Mesoscale and Nanoscale Physics
Simulating multi-node Weyl semimetals in a Mixed Floquet lattice
Goutham Vinjamuri, Ashutosh Dubey and Ankur Das
In this work, we simulate Weyl semimetal phases with multi-nodes containing 2, 4, 6, and 8 Weyl nodes, in a mixed Floquet synthetic
lattice generated by driving a one-dimensional chain with two incommensurate drives. In contrast to the integer-quantized response of Chern
insulators, we obtain a momentum-resolved power-transfer signature, where coupling the drives to fixed momenta results in quantized power-transfer for each 2D slice corresponding to that momentum, thereby locating the Weyl nodes in the low-frequency limit. Further, we explicitly show for the Weyl phase with 2 nodes, in the adiabatic limit, the half-filled state exchanges energy between the two drives at a rate that converges to the projected Weyl-node separation equal to the
Fermi-arc length of the Weyl semimetal.
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Mesoscale and Nanoscale Physics
Charge imprinting biases topology of correlated insulator in hBN-aligned rhombohedral multilayer graphene
Lei Qiao, Xin Lu, Fu-Chun Zhang et al. (+1 more)
Rhombohedral multilayer
graphene aligned with hexagonal boron nitride (RMG-hBN) hosts correlated Chern phases, but the microscopic role of hBN stacking remains unclear, especially when the active carriers are displaced away from the moiré interface. Using Hartree-Fock calculations over layer numbers, twist angles, displacement fields, fillings, and hBN
alignments, we show that correlated
insulators are most robust at small twist angles and intermediate layer number ($N\simeq 6$), where bandwidth suppression is balanced by layer delocalization of the wavefunctions of the active carriers. Under moiré-distant conditions at filling $\nu=1$, the
topology of the insulating state is strongly biased by charge imprinting: the hBN
alignment shapes the occupied valence-band charge texture near the interface via moiré potential, which acts through long-range Coulomb interactions as a remote electrostatic template for doped conduction electrons. Depending on the
alignment, this template favors either triangular charge localization associated with trivial
insulators or honeycomb-like charge networks compatible with Chern
insulators. Our results identify valence-band charge textures as a microscopic route by which a remote moiré interface controls correlated
topology in multilayer
graphene.
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All authors Lei Qiao, Xin Lu, Fu-Chun Zhang, Jianpeng Liu
Optics
Attosecond Path Qubits in High-Harmonic Generation: Classical Dephasing and Trace-Out Decoherence
A. Marchisio, C. Granados, M. F. Ciappina et al. (+1 more)
High-harmonic generation (HHG) is governed by interference between electron trajectories. We propose that the dominant short and long trajectories define an experimentally addressable two-level subsystem: an attosecond path
qubit (APQ). We formulate a trajectory-resolved density
matrix to identify two distinct coherence-loss mechanisms: classical dephasing from ensemble averaging and
quantum decoherence arising from the trace-out of unobserved degrees of freedom. By investigating shot-to-shot fluctuations and unresolved transverse momentum, we demonstrate that while dephasing suppresses coherence through averaging, the “trace-out” channel produces mixed states even for fixed driving parameters. We explore how these mechanisms modify APQ purity and show that mode selection and conditioning provide operational routes to isolate them. These results establish a reduced-state framework for diagnosing coherence loss in HHG and for engineering trajectory-based
quantum states in attosecond interferometry.
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All authors A. Marchisio, C. Granados, M. F. Ciappina, O. Cohen
Materials Science
Breaking symmetry to create a parallel-plate varactor dielectric with unparalleled microwave performance
Florian Bergmann, Matthew R. Barone, Zishen Tian et al. (+24 more)
Voltage-tunable capacitors (varactors) are key to microwave
circuits. Tunable dielectric varactors outperform competing technologies in almost every relevant metric but usually suffer from high dielectric loss. In contrast, Ruddlesden-Popper (RPs) dielectric thin films have remarkably low microwave loss. Unfortunately, their crystallographic
symmetry has until recently dictated an in-plane device structure, precluding the favorable out-of-plane parallel-plate varactor design for minimized size and maximized electric field in the tunable dielectric. Guided by theory, we report RPs akin to the widely studied tunable microwave dielectric BaxSr1-xTiO3. Assembling these same atoms into the first RP phase with broken out-of-plane
symmetry, we achieve a low-loss, out-of-plane tunable dielectric thin film. The highest performing film, (ATiO3)nAO film with A = Ba0.45Sr0.55 and n = 8, unlocks a tenfold improvement in the figure of merit for out-of-plane tunable dielectrics at 10 GHz, paving the way for a new generation of tunable monolithic microwave integrated
circuits.
