Papers

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Physics

Friday 31 July

Geophysics

Ocean Surface Gravity Waves Excited by the 2022 Eruption of Hunga Tonga-Hunga Ha'apai Volcano

Kiwamu Nishida, Mie Ichihara, Tatsuya Kubota et al. (+1 more)

On 15 January 2022, a massive underwater eruption occurred at the Hunga Tonga-Hunga Ha'apai Volcano. The plume reached the mesosphere, and the eruption excited a significant atmospheric Lamb wave, which forced the tsunami. The complicated tsunami waveforms due to ocean-atmosphere coupling prevented inferring the force history of the excitation. To address this, we analyze ocean surface gravity waves (OSWs) from 15 to 40 mHz, which are decoupled from the Lamb wave due to their slower phase velocities. Modeling these OSWs, we infer that the excitation started at 4:00 UTC with an amplitude of $10^{10}$ N and lasted for 5 hr, followed by a sub-event at 8:40 UTC. The observations suggest an initial blowout of seawater above the summit and a subsequent outflow that excited a tsunami below 5 mHz. The 2 hr delayed OSW excitation from 6 to 15 mHz may indicate seawater inflow into the crater.

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All authors Kiwamu Nishida, Mie Ichihara, Tatsuya Kubota, Takashi Tonegawa

Quantum Physics

Parent Hamiltonian and intrinsic phase transition in non-Hermitian photonic systems

Yuntao Xiao, Yuchen Guo, Xiaojian Huang et al. (+6 more)

Non-Hermitian systems host phenomena absent in Hermitian physics, but realizing Hamiltonians with intrinsic non-Hermitian properties remains challenging. The theoretical method of non-Hermitian parent Hamiltonian (NH-PH) enables the construction of a non-Hermitian system from a pair of matrix product states (MPSs) with tailored properties. Here, we report the first experimental generation of NH-PHs. This generation starts from MPSs that represent asymmetric Affleck–Kennedy–Lieb–Tasaki (AKLT) states. The construction is validated with single photons via imaginary-time evolution of the generated NH-PH to obtain its left and right ground states. We then characterize the properties of the system by measuring four different order parameters that probe non-reciprocal correlations, chiral imbalance, and conventional antiferromagnetic correlations. Furthermore, extending the framework to a larger system with a different model, we observe an intrinsic non-Hermitian phase transition, manifested by abrupt jumps of an order parameter when the designated zero-energy modes cease to be the globally lowest-energy states. Our work provides the first experimental realization and characterization of non-Hermitian Hamiltonians with controllable and customizable properties, opening new avenues for exploring intrinsic non-Hermitian phenomena across diverse physical platforms.

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All authors Yuntao Xiao, Yuchen Guo, Xiaojian Huang, Huixia Gao, Dengke Qu, Lei Xiao, Kunkun Wang, Shuo Yang, Peng Xue

Quantum Physics

The Shape of Information: Global Information Geometric Limits in Multi-task Quantum Systems

Zishuo Ren, Ziyang Chen and Hong Guo

Future quantum networks are expected to perform multiple tasks simultaneously within a single system, such as integrated sensing and communication (ISAC) architectures. Despite various metrics, we find that the evaluation of multiple tasks can be unified by their information capacity, and the total task capacity is not determined simply by addition, but is fundamentally constrained by an information geometry which we call the global quantum Fisher information matrix (g-QFIM). With this insight, we derive a non-asymptotic, measurement-independent upper bound on the Holevo information for multi-task systems, which takes a Shannon-capacity-like form. It not only quantifies the capacity limit, but also the allocability. Our results reveal a structural phase transition in multi-task performance under resource variation, where additional physical resources no longer increase independent task capacity but instead concentrate more information into a new mono-task mode. Numerical simulations based on photonic phase encoding and realistic noise channels confirm these predictions. This work establishes a unified information-geometric principle for quantum multi-task systems, with implications for the design of future quantum networks and ISAC architectures.

