Atmospheric and Oceanic Physics
Anthropogenic Heat in Urban Climate Systems: Forcing, Sensitivity, and Feedback
Dan Li, Alvin Christopher Galang Varquez, Ting Sun et al. (+4 more)
Anthropogenic heat flux, the heat released to the environment from human activities such as building energy use, transportation, industrial processes, and human metabolism, is a defining feature of the urban
climate system. It is an important contributor to the urban heat island (UHI) effect and influences a wide range of urban meteorological processes. Its significance extends beyond urban climatology because of its close connections to energy consumption, greenhouse gas emissions, and
climate adaptation. Despite decades of research, anthropogenic heat flux remains one of the least well-constrained components of the urban energy balance. Moreover, its climatic significance has often been assessed from an applied perspective, with less emphasis on developing transferable physical understanding of how anthropogenic heat flux acts as a forcing, how urban temperatures respond, and how feedbacks modify that response. This review develops a forcing-response-feedback framework for synthesizing current understanding of the role of anthropogenic heat flux in the urban
climate system and identifies priorities for future research.
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All authors Dan Li, Alvin Christopher Galang Varquez, Ting Sun, Yuya Takane, Jiachuan Yang, Mingze Ding, David Sailor
Superconductivity
Entropy mapping under uniaxial pressure utilizing the elastocaloric effect
Zhenhai Hu, You-Sheng Li, Aleksei V. Frolov et al. (+8 more)
Uniaxial pressure is a powerful tuning parameter for
quantum materials, but conventional thermodynamic probes such as specific heat are difficult to realize in the constrained geometries of strain apparatus. We develop a quantitative analysis framework for a.c. elastocaloric effect measurements that enable the reconstruction of the absolute
entropy and hence specific heat across complex phase diagrams. The absolute accuracy is achieved by combining measurements in the strong coupling regime at low frequencies with high signal-to-noise measurements in the quasi-adiabatic regime at high frequencies. Applying the approach to the correlated
superconductor Sr$_2$RuO$_4$, we obtain an absolute
entropy map across the phase diagram including across phase transitions deep into the superconducting state. We demonstrate that from such data one can derive the absolute specific heat which is currently not possible through other approaches. This data reinforces the finding that the quenching of
entropy within the
superconductor Sr$_2$RuO$_4$ is strongest at the critical strain consistent with the superconducting gap being maximized at the Van Hove singularity (VHs). Furthermore, we demonstrate that, although $\Delta c /(\gamma T) $ does increase at the VH strain, this increase is much weaker than previously inferred from more indirect caloric experiments.
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All authors Zhenhai Hu, You-Sheng Li, Aleksei V. Frolov, Fabian Jerzembeck, Manuel Brando, Naoki Kikugawa, Dmitry A. Sokolov, Hilary M. L. Noad, Andrew P. Mackenzie, Michael Nicklas, Andreas W. Rost
Plasma Physics
Tunable high-charge relativistic electron beams via direct laser acceleration in hohlraum-preheated foam targets
Ziyao Wang, Jieru Ren, Zhigang Deng et al. (+28 more)
Direct
laser acceleration (DLA) in near-critical-density (NCD)
plasmas can efficiently generate high-charge relativistic electron beams, yet beam parameters depend critically on precise
plasma state manipulation. Solid-ablation NCD
plasmas evolve rapidly, posing severe controllability challenges. We produce NCD
plasma via indirectly heating foam targets with ns
laser driven hohlraum soft X-ray. Electrons are generated through irradiating the
plasma with another picosecond
laser. Tuning the
laser pulse delay $\tau$ enables control of
plasma profiles and beam parameters. Experiments show that when the foam is heated ($\tau$ = 6 ns, 9 ns), the beam exhibits $T \sim 13$ MeV effective temperature, $E_k \sim 80$ MeV cutoff energy, and hundreds of nC/sr charge for $E_k > 7.5$ MeV. These values are significantly higher than those from solid-foil ($T$ $\sim$ 2.7 MeV, $E_k$ $\sim$ 20 MeV, $Q$ $\sim$ 9 nC/sr) and cold-foam ($T$ $\sim$ 12 MeV, $E_k$ $\sim$ 50 MeV, $Q$ $\sim$ 5 nC/sr) interactions. At a longer delay of $\tau$ = 15 ns, the charge increases further while the temperature decreases, and at a shorter delay of $\tau$ = 3 ns, both temperature and charge are lower. 3D PIC simulations link these observations to the interplay between the microstructure of the cold foam and the evolving
plasma density profile at different delay times, which together determine the beam charge, effective temperature, and divergence. The finding provides a routine to generate and tailor the relativistic electron beams, which is essential for designing
laser-driven electron sources for high energy density physics and photonuclear reaction applications.
