Astrophysics of Galaxies
The MICADO first light imager for the ELT: Simulated Observations of Star Forming Clumps at Cosmic Noon
Matteo Simioni, Carmelo Arcidiacono, Andrea Grazian et al. (+18 more)
Galaxies at
redshift z$\sim$2-6 exhibit prominent
star-forming regions (clumps). Characterisation of these
galactic structures requires both high sensitivity and spatial resolution of $\sim$100 pc or less. Currently, these spatial scales are achievable only with the aid of strong gravitational
lensing. However,
lensing introduces model-dependent uncertainties and limits the sample to
galaxies behind massive clusters. The upcoming 40m-class
telescopes, such as the ESO Extremely Large
Telescope (ELT), will enable routine studies of clumps in ubiquitous, non-lensed z$\ge$2
galaxies. We assess the capability of MICADO, the first-light imager and spectrograph of the ELT, to characterise clumps in non-lensed z=2
galaxies. Specifically, we focus on two representative observing scenarios, providing the basis for an early scientific exploitation of the instrument. We modelled clumps in an idealised z=2
star-forming
galaxy and produced mock MICADO observations in both broad- and narrow-band imaging. The latter leverages the strong emission lines typical of clumps to improve detection and characterisation. Reaching UV rest-frame magnitudes of clumps as faint as M$_{UV} \sim -15$ in optimal observing conditions, MICADO will be able to efficiently characterise clumps in non-lensed z=2
galaxies down to R$_{e} \sim 20$ pc. Moreover, the full MICADO $\sim$1 arcmin$^2$ field of view enables efficient surveys of multiple targets. This study demonstrates MICADO's potential to fill a crucial observational gap, shedding new light on clump formation and
evolution at
cosmic noon. Accurate PSF reconstruction will be crucial to fully harness this capability as it significantly impacts clump detection and characterisation, especially at the smallest sizes ($<$40 pc).
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All authors Matteo Simioni, Carmelo Arcidiacono, Andrea Grazian, Marco Gullieuszik, Elisa Portaluri, Alvio Renzini, Benedetta Vulcani, Anita Zanella, Francesca Annibali, Michele Cirasuolo, Richard Davies, Natascha Förster Schreiber, Johanna Hartke, Hanindyo Kuncarayakti, Matteo Messa, Stefan Raffetseder, Letizia Scaloni, Elena Valenti, Eros Vanzella, Joël Vernet, Roland Wagner
Mesoscale and Nanoscale Physics
Creation and characterization of leviton excitations in tight-binding chains
Stephen R. McMillan, Thomas Frederiksen and Géza Giedke
Levitons are minimal-excitation electronic wave packets generated by Lorentzian voltage pulses and constitute a central resource for electron
quantum optics. Their creation and defining properties are usually formulated in continuum scattering descriptions, whereas many candidate platforms for integrated electronic
quantum circuits are finite, discrete, and strongly shaped by
lattice dispersion. We study leviton generation in finite one-dimensional tight-binding chains of non-interacting
fermions driven by time-dependent voltage pulses. Using the single-particle density
matrix, we resolve the excitation above the initial
Fermi sea and quantify its quality through the average excitation number and its fluctuations. We find that clean leviton-like states emerge only in an intermediate regime where the pulse is slow enough to be resolved by the dynamics on the
lattice, but not so slow that truncation and finite-size effects distort the Lorentzian profile in the time domain. Lorentzian pulses (even if truncated) systematically outperform non-Lorentzian pulse shapes in approaching the low-noise limit with increasing system size. We further identify finite-
lattice signatures associated with band filling, pulse amplitude, linear voltage-drop geometry, and residual deviations from the continuum integer-charge condition. These results establish a microscopic framework for understanding leviton formation beyond the ideal continuum limit and for evaluating
lattice-based platforms for coherent few-electron transport.
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Earth and Planetary Astrophysics
Sea Ice as an Origin of Life Location for Hycean and Ocean Worlds
Edouard F. L. Barrier, Nikku Madhusudhan and Frances E. Rigby
Water worlds with potential deep oceans are at the forefront of currently observable exoplanetary habitability. The standard requirements for habitability are the presence of an energy source, a source of nutrients, and a solvent, all of which can be met in
exoplanets with deep
liquid water oceans. Such
planets may be numerous, ranging from hycean worlds and ocean worlds to terrestrial-size
planets with enhanced water content. However, abiogenesis requires additional conditions, namely a mechanism to accumulate nutrients to the high concentrations required for prebiotic chemistry, and an energy source to drive the chemistry. A deep ocean, and in some cases the high-pressure ice layers underneath, has traditionally been thought to prevent the required concentrations. Here we outline a location where nutrients could be concentrated in sufficiently high quantities to make abiogenesis possible – at the interface between the open ocean and the surface ice shelf. Using a 3D General Circulation Model, we explore cases corresponding to several candidate habitable
exoplanets which might have dayside sea ice. We discuss how the
planet's
climate influences the nature and behaviour of the sea ice. We investigate the ability of small-scale ice formation and melting processes to concentrate nutrients to prebiotically useful levels, and also explore the potential for meteoritic impactor fragments to provide a platform for prebiotic chemistry. We find that both of these mechanisms may plausibly provide concentrated chemical feedstock for prebiotic chemistry, which adds an important new perspective when evaluating the prospects of habitability in
planets with deep oceans.
