Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Thursday 9 July

Fluid Dynamics

Physics-informed neural networks for shock capturing in inviscid flows around an airfoil

Jiahao Song, Wenbo Cao and Weiwei Zhang

Physics-informed neural networks (PINNs) have shown promise in solving partial differential equations (PDEs). However, shock capturing remains challenging for PINNs, particularly in steady flows around an airfoil, where shocks may not even be captured. In this study, we point out that the steady Euler equations used to construct the loss function impose weak constraints, which make it difficult to correct the continuous function approximation preference of neural networks, causing gradient descent to converge to a smooth local optimum. Based on this insight, we propose to strengthen the physical constraints by reconstructing steady shock capturing as a temporal evolution process governed by the unsteady Euler equations. The temporal evolution law of the flow field guides gradient descent, thereby alleviating its tendency to converge to smooth local optima and ensuring shock formation. We introduce a PDE loss function incorporating a pseudo-time stepping mechanism to obtain the steady state solution without solving the unsteady Euler equations over a long time interval. In addition, we develop a simplified formulation of the Euler equations to reduce the complexity of the PDE loss function, thereby improving shock capturing accuracy. By solving four forward problems involving different flow conditions and geometries, we verify that the proposed method achieves high accuracy in shock capturing while reducing the wall time to one-seventh of that required by existing advanced methods. Moreover, the proposed method demonstrates its capability to solve a parametric problem involving the angle of attack and Mach number without relying on any labeled data.
Read the full abstract

Mathematical Physics · Cross-listed from math.DS

Complex dynamics perspective for birational maps of the plane arising from cluster algebra mutations

Andrei Grigorev, Krishna Chaitanya Kalidindi, Andres Quintero Santander et al. (+1 more)

Using the methods of holomorphic dynamics we investigate planar birational mappings that arise from the theory of cluster algebras and integrable systems. Computing dynamical degrees of these mappings, many of which are greater than one, allows us to show that many of the mappings do not have a conserved quantity (nor an invariant fibration). In most of the examples, invariant fibrations can also be ruled out by finding superattracting periodic points. This answers a question posted by Machacek and Ovenhouse 2024 and by Chen and Li 2024. Moreover, having found a good algebraically stable model for the mappings and having computed the dynamical degree, we can then apply results from the ergodic theory of birational maps to produce invariant measures with positive entropy and positive Lyapunov exponents.
Read the full abstract

All authors Andrei Grigorev, Krishna Chaitanya Kalidindi, Andres Quintero Santander, Roland Roeder

Cosmology and Nongalactic Astrophysics

Phantom crossing from the Standard Model and General Relativity

Jinglong Liu, Tucker Manton, Yifu Cai et al. (+1 more)

Suggestions of a late-time phantom crossing from DESI baryon acoustic oscillation measurements, combined with cosmic microwave background and Type-Ia supernova observations, have renewed interest in non-standard dark energy models. In this Letter, we propose a new realization of a low redshift phantom crossing using only well understood ingredients from fermion condensation and general relativity. Our construction relies on the interplay between effective quintom-like dark energy and backreaction from non-linear structure formation. The full cosmological evolution is consistent with $\Lambda$CDM until low redshift, where the backreaction starts to become prominent and a phase transition occurs. At this point, the total dark energy equation of state first crosses $w_{\text{DE}}=-1$ from above. For benchmark values of the backreaction energy density, a second crossing from below occurs at a lower redshift, as suggested by recent observation. Fitting our theoretical model with CPL parametrization, we find the result is consistent with the combined DESI+CMB+SNIa data analysis with DESY5, PantheonPlus, and Union3 datasets. Specifically, for backreaction density parameter $\Omega_{\rm BR}(z=0) = 0.0572$, the CPL parametrization gives the phantom crossing redshift $z_* \simeq 0.35$, $w_0 \simeq -0.76 $ and $w_a \simeq -0.93$.
Read the full abstract

All authors Jinglong Liu, Tucker Manton, Yifu Cai, Antonino Marciano

High Energy Astrophysical Phenomena

The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey–IV. Survey update and an atlas of 205 non-recycled southern pulsars

N. D. R. Bhat, C. P. Lee, S. J. McSweeney et al. (+13 more)

The SMART survey is an ambitious effort to conduct sensitive searches for pulsars and fast transients at 140-170 MHz. The novelty of voltage recording, long dwell times and the high-time and -frequency resolutions exchange a large survey speed for high computational cost. The survey covers the entire sky south of +30 degree in declination through a series of dedicated campaigns, accumulating 4 PB of data. The large volumes of data necessitate processing to be approached in multiple phases, and the initial searches focused on a shallow survey of parts of the skies, as reported in earlier papers. These data are also processed for re-detections of hundreds of known pulsars in the southern sky, many of which are also the first detections below 400 MHz. This paper is motivated by the need to address the inherent difficulties in handling large amounts of voltage data and software/processing challenges for routine pulsar detections, and also by the fast-evolving landscape of the SKA Observatory (SKAO). With the construction ramping up towards the full-scale SKA-Low, a low-frequency catalogue of detectable pulsars in the southern sky will prove to be a valuable reference for science verification. A growing sample of low-frequency detections and measurements will also prove invaluable in a variety of science applications including population studies, survey simulations and emission beam models, refining interstellar medium models for electron densities and the spatial distribution of turbulence, and also for forecasting the detection prospects and survey yield from pulsar surveys planned with SKA-Low. We present various data products, including pulse profiles, time series and multi-channel folded archives, along with the measurements of dispersion and rotation measures, and mean flux densities, and this will be periodically updated as more detections flow on from the ongoing data processing.
Read the full abstract