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All authors Florian Bergmann, Matthew R. Barone, Zishen Tian, Aiden Ross, Gerhard H. Olsen, Meagan C. Papac, Samuel Freed, Bryan T. Bosworth, Nicholas R. Jungwirth, Eric J. Marksz, Tomasz Karpisz, Noah Schnitzer, Lopa Bhatt, David A. Muller, Dylan Sotir, Akash Surampalli, Veronica Goian, Christelle Kadlec, Stanislav Kamba, Asher Hansen, Nathan Rongitsch, Dmitri A. Tenne, Ichiro Takeuchi, Long-Qing Chen, Lane W. Martin, Nathan D. Orloff, Darrell G. Schlom
Instrumentation and Methods for Astrophysics
ELMA: ELlipse-based bar MAjor axis estimator
Bruna R. Bragança de Lima, Andressa Wille, Rafael S. de Souza et al. (+1 more)
Galactic bars are key non-axisymmetric structures in disk
galaxies, driving angular-momentum redistribution and contributing to secular
evolution, central mass build-up, and the formation of
nuclear structures. Robust and homogeneous measurements of bar length, however, remain challenging, particularly for large imaging surveys, where manual estimates are time-consuming and sensitive to methodological choices. We introduce elma, a standalone, pip-installable Python package for automated bar-length estimation in
galaxies already identified as candidate barred systems. The method operates directly on two-dimensional imaging data, using iterative elliptical-isophote fitting to trace the radial ellipticity profile and identify a projected bar-length estimate from the semi-major axis associated with the local maximum in ellipticity. Using the image WCS information and a user-supplied
redshift, elma converts angular measurement into a projected physical length. We demonstrate the package on JWST/NIRCam imaging of barred
galaxies in the GOODS-South field. The code is released under the MIT license at a repository in Github.
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All authors Bruna R. Bragança de Lima, Andressa Wille, Rafael S. de Souza, Ana L. Chies-Santos
Solar and Stellar Astrophysics
DEM analysis of the 6 September 2011 large-scale coronal wave
Amaia Razquin, Astrid M. Veronig and Karin Dissauer
Large-scale coronal waves are globally propagating intensity enhancements in extreme-ultraviolet (EUV) and soft X-ray (SXR) observations, associated with
solar flares and coronal mass ejections (CMEs). They are interpreted as low-coronal signatures of a large-amplitude fast magnetosonic wave. On 6 September 2011, a fast (v = 1000 km/s) large-scale coronal wave accompanied an eruptive X2.1 class
flare. A segment of the wave front temporarily dissappeared in EUV channels sensitive to quiet-Sun
plasma, while it remained visible in higher temperature channels. We apply differential emission measure (DEM) diagnostics to SDO/AIA EUV observations to derive local density, temperature, emission measure, and DEM distributions, and examine their temporal
evolution during the wave passage. The wave passage causes increases of 6-8% in density and 10-18% in temperature. While the density increase is comparable to earlier reports, the temperature increase exceeds expectations. This indicates that the temperature enhancement cannot be explained by compressional adiabatic heating alone, and instead suggests the presence of additional heating mechanisms, such as
magnetic reconnection or wave mode conversion. During the temporary disappearance of the wave, the
plasma parameters at the wave front increase, but with a strong spatial variability, with density increases ranging from 1% to 10%. The initial temperature in the affected area is notably higher than typical quiet-Sun regions (T > 1.7 MK), which allows
plasma to be heated beyond the peak response of the AIA 193 and 211 Åchannels. We conclude that the apparent temporary disappearance of the wave front is primarily due to the combined effects in the intensity of the CME-associated coronal dimming following the wave and the wave itself, with heating further reducing its detectability in channels sensitive to quiet-Sun temperatures.
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Instrumentation and Methods for Astrophysics
Advancing Astrophysics with the SKA II
Anna Bonaldi, Tyler L. Bourke, Philippa Hartley et al. (+45 more)
Advancing Astrophysics with the SKA II (AASKAII), written by our science community, outlines the transformative scientific advances that will be enabled by the SKA
telescopes. In the decade since the publication of the previous edition,
telescope designs have matured, construction has commenced, and the SKA Organisation has evolved into the SKA Observatory (SKAO). At the same time, observations from SKA precursor and pathfinder
telescopes have provided new insights into longstanding scientific challenges while revealing entirely new phenomena. Published in advance of the first science verification campaign for the SKA Observatory, this volume looks ahead to the coming decades of discovery and innovation in
radio astronomy. AASKAII spans the broad range of scientific research enabled by the SKA
telescopes, SKA-Mid and SKA-Low. The contributions are organised into six thematic categories according to their scientific focus. The opening section presents overview chapters from the SKA Science Working Groups, around which our community is organised. Each overview provides the broader context that connects the contributions in this volume to the key scientific questions being pursued by their respective communities.
