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Physics

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Thursday 23 July

High Energy Physics (Theory)

Gauge-Theoretical Method in Solving Zero-curvature Equations III –Gauge Theoretical Method and the Bäcklund Transformations for Solitons–

Takahiro Azuma and Takao Koikawa

In soliton theory, both the gauge-theoretical method and the Bäcklund transformation yield soliton equations from the compatibility condition of a pair of linear equations. Therefore, it is necessary to clarify the similarities and differences between these two methods. The Bäcklund transformation defines a transformation from one soliton solution to another. In particular, restricting the transformation to solutions with different soliton numbers yields interesting insights. Using several examples, we demonstrate how soliton solutions with different soliton numbers are constructed.
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Physics and Society · Cross-listed from econ.GN

Accelerating fossil gas independence in Europe

Lukas Franken, Iegor Riepin and Tom Brown

Recent price shocks have prompted calls to curb Europe's dependence on fossil gas imports, but the cost of this goal, and the consumer protection it affords, remain uncertain. Here we address this gap by imposing constraints on fossil gas supply in a European energy system model that co-optimises abatement across all gas uses at high spatio-temporal resolution. Cutting import reliance proves economically compelling: through savings in power generation and low-temperature heat in industry and buildings, Europe can halve its natural gas consumption for 16bnEUR/a, aligning demand with the continent's production capacity of 200 bcm. This extra system cost is comparable to what consumers spend today on a 2 EUR/MWh rise in gas import prices. However, this sovereignty alone does not shield consumers from global gas price volatility: we find that, even at a small share of the mix, gas remains dominant in shaping the marginal electricity price, leaving consumers exposed without additional policy measures.
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Fluid Dynamics

Effect of free-stream turbulence on a moderate adverse pressure gradient turbulent boundary layer developing over an airfoil

Tomek Jaroslawski and Francesco Scarano

Turbulent boundary layers (TBLs) subjected to adverse pressure gradients (APGs) are common to industrial aerodynamic applications, yet the effect of freestream turbulence (FST) on TBLs developing under moderate APGs remains insufficiently understood. Wind-tunnel experiments were conducted to investigate the effects of FST on a developing TBL over a NACA 0015 airfoil. Varying the angle of attack (2 and 4$^\circ$) adjusted the pressure gradient, and hotwire anemometry measured boundary layer properties at different chordwise positions ($x/c$ = 0.400–0.625, with $\beta = \delta^*/\tau_0 dP/dx$ = 0.2-1.5). The FST level was increased using static grids, resulting in levels ranging from 0.15 to 6$\%$. The chord-based Reynolds number was kept constant at around 250,000 for all configurations. The results show that increasing FST systematically modifies the mean-flow development of the APG boundary layer. Higher FST levels reduce the shape factor and partially suppress the APG-induced wake in the mean velocity profile, while increasing the skin-friction coefficient towards values closer to canonical ZPG behaviour. The streamwise velocity variance is amplified in both the inner and outer regions, and spectral analysis shows that this increase is associated with energetic large-scale motions introduced by the freestream turbulence, with characteristic wavelengths of order $\lambda_x/\delta \approx 13$. These large scale structures penetrate into the boundary layer and contribute to the near-wall variance, with a stronger effect observed as the adverse pressure gradient increases. The results show that FST is a governing parameter in developing APG TBLs over airfoils and that its influence is amplified by the pressure gradient. It must therefore be considered when interpreting mean-flow evolution, turbulence statistics, and scale interactions in realistic aerodynamic environments.
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Materials Science

Complete Raman Tensor Determination in Birefringent $\beta$-Ga$_2$O$_3$ by Single-Stage Hyperspectral Analysis of Polarization Angle-Resolved Raman Spectra

Hans Tornatzky, Jonas Rose, Moritz Meißner et al. (+5 more)

The low symmetry of the monoclinic phase of Ga$_2$O$_3$ leads to pronounced optical anisotropy and, consequently, to birefringence, which strongly affects the Raman response. Because Raman scattering is fundamentally sensitive to the polarizability of a material, this anisotropy must be carefully accounted for in order to extract quantitative information - an effort that has only recently been shown to be feasible in such media. Here, we report Raman measurements from all three principal crystal planes $(100)$, $(010)$, and $(001)$, as well as from the $(\overline{2}01)$-plane of a $\beta$-Ga$_2$O$_3$ single crystal. By combining polarization angle-resolved Raman spectroscopy (PARRS) with a newly developed fitting procedure and explicitly accounting for birefringence, we achieve full spectral separation and quantitatively determine the energies and relative Raman tensor elements of all 15 Raman-active modes.
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All authors Hans Tornatzky, Jonas Rose, Moritz Meißner, Benjamin M. Janzen, Zbigniew Galazka, Juan Sebastián Reparaz, Manfred E. Ramsteiner, Markus R. Wagner

Astrophysics of Galaxies

Measuring Outflow Distances in NGC 5548 Using Absorption-Line Variability Diagnostics

Yaqi Chen, Zhicheng He and Guilin Liu

AGN-driven outflows serve as a key channel through which the energetic central engine influences host galaxy evolution. Among the physical properties of outflows, their radial distance from the galactic nucleus is particularly important for assessing AGN feedback. In this study, we investigate the UV outflow components in NGC 5548 by analyzing the variability of C IV absorption troughs in optical spectra obtained through multiple HST observations during 2013 and 2014. We construct a set of variability-based diagnostic events, labeled G1 and G2, which are sensitive to the recombination timescale ($t_r$) of ionized gas. By combining these with mock light curves generated using a damped random walk (DRW) model, we numerically establish a mapping between the G1 event probability and $t_r$. This approach allows us to constrain the radial distances of outflow components 1 and 6, whose absorption variability is primarily driven by changes in the incident ionizing continuum, to be $0.77^{+0.10}_{-0.10}$ and $1.72^{+1.74}_{-1.72}$ pc, respectively. These results are consistent with those obtained using a different method in our previous study, as well as with values reported in the literature.
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High Energy Physics (Phenomenology)