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All authors Ziyao Wang, Jieru Ren, Zhigang Deng, Wenqing Wei, Wei Qi, Olga N. Rosmej, Nikolay E. Andreev, Sergey Yu. Gus'kov, Rafael Yakhin, Yifang Gao, Bubo Ma, Mingzhe Yang, Shizheng Zhang, Xuyang Luo, Dieter H. H. Hoffmann, Peng Zhou, Ke Jiang, Taiwu Huang, Bo Cui, Weiwu Wang, Shaoyi Wang, Quanping Fan, Zhurong Cao, Sixin Wu, Yue Yang, Leifeng Cao, Yuqiu Gu, Yuchi Wu, Weimin Zhou, Zongqing Zhao, Yongtao Zhao
Soft Condensed Matter
Rheology and Dynamic Arrest in Colloidal Depletion Gels Mediated by Surface Brush Density
Ziye Zhuang, Robert A. Campbell, Safa Jamali et al. (+1 more)
We use the density of surface-grafted
polymers as a geometry-preserving control parameter for tuning the rheology of colloidal depletion gels. Reducing brush density accelerates gelation and produces gels with higher plateau storage modulus and yield stress. This mechanical enhancement is not accompanied by increased local densification; low-brush networks exhibit lower average contact number and reduced spatial heterogeneity while displaying stronger elastic responses than their high-brush counterparts. Our findings demonstrate a reduced coordination threshold to form elastic nodes in the low-brush gel network. In addition, low-brush gels relax more slowly, accumulate less creep deformation, and exhibit lower effective noise temperatures within the Soft Glassy Rheology framework. These results establish surface-brush density as an experimentally accessible control parameter for colloidal depletion gel rheology with coupled changes in effective attraction, network architecture, and contact kinematics.
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All authors Ziye Zhuang, Robert A. Campbell, Safa Jamali, Ali Mohraz
Nuclear Experiment
Revised $^{45}$V($p,\gamma$)$^{46}$Cr reaction rate and its impact on the production of $^{44}$Ti in core-collapse supernovae
R.S. Sidhu, Y. Luo, C. Sarma et al. (+2 more)
The thermonuclear $^{45}$V($p,\gamma$)$^{46}$Cr reaction is the primary leakage pathway from the $^{44}$Ti–$^{45}$V quasi-
equilibrium cluster during $\alpha$-rich freeze-out in core-collapse
supernovae (CCSN), governing the final abundance of the $\gamma$-ray-emitting isotope $^{44}$Ti. A recent high-resolution $\gamma$-ray study [C. Cousins et al., Phys. Rev. Lett. 136, 252701 (2026)] identified ten previously unknown low-
spin proton-unbound states in $^{46}$Cr, enabling the first experimentally constrained $^{45}$V($p,\gamma$)$^{46}$Cr reaction rate using the AME2020 mass excess, $\text{ME}(^{46}\text{Cr}) = -29472(11)$~keV. Here, we adopt the four-fold more precise CSRe mass excess $\text{ME}(^{46}\text{Cr}) = -29477.2(2.6)$~keV [M.~Wang et al., Phys. Rev. C 106, L051301 (2022)] to recalculate the reaction rate. Including
proton capture on the ground and first two excited states of $^{45}$V alongside new shell-model
proton spectroscopic factors, we reduce mass-related rate uncertainties to a subdominant level. The revised rate is up to 69% higher than that of Cousins et al. at $\alpha$-rich freeze-out temperatures ($T \simeq 1.5$–$2$~GK). CCSN nucleosynthesis calculations show this revised rate increases the ejected $^{44}$Ti yield by $\sim$26% in a $20\,M_\odot$ model compared to The et al. [ApJ 504, 500 (1998)], while causing negligible changes for the SN~1987A trajectory. We demonstrate that $^{44}$Ti production sensitivity is dictated by the ejecta electron fraction ($Y_e$): the reaction significantly affects
proton-rich ejecta ($Y_e \approx 0.50$) but has little impact on
neutron-rich ejecta ($Y_e \approx 0.496$), where lower free-
proton abundances suppress reaction flow. This reconciles conflicting results from past sensitivity studies.
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All authors R.S. Sidhu, Y. Luo, C. Sarma, M. Wiescher, X. Xu
Chaotic Dynamics · Cross-listed from eess.SY
A (Purely) Graph-Theoretic Approach to Synchronization of Nonlinear Dynamical Networks
Aandrew Baggio Sahaya Arokiadoss and G. Arunkumar
Synchronizing nonlinear dynamical networks typically requires solving
matrix inequalities or detailed system models, which fail for large networks. This paper offers a simple fix : a purely graph-theoretic framework using only a single Lipschitz-like bound on the dynamics. Coupling strengths are computed directly from the digraph, bypassing inequality solvers entirely. The method succeeds where existing approaches encounter infeasibility due to connectivity patterns. It examines only $n-1$ directed paths per strongly connected component versus $\frac{n(n-1)}{2}$ undirected paths before, achieving $O(n^3)$ complexity. Results show network connectivity can be exploited to synchronize a large class of nonlinear dynamical networks.
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Quantum Physics
On the Expressive Power of the Transverse-Field Ising Model for Graph Learning
Mehdi Djellabi and Louis-Paul Henry
We study the
quantum evolution induced by graph-indexed Ising
Hamiltonians as a source of structural signal for graph learning. Graph
automorphisms preserve
symmetries of the
Hamiltonian, and these
symmetries constrain the
quantum evolution in a way that turns time-dependent local measurements into informative probes of graph structure. Leveraging this idea, we introduce QDAGer, a
quantum-inspired graph-pair
Transformer that injects
quantum-dynamical features from time series of node occupations and connected two-point correlators directly into the
attention mechanism. We apply QDAGer to learning Graph Edit Distance (GED), an NP-hard similarity measure, using either a direct permutation-invariant
embedding discrepancy or an
alignment-based surrogate loss. Experiments on multiple GED
benchmarks under different edit cost settings show that the proposed dynamical features provide a stronger inductive bias than classical structural alternatives under the same training protocol. In addition, we report ablations where the dynamical signal is replaced by standard random-walk and heat-kernel features while keeping the architecture fixed, highlighting that the gain comes from the injected dynamics rather than model capacity alone.
