Optics
A fully integrated dispersion-managed femtosecond mode-locked laser
Xurong Li, Xuan Yang, Zheru Qiu et al. (+7 more)
Femtosecond
lasers underpin applications ranging from material processing to corneal surgery, while their regular pulse trains form optical frequency combs that have revolutionized timekeeping, spectroscopy, and metrology. On-chip optical frequency combs, such as Kerr microcombs, have enabled high-repetition-rate applications in optical communications and microwave photonics. However, integrated chip-scale sources operating at low repetition rates (100 MHz to 1 GHz), crucial for high peak intensities, remain elusive, as existing devices typically operate well beyond 10 GHz. Here, we demonstrate a self-starting, photonic integrated mode-locked
laser based on a dispersion-managed architecture that accesses this regime. The
laser combines erbium-implanted silicon nitride gain waveguides, integrated chirped Bragg gratings, and a
semiconductor saturable absorber mirror to generate optical pulses with repetition rates from 0.5 to 1.2 GHz, pulse durations as short as 300 fs, and mode-locking thresholds down to 27.3 mW. The output forms a passively stable optical frequency comb with a comb-line drift below 1% of the repetition rate, surpassing the stability of commercial fiber
lasers by two orders of magnitude. Leveraging this ultra-low threshold, we achieve complete hybrid integration by co-packaging the
laser with a telecom-grade 980-nm III-V pump diode chip inside a compact photonic module. The resulting electrical-in/optical-out module delivers turnkey, stable mode-locked pulses, providing a compact, low-power, and vibration-insensitive foundry-compatible platform for field-deployable optical metrology and precision sensing.
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All authors Xurong Li, Xuan Yang, Zheru Qiu, Jiale Sun, Xinru Ji, Jianqi Hu, Grigorii Likhachev, Yichi Zhang, Ulrich Kentsch, Tobias Kippenberg
Instrumentation and Methods for Astrophysics
Unsupervised Domain Adaptation for Multitask Image Analysis in Realistic Context with Extreme Label Shift; Application to the CTAO first Large Sized Telescope
Michaël Dell'aiera, Thomas Vuillaume and Alexandre Benoit
Unsupervised domain adaptation is a widespread set of methods that leverages the knowledge of a labeled source domain to train a model to perform well on a related unlabeled target domain. They generally introduce an auxiliary adaptation-related task that can be integrated into the multitask paradigm, which aims to merge multiple single-task models into a unified architecture. In this paper, we propose to associate domain adaptation and multitask balancing in the realistic context of an extreme class imbalance. Therefore, we propose a combined framework to cover and validate these approaches, and evaluate its performance in the physics-based context of the Cherenkov
Telescope Array Observatory (CTAO). Along with a comparative study of some relevant adaptation techniques, we highlight the impact of extreme label shift and extend the investigations on importance weighting to rectify it. The complete code and results are published and available as open-source resources on Zenodo.
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Astrophysics of Galaxies
A Chemical Inventory of the Disk around the Class 0 Protostar L1527 IRS with ALMA
Merel L.R. van 't Hoff, Łukasz Tychoniec, John J. Tobin et al. (+1 more)
Planet formation starts in disks that are still embedded within their natal envelopes. Here, we compile an extensive inventory of the chemical composition of the disk and envelope ($<$ 3500 au) around the Class 0 protostar L1527 IRS. Using all publicly available ALMA (Atacama Large Millimeter/submillimeter Array) data, we report the detection of 40 molecules, including isotopologues. Of these, 23 are different molecular species and 29 are reported here for the first time toward L1527 in ALMA observations. CH$_3$OH is the only complex organic molecule detected, while the hydrocarbon CH$_3$CCH is the largest molecule detected. Overall, only a few programs are sensitive enough to detect emission unambiguously originating from the disk based on the kinematics. Nitrogen-bearing molecules are predominantly detected on more extended scales, while hydrocarbons show a distinct tail roughly along the southeastern
outflow cavity wall, probably due to a stronger UV field in the eastern
outflow lobe. The L1527 IRS protostellar system is not rich in sulfur-bearing molecules, with only strong emission observed for CS and SO. Overall, the envelope appears dominated by a carbon-rich chemistry, which seems to transition into an oxygen-rich chemistry in the disk. We calculate column densities of all detected species, providing a starting point to quantify the chemical diversity among young disks and the chemical
evolution of the
planet-forming material.
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All authors Merel L.R. van 't Hoff, Łukasz Tychoniec, John J. Tobin, Daniel Harsono
Quantum Physics
A Design Space Study of Density Matrix Parameterizations for Diffusion-Based Quantum State Tomography
Shuangu Chang
Diffusion-based
quantum state
tomography (QST) has shown promising results, but all existing methods implicitly adopt a single parameterization (typically Cholesky) without systematic evaluation. We present the first design space study of density
matrix parameterizations for
diffusion QST, introducing a
geometric framework based on the Jacobian Gram
matrix $\mathbf{J}^\top\mathbf{J}$. Our calibration of seven parameterizations at 2- and 3-
qubit scales, validated by end-to-end training, reveals that
geometric conditioning alone does not predict end-to-end performance: at 3-
qubit scale, Hermitian direct ($\kappa = 2.0\times$) performs worse than Cholesky ($\kappa = 27\times$) at all shot levels—a $13.5\times$ isotropy advantage that translates into a fidelity disadvantage of up to $+0.51$. The 2-
qubit ranking (Hermitian $>$ Bloch) reverses at 3
qubits (Bloch 0.907 vs.\ Hermitian 0.394). We provide a
geometric explanation: unbounded parameterizations suffer projection-induced information loss because the PSD constraint couples diagonal and off-diagonal coordinates in ways the unconstrained model cannot respect, whereas the Bloch representation places the maximally mixed state at the center of the valid region, minimizing projection loss.
