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Physics

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Monday 5 October

Soft Condensed Matter

Domain of Applicability of the Distorted Wave Born Approximation (DWBA): A Critical Analysis for X-ray and Visible-Light Interface Scattering

Reinhard Sigel

The Distorted Wave Born Approximation (DWBA) is established for X-ray interface scattering, yet its domain of applicability has never been stated explicitly. The DWBA implicitly rests on the small refractive index deviation (SRID) condition - satisfied by X-rays ($|n-1| \sim 10^{-6}$) but violated by visible light ($|n-1| \sim 0.5$). The DWBA mixes microscopic and macroscopic Maxwell equations, whereas a rigorous optical theory must be built on the macroscopic Maxwell equations and constitutive relations. Rigorous alternatives for two specific inconsistencies in the standard DWBA are discussed. The Extended Transfer Matrix Approach (ETMA) for visible-light interface scattering is outlined.
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Computational Physics

A Gauge-Inspired Coupled Fokker–Planck System for Multistate Stochastic Dynamics: Formalism and 1-D Numerical Implementation

Francesco Pio De Cosmo, Gianluca Di Natale and Leandro Cieri

Extending the Fokker–Planck equation to a coupled system of equations through non-Abelian symmetry groups offers a powerful theoretical framework for coupled multi-state stochastic systems. However, translating this abstract gauge field formulation into viable numerical predictions remains an unaddressed challenge. Motivated by our previous work on ice crystal habit evolution, in this work we bridge this gap by presenting the first numerical solver for an SU(2) gauge-coupled Fokker–Planck system in (1+1) dimensions. Using an operator-splitting scheme combined with a non-oscillatory advection solver, our algorithm strictly ensures probability conservation, non-negativity, and numerical stability. We demonstrate that non-Abelian gauge coupling acts as a cross-reactive feedback loop that fundamentally alters system dynamics, driving continuous probability exchange between states, suppressing localised density peaks, and forcing long-time spatial delocalisation. Validated across linear and quadratic coupling regimes up to strong interactions (g <= 1.0), this work establishes the foundational computational infrastructure needed to integrate complex multi-state physics. Overall, while our approach provides a key step toward improving ice cloud representation in atmospheric and climate models, the underlying physical framework and computational engine remain fundamentally general and multidisciplinary, offering a versatile paradigm for any domain requiring coupled multi-state stochastic equations.
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Fluid Dynamics

A semi-infinite hydraulic fracture propagating in a poroelastic medium

Evgenii Kanin, Andreas Möri, Dmitry Garagash et al. (+1 more)

We solve the near-tip coupled hydromechanical problem of a hydraulic fracture propagating in a permeable poroelastic medium, represented locally as a semi-infinite crack moving at constant velocity. In the moving tip frame, all fracture fields are steady. The porous solid obeys linear poroelasticity, fracture propagation follows LEFM, fluid flow within the tensile fracture is governed by lubrication theory, and the fracturing and pore fluids are treated as identical Newtonian liquids. The primary unknowns are the fracture opening and the fluid displacement function along the fracture, determined from the resulting non-linear system of equations. In a viscosity–toughness scaling, the problem depends on four dimensionless parameters: a dimensionless permeability $\varrho$ (associated with the intensity of fluid leak-in), a dimensionless effective confining stress $\Sigma_0'$ (measuring the relative importance of fluid leak-off and leak-in), the drained–undrained Poisson's ratio contrast $\beta$, and the poroelastic stress coefficient $\eta$. The solution evolves from a drained, toughness-dominated near-tip asymptote with uniform net pressure to an undrained, storage-viscosity-dominated far-field asymptote. Numerical solutions are obtained over parameter ranges representative of various rock types. The fully coupled model is compared with simplified models, namely uncoupled and one-way coupled formulations, over distances from the fracture front spanning laboratory-to-field scales. The resulting relative difference maps in the $(\varrho,\Sigma_0')$ parameter space identify four characteristic regimes: negligible poroelastic effects, dominance of the direct mechanical poroelastic response, importance of the poroelastic backstress, and a fully coupled regime. The latter occurs mainly at large $\varrho$ and small $\Sigma_0'$, corresponding to strong leak-in relative to leak-off.
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All authors Evgenii Kanin, Andreas Möri, Dmitry Garagash, Brice Lecampion

Mesoscale and Nanoscale Physics

Real-Space Interference from Quantum Metric

Bo-Qing Wu, Xing-Lei Ma, Jin-Xin Hu et al. (+2 more)

Real-space interference of wave packets is governed by their central momentum separation and momentum width, which set the oscillation wavelength and spatial envelope, respectively. Here, we show that in crystalline systems, quantum metric distribution in an isolated band can similarly give rise to real-space interference through the evanescent tails of a localized bound state. The location and width of a quantum metric hot spot in the momentum space set a complex wavevector as one evanescent plane wave component of a bound state. Consequently, with multiple quantum metric hot spots, the density distribution of a bound state or the total density of two spatially overlapped bound states exhibits an interference pattern, where the oscillation period and long-range decay length are determined by the momentum-space separation of the hot spots and the width of the narrowest hot spots, respectively. This quantum-geometric interference is particularly pronounced in (nearly) flat bands, where competing scales from band dispersion are suppressed. Furthermore, we demonstrate that using a Josephson STM the real-space interference can be experimentally observed through the tip-position dependence of the Josephson critical current. Our results reveal a direct correspondence between momentum-space quantum geometry and real-space interference, showing how bound-state profiles encode the momentum-resolved quantum metric.
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All authors Bo-Qing Wu, Xing-Lei Ma, Jin-Xin Hu, Jinchao Zhao, K. T. Law

High Energy Physics (Theory)