All authors N. D. R. Bhat, C. P. Lee, S. J. McSweeney, B. W. Meyers, C. M. Tan, M. Xue, Q. Fu, N. A. Swainston, S. M. Ord, G. J. Sleap, S. E. Tremblay, W. van Straten, A. Williams, C. Di Pientrantonio, C. J. Harris, P. J. Elahi

Mathematical Physics

The Periodic Table and the Group SO(4,4): II. Double SO(4,2)-tower

V.V. Varlamov

A group-theoretic interpretation of the periodic system of elements is given within the framework of the weight diagram of the Lie algebra $\mathfrak{so}(4,4)$ of the fourth rank, where the four quantum numbers $n$, $l$, $m$, $s$ correspond to the eigenvalues (weights) of the Cartan generators of the maximal Abelian subalgebra (the maximal torus of the group SO(4,4)). It is shown that the root system of the algebra $\mathfrak{so}(4,4)$ forms a regular four-dimensional self-dual polyhedron (24-cell). The action of the fourth Cartan generator associated with spin leads to a splitting of the Cartan-Weyl basis of the algebra $\mathfrak{so}(4,4)$ into two structurally identical bases, each of which is isomorphic to the Yao basis of the subalgebra $\mathfrak{so}(4,2)$ (the Lie algebra of the conformal group). At this point, a four-dimensional 24-cell is projected onto two three-dimensional cuboctahedra, each of which defines the root system of the subalgebra $\mathfrak{so}(4,2)$. This splitting physically corresponds to spin doubling (two-valuedness). The structure of the energy levels of a periodic system is studied, the states of which (chemical elements) are represented as nodes of the weight diagram of the group algebra $\mathfrak{so}(4,4)$. The structure of the double SO(4,2)-towers of Mendeleev, Seaborg, and 10-periodic extension is examined in detail. The period doubling associated with the sequence of period lengths 2, 8, 8, 18, 18, 32, 32, $\ldots$ of the periodic system of elements is explained by the action of the fourth Cartan generator. It is shown that antimatter (Mendeleev anti-table consisting of antihydrogen, antihelium, antilitium, $\ldots$) is naturally included in the general group-theoretic scheme of description of the periodic table.
Read the full abstract

Quantum Physics

Decomposition-Based QAOA for Maximum Coverage Location Problem in Satellite Constellation Design

Divya Sisodiya, Amiratabak Bahengam, Hang Woon Lee et al. (+1 more)

An increase in earth observation missions has increased the demand of efficient design and optimization of satellite constellations. Maximizing coverage of the target while effectively utilizing the limited orbital resources is one of the critical design challenges for complex combinatorial optimization problems. The maximal covering location problem (MCLP), serves as a base for orbital coverage modeling, is NP-hard and computationally intractable for large-constellation instances. Using heuristics, metaheuristics, and mixed-integer linear programming, classical solvers have achieved optimal or near-optimal results, yet their scalability is limited as the problem size increases. Quantum computing advancements, including the quantum approximate optimization algorithms, offer a potential solution to NP-hard combinatorial optimization problems. Current quantum hardware limitations, such as low qubit counts and circuit depth, restrict solutions for small-scale instance problems. To address this challenge, this paper proposes a scalable quantum optimization framework for MCLP in satellite constellation design. A decomposition-based quantum methodology is proposed, in which large MCLP instances are partitioned into subgraphs by classical decomposition, optimized independently via quantum optimization circuits, and combined using quantum reconstruction strategies. Computational results across different constellation sizes reveal better scalability in less time while maintaining competitive coverage performance compared to classical solvers.
Read the full abstract

All authors Divya Sisodiya, Amiratabak Bahengam, Hang Woon Lee, Hao Chen

Materials Science

Perpendicular magnetic anisotropy tuning of macrospin-to-vortex transitions in Co-based artificial spin-vortex ice

Yu Maruyama, Amrit Kumar Mondal, Bijaya Kharel et al. (+4 more)

We investigate the macrospin-to-vortex (MS-to-V) transition in Co-based artificial spin-vortex ice (ASVI) in the presence of perpendicular magnetic anisotropy (PMA) by spin-wave spectroscopy. Detailed micromagnetic simulations using mumax3 reveal that the PMA modifies the magnetic energy landscape and facilitates vortex formation, suggesting that PMA can enhance the transition probability. To seek experimental validation of this hypothesis, we prepared Ti (3 nm)/Co (10 nm)/Ti (3 nm)/Pt (2 nm) (TCT) and Ti (3 nm)/Co (10 nm)/Pt (2 nm) (TCP) multilayer stacks. Vibrating sample magnetometry measurements confirm that the TCP film exhibits a larger PMA than the TCT film. Using these stacks, we then investigate the MS-to-V transition probability in ASVIs and found that TCP ASVIs exhibit a higher transition probability than TCT ASVIs, in agreement with the simulation prediction. These findings identify PMA as an effective design parameter for controlling vortex formation in ASVIs and provide a promising route toward task-dependent tuning of fading-memory properties for physical reservoir computing based on artificial spin lattices.
Read the full abstract

All authors Yu Maruyama, Amrit Kumar Mondal, Bijaya Kharel, Ryo Ohshima, Jorge Puebla, M. Benjamin Jungfleisch, Masashi Shiraishi

Quantum Physics

Center-of-Mass Bounds and Harmonic Extremality

Arseny Pantsialei

We study the center-of-mass observable in one-dimensional many-body systems with translation-invariant interactions and extend the harmonic-rigidity mechanism from the one-body setting to an interacting many-body problem. We prove a sharp upper bound on the ground-state center-of-mass fluctuation in terms of the active spectral gap associated with the center-of-mass probe, and show that this bound does not require any positivity assumption on the ground state. In the positivity class, we characterize the equality case completely. Exact saturation occurs if and only if the external one-body traps are harmonic with a common frequency, while the interaction may remain arbitrary within the translation-invariant class. We also identify a natural rigidity defect measuring deviation from the harmonic extremal situation and prove quantitative near-saturation estimates controlling both the variance deficit and the spectral weight outside the first active shell. In this way, the paper establishes harmonic confinement as the unique static extremizer for the rigid interacting center-of-mass mode at fixed active gap.
Read the full abstract