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Computational Physics · Cross-listed from cs.LG
Latent-MoE: Domain-Aware Mixture-of-Experts for PDEs with Multi-Regime Physics
Hanwen Wang and Paris Perdikaris
Physics-informed neural networks (PINNs) struggle on PDEs whose governing physics varies across the domain. We trace this to a structural property of standard coordinate networks: their neural tangent kernel (NTK) is translation-variant and lets training points of large coordinate magnitude disproportionately influence predictions elsewhere, producing long-range coupling and gradient conflict during training. We show analytically and empirically that mixture-of-experts (MoE) architectures with centered, compact-support routers yield a uniformly banded NTK whose kernel-regression weights decay exponentially with distance, localizing the learning. Building on this, we propose Latent-MoE, which interleaves domain-aware MoE blocks within a shared backbone. Unlike FB-PINNs or X-PINNs, which rigidly partition both the domain and the parameters so that the parameters on different subdomains are updated independently, Latent-MoE is designed to preserve the localization benefit of domain-aware routing while allowing capacity to flow across regions through the shared backbone. On standard homogeneous-physics
benchmarks Latent-MoE is competitive with established baselines; on
benchmarks with multi-stage time-variable physics, where global models and rigid domain decompositions both fall into spurious solutions, it improves over them by more than an order of magnitude, with markedly reduced gradient conflict during training.
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High Energy Physics (Phenomenology)
Higgsino Dark Matter Interpretation of the LZ High-Recoil Event in the GNMSSM with TeV-Scale Gauginos
Subhadip Bisal, Junjie Cao and Fei Li
The
nuclear recoil event at approximately 248 keV reported by the LUX-ZEPLIN collaboration motivates an investigation of endothermic dark matter scattering. We study this within the General Next-to-Minimal Supersymmetric Standard Model (GNMSSM), with Higgsino-dominated neutralino DM undergoing the $Z$-mediated transition $\widetilde{\chi}_1^0N\to\widetilde{\chi}_2^0N$. In the conventional thermal Higgsino limit of the MSSM, the observed relic abundance selects a mass near 1.1 TeV, while a neutralino splitting of a few hundred keV typically requires gaugino masses of order $10^7$ GeV. In the GNMSSM, Higgsino-Singlino mixing introduces an additional contribution to the splitting that can cancel the gaugino-induced contribution, allowing sub-MeV splitting with multi-TeV gauginos. This mixing also modifies the inelastic scattering coupling and annihilation rates, while coannihilation with sleptons provides freedom in obtaining the observed relic abundance. We present six
benchmark points with DM masses of 0.6-1.1 TeV, neutralino splittings of 333-350 keV, and gaugino masses of 2-5 TeV. These points reproduce the observed relic abundance and satisfy direct-detection,
Higgs,
flavor, and
collider constraints. Within the Standard
Halo Model and extended-likelihood analysis, all six points yield $\Delta\chi^2<1$ relative to the best fit. Our results show how the GNMSSM can accommodate the LZ high-
recoil event without an ultraheavy gaugino sector. A quantitative assessment of
solar-capture and
neutrino-
telescope constraints remains necessary for establishing viability.
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Mathematical Physics
Equation of Motion for Thermodynamic Systems and Their Dynamical Equivalence with Mechanical and Electrical Systems
E Aydiner
Changes in the internal energy of a thermodynamic system are fundamentally described by the first law of thermodynamics. However, the first law has a highly compact form that does not explicitly reveal the dynamics of the system or provide a corresponding equation of motion. While equations of motion can be written explicitly for mechanical and electrical systems, an analogous dynamical formulation for thermodynamic systems has, to our knowledge, not been established directly from the first law. In this work, we show that, through dimensional reduction, the first law can be transformed from its compact thermodynamic form into an explicit equation of motion for an open thermodynamic system. Remarkably, the resulting equation has the same mathematical structure as the equations governing a driven damped harmonic oscillator and a driven series RLC
circuit. Detailed dimensional analyses of the derived equation and the effective coefficients further confirm the dimensional consistency of the formulation. We further perform a systematic comparison of the mechanical, electrical, and thermodynamic systems and show that, despite their distinct physical origins, they share the same universal dynamical structure. Finally, we construct a Lagrangian formulation of the thermodynamic system and establish its correspondence with the Lagrangian descriptions of the mechanical and electrical systems. These results demonstrate that an explicit equation of motion can be generated directly from the first law of thermodynamics and reveal a common dynamical framework underlying thermodynamic, mechanical, and electrical systems.
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High Energy Physics (Phenomenology)
Not so good $\nu$s for Higgsino dark matter as LZ excess: stringent limits from Super-Kamiokande and IceCube
Debajit Bose, Akash Kumar Saha, Deep Jyoti Das et al. (+9 more)
The LUX-ZEPLIN (LZ) collaboration has recently reported a single
nuclear recoil event at a high
recoil energy of about 250 keV. This has been interpreted as inelastic scattering of dark matter that is a supersymmetric Higgsino with a mass splitting between the neutral states of a few 100 keV. Such dark matter may be captured at high
recoil in the Sun through scattering on heavy elements in it, and annihilate to $W^+W^-$ and $ZZ$, in turn giving rise to a
neutrino flux detectable on Earth. Using measurements of atmospheric electron- and
muon-
neutrino fluxes by Super-Kamiokande and IceCube, we constrain thermal and non-thermal Higgsino dark matter, excluding inter-state mass splittings $\lesssim 557$ keV. This disfavors Higgsino-like interpretations of the LZ event for standard
halo velocities.