Gravitational scattering amplitudes in collinear and high-energy limits

Lorenzo Pietrini

In this thesis we study the high-energy and collinear behaviour of gravitational scattering amplitudes and their relation to classical scattering and radiation observables. Multi-Regge kinematics, characterised by a strong rapidity ordering, provides the factorised building blocks governing the leading logarithmic structure. Relaxing this ordering to next-to-multi-Regge kinematics allows two neighbouring particles to have comparable rapidities and provides the real emission building blocks entering at next-to-leading logarithmic accuracy. We extract the next-to-multi-Regge impact factor from tree-level MHV amplitudes for pure gravitons and derive its gravitational splitting functions. We then use BCFW recursion relations to reconstruct the five-point tree amplitude for two massive scalars scattering with the emission of one graviton. Its high-energy limit yields the massive scalar–graviton impact factor and, through the KMOC formalism, a representation of the leading high-energy collinear waveform. Finally, by sewing the relevant vertices across unitarity cuts, we construct the elastic \(H\) kernel, its radiative extension and a classical next-to-multi-Regge kernel. The latter reproduces the standard \(H\) kernel in the multi-Regge limit and the universal Weinberg current in the soft limit.
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Optics · Cross-listed from cs.LG

Targeted search shows that random-device testing underestimates worst-case error in a simulated wave-based neural operator

Samrendra Roy, Jason Yoo, Souvik Chakraborty et al. (+1 more)

Wave-based processors promise fast, energy-efficient Fourier layers for neural operators. They are usually validated on randomly sampled devices, but using them requires knowing how large their error can become under fabrication and alignment variation. In a stylised numerical case study, a hybrid Fourier neural operator runs its four spectral layers on simulated coherent 4f processors with 32 toleranced knobs, whose half-widths are representative rather than calibrated. For 120 models (four tasks, six training methods, five seeds), we compared the worst of N random in-spec devices with a searched one. On a deterministic simulator with one frozen draw of the random static errors, the searched device's held-out error was 1.08-3.10 times the maximum over 200 Monte Carlo devices and 1.06-2.71 times that over 1000. With 20 fresh static draws, it still exceeded the maximum over 200 random devices in 116 of 120 models. Under uniform sampling, the probability of drawing such a device is at most 0.37% per model (two-sided 95% Clopper-Pearson), which says nothing about how large its error is. The gap persisted with uniform or Sobol' sampling at the search's budget, shared knobs, a second crosstalk model, box scales of 0.25-2 and a pixel-level device model. Models trained only with random static errors reached 3.7-39.9 times their nominal error on searched devices, and fine-tuning on random and gradient-searched devices gave the lowest searched error of the six in all 20 task-seed pairs. For two heat-exchanger quantities, a search targeted at each exceeded the worst of 1000 random devices in all 39 models, and hence the Wilks 95/95 limit (worst of 59). For the mean pressure of 11 models, no random device exceeded a 1% error threshold, but the searched device did. Random testing estimates how often errors exceed a threshold; worst-device search gives a lower bound on how large they can be.
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All authors Samrendra Roy, Jason Yoo, Souvik Chakraborty, Syed Bahauddin Alam

Chemical Physics

What Rate Theories Compute: Chemical kinetics from Arrhenius to machine-learned potentials

Rodney S. Ruoff

Major advances in chemical rate theory changed what was computed and what a barrier meant. I organize this conceptual history around those changes, while retaining the controlled corrections and limiting relations between theories. The calculated quantities include an empirical rate constant, a collision count, a thermodynamic activation free energy, a statistical flux across a dividing surface, a stochastic escape rate, an energy-resolved microcanonical rate, a quantum flux correlation function, and an ensemble of reactive paths computed with electronic-structure or machine-learned potentials. I compare the assumptions with the limits stated by the pioneering authors. A rate constant is inferred from measurements under a stated rate law; its temperature dependence defines an apparent activation energy $E_a$. Activation free energy $\Delta G^{\ddagger}$, activation enthalpy $\Delta H^{\ddagger}$, activation entropy $\Delta S^{\ddagger}$, the prefactor, transmission coefficient $\kappa$, and saddle height require a kinetic model and, where relevant, a standard state, dividing surface, ensemble, and dynamical correction for their interpretation in a rate calculation. In hydrogen transfer by soybean lipoxygenase-1, similar single-isotope activation parameters accompany a large change in isotope-sensitive dynamics. Five rate benchmarks illustrate the errors different comparisons test and motivate seven reporting items. These distinctions guide comparisons of rates and interpretations of activation parameters.
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Quantum Physics

X2C-inspired approximation of the Dirac coupling operator in a multiwavelet basis

Quentin Pitteloud, Jacopo Masotti and Luca Frediani

We present a method to obtain the proven exact 2-component (X2C) method, normally applied to Gaussian-type fixed Hilbert bases, in an adaptative non-uniform grid basis of the Hilbert space, namely Multiwavelets. The X2C method manages to block-diagonalise the Dirac Hamiltonian restricted to the subspace of the basis, in an energy-independent manner. The method takes inspiration from the success of the atomic mean-field X2C method on the Gaussian bases to represent the coupling operator as a projector onto the small components of the eigenstates of the constituent atoms of the system.
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High Energy Physics (Theory)

Soft-photon theorem near static spherical horizons in generic dimensions

Kai-Yu Zhang

We study Maxwell theory near a nonextremal bifurcate Killing horizon in a general static, spherically symmetric spacetime of dimension $D>3$. We impose near-horizon boundary conditions in a regular Eddington–Finkelstein chart that retain both radiative and Coulombic data, and construct the associated horizon phase space and large-$U(1)$ charge. At null infinity, the radiative falloff depends on the spacetime dimension and involves half-integer powers in odd $D$, whereas a nonextremal horizon at finite radius supports radiative data with an ordinary integer-power expansion. Expanding the horizon fields in Killing frequency and spherical harmonics, we derive the associated soft-photon relation from the large-$U(1)$ Ward identity. For comparison, we express the flat-space leading soft-photon theorem using the same spherical harmonics and commutator normalization as the horizon modes. In $D=4$, the two relations have the same soft-frequency dependence and the same angular dependence of the hard-charge terms, whereas for $D>4$ the flat-space relation contains additional dimension-dependent frequency and angular factors.
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Atmospheric and Oceanic Physics