Soft Condensed Matter

Basin-volume distributions in monodisperse particle packings – the soul of memory

Varda F. Hagh, Zhaoning Liu and Sidney R. Nagel

Mechanically stable packings of $N$ particles in $d$ dimensions lie at the minima of an $Nd$-dimensional potential energy landscape. Starting from random initial particle positions, the system can relax using gradient-based optimization until it arrives at one of the equilibrium states; all initial conditions that end at the same minimum belong to the same catchment basin. We measure the distribution of the catchment basin volumes for indistinguishable monodisperse soft spheres in both $d=2$ and $d=3$. Ordering the basins at each system size, $N$, according to their volume, $P_N(n)$, from the largest at $n=1$ to smaller at larger $n$, we find a very wide distribution of volumes which is similar in both dimensions: $P_N(n) \approx A_Nn^{-\alpha}$ with $\alpha \approx 1$ which, in our most favorable cases, extends over $7$ decades. We explore aspects of the connectivity of the basins, show that their structure is highly contorted, and demonstrate how these results may be used to understand the imprinting of memories in cyclic strain studies of solids.
Read the full abstract

Quantum Physics

Equivariant Quantum Clustering with Differential Privacy: Parameter-Efficient Privacy-Preserving Analysis Across Heterogeneous Sensitive Datasets

B. M. Taslimul Haq, Md Arifur Rahman, Tawfiq Al Islam Foysal et al. (+2 more)

Privacy-preserving clustering is critical for analyzing sensitive data in healthcare, cybersecurity, and enterprise applications, where maintaining data confidentiality must be balanced with analytical performance. This paper presents Equivariant Quantum Clustering (EQC), a parameter-efficient framework that integrates symmetry-aware quantum circuits with differential privacy to improve the privacy-utility tradeoff. EQC employs p4m equivariant parameter sharing to reduce circuit complexity while preserving informative feature representations. The framework is evaluated on three privacy-sensitive datasets: NSL-KDD, CERT Insider Threat v6.2, and a synthetic MIMIC-III clinical dataset. On the NSL-KDD benchmark, EQC achieves 79.3% clustering accuracy while reducing membership inference attack success to 38.3% under a privacy budget of {\epsilon} = 1.0 and {\delta} = 10^-5, outperforming representative classical and quantum baselines. Ablation studies indicate that the performance gains primarily arise from parameter-efficient circuit design combined with differential privacy. The results demonstrate that EQC provides a practical quantum-ready framework for secure and privacy-preserving clustering across heterogeneous sensitive datasets.
Read the full abstract

All authors B. M. Taslimul Haq, Md Arifur Rahman, Tawfiq Al Islam Foysal, Abdullah Al Noman, Abir Ahmed

High Energy Astrophysical Phenomena

Multi-wavelength Constraints on the Transient EP250905a

J. Quirola-Vasquez, P. G. Jonker, A. Levan et al. (+30 more)

Fast X-ray transients (FXTs) are a diverse class of high-energy suggested origins, ranging from stellar explosions to compact object mergers. The Einstein Probe (EP) satellite discovers approximately 100 FXTs per year. We aim to constrain the physical origin of EP250905a. We analyze X-ray, optical, near-infrared (NIR), and radio temporal and spectral properties of EP250905a. In addition, we assess the possible role of weak gravitational lensing in shaping its observed characteristics. EP250905a fades rapidly in X-rays, and we detect no NIR or radio emission, but we detect early optical emission that rapidly fades beyond the detection limits. Two nearby galaxies are identified for which we derive spectroscopic redshifts of $z=0.374$ (G1) and $z=2.714$ (G2). Our analysis favors G2 as the host of the FXT EP250905a. The angular separation of 2.56\arcsec\, between the FXT's optical counterpart and the center of the G1 galaxy suggests the emission of the FXT might be moderately magnified by lensing effects ($\mu\approx3.9$) given the inferred Einstein radius of G1 ($\theta_E\approx1.9$ arcsec). The data are best explained as an afterglow from a mildly off-axis structured jet at $z=2.714$, providing a consistent broadband interpretation that also allows for weakly lensed emission of EP250905a.
Read the full abstract

All authors J. Quirola-Vasquez, P. G. Jonker, A. Levan, D. B. Malesani, F. E. Bauer, A. Martin-Carrillo, G. Corcoran, D. Mata Sanchez, R. A. J. Eyles-Ferris, F. Carotenuto, M. Ravasio, J. Sanchez-Sierras, J. Bright, J. A. Chacon, L. Cotter, F. J. Cowie, N. Sarin, M. A. P. Torres, J. N. D. van Dalen, A. P. C. van Hoof, V. D'Elia, P. Jakobsson, N. Habeeb, S. Kobayashi, A. Saccardi, M. De Pasquale, D. Xu, Y. H. Cheng, R. D. Liang, H. Sun, Y. Wang, W. Yuan, W. D. Zhang

General Relativity and Quantum Cosmology

An analytic model for a total process of gravitational collapse: From star to Schwarzschild black hole

