Quantum Physics
Benchmark of Pauli Correlation Encoding for different optimisation problems
Fernando Alonso, Colomán Samprón, Jacobo Veiga et al. (+2 more)
The continuous progress of
quantum technologies has spurred the exploration of their potential applications across diverse fields, particularly in combinatorial optimisation. In this work, we study a
quantum-classical optimisation framework based on Pauli Correlation Encoding, an encoding scheme that can represent m binary variables using a
polynomial number of
qubits. To evaluate the performance of the method, we use three classical optimisation problems against the instances of the QOPTLib
benchmark. The study includes an analysis of the impact of the compression order of the encoding scheme, the problem structure, and hyperparameter selection on solution quality, as well as the role of post-processing in improving performance. Additionally, we study the effect of shot-based execution and hardware noise, showing how these factors influence both the accuracy of expected value estimation and the overall dynamics of the optimisation process. The results indicate that the proposed PCE-based framework achieves competitive performance against the
benchmark and, in several cases, obtains equivalent or even superior solutions, highlighting its potential as an efficient encoding strategy for
quantum optimisation in the NISQ and near fault-tolerant era.
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All authors Fernando Alonso, Colomán Samprón, Jacobo Veiga, Mariamo Mussa Juane, Andrés Gómez
High Energy Astrophysical Phenomena
A thick-shell formalism for pulsar wind nebulae based on energy conservation
N. Bucciantini and B. Olmi
One of the most powerful approaches to model the structural and spectral
evolution of wind bubbles, and
pulsar wind nebulae in particular, is based on the one-zone thin-shell formalism. By solving a set of simple equations, one can relate the spectral properties of these systems to the physical properties of the
pulsar and
supernova remnant. Due to its predictive power, this approach has been widely used both to fit existing objects and in population synthesis. However, there are inconsistencies when applied to the Crab nebula that have never been fully accounted for, casting doubts on its reliability. We introduce a new and more flexible formalism based on energy conservation that reconciles the observed structural and spectral properties of the Crab nebula, solving the inconsistencies, and provides a more realistic description of wind-bubble
evolution. The equations of the formalism are presented and discussed, together with simplified solutions and more complex ones including radiation losses. Implications for the modeling of wind bubbles and
pulsar wind nebulae are illustrated. We also introduce a new high-order upwind-implicit scheme for particle-spectrum
evolution that ensures high accuracy in energy conservation, and an algebraic-vectorizable approach for synchrotron self-Compton emission in the full Klein-Nishina regime that avoids costly interpolations and integrations. We reproduce the Crab nebula structural properties and spectrum, accounting for the difference in convergence age between the optical filaments and the
radio bubble, thereby removing the inconsistencies. The spectral accuracy of this approach is comparable to that of the standard one, but it is superior in reproducing structural properties and accounting for geometrical effects such as a thick layer of mixed material and the lack of efficient coupling between the wind bubble and the surrounding medium.
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Statistical Mechanics
Nonequilibrium nucleation theory for nonconserved fields: from active matter to population dynamics
Michalis Chatzittofi, Noah Ziethen, Cesare Nardini et al. (+1 more)
Classical nucleation theory (CNT) describes the formation of a stable phase from a metastable one. In
equilibrium systems, it quantifies the free-energy competition between a favorable bulk gain and an unfavorable interfacial cost. For systems without detailed balance, the corresponding nonequilibrium nucleation theory (NNT) was so far developed only for cases with a conserved order parameter, such as active fluid-fluid phase separation. Here we construct the NNT for systems with a (single, scalar) nonconserved order parameter. Unlike in the conserved case, the nucleation barrier controlling (noise-driven) droplet growth is profoundly altered by deviations in the interfacial density profile from the one arising during (deterministic) droplet relaxation. The barrier can nonetheless be analysed by carefully defining the reaction coordinate (droplet radius) to project out those deviations. We give explicit NNT predictions for models drawn from population dynamics and active matter, finding excellent agreement with numerical studies.
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All authors Michalis Chatzittofi, Noah Ziethen, Cesare Nardini, Michael E. Cates
Instrumentation and Methods for Astrophysics
Performance Testing of a Trillium-based 21-Positioner Module for Stage-5 Telescopes
Oliver Pineda Suárez, Jonathan Wei, Malak Galal et al. (+4 more)
Evaluating the performance metrics of theta-phi robotic positioners is crucial to gather insights into the system's behavior and ensure their reliability during operation in Stage-5
telescopes such as the Chinese MUST, the American Spec-S5 and the European WST. With a careful analysis of these metrics, a comprehensive characterization of the system's strengths is obtained, alongside a clear identification of aspects requiring improvement. Thus, providing potential avenues for streamlining and optimizing its design and functionality. In this paper we present the results of the positioning performance and angular tilt tests conducted on 6.2-mm pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The fiber positioners from the tested prototype adopt a mechanical design based on the Trillium open design from the Lawrence Berkeley National Laboratory (LBNL) and were produced by the Japanese company Orbray. The evaluated performance metrics of positioning repeatability, datum repeatability, backlash, non-linearity, and angular tilt were measured and compared to the desired performance for Stage-5
telescopes. The positioners exhibited a generally acceptable performance, although noticeable anomalies affecting several metrics were identified and will require mitigation in subsequent prototypes. Nevertheless, the results indicate promising performance suitable for Stage-5
telescope instrumentation, provided that these issues are successfully resolved.
