Physics and Society
The ring wants to be broken
Alexei Vazquez
The Ramsey community number $r_\kappa$ is the minimum network size at which a graph's connectivity is better described by a partition into communities than by no partition, under a prescribed community-detection rule. It was introduced through numerical simulations of networks grown by local rules, which suggested that community structure can emerge without any node heterogeneity. Here I compute $r_\kappa$ analytically for the simplest homogeneous, locally wired graph: the circulant ring
lattice $C_n(1,\dots,c)$. Using a Bernoulli
stochastic block model with symmetric $\mathrm{Beta}$ priors as the detection rule, the
Bayesian evidence for a balanced two-community partition and for the unpartitioned network are both obtained in closed form, so the transition between them can be located exactly. The result is a sharp dependence on the interaction range: the plain cycle ($c=1$) is never partitioned, its two-community posterior decaying as $n^{-(2\alpha+3)}$, so $r_\kappa=\infty$; but the next-nearest-neighbour ring ($c=2$) acquires a finite $r_\kappa\simeq 35$ nodes, above which the partition is preferred with a log-evidence growing as $(\ln 2)\,n$. This provides an exactly solvable instance of community emergence in a network with no built-in communities, and shows that a minimal amount of local connectivity is enough to break the ring.
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Medical Physics
Accelerating MRI Colon Volume Measurements and Reducing Inter-Observer Variation through Automatic Segmentation and Human-in-the-Loop Correction
Abi Spicer, Stephen Lloyd-Brown, Neele Dellschaft et al. (+6 more)
The movement distribution, and volume of both chyme and gas in the colon, are important metrics to understand colonic function in health, disease, and the effects of treatments and different foodstuffs. Current methods available for assessment of these colonic contents using MRI consist mainly of manual
segmentation or semi-automatic
segmentation. However, these methods of
segmentation are very labour intensive and too slow for clinical applications, require expert knowledge and some semi-automatic methods require use of bowel preparation. MRI scans were acquired in 2 breath holds using mDIXON sequences. We used the 'No New U-Net' (nnU-Net) ML model to automatically segment the colon, including colonic regions (ascending, transverse, descending and sigmoid-rectal). The ML-generated masks were corrected manually and the time taken for correction was recorded. ML
segmentations were compared to both manual
segmentations and observer corrected ML (CorrML)
segmentations. Observer repeatability was also evaluated for both manual and CorrML methods to create a
benchmark for the allowable error in the automatic
segmentations. Analysis time was significantly reduced (p<0.0001) from 56 mins (+-11 mins (SD)) for manual masks to 11 mins (+-5 mins (SD)) for CorrML masks. Both DICE and ICC values showed excellent agreement between manual, ML and CorrML
segmentations for whole colonic volume (ICC = 0.96) whilst regional volumes were good-excellent (ICC = 0.80-0.95). Inter-observer repeatability was improved when using CorrML methods over manual
segmentation (ICC manual > 0.89, CorrML > 0.93). Analysis time was reduced by over 80% when using CorrML methods and whole colonic volumes measured by ML would be suitable for use with minimal checks. Hence the methods proposed here would be clinically useful.
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All authors Abi Spicer, Stephen Lloyd-Brown, Neele Dellschaft, Luca Marciani, Robin Spiller, Maura Corsetti, Penny Gowland, Xin Chen, Caroline Hoad
Atmospheric and Oceanic Physics · Cross-listed from stat.AP
Inverse Suitability: Identifying Condition Difficulty and Rider Skill from Behavioural Outcomes via Continuous-Item Response Theory
Fabio Carucci
Suitability scoring for outdoor activities (kitesurfing, paragliding, ski touring) maps environmental conditions to a go/no-go verdict via expert-defined curves. These curves conflate two distinct quantities: the intrinsic difficulty of a condition and the skill of the person facing it. We introduce Inverse Suitability, a continuous-item Item Response Theory (IRT) model that identifies both from behavioural outcomes alone. Each outcome is a triple (rider r, condition metric x at site s, binary outcome y); we model P(y=1) = sigma(a (theta_r - delta(x, s))), where theta_r is latent rider skill, delta(x, s) is a latent difficulty function anchored to a physics-derived expert curve as its prior, and a is a discrimination parameter. The formulation is strictly more general than a single suitability curve, which it recovers exactly when skill is integrated out under the population distribution. Parameters are estimated by marginal maximum likelihood with Gauss-Hermite quadrature; identification holds when the rider-by-condition incidence graph is connected, with a documented single-curve fallback otherwise. We validate via synthetic recovery: on a reference cohort (80 riders times 30 outcomes) the model recovers latent skill at r = 0.96, locates the difficulty minimum within 3 units of ground truth, and improves held-out Brier Skill Score by +0.33 over the expert-curve baseline. The recovered difficulty function defines a measurable, site-level construct, an intrinsic difficulty atlas, that existing meteorological observation networks do not capture. All results reproduce from a single command on synthetic data, requiring no proprietary observations.