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Superconductivity
Bridging ambient- and high-pressure superconductivity in La$_2$LnNi$_2$O$_7$ films
Motoki Osada, Chieko Terakura, Shusaku Imajo et al. (+9 more)
The discovery of high critical-temperature $T_{\mathrm{c}}$ superconductivity near 80 K in
bilayer nickelates under high pressure has sparked extensive studies. While superconductivity exceeding 40 K was subsequently discovered at ambient pressure in compressively strained films, the relationship between ambient- and high-pressure regimes remains an open question. Here we present a systematic investigation of superconductivity in compressively strained La$_2$LnNi$_2$O$_7$ films (Ln = lanthanides) at ambient and high pressures. The normal-state resistivity at ambient pressure, revealed by suppressing superconductivity with
magnetic fields of 59 T, tends toward $T^2$ behaviour. Under high pressure in a cubic-anvil
cell, $T_{\mathrm{c}}$ was enhanced from 41-42 K at ambient pressure to 67-73 K at 16 GPa. On the other hand,
lattice compression induced by Ln substitution, which may mimic effects of pressure, lowers $T_{\mathrm{c}}$. In both cases, $T_{\mathrm{c}}$ correlates with the
evolution of normal-state transport between $T^2$ and $T$-linear behaviour, offering insight into the interplay between
lattice structure and superconductivity in
bilayer nickelates.
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All authors Motoki Osada, Chieko Terakura, Shusaku Imajo, Jean-Baptiste Morée, Akiko Kikkawa, Masamichi Nakajima, Hsiao-Yi Chen, Yusuke Nomura, Koichi Kindo, Ryotaro Arita, Yoshinori Tokura, Atsushi Tsukazaki
Materials Science
Active learning molecular beam epitaxy of complex quantum materials
Raghutheja Bollampally, Soumya Sankar, Yuqi Qin et al. (+1 more)
The integration of machine learning (ML) into materials science offers a transformative pathway toward fully autonomous synthesis workflows. For precise thin-film deposition techniques like molecular beam epitaxy (MBE), this automation is critical to overcome the time-consuming, manual
navigation of high-dimensional thermodynamic phase spaces. Existing approaches for ML-assisted thin film growth predominantly rely on continuous
Bayesian optimization (BO) models that assume smooth parameter landscapes. Consequently, they struggle to capture the abrupt crystallographic phase boundaries and narrow growth windows inherent to binary
quantum materials. Here, we demonstrate an active learning protocol based on Sequential Model-Based Optimization (SMBO) designed specifically for the closed-loop MBE of such compounds. To overcome the limitations of continuous models while retaining the efficient exploration-exploitation logic of traditional BO, we combine a random forest surrogate model capable of capturing highly non-linear phase transitions and thermodynamics constraints of the growth process with an expected improvement function to predict optimum growth parameters. We apply this combined SMBO framework to the MBE of the topological Weyl ferromagnet Fe$_3$Sn, which exists as a metastable line compound. Using a small initial training set of fewer than twenty growth iterations, our active learning loop rapidly navigates a complex optimization landscape to identify an optimum growth window bounded by sharp transitions. Within only four active learning iterations, the absolute predictive error is halved to $\approx10\%$. This data-efficient framework paves the way for the autonomous discovery and thin-film synthesis of functional
quantum materials.
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All authors Raghutheja Bollampally, Soumya Sankar, Yuqi Qin, Berthold Jäck
Instrumentation and Methods for Astrophysics
The Roman Coronagraph Community Participation Program: Using the Zernike wavefront sensor for a full characterisation of the Roman Space Telescope and the Coronagraph Instrument
Arthur Vigan, Alexis Bidot, Vincent Chambouleyron et al. (+4 more)
The Roman Space
Telescope Coronagraph Instrument (CGI) will demonstrate a series of technologies and techniques to enable the direct detection of reflected-light
planets with space-based observatories. Among the several available observing modes and coronagraphic devices embarked in CGI, there is the transmissive dual-path Zernike wavefront sensor (ZWFS) that could be used to directly measure optical aberrations in the system. The dual-path ZWFS is currently unsupported, but in this work we advocate for the commissioning of this unique observing mode. We investigate the sensitivity of the ZWFS using CGI simulator and other tools developed and supported by the Roman community participation program (CPP). This type of analysis is crucial for understanding the stability of the Roman observatory and to prepare the path towards HWO.
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All authors Arthur Vigan, Alexis Bidot, Vincent Chambouleyron, Garreth Ruane, Laurent Pueyo, Mamadou N'Diaye, Kjetil Dohlen
High Energy Physics (Phenomenology)
Bound-state spectra of $\chi_{cJ}$ in finite nuclei and the universal pattern of mass levels
Tian-Le Gao, Ze-Hua Zhang and Xiang Liu
In this work, we investigate possible $\chi_{cJ}$–
nuclear bound states with $J=0,1,2$ using in-medium mass shifts generated by virtual $D^{(*)}\bar{D}^{(*)}$ loops within an unquenched framework. The resulting $\chi_{cJ}$–
nucleus potentials are constructed in the local density approximation, and the bound state spectra are calculated for $^{12}{\rm C}$, $^{16}{\rm O}$, $^{40}{\rm Ca}$, $^{90}{\rm Zr}$, $^{197}{\rm Au}$, and $^{208}{\rm Pb}$. Bound states are obtained for all systems considered. The $\chi_{c0}(1P)$ and $\chi_{c1}(1P)$ spectra are nearly degenerate, whereas the larger in-medium mass shift of $\chi_{c2}(1P)$ leads to deeper binding. Although the absolute bound state energies depend appreciably on the cutoff parameter, the energy differences relative to the $1s$ level are considerably less sensitive to it and exhibit a regular pattern that decreases approximately as $A^{-2/3}$ with increasing
nuclear mass number. A cosh-type potential with a common
nuclear geometry provides a compact description of these spectra. The predicted bound-state structures and level-spacing systematics could be investigated in future high-statistics near-threshold photoproduction experiments at the upgraded JLab facility.