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All authors Oliver Pineda Suárez, Jonathan Wei, Malak Galal, Melina Daniilidis, Maxime Rombach, Sébastien Pernecker, Jean-Paul Kneib
Cosmology and Nongalactic Astrophysics
Impact of lensing magnification on the power spectrum turnover
Yolanda Dube, Roy Maartens, Bikash R. Dinda et al. (+2 more)
The turnover scale $k_0$ of the matter power spectrum – and consequently of the standard
galaxy power spectrum monopole – encodes a fundamental signature of matter-radiation equality and constitutes an important standard ruler independent of
baryon acoustic oscillations. In principle, we can detect the turnover at multiple
redshifts and amplify the signal by stacking
redshift bins. However, in spectroscopic surveys reaching high
redshifts, such as the Euclid H$\alpha$ survey and the proposed MegaMapper Lyman-break
galaxy survey, the monopole of the observed
galaxy power spectrum receives a scale-dependent correction from
lensing magnification. This can modify the signal shape and shift the turnover scale, undermining its use as a standard ruler. Using mock surveys similar to Euclid and MegaMapper, we forecast this shift and the consequent bias in the turnover scale that is recovered from the mock data. The shift in the turnover scale grows with
redshift, leading to a maximum bias of $\sim 0.4\sigma$ (Euclid-like) and $\sim 3.6\sigma$ (MegaMapper-like). To avoid a bias $>1\sigma$, the maximum
redshift for a MegaMapper-like survey is $z\approx 2.9$. Data in the remaining range $2.9\lesssim z\le 5$ does not directly provide a reliable recovery of the intrinsic turnover. In fact, we find that the turnover vanishes in a MegaMapper-like survey for $z\gtrsim 3.7$. Our results show that the
lensing correction to the monopole should be included and carefully modelled when surveys are used to measure the cosmological turnover at high
redshifts.
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All authors Yolanda Dube, Roy Maartens, Bikash R. Dinda, Sêcloka L. Guedezounme, Sheean Jolicoeur
Materials Science
Self-Aligned Metallic-Semiconducting Phosphorus Nanoarrays Driven by Facet Engineering
M. Bassotti, M. Tallarida, J. Dai et al. (+10 more)
Two-dimensional (2D) materials often require specific substrate terminations for epitaxial stabilization, yet the search for suitable templates has largely focused on low-index metal surfaces, which may not provide the optimal conditions for the growth of new phases. Here, we show that
crystal-facet engineering on curved Cu surfaces enables the stabilization, within a single preparation step, of two distinct 2D phosphorus phases with different electronic properties. Hexagonal blue phosphorene forms on Cu(111) terraces, whereas a previously unreported skewed-square phosphorus phase is stabilized on Cu(513) facets. By combining complementary microscopy and spectroscopy techniques with theoretical calculations, we determine the structural and electronic properties of this new phase, which displays semiconducting character, in contrast to the metallic behavior of blue phosphorene. The coexistence of these two competing phases gives rise to a metal-to-semiconducting transition of the 2D phosphorus layer over the substrate. Locally, the competition between the two phases gives rise to self-aligned nanoarrays of alternating metallic and semiconducting phosphorus terraces. These results establish
crystal-facet engineering as a practical route for discovering and stabilizing emergent 2D material phases on high-index substrates, while also enabling the engineering of nanostructures with tailored electronic properties through a simple and scalable growth process.
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All authors M. Bassotti, M. Tallarida, J. Dai, S. Salaverria, P. Angulo-Portugal, L. Fernandez, A. El-Sayed, J.E. Ortega, A.A. Makarova, Dimas G. de Oteyza, D.Yu. Usachov, A. Verdini, F. Schiller
Materials Science
First-Principles Study of Novel Lead-Free Double Perovskite e̱ta}2SnGeX6 (e̱ta} = K, Rb; X = Cl, Br, I) for thermomechanical, optoelectronic and outstanding thermoelectric applications
Jubair Hossan Abir, Tauhidur Rahman, S.S.B. Pallab et al. (+3 more)
In this study, the structural, mechanical, electronic, optical, and thermoelectric properties of the novel lead-free halide double perovskite series beta2SnGeX6 (beta = K, Rb; X = Cl, Br, I) are systematically investigated using density functional theory (DFT). Calculated formation energies, Tolerance factors, and octahedral factors confirm that all six compounds exhibit robust thermodynamic stability within a highly symmetric cubic geometry. Mechanical analysis derived from elastic parameters characterizes the entire series as fundamentally ductile, ensuring high processing elasticity and resistance to micro-cracking during device manufacturing. Electronic band structures reveal direct bandgaps showing exceptional composition-dependent tunability from 1.44 eV down to 0.64 eV via progressive halogen substitution. The wide gap chloride variations are optimized for single-junction photovoltaic absorbers, while the narrower-gap bromide and iodide analogs show immense promise for tandem
solar architectures and near-infrared photodetectors. Thermoelectrically, heavy constituent atoms introduce strong
lattice anharmonicity and intense high-temperature Umklapp
phonon scattering, significantly suppressing
lattice thermal conductivity. Combined with low carrier effective masses that optimize electrical transport, the iodide compounds achieve higher power factors and outstanding dimensionless figures of merit (ZT = 2.4 for K2SnGeI6 at 1000 K). Ultimately, these lead-free double perovskite family emerges as an environmentally benign and versatile platform for next-generation green optoelectronics and solid-state waste-heat recovery.