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High Energy Physics (Phenomenology)
NNLO soft functions for heavy-quark pair production at hadron colliders
Guido Bell, Alessandro Broggio, Sebastian Edelmann et al. (+2 more)
We generalise the SoftSERVE framework for the automated computation of soft functions involving final-state heavy
quarks in back-to-back kinematics up to next-to-next-to-leading order (NNLO) in the strong-coupling expansion. Our
algorithm employs suitable phase-space parameterisations for both massive and mixed massless-massive contributions, allowing for an efficient numerical evaluation. Focusing on SCET$_\mathrm{I}$ observables that satisfy non-Abelian exponentiation, we present explicit results for the 0-jettiness soft function in hadronic top-
quark pair production in the form of two-dimensional grids. We describe the renormalisation procedure in detail and discuss the singular behaviour of the tripole colour correlations in the threshold limit.
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All authors Guido Bell, Alessandro Broggio, Sebastian Edelmann, Matthew A. Lim, Rudi Rahn
Optics
Scalable laser micro- and nanostructuring of mould inserts for functional injection-moulded polymer surfaces
Petr Hauschwitz, Elena Čižmárová, Jiří Bobek et al. (+10 more)
Functional
polymer surfaces with tailored wettability, antibacterial and adhesion properties are increasingly required in medical, packaging and consumer applications.
Laser structuring of steel mould inserts followed by injection moulding offers a scalable manufacturing route, but conventional single-beam texturing has limited throughput. Here, we present a selective acceleration strategy that applies different
laser techniques to micro- and nanostructuring. Deep microhole drilling was accelerated up to 20-fold by operating an ultrashort-pulse fibre
laser at a repetition rate of 1 MHz in single-beam mode. For
laser-induced periodic surface structures (LIPSS), line-beam shaping with a spatial light modulator increased productivity by 35-fold, reaching processing speeds above 100 cm$^2$ min$^{-1}$ while retaining sub-micrometre fidelity. Replication experiments with polypropylene (PP), PA66 and ABS confirmed successful transfer of micro- and nanostructures, with PP showing the highest fidelity.
Vacuum-assisted injection moulding increased replicated feature height by 56–283 percent. All
laser-textured PP surfaces showed higher static water contact angles than the untreated reference, reaching approximately $134^\circ$ in the Wenzel regime. Structured PA66 surfaces reduced bacterial retention by up to 99.8 percent for E. coli and approximately 90 percent for S. aureus.
Laser texturing also increased the shear strength of PP joints bonded with a non-optimised adhesive by up to 30-fold. This approach provides a practical, coating-free route to functional
polymer components and helps bridge the gap between laboratory
laser texturing and industrial injection moulding.
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All authors Petr Hauschwitz, Elena Čižmárová, Jiří Bobek, Hana Pištěková, Vladimír Sedlařík, Milan Kocáb, Radka Bičišťová, Martin Procházka, Jan Brajer, Jiří Mužík, Martin Smrž, Michal Chyla, Tomáš Mocek
Medical Physics · Cross-listed from eess.IV
Lost in k-Space: An Open-Source MR-Physics Escape Room
Sabine Melanie Räuber, Marta Brigid Maggioni and Francesco Santini
Introduction. Operating an MR scanner for technical and clinical research requires multidisciplinary competencies beyond MR physics, including safety management and teamwork. Gamification, particularly educational escape rooms, have been associated with improved motivation, engagement and knowledge retention in health professional education. Materials and Methods. We developed an MR-physics-themed educational escape room for the 41st Annual Meeting of the ESMRMB. Designed for teams of four with a time limit of 25 minutes, the room reproduced the atmosphere of an MR control room. The five puzzles covered the Larmor equation, sequence composition, MR safety and acoustical identification of MR sequences. Custom ESP32 electronics allowed the puzzles to communicate in real time with each other and with the game master Results. The room ran without technical interruptions and was played by 39 teams (approximately 160 participants); 12 solved it (escape rate 31%), with a median solution time of 21 minutes and 53 seconds. Early-career researchers acted as game masters. Discussion. The escape rate aligns with comparable activities targeting scientific audiences. Difficulty can be tuned by adjusting puzzle obscurity, component availability, required prior knowledge and mental leaps. A modified version could usefully supplement mandatory MR safety training. Code, schematics, machining files and documentation are released as open source.
