing inland sabkha, attributed to the considerable geological complexity that is characteristic of mature coastal sabkha environments. Carrying out a high resolution seismic survey in sabkha environments is therefore necessary to mitigate near surface velocity effects.
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All authors A. Eleslambouly, M. Y. Ali, A. El Husseiny, A. A. Al Shuhail, F. Bouchaala, S. M. Hanafy, J. Matsushima
Geophysics
Recovery of low-magnitude seismic events before the July 29, 2025, Kamchatka megathrust earthquake using waveform cross-correlation enhanced by the addition of stochastic noise
Ivan Kitov
The July 29, 2025, Kamchatka megathrust earthquake is one of the largest events in the 21st century. It is likely the best-instrumented case, with numerous stations at regional and teleseismic distances, including high-performance seismic arrays of the International Monitoring System (IMS). The waveform cross-correlation (WCC) method applied to seismic arrays allowed a significant improvement in signal detection accompanied by enhancements in phase association
algorithms. Since the WCC detector is the core
algorithm of the matched filter method, its efficiency critically depends on the ambient seismic noise coherency with the template signal, with fully
stochastic noise providing optimal detection conditions. To suppress the coherent noise component and improve WCC detection, we add a numerically generated random noise sequence adjusted in amplitude to the natural noise. This method is similar to noise whitening used in many acoustic applications, but in this study, it is applied before the matched filter is used. The detection threshold gain can be several times higher than that obtained with a pure WCC detector. The recovery of the low-magnitude seismicity obtained by the WCC applied to the IMS arrays and three-component stations prior to the July 29, 2025, Kamchatka earthquake is significantly improved by the random noise addition.
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Data Analysis and Statistics
Rethinking Total Absorption Gamma Spectroscopy Deconvolution: Supervised Machine Learning vs Response-Matrix Methods
J. Balibrea-Correa, E. Nácher, C. Fonseca-Vargas et al. (+1 more)
The extraction of $\beta$-feeding distributions in Total Absorption $\gamma$-ray Spectroscopy constitutes a challenging inverse problem, particularly in
nuclei with complex decay schemes involving a large number of excited states. In such cases, the measured spectrum arises from the superposition of many detector response functions, making the determination of the individual feedings intrinsically ill-posed and highly sensitive to the methodology employed. In this work, we present a systematic comparison between supervised Machine-Learning techniques and Response-
Matrix methods using realistic Monte Carlo simulations of an experimental Total Absorption Spectrometer. Supervised Machine-Learning approaches construct a non-parametric
estimator that infers level feedings from the measured spectrum after a training stage, whereas Response-
Matrix methods determine the feeding distribution by directly minimizing the difference between measured and reconstructed spectra. Our results show that supervised Machine-Learning techniques achieve superior accuracy in the reconstruction of individual feeding intensities, whereas Response-
Matrix methods provide robust and physically consistent initial solutions. These findings support a hybrid strategy in which a Response-
Matrix method is first used to obtain an initial feeding estimate, which is then refined using a supervised Machine-Learning approach to achieve improved overall accuracy.
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All authors J. Balibrea-Correa, E. Nácher, C. Fonseca-Vargas, J. L. Tain
Applied Physics
SH-SAW Acousto-Electric Amplifier in Epitaxial InGaAs on Lithium Niobate on Insulator
Chuan Tian, Christopher Heidelberger and Siddhartha Ghosh
This work demonstrates shear-horizontal surface acoustic wave (SH-SAW) acoustoelectric (AE) amplification on an epitaxial InGaAs / X-cut lithium niobate on
insulator (LNOI)
heterostructure formed by Al2O3-mediated wafer bonding. Deployable passivated devices show a stable fundamental-mode non-reciprocity of 32 dB/mm at 1.11 GHz (30 V bias, 64 mW consumed), while unpassivated devices reach 174 dB/mm across 1.1-2.8 GHz, reported as upper bounds. Device characterization establishes the role of mode-dependent K^2 in determining the achievable gain.