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High Energy Astrophysical Phenomena
The initial evolution of SN 2011dh: The importance of inhomogeneities
Claes-Ingvar Bjornsson
SN 2011dh is rather unique in that it offered detailed observations of the initial phase in the
radio as well as optical regimes. This makes possible a comparison between models used to deduce properties of the outer envelope of the
supernova ejecta. It is shown that a consistent description suggests the forward shock to have started in the piston phase with constant velocity, and only later, around 50 days, transitioned to the standard model, which is independent of initial conditions. In addition, observations imply that the
radio source is inhomogeneous with a covering factor of, approximately, 50%. It is emphasised that the deduced properties of the synchrotron source are very sensitive to the presence of inhomogeneities; for example, a covering factor of 50% increases the ratio of the energy densities of relativistic electrons and
magnetic field by several orders of magnitude as compared to a homogeneous source. The shallow density gradient in the envelope causes substantial deceleration of the forward shock. This is used to argue that the
magnetic field strength scales inversely with radius rather than inversely with time; this is similar to SN 1993J.
Attention is also drawn to the similarities between the flat spectra of compact, extragalatic
radio sources and the
evolution of
radio supernovae; e.g., the scaling of the
magnetic field and the constant brightness temperature.
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Cosmology and Nongalactic Astrophysics
eROSITA cosmology with galaxy groups: Hot gas budget out to the virial radius
H. Khalil, A. Finoguenov, D. Eckert et al. (+4 more)
Non-gravitational processes that expel hot gas beyond the virial regions of groups and clusters of
galaxies, known collectively as baryonic feedback, play a key role in reshaping the matter distribution of the Universe on Mpc scales. We use eROSITA observations of a complete sample of 25
galaxy groups selected from the first public release of the eROSITA-DE data (eRASS1) and identified with the Two Micron
Redshift Survey optical group catalogue (2MRS). We extract and fit surface brightness (SBx) profiles and present hot gas mass and hot gas fraction profiles out to $R_{200}$. We perform a
Bayesian analysis of $M_{\mathrm{gas}}-M_{\mathrm{tot}}$, $L_{\mathrm{X}}-M_{\mathrm{tot}}$, and $L_{\mathrm{X}}-M_{\mathrm{gas}}$ relations, taking into account the aperture covariance effects. At $R_{500}$, we report uniformly flat SBx profiles with a mean $\beta$ parameter of $0.38 \pm0.04$, steepening to $\beta = 0.76\pm0.19$ beyond $R_{500}$. We measure a sub-
cosmic hot gas fraction at the median mass of our sample $M_{500} = 2.54\times10^{13}M_{\odot}$ of $ f_{\mathrm{gas,500}} = 4.32\pm0.42\%$. Similarly, at $R_{200}$ and the median mass $M_{\mathrm{ 200}} = 3.69\times10^{13}M_{\odot}$, we obtain $f_{\mathrm{gas,200}}=5.78\pm0.69\%$. Our $f_{\mathrm{gas}}-M_{\mathrm{tot}}$ and $L_{\mathrm{X}}-M_{\mathrm{tot}}$ relations show significant deviations from the predictions of the strong feedback variants of the FLAMINGO simulation ($2.5\sigma$ to $8.0\sigma$ tension), while fiducial FLAMINGO and BAHAMAS provide the closest match to our measurements. Using our measured
baryon fractions and the SP(k) model, we infer a $10\%-15\%$ reduction in the matter power spectrum at $k = 5\ h\ \mathrm{Mpc}^{-1}$ relative to a dark matter-only universe, in agreement with fiducial FLAMINGO and BAHAMAS, while revealing a growing tension on smaller scales with the strong feedback variants.
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All authors H. Khalil, A. Finoguenov, D. Eckert, R. Seppi, E. Tempel, L. Lovisari, F. Gastaldello
Solar and Stellar Astrophysics
A Catalog of Homogeneously Derived Stellar Parameters for Spectroscopic Survey Stars
Stefan Y. Stefanov, Evelina Zaharieva, Djemma Ruseva et al. (+9 more)
Uniformly derived
stellar parameters are vital for
exoplanet demographic studies because they directly influence the inferred planetary masses, radii, and bulk densities. This study presents a new homogeneous catalog of physical
stellar parameters for 5533 single
stars observed by the HARPS, HIRES, and CARMENES radial-velocity (RV) surveys.