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All authors Jubair Hossan Abir, Tauhidur Rahman, S.S.B. Pallab, Md. Sharear Aman, R. S. Islam, S. H. Naqib
Atmospheric and Oceanic Physics
Persistence without Multifractality in Tropical Atlantic SST Indices: Scaling-Range Artefacts and a Reappraisal of the ENSO Association
Sebastián Jaroszewicz, Nahuel Mendez, Maria P. Beccar-Varela et al. (+1 more)
We investigate the scaling properties of three weekly tropical Atlantic sea-surface-temperature indices (SAT, TSA and the interhemispheric gradient TASI) over 1981–2025 using multifractal detrended fluctuation analysis and its sign-preserving cross-correlation extension. Exponents are estimated over $s\in[18,100]$ weeks, bounded by $s_{\min}\gtrsim6(m+1)$ for second-order detrending and a crossover near 100 weeks. On these scales all three indices are strongly persistent and locally non-stationary ($h(2)=1.32$–$1.35$). Comparison with shuffled and phase-randomised surrogates shows that none of the indices are multifractal within record resolution. SAT ($\Delta h=0.077$) and TASI ($\Delta h=0.054$) are fully consistent with both null models. Although TSA yields a larger width ($\Delta h=0.217$), its increasing $h(q)$ implies the unphysical condition $f(\alpha)>1$, indicating a crossover rather than a multiplicative cascade. At the available record length ($N\approx2300$), apparent multifractal widths are not identifiable because confidence intervals overlap and rankings remain sensitive to analysis choices. The increments are only mildly leptokurtic, excluding heavy tails as the source of the apparent widths. Pairwise couplings reveal strong positive cross-correlations between the regional indices and anticorrelation of the gradient with both, all described by a single cross-scaling exponent, consistent with monofractal behaviour. A lagged analysis further shows that the previously reported TASI–ENSO association disappears after surrogate testing accounting for multiple lags. These results substantially revise downward previous estimates of multifractal strength in tropical Atlantic SST and show that reported widths should not be interpreted without verifying both the sign of $h'(q)$ and the stability of the scaling range.
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All authors Sebastián Jaroszewicz, Nahuel Mendez, Maria P. Beccar-Varela, Maria Cristina Mariani
Statistical Mechanics
Thermodynamics of photonic nonlinear Aharonov-Bohm cages
Stefano Iubini and Carlo Danieli
We investigate
equilibrium and non-
equilibrium thermodynamics of one-dimensional photonic diamond
lattices with Kerr nonlinearity. The
equilibrium phase diagram is obtained as a function of the synthetic
magnetic flux acting on each plaquette. In the linear regime, the
magnetic flux can induce Aharonov-Bohm caging, flattening all Bloch bands and suppressing particle and energy currents. In this caging regime, non-vanishing currents are enabled by nonlinearity. By imposing stationary temperature- and chemical potential- imbalances at the system boundaries, we show that at weak nonlinearity fine tuning the flux at the Aharonov-Bohm caging transforms the system from a conductor to an
insulator. For intermediate nonlinear strength, the system remains conducting for all
magnetic fluxes; however, the caging condition significantly enhances the Seebeck coefficient and thermoelectric figure of merit, improving the thermoelectric features of the system. Our results give evidence of a novel route towards optimization of coupled transport devices, based on the control of linear versus nonlinear conduction channels via a synthetic
magnetic flux.
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High Energy Physics (Phenomenology)
Radiative decay of fully-heavy tetraquark into quarkonium
Hao Yang, Songlin Lyu and Bingwei Long
We present a comprehensive study of the radiative decays of fully heavy tetraquarks ($T_{4c}$, $T_{4b}$) and mixed heavy-
flavor tetraquarks ($T_{bc\bar{b}\bar{c}}$) into charmonium/bottomonium states, within the nonrelativistic QCD factorization framework. Numerical result indicates that the decay widths of fully charm tetraquark $T_{4c}$ into $\gamma J/\psi (\eta_c)$ are around 1 MeV. Crucially, the $\gamma J/\psi$ signal channel receives less experimental background near the $J/\psi J/\psi$ threshold, providing a compelling way to search for the possible tetraquark states X(6200). For $T_{4b}$, the decay width is highly suppressed by the bottom
quark mass, just lying in tens eV level. We further find that the decay widths of $T_{bc\bar{b} \bar{c}} \to \gamma \Upsilon$ exceed those to $\gamma J/\psi$ by 3-4 orders of magnitude, indicating preferential $c\bar{c}$-pair annihilation over $b\bar{b}$. These radiative decay modes can be measured in the future experiments, and are helpful to understand the inner structure of the full heavy tetraquark.
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Mesoscale and Nanoscale Physics
Theory of In-Plane Orbital Magnetization with Layer Hybridization
Jin-Xin Hu, Zi-Ting Sun and Yugui Yao
The modern theory of orbital magnetization successfully describes the response of Bloch electrons to
magnetic fields in fully periodic
crystals, but it does not directly address the distinct regime of an in-plane field in multilayer systems with layer hybridization. Coherent interlayer tunneling allows electrons to form circulating current loops, producing an in-plane orbital response that is absent in a strictly two-dimensional limit and qualitatively different from the conventional three-dimensional one. Here we develop a theory of in-plane orbital magnetization for this transdimensional regime, where the layer thickness is comparable to the vertical mean free path. Starting from the current-loop picture, we construct the in-plane orbital angular momentum operator and derive exact expressions for the orbital
magnetic moment and the in-plane orbital
magnetic susceptibility. As an application, we predict a gate-tunable in-plane orbital magnetoelectric effect in layered materials. Our framework establishes a general foundation for in-plane orbital responses and suggests new opportunities for orbitronics in layer-hybridized
quantum materials.
