Chemical Physics
SONIC: Symmetry-Oriented Non-redundant Internal Coordinates
Vincenzo Barone
Internal coordinates are the natural
language of molecular structure, but automatic non-redundant constructions remain difficult for fused rings, high coordination, molecular
symmetry, and weakly bound fragments. We present SONIC (
Symmetry-Oriented Non-redundant Internal Coordinates), implemented in SMITH, as a deterministic construction of localized,
symmetry-adapted generalized internal coordinates. SMITH accepts a frozen molecular state, supplied
topology or primitives, or Cartesian input through a revision-pinned standalone perception kernel. It classifies ordinary primitives, adds chemically typed special and composite families, protects ring and fragment coordinates, and performs block-local rank reduction using analytic Wilson B rows. Local pseudosymmetry orders center, ring, and bond domains, while exact molecular point-group projection is applied within homogeneous blocks. The output is a frozen coordinate contract with human-readable decompositions,
symmetry and rank diagnostics, analytic first derivatives, and optional Gaussian 16 serialization. Optimization, internal-to-Cartesian realization, force fields, and higher-order Hessian transformations remain downstream responsibilities. Validation covers acyclic, fused, bridged, high-coordinate, non-covalent, and eta3 metal-complex cases, including rotation/permutation invariance, Python/Fortran checks, and independent GIC evaluation.
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Physics Education
A First Africa Wide Amateur Radio Contact Experiment with the International Space Station
Domingos Barbosa, Miracle Chibuzor Marcel, Declan Kirrane et al. (+7 more)
The Amateur
Radio on the International Space Station (ARISS) program is recognized by its great Science, Technology, Engineering, and Mathematics (STEM) impact: it brings space science to education and outreach initiatives by enabling direct contact with astronauts in orbit and other space savvy professionals. Strategic partnerships between ARISS and digital platforms for citizen science act as a powerful real-world STEM motivator and can overcome logistical barriers, demonstrating a scalable model for inclusive outreach, sparking curiosity in space exploration and STEM careers among underrepresented communities. As a case study, this article focus on the impact of an historic milestone: on April 18$^{th}$ 2025 the Pan-African Citizen Science e-Laboratory (PACS e-Lab) orchestrated the first Africa-wide ARISS contact experiment and connected 300 students, educators, and STEM enthusiasts from 38 African nations and beyond with NASA astronaut Nichole Ayers aboard the ISS Expedition 72. Within the African context, this initiative not only inspired a new generation of African scientists, but it also set a precedent for wider collaboration on space science education across the continent. Strategic partnership between ARISS and PACs e-LAB promotes capacity building through international and regional cooperation on space science and adds a new "New Space" narrative that emphasizes the interconnectedness of space with our daily lives and the possibility that everyone has to be a part of it.
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All authors Domingos Barbosa, Miracle Chibuzor Marcel, Declan Kirrane, Miguel Avillez, Amare Abebe Gidelew, Carla Sharpe Mitchell, Vidvuds Beldavs, Claudio Ariotti, Stefan Dombrowski, Peter Kofler
Strongly Correlated Electrons
AIMS: an AI experimentalist turns uncertainty into quantum matter discovery
Siyuan Qiu, Philip D. Suh, Nhat Huy Tran et al. (+13 more)
Most AI
agents act only after scientists have defined the task. Discovery is harder under practical uncertainties: the probe may not be where it is expected, the signal may occupy only a small region of a disordered sample, and the evidence may not distinguish among competing explanations. Here we show that an AI
agent can decide what evidence an uncertain experiment needs next, and act on it. Beyond automation, AIMS, an uncertainty-aware experimentalist for cryogenic microwave impedance microscopy, quantifies uncertainty where it originates, in perception, sampling, and interpretation, and converts each into its own corrective action rather than a single confidence score. Given only an open objective, AIMS relocated a probe lost during cooldown while flagging its own unreliable estimates, mapped twist angle disorder to locate the strongest correlated states in twisted
bilayer MoSe$_2$, and uncovered a paradox: the half-filled stripe that classical theory predicts should melt first survived longest. Distinguishing an incomplete model from a wrong mechanism, AIMS commissioned a beyond-mean-field calculation and an independent structural measurement as the decisive tests, revising its interpretation as each arrived:
quantum motion reverses the classical hierarchy, stabilizing the half-filled stripe while destabilizing its neighbors. These uncertainty-to-action loops are generic to scanning probe experiments, and AIMS turns uncertainty from an obstacle into a driver of discovery.