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Fluid Dynamics · Cross-listed from math.NA
A novel compact scheme for second-order fluxes applied to the Spectral Difference method
Guido Lodato and Niccolò Tonicello
The discretization of second-order (viscous) terms in Discontinuous Spectral Element Methods (DSEMs) typically relies on an auxiliary gradient variable, whose treatment at element interfaces affects the accuracy and stability of the scheme. The Bassi-Rebay (BR1) formulation is attractive for its simplicity and parameter-free character, but suffers from sub-optimal convergence at even
polynomial orders and requires an extended five-element stencil. Inspired by Huynh's Flux Reconstruction formulation, we develop a compact, fully-centered scheme for second-order fluxes within the Spectral Difference (SD) method. The proposed approach modifies the reconstruction of the auxiliary gradient using interface-dependent, one-sided continuous fluxes, reducing the stencil from five to three elements while preserving the centered and parameter-free nature of BR1. The formulation is developed in one dimension and extended to multiple dimensions. Temporal eigenanalysis is used to characterize its dissipation and dispersion properties, including the effects of interior penalty terms. Numerical tests consider the linear
diffusion equation, an under-resolved localized Dirac's delta, the nonlinear porous medium equation, and implicit large-eddy simulations of the three-dimensional Taylor-Green
vortex at $\mathrm{Re}=1600$ and $5000$. The compact scheme restores the expected convergence order for all
polynomial degrees, including even orders, and reduces spurious oscillations in under-resolved and nonlinear regimes. It also remains stable in turbulent cases where the standard formulation fails, owing to improved damping of high-wavenumber numerical modes. The proposed approach provides an attractive compact alternative to BR1 for second-order fluxes in the SD method.
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Mesoscale and Nanoscale Physics
Symmetry Breaking by Interfacial Dead Layers: Observation of Forbidden Self-Induced Spin-Orbit Torque in Symmetric Ferromagnets
Athira Ravindran K, Raghvendra Posti, Manish Kumar Mohanta et al. (+8 more)
Conventionally,
spin-orbit torques (SOTs) in ferromagnets require heavy-metal layers or engineered structural asymmetry to break inversion
symmetry. In this work, we report the observation of robust, self-generated SOTs in a nominally symmetric, heavy-metal-free MgO/NiFe/MgO trilayer - a geometry where such torques are theoretically forbidden. By combining harmonic
Hall measurements with SQUID magnetometry and X-ray photoelectron spectroscopy, we identify the
symmetry-breaking origin: a 1.8 nm
magnetic dead layer at the bottom interface. Crucially, we demonstrate a quantitative agreement between our data and the drift-
diffusion theory predicted by Kim and Lee, yielding a theoretically extracted dead-layer thickness (1.2 nm) which matches structural characterization. Furthermore, density-functional calculations confirm that NiFe possesses sufficient intrinsic
spin Hall conductivity to support the observed
spin currents. These results reframe the parasitic dead layer as a functional spintronic component, establishing a universal, all-
ferromagnetic route to SOTs in standard
magnetic heterostructures.
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All authors Athira Ravindran K, Raghvendra Posti, Manish Kumar Mohanta, Abhishek Kumar, Damanpreet Kaur, Alberto Anadón, Sebastien Petit-Watelot, Juan-Carlos Rojas-Sánchez, Michel Hehn, Puru Jena, Debangsu Roy
Mesoscale and Nanoscale Physics
Buried germanium quantum well proximitised by magnetic field-resilient superconducting platinum iridium germanosilicide
Praveen Viswanathan, Erik Lemmens Sjöstrand, Davide Costa et al. (+8 more)
Hybrid
superconductor-
semiconductor systems provide a versatile platform for
quantum technologies, ranging from superconducting-
spin interfaces to topological
quantum devices. Progress toward scalable implementations requires
superconductors that exhibit high critical fields ($>1$T) at accessible temperatures integrated with low-disorder
semiconductor heterostructures. Here we demonstrate a superconducting platinum iridium germanosilicide (PtIrSiGe), with critical out-of-plane
magnetic field up to $B_{\perp} = 1.9$T and critical temperature of $T_c\sim 1.85$K, integrated with planar germanium with mobility $\mu = 1.3\times 10^6$cm$^{2}$/Vs via top-down lithography fabrication. We show that the integrity of the germanium
quantum well and mobility and density of the 2D hole gas are preserved despite annealing at $500\deg$C, a temperature comparable to that used for strained germanium epitaxy. We further demonstrate proximitisation of a buried germanium
quantum well in a gate-defined Josephson junction/SQUID on a Ge/SiGe
heterostructure.
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All authors Praveen Viswanathan, Erik Lemmens Sjöstrand, Davide Costa, Marinus Fischer, Athique Ahmed, Sara Martí-Sánchez, Lucas E. A. Stehouwer, Jordi Arbiol, Anasua Chatterjee, Giordano Scappucci, Karina L. Hudson
Optics
In-situ integrated nonlocal Huygens metasurfaces enable robust vortex beams from multimode fibers
Mingke Jin, Jieyu Zheng, Chaoyang Wang et al. (+4 more)
A fundamental hurdle for multimode fiber (MMF) integrated photonics is achieving robust and deterministic wavefront shaping against fiber perturbation, which induces random modal interference and scrambles the real-space output into speckle patterns. Existing wavefront shaping methods typically rely on pixelated phase or polarization pre-compensation, rendering them highly sensitive to fiber deformation. Here, we show that in-situ integration of a silicon nonlocal metasurface onto an MMF end facet enables direct conversion of arbitrary speckle patterns into optical
vortex beams without pre-compensation. The metasurface supports overlapped Mie resonances and nonlocal bound states in the continuum (BICs), yielding high-transmission bands by satisfying the generalized nonlocal Huygens condition. Through momentum-space coupling between MMF modes and Huygens-BICs with topological polarization-
vortex nature, the output maintains doughnut-shaped profiles under static and dynamic perturbations, demonstrating exceptional robustness against fiber deformation. This approach provides a compact,
alignment-tolerant platform for robust structured light generation in MMFs for endoscopy, optical trapping and communications.