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All authors Debajit Bose, Akash Kumar Saha, Deep Jyoti Das, Rinchen Sherpa, Abhijeet Singh, Durba Ghosh, Jaya Doliya, Subhadip Bouri, Biprajit Mondal, Ranjini Mondol, Nirmal Raj, Ranjan Laha
High Energy Physics (Theory)
Logarithmic correction to the entropy of near-extremal higher-curvature black holes
Pablo Bueno, Pablo A. Cano, Robie A. Hennigar et al. (+3 more)
The spherically symmetric sector of broad classes of $D$-dimensional gravitational theories can be effectively described by general two-dimensional Horndeski theories. Exploiting this correspondence, we study the low-temperature dynamics of near-extremal black hole solutions of the parent theories by deriving a universal near-horizon effective description in terms of Jackiw–Teitelboim (JT)
gravity. We explicitly show that the logarithmic
quantum correction to the
entropy, $S_{\rm JT}=\frac{3}{2}\log \left(T/T_{\rm breakdown} \right)$, previously derived for near-extremal black holes in Einstein
gravity coupled to matter from the one-loop exact JT partition function, is universal across all models admitting an effective two-dimensional Horndeski description. We determine the general form of the scale at which this correction becomes dominant, $T_{\rm breakdown}$, in terms of the data of the $D$-dimensional theories. We illustrate our general results with charged black holes in Lovelock gravities and regular black holes in Quasitopological gravities.
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All authors Pablo Bueno, Pablo A. Cano, Robie A. Hennigar, Javier Moreno, Ángel J. Murcia, Guido van der Velde
High Energy Physics (Phenomenology)
Inelastic Singlet-Doublet Fermion Dark Matter in light of the 248 keV LZ event
Debasish Borah, Sujit Kumar Sahoo, Narendra Sahu et al. (+1 more)
Recently, the LUX-ZEPLIN (LZ) collaboration reported the observation of a single dark matter (DM)-
nucleus scattering event at a
nuclear recoil energy of $248\pm23_{\rm stat}\pm23_{\rm sys}$ keV, corresponding to an exposure of 2.84 tonne-year. The absence of events at lower
nuclear recoil energies in the predicted spectrum is naturally explained if the underlying process is inelastic DM-
nucleus scattering. Motivated by this, we investigate the singlet-doublet
fermion DM model, in which the DM consists of two pseudo-Dirac states: the Majorana nature of the lighter state forbids tree level $Z$-mediated elastic scattering identically, while the same states enable inelastic DM-
nucleus scattering via $Z$ exchange, with any residual elastic scattering proceeding only through a suppressed
Higgs-mediated channel. We further extend the model with a $Z_2$-even scalar triplet, which is responsible both for generating the pseudo-Dirac splitting and for realizing Majorana
neutrino masses via the Type-II seesaw mechanism.
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All authors Debasish Borah, Sujit Kumar Sahoo, Narendra Sahu, Shashwat Sharma
Nuclear Experiment
Precision $\beta$-delayed charged-particle emission spectroscopy at FRIB: Proof of principle with the $\beta$-decay of $^{25}\mathrm{Si}$
E. A. M. Jensen, J. M. Eder, P. H. Pedersen et al. (+16 more)
We report on the $\beta$-delayed
proton and $\gamma$-ray emission from $^{25}\mathrm{Si}$, measured at the Facility for Rare Isotope Beams (FRIB). Low-energy $^{25}\mathrm{Si}$ ions extracted from the Advanced Cryogenic Gas Stopper were implanted into a thin carbon foil surrounded by a compact, highly segmented array of silicon detector
telescopes and two high-purity germanium detectors. This setup provides high-resolution charged-particle spectroscopy, establishing a proof of principle for precision stopped-beam decay studies at FRIB. We reconstruct the $^{25}\mathrm{Si}$ decay scheme, resolving new high-energy
proton transitions and determining the feeding to excited states in $^{24}\mathrm{Mg}$. The observation of spectral interference patterns enables firm
spin and parity assignments for highly excited states in $^{25}\mathrm{Al}$. The $^{25}\mathrm{Si}$ $\beta$-strength distribution is extracted and compared with large-scale shell-model calculations.