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All authors Anna Bonaldi, Tyler L. Bourke, Philippa Hartley, Tao An, Marc Audard, Olga Bayandina, Nicola Bellomo, Eleonora Bianchi, Marta Burgay, Joseph Callingham, Stefano Camera, Viviana Casasola, Virginia Cuciti, Philippa Cole, Neeraj Gupta, Catherine L. Hale, Ian Harrison, Jason Hessels, Tim Huege, Bhal Chandra Joshi, Aris Karastergiou, Dharam Lal, Adrian Liu, James Miller-Jones, S. A. Mao, Javier Moldon, Leah K. Morabito, Katharine Mulrey, Shane O'Sullivan, Divya Oberoi, D.J. Pisano, Kaustubh Rajwade, Mark T. Sargent, Rohit Sharma, Marta Spinelli, Xiaohui Sun, Fatemeh S. Tabatabaei, Cathryn Trott, Jacco Th. van Loon, Tessa Vernstrom, Jeff Wagg, Jing Wang, Ke Wang, Sven Wedemeyer, Jennifer L. West, Patrick Woudt, Jun Yang, Pietro Zucca
High Energy Physics (Phenomenology)
Revisiting the role of saturation in diffractive vector meson production
Heikki Mäntysaari, Hendrik Roch, Björn Schenke et al. (+2 more)
We perform a global
Bayesian analysis of coherent and incoherent diffractive $\mathrm{J}/\psi$ photoproduction in $\gamma+p$ and $\gamma+\mathrm{Pb}$ collisions using a Color Glass Condensate (CGC)-based framework and ultraperipheral collision data from the Large
Hadron Collider (LHC), corrected for the expected effect of electromagnetic dissociation (EMD). Using Gaussian-process emulators of the underlying CGC calculations, we infer model parameters from a combined set of HERA and LHC measurements. We find that the $\gamma+\mathrm{Pb}$ data with EMD correction substantially reduce the previously observed tension between
proton and
nuclear datasets, enabling a consistent simultaneous description of diffractive $\mathrm{J}/\psi$ production in $\gamma+p$ and $\gamma+\mathrm{Pb}$ collisions within the CGC framework.
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All authors Heikki Mäntysaari, Hendrik Roch, Björn Schenke, Chun Shen, Wenbin Zhao
Instrumentation and Methods for Astrophysics
Lightstack: A Python Package for Creating Photometric Data Cubes
Andressa Wille, Rafael S. de Souza, Ana L. Chies-Santos et al. (+3 more)
Multi-band photometry traces diverse physical processes across a wide range of wavelengths. In recent decades, this field has been driven by the rapid growth of multi-imaging
datasets, from high-resolution observation from Hubble Space
Telescope and James Webb Space
Telescope to the forthcoming large-scale surveys enabled by the Roman Space
Telescope and Rubin Observatory, for example. In this work, we present lightstack, a Python package for combining standalone images into photometric data cubes. The workflow consists of three main steps: cropping a region of interest from a mosaic across all available filters; stacking the images to construct the data cube; and performing PSF matching on the cube. This package is intended for preparing data for studies involving multi-band photometry. The code is released under an MIT license and is available on GitHub together with a Jupyter tutorial notebook. The version used for this publication (v0.2.1) is archived on Zenodo.
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All authors Andressa Wille, Rafael S. de Souza, Ana L. Chies-Santos, Thallis Pessi, Emille E. O. Ishida, Alberto Krone-Martins
Earth and Planetary Astrophysics
A long-term spectro-temporal study of Jovian X-ray and Ultraviolet response to solar activity
Megha Tomer, Mayukh Pahari, Anurag Baruah et al. (+1 more)
We present results from a multi-decade investigation of
solar activity-driven variability in Jupiter's emissions, using
solar X-ray flux and sunspot numbers as activity indicators and ultraviolet (UV) and X-ray observations from the International Ultraviolet Explorer (IUE; 1978-1996) and the Chandra X-ray Observatory (2011-2021). Analysis of 51 high-SNR UV spectra spanning two
solar cycles shows that Jupiter's Ly$\alpha$ emission contains narrow and broad components, likely associated with the disk and auroral regions, respectively. The Ly$\alpha$ line and the 1330-1400 Angstrom continuum flux closely follow variations in
solar X-ray flux and sunspot numbers throughout all phases of two consecutive
solar cycles, indicating a direct connection with
solar irradiation processes, including resonant scattering of
solar Ly$\alpha$
photons and photoelectron-driven atmospheric excitation. In contrast, ionised UV lines such as Fe II (1608 Angstrom and 1575 Angstrom) show no correlation with
solar activity over a
solar cycle, suggesting an internal or magnetospheric origin, potentially linked to Io-derived charged particles or UV/X-ray radiation. To determine whether Jupiter's X-ray response resembles its UV response to
solar activity, we analysed 29 Chandra/HRC observations obtained during 2014-2021 and two Chandra/ACIS observations from 2011. Significant X-ray
flares are detected in both ACIS and HRC lightcurves 7-15 days after major reported coronal mass ejections (CMEs). Post-CME ACIS auroral spectra reveal a significant ($\geq 3\sigma$) Ne$^{8+}$ emission feature ($\sim$0.94-0.98 keV) near 70-80$^\circ$ latitude at Jupiter's north pole. Owing to the high ionisation energy required ($\sim$1.19 keV for the Ne VIII to Ne IX bound-bound transition), this feature is unlikely to arise from local interactions, supporting CME-driven auroral excitation on Jupiter.