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All authors Siyuan Qiu, Philip D. Suh, Nhat Huy Tran, Xirui Wang, Heonjoon Park, Kutay Akin, Kevin K. S. Multani, Seungwon Jung, Wenkai Cai, Xinyu Liu, León Garcia, Ziyan Zhu, Chunjing Jia, Zhantao Chen, Zhixun Shen, Zhurun Ji
Quantum Physics
Efficient Exact Quantum Sampling from the Sun-Wootters Distribution for Optimal Polynomial Intersection
Sunghyeon Jo
Optimal
Polynomial Intersection (OPI) is a structured optimization problem for which Decoded
Quantum Interferometry (DQI) attains a satisfaction guarantee governed by the semicircle law. Sun and Wootters recently showed that, for balanced OPI over
prime fields, a
Fourier-defined distribution $P_u$ gives a strict worst-case improvement from limiting rate $0.6225$ onward and asymptotically perfect solutions from rate $0.7496$ onward, and asked whether $P_u$ can be sampled efficiently. We answer this question for Reed–Solomon OPI parameters satisfying their exponent condition strictly below the dual Johnson radius. Under coherent membership-oracle access, we give a bounded-error
polynomial-time
quantum sampler for $P_u$. The ideal
circuit samples $P_u$ exactly conditioned on success, while a finite-precision implementation achieves any prescribed inverse-
polynomial total-variation error. Consequently, every fixed limiting rate $0.6225\le r<1$ admits a strict worst-case improvement over the DQI semicircle value, and every limiting rate $r\ge 3/4$ admits solutions of satisfaction $1-o(1)$ with high probability. The
algorithm coherently sums the amplitudes of all low-weight errors in each syndrome class using deterministic complete list decoding. Complete Reed–Solomon list decoding and the Sun–Wootters denominator estimate make the list size and postselection overhead
polynomial. In concurrent and independent work, Horinaga and Yamakawa obtain worst-case OPI
algorithms over
prime-power fields and exact satisfaction at every fixed rate strictly above $3/4$.
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Applied Physics
Full-band reciprocal parametric amplification in coupled oscillator arrays
Benjamin Kauffman and Jayson Paulose
Parametric resonance provides a versatile mechanism to manipulate wave signals in time-modulated metamaterials, but typically operates within narrow wavelength or frequency ranges. Here, we show that one-dimensional arrays of coupled resonators can generically exhibit parametric amplification across an entire band under standing-wave parametric modulation. We develop a general physical framework to describe the parametric resonance of isolated bands, derive modulation conditions needed to achieve full-band amplification for a given band, and demonstrate their validity in a model of active mechanical metamaterials based on tunable membrane resonator arrays. We numerically demonstrate applications of the proposed strategy in distortion-free amplification and temporal splitting of wave packets, with results in quantitative agreement with our theoretical calculations. Our strategies for broadband amplification can be generalized to other active wave media with nearly flat or cosine-like dispersion relations, with potential applications in loss-mitigation, noise squeezing, and programmable wave manipulation.
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Applied Physics
Quantitative Infrared Thermographic Assessment of Hand Cooling Dynamics During Controlled Contact with Metal Plates
Pengfei Zhu, Hai Zhang, Stefano Sfarra et al. (+5 more)
This study investigates the spatiotemporal thermal response of human hands during controlled contact cooling using short wave infrared (SWIR), mid wave infrared (MWIR), and long wave infrared (LWIR) thermography. Three participants simultaneously placed one hand on a cooling metal plate and the contralateral hand on a reference plate maintained near room temperature. Temperature
evolution was analyzed in five anatomical regions, including the distal finger, proximal finger, vessel associated region, non vessel region, and forearm. Quantitative metrics, including temperature variation, bilateral temperature difference, initial cooling rate, and frequency-domain amplitude, were extracted from the thermal image sequences. The results showed that the finger regions exhibited the largest temperature reductions and highest cooling rates, indicating greater sensitivity to thermal stimulation than the dorsal hand and forearm. MWIR and LWIR measurements revealed highly consistent cooling dynamics, while LWIR imaging provided enhanced thermal contrast and sensitivity. Frequency-domain analysis demonstrated that the dominant thermal response was concentrated in the low frequency range below 0.05 Hz. Furthermore, pixel-wise cooling rate maps highlighted substantial spatial heterogeneity across the hand surface. Numerical bioheat simulations confirmed that blood perfusion and skin plate contact conductance are key factors governing the cooling response. These findings demonstrate the potential of dynamic infrared thermography as a non-contact tool for assessing peripheral thermoregulation and vascular function during controlled cooling experiments.
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All authors Pengfei Zhu, Hai Zhang, Stefano Sfarra, Clemente Ibarra-Castanedo, Manyi Zhu, Guoqing Ren, Stefano Sfarra, Xavier Maldague
Applied Physics · Cross-listed from q-bio.SC
The Origins of Transient Bimodality
Kaan Öcal, Augustinas Sukys, Aanjaneya Kumar et al. (+1 more)
Many dynamical systems exhibit diverse modes of behavior. In biology, such modes can represent individual or
cell fates. While the emergence of multimodality is commonly studied, transient bimodality is much less well understood. Under transient bimodality, a system moving from a well-defined initial to a final state transiently undergoes a bifurcation into multiple probability modes. This noise-driven phenomenon can significantly impact processes such as
cell differentiation and speciation in the presence of changing environmental conditions. We detail a theoretical approach for understanding transient bimodality connecting results from ecology, optics, chemical reaction networks and
cell biology, propose a “minimal model” of transient bimodality and derive a general criterion for its presence. We show that fast-to-slow dynamics can lead to transient bimodality in addition to the well-known case of slow-to-fast dynamics. Finally, we discuss the role of transient bimodality across the scientific literature, with emphasis on biochemical kinetics and gene regulation.