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Solar and Stellar Astrophysics
Asteroseismic Analysis of the Merger Product Red Giant in the $\gamma$ Persei System
Rozália Z. Ádám, László Molnár, Róbert Szabó et al. (+7 more)
Context. $\gamma$ Persei is a long-period eclipsing binary system ($P\approx 14.6$ years) containing a red
giant primary, and it is well known for its multi-faceted classification as a visual and spectroscopic binary. Its brightness and binary nature together make it a valuable target for both photometric and spectroscopic studies, particularly in the context of asteroseismology and
stellar evolution, as the primary
star likely formed through a
stellar merger. Aims. We aim to determine the seismic parameters $\nu_{\rm max}$, $\Delta \nu$, and the oscillation amplitudes of the primary component, an evolved
giant, to estimate its seismic mass $-$ which we can compare to its estimated dynamic mass. Methods. We use Transiting
Exoplanet Survey Satellite (TESS) data obtained during Sectors 58, 85, and 86 and to complement the space-based observations, we incorporate high-resolution RV measurements acquired by the
Stellar Observations Network Group (SONG) during two distinct epochs; 2017 and 2024. Results. We successfully detect
solar-like oscillations in $\gamma$ Per and infer a seismic mass of $3.25\pm0.13$ M$_\odot$, which is slightly below the dynamical mass. We find the photometric oscillation amplitudes to be significantly lower than predicted from scaling relations, but in line with other high-mass red
giants. We also find that radial velocity amplitudes along the Hertzsprung-Russell diagram cannot be fitted uniformly with current scaling relations.
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All authors Rozália Z. Ádám, László Molnár, Róbert Szabó, Csilla Kalup, Frank Grundahl, Daniel Huber, Mads Skakke Fredslund, Pere L. Pallé, Dóra Tarczay-Nehéz, Jonatan Rudrasingam
Physics and Society
Robust for the Wrong Reasons: The Representational Geometry of LLM Robustness to Science Skepticism
Minjong Cheon
Large
language models (LLMs) are increasingly consulted on contested scientific questions, raising the concern that they will sycophantically retreat from established consensus when a user signals doubt – drifting toward a false balance that treats settled science as one view among several. We test this across three open instruction-tuned models (Llama-3.1-8B, Qwen2.5-7B, Mistral-7B), three consensus-science domains (
climate, vaccines,
evolution), and single- and multi-turn settings, combining behavioral measurement with linear probing and activation patching. We do not observe sycophantic retreat. Instead, models show three distinct policies under the same skeptical pressure: reactive assertion, where consensus assertion increases rather than decreases (Llama); surface hedging, where tone softens while the position holds (Qwen); and non-response (Mistral). Pairwise judgments confirm the reactive shift is stance, not style (63.6%, p=.007), and a decomposition identifies increased consensus assertion, not false balance, as its driver (beta=+0.042 per dose, p<1e-77). Linear probes localize the divergence to middle layers – perfect separation in Llama and Qwen versus 72% in Mistral, with non-overlapping confidence intervals – indicating the non-responsive model does not linearly represent the skepticism signal at all. Crucially, this robustness does not transfer: it attenuates across domains and, in the safety-critical vaccine domain, can reverse, with myth-rebuttal weakening under skeptical pressure. We synthesize these into a four-way taxonomy separating active from accidental robustness, and argue that behavioral evaluation alone cannot distinguish a model that resists skepticism because it understands the signal from one that only appears to resist because it fails to perceive it.
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Soft Condensed Matter
Curvature-driven wall accumulation in chiral active particles
Alessandro Petrini, Raphaël Maire, Umberto Marini Bettolo Marconi et al. (+1 more)
We study a dilute system of non-motile
chiral active particles confined in geometries ranging from straight channels to circular enclosures. Activity is introduced through
chiral particle-wall interactions, modeled as tangential wall forces that generate the edge currents characteristic of
chiral active matter. Remarkably, although the particles lack self-propulsion, these boundary currents induce density inhomogeneities. We show that boundary
curvature drives a wall accumulation phenomenon: particles remain uniformly distributed in straight channels but accumulate near the boundaries of circular confinements. Numerical simulations and a hydrodynamic theory for the density and momentum fields consistently capture this
curvature-induced wall-accumulation. These results identify boundary
curvature as a fundamental control parameter for
chiral edge transport and confinement-induced organization, with potential experimental relevance to spinning colloids and granular spinners.
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All authors Alessandro Petrini, Raphaël Maire, Umberto Marini Bettolo Marconi, Lorenzo Caprini
Superconductivity
Fermiology and spin polarization of topological surface states in PtBi$_2$
Anders Christian Mathisen, Xin Liang Tan, Stefanie Suzanne Brinkman et al. (+12 more)
Layered PtBi$_2$ is a candidate for topological superconductivity arising in
Fermi-arc surface states. Using
spin- and angle-resolved photoemission spectroscopy, we demonstrate that the
Fermi arcs in PtBi$_2$ are singly degenerate and
spin-polarized, which establishes their nontrivial
topology and constitutes a necessary condition for topological superconductivity. We further uncover a pronounced surface-termination dependence of the
Fermi-arc dispersion, yielding either nearly flat or approximately linear bands in agreement with first-principles calculations. Together, the observed
spin polarization and termination-dependent bandwidth of the
Fermi-arc surface states identify key ingredients underlying the potential emergence of topological superconductivity in PtBi$_2$.