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All authors Megha Tomer, Mayukh Pahari, Anurag Baruah, Renu Malhotra
Applied Physics
Determination of the intrinsic mechanical quality factor in high-stress silicon nitride resonators
Geena Benga, Vincent Dumont, Wei Wang et al. (+6 more)
Recent advances in silicon nitride nanomechanical resonators have pushed mechanical quality factors to ultra-high values by combining stress-induced dissipation dilution with mode-shape engineering. Neither mechanism alters the intrinsic quality factor $Q_{\mathrm{intr}}$. Targeting the intrinsic loss itself therefore remains an untapped route to even higher $Q$. Doing so first requires reliable quantification of $Q_{\mathrm{intr}}$, which has proven challenging. Here we present a robust methodology that quantifies $Q_{\mathrm{intr}}$ by combining automated mode identification with systematic ringdown measurements over a large number of mechanical modes. Applied to high-stress silicon nitride membranes, it reveals a systematic dependence of $Q_{\mathrm{intr}}$ on thickness that cannot be described using established models, particularly in the ultra-thin limit. We account for this trend with a phenomenological model that incorporates a thickness-dependent loss channel. Together, our method and model open a route toward a microscopic understanding of intrinsic dissipation and toward directly mitigating its loss channels.
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All authors Geena Benga, Vincent Dumont, Wei Wang, Nicola Cavalleri, Ariane Giesriegl, Silvan Schmid, Christian L. Degen, Antonius Armanious, Alexander Eichler
High Energy Physics (Theory)
Fortuity beyond counting: an explicit construction
Stefano Giusto, James Inglis and Rodolfo Russo
We reconsider the "fortuity” mechanism in the D1D5 CFT focusing on the K3 symmetric orbifold. Going beyond the counting of BPS states, we investigate perturbatively how the explicit form of the BPS
cohomologies is modified by the twist-two deformations. We calculate the action of the supercharges in the sector $(h,j)=(1,0)$ for different values of the central charge and derive explicit expressions for the primary states. Equipped with this information, we compare some protected three-point couplings in the free and the
gravity regime. We show that agreement between the two descriptions imposes non-trivial constraints on the identification of monotone and fortuitous states. In particular, we argue that the map relating theories with different values of the central charge must and can be defined so as to commute with the supercharges that define the cochain complex. We then study the three-point correlators between the fortuitous and monotone states identified in our analysis to assess whether the two sectors are dynamically decoupled. We find an explicit example of a non-vanishing coupling between two monotone and a fortuitous state, providing evidence that the two sectors are dynamically connected.
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Fluid Dynamics
Planar Lagrangian transport and scalar-gradient organization in a turbulent reacting shear layer
Sriram P. Kalathoor and Joseph C. Oefelein
We analyze planar Lagrangian transport and scalar-gradient organization in a supersonic, reacting hydrogen-air temporal mixing layer using time-resolved mid-plane data from a three-dimensional direct numerical simulation. The analysis combines forward/backward finite-time Lyapunov exponent (FTLE) fields, operational FTLE-ridge skeletons, Cauchy-Green deformation measures, shear-LCS metrics, and planar
hyperbolic geodesic-LCS extraction to examine how finite-time stretching structures the reacting shear layer. The time-resolved FTLE ridges identify repelling and attracting finite-time transport skeletons in the constrained two-dimensional slice, from which ridge geometry, intersection occupancy, persistence, and scalar-conditioned transport are quantified.
Hyperbolic geodesic LCS are extracted from Cauchy-Green tensors reconstructed from planar flow maps as strainlines seeded at high-$\lambda_{\max}$ normal maxima, providing a variational counterpart to the operational FTLE-ridge skeleton. We then relate the transport skeleton to temperature, mixture fraction, and a reaction intermediate. The results show localized forward/backward ridge overlap, strong scalar-gradient enrichment, finite-time geodesic LCS that occupy the same high-strain transport skeleton, residual direction-dependent separation from a time- and cross-stream-stratified null model, and scalar-response lags that remain compact relative to decorrelation and FTLE-integration scales. Together, these results provide a transport-oriented characterization of coherent structures and their role in mid-plane mixing within a compressible reacting shear flow.
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Solar and Stellar Astrophysics
V7995 Sgr: A New FU Orionis Accretion Outburst Near NGC 6589/6590
Lynne A. Hillenbrand, Kishalay De Adolfo S. Carvalho, Dan Stern et al. (+2 more)
We announce a new FU Orionis type outburst that reached peak brightness in late 2024, following a steep 4.6 month photometric rise of -2.85 mag in the $r$ band. This rapid brightening at all wavelengths was preceeded in the infrared by a much shallower rise over 4 years. The progenitor object was an unstudied young
stellar object having a flat-spectrum type spectral energy distribution, and extended nebulosity. We present multi-wavelength lightcurves covering the photometric low-state, the outburst, and early post-outburst epochs. Optical imaging shows a concurrent brightening of the extended nebular environment. We also present follow-up optical/near-infrared spectroscopy taken 1.5 years after the inferred photometric peak. The spectra confirm an FU Ori type outburst. The outburst source exhibits a mixed-temperature absorption spectrum, formed in an
accretion disk, and it shows several line species with blueshifted absorption profiles that are formed in a strong wind.