Hall-effect measurements of the transferred InGaAs serve as a quantitative diagnostic: the extracted carrier density, elevated by unintentional silicon doping during epitaxy, accounts for the absolute AE gain when inserted into the analytical model and identifies epitaxial process control as a clear lever for further enhancement. We further identify ambient oxidation of the bare InGaAs surface as a distinct aging mechanism that extinguishes the AE response within weeks, and show that an InP or ALD Al2O3 passivation layer suppresses it, at the cost of redistributing the piezoelectric field away from the channel. These results establish InGaAs-on-LNOI as a compact, low-power platform for non-reciprocal RF components and acoustoelectric delay lines, with strong relevance to in-band full-duplex (IBFD) transceivers and spectrum-efficient wireless front ends.
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Instrumentation and Detectors
The VORTEX cavity for the RADES axion haloscope
Jose María García-Barceló, Cristian Cogollos, Babette Döbrich et al. (+3 more)
One of the major challenges in
axion dark matter haloscope searches is a loss-less tuning mechanism that is able to cover a significant frequency range around the haloscope's central frequency. In this article, we report on the implementation and performance of an
axion haloscope dubbed Vertical-cut Optimised Resonant Tunable cavity for dark matter EXploration (
VORTEX) centred at $8.5$ GHz with a tuning range of around $800$ MHz. The performance of this setup is measured at temperatures in the mK range and compared to simulation. In addition, we test the cavity-mode structure of this cavity type directly via the `bead-pull method' and observe satisfactory agreement with expectations. The arrangement is poised to be used in an upcoming RADES (Relic
Axion Detection Exploratory Setup) data-taking campaign employing a $12$ T solenoid magnet.
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All authors Jose María García-Barceló, Cristian Cogollos, Babette Döbrich, David Kittlinger, Diego Nicolas Lobato-De La Cruz, Walter Wuensch
Atomic Physics
Collimation of dense atomic beams by Swept Velocity Shelving
Francesca Famà, Benedikt Heizenreder, Ananya Sitaram et al. (+4 more)
Engineering continuous, high-flux, and collimated atomic beams is a useful resource for metrology and material deposition. Developments in this area have been essential for the
evolution of cold-atom based
quantum experiments, yet the ubiquitous balanced-force methods such as transverse molasses cooling degrade at high atomic flux due to absorption-induced force imbalance. We introduce a collimation scheme that combines the use of a broadband transition for velocity shifting with a narrowband transition for velocity selection, enabling velocity-selective beam collimation without relying on balanced-power counter-propagating beams. Collimated atoms are shelved in a long-lived internal state, reducing the total light scattering and providing a state-heralded collimated beam. Simulations using strontium as a model system show a highly effective collimation process that does not suffer from absorption-induced force-imbalance and experimental results agree well with these predictions.
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All authors Francesca Famà, Benedikt Heizenreder, Ananya Sitaram, Camila Beli, Robert J.C. Spreeuw, Stefan A. Schäffer, Florian Schreck
Accelerator Physics · Cross-listed from cond-mat.mtrl-sci
Automating the analysis of micron-scale synchrotron diffraction data on inhomogeneous polycrystalline samples: a solid oxide electrolysis cell case study
Liam A. V. Nagle-Cocco, Christopher A. Crain, Michael J. Dzara et al. (+6 more)
A novel approach to post mortem characterisation of electrochemical and photovoltaic devices is spatially-resolved diffraction using a hyper-focused, micron-width x-ray beam to examine the distribution of degradation products and strain, a technique called $\mu$-XRD. Aside from the experimental difficulties associated with beam focusing and sample preparation, which are themselves non-trivial, the analysis of resulting data is complex and challenging, with full Rietveld analysis rarely attempted in literature. The difficulty lies in the size of the data, which may consist of hundreds or even thousands of diffraction patterns with very different crystallographic phase compositions depending on position within the device, and the difficulty in fitting the data due to the presence of many phases at the same position, including possible degradation products which may be difficult to index and assign to known phases. In this paper, we present a fully-automated open access Python routine for performing phase identification and Rietveld analysis on 2D
datasets of diffraction pattern taken at micron-scale positions, measured over the cross-section of a chemically inhomogeneous device with polycrystalline phases. Solid
oxide electrolyser
cells are a promising technology for green hydrogen production which can utilise waste heat to split water at higher efficiencies than low-temperature electrolysis techniques such as
polymer electrolyte membranes, but exhibit many degradation modes due to the high operating temperatures. We present a case study using our analysis protocol on an SOEC fragment encompassing the air electrode, cation
diffusion barrier, electrolyte, and fuel electrode. With modification, this protocol could be applied to other devices such as all-solid-state batteries, wet-electrolyte battery electrodes, solid
oxide fuel
cells, photovoltaic devices, and metal-
oxide pseudocapacitors.
