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Physics

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Sunday 30 August

High Energy Physics (Phenomenology)

Finite-Width Dissolution of Radial Spectroscopy in Single-Top Mesonic Correlations

Bing-Dong Wan and Shuo Yang

Within the heavy-mass expansion, the pole width of a system containing one unstable heavy constituent inherits the constituent width up to $\mathcal O(\Lambda_{\rm kin}^2/m_Q^2)$ corrections, while radial splittings remain $\mathcal O(\Lambda_{\rm rad})$. The top quark is an extreme realization of this hierarchy. We implement the complex top pole mass in an instantaneous Bethe–Salpeter framework, where a biorthogonal Hellmann–Feynman relation realizes width inheritance at the operator level and an artificial heavy-mass scan confirms the predicted $m_Q^{-2}$ suppression. The low-pole source-projected response has a single broad maximum at the physical top width in the $t\bar b$, $t\bar c$, and $t\bar u$ channels. Full width-dependent non-Hermitian re-diagonalization and a direct full-matrix resolvent evaluation confirm the progressive dissolution of the small-width radial maxima. Thus stable-top eigenvalues survive as reference poles but not as a resolvable multi-peak spectrum; they may instead leave qualitative, process-dependent $Wb\bar q$ signatures, such as a broad threshold enhancement or modified color flow.
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Saturday 29 August

Materials Science

Exact benchmarks for the plasmon-pole approximation: Multi-scale screening and the breakdown of the quasiparticle picture

Michael O. Atambo

The $GW$ approximation is the gold standard for calculating quasiparticle band structures, yet its computational cost frequently necessitates the use of the plasmon-pole approximation (PPA). While PPA is known to be highly accurate for simple metals and weakly correlated semiconductors, its regime of validity in materials with competing energy scales remains poorly quantified. Here, we construct an exact, numerical benchmark of the PPA using the Lehmann representation of the density response on finite one-dimensional Hubbard clusters. By analytically convolving the exact non-interacting Green's function $G_0$ with the exact pole representation of the screened interaction $W$, we compute the $GW$ self-energy without numerical frequency integration. We demonstrate that in single-scale Mott insulators, the moment-conserving PPA is essentially exact. However, in multi-band semiconductors where interband transitions introduce a low-energy screening channel that competes with high-energy Mott fluctuations, the PPA systematically misjudges the quasiparticle gap by several electron-volts. Furthermore, we show that strong multi-pole screening can drive the exact quasiparticle weight $Z \to 0$, destroying the quasiparticle picture-an effect entirely missed by the PPA, which artificially stabilizes sharp quasiparticles. Finally, we propose a computationally inexpensive diagnostic based on the polydispersity of the loss function's spectral weight, which accurately predicts PPA failure ab initio. Our results provide a rigorous framework for assessing the validity of dynamical screening approximations in strongly correlated materials.
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Quantum Physics

Encrypted Redundancy as a Diagnostic Resource: Relational Diagnosis in Quantum Encrypted Cloning

Gabriele Gianini, Omar Hasan, Stelvio Cimato et al. (+1 more)

Quantum encrypted cloning encodes an unknown state into several encrypted components, each offering an alternative way to recover it later. We show that this redundancy can also serve for one-shot fault diagnosis: instead of inspecting the encrypted state, we measure relational Pauli observables testing consistency conditions imposed by the encoding. The canonical Yamaguchi–Kempf scheme encodes the input into \(n\) signal–key pairs, all carrying the same coherent Bell label, plus a transformed copy of the input qubit. Comparing the labels of two pairs yields a deterministic check that localizes an anomalous pair and identifies its Pauli-error class without revealing the label. Such checks cannot tell whether the signal or the key of that pair is faulty, and no measurement on the pairs can (we prove that they already generate the whole group of deterministic state-blind observables supported there, of rank \(2(n-1)\)). This ambiguity matters: a faulty signal costs one redemption path, a faulty key threatens them all. However, retaining also the transformed input qubit contributes exactly two further independent checks, at any multiplicity, and these suffice to identify any single fault drawn from the single-qubit Pauli set. For three clones this gives six checks in all, and we prove that no smaller set of state-blind observables achieves the same resolution. Across clone multiplicities, parity governs how many components must be measured jointly to reach this resolution, not the resolution itself. These findings are then abstracted into a general framework — state-blind observables, deterministic healthy references, syndrome-induced fault partitions, redemption-oriented sufficiency — yielding relational diagnosability: a syndrome need not identify every fault, only enough of it to select a safe redemption path.
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All authors Gabriele Gianini, Omar Hasan, Stelvio Cimato, Ernesto Damiani

Quantum Physics

Non-Markovian Quantum Decay in Complex Environments: A Hyperstatistical Approach

Nicola Fabiano

The exponential decay of an unstable quantum state, as described by standard Markovian theories such as Fermi's Golden Rule, assumes a simple, structureless environment. However, in complex environments characterized by disorder, long-range interactions, or strong fluctuations, local decay rates fluctuate, leading to non-Markovian dynamics and power-law “long-time tails.” In this paper, we apply the recently proposed hyperstatistics framework to the problem of quantum decay in such complex environments. By considering a $\gamma$-distribution of local decay rates across mesoscopic domains, we derive a macroscopic survival probability governed by a $q$-exponential function. We then use the $q$-generalized Gamma function, defined via the Mellin transform of the $q$-exponential, to calculate the moments of the decay-time distribution. We show that the mean quantum lifetime is $\langle t\rangle = \int_0^\infty P(t)\,dt= [\langle\Gamma\rangle(2-q)]^{-1},$ and is therefore finite for $q<2$. The convergence of the second moment, and hence of the lifetime variance, instead requires the stricter condition $q<3/2$. These results provide a refined physical interpretation: for $1<q<3/2$ both the mean lifetime and its variance are finite; for $3/2\le q<2$ the mean lifetime remains finite but lifetime fluctuations become infinitely broad; and for $q\ge2$ the mean lifetime itself diverges, corresponding to a truly trapped, localized, or Griffiths-like regime.
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Optics