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All authors Lynne A. Hillenbrand, Kishalay De Adolfo S. Carvalho, Dan Stern, Evan Portnoi, Nicholas Earley
Materials Science
Effective masses, Burstein-Moss shift, and bandgap renormalization in degenerate Al-doped ZnO from broadband ellipsometry and Hall measurements
S. Mishra, L. A. Enrique, D. Cespedes et al. (+7 more)
A comprehensive methodology is developed to extract electron and hole effective masses in degenerate
semiconductors through a simultaneous global fit of carrier concentration dependence of bandgap and
plasma energy, explicitly incorporating band nonparabolicity. Broadband spectroscopic ellipsometry combined with
Hall effect analyses enables accurate determination of the bandgap,
plasma energy and carrier concentrations. The dielectric function of sputtered Al-doped ZnO thin films are modeled in the fundamental absorption region using an Elliott based model with overlapping excitonic transitions and Urbach tails, while free carrier absorption is described by a modified sernelius formula. Wide carrier concentrations are achieved via controlled deposition and post-annealing, revealing changes in electron effective masses and deviations from
parabolic dispersion. Two nonparabolic models are compared, Pisarkiewicz, assuming spherically symmetric band with a step-function approximation of the
Fermi-Dirac distribution and Nilsson, incorporating thermal and
impurity effects. The latter is shown to capture accurately band nonparabolicity, yielding effective masses and nonparabolicity parameter consistent with bandgap
evolution. This approach quantitatively separates Burstein-Moss shift and bandgap renormalization, reproducing carrier dependent bandgap shifts across a wide concentration range. Neglecting valence band contributions introduces systematic bias. Bandgap renormalization is further evaluated using plasmon pole and random phase approximations, underscoring the importance of many-body screening. This framework also enables determination of the Mott critical concentration and the fundamental absorption edge onset. Collectively, these results establish a reliable methodology for extracting band-structure parameters and bandgap shifts, extendable to other transparent conducting
oxides.
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All authors S. Mishra, L. A. Enrique, D. Cespedes, E. Perez, E. Serquen, F. Bravo, P. Llontop, F. Ruske, L. Korte, J. A. Guerra
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Critical Percolation as a Synthetic Data Model for Interpretability
Aryeh Brill and Tom Ingebretsen Carlson
Neural networks learn features that reflect the hierarchical, multi-scale structure of natural data. Synthetic
datasets used to evaluate interpretability methods typically lack this structure, limiting their value as realistic toy models. To close this gap, we introduce a family of synthetic
datasets consisting of hierarchical functions defined on critical mean-field percolation clusters embedded in a high-dimensional data space. The percolation data consists of sparse, low-dimensional fractal clusters with a power-law size distribution. Latent variables modeling a taxonomic hierarchy generate each data point's target value. The data model is analytically tractable with known critical exponents that fix its properties without requiring hyperparameter tuning. We leverage a mapping between percolation clusters, random trees, and additive coalescence to propose an almost linear-time
algorithm to jointly sample a random tree and its hierarchical latent decomposition, enabling data generation at arbitrary scale. Using probing experiments, we find that the model's ground-truth latent variables can be linearly decoded from neural network activations. Together, sparsity, self-similarity, power-law statistics, and analytical tractability make critical percolation a principled testbed for interpretability research.
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Quantum Physics
Effective discrete-modulated continuous variable QKD under general attacks using dimension reduction
Mariana Navarro, Mateus Araújo, Antonio Acín et al. (+1 more)
Continuous variable
quantum key distribution via discrete modulations ensures information-theoretic security using standard telecom technologies, providing affordable and scalable
quantum communications with simplified classical postprocessing. However, existing security proofs against general attacks often rely on restrictive assumptions, such as a bounded dimension for coherent states, or require impractically large block sizes. In this work, we develop a finite-size security analysis that removes these limitations while incorporating realistic experimental features. Our approach combines an optimization under infinite dimensions, a security proof against general attacks, a trusted detector model accounting for the receiver imperfections, and postselection strategies to reuse discarded measurement outcomes. We report positive key rates in the finite-size regime for relevant block sizes of the order of $10^7$. These results contribute to narrowing the gap between theoretical security proofs and practical implementations of discrete-modulated continuous variable
quantum key distribution protocols.
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All authors Mariana Navarro, Mateus Araújo, Antonio Acín, Carlos Pascual-García
Adaptation and Self-Organizing Systems
Synchronization modes in bipartite oscillator networks
Pau Pomés, Bastian Pietras and Ernest Montbrió
Collective oscillations in neuronal systems often arise from interactions between excitatory and inhibitory populations rather than from recurrent coupling within a single ensemble. Motivated by the coexistence of strongly and partially synchronized regimes in such systems, we study the Kuramoto Sakaguchi model on a bipartite network. Despite its minimal structure, the model exhibits rich collective dynamics, including both continuous and discontinuous transitions from full synchrony to partial synchrony (PS). In the PS regime, global oscillations fail to entrain one of the two populations, whose oscillators display quasiperiodic dynamics with an average frequency that can significantly deviate from that of the global field, as observed in neuronal networks. We show that this PS state constitutes an example of self-organized quasiperiodicity, arising here in the canonical Kuramoto Sakaguchi model despite its purely linear global coupling.
