Atmospheric and Oceanic Physics · Cross-listed from cs.LG
KNOU-Flood: Advancing global streamflow forecasting with lead-aware probabilistic machine learning
Minjong Cheon
Global streamflow
forecasting supports flood preparedness, yet data-driven models trained on reanalysis lose skill when driven by operational forecasts, increasingly so with lead time. AIFL addresses this shift with a two-stage transfer-learning recipe and a deterministic LSTM, but it feeds one forecast lead time into the whole input window and gives no uncertainty. We ask how far this open recipe can be extended without changing its recurrent core. KNOU-Flood keeps a single-layer LSTM and the two-stage training and changes the information around it: a longer input window (424 days), lead-aware forecast inputs, GraphCast as a second forecast source next to ECMWF HRES, and a latent-noise ensemble trained with the fair CRPS. We compare against a re-implementation of the AIFL recipe (its code is not public) under identical data, stations, splits and metrics. Our contributions are threefold. First, over three seeds and 2,099 test basins (2021-2023), KNOU-Flood reaches a median KGE' of 0.65 at LT1 and 0.48 at LT10 against 0.62 and 0.34, with significant gains at all ten lead times under two scoring protocols, also against a 1024-unit baseline and on held-out basins (one seed each). Second, identical weights give an LT10 KGE' of 0.18 or 0.34 depending on how forecasts are fed, so much of the lead-time decay reported for AIFL is an input-protocol effect; the probabilistic head contributes most to the gain, followed by the raw GraphCast channels, the longer window and mixed fine-tuning. Third, the ensembles reach lower CRPS than probabilistic versions of the baseline, are nearly calibrated with inference-time dropout, and detect 1.5- and 2-year floods better than all baselines; the benefit for rarer floods depends on the seed, and an exploratory tail-weighted variant improves 10-year and larger events. KNOU-Flood is a controlled extension of an open recipe, not a new architecture.
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General Physics
Inflationary Dynamics and CMB Constraints in $f(T,L_m)$ gravity
Suchita Patel, Sai Swagat Mishra and P.K. Sahoo
We investigate slow-roll inflation in a modified teleparallel framework with a non-minimal coupling between torsion and the matter sector. Focusing on Starobinsky-type plateau inflation, we derive the modified background dynamics and the corresponding slow-roll observables, and examine how the gravitational couplings affect the scalar spectral index, tensor-to-scalar ratio, and running of the spectral index. The model continuously recovers the standard Starobinsky scenario in the appropriate weak-coupling limit, while the matter–geometry coupling produces a non-monotonic modification of the inflationary predictions. We find that weak couplings leave the standard predictions essentially unchanged, whereas stronger couplings can significantly shift the scalar spectral index and eventually become incompatible with current
cosmic microwave background constraints. The quadratic torsion correction has a comparatively mild impact within the controlled low-energy regime, primarily affecting the tensor amplitude. We confront the resulting predictions with the Planck and BICEP/Keck constraints and find that the model remains viable over a broad range of the inflationary parameter space. Our results demonstrate that the matter–geometry coupling can leave a potentially testable imprint on
primordial observables while retaining the successful plateau-inflation phenomenology of the Starobinsky scenario.
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Instrumentation and Methods for Astrophysics
An Assessment of the Triangulation Capabilities of a Multi-Site All-Sky Infrared Camera Array
Abraham Loeb, Alex Delacroix, Ezra Kelderman et al. (+2 more)
The Galileo Project operates three autonomous multi-camera observing sites near Las Vegas, Nevada, separated by baselines of $2$ and $10\,$km, with the goal of characterizing the populations of natural and human-made objects that cross the sky and thereby isolating any event that fits none of them. Each site carries an array of eight long-wave infrared (LWIR) cameras arranged in a fixed dome-like structure, an IR-Dalek, providing $360^{\circ}$ azimuthal coverage. We report the commissioning of the three arrays and present the triangulation pipeline built on them. Because our targets are not assumed to follow any particular trajectory, we depart from the parametric fits standard in meteor work and estimate the instantaneous three-dimensional position at each time step as the point that minimizes the weighted sum of squared distances to the simultaneous lines of sight, weighting each camera by its own pointing uncertainty and by its range to the object. We describe the intrinsic and extrinsic calibration procedure, which uses Automatic Dependent Surveillance-Broadcast (ADS-B) aircraft as reference sources in the absence of
stars or fixed landmarks in the LWIR field of view, and the multi-sensor track association scheme that decides which detections belong to the same object. Using one week of data (2026 May 24-30; $1{,}650$ camera-hours, $2.1\times10^{8}$ detections and $5.3\times10^{6}$ tracks), we validate the recovered positions, speeds and accelerations against ADS-B records, recovering distances to within $5$% for $99$% of the aircraft solved from three sites and for $83$% of those solved from a single site pair and speeds to within $5$% for $78$% and $63$% of them respectively. We characterize the identification completeness of the array, which is set by apparent size: the $50$% identification threshold falls at $1.8$ pixels of apparent wingspan.