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All authors Liam A. V. Nagle-Cocco, Christopher A. Crain, Michael J. Dzara, Mathias A. Kiefer, Madeline G. Port, Tolga Han Ulucan, Madeline Van Winkle, Oscar Hathaway, Nicholas A. Strange
Chemical Physics
Transcorrelated Random-Phase Approximation
Abdallah Ammar, Enzo Monino, Anthony Scemama et al. (+2 more)
We extend the random-phase approximation (RPA) to the non-Hermitian transcorrelated (TC)
Hamiltonian, which explicitly includes three-body interactions generated by a Jastrow correlation factor. We consider both the direct RPA (dRPA) and RPA with exchange (RPAx). We apply the resulting TC-dRPA and TC-RPAx methods to calculate ground-state correlation energies and vertical excitation energies for atoms (\ce{He} and \ce{Ne}) and small molecules (\ce{H2O}, \ce{NH3}, \ce{CH4}, and \ce{H2CO}). For ground-state correlation energies, the TC treatment substantially improves accuracy and accelerates basis set convergence, reducing errors by nearly an order of magnitude relative to conventional RPA calculations. By contrast, it yields only marginal improvements in vertical excitation energies. We attribute this limited effect to the ground-state optimization of the Jastrow factor, which does not adequately capture the distinct electronic character of excited states. These results establish TC-RPA as an accurate and computationally efficient approach to ground-state energetics, while highlighting the need for state-specific Jastrow optimization to achieve reliable descriptions of excited states.
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All authors Abdallah Ammar, Enzo Monino, Anthony Scemama, Emmanuel Giner, Pierre-François Loos
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Ultrafast Nonthermal Lattice Destabilization and Suppression of Polar Optical Scattering in Electronically Excited $\alpha$-SiO$_2$ from First-Principles and Deep Neural Network Potential Modeling
Iyyappa Rajan Panneerselvam, Mark Yeung, Charlotte Palmer et al. (+2 more)
We present a multiscale first-principles-to-machine-learning approach to investigate ultrafast
lattice dynamics in electronically excited $\alpha$-SiO$_2$. Ab initio molecular dynamics (AIMD) based on electronic-temperature-dependent density functional theory (DFT) are used to train electronic-temperature-dependent deep neural network potentials (DNNPs). The use of DNNPs enables atomistic modeling at near-DFT accuracy of large $\alpha$-SiO$_2$
cells with thousands of atoms. In particular, DNNPs allowed us to obtain accurate
phonon band structures and molecular dynamics (MD) of $\alpha$-SiO$_2$ excited by a sudden increase in electronic temperature. With increasing electronic temperature, $T_e$, pronounced
lattice destabilization of $\alpha$-SiO$_2$ is found, as evidenced by violations of elastic stability criteria, substantial volumetric expansion, a sharp reduction of the bulk modulus, and progressive weakening of Si-O bonding due to antibonding-state occupation. From the electronic and
phonon band structures, we estimated the Frohlich coupling constant, which decreases as $T_e$ increases, suggesting a crossover to a nonpolar phase of $\alpha$-SiO$_2$ at elevated electronic temperature. This is corroborated by the Bader charge analysis. We also suggest that polar optical
phonon scattering should be strongly suppressed at $T_e > 2$ eV. From large-
cell DNNP-MD simulations, we show that a well-defined thermal
equilibrium, as defined by the Maxwell-Boltzmann distribution, is not achieved over the first few hundred femtoseconds. This behavior explains the non-monotonic equilibration of the kinetic temperature after a sudden rise of $T_e$. After $T_e$ is raised to 2.6 eV, Si and O atoms first equilibrate separately at two different temperatures, suggesting an atomic fluid phase, in agreement with recent experimental and theoretical findings.