Advanced Statistical Analysis of Linear and Nonlinear Regge Trajectories for Light Non-strange Mesons

S.S. Afonin

A rigorous statistical analysis of Regge-type trajectories for light non-strange meson mass spectra is carried out, which explicitly accounts for experimental uncertainties. We test three scenarios: a linear model with distinct radial ($n$) and orbital ($l$) slopes (Model 1), a linear model with a universal slope (Model 2), and a nonlinear model featuring a universal slope and a Dirac-Coulomb-type term $\propto (l+1)^{-1}$ (Model 3). Optimization is performed using a nonlinear $\chi^2$ minimization framework, where the intrinsic theoretical model uncertainty is determined self-consistently by enforcing $\chi^2/\text{dof} = 1$. To ensure robust model selection, we employ the Akaike and Bayesian information criteria alongside complementary statistical tests. Our analysis demonstrates that moderate deviations from linearity in the Regge spectrum are predominantly localized within the $S$-wave resonance sector. These distortions are successfully accommodated by the nonlinear correction in Model 3, from which an approximate Coulomb-type degeneracy, $m^2(n,l) \propto n+l$, emerges as a statistically robust feature. Furthermore, we show that the $l$-dependent correction to the principal quantum number in light non-strange mesons is consistent with the leading-order relativistic correction to the Coulomb problem.
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Astrophysics of Galaxies

A RELHIC twin candidate near the galaxy M51

Qingze Chen, Jie Wang, Yingjie Jing et al. (+7 more)

We report the discovery of a pair of H I clouds near M51 (NGC 5194) using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These clouds have no optical counterparts and are potential candidates for Reionization-Limited H I Clouds (RELHICs). We search for compact H I sources in deep FEASTS observations using SoFiA and remove objects with optical counterparts through cross-matching with the DESI Legacy Imaging Surveys. The remaining candidates are modelled as hydrostatic H I structures embedded in Navarro-Frenk-White dark matter haloes and compared with RELHIC predictions and TNG50 simulations. We identify two H I clouds, Cloud S and Cloud N, at projected distances of 70–90 kpc from M51. Each cloud has an H I mass of approximately 10^6.5 solar masses, a velocity dispersion of about 20 km/s, and no detectable optical counterpart down to a g-band surface brightness limit of approximately 27.5 mag arcsec^-2. Their stellar luminosities are constrained to be below 10^5 solar luminosities. Their H I properties are consistent with RELHIC predictions, corresponding to host halo masses of 3.7 +- 0.4 * 10^9 solar masses. Cloud S and Cloud N are promising but not definitive RELHIC candidates. A tidal origin remains possible in the interacting M51 system, especially because the clouds are unresolved by FAST and Cloud N may show a velocity gradient. Future high-resolution interferometric observations will be crucial for distinguishing between starless dark matter haloes and tidal debris.
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All authors Qingze Chen, Jie Wang, Yingjie Jing, Chen Xu, Tiantian Liang, Zerui Liu, Zhipeng Hou, Yiwei Xu, Cheng Cheng, Wei Du

High Energy Physics (Theory)

Selecting Complex Extremal Surfaces with the Kontsevich–Segal–Witten Criterion

Wu-zhong Guo

Complex extremal surfaces naturally arise in holographic observables associated with timelike subregions in AdS/CFT and with holographic observables in dS/CFT, but their integration contours are generally ambiguous. In this work, we propose a method for constructing complex bulk metrics from families of complex extremal surfaces, thereby generating candidate complex geometries relevant to the gravitational path integral. This construction provides a concrete realization of how complex bulk geometry may emerge from timelike entanglement, extending the familiar idea that spacetime geometry is encoded in quantum entanglement. We use the Kontsevich–Segal–Witten (KSW) criterion as a strong consistency condition to constrain the corresponding contours. The same framework also explains why spacelike entanglement naturally selects a real Lorentzian section. In several AdS and dS examples, the KSW condition uniquely determines the admissible contour within the class considered. We also identify configurations for which the resulting complex geometry violates the KSW bound near the asymptotic boundary, revealing both the scope and the limitations of the construction. These results highlight KSW admissibility as a useful organizing principle for complex saddles in real-time holography.
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Astrophysics of Galaxies

Dissecting the multiple-component outflow in NGC 5548 with absorption-line Variability

Yaqi Chen, Zhicheng He and Guilin Liu

AGN-driven outflows are routinely invoked as a key agent of supermassive black holes to regulate the evolution of galaxies. The radial distance from the central engine is a crucial parameter for evaluating the impact of these outflows on the host galaxy. In this work, we estimate the radial distances of ultraviolet (UV) outflow components in NGC 5548 using the most up-to-date absorption-line variability method, combined with multi-epoch HST/COS spectroscopy from the 2014 AGN STORM campaign and archival data observed in 2013. The recombination timescale (tr) of the absorbers are measured by analyzing the detection rate curves of absorption-line variability. In particular, the detection rate curves of the absorption troughs showing blended multiple velocity components are featured by distinct “multi-step' profiles, allowing for measuring tr for individual components. Among the 6 identified outflow components, four are found to be a few pc from the center and two are 30-40 pc away. Our results agree well with the more reliable results in the literature on components 1 and 4, and show overall consistency with previous works, demonstrating the power of our new methodology especially when it is aided by densely sampled HST spectra.
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High Energy Astrophysical Phenomena