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All authors Abraham Loeb, Alex Delacroix, Ezra Kelderman, Eric Masson, Regina Sarmiento
High Energy Astrophysical Phenomena
Classification of X-ray Binaries in NGC 6946 with the use of Multiwavelength Data
Senay Avdan, Hasan Avdan, Eda Sonbas et al. (+1 more)
We identified X-ray binary (XRB) candidates in the
galaxy NGC 6946 using archival Chandra data. A total of 98 XRB candidates were detected within the 0.3$-$8 keV energy range, with luminosities between 10$^{36}$ and 10$^{40}$ erg~s$^{-1}$. X-ray color-color diagrams were constructed for these sources, classifying 57 as high-mass X-ray binaries (HMXBs) and 8 as low-mass X-ray binaries (LMXBs). The X-ray temporal variability of the sources was analyzed, revealing that 40 sources exhibit variability and 26 are classified as transient sources. Possible optical counterparts for 57 sources were identified using Hubble Space
Telescope (HST) images. Based on the color-magnitude diagrams (CMDs), 40 sources were found to have masses greater than 8M$_{\odot}$ and were classified as HMXBs. Seventeen sources with masses between 5 and 8M$_{\odot}$ were classified as intermediate-mass X-ray binaries (IMXBs). The remaining sources, for which optical counterparts could not be identified, were assumed to be LMXBs. The X-ray luminosity functions (XLFs) derived for HMXBs and LMXBs, identified through both X-ray and optical classification, were best described by a single power-law model ($\alpha \sim$ 1.3$-$1.6). We supplemented traditional classification methods with a machine learning (ML) approach based on multiwavelength photometry. While traditional methods identified no AGN candidates, the ML approach detected a significant AGN population. The spatial resolution of the observing instruments and the limits of the training database hinder the reliability of the ML classifications, thus highlighting a key challenge in combining these methods for extragalactic X-ray source
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All authors Senay Avdan, Hasan Avdan, Eda Sonbas, Kalvir S. Dhuga
Strongly Correlated Electrons
Disorder into Correlation: A Microscopic Mechanism for Sub-McIntyre Avalanche Noise
Shafat Shahnewaz, Hannaneh Karimi, Joe C. Campbell et al. (+1 more)
Avalanche multiplication is intrinsically
stochastic, yet experiments reveal excess noise below the minimum predicted by McIntyre's local-field theory. The microscopic origin of this noise suppression remains incompletely understood. We show that polar-optical-
phonon emission, confined to a narrow forward cone, competes with elastic
alloy scattering that diffuses field-collimated hot carriers out of the cone. Suppressed
phonon cooling narrows the ionization path beyond the dead space and synchronizes successive ionizations into a dynamic staircase. This explains the low noise of Sb-based
alloys and HgCdTe and makes
alloy disorder a design parameter.
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All authors Shafat Shahnewaz, Hannaneh Karimi, Joe C. Campbell, Avik W. Ghosh
High Energy Astrophysical Phenomena
Relaxation of a Vlasov gas to an inhomogeneous state due to phase space mixing in an axisymmetric potential: A Newtonian analogy of the Kerr orbital motion
Ana Laura García-Perciante, Merce Guerrero, Darío Núñez et al. (+1 more)
We explore the dynamics of a Vlasov gas propagating in an external axisymmetric potential consisting of a central potential with an additional quadrupolar component which gives rise to two potential wells along the
symmetry axis. Employing independently $N$-particle simulations and statistical methods, we show that an initially homogeneous and isotropic configuration evolves to an inhomogeneous final state with overdensities located at the wells. The quadrupolar component is chosen such that the equations of motion form an integrable
Hamiltonian system, which allows one to compute the final state of the gas analytically. On the one hand, this allows one to compare the late-time behaviour of the simulations with an analytic prediction and on the other hand to understand the relaxation process through phase space mixing. Our model constitutes a Newtonian analogue of the particle motion in a Kerr spacetime, and we discuss possible applications to recently observed astrophysical phenomena.