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All authors E. A. M. Jensen, J. M. Eder, P. H. Pedersen, A. Adams, M. J. G. Borge, B. A. Brown, J. Dopfer, H. O. U. Fynbo, B. S. O. Johansson, B. Jonson, M. Madurga, J. S. Nielsen, K. Riisager, C. S. Sumithrarachchi, L. J. Sun, O. Tengblad, L. E. Weghorn, T. Wheeler, C. Wrede
Materials Science
Temperature-Dependent nonlinear optics from first-principles: Second-Harmonic Generation in few-layers MoS$_2$
Anna Romani, Claudio Attaccalite and Myrta Grüning
We present a first-principles real-time approach to study non-linear response of solids at finite temperature. Finite temperature effects are included as renormalization of the quasiparticle energies and a dephasing term proportional to the quasiparticle lifetimes. We evaluate electron-
phonon matrix elements from Density-Functional Perturbation Theory for
lattice dynamics and then calculate quasiparticles renormalization and lifetime from the Fan and Debye-Waller terms of the electron self-energy. Electron excitations are treated at the independent particle level of approximation. We apply the approach to the second-harmonic generation (SHG) in monolayer and trilayer MoS$_2$. We observe a nontrivial temperature-dependence of the SHG due to a strong
crystal-momentum dependent quasiparticle renormalization. From the
phonon-mode analysis we find that the coupling with acoustic and shear modes determines the overall
crystal-momentum dependence respectively in monolayer and trilayer MoS$_2$. The nontrivial temperature-dependence of the SHG can help rationalize the increase of SHG intensity with increasing temperature observed in monolayer MoS$_2$ at a given
laser energy [Adv. Optical Mater. 8, 2000441 (2020)].
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High Energy Astrophysical Phenomena
Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic Plasma
Agnieszka Wierzchucka, Pablo J. Bilbao, Robert J. Ewart et al. (+2 more)
Using analytic theory, radiative particle-in-
cell (PIC) simulations, and fluid simulations, we show that relativistic, synchrotron-cooling, collisionless, high-$\beta$ pair
plasmas filament into a two-phase medium. This process occurs through the interplay of the synchrotron cooling instability (SCI) with the synchrotron firehose instability (SFHI). One phase has high
plasma~$\beta$ and is infested with small-scale firehose fluctuations, which scatter particles and pin the pressure anisotropy to the firehose-marginal level. The other phase has much lower~$\beta$, causing the suppression of firehose modes and thus allowing large pressure anisotropies. We propose a fluid model for this two-phase
plasma, which we use to study the linear and nonlinear
evolution of the SCI and SFHI, and to predict the emergence time of the two-phase structure.
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All authors Agnieszka Wierzchucka, Pablo J. Bilbao, Robert J. Ewart, Dmitri A. Uzdensky, Alexander A. Schekochihin
Cosmology and Nongalactic Astrophysics
Filament-Arm Node Systems (FANS): A new probe of the winding and chirality of the cosmic web
Pedro da Silveira Ferreira and Renyue Cen
We define Filament-Arm Node Systems (FANS), a new class of
cosmic-web objects consisting of multiple filament arms connected to a common node, and use their geometry to construct an object-based test of
cosmic chirality. With the
cosmic-web node providing a natural reference point, FANS span characteristic scales of ~60Mpc/h, allowing the coherent winding of their arms around the node to be measured directly. We define
cosmic spirality as the amplitude of this winding and handedness as its signed clockwise (CW) or counter-clockwise (CCW) sense. We further introduce an axis-conditioned extrinsic
estimator that searches for the projected signature of a coherent three-dimensional axial pattern of the handedness field, corresponding to a preferred axis of winding. Applying these measurements to two distinct SDSS filament reconstructions, and assessing their significance with sign-flip nulls and 27 controlled variations of the FANS construction parameters, we find no significant preference for CW or CCW winding, either globally or around a preferred axis. The data are therefore consistent with parity
symmetry, as expected in standard LCDM cosmology. We additionally find that
cosmic spirality decreases with
cosmic time, a trend that may reflect the gravitational straightening of filament arms. These first constraints establish FANS as a new probe of
cosmic-web
symmetry and large-scale morphology and provide a baseline for future parity tests with the much larger filament samples expected from upcoming surveys.
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High Energy Physics (Theory)
Eikonal Scattering of Two D0-branes with Graviton Emission
Paolo Di Vecchia and Dawid Maskalaniec
We study the emission of a massless closed-string state in the scattering of two D0-branes using the boundary-state formalism. We compute the corresponding five-point amplitudes for graviton and dilaton emission in bosonic string theory and in type II superstring theory, and analyze their field-theory limit. For nonzero impact parameter, the resulting amplitudes are reproduced by an independent calculation in the worldline formulation of the corresponding low-energy theory.
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Lattice Field Theory
Sector-Resolved Flow Sampling for Topologically Frozen Lattice Gauge Theories
Ankur Singha, Jacob Kauffmann, Karl Jansen et al. (+3 more)
Topological fluctuations are essential to nonperturbative gauge theories but become increasingly difficult to sample toward the continuum limit, where Markov chains can freeze in sectors of fixed topological charge. We introduce a generative sampler, a mixture of sector-resolved samplers (MSRS) that explicitly resolves these sectors and exploits a key advantage of generative models, the ability to directly evaluate the domain-restricted partition function and thereby determine the relative weights of disconnected sectors. We train a generative model in a reference topological sector combined with a bijective topological shift that deterministically maps its samples to other sectors. We demonstrate the method in two-dimensional compact U (1)
lattice gauge theory, where it reproduces the topological-charge distribution and yields an unbiased susceptibility in a regime where hybrid Monte Carlo is frozen and overrelaxation gives inaccurate estimates. Our approach also outperforms existing flow-based samplers by orders of magnitude. These results demonstrate that explicit sector resolution provides a promising route to overcoming topological barriers in
lattice gauge theory.