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All authors Kaan Öcal, Augustinas Sukys, Aanjaneya Kumar, James Holehouse
Optics
Robust Fano-like Antiresonances in Large-Area Au-coated Ag-Nanoisland Ensembles
Valeria Nocerino, Francesca Di Carlo, Bruno Miranda et al. (+3 more)
We report robust Fano-like spectral profiles in substrate-supported Au-coated Ag nanoislands fabricated by solid-state dewetting followed by Au overgrowth. Combining electrostatic modal analysis, full-wave simulations, and linear transmission spectroscopy, we investigate the origin of these profiles, their tunability, and their robustness against morphological disorder. Increasing the Au coating thickness progressively red-shifts the low-energy resonance and transfers spectral weight to it from the high-energy resonance, whereas the Fano-like antiresonant dip undergoes a limited spectral displacement. The electrostatic modal analysis identifies this dip as the signature of destructive interference between superradiant and subradiant hybridized modes, and its weak spectral
evolution is consistently reproduced by theory, simulations, and experiments. These results establish Au-coated Ag nanoislands as a scalable, lithography-free platform for engineering robust yet tunable Fano-like optical responses accessible through standard far-field spectroscopy.
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All authors Valeria Nocerino, Francesca Di Carlo, Bruno Miranda, Luca De Stefano, Principia Dardano, Carlo Forestiere
Astrophysics of Galaxies
Fragmentation of massive clumps: constant mass fraction and growing mass inequality of cores
Zu-Jia Lu and Qi-Tian Chen
The fragmentation of massive molecular clumps into dense cores sets the initial conditions for
stellar clusters, yet how core mass distributions evolve remains unclear. Using the ALMAGAL survey (1,013 clumps and 6,348 cores), we analyze the Gini coefficient of core mass distributions for the 514 clumps containing at least four cores ($N_{\rm frag} \ge 4$), which host 5,728 cores in total. We find that the most massive core consistently accounts for $\sim 38\%$ of the total core mass ($f_{\rm core,max} \approx 0.38$), with no systematic trend with the total mass of the core per clump $M_{\rm core,tot}$. The Gini coefficient increases with total core mass ($M_{\rm core,tot}$, $r=0.55$) and evolutionary stage ($L/M$, $r=0.38$). Clumps with $L/M > 6.0$ have significantly higher Gini values (median $0.62$) than those with $L/M \le 6.0$ (median $0.49$; $p = 4.23\times10^{-15}$). These results demonstrate that while the mass fraction of the most massive core is constant, overall mass inequality among cores grows systematically as clumps evolve.
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Optics
Bridging Relativistic Twisted Fermion Beams and Photonic OAM Flux in Gauged Hopf Lattices: Emergent Topological Analogs
Aaron Michael Kinder
Recent work has demonstrated non-diffractive topological
spin textures (Skyrmion- and meron-like) that persist in the core of diffracting relativistic twisted
fermion beams [1]. Here we present numerical simulations of an analogous photonic system: Laguerre-Gaussian (LG) twisted
photon packets coupled to a gauged
Hopf lattice with discrete flux flywheels. Our results reveal emergent behavior of the same qualitative class, including persistent core features under propagation, mean survival approx 0.150 at critical lambdat = 2 clustering tightly with the mystery scale e^{-2} approx 0.1353 and residual R approx 0.1375, golden-angle correlations in the OAM mode ladder, and topological residuals with long-lived structure. Multi-l simulations further exhibit z-resolved flux transfer and twist dynamics that play a role analogous to probability-current continuity in the fermionic setting. These findings suggest photonic platforms as accessible analogs for exploring topological textures in structured waves, and they formalize a concrete computational bridge between relativistic twisted matter waves and topological photonics.
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Earth and Planetary Astrophysics
The Polana-Eulalia Complex with JWST NIRSpec: Connections to Bennu, Ryugu, and Outer Solar System Bodies
Lucas McClure, Joshua Emery, Driss Takir et al. (+8 more)
Carbon rich [C complex] asteroids provide insight into the early
Solar System, and families of C complex asteroids serve as robust samples for learning about the internal structure of planetesimals and the materials of the protoplanetary disk. This work investigates the compositions of asteroids within the Polana Eulalia Complex [PEC] through analyses of JWST NIRSpec. Obtained as part of the Spectral Analysis of Main Belt Asteroids in the 3 um Region [SAMBA3] project. NIRSpec observations were conducted for the namesake asteroid of the Eulalia family, [495] Eulalia, as well as three members from the Polana family: [2441] Hibbs, [6712] Hornstein, and [6769] Brokoff. Analyses of the 2.7 um region demonstrate that PEC asteroids exhibit absorptions associated with Mg rich phyllosilicates, in turn underscoring high, though incomplete, degrees of aqueous alteration in the past for both PEC families. Although consistent in regard to composition, [142] Polana and [495] Eulalia show deeper 2.7 um bands than the Polana family asteroids, suggesting slight differences in the degrees of aqueous alteration between large and small PEC asteroids. Minor absorptions from 3.0 to 4.0 um indicate that [495] Eulalia's surface may contain more carbonates than [142] Polana, which potentially highlights slight differences between each family's formation and
evolution. Additionally, PEC asteroids also show spectral consistency with Bennu and Ryugu, reinforcing their shared origin in the PEC. Minor absorptions in PEC asteroid spectra also connect to small bodies within and beyond the Main Belt, providing further evidence of outer
Solar System formation for the PEC parent bodies.