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All authors Ana Laura García-Perciante, Merce Guerrero, Darío Núñez, Olivier Sarbach
Strongly Correlated Electrons
Correlated Low-Energy Model of Monolayer 1H-NbS$_2$: A cRPA+DMFT Study
Karollaine C. Leite, Jorge L. B. de Faria, Luiz Antonio Ribeiro Junior et al. (+3 more)
Monolayer $1\mathrm{H}\text{-}\mathrm{NbS}_2$ hosts a well-separated metallic band of predominant Nb-$d_{z^2}$ character, providing an ideal platform to probe electronic correlations within a single-band setting. In this work, we present a comprehensive study of $1\mathrm{H}\text{-}\mathrm{NbS}_2$ by combining first-principles Wannier interpolation, constrained random-phase approximation (cRPA), and DFT+DMFT. We show that an effective single-band model accurately captures the low-energy electronic structure, reproducing key experimental features from ARPES and STS $dI/dV$ spectra, including a characteristic Van Hove singularity. While static DFT+$U$ fails to describe the correlated metallic nature of the system, DFT+DMFT successfully accounts for the spectral weight redistribution and dynamic correlations. By defining the cRPA target subspace directly within the isolated Nb-$d_{z^2}$ band, we obtain a renormalized local interaction of $U_{\mathrm{cRPA}} = 1.138~\mathrm{eV}$. This interaction stabilizes a strongly correlated metallic state that remains robust upon cooling. Remarkably, this minimal single-band model captures a spectral broadening similar to that previously reported in more elaborate treatments - incorporating larger local interactions ($U \sim 1.8~\mathrm{eV}$, derived from a multiorbital cRPA construction), intersite Coulomb terms ($V$), and electron-
phonon coupling - demonstrating that a consistently downfolded local interaction alone can already capture key aspects of the experimentally observed low-energy behavior of monolayer $1\mathrm{H}\text{-}\mathrm{NbS}_2$.
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All authors Karollaine C. Leite, Jorge L. B. de Faria, Luiz Antonio Ribeiro Junior, Alexandre C. Dias, Helena Bragança, Alberto S. de Arruda
Mathematical Physics · Cross-listed from math.NT
Sequential exponential-motivic periods in spatially cut-off $\phi^4_2$
Juan Carlos Sampedro
We represent constructive integrals in spatially cut-off $\phi^4_2$ by sequences of exponential-motivic periods. For a nonzero spatial cutoff, a single Galois transformation makes the partition periods diverge in modulus along every sequence of approximations satisfying the constructive estimates. For a fixed cutoff presentation, we characterize the subgroup of transformations admitting a bounded realization on the free field's $L^1$ space and prove that all fixed-observable limits on this subgroup are a common scalar multiple of their physical values. A one-variable quartic example shows that all transformed fixed-observable sequences can converge without such a bounded realization, with limits that are not proportional to the physical values.
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Materials Science
Agentic Resource Allocation for Batch Multi-Objective Bayesian Optimization in Autonomous Materials Discovery
Robert Robinson, Shakti Prasad Padhy, Sushant Sinha et al. (+6 more)
The discovery and development of advanced materials is a challenging process constrained by the high time and monetary costs of synthesis, processing, and characterization. The underlying design spaces can be enormous, often with multiple competing objectives.