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All authors Anders Christian Mathisen, Xin Liang Tan, Stefanie Suzanne Brinkman, Kristian Mæland, Fabian Göhler, Øyvind Finnseth, Grigory Shipunov, Falk Pabst, Manuel Alonso Lemos, Balasubramanian Thiagarajan, Craig Polley, Björn Trauzettel, Anna Isaeva, Jorge I. Facio, Hendrik Bentmann
Quantum Physics · Cross-listed from cs.LG
Hybrid quantum-classical neural network for sentiment analysis
Giacomo Cappiello, Filippo Caruso, Xing Liang et al. (+1 more)
Quantum machine learning has recently emerged as a promising paradigm that leverages the expressive power of
quantum circuits to address complex learning tasks. In this work, we investigate the applicability of hybrid
quantum-classical neural networks to sentiment analysis, a central problem in natural
language processing. We focus on a
dataset of tweets related to COVID-19, where the textual content is vectorized using TF-IDF and fed into both classical feedforward networks and hybrid architectures incorporating parameterized
quantum circuits. Our results show that hybrid models can achieve accuracy comparable to the classical baseline, while exhibiting distinct learning dynamics, especially in terms of validation loss and accuracy, that suggest a richer representational capacity. Moreover, when applying transfer learning to an SMS spam classification task, the hybrid models consistently outperform the classical counterpart, achieving an accuracy increase of 15 percentage points (from 66% to 81%) on the spam class, demonstrating enhanced generalization. These findings highlight the feasibility of employing QML for natural
language processing and point toward the potential advantages of hybrid models as
quantum hardware continues to advance.
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All authors Giacomo Cappiello, Filippo Caruso, Xing Liang, Dimitrios Makris
High Energy Astrophysical Phenomena
Colour evolution in the radio afterglow of GRB 241025A
S. Giarratana, O. S. Salafia, L. Nava et al. (+10 more)
We present the observing campaign of the afterglow of GRB241025A, a gamma-ray burst (GRB) whose
prompt emission has been simultaneously detected by Swift, Einstein Probe,
Fermi/GBM, SVOM, Konus-Wind and VZLUSAT-2 3U CubeSat. Our multi-wavelength campaign comprises
radio, near-infrared, Optical and X-ray observations. The afterglow was clearly detected in all bands. We performed a semi-empirical fit of the data, showing that the afterglow behaviour can be reasonably reproduced by a single component, i.e. an ultra-relativistic shock. However, the results from the semi-empirical fit are inconsistent with the predicted
evolution from the standard afterglow model in the slow cooling regime. Specifically, we found that at early times the synchrotron self-absorption frequency $\nu_a$ should be at higher frequencies with respect to the ones sampled by our campaign, in order to explain the observed colour
evolution in
radio, namely the spectral
evolution in time. To reconcile the prediction from the standard model with the observed data set, we fit the observations with a semi-analytical model, including a multiplicative factor $\tau_{enh}$ to the optical depth which, in turn, artificially increases $\nu_a$. We found that the
radio colour
evolution, together with the near-infrared, optical and X-ray emission, can be described reasonably well by a forward shock from a structured jet, provided that the optical depth in the shocked material is enhanced by a factor $\tau_{enh}=500$. We suggest that such enhancement in the optical depth can result from a population of cold electrons in the downstream material, i.e. electrons that were not accelerated by
Fermi I process at the shock front, in agreement with the theoretical expectations previously reported in the literature. Overall, our work underscores the importance of systematic, multi-frequency, multi-epoch
radio follow-ups of these extreme events.
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All authors S. Giarratana, O. S. Salafia, L. Nava, G. Ghirlanda, M. Giroletti, S. Antier, M. Pillas, T. Hussenot-Desenonges, A. Iskandar, M. Tanasan, G. Oganesyan, N. Di Lalla, N. Omodei
General Relativity and Quantum Cosmology
Neutron stars with primary scalar hair
Hamza Boumaza, Christos Charmousis, David Langlois et al. (+1 more)
We investigate static and spherically symmetric
neutron star solutions endowed with primary scalar hair in a subfamily of Degenerate-Higher-Order-Scalar-Tensor (DHOST) theories of
gravity. By solving the modified Tolman-Oppenheimer-Volkoff (TOV) equations, we construct
equilibrium configurations for polytropic and realistic equations of state and analyse the impact of the scalar hair on the
stellar structure. We examine the resulting metric and scalar field profiles as well as the mass-radius relation, showing deviations from the predictions of General Relativity (GR). Positive scalar charges lead to more compact
stars than in GR and, above a critical threshold, to singularities. Observations could therefore put stringent constraints on the parameters characterising the beyond-GR effects in these theories and their potential scalar hair.
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All authors Hamza Boumaza, Christos Charmousis, David Langlois, Etienne Ligout
Optics
Mapping Source-Resolved Phase-Noise Transfer in Soliton Microcombs
Zhongan Zhao, Aleksandr Razumov, Viswanathan Sankar et al. (+2 more)
Phase noise limits the coherence and stability of
soliton microcombs, yet its origin is difficult to trace because multiple noise sources act simultaneously. It is often represented by common-mode and repetition-rate components, but how each physical source contributes to these components remains unclear. We combine subspace tracking with multi-source Ikeda-map simulations, switching each source and the Raman nonlinearity on and off to isolate its contribution. Without Raman, pump phase noise is purely common-mode, while shot noise and amplified spontaneous emission drive the repetition rate noise. With Raman, the nonlinearity coherently converts pump phase noise from common-mode into repetition-rate noise without introducing an independent noise source, yielding a
parabolic linewidth profile with a quiet-point minimum below the pump linewidth. When all noise sources are present, shot noise, ASE, and RIN raise the common-mode floor and shift this minimum toward the pump, setting the achievable noise floor. The intracavity dynamics thus do not merely carry noise but actively partition it, providing a mechanistic basis for low-noise microcomb design.