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Quantum Physics
Quantum ring all-reduce: communication and privacy advantages for distributed learning
María Gragera Garcés and Lirandë Pira
Machine learning models have scaled to unprecedented sizes, making training across distributed devices the de facto standard in the field. In this work, we explore how
quantum communications can make distributed training both more communication-efficient and information-theoretically private, for both classical and
quantum learning models. Ring all-reduce is the foundational communication primitive for large-scale distributed training. We present a
quantum version that reduces per-link online communication by a provably optimal factor of two using pre-shared
entanglement and superdense coding, without requiring the learning model or gradient computation to change. Beyond bandwidth, the primitive enables
privacy guarantees that are information-theoretically impossible for any classical protocol, achieving composable {\epsilon}-secure aggregation, via verified
entanglement, at a 2x overhead in GHZ copies. Our hybrid
quantum-classical communication architecture yields simultaneous communication and security advantages for large scale distributed training, regardless of whether the learning itself is
quantum or classical. Finally, we characterise
quantum advantages in gradient conflict detection for server-to-client communication under bandwidth constraints, a setting that arises after ring all-reduce is completed, when full gradient broadcast to external clients is infeasible. Two variants of the problem admit different separations. For margin-based
alignment testing (GapIP_{\tau}), the
quantum advantage is quadratic in the margin parameter: \widetilde{O}({\tau}^{-1}\log P)
qubits versus \widetilde{O}(\min(\{\tau}^{-2},P)) bits. For sign-consistency
auditing against a private parameter matching (TieAudit_{\epsilon}), the advantage represents an exponential separation in communication complexity: \Omega(\sqrt{P}) bits whereas O({\epsilon}^{-2}\log P)
qubits suffice.
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High Energy Physics (Phenomenology)
Renormalization of axial anomaly in SU(N)$\times$U(1)
Tanmoy Pati and Narayan Rana
Defining $\gamma_5$ within dimensional regularization remains a fundamental challenge. Larin's prescription addresses this by introducing additional renormalization constants to restore standard and
chiral Ward identities. While these constants are known up to four loops in pure
quantum chromodynamics, current precision Standard Model phenomenology requires extending these corrections to mixed gauge sectors. In this article, we propose a novel technique utilizing form factors and the universality of infrared divergences to compute these constants. Applying this framework, we present the new three-loop results for the renormalization constants, as well as the pure-singlet contributions to the
quark axial-vector form factor, for a mixed $SU(N) \times U(1)$ gauge group.
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Quantum Physics
Phase locking nuclear spins in silicon with spin-orbit coupling
Habitamu Y. Walelign, Manas Ranjan Sahu and John M. Nichol
Because they have such long coherence times,
nuclear spins have extraordinary potential for use in
quantum information processing devices. However, coherent
nuclear spin control generally requires external phase references, such as microwave control fields. Here, we phase-lock a $^{29}$Si
nuclear spin ensemble in a silicon
quantum dot using only the internal electronic
spin-orbit coupling as a phase reference. When driven with the
quantum-dot electrons, the
nuclear spins align themselves to a phase determined by the electronic
spin-orbit coupling and the timing of the drive protocol. This enables us to measure the coherent precession and inhomogeneous dephasing of the
nuclear spins. We corroborate our results with detailed numerical simulations of the many-body electron
nuclear system. Our work opens new routes for coherently controlling solid-state
nuclear spin ensembles.
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Mesoscale and Nanoscale Physics
Diagnosing the origin of quantum oscillation beating in graphene
Akash Adhikary, Sunit Das, Divya Sahani et al. (+2 more)
Magnetic quantum oscillations are usually periodic in inverse
magnetic field, and their amplitude can show beating when two nearby frequencies interfere. In
graphene-based hexagonal systems, such beating can arise from strain-induced pseudomagnetic fields, unequal valley populations, valley-dependent energy shifts,
spin-orbit coupling-induced band splitting, or Kekulé distortions. Here, we show that the carrier density and
magnetic field dependence of the beating nodes can distinguish these mechanisms. Starting from Onsager's quantization relation, we derive scaling relations for the critical carrier density $N_c$ for the beating nodes as a function of critical
magnetic field $B_c$. A pseudomagnetic field gives $N_c\propto B_c^2$, whereas a density-independent valley imbalance gives $N_c\propto B_c$. A constant Dirac-band energy splitting by Zeeman-like
spin-orbit coupling also gives quadratic field scaling, but with a different node sequence: $N_{c,j}\propto(2j+1)B_{c,j}^2$ for a pseudomagnetic field and $N_{c,j}\propto(2j+1)^2B_{c,j}^2$ for energy splitting, where $j$ labels the beating node indices. These results provide quantitative constraints on different microscopic origins of valley- and
spin-dependent band splittings in
graphene-based systems.
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All authors Akash Adhikary, Sunit Das, Divya Sahani, Aveek Bid, Amit Agarwal
Instrumentation and Methods for Astrophysics
Instruments for Focal Plane X-Ray Polarimetry in the Next Decade
Fabio Muleri, Stefano Cesare, Enrico Costa et al. (+18 more)
The successful detection of X-ray polarization from many celestial sources belonging to different classes by the IXPE mission has opened a new window in X-ray astronomy. While an impressive number of scientific topics have already been addressed by IXPE, many of them would benefit from a new class of instrumentation that could be launched on a relatively short time scale. In this contribution, we present the development activities of a focal-plane polarimeter whose goal is to extend the energy range of IXPE up to tens of keV, with better sensitivity and lower background. Our design is based on the use of multilayer mirrors and stacked instrumentation, comprising either a low- or medium-energy imaging photoelectric polarimeter and an active Compton polarimeter. Such an approach relies on hardware with flight heritage and – although still under development for the specific application in X-ray polarimetry – it has the potential to answer compelling scientific questions and to soon become competitive from the point of view of feasibility for space applications.