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All authors Iyyappa Rajan Panneerselvam, Mark Yeung, Charlotte Palmer, Brendan Dromey, Lorenzo Stella
Accelerator Physics
The Ponderomotive Effects of Narrow-band, Superconducting Resonators in Open and Closed Loop
Jacob Brown, Alexander Sukhanov, Crispin Contreras-Martinez et al. (+6 more)
In this work, we present measurements of ponderomotive instabilities in narrow-band, coaxial resonators in open and closed control loop systems. We show an analytical scheme we will use in future studies to examine the dependency of open loop stability on mechanical parameters. Analytical and simulation models are used to predict the onset of the oscillatory instability in half wave resonators with active disturbance rejection control for amplitude and phase stabilization. We demonstrate that for high amplitude controller bandwidths, ponderomotive oscillations can couple with the controller frequency response via higher harmonics and lower the threshold for the oscillatory instability. We reaffirm the superiority of in-phase/quadrature $(I/Q)$ component control in regards to preventing the oscillatory instability, and show how the phase controller can amplify the crosstalk of disturbances in amplitude and phase control. In cases with large disturbances, this effect can lead to instabilities not present in $I/Q$ control.
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All authors Jacob Brown, Alexander Sukhanov, Crispin Contreras-Martinez, Vyacheslav Yakovlev, Sang-hoon Kim, Shen Zhao, Ting Xu, Walter Hartung, Wei Chang
Physics and Society
Occupational Convergence or Divergence? Mapping Labor Market Structural Shifts Driven by AI Penetration
Rafiazka Hilman and Julia Koltai
Artificial intelligence (AI) is rapidly becoming a defining feature of contemporary labor
markets, yet it remains unclear whether its
diffusion is producing a common set of competencies across occupations or deepening occupational divisions. We investigate how AI related skill demand is reshaping labor
market structure using large scale online vacancy data from ten countries spanning the Global North and Global South. Combining natural
language processing, a large
language model, and multilevel bipartite network analysis, we map relationships between occupations, required skills, and career stages in the emerging AI economy. We find that AI demand is overwhelmingly concentrated within a narrow technical core, with approximately three quarters to four fifths of AI related vacancies located in STEM occupations across all countries. AI intensive jobs consistently emphasize Python, SQL, machine learning, and data analysis, generating convergence among highly exposed occupations. However, this convergence does not extend across the wider labor
market. Instead, AI competencies remain largely confined to technical domains and are most strongly demanded at labor
market entry. These findings reveal convergence within an AI exposed core but divergence between that core and the rest of the occupational structure. Rather than democratizing opportunities, AI appears to reinforce occupational stratification, raising barriers to entry and concentrating the benefits of AI adoption among workers and occupations with prior technological advantages.
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Computational Physics · Cross-listed from quant-ph
Quantum Optimal Control at Intermediate Times: Controlling Revivals in Spin Chains
Juan J. Omiste and Ignacio R. Solá
Standard
Quantum Optimal Control (QOC) protocols typically maximize a physical objective just at a final target time. However, tracking or measuring the
quantum state during the time
evolution requires the control at intermediate stages of their
evolution. In this work, we extend QOC to accommodate the simultaneous optimization of observables at arbitrary intermediate times. Using a variational approach, we show that intermediate observations induce discontinuities in the costate trajectory, which can be handled with a Krotov
algorithm leading to monotonic optimization and convergent results in the limit of zero temporal measurement windows. We apply this multi-time formulation to a Heisenberg XXX
spin chain to control the propagation, including field-free revivals, of a Dicke state excitation. Our results demonstrate that simultaneous optimization of the same observable reshapes the driving field to balance intermediate targets with final populations. Finally, we show how this framework enables dynamic tracking of
spin excitations and the active manipulation of post-pulse
quantum state revivals.
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Optics
Mode-Selective and Anharmonicity-Controlled Energy Transport in Cavity-Coupled Water
Sachith Wickramasinghe, Michael Fowler, Gerrit Groenhof et al. (+1 more)
Recent experiments demonstrate the modification of chemical dynamics via cavity-enhanced vibrational energy transport. Here, we provide a microscopic account of both photonic and mode-selective energy transport using direct mesoscale on-the-fly simulations and provide the mechanistic principles of cavity-modified transport under vibrational strong coupling. We find that molecular anharmonicity plays a crucial role in dictating photonic transport, and driving-dependent photonic localization occurs when coupling cavity modes to a highly anharmonic mode of the molecular system. We demonstrate this in cavity-coupled water by tuning the
photon frequency (at normal incidence) close to either the harmonic (or weakly anharmonic) bending mode or the anharmonic stretching modes of water. We confirm our understanding using a simple model system by reproducing the photonic transport and its localization. We also demonstrate that the
diffusion of mode-selective temperature, quantified via the variance of the H-O-H bond angle or of the O-H bond length, is highly dependent on the cavity
photon frequency. We show that the cavity
photon frequency can be used as a tuning knob to achieve and control mode-selective energy transport. We also provide a simple analytical understanding of this phenomenon. Our results highlight the rich dynamical interplay of molecular and photonic degrees of freedom that persist in real atomistic systems.