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Medical Physics · Cross-listed from eess.IV
Efficient Image Registration for Ultrasound Localization Microscopy by Obtaining Gradients via Integration Across Iterations
Jipeng Yan, Chang Liu, Hengchang Liu et al. (+4 more)
Tissue motion correction through image registration is essential for ultrasound localization microscopy (ULM). Parametric image registration is commonly formulated as an optimization problem where motion parameters are iteratively updated to maximize image similarity, and used optimization
algorithms typically rely on gradient information, the explicit evaluation of which can become computationally demanding. This work investigates Extremum Seeking Control (ESC) as an alternative to explicit derivative evaluation in image registration. By obtaining descent information via integrating perturbed and demodulated image similarity metric across iterations, ESC avoids differentiation of the image similarity metric with respect to motion parameters in each iteration. The classical ESC, whose optimization behavior approximates that of classical gradient descent (GD), is first compared with GD for affine image registration using simulated ground-truth motions derived from a beating ex vivo porcine heart
dataset. The results show that ESC achieves registration accuracy and convergence behavior comparable to GD while reducing per-iteration computational cost by approximately 3.5-fold. ESC is subsequently employed in a two-stage motion correction pipeline, where affine registration compensates for global tissue motion and B-spline registration corrects residual local deformation. The proposed method is applied to ULM imaging of a beating ex vivo porcine heart and achieves a spatial resolution of 219 um, substantially below the half-wavelength diffraction limit of 321 um associated with 2.4 MHz diverging-wave imaging. These results demonstrate that ESC provides an effective alternative to explicit derivative evaluation in ULM image registration, enabling accurate motion correction and high-quality super-resolution imaging.
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All authors Jipeng Yan, Chang Liu, Hengchang Liu, Biao Huang, Meng-Xing Tang, Yingxiang Liu, Ying Tan
High Energy Astrophysical Phenomena
Pinning Down the Geometry of the Type Ic Broad-Line Supernova 2026gzf
Xudong Wen, Yi Yang, Jing Lu et al. (+11 more)
Type Ic broad-line
supernovae (SNe Ic-BL) are often associated with energetic explosions that display a
prompt outburst of high-energy emission. Since their progenitor lost the H and He envelopes before the explosion exposing the C/O core, their explosion dynamics and geometry can be seen in an unobscured and undistorted way. We present imaging polarimetry and spectropolarimetry of the Type Ic-BL SN 2026gzf obtained 4.6 and 16.5 days after the X-ray shock breakout, which was recorded by the Einstein Probe satellite as EP260321a, showing it to be one of the softest and intrinsically dimmest extragalactic fast X-ray transients. The persistent low continuum polarization indicates that the outer layer of SN 2026gzf is mostly spherical, suggesting the explosion did not significantly disrupt the progenitor envelope. At day 16.5, the calcium near-infrared triplet displays a peak polarization above 1.5%. The geometry of the associated line opacity is also compatible with an axisymmetric configuration. The spatial distribution of such oxygen-burning ashes thus indicates the presence of a
symmetry axis of the excitation structure within the nearly spherical ejecta. The Ca II triplet profile is dominated by a primary component spanning ~25,000–40,000 km/s, alongside a distinct secondary component extending above 28,000 km/s whose polarization implies a non-axisymmetric, complex excitation geometry toward the outer ejecta By implementing a three-dimensional Monte-Carlo calculation, we infer that a viewing angle of ~40 degree from the
symmetry axis of the excitation structure could plausibly reproduce the observed spectral and polarization profiles of the Ca II triplet.
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All authors Xudong Wen, Yi Yang, Jing Lu, Lifan Wang, J. Craig Wheeler, Miika Pursiainen, QiuJu Huang, Bao Wang, Xuefeng Wu, Alexei V. Filippenko, Wolfgang E. Kerzendorf, Giorgos Leloudas, Steve Schulze, Ferdinando Patat
Mathematical Physics · Cross-listed from math.AP
Polyconvexity implies Hill's inequality in ${\rm SL}(2)$
Ionel-Dumitrel Ghiba, Maximilian P. Wollner and Patrizio Neff
For compressible nonlinear isotropic elasticity it is well known that rank-one convexity, polyconvexity and the monotonicity of the Cauchy stress tensor with respect to the logarithmic stretch tensor (the true-stress-true-strain monotonicity, TSTS-M$^+\!$) are independent constitutive conditions which should, however, all together be satisfied for a physically meaningful description of idealized elastic materials. In the incompressible case, TSTS-M$^+\!$ turns into Hill's inequality since the Cauchy stress $\boldsymbol{\sigma}$ reduces to the Kirchhoff stress $\boldsymbol{\tau}$. Hill's inequality requires then monotonicity of the Kirchhoff stress in terms of the logarithmic stretch tensor evaluated for incompressible response. In this paper we clarify how the a priori independent notions of Legendre-Hadamard ellipticity (LH), polyconvexity and Hill's inequality are nevertheless intimately connected. More precisely, by providing several alternative proofs, we show that both LH-ellipticity (rank-one convexity) and polyconvexity imply the weak Hill inequality in the incompressible two-dimensional case.