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All authors Fabio Muleri, Stefano Cesare, Enrico Costa, Walter Cugno, Klaus Desch, Alessandro Di Marco, Sergio Fabiani, Riccardo Ferrazzoli, Markus Gruber, Daniel Heuchel, Saba Imtiaz, Jochen Kaminski, Dawoon Edwin Kim, Alessandro Lacerenza, Carlo Lefevre, Hemanth Manikantan, Vladislavs Plesanovs, John Rankin, Ajay Ratheesh, Alda Rubini, Paolo Soffitta
Astrophysics of Galaxies
A merger shock traced by radio arcs and ultra-long radio tails in galaxy cluster A2142
Chong Ge, Ming Sun, Chris Nolting et al. (+2 more)
Abell 2142 (A2142) is a massive, nearby
galaxy cluster undergoing a complex merger. It exhibits an elongated X-ray morphology along the northwest-southeast axis and hosts four known cold fronts. Using XMM-Newton observations, we detect a merger shock on the northwest side of the cluster with a Mach number of $M \sim 1.3$. The observed shock front and four cold fronts can be reproduced by numerical simulations of an off-axis merger with a large impact parameter, which imparts significant angular momentum to induce the sloshing of the subcluster core and large-scale ambient gas. In projection, the shock front is spatially coincident with arc-shaped
radio filaments observed behind the prominent head-tail
radio galaxies T1 and T2. We interpret these
radio arcs as partial
vortex ring structures (resembling “smoke rings”) produced by the interaction of the merger shock with the low-density cocoons of
radio galaxies. The shock strips and rolls the jet cocoon into a toroidal
vortex, as predicted by recent magnetohydrodynamic simulations. We further demonstrate that the merger shock can significantly elongate the
radio tails by re-accelerating aged relativistic electrons and stretching the tail
plasma via the post-shock wind. This process provides a natural explanation for the $>$500 kpc tail observed in this and other merging clusters. Our findings establish
radio arcs and ultra-long
radio tails as independent, complementary tracers of merger shocks in
galaxy clusters. Our results demonstrate that merger shocks can reshape both the thermal and non-thermal components of
galaxy clusters, and that tailed
radio galaxies serve as sensitive probes of intracluster medium weather.
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All authors Chong Ge, Ming Sun, Chris Nolting, Fabio Gastaldello, Dominique Eckert
High Energy Physics (Theory)
The magic of the gravitational vacuum
Samir D. Mathur
The black hole information paradox challenges us to do something that is seemingly impossible: find a violation of the semiclassical approximation in a region where all
curvatures are low. The vecro hypothesis proposes a structure of the gravitational
vacuum that can accomplish this task. In this article we explain the hypothesis, and give a
lattice model to describe the essence of its idea. The
Hamiltonian of the model is completely local, but the
vacuum exhibits correlations among planck scale fluctuations which fall off relatively slowly with distance. These extended-scale correlations are able to `feel around' the region where a closed trapped surface is about to form, and to react by nucleating fuzzball structure that destroys semiclassical spacetime.
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Quantum Physics
Observation of alignment tensor effects in metastability-exchange collisions with highly polarized 3He ensembles
Yida Sha, Kaiwen Yi, Xingqing Jin et al. (+2 more)
Highly polarized 3He ensembles prepared by metastability-exchange optical pumping (MEOP) have been widely used in precision measurements and fundamental physics. Metastability-exchange (ME) collisions, serving as the basis of MEOP, are traditionally described in terms of atomic orientation, while the significant contributions of metastable
alignment tensor at high polarization remain unexplored. In this work, we develop a linearized model under mean-field approximation to investigate
alignment tensor effects in highly polarized 3He , which originate from the metastable F = 3/2
manifold and are revealed through ME-induced relaxation and frequency shift. By means of free-induction-decay (FID) measurements, a pronounced dependence on
nuclear polarization is experimentally observed in the response of the ground-state-metastable hybrid 3He ensembles to the external
magnetic field. Furthermore, after obtaining the characteristics of tensor-induced phenomena, we demonstrate good agreement between the experiment and the theory. This work advances the understanding of
nuclear spin dynamics in highly polarized 3He using MEOP. It further provides applications in systematic error correction of high-accuracy magnetometry, as well as in optimal protocol for the generation of
nuclear spin-squeezed states.