Reliable iToF Depth Sensing via Sensor-Intrinsic Uncertainty Modeling and State-Space Restoration

Yansong Du, Yutong Deng, Yuting Zhou et al. (+7 more)

Indirect time-of-flight (iToF) cameras provide compact and cost-effective dense depth measurements, but their ranging accuracy is often degraded by sensor-intrinsic uncertainty under practical imaging conditions. Spatially uniform or range-only Gaussian perturbations cannot accurately reproduce the range-dependent and signal-dependent noise characteristics of real iToF measurements, leading to a synthetic-to-real gap for learning-based restoration. To address this problem, we propose a joint depth-uncertainty modeling and restoration framework for reliable iToF sensing. A sensor-intrinsic depth-uncertainty model is first developed from calibrated tap responses, returned-signal levels, and sensor noise statistics through a depth-oriented weighted least-squares formulation. The resulting pixel-wise uncertainty is used for heteroscedastic depth synthesis and uncertainty-aware restoration supervision. Based on this heteroscedastic data synthesis, we further develop a U-shaped restoration network with Depth Visual State Space (DVSS) blocks, which combine long-range state-space modeling with convolutional spatial-channel refinement for structure-preserving depth recovery. Experiments on synthetic data and measurements captured by an in-house iToF prototype validate the proposed uncertainty model under varying range and returned-signal conditions. Controlled comparisons with fixed and range-aware Gaussian noise, together with evaluations on U-Net, Restormer, and DVSS, further demonstrate that the proposed synthesis consistently benefits different restoration backbones. The complete framework achieves 40.85~dB PSNR and 2.54 mm MAE on the synthetic test set, and 35.42 dB PSNR and 4.87 mm MAE on real iToF measurements.
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All authors Yansong Du, Yutong Deng, Yuting Zhou, Zhancong Xu, Yingjia Lu, Mengdi Wang, Feiyu Jiao, Bangyao Wang, Zhaoxiang Jiang, Xun Guan

Classical Physics

The Schwitters Memorial Problem: A Car Speeds Across a Triangular Bump

William H. Press

Most drivers slow down for speed bumps, sometimes to almost a stop, as if each speed bump were a stop or yield sign. The late Roy Schwitters and I shared the view (here called the Schwitters Doctrine) that one should take the bumps at a speed of at least 60 or 70 kph (35 to 45 mph), not because we were scofflaws, but because we found, based on informal experiments, that the traverse was less jarring at high speeds than at low. Here, the problem is worked in terms of the geometry of the wheels on the road and two coupled, damped harmonic oscillators representing the suspension of the car and the driver's cushioned seat. The Schwitters Doctrine is recovered, but not in the way that one expects.
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Classical Physics

Free Precession Revisited: A Vector-Only Analysis of Gyroscopic Dynamic Equilibrium

Dan I. Hariton

This paper presents a self-contained, vector-only formulation of gyroscope precession about a fixed pivot – gravity-driven, not the torque-free Euler-Poinsot case. The derivation of its governing equation uses vector integrals and cross products of intrinsic vectors, with no component decomposition; no tensor or dyadic formalism, matrix or Euler angle enters. Inertia about the center of mass enters through two mass integrals alone: the polar second moment of mass $J_0$ (isotropic) and the vector operator $\vec F$ (the rest, including all non-isotropic inertia). Using material time derivatives referenced to the inertial observer, the torque about the pivot is assembled once from the complete acceleration of each mass element, giving an exact, unified vector equation for steady precession. The balance of the gravity torque against this inertia torque reproduces the classical steady-precession relation of the heavy symmetric top exactly at non-vertical tilts, on both the slow and fast branches, with the horizontal-shaft case exact rather than approximate. Closed forms are given for the disk, sphere, and circular and rectangular toruses. The constant tilt angle of dynamic equilibrium is explained as torque equalization: the two torques about the pivot balance exactly at that tilt and unequally on either side of it, treated throughout as a geometric function of the tilt under constant precession and self-spin rates, and never as a function of time. Informationally equivalent to the classical description, the work contributes, in order, an interpretation (the classical balance read in torque vectors throughout) and the vector method as its tool. The exact relation predates this work: Klein and Sommerfeld stated it in 1897, Brand in 1930. Begun by the author in 1975 and re-verified symbolically, the work is intended for undergraduate readers, with every step of the derivation stated.
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2609.02937 · 29 Aug · 71 pages, 9 figures, 10 tables. Ancillary files: supporting numerical results, forward-and-inverse precession solver, ancillary comparison file, verification package and sweep program. Version 2: text revised throughout; Author's Note added; Appendix G (the comparison with Brand) replaced by the ancillary comparison file, which adds Klein and Sommerfeld; references corrected and added

Abstract PDF $EQLB ×2$GRAV ×2$GEOM ×1$MTRX ×1 +1

Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG

Efficient Context-Limited Telescope Bibliography Classification for the WASP-2025 Shared Task Using SciBERT

Madhusudhana Naidu

The creation of telescope bibliographies is a crucial part of assessing the scientific impact of observatories and ensuring reproducibility in astronomy. This task involves identifying, categorizing, and linking scientific publications that reference or use specific telescopes. However, this process remains largely manual and resource intensive. In this work, we present an efficient SciBERT-based approach for automatic classification of scientific papers into four categories - science, instrumentation, mention, and not telescope. Despite strict context-length constraints (maximum 512 tokens) and limited compute resources, our approach achieved a macro F1 score of 0.89, ranking at the top of the WASP-2025 leaderboard. We analyze the effect of truncation and show that even with half the samples exceeding the token limit, SciBERT's domain alignment enables robust classification. We discuss trade-offs between truncation, chunking, and long-context models, providing insights into the efficiency frontier for scientific text curation.
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General Physics