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All authors Mingke Jin, Jieyu Zheng, Chaoyang Wang, Yuhao Fang, Gongkai Zhang, Min Qiu, Jingyi Tian
High Energy Physics (Phenomenology)
Prospects for early heavy-quark measurements at the EIC
Allencris John Rubesh Rajan and Laboni Manna
We assess the prospects for inclusive heavy-
quark-pair electroproduction in electron-
proton ($ep$) and electron-
nucleus ($e$A) collisions, alongside double-charm-pair ($D^0 \bar{D}^0$ and $D^0D^0$) electroproduction in $ep$ collisions, during the early operational phase of the Electron-Ion
Collider (EIC). Based on the anticipated beam energies and luminosities of the EIC, we estimate the total cross sections and differential distributions for
photon virtuality $Q^2$, heavy-
quark transverse momentum, and rapidity. This analysis evaluates different Bjorken-$x$ ($x_{\rm Bj}$) intervals across a range of $Q^2$ values. Expected event yields are estimated from the projected integrated luminosities of the early science programme, demonstrating the substantial improvement in statistical precision over previous HERA measurements at moderate and large $x_{{\rm Bj}}$. For electron–
nucleus collisions, we compute the
nuclear modification ratio $R^{e\text{A}}$ within collinear factorisation using
nuclear parton distribution functions, and identify the kinematic regimes in which shadowing, anti-shadowing, and EMC-like suppression are accessible with early EIC data. These results are intended to serve as a parton-level baseline to support feasibility studies and to provide a reference for future higher-order theoretical and experimental investigations at the EIC.
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Fluid Dynamics
Memory-Generated Transport Geometry: Curvature, Holonomy, and Irreversibility
Mounir Kassmi
Memory is traditionally incorporated into transport theory as a constitutive correction acting on an already prescribed kinematic structure. Here we develop a different framework in which finite
memory itself generates the geometry of transport. By reconstructing deformation from causal transport histories, the instantaneous velocity gradient is replaced by a
memory-dependent transport connection whose ordered
evolution gives rise to noncommutativity,
curvature, and holonomy in transport-history space. We show that finite
memory generates a nonvanishing
geometric contribution to transport even in time-periodic, irrotational flows, providing a purely kinematic mechanism for irreversible Lagrangian transport without invoking vorticity, constitutive nonlinearities,
stochastic forcing, or explicit
symmetry breaking. We introduce an intrinsic
curvature invariant, independent of the transport representation that measures the accumulated
geometric structure generated by transport history. The framework predicts universal scaling governed by the dimensionless parameter (\omega\tau_m), identifies a characteristic
memory scale (tau_c) separating rapid
geometric accumulation from asymptotic saturation, and reveals a monotonically decreasing
memory susceptibility with globally concave accumulation dynamics. Numerical simulations confirm these predictions and show that
geometric irreversibility emerges through progressive
curvature accumulation rather than resonance-driven amplification. These results establish finite
memory as a generator of an intrinsic
geometric structure rather than merely a modifier of dynamical
evolution, revealing causal history as the microscopic origin of
curvature, holonomy, and irreversible transport across a broad class of non-Markovian systems.
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Quantum Physics
Time Dilation and center of Mass Normalization in the Page-Wootters Formalism
Juan Sebastian Ardenghi
In this work, we study the emergence of relativistic effects in a composite
quantum clock within the Page-Wootters relational formulation of
quantum mechanics. We consider a system with internal and center-of-mass degrees of freedom and analyze the conditioned
evolution of the center-of-mass relative to the internal system treated as an internal clock. We show that the internal sector exhibits an effective time dilation. Retaining the full mass-energy structure of the composite particle, a back-reaction of the internal energy on the center-of-mass sector appears through an operator-valued normalization factor. As a direct consequence of the back-reaction, the conditioned center-of-mass dynamics is governed by a Schroodinger equation that is non-local in the clock time, with an effective temporal non-locality of the order of the Compton time of the composite system. Applying the formalism to a center-of-mass momentum superposition, we find that the interferometric visibility acquires a correction that is quadratic in the internal energy, and therefore depends on the absolute distribution of clock energies rather than only on the energy gaps that control the standard time-dilation dephasing. Although this correction is parametrically small, it is a generic feature of relativistic composite clocks and can, in principle, be isolated through a differential visibility measurement comparing clocks with equal transition frequency but different mean internal energies.
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High Energy Physics (Theory)
Nonperturbative Stabilization of D-Instantons in the Bosonic IIB Matrix Model
Yu-An Chen, Hikaru Kawai, Henry Liao et al. (+1 more)
We study the bosonic type IIB (IKKT)
matrix model and the fate of the D-instanton positions $p^{(i)}_\mu$, the diagonal components of the $d$ Hermitian
matrices, whose one-loop effective potential infamously drives them to a single point. We show that this collapse is an artifact of the leading (one-loop) truncation, while the actual non-collapse of the $p^{(i)}_\mu$ is a nonperturbative effect: it is invisible at one loop but already present in the exact (all-loop) two-body interaction. Since the two-body sector of the $N\times N$ model factorizes into copies of $N=2$, this interaction is captured exactly by the $\mathrm{U}(2)$ model, and we find that the two D-instantons do not collapse onto each other. To set up the computation, we gauge-fix the $\text{U}(N)$
symmetry in a way that keeps the diagonal and off-diagonal sectors distinct, and we handle the residual $\mathrm{U}(1)^N$
symmetry with an auxiliary-ghost BRST construction. This construction generates a new ghost four-leg vertex; the resulting Faddeev-Popov determinant admits a systematic large-separation expansion that organizes the effective potential into a many-body decomposition, separating the interaction into two-body, three-body, and higher-body contributions. The exact $N=2$ partition function is finite at finite separation; its naive Lorenz-gauge form develops a negative region at separations of order one, which we trace to a Gribov ambiguity of the Lorenz gauge and resolve with the maximal diagonal gauge–the classical frame containing the perturbative
vacuum–where the short-distance force is finite and repulsive, so that the two-body potential develops a stable minimum at finite separation. These results are consistent with a stable, non-collapsed distribution of the $p^{(i)}_\mu$; establishing the detailed distribution and full $N$-body non-collapse requires the higher-body potentials and is left to future work.