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All authors Sachith Wickramasinghe, Michael Fowler, Gerrit Groenhof, Arkajit Mandal
Space Physics · Cross-listed from astro-ph.SR
Averaging Effects on the Solar Wind Alfven Mach Number: Implications for Switchbacks and Alfven Transition
Joshua Goodwill, Subash Adhikari, Francesco Pecora et al. (+10 more)
Averaging techniques in
solar wind measurements have been a longstanding subject of debate. Using Parker
Solar Probe (PSP) observations from encounters 1 to 19, we investigate how averaging timescales influence the characterization of turbulent properties across the Alfvenic transition. We compute the rolling mean Alfven Mach number over various averaging intervals, which are then analyzed against switchbacks,
magnetic fluctuation energy, and correlation time. We find that the distribution of subAlfvenic intervals is relatively insensitive to judiciously-chosen averaging scales. In contrast,
magnetic fluctuation energies increase systematically with larger averaging window, while maintaining a consistent profile across the Alfven transition. We further show that the effective
magnetic correlation time decreases with decreasing heliocentric distance and MA, reaching values of several minutes approaching MA =1. These results demonstrate the importance of choosing physically meaningful backgrounds for
turbulence parameters, such as the correlation scales, and their impacts on characterizing the
solar wind.
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All authors Joshua Goodwill, Subash Adhikari, Francesco Pecora, Rayta Pradata, Jiaming Wang, Sujan Prasad Gautam, Manuel E. Cuesta, Orlando Romeo, David Ruffolo, Panisara Thepthong, Peera Pongkitiwanichakul, Rohit Chhiber, William H. Matthaeus
Classical Physics · Cross-listed from cond-mat.stat-mech
Deriving the second law of thermodynamics and exploring its boundaries
Yu Qiao
The second law of thermodynamics still lacks a general proof applicable to classical and
quantum systems across broad ranges of degrees of nonequilibrium, particle interactions, and time scales. In this paper, we show that from Boltzmann's assumption of equal a priori probabilities, the second law naturally emerges via the phase-space continuity equation for the macrostate-level probability $f$ defined over fixed $\Omega$-intervals, where $\Omega$ is the number of microstates. Further analysis suggests a more general assumption underlying the second law: $f$ increases monotonically with $\Omega$, i.e., $\partial f/\partial \Omega > 0$. Based on these findings, the second law can be readily derived for fully chaotic systems. The derivation does not rely on dynamical details, highlighting the statistical nature of
entropy increase. For the dilute hard-sphere gas model considered in the H-theorem, the second law may also be established through a simplified approach that requires the Boltzmann equation but does not use the H-function. In contrast, if the positive correlation between $f$ and $\Omega$ breaks down, i.e., $\partial f/\partial \Omega \leq 0$ (e.g., because of local nonchaoticity), the second law of thermodynamics may not apply:
entropy can decrease spontaneously with no energetic penalty, and the system can reach an intrinsic-nonequilibrium steady state.
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Data Analysis and Statistics · Cross-listed from astro-ph.GA
Changing-Look AGNs from DESI. VI. Host Galaxies
Shengxiu Sun, Linhua Jiang, Wei-Jian Guo et al. (+2 more)
Changing-look (CL) AGNs trace rapid changes in
nuclear activity, but their connection to host
galaxy properties remains unclear. We present a study of the host
galaxies of 105 CL AGNs previously selected by comparing DESI and SDSS data. We apply a two-epoch spectrophotometric decomposition to the DESI and SDSS spectra of the 105 objects. Meanwhile, HSC images are used to constrain their varying AGN components and non-varying
stellar population components. We find that 79 of the 105 (75.2%) CL AGN hosts are quiescent
galaxies, and 31/105 (29.5%) also show post-starburst signatures. We focus on 82 CL AGNs with extended host emission in the HSC images and compare them with extended
quasars at similar
redshift and
stellar mass. Their
star formation activity, Balmer absorption, and quiescent fractions are broadly consistent with those of the comparison
quasars, although post-starburst hosts are more common among the CL AGNs. Our CL AGNs with extended host emission are more often quiescent than those with compact morphology, but this difference is not apparent after matching in
redshift and
stellar mass. The $\mathrm{O\, \small II}$ and $\mathrm{O\, \small III}$ narrow lines show no population-wide response to the continuum and broad line changes, consistent with the slower response expected from the narrow line region. Together, these results favor changes in the central supermassive black hole
accretion rate as the main origin of the CL transitions.