The Extended Ultrahigh-energy Gamma-Ray Emission in the Vicinity of PSR J2238+5903

Zhen Cao, F. Aharonian, Y.X. Bai et al. (+327 more)

We present a comprehensive analysis of the recently discovered TeV gamma-ray source, LHAASO J2238+5900. Based on data collected from the LHAASO, our fitting results suggest that the source is significantly extended with an angular extension of 0.54{\deg} \pm 0.01{\deg} and is spatially coincident with the pulsar PSR J2238+5903. Its spectrum is characterized by a power-law with a cutoff at 41.0\pm 3.5 TeV. Additionally, the source exhibits a significant signal of 7.9\sigma above 100 TeV, implying that it is a PeVatron candidate. While the gamma-ray emission is consistent with a pulsar wind nebula (PWN) scenario, the relatively large extension size also allows for a halo interpretation, potentially caused by electron-positron pairs escaping from the PWN.
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All authors Zhen Cao, F. Aharonian, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, W. Bian, J. Blunier, A.V. Bukevich, C.M. Cai, W.Y. Cao, Zhe Cao, J. Chang, J.F. Chang, E.S. Chen, G.H. Chen, H.K. Chen, L.F. Chen, Liang Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.B. Chen, X.J. Chen, X.P. Chen, Y. Chen, N. Cheng, Q.Y. Cheng, Y.D. Cheng, M.Y. Cui, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, L.X. Dai, Z.G. Dai, Danzengluobu, Y.X. Diao, A.J. Dong, X.D. Duan, J.H. Fan, Y.Z. Fan, J. Fang, J.H. Fang, K. Fang, C.F. Feng, H. Feng, L. Feng, S.H. Feng, X.T. Feng, Y. Feng, Y.L. Feng, S. Gabici, B. Gao, Q. Gao, W. Gao, C. Ge, M.M. Ge, T.T. Ge, L.S. Geng, G. Giacinti, G.H. Gong, Q.B. Gou, M.H. Gu, W.M. Gu, F.L. Guo, J. Guo, K.J. Guo, X.L. Guo, Y.Q. Guo, R.P. Han, O.A. Hannuksela, M. Hasan, H.H. He, H.N. He, J.Y. He, X.Y. He, Y. He, S. Hernández-Cadena, C. Hou, X. Hou, H.B. Hu, S.C. Hu, D.H. Huang, F. Huang, J.J. Huang, X.L. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Z.J. Huang, A. Inventar, X.L. Ji, H.Y. Jia, K. Jia, H.B. Jiang, K. Jiang, X.W. Jiang, Z.J. Jiang, M. Jin, S. Kaci, M.M. Kang, I. Karpikov, D. Khangulyan, D. Kuleshov, W.H. Lei, Cheng Li, Cong Li, D. Li, F. Li, H.B. Li, H.C. Li, Jian Li, Jie Li, K. Li, L. Li, R.L. Li, T.Y. Li, W.L. Li, X.R. Li, X.Y. Li, Y. Li, Zhe Li, Zhuo Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, D.B. Liu, H. Liu, J. Liu, J.L. Liu, J.R. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, T. Liu, W. Liu, Y. Liu, Y. Liu, Y.N. Liu, Y.Q. Lou, Q. Luo, Y. Luo, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, I.O. Maliy, J.R. Mao, Z. Min, W. Mitthumsiri, Y. Mizuno, G.B. Mou, A. Neronov, K.C.Y. Ng, S.C.-Y. Ng, M.Y. Ni, L. Nie, L.J. Ou, Z.W. Ou, P. Pattarakijwanich, Z.Y. Pei, D.Y. Peng, J.C. Qi, M.Y. Qi, J.J. Qin, H.L. Qu, A. Raza, C.Y. Ren, M.Q. Ruan, D. Ruffolo, A. Sáiz, D. Savchenko, D. Semikoz, L. Shao, O. Shchegolev, Y.Z. Shen, X.D. Sheng, F.W. Shu, H.C. Song, Yu.V. Stenkin, Y. Su, C.Y. Sun, D.X. Sun, H. Sun, J.X. Sun, M. Sun, Q.N. Sun, X.N. Sun, Z.B. Sun, N.H. Tabasam, J. Takata, P.H.T. Tam, H.B. Tan, Q.W. Tang, R. Tang, Z.B. Tang, W.W. Tian, C.N. Tong, L.H. Wan, C. Wang, D.H. Wang, G.W. Wang, H.G. Wang, J.C. Wang, J.F. Wang, J.S. Wang, K. Wang, Kai Wang, Kai Wang, L.P. Wang, L.Y. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y. Wang, Y.D. Wang, Z.H. Wang, Z.X. Wang, Zheng Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, S.S. Weng, C.Y. Wu, H.R. Wu, Q.W. Wu, S. Wu, X.F. Wu, Y.S. Wu, S.Q. Xi, J. Xia, G.M. Xiang, D.X. Xiao, G. Xiao, Y.F. Xiao, B.H. Xie, Y.L. Xin, H.D. Xing, Y. Xing, D.R. Xiong, B.N. Xu, C.Y. Xu, D.L. Xu, R.X. Xu, S.S. Xu, L. Xue, D.H. Yan, T. Yan, C.Y. Yang, F.F. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, W.X. Yang, Z.H. Yang, Z.G. Yao, X.A. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Y.H. Yu, Q. Yuan, H. Yue, H.D. Zeng, T.X. Zeng, W. Zeng, X.T. Zeng, M. Zha, B. Zhang, B.B. Zhang, B.T. Zhang, C. Zhang, H. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.Y. Zhang, L.Y. Zhang, Li Zhang, P.F. Zhang, R. Zhang, R.Y. Zhang, S.R. Zhang, S.S. Zhang, S.Y. Zhang, W. Zhang, X. Zhang, X.L. Zhang, X.P. Zhang, Yi Zhang, Yong Zhang, Z.P. Zhang, J. Zhao, L. Zhao, L.Z. Zhao, X.H. Zhao, F. Zheng, T.C. Zheng, B. Zhou, H. Zhou, J.N. Zhou, L. Zhou, M. Zhou, P. Zhou, R. Zhou, X.X. Zhou, X.X. Zhou, B.Y. Zhu, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, Y.F. Zhu, Z.F. Zhu, Y.C. Zou, X. Zuo