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All authors Yu-An Chen, Hikaru Kawai, Henry Liao, Cheng-Tsung Wang
Astrophysics of Galaxies
Ubiquitous Interstellar Neutral Helium Detected with JWST
Jane R. Rigby, D. Koutroumpa, M. Galeazzi et al. (+8 more)
We report the discovery of ubiquitous neutral helium emission in sky spectra taken with JWST's NIRSpec instrument. The emission, with a wavelength of 1.0833 micron, resembles one of the "sky lines" that are seen by ground-based observatories. We examine this emission in all suitable NIRSpec spectra in the public archive, totaling 22 days of exposure time. We find that this He I emission is almost always present: it is well-detected in 80 percent of the observations, and in 53 percent of the individual exposures. The emission is highly time-variable: at a given pointing, the line intensity can vary by factors of several over the course of a day. The He I emission is strongest when JWST crosses through the cone of interstellar neutral helium that is gravitationally focused by the sun; intensity during the cone crossing is anti-correlated with
solar activity. The low
redshift and narrow velocity width of the He I line, and the elevated intensity when JWST crosses through the focusing cone, together indicate that origin of the He I emission is cold Milky Way gas passing through our
solar system. JWST provides a new way to study this interstellar gas, revealing new insights such as extreme variability on timescales of hours to days, which has not been previously reported.
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All authors Jane R. Rigby, D. Koutroumpa, M. Galeazzi, T. Hutchison, K. D. Kuntz, Rosalia O'Brien, Marshall Perrin, F. S. Porter, Yu. Ralchenko, B. M. Walsh, Brian Welch
Fluid Dynamics
Exact solution for the motion of a rigid particle with $\boldsymbol{S_4}$ and $\boldsymbol{C_{2v}}$ symmetry settling under gravity in a viscous fluid
Piotr Zdybel and Maria L. Ekiel-Jeżewska
We provide an exact and complete solution for the dynamics of a rigid particle of uniform density with $C_{2v}$ and $S_4$
symmetry, settling under
gravity in a viscous fluid at a Reynolds number much smaller than unity. The $S_4$
symmetry renders the problem exactly integrable, with all orbits labelled by a single conserved quantity $0\le C\le 1$. We show that, for $0<C<1$, there are two different time scales, which lead to quasi-periodic
evolution, with a significant time-dependent horizontal displacement. We obtain the tilt $\theta$ and
spin $\psi$ Euler angles as periodic Jacobi
elliptic functions of time, and the azimuthal angle $\phi$ through an incomplete
elliptic integral of the third kind with a complex characteristic, which splits $\phi$ into a uniform drift and a strictly periodic modulation. The orientation period and the drift rate (corresponding to a constant angular velocity around the
gravity direction) follow in a closed form. The vertical centre-of-mass displacement is obtained in terms of periodic in time incomplete
elliptic integrals, and the periodic orbit-averaged settling velocity reduces to a single ratio of complete
elliptic integrals. The horizontal component of the motion in the laboratory frame of reference is obtained exactly and algebraically in terms of all three Euler angles, so it is quasi-periodic. The horizontal component of the centre-of-mass position traces rosette-like, in general open curves confined by two concentric `envelope' circles. We determine very simple exact expressions for radii of both envelopes and demonstrate that they tend to infinity for a family of shapes with the rotation-translation coupling decreasing to zero. We also explain the origin of cusps at the rosette-like trajectory and provide a commensurability condition selecting strictly periodic rosettes.
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Pattern Formation and Solitons
Rogue Wave Statistics from a Sparse Coherent Structure Decomposition
Yuchen He, Amin Chabchoub and Zhan Wang
While conventional rogue wave statistical models rely on linear or weakly nonlinear descriptions of random seas, we demonstrate experimentally that moderately or strongly nonlinear wave fields can be represented by sparse ensembles of coherent
soliton-like packets. These packets exhibit log-normal amplitude distributions together with uniformly distributed phases and peak emergence times. This sparse coherent structure framework naturally leads to an extreme value description in which the probability of exceedance is governed by the tail of the coherent-structure amplitude distribution. The prediction is validated against laboratory hydrodynamic experiments across a variety of unidirectional sea states, showing good agreement with the experimental observations and comparing favourably with conventional statistical prediction models while retaining analytical simplicity. Our results provide a direct physics-based link between sparse coherent structures and rogue wave probabilities, with broader implications for nonlinear wave physics in optics, cold gases, and
plasmas.