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All authors Shengxiu Sun, Linhua Jiang, Wei-Jian Guo, Sarah E. I. Bosman, Zhiwei Pan
General Physics
Metric–Measure Geometry and Geometric Analogues of Holographic Extremal Surfaces
Rohit Dhormare
We develop a
geometric framework based on metric–measure spaces $(M,g,f)$, where the function $f$ defines a deformation of the Riemannian measure motivated by Perelman's formulation of
Ricci flow. Within this setting, we introduce measure-weighted hypersurfaces and associated
geometric functionals, and derive modified extremality conditions for codimension-one and codimension-two submanifolds. These conditions provide intrinsic
geometric analogues of extremal surface equations, arising solely from the metric–measure structure and independent of
holographic duality or
quantum field theoretic input. We further define a generalized functional combining a measure-weighted
geometric term with an effective bulk contribution and analyze its variational properties. The resulting Euler–Lagrange equation exhibits a structural correspondence with semiclassical generalized
entropy functionals, while maintaining a purely
geometric interpretation distinct from thermodynamic
entropy in the sense of Perelman's $W$-functional. Applications to Schwarzschild and Anti-de Sitter geometries illustrate the emergence of preferred
geometric scales and the modification of ultraviolet scaling behavior induced by the function $f$. These results suggest that metric–measure geometry provides a minimal framework in which key structural features of extremal surface constructions can arise from intrinsic
geometric principles.
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Applied Physics · Cross-listed from quant-ph
On Optimal Measurement-State Preparation via Geometric Transport of the Squeezing Ellipse
Vsevolod Salakhutdinov and Nikolay Kalinin
Preparation of optimal measurement states is a key requirement in
quantum metrology utilizing squeezed states. We discuss a
geometric framework that transforms an initially misaligned squeezed input into a measurement-optimal state in SU(2)-symmetric systems. Within this framework, the orientation of the squeezing ellipse constitutes an additional
geometric degree of freedom and evolves as the mean state follows a controlled trajectory on the unit sphere. The resulting rotation of the ellipse is determined by the geometry of the path and, for the relevant class of transformations, depends on the solid angle enclosed by the trajectory, establishing a connection with the
geometric phase. The discussed framework is applicable to different physical platforms. As a particular example, we consider polarization-squeezed light and outline a possible implementation using a continuously varying birefringent element.
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Optics
Frequency-Domain Analysis of Wave Scattering by Spatially Dispersive Metasurfaces Using the Method of Auxiliary Sources
Minas Kouroublakis, Nikolaos L. Tsitsas and Yehuda Leviatan
Spatially dispersive metasurfaces exhibit angle-dependent responses that cannot be accurately modeled using conventional local susceptibilities. Extended Generalized Sheet Transition Conditions (GSTCs) have been introduced to account for spatial dispersion by incorporating spatial derivatives of the electromagnetic fields. In this work, these extended GSTCs are integrated into the Method of Auxiliary Sources (MAS), resulting in a meshless simulation framework for the analysis of spatially dispersive metasurfaces. The proposed formulation is developed for infinite planar, finite planar, polygon shaped, and cylindrical metasurfaces, while it is general and also applicable to bianisotropic spatially dispersive metasurfaces. For validation, the numerical examples consider Lorentz-type spatial resonators, consistent with previously published studies. The extended GSTCs are enforced within the MAS via appropriate placement of auxiliary sources. Numerical results are presented for several geometries, including planar, polygonal, semicircular, and cylindrical metasurfaces. The obtained results show very good agreement with previously published data, demonstrating the accuracy and flexibility of the proposed method.