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Instrumentation and Methods for Astrophysics
Motorized Mount for the 3-DoF Folding Mirror 2 of the VLT's BlueMUSE Instrument
Gloria Mellinand, Diane Chapuis, Malak Galal et al. (+10 more)
BlueMUSE is a blue-optimized, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large
Telescope (VLT). The project is now fully entering design phase. With an optimized transmission down to 350 nm, spectral resolution of R~3500 on average across the wavelength range, and a large FoV (1 arcmin2), BlueMUSE will open up a new range of
galactic and extragalactic science cases facilitated by its specific capabilities. To meet the stability demands required for BlueMUSE, motorized mounts for precise and repeatable positioning of key optics are developed. This paper explores candidate mechanical designs for BlueMUSE's Folding Mirror 2 (FM2), a high-precision mirror mount with three degrees-of-freedom: tip, tilt rotations, and vertical translation. The study includes a comparative performance analysis through theoretical simulations, details the mechanical, software and electronics architecture of the chosen design, as well as the dedicated optical setup design to characterize repeatability, precision, and thermal stability. The resulting performance of the chosen FM2 mount is then evaluated against the specified requirements for BlueMUSE.
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All authors Gloria Mellinand, Diane Chapuis, Malak Galal, Eirini Tagkoudi, Evan Touraine, Sébastion Pernecker, Rémi Giroud, Alexandre Jeanneau, Florence Laurent, Johan Richard, Chris Coote, Jon Moller, Jean-Paul Kneib
Quantum Physics
Sensitive endoscopic diamond magnetometer for non-contact sensing in confined environments
Johannes Wesseler and Roland Nagy
Transitioning
quantum magnetometry from laboratory environments to real-world applications has been limited by a persistent trade-off between sensor miniaturization and
magnetic sensitivity. While bulky systems can achieve high sensitivity, endoscopic probes commonly suffer from inefficient fluorescence collection and reduced performance. Here we resolve this trade-off and present a miniaturized diamond
quantum magnetometer with a 6 mm diameter endoscopic sensor head, achieving a
magnetic-field sensitivity of 91 pT/sqrt(Hz) with a 2 kHz measurement bandwidth in a magnetically unshielded environment. The fluorescence collection bottleneck is overcome by separating excitation and collection into different cores of a fused multi-core fiber bundle, coupled to the diamond through a custom high-numerical-aperture micro-objective. A compact FPGA-based backend performs microwave control, lock-in detection and real-time resonance tracking, enabling robust operation during
magnetic-field imaging. To demonstrate the practical utility of the miniaturized sensor, we image the
magnetic field of a commercial lithium-ion pouch
cell during charge and discharge and reconstruct depth-integrated current-density maps of the current flow. These results show that endoscopic diamond magnetometers can combine high sensitivity with a probe geometry suitable for confined, unshielded measurements, opening new avenues in battery technology and beyond.
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Soft Condensed Matter
On the emergence of molecular tilt in a ferroelectric smectic liquid crystal with broken director-inversion symmetry
Aitor Erkoreka, Mauricio Vera-Arévalo, Alberto Concellón et al. (+5 more)
The origin of some mesophases of the ferroelectric nematic realm is not yet well understood. In this work we study the highly polar
liquid crystal MIO, a close structural analogue of the prototypical ferroelectric nematogen DIO, which exhibits a ferroelectric smectic A to ferroelectric smectic C (SmAF-SmCF) phase transition. Calorimetric, dielectric and light-scattering experiments reveal that it is a second-order phase transition with mean-field behavior, and is driven by the softening of the tilt elastic constant accompanied by the divergence of the amplitude of the associated dielectric mode.
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All authors Aitor Erkoreka, Mauricio Vera-Arévalo, Alberto Concellón, Sergio Diez-Berart, Jordi Sellarès, Adrià Gràcia-Condal, Ibon Alonso, Josu Martinez-Perdiguero
General Relativity and Quantum Cosmology
Non-trivial boundary conditions in general-relativistic models
Davide Astesiano, Matteo Luca Ruggiero and Federico Re
We propose an alternative interpretation of dark matter effects within the framework of General Relativity. In particular, we suggest that, in astrophysical and cosmological contexts, different initial assumptions about a system inevitably lead to different interpretations of the same phenomena. As a concrete example, we examine self-gravitating systems composed of an axially symmetric rotating
dust fluid and show that effects typically attributed to the presence of additional matter, can instead be reproduced through an appropriate choice of initial and boundary conditions for the equations governing the system.
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Instrumentation and Methods for Astrophysics
Design and Testing of the Motorized 2-DoF Folding Mirror 1 for the VLT BlueMUSE Instrument
Gloria Mellinand, Diane Chapuis Kerouanton, Malak Galal et al. (+9 more)
BlueMUSE is a blue-optimized, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large
Telescope (VLT). The project is now fully entering the design phase. With an optimized transmission down to 350 nm, spectral resolution of R$\sim$3500 on average across the wavelength range, and a large FoV (1 arcmin), BlueMUSE will open up a new range of
galactic and extragalactic science cases facilitated by its specific capabilities. In this paper, we present the design, implementation and evaluation of the motorized mount developed for Folding Mirror 1 (FM1) of the VLT BlueMUSE instrument. The mount provides two degrees of freedom in tip and tilt and is engineered to correct misalignments caused by environmental variations. The preliminary results demonstrate that the motorized FM1 tilt mount achieves the required precision and maintains
alignment stability within the tight tolerances defined by the BlueMUSE project.