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Quantum Physics
A Highly Accurate Fast Decoding Framework for QLDPC codes Accelerated by Noise Perturbation and Ensemble Decoding
Mainak Bhattacharyya and Ankur Raina
A well-balanced decoder has been central to the development of modern fault-tolerant
quantum computing. However, the inherent
topologies of
quantum error correcting codes can limit the performance of many well-studied decoding
algorithms. In this work, we introduce Noise Assisted Ensemble Decoding (NAED), a highly accurate decoding framework with a significant advantage in real-time speed. NAED constructs an ensemble of Tanner forests, obtained as acyclic subgraphs of the original Tanner graph, and performs exact inference on each Tanner forest using a lightweight dynamic programming
algorithm. The forest construction is guided by synthetic soft information derived jointly from the measured syndrome and channel statistics, with controlled noise perturbations generating diverse yet informative decoding
matrix column orderings for the Tanner forest construction across the ensemble. Our
benchmark results show that the proposed synthetic soft information-driven construction and inference on the Tanner forests can achieve improved or comparable decoding performances to the state-of-the-art decoding solutions, such as BP+OSD$0$, while also providing orders-of-magnitude improvements in per-round decoding speed under
circuit-level noise.
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Solar and Stellar Astrophysics
Sector-based morphological analysis of four planetary nebulae (J 320, NGC 2610, A 6672 and PRTM 1) observed with UVIT/ASTROSAT
Anisha Hazra, Ranjan Kumar, Sonika Piridi et al. (+1 more)
Four planetary nebulae (PNe), Jonckheere 320, NGC 2610, A 6672, and PRTM 1, have been imaged in the far-ultraviolet (FUV) filter F148W ($\lambda_{\mathrm {eff}} = 1481\, \mathring{A} $) using the Ultraviolet Imaging
Telescope (UVIT) onboard ASTROSAT. The FUV images reveal faint extended emission structures surrounding the bright central
star. A novel sector-based structural analysis technique was employed to examine the detailed FUV morphologies of PNe. In this method, sector strengths were calculated for each nebula and used to classify their structures. Our results show that Jonckheere 320 exhibits a polypolar morphology, while NGC 2610 and PRTM 1 display spherical structures. In contrast, A 6672 shows irregular or elliptical features in the FUV.
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All authors Anisha Hazra, Ranjan Kumar, Sonika Piridi, Ananta C. Pradhan
Quantum Physics · Cross-listed from cs.PL
Quantum Uncomputation of Clean and Dirty Ancilla Qubits
Chenke Liu, Li Zhou and Boning Meng
Automatic uncomputation aims to provide programming-
language-level support to facilitate the correct and safe use of ancilla
qubits in
quantum computing, but efforts have only been made for clean ancillas, leaving dirty ancillas unexplored. We present a unified formalization of the uncomputation of both clean and dirty ancillas. For the first time, we prove that checking the existence of uncomputation is coNP-hard. We introduce two complementary synthesis-oriented existence checking methods: a syntax-directed static
reasoning system and a rewrite-based normalization procedure (\RwUnx), together forming a top-down pipeline. We implement \RwUnx in Qiskit. Compared with the state-of-the-art \Reqompx, \RwUnx handles practical
benchmarks with complex dependencies where \Reqompx does not, and achieves higher success rates in random-
circuit experiments.
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Mathematical Physics
Eigenvalue asymptotics for the one-particle density matrix and one-particle kinetic energy density operator
Søren Fournais and Alexander V. Sobolev
Let $\psi({\mathbf x})$, ${\mathbf x} \in{\mathbb R}^{3N}$, be an eigenfunction of the $N$-particle atomic Schrödinger operator. We consider the one-particle density
matrix $\gamma(x, y)$ and one-particle kinetic energy density $\varkappa(x, y)$, $x, y\in {\mathbb R}^3$, associated with the eigenfunction $\psi$. Both functions play a central role in
quantum chemistry computations of atomic and molecular bound states: the knowledge of the
eigenvalue behaviour of the integral operators ${\sf{\Gamma}}$ and ${\sf{K}}$ with kernels $\gamma(x, y)$ and $\varkappa(x, y)$ serves to estimate the errors due to finite-dimensional approximations. We find the following asymptotic formulas for their
eigenvalues $\lambda_k({\sf{\Gamma}})>0$ and $\lambda_k({\sf{K}})>0$: \[ \lim_{k\to \infty} k^{\frac{8}{3}} \,\lambda_k({\sf{\Gamma}}) = A^{\frac{8}{3}},\quad \lim_{k\to \infty} k^2\,\lambda_k({\sf{K}}) = B^2, \] where $A$ and $B$ are non-negative constants given explicitly in terms of the eigenfunction $\psi$. These asymptotics are determined by the singularities of the function $\psi$ at pair coalescence points of the particles. To identify and isolate these singularities we use some recent regularity results for $\psi$. At the last step we apply Birman-Solomyak spectral asymptotics results for pseudodifferential operators with homogeneous symbols. In the special case where the eigenfunction $\psi$ is totally antisymmetric, it exhibits enhanced regularity, which leads to a faster decay of the
eigenvalues $\lambda_k(\sf{\Gamma})$ and $\lambda_k(\sf{K})$. The asymptotic formulas take the form \[ \lim_{k\to \infty} k^{\frac{10}{3}} \,\lambda_k({\sf\Gamma}) = \big(A_{asym}\big)^{\frac{10}{3}},\quad \lim_{k\to \infty} k^{\frac{8}{3}} \,\lambda_k({\sf K}) = \big(B_{asym}\big)^{\frac{8}{3}}, \] where $A_{asym}$ and $B_{asym}$ are non-negative constants given explicitly in terms of the gradient of $\psi$.