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All authors Zhongan Zhao, Aleksandr Razumov, Viswanathan Sankar, Jasper Riebesehl, Darko Zibar
High Energy Physics (Theory)
Tuning quantum magic of pure quantum chaotic states with a gravity dual
Antonio M. García-García, Xianlong Liu and Jie-ping Zheng
Quantum magic is a fundamental resource that quantifies to what extent
quantum states can be efficiently simulated on a classical computer. We study it for states constructed from the Sachdev-Ye-Kitaev (SYK)
Hamiltonian with $N$ Majoranas by the fermionic anti-flatness (FAF). We show analytically that, in the large $N$ limit, the
quantum magic of pure Kourkoulou-Maldacena (KM) states, dual to a
quantum black hole with an end-of-world particle behind the horizon, is linear in $N$ with a slope, depending on the black hole temperature, that can be tuned between zero and $1/2$. By contrast, the FAF of Gaussian states evolved in real time with the SYK Hamitonian approaches $\approx N/2$ exponentially at a rate given by a multiple of the leading Ruelle-Pollicot resonance. Subleading corrections in $N$ for SYK energy eigenstates, computed numerically for $N \leq 54$ by combining Krylov subspace with GPU acceleration techniques, decay exponentially with $N$, but power-law if the SYK couplings are sparsified, and are order of magnitude larger for states close to the ground state, a region with an established
gravity analogue. Our results offer new insights about the relation between
quantum information,
quantum chaos and low-dimension
quantum gravity.
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Instrumentation and Methods for Astrophysics
$J$ and $H$ band sky brightness measurements from polar day to polar night at Dome A, Antarctica
Jinji Li, Bin Ma, Haonan Yang et al. (+9 more)
The near-infrared (NIR) sky brightness is a fundamental parameter for evaluating the performance of ground-based infrared observatories. Dome~A on the Antarctic plateau offers exceptional atmospheric conditions, yet its NIR sky background has not been continuously monitored. We present the first continuous $J/H$-band measurements of the sky background at Dome~A from polar day to polar night, and characterize their median levels and temporal variability. The Antarctic Infrared Binocular
Telescope (AIRBT), operating in the $J$ and $H$ bands, obtained continuous fixed-pointing observations from February to May 2024, which were used to measure the NIR sky background. The median sky brightness is $5.2/2.9$ and $15.3/13.4~\mathrm{mag~arcsec^{-2}}$ in $J/H$ bands during daytime and nighttime, respectively. The twilight–nighttime boundaries occur at
solar elevations of $-9.3^\circ$ in $J$ and $-7.4^\circ$ in $H$. At the same
solar elevation, the NIR sky background during the polar night is darker by about $0.1$ and $0.4~\mathrm{mag~arcsec^{-2}}$ in the $J$ and $H$ bands compared with the period of regular day–night alternation. During the polar-night period, the nighttime sky brightness in the $H$ band shows a more evident association with the sunspot number, while the corresponding trend in the $J$ band is weaker. These results reveal systematic differences in sky background between polar and non-polar environments and between polar night and regular day–night cycles. The measured sky brightness may be elevated, as the observations were conducted near
solar maximum, highlighting the importance of long-term monitoring across the
solar cycle.
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All authors Jinji Li, Bin Ma, Haonan Yang, Pu Lin, Zhongnan Dong, Michael C. B. Ashley, Lu Feng, Yi Hu, Zhaohui Shang, Yun Shi, Shijie Sun, Xu Yang
Optics
Physics-based self-supervised learning of a deep network for single-shot in-line hologram reconstruction
Dylan Brault, Félix Riedel, Corinne Fournier et al. (+2 more)
Digital in-line
holographic microscopy is a computational imaging method useful for characterizing the refractive properties of a sample, i.e. the phase shift and absorption. This indirect measurement technique captures a diffraction pattern and uses reconstruction
algorithms to retrieve the optical properties of the sample. Since only the intensity of the diffracted wave is recorded on the sensor, this inversion is not trivial, and simple backward propagation leads to artifacts known in optics as the “twin-image”. With advances in deep learning, various
algorithms have been developed for the reconstruction of in-line holograms, providing computationally efficient alternatives to iterative
algorithms. These
algorithms rely either on supervised learning, which requires ground truth knowledge, or physics-based self-supervised
algorithms that require additional information, like phase diversity, but require multiple holograms for inference. This paper introduces a new self-supervised physics-based deep learning strategy that leverages phase diversity during training and then reconstructs sample's transmission function from a single in-line hologram during inference. We introduce five
datasets of simulated and experimental in-line holograms of beads and bacteria. The proposed method produces accurate quantitative reconstructions similar or even more accurate than those obtained by regularized inversion while reducing the computational time by a factor of 1000.