Bayesian optimization (BO) provides a principled approach for efficiently navigating such spaces, but most workflows rely on fixed exploration-exploitation policies that lack the capacity to adapt to shifting constraints in dynamic campaigns typical of self-driving laboratories. In this work, we develop a multi-objective BO framework for
alloy design under resource constraints, benchmarking strategies for adaptive policy tuning at each iteration. Our evaluation covers a septenary refractory high-
entropy alloy (RHEA) system focused on maximizing melting temperature and minimizing density, and an Fe-Co-Ni-based soft
magnetic alloy system targeting saturation magnetization, coercivity, and hardness. We compare an exploitation-focused strategy, a fixed mixed exploratory/exploitative policy, and two distinct LLM-based adaptive strategies with different approaches to batch allocation and campaign signal interpretation, evaluated across baseline and mid-campaign resource event conditions including budget reductions, timeline cuts, and combined disruptions. Our results show that mixed allocation strategies accumulate substantially more mutual information than the exploitation-focused baseline at a proportionally smaller cost to hypervolume and optimization speed, with adaptive strategies outperforming a fixed-mixed allocation policy by adjusting their allocation in response to both evolving campaign statistics and resource constraints. These findings suggest that adaptive resource allocation offers a favorable tradeoff for materials discovery campaigns in reducing predictive uncertainty on Pareto-optimal compositions.
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All authors Robert Robinson, Shakti Prasad Padhy, Sushant Sinha, Sk Md Ahnaf Akif Alvi, Juan Florez Coronel, Brent Vela, Trevor Hastings, Douglas Allaire, Raymundo Arróyave
High Energy Physics (Theory)
Anomaly-free six-dimensional $Sp(1)_R$-gauged supergravities
Katrin Becker, Ergin Sezgin and Qi You
We study anomaly constraints in six-dimensional $N=(1,0)$ supergravity with gauged $Sp(1)_R$
symmetry, one tensor multiplet, $n_V$ vector multiplets and $n_H$ hypermultiplets. Imposing cancellation of local gravitational, gauge and mixed anomalies, together with the
embedding of the anomaly coefficients in a unimodular rank-two string charge
lattice, the number of vector multiplets is sharply constrained: the only allowed positive values are $n_V=12$ and $n_V=96$. For a neutral abelian factor, or drone, the anomaly equations force the corresponding row and column of the abelian gauge-kinetic
matrix to vanish. Such a factor therefore cannot be retained as an ordinary propagating vector multiplet. For $n_V=96$, within the class of semisimple non-$R$ gauge
algebras containing no $A_1$ or $A_2$ factor, the exhaustive spectra-assembly calculation yields no drone-free spectrum. For $n_V=12$, the semisimple non-$R$ branch is necessarily $A_1^3$. In the doublet/adjoint truncation described in the text, we find $4{,}337{,}331$ consistent models, classified by $102$ anomaly-vector classes. We also consider the reductive branch $A_2\times U(1)\times Sp(1)_R$. For $A_2$ representations in $\{\mathbf 1,\mathbf 3,\overline{\mathbf 3}, \mathbf 6,\overline{\mathbf 6},\mathbf 8\}$ and primitive $U(1)$ charge assignments with $|q|\le 2$, we find $178{,}538$ solutions, classified by $21$ sets of anomaly vectors.
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Instrumentation and Methods for Astrophysics
Shared Geometry Is Not Shared Physics: A Layerwise Test of the Platonic Representation Hypothesis in Astronomy
Kshitij Duraphe, Aravind Kannappan, Dun Li Chan et al. (+4 more)
In this paper we investigate whether geometrically aligned astronomical representations are also scientifically interchangeable. We analyze every layer's representation from 36 pretrained models using cross-matched optical images, infrared images, and spectra. All 139 analyzed model-survey comparisons show significant local-neighborhood
alignment somewhere in the network after accounting for the search over depth. However,
alignment does not generally increase with network depth and can be stronger for the changes between consecutive computational blocks than for the block outputs themselves. We find that geometry-selected stages under-perform label-selected stages in every image-transfer comparison; moreover, every final HSC-COSMOS-Web model pair is aligned while every
redshift transfer has negative R^2. Models can therefore recover a similar cross-survey geometry among astronomical objects without recovering a survey-invariant linear encoding of the physical properties tested here.