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Quantum Physics

Optically Resolved Excited State Hyperfine Structure of a Silicon Colour Centre in the Telecom Bands

Austin Woolverton, Nicholas Brunelle, Mehdi Keshavarz et al. (+8 more)

Nuclear spin qubits in silicon offer exceptionally coherent quantum memory, and optically-interfaced spins are a promising platform for both quantum networking and distributed quantum computing. It has been proposed that emitters with diamagnetic ground states may permit an optical interface to nuclear spin memories via metastable, hyperfine-coupled excited states while suppressing key sources of decoherence. Until now, direct optical observation of suitable transitions in silicon colour centres has remained elusive. Here we characterize the singly-ionized interstitial aluminum donor (Al$_\mathrm{i}^+$) in isotopically purified $^{28}$Si and find several novel features of this little-studied defect. We measure bright emission and strong optical transitions and, in contrast to previous studies of this centre, attribute its emission to an exchange-split spin triplet and singlet level of the lowest-energy 1s:T$_2$ excited state. We measure the excited-state lifetimes and, as a consequence of its narrow emission linewidth, observe the fine and hyperfine structure of the long-lived triplet state. This constitutes the first measurement of an optically-resolved hyperfine structure in the excited state of a telecommunications-band silicon colour centre.

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All authors Austin Woolverton, Nicholas Brunelle, Mehdi Keshavarz, Laurent Bergeron, Evan R. MacQuarrie, Yehudah Ackermann, Melanie Gascoine, Nikolay V. Abrosimov, Stephanie Simmons, Daniel Higginbottom, Michael Thewalt

Soft Condensed Matter

Covariance-Driven Momentum Rectification at Liquid-Vapor Interfaces Near Wetting Transitions

Nelson Bolívar, Gabriel Abellán and Ivaylo Vasilev

Zero-mean forcing can generate directed transport when a medium responds in a spatially structured way and the relevant symmetries are broken. Liquid-vapor interfaces are a useful setting for this problem because surface-tension gradients, wetting dynamics, vapor exchange, capillary and acoustic waves, electro-ionic screening, thermal noise, and boundary compliance can all carry momentum. We develop a conservative continuum model in which the central object is the covariance between a local response field and a zero-mean tangential drive, $\langle Mf\rangle-\langle M\rangle\langle f\rangle$, embedded in an explicit momentum ledger. In a minimal diffuse-interface realization, this covariance gives the phase-selective drift law $U\propto\epsilon_h\Theta\sin\varphi$ for a Marangoni-driven liquid-vapor interface above a structured wall, with exact nulls when the symmetry is restored. Wetting susceptibility then acts as a bounded gain factor: first-order spinodal conditions provide the useful amplification regime, critical wetting saturates because interfacial unbinding removes the short-range drive, and bulk criticality suppresses the channel as the interface disappears. Additional reservoirs - phase change, waves, thermal transport, electro-ionic coupling, compliance, and fluctuations - are treated as compensating channels to be isolated by sign reversals, scaling laws, and budget closure. The result is neither a new microscopic force nor an apparatus-level claim, but a symmetry-constrained accounting scheme for rectified momentum transfer in water-based interfacial systems. Reduced numerical calculations illustrate the phase-selection rules, bounded spinodal gain, momentum-budget closure, transverse chirality, and grid convergence.

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Nuclear Theory

Two unitary limits in low-energy $s$-wave neutron scattering on superfluid nuclei

Yoshihiko Kobayashi and Masayuki Matsuo

Low-energy $s$-wave scattering in weakly bound superfluid nuclei is strongly influenced by pairing correlations. In this work, we present an analytical study of low-energy $s$-wave quasiparticle scattering within the coordinate space Hartree-Fock-Bogoliubov framework using a schematic square-well model. Analytical expressions for the phase shift, elastic cross section, scattering length, and effective range are derived in a unified manner. We demonstrate that pairing correlations give rise to two distinct unitary limits, characterized by the divergence of the scattering length. One corresponds to the particle-like unitary limit, which persists even without pairing and is well described by the effective range expansion. The other is a pairing-induced hole-like unitary limit associated with quasiparticle resonances, leading to a breakdown of the effective range expansion. These results clarify the validity of the effective range expansion and highlight the essential role of resonance poles in describing low-energy $s$-wave quasiparticle scattering in superfluid nuclei.