Stellar parameters are determined using a
Bayesian framework with two independent sets of
stellar evolutionary models: MIST and PARSEC, using published spectroscopic parameter estimates and catalog values as priors. The resulting
stellar effective temperatures, masses, radii, and surface gravities are compared and evaluated for consistency with
stellar parameters listed in major
exoplanet catalogs. While our estimates show consistency with those listed in external catalogs, we identify method-dependent differences in
stellar masses for low-mass and pre-main-sequence
stars, as well as G and K
giants, where isochrone-based solutions may be affected by age-mass degeneracies. For low-mass
stars such as M-
dwarfs, the catalog provides masses derived from established mass-luminosity empirical relations, which tend to be more reliable. This catalog provides the largest uniformly derived
stellar reference sample for Doppler survey targets and also illustrates the applicability and limitations of
stellar-parameter homogenisation methods for future RV
exoplanet demographics studies.
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All authors Stefan Y. Stefanov, Evelina Zaharieva, Djemma Ruseva, Milen Minev, Denitza Stoeva, Volker Perdelwitz, Lev Tal-Or, Jerusalem T. Teklu, Elena Vchkova Bebekovska, Desislava Antonova, Vladimir Bozhilov, Trifon Trifonov
Cosmology and Nongalactic Astrophysics
Large eROSITA X-ray sources as 2MRS galaxy groups
A. Finoguenov, R. Seppi, D. Eckert et al. (+5 more)
We aim to exploit the large area coverage, good sensitivity, and low instrumental background of eROSITA to detect the faint surface brightness emission of
galaxy groups from the Two Micron All Sky Survey
Redshift Survey (2MRS). Using the data from eROSITA-DE Data Release 1, including images, exposure maps, and local background maps, we performed a wavelet decomposition of image mosaics in the 0.6–2.3 keV band at angular scales of 1/8-16'. We adopted 8-16' scales for source detection and 2-4' scales to improve catalog purity. A novel identification method based on the ranked partial Hausdorff distance fully exploits the X-ray image and group membership information. Random catalogs were used to control match purity, and the identification threshold was chosen to maximize the catalog size at a fixed purity. {We present a catalog of 619 X-ray
galaxy groups with 80% purity, and define subsamples with 90% and 97% purity. Bright sources closely match the AXES-2MRS catalog (which is based on ROSAT All Sky Survey data analysis on spatial scales of 12-24'). The X-ray luminosity function of our groups agrees with previous studies down to 5.e41 erg/s. Using dynamical mass estimates, we find that the X-ray counterpart completeness for groups with >=4 members exceeds 60% for masses >2e13 Msun. We modeled the 2MRS group catalog and justify the inclusion of two-member groups in the identification. This study demonstrates that large X-ray sources on spatial scales relevant for cosmological studies of baryonic distributions can be reliably detected and identified using nearby
galaxy group catalogs.
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All authors A. Finoguenov, R. Seppi, D. Eckert, H. Khalil, J. Kosowski, E. Tempel, F. Gastaldello, L. Lovisari
General Relativity and Quantum Cosmology
Thermomechanics of Horndeski Scalar Hair with Spacelike Gradients
Marcello Miranda, Marco Sebastianutti and Andrea Giusti
We develop a thermomechanical framework for viable Horndeski scalar hair with spacelike scalar-field gradients. Adapting the $(1{+}1{+}2)$ formalism to the scalar configuration, we apply the effective imperfect-fluid decomposition to the model and derive general results governing its thermomechanical properties. Specifically, we infer the constitutive relations for the effective medium, in both observer-dependent and observer-independent approaches, thereby identifying the conditions under which the scalar hair admits thermomechanical interpretations. The observer-dependent approach leads to an analogy with anisotropic media characterized by a preferred spatial direction, whereas the observer-independent view shows similarities with layered media. The general results are then specialized to static, spherically symmetric configurations with scalar hair depending solely on the areal radius. Interestingly, this scenario allows us to connect the thermomechanical framework with the Tolman–Ehrenfest criterion for thermal
equilibrium.
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History and Philosophy of Physics
Astrobiology and the Transformation of Scientific Epistemology
Kristina Šekrst
Astrobiology occupies an unusual position within the philosophy of science. Confronted with the n = 1 problem - having only a single example of life to study - it attempts to investigate life beyond Earth while relying entirely on Earth's biosphere as its reference point, a constraint that creates unique epistemic challenges. Unlike traditional sciences with clear predictive frameworks, astrobiology operates as what we might call a transient science: a discipline functioning without foundational certainties, relying predominantly on abductive
reasoning, and confronting hypotheses that may remain untestable for decades. It is, in essence, a science of absence - of evidence, certainty, and analogy - where progress lies in refining conceptual and experimental tools to recognize unfamiliar forms of life. This positions astrobiology alongside emerging fields like artificial intelligence and cognitive science within a broader transformation of how scientific knowledge is constructed when dealing with phenomena that transcend direct empirical access.
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High Energy Physics (Phenomenology)
VERaiPHY – Validation & Evaluation for Robust AI in PHYsics
Gaia Grosso, Ramon Winterhalder, Lydia Brenner et al. (+2 more)
Modern machine learning is leading to substantial gains in precision, flexibility, and computational efficiency in fundamental physics. Statistical validation, uncertainty quantification, and robustness assessment are less systematically addressed. The VERaiPHY initiative (Validation & Evaluation for Robust AI in PHYsics) is a series of articles developed within the PHYSTAT programme, aimed at establishing statistical standards for the development, evaluation, and deployment of ML techniques. Each article focuses on a specific methodological domain from a statistics perspective and clarifies statistical questions, tests, and the interpretation of results. This opening article establishes the probabilistic, statistical, and machine learning foundations that the later contributions assume, together with the notation used throughout.