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All authors Kshitij Duraphe, Aravind Kannappan, Dun Li Chan, Okiki Famutimi, Yaswant Sai Ejjagiri, Michael J. Smith, John F. Wu
Instrumentation and Methods for Astrophysics
LoFreq-SETI: A Low-Frequency Technosignature Search Pipeline for the LWA Swarm
Craig A. Taylor, Lillian Ekness and Chenoa Tremblay
The search for extraterrestrial intelligence (SETI) is conducted across the electromagnetic spectrum to understand the prevalence and distribution of intelligent life in the universe. At
radio frequencies, this effort focuses on searching for "technosignatures", observable indicators of technological activity consistent with our understanding of an advanced civilization. Historically, the microwave regime from 1-10 GHz has been the primary frequency range searched for these technosignatures, but recent SETI experiments utilizing low-frequency
radio telescopes, such as the Low Frequency Array (LOFAR), Murchison Widefield Array, and MeerKAT
radio telescope have explored the insufficiently studied frequency range below 1 GHz. However, the lowest
radio frequencies ($<$100 MHz) have been even less explored for technosignatures, despite significant human communication signals occupying this band. The Long Wavelength Array (LWA) is a low-frequency (3-88 MHz) interferometer array
telescope collaboration comprised of dipole 'stations' distributed across the Southwestern United States, and the LWA Swarm is the aperture synthesis
telescope consisting of interconnected LWA stations operating as a long baseline interferometer. Here we present a narrowband technosignature pipeline using the Breakthrough Listen Interesting Signal Search
algorithm for raw beamformed single-station LWA data and outline its planned extension to correlated visibilities from the LWA Swarm. We demonstrate the pipeline on a limited selection of fast
radio burst observations to evaluate the data processing and spatial coincidence filtering for a future observing campaign of
exoplanet systems.
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Solar and Stellar Astrophysics
A forest of emission lines observed by Sunrise III/SUSI above the solar limb
J. S. Castellanos Durán, F. A. Iglesias, S. K. Solanki et al. (+31 more)
We present off-limb spectroscopy using low-straylight data from the Sunrise Spectropolarimeter and Imager (SUSI) onboard the Sunrise III stratospheric
solar observatory. A spatial scan with SUSI's slit almost parallel to the local limb reached from within the
solar disc to 6.5 Mm off-limb. The wavelength range spanned from 407.6 to 410.25 nm. We detected a total of 174 spectral lines in emission off-limb, a 2.5-fold increase over previous reports. Surprisingly, 122 of these lines begin to appear in emission already on the disc, although close to the limb. In addition, one-fifth of relatively prominent emission lines are due to rare-earth and heavy elements and molecules, where the absorption lines of these transitions are typically weak on-disc.
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All authors J. S. Castellanos Durán, F. A. Iglesias, S. K. Solanki, A. Lagg, I. Milic, H. N. Smitha, D. Vukadinović, T. L. Riethmüller, A. Gandorfer, A. Feller, J. Blanco Rodríguez, D. Orozco Suárez, Y. Katsukawa, J. Hölken, J. C. del Toro Iniesta, S. Rao, M. Sánchez Toledo, K. Singh, P. Bernasconi, T. Berkefeld, A. Alvarez-Herrero, M. Kubo, V. Martínez Pillet, B. Grauf, M. Carpenter, A. Bell, H. Strecker, A. L. Siu-Tapia, P. Santamarina Guerrero, Y. Kawabata, T. Matsumoto, R. T. Ishikawa, E. Harnes, T. Oba
High Energy Physics (Phenomenology)
Energy shift and decay width of kaonium from coupled-channel one-loop chiral amplitudes
Alireza Beygi
Using two fitted coupled-channel one-loop
chiral amplitudes, we investigate the strong-interaction energy shift and decay width of the hypothetical Coulomb-bound $K^+ K^-$ hadronic atom, kaonium. We obtain ground-state widths of 1.67 and 0.92 keV, which are both larger than previous kaonium predictions, including the 0.30 keV result obtained from a non-perturbative treatment based on leading-order
chiral perturbation theory. Although the $K^+ K^-$ scattering lengths obtained from the two one-loop amplitudes have nearly equal imaginary parts, their real parts have opposite signs; thus, the leading absorptive contributions to the widths are similar, while the Coulomb corrections act in opposite directions. The kaonium width therefore depends on both the real and imaginary parts of the near-threshold strong amplitude. Despite the increased ground-state width, the first three $s$-wave levels remain separated. In
photon fusion, at fixed pole area and resonance position, the increase in the intrinsic width has a negligible effect on the line shape after including Belle's experimental resolution.