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Fluid Dynamics

Coupled Rayleigh–Taylor and Faraday instabilities in vertically vibrated cylindrical containers

Tianyi Chu, Benjamin Wilfong, Timothy Koehler et al. (+2 more)

Interfacial instabilities govern the mixing in confined multiphase flows. Yet, the two mechanisms that drive them are usually studied independently: the pressure-gradient-driven Rayleigh–Taylor (RT) instability, which amplifies long-wavelength modes, and the parametrically forced Faraday instability, which selects shorter-wavelength harmonic or subharmonic modes. When an adverse density contrast and vertical vibration act together, the two compete, and neither alone describes the response. We use Floquet analysis to characterize the onset, growth, modal structure, and velocity fields of Faraday–RT waves in a vertically vibrated cylinder, resolved by azimuthal wavenumber, radial (Bessel) mode, and Floquet harmonic. The formulation recovers the classical RT and Faraday limits and reproduces the instability onset at the frequencies measured experimentally. For a free-sliding interface, increasing the vibration amplitude shifts the dominant instability mechanism from RT growth to subharmonic and then harmonic Faraday responses. Lateral confinement can also stabilize individual RT modes, which is not possible in an unbounded domain, although other Faraday modes may remain unstable. Pinning the contact line couples radial modes that otherwise evolve independently, allowing the unstable mode to be a superposition of RT-unstable and Faraday-stable components. This superposition alters the instability mechanism, producing a richer radial pattern. Reconstruction of the unstable modes shows the (linear) velocity fields that imaging cannot access and demonstrates how the instabilities can change the flow more broadly.

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All authors Tianyi Chu, Benjamin Wilfong, Timothy Koehler, Ryan M. McMullen, Spencer H. Bryngelson

General Relativity and Quantum Cosmology

Excitation region of Kerr black hole quasinormal modes from Stokes geometry

Naritaka Oshita

We investigate the excitation region of black hole quasinormal modes (QNMs) from both analytical and numerical perspectives. On the analytical side, we propose that the QNM excitation radius is identified by the dominance switching of WKB solutions across an anti-Stokes line. Based on this picture, we derive the condition for the QNM excitation radius in Kerr spacetime. In the Schwarzschild limit with mass $M$, we reproduce the previously known value $r=2.556929 M$, which differs from the light ring radius $r=3M$. We also show that the excitation radius is independent of the angular mode $\ell$ in the high-overtone limit. As an independent approach, we employ the numerical convergence test of QNM-plus-tail expansion and obtain values consistent with the Stokes geometry in the high-overtone limit at low and intermediate spins. In the extremal limit, the QNM convergence radius approaches the outer horizon, which is captured by the Stokes geometry of the zero-damping modes, rather than the high-overtone limit. This is consistent with the fact that the ringdown is dominated by zero-damping modes in the extremal limit. Based on the complementary analysis of Stokes geometry and the convergence test, we argue that in general, the QNM excitation radius depends on the QNM overtone number, giving rise to an effective QNM convergence region.

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Mesoscale and Nanoscale Physics

Symmetry selection rule for the band-edge shift current in two dimensions

Felipe Pérez Riffo, Matías Castro, Leonor Chico et al. (+2 more)

The shift current is the intrinsic bulk photovoltaic response of a crystal without an inversion center. In graphene multilayers, calculations report large band-edge shift currents that reverse sign under a gate, a behavior that neither the quantum metric nor the Berry curvature captures. We show that this follows from a symmetry principle. At the absorption edge of a gapped, inversion-broken two-dimensional Dirac-like system, an emergent rotational symmetry forbids the response, and the trigonal warping switches it on linearly in its strength, an angular selection rule that unifies multilayer graphene and the kagome lattice. The released current is governed by a signed, detuning-weighted three-point Bargmann invariant: the optical amplitude stays fixed while the sign alignment of the Bargmann triangles grows with the warping, invisible to any positive-definite figure of merit. In bilayer and trilayer graphene the gate alone reverses the sign, making the band-edge shift current a gate-switchable bulk photovoltaic response.

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All authors Felipe Pérez Riffo, Matías Castro, Leonor Chico, L.E.F. Foa Torres, Eric Suárez Morell

Earth and Planetary Astrophysics

Asymmetric, variable H$\alpha$ line profile in planetary mass object SR 12 c

Jun Hashimoto, Yuhiko Aoyama, Michihiro Takami et al. (+1 more)