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All authors Gaia Grosso, Ramon Winterhalder, Lydia Brenner, Louis Lyons, Tilman Plehn
Quantum Physics · Cross-listed from eess.SP
M-QAM MIMO Maximum-Likelihood Detection with QAOA: ML-Rate Offline Angle Design and Correlated Infinite-Size Spin-Glass Models
Burhan Gülbahar
The
quantum approximate optimization
algorithm (QAOA) targets NP-hard maximum-likelihood (ML) detection in multiple-input multiple-output (
MIMO) systems. Existing $M$-ary quadrature amplitude modulation (M-QAM) detectors design angles by expected Ising energy: online per instance, warm-started, or ramped, while train-once designs remain B/QPSK-only or block-local, leaving M-QAM without a size-scalable
benchmark. Their infinite-size
spin-glass theory assumes independent disorder, matching the retained covariances at B/QPSK but not M-QAM's correlated couplings and fields. We develop a correlated infinite-size multi-species
spin-glass framework whose covariance-matched evaluators make that energy an offline objective with a size-scalable
benchmark. In addition, the ML rate, the exponential rate of sampling the ML string, is for the first time exploited for QAOA angle design in
MIMO detection. The energy evaluator is $q$-free at $O(p\,4^p)$ cost while the ML rate transfers angles from a fixed $q_{\rm ref}$-
qubit reference. Tests reach 4096-QAM, 128
antennas, $p=30$ and per-symbol SNR 0-45 dB. In simulations, ML rates fall as a power law $r_0\,p^{-\alpha}$, with larger exponents for the sampling design, which tracks exact ML at $5\times5$ 16-QAM (0-20 dB) and $3\times3$ 64-QAM (8-28 dB) while its bit-error rate (BER) advantage widens with SNR to two orders of magnitude. The approach points toward near-optimum decoding on deeper noiseless fault-tolerant
quantum (FTQ)
circuits.
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Materials Science
Vacancy-Driven Electronic Reconstruction in Monolayer PtSe$_2$: Formation Thermodynamics and Charge States
Xiwen Gai, Jingang Wang and Tianxing Ma
Layered transition metal dichalcogenides are an important platform for two-dimensional materials, where the inevitable intrinsic defects provide new degrees of freedom for tuning their physical properties. Based on first-principles calculations, this work systematically investigates the formation energies, charge states, and electronic structural characteristics of V$_{\mathrm{Pt}}$, V$_{\mathrm{Se}}$, and composite vacancies in monolayer PtSe$_2$. The results indicate that while vacancy formation energies are highly sensitive to chemical potentials, the V$_{\mathrm{Se}}$ structure consistently exhibits the lowest formation energy. The charge defect calculation reveals the stable charge state intervals of V$_{\mathrm{Se}}$ and V$_{\mathrm{Pt}}$ as a function of the
Fermi level, thus describing the
evolution of the charge states of intrinsic vacancies at different electronic chemical potentials. Climbing Image Nudged Elastic Band calculations reveal high migration barriers for V$_{\mathrm{Se}}$ and V$_{\mathrm{Pt}}$, indicating strongly hindered vacancy
diffusion at room temperature, while short Ab Initio Molecular Dynamics simulations confirm the absence of immediate structural collapse within the simulated time window. Optical property calculations indicate that point defects significantly alter the dielectric response of monolayer PtSe$_2$ and generate new low-energy absorption channels associated with in-gap defect states. These findings provide new insights into defect-mediated electronic and optical property modulation in monolayer PtSe$_2$, offering guidance for its potential device design.
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Materials Science
Atomistic Structure Generation and Neural-Network Screening of Hard Carbons to Identify High-Capacity Sodium Storage
Harry Mclean, Aiden Daniel Emery, Theodore Thomas Walton et al. (+2 more)
Hard carbons are established anodes for lithium-ion batteries and leading candidates for sodium-ion batteries, yet their electrochemical performance is governed by a heterogeneous network of graphitic domains, defects, and nanopores that conventional atomistic methods cannot model at the required length scales. We combine universal machine-learned interatomic potentials with the RAFFLE structure-generation framework to construct 13,096 realistic hard carbon models containing up to 4,378 atoms, matching experimentally measured densities, porosities, and sp$^2$/sp$^3$ bonding fractions. Explicit sodium intercalation of representative structures reproduces the characteristic sloping-to-plateau voltage profiles, revealing that capacity increases with decreasing carbon density and increasing porosity. To screen the full library, we train a lightweight neural-network surrogate that predicts capacity directly from the host using frozen universal-potential descriptors augmented by
geometric void features. The surrogate identifies high-capacity candidates exceeding 800 mAh g$^{-1}$, which are validated by full intercalation calculations. This scalable framework links hard carbon microstructure to sodium-storage performance and provides atomistic design principles for high-capacity anodes. More broadly, the workflow enables systematic exploration of synthesis-dependent amorphous microstructures, including precursor chemistry, pyrolysis, heteroatom doping, and pore engineering, providing a route toward atomistically informed hard carbon design.