Cosmological Perturbations and Observational Constraints on Spinor Field Quintessence Dark Energy

Mahendra Goray

We investigate the linear perturbation cosmology of a spinor-field realization of quintessence dark energy by implementing the model in the Einstein–Boltzmann solver CLASS. The model parameters are constrained using a Markov Chain Monte Carlo analysis with Pantheon$^{+}$ Type Ia supernovae, cosmic chronometers, DESI DR2 baryon acoustic oscillations, redshift-space distortions, and Planck 2018 CMB distance-prior data. For the full combined dataset, we obtain $w_{\rm de}=-0.9710^{+0.0206}_{-0.0206}$, $\Omega_{m0}=0.2939^{+0.0047}_{-0.0047}$, and $H_0=66.23^{+0.55}_{-0.53},\mathrm{kms^{-1}Mpc^{-1}}$. The corresponding perturbation quantities are $\sigma_8=0.7537^{+0.0076}_{-0.0075}$ and $S_8=0.7459^{+0.0067}_{-0.0065}$. We find that the spinor-quintessence model closely reproduces the predictions of a phenomenological constant-$w$ model in the matter power spectrum, growth-rate observable $f\sigma_8$, growth index, and CMB temperature anisotropy spectrum, with deviations generally below the percent level. A comparison with $\Lambda$CDM and $w$CDM shows statistically indistinguishable fits, although the Bayesian information criterion favors the simpler $\Lambda$CDM model. Our results demonstrate that the spinor-field quintessence scenario remains consistent with current expansion-history and structure-growth observations when its perturbation evolution is treated consistently, providing a field-theoretically motivated realization of constant-$w$ dark energy at the background and linear perturbation levels.
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Mathematical Physics

Fock-Space Formulation of the Boltzmann Collision Operator for Maxwell Molecules

Ilya Karlin

We develop a representation-independent symmetric-Fock formulation of the nonlinear Boltzmann collision operator for Maxwell molecules. Starting from the standard velocity-space operator, we give a short derivation of Bobylev's Fourier identity and isolate its characteristic structure: two linearly related Fourier arguments followed by multiplication. We then prove, independently of collision geometry and of any coordinate realization, a canonical lift–fusion intertwining theorem: one-particle linear maps lift to the two incoming Fock legs and symmetric-algebra multiplication fuses them into a single outgoing state. Bargmann coordinates make this intrinsic construction especially transparent, but do not define it; Bobylev's collision maps subsequently select the Maxwell vertex from the already graded lift–fusion class. The resulting bilinear map obeys the exact grading \[ \widehat{\mathcal Q}(\mathscr H_p,\mathscr H_q)\subseteq\mathscr H_{p+q}, \] which gives an intrinsic origin for the triangular structures of Maxwell kinetics. Its one-vacuum restriction yields the complete Wang Chang–Uhlenbeck spectrum, while moment adaptation makes the nonequilibrium hierarchy strictly triangular and every finite compatible Fock jet an exact autonomous factor with global exponential relaxation. For the inhomogeneous problem, we extend realization covariance to the nonlinear two-leg vertex and evaluate the moving-frame connection independently through Hermite-function and Fourier realizations. The two routes give the same abstract Fock propagation and the same first Chapman–Enskog source; its traceless level-$2$ and vector level-$3$ sectors are relaxed by the exact Maxwell rates, giving $\Pr=2/3$. This provides an explicit computational demonstration that coordinate realizations may be chosen for economy without entering the structural Fock formulation.
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Mathematical Physics

Alternative-mean trace divergences: geometry, data processing, and barycenters

Trung Dung Vuong, Hiroki Shudo and Hiroyuki Osaka

Let $f:(0,\infty)\to(0,\infty)$ be a nontrivial normalized operator monotone function and set $s=f'(1)$. We introduce the alternative-mean trace functional $$ \altPhi_f(A,B) :=\Tr(A\nabla_s B) -\Tr\!\left( f(A^{-1}\sharp B)\,A\,f(A^{-1}\sharp B) \right). $$ on the positive definite cone. We prove that $\altPhi_f$ is a quantum divergence in the sense of Bhatia–Gaubert–Jain whose diagonal Hessian induces a positive multiple of the Bures–Wasserstein Riemannian metric. We also establish the sharp comparison $$ s(1-s)d_{\rm BW}(A,B)^2 \le \altPhi_f(A,B) \le (1-s+s^2)d_{\rm BW}(A,B)^2. $$
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Atmospheric and Oceanic Physics

Is the Atmosphere Really Such a Good Blanket?

Slavoljub Mijovic

The incorrect application of the current methodology for treating and averaging Earth's surface temperatures has contributed to contradictions and misinterpretations in different scientific disciplines, particularly in climate change and global warming research. The methodology previously proposed by the author addresses these shortcomings and provides a physically based framework for further analysis. This paper demonstrates that the contribution attributed to the atmosphere in determining the warming of the Earth's surface may be substantially overestimated, with the estimated effect differing by approximately 10 degrees Celsius from the conventional interpretation. The analysis is based on the ERA5 reanalysis dataset produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), using hourly skin temperature data for 1950-2025 on a global grid of approximately 1.04 million cells representing the Earth's surface. The proposed method enables an absolute assessment of global warming, confirms the long-term warming trend, and provides a comparative analysis with results obtained using the conventional methodology.
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Optics

Artificial Intelligence in a Photonic Temporal Processor

Youlve Chen, Jinlong Xiang, Yimin Hu et al. (+13 more)