The interface of data assimilation and machine learning

Eviatar Bach

Data assimilation (DA) is the process of combining forecasts from a model with observations in order to optimally estimate the state of a system. This is critical for chaotic systems, such as the atmosphere, since if observations are not continually assimilated the model will quickly lose skill. DA is routinely performed (usually every 6 hours) at operational forecasting centres around the world. In this article we discuss the interface of machine learning (ML) and DA. This is still an emerging and quickly developing field, and this article tries to give an overview of some of the main topics and methods.
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Materials Science

Conditions for Altermagnetism in RuO2

Himanshu Mavani, Zhonglin He and Evgeny Y. Tsymbal

The magnetic ground state of rutile RuO2 remains disputed, raising a central question: under what structural and chemical conditions can this material support altermagnetism? We address this question by combining a critical assessment of experimental and theoretical studies with first-principles calculations of epitaxial strain, point defects, doping, and interfaces. Bulk-sensitive measurements reported in the literature are consistent with a nonmagnetic ground state, while magnetic signatures in thin films depend strongly on their structural environment and do not necessarily establish homogeneous altermagnetic order. Our calculations identify substrate-imposed epitaxial strain as the leading factor favoring altermagnetism among the conditions examined and predict several substrate-orientation combinations that stabilize an altermagnetic ground state. Carrier doping and chemical substitution modify this strain-induced magnetism in distinct ways. Uniform hole doping strengthens the magnetic tendency, whereas Ru vacancies provide little benefit and can weaken the magnetic state through local structural distortions. Cr or Mn substitution, by contrast, enhances Ru magnetic moments and further stabilizes the strained altermagnetic phase. These results distinguish the effects of carrier doping from those of local structural and chemical changes and identify concrete routes to realizing altermagnetism in RuO2 films.
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High Energy Physics (Phenomenology)

Neutral Pseudoscalar Mesons, Hadron Light-by-Light Scattering, and the Muon Anomalous Magnetic Moment

Cong-Cong Ye, Yu-Chen Hu, Minghui Ding et al. (+1 more)

Continuum Schwinger function methods\linebreak (CSM) are used to provide estimates of pseudoscalar meson pole contributions - $\mathsf P = \pi^0$, $\eta$, $\eta^\prime$, $\eta_c$, $\eta_b$ - to the muon anomalous magnetic moment. The analysis framework is benchmarked via successful applications to an array of other meson and nucleon properties. It uses the leading order CSM truncation, augmented by a parametrisation of non-Abelian anomaly effects, to deliver an internally consistent treatment of all the pseudoscalar–two-photon transition form factors required to complete such a calculation. Employing those form factor predictions, the following results are obtained (units $10^{-11}$): $a_\mu^{\pi^0} + a_\mu^{\eta} + a_\mu^{\eta^\prime} = 84.3(0.8)$ - a value lower than some other contemporary estimates; $a_\mu^{\eta_c} = 0.82(0.04)$; and a value of $a_\mu^{\eta_b}$ that is negligible. The total contribution is $\sum _{\mathsf P} a_\mu^{\mathsf P} = 85.1(0.8) / 10^{11}$. Our analysis suggests that this pole contribution to $a_\mu$ is still not known with precision better than 5%.
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All authors Cong-Cong Ye, Yu-Chen Hu, Minghui Ding, Craig D. Roberts

Astrophysics of Galaxies

Barium and europium abundances from the Gaia-ESO Survey using The Cannon

Pradosh Barun Das, Francesca Primas, Gayandhi De Silva et al. (+3 more)

Neutron-capture element abundances encode the time-dependent interplay between slow (s-) and rapid (r-) nucleosynthetic processes and provide critical constraints on Galactic chemical evolution. In particular, barium and europium provide important tracers of s-process and r-process nucleosynthetic enrichment, respectively. Large spectroscopic surveys enable robust statistical studies of these elements; however, determining reliable elemental abundances at intermediate spectral resolution remains challenging. Our aim was to derive homogeneous and statistically well-characterised stellar parameters and chemical abundances of Ba and Eu (hereafter collectively referred to as stellar labels) for the Gaia-ESO Survey HR15N dataset. We applied The Cannon to 36,263 FLAMES/GIRAFFE HR15N spectra (R~19,200), using a model trained on 782 stars with high-quality reference stellar labels drawn from the Gaia-ESO DR5 homogenised catalogue. The model infers Teff, log g, [Fe/H], v sin i, A(Ba), and A(Eu); its reliability was quantified through multi-dimensional quality flags and detection strength of the Ba and Eu features. Our final catalogue contains stellar parameters for 36,263 spectra, with ~21,000 and ~400 reliable Ba and Eu abundances, respectively, satisfying multiple flagging criteria. We obtained median uncertainties of ~38 K in Teff, ~0.08 dex in log g, ~0.04 dex in [Fe/H], ~0.06 dex in A(Ba), and ~0.02 dex in A(Eu). External validation against the Gaia Benchmark Stars, GALAH DR4, and multiple open clusters shows good agreement across independent reference datasets. The resulting catalogue includes newly determined Ba and Eu abundances that complement those available from previous analyses, thereby enabling investigations of neutron-capture enrichment patterns in open clusters. The model framework can readily be adapted to upcoming wide-field spectroscopic surveys such as 4MOST, WEAVE, and WST.
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All authors Pradosh Barun Das, Francesca Primas, Gayandhi De Silva, Guillaume Guiglion, Daniel B. Zucker, Melissa Ness

