Accelerator Physics
Coherent collective amplification of terahertz microbunching seeded by laser frequency beating in relativistic electron beams
Wencai Cheng, Yin Kang, Kaiqing Zhang et al. (+5 more)
High-power, continuously tunable terahertz sources based on free-electron
lasers require precise control of electron-beam microstructures. Quantitative prediction of the modulation amplitude across a broad frequency range remains challenging because the
laser-induced distribution and its collective
evolution must be treated together. To describe this coupled
evolution, a nonlinear model is developed for microbunching seeded by a frequency-beating
laser heater. The non-Gaussian heater-exit distribution is obtained by optical phase averaging and propagated through multistage compression in six-dimensional phase space. Source-induced correlations are retained, with space charge, coherent synchrotron radiation, and
radio-frequency wakefields evaluated self-consistently. The wavelength-dependent bunching response is thereby connected to the
laser beat frequency,
laser power, and compression partition. The short-wavelength double peak is found to be governed mainly by longitudinal space charge, while bunching near a selected wavelength can be enhanced by redistributing compression at fixed total compression. The predicted source modulation and downstream response are benchmarked against Elegant and IMPACT-Z, respectively. Experimental measurements of the wavelength-dependent bunching factor at different
laser pulse energies are found to agree well with the trends predicted by theory and simulation. The resulting framework provides a computationally efficient and predictive route to optimizing electron-beam microbunching for tunable, high-power terahertz generation at free-electron-
laser facilities.
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All authors Wencai Cheng, Yin Kang, Kaiqing Zhang, Zhen Wang, Duan Gu, Guangling Chen, Chao Feng, Haixiao Deng
Quantum Physics
Thermal entanglement on a frustrated tetrahedron: Probing quantum resources through concurrence and stabilizer structure
Reza Pourkhodabakhshi, Francis Dominie, Deep Gajera et al. (+1 more)
In a frustrated
spin system, highly entangled eigenstates can form a separable thermal mixture. We study this distinction for four
spin-$1/2$ moments on a tetrahedron, the elementary unit of the pyrochlore
lattice, with the general four-parameter exchange
Hamiltonian. Tetrahedral
symmetry allows a restricted search over thermal-state decompositions to be carried out by linear optimization, yielding an upper bound on multipartite concurrence and explicit separable decompositions where this bound vanishes. At low temperature, the concurrence maps show extended separable regions near the all-in–all-out limit, whereas suppression near the
spin-ice point is narrowly localized. Heating broadens the latter region as nearby multiplets are repopulated. The optimization identifies fully separable thermal states even when the eigenstate-averaged concurrence remains large. Negativity independently confirms finite-temperature
entanglement in selected coupling regions. A mixed-state stabilizer Rényi diagnostic, used to explore
quantum magic, favours different couplings and can increase locally with temperature. These results connect thermal
entanglement to the splitting and population of
symmetry multiplets, and provide a practical basis for identifying frustrated
spin configurations for studies of
quantum resources beyond the ground-state limit.
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All authors Reza Pourkhodabakhshi, Francis Dominie, Deep Gajera, Stephanie H. Curnoe
Physics and Society
BanglaShop-CRS: A User-Centric Bangla Dataset for Conversational Recommendation
Tabia Tanzin Prama, Christopher M. Danforth and Peter Sheridan Dodds
Conversational recommender systems~(CRS) enable users to express preferences, constraints, and feedback through natural
language interaction. However, existing CRS resources are concentrated in English and other high-resource
languages, leaving Bangla and code-mixed Bangla–English settings underrepresented. To address this gap, we introduce BanglaShop-CRS, a large-scale user-centric synthetic Bangla conversational recommendation
dataset grounded in real e-commerce behavior. It contains 27,178 multi-turn dialogues, 274,802 utterances, and 3.6M
tokens across 10 product domains. Our generation pipeline incorporates user purchase histories, positive and negative feedback, and review texts to maintain consistency between dialogue content and user preferences. We evaluate BanglaShop-CRS under catalog-constrained and open-vocabulary recommendation protocols. Results show that dialogue context improves recommendation quality, while fine-tuning yields further gains across models. Human evaluation by five native Bangla-speaking annotators confirms the fluency, informativeness, logicality, and coherence of the dialogues, with significant agreement across all dimensions. Factual-grounding evaluation further shows stronger
alignment with correct than shuffled user records, with substantial inter-annotator agreement ($\kappa=0.65$) and comparable human and GPT-5.1 judgments. BanglaShop-CRS provides a scalable
benchmark for advancing conversational recommendation in Bangla.
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Physics and Society
Ensuring proportionality: a logical model for compensatory seats added to multi-member constituencies
Frederik Ravn Klausen
How many compensatory seats are needed to ensure (full) proportionality in two-tier electoral systems with multi-member constituencies? This question is answered by estimating the discrepancy between seats and votes rigorously, probabilistically and empirically. In 1919, Pólya showed that the Jefferson/D'Hondt method favours large parties. This seat surplus accumulates across constituencies. In some countries (e.g., Portugal, Poland, Spain and Turkey), this accumulation directly leads to quantifiable disproportionality in the final parliament. Elsewhere compensatory seats counteract this accumulated seat surplus. Using a logic-first approach, closed formulas for the required number of compensatory seats are derived given regional and national apportionment methods, the number of relevant parties $n$ and the size of the largest party $p$. If there are $c$ constituencies, it is derived logically that a two-tier system built on local D'Hondt apportionment in multi-member constituencies needs around $\frac{c}{2}(n-\frac{1}{p})$ compensatory seats to ensure proportionality. In words, that is half a compensatory seat per constituency times a number that increases with the number of parties and the size of the largest party. The validity of the derived formulas is analysed empirically using the extensive recent CLEA
dataset. Many quantities do not depend much on the total parliament sizes, which means that the variance can be reduced by artificially varying the house sizes. Portugal, Poland, Spain and Turkey all employ a one-tier D'Hondt system and the analysis shows that if they were to add compensatory seats to the system, reasonable numbers would be 40, 75, 75 and 120, assuming that no other properties of the systems change.