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All authors Harry Mclean, Aiden Daniel Emery, Theodore Thomas Walton, Ned Thaddeus Taylor, Steven Paul Hepplestone
Optics
Neutron Interferometers from Stacked Holographic Photopolymer Gratings
Saba Shams-Lahijani, Tobias Jenke, Juergen Klepp et al. (+2 more)
Long-wavelength
neutron interferometry using discrete optical elements is notoriously challenging due to stringent
alignment and stability requirements. Here, we introduce a monolithic double-Laue
neutron interferometer fabricated from a stack of commercial Bayfol HX photopolymer films. By recording
holographic gratings simultaneously in multiple layers, we create a robust device that is inherently aligned, bypassing traditional stability problems. We demonstrate the device's function by observing the characteristic interference fringes in the diffracted intensity of both light and very cold
neutrons. The interferometer is then used to perform in-situ characterization of the
neutron beam's spectral profile, demonstrating its utility as a compact spectrometer. Our work establishes stacked
holographic gratings as a simple, versatile, and powerful platform for matter-wave interferometry and metrology.
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All authors Saba Shams-Lahijani, Tobias Jenke, Juergen Klepp, Christian Pruner, Martin Fally
Soft Condensed Matter
Hydrodynamic Mode Coupling: Effects of density variations in nanoscale channel flows
L. Heitmeier and J. S. Hansen
We apply a modal framework for investigating the effect of density variations on
gravity-type driven flows at the nanoscale. Using eigenfunction decomposition of the density and acceleration fields, each shear-pressure mode is separated into a homogeneous contribution and an inhomogeneous contribution determined by the
Fourier amplitudes of the density and applied acceleration. This decomposition provides a direct means of identifying how density variations and external forcing couple and govern the flow behavior. We first revisit the Poiseuille flow and show that for channel heights larger than the characteristic intermolecular distance the homogeneous contribution dominates the long wave length (small wave vector) response, consistent with previous simulation results. In contrast, for sinusoidally driven flow, selective excitation of acceleration modes can produce the opposite behavior, with the inhomogeneous contribution dominating the long wave length response. The results show that the effect of the density variations depends on the specific flow; specifically the detailed mode coupling between the acceleration and density fields. The framework presented here provides a direct systematic approach for understanding and predicting the flow depending on the applied acceleration.
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Plasma Physics
Influence of the ectonic emission mechanism on the collisionless expansion of a multicomponent cathode plasma
Vasily Yu. Kozhevnikov
In this paper, the authors delve into the collisionless kinetic theory of planar
vacuum diodes to investigate how a pulse-periodic (ectonic) cathode
plasma emission mechanism influences the non-thermal expansion of the cathode
plasma and "anomalous" ion acceleration. Another aspect explored in this paper is how pulse-periodic emission affects the comparative dynamics of motion of multi-charged ions from the cathode material. Using kinetic theory, we conclude that the ectonic emission mechanism affects both the macroscopic picture of
plasma expansion and the intricacies of electric potential redistribution over one complete emission period.
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Biological Physics
An information-theoretic perspective on feed-forward loop abundances in transcriptional networks
Mintu Nandi, Sudip Chattopadhyay and Suman K Banik
In the transcriptional networks of Escherichia coli and Saccharomyces cerevisiae, the eight feed-forward loop (FFL) motifs occur at markedly different frequencies. Although previous studies have linked the abundant C1- and I1-FFLs to specific dynamical functions, a common account of the broader pattern is lacking. To address this gap, we adopt an information-theoretic approach. An FFL transmits information through two paths that share an input and converge on an output, suggesting that their interaction may contribute to differences among motifs. To investigate this, we decompose input-output mutual information (MI) into pathway MI and interference MI (IMI). Here, the pathway MI collects the contributions of individual pathways, whereas IMI identifies the contribution that arises from their interference. We find that within a representative parameter regime, IMI values of FFLs produce a hierarchy that closely resembles the abundance ordering in E. coli, whereas total and pathway MIs do not. Motivated by this observation, we perform constrained optimization that identifies parameter regimes compatible with abundance-like targets for both S. cerevisiae and E. coli. We relate the optimized IMI hierarchy to pathway interference strength and local pathway sensitivities to understand the underlying biophysical origin. Our framework thus probes the correspondence between pathway interference, information transmission, and motif-abundance hierarchies.
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Optics
Real-time estimation of the transmission matrix of an atmospheric channel
Cade Peters, Raphael Bellossi, Douglas McDonald et al. (+3 more)
Optical wavelengths have received significant
attention in free-space channels and are vital for applications in communications, imaging and sensing. Their widespread implementation is motivated by a variety of factors including improved bandwidths, increased security and higher energy efficiency. However, these advantages cannot be fully brought to bear in real-world scenarios due to the deleterious effects of atmospheric
turbulence. Induced by small temperature and pressure fluctuations in the environment that vary rapidly in space and time, these effects cause significant power losses which decrease SNR, induce severe crosstalk in communication links, and greatly limit resolution of long-range imaging systems. To overcome this, we numerically and experimentally investigate the reconstruction of the transmission
matrix of a time-evolving atmospheric channel with a real-time recursive optimization routine. We demonstrate that this estimation technique is able to keep up with the
evolution of the channel and enables a significant improvement of communication-relevant quantities such as the coupling of the received light into a single-mode fiber while notably reducing the probability and duration of power outages, even in strong
turbulence. Our results have immediate applications in free-space optical communication in both the classical and
quantum regimes.