Young, forming planetary-mass objects often exhibit clear signatures of ongoing mass accretion and are thought to accrete material through processes analogous to those operating in young stars. In this study, we present high-spectral-resolution observations of asymmetric and time-variable H$\alpha$ line profiles from the planetary-mass companion SR~12~c. The H$\alpha$ line was observed at a resolving power of $R \sim 49,000$–40{,}000 (corresponding to 6.1–7.5~km~s$^{-1}$) using the High Dispersion Spectrograph (HDS) on the 8.2 m Subaru Telescope. Strong H$\alpha$ emission is clearly detected, while higher-order Balmer lines (H$\beta$, H$\gamma$, and H$\delta$) are not detected due to their faintness. The H$\alpha$ line profiles are well spectrally resolved and exhibit blueshifted emission peaks, which can be interpreted as arising from either (a) emission partially absorbed by redshifted accreting material along the line of sight and/or (b) geometric occultation by the inner circumplanetary disk. Moreover, the H$\alpha$ flux shows significant variability at 43.6~$\pm$~6.4~% relative to the peak flux on hourly timescales. During a continuous 2.5-hour observing sequence, the emission component peaking at approximately $-30$~km~s$^{-1}$ weakened over the first hour. Subsequently, an emission component centered near $-10$~km~s$^{-1}$ became dominant and remained stable for the remaining 1.5 hours. We discuss possible interpretations of this behavior. Overall, these results support that magnetospheric accretion is operating in the planetary-mass object SR~12~c while a scenario combining boundary-layer accretion with a failed wind cannot be ruled out.

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All authors Jun Hashimoto, Yuhiko Aoyama, Michihiro Takami, Shinsuke Takasao

Quantum Physics

Error-Generator-Level Compression for Fast Quantum Gates

Razvan Stanescu and Hugo Ribeiro

Fast quantum gates in multilevel systems require suppressing many coherent-error channels using pulses that remain simple to implement. We introduce error-generator-level compression, a Magnus-based control principle that minimizes the complete projected error generator at a chosen perturbative order while restricting the implemented waveform to a few independently adjustable coefficients. This construction preserves all modeled computational and leakage errors rather than truncating the pulse by error channel, while its generator-level objective directly penalizes residual eigenphases that can signal departure from the perturbative regime. For fast transmon gates, a three-parameter pulse suppresses errors by orders of magnitude, outperforms grid-optimized leading- order DRAG over the gate-time range studied, and approaches a fully parameterized 17-parameter Magnus correction. The compressed pulse is also substantially less sensitive to the illustrative finite-bandwidth filtering model considered here.

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Solar and Stellar Astrophysics

A New Approach to Modeling Line Shapes with Quasi-H$_2^+$ Satellites in Stellar Atmospheres

Jackson R. White, Thomas A. Gomez, Mark C. Zammit et al. (+6 more)

Theoretical spectral line shapes describe the distribution of opacity due to bound electronic transitions in hot dense plasmas and are used to fit emergent spectra from many astrophysical sources. Deficiencies in line broadening theory have been proposed as a possible explanation for unresolved discrepancies between theoretical and observed spectra in white dwarf star atmospheres and laboratory experiments at white dwarf star photosphere conditions. One possible source of these discrepancies is the formation of quasi-molecules. Quasi-molecules are close (unbound) collisions between atoms, which broaden line shapes and create additional satellite lines. Quasi-molecules are challenging to implement into traditional line shape codes and have historically required a number of physical approximations beyond what is used in standard Stark broadening models. Here we present a new approach to calculating line shapes with quasi-molecular resonances, using a novel multiple-basis method that considers both atomic and molecular states. We implement this approach into a simulation line shape code, present hydrogen Lyman-series line shapes with quasi-H$_2^+$ resonances, and demonstrate the impact our new line shapes have on hydrogen-atmosphere white dwarf star model spectra. We find that our new approach leads to broader quasi-molecular features that agree well with observed spectra in initial comparisons.

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All authors Jackson R. White, Thomas A. Gomez, Mark C. Zammit, Michael H. Montgomery, Bart H. Dunlap, Ivan Hubeny, Dmitry V. Fursa, Igor Bray, Don E. Winget

High Energy Astrophysical Phenomena

Strongly Magnetized Super-Eddington Accretion: How Spin and Accretion Rate Regulate Energy Output and Mass Loss

Tom Man Kwan, Lixin Dai, Cheuk Kwan Kan et al. (+5 more)