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Materials Science
Distilling universal machine-learning potentials for moiré lattices across one million atoms
Thomas Huang, Yueyao Fan, Kaichen Xie et al. (+7 more)
Atomic reconstruction reshapes moiré materials across multiple scales, from local structure and polarization textures to global electronic
topology, yet direct ab initio modeling becomes prohibitive for large superstructures such as marginal-twist-angle moirés and moiré-of-moirés. We develop MoiréMLIP by fine-tuning a universal atomistic model on the density functional theory labeled Moiré Kaleidoscope
dataset, which spans transition metal dichalcogenide compositions,
symmetries, stackings, and twist angles. MoiréMLIP reproduces ab initio reconstruction with force errors of 6–8\,meV/Å and transfers to smaller twist angles and unseen structures. Knowledge
distillation yields MoiréMLIP-mini, which retains this accuracy while extending single-GPU inference to one million atoms. Applied to an alternate-twist MoTe$_2$ trilayer, it reveals a hierarchical polarization network spanning tens of nanometers arising from large moiré-
cell distortions sharply localized along the moiré-of-moiré domain walls. These results overcome key accuracy, transferability, and scaling bottlenecks of existing atomistic models and enable predictive simulations across emergent moiré length scales.
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All authors Thomas Huang, Yueyao Fan, Kaichen Xie, Bolun Li, Kaijie Yang, Jenna A. Bilbrey, Eric Bylaska, Peter V. Sushko, Di Xiao, Ting Cao
Earth and Planetary Astrophysics
Closing the Gap: A Test of the Streaming Instability Using Simulations and Observations of the Cold-Classical Kuiper Belt Size Distribution
Weston Hall, Jacob B. Simon, Jeonghoon Lim et al. (+2 more)
How planetesimals form is a major open question in studies of
planet formation, as the growth of smaller solids must overcome barriers such as radial drift, fragmentation, and bouncing. The leading model is that planetesimals form by the gravitational collapse of dense particle clumps that have been aerodynamically collected via a process known as the streaming instability (SI). While the SI has passed several observational tests, a critical test remains: a successful comparison with the size distribution of
Solar System planetesimals. In this work, we conducted a series of SI simulations for a range of input parameters and combine a more careful accounting of initial planetesimal mass with more advanced statistical techniques compared to previous studies in order to compare the simulation outcomes against observations of the most
primordial population in the
solar system: the Cold Classical Kuiper Belt (CCKB). Using both cumulative distribution function (CDF) model parameters and distribution comparison methods like the Kolomogorov-Smirnov test, we show that, when planetesimal masses are measured at formation and analyzed with modern statistical methods, the SI-predicted size distributions can quantitatively reproduce the high-mass end of the observed CCKB size distribution, though the extent of the agreement depends on the physical parameters chosen, providing further support for the SI theory of planetesimal formation.
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All authors Weston Hall, Jacob B. Simon, Jeonghoon Lim, Daniel Carrera, Matthew Small
Mesoscale and Nanoscale Physics
Exchange-controlled quantum beats and entanglement in an exciton–bimodal-cavity system
Cesar E. P. Villegas, Victor P. Brasil, Pedro A. S. Contri et al. (+2 more)
We theoretically demonstrate tunable population transfer and
entanglement generation in a two-
exciton system coupled to a bimodal optical cavity, including an
exciton-
exciton exchange interaction. By using dressed-state transformations and Löwdin partitioning, we derive effective
Hamiltonians that identify three dynamical time scales: local polaritonic oscillations, long-period dressed-state beats, and direct excitonic exchange. We apply the framework to
graphene nanoribbon
excitons, using excitonic energies, transition dipoles, and lifetimes obtained from first-principles calculations to parameterize the model. In the small- and moderate-exchange regimes, the dynamics become multiscale, and the beat channel sustains sizable
quantum entanglement over long dissipative time windows. In the large-exchange regime, the excitonic
Hamiltonian dominates and drives nearly complete population transfer between excitonic states over many coherent cycles. The resulting analytical expressions provide direct design rules connecting the beat period, transfer amplitude, and coherent-cycle number to the exchange interaction, cavity detuning, and light–matter coupling. Our results establish a controllable route for engineering long-lived
entanglement and coherent excitonic operations in
exciton–bimodal-cavity systems.