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All authors Lucas McClure, Joshua Emery, Driss Takir, Julia de Leon, Mario de Pra, Brittany Harvison, Bryan Holler, Javier Licandro, Tania Le Pivert-Jolivet, Joseph Masiero, Noemi Pinilla-Alonso
Biological Physics · Cross-listed from q-bio.NC
Emergent topological structure in spontaneous brain-organoid activity
Eve Bodnia, Margaux Basart, Sofie Hai et al. (+5 more)
Neural activity is widely held to organize on low-dimensional structure embedded in a high-dimensional state space. Persistent homology reads such structure directly from the pattern of pairwise correlations, without assuming in advance which variables are relevant. We apply persistent homology to microelectrode-array (MEA) recordings of spontaneous activity from human (Lancaster) and mouse (Pasca) cortical organoids, spanning 25-197 sorted units, and ask whether topological data analysis resolves structure at the node counts that neural recordings actually deliver. Building weighted networks in correlation space and characterizing them by Vietoris-Rips filtration, we find that the first homology (H1, loops) rises significantly above a rate- and population-preserving null in 14 of 18
datasets, all of which remain significant after correction for testing 18
datasets. Random removal of neural units leaves the loops largely intact. Removing the units that form the loops disrupts them more than removing equally connected units does. Topological richness grows with network size, and second homology (H2) exceeds the null only in the larger networks. These results show that persistent homology resolves structured
topology in neural recordings at the scale experiments actually deliver.
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All authors Eve Bodnia, Margaux Basart, Sofie Hai, Lenzie Ford, Nina Miolane, Kenneth S. Kosik, Dirk Bouwmeester, Lincoln D. Carr
Quantum Physics
Split-quaternionic structure and canonical quantization of the Bateman dual oscillator
Mathieu Beau
Bateman's dual oscillator embeds a damped harmonic oscillator and an independent anti-damped adjoint coordinate in a conservative doubled system. We develop a split-quaternionic formulation that remains consistent from the classical equations through ordinary complex canonical quantization. The doubled dynamics is written as a two-sided hypercomplex
evolution whose conserved indefinite quadratic form is the split norm, while the sign of the generator square unifies the underdamped, overdamped, and critical regimes. The Bateman Lagrangian is recovered as a real scalar action on the split-complex configuration subalgebra. After quantization, operator-valued split quaternions belong to the complexified
algebra $\mathbb C\otimes_{\mathbb R}\mathbb H_s\simeq M_2(\mathbb C)$. Noncommuting mechanical components require a symmetrized
quantum split norm, which exactly reproduces the symmetrically ordered canonical
Hamiltonian. Null idempotents resolve the crossed canonical structure of the doubled phase space. In particular, damping yields $[m\dot{\widehat y},m\dot{\widehat x}]=\mathrm{i}\hbar m\gamma$ and a Robertson–Schrödinger uncertainty relation. The limit $\gamma\to0$ retains the doubled positive/negative geometry; the ordinary single-oscillator Heisenberg relation is recovered only after selecting the positive normal mode, or by undoubling before quantization. The scalar split action gives the exact quadratic propagator and Gaussian
evolution. A formal trace over the auxiliary coordinate is finally compared with high-temperature Caldeira–Leggett dynamics, clarifying that the doubled model is a coherent zero-noise
embedding rather than a microscopic reservoir theory.
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Strongly Correlated Electrons
Stroboscopic stability of a Floquet chiral spin liquid beyond the folding frequency
Didier Poilblanc
We study the two-step Floquet dynamics of the
chiral $J_1$-$J_2$-$K$ Heisenberg model on the $4\times4$
torus, alternating its non-
chiral Heisenberg part $H_{AF}$ and its
chiral plaquette part $H_K$, at a parameter point where the static model hosts a quasi-degenerate, spectrally isolated
chiral-
spin-
liquid (CSL) topological doublet. The one-period propagator is computed exactly in all
symmetry sectors. Decreasing the frequency, the doublet survives the drive far beyond the frequency $\omega_{res}\simeq 11.5 J_1$ at which folded states first cross it in quasienergy: the time-averaged energy of the Floquet eigenstates, which orders the folded spectrum, shows that the doublet remains the isolated bottom of the spectrum down to $\omega\simeq 6J_1$, while stroboscopic time
evolution over thousands of periods shows no heating for $\omega\gtrsim\omega_{res}$ and only slow absorption below. The quasienergy resonances of the folded regime are invisible in the average energy, identifying them as parametrically weak avoided crossings. We argue that this mechanism, stability controlled by local energy scales rather than by the extensive many-body bandwidth, is of the type expected to survive in the thermodynamic limit, where a prethermal Floquet CSL should persist for $\omega$ above a threshold set by local scales, with heating times exponentially long in $\omega/J_1$, a
conjecture that larger clusters can now test. Consistently, the optimal $D=3$
chiral PEPS of the static problem still describes the driven doublet deep in the folded regime, with an essentially unchanged local tensor. Finally, we show that the drive is realizable on existing
quantum simulators, via an explicit digital pulse sequence of XY-type two-
spin gates on the four bond colours of the square
lattice, with an infidelity of $1.5\times10^{-5}$ per period.