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All authors Yida Sha, Kaiwen Yi, Xingqing Jin, Matteo Fadel, Xiang Peng
Geophysics · Cross-listed from cs.LG
Constrained hybrid modelling to predict microbial dynamics and organic matter turnover in soil systems
Paul Collart, Juergen Gall, Andrea Schnepf et al. (+2 more)
Soil microorganisms control organic matter cycling and largely determine how soil systems can cope with and mitigate
climate change and environmental threats. Representing microbial dynamics in process-based soil models is therefore critical to predict carbon cycling in soils, albeit highly challenging to inform from data. One promising approach to improve their parametrisation is the integration of genomic data, yet modelling the complex and unknown relationship between genomes and the processes the microbes are driving is an unsolved problem. In this work, we present the first hybrid modeling framework for deriving biokinetic parameter values of a process-based soil organic matter turnover model from metagenome-inferred functional traits based on DNA sequencing data. Our model predicts biokinetic parameters of the process-based model from genomic trait data with a neural network and integrates constraints from ecological theory and literature to ensure realistic behavior, even of non-observed state variables. We evaluate our method on synthetic genomic trait
datasets of varying complexity and on real data, showing that our approach improves performance over multiple baselines and learns the dynamics of unmeasurable components of the process-based model effectively, even for small training
datasets.
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All authors Paul Collart, Juergen Gall, Andrea Schnepf, Holger Pagel, Lars Doorenbos
Quantum Physics
Effective Faraday interaction between light and Helium-3 nuclear spins in a multi-pass cell
Kaiwen Yi, Yida Sha, Zejia Lin et al. (+2 more)
Helium-3
nuclear spins form an exceptionally stable
quantum system with extremely long coherence time, offering exciting opportunities for
quantum technologies. In particular,
nuclear spin-squeezed states promise enhanced precision for sensing tasks and tests of new physics. A central challenge for all these applications is the realization of a controllable light-
nuclear spin interface. Here we experimentally demonstrate such an interface by exploiting metastability-exchange collisions in a low-pressure helium-3 gas
cell at room temperature. A
radio-frequency discharge produces a small population of metastable atoms that both enables efficient optical pumping and mediates an effective Faraday interaction between the collective
nuclear spin and an optical probe. We quantitatively characterize the strength of this interaction as a function of the
nuclear polarization, applied
magnetic field, and probe-beam parameters. Moreover, we show that using a multi-pass
cell enhances this interaction by effectively increasing the optical depth. Extrapolating to a tenfold increase of the probe power used in the present experiment, we project a measurement-induced squeezing rate of 0.52 s$^{-1}$. Our results provide a practical pathway for optical access to helium-3
nuclear spins and open prospects for generating long-lived, macroscopic
nuclear spin-squeezed states for
quantum metrology.
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All authors Kaiwen Yi, Yida Sha, Zejia Lin, Matteo Fadel, Xiang Peng
High Energy Physics (Phenomenology)
Theory Calculations for LDMX and LOHENGRIN beyond Coherent Bethe-Heitler Scattering
Martin Schürmann, Herbert K. Dreiner and Rhorry Gauld
The Light Dark Matter eXperiment (LDMX), DarkSHINE, and LOHENGRIN are proposed new experiments. They aim to search for missing momentum signals sourced by the direct production of dark
photons with masses in the MeV-GeV range in bremsstrahlung processes, in which an electron beam of a few GeV scatters off a fixed target. So far, the signal characteristics, i.e. the behavior of the recoiling electron, have mostly been studied in coherent Bethe-Heitler electron-
nucleus scattering with a dark
photon that couples only to the Standard Model charged
leptons. In this work, we present the calculations of the differential cross sections of all contributing real emission processes up to third order in the electromagnetic fine structure constant and fourth order in the kinetic mixing parameter associated with the dark
photon. We consider a dark
photon coupling to both the beam electron and the hadronic target and we take into account the scattering off both the target
nucleus and its
nuclear constituents. Besides real emission processes, we also discuss virtual dark
photon contributions and their relevance for the signal prediction. After discussing the different phase space regions and constraints emerging from the experimental setups, we show numerical results of the cross sections and differential distributions, including the signal and dominant background. Within our framework, we find that the LOHENGRIN experiment will require an extension of its HCAL to effectively veto background processes originating from diffractive scattering. Apart from that, the contributions beyond coherent Bethe-Heitler scattering, in the presence of realistic experimental selections, have only a limited effect on the predicted signal and background in the relevant dark
photon mass range.
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Computational Physics · Cross-listed from cs.LG
Quantum-classical physics-informed Kolmogorov-Arnold networks for PDEs
Xiang Rao and Yuxuan Shen
We develop QCPIKAN, the first
quantum-classical physics-informed Kolmogorov-Arnold network designed to solve partial differential equations (PDEs). Built upon Chebyshev-
polynomial KAN layers and parameterized
quantum circuits, this hybrid framework embeds physical constraints into the training loss to enforce physical consistency. Our theoretical investigations grounded in approximation theory prove that this design accelerates high-frequency error convergence to an exponential rate and effectively mitigates numerical dispersion. We validate the framework across three typical seepage scenarios in porous media, including single-phase flow, component transport and two-phase flow. Compared with existing
quantum-classical physics-informed neural networks, QCPIKAN achieves superior performance in global prediction accuracy, local error control, dynamic
evolution tracking and displacement front localization. This work provides a robust and efficient alternative for solving complex PDEs.
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