Strongly magnetized super-Eddington accretion flows power many important astrophysical systems, but how black hole parameters control their output is unclear. We present 32 general relativistic radiation magnetohydrodynamics simulations of super-Eddington magnetically arrested disks onto stellar-mass black holes, varying mass ($M_{\rm BH}= 5, 15, 30\,M_{\odot}$), spin ($a=0,0.9$), and accretion rate ($\dot{M}_{\rm acc} \approx 1-2000\,\dot{M}_{\rm Edd}$). We find that black hole spin and accretion rate jointly regulate wind loss rates and energy output efficiencies, while black hole mass has no effect over the mass range studied here. The BH accretes only $10-40\%$ of the mass supplied to the accretion flow, while the rest is expelled in winds. This accretion fraction decreases with mass supply rate and is lower for high-spin systems. Both spin states produce strong magnetically driven outflows. For $a = 0$, the wind kinetic, radiative, and electromagnetic efficiencies are modest and show little variation across the full simulated range of accretion rates. For $a = 0.9$, both wind power and jet power increase super-linearly with $\dot{M}_{\rm acc}$, with the jet power saturating beyond $\dot{M}_{\rm acc} \sim 100\,\dot{M}_{\rm Edd}$. Radiation is strongly beamed along the funnel, with inverse beaming factors exceeding $100$ for high-spin, high-$\dot{m}$ models viewed face-on. Our results establish that rapid BH spin boosts energy-extraction efficiency, while high accretion rate amplifies total power. We provide scaling relations for luminosities, jet power, accretion ratio, and beaming, offering a framework for interpreting observations of ULXs and other super-Eddington systems.

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All authors Tom Man Kwan, Lixin Dai, Cheuk Kwan Kan, Zepei Xing, Tassos Fragos, Matthew Middleton, Tao Ji, Feng Yuan

Cosmology and Nongalactic Astrophysics

An E-value Reanalysis of DESI's Dynamical Dark Energy Signal

Jinyoung Kim, David F. Mota and Andrius Tamosiunas

Cosmological surveys such as DESI release data in stages, and each release reprocesses earlier observations and supersedes its predecessor. Testing the same hypothesis at every release inflates the false-positive rate, and only the collaboration can estimate the cross-release covariance that an exact combination needs. We show how to combine evidence across such releases using public products alone. From each release we compute an e-value, a non-negative statistic with expectation at most one under the null, and we average these e-values with weights fixed in advance. Provided each release's own likelihood is correct, this average controls the false-positive rate at every release under arbitrary dependence between releases. For DESI BAO at a fixed Planck background, DR2 alone gives an e-value of $33.97$ against $\Lambda$CDM ($p \le 0.0295$) under our reference test specification, a flat prior on $(w_0, w_a)$ over a fixed box. The equal-weight average of DR1 and DR2 is $17.51$ ($p \le 0.0571$), below the rejection threshold of $20$. We did not fix these weights before DR2 was published, and the weights we now fix ahead of DR3 give $p \le 0.0874$ at DR2. Without a model of the cross-release covariance, an exact combination that counts each observation once can take any value. Under explicit models it ranges from below the threshold to nearly double the DR2 value, depending on the structure assumed. The evidence is concentrated in the LRG2 bin, which also changed most between releases. Without it the DR2 e-value falls to $0.49$, and a look-elsewhere correction over the seven redshift bins leaves no rejection. DR2 does not reject under wider priors either. The signal is therefore fragile and specification-dependent. We recommend that surveys report per-release e-values with a stated test specification and a combination rule fixed in advance, and publish the cross-release covariance.

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Mathematical Physics · Cross-listed from math.AP

Recovery of a Null Form in the Wave Equation from Scattering Data

Joel Nathe

We use highly oscillatory geometric optics solutions to solve the inverse problem for the system $$ \square \begin{bmatrix} u^{(1)}\\ u^{(2)}\\ \vdots\\ u^{(n)}\end{bmatrix} = \sum_{k\geq l=1}^n \left(Q_0(u^{(k)},u^{(l)}) \begin{bmatrix} q_{1kl}\\q_{2kl}\\\vdots\\q_{nkl} \end{bmatrix} + \sum_{i>j=1}^d Q_{ij}(u^{(k)},u^{(l)})\begin{bmatrix} p_{1ijkl} \\ p_{2ijkl} \\ \vdots \\ p_{nijkl} \end{bmatrix}\right), $$ where $Q_0$ and $Q_{ij}$ are the symmetric and anti-symmetric bilinear null forms. We present solutions in both the linear and weakly nonlinear regimes. In the linear regime, we show that the coefficients of order $h^3$ determine an injective light-ray transform of a vector field which depends on the coefficients $q_{rkl}, p_{rijkl}$. In the weakly nonlinear regime, we see that the coefficients of order $h$ determine the non-abelian light ray transform for matrices associated with the coefficients. While we do not have an injectivity result for this case, we do have one if we assume the coefficients do not depend on the time variable $x_0$, as our coefficients instead determine an injective non-abelian X-ray transform.