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Plasma Physics
Assessment of 0-D L-H Power Threshold Scaling and Regression Stability in DIII-D with Applied 3D Magnetic Fields
Michael O Hanson, George R Tynan and Dmitri M Orlov
A database of 192 L-H transitions in DIII-D is used to assess the effects of applied three-dimensional (3D)
magnetic fields on the H-mode power threshold and the stability of zero-dimensional (0-D) empirical regressions. The
dataset includes nominally axisymmetric discharges and discharges with resonant or non-resonant
magnetic perturbations. Filtering criteria reduce uncertainties associated with absorbed power, neutral-beam modulation, and fast-ion losses, while applied-field components are quantified using
equilibrium reconstruction and spectral analysis. Measured threshold powers show substantial scatter and systematic deviations from the 2008 ITPA multi-machine scaling, including for discharges without applied perturbations. TRANSP modeling indicates that empirical estimates can substantially underpredict fast-ion losses, particularly at low
plasma current and with non-axisymmetric fields. Adding global 3D-field metrics does not robustly isolate the effects of applied perturbations. A fully unconstrained regression retains a 70% residual root-mean-square error and produces nonphysical parameter dependencies, including a
plasma surface-area exponent of 2.79. Extrapolations to ITER-relevant conditions consequently have broad confidence intervals. These results show that hidden-variable dependencies can strongly affect empirical threshold parameterizations even in a restricted single-machine
dataset. Machine-specific conditions, local edge physics, and power-accounting uncertainties limit the predictive capability of purely 0-D scalings. Improved predictions for ITER and future devices will require better fast-ion-loss treatment and physics-based, edge-localized quantities.
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Quantum Physics
Alex Steiner, Gerard Anglès Munné, Robert Freund et al. (+9 more)
Holography is a central concept at the intersection of
gravity, condensed matter theory, and
quantum information, linking the interior bulk of a system to its boundary. A model realizing key features of
holographic systems is the
holographic pentagon code by Pastawski et al. Here we experimentally implement instances of the
holographic pentagon and heptagon codes with trapped ions and test their properties: For the pentagon code, we recover logical bulk
qubits from their nearby boundary and test the Ryu-Takayanagi
entanglement area law. For the heptagon code, we show that the transversal Hadamard gate native to the constituent Steane codes induces a single-
qubit, correctable error in the
holographic code. Our implementation paves the way towards the use of
holographic quantum codes for
quantum information processing.
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All authors Alex Steiner, Gerard Anglès Munné, Robert Freund, Ivan Pogorelov, Michael Meth, Robert J. Harris, Gavin Brennen, Thomas M. Stace, Thomas Monz, Rainer Blatt, Felix Huber, Martin Ringbauer
Mesoscale and Nanoscale Physics
Observation of Critical Current Minimum in Super-Honeycomb Josephson Junction Arrays
Melissa Mikalsen, Alexander-Georg Penner, Samuel D. Escribano et al. (+5 more)
Superconductor-
semiconductor Josephson junction arrays are a uniquely tunable platform for studying collective
quantum phenomena, particularly in the regime where localized Andreev bound states can hybridize across the
lattice when the physical separation between adjacent junctions is smaller than their coherence length ($\xi_{\text{ABS}}>d_{\text{JJ}}$). Here, we investigate three distinct Al-InAs Josephson junction arrays: a square array and super-honeycomb array fabricated within this ${\xi_{\text{ABS}}>d_{\text{JJ}}}$ regime, as well as a larger-spacing super-honeycomb control device designed such that $\xi_{\text{ABS}}\lesssim\!~d_{\text{JJ}}$. Under an out-of-plane field, critical current peaks emerge at rational filling factors, reflecting stable
vortex configurations in the
lattices. In the super-honeycomb
lattice,
vortices localize to distinct non-identical plaquettes at different filling factors, as predicted by frustrated XY model simulations. A rotating in-plane field yields periodic critical current oscillations that reflect the Rashba
spin-orbit coupling inherent to the InAs
quantum well. Surprisingly, at $f = 1$, the closely spaced super-honeycomb array exhibits a distinct critical current minimum as the magnitude of the in-plane field increases, a signature absent in the square array and large-spacing super-honeycomb array. These results indicate that this signature is jointly influenced by the unique geometry of the super-honeycomb
vortex lattice and by long-range inter-junction hybridization.
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All authors Melissa Mikalsen, Alexander-Georg Penner, Samuel D. Escribano, Nadav Drechsler, Arunav Bordoloi, Jacob Issokson, Yuval Oreg, Javad Shabani
Medical Physics
Theoretical derivation of blood velocity from TOF-MRA based artery centerline
Abrar Faiyaz
Time-of-flight
magnetic resonance angiography (TOF-MRA) is widely used for nonin-vasive visualization of arterial anatomy, but extracting hemodynamics like blood velocity typically requires supplementary phase-contrast scans, tagging or multi-TE images. This study proposes a novel, physics-informed computational framework to extract variable fluid velocity directly from standard TOF-MRA signal profiles. We analytically expand the approach-to-steady-state Bloch equations to include convective flow, establishing a mathematical relationship between the spatial decay of longitudinal magnetization and fluid velocity. The velocity derivation was further extended to pointwise estimation over a 1-D centerline, overcoming the limitations of constant-velocity assumptions. To validate and solve this problem, a MATLAB (R2025b) simulation framework was developed to model fluid flow in two variable-geometry flowing tube cases, i.e., continuous narrowing and focal stenosis, under synthetic scanner noise. A global inverse optimization approach utilizing Dual-Tikhonov regularization was applied to stably invert the ill-posed transit time integral, actively penalizing high-frequency numerical ringing while preserving structural curves. The computational simulations successfully recovered ground-truth point-wise velocities, tracking gradual hemodynamic accelerations and sharp stenotic jets. This theoretical framework and the example centerline TOF-MRA signal intensity pro-vide a robust mathematical proof-of-concept that quantitative, localized functional he-modynamic metrics can be extracted from standard structural MRA imaging, establishing a foundation for advanced flow quantification without requiring additional scan time.