Optics

Structured Cavity Quantum Electrodynamics

Shunfa Liu, Jiantao Ma, Hanqing Liu et al. (+9 more)

A cavity quantum electrodynamics (cQED) system consisting of a confined single photon and a single quantum emitter serves as a fundamental block for quantum optics and photonic quantum technologies. The canonical optical mode employed in the conventional cavity quantum electrodynamics features a uniform polarization distribution, leading to the scalar light-matter interaction in most existing experiments. Despite the rapid progress in the generation of structured light with spatially varied polarizations, the structured light-matter interaction, especially at the single quanta level, is highly intriguing yet largely unexplored. Here, we present the structured light-matter interaction at the single-photon level in a semiconductor cavity quantum electrodynamics system. Four distinct structured cavity modes that are spectrally close to each other are constructed in a micropillar cavity. By spatially locating a single epitaxial quantum dot (QD) at the periphery of a semiconductor micropillar cavity and spectrally tuning the QD emission wavelength into the resonances of the structured cavity modes, cavity-enhanced single-photon emissions with spin-locked chiral orbital angular momentum (OAM) and engineerable spin-orbit entanglements are achieved within a single wavelength-scale device. Our work opens an unexplored paradigm of structured quantum light-matter interactions and may further advance chiral quantum optics and high-dimensional photonic quantum technology.
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All authors Shunfa Liu, Jiantao Ma, Hanqing Liu, Yangpeng Wang, Xueshi Li, Haiqiao Ni, Zhichuan Niu, Kai Zou, Yun Meng, Xiaolong Hu, Xuehua Wang, Jin Liu

Data Analysis and Statistics

A framework for general discrete probability calculations

Kacper Topolnicki and Roman Skibiński

Probability follows a simple and concise set of rules. In practice, however, reason- ing about probability may be highly unintuitive and this leads to the possibility of miscalculations even for simple problems. We present an approach to facilitate the correct description of systems governed by discrete probability. The methods described in this paper allow making general statements about the values of prob- ability. This information can next be used to calculate any probability related to the system described by the statements. In case there are too few statements to provide a unique answer, entropy maximization is used to fill in the miss- ing information. The approach has wide potential applications that range from experimental physics to natural language analysis. The theoretical framework described here is also the basis of a software implementation that is designed to be straightforward to extend and requires only popular python libraries, numpy, torch, sympy, and scipy.
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Instrumentation and Methods for Astrophysics

GCR Spectra Reconstructed with Neutron Monitor Yield Function and Artificial Neural Networks: Comparison of Two Methods

Stepan Siruk, Vladislav Alekseev, Victor Kuzminov et al. (+2 more)

We present a framework that reconstructs time-resolved galactic cosmic-ray (GCR) proton and helium energy spectra from the global neutron monitor network, providing data about GCR flux without direct satellite observations. Two methods are utilized and compared: a calibrated yield function plus force-field scheme and artificial neural networks trained on multi-station neutron monitor count rates coupled with heliophysical indices. The reconstructed spectral time series reproduce both large-scale solar-cycle modulation and short-term disturbances and extend to periods lacking daily spacecraft data, including 2006-2011 (consistent with PAMELA) and 2019-2022 (consistent with AMS-02 Bartels rotation averages). Artificial neural networks deliver excellent performance across energies, with markedly lower mean absolute percentage error and $\chi^2/\mathrm{dof}$ near unity. A thorough validation confirms robustness and establishes neutron monitors as an effective real-time GCR spectrometer that can be utilized for various purposes.
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All authors Stepan Siruk, Vladislav Alekseev, Victor Kuzminov, Rustam Yulbarisov, Andrey Mayorov

Cosmology and Nongalactic Astrophysics

Reviving the Affleck-Dine Curvaton Scenario with Compensated Isocurvature Perturbations

Masahiro Kawasaki and Shunsuke Neda

We revisit the Affleck-Dine curvaton scenario in the framework of supersymmetry, taking Q-ball formation into account. In this scenario, a scalar field carrying baryon number, namely the Affleck-Dine field, generates both the curvature perturbations and the baryon asymmetry of the Universe. However, correlated baryon isocurvature perturbations are inevitably generated, resulting in excessively large correlated matter isocurvature perturbations. We propose a mechanism to suppress them, in which the correlated baryon isocurvature perturbations are canceled by anti-correlated dark matter isocurvature perturbations, thereby realizing compensated isocurvature perturbations. We show that the scenario can simultaneously account for the baryon asymmetry and the observed curvature perturbations of the Universe without generating excessively large matter isocurvature perturbations.
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Quantum Physics

On-chip Radio Frequency Maser

Hongliang Wu, Zhengtao Wang, Yuchen Han et al. (+6 more)