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All authors Cesar E. P. Villegas, Victor P. Brasil, Pedro A. S. Contri, Kevin Lizárraga, Jonas Maziero
Chaotic Dynamics · Cross-listed from cs.LG
Physics is the Best Teacher: Consistency Learning for Time-Invariant Operators of Chaotic Dynamics
Lufang Chiang, Jiachen Yao, Thomas Y.L. Lin et al. (+1 more)
Accelerating the prediction of long-term behavior in chaotic systems is crucial in scientific computing. However, existing methods rely on numerical solvers or autoregressive models that advance one small step at a time, which makes long horizons expensive. We instead view this problem as learning the system's time-invariant
evolution operator, which jumps the state across a large time span in a single evaluation. To this end, we derive the consistency equations a time-invariant operator must satisfy, with differential and compositional objectives in physical time. These equations also connect the learned operator to the physics-prescribed instant dynamics, enabling physics
embedding in consistency learning. Across five chaotic systems, we find that physics-distilled consistency makes both short-term trajectories and long-term statistics more accurate. The learned operator survives temporal extrapolation and requires one-tenth as many evaluations as autoregressive rollout, offering an efficient route to long-term simulation of chaotic dynamics.
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All authors Lufang Chiang, Jiachen Yao, Thomas Y.L. Lin, Anima Anandkumar
Chemical Physics
PyCC: A Reference Quantum Chemistry Python Package for Education, Validation, and Rapid Prototyping
T. Daniel Crawford, Benjamin G. Peyton, Zhe Wang et al. (+6 more)
PyCC is a Python-based
quantum chemistry package that emphasizes coupled cluster and related methods. Developed over the last five years, PyCC's purpose is to provide a clear reference implementation that will serve as a validation suite for production code, a platform for rapid prototyping and testing of new methods, and an educational resource for newcomers to the field. The package covers both closed- and open-shell single-determinant references in spatial- and
spin-orbital formulations for the coupled cluster hierarchy through triples-including methods such as CC3, as well as for MP2 and CI methods. PyCC provides a broad range of molecular properties such as analytic first and second energy derivatives including gradients, Hessians, polarizabilities and atomic polar tensors, as well as non-energy-derivative properties, such as velocity-gauge atomic polar tensors and diagonal Born-Oppenheimer corrections, plus dynamic linear response functions, and excitation energies. The package includes a number of unique capabilities, such as real-time CC propagation (up through CC3), atomic axial tensors for simulating vibrational circular dichroism spectra at the MP2 and CI levels, and local correlation methods including perturbation-aware correlation domains. The code is designed around a shared Wavefunction base and a method-agnostic derivative layer that enables a new method to inherit the full property set once it supplies its reduced densities and their first-order responses. PyCC is fully open source and available on GitHub under the BSD 3-clause license.
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All authors T. Daniel Crawford, Benjamin G. Peyton, Zhe Wang, Aparna Krishnan, Brendan M. Shumberger, Jose Madriaga, Joshua Atta-Kumi, Aaron De Clercq, Ritvik Prabhu
Fluid Dynamics
Transparent 3D-printed flow cells for porous media studies with proof-of-concept on two-phase flow-reversal asymmetry
Yann Dumay, J. Kevin Pierce, Julie Delhaie et al. (+2 more)
Porous media experiments commonly rely on geometry-controlled and optically transparent experimental flow
cells. Examples include studies of flow structure, solute mixing, multiphase flow, bacterial dynamics, and reactive transport. Here, we provide a reproducible and open-source protocol to fabricate transparent monolithic porous flow
cells by stereolithography 3D printing. The protocol covers digital design, resin printing, internal flushing, and resin coating. The flushing and coating steps are central to the workflow, enabling enclosed single-material
cells to be cleared of uncured resin and made optically transparent for direct imaging. The protocol produces optically transparent, millimetre-scale, and quasi-two-dimensional flow
cells suitable for simultaneous pressure and image-based measurements. As a proof of concept, we study flow-reversal asymmetry in steady oil-air two-phase flow in quasi-two-dimensional Hele-Shaw
cells containing either triangular or cylindrical obstacles. Directional differences are quantified from pressure measurements and from image-based active-width measurements. The triangular geometry produces a clear directional response, whereas the cylindrical geometry remains symmetric within experimental uncertainty. These results demonstrate that our fabrication protocol can link digitally designed pore geometries to macroscopic pressure response and steady-state two-phase flow organisation. By making the design files, scripts, and manufacturing workflow openly available, we aim to make 3D-printed flow
cells readily adaptable to other experimental systems and research fields.