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Physics and Society

An agent-based model of the formation and evolution of common ground

Mengbin Ye, Wooseok Jung, Tony J. Mathew et al. (+2 more)

The existence of a communal common ground is vital for collective action and coordination in a population, but the micro-level cognitive and social processes that lead to the formation and evolution of common ground at the macro-level are undertheorised and have not been rigorously explored. In this work, we adopt a formal approach and develop an agent-based model that describes repeated grounding attempts between agents interacting on a network, with an explicit distinction between a sender agent and a receiver agent during an interaction involving sharing information. Several key novel features enable us to capture a range of different interaction contexts: we allow for the interaction to result in either acceptance or rejection, the receiver's response may be lost to the sender, and the sender can interpret this lack of response as either acceptance or rejection (or even something in between). A campaign of Monte Carlo simulations reveals how different interaction contexts, as well as the available information for sharing, result in different emergent phenomena, such as a global communal common ground, fragmentation into multiple clusters of differing common ground, and even the total loss of any shared common ground. This work highlights the potential for using mathematical models to study micro-macro links in cultural dynamics, including identifying ways to facilitate interactions to foster the emergence of a global communal common ground.

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All authors Mengbin Ye, Wooseok Jung, Tony J. Mathew, Lorenzo Zino, Yoshihisa Kashima

Instrumentation and Methods for Astrophysics

On-sky results from REDWOODS, a platform at Lick/ShaneAO for testing second stage AO technologies

Benjamin L. Gerard, Dominic F. Sanchez, Aditya R. Sengupta et al. (+11 more)

REDWOODS is a new sub-testbed within the Shane Adaptive Optics (AO) system at Lick observatory, developed to test second stage AO wavefront sensing and control technologies, including a Self-Coherent Camera with optional broadband Wynne corrector, two different three-sided fully reflective highly broadband pyramid wavefront sensor modes, and multi-wavefront sensor single conjugate AO control. We present project results to date, including on-sky data.

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All authors Benjamin L. Gerard, Dominic F. Sanchez, Aditya R. Sengupta, Chris Ratliff, Sylvain Cetre, Elinor Gates, Daren Dillon, Bautista Fernandez, Brian Bauman, Lisa Poyneer, Aaron Lemmer, Rebecca Jensen-Clem, Phillip Hinz, Bruce Macintosh

Materials Science

Molecular beam epitaxy synthesis of ternary nitride PrTaN$_2$ and its crystal structure determination

Kosuke Takiguchi, Yoshiharu Krockenberger, Eisuke Magome et al. (+2 more)

We report the discovery of a novel ternary nitride PrTaN$_2$ synthesized as a thin film using molecular beam epitaxy. The combination of e-beam evaporation for refractory elements and a radio-frequency nitrogen radical source enables growth under a highly nitriding environment, providing access to phases not readily obtained in bulk synthesis. Structural characterization by X-ray diffraction and high-angle annular dark-field scanning transmission electron microscopy reveals that the compound crystallizes in an orthorhombic structure and grows with a well-defined orientation on YAlO$_3$ substrates, while remaining essentially strain-free. To determine the crystal structure from limited thin-film diffraction data, we developed a fitting procedure based on structure factors. By combining extinction rules with constraints from Wyckoff positions, the number of fitting parameters is significantly reduced, enabling reliable structure determination. Systematic exclusion of alternative candidate phases in the Pr-Ta-N system, together with structure factor fitting, identifies the space group as $P222$ and determines the atomic coordinates. The present results demonstrate that thin-film growth with molecular beam epitaxy can stabilize previously unexplored ternary nitrides, and establish a practical approach for structural determination in such systems. This work provides a pathway for the exploration of new complex nitride materials.