Optical neural networks (ONNs) promise high-throughput and energy-efficient artificial intelligence, yet essentially all implementations so far encode information across space either in free-space arrays or in integrated waveguide meshes, tying the number of neurons to the number of physical components and fixes the routing topology at fabrication. Here we show that moving the computation into time decouples computational dimension from hardware dimension. Exploiting space-time duality, we implement optical diffraction and interference entirely in time domain, using thin-film lithium niobate modulators as time lenses and temporal masks, with chromatic dispersion providing the coupling between successive temporal neurons. We experimentally verify high-order, complex-valued matrix-matrix multiplications using just a single optical input/output port, scaling the computational dimensions far beyond the channel count. By incorporating optical feedback, we extend this platform into versatile neural networks, where the network layers, neuron numbers, and synaptic connections are fully programmable and in-situ trainable. Our temporal diffractive neural networks are successfully validated on various classification benchmarks, alongside image and video generation tasks. Notably, using this platform we demonstrate an all-analogue generative pipeline in which the latent variable is drawn directly from amplified spontaneous emission, so that no digital sampling or electronic modulation appears anywhere in the generative path. Furthermore, high-resolution images and videos are generated at high frame rates, outperforming state-of-the-art modulator-refresh-limited optical generative systems. These results establish a unified photonic temporal computing framework, providing a scalable and deployable pathway toward next-generation machine intelligence.
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All authors Youlve Chen, Jinlong Xiang, Yimin Hu, Yuchen Yin, Chaojun Xu, Zhengshun Lei, Xin Wang, Yufeng Zhang, Yixiao Zhu, Qunbi Zhuge, Junwen Zhang, Wei Chu, Tao Lin, Yikai Su, Zhipei Sun, Xuhan Guo

General Relativity and Quantum Cosmology

How much of the black hole ringdown is sourced within the light ring?

Mark Ho-Yeuk Cheung

Not much. It has been proposed that applying a rational filter to a black hole ringdown gravitational waveform reveals a direct wave component sourced near the event horizon. By solving the Teukolsky equation for a point particle plunging into a Kerr black hole, I show that the maximum amplitude of the waves sourced within the prograde light ring is $\lesssim 10\%$ that of those sourced by the full trajectory no matter if the waves are filtered or not. This agrees with the interpretation of quasinormal modes as waves orbiting the light ring and the direct wave as the power of these modes redistributed in time. Therefore, both quasinormal modes and direct waves are more a probe of the light ring than the near-horizon region. For GW250114, I estimate that the component of the waves sourced within the light ring have a signal-to-noise ratio $\rho \lesssim 1$ measured after the peak of the filtered waves.
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High Energy Physics (Experiment)

First Measurement of Solar Neutrinos through Elastic Neutrino-Electron Scattering at the keV Scale

XENON Collaboration: E. Aprile, J. Aalbers, K. Abe et al. (+169 more)

We report on the first measurement of low-energy solar neutrinos through elastic neutrino-electron scattering in a dark matter experiment, establishing the lowest energy threshold for any neutrino detection to date. The measurement utilizes data from the first two science runs of XENONnT, corresponding to an exposure of 2.46 t $\cdot$ y, and covers electron recoil energies between 1 keV and 140 keV, providing sensitivity to solar neutrinos with energies down to 17 keV. We reject the background-only hypothesis with a statistical significance of $5.0\sigma$ and measure a solar $pp$ neutrino flux of $(10.2 \pm 2.0) \times 10^{10}$ cm$^{-2}$ s$^{-1}$. The result is larger, but statistically consistent with the previous measurement by Borexino at $1.9\sigma$. Together with recent observations of coherent elastic neutrino-nucleus scattering of $^8$B solar neutrinos in XENONnT and other liquid-xenon time projection chambers, these results demonstrate the growing potential of liquid xenon detectors for neutrino physics down to the keV-scale and represent an important milestone towards a next-generation multipurpose observatory.
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All authors XENON Collaboration: E. Aprile, J. Aalbers, K. Abe, M. Abu Rmilah, M. Adrover, S. Ahmed Maouloud, L. Althueser, B. Andrieu, E. Angelino, D. Antón Martin, S. R. Armbruster, F. Arneodo, L. Baudis, M. Bazyk, V. Beligotti, L. Bellagamba, R. Biondi, K. Boese, R. M. Braun, G. Bruni, R. Budnik, C. Cai, C. Capelli, J. M. R. Cardoso, A. P. Cimental Chávez, A. P. Colijn, J. Conrad, J. J. Cuenca-García, H. Dai, V. D'Andrea, L. C. Daniel Garcia, M. P. Decowski, A. Deisting, C. Di Donato, P. Di Gangi, S. Diglio, K. Eitel, S. el Morabit, R. Elleboro, A. Elykov, A. D. Ferella, C. Ferrari, H. Fischer, T. Flehmke, M. Flierman, R. Frankel, D. Fuchs, W. Fulgione, C. Fuselli, F. Gao, R. Giacomobono, R. Glade-Beucke, L. Grandi, J. Grigat, M. Guida, P. Gyorgy, R. Hammann, C. Hils, L. Hoetzsch, N. F. Hood, A. Hurhina, M. Iacovacci, Y. Itow, J. Jakob, F. Joerg, Y. Kaminaga, S. Kazama, P. Kharbanda, M. Kobayashi, D. Koke, K. Kooshkjalali, A. Kopec, E Kozlova, H. Landsman, L. Levinson, A. Li, H. Li, I. Li, S. Li, Z. Liang, Y.-T. Lin, S. Lindemann, M. Lindner, K. Liu, M. Liu, F. Lombardi, J. A. M. Lopes, G. M. Lucchetti, T. Luce, Y. Ma, C. Macolino, G. C. Madduri, J. Mahlstedt, F. Marignetti, T. Marrodán Undagoitia, K. Martens, J. Masbou, S. Mastroianni, V. Mazza, J. Merz, M. Messina, A. Michel, K. Miuchi, R. Miyata, A. Molinario, S. Moriyama, M. Murra, J. Müller, K. Ni, C. T. Oba Ishikawa, U. Oberlack, K. Otsuzuki, S. Ouahada, B. Paetsch, Y. Pan, Q. Pellegrini, J. Pienaar, M. Pierre, G. Plante, T. R. Pollmann, F. Pompa, A. Prajapati, L. Principe, J. Qin, A. Ravindran, A. Razeto, L. Sanchez, J. M. F. dos Santos, I. Sarnoff, G. Sartorelli, M. T. Schiller, P. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, F. N. Semler, P. Shagin, X. Shen, S. Shi, H. Simgen, Z. Song, A. Stevens, C. Szyszka, A. Takeda, Y. Takeuchi, P.-L. Tan, D. Thers, G. Trinchero, C. D. Tunnell, K. Valerius, S. Vecchi, S. Vetter, G. Volta, B. von Krosigk, C. Weinheimer, D. Wenz, C. Wittweg, V. H. S. Wu, Y. Xing, D. Xu, Z. Xu, M. Yamashita, J. Yang, L. Yang, J. Ye, M. Yoshida, G. Zavattini, Y. Zhao, M. Zhong, T. Zhu