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All authors Cade Peters, Raphael Bellossi, Douglas McDonald, Andrew Forbes, Szymon Gladysz, Giacomo Sorelli
Soft Condensed Matter
Effect of Convection Rolls in Motility-Induced Phase Separation of Active Janus Particles
Poulami Bag
We numerically study motility-induced phase separation of active particles in two-dimensional convection rolls. We analyse local packing-fraction distributions, density fluctuations, the corresponding phase diagrams, and diffusivity curves to characterise the interplay between self-propulsion, global packing fraction, and advection strength. In the weak-flow regime, the system exhibits phase separation characterised by bimodal density distributions, slowly decaying density fluctuations, and a sharp reduction in diffusivity. Increasing advection suppresses clustering by enhancing particle transport and reducing trapping, leading to a shift in the critical self-propulsion velocity for motility-induced phase separation and a shrinkage of the spinodal region. Beyond the intuitive suppression of clustering by weak-flow advection, our results reveal several non-trivial phenomena including a reentrant phase behaviour where extremely high self-propulsion hinders motility-induced phase separation by facilitating particle escape from dense regions. We also observe that the density distributions strongly depend on roll periodicity. These findings demonstrate that convection rolls provide an effective means to control non-
equilibrium collective behaviour in active matter.
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Earth and Planetary Astrophysics
Radar observations of Europa in 2011-2024: New insights into radar scattering properties
Tunhui Xie, Jean-Luc Margot, Sebastiano Padovan et al. (+5 more)
Three of Jupiter's Galilean satellites - Europa, Ganymede, and Callisto - are of particular scientific interest due to their icy shells and suspected subsurface oceans. However, the radar properties of the icy satellites have not been measured since observations in 1987-1991. Because
radio waves can penetrate pure ice to considerable depths, radar observations provide a powerful means of characterizing the subsurface properties of the icy shells of these satellites, offering key insights into planetary
evolution. We have observed Europa using the Goldstone 3.5-cm
Solar System Radar and the Green Bank
Telescope (GBT) in 2011-2024 in order to address a longstanding gap in the radar studies of these moons. In this paper, we present the most longitudinally comprehensive set of radar measurements of Europa to date and describe its disk-integrated radar properties. On the basis of monostatic Goldstone data, we find radar albedo values in two circular polarizations of $\hat\sigma_{\rm OC}$ = 0.92 $\pm$ 0.11 and $\hat\sigma_{\rm SC}$ = 1.35 $\pm$ 0.13 (unweighted mean and root-mean-square dispersion), with a circular polarization ratio of $\mu_c$ = 1.44 $\pm$ 0.12 (weighted mean and root-mean-square dispersion). Values obtained bistatically at the GBT are similar. The $\mu_c$ values suggest a leading-vs-trailing side dichotomy in radar scattering properties on Europa. Our results support the existence of the coherent backscatter opposition effect (CBOE), currently the most widely accepted physical mechanism that explains the unusual radar scattering properties of the icy Galilean satellites. Because we observed Europa with a bistatic configuration, we can place a lower bound on the width of Europa's CBOE peak equal to 36 arcsec, which provides an upper bound of 32 m ($\sim$1000 wavelengths) on the penetrating depth of X-band radar waves at Europa.
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All authors Tunhui Xie, Jean-Luc Margot, Sebastiano Padovan, Frank Ghigo, Will Armentrout, Joseph S. Jao, Jon D. Giorgini, Joseph Lazio
Quantum Physics
Universal quantum theory from dynamical consistency
Chiara Marletto and Vlatko Vedral
We argue for the universality of
quantum theory using a dynamical consistency argument, within a specific
Hamiltonian setting. We analyse two different types of coupling between simple
quantum harmonic oscillators. Each illustrates an aspect of the free and interacting
quantum fields and shows the inadequacy of semiclassical models. In particular, we establish that requiring the canonical
algebra to be preserved under joint
unitary dynamics rules out specific hybrid classical-
quantum models. We apply our
reasoning to the gravitational field in the linear regime, coupled to the quantised electromagnetic field and, separately, to quantised matter. We conclude with a comparison to DeWitt's analysis of
quantum measurement, in which the apparatus, if classical, must be at least
stochastic to preserve the Heisenberg Uncertainty Principle. We also note that
stochastic models are inconsistent with the strict version of conservation principles, even if they comply with a probabilistic (on average) conservation.
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High Energy Physics (Phenomenology)
Lei Yang, Wen-Hao Yao, Yu-Kun Song et al. (+1 more)
We investigate the polarization correlation of back-to-back
gluon pairs in unpolarized $pp$ collisions and compute their density
matrix. For
gluon pairs produced through $q\bar{q}$ annihilation, the linear polarization correlation is sizable, even reaching unity when the final-state
gluons are emitted perpendicular to the beam direction in the $q\bar{q}$ rest frame. Combining with the fact that their helicity remains maximally correlated across different scattering angle, the
gluon pair system thus resides in a maximally entangled Bell state in this configuration. In contrast, for the $gg\to gg$ channel, both the helicity and linear polarization correlations are considerably suppressed, producing a separable state. Nonetheless, it still retains an appreciable linear polarization correlation of about $11\%$ at central scattering in unpolarized collisions. The linearly polarization correlation of the back-to-back
gluon pair can further increase when the incoming
gluons are circularly polarized. Employing the anisotropy of energy correlators, we demonstrate that the linear polarization correlation of
gluon pairs can be extracted from the $\cos 2\Delta\Phi$ modulation.
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All authors Lei Yang, Wen-Hao Yao, Yu-Kun Song, Shu-Yi Wei