Sinya Aoki and Jorge Ovalle

We present an exact analytical model describing a complete gravitational collapse of matter from horizonless initial conditions to black hole formation, tracing the full evolution of the horizon $H(t)$ from its formation at microscopic scales to macroscopic stabilization. The solution reveals two main stages: (i) a dynamical horizon growth, where an apparent horizon $H(t)$ emerges at a critical time $t_b$ until reaching its final size $h=2 M$, demonstrating how trapped surfaces form dynamically in finite time, and (ii) a {naked-}singularity resolution, where an integrable Ricci curvature singularity ($R^\mu{}_\nu \sim r^{-2}$) develops at $r=0$, but remains causally hidden by the horizon growth, preserving weak cosmic censorship without exotic matter. The model could offer a framework to study the quantum-to-classical transition ($H(t) \sim \ell_{\rm Planck}$).
Read the full abstract

Materials Science

Helically Enhanced Chiroptical Response and Symmetry Breaking in Conjugated Polymers

Aaron Forde, Braden M. Weight, Prashanna Poudel et al. (+5 more)

Chiral $\pi$-conjugated polymers are an attractive material platform for spin polarized carrier-transport and spectroscopy, but fundamental considerations for how torsional disorder influences the response properties of the material have not been considered. Here we combine atomistic electronic structure modeling with with experimental spectroscopic measurements to examine symmetry breaking in the prototypical $\pi$-conjugated polymer polyacetylene, (CH)$_x$. Chiral (CH)$_x$ oligomers are generated in distinct conformations which differ in their out-of-plane tonsorial ordering. We find that a helical conformation introduces orders of magnitude enhanced chiroptical activity due to a solenoid effect. This effect is visualized by the Transition Chiral Tensor analysis which shows signatures of domain ordering which eliminates destructive interference between electric and magnetic contributions. These findings highlight the capability to develop a hierarchical interpretation relating local, fragment symmetry breaking to global, nonlocal interactions governing chiroptical response in emerging chiral materials.
Read the full abstract

All authors Aaron Forde, Braden M. Weight, Prashanna Poudel, Avadh Saxena, Zeev Valy Vardeny, Christoph Boehme, Alan Bishop, Sergei Tretiak

Medical Physics · Cross-listed from eess.IV

ConRad: Efficient Conformal Prediction for Radiomics

Matt Y. Cheung, Ashok Veeraraghavan and Guha Balakrishnan

Radiomic features derived from medical images and segmentation masks are used to support decision making in clinical imaging pipelines. In practice, these features are often computed from predicted masks, but segmentation models can be overconfident or poorly calibrated, making derived measurements appear more reliable than they are. Conformal prediction (CP) provides distribution-free prediction intervals with finite-sample marginal coverage guarantees, but black-box intervals for segmentation-derived radiomics can be inefficient because they ignore test-time information about image appearance, mask geometry, and segmentation uncertainty. We propose ConRad, a conformal framework for scalar radiomic targets that uses covariates derived from the predicted mask, input image, predicted radiomics, and boundary uncertainty to construct adaptive intervals while maintaining coverage. Across five 2D medical imaging datasets and 171 retained radiomic targets, we show that ConRad improves feature-level efficiency compared to baselines while maintaining near-nominal empirical coverage. Ablation results further indicate that segmentation boundary uncertainty features are the largest contributors to interval efficiency.
Read the full abstract

High Energy Physics (Phenomenology)

$Z^\prime$ Portal Dark Matter with Observable $\Delta N_{\rm eff}$

Ang Liu, Zhi-Long Han and Fei Huang

In the conventional $Z^\prime$ portal dark matter scenario, the prediction of detectable dark matter $\chi$ typically relies on the collider sensitivities of $Z^\prime$ and direct detection, where the Majorana type right-handed neutrinos are usually assumed. However, if the right-handed neutrinos $\nu_R$ are Dirac type, they will contribute to the additional effective number of relativistic species $\Delta N_{\rm eff}$, which brings different detectable predictions for $Z^\prime$ portal dark matter. In light of the great improvement of $\Delta N_{\rm eff}$ for the upcoming experiments, we investigate the $Z^\prime$ portal dark matter with Dirac type $\nu_R$. Under the $U(1)_{B-L}$ symmetry, this model includes $\nu_R$ with $U(1)_{B-L}$ charge $Q_{\nu_R}=-1$ and $\chi$ with arbitrary $Q_\chi$ beyond the SM. Based on the relation in the production of $\chi$ and $\nu_R$, both the WIMP and FIMP dark matter through the $Z^\prime$ portal scenario are considered. We perform a comprehensive exploration of the viable parameter space under the constraints from $\Delta N_{\rm eff}$ induced by thermal and non-thermal $\nu_R$, perturbative limit, dark matter direct and indirect detection, and collider searches of $Z^\prime$.
Read the full abstract

Instrumentation and Methods for Astrophysics

Robust Heteroskedastic Matrix Factorization: A Generalization of PCA that Flags Outliers and Handles Missing Data

Thomas Hilder, David W. Hogg, Andrew R. Casey et al. (+1 more)

We present Robust Heteroskedastic Matrix Factorization (RHMF), a generalization of Principal Component Analysis (PCA) that is robust to outliers, handles per-feature uncertainties and missing data, and automatically flags per-feature and per-object anomalies. RHMF is useful both in recovering a low-dimensional embedding unspoiled by bad data or anomalies, and in identifying those anomalies. It utilises an iterative reweighting algorithm that implicitly maximizes a Student-t likelihood. This admits an equivalent probabilistic interpretation as fitting a hierarchical model with per-data-point latent variances. We deliver a fast JAX implementation, Robusta-HMF, and practical guidance for users. We demonstrate the ability of the model to identify and mitigate outliers of different classes. Identification accuracy is contingent on the choice of hyperparameters, but we show that these can be set reliably by cross-validation. We also apply RHMF to RVS spectra from Gaia DR3 to find main-sequence stars that are strange relative to their neighbors in color-magnitude space. We highlight specific examples, including a known binary hosting a Be star, and M-dwarfs with subtle emission in the Ca II triplet lines, indicative of accretion or magnetic activity, which would not be obvious to identify by eye.
Read the full abstract

All authors Thomas Hilder, David W. Hogg, Andrew R. Casey, Hans-Walter Rix

Quantum Physics

Experimental demonstration of entanglement sudden death induced by natural dissipation

Yan Wang, Hao-Long Zhang, Jia-Hao Lü et al. (+5 more)

Any quantum system inevitably interacts with its natural environment, which can be modeled as a Markovian reservoir consisting of a continuum of electromagnetic field modes. The quantum coherence of qubits in a zero-temperature natural reservoir decays asymptotically, whereas the quantum entanglement of two qubits coupled to such reservoirs may disappear in a finite time. This phenomenon, referred to as entanglement sudden death (ESD), has been simulated with artificially engineered dissipative channels, but ESD induced by natural dissipative channels has not been confirmed. We here present the first demonstration of natural-dissipation-induced ESD for two photonic qubits, each stored in a leaky resonator of a superconducting circuit. The disentanglement dynamics of the two photonic qubits is monitored with two ancilla superconducting qubits, which can be controllably coupled to the corresponding leaky resonators. The techniques developed in our experiment pave the way for experimental exploration of entanglement dynamics in natural environments.
Read the full abstract

All authors Yan Wang, Hao-Long Zhang, Jia-Hao Lü, Ken Chen, Wen Ning, Li-Hua Lin, Zhen-Biao Yang, Shi-Biao Zheng

Quantum Physics

(2,m)-threshold quantum data hiding

Donghoon Ha and Jeong San Kim

We consider multiparty quantum state discrimination and present a multiparty quantum data-hiding scheme for one classical bit to be shared among multiple parties. In the proposed scheme, any pair of parties can collaborate to perfectly recover the hidden bit through a joint measurement, whereas measurements based on local operations and classical communication(LOCC) performed even by all parties reveal only an arbitrarily small amount of information. We further provide bounds on the optimal LOCC discrimination of multiparty quantum states. The proposed scheme can be implemented using only separable states of low-dimensional quantum systems, enhancing its practical feasibility.
Read the full abstract

Accelerator Physics

Multi-GeV Electron Combs from a Plasma Wakefield Accelerator

Chaojie Zhang, Douglas Storey, Alexander Knetsch et al. (+16 more)

Plasma accelerators now produce GeV-class electron beams with brightness and stability sufficient to drive free-electron lasers. Beyond this, they possess a unique yet largely unexplored capability: shaping the phase space of the beam in situ during injection, on femtosecond or shorter timescales. Here we demonstrate this capability by generating a multi-GeV electron comb comprising more than ten microbunches simultaneously separated in both energy and time. Periodic pinching of the drive beam inside its self-excited plasma wake sequentially injects microbunches via ionization of embedded helium atoms at successive betatron oscillations, while the gently varying plasma density maps each bunchlet to a distinct wake phase, compressing electrons trapped over a ~17 cm region into a comb only micrometers long. Individual microbunches exhibit percent-level energy spreads, energy spacing up to ten percent, and contain several picocoulomb charge. The percent-level spreads and parabolic energy-spacing trend provide experimental evidence for sub-femtosecond microbunch durations and few-femtosecond separations as revealed by beam-loading analysis and confirmed by particle-in-cell simulations. This work demonstrates femtosecond, in-situ phase-space shaping in plasma accelerators, paving the way for electron beams with tailored energy-time structure.
Read the full abstract

All authors Chaojie Zhang, Douglas Storey, Alexander Knetsch, Brendan D. O'Shea, Robert Ariniello, Sébastien Corde, Thamine N. Dalichaouch, Claudio Emma, Ole G. Finnerud, Spencer Gessner, Claire Hansel, Valentina Lee, Carl A. Lindstrøm, Michael Litos, Nathan Majernik, Kenneth A. Marsh, Warren B. Mori, Mark J. Hogan, Chan Joshi

Optics

Long-range coupling enabled multiband group-velocity control of topological edge states from slow light to light stopping

Junhao Yang, Jiarui Wang, Jingyu Liu et al. (+2 more)

Topological edge states provide robust optical transport immune to disorder, yet their propagation velocity is usually constrained by the intrinsic band dispersion, limiting dynamic control of topological light transport. We introduce long-range next-nearest-neighbor (NNN) couplings into a Harper–Hofstadter photonic lattice and establish a versatile platform for group-velocity engineering. We demonstrate that the NNN couplings play two distinct roles: the vertical coupling opens a previously closed topological band gap by lifting the degeneracy of bulk bands, while the horizontal coupling reshapes the edge-state dispersion through momentum-dependent corrections, enabling controllable topological slow-light transport. Furthermore, the band-gap Chern numbers associated with different gaps exhibit opposite signs, giving rise to topological edge states with opposite chiralities. Propagation simulations reveal robust unidirectional transport of these counter-chiral edge states with reduced group velocities. By continuously tuning the NNN coupling strength, the group velocity of topological edge modes can be reduced toward zero at specific momenta, resulting in topological light-stopping effects. These results demonstrate that long-range NNN couplings provide an effective mechanism for engineering momentum-dependent topological group velocities and offer new possibilities for robust slow-light devices, optical delay lines, and multiband integrated photonic systems.
Read the full abstract

All authors Junhao Yang, Jiarui Wang, Jingyu Liu, Shirong Lin, Xinyuan Qi

Solar and Stellar Astrophysics

Investigation on the Relation between Active Regions' Compliance with Empirical Laws and Flare Productivity

Jinhui Pan, Rui Liu, Jiangtao Su et al. (+1 more)

It remains evasive whether solar active regions (ARs) obeying or violating Hale's polarity law, Joy's tilt law, and the hemispheric helicity rule (HHR) differ in flare productivity. Here we conduct a comprehensive statistical analysis of ARs during the Solar Cycle 24 and the ascending phase of Cycle 25. ARs are automatically detected from full-disk line-of-sight magnetograms acquired by the Michelson Doppler Imager (MDI) and the Helioseismic and Magnetic Imager (HMI). We calculate tilt angles via flux-weighted polarity centroids, estimate magnetic twist by the force-free parameter $\alpha_{\mathrm{best}}$ from HMI vector magnetograms, and measure flare productivity using the flare index (FI) built from GOES C-class-and-above events. Our results substantiate that the majority of ARs follow the aforementioned three empirical laws. The compliance rate tends to be higher for ARs emerging at higher latitudes or having larger centroid distance, while total unsigned magnetic flux exerts limited influence, with a clear positive correlation only for Hale's law. Overall, FI shows no significant discrepancies across different compliance groups, except that Cycle 24 ARs that satisfy Hale's and Joy's laws but violate the HHR exhibit higher FI than other groups. We also identify empirical thresholds for centroid distance and total unsigned flux, above which the median FI of binned ARs becomes nonzero. Combining the flux and distance thresholds effectively separates flare-productive from flare-quiet ARs. We hence conclude that the flare productivity of ARs is not dependent on the compliance with the empirical laws, but more closely associated with sufficiently large and strong magnetic systems.
Read the full abstract

All authors Jinhui Pan, Rui Liu, Jiangtao Su, Jie Jiang

Solar and Stellar Astrophysics

RedDots: Magnetic field of the nearby active M dwarf GJ 729, and a search for companions

E.L. Brown, S.V. Jeffers, S.C. Marsden et al. (+5 more)

M dwarfs are prime targets for discovering exoplanets, and the nearest M dwarfs to the Sun provide among the best opportunities for follow-up detailed exoplanet characterization. GJ 729, the seventh closest M dwarf to the Sun, presents significant challenges for exoplanet detection due to its high levels of magnetic activity. To address this, we present a detailed analysis of GJ 729's magnetic field and its variability, followed by a search for exoplanets beneath the activity-induced noise in the stellar radial velocity. The geometry of GJ 729's large-scale magnetic field was reconstructed using new and archival spectropolarimetric data for a total of four epochs spanning 10 years. Results indicate a weak large-scale field ranging from 50 to 145 G, and an evolving non-axisymmetric field geometry that varies from poloidal dominated to a near-equal poloidal-toroidal configuration. We modeled activity-induced radial velocity variations using Gaussian Process Regression and activity diagnostics, and searched for planetary companions using ~90 d of high-cadence spectra taken contemporaneously with the high-precision CARMENES and HARPS spectrographs. Activity-only and activity + Keplerian models offered statistically equivalent fits, with a consistently preferred Keplerian period of ~7 d and amplitude of ~1.9 m/s across a range of activity modeling approaches. This could relate to an Earth-mass or Super-Earth planet, or residual stellar activity with power concentrated at a multiple of the rotation half-period. Our findings provide insight into the magnetic behavior of fully convective M dwarfs, and highlight the potential and challenges of detecting Keplerian RV signatures that are only a fraction of activity amplitudes.
Read the full abstract

All authors E.L. Brown, S.V. Jeffers, S.C. Marsden, F. Liebing, S. Bellotti, J.R. Barnes, C.A. Haswell, V. Koseleva

Soft Condensed Matter

Active Particles Imprint Persistent Percolating Networks in Polymer Condensates

Ligesh Theeyancheri, Jennifer L. Ross and J. M. Schwarz

Fluid condensates readily exchange components and reorganize, and in doing so typically erase structural history. Using simulations of sticker-spacer polymers in an active particle bath, we show that activity drives condensates from compact droplets into system-spanning percolated networks by enhancing interchain connectivity, suppressing intrachain collapse, and increasing topological constraints through interchain winding. The network persists after the active particles are removed, despite continued polymer exchange and contact turnover, revealing a fluid-like state with activity-induced topological imprinting. Hence, activity can write long-lived structural organization and memory into fluid condensates.
Read the full abstract

Quantum Physics

Nuclear Many-Body Systems as Benchmarks for Quantum Computing

Sota Yoshida, Alessandro Baroni, Takayuki Miyagi et al. (+1 more)

We present a framework for benchmarking quantum algorithms for nuclear many-body systems based on realistic nuclear Hamiltonians such as chiral effective field theory. To this end, we introduce a workflow that maps nuclear interactions in second quantization formalism to qubit Hamiltonians. This enables the systematic construction of benchmark instances spanning no-core and valence-space formulations with two-body (NN) and selected three-body (3N) interactions. Then, we proceed to provide resource estimates for three representative eigenvalue algorithms: Quantum Phase Estimation, Quantum Krylov methods, and Observable Dynamic Mode Decomposition. We compare their resource requirements in terms of T-gate counts and system size, and examine the impact of model-space choices and many-body interactions. The primitives included in our analysis are Trotterization, Qubitization, and Quantum Singular Value Transformation. Our results quantify scaling trends across algorithms and problem classes, and provide a basis for consistent comparisons of quantum approaches to nuclear many-body problems. The implementation is provided by the NuQuLib software stack.
Read the full abstract

All authors Sota Yoshida, Alessandro Baroni, Takayuki Miyagi, Ermal Rrapaj

Instrumentation and Methods for Astrophysics

Catching Disguised Transients with ASTRANet: Anomaly-Aware Spectroscopic Classification and Conformal Calibration

Argyro Sasli, Maojie Xu, Alexandra Junell et al. (+21 more)