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Mathematical Physics · Cross-listed from math.DS
Dynamics of planar integrable Kepler billiards with a focused hyperbolic branch
Daniel Jaud and Lei Zhao
We consider the integrable dynamics of a planar Kepler billiard in the plane bounded by a branch of a hyperbola focused at the Kepler center. As a sequel to our previous work \cite{JZ2}, we use the existence of the foci-caustic circle to identify an
elliptic curve on which the dynamics is linearized and we analyze Cayley's condition on $n$-periodic orbits in this setting. By taking various limits also we discuss the dynamics of planar Kepler billiards with boundary being a focused
parabolic arc, as well as a straight line. In this last case, our approach offers a different way to deduce the
elliptic curve as in \cite{Felder}.
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High Energy Astrophysical Phenomena
Studying the Intermittency of Magnetized Interstellar Medium by Synchrotron Polarization Intensity and its Gradient
Ru-Yue Wang and Jian-Fu Zhang
Based on synthetic polarization observations, we qualitatively investigate the intermittency of the magnetized interstellar medium (ISM) through synchrotron polarization intensity (SPI) and synchrotron polarization gradient (SPG). Three principal findings emerge from our analysis: (1) The intermittency of the magnetized ISM is strongly modulated by magnetization and compressibility, with pronounced modulation effects predominantly observed in regimes characterized by strong magnetization and high compressibility. (2) The characterized intermittency of the magnetized ISM demonstrates a dependence on the electron spectral index under conditions where the random
magnetic field dominates. (3) SPG enables the identification of finer three-dimensional fractal structures in the case of strong Faraday depolarization. The synergistic application of SPI and SPG substantially enhances the reliability of probing magnetized ISM intermittency from real observations.
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Mathematical Physics · Cross-listed from math.AP
The nonlinear Schrödinger equation on products of $\mathbb{R}^N$ and compact metric graphs
Nicola Soave, Gianmaria Verzini and Lorenzo Villata
We study the stationary focusing nonlinear Schrödinger equation on the product $\mathbb{R}^N \times \mathcal{G}$ of the Euclidean space with a compact metric graph, in the mass-constrained variational setting. Such a product is a hybrid structure of a new type: all its faces are $(N+1)$-dimensional and are glued along interfaces of codimension one, so that the energy space is a genuine Sobolev space, while both the metric and the
topology of the graph enter the variational problem. We first develop the functional framework, giving two equivalent descriptions of $H^1(\mathbb{R}^N \times \mathcal{G})$, introducing partial rearrangements in each of the two variables together with the corresponding Pólya–Szegő inequalities, and proving Gagliardo–Nirenberg inequalities in a localized form, with a comparison of the optimal constants with those of $\mathbb{R}^{N+1}$ and of the half-space. We then study the mass-constrained problem. Ground states exist for every mass when $2<p<2_*:=2+4/(N+1)$. At the critical exponent $p=2_*$, they exist below a graph-dependent threshold lying between one half of the Euclidean critical mass and the full Euclidean critical mass. The latter value is attained when the graph admits a cycle covering, whereas the threshold is exactly halved in the presence of a terminal edge. In both cases, the threshold is sharp. For $2_*<p<2+4/N$ global minimizers do not exist, but we prove the existence of local minimizers below a further mass threshold, for which we give an explicit lower bound. Finally, we describe the dimensional crossover: below a critical mass the minimizers do not depend on the graph variable, and we characterize the threshold below which the semi-trivial solution is a local minimizer in terms of the first nonzero
eigenvalue of the Kirchhoff
Laplacian on $\mathcal{G}$.
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History and Philosophy of Physics · Cross-listed from cs.CL
Tracing individual knowledge trajectories in a changing field: the case of general relativity and gravitation
Raphael Schlattmann and Malte Vogl
Historians have reconstructed the twentieth-century transformation of general relativity and gravitation (GRG) at the field level and through individual careers, but connecting these scales requires a way to compare researchers with the changing field over time. We develop such a comparison, setting a researcher's publications and references against GRG field literature from the same, earlier, and later two-year periods. Building on Own Vocabulary and
Embedding Density Estimation from our earlier two-case study (arXiv:2501.00391), we extend the analysis to the fifty most-published authors in a NASA/ADS corpus of about 180,000 GRG records (1911 to 2000) and add two citation-based measures, Referenced Vocabulary and Citation Identity. The four measures compare an author's written
language, cited literature, semantic neighbourhood, and cited-authority configuration with the surrounding field. The earlier cases suggested that closer field-vocabulary
alignment accompanies a denser semantic neighbourhood. Across the fifty authors this holds only partially. Written and cited vocabularies tend to move together, usually resembling later GRG literature as the field turned towards astrophysical and cosmological research. Semantic neighbourhoods more often lie where the field's publications were concentrated in earlier periods, while co-citation patterns follow no single temporal direction, and the two citation measures frequently place the same researcher differently despite drawing on identical reference lists. Individual trajectories can thus combine vocabulary tied to later field states with older semantic or citation structures, and these divergent cases mark patterns for closer historical investigation. The approach transfers to other fields with defensible corpus boundaries and adequate coverage of texts, references, and disambiguated author identities.