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All authors Dylan Brault, Félix Riedel, Corinne Fournier, Thomas Olivier, Loïc Denis
High Energy Physics (Phenomenology)
Dynamics of Self-Interacting Dark Sectors
Esau Cervantes
This thesis investigates the dynamics of self-interacting dark sectors in the early Universe populated through the freeze-in mechanism. The main focus is on scenarios with self-number-changing reactions of the form $2\leftrightarrow3$, and on how these interactions modify the thermal history and phenomenology of the dark sector. Several realizations are studied, including scalar theories with $\mathbb{Z}_2$ and $\mathbb{Z}_3$
symmetries, self-interacting dark matter coupled to an unstable mediator, and cannibal dark matter production during non-instantaneous reheating. The thermal
evolution is obtained by solving coupled Boltzmann equations for the relevant number densities and temperatures, accounting for both freeze-in production and cannibal interactions. The resulting parameter space can be strongly constrained, effectively invisible, or potentially accessible to future searches, depending on the realization considered. Finally, the thesis studies a hidden U(1) gauge sector populated via freeze-in, where continuous energy injection can induce an inverse first-order phase transition and temporarily restore the symmetric phase, linking phase-transition dynamics and chemical equilibration in hidden sectors.
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Cellular Automata and Lattice Gases
Analysis of the asymptotic density of endogamous diploid cellular automata
Henryk Fukś and Nazim Fatès
We investigate the asymptotic behaviour of diploid Elementary Cellular Automata (ECA), that is, the
stochastic mixtures between two ECAs. In this model, each
cell independently applies one rule with probability $\lambda$ and the other rule with probability $ 1 - \lambda$. Focusing on the endogamous diploids where the two ECAs are related by the reflection or conjugation
symmetry, we analyse how the density varies as function of $\lambda$, the “degree of mixing” of these two rules. We propose a classification into six distinct classes depending on the profile of the density vs. $\lambda$ curve. We take various examples for each class and we analyse to which extent the local structure approximation succeeds to predict the asymptotic density. Our results show that for rules in which the asymptotic density depends linearly on $\lambda$, the local structure approximation reproduces the exact dependence of the density on $\lambda$. For rules with differentiable but nonlinear dependence, the approximation either becomes exact at a finite order or converges rapidly to the exact solution as the order increases. For rules with first-order phase transitions, finite-order approximations progressively approach a sharp transition profile with increasing order. In contrast, for rules exhibiting a second-order phase transition, even high-order approximations fail to capture the qualitative features of the transition. (no bifurcation is observed). Finally, we give examples of two diploid rules for which we succeed to compute the density at each time step.
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General Relativity and Quantum Cosmology
Phase Transitions with Lyapunov Exponents under Einstein and String Frames in Dilatonic Reissner–Nordström–AdS Black Holes
Hocheol Lee and Bogeun Gwak
We investigate Lyapunov exponents as dynamical probes of black hole phase transitions in dilatonic Reissner–Nordström–AdS black holes within Einstein–Maxwell–dilaton theory. The thermodynamic quantities and the Lyapunov exponent of charged probe particles were analyzed in both the Einstein and string frames, thus providing a direct comparison between the thermodynamic phase structure of the black hole and that captured by the Lyapunov exponent. Thermodynamic quantities, including the Hawking temperature and Wald
entropy, remained constant under conformal frame transformations, yielding identical phase structures in the two frames. In contrast, the Lyapunov exponent exhibited non-trivial frame dependence for massive probe particles due to dilaton coupling, while no frame dependence was found in the massless limit. Numerical analysis revealed that the phase structure features captured by the Lyapunov exponent, including characteristic cusp behavior and transition points, were independent of the choice of frame, despite the Lyapunov exponent itself being frame-dependent. Therefore, the Lyapunov exponent exhibited frame-dependent values, while the critical structure it captures remained constant across conformal frames.
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Quantum Physics
Growth of Schrödinger cats in particle-number measurement schemes
S. B. Korolev, A. A. Silin, A. A. Poshevkina et al. (+1 more)
In this work, we investigate the generation of squeezed Schrödinger cat states in schemes based on
photon-number-resolving measurements on multimode Gaussian states. We derive analytical expressions for the states generated in two- and three-mode schemes, as well as formulas for their fidelity with squeezed Schrödinger cat states. We analyze how the amplitude of the generated states scales with the number of detected particles. Furthermore, we derive an upper bound on the achievable generation fidelity and identify the conditions under which multimode schemes can enhance the quality of the generated states.
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All authors S. B. Korolev, A. A. Silin, A. A. Poshevkina, T. Yu. Golubeva
General Relativity and Quantum Cosmology
Chaotic behaviors of particles around the black hole with an anisotropic matter immersed in a magnetic field
Khusan Alibekov, Hocheol Lee, Pakhlavon Yovkochev et al. (+4 more)
We present an exact solution to the Einstein-Maxwell equations that describes a static black hole coexisting with anisotropic matter immersed in an external
magnetic field, obtained via the Harrison transformation. Our findings reveal that an increase in the anisotropic matter parameter systematically suppresses the local chaotic behavior, as indicated by a reduction in the Lyapunov exponent. Conversely, variations in the external
magnetic field lead to qualitative changes in global chaotic behavior. This is analyzed through Poincaré sections, which demonstrate transitions between regular and chaotic trajectories resulting from the nonlinear gravitational-
magnetic interactions. These factors play distinct yet complementary roles in shaping chaotic particle dynamics around black holes. This study would offer a new theoretical framework for exploring nonintegrable particle motion within magnetized black hole spacetimes.