Room-temperature solid-state masers offer exceptional frequency selectivity and ultra-low noise for weak-signal detection. However, their reliance on bulky metallic resonators has significantly hindered integration, miniaturization, and extension to lower frequencies. Here, we demonstrate the first on-chip radio-frequency maser operating at room temperature, exploiting optically pumped triplet states of pentacene. The device produces stimulated emission at 106.62 MHz and enables ultra-sensitive microwave magnetic-field detection with a sensitivity of ($\sim 10\,\rm{fT/\sqrt{Hz}}$), functioning simultaneously as a local oscillator and a sensor. By actively controlling microwave dissipation, we achieve efficient regulation of the maser output, revealing a key mechanism for tuning emission in open cavity-free systems. This work extends pentacene-based masers into the radio-frequency regime and establishes a highly integrated on-chip architecture for room-temperature masers, offering a new pathway toward portable quantum devices.
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All authors Hongliang Wu, Zhengtao Wang, Yuchen Han, Liu Yang, Zhiwei Wang, Yeliang Wang, Dezhi Zheng, Bo Zhang, Jun Zhang

Solar and Stellar Astrophysics

HARPS Abundances with Korg I: 22 Element Abundances for 426 Red Giant Stars

Sarah E. Aquilina, Melissa Ness, Adam J. Wheeler et al. (+1 more)

Large stellar surveys have revealed the global abundance structure of the Milky Way, but small high-fidelity spectral samples offer a critical complement of nucleosynthetic depth. We aim to access the encoded information in an ensemble of abundances by leveraging highest-quality spectra. We used HARPS spectra (R=115,000) to determine (Teff, log(g), [M/H], vmic and vsini) and 22 element abundances (Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Fe, Ni, Zn, Sr, Y, Zr, Mo, Ba, La, Ce, Nd and Eu) for 426 red giant stars at a median internal precision of $\sim$0.02 dex evaluated from analysing repeat observations of a subset of stars. Stellar parameters and line-by-line abundances were obtained using the modern spectral synthesis code Korg – the first time it has been used for HARPS. Comparisons with the literature reveal good overall agreement. A minor 0.1 dex offset in metallicity and specific discrepancies in individual element abundances are attributed to local thermal equilibrium assumptions and inaccuracies in atomic data. We show that 22 individual elements can be collapsed into a generative 6-parameter latent-variable model of shared enrichment patterns expressed in different per-star fractions; this model accurately generates the abundances with a median $\chi_{reduced}^2 = 6$. We report element gradients with respect to selected elements from different nucleosynthetic families. These gradients are a measure of inter-element production efficiencies and indicate multiple r-process production sites. Our analysis shows that abundances occupy a low-dimensional subspace, but joint (gradient-based) information encodes nucleosynthetic signatures. We have developed a Korg-pipeline to apply across evolutionary states on high-resolution spectra to provide our precision catalogue to serve as empirical constraints on chemical evolution and as a set of benchmark red giant abundance measurements.
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All authors Sarah E. Aquilina, Melissa Ness, Adam J. Wheeler, Sven Buder

Quantum Physics

A Quantum Interface Between Neutral-Atoms and Trapped-Ions Quantum Registers

Ayelet Hasson, Gal Dekel, Ehud Shahar et al. (+2 more)

Hybrid quantum systems combining neutral atoms and trapped ions offer the prospect of integrating the scalability of atom arrays with the high-fidelity control available in trapped-ion platforms. Here we propose and analyze a quantum interface between individually trapped neutral atoms and a trapped-ion crystal. In our scheme, a neutral 88Sr atom trapped in optical tweezers interacts with a small 88Sr+ ion crystal, and by exciting the atom to a Rydberg state, the atom-ion polarization interaction is strongly enhanced, resulting in a state-dependent modification of the ions' collective motional modes. We show that this shift enables conditional control of a MS gate, allowing the neutral atom to act as a control qubit for an entangling operation between two ions. We investigate the feasibility of the scheme by analyzing Rydberg trapping in the combined optical tweezers and Paul trap potentials, identifying negative-polarizability Rydberg states as particularly favorable for stable confinement. We further evaluate the relevant trapping conditions, Rydberg lifetimes, and coherence requirements, and show that the proposed interface is compatible with realistic experimental parameters. These results establish a practical route toward deterministic atom-ion hybrid quantum gates and quantum interfaces.
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All authors Ayelet Hasson, Gal Dekel, Ehud Shahar, Nitzan Akerman, Roee Ozeri

High Energy Physics (Theory)

Flavour current correlators and the non-Abelian hydrodynamic approximation: the charged sector

Thomas Apostolidis, Matti Järvinen, Elias Kiritsis et al. (+3 more)

Flavor-current correlators are studied in strongly-coupled dense (holographic) matter, at finite quark chemical potential $\mu_q$ and finite isospin asymmetry. The non-Abelian hydrodynamic description of the charged currents is derived in the presence of an isospin chemical potential $\mu_3$. The two-point correlators of charged currents are then computed holographically at finite quark and isospin chemical potentials. In the near-extremal hydrodynamic regime, $\omega, k, T, \mu_3 \ll \mu \equiv \sqrt{\mu_q^2+\mu_3^2}$, relevant for cold strongly coupled matter, the IR properties of the correlators are studied. It is shown that in this regime, the correlators agree with the non-Abelian hydrodynamic predictions. Therefore, the traditional regime of validity of standard hydrodynamics extends beyond $\omega, k \ll T \ll \mu$ to the so-called extended hydrodynamic regime $T\ll \omega, k \ll \mu$. The holographic product formula is applied to the present non-Abelian system, and is used to propose an extended hydrodynamic approximation capturing both hydrodynamic-like poles and the leading effect of AdS$_2$ poles, by resumming the low-$\omega$ logarithms. The results are verified through a detailed numerical analysis of the exact correlators and quasi-normal mode spectrum.
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All authors Thomas Apostolidis, Matti Järvinen, Elias Kiritsis, Francesco Nitti, Andrea Olzi, Edwan Préau