Materials Science

Vibrational Origin of the Barocaloric Effect in the Spin-Crossover Complex Fe(pap-5NO2)2: A Combined DFT and Mean-Field Study

Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng et al. (+2 more)

Despite the barocaloric performance recently reported for the spin-crossover complex Fe(pap-5NO2)2, the microscopic origin of its pressure-induced entropy change remains poorly understood. In particular, the relative contributions of vibrational, configurational, and spin degrees of freedom to the barocaloric response have not yet been quantitatively established. Here, we develop a theoretical framework that combines density functional theory (DFT) calculations with an effective mean field Hamiltonian to investigate the barocaloric effect in this spin-crossover complex. Vibrational frequencies of the low-spin (S = 0) and high-spin (S = 2) states obtained from first-principles calculations are incorporated into a thermodynamic model that explicitly accounts for configurational, spin, and lattice entropy contributions. By establishing a correspondence between the vibrational spectra of both spin states through displacement-vector overlap analysis, we identify low and mid frequency metal-ligand vibrations as the primary microscopic origin of the vibrational entropy change. The proposed model quantitatively reproduces the experimentally reported barocaloric entropy change for a pressure variation of 2 kbar, corresponding to a maximum reversible entropy change of approximately 70 J kg-1 K-1, and predicts a spin-crossover temperature of T_1/2 = 313 K under ambient pressure, in excellent agreement with the experimental value of 308 K. Analysis of the entropy components reveals that lattice entropy associated with molecular vibrations accounts for approximately 84% of the total barocaloric response, whereas configurational and spin contributions are comparatively small.
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All authors Alan de Souza, Antonio M. dos Santos, Yongqiang Cheng, Vinícius S. R. de Sousa, Mario Reis

Quantum Physics

The resource cost of magic in a code block

Jiachen Shen and Hui Zhong

We bound the magic of a post-selected logical measurement by the resource that produced it. The setting is one code block with one logical qubit and an adaptive protocol that measures, feeds forward and accepts. The witness reads the accepted effect against the free set of the resource theory of magic, outcome by outcome and not on the averaged channel, since a channel can be free while one of its outcomes measures the magic axis. Our first bound is unconditional. The accepted magic is at most a constant times the summed distance of the cells from the free set. The second is the main result. When the resource cells sit inside a bounded-spread exact-recovery skeleton, the recovery puts every insertion history below a threshold onto a single free branch, transcript by transcript, so only connected clusters reaching the threshold contribute and an exact-component expansion controls their weight. With a threshold linear in the code distance, polynomially many cells of bounded insertion degree and per-cell dilation amplitude $O(1/d)$, the accepted magic times the acceptance probability is at most $\exp[-\Omega(d\log d)]$. Post-selection is disposed of before accepted transcripts are summed, so a branch of vanishing probability cannot be amplified into a magic effect. The threshold is certified from a circuit, and we run it on one exact round of stabilizer measurement followed by a split readout, which measures logical $X$ on the accepted fibre and logical $Z$ on the rejected ones. That certifies a threshold equal to the code distance for every single-layer pattern of weak $Z$-rotations, one per data qubit, so the hypotheses are met by a family and not one design. A member carries magic only if its support contains a logical $Z$ string. One member attains the exponent, again at the level of the accepted effect. Suppression is set by the threshold and not by the topology of the block.
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Solar and Stellar Astrophysics

MEGARA Stellar Spectral Library. Second Release

E. Carrasco, M. Lira-Franco, M.L. García-Vargas et al. (+6 more)

We present the second release of the MEGARA spectral library, MEGASTAR, which now includes all spectra collected during ten observing semesters at the Gran Telescopio CANARIAS. This new release supersedes our first release and incorporates a substantial number of additional observations (2000 new spectra), obtained at high spectral resolution, R(FWHM)$\sim$20000, in two wavelength ranges centred on H${\alpha}$ (6420 - 6790 A) and on the CaII triplet (8370 - 8885 A). The aim of this paper is to introduce MEGASTAR DR2 to the community as its high-resolution spectra can serve as a valuable resource for numerous types of research. In particular, we will use MEGASTAR spectra to construct SSP blocks within the HR-PyPopStar evolutionary synthesis models. The stars were observed using the integral field spectroscopy mode of the instrument. We process the data in a uniform way with the MEGARA data reduction pipeline. We estimate the stellar flux by adding the spectra from 37 spaxels, centred on the spaxel with the highest flux in the IFU reconstructed image. This approach guarantees that the effective slit width, and therefore the spectral resolution, are the same for all spectra. The second MEGASTAR release consists of 2838 spectra corresponding to 1408 stars, providing a better coverage of the stellar parameter space than the first release. The spectra were acquired with an average continuum S/N of about 215. This second release meets the standards of a modern empirical library: it offers reliable calibrations, data free from slit effects, observations of a large number of stars, and provides high spectral resolution to model both individual stellar clusters and entire galaxies observed with MEGARA.
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All authors E. Carrasco, M. Lira-Franco, M.L. García-Vargas, M. Mollá, N. Cardiel, A. Gil de Paz, P. Gómez-Alvarez, S. R. Berlanas, I. Millán-Irigoyen

Quantum Physics

Parametric amplification in a Kerr Oscillator based on Ne FIB Nanobridges

Parth Bhandari, Laith Meti, Gemma Chapman et al. (+3 more)

Superconducting circuits play a crucial role in the advancement of quantum computing and quantum sensing. Typically such circuits require the presence of a non-linear element, where the engineered anharmonicity (Kerr factor) and resonant linewidth determine the potential applications of the circuit. In this work we have fabricated Nb-based CPW resonators embedded with a DC SQUID incorporating Nb nanobridges as the weak links. We use two-tone spectroscopy to study the non-linear behaviour of the device at 15 mK up to a field of 2.48 mT. Under the application of a blue-detuned pump, the device shows a decrease in the resonant frequency which is used to estimate the Kerr factor. We further apply a red-detuned pump to go beyond the bifurcation threshold and observe the appearance of an additional idler mode with net gain. The gain of the device was maximized by further decreasing the pump frequency, showing a maximum amplification of 15 dB. Finally, we show agreement between the Kerr non-linear oscillator model and the measured transmission spectrum, and highlight further design modifications to improve the gain and bandwidth of such devices.
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All authors Parth Bhandari, Laith Meti, Gemma Chapman, Edward Romans, John Gallop, Ling Hao

Quantum Physics

Quantum optomechanics with arbitrary mirror displacement: nonlinear Langevin equation with non-Markovian back-action noises

Adrian E. Rubio Lopez, Hing-Tong Cho and Bei-Lok Hu

Quantum optomechanics (QOM) explores the interaction between a quantum field, often confined in a cavity, and the quantum motion of mirrors, membranes or material media, usually assumed slow enough with negligible particle production, which is the central concern of dynamical Casimir effects, and a drive laser field for effective control. This rapidly developing field has a wide range of applications, from quantum sensing to the detection of gravitational waves. Because the opto-mechanical coupling is nonlinear, most theoretical investigations assume that the amplitude of mirror motion $x$ remains small. Recent years saw several papers treating $x^2, x^3$ orders in the mirror displacement. In our work we take a different route, deploying the functional perturbative method presented in [1] and enriched in [2], applicable for sufficiently weak opto-mechanical couplings. With this we can treat arbitrary displacement of the mirror, not just at a higher order in a power series expansion in $x$. We first derive the influence action of the quantum field and its non-Markovian noises back-reacting on the moving mirror with self-consistency. From it we derive a nonlinear Langevin equation driven by these back-action noises from the quantum field. We then show how results from our general modeling and treatment can be linked with the models and the Langevin equations presented in the literature, starting with the popular radiation pressure $Nx$ coupling, with $N$ the photon number, up to the recent $x^3$ order results. We hope this new approach and the results presented here can provide useful theoretical support for high precision QOM experimentation in the future.
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Mathematical Physics · Cross-listed from math.DG

Positive mass and rigidity for asymptotically flat tangent bundles

Sajjad Lakzian

Let $(M,g)$ be an asymptotically flat manifold such that its tangent bundle $TM$ is diffeomorphically asymptotically Euclidean. We prove a positive mass theorem and a positive mass rigidity theorem for a natural class of asymptotically flat metrics $\widetilde g$ on $TM$ exhibiting slow asymptotic decay. These metrics are constructed by interpolating, along the horizontal distribution of $TM$, between the Euclidean metric and the base metric $g$ near infinity. The main difficulty is that the induced metrics on $TM$ decay below the standard threshold for the ADM mass in dimension $2n$; nevertheless, we show that their asymptotic mass is well-defined in a generalized sense and is determined by geometric data on the underlying manifold $M$.
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Mathematical Physics · Cross-listed from math.NT

Analogue of Cardy's formula on the 60-degree parallelogram: a modular approach

Cody R. Strouse

The Cardy-Smirnov function of a four-marked planar domain encodes the conjectural scaling limit of the crossing probability for critical percolation. Cardy predicted a closed formula for this limit on the rectangle in the cases of both site and bond percolation, and Smirnov proved the formula together with conformal invariance for critical site percolation on the triangular lattice. Kleban and Zagier later showed that on the rectangle the function admits a modular interpretation: it is determined by a modular functional equation together with a mild analytic ansatz. We carry out the analogue on the $\pi/3$ parallelogram. We derive a closed conformal-map formula for the Cardy-Smirnov function as an incomplete beta integral, prove a closed modular formula realizing it as an integral of the modular form $\eta(\tau)^2\eta(3\tau)^2$, and establish a uniqueness theorem showing that a single functional equation, together with a $q$-expansion ansatz and a nondegeneracy condition, determines the function uniquely.
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Quantum Physics

The ZZ feature map induces a signless Laplacian metric: a closed-form classical surrogate for quantum kernel regression