Instrumentation and Methods for Astrophysics

The First Decade of Breakthrough Listen

David H.E. MacMahon and Daniel J Czech

Breakthrough Listen (BL), launched in July 2015 with a 10-year, \$100M commitment from the Breakthrough Prize Foundation, is the most comprehensive search for technosignatures ever conducted. This paper reviews the program's first decade from the facilities and instrumentation perspective: the digital backends and data recorders, the signal-processing pipelines, the data archive, and the observatory partnerships that made the science possible. We organize the decade into three architectural eras. In Generation 1 (2016--2019), BL deployed packetized raw-voltage wideband recorders on the 100-m Green Bank Telescope and the 64-m Parkes telescope, enabling targeted surveys of thousands of nearby stars across $\sim$0.7--8 GHz. In a network-expansion phase (2020--2023), BL extended its instrumentation to partner facilities including the Sardinia Radio Telescope and international LOFAR stations, and developed verification frameworks that proved essential when the program's highest-profile signal candidates emerged. Since 2023, BL has operated in a fully commensal era: Ethernet-based, commodity-GPU backends riding on routine observatory operations: COSMIC at the Karl G. Jansky VLA, a revived Allen Telescope Array with deployed real-time deep-learning pipelines, and an autonomous multi-beam commensal survey at MeerKAT (BLUSE; $>$1.2 million pointings since mid-2022). Over the decade, capturing data at ever higher rates forced a systematic approach to compression and archiving; the storage estate grew to $\sim$42 PB of capacity ($\sim$31 PB in use) across seven systems on four continents by March 2026. We conclude with engineering lessons (commodity hardware over bespoke hardware, open data as a first-class requirement, commensal science as backend validation, and verification frameworks built before they are needed) and with the outlook for SKA-era commensal technosignature science.
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2610.07482 · 5 Oct · Keynote paper (Rudolf Pesek Lecture), 55th IAA Symposium on the Search for Extraterrestrial Intelligence (SETI), Session A4.1 "SETI Science and Technology". Presented at the 77th International Astronautical Congress (IAC 2026), Antalya, Türkiye, 5-9 Oct 2026; to appear in the IAC proceedings. 11 pages, 2 figures, 2 tables

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Solar and Stellar Astrophysics

High-Angular-Resolution Survey of Stars within 18 pc of the Sun: Part I

F. Carolina Rojas-Galindo, Valeri G. Orlov, Rene A. Mendez et al. (+1 more)

We present the rationale, design, methodology, and observational facilities of a high-angular-resolution imaging survey of stars within 18~pc of the Sun. Our comprehensive sample consists of 2047 stars compiled from Gaia eDR3 and complementary catalogs. The main goal is to observe as many stars from this sample as possible using high-angular-resolution techniques, considering their inherent limitations, to perform astrometry of known binary systems and determine detection limits for secondary components for each observed star. This approach may also allows us to identify previously unresolved stellar companions. Observations were carried out using the 2.1-m telescope at OAN-SPM in the North and the 3.58-m NTT in the South, employing high-speed cameras for speckle imaging. We obtained observations of 703 stars with V < 14 mag at OAN-SPM, and 645 stars with I < 16 mag at the NTT, of which 140 stars were observed in both hemispheres, for a total of 1208 unique stars observed. In this paper: (1) we present the construction of the catalog of 2047 stars within 18 pc; (2) using a control sample of 70 known close binaries within 18 pc with separations 1", we show that selecting targets based on Gaia quality parameters commonly used as binarity indicators–RUWE, ipd_frac_odd_win, and ipd_frac_multi_peak–can miss a significant fraction of binaries, justifying our unbiased, volume-limited survey; and (3) we present the results of pilot observations conducted with the 2.1 m telescope at OAN-SPM in July 2022. A full analysis of the complete sample will be presented in of forthcoming papers.
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All authors F. Carolina Rojas-Galindo, Valeri G. Orlov, Rene A. Mendez, Wolfgang Brandner

Astrophysics of Galaxies

The Rogue One: A Dark Matter-Dominated Dwarf in the Trail of Dark Matter-Deficient Galaxies

Daniel Vaz, Arsen Levitskiy, Duncan Forbes et al. (+6 more)

We present the first measurement of the stellar velocity dispersion of LEDA 4014647, a compact dwarf galaxy spatially aligned with the NGC 1052 trail, a linear chain of dark matter-deficient galaxies (DMDGs) proposed to have formed in a single high-speed dwarf$-$dwarf collision $\sim 8$ Gyr ago. Using integral-field spectroscopy obtained with the Keck Cosmic Web Imager (KCWI), we measure a stellar velocity dispersion of $\sigma = 15.8 \pm 2.0$ km s$^{-1}$ within the half-light radius ($R_\mathrm{e}$). We derive a dynamical mass within the 3D half-light radius of $M_\mathrm{dyn}(<r_{1/2}) = (1.5 \pm 0.4) \times 10^8\,M_\odot$, a factor of $\sim 3$ larger than the enclosed stellar mass, implying a DM fraction of $f_\mathrm{DM} = 0.7 \pm 0.1$ at $r_{1/2}$. Full-spectrum stellar population fitting yields an old ($t \approx 13$ Gyr) and metal-poor ($[\mathrm{M/H}] \approx -1.2$ dex) stellar population, consistent with independent photometric estimates and predating the proposed collision epoch. LEDA 4014647 is therefore a DM-dominated system, and cannot have formed from the DM-free, shock-compressed gas that produced the proposed trail DMDGs DF2, DF4, and DF9. Its nature, however, remains an open question: while a chance-projection along the trail axis is a possible explanation, its old stellar population, compact morphology, and DM content are also consistent with the surviving collisionless remnant of one of the progenitor dwarfs of the dwarf$-$dwarf collision. Distinguishing between these two scenarios will ultimately require deeper spectroscopy to tighten the stellar population and DM halo constraints, and targeted $N$-body and hydrodynamical simulations tracking the post-encounter fate of the progenitors.
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All authors Daniel Vaz, Arsen Levitskiy, Duncan Forbes, Aaron J. Romanowsky, Jonah Gannon, Jean P. Brodie, Yimeng Tang, Kenji Bekki, Warrick J. Couch

Astrophysics of Galaxies

Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) III. CH$_3$OH isotopic fractionation in the low-mass protostar BHR71-IRS1