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Applied Physics
Study of GeSn Selective Area Growth with Demonstration of SWIR Light Detection
Hryhorii Stanchu, Quang Minh Thai, Rajesh Kumar et al. (+16 more)
As germanium-tin (GeSn) epitaxial growth quality continuously improves, the search for an efficient integration strategy of GeSn optoelectronics devices into complementary metal-
oxide-
semiconductor (CMOS) manufacturing line also accelerates. Selective area growth (SAG) on patterned substrate emerges as a promising approach for this quest, with locally controlled growth of GeSn
laser/detector suitable for either co-integration with silicon-based waveguide structure or stand-alone module like focal plane array. In this work, we report successful GeSn SAG with Sn content ranging from 3.2% to 8.7% of good optical quality, with demonstration of tunable GeSn SAG photoluminescence and GeSn SAG photoconductor device, the latter with detection cutoff wavelength up to 2 um. In addition, we present a comprehensive study of GeSn SAG condition at different window sizes, from 2 um to 100 um, and shapes: circle, square, octagon, and rectangle. Presence of loading effect is revealed, where GeSn growth rate increases as pattern fill factor and window size shrink. It introduces a different growth condition compared to thin film growth, which can weaken or inhibit Sn incorporation at very small window size and induce Sn segregation in high Sn content SAG growth.
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All authors Hryhorii Stanchu, Quang Minh Thai, Rajesh Kumar, Fernando M. de Oliveira, Kushal Dahal, Xuehuan Ma, Sudip Acharya, Justin Rudie, Alexander Golden, Joshua M Grant, Matthew Cook, Stephen Margiotta, Xiaoxin Wang, Jifeng Liu, Perry C. Grant, Baohua Li, Wei Du, Gregory Salamo, Shui-Qing Yu
Cosmology and Nongalactic Astrophysics
Origin of the Sloshing Spiral in the Abell 2107 Galaxy Cluster
Muhammed K{\i}yami Erdim
We present a detailed thermodynamic analysis of a sloshing spiral discovered in the intracluster medium (ICM) of the
galaxy cluster Abell 2107, based on deep Chandra X-ray Observatory observations. Spectral analysis reveals that the spiral arm is significantly cooler and exhibits lower
entropy and higher
metallicity compared to the surrounding ICM, consistent with an origin in the cool, dense cluster core. We detect three cold fronts at the edges of the spiral, roughly aligned along an east-west axis. This
alignment is consistent with predictions from numerical simulations of off-axis merger events. Subregion analysis of the spiral shows that the coldest and lowest-
entropy gas is concentrated in the central part of the arm, while the side regions show evidence of mixing and interaction with the ambient medium. Among the examined thermodynamic quantities,
entropy provides the most robust contrast between the sloshing gas and its surroundings. Notably, no optical or X-ray counterpart to a potential perturber is detected, suggesting that the responsible perturber may currently be below the detection limit or otherwise difficult to identify, while a dark matter-dominated or dark matter-only subhalo remains one possible scenario. Our findings provide new insights into the dynamical history of A2107 and demonstrate the importance of deep X-ray exposures for revealing subtle ICM structures in apparently relaxed clusters.
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Materials Science
Phase nucleation, coarsening and evolution pathways of a sputtered nanostructured Inconel 725 alloy during heat treatment
Ruqing Cao, Ikponmwosa J. Iyinbor, Andrea M. Hodge et al. (+1 more)
Physical vapor deposition enables the fabrication of nanostructured superalloys with unique defect architectures, yet their phase
evolution pathways can differ significantly from those of conventionally processed
alloys. In this study, the effects of solution and aging treatments on phase selection and precipitation behavior in sputtered Inconel 725 films with an initially uniform columnar nanotwinned structure were systematically investigated. Direct aging at relatively low temperatures promoted extensive {\delta}-phase precipitation at twin boundaries and defect-rich regions, which depleted Nb from the {\gamma}
matrix and suppressed {\gamma}'/{\gamma}" precipitation. In contrast, high-temperature solution treatment induced recrystallization and eliminated the nanotwinned structure, significantly reducing {\delta}-phase precipitation and increasing Nb availability to enable the formation of ultrafine spherical {\gamma}'/{\gamma}" precipitates within a refined {\gamma}
matrix (<1 {\mu}m). Subsequent aging treatments promoted elemental partitioning and drove the morphological
evolution of {\gamma}'/{\gamma}" precipitates from spherical to lenticular forms, while {\delta} precipitation became increasingly concentrated along grain boundaries. This spatial separation of intragranular {\gamma}'/{\gamma}" and grain-boundary {\delta} phases enabled simultaneous precipitation strengthening and grain stabilization, resulting in hardness values approaching 9 GPa. As a whole, this study demonstrates that the initial templates provided by defect structures can govern phase selection and precipitation pathways, providing a strategy for tailoring microstructure and achieving synergistic strengthening in nanostructured superalloys.