Geophysics · Cross-listed from cs.CV

Latent Variable-Mediated Cross-Learning for Few-Shot Acoustic Impedance Imaging

Junheng Peng, Yong Li, Mingwei Wang et al. (+1 more)

Acoustic impedance imaging is a fundamental yet severely ill-posed problem in subsurface analysis: the seismic wavelet is unknown, observations are band-limited, and labeled well-log samples are extremely scarce (typically <1% of all traces). Existing semi-supervised deep learning methods mitigate few-shot problem by incorporating forward modeling, yet they either rely on inaccurate prior wavelet assumptions or introduce auxiliary networks, leading to unstable optimization and degraded performance. We propose RD-SCL, a novel framework that integrates regularized deconvolution with semi-supervised cross-learning. At its core lies a differentiable, closed-form first-order Tikhonov deconvolution operator that dynamically estimates the latent wavelet in the frequency domain during training, providing stable physics-guided feedback without explicit auxiliary networks and fixed wavelet priors. Building on this operator, we design a symmetric cross-learning that enforces consistency between predictions on labeled and unlabeled data, thereby effectively exploiting abundant unlabeled traces. Extensive experiments on the SEAM and Marmousi 2 benchmarks demonstrate that RD-SCL consistently outperforms state-of-the-art supervised and semi-supervised methods, achieving substantial gains with lower computational cost. With only 56.5k learnable parameters and competitive runtime, RD-SCL offers a practical, physically consistent, and efficient solution for acoustic impedance imaging.
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All authors Junheng Peng, Yong Li, Mingwei Wang, Yi Bao

Quantum Physics

Compact deterministic liquid-crystal polarization controller with single-measurement direct control

Ren-De Liu, Jie Wang, Dong-Dong Li et al. (+9 more)

Polarization controllers (PCs) and their control algorithms are critical for compensating environmental disturbances and maintaining signal fidelity in polarization-sensitive photonic systems. However, existing controllers often involve trade-offs among key performance metrics,while associated control algorithms either converge inefficiently or require multiple state-of-polarization (SOP) measurements. This work presents a compact deterministic liquid-crystal polarization controller (LC-PC) with balanced overall performance, featuring low insertion loss (<1 dB), low driving voltage (<6 V), and full Poincaré sphere coverage. The device exhibits highly predictable and repeatable polarization modulation characterized by SOP-independent trajectory normal vectors, enabling a single-measurement direct-calculation algorithm using pre-characterized rotation axes and voltage-to-rotation relationships, with degree-level polarization control accuracy. The combination of this compact deterministic LC-PC and its efficient control scheme provides a practical solution for polarization management in quantum key distribution, optical sensing, and advanced photonic systems.
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All authors Ren-De Liu, Jie Wang, Dong-Dong Li, Xian-Chang Du, Dao-Zhong Xiao, Shuai Li, Chuan-Yang Ding, Yan-Lin Tang, Yang Li, Sheng-Kai Liao, Teng-Yun Chen, Shi-Biao Tang

Astrophysics of Galaxies

Accurate Extragalactic Magnetic Fields from Faraday Rotation with Optimal Dispersion Measure Estimators

Hilay Shah, Mark Krumholz, Naomi McClure-Griffiths et al. (+1 more)

Faraday rotation measures (RMs) are one of our few observational tools for measuring magnetic field strengths in extragalactic systems, but converting an RM to a magnetic field estimate requires knowledge of the electron column density – the dispersion measure (DM) – to the RM source. Because DMs are difficult to measure for most extragalactic radio galaxies, observers have adopted a range of strategies to estimate them from more easily measured quantities, but the accuracy of these approaches is poorly known. To address this, we carry out simulated observations of high-resolution magnetohydrodynamic simulations of a range of galactic environments to explore the performance of various possible DM estimators. We obtain the best results using an estimator $\mathrm{DM} \propto \mathrm{EM}^{\alpha} \ N_\mathrm{Hi}^{\beta}$, where EM is the emission measure and $N_\mathrm{Hi}$ is the atomic hydrogen column density, with exponents $\alpha \approx 0.2-0.4$ and $\beta \approx 0-0.1$ depending on galactic environment (e.g., galaxy centres versus outskirts, and dwarfs versus spirals). We show that the variation of these exponents with environment can be understood in terms of simple physical arguments. Based on our tests, we provide recommended best practices for extracting galactic magnetic fields from RM data as a function of galactic environment and of proxy data availability, and show that using these methods one can obtain field measurements that are accurate to a few tenths of a dex. This work therefore represents an important step toward making use of RM data from next-generation surveys with the SKA.
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All authors Hilay Shah, Mark Krumholz, Naomi McClure-Griffiths, Zipeng Hu

Exactly Solvable and Integrable Systems

Lax pairs and $r$-matrices for some two-dimensional isotropic oscillators

Govind S. Krishnaswami, Garima Rajpoot and Srividya N. Vaidya

This paper concerns Lax pairs for circularly symmetric harmonic, Fock-Darwin-type and quartic anharmonic oscillators in two dimensions. Although the 2d isotropic harmonic oscillator is bi-Hamiltonian, its recursion operator does not lead to a Lax pair, nor do we obtain such a pair by taking a limit of the harmonic Calogero model. On the other hand, we show that this superintegrable harmonic oscillator admits a $4 \times 4$ block-form Lax pair with spectral parameter giving two conserved mode energies in involution and a corresponding dynamical $r$-matrix. Interestingly, we also find $2 \times 2$ Lax pairs with spectral parameter that give all three independent conserved quantities satisfying a nonabelian Poisson algebra, thereby providing a simple example of a Lax pair whose conserved quantities are not all in involution. Next, we construct a family of $su(2)$ Lax pairs and $r$-matrices for the quadratic+quartic isotropic anharmonic oscillator. This is then extended to an isotropic oscillator with a rotational energy, which may be viewed as the Fock-Darwin oscillator with a quartic potential. With a change of variables, these Lax pairs and $r$-matrices also apply to the Rajeev-Ranken model, although its noncanonical Poisson structure is distinct from that of the anharmonic oscillator.
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Optics