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All authors Ankur Singha, Jacob Kauffmann, Karl Jansen, Jacob Finkenrath, Vipul Arora, Shinichi Nakajima
Quantum Physics
QROB: Quantifying Realization Overhead in Quantum Compilation via Reverse Construction
Jintao Li, Kaiqi Li, Rui Wang et al. (+7 more)
Quantum compilation reconciles a program's idealized interaction
topology with hardware locality constraints, yet evaluations at scale lack calibrated references for realization overhead. We present QROB, a scalable reverse-construction methodology that generates compilation instances backward from directly realizable configurations, retaining the inverse paths as feasible, compiler-independent references. QROB provides a common evaluation substrate for NISQ SWAP routing and fault-tolerant
lattice-surgery scheduling, while extending its reference-preserving principle to capacity-constrained
quantum memory-access scheduling. Across systems ranging from 9 to 156
qubits, evaluations highlight QROB's utility as both a diagnostic
benchmark and a data source. First, for compiler characterization, QROB reveals substantial realization gaps in existing tools, with NISQ compilers incurring up to 24.1x the reference SWAP cost and fault-tolerant compilers requiring up to 7.0x the reference makespan. Second, as a supervision source for data-driven compilation, a router trained on QROB references outperforms Qiskit SABRE on 84.8% of real-world application
circuits. Finally, on real hardware, QROB reference realizations achieve a median mirror-
circuit survival rate 1.65x that of full Qiskit O3 compilations across three 156-
qubit IBM Heron-r2 processors, demonstrating that closing algorithmic compilation gaps translates directly into physical fidelity gains.
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All authors Jintao Li, Kaiqi Li, Rui Wang, Yilun Zhao, Kaixuan Huang, Ying Wang, Jialin Zhang, Zheng-An Wang, Xiaoming Sun, Heng Fan
Mesoscale and Nanoscale Physics
Simple invariants for band topology
Adam Yanis Chaou, Adolfo G. Grushin and Peru d'Ornellas
Despite the exhaustive understanding gathered around non-interacting topological states of matter, there is no single method capable of systematically delivering simple, numerically efficient topological invariants that is applicable to all crystalline and non-crystalline systems alike. Here we revisit the spectral localizer operator, constructed from the
Hamiltonian and position operators, and show how it can be treated it as an auxiliary zero-dimensional
Hamiltonian whose
topology encodes the higher dimensional phases of the parent
Hamiltonian. Its classification reduces every topological invariant to a
matrix signature or the sign of a Pfaffian for an appropriate localizer, both of which are simple to interpret and efficient to compute in real space. We validate this approach by deriving simple real-space invariants for weak and rotationally invariant crystalline phases that were previously beyond the grasp of the spectral localizer formalism, atomic limits that escape scattering invariants, phases that evade
symmetry-based indicator methods, as well as phases that had no previously known invariant. Our work provides a systematic way to construct any non-interacting topological invariant for a crystalline or non-crystalline systems, opening avenues to classify and predict the
topology of previously unexplored classes of materials.
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Instrumentation and Methods for Astrophysics
Search for Long-Transient Gravitational Waves from Supernova SN2023ixf using GFH-v2 Pipeline
Sandhya Sajith Menon, Lorenzo Pierini, Pia Astone et al. (+24 more)
We present a directed search for long-transient gravitational waves from the possible newborn magnetar remnant of SN2023ixf, a nearby Type II core-collapse
supernova in the M101
galaxy. The analysis uses LIGO Hanford and Livingston data from Engineering Run 15, using coincident data lying within the on-source window associated with the
supernova. We target signals from a rapidly rotating, non-axisymmetric
neutron star whose
spin-down is dominated by gravitational-wave emission, producing a power-law decrease in frequency and a corresponding decrease in strain amplitude. The search is performed with the GFH-v2 pipeline, based on the Generalized Frequency Hough transform. No candidate survives the coincidence and follow-up analysis. We therefore set upper limits on the maximum detectable distance as a function of initial frequency and ellipticity. For the highest ellipticity interval, the 90% upper limits reach distances of about 1-2.5~Mpc across most of the analysed band. Although these limits are below the distance to M101, the search provides the first application of GFH-v2 to a nearby core-collapse
supernova and characterizes its performance on real detector data.