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All authors Gloria Mellinand, Diane Chapuis Kerouanton, Malak Galal, Axel Nicolier, Aurélien Genin, Zeno Amann, Sébastien Pernecker, Rémi Giroud, Alexandre Jeanneau, Florence Laurent, Johan Richard, Jean-Paul Kneib
Solar and Stellar Astrophysics
Revealing {\alpha}-Element's Past with Subaru/IRD: Oxygen Abundance of 35 Very Metal-Poor Stars from Near-IR OH lines
Bakuh Danang Setyo Budi, Wako Aoki, Nicholas Storm et al. (+10 more)
Oxygen abundances in very and extremely metal-poor (V/EMP)
stars provide critical constraints on early massive
stars' nucleosynthesis. An Oxygen abundance analysis is presented for 35 V/EMP
stars (-4.0<[Fe/H]< -1.5) using near-infrared H-band OH vibro-rotational lines from high-resolution Subaru/IRD spectra. To examine the reliability of these NIR OH lines, the results are compared with the abundances obtained from the 3D/NLTE-insensitive forbidden [OI] 6300Å line using archival high-resolution optical spectra. After homogeneously rederiving
stellar parameters and 1D/NLTE Fe abundances using
Gaia photo-astrometry and literature optical Fe equivalent width data, oxygen abundance from OH and [OI] lines is determined through 1D/LTE spectral synthesis. A sensitivity analysis confirms that near-IR OH lines are highly sensitive to the adopted temperature compared to the forbidden line. A temperature-dependent discrepancy between the tracers is identified: in cool red
giants (Teff <4600 K), OH-based abundances are systematically lower than [OI]-based abundance by 0.05 to 0.25 dex, while warmer red
giants show higher OH-based abundances as expected from 3D effects. Despite this systematic offset, the numerous measurable NIR OH lines yield significantly smaller random abundance errors than that of the single, weak [OI] line. Leveraging this statistical precision, an empirical calibration as a function of Teff, log g, [Fe/H], and [C/Fe] is derived to align the 1D/LTE OH abundances onto the [OI] scale. Applying this correction substantially reduces the scatter and temperature dependence in the [O/Fe] versus [Fe/H] plane and flattens the trend, bringing the results into fairly good agreement with
Galactic chemical
evolution models.
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All authors Bakuh Danang Setyo Budi, Wako Aoki, Nicholas Storm, Miho Ishigaki, Tadafumi Matsuno, Teruyuki Hirano, Masayuki Kuzuhara, Jun Nishikawa, Masashi Omiya, Takayuki Kotani, Tomoyuki Kudo, Sebastien Vievard, Motohide Tamura
Mesoscale and Nanoscale Physics
Electron state tomography from quasiparticle interference maps
A. Razanajatovo, J. Cayssol and C. Dutreix
Characterizing electronic band structures requires precise knowledge of wave functions and their
quantum geometry. Here, we introduce a
tomography method to reconstruct the density
matrix of electron states from quasiparticle interference maps around single
impurities. We consider two-orbital models on a honeycomb
lattice, relevant to
graphene heterostructures and direct-gap
semiconductors. For on-site
impurities, backscattering between time-reversed states directly maps the density
matrix populations and coherences into distinct orbital contributions in the interference map. While local probes usually lack orbital resolution, these orbital contributions transform under distinct
symmetry group representations and can thus be disentangled to reveal the density
matrix and
quantum geometric tensor of the scattering states. This establishes
impurities as tomographic probes for band structures in scanning tunneling microscopy using conventional, unpolarized tips.
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Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Investigating Inductive Biases for Machine Learning Emulation of Sudden Stratospheric Warmings in Idealised Isca Simulations
Oskar Bohn Lassen, Simon Driscoll, Stephen I. Thomson et al. (+2 more)
Machine-learning emulators are increasingly used for weather prediction and have the potential to extend skill on subseasonal-to-seasonal timescales by learning dynamically important sources of predictability. A key challenge is whether the models can exploit predictability anchors, such as stratospheric variability, that influence tropospheric circulation beyond short lead times. We test how architectural inductive bias affects emulation of sudden stratospheric warming (SSW) dynamics using paired idealised Isca simulations that differ only in an imposed wave-2 heating perturbation. Across convolutional,
transformer, and graph-based architectures trained for one-step prediction, model differences are modest when the stratosphere is dynamically quiet but widen substantially when SSW-like variability is active. Our results identify explicit three-dimensional vertical coupling as a key inductive bias for machine-learning emulation of stratospheric dynamics. However, Eliassen-Palm flux diagnostics show that low forecast error does not guarantee physically faithful wave-mean-flow interaction, with coherent errors remaining in stratospheric wave-driving structure.
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All authors Oskar Bohn Lassen, Simon Driscoll, Stephen I. Thomson, Sebastian Schemm, Francisco C. Pereira
High Energy Physics (Phenomenology)
Diffractive Production of Heavy Quarkonia at the Electron Ion Collider
Mohammad Yousuf Jamal, Ajaharul Islam, Aritra Bandyopadhyay et al. (+1 more)
We study diffractive photo- and electroproduction of the $S$-wave heavy quarkonia $J/\psi$, $\psi(2S)$, and $\Upsilon(nS)$ at energies relevant for the Electron-Ion
Collider (EIC). The production amplitude is evaluated while retaining the full transverse-momentum ($\ell_t$) dependence of the hard two-
gluon kernel, that is, without expanding the impact-parameter Bessel kernel as is done in the small-size color-dipole limit. The quarkonia light-cone wave functions are built from Cornell-potential solutions of the Schrödinger equation, normalized to the measured leptonic widths, and combined with a modern collinear
gluon distribution. After benchmarking the framework against the full set of HERA charmonium cross-section ratio data, we provide a consistent set of bottomonium cross-section ratio predictions in EIC kinematics. We find that the full $\ell_t$-resolved treatment systematically improves the description of the radially excited states relative to the leading dipole limit, and we identify the kinematic windows where this difference is largest.