Time-domain surveys discover thousands of transients per year, but the spectroscopic identification of rare and physically peculiar objects remains rate-limited by closed-set classifiers that confidently assign every input to a known class – including spectra that genuinely belong to no known class. We present the ASTRANet framework, a confidence-aware infrastructure for spectroscopic transient classification built around three coupled modules: a hierarchical spectral classifier that operates directly on observer-frame spectra without requiring host-galaxy redshift or spectral phase as inputs; an anomaly detection layer (ASTRANet-Sentinel) that non-linearly combines $16$ embedding-space anomaly scores spanning four physically motivated families; and a conformal uncertainty quantification layer (ASTRANet-CP). We validate the framework on a held-out evaluation set of $289$ rare and out-of-taxonomy transients spanning $11$ classes deliberately excluded from training, chosen to span the full physical diversity of the rare-anomaly population: AGN-related outliers, GRB-related events, gap transients, novae, and peculiar supernovae. Through five astrophysically distinct failure modes of closed-set classifiers, we show that classifier-internal uncertainty and embedding-based anomaly detection are structurally complementary axes of confidence rather than alternative implementations of the same estimator. We further introduce AD-stratified Mondrian conformal prediction (AD-MCP) within ASTRANet-CP, achieving uniform conditional coverage across anomaly-score strata where vanilla Mondrian under-covers in the operational regime. This establishes the methodological infrastructure for confidence-aware spectroscopic discovery in the Vera C.\ Rubin Observatory era.
Read the full abstract

All authors Argyro Sasli, Maojie Xu, Alexandra Junell, Hailey Markoff, Avyukt Raghuvanshi, Felipe F. Nunes, Theophile Jegou Du Laz, Jesper Sollerman, Christoffer Fremling, Drew Oldag, Antoine Le Calloch, Sushant Sharma Chaudhary, Sneha Maharjan, Maxine West, Benny Border, Nabeel Rehemtulla, Richard Dekany, Joahan Castaneda Jaimes, Russ R. Laher, Reed Riddle, Mansi M. Kasliwal, Matthew J. Graham, Ashish A. Mahabal, Michael W. Coughlin

Disordered Systems and Neural Networks · Cross-listed from cs.LG

An exact information theory of generalization phase transitions in Bayesian diffusion models

Henry Hunt, Mason Kamb and Surya Ganguli

How diffusion models circumvent the curse of dimensionality to learn complex distributions over high dimensional spaces from a finite training set, instead of memorizing it, remains a fundamental mystery. To address this, we introduce analytically tractable Bayesian information restricted diffusion (BIRD) models, in which each pixel observes restricted information about noisy data. A BIRD model time-reverses diffusion by inferring which past training sample produced its current restricted observation using the Bayesian posterior. This model class generalizes existing analytical diffusion models that use spatially local information restriction. We show that spatially local BIRD models closely approximate trained diffusion models early in training, across different architectures such as UNets and DiTs. Under minimal assumptions on the data distribution, we identify an information-theoretic phase boundary between memorization and generalization in the joint space of amount of training data, time in the reverse generative process, and amount of information restriction: a BIRD model memorizes when the mutual information between its restricted noisy observations and the training data exceeds the log number of training points, and it generalizes otherwise. Experiments across a range of datasets confirm our theoretically predicted location for the transition. We find that generation proceeds near the edge of memorization: both spatially local BIRD models and early-training diffusion models track the memorization-generalization phase boundary by increasingly restricting information over time. Overall, our results reveal a fundamental role for information restriction in generative AI to circumvent the curse of dimensionality.
Read the full abstract

High Energy Physics (Phenomenology)

Study of exotic hadron states in the $DD^{*}$ system via the complex momentum representation and Green's function method

Di Wu, Mao Song, Jian-You Guo et al. (+3 more)

In this paper, we propose a novel approach to investigate exotic hadronic states. For the $DD^{*}$ system, we employ the projection operator method to derive the momentum-space interaction potential. Subsequently, the complex momentum representation (CMR) method is adopted to realize a unified description of bound states, resonant states, and the continuum. By combining the Green's function and the CMR, the scattering phase shifts and cross sections are determined. This integrated approach provides a comprehensive framework for analyzing the scattering dynamics of the $DD^{*}$ system. In the hadronic molecular state framework, the $X(3872)$, $T_{cc}^+$, and $Z_c(3900)$ states can be consistently explained as bound states, while the $G(3900)$ can be interpreted as a $P$-wave resonant state. The decomposition of the scattering phase shifts and cross sections facilitates understanding the roles of resonant and continuum spectrum.
Read the full abstract

All authors Di Wu, Mao Song, Jian-You Guo, Gang Li, Xuan Luo, Peng Wang

Nuclear Experiment

A study of neutrinoless double electron capture in $^{40}$Ca from the AMoRE experiment

AMoRE Collaboration: A. Agrawal, V.V. Alenkov, P. Aryal et al. (+106 more)

The search for neutrinoless double electron capture ($0\nu\mathrm{2EC}$) provides a sensitive probe of lepton-number violation and the Majorana nature of neutrinos. We investigate the $0\nu\mathrm{2EC}$ decay of $^{40}$Ca using cryogenic detectors equipped with metallic magnetic calorimeters in the AMoRE-I experiment. The analysis is based on a physics dataset corresponding to a total exposure of 7.32 kg$\cdot$yr from thirteen $^{40}$Ca$^{100}$MoO$_4$ crystals. No significant excess is observed, and a lower limit on the half-life is obtained as $T^{0\nu}_{1/2} > 1.7 \times 10^{22}$ yr at 90$\%$ confidence level. An improved sensitivity is expected for the upcoming AMoRE-II experiment. These results demonstrate the potential of CaMoO$_4$ detectors to explore rare decay processes beyond the primary $^{100}$Mo $0\nu\beta\beta$ search program.
Read the full abstract