A. Coutens, F. Cruz-Sáenz de Miera, J. K. Jørgensen et al. (+26 more)

[Abridged] Methanol is a complex organic molecule detected in both ice and gas toward star-forming regions. Due to its high abundance, its rarer isotopologues, including the deuterated ones, are also commonly detected. Our aim is to determine the column density and deuterium fractionation of methanol in the low-mass protostar BHR71-IRS1. We analyzed data from a large spectral survey of BHR71-IRS1 carried out as part of the ALMA Large Program Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS). We used the CASSIS software to identify the lines of the methanol isotopologues and constrain their column densities under the assumption of local thermodynamic equilibrium. We detected CH$_3$OH, $^{13}$CH$_3$OH, CH$_3$$^{18}$OH, CH$_3$OD, CH$_2$DOH, CHD$_2$OH, and CD$_3$OH at the continuum peak position. In addition, CH$_3$$^{17}$OH is tentatively detected, while CD$_3$OD is not detected, although a few faint lines could be present toward a position redshifted from the continuum peak. The column densities of the main isotopologue obtained from $^{13}$CH$_3$OH and CH$_3$$^{18}$OH are consistent, assuming nominal $^{12}$C/$^{13}$C and $^{16}$O/$^{18}$O ratios of 68 and 557, respectively. The CH$_2$DOH/CH$_3$OD column density ratio is equal to 7$\pm$2. The statistically corrected D/H ratio is higher for CH$_2$DOH (1.9$\pm$0.6 %) than for CH$_3$OD (0.8$\pm$0.2 %). The level of deuteration after statistical correction increases with the number of D atoms in the methyl group, reaching 23$\pm$5 % for CD$_3$OH/CH$_3$OH. These trends are similar to other low-mass protostars such as IRAS~16293–2422 and HOPS 373SW, but seem to differ from the eruptive young star V883-Ori. Similar studies with comparable datasets will be carried out for the other COMPASS sources to determine if factors such as environmental conditions and evolutionary states impact the deuteration of methanol.
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All authors A. Coutens, F. Cruz-Sáenz de Miera, J. K. Jørgensen, M. N. Drozdovskaya, J.-E. Lee, A. L. Plunkett, D. Harsono, S. Maret, A. Belloche, J. Ferrer Asensio, M. L. R. van't Hoff, J.-H. Jeong, Á. Kóspál, B. A. McGuire, P. Nazari, S. Spezzano, Z. Telkamp, Y.-L. Yang, H.-S. Yun, S. Zeng, A. Andreu, J. Bergner, C.-H. Kim, N. F. W. Ligterink, Y. Lin, S.-Y. Liu, M. Lützen, P. Marchand, M. Rao

Mathematical Physics

Conformal invariance of the six-vertex model's height function

Emile Averous, Hugo Duminil-Copin, Tiancheng He et al. (+2 more)

In this paper, we show that the height function of the six-vertex model in simply connected domains with piecewise constant boundary conditions converges to the Gaussian Free Field (GFF) with Dirichlet boundary conditions. This implies the conformal invariance of the scaling limit of the model. The argument relies on the full plane GFF convergence combined with Reflexion Positivity and qualitative estimates. The proof works for a wide range of spectral parameters $\Delta$ (among which $\Delta$ close to $0$, and between $-1$ and $-1/2$) making this paper the first instance of a conformal invariance result for a continuum of models. The paper has consequences for other models, including the FK percolation with cluster-weight $q=4$ and the Ashkin-Teller model, which we will pursue in future work.
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All authors Emile Averous, Hugo Duminil-Copin, Tiancheng He, Piet Lammers, Ioan Manolescu

Astrophysics of Galaxies

Life in the Cosmic Neighbourhood: Galactic Habitable Zones in the EAGLE Simulations

Luke A. Barnes, Geraint F.Lewis, Jaime Salcido et al. (+3 more)

When and where is life most likely to form in the universe? We use the EAGLE cosmological hydrodynamical simulations to investigate the prevalence and properties of life-friendly cosmic environments on galactic scales. Our model for the occurrence of observers depends on main-sequence stars, the production and distribution of metals, and the formation of habitable planets. We also take into account five potentially life-extinguishing processes: core-collapse supernovae, Type Ia supernovae, star-star interactions, gamma ray bursts and quasars. We characterise the amount of time that the universe creates on habitable planets per unit mass of baryons and stars in the universe, as a function of galaxy mass and galactocentric distance. As expected, early universe, newly formed, high star formation rate galaxies are the most dangerous. The present-day Milky Way is typical of habitable galaxies: efficient creation of habitable time, and low probability of cosmic catastrophes.
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All authors Luke A. Barnes, Geraint F.Lewis, Jaime Salcido, Pascal Elahi, Miroslav D. Filipovic, Richard G. Bower

Fluid Dynamics

Erasing and Regenerating the Turbulent Cascade Arrow

Yang Zhao, Daocheng Zhou and Hongfu Zhang

Which information tells a turbulent flow which way to cascade? We apply Haar-distributed Hermitian phases that retain prescribed same-mode quadratic information, including modal amplitudes, the energy spectrum, and same-mode two-time correlations. For the phase-Haar ensemble, the expectation of any integrable odd flux functional is zero. Finite ensembles strongly suppress mean transfer and forward-event bias in the primary block. An independent block retains sign separation but fails the scale-8 mean criterion. In matched evolution protocols, nonlinear Navier-Stokes dynamics restores the selected signed-flux scalar close to its natural reference, whereas linear evolution and an amplitude-matched frozen control do not. Flux and a local cubic geometry scalar recover together, yet high local correlation can survive erasure of the arrow. Signed transfer thus requires information beyond the retained quadratic record; the tested nonlinear dynamics rebuilds it.
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Chemical Physics