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Nuclear Theory
Sensitivity of the $^{229m}$Th clock transition to the fine-structure constant in a Skyrme-Hartree-Fock-BCS approach
Nikolay Minkov and Adriana Pálffy
The sensitivity of the $^{229m}$Th isomer transition frequency to the possible temporal variation of the fine-structure constant $\alpha$ is investigated theoretically. We evaluate both the Coulomb as well as the isomer energies in a selfconsistent Hartree-Fock plus Bardeen-Cooper-Schrieffer (BCS) approach with Skyrme energy density functional, taking a detailed account of the
nuclear shape deformation and pairing correlations. Our results show that by a fine tuning of the pairing strengths and considering axial octupole deformation, the model can predict a very low isomer energy below the keV limit, which is not accessible in the presence of imposed reflection
symmetry. Furthermore, in the model solution with octupole deformation, the difference between the Coulomb energy in the isomeric and ground states is one order of magnitude larger than for the case with imposed reflection
symmetry. These results allow for a fully theoretical prediction of the sensitivity of the isomer transition frequency to $\alpha$ in the framework of a microscopic
nuclear model, yielding values of $K\sim 10^3-10^4$, and for a deeper understanding of its underlying physical conditions.
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Astrophysics of Galaxies
The Spitzer Data Fusion - A Far-Ultraviolet to Far-Infrared Multi-Wavelength Database in Spitzer Extragalactic Survey Fields
Mattia Vaccari
I present the Spitzer Data Fusion, a multi-wavelength photometric database providing far-ultraviolet to far-infrared flux measurements, together with photometric and spectroscopic
redshifts, for 4.4 million IRAC-selected sources over 65\,deg$^2$ in eight of the most widely studied extragalactic survey fields. A companion product, the SERVS Data Fusion, provides 2.8 million sources over 18\,deg$^2$ selected from deeper Spitzer warm-mission imaging. Catalogs are band-merged with wavelength-dependent matching radii, astrometrically registered against 2MASS, and distributed as FITS binary tables, one per field, as \href{https://doi.org/10.5281/zenodo.6120913}{DOI: 10.5281/zenodo.6120913} and as CDS/VizieR \href{https://cdsarc.cds.unistra.fr/viz-bin/cat/II/377}{catalog II/377}. The database is intended as a community resource for photometric
redshift calibration, spectral energy distribution fitting, sample selection and multi-wavelength cross-identification, and is a natural bridge between the Spitzer legacy fields and ongoing Euclid, Rubin and SKA precursor surveys.
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High Energy Physics (Phenomenology)
Baryon-to-meson ratios in the Lund jet plane: resolving string-junction and thermal-fragmentation effects
Robert Vertesi
Baryon-to-
meson ratios inside charged jets are studied in the Lund jet plane using PYTHIA simulations of pp collisions at $\sqrt{s} = 14$ TeV, with 15 < $p_{\rm T}^{\rm ch,jet}$ < 30 GeV/$c$ in an acceptance compatible with the future ALICE 3 detector. Jets are reclustered with the Cambridge–Aachen
algorithm and identified
hadrons are tagged at the splitting where they first separate from the leading branch. Three model configurations are compared: Monash, color reconnection beyond leading color (CR-BLC), and CR-BLC combined with thermodynamical string fragmentation (Thermal+CR-BLC). The $\Lambda_c^+/{\rm D}^0$ ratio rises with $\log(1/z)$ in the two configurations that include color-string junctions and is approximately flat under Monash. The same trend is present at the first Cambridge–Aachen branching, indicating that the effect is set at the level of the color
topology rather than through the cumulative action of many soft splittings. Light- and strange-sector ratios show no $z$-dependent signature of either mechanism, but the angular projection reveals non-trivial structure at the first branching that is washed out when emissions are summed. The Cambridge–Aachen declustering and the Lund plane together separate the kinematic signatures of the two
baryon-enhancement mechanisms in PYTHIA and provide observables accessible to future ALICE 3 measurements.
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Quantum Physics
Universal entanglement embezzlement and divergent nonlocal magic from generic local chaotic quantum evolution
Matias Karjula, Teemu Ojanen, Kim Pöyhönen et al. (+2 more)
We show that, starting from a product state, local
unitary quantum evolutions generate intermediate states which exhibit a multiscale
entanglement-spectrum structure required for universal
entanglement embezzlement. This facilitates
entanglement extraction from a catalyst many-body state while leaving it asymptotically unchanged. Remarkably, these atypical structures emerge generically at intermediate stages, well before reaching maximum
entropy where thermalization has flattened out the spectral hierarchy. The resulting state is accompanied by nonlocal nonstabilizerness that diverges with the system size, consistent with a recently established equivalence between universal embezzlement and divergent nonlocal magic. Thus, without any fine tuning, a chaotic
quantum evolution generates intermediate states which form a universal family of catalytic reservoirs.