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All authors Kosuke Takiguchi, Yoshiharu Krockenberger, Eisuke Magome, Yoji Kunihashi, Hideki Yamamoto

Materials Science

Knudsen-Controlled Switching of Thermal Conductivity Response by Targeted Phonon Excitation

Shixian Liu, Tianhao Li, Fei Yin et al. (+4 more)

Targeted phonon excitation offers a route to dynamically control heat conduction, yet no general principle predicts whether a spectrally selective nonequilibrium phonon population will enhance or suppress thermal transport. A Knudsen-controlled competition between the increased contribution of long-mean-free-path phonons and excitation-enhanced intrinsic scattering governs the sign of the thermal-conductivity response. First-principles three-phonon scattering rates combined with phonon-tracking Monte Carlo simulations are used to examine Ge, Si, and 3C–SiC from bulk crystals to confined nanofilms. In bulk systems, excitation-enhanced scattering dominates and thermal conductivity is predominantly suppressed. In nanofilms, by contrast, low-frequency excitation can increase the contribution of quasi-ballistic heat-carrying channels and enhance thermal conductivity, whereas higher-frequency excitation is predominantly suppressive. At fixed background temperature and excitation strength, these opposite responses are organized in a frequency–Knudsen map based on the normalized target frequency, $\omega_{\mathrm t}/\omega_{\mathrm D}$, and the Knudsen number, $\mathrm{Kn}$. The resulting framework provides a general physical basis for controlling nonequilibrium heat transport beyond static phonon engineering.

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All authors Shixian Liu, Tianhao Li, Fei Yin, Yu He, Alexander A. Barinov, Han Meng, Nuo Yang

Nuclear Theory

Intruder structure, deformation, and $E2$ strengths in $^{14}\mathrm{C}$ from an ab initio perspective

Mark A. Caprio

The semimagic nucleus $^{14}\mathrm{C}$ lies just above the $N=8$ island of inversion, raising the possibility of low-lying intruder states and associated deformation. Through ab initio no-core configuration interaction calculations, we shed light on the role of intruder structure, quadrupole deformation, and Elliott SU(3) symmetry in $^{14}\mathrm{C}$. The results also highlight the influence of mixing between normal and intruder states on the strengths of the $E2$ transitions from the first two $2^+$ states.

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Thursday 30 July

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

Astrophysics of Galaxies

Broad Paschen lines as black hole mass tracers: A reverberation mapping calibration

Shengxiu Sun, Sarah E. I. Bosman, Frederick B. Davies et al. (+4 more)

Single-epoch (SE) black hole mass estimators based on rest-frame ultraviolet or optical broad lines can be limited by dust attenuation or wavelength coverage. We calibrate estimators based on broad Paschen P$\alpha$ and P$\beta$ directly against reverberation mapping (RM) masses. We obtained LBT/LUCI near-infrared spectra of 27 SDSS-RM quasars and combined them with archival Paschen measurements for AGNs with RM masses. After continuum subtraction, we measured line luminosities and full widths at half maximum (FWHMs) using multi-component and single-Gaussian profile models. We fitted $\log(M_{\rm BH}/M_\odot)=a+b\log(L/10^{41}\,{\rm erg\,s^{-1}})+c\log({\rm FWHM}/10^3\,{\rm km\,s^{-1}})$, including intrinsic scatter. The fiducial relations use photometrically corrected line luminosities and FWHMs of the combined broad profiles. For P$\alpha$, we obtain $(a,b,c)=(6.86^{+0.24}_{-0.25},0.47^{+0.11}_{-0.10},1.24^{+0.49}_{-0.48})$ with an intrinsic scatter of $0.28^{+0.08}_{-0.06}$ dex. For P$\beta$, we obtain $(7.00\pm0.24,0.48^{+0.10}_{-0.09},0.91^{+0.46}_{-0.47})$ with a scatter of $0.32^{+0.08}_{-0.06}$ dex. Relations using single-Gaussian widths, 5100 Å continuum luminosities, or fixed virial slopes have scatters consistent within the uncertainties. These relations provide complementary mass estimators when ultraviolet or optical broad lines are attenuated or unavailable. They should be applied within the parameter ranges of the calibration sample and remain subject to the systematic uncertainty associated with the RM virial factor.

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All authors Shengxiu Sun, Sarah E. I. Bosman, Frederick B. Davies, Klaudia Protušová, Benedetta Spina, Linhua Jiang, Danyang Jiang

High Energy Astrophysical Phenomena

Arcminute Microkelvin Imager observations at 15.5 GHz of the tidal disruption event Swift J164449.3+573451 from 2011 Mar to 2014 Mar

David A. Green

Radio monitoring of the tidal disruption event Swift J164449.3+573451 at 15.5 GHz with the Arcminute Microkelvin Imager is reported. The results from 308 observations made from 2011 Mar to 2014 Mar are presented. These show a steady rise in flux density from $\approx$3 mJy (three days after the initial $\gamma$-ray detection of Swift J164449.3+573451), to a peak of nearly 30 mJy $\approx$140 days later, followed by a steady decline.