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All authors Sandhya Sajith Menon, Lorenzo Pierini, Pia Astone, Cristiano Palomba, Francesco Safai Tehrani, Lorenzo Silvestri, Ornella Juliana Piccinni, Simone Dall'Osso, Stefano Dal Pra, Sabrina D'Antonio, Sergio Frasca, Dafne Guetta, Paola Leaci, Michal Bejger, Alicia Calafat, Evan Goetz, Rafel Jaume Amengual, Ian Jones, David Keitel, Andrzej Krolak, Iuri La Rosa, Andrew Melatos, Joan-Rene Merou, Lorenzo Mirasola, Claudio Salvadore, Alicia M. Sintes, Karl Wette
Materials Science
High-Field Electron Transport in AlGaN alloys: A Full-Band Monte Carlo Study Based on Ab Initio Supercell Calculations
Animesh Datta, Matinehsadat Hosseinigheidari and Uttam Singisetti
AlGaN
alloys are promising wide and ultra-wide-bandgap
semiconductors for next-generation power and RF electronics applications. To realize the full potential of AlGaN based devices, it is important to understand the electron transport to accurately predict device performance and identify material limits under various operating conditions. In this work, the high-field electron transport properties of AlxGa1-xN are investigated using a supercell based full band Monte Carlo method. The supercell approach is employed to explicitly capture the true disorder of the
alloy system, enabling a more realistic description of carrier transport. The velocity field characteristics are calculated across a range of Al compositions to evaluate key transport metrics, including peak velocity, saturation velocity, and critical electric field. The role of different scattering mechanisms is studied in detail to understand the high field transport mechanism in the AlGaN
alloy system. In addition to steady state transport, transient electron dynamics are examined for various Al fractions to study velocity-overshoot behavior, which is especially important for improving the performance of scaled RF devices. Finally, the temperature dependence of the velocity field characteristics in ultra-wide-bandgap Al0.75Ga0.25N is investigated to assess its transport performance under high temperature conditions. These results provide a detailed understanding of high-field transport in AlGaN
alloys and offer guidance for the design of AlGaN-based RF and power electronic devices.
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Disordered Systems and Neural Networks · Cross-listed from math.PR
Efficient computation of the asymptotics of extensive-rank HCIZ integrals
Antoine Maillard and Jean-Christophe Mourrat
We study the high-dimensional asymptotics of Harish-Chandra-Itzykson-Zuber (HCIZ) integrals in the extensive-rank regime. The limit of these integrals is governed by a one-dimensional boundary-value hydrodynamical problem originally derived by Matytsin (1994) and rigorously proved by Guionnet and Zeitouni (2002). Despite its wide-ranging applications, explicit solutions to this problem are known only in a few specific cases. In this work, we introduce an efficient numerical scheme based on a particle discretization and prove its convergence to the continuous boundary-value problem for generic boundary densities. We validate our approach against known analytical solutions and apply it to generic densities, uncovering interesting dynamical phenomena. The high-dimensional limit of HCIZ integrals appears in various contexts, from the large deviations of random
matrix spectra to the limiting free energy of disordered systems, high-dimensional statistics, and machine learning. As such, our contribution opens the way towards the numerical exploration of a wide range of high-dimensional models that were previously intractable.
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Mathematical Physics · Cross-listed from math.AP
The Dirichlet problem for a non-commutative elliptic operator in the ball
A. Moreno García, D. Alfonso Santiesteban and R. Abreu Blaya
In this paper we establish a necessary and sufficient condition for the solvability of the Dirichlet problem in the unit ball $\mathbb{B}$ for the second order system $\partial_{\underline{x}} f\partial_{\underline{x}}=0$, where $\partial_{\underline{x}}$ stands for the Clifford-
algebra valued Dirac operator in $\mathbb{R}^m$. We prove that the problem admits a solution whenever the boundary data belong to $C^1(\partial\mathbb{B})$. Conversely, we construct explicit counterexamples showing that solvability may fail if this smoothness assumption on the boundary is not satisfied. Moreover, in contrast with the standard commutative setting, we show how that solutions exhibit a regularity one order less than the boundary data, when the latter belong to $C^{k,\nu}(\partial\mathbb{B})$.
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Mathematical Physics · Cross-listed from math.PR
Weighted isoperimetry implies percolation
Ivailo Hartarsky, Franco Severo and Augusto Teixeira
Consider an infinite edge-weighted graph satisfying an isoperimetric inequality of the type $\|\partial A\|\geq C|A|^\alpha$ for some $\alpha,C>0$, where $\|\partial A\|$ denotes the weighted size of the edge boundary of $A$. We prove that, for $C$ large enough depending on $\alpha$, if each edge is open independently with probability given by its weight, then any vertex is connected to infinity with positive probability. The result also holds under weaker isoperimetric assumptions and on finite graphs. The proof brings a new perspective on the recent proof of the Benjamini–Schramm
conjecture concerning the same problem with homogeneous weights. The crucial novelty in our proof is that, rather than simply counting cutsets, we introduce a new Peierls argument which takes into account internal and external connectivity costs in addition to the cost of the blocking surface. We provide two applications for the above result. First, we show that every non-summable long-range percolation on $\mathbb{Z}^d$, $d\geq 2$, admits a percolating truncation, solving a
conjecture of Sidoravicius, Surgailis and Vares and its generalization by Friedli and de Lima. Secondly, we show that there exists a universal constant $C < \infty$ such that $p_{\mathrm{c}} \leq C/\Delta$ for every transitive graph of superlinear growth and vertex degree $\Delta$, thus proving a
conjecture of Easo and Hutchcroft.