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All authors Matias Karjula, Teemu Ojanen, Kim Pöyhönen, Tapio Ala-Nissila, Moein N. Ivaki
Physics and Society
Modelling opinion dynamics during crises as complex contagion with feedback
Junxiang Huang and Mikhail Prokopenko
Crises and population responses can form coupled dynamical systems, with crisis conditions shaping protective behaviours and collective responses altering the crisis trajectory. Existing models rarely capture both evolving crisis conditions and the reinforcement-dependent spread of competing behaviours. We propose a complex contagion with feedback (CCF) model that couples competing complex contagion with crisis dynamics through bidirectional feedback.
Agents stochastically switch between competing states according to social reinforcement and adoption complexity, which is influenced by crisis conditions and information campaigns, while population-level behavioural change feeds back into the crisis. We formulate and analyse the model for a well-mixed population, characterising its
equilibria and associated stability conditions. As a case study for model validation, we integrate CCF model with a census-calibrated
agent-based model of COVID-19 transmission in Australia to represent social distancing adoption and discontinuation. We compare the CCF model with an existing opinion dynamics model and find that, despite using fewer parameters, it achieves comparable performance in reproducing recurrent infection waves. The resulting framework is parsimonious, analytically tractable, and can be adapted to different types of crises.
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Quantum Physics
Theory-agnostic nonclassicality certification in an integrated photonic circuit
Vinicius P. Rossi, Emanuele Polino, Beatrice Polacchi et al. (+8 more)
Certifying nonclassicality without assuming any particular underlying physical theory constitutes both a foundational challenge and a requirement for device-independent protocols. Realizing such theory-independent certification in scalable architectures is essential for connecting fundamental tests with emerging
quantum technologies. Integrated photonic
circuits are a leading platform for scalable
quantum information processing, motivating the development of rigorous methods to certify the nonclassical resources underpinning
quantum advantage. In this paper, we report a theory-independent certification of generalized contextuality on a three-mode integrated photonic
circuit. Our approach combines theory-agnostic
tomography with simplex-embeddability certification—a framework that requires no assumptions about the underlying physical theory—and applies it to experimental data from a three-mode photonic
circuit seeded by single
photons. An independently constructed
quantum model of the experiment provides a consistency check on the observed nonclassicality, without entering the certification as a theoretical assumption. The method rules out simplex-embeddability for our experimental data, providing robust, theory-independent evidence that our photonic
circuit exhibits nonclassicality.
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All authors Vinicius P. Rossi, Emanuele Polino, Beatrice Polacchi, Valeria Cimini, David Schmid, John H. Selby, Giacomo Corrielli, Andrea Crespi, Roberto Osellame, Fabio Sciarrino, Ana Belén Sainz
High Energy Physics (Theory)
The geometry of multiloop Feynman Integrals from the Scattering Facet
José Ríos-Sánchez and Germán Rodrigo
The Scattering Facet (SF) of the Cosmological Polytope is a positive geometry defined from a Feynman diagram and encoding its combinatorics. Its canonical differential form reproduces the result of the integration over the energy components of loop momenta in scalar Feynman integrals, and is therefore closely related to the Loop-Tree Duality (LTD). In this article, we present a novel description of the SF as a base-fiber geometry. The fibers are a family of polytopes called deformed graphical zonotopes, which have a natural interpretation in terms of the causal
evolution of the underlying Feynman diagram, and capture interesting information on scattering amplitudes. This decomposition of the SF induces a description of the canonical form leading to the so-called causal representation. Moreover, it provides new mathematical tools that allow us to characterize all its regular triangulations. Canonical forms obtained from these triangulations correspond to spanning tree representations, matching the original LTD amplitudes expressed as a sum over spanning trees. This geometrical viewpoint provides us with new methods to obtain the causal and spanning tree representations, without the need of performing any integration.
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Medical Physics · Cross-listed from cs.CV
Video-Based Markerless Motion Capture for Clinical and Rehabilitation Biomechanics: A PRISMA-ScR Scoping Review of Validated Architectures, Clinical Readiness, and Emerging Methods
Florian Delaplace, Elodie Piche, Frédéric Chorin et al. (+1 more)
Background..
Video-based markerless motion capture promises movement analysis without the cost, space and skin-marker constraints of optoelectronic systems, with particular potential for clinical and rehabilitation settings. Whether validated pipelines yet deliver clinically acceptable biomechanics, and how they relate to the underlying computer-
vision research, remains unclear. Methods. We conducted a scoping review following the PRISMA extension for Scoping Reviews, with a registered protocol and searches of PubMed, Scopus and IEEE Xplore (January 2015 to February 2026; the computer-
vision scan was updated to July 2026). A dual-tier design paired a primary corpus of validated biomechanical studies with a complementary, curated and deliberately non-exhaustive corpus of emerging computer-
vision work, used qualitatively. We charted study characteristics, pipeline architecture, validation methods and joint-angle accuracy. Results. We included 117 studies, most published from 2024 onward and conducted on healthy adults walking in a laboratory. Pipelines formed five architectural families across
monocular and multi-camera modalities; most reported raw joint angles without biomechanical refinement. Sagittal lower-limb agreement clustered around 5 to 6{\textdegree}, generally short of clinical acceptability, while out-of-plane kinematics, kinetics, and pathological or older populations were rarely validated. Emerging computer-
vision building blocks (foundation-model mesh recovery, differentiable inverse kinematics,
video-based kinetics) were almost absent from validated studies. Conclusions.