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All authors Khusan Alibekov, Hocheol Lee, Pakhlavon Yovkochev, Bobomurat J. Ahmedov, Bum-Hoon Lee, Ahmadjon Abdujabbarov, Wonwoo Lee
Classical Physics
The slope of the friction law of hertzian-asperity–based metainterfaces has a finite positive lower bound
Julien Scheibert
Metainterfaces can realize specified evolutions of their friction force as a function of the confining normal force (friction law), thanks to the design of the individual radii and heights of a population of independent hertzian asperities. However, not all friction laws are achievable. Here I show that, contrary to a suggestion from the literature, the slope of the friction law has a finite positive lower bound. This result is useful to identify friction laws that are not accessible to metainterfaces.
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Quantum Gases
Interaction-rotation driven localization-delocalization crossover in Fock space: An exact diagonalization study on trapped Bose gas
Mohd Talib and M. A. H. Ahsan
We study the localization-delocalization crossover and
quantum entanglement with varying numbers of interacting
bosons for the nonrotating and the rotating cases. The many-body ground state within subspaces of given total angular momentum is obtained via exact diagonalization and analyzed using the inverse participation ratio (IPR), the information (Shannon)
entropy and the von Neumann
entanglement entropy. In the non-rotating case, a crossover from localization to delocalization is observed with increasing interaction, characterized by decreasing value of IPR with corresponding increase in information
entropy and von Neumann
entanglement entropy, arising from interaction-induced depletion of Bose-Einstein condensate. When subjected to rotation, the system is driven further towards delocalization due to rotation-induced depletion of Bose-Einstein condensate. The crossover from localization to delocalization is indicated by distribution of the eigenstate weights over an increasing number of basis states in the many-body
Hilbert space. The consistent behavior of IPR, information
entropy and von Neumann
entanglement entropy with respect to interaction and rotation demonstrates that these quantities provide a unified characterization of the localization-delocalization crossover. Results on computed von Neumann
entropy show that localized states exhibit weak
entanglement while delocalized states are characterized by strong
entanglement within the
quantum many-body system.
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Quantum Physics
LUCI on IBM Hardware: Error Suppression with Almost Half Syndrome Density
Younghun Kim, Spiro Gicev, Martin Sevior et al. (+1 more)
Long-lived logical
qubits are essential for fault-tolerant
quantum computation. However, the practical performance of traditional error correction protocols relies on performing specific syndrome
circuits, causing vulnerability to hardware defects and imposing rigid connectivity constraints. Recent theoretical findings have proposed that flexible subroutine
circuits within the LUCI framework can maintain space-time distance in the presence of isolated or broken components, albeit at the expense of temporal distance. However, these approaches have solely targeted defect avoidance and have not yet been demonstrated to suppress errors with reduced temporal distances on physical hardware. In this work, we propose a reset-free scenario for the LUCI framework and experimentally
benchmark it on IBM
quantum hardware. By asymmetrically scaling the $X$ or $Z$ distance, we compare our reset-free approach against the standard surface code and successfully demonstrate error suppression ratios for targeted logical Pauli errors. Remarkably, despite a nearly halved syndrome density in time, which requires two subroutine rounds for full syndrome extraction, the LUCI framework remains competitive with the rotated surface code implementation. In the LUCI framework, we observe error suppression of $1.75(10)$ for logical $X$ errors and $1.93(12)$ for logical $Z$ errors, whereas the standard approach yields $ 1.58(13)$ and $2.44(7)$, respectively. These results demonstrate that dynamic codes outperform standard methods by avoiding highly noisy components, even without physical defects, while preserving logical boundaries. Our findings challenge the conventional dependency on static fault-tolerant architectures by verifying the feasibility and efficacy of the LUCI framework on physical hardware and pave the way for hybrid, hardware-compatible code designs in
quantum computing.
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All authors Younghun Kim, Spiro Gicev, Martin Sevior, Muhammad Usman
Astrophysics of Galaxies
Distance Determination of Southern Galactic Plane Supernova Remnants with the Mopra CO Survey and DECaPS 3D Dust Map
Fupeng Liu, He Zhao, Biwei Jiang et al. (+2 more)
Accurate distance measurements to
supernova remnants (SNRs) are crucial for understanding their physical properties, evolutionary processes, and role in the
Galactic interstellar medium (ISM) cycle. In this study, we apply for the first time to the southern
Galactic plane a distance determination method that utilizes CO emission data from the Mopra survey to identify molecular clouds (MCs) interacting with SNRs. By combining this with extinction-distance profiles from the DECaPS three-dimensional (3D) extinction map, we directly measure the distances to the associated MCs, thereby obtaining precise distances to the remnants. To overcome the extinction-missing bias in extremely dense regions where the 3D map suffers from a deficit of background
stars, we supplement our analysis with two-dimensional (2D) extinction maps as cross-validation. Applying this method, we have derived precise distances for nine SNRs: G290.1-0.8 (7.32+0.60/-0.47 kpc), G292.2-0.5 (10.85+0.43/-0.68 kpc), G296.1-0.5 (4.59+0.18/-0.19 kpc), G296.8-0.3 (8.74+0.40/-0.29 kpc), G298.6-0.0 (6.50 +/- 0.21 kpc), G312.4-0.4 (3.60+0.19/-0.23 kpc), G332.4-0.4 (2.66+0.23/-0.15 kpc), G335.2+0.1 (2.76+0.37/-0.31 kpc), and G353.6-0.7 (1.81+0.18/-0.14 kpc). Additionally, we established a robust lower distance limit of 1.34 kpc for G351.7+0.8.