Coupled cluster theory for multireference and open-shell molecules

Sarai Dery Folkestad and Henrik Koch

We introduce a simple coupled cluster approach for multireference and open-shell systems. In the restricted active space coupled cluster framework, the cluster operator only includes excitations from doubly occupied to virtual orbitals, and this ensures the individual operators commute among each other. The ground and excited states are obtained by diagonalisation of the coupled cluster similarity transformed Hamiltonian in a restricted active space. We demonstrate the framework for the RAS-CCSD model, where single and double excitations are included in the cluster operator, and likewise for a complete active space. We consider systems with multireference character and open-shell systems in a spin-adapted manner. The approach captures significantly more dynamical correlation than without the coupled cluster similarity transformation.
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High Energy Physics (Theory)

Quantum Algorithms for Finding Vacua in the ADK Landscape

Shirabe Endo and Yuta Hamada

We study quantum algorithms for finding a vacuum with a small cosmological constant in the toy model for string Landscape proposed by Arkani-Hamed, Dimopoulos, and Kachru. First, we construct a function-value oracle and use it for Grover search with query complexity $\mathcal{O}(2^{N/2})$, where $N$ is the number of scalar fields. Then, we point out that, by exploiting the linearity of the vacuum energy, the problem can be reduced to a collision problem between two blocks of the bit string. With this structure, we construct two quantum algorithms with query complexity $\mathcal{O}(2^{N/3})$. Compared with the pseudo-polynomial classical algorithm of Denef and Douglas, the quantum algorithms yield a large reduction in computational cost for the physically motivated parameter values.
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Fluid Dynamics

Number Theory of Decaying Turbulence 3: Comparing with Physical and Numerical Experiments

Alexander Migdal and Wei Wang

We compare the predictions of the Euler-ensemble solution of freely decaying incompressible turbulence with simulations and experiments: the scaling function of the energy spectrum, the index of the second-order structure function and the decay laws. The predictions have a fixed shape; only their normalization and scale are fitted. In the final $4096^3$ direct numerical simulations of Rodhiya and Sreenivasan, the turbulent attractor is selected by a parabola law for the growth of the bulk length. Along it the collapsed spectrum depends only on the instantaneous Reynolds number, identically for Saffman and Loitsyansky initial spectra; extrapolated to infinite Reynolds number, it agrees with the theory to 1% in the bulk of the enstrophy range, below the dissipation range. The energy balance holds exactly. The energy integral of the theory diverges in the infrared, so energy and enstrophy depend on how a finite flow cuts off the spectrum: with a sharp cutoff $k_0$, the decay laws, energy $\propto t^{-5/4}$ and enstrophy $\propto t^{-9/4}$, are reached only when the cutoff enters the $k^{-7/2}$ tail of the spectrum. Such a cutoff is only an estimate; the reliable test is the bulk of the spectrum. Fitted to the simulations, the cutoff lies at the lower edge of the bulk, where the spectrum still carries the initial data, and the decay exponents depend on the initial infrared spectrum. In the Max Planck wind tunnel at $Re_\lambda$ up to 5779, the longitudinal index extrapolated to infinite Reynolds number matches the odd ensemble with one scale parameter at large separations, where standard crossover forms fail. The freely decaying turbulent blob of Matsuzawa et al. is too small, too inhomogeneous and too weak to display the attractor. The theory is derived in the first two papers of this series.
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Mesoscale and Nanoscale Physics

Direct synthesis of moiré graphene with twist-tuned hybridization

Seunghyun Park, Daniel T. Larson, Zeyu Hao et al. (+5 more)

Twisted van der Waals (vdW) systems provide a powerful platform for exploring emergent correlated phenomena, including superconductivity, magnetism, and topological phases. The twist angle offers a continuous tuning parameter for modifying the underlying Hamiltonian, however, precise and reproducible control remains challenging. Existing approaches are limited by single-use device architectures, restricted angular precision, or vertical probing geometries. Here we introduce a reconfigurable graphene-based moiré platform in which two independently fabricated layers are mechanically assembled and rotated in situ using a micro-electromechanical system (MEMS). Raman spectroscopy confirms the formation and robustness of the twist-induced moiré potential and enables continuous, deterministic control of the twist angle. The moiré potential folds the electronic band structure and activates the longitudinal optical (LO) phonon mode, allowing us to map its dispersion and directly visualize the moiré momentum. Angle-dependent electronic band hybridization is resolved through the evolution of the double-resonant 2D mode. Near \(0^\circ\), an emergent asymmetry of the \(\Gamma\)-point G-mode phonon reveals phonon band folding and hybridization driven by the moiré superlattice potential and interlayer relaxation. Our platform provides a reproducible Raman reference for twisted bilayer graphene while eliminating device-to-device variability. More broadly, it establishes the twist angle as a deterministically controllable parameter for systematic studies of correlated and topological phenomena in moiré quantum materials.
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All authors Seunghyun Park, Daniel T. Larson, Zeyu Hao, Takashi Taniguchi, Kenji Watanabe, Efthimios Kaxiras, Yuan Cao, Amir Yacoby

High Energy Astrophysical Phenomena

Adaptive proposals for nonparametric equation-of-state inference with RIFT: iterative Gaussian-process refinement in a compressed sequence representation

R. O'Shaughnessy and Z. Zhu

Nonparametric equation-of-state (EOS) inference evaluates the likelihood on a finite ensemble drawn from a prescribed functional prior. Reweighting that ensemble suffices for the binary neutron stars detected so far, and loses effective sample size only once the likelihood concentrates — which needs third-generation catalogues, or extra electromagnetic and nuclear-theory information folded into the same target. We develop and validate an adaptive-proposal procedure that leaves the base prior fixed: data-informed generations are combined by multiple importance sampling and, where that degenerates at large catalogue size, by a calibrated Gaussian projection. We implement it in two representations — a compressed principal-component parametrization of the neutron-star sequence, whose draws need no stellar-structure solve, and a sound-speed parametrization with a differentiable Tolman–Oppenheimer–Volkoff solver — both on a constrained low-density-to-pQCD bridge. Because that anchor, and not the bridge, fixes the low-density prior, we rebuild the ensemble with a crust-plus-chiral-EFT anchor in place of the wide nuclear metamodel: the maximum-mass prior is unmoved, the radius gains a hard prior ceiling at the measured NICER value. GW170817 with the specified NICER and radio factors gives the calibration-conditional $R(1.4\,M_\odot)=11.7\pm0.4$km; in a synthetic $1000$-event catalogue it reproduces the mean fixed-prior $\Lambda(1.4\,M_\odot)$ to $0.4$%, $1.5$ times wider, as the fixed archive's effective sample size falls from $\sim\!470$ to 22.
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Mesoscale and Nanoscale Physics · Cross-listed from cs.AI