Video-based markerless capture is not yet interchangeable with marker-based systems for clinical joint kinematics, and it remains barely validated where rehabilitation needs it most: older and pathological populations, out-of-plane kinematics, and kinetics. Mapping this evidence gap onto emerging computer-
vision advances, we propose hypothesis-generating design guidelines, not a validated method, to steer the next generation of pipelines toward accessible, clinically meaningful movement analysis.
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All authors Florian Delaplace, Elodie Piche, Frédéric Chorin, Raphael Zory
Quantum Physics
Impact of a CSS quantum error correction code in underwater quantum key distribution
Juliette Florin, Nicolas Le Josse, Arnaud Coatanhay et al. (+1 more)
Quantum key distribution (QKD) enables secure
underwater communications essential for maritime infrastructure.
Underwater optical channels introduce substantial
photon loss (erasures) and ambient noise that degrade QKD performance. This paper investigates whether two four-
qubit Calderbank-Shor-Steane (CSS)
quantum error correction codes (QECC) mitigate these impairments in vertical
underwater communication BB84 QKD protocol. After developing a comprehensive
stochastic channel model incorporating
photon loss,
geometric spreading, and
solar noise, we assess the viability of QECC through the analytical study of the
quantum bit error rate (QBER) and the secure key rate (SKR) with and without security depending on the signal-to-noise ratio (SNR) validated against Monte Carlo simulations. The standard four-
qubit CSS code achieves a 3 dB SNR gain at the QBER 11% security threshold; the discard code variant achieves 4.5 dB. However, QECC includes an encoding overhead that reduces the SKR. We demonstrate a crucial relationship between the SKR and the probability of arrival of the sent
photon. Analysis shows that QECC is beneficial exclusively in marginal SNR regimes; at high SNR, raw BB84 dominates. For an ocean Type III Jerlov water scenario with sunlight coming from the sun located at the top of the atmosphere, we identify operational depth-range windows where QECC enables communication otherwise infeasible. This analysis establishes that error correction deployment must be scenario-dependent: extend operational range at the cost of throughput when SNR is marginal, or prioritize key generation rates at high SNR.
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All authors Juliette Florin, Nicolas Le Josse, Arnaud Coatanhay, Gilles Burel
General Relativity and Quantum Cosmology · Cross-listed from math.DG
Mathias Braun and Xue-Mei Li
We introduce a codimension one construction of coarse
Ricci curvature in Lorentzian geometry. Using the $1$-Lorentz-Wasserstein distance $\ell_1$, we compare probability measures supported on small spacelike hypersurfaces through nearby events and recover, in a precise asymptotic regime, the ambient
Ricci curvature in future-directed unit timelike directions, with a universal dimensional prefactor reflecting this codimension one construction. The construction echoes the Raychaudhuri equation, which relates the
evolution of spatial volume expansion along timelike geodesics to
Ricci curvature. Our quantitative estimates rely on transport maps with controlled displacement, constructed through a Moser-type flow. At leading order, the slice construction is insensitive to smooth weights. By smearing the spacelike slices into thin timelike tubes and calibrating the temporal and spatial scales, we recover the timelike Bakry-Émery tensor $\mathrm{Ric}+\mathrm{Hess}\,V$ associated with the weighted reference measure $\smash{\mathfrak{m}=\mathrm{e}^{-V}\,\mathrm{vol}_g}$.
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Mathematical Physics
Contact canonoid maps and their conserved and dissipated quantities
R. Azuaje
We study conserved and dissipated quantities associated with contact canonoid transformations and their extension to possibly singular smooth maps. The defining condition is imposed on the pulled-back contact one-form, without requiring it to remain contact. A
polynomial construction produces first integrals from one-forms having the same dissipation rate as the original contact form. Two normalizations extend this construction to maps whose associated
Hamiltonians have different dissipation rates. On the set where the associated
Hamiltonian is nonzero, we construct a smooth invariant endomorphism whose traces are conserved. This construction includes zeros of the original
Hamiltonian, where the endomorphism vanishes. We relate the tensor traces to the coefficients of the
Hamiltonian-normalized
polynomial and obtain an upper bound of n functionally independent trace invariants in dimension 2n + 1. A five-dimensional singular map attains this bound. Examples include singular maps for the damped free particle, a transformation with unequal dissipation rates, the damped harmonic oscillator, and motion under
gravity with linear friction.
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Instrumentation and Methods for Astrophysics
The Nancy Grace Roman Space Telescope Coronagraph Community Participation Program
Dmitry Savransky, Vanessa P. Bailey, Schuyler G. Wolff et al. (+53 more)
In preparation for the operational phase of the Nancy Grace Roman Space
Telescope, NASA has created the Coronagraph Community Participation Program (CPP) to prepare for and execute Coronagraph Instrument technology demonstration observations. The CPP is composed of 7 small, US-based teams, selected competitively via the Nancy Grace Roman Space
Telescope Research and Support Participation Opportunity, members of the Roman Project Team, and international partner teams from ESA, JAXA, CNES, and the Max Planck Institute for Astronomy. The primary goals of the CPP are to prepare simulation tools, target databases, and data reduction software for the execution of the Coronagraph Instrument observation phase. Here, we present the current status of the CPP and its working groups, along with plans for future CPP activities up through Roman's launch. We also discuss plans to potentially enable future commissioning of currently-unsupported modes.