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All authors Fupeng Liu, He Zhao, Biwei Jiang, Jun Li, Zhe Zhang
General Relativity and Quantum Cosmology
Rotating Black Holes and the Kerr/CFT Correspondence in Einstein-Bumblebee Gravity
Yu-Qi chen, Jin-Yang Shen and Hai-Shan Liu
We constructed rotating black holes with equal angular momentum in five dimensional Einstein-Bumblebee
gravity with and without cosmological constant. Their thermodynamic properties are examined via two distinct methods: the Wald formalism and the Komar integral. Notably, the conserved charges, including mass, angular momentum, and
entropy, computed from these two approaches differ by a constant prefactor that is solely determined by the Bumblebee coupling. Subsequently, we apply the Kerr/CFT correspondence to derive the microscopic
entropy of these black holes and find that it precisely reproduces the
entropy in Komar-integral version, rather than the Wald
entropy.
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High Energy Physics (Theory)
Lubkin-Page typicality bounds for Type~II von~Neumann factors
Zhi-Wei Wang and Samuel L. Braunstein
Typicality arguments for emergent spacetime rely on the Lubkin-Page bounds, which show that generic
quantum states have vanishing correlations between subsystems. These bounds assume a tensor-product
Hilbert space (a Type~I von~Neumann
algebra), but the observable
algebras in
quantum field theory and
quantum gravity are generically Type~II or Type~III, raising the question of whether the bounds survive. We prove that they do for all Type~II von~Neumann factors. For the hyperfinite Type~II$_1$ factor with a tripartite decomposition $R \cong A \otimes B \otimes E$, the mutual information between subsystems $A$ and $B$ vanishes as $O((d_A d_B / d_E)^2)$ in finite-dimensional approximations, provided $d_A d_B \leq d_E$ (
Theorem~1). For Type~II$_\infty$ factors, including the gravitational
algebras constructed via the crossed-product method by Witten and by Chandrasekaran, Longo, Penington, and Witten, the bound acquires an additional exponential suppression controlled by the Bekenstein-Hawking
entropy (
Theorem~2). We identify the obstructions to extending the result to Type~III factors and discuss the open question of whether the commutant of the observable
algebra can serve as a natural thermal bath that tightens the bound further.
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High Energy Physics (Phenomenology)
Refined Sensitivity Estimates for Single-Molecule Magnet Dark Matter Detectors
Andrew Eberhardt, Tomoya Fukui, Ryosuke Takehara et al. (+8 more)
We revisit the sensitivity of Single Molecule Magnet (SMM)
crystals as detectors for low-mass dark matter. In previous work, we established the concept of the “
magnetic bubble chamber”, where energy deposited by dark matter triggers a
magnetic avalanche in a metastable
crystal. The original sensitivity estimates relied on a conservative criterion requiring the
spin relaxation time to be strictly shorter than the thermal
diffusion time. Here, we demonstrate that this criterion effectively ignores the
stochastic nature of
spin relaxation. We derive a refined analytic estimate which accounts for the fraction of
spins that relax even when
diffusion is fast. We show that the Zeeman energy released by this fraction contributes to local heating, significantly lowering the energy threshold for avalanche formation. We present simulation results confirming this effect and report on experimental verification of the assumed low-temperature thermal properties of two representative SMM
crystals, Mn$_{12}$-acetate and Mn$_{32}$. Together, these efforts extend this pathfinder program toward the realization of SMM-based detectors with controlled material properties and enhanced dark matter sensitivity.
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All authors Andrew Eberhardt, Tomoya Fukui, Ryosuke Takehara, Ryotaro Ohno, Yuta Mizukami, Kenichiro Hashimoto, Takanori Fukushima, Shigeki Matsumoto, Tom Melia, Kouki Nozaki, Surjeet Rajendran
High Energy Physics (Phenomenology)
Phenomenology of genuine twist-three distributions from a global QCD analysis
Guillermo Portela and Alexey Vladimirov
We present an extraction and phenomenological study of genuine twist-three parton distribution functions (PDFs) through a global QCD analysis of the structure function $g_2$ in deep-inelastic scattering (DIS), its moment $d_2$, and single-/double-
spin asymmetries in semi-inclusive DIS (SIDIS). The unified description of these processes clearly confirms the universality of genuine twist-three PDFs and the validity of QCD factorization
theorems at this subleading level. The extraction is accompanied by several validation tests, tests of sum rules, comparisons with earlier literature, computation forces and average transverse momentum of partons. As a by-product, we also obtain Sivers and worm-gear-T transverse momentum dependent (TMD) distributions, which allows us to construct a tomographic picture of the
proton based on substantially broader data.