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All authors Ruqing Cao, Ikponmwosa J. Iyinbor, Andrea M. Hodge, Timothy J. Rupert
Medical Physics
Continuous 3-D Latent Diffusion for Medical Image Generation and Reconstruction
Youness Mellak, Antoine De Paepe, Dimitris Visvikis et al. (+1 more)
High-resolution three-dimensional (3-D) medical latent
diffusion remains limited by the cost of decoding full volumes, which existing latent autoencoders (AEs) handle through overlapping sub-volume decoding. We propose a continuous 3-D latent
diffusion model framework for computed
tomography (CT) and
magnetic resonance imaging (MRI) generation and measurement-guided reconstruction, built on a coordinate-rendering autoencoder (CoRe-AE). Its decoder applies its convolutional stage once on the compact latent grid and renders voxel intensities from spatial coordinates through a lightweight implicit head, evaluated in
memory-bounded chunks. This design avoids overlapping sub-volumes and remains differentiable with respect to the latent, so that the decoder can be used inside measurement-guided reconstruction. The framework was evaluated on CT volumes of 512\textsuperscript{3} voxels and MRI volumes of 256\textsuperscript{3} voxels. At 512\textsuperscript{3}, the decoder was 4–18 times faster than the MAISI and 3D MedDiffusion AEs and required the lowest peak graphics processing unit (GPU)
memory, including when its gradient was computed. CoRe-AE also achieved the highest peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) among the evaluated AEs on both modalities. The resulting frozen 3-D latent prior generated full volumes without patch seams and, without retraining, reconstructed sparse-view CT and accelerated MRI through hard data consistency, within 2.4–4.9 dB PSNR of the pixel-domain decomposed
diffusion sampler (DDS). A single volumetric latent prior thus supports both generation and reconstruction of high-resolution medical volumes on one GPU. Our code and pretrained weights are available at https://github.com/Mellak/continuous-3d-latent-
diffusion.
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All authors Youness Mellak, Antoine De Paepe, Dimitris Visvikis, Alexandre Bousse
Fluid Dynamics
On the collapse of three point vortices on surfaces
Theodore D. Drivas, Boris A. Khanikati and Valeriya A. Khanikati
Point
vortices represent an important reduced model describing two-dimensional ideal fluid dynamics. It is well known that there exist three-
vortex configurations on the Euclidean plane $\mathbb{R}^2$ that exhibit finite-time singularities, i.e., collapse to a single point. Moreover, in $\mathbb{R}^2$, such collapses occur only self-similarly. Here, we investigate the extent to which this phenomenon persists on curved surfaces. We show that self-similar collapse is a universal feature of surfaces of nonnegative constant
curvature, namely the plane and the sphere. In contrast, on the
hyperbolic plane, it is shown that self-similar collapsing solutions do not exist with respect to any distance variable defined by an analytic function of the geodesic distance. Finally, we establish the existence of nearly self-similar collapse of three
vortices on arbitrary smooth surfaces embedded in $\mathbb{R}^3$.
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Materials Science
Instability-Avoiding Active Learning for Cluster Expansions in Complex Multielement Materials
Michael J. Waters and James M. Rondinelli
The high efficiency of cluster expansions make them appealing for studying chemical disorder in complex composition spaces such as in multi-principal element
alloys (MPEAs). Several works have attempted to address the rapidly growing training cost with number of chemical species through active learning, transfer learning, and chemical
embedding. However, many composition spaces have large regions where the host
lattice becomes dynamical unstable, which are often avoided a priori so as to not generate expensive but inapplicable training data. Here, we demonstrate a procedure for integrating stability classification within an active learning workflow to autonomously avoid calculations for unstable structures. Our workflow augments the stability classification procedure with Mahalanobis distance-based structure selection to ensure model robustness by training set diversification. We
benchmark our methods by training a cluster expansion for the complex FCC MPEA spanning the Ni-Fe-Cr-Al-Ti-Si
alloy space, in which only Ni and Al are thermodynamically stable as FCC
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Nuclear Theory
Wounded parton scaling of multiplicities in ultra-relativistic light- and heavy-ion collisions
Rupam Samanta, Piotr Bozek and Wojciech Broniowski
Multiplicities of charged particles produced in O+O, Ne+Ne, Xe+Xe, and Pb+Pb collisions at $\sqrt{s_{NN}} \sim 5$~TeV are studied in a uniform way within a wounded parton Glauber framework with overlaid negative binomial fluctuations. In this model, the nucleon's inelastic interaction is modeled via its constituent partons, whose number is a parameter, with best description obtained with four partons per nucleon. We fit directly the experimental multiplicity distributions (histograms), using the same model parameters for each reaction. The fit is performed in the c=1–80 $\%$ centrality range. Avoiding the most peripheral events makes the method insensitive to the normalization issues caused by the difficulty in separating the Coulomb interactions, whereas the most central collisions may involve a different particle production mechanism. We find a proper model description of multiplicity distributions across all the studied systems for $c \lesssim 1\%$.
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Materials Science
Bond reconstruction and vacancy clustering in monolayer silicon carbide from first principles
Péter Udvarhelyi
Bond reconstruction in vacancy-related structures affects their formation energies,
symmetries, and electronic and optical properties. Using density functional theory, we investigate bond reconstruction mechanisms of monovacancies and vacancy aggregates in monolayer silicon carbide. Multiple bond descriptors reveal that isolated monovacancies undergo both in-plane reconstruction and out-of-plane distortion, which together shape their stability and electronic structure. For compact vacancy aggregates, we show that bond reconstruction acts as a key stabilization mechanism. However, in carbon monovacancy, reconstruction suppresses optical activity. In contrast, a highly stable aggregate composed of three carbon vacancies surrounding a silicon vacancy emerges as a promising infrared color-center candidate, combining a triplet ground state with a favorable Debye-Waller factor of the emission. These results highlight the role of bond reconstruction in defining the
quantum properties of vacancy defects in two-dimensional silicon carbide.
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Chaotic Dynamics
Integrability-breaking phase transitions in stadium-like billiards
Anne Kétri P. da Fonseca and Edson D. Leonel
We investigate integrability-breaking transitions in two classes of stadium-like billiards with
parabolic boundaries. While focusing boundaries generate a mixed phase space in which regular islands coexist with a chaotic sea, dispersing boundaries produce a fully chaotic phase space for any finite boundary deformation. By analyzing the scaling behavior of the roughness $\omega$, we identify two qualitatively distinct transitions: a continuous transition for the focusing geometry and a first-order transition for the dispersing one. We determine the corresponding critical exponents and establish the associated scaling laws. For the continuous transition, we further provide a complete characterization within the framework of critical phenomena by identifying the broken
symmetry, the order parameter and its diverging susceptibility, the elementary excitations responsible for chaotic
diffusion, and the topological defects governing transport. These results establish a statistical-mechanics framework for describing integrability-breaking transitions in
Hamiltonian billiards and suggest that the concepts of critical phenomena naturally extend to deterministic nonlinear dynamical systems.
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Statistical Mechanics
Representation-Dependent Machine Learning of the Isotropic-Nematic Transition in the Lebwohl-Lasher Model
Maninder Kaur, Aojie Xue and David P Landau
Machine-learning detection of phase transitions depends not only on the learning
algorithm, but also on whether the input representation preserves the
symmetries of the system. We examine this for the weak first-order isotropic–nematic transition of the three-dimensional Lebwohl–Lasher model, whose apolar and continuously degenerate nematic phase makes raw molecular configurations a challenging input for unsupervised learning. Principal component analysis (PCA) and a convolutional autoencoder (CAE) fail to identify the transition from raw configurations because rotationally equivalent nematic states can appear far apart in the input space. When the same configurations are transformed into a rotationally invariant local-correlation representation, both methods recover transition-sensitive signatures and bimodal coexistence distributions. A supervised three-dimensional convolutional neural network (CNN), by contrast, accurately predicts the scalar order parameter from raw configurations when given order-parameter labels. The Lebwohl-Lasher model therefore separates unsupervised phase discovery from supervised order-parameter regression and shows that
symmetry-respecting input representations are needed for unsupervised machine learning in orientationally ordered systems.
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Optics
Measuring the dipole phase of Bloch-trajectory harmonics using a monolithic interferometer
Mohanad Awad, Julian Späthe, Paramjit C. Yadav et al. (+10 more)
Uncovering the dipole phase of gas-phase high harmonic generation was instrumental to understanding the recollision physics underlying attosecond pulse generation. Corresponding measurements in the condensed phase have not yet yielded a consistent picture. Here, we present a compact and inherently stable approach to high-harmonic interferometry in thin-film solids. We employ it to reveal the dipole phase of high-harmonic generation in polycrystalline ZnO, driven by broadband mid-IR
laser pulses. We demonstrate that, under the conditions of our experiments, recollisions facilitated by Bloch oscillations represent the dominant contribution to high-harmonic generation just above the bandgap.
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All authors Mohanad Awad, Julian Späthe, Paramjit C. Yadav, Mandakini Bhat, Zsolt Divéki, Eric Cormier, Bálint Kiss, Eszter Baradács, János Tomán, Zoltán Erdélyi, Thomas Siefke, Adrian N. Pfeiffer, Matthias Kübel
Chemical Physics
Stochastic Resetting: A Non-Equilibrium Framework for Prediction, Inference and Design
Tommer D. Keidar, Sagi Meir, Nir Sherf et al. (+4 more)
Stochastic resetting has evolved from a simple model of diffusive search acceleration into a general framework for predicting, inferring, and controlling
stochastic dynamics far from
equilibrium. Its defining features, i.e., the creation of non-
equilibrium steady states and the acceleration of first-passage kinetics, are increasingly relevant across physical chemistry, from biological restart mechanisms to molecular simulations and colloidal experiments. We review the renewal theory underlying
stochastic resetting and show how it enables prediction of reset dynamics from properties of the underlying process, while also allowing the latter to be inferred from the resetting-accelerated dynamics. We then discuss applications to state preparation, enhanced sampling, kinetic inference, and training and sampling of machine learning models. Finally, we review recent advances in adaptive resetting, environmental feedback, many-body dynamics, and thermodynamic costs of resetting. These developments establish new opportunities for controlling
stochastic dynamics with resetting across theory, simulations, and experiments.
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All authors Tommer D. Keidar, Sagi Meir, Nir Sherf, Rémi Goerlich, Shlomi Reuveni, Yael Roichman, Barak Hirshberg