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Chemical Physics
Wavefunction-based periodic quantum chemistry
Hong-Zhou Ye and Timothy C. Berkelbach
High-accuracy molecular
quantum chemistry offers a promising toolbox for applications to condensed-phase systems, but this field is difficult to enter due to its combination of topics from molecular
quantum chemistry, solid-state physics, and numerical methods. Aiming to ease this transition, we present a comprehensive, pedagogical tutorial on periodic
quantum chemistry calculations, using both mean-field and correlated theories. The subtleties of periodic Coulomb interactions are discussed in detail, focusing on the Ewald summation approach. We describe the two most popular periodic, one-electron basis functions—plane waves and periodic linear combinations of atomic orbitals—and we give formulas for all
Hamiltonian integrals. Next, we explain the use of $k$-point sampling as a
symmetry adaptation of supercell basis functions and the associated savings in computational costs as well as the use of density fitting and related approximations to further reduce costs. We present the working equations of a few example periodic
quantum chemistry methods, including Hartree-Fock theory, perturbation theory, and coupled-cluster theory, and we discuss their finite-size errors and convergence to the physically relevant thermodynamic limit. Finally, we briefly discuss local correlation and
quantum embedding theories, which are especially appropriate for periodic systems due to their
lattice translational
symmetries.
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Chemical Physics
Quantum Computing Enabled ab initio Molecular Dynamics Simulations
Susanta Das, Subhamoy Bhowmik, Zhen Li et al. (+4 more)
We demonstrate a
quantum-classical workflow for ab initio molecular dynamics (AIMD) in which
quantum measurements from a chemistry-inspired LUCJ ansatz are post-processed using Sample-based
Quantum Diagonalization (SQD) to recover determinant subspaces and deliver energies and analytical
nuclear gradients for dynamics. As an exact
benchmark, we use full configuration interaction (FCI) in the STO-3G basis, enabling a direct assessment of the accuracy of SQD. In gas-phase
benchmarks, SQD reproduces FCI energies and gradients to within 1 kcal mol$^{-1}$ of the FCI reference and yields stable AIMD trajectories. In explicit-solvent QM/MM simulations, SQD retains this agreement, matching FCI energy fluctuations and RMS gradient profiles and reproducing solute-solvent structure as quantified by radial distribution functions. Overall, these
benchmarks establish LUCJ+SQD as a practical route for integrating current
quantum hardware into QM/MM molecular dynamics and provide an early demonstration of condensed-phase QM/MM dynamics driven by a
quantum electronic-structure engine.
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All authors Susanta Das, Subhamoy Bhowmik, Zhen Li, Milana Bazayeva, Danil Kaliakin, Akhil Shajan, Kenneth M. Merz Jr
Geophysics
Joint measurement of cosmic-ray muons and seismic w av es at laboratory scale
J. Matsushima, M. Kodama, M. Y. Ali et al. (+7 more)
Current geophysical exploration methods face challenges in accurately determining gas saturation levels and elastic constants with adequate spatial resolution. Seismic wave velocity is a critical physical property in these techniques, but it introduces uncertainties because of its composite nature involving density and two elastic constants (e.g. bulk and shear modulus), which exhibit a trade off relationship. We propose a novel approach that integrates
cosmic ray
muon detection with seismic exploration to independently resolve P and S wave velocities into their constituent elastic constants and densities. First, we utilized a fluid substitution approach based on Gassmann s model to illustrate the benefits of incorporating density information in predicting gas saturation levels in pores. This supports the advantage of decomposing seismic wave velocity into density and two elastic constants. Second, to validate the applicability and performance of the proposed method, which involves separating seismic wave velocity into density and two types of elastic constants,
muon and ultrasonic data were collected in laboratory experiments on two different targets: an acrylic block and an aluminium block. Upon
muon observation, a relationship is established to convert
muon flux into density length, considering the characteristics of the building housing the laboratory and the direction of
muon arrival at specific positions within the building. Although there is potential for enhancing the accuracy of the derived physical properties such as density, bulk modulus, and shear modulus, the feasibility of this method has been successfully demonstrated at the laboratory scale.
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All authors J. Matsushima, M. Kodama, M. Y. Ali, F. Bouchaala, M. Kodama, H. K.M. Tanaka, T. Kin, H. Basiri, T. Yokota, M. Suzuki