2d-fet-bench: from spatial reasoning to fet design on flakes

Dunzhi Zhou, Chengyu Zhu, Gang Qiu et al. (+1 more)

Field-effect transistor (FET) layouts on exfoliated two-dimensional flakes are typically drawn by hand for each flake, placing contacts and gates to match its position and outline in optical micrographs. To our knowledge, no executable benchmark tests whether language-model agents can perform this flake-specific construction reliably. We introduce 2D-FET-Bench V2, a benchmark of 128 layout tasks built from microscopy-derived flake contours, including hole-containing flakes and multi-flake tasks. Each task supplies a textual device specification and contour coordinates. An agent generates typed polygon and path operations rendered to GDSII. A deterministic verifier checks geometric and structural requirements, and a separate integrity check verifies that the supplied contours remain unchanged. Scripted reference layouts pass all 128 tasks, showing that every task is solvable. We evaluate six models and seven workflow and scaffold variants of GPT5.6-Luna, with five attempts per task. The best-performing configuration in the six-model panel, GPT5.6-Luna with ReAct-3, passes 62.3% of attempts and solves 80.5% of tasks at least once (coverage) and 43.8% in all five attempts (consistency). ReAct-3 exceeds the one-pass Plan-and-Execute by 27.0 pass@1 points at 2.46 times the tokens. An expert audit of one sampled verifier-passing layout per covered task, across five ReAct-3 configurations, accepts 56.4% to 63.5% of them. The benchmark evaluates geometric and structural FET layout construction.
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All authors Dunzhi Zhou, Chengyu Zhu, Gang Qiu, Caiwen Ding

Quantum Physics

White paper: 1-10 Hz matter-wave interferometer to test the spin entanglement witness for quantum gravity

Sougato Bose, Anupam Mazumdar, Marko Toroš et al. (+118 more)

In this white paper, we highlight the importance of the ($1-10~{\rm Hz}$) frequency range for laboratory tests of the quantum nature of gravity using the quantum gravity-induced entanglement of masses (QGEM) protocol. QGEM requires matter-wave interferometers with masses ($m\sim10^{-15}-10^{-14}~{\rm kg}$), brought within separations ($d\sim30-50~\mu{\rm m}$), while maintaining spatial superpositions of ($1-20~\mu{\rm m}$) and coherence for ($\tau\sim 0.1 - 1~{\rm s}$). These requirements make low-frequency environmental noise a central experimental challenge and place QGEM in a regime closely related to the low-frequency goals of the Einstein Telescope (ET) and the Cosmic Explorer (CE). In particular, QGEM is sensitive to relative acceleration noise (RAN) and to gravity-gradient noise (GGN) generated by seismic and other environmental mass-density fluctuations. For representative parameters $m=10^{-14}~{\rm kg}$, $\Delta x=10~\mu{\rm m}$, and $\tau=1~{\rm s}$, the differential acceleration-noise amplitude spectral density must be suppressed well below the $10^{-15}~{\rm m\,s^{-2}/\sqrt{Hz}}$ level to keep acceleration-induced dephasing below the relevant experimental scale. Achieving this level of low-frequency noise suppression is therefore a key requirement for QGEM and closely parallels the seismic and gravity-gradient noise challenges that ET and CE address.
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All authors Sougato Bose, Anupam Mazumdar, Marko Toroš, Tian Zhou, Tadeusz Adach, Niayesh Afshordi, Agya Sewara Alam, Alexandre Arbey, Navdeep Arya, Simon Baier, Peter F. Barker, Angelo Bassi, Ettore Bernardi, Lorenzo Braccini, Robert Brandenberger, Daniel Braun, Guri K. Buza, Luigi Cacciapuoti, Carlo Cepollaro, Lin-Qing Chen, Yanbei Chen, Ralph Jason Costales, Marion Cromb, Álvaro de la Cruz-Dombriz, Catalina Curceanu, Shubhang Dadhich, Debarshi Das, Saurya Das, Pratika Dayal, Subhadeep De, Ema Dimastrogiovanni, Lajos Diósi, Or Dobkowski, Kemal Döner, Brian D'Urso, Gurudev Dutt, Shafaq Gulzar Elahi, Samira Elghaayda, Matteo Fadel, Samuel Fedida, Omer Feldman, Fabiano Feleppa, Ron Folman, Joshua Foo, Paolo Fragolino, Laurent Freidel, Giulio Gasbarri, Marco Genovese, Andrew Geraci, Menachem Givon, Cisco Gooding, Jonathan M. H. Gosling, Piotr T. Grochowski, David Groswasser, Mustafa Gündoğan, Ekim Taylan Han{\i}meli, Bas Hensen, Dipankar Home, Richard Howl, Yonathan Japha, Maciej T. Jarema, Rainer Kaltenbaek, Adrian Kent, Eva Kilian-Rademacher, M. S. Kim, Jarosław K. Korbicz, Timothy Kovachy, Samuel Kováčik, Ohkyung Kwon, Gaetano Lambiase, Naor Levi, Iarley P. Lobo, Leon Loveridge, Adrian Lupascu, Paolo Luppi, Marta Maria Marchese, Antonino Marcianò, Aaron G. Markowitz, Chiara Marletto, Ryan J Marshman, J. D. D. Martin, Florian Millo, Gavin W. Morley, Maria Muretova, Sebastian Murk, Robin Oberfrank, Daniel K. L. Oi, Jerzy Paczos, Papadopoulos Stylianos, Matteo G. A. Paris, Mauro Paternostro, Alessandro Pesci, Luciano Petruzziello, Fabrizio Piacentini, Tanmay Kumar Poddar, Sofia Qvarfort, Markus Rademacher, Dennis Rätzel, Anna Chiara Rescigno, Ryan Rizaldy, Albert Roura, Carlos Sabín, Barry C. Sanders, Martine Schut, Helen M Sheehy, Suprit Singh, Aninda Sinha, Urbasi Sinha, Peter Skakunenko, Michael E Tobar, Géza Tóth, Hendrik Ulbricht, Gislaine Varão, Vlatko Vedral, Vincent Vennin, Francesca Vidotto, Giuseppe Filiberto Vitale, Marko Vojinović, Chenan Wei, Qian Xiang, Magdalena Zych