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All authors Dmitry Savransky, Vanessa P. Bailey, Schuyler G. Wolff, Maxwell A. Millar-Blanchaer, Jason Wang, Lisa Altinier, Ramya Anche. Pierre Baudoz, Beth Biller, Sarah Blunt, Wolfgang Brandner, Marah Brinjikji, Oscar Carrión-González, Amanda Chavez, Elodie Choquet, David Doelman, Julien H. Girard, Alexandra Z. Greenbaum, Samantha N. Hasler. Justin Hom, James G. Ingalls, Stephen R. Kane, N. Jeremy Kasdin, Oliver Krause, Masayuki Kuzuhara, Alexis Lau, Zhexing Li, John Livingston, Patrick J. Lowrance, Kevin Ludwick, Bruce Macintosh, Eric Mamajek, Mark Marley, Johan Mazoyer, Bertrand Mennesson, Toshiyuki Mizuki, Sarah E. Moran, Naoshi Murakami, Jun Nishikawa, Malachi Noel, Laurent Pueyo, Sergi Hildebrandt Rafels, Jason Rhodes, Tyler Robinson, Robert J. De Rosa, Matthias Samland, Nicholas Schragal, Jürgen Schreiber, Jennifer Sobeck, Karl Stapelfeldt, Motohide Tamura, Taichi Uyajma, Arthur Vigan, Michele Woodland, Marie Ygouf, Kenta Yoneta, Robert T. Zellem, Neil T. Zimmerman
Quantum Physics · Cross-listed from cs.LG
Learning to Program Adaptive Non-Local Observables for Machine Learning
Yu-Ting Lee, Samuel Yen-Chi Chen and Huan-Hsin Tseng
Quantum neural networks (QNNs) are typically built from variational
quantum circuits (VQCs), which are limited by local measurements. Adaptive non-local observables (ANO) address this by jointly optimizing
circuit parameters and multi-
qubit measurements. However, existing ANO-based VQCs learn only a single static observable that remains invariant across all inputs. We propose QFWP-ANO, a novel architecture which employs a classical hypernetwork to dynamically program VQC parameters and/or non-local observables conditioned on each input. On multivariate time-series
forecasting across four ETT
datasets, QFWP-ANO achieves the lowest MSE in 16 of 20 settings and second-lowest in the remaining four, surpassing ANO-based and other strong baselines. On reinforcement learning tasks, QFWP-ANO consistently surpasses ANO-VQCs. Our results establish input-conditioned ANO as an effective approach for enhancing QNNs.
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Chemical Physics
Variational computation of anharmonic ground and excited vibrational eigenstates using bound Quartic Force Fields: Application with MCTDH and ElVibRot
Ali Al-Jaaidi, David Lauvergnat and Daniel Peláez
In this work we introduce the use of Quartic Force fields (QFF) potential expansions in the context of variational calculations. Such potentials are commonly employed in molecular Vibrational Second-Order Perturbation Theory (VPT2) studies, for which equations explicitly dependent on the QFF parameters exist. However, QFF are unbound potentials for more or less large displacements from the reference point and, most of the time, this prevents their use in conjunction with variational wavepacket-based calculations. In this work, we propose a general correction to QFFs and introduce a fully automated numerical approach to avoid their unbound character. Our corrected potentials, bound QFF (bQFF), do not exhibit appreciable modification of the local topography around the region of interest for infrared spectroscopy. As a consequence of this, we can affirm that the vibrational eigenstructure (
eigenvalues, eigenstates) remains essentially unaltered by our correction. To illustrate their numerical stability, we have interfaced our bQFF routines in combination with to two well-established
quantum simulation software packages MCTDH and ElVibRot which feature variational approaches. More specifically, our bQFFs are separable and hence directly expressible as MCTDH operators. Furthermore, concerning the size of our bQFF expansion, we show that it is possible to tensor-decompose our bQFF in Canonical Polyadic form (CP-bQFF). We use the Monte Carlo Canonical Polyadic decomposition
algorithm for this. CP-bQFF results are virtually identical to uncompressed bQFF, but the computational efficiency is largely improved. Our approach paves the way for the automated variational study of anharmonic eigenstates in molecular systems within the reach of QFF-based potentials, using either time-dependent or time-independent schemes.
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Materials Science
Adaptive Substrate Support Based on Thin-Film Piezoelectric Actuators
Ertuğ Şimşek, Bas Jansen, Marcelo Ackermann et al. (+1 more)
Advanced lithography scanners require extreme substrate flatness in the range of nanometers to prevent focus errors. Such a flatness is challenging to reach and maintain using static substrate supports. Active correction concepts using bulk piezoelectric or linear actuators become prohibitive due to wiring and volume limitations, considering the thousands of pillars required. In this work, we present to our knowledge the first ever demonstration of an active substrate support concept based on thin-film piezoelectric actuators. The working principle, fabrication steps, and characterization of a proof-of-principle device, supported by finite element modeling (FEM), are presented in detail. The fabricated device shows a displacement above 9 nm, which is sufficient to correct some of the focus errors in lithography systems. We foresee that this new concept may open the way towards smaller chip dimensions and improved yield.