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All authors Yann Dumay, J. Kevin Pierce, Julie Delhaie, Pooja Singh, Erika Eiser
Geophysics
Eigenwaves: Finite-frequency Eigenrays in Elastic Anisotropic Media
Zvi Koren
The Eigenray method solves two-point boundary-value ray-tracing problems in heterogeneous anisotropic elastic media using a variational formulation based on the eikonal equation. Here, we extend the method to finite frequencies using the trajectory-mechanics formulation in which finite-frequency effects are represented by a frequency-dependent potential that couples phase and amplitude. We show that finite-frequency propagation can be described within the same variational framework through an equivalent effective medium, preserving the structure of the original method while introducing corrections to trajectories, phase, amplitudes,
geometric spreading, wavefront
curvature, and caustic behavior. The resulting Eigenwave formulation requires only local modifications of the ray velocity and its derivatives and reduces to classical ray theory in the high-frequency limit. Numerical examples involving multipathing and cusp caustics demonstrate accurate modeling of finite-frequency propagation effects. While ray-based amplitudes become unreliable near caustics, a phase-space (Maslov) treatment successfully reproduces finite-difference wavefield solutions. These results establish Eigenwave theory as a unified framework connecting ray theory and finite-frequency wave propagation in heterogeneous anisotropic media.
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High Energy Physics (Phenomenology)
Dijet acoplanarity as a function of flattenicity in proton-proton collisions at $\sqrt{s}=13$ TeV
Jesus Eduardo Muñoz Mendez and Antonio Ortiz
One of the most important discoveries at the LHC is the presence of effects associated with
quark-
gluon plasma (QGP) formation in
proton-
proton (pp) collisions. The origin of these observations remains unknown. Since event selection in many studies relies on multiplicity-based
estimators known to introduce selection biases, alternative approaches must be explored to elucidate the origin of these phenomena. This contribution presents a comparison of different event classifiers used in LHC experiments, aiming to assess their mutual compatibility. Results for pp collisions at $\sqrt{s}=13$ TeV simulated with PYTHIA 8 indicate that the different classifiers introduce biases that can obscure any evidence of QGP formation in small systems. However, these biases are significantly reduced or absent in events triggered with flattenicity. This finding motivates the application of flattenicity in dijet acoplanarity studies used to search for jet quenching effects. While multiplicity-based
estimators produce an azimuthal broadening in high-multiplicity compared with minimum-bias pp collisions, even in PYTHIA 8 that does not incorporate jet quenching, events triggered with flattenicity show no such broadening. This suggests that this novel tool could be exploited by LHC experiments to refine jet-quenching searches in small systems.
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Statistical Mechanics · Cross-listed from q-bio.PE
Fluctuation theorems and exact multi-allele fixation probabilities
Emil A. Yuzbashyan, Alexander Feigel and Alexandre V. Morozov
A mutant gene that appears in a finite population will, in the long run, either disappear from it or become fixed, so that all members of the population will carry a copy of the mutant gene. Determining the fixation probability of a mutant gene is thus a prerequisite for modeling evolutionary dynamics in finite populations. Within the
diffusion theory framework, the mutant's competition with the wild-type genes is described by the closed-form solution of a one-dimensional backward Kolmogorov equation for the mutant fixation probability, derived by Motoo Kimura in 1962. However, in asexual populations the rate of adaptation and the relative importance of alternative evolutionary pathways are shaped by clonal interference - the competition between several lineages arising from distinct beneficial or deleterious mutations. Quantitative descriptions of clonal interference require computing fixation probabilities in populations where multiple alleles are present simultaneously - a formidable mathematical problem which amounts to solving a multi-dimensional backward Kolmogorov equation. Here, we employ fluctuation
theorems (a set of exact equalities in non-
equilibrium statistical mechanics) in order to re-derive Kimura's fixation probability formula. When extended to multi-allele systems, fluctuation
theorems provide a constraint which must be satisfied by any valid set of fixation probabilities. Moreover, we present a recursive analytical solution of the multi-allele fixation probability problem. We use our formalism to study the fate of a novel beneficial mutation in a clonal interference scenario, discovering substantial deviations between our exact treatment and the mean-field approximation in which the target mutation competes with a single effective genotype. Our formalism can be used to replace both explicit simulations and approximate analytical results in models of asexual
evolution.
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