Solar and Stellar Astrophysics

Axial-Dipole and Equatorial-Dipole Coronal Holes: Congruent Magnetic Geometry, Divergent Evolution

Olga A. Panasenco, Yi-Ming Wang, Samuel T. Badman et al. (+2 more)

While the Sun's polar fields reverse, the axial dipole is weak and low-latitude coronal holes are common. Equatorial-dipole coronal holes (EDCHs) appear when the equatorial dipole is strong, forming at its magnetic poles, similar to the axial-dipole coronal holes (ADCHs) of minimum. Not every low-latitude hole qualifies: the 2024 maximum was quadrupole-led. Parker Solar Probe found fast wind from an EDCH deeply sub-Alfvénic at $9.9\,R_\odot$, at only $60\%$ of an asymptotic speed matching polar wind, which is usually thought to accelerate faster. We ask whether coronal structure predicts this, using potential-field models of synthetic and observed fields at three cycle phases. We show that pure axial and equatorial dipoles are exactly congruent, with the same open areas and core expansion factors, so any difference must arise from orientation relative to the differential-rotation pattern or from the surrounding multipoles. We find that ADCHs are stationary, sustained by converging meridional flow, whereas EDCHs depend on an equatorial dipole that active-region emergence builds and flux transport dismantles: over $18$-day sequences the axial-dipole strength at minimum is steady to $1\%$, while the equatorial dipole varies by $21\%$ at maximum and $8\%$ in the declining phase. Most open flux in EDCHs expands less than in ADCHs, but their boundaries are pseudostreamer-dominated, with non-monotonic expansion. Despite these differences, magnetic geometry alone does not predict slower acceleration in EDCHs; we argue that any real difference points to extended heating by reflection-driven Alfvén-wave turbulence, perhaps fed differently at those boundaries, which potential-field models cannot capture.
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All authors Olga A. Panasenco, Yi-Ming Wang, Samuel T. Badman, Adam J. Finley, Yeimy J. Rivera

Fluid Dynamics

(Why) Jets quantise trapped acoustic modes

Brandon Yeung, Michael N. Stavropoulos, Vincent Jaunet et al. (+2 more)

High-subsonic turbulent jets trap acoustic modes in their potential core. The modes lie in narrow frequency bands that are $O(0.1)$-wide in Strouhal number, $St$. By studying a Mach 0.9, Reynolds number $10^6$ jet, this work confirms an earlier hypothesis: each band is made up of $O(10)$ discrete frequencies, $\Delta St \sim O(0.01)$ apart. To resolve them, we collect $O(100\,000)$ snapshots from dedicated schlieren experiments and large-eddy simulations (LES), and apply spectral proper orthogonal decomposition (SPOD). Our SPOD algorithm uses sine tapers and enforces the jet's rotational and reflectional symmetries. For both the schlieren and the LES, the trapped SPOD modes are bounded in the $St$-$x$ and $St$-$k$ planes, where $x$ and $k$ are respectively the axial coordinate and wavenumber. The bounds quantise the modes in $St$, $x$, and $k$, such that the $n_x$th mode in $St$ has $n_x$ antinodes along $x$ and $k$. We then predict trapped modes with local, global, modal, and non-modal stability theories. We find evidence of a competition between modal and non-modal stability. From only the theoretical bounds, we build a simple in-phase standing-wave resonance model that predicts the quantised global-mode frequencies.
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All authors Brandon Yeung, Michael N. Stavropoulos, Vincent Jaunet, Peter Jordan, Oliver T. Schmidt

Astrophysics of Galaxies

BRAHMa: Bar Recognition And Hatching using Machine learning – a framework for oriented bounding box detection of galactic bars

Rajit Shrivastava, Narendra Nath Patra and Keerthi K

Galactic bars are fundamental components in studies of dark matter, galaxy evolution, and secular dynamics. However, current methods for measuring bar properties suffer from significant limitations. Manual and crowdsourced catalogs are not scalable to next-generation surveys, while recent machine learning (ML) approaches based on pixel-wise segmentation are computationally intensive and require complex post-processing to extract physical parameters. In this paper, we introduce BRAHMa (Bar Recognition And Hatching using Machine Learning), a publicly available tool based on an oriented-bounding-box YOLO11x model, designed for the rapid and objective detection of galactic bars. Our model was initially trained on synthetic data (Shrivastava 2025), validating its efficacy before training with real data. BRAHMa was trained on bar masks from the Galaxy Zoo 3D (GZ-3D) citizen science project, utilizing images from the DESI Legacy Survey. We address the inherent challenge of 'ground truth' in astronomical data by comparing GZ-3D labels with the Hoyle dataset for 586 common galaxies. This comparison yields a baseline mean absolute error of 0.99 kpc between the GZ3D-derived and Hoyle measurements for 586 common galaxies, providing an empirical reference for catalogue-to-catalogue disagreement. Our BRAHMa tool achieves an L1 error of 1.1 kpc on a large set of 3,150 galaxies from the Hoyle dataset, demonstrating performance that approaches this fundamental limit. We further validate the model's robustness by applying it to distinct datasets, proving its generalizability. BRAHMa provides a scalable and reliable method for bar extraction, enabling large-scale morphological studies. The tool is publicly available through the BRAHMa web interface. (https://brahma-bar-detector.netlify.app/)
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