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All authors Ertuğ Şimşek, Bas Jansen, Marcelo Ackermann, Muharrem Bayraktar
Materials Science
Low Temperature Halide Assisted HVPE Growth of Single Crystal AlN Films
K. Udwary, M. Smeaton, J.S. Mangum et al. (+6 more)
Low defect, single polarity aluminum nitride layers grown by halide vapor phase epitaxy (HVPE) methods have classically needed growth temperatures well exceeding 1100{\deg}C with many of the best results being grown in the range of 1400{\deg}C. These high temperatures have typically been required to obtain Al-polar AlN films with smooth morphologies and high crystalline quality. However, these elevated temperatures make the use of quartz reactor chambers difficult, as quartz begins to soften at 1200{\deg}C, and requires specially designed reactors. This study examines the use of anhydrous hydrogen chloride (HCl) gas, injected directly to the growth surface, to suppress inverted polarity grains that form at low growth temperatures. This method allows for high quality, single
crystal AlN layers with a growth temperature of just 1000{\deg}C in a quartz reactor chamber. With this method, AlN layers of 5 um thickness were grown on c-plane (0 0 0 1) sapphire, with a growth rate of 20 um/hour, and a resulting full-width at half-maximum (FWHM) of symmetric (0 0 0 2) rocking curve reflection under 400 arcsec and asymmetric (1 0 -1 2) reflection under 1000 arcsec. Electron backscatter diffraction measurements showed the suppression of inversion domains with increasing free HCl, resulting in smoother and higher quality films.
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All authors K. Udwary, M. Smeaton, J.S. Mangum, R. Gannon, G. Dodson, B. Tellekamp, K.L. Schulte, J.H. Leach, J. Simon
Solar and Stellar Astrophysics
A homogeneous analysis of archival and new low-resolution spectra of YZ Cancri
Zhibin Dai, Lihuan Yu, Jiao Li et al. (+2 more)
YZ Cancri is an SU UMa-type
dwarf nova with sparse and heterogeneous optical spectroscopy. We present a homogeneous analysis of archival outburst-related spectra and seven new low-resolution quiescent spectra. We consistently characterize the Balmer, He I, Fe II, O I, and occasional He II and Bowen features, and assess which state-dependent differences are robustly supported. We applied a common continuum-normalization and line-measurement procedure, measuring equivalent widths, integrated line intensities, and selected profile parameters, and comparing line morphologies and intensity ratios between quiescent and outburst-related states. Because the spectra have modest and nonuniform resolving power and are not orbital-phase resolved, profile widths and centroid shifts are used only as relative diagnostics. Outburst-related spectra are dominated by broad Balmer absorption or composite profiles, whereas quiescent spectra show strong single-peaked Balmer and He I emission, recurrent Fe II {\lambda}5169, and weak O I {\lambda}7772 emission. He II {\lambda}4686 is detected in only two quiescent exposures, and the Bowen blend in one. The quiescent Balmer decrement is relatively flat, while the He I ratios show substantial exposure-to-exposure scatter. The measured Fe II ratios show no clear systematic departure from optically thin reference values, although blending limits their interpretation. These spectra establish an empirical state-dependent description of YZ Cnc and provide a reference
dataset for future phase-resolved, higher-resolution spectroscopy.
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All authors Zhibin Dai, Lihuan Yu, Jiao Li, Xuefei Chen, Zhanwen Han
Solar and Stellar Astrophysics
The emergence of a [WC] star in Sakurai's object
W. Marcolino, P. A. M. van Hoof, V. C. Maria et al. (+9 more)
Sakurai's object provides a rare opportunity to observe
stellar evolution on human timescales. Since its born-again event and detection in 1996, its
evolution has been extensively monitored, and recent optical spectroscopy has suggested the emergence of [WR]-type emission features. In this Letter, we present a secure spectroscopic identification of its central
star based on new VLT/FORS2 observations and NLTE expanding atmosphere models. Several observed emission lines arise in a [WR]-type
stellar wind, establishing the central
star as a [WR] object. The strongest
stellar features are due to C II-III and He I. We derive the
stellar and wind parameters of Sakurai's object and discuss its evolutionary status. The [WR]
star is much cooler (Teff ~ 30.5 kK) than the born-again
star V605 Aql (Teff} ~ 95 kK), which erupted about 80 years earlier. The inferred temperature is lower than predicted by models suppressing convective mixing efficiency during the VLTP, but is consistent with higher time-resolution calculations involving slightly lower-mass (<~ 0.6Msun) remnants. Continued spectroscopic monitoring and atmospheric modelling will be crucial for tracing its reheating curve and constraining the physics of this rapid evolutionary phase.
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All authors W. Marcolino, P. A. M. van Hoof, V. C. Maria, H. Todt, G. C. Van de Steene, J. A. Toalá, S. Kimeswenger, M. Hajduk, J.-C. Bouret, D. Tafoya, D. Barría, A. A. Zijlstra
Quantum Physics
Resonance-Protected Pointer States: Stationary-Phase Analysis of Entanglement in an Environment-Coupled Two-Spin System
Kentaro Urasaki
In this manuscript, we analyze the dynamics of a model in which two
spin-1/2 systems are each coupled noncommutingly to a static environmental field and to a self-
Hamiltonian, while also being mutually coupled through a $\sigma_y^{(1)}\sigma_y^{(2)}$ interaction. By constructing an exact solution that exploits parity
symmetry, and by applying the stationary-phase approximation (the saddle-point method) in the continuum limit of the environmental field, we show that coherence associated with the ordinary isolated stationary point decays as $t^{-1}$, whereas, under the resonance condition at which the local effective fields of the two
spins cancel each other, only the coherence between a pair of maximally entangled, Bell-type states- the eigenbasis of the inter-system coupling-survives, decaying via the anomalously slow power law $t^{-1/2}$. Through a comparison with the pointer-basis theory of W. H. Zurek and coworkers (the 1981 and 2005 models), we further reveal a mechanism not reducible to local coupling: in this system, the pointer observable is determined not by the individual system-environment couplings but by a statistical resonance condition between the two environments.