Erkut Tekeli

Bandwidth-tuned quantum kernels have been shown to lose their advantage over classical kernels and to resemble radial basis function kernels, but the analytical support for that observation rests on separable encoding circuits and captures entangling circuits only qualitatively. We close this gap for the ZZ feature map. We prove that in the small-bandwidth regime the induced kernel has, to leading order, the anisotropic Mahalanobis geometry defined by M = I + pi^2 Q, where Q is the signless Laplacian of the entanglement graph, and that it admits a parameter-free Gaussian surrogate matching it through second order. The quadratic structure persists at any fixed depth as a pullback of the Fubini-Study metric. The anisotropy depends entirely on a phase convention: under the unshifted convention the metric is the identity irrespective of entanglement, which accounts analytically for the isotropic resemblance previously reported. The derivation is verified against direct simulation for path, cycle and complete graphs, with relative error below 10^-3. The corresponding classical kernel requires no fitted parameters and no quantum simulation. Compared with the quantum kernel on two near-infrared spectroscopic benchmarks, across four targets, five preprocessing pipelines and 100 resampled splits per cell, the paired 95% bootstrap interval contains zero in 18 of 20 cells, the typical relative difference in test error is 2.7%, and the two families select the same preprocessing pipeline in 96% of splits. The regime in which the reduction fails adds no robust predictive value: restricting the grid to the classical regime improves mean test error by 3.8%, a gain that an equally large random restriction does not reproduce.
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Earth and Planetary Astrophysics

A semi-analytical surrogate model for giant planet evolution: bypassing ordinary differential equation solvers with localised thermodynamics, softplus asymptotes, and B-spline photometry

Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay et al. (+7 more)

Context. Evolutionary models translate the observable luminosity, temperature, and colours of giant planets and brown dwarfs into mass and age. Generating their cooling tracks normally requires integrating the internal energy over time with an ordinary differential equation (ODE) solver coupled to pre-computed atmospheric grids, which becomes numerically stiff at sharp transitions such as cloud condensation and the onset of electron degeneracy, and is fragile inside Bayesian retrievals. Aims. We aim to generate continuous cooling tracks and photometric light curves directly from discrete atmospheric grids, without an ODE solver. Methods. We mapped the grids into a logarithmic thermodynamic space and extracted localised surrogate models with Gaussian-weighted regressions at fixed planetary parameters. We fitted the entropy and cooling rate against the internal temperature using bounded piecewise softplus functions to capture structural and cooling-rate transitions; the radius was fitted on the same temperature axis; and band photometry was represented with fixed-knot cubic B-splines. The age followed from numerical integration of these analytic functions, and uncertainties were propagated from the residual scatter of each fit. Results. The surrogate, CoolTrack, reproduces the transition into electron degeneracy and the L-to-T spectral-type transition in the colour-magnitude diagram, converges on Solar System benchmarks, and evaluates a full evolutionary track in milliseconds on a standard desktop CPU. Conclusions. By removing the forward-modelling bottleneck, CoolTrack is suitable for direct use in Bayesian retrieval pipelines, where the age, mass, and formation entropy of a planet can be inferred jointly with its atmospheric properties.
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All authors Christian Wilkinson, Jonas Wehrung-Montpezat, Benjamin Charnay, Mathilde Mâlin, Lukas Delaye, Anne-Marie Lagrange, Vito Squicciarini, Johan Mazoyer, Stéphane Mazevet, Baptiste Perrier

Disordered Systems and Neural Networks · Cross-listed from math.PR

Algorithmic threshold for high-dimensional projection pursuit I: general theory

Brice Huang, Mark Sellke and Nike Sun

We study a null model of high-dimensional projection pursuit: we are given $M$ points sampled i.i.d. from a standard gaussian in $N$ dimensions, where $M,N\to\infty$ with $M/N\to\alpha\in(0,\infty)$. Our goal is to characterize the possible empirical distributions of these points' projections along a data-dependent direction $x$, which ranges over either the sphere $S_N=\sqrt{N}\mathbb{S}^{N-1}$ or cube $\Sigma_N=\{-1,+1\}^N$. We consider this problem in an algorithmic setting, where $x$ must be the output of an algorithm with dimension-free Lipschitz dependence on the input; this class of algorithms includes general gradient-based methods such as Langevin dynamics and approximate message passing (AMP). Our main result exactly characterizes the set of empirical distributions attainable by this class in terms of a one-dimensional stochastic control problem. As a consequence of our main result, we obtain exact algorithmic thresholds for optimizing the Hamiltonian of a spherical or Ising perceptron model with general bounded continuous activation. For the spherical problem, independent work of Montanari and Zhou (2024) characterized the empirical distributions attainable by a related two-stage AMP algorithm, also in terms of stochastic control. Our proof of hardness builds on the branching overlap gap property introduced in earlier work by the first two authors. Our main innovation is to develop stochastic control theory within the branching OGP framework, significantly expanding the settings in which it locates an exact algorithmic threshold. Notably, our methods apply even though the non-algorithmic problem of characterizing all feasible projections remains a major outstanding challenge. For the matching algorithmic result, we construct a new incremental AMP algorithm that acts on a Brownian-bridge revelation of the gaussian disorder and simulates the same family of controlled SDEs.
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Materials Science

PINN-Phase: Physics-informed neural integration for accurate, generalizable and scalable multiphase-field evolution

Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger et al. (+1 more)

The value of polycrystal phase-field simulations for materials exploration depends on whether individual grains, not only aggregate statistics, evolve correctly in time. We introduce PINN-Phase, a neural time integrator that advances the multiphase field autonomously and enforces phase bounds and unit sum at every step. It learns from physical targets evaluated on its own predicted states, without reference trajectories in training. A hybrid realization meets all predefined criteria with fixed weights on seven of eight prospective unseen two-dimensional microstructures and both stress cases. It also keeps the exact survivor set in five of six unseen 128^3 microstructures over 24,000 steps. A separately trained phase-local realization with 2,160 parameters, trained at 48^3 with eight grains, runs with unchanged weights on microstructures with up to 5,000 grains. With 1,000 and 5,000 grains it reproduces 4,540 of 4,543 reference grain extinctions by identity within their timing tolerance; the other three straddle the evaluation horizon. Typical per-grain volume errors stay nearly constant from 150 to 5,000 grains, while a few large grains later exceed the volume criterion. Time-rescaling controls show that statistics compared at matched coarsening states cannot detect a 3% clock error. In a virtual isothermal hold, that error ends the hold prematurely in all 34 decisions, whereas PINN-Phase stays within 0.3% of the reference time to target. These results hold within the tested microstructure families.
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All authors Seifallah Elfetni, Sascha Thinius, Peter H. Seeberger, Theodore Tyrikos-Ergas

High Energy Physics (Experiment)

Evidence for the dead-cone effect in bottom quark initiated jets produced in proton-proton collisions at $\sqrt{s}$ = 13 TeV

CMS Collaboration

The suppression of collinear gluon emissions from a massive quark, or the “dead-cone effect,” is the primary manifestation of quark mass effects in parton showers. A proton-proton collision data set recorded by the CMS experiment at $\sqrt{s}$ = 13 TeV with an integrated luminosity of 59.8 fb$^{-1}$ is analyzed. A differential measurement is presented of the emission density of bottom quark jets, studied as a function of the angular separation between iteratively declustered subjets. The measurement is performed in bottom quark initiated jets with transverse momenta between 40 and 200 GeV originating from top quark pair production. Compared to data, a parton shower Monte Carlo model that includes the dead-cone effect is favored, while a model without the dead-cone effect is disfavored with a significance of 4.3 standard deviations.
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Superconductivity

Controlling Intertwined Electronic Orders in FeSe with Exfoliation

Wenyao Liu, Gabriel Natale, Kyung-Mo Kim et al. (+14 more)

Controlling intertwined electronic orders in two-dimensional superconductors offers an effective route to answering fundamental questions and engineering new quantum devices. However, tuning the balance between competing orders typically requires complex chemistry, strain, or interface engineering. Here, we show that a pristine alternative is the dimensional reduction of the unconventional superconductor FeSe. Exfoliation suppresses the bulk electronic nematic response and switches the superconducting symmetry from bulk s-wave to d-wave-dominant. Transport, electron microscopy, and Raman spectroscopy establish the substantial weakening of nematic order in thin flakes. To probe superconductivity, we perform angle-dependent Andreev reflection spectroscopy on pristine crystal edges. As the junction's orientation is rotated, the spectra evolve from zero-energy bound states to coherence peaks. The injection angle, field, and temperature dependence, along with theoretical modeling, confirm that exfoliation switches the superconducting symmetry. Our results suggest a versatile superconducting platform for engineering quantum orders and provide fresh insights into the underlying pairing mechanisms.
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All authors Wenyao Liu, Gabriel Natale, Kyung-Mo Kim, Birender Singh, Piyush Sakrikar, Stephen D. Funni, Leo Kondo, Augustin Davignon, Antoine de Lagrave, Kota Ishihara, Michael Geiwitz, Maia G. Vergniory, Takasada Shibauchi, Jun Sung Kim, Michał Papaj, Judy J. Cha, Kenneth S. Burch{\dag}

Other Condensed Matter

Dynamical backaction in nanoscale superfluid electromechanics

Marek Talíř, Filip Novotný, Balázs Szalai et al. (+2 more)

Nanofluidic acoustic resonators employing superfluid $^4$He can be used to study quantized vortices from collective behavior in two-dimensional superfluid turbulence down to few individual vortices created by rotation. In order to improve sensitivity to the level needed for probing individual quantized vortices, readout mechanisms employing optomechanical or optomechanics-inspired approaches seem to be promising in this regard. In this work, we develop an electromechanical system, which couples a 4$^\mathrm{th}$ sound acoustic resonance to a superconducting LC tank circuit in a sideband-resolved regime. Using this system, we demonstrate electromechanically induced transparency (EMIT), optical spring effect and optomechanical sideband damping and amplification. Furthermore, by rotating the cryostat, we demonstrate sensitivity to quantized vortices, which can become trapped and released in avalanche-like process inside the nanofluidic volume.
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All authors Marek Talíř, Filip Novotný, Balázs Szalai, Nasiruddin Mondal, Emil Varga

Materials Science

Elastic properties of amorphous LiTaCl$_6$ solid-state electrolyte

Xiaolin Liu and De-en Jiang

Amorphous solid-state electrolytes are attractive candidates for safe, high-energy-density all-solid-state batteries, yet their mechanical properties remain poorly understood from a computational perspective. Here, we investigate the elastic behavior of the recently discovered amorphous superionic Li-ion conductor LiTaCl$_6$ using density-functional-theory (DFT)-based methods, including unrelaxed static, relaxed static, and strain fluctuations from molecular dynamics (MD) simulations in the isobaric–isothermal (NPT) ensemble with DFT-trained machine-learning force fields (MLFFs). While the unrelaxed static method predicts a Young's modulus an order of magnitude higher than the experiment, the relaxed static method—commonly applied to crystalline electrolytes—still overestimates the modulus by more than 170%. In contrast, the MD approach using MLFFs yields a Young's modulus of $2.84 \pm 0.26$ GPa, which quantitatively agrees with the experimental value of $2.91 \pm 0.32$ GPa. Using the MLFF-MD approach, we further predict bulk modulus (4.44 GPa), shear modulus (1.02 GPa), and Poisson's ratio (0.39) for amorphous LiTaCl$_6$ and conclude that elastically it behaves like a soft polymer or gel. These results demonstrate that amorphous superionic materials possess some unique elastic properties and that, among the methods examined, only the MLFF-MD approach yields quantitative agreement with experiment, highlighting the necessity of a dynamical treatment to simulate their elastic response, consistent with recent findings for crystalline superionic conductors.
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