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High Energy Physics (Theory)
(Anti-)De Sitter null strings and Carroll-Weyl symmetry
Ulf Lindström and Bo Sundborg
We construct a $dS_d$ null string in a novel way by lifting the standard tensionless string to $R^{1,d}$. Gauging worldsheet scale
symmetry introduces terms in the action breaking translation invariance, but preserving the $dS_d$
symmetry $SO(1,d)$. Choosing a De Sitter symmetric gauge fixing of the scale
symmetry yields a $d$ dimensional theory which we show has all the expected properties of $dS_d$ tensionless strings. The action happens to be the intriguing Carrol-Weyl symmetric string action in $R^{1,d}$, now with a clear target space interpretation in $d$ dimensions. That it does not, as recently claimed, represent a ($d+1$)-dimensional string in flat ($d+1$)-dimensional Minkowski space settles an apparent issue with the Carrol-Weyl string model. Furthermore, while there are clear obstacles for similar formulations of tensile strings in (A)dS backgrounds, our new insights are easily modified to the formulation of Anti-De Sitter tensionless strings. That our construction generates a curved geometry purely algebraically may have even wider applications.
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Statistical Mechanics
Directional memory of early spectral selection during spinodal decomposition in finite systems
Boliang Yu, Ruixin Zhou and Zheng Zhang
Cahn-Hilliard phase separation turns small composition fluctuations into coarsening domains. In
Fourier space, the pattern forms a ring whose angular intensity favors an axis. We ask whether the axis favored early in an
evolution remains related to the axis favored later in the same
evolution. We analyze two-dimensional simulations with isotropic initial fluctuations and no imposed direction. We introduce $Q_2$, a normalized angular average over the
Fourier spectrum, as a measure of the strength and direction of spectral anisotropy. Linear growth amplifies different wave numbers at different rates, selecting an early axis from the angular imbalances in the initial spectrum. This axis remains correlated with the late axis during coarsening. At a fixed time, shallow quenches show stronger early-late
alignment. This advantage disappears when the quenches are compared at similar stages of domain growth. Adding the early $Q_2$ to a prediction based on quench depth, mean composition, and box size reduces the mean absolute error for late $Q_2$ by $3.53\%$. This reduction disappears when only the magnitude of the early $Q_2$ is retained, or when its direction is replaced by the direction from another
evolution. The early
Fourier intensity therefore carries information about the later state of the same evolving field.
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Statistical Mechanics
Topographic Disorder, Wind Coupling, and Directional Fire Spread: Critical Behavior in a Terrain-Weighted Forest Fire Model
Juan M. Florez, Eric Suárez Morell, Cristian Millan et al. (+1 more)
We introduce the Terrain-Weighted Forest Fire Model (TFFM), a
lattice model in which fire spreads on a spatially correlated Gaussian height field with the asymmetric bond probability $p_{i\to j}=\mathrm{clip}[e^{-\beta+\gamma(h_j-h_i)},0,1]$, plus an additive wind bias. Simulations on
lattices up to $L=8192$ reveal a sharp active-to-inactive transition whose critical suppression threshold $\beta_c$ is even in $\gamma$, decreases with $|\gamma|$, and decreases as the terrain correlation length $\sigma_h$ is reduced: slope asymmetry acts as a suppressant because downhill bonds are penalized and fire stalls at local elevation maxima. For rough terrain and low tree density the fire fails to percolate even at zero suppression. Finite-size scaling on a fine $\beta$ grid at $L=2048$–$8192$ gives a correlation-length exponent $\nu=1.8\pm0.17$ from both the susceptibility peak and the width of the transition, and a front-velocity exponent $\delta=0.34\pm0.03$, identical for smooth and rough terrain; neither matches directed percolation ($\nu_\perp=0.73$, $\nu_\parallel-\nu_\perp\approx0.56$) or isotropic percolation ($\nu=4/3$, $\approx0.18$). The single-seed survival probability at $\beta_c$ is independent of $L$ and decays extremely slowly, with a running exponent falling from $\approx0.09$ to $\approx0.04$, excluding directed percolation and pointing to a survival probability that remains finite at criticality, consistent with the $L$-independent value $P^*\approx0.5$ at which $P_{\rm surv}$ drops to zero. Wind raises $\beta_c$ by a factor of $2$–$4$, produces a sharp onset of downwind fire-scar drift at weak coupling, and, at high terrain coupling, decreases the burned fraction at boundary crossing—a terrain-wind competition effect absent from isotropic bond-disorder models. The model yields fire-risk thresholds and fire-scar signatures comparable to satellite burn-scar data.
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All authors Juan M. Florez, Eric Suárez Morell, Cristian Millan, J. Restrepo
Chemical Physics
Hemoglycin as a Candidate for Permanent Memory
Julie E. M. McGeoch and Malcolm W. McGeoch
The Hemoglycin
polymer of glycine derived from space is terminated by iron and silicon to form a three-dimensional regular
lattice with a high density of silicon tetrahedral vertices. Divalent cation bridges bypass vertices to facilitate electron conduction axially from layer to layer of the
lattice. In principle, the exact distribution of Mg or Ca ions around each vertex can encode a very large amount of information. In space where the
polymer forms in a molecular cloud the current derived from
photon input will fade but in-fall hemoglycin in life forms on habitable
planets like Earth, could be contained behind lipid electronic barriers of the nervous system in
neurons or glia. Energy minimization of the permutations for magnesium or calcium occupancy showed deeper binding for calcium-dominated configurations. A low energy state with two independent magnesium to calcium substitutions appears to be key to the maintenance of long-term chemical modification. This state could be read via a pulse train that induced the matching spatial distribution of calcium to render adjacent insulating
lattice regions conductive and provide a completed conduction path, signaling recognition. Writing of information may involve spatial modulation of the Na/Ca exchanger within the lipid membrane.