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Optics
Offset Dual Microcombs in a Single Microresonator: Kerr-Raman Interleaved Combs
Renhong Gao, Qifeng Hou, Xinzhi Zheng et al. (+12 more)
Integrated Kerr microcombs have emerged as a central platform for chip-scale nonlinear photonics. One of their most compelling applications is dual-comb technology, which enables fast, high-resolution, coherent optical spectroscopy, precision metrology, ranging, and ultrasensitive sensing by interfering two frequency combs with slightly different repetition rates. However, no effective strategy yet exists to synergistically excite multiple spatial mode families, manage mode competition and energy partitioning, and precisely engineer dispersion, leaving offset co-propagating dual-microcombs in a single resonator elusive. Here we demonstrate a new mechanism for offset dual microcombs formation via Kerr-Raman interleaving for the first time, by leveraging single Raman-active thin-film lithium niobate microrings. Two spatial mode families with high loaded Q factors up to 5 million are dispersion engineered to have nearly identical free-spectral-ranges but a designed relative frequency offset. Stimulated Raman scattering efficiently generates a Raman comb in one family alongside a Kerr comb in the other. The two combs interleave with a fractional offset to form a broadband, densely interleaved spectrum. Pumping the microring at only 320 mW yields Kerr-Raman interleaved dual combs both featuring nearly identical repetition rates around 102 GHz with a small difference of 675 MHz, a relatively flat envelope exceeding 29 nm and an intrinsic comb-line linewidth of 410 Hz. Our results establish offset dual-comb generation in a single microresonator, enabling compact dual-comb sources for chip-scale precision spectroscopy, Vernier-enhanced sensing, and advanced
quantum photonics.
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All authors Renhong Gao, Qifeng Hou, Xinzhi Zheng, Bin Li, Guanghui Zhao, Yingnuo Qiu, Xinke Xing, Boyang Nan, Yixuan Yang, Saisai Sun, Kunpeng Jia, Zhenda Xie, Jintian Lin, Shining Zhu, Ya Cheng
Instrumentation and Methods for Astrophysics
Supporting users in their observation preparation - the ESO ObsPrep tool
Monika G. Petr-Gotzens, Vincenzo Forchi, Andrea Mehner et al. (+6 more)
Ground based observatories are experiencing significant technological advances and
telescopes are getting equipped with highly complex instruments to enable cutting-edge astronomical research. The increasing complexity of such instruments displays a challenge to their users when they want to plan and prepare specific observation programmes, that often request to define large amount of detailed instrument-specific information. Therefore, at ESO we developed an Observation Preparation tool (in short ObsPrep tool), which provides a layer of abstraction over the instrument-specific technical details and tries to harmonize the users experience when being faced with the preparation of observation blocks for different complex instruments. The ObsPrep tool allows interactive planning of the observations by visualization of various actions and observing strategies. In a joint approach by software engineers and astronomers, ObsPrep was started as a stand-alone java desktop application and over the years has evolved into an angular based web-application. It is now fully integrated in ESOs general use phase2 user interface (p2) that allows ESO users to create, modify, or delete observation blocks. Here we present the core functionalities of ObsPrep, as well as its special features and how the user interface integrates into ESOs generic phase2 observation preparation tool. We also outline the upcoming plans to incorporate the observation preparation for the instruments of the next generation of ESOs large
telescopes, the ELT, into ObsPrep.
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All authors Monika G. Petr-Gotzens, Vincenzo Forchi, Andrea Mehner, Thomas Bierwirth, John Pritchard, Ahmed M. Khan, Olivier R. Hainaut, Kevin Knecht, Andre Graca
High Energy Physics (Phenomenology)
Scheme transformations as the gauge group of DGLAP: sum rules, classification and solution
Tommaso Rainaldi
A parton density depends on the renormalization scheme, and any two schemes are connected by a transformation that preserves the DGLAP form of the
evolution. In Mellin space such a transformation acts on the
evolution kernels as a gauge transformation, and we take this point of view throughout the discussion. For the unpolarized densities we first ask which transformations also preserve the charge-conjugation and
flavor symmetries of the
evolution kernels and the momentum and valence number sum rules. The
symmetries reduce the transformation to a few blocks, and the sum rules constrain only two Mellin moments, where they leave a single freedom, the split of momentum between the
quark singlet and the
gluon, and freeze the valence numbers. The resulting classification is complete, because with asymptotic freedom as a boundary condition a change of scheme is determined by its action on the kernels. Inside this group, the transformations that preserve positivity form a
semigroup, and the same argument covers the polarized densities. A transformation that fails only the sum rules is not lost either, since a normalization that the sum rules themselves determine repairs it, and we use this to define collinear densities as integrals of transverse-momentum-dependent densities without giving up the sum rules. We then use the same gauge freedom to solve the
evolution. Gauging the kernel away reduces DGLAP at any order to a single second-order linear equation plus a quadrature, and it organizes the estimate of missing higher orders in a way that respects the sum rules exactly.
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