Polarization vector conjugation in a photonic integrated circuit

Anna J. Miller, Carson G. Valdez, Anne R. Kroo et al. (+5 more)

We show how to perform polarization conjugation of light in a simple apparatus without any nonlinear optical materials, based on self-configuring Mach-Zehnder interferometers fed by a polarization splitter. This allows us to completely and automatically remove the polarization variations on a single beam or mode propagating through an optical system with arbitrary birefringence, such as a conventional optical fiber, and compensate polarization variations experienced in the forward direction by propagating the conjugated beam back through the system and recreating the original polarization at the source. We demonstrate this polarization conjugation in an optical fiber setup in different orientations with a measured polarization extinction ratio of -30 dB for the returned beam.
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All authors Anna J. Miller, Carson G. Valdez, Anne R. Kroo, Marko Šimić, Marek Vlk, Charles Roques-Carmes, David A.B. Miller, Olav Solgaard

Solar and Stellar Astrophysics

On the numerical reliability of nonadiabatic pulsation solutions in AGB envelopes

Jan Zalewski

We re-examine integration methods of linear nonadiabatic radial pulsations in the envelopes of AGB and post-AGB stars using the subspace shooting formulation. In the article the accuracy of the direct integration, the Riccati based method and a continuous renormalization nonlinear integration method are examined. The last method is not widely used in stellar pulsation studies and is therefore of interest in the present comparison. A tracking transformation of the two independent solution vectors is introduced. It helps to improve the accuracy and stability of the solution and can be readily implemented for any of these integration methods. Minimum singular value maps are used to examine the structure of the pulsation spectrum over the complex-frequency plane and also to assess the fidelity with which the integration methods transport the solution subspace. These maps provide a practical alternative to the customarily used maps based on the determinant. We use these maps together with the eigenfrequency spectra to establish mesh conditions required for the reliable transport of the solution subspace, especially in the nonlinear methods. To measure the quality of the subspace transport a spillover measure is introduced. Using this measure it is also possible to verify the placement of the inner boundary, which in the case of radial modes, cannot be guided by propagation criteria based on the Lamb frequency. Visual inspection of the eigenfrequency spectra, the singular value maps, or the eigenmode amplitudes and behavior in the deep envelope does not necessarily imply preservation of the transported-solution subspace. The spillover measure provides a much clearer indicator. This approach provides explicit quantitative diagnostics for assessing the reliability of strongly nonadiabatic pulsation calculations in AGB/post-AGB stellar envelopes.
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High Energy Astrophysical Phenomena

Relativistic Oblique Shocks at Finite Temperature: Detachment Angle, Shock Polars, and the Turning Parameter

Rushikesh Ashok Sonkusale, Anshuman Verma and Ritam Mallick

Oblique shocks are ubiquitous in high-energy astrophysical environments, yet a systematic analytical treatment of how finite upstream temperature influences the maximum deflection angle has been lacking. We address this problem by developing a unified thermodynamic framework based on a novel dimensionless quantity, the turning parameter, which encapsulates the equation of state, upstream Mach number, and thermal state of the flow into a single variable. Starting from the relativistic Rankine-Hugoniot conditions and the Taub adiabat, we derive a compact turning relation and a first-order perturbative expansion in the upstream thermal parameter. We show that any finite upstream temperature monotonically suppresses the maximum deflection angle relative to the cold-fluid limit, implying that cold models systematically overestimate shock attachment. In the combined ultra-thermal and ultra-relativistic limit, the turning parameter saturates to a universal value, yielding an asymptotic detachment angle that depends only on the equation of state. Numerical shock-polar calculations validate the analytical results and reveal a non-monotonic dependence of the detachment angle on the Mach number at intermediate temperatures, arising from the competition between thermal pressure and bulk kinetic energy-a distinctly relativistic thermal effect absent in both the cold and ultra-hot limits. As an illustrative astrophysical application, we apply the framework to the Crab pulsar wind nebula, demonstrating how finite-temperature effects modify the termination-shock morphology and the observed torus geometry.
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Fluid Dynamics

Fractal Scaling of Moffatt Vortices in Triangular Cavity Flow

Rathindra Nath Basak, Sougata Biswas and Jiten C. Kalita

This study examines the formation, quantification, and fractal characterization of corner vortices in slow viscous incompressible flow within a triangular cavity. The governing Navier-Stokes equations are solved numerically using a pressure-based coupled solver, and the resulting vortex cascade is analyzed through the size and intensity ratios of successive eddies in the spirit of Moffatt's theory of corner vortices. The fractal properties of the vortex sequence are then investigated using the area-perimeter method. An empirical relation is proposed to estimate the fractal dimension of any successive vortex in the cascade for arbitrary grid resolution. The results demonstrate that the corner vortices possess non-integer fractal dimensions between 1 and 2, and that this dimension is systematically linked to vortex size and intensity. The influence of Reynolds number on the fractal scaling is also examined. Finally, a comparative analysis of self-similarity in triangular and square cavities confirms that the observed corner-vortex cascade exhibits robust fractal behavior across geometries and flow regimes.
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Superconductivity

Evidence for fully-gapped superconductivity in BCS superconductor NiBi3

Atul Gangwar, Kunal Yadav, S.Patnaik et al. (+1 more)