All authors AMoRE Collaboration: A. Agrawal, V.V. Alenkov, P. Aryal, J. Beyer, B. Bhandari, R.S. Boiko, K. Boonin, O. Buzanov, C.R. Byeon, N. Chanthima, M.K. Cheoun, J.S. Choe, Seonho Choi, S. Choudhury, J.S. Chung, F.A. Danevich, M. Djamal, D. Drung, C. Enss, A. Fleischmann, A.M. Gangapshev, L. Gastaldo, Y.M. Gavrilyuk, A.M. Gezhaev, O. Gileva, V.D. Grigorieva, V.I. Gurentsov, C. Ha, D.H. Ha, E.J. Ha, D.H. Hwang, E.J. Jeon, J.A. Jeon, H.S. Jo, J. Kaewkhao, C.S. Kang, W.G. Kang, V.V. Kazalov, S. Kempf, A. Khan, S. Khan, D.Y. Kim, G.W. Kim, H.B. Kim, Ho-Jong Kim, H.J. Kim, H.L. Kim, H.S. Kim, M.B. Kim, S.C. Kim, S.K. Kim, S.R. Kim, W.T. Kim, Y.D. Kim, Y.H. Kim, K. Kirdsiri, Y.J. Ko, V.V. Kobychev, V. Kornoukhov, V.V. Kuzminov, D.H. Kwon, C.H. Lee, DongYeup Lee, E.K. Lee, H.J. Lee, H.S. Lee, J. Lee, J.Y. Lee, K.B. Lee, M.H. Lee, M.K. Lee, S.W. Lee, Y.C. Lee, D.S. Leonard, H.S. Lim, B. Mailyan, E.P. Makarov, P.B. Nyanda, Y. Oh, S.L. Olsen, S.I. Panasenko, H.K. Park, H.S. Park, K.S. Park, S.Y. Park, O.G. Polischuk, H. Prihtiadi, S. Ra, S.S. Ratkevich, G. Rooh, E. Sala, M.B. Sari, J. Seo, K.M. Seo, B. Sharma, K.A. Shin, V.N. Shlegel, K. Siyeon, J. So, N.V. Sokur, J.K. Son, J.W. Song, N. Srisittipokakun, V.I. Tretyak, R. Wirawan, K.R. Woo, H.J. Yeon, Y.S. Yoon, Q. Yue

Quantum Physics

Robust Quantum Learning through Hamiltonian Reservoir Computing

Youya Xu, Chengyong Yu and Sanjib Ghosh

Quantum learning provides a versatile paradigm for information processing by exploiting the intrinsic representational capacity of high-dimensional Hilbert spaces. Here, we investigate a Hamiltonian-encoding framework for quantum reservoir computing that simultaneously addresses three key challenges in quantum learning: trainability, hardware efficiency, and information stability. In this framework, input data are directly mapped onto a fixed Hamiltonian and transformed into expressive nonlinear features through quantum dynamical evolution. By employing the reservoir-computing paradigm, the approach naturally circumvents the barren plateau problem in quantum learning landscapes. We validate the framework across two complementary platforms: an analog superconducting array processor and a digital gate-based quantum circuit implementation. Despite their fundamentally different realizations, both platforms exhibit comparable representational power and achieve competitive learning performance, establishing a unified framework for cross-platform quantum learning. While both implementations achieve comparable performance, the analog processor may offer a more hardware-efficient realization by bypassing the temporal overhead of gate-based decomposition and thereby making more effective use of finite coherence times, albeit at the expense of universality. Furthermore, we find that finite dissipation suppresses quantum-scrambling-induced instabilities at long evolution times and can enhance learning performance, revealing a constructive role for environmental coupling in stabilizing quantum learning dynamics. Collectively, these results establish Hamiltonian-encoded reservoir computing as a compact, expressive, and hardware-efficient paradigm for quantum learning on current-generation quantum platforms.
Read the full abstract

Solar and Stellar Astrophysics

A Transport Theory of Turbulent Coronal Heating in General Geometry

Jonathan Squire, Benjamin D. G. Chandran, Toby Adkins et al. (+3 more)

Magnetic geometry shapes how turbulence transports and dissipates energy in strongly magnetized plasmas. The solar corona, a maze of open and closed flux tubes with sharp transverse gradients, is a prominent example, yet most wave-turbulence models of coronal heating assume symmetric flux tubes or add geometric effects in ad hoc ways. Here we develop a geometry-complete multiscale transport theory for reduced-magnetohydrodynamic turbulence in an arbitrary background field, retaining squashing (magnetic shear), transverse gradients, curvature, and gravity at the same order as standard expansion-driven reflection, and coupling fast, anisotropic fluctuations to slow background evolution through conservation laws. Applied to the corona, it recovers the standard reflection-driven turbulent cascade in smooth regions such as coronal-hole interiors, but predicts that in structured regions geometry-driven channels can dominate: squashing drives reflection even when parallel Alfvén-speed gradients are weak; curvature and non-radial geometry drive compressive heating channels; and waves catalyze the relaxation of velocity shear into heat. The same dynamics drive cross-field transport of mass, composition, momentum, and heat across open-closed interfaces, at rates rivaling the field-parallel supply from the base. These effects bias heating to low altitudes in structured regions, giving a physical basis for the coronal-hole–boundary corrections used in empirical wind-speed predictors. Additionally, the framework's slow-timescale transport equations could be evolved in time, providing a route to a global, geometry-aware model of a structured wave-driven corona and wind. More broadly, the theory provides an energy-consistent account of turbulence, geometry, and transport effects relevant to various astrophysical and terrestrial settings, from magnetospheres and accretion flows to fusion experiments.
Read the full abstract

All authors Jonathan Squire, Benjamin D. G. Chandran, Toby Adkins, William A. Clarke, Romain Meyrand, Matthew W. Kunz