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Instrumentation and Methods for Astrophysics

Cassiopee: Defining the next-generation deformable mirror and high-speed SWIR camera for adaptive optics applications

B. Neichel, T. Fusco, F. Oyarzun et al. (+14 more)

Future adaptive optics (AO) systems for astronomy, optical communications, space situational awareness, and laser-based defense require a new generation of components operating at unprecedented speed, sensitivity, and precision. We present a systematic approach to defining the specifications of two key technologies: a large-format, high-cadence SWIR camera and a high-order deformable mirror (DM). Starting from four representative use-cases, high-contrast exoplanet imaging, free-space optical communications, satellite observation, and laser focusing, we derive detailed AO error budgets to identify the dominant performance drivers. This analysis defines quantitative requirements for the DM (actuator count, stroke, bandwidth, electronics) and the camera (read noise, quantum efficiency, frame rate, latency, and dark current), developed in close collaboration with industrial partners. We then describe an integrated experimental testbed designed to validate both components in a closed AO loop under atmospheric and system-level disturbances representative of astronomical and telecom applications. Finally, we outline the roadmap toward on-sky validation with EKARUS, the new AO facility at Asiago Observatory, bridging the gap between component qualification and deployment in future extremely large telescopes and ground-to-space optical links.

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All authors B. Neichel, T. Fusco, F. Oyarzun, V. Chambouleyron, J.-F. Sauvage, C.-T. Héritier, J. Charton, C. Pravert, F. Clop, L. Maillet, M. Laslandes, J.-L. Gach, D. Boutolleau, P. Feautrier, P. Bruno, Y. Wanwanscappel, C. Bremond

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

Solar and Stellar Astrophysics

JW-FD: A 15-Year Multimodal Dataset for Solar Flare Forecasting

Shao Mingfu, Lin Jiaben, Wang Hui et al. (+4 more)

Solar flares drive severe space weather hazards, and forecasting their occurrence remains a central challenge for both heliophysics and operational space weather services. Data driven methods require long horizon datasets in which images, magnetic features, and flare labels are coregistered in space and time. We present JW-FD (JW-Flare Dataset), a 15 year multimodal release spanning 1~January~2011 through 31~December~2025, constructed from SDO/HMI line of sight magnetograms, NOAA Solar Region Summary reports, and NOAA X-ray flare event lists. The dataset comprises 3{,}064 independent active regions and 1{,}991{,}247 coregistered magnetogram crops, together with FITS, PNG, CSV, and MP4 modalities. Each sample provides 29 magnetic features linked to configurable flare labels under a strict pre-eruption window spanning seven forecast horizons and four GOES intensity thresholds. An 8:1:1 split at the active region level is adopted to prevent temporal leakage between partitions. PNG branches are released at six magnetic saturation thresholds, and internal Transformer experiments on $\geq$C1.0 forecasting suggest $B_{\mathrm{th}}=1000$~G as a preliminary default, although the optimal saturation is model and task dependent. The open source construction pipeline is available at https://github.com/Xiaoxuan-1/JW-FD.

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All authors Shao Mingfu, Lin Jiaben, Wang Hui, Tong Liyue, Yang Chen, Zhang Yin, Li Yuyang

High Energy Astrophysical Phenomena

Microscopic Interaction versus Purely Gravitational Coupling in Strange Quark Stars Admixed with Dark Matter: A One-Fluid and Two-Fluid Comparison

J. Sedaghat, G. H. Bordbar, M. Haghighat et al. (+1 more)

In this study, we investigate strange quark stars (SQSs) admixed with scalar dark matter (DM), focusing on the role of microscopic interactions versus purely gravitational coupling. Our results demonstrate that while the interacting one-fluid model yields viable configurations with M_TOV > 2M_sun that satisfy current pulsar M-R measurements alongside the tidal deformability (Lambda) constraints from GW170817, the noninteracting two-fluid model more robustly meets both existing GW170817 limits and the tighter Lambda bounds anticipated from next-generation gravitational-wave detectors.

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All authors J. Sedaghat, G. H. Bordbar, M. Haghighat, S. M. Zebarjad

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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