We investigate the physical characteristics, normal state and superconducting properties of NiBi3 single crystals. Measurements of electrical resistivity, magnetization, and London penetration depth demonstrate a superconducting transition temperature, Tc=4.0 K, with a sharp transition in resistivity (Tc = 0.20 K) and RRR = 18, reflecting the high quality of NiBi3 single crystals. With both orientations H perpendicular b and H parallel b of NiBi3 single crystals, we estimated the upper critical field, Hc2, from the magnetization data. In both orientations, Hc2 is significantly smaller than the Pauli limit, suggesting the orbital pair breaking in superconducting state. The coherence length, xi(0) = 26.78 nm, electron-phonon coupling constant, lambda(e-p) = 0.81, and penetration depth, lambda0 = 181.8 nm, suggest type-II superconductivity in NiBi3. In the superconducting state, lambda(T) is best described by an s-wave BCS model and does not have linear or quadratic dependency with T, which is in line with the expectation for a node-less superconducting order parameter. The temperature evolution of the superfluid density, obtained from lambda(T), reveals a fully gapped superconductivity in NiBi3, with a superconducting gap = 4.07. All the results from the present study indicate that NiBi3 is a typical type-II, BCS-like, moderately strong coupled, and fully gapped superconductor in the dirty limit.
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All authors Atul Gangwar, Kunal Yadav, S.Patnaik, Sandip Chatterjee

Nuclear Theory

Searching for initial state fluctuations in heavy ion collisions at FAIR energy using Principal Component Analysis

Ekata Nandy and Subhasis Chattopadhyay

In high energy heavy ion collisions, the initial configurations of the colliding nuclei play an important role in determining the reaction type and the products of the reaction. The initial arrangement of nucleons within the overlap region of two colliding nuclei is generally asymmetric and such asymmetries reflect themselves in the measurement final state momentum anisotropy. Also initial distribution of the nucleons are subjected to large quantum fluctuation causing large energy deposition in a small region. The final state observables related momentum anisotropies although sensitive to such localized fluctuations but their true effect gets diluted because these observables are calculated by averaging over a set of events. Also, such fluctuations in the initial states are random and uncontrolled. Thus, identifying their effect from event-averaged final state observable is difficult. However, it would be interesting to know the origin of such fluctuations and how these fluctuation are eventually translated to the final state. In this work, we at first introduce such localized fluctuations in the initial configurations, also called hot spots, by implementing spatial rearrangements of nucleon position in the colliding nuclei in the central Pb+Pb collisions at E$_{lab}$=20 AGeV ($\sqrt{s}$=6.27 GeV) using the UrQMD event generator. Then the final state distributions of one or two dimensional variables e.g., ($\eta$, $\phi$, $p_T$) and ($\eta-p_T$, $\phi-p_T$, $\eta-\phi$) of the produced pions are analysed using the principal component analysis (PCA) technique. The eigenvalues of the principal components have been studied for various initial configurations, event fractions containing hot spots in the initial condition and for event centralities with an aim to find it's sensitivity to the initial hot spot configurations.
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Optics

Statistical Analysis of Speckle Fields

Ian D. Min-Roberts, Wojciech Rozmus and Pierre A. Michel

Speckles, or laser hot spots, are the intensity maxima of optically smoothed laser beams that seed instabilities, making a quantitative statistical description of speckles of interest. Earlier statistical theories estimated the number of speckles above an intensity level set for optically smoothed beams produced by random phase plates, using an ansatz that relates intensity maxima to the maxima of the real and imaginary components of the underlying complex Gaussian electric field. Here, we count speckles directly from the laser intensity field, treating it as a $\chi_2^2$ random field and imposing the local maximum conditions without a single-component ansatz. We evaluate the theory for square, circular, annular, and Gaussian aperture spectra, and include induced spatial incoherence as a temporal smoothing mechanism. Monte Carlo simulations confirm the theory and show improved accuracy relative to the earlier ansatz-based formulation. Applications include a simple SBS reflectivity model using the resulting speckle statistics, and a comparison between speckle-driven and thermal noise density-fluctuation spectra.
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Optics

Monolithic Magneto-Optical Mach-Zehnder Isolator Using Laser-Annealed Iron Garnet on a Silicon Waveguide

Tomoya Sugita, Reona Motoji, Yuki Yoshihara et al. (+5 more)

Stable silicon photonic circuits require monolithically integrated optical isolators based on magneto-optical garnet. However, crystallizing the garnet by conventional furnace annealing exposes the entire chip to high temperature and degrades the silicon waveguides and the metal electrodes. Here we avoid this degradation by using local laser annealing in vacuum to crystallize cerium-substituted yttrium iron garnet (Ce:YIG), deposited by ion beam sputtering without a seed layer, directly within a silicon-based Mach-Zehnder interferometer. A 915 nm beam heats only the garnet region confined in micrometer-scale trenches, leaving the surrounding circuit and electrodes intact. The device achieves an isolation ratio of 13.6 dB at a wavelength of 1540 nm, corresponding to a Faraday rotation of 0.092$\deg$/$\mu$m, with an insertion loss of 20.4 dB and a propagation loss of 9.5 dB. Transmission electron microscopy reveals the crystallized Ce:YIG and a ~10 nm boundary region at the interface with the Si waveguide. These results demonstrate that thermally sensitive silicon photonic devices and magneto-optical thin films requiring high-temperature processing can be integrated by a high-throughput technique compatible with mass production.
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All authors Tomoya Sugita, Reona Motoji, Yuki Yoshihara, Dan Maeda, Hiroki Yamamoto, Hibiki Miyashita, Kazushi Ishiyama, Taichi Goto