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Cosmology and Nongalactic Astrophysics
meer21cm: an Analysis Pipeline and Comprehensive Toolkit for HI Intensity Mapping
Zhaoting Chen, Steven Cunnington, Daniel Tassie et al. (+23 more)
We present meer21cm, a comprehensive python package for cosmological data analysis of single-dish HI intensity mapping surveys. This package is simple to use, with a modularised code structure designed for interactive usage. meer21cm is designed for data analysis, with particular focus on the UHF-band observation of MeerKAT Large Area Synoptic Survey (MeerKLASS). We explicitly impose meer21cm to be survey-oriented, ensuring consistent modelling of observational effects in the clustering power spectrum with the survey specifications and data analysis choices. meer21cm covers a large range of data analysis procedures post calibration, including data read-in, foreground cleaning, power spectrum estimation, mock simulation, transfer function corrections and parameter inference. It handles both meer21cm intensity maps and overlapping
galaxy catalogues, allowing for multi-tracer and cross-correlation analysis between MeerKLASS and optical
galaxy surveys. Tested with a simulated survey of ten $750\,$deg$^2$ sky patches in the
redshift sub-band $0.6\,{<}\,z\,{<}\,0.8$, the meer21cm pipeline achieves per-cent accuracy in the power spectrum estimation for $k \in [0.02, 0.2]\,{h{\rm Mpc}^{-1}}$, with deviations $\lesssim 0.5\sigma$ between the mock and the model power spectra, where $\sigma$ is the signal variance. The meer21cm package is publicly available and easy to install, with a comprehensive documentation website at https://meer21cm.readthedocs.io
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All authors Zhaoting Chen, Steven Cunnington, Daniel Tassie, Alkistis Pourtsidou, Laura Wolz, Gabriele Autieri, Matilde Barberi-Squarotti, José Luis Bernal, Phil Bull, Stefano Camera, Isabella P. Carucci, Brandon Engelbrecht, José Fonseca, Karin Fornazier, Keith Grainge, Jiakang Han, Wenkai Hu, Melis O. Irfan, Piyanat Kittiwisit, Yichao Li, Sefa Pamuk, Mario G. Santos, Marta Spinelli, Jingying Wang, Amadeus Witzemann, Boyan Zhao
Quantum Gases
Elastic Modulus in One-Dimensional Quantum Droplets
Rui Zhang, Tianmiao Zhang, Huan-Bo Luo et al. (+1 more)
Quantum droplets (QDs) are self-bound states of ultradilute
quantum fluids stabilized by the interplay between the Lee Huang-Yang (LHY)
quantum-fluctuation correction and the mean-field interaction, providing a useful platform for exploring macroscopic
quantum phenomena. Recent studies on three-dimensional QDs have introduced the concept of bulk modulus and revealed its connection with the breathing-mode frequency, thereby linking the elastic response of QDs to their collective dynamics. Motivated by this progress, we investigate the elastic modulus of one-dimensional QDs. Based on a super Gaussian variational ansatz, we systematically derive the elastic modulus B and analyze its dependence on the interaction strength and particle number. The analytical predictions are further validated by numerical simulations based on imaginary time
evolution and the spatial scaling method. We also establish a quantitative relation between the elastic modulus and the eigenfrequency of the breathing mode. In addition, by incorporating corrections to the droplet width beyond the Thomas
Fermi approximation, we obtain the dependence of the ratio {\eta} = B/2 on the control parameters g and N. Unlike the three-dimensional case, where the corresponding ratio follows a simple power-law scaling, the one-dimensional system is affected by the
soliton-to-droplet crossover, leading to a more intricate dependence of {\eta} on g and N. Our results show that, in the high-particle-number regime, the elastic modulus asymptotically approaches a limiting value determined mainly by the interaction strength, whereas in the low-particle-number regime it depends on both the particle number and the interaction strength.
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All authors Rui Zhang, Tianmiao Zhang, Huan-Bo Luo, Zibin Zhao
Earth and Planetary Astrophysics
TESS's First Bound Microlensing Planet: A Binary Microlensing Event Revealing a Planetary Companion toward the Galactic Plane
Mallory Harris, Diana Dragomir, Etienne Bachelet et al. (+2 more)
We report the discovery of
Gaia23bra b, the first gravitationally bound microlensing
planet detected by the Transiting
Exoplanet Survey Satellite (TESS). Initially flagged as a single-lens event by the
Gaia Science Alerts system,
Gaia23bra was serendipitously observed by TESS over two consecutive sectors. During those TESS sectors, the light curve of the event displayed caustic-crossing features characteristic of a binary-lens event. Joint modeling of
Gaia and TESS photometry with pyLIMA, supplemented by
stellar parameter inference using pyLIMASS, suggests a K
dwarf ($M_L = 0.79^{+0.19}_{-0.17}\,M_\odot$) hosting a Jovian
planet with $M_P = 1.63_{-0.38}^{+0.42}\,M_{\rm Jup}$ at a projected separation of $a_{\perp,\min} \approx 4.8\,\mathrm{AU}$. This result underscores the synergy between high-cadence photometry and long-baseline monitoring for robust microlensing characterization. Its location along the
Galactic Plane highlights TESS's unexpected capacity for microlensing science through its all-sky coverage and its potential to detect
planets in regions beyond the
Galactic Bulge.
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All authors Mallory Harris, Diana Dragomir, Etienne Bachelet, Michael Fausnaugh, Samson Johnson