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All authors Mohammad Yousuf Jamal, Ajaharul Islam, Aritra Bandyopadhyay, Santosh K. Das
Astrophysics of Galaxies
Disentangling the Distant Stellar Halo Using K-Giants in the DESI Year 3 Data
Namitha Kizhuprakkat, Andrew P. Cooper, Wenting Wang et al. (+42 more)
We present a sample of 88,959 K-
giants from DESI Milky Way Survey Year 3 data, which we use to characterize the chemo-dynamical properties of the
stellar halo at Galactocentric distances of 12 to ~100 kpc. Using HDBSCAN, we identify five prominent
stellar halo substructures: Aleph, the Sagittarius stream,
Gaia Sausage-Enceladus (GSE), Cetus-Palca and the Orphan-Chenab stream. We present the properties of each of these structures as they appear in our catalog, and examine how uncertainties on distance affect the characterization of substructure with this approach. We also examine regions associated with previously reported overdensities (such as the Virgo Overdensities and the Sagittarius spur) that we do not recover with HDBSCAN. The size and distance range of our catalog allows us to explore in detail the residual
stellar halo, comprising
stars that we do not associate with any substructure. We find that samples of ~2000 outer
halo stars with both highly prograde and highly retrograde angular momenta have similar
metallicity distribution functions (MDFs), which do not resemble the MDFs of either GSE or Sagittarius. Both the prograde and retrograde residual
halo MDFs are bimodal, with a metal-poor peak at [Fe/H] ~ -2 and a metal-rich peak at [Fe/H] ~ -1.3 (prograde) or -1.5 (retrograde). The MDF for lower angular momentum residual
halo K-
giants does not show clear evidence for a metal-poor peak, and broadly resembles the MDF of GSE, even at much lower binding energies than GSE itself. We discuss possible interpretations of these findings for GSE
accretion scenarios.
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All authors Namitha Kizhuprakkat, Andrew P. Cooper, Wenting Wang, Amanda Byström, Joan Najita, Sergey E. Koposov, Guillaume Thomas, Songting Li, Ruizhi Zhang, Carlos Allende Prieto, Mika Lambert, Oleg Y. Gnedin, Alexander H. Riley, Jessica N. Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Axel de la Macorra, Peter Doel, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Dick Joyce, Robert Kehoe, Theodore Kisner, Anthony Kremin, Martin Landriau, Laurent Le Guillou, Marc Manera, Aaron M. Meisner, Ramon Miquel, Will Percival, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Ray Sharples, Joseph H. Silber, David Sprayberry, Gregory Tarlé, Benjamin A. Weaver, Hu Zou
Disordered Systems and Neural Networks
Extracting effective scaling exponents in finite-size hyperuniform systems
Yuan Liu, Xurui Li, Jianxiang Tian et al. (+2 more)
Hyperuniform systems strongly suppress long-wavelength density fluctuations, which is quantitatively characterized by the small-wavenumber scaling. In finite samples, however, accurately estimating the hyperuniformity exponent {\alpha} can be challenging. The inferred value depends strongly on the range of length scales accessible in the measurement, finite-size effects, and the specific characterization method employed, whether based on
Fourier-space structure factors, real-space density fluctuations, or dynamical probes such as
diffusion spreadability. In particular, the structure-factor method provides the most direct estimate of {\alpha}, but is sensitive to empirical low-k fitting cutoffs. The number-variance method offers a real-space Class-like diagnosis, but contributes a numerical exponent only when the finite-size data retain Class III-like scaling information. The spreadability method provides a smoother dynamic estimate and reduces configuration-level fluctuations, but requires a physically admissible long-time fitting window. Here, we develop a practical method-aware protocol for robust estimation of the effective scaling exponent {\alpha} in finite-size hyperuniform point configurations, combining three complementary methods with distinct roles. Our protocol summarizes the method-specific estimates through a joint empirical
estimator and reports the internal dispersion among the participating methods to determine the optimal estimate.
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All authors Yuan Liu, Xurui Li, Jianxiang Tian, Xunwang Yan, Ge Zhang
Plasma Physics
Wake Perturbations in Laser- and Beam-Driven Plasma Wakefield Accelerators: A Symmetry-Based Multipole Classification
Andrei C. Berceanu and Alessio Del Dotto
We review beam-quality physics in
laser-driven (LWFA) and beam-driven (PWFA)
plasma wakefield accelerators through the
symmetry group of the idealised blowout wake – axisymmetry $\mathrm{SO}(2)_\phi$, adiabatic longitudinal translation, and propagation-direction parity. Transverse perturbations of the wake are classified by an integer azimuthal multipole order $m$ labelling the irreducible representations of $\mathrm{SO}(2)_\phi$, with the lowest beam-quality observables coupling at a specific multipole: the bunch centroid at $m=1$, cross-plane emittance coupling at $m=2$. A
symplectic analogy relates transverse matching to longitudinal beam loading. Several phenomena common to LWFA and PWFA – hose instabilities, pulse-front-tilt jitter, spot-asymmetry emittance growth, polarisation-dependent centroid motion, resonant cross-plane mixing – populate the two lowest non-trivial $m$-channels and admit a unified discussion. The positron-witness problem reorganises in the same
language: each known mitigation abandons one specific feature of the uniform-density blowout, drawn from a finite set. The classification also raises the possibility of an $m=3$ response channel whose magnitude remains open. We note the connection to
symmetry-equivariant
Bayesian optimisation of
plasma accelerators.