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Astrophysics of Galaxies
Searching for low-surface-brightness galaxies with compact neural networks A parameter-efficient approach to first-pass selection of diffuse galaxy in HSC-SSP imaging
Günther K. Heemann, Henri Cecatka and Dominik J. Bomans
Low-surface-brightness
galaxies (LSBGs) trace a diffuse and observationally challenging regime of
galaxy formation that remains highly susceptible to selection effects in optical surveys. We present a hybrid LSBG detection pipeline that integrates compact convolutional neural networks (cCNs) as a morphological validation stage within a multi-step detection framework applied to HSC-SSP imaging. Permissive low-threshold source detection with SEP is followed by cCN-based morphological filtering, physically motivated consistency checks, and parametric surface-brightness modelling with galfitm. The cCN is deliberately constrained to ${\sim}10^4$ trainable parameters to match the spatial scales of diffuse emission and ensure computational efficiency at survey scale. The cCN reduces the initial detection set of ${\sim}77\times10^6$ objects by more than four orders of magnitude while recovering essentially all literature LSBGs that pass the detection stage. The resulting Gold catalog of 5156 candidates occupies the characteristic loci of LSBGs in colour-colour and structural parameter space, in close agreement with previously published HSC-SSP based samples. Cross-matching with SDSS and DESI spectroscopic
redshifts confirms that the pipeline identifies genuine nearby diffuse
galaxies. Compact neural networks provide a robust and computationally scalable morphological filter for LSBG searches, effectively bridging classical detection pipelines and large general-purpose deep architectures. The pipeline is detection-limited rather than selection-limited, identifying the initial source extraction stage as the primary target for future improvement.
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Quantum Physics
Conditional non-Hermitian acceleration of multiphoton atomic transitions
Marcos V. S. de Paula, Alexandre P. Costa and A. V. Dodonov
Continuous monitoring can convert a dissipative channel into a resource for accelerating otherwise slow multiphoton transitions. We consider a three-level atom in a $\Lambda$ configuration and condition the
evolution on the absence of
photon emission through an auxiliary monitored decay channel. The resulting no-jump dynamics is governed by a non-Hermitian Rabi-type
Hamiltonian. Using Floquet theory and Brillouin–Wigner projection-operator perturbation method, we derive effective two-state descriptions of odd-multiphoton resonances in the semiclassical and
quantum Rabi models. The effective population-transfer rate, defined as the inverse of the time required for the first complete transfer between the atomic states, is maximized at an exceptional point, where its enhancement factor approaches $\pi/2$, corresponding to an approximately $57\%$ increase over the Hermitian value. Numerical results for three- and five-
photon resonances closely reproduce the analytical transition times and yield non-negligible postselection probabilities. By contrast, the complete unconditioned dissipative
evolution does not exhibit the same population-transfer enhancement. These results demonstrate a speed–success trade-off for measurement-conditioned multiphoton state transfer.
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Mesoscale and Nanoscale Physics
Long-range exchange interaction controls the fine structure of excited trion states in semiconductor quantum dots
M.M. Glazov and E.L. Ivchenko
We develop a microscopic theory of the long-range electron-hole exchange interaction in charged
excitons (trions) confined in
semiconductor quantum dots. While the ground-state singlet trion remains degenerate in the
spin component of unpaired charge carrier by time-reversal
symmetry, excited trion states exhibit a rich fine structure resulting from the interplay of electron-electron and electron-hole exchange interactions. We derive the effective long-range exchange
Hamiltonian for both the
spin-$3/2$ heavy-hole and a simple
spin-$1/2$ valence band models. The long-range exchange interaction mixes singlet and triplet trion configurations, giving rise to anisotropic fine-structure splittings and related polarization-dependent optical spectra determined by the
quantum-dot shape. Analytical expressions are obtained for the long-range exchange parameters. The developed theory establishes a unified microscopic description of the fine structure of excited trions in
semiconductor quantum dots and provides a framework for interpreting polarization-resolved optical spectroscopy of charged excitonic complexes.
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Atomic Physics
Resonant photoionization dynamics during optical trapping of lithium atoms
K. Foster, S. Majumdar and D. Fischer
Photoionization induced by trapping and auxiliary
laser fields is an inherent feature of many
laser-cooling and optical trapping experiments, yet its microscopic dynamics are rarely investigated directly. In this work, we employ a reaction microscope implementing an event-by-event photoionization time
retrieval technique to extend momentum-resolved photoelectron spectroscopy to continuous-wave
laser–atom interactions. We investigate low-intensity multicolor photoionization of
laser-cooled lithium atoms confined in an all-optical trap. Complete three-dimensional electron momentum distributions and kinetic-energy spectra recorded for different
laser wavelengths and polarization configurations identify resonant excitation of the $5p$ and $5f$ states and reveal an additional ionization channel following spontaneous decay from the $5f$ to the $4d$ state. A pronounced polarization dependence of the photoionization yield is explained by
magnetic-sublevel selection rules and the coherent interference of different virtual excitation pathways. These results demonstrate that reaction microscopy combined with event-by-event time reconstruction provides a powerful approach for investigating microscopic electronic dynamics in
laser-cooled atomic systems and offers new insight into photoionization processes occurring during optical trapping.