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Plasma Physics
Hamiltonian Particle Dynamics in Fusion Plasmas: Orbital Tomography and Spectrum Analysis for Energy and Momentum Transport under Resonant Non-Axisymmetric Perturbations
Yiannis Antonenas
This thesis investigates the impact of resonant mode-particle interactions on transport and confinement in toroidal fusion
plasmas. Using analytical and numerical approaches, we study how intrinsic and externally applied
magnetic perturbations affect
plasma particles with different kinetic characteristics, focusing on resonant interactions with guiding-center motion. We develop a novel, computationally efficient method based on Action-Angle variables to identify resonance locations and characterize resonances in guiding-center phase space, including the number of islands in resonance chains and the formation of transport barriers. Using the drift center (DC) approximation, we derive analytical expressions for orbital frequencies and the kinetic $q$ factor for large-aspect-ratio (LAR)
equilibria. These results provide the conditions for mode-particle resonances, which can strongly influence particle, momentum, and energy transport and, consequently,
plasma confinement. The analytical results are validated against numerical simulations, demonstrating an efficient tool for predicting transport barriers and energetic-particle behavior under non-axisymmetric perturbations. We further extend the orbital-frequency analysis from LAR
equilibria to numerically reconstructed, realistic
equilibria using a computationally efficient, semi-analytical geometrical method applicable to arbitrary unperturbed
equilibria. Finally, for the LAR
equilibrium, we extend the analysis to time-dependent perturbations and demonstrate the emergence of Arnold
diffusion in guiding-center phase space, highlighting the role of the Arnold web in particle transport. Overall, this work advances the understanding of mode-particle resonant interactions and provides computational tools for predicting transport and confinement in realistic fusion configurations.
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Disordered Systems and Neural Networks
A Bifurcation Theory for the Equilibria of Modern Hopfield Networks
Vincenzo Maria Schimmenti and Matteo Ciarchi
Modern Hopfield networks provide a unifying framework for associative
memory,
transformer attention,
diffusion-based generative models, and biological attractor dynamics, linking these systems through a common energy-based dynamics in which states are updated toward weighted combinations of stored patterns. Across these settings, network dynamics is determined by the organization of the energy landscape and the bifurcations of its fixed points. Despite their central role, a general theory of these bifurcations has remained unavailable beyond specific architectures and idealized pattern ensembles. Here we derive stability and bifurcation criteria for the fixed points of general convex-dual Modern Hopfield networks for a general statistics of the stored patterns. Applying this framework to random, block-correlated, and infinitely hierarchical pattern ensembles, we show how
memory correlations systematically organize the emergence of hierarchical attractors through successive bifurcations. We further demonstrate that these predictions quantitatively describe
retrieval bifurcations in MHNs storing patterns sampled from MNIST, and recapitulate the hierarchical organization of hematopoietic
cell identities. Our results establish a general bifurcation theory for Modern Hopfield networks and identify the organization of fixed points as a unifying principle underlying their computational and biological behavior.
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Mathematical Physics · Cross-listed from cs.LG
Local gradient neural operator
Baiming Zhang, Jinsong Tang, Ying Xu et al. (+2 more)
Field temporal prediction and source identification constitute canonical problems in dynamical systems. Conventional approaches to these problems depend on a thorough understanding of the governing partial differential equations (PDEs). Recently, deep learning, as represented by neural operators, has provided a data-driven paradigm for addressing such tasks. However, most existing global neural operators for PDEs require large training
datasets and many learnable parameters, with limited interpretability and generalization. We propose the local gradient neural operator (LGNO) as a lightweight and interpretable alternative for field temporal
evolution prediction and source identification in typical mechanical problems. The method builds on priors from nonlinear gradient discretization and uses multilayer perceptron convolutional layers to learn translation-invariant local kernels that resemble discrete stencils. A zero consistent stencil factorization separates coefficient learning from field reconstruction, rendering the learned operators more transparent. For problems with
symmetries, network folding shares equivalent components and reduces parameter counts. We evaluate the method on PDE
benchmarks covering linear and nonlinear, static and dynamic, and low and high dimensional cases. Results show that LGNO maintains accuracy, parameter efficiency, and rollout stability across these tasks, and further exhibits wide applicability to mechanical problems including
diffusion, flow, and
quantum phenomena.
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All authors Baiming Zhang, Jinsong Tang, Ying Xu, Lihua Chen, Shiying Xiong
Mathematical Physics
Classification of Conformally Covariant 2-Tensors from the Kulkarni–Nomizu Product in Dimension 4
Yury N. Berdinsky
We classify all natural, conformally covariant, symmetric (0,2)-tensors of conformal weight -2 and differential order less than or equal to 4 in dimension 4, built from the metric, the Schouten tensor, covariant derivatives, and the Kulkarni-Nomizu product. We prove that the space of such tensors is exactly 2-dimensional, spanned by the Bach tensor (order 2) and the Eastwood-Singer tensor (order 4). The algebraic core is formally verified using Lean 4 with Mathlib. The 8x11 constraint
matrix and divergence-free condition are verified computationally with exact rational arithmetic. Both English and Russian versions provided; Russian version available as ancillary.
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