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High Energy Astrophysical Phenomena
TransFit-MAG: Self-Consistent Modeling of Magnetar-Powered Transients from Shock Breakout to Spin-Down Heating
Jing-Yao Li, Liang-Duan Liu, Yun-Wei Yu et al. (+2 more)
Magnetar engines are widely invoked to power luminous optical transients, but their early emission depends on the coupled
evolution of engine injection, shock heating, adiabatic cooling, and radiative
diffusion. We present TransFit-MAG, a time-dependent radiative-
diffusion framework for magnetar-powered transients. The model couples the TransFit
diffusion solver to the dynamics of a magnetar-inflated
pulsar wind nebula (PWN) and its forward shock propagating through homologously expanding ejecta, calculating the internal radiation-energy distribution, photospheric
evolution, shock-heating location, and emergent luminosity self-consistently. For different parameter values, the model naturally produces well-separated double peaks, partially merged peaks, or single broad peaks. These results suggest that early bumps and broad single peaks in engine-powered transients may be understood within a unified engine–shock–
diffusion framework, in which the observed diversity reflects the coupled
evolution of central-engine power, shock propagation, and radiative transport through expanding ejecta. As an illustrative application, we fit the multiband optical light curves of the double-peaked SLSN-I LSQ14bdq.
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All authors Jing-Yao Li, Liang-Duan Liu, Yun-Wei Yu, Guang-Lei Wu, Yu-Hao Zhang
Quantum Physics
Field Demonstration of a Multi-User Continuous-Variable Quantum Access Network for Quantum-to-the-Home
Junpeng Zhang, Xu Liu, Qijun Zhang et al. (+12 more)
Realizing scalable
Quantum-to-the-Home (QTTH) faces a bottleneck: link asymmetry in broadcast continuous-variable
quantum access networks (CV-QANs) hinders the selection of a globally optimal modulation variance. We demonstrate a downstream broadcast CV-QAN connecting a
Quantum Line Terminal (QLT) to multiple
Quantum Network Units (QNUs) over commercial fiber. Operating within a trusted local network domain, we establish a multi-user utility model to select the optimal shared variance, balancing network efficiency and user
fairness. Supported by robust digital signal processing, our 1:16 field trial achieves Mbit/s-level asymptotic secure key rates, bridging theoretical protocols with Fiber-to-the-Home reality and guiding future scalable access architectures.
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All authors Junpeng Zhang, Xu Liu, Qijun Zhang, Yifeng Liang, Yue Yu, Peng Huang, Huasheng Li, Yingming Zhou, Jingyu Yang, Chunchen Li, Yunfan Chen, Cheng Zheng, Ciqing Deng, Tao Wang, Guihua Zeng
Fluid Dynamics
On the governing mechanism of unsteadiness in bow shock-induced three-dimensional separation
S. Vayala, K. Ramachandra, K. Abhishek et al. (+2 more)
We investigate the driving mechanism of low-frequency unsteadiness in bow shock-turbulent boundary layer interactions due to protuberances. Wind tunnel experiments are conducted at a freestream Mach number of 2.87 with protuberances of different shapes and sizes. From time-resolved surface pressure measurements and schlieren imaging, the unsteadiness is characterized by low-frequency shock oscillations, with a Strouhal number of $St_{\delta}\sim 0.01$ based on the boundary layer thickness ($\delta$), while the separated region exhibits predominantly mid-frequency pressure oscillations, with $St_{\delta} \sim 0.1$. Mid-span separation length, $L_{sep}$, is identified as a key parameter in determining time and length scales of shock oscillations. Further details of the interaction are examined through compressible adaptive detached eddy simulations for one particular case, viz.,the cubical protuberance of side 15 mm. A detailed modal analysis using proper orthogonal decomposition (POD) is performed with the 3-D data from computations. Flapping of shock-foot about mid-span was apparent, over and above the coherent to-and-fro oscillations, with the dominance of anti-symmetric mode in the POD of wall pressure fluctuations. The motion of the shock foot is initiated near mid-span, while the shock foot at other spanwise locations lags behind. The flap and asymmetries are related to the spanwise extent of reverse flow. From the reconstructed 3-D flow field using low-frequency modes, along with corroborating observations from the two-point correlations, it is inferred that the imbalance and time lag between the mass injected into the separated region at reattachment and the mass leaving spanwise at the horseshoe
vortex core govern the observed shock motion.
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All authors S. Vayala, K. Ramachandra, K. Abhishek, N. R. Vadlamani, R. Sriram
Statistical Mechanics
Classical dissipative search of unstructured database
A.E. Allahverdyan and Y. Bisharyan
We propose a physical realization of the unstructured database search that works via classical, dissipative model of spherical
spins. The database is implemented via
spin-
spin couplings, where the selected coupling refers to a larger
ferromagnetic interaction between two selected
spins. The low-temperature
equilibrium of this model leads to magnetization strongly concentrated on the selected
spins, which means that the search is complete. The search time refers to the relaxation time to
equilibrium from a homogeneous initial state, and is described via Langevin equations. This time scales as ${\cal O}(M^a)$ with $a<1/2$, where $M$ is the database volume. This is faster than Grover's search, showing how a dissipative, classical analog computer can overcome the
quantum unitary computer.
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