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Optics
Direct Laser Interference Patterning of Functional Metal Surfaces: From Written Geometry to Functional Interfaces
Petr Hauschwitz
Direct
laser interference patterning (DLIP) generates periodic micro- and nanoscale structures with increasing precision and throughput, yet similar geometries can produce fundamentally different functional responses. This review examines why morphology alone cannot predict friction, wetting and ice adhesion, bacterial response,
cell behaviour, optical performance or electrochemical and photovoltaic function. DLIP is treated as a model system in which the optically prescribed geometry can be distinguished from the interface realised during processing. The written period is separated from relief depth, aspect ratio, hierarchical topography, surface chemistry, ageing and process history. Functional response is interpreted as a two-stage process: geometry creates the opportunity for interaction with an external
agent, while the realised interface determines how that interaction becomes measurable performance under a specific interfacial state. A curated, metals-centred evidence base spanning tribology, wetting and anti-icing, antibacterial and biomedical surfaces, optics, electrochemistry, energy devices and manufacturing shows that period-depth coordinates alone rarely predict function across domains. Geometry remains highly transferable in optical systems and controlled mechanical contacts, whereas biological, state-dependent and device-level functions also depend on surface state, operating conditions and system architecture. The framework reconciles conflicting observations and identifies which variables are transferable and which remain context-dependent. Predictive DLIP surface engineering therefore requires identification of the interacting
agent, separation of written geometry from the realised interface, isolation of variables governing interfacial coupling and evaluation through direct, mechanism-specific endpoints.
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Instrumentation and Detectors
Optimization studies of silicon remoTES cryogenic calorimeters
G. Angloher, M.R. Bharadwaj, A. Boehmer et al. (+42 more)
The remoTES design, developed within the COSINUS experiment, enables a broader range of materials to be operated as cryogenic calorimeters read out with Transition Edge Sensors (TESs). In this configuration, the TES is fabricated onto a separate chip and thermally coupled to the absorber via a gold (Au) link. The remoTES concept has been successfully tested on various target materials. To further enhance detector performance and to fully exploit the advantages of the remote coupling design a series of optimization studies has been conducted using silicon (Si) absorbers as
benchmark. This work presents an evaluation of several measurements aimed at reducing the thermal boundary resistance and enhancing signal transmission across Si remoTES interfaces, specifically from the absorber to the
phonon collector and from the
phonon collector to the TES. By testing a new Au link design and three distinct
phonon collector configurations, Au, copper, and aluminum (Al)/Au, we achieved a baseline resolution of (21.5 +/- 0.3)eV using the Al/Au
phonon collector.
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All authors G. Angloher, M.R. Bharadwaj, A. Boehmer, S. Braun, M.R. Cababie, I. Colantoni, I. Dafinei, N. Di Marco, C. Dittmar, F. Ferella, F. Ferroni, S. Fichtinger, A. Filipponi, M. Friedl, D. Fuchs, L. Gai, M. Gapp, M. Heikinheimo, K. Heim, K. Huitu, M. Kellermann, R. Maji, M. Mancuso, L. Pagnanini, F. Petricca, S. Pirro, F. Proebst, G. Profeta, A. Puiu, F. Reindl, K. Schaeffner, J. Schieck, P. Schreiner, C. Schwertner, P. Settembri, K. Shera, M. Stahlberg, A. Stendahl, M. Stukel, C. Tresca, S. Yue, V. Zema, Y. Zhu, L. Ziegele, N. Zimmermann
Quantum Physics
Quantum Coordination and Nonlocal Games: Theory and Applications
Husein Natur and Uzi Pereg
Coordination is a fundamental primitive in communication and information theory, in which distributed systems must collectively generate correlated behavior rather than merely exchange messages. In
quantum networks, the nature of
entanglement,
quantum measurements, and nonclassical correlations introduces coordination possibilities unavailable classically. This article reviews recent advances in coordination over classical and
quantum communication networks, focusing on empirical and strong coordination in multi-user settings. We consider the implications of coordination for nonlocal games, showing how it provides a natural framework for understanding the correlations that enable spatially separated players to improve their probability of winning. We present a unified framework for coordination using classical or
quantum communication and pre-shared correlation resources. The review covers simulation of both
entanglement and separable correlations across a variety of network architectures, including two-node, cascade, broadcast, and multiple-access networks. We study the operational differences between empirical and strong coordination, and the tradeoffs between communication and correlation resources, such as pre-shared randomness and
entanglement. Coordination plays a major role in device-independent
quantum key distribution (DI-QKD) schemes, in which parties can generate a secret key even if the devices used in the process have been prepared by an adversary. Furthermore, we examine the role of coordination in
quantum repeaters, where distributed
entanglement serves as a resource for long-distance
quantum communication. The review highlights connections between coordination theory and applications such as distributed
quantum systems,
quantum internet architectures, and future communication networks.
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Strongly Correlated Electrons
Spin Polarization of a Two-Dimensional Electron Liquid
G. A. Nikolaev, M. E. Sergeev, I. V. Kukushkin et al. (+1 more)
We show experimentally that the longitudinal resistance of a strongly correlated two-dimensional electron system provides a quantitative measure of its
spin polarization. Using electrically detected electron
spin resonance to independently calibrate the
spin state, we establish a parameter-free relation between magnetotransport and
spin polarization, allowing the latter to be determined from transport alone. This approach enables the
magnetic state of the electron
liquid to be mapped across a broad range of carrier densities and
magnetic fields.
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All authors G. A. Nikolaev, M. E. Sergeev, I. V. Kukushkin, A. V. Shchepetilnikov