Strongly Correlated Electrons
Landscape of incompressible crystals of hard-core bosons on the square-kagome lattice
Pratyay Ghosh
We investigate a hard-core
boson model on the square-kagome
lattice using hierarchical mean-field theory beyond the conventional unit-
cell description. We show that the conventional description of the square-kagome
lattice based on its smallest unit
cell does not fully capture the hierarchy of incompressible states supported by the
lattice, but only captures the two compact-localized-state-based phases at densities $5/6$ and $2/3$. Within our approach, we reproduce these previously established phases and uncover additional incompressible states enabled by enlarging the variational cluster. Among these, the $\rho=3/4$ phase is found to be particularly robust, which, through the Matsubara-Matsuda mapping, corresponds to a half-magnetization plateau in the
spin-$1/2$ XXZ model. We further apply our approach to two experimentally relevant square-kagome compounds using exchange parameters obtained from first-principles calculations. The calculated magnetization processes are in good agreement with available experimental results and predict additional plateau structures in these materials.
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Astrophysics of Galaxies
Optical Counterparts of MeerKLASS L-band and UHF-band surveys
M. Klein, S. Mangla, J. Mohr et al. (+7 more)
Context: Wide-area
radio continuum surveys require reliable optical and infrared counterpart identification, but high optical source densities and extended or multi-component
radio morphologies make this challenging. Aims: We present optical and infrared counterpart catalogs for MeerKLASS L-band and UHF-band on-the-fly continuum sources using KiDS DR5 and DESI Legacy Imaging Surveys DR10 (LS DR10), including counterpart probabilities,
redshifts, and host-
galaxy properties. Methods: We developed the
Stellar-mass Enhanced Density Association (SEDA) method, an empirical framework that compares candidate densities around
radio positions with those in a position-displaced control catalog. For
galaxies we use positional offset,
stellar mass, and
redshift;
quasar candidates are treated separately using offset and mid-infrared selection. A second-pass search associates multi-component
radio sources with common hosts. Results: In the L-band survey, we identify 20,400 KiDS-based counterparts with $P_{\rm true}>0.5$, corresponding to 66% of L-band sources within the KiDS footprint. In the UHF-band survey, we identify 61,633 LS DR10 counterparts, corresponding to 81% of the
radio sources. Spectroscopic
redshifts are available for 22% and 44% of the L-band and UHF-band counterparts, respectively. The
redshift distributions show low-
redshift star-forming
galaxies, intermediate-
redshift radio galaxies, and a high-
redshift tail dominated by
quasars. SEDA also recovers rare
radio-loud
quasars, including QSO J2318-3113 at $z=6.44$ and UHF_DR1 J+111111.8+053626.6 at $z=5.24$. Conclusions: SEDA provides a data-driven route to counterpart identification for wide-area
radio surveys with complex source morphologies. The catalogs enable future MeerKLASS studies of
radio source populations, host-
galaxy demographics, and rare high-
redshift radio quasars.
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All authors M. Klein, S. Mangla, J. Mohr, S. Chatterjee, K. Grainge, S. Paul, M. G. Santos, O. M. Smirnov, C. Tasse, L. Wolz
Materials Science
Jsymm: A Python package for symmetry analysis of exchange tensors in magnetic Hamiltonians
A.S. Sergeev and S.V. Streltsov
Symmetries of a
crystal often restrict its physical properties. In particular, they determine possible forms of the tensors that describe interatomic exchange interaction, which governs a wide range of
magnetic phenomena. Computationally demanding first-principles calculations of the exchange tensors can be greatly simplified by taking the
symmetry constraints into account. Here, we present Jsymm, a Python package that derives the most general
symmetry-compatible form of the exchange tensors directly from the crystallographic data. For any bond formed by
magnetic ions, Jsymm produces the tensors of the Dzyaloshinskii-Moriya and anisotropic Heisenberg exchange interaction in symbolic form, as well as the tensors for all other bonds related to it by
symmetry. This reduces the number of independent model parameters, dramatically lowering the computational cost of the ab initio calculations and preventing unphysical results arising from
symmetry violations. The package accepts standard CIF files and provides a web interface in addition to an interactive text mode and a Python library. We demonstrate its utility on La$_2$CuO$_4$ and $\alpha$-Fe$_2$O$_3$, reproducing known
symmetry constraints and revealing additional relations between components of the exchange tensors of different bonds.
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High Energy Astrophysical Phenomena
Phase-resolved QPO Analysis of GX 339-4: Improved Technique and Consistent Behaviors between QPOs and Broadband Noise
Jin Qin, Hua Feng, Liang Zhang et al. (+5 more)
The nature of low-frequency quasi-periodic oscillations (QPOs) in black hole X-ray binaries remains unclear, and their relationship with the accompanying broadband noise (BBN) is still under debate. Here, we propose an improved variational mode decomposition (VMD) technique. Compared with the original
algorithm that requires iterative, case-by-case parameter tuning, the new
algorithm automatically and consistently determines the relevant VMD parameters based on the QPO central frequency and width measured from the power spectral density (PSD). This enables a more robust phase determination for QPOs and can also be applied to the study of BBN. We found that, for low-frequency type-C QPOs without significant harmonics in the black hole X-ray binary GX 339-4, the spectral properties of the QPOs and BBN are statistically consistent with each other: (1) the
photon index is positively correlated with count rate as a function of phase, and (2) the PSD ratio spectra across different energy bands show no statistically significant QPO-like structures near the QPO frequencies, indicating that both components share the same energy dependence. These suggest that QPOs and BBN may be driven by the same physical processes. The QPO models based on
geometric modulation struggle to account for the results, while those invoking corona oscillations are favored.
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All authors Jin Qin, Hua Feng, Liang Zhang, Lian Tao, Qing-Cang Shui, Qing-Chang Zhao, Shu Zhang, Shuang-Nan Zhang
High Energy Physics (Theory)
Emergent gravitational action from non-local $T\bar T$-like deformations
Yun-Ze Li, Bo-Rui Li, Yu-Xiao Liu et al. (+1 more)
We study the gravitational effective action induced, at first order in the deformation parameter, by non-local $T\bar T$-like deformations of
quantum field theories. Using a heat-kernel formulation, we extract the local
geometric terms generated by stress-tensor two-point functions, and apply the construction to free
fermions, massive Maxwell theory, and second-order Yang-Mills theory. While the resulting coefficients are generally model dependent, conformal field theories contain a universal sector fixed by the central charge $C_T$. After regularization and renormalization, this sector yields finite, scheme-independent contributions organized into a finite set of
curvature invariants. We further analyze trace-trace deformations, for which the relevant contact terms are determined by the Weyl anomaly, and derive the corresponding finite gravitational action for a general class of minimal non-local kernels. These results provide a
quantum effective-action realization of induced
gravity in which universal conformal data determine calculable contributions to the emergent
geometric response.
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All authors Yun-Ze Li, Bo-Rui Li, Yu-Xiao Liu, Song He
Mesoscale and Nanoscale Physics
One-dimensional Dirac modes in the core of a pentagonal topological crystalline insulator nanowire
Saeed Samadi, Rafał Rechciński, Marta A. Chabowska et al. (+1 more)
We investigate the electronic band
topology of recently fabricated pentagonal IV-VI
semiconductor nanowires, which contain five radial $\{111\}$ twin planes meeting at the nanowire axis. Tight-binding calculations show that, when the bulk band structure is inverted and the twin planes in the nanowire are cationic, the spectrum contains two spatially separated helical Dirac crossings near $\overline{\Gamma}$: one localized at the core and the other at the outer surface. When the twin planes are anionic, the corresponding spectra remain gapped. The crossings originate from the hybridization of five helical channels associated with the twin-plane edges, whose odd number leaves one Kramers pair near the nanowire axis and the other at the outer boundary. Realistic multiorbital calculations for $\mathrm{Pb}_{0.4}\mathrm{Sn}_{0.6}\mathrm{Te}$ predict well-developed core and surface modes at nanowire thicknesses of approximately 50~nm and above. These results establish pentagonal SnTe-class nanowires as an experimentally accessible realization of spatially separated helical channels bound to the axial defect and the outer boundary.
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All authors Saeed Samadi, Rafał Rechciński, Marta A. Chabowska, Ryszard Buczko
Chemical Physics
Rotational spectra and de-perturbation analysis for ground state ytterbium oxide, YbO
Richard J. Mawhorter, Sean Jackson, Charles Brainin et al. (+4 more)
A combination difference analysis of
Fourier transform microwave spectroscopy (FTMW) measurements of $^{174}$YbO combined with earlier near-infrared chemiluminescence data have resulted in much improved YbO rotational and centrifugal distortion constants. These have been confirmed in a multi-isotopologue analysis of further FTMW measurements of $^{172}$YbO and $^{176}$YbO and an analysis of
nuclear-size-dependent Born-Oppenheimer breakdown effects in the molecule. Multiple excited electronic states overlap with low-lying excited vibrational levels of the electronic ground state leading to irregularities in its vibrational spacings and other previously observed electronic
manifolds. This has been modeled with a
matrix of the vibrational levels of the ground and multiple interacting states assuming Morse potentials and including electronic
Hamiltonian matrix elements mixing the states. Vibrational level overlaps were calculated numerically assuming Morse vibrational wavefunctions. The resulting de-perturbed potentials for the states inform continuing experimental and theoretical work on this and other ytterbium-containing molecules.
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All authors Richard J. Mawhorter, Sean Jackson, Charles Brainin, Trevor J. Sears, Peter F. Bernath, Philipp Buschmann, Jens-Uwe Grabow
High Energy Physics (Phenomenology)
QCD analytic coupling
I.A. Zemlyakov, I.L. Chuev and A.V. Kotikov
A brief overview of QCD analytic coupling is presented, mainly following the results obtained in [1]. An application to the pion-
photon transition form factor is demonstrated.
Materials Science
Tuning the Optoelectronics of Mixed-Semiconductors through the interplay of Quantum confinement and Stoichiometry Engineering
Kanha Ram Khator, Anupam Manna, Amlandeep Nayak et al. (+3 more)
All-inorganic cesium lead bromide (CsPbBr3) nanocrystals (NCs) have established themselves as an emerging
semiconductor for next-generation optoelectronic technologies due to their unique combination of properties, such as near unity photoluminescence
quantum yields, narrow color pure emission, and exceptional defect tolerance. Although size-dependent optical signatures of these NCs are well reported, the complexity of mixed ionic-electronic transport remains largely unexplored. In this study, we provide a comprehensive analysis of size-dependent charge transport by decoupling ionic and electronic transport dynamics through carefully designed transient current and space charge limited current measurements. By employing NCs of different sizes ranging from 5.6 nm to 11.3 nm in thin films, we provide a comprehensive understanding of
quantum confinement effects and related synthetic chemistry. Contrary to popular beliefs of
quantum confinement and band gap broadening, our results demonstrate that the smallest NCs exhibit the most efficient transport characteristics, evidenced by the lowest activation energy (hole activation energy = 78 meV) for hole transport and the highest barrier for vacancy-mediated ion migration (ion activation energy = 370 meV). This work paves a way forward for perovskite-based efficient
quantum devices, by demonstrating that moving into a strong
quantum confinement regime, a superior charge transport can be facilitated, when supported by carefully tailored stoichiometry.
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All authors Kanha Ram Khator, Anupam Manna, Amlandeep Nayak, Pravat Nayek, Prasenjit Mal, Satyaprasad P Senanayak
Strongly Correlated Electrons
Correlated topological-polarization surface states in the narrow-gap insulator FeSb2
Takahiro Iwagaki, Hideki Matsuoka, Ginta Hoshino et al. (+7 more)
Strong electron correlations and band
topology each generate rich
quantum phases, but conflicting elemental requirements have largely kept them apart. Topological polarization offers a route to unite them, producing polar surface states from bonding charge without
spin-orbit coupling and thereby extending band
topology to correlated 3d transition-metal compounds. Here we demonstrate that epitaxial thin films of the narrow-gap
insulator FeSb2 host metallic polar surface states of topological-polarization origin, governed by the strong correlations of the bulk. Nonreciprocal surface transport emerges only below the onset temperature of a correlation-driven reconstruction of the bulk Fe 3d orbital occupation, providing direct evidence of bulk-edge correspondence in a correlated topological system. Moreover, electrostatic gating drives this correlated surface across a
quantum phase transition into a
ferromagnetic or possibly altermagnetic state. Our results establish topological polarization as a design principle for correlated topological phases in a broad range of materials.
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All authors Takahiro Iwagaki, Hideki Matsuoka, Ginta Hoshino, Kanata Watanabe, Shungo Aoyagi, Shunsuke Kitou, Yuiga Nakamura, Motoaki Hirayama, Takashi Koretsune, Naoya Kanazawa
Earth and Planetary Astrophysics
Exploration of Exoplanet Atmospheres with the James Webb Space Telescope
Sasha Hinkley and David K. Sing
The James Webb Space
Telescope (JWST) is providing transformative characterization capabilities for the study of both transiting and directly imaged extrasolar
planets. Observations deep into the infrared in the form of both spectroscopy and coronagraphic imaging means that JWST is uniquely sensitive to most of the physical processes that dictate the properties of exoplanetary atmospheres. The observatory's thermal and pointing stability directly translates into the extreme photometric precision needed for exquisite transiting
exoplanet photometry, as well as highly sensitive coronagraphic observations. Over the mission's 20-25 year lifetime, roughly 10$^4$ hours will be dedicated to observations of
exoplanet atmospheres, providing a legacy data archive that will allow population-level characterization of
exoplanet atmospheres spanning terrestrial
planets, sub-Neptunes and gas
giants. This effort will also assess the prevalence of atmospheres of rocky
planets and thus the degree to which such
planets may have conditions conducive to habitability.
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High Energy Physics (Phenomenology)
Descoped and Upscoped FCC-ee Running Scenarios in the SMEFT
Eugenia Celada, Elie Hammou, Jaco ter Hoeve et al. (+1 more)
We present projections for the sensitivity to new physics of descoped and upscoped FCC-ee scenarios in the framework of the Standard Model Effective Field Theory (SMEFT). Starting from the baseline FCC-ee programme, we analyse the subsequent impact of, first, removing the top-
quark run, then reducing the beam power from 50 MW to 30 MW, and finally removing two interaction points (IPs), in all cases propagating the resulting loss in top-
quark mass precision through increased parametric uncertainties. We also analyse the possibility of a staged top-
quark run, where the top-
quark run is partially restored in case funding becomes available only at a later stage. Motivated by the trade-off between beam power and operational costs, we also consider two upscoped scenarios, either through a uniform increase in luminosity across all energy runs, or through a luminosity enhancement targeting exclusively the top-
quark run. We explore the sensitivity and limitations of each scenario and highlight in particular the complementarity between the FCC-ee projections and the (HL)-LHC measurements. By comparing the physics impact of the different running scenarios with the FCC-ee baseline, we show explicitly the importance of the top-
quark run, indicating that a substantial fraction of the FCC-ee physics potential depends on it.
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All authors Eugenia Celada, Elie Hammou, Jaco ter Hoeve, Marion O.A. Thomas
Instrumentation and Methods for Astrophysics
NestyNet. I. Physics Functions Are Hard to Fit with Neural Networks: A Framework for Accurate Surrogates and Analytic Derivatives
Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis et al. (+2 more)
Many of the smooth functions that matter most in physics are precisely the ones that standard neural network methods struggle to fit accurately. Here we present NestyNet, a coupled model-and-optimizer framework capable of fitting such targets to high accuracy while also delivering their gradients, Hessians,
Laplacians, and antiderivatives analytically and at low cost. This makes it a natural substrate for scientific machine learning tasks. The model is a deterministic segmented analytic surrogate, and its optimizer is a second-order Levenberg–Marquardt scheme whose damping and linear solves are tailored to the stiff, strongly correlated parameter geometries induced by multiscale and sharply structured targets typical in physics and other scientific applications. On the AI Feynman
benchmark of 120 physics equations, NestyNet achieves median improvement factors of $2\,100\times$ for function values, $1\,400\times$ for first derivatives, and $780\times$ for second derivatives relative to standard neural networks trained with first-order optimization (Adam). Even after refining those fits with quasi-Newton (L-BFGS) optimization, the corresponding improvements are $540\times$, $450\times$, and $250\times$. Owing to the analytic design it is up to $\approx 44\times$ faster than vectorized automatic-differentiation (autograd) baselines, with a margin growing with model size. The same analytic-derivative framework also supports vector- and complex-valued targets, measurement uncertainties in both inputs and outputs, and constraints, and its modules can be composed flexibly to build scientifically useful model architectures, all without reverting to autograd. Together, these components provide a practical modular framework for fitting difficult scientific surrogates while delivering accurate differential operators for subsequent analysis.
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All authors Rodrigo Ibata, Wassim Tenachi, Foivos Diakogiannis, Neil Ibata, Anirudh Shankar
General Relativity and Quantum Cosmology
A Novel Kerr-like Black Hole in a General Double Power Law Dark Matter Environment: Geometry, Spectroscopy, and Energy Extraction
Supakchai Ponglertsakul and David Senjaya
We construct a novel Kerr-like black hole solution embedded in a general double power law dark matter environment by applying the Newman–Janis
algorithm to a Schwarzschild-like seed geometry. This framework provides a unified rotating spacetime for arbitrary double power law density profiles and reveals how dark matter modifies the horizon structure, extremal
spin, and
curvature properties of rotating black holes. Remarkably, we find that the rotation–
halo interplay can eliminate essential
curvature singularities for Dehnen-type profiles with $\gamma\leq2$, despite the singular nature of the corresponding static configurations. We then investigate the spectroscopic signatures of the dark matter environment through massive scalar perturbations in the Dehnen $(1,4,\gamma)$
halo. Using an analytical low-frequency matching method, we derive the quasibound state spectrum, the onset condition for scalar cloud formation, and superradiant amplification factor, showing that the
halo parameters $\rho_0 r_0^3$ and $\gamma$ leave characteristic imprints on the scalar spectrum. Increasing the
halo density or the cusp strengthens the binding of quasibound states and enhances their decay, shifts the scalar cloud threshold, and suppresses superradiant amplification effectivity by narrowing the allowed frequency window and lowering the amplification factor peak. Finally, we analyze rotational energy extraction from thermal scalar fields and demonstrate that the efficiency is controlled by the interplay between the thermal spectrum and the superradiant instability, with lower temperatures and less cuspy density profiles yielding more efficient energy extraction.
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Astrophysics of Galaxies
Cosmological Distance Measurements of High Redshift Blazars: OJ 248 (z=0.939) and 4C +38.41 (z=1.814)
Young-Bin Shin, Sang-Sung Lee, Sincheol Kang et al. (+3 more)
In this study, we estimated the angular diameter distances to two high-
redshift active
galactic nuclei (AGNs), OJ 248 (z = 0.939) and 4C +38.41 (z = 1.814), using 43 GHz
radio light curves. The aim of this work is to extend AGN variability-based distance measurement methods to the high-
redshift regime. The distance estimates were analyzed under two assumptions for the maximum intrinsic brightness temperature TB,int: (1) the equipartition temperature, and (2) the sample-averaged TB,int. As a representative result, when adopting the equipartition temperature, the angular diameter distances to OJ 248 and 4C +38.41 are estimated to be 7592.7 +/- 396.7 Mpc and 11069.8 +/- 1216.9 Mpc, respectively. In addition, Doppler factors were calculated using the inverse-Compton method, and additional distance estimates were obtained based on these values. Our error budget analysis shows that the most significant systematic uncertainty arises from epoch selection. These results indicate that systematic effects have a substantial impact on the derived distance estimates and limit their reliability, particularly in the high-
redshift regime. Reducing these uncertainties will require improved observational cadence and reduced post-fit noise. AGN variability provides an alternative approach to distance estimation. However, our results reveal significant limitations in the current methodology and indicate that further methodological and observational improvements are required before its cosmological applicability can be reliably assessed.
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All authors Young-Bin Shin, Sang-Sung Lee, Sincheol Kang, Whee Yeon Cheong, Chanwoo Song, Jeffrey A. Hodgson
Astrophysics of Galaxies
Investigating radio source population and spatial characteristics of diffuse Galactic synchrotron emission in the GAMA-23 field with uGMRT Band-3
Rashmi Sagar, Abhirup Datta and Aishrila Mazumder
We present upgraded
Giant Meterwave
Radio Telescope (uGMRT) Band-3 observations of the
Galaxy and Mass Assembly (GAMA)-23 field. The observations consist of a total of 33 hours spread over 50 pointings, corresponding to $\sim$56 minutes per pointing at the central frequency of 325 MHz. The final image mosaicked from these pointings has a central off-source RMS noise of $109\,\mu\mathrm{Jy}/\mathrm{beam}$ and covers an area $65.31\,\text{deg}^2$ with a resolution of $15.8''$. This wide-area deep-field observation provides a
radio source catalog of 5741 sources with flux densities ${\geq}5{\sigma}$. We present complementary uGMRT observations overlapping with the high-frequency Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe survey. We derived the spectral index from the matched sources in the GAMA-23 field for the first time. We have studied the statistical properties of diffuse
Galactic synchrotron emission (DGSE) in the GAMA-23 field using six different latitude target pointings. We fitted DGSE in the form of power law $C_{\ell} = A(1000/{\ell})^{{\beta}}$. Our DGSE amplitude range of $A = 1-20\,{\text{mK}}^2$ and $\beta$ varies between $1.5$ and $2.4$. This work presents one of the first characterizations of DGSE in the southern sky at 325 MHz, setting a precedent for foreground modeling required for sensitive
radio observations with the upcoming SKA.
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High Energy Astrophysical Phenomena
A broadband outburst of the compact steep-spectrum quasar 3C 138 in 2024-2026
T. V. Mufakharov, Yu. V. Sotnikova, V. V. Vlasyuk et al. (+20 more)
After several decades of relative quiescence, the compact steep-spectrum
quasar 3C 138 entered an active phase in 2024-2026, exhibiting strong broadband flaring. We investigate its multiwavelength behaviour using dense multifrequency
radio monitoring at 1-22 GHz with RATAN-600 and RT-32, optical R-band observations with Zeiss-1000 and AS-500/2, X-ray measurements with Swift/XRT and SRG/ART-XC, and the
Fermi-LAT $\gamma$-ray light curve. The
radio brightening accelerated after 2022 and was strongest at the highest frequencies. The
radio spectra hardened markedly, with the 11-22 GHz spectral index evolving from steep to flat or inverted during the active phase. The X-ray flux increased by more than a factor of three during 2025-2026, while the
photon index hardened from $\Gamma_{\rm X}\simeq 1.6$ to $\Gamma_{\rm X}\simeq 0.9$ and softened back after the peak.
Flare decomposition revealed five $\gamma$-ray
flares and a sequence of optical subflares during the later stages of the activity. The $\gamma$-ray, X-ray, and optical maxima occur within a $\simeq 13$-day interval, suggesting a common activity episode, whereas the
radio brightens more gradually and in a frequency-dependent manner. Under the adopted compact-zone geometries, the sparse two-state spectral energy distributions (SEDs) can be represented by one-zone synchrotron self-Compton (SSC) solutions, while the relative contribution of external Compton (EC) remains geometry dependent. The
flare shifts the modelled energy partition towards relativistic electrons. These results favour a longer-lived, core-dominated activity phase, with later high-energy and optical
flares superposed on the opacity-driven
radio evolution of an emerging synchrotron component.
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All authors T. V. Mufakharov, Yu. V. Sotnikova, V. V. Vlasyuk, S. Yu. Sazonov, M. L. Khabibullina, A. G. Mikhailov, A. B. Pushkarev, T. An, Y. A. Kovalev, Y. Y. Kovalev, A. V. Popkov, M. A. Kharinov, G. S. Uskov, I. Yu. Lapshov, E. V. Filippova, A. Yu. Tkachenko, K. V. Iuzhanina, A. K. Erkenov, R. Yu. Udovitskiy, O. I. Spiridonova, I. A. Rakhimov, T. S. Andreeva, A. A. Ogloblin
Soft Condensed Matter
True and Quasi Long-Range Order in Malthusian Flocks
Patrick Jentsch and Anna Erzberger
Living matter undergoes continuous turnover. The hydrodynamic theory of Malthusian flocks describes polar active matter with turnover, but its phase diagram and nonlinear scaling behavior is not well understood. Using a nonperturbative renormalization group approach, rotationally invariant to second order in derivatives, and without defects, we explicitly obtain the strong-coupling fixed point governing true long-range order, uncover a quasi long-range ordered phase, and identify a critical point similar to, but distinct from the Berezinskii-Kosterlitz-Thouless universality class at the transition.
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High Energy Astrophysical Phenomena
Prospects for characterizing Population III remnants with next-generation gravitational-wave observatories
N. V. Krishnendu, Patricia Schmidt and Geraint Pratten
The most distant gravitational-wave (GW) detection by LIGO, Virgo and KAGRA so far is a binary black hole (BBH) merger at a
redshift of $z\sim 1.1$, corresponding to a luminosity distance of $D_L \sim 8 \, \rm Gpc$. The next-generation GW detectors, the Einstein
Telescope (ET) and
Cosmic Explorer (CE), will detect mergers beyond the peak of
star formation at $z_{\rm peak}\sim 2$, enabling the direct detection of the remnants of the first
stars in the early Universe. Realising this science potential requires accurate inference of the
redshift, sky localization and intrinsic properties of the most distant mergers. In this work, using a fully
Bayesian framework and an astrophysically motivated model, we study Population III remnants with an ET-CE detector network and quantify the measurement uncertainties in
redshift, sky localisation, intrinsic masses and
spins for BBHs at $z \geq 15$. Considering an optimistic ($5\, \rm Hz$) and pessimistic ($10\,\rm Hz$) lower cutoff frequency for the detectors' sensitivity, we show that the $5\, \rm Hz$ configuration consistently improves the
redshift inference for
spin-precessing binaries. We also find that the source-frame component masses can be measured to within $\sim 12\%$ on average, and that the highest-
redshift sources in the population can be reliably characterised. In contrast, we find only modest constraints on the BH
spins. The improved low-frequency sensitivity also extends the
redshift reach of the detector network, enabling events injected at $z_{\rm true}\simeq19.8$ to be confidently identified as originating beyond $z\simeq18.5$ at $90\%$ credibility, compared to a maximum lower-bound
redshift of $z\simeq17.5$ for the $10\,\rm Hz$ configuration. Improved detector sensitivity below $10\, \rm Hz$ also reduces the sky-localisation uncertainties, which are essential for cosmological cross-correlation.
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Statistical Mechanics
Computing Shear Viscosities from Molecular Dynamics Simulation: Comparing the OrthoBoXY Approach with the Green-Kubo Method
Marcel Brandt, Ralf Ludwig and Dietmar Paschek
We calculated shear viscosities of 15 neat molecular
liquids from
equilibrium molecular dynamics (MD) simulations using the OrthoBoXY approach and compare them to viscosities calculated via the Green-Kubo method. Data from both methods agree very well. Here, we show how to avoid pitfalls while computing the OrthoBoXY-data to obtain optimal results. From simulations of multiple system sizes, we could verify that the viscosity of molecular
liquids is not influenced by finite size effects down to systems as small as 250 molecules. Moreover, we demonstrate that also the standard error of the viscosity is nearly independent of the system size. This is shown to be a consequence of a compensation effect of an increasing accuracy of the self-
diffusion coefficients with increasing systems-size and the system-size dependent weighting according to the OrthoBoXY-equation. As a consequence, we suggest that it is preferable to run simulations of smaller systems with longer simulation times rather than larger systems with shorter simulation runs. In addition, we discuss a refinement of the recently introduced "recipe" for OrthoBoXY simulations block-lengths $\tau_\mathrm{block}$. Based on data from simulations with varying run-lengths, we suggest the following modification: for highly viscous systems, the value of $\tau_\mathrm{block}$ might safely be scaled by a factor of $1/8$, significantly reducing the computational resources needed. For less viscous systems, the value of $\tau_\mathrm{block}$ might safely be scaled by a factor of $1/4$. For systems with high fluidity, the value of $\tau_\mathrm{block}$ should not be scaled down in order to achieve reliable results. When using a smaller system size of 250 molecules, these refinements are leading up to a 24-fold reduction in computational cost compared to the previous recommended set-up without sacrificing numerical accuracy.
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Chemical Physics · Cross-listed from cs.HC
Temporal Tracking of Reeb-Space Sheets
Mohit Sharma, Petar Hristov, Talha Bin Masood et al. (+1 more)
Time-varying bivariate fields arise in many scientific applications, where the relationship between two scalar quantities evolves over time. While topological methods such as merge trees provide an effective framework for identifying and tracking features in univariate data, analogous approaches for bivariate fields remain comparatively underexplored. Reeb spaces extend topological analysis to multivariate data by representing fiber connectivity through a collection of interconnected sheets, making these sheets natural candidates for describing bivariate structures. However, establishing temporal correspondences between sheets is challenging due to the structural complexity of Reeb spaces, sensitivity to noise, and the difficulty of defining meaningful similarity measures across timesteps. We present a framework for tracking Reeb space sheets in time-varying bivariate fields. The method establishes correspondences between sheets in consecutive timesteps using complementary similarity measures defined in the spatial domain and the range space. We evaluate the method on a synthetic
torus dataset and two time-varying molecular electronic structure
datasets. The results show that Reeb space sheet tracking reveals persistent structures and highlights interesting intervals of temporal change. Overall, the results demonstrate that Reeb space sheets can serve as trackable topological structures and provide a foundation for the visual analysis of time-varying bivariate data.
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All authors Mohit Sharma, Petar Hristov, Talha Bin Masood, Ingrid Hotz
Astrophysics of Galaxies
Ruffled Feathers: Merger-driven galaxy size growth and structural transformation in EAGLE
Kai Wang, Carlton Baugh, Sownak Bose et al. (+9 more)
Galaxy mergers drive both the size growth and the transformation from discs to spheroids, yet the prescriptions used to model these processes in semi-analytic frameworks have not been tested against the realistic merger population in cosmological hydrodynamical simulations. Using $\approx 4{,}500$ mergers identified in the EAGLE simulation, we test an energy-conservation
estimator for post-merger
galaxy sizes and quantify merger-driven morphological transformation. The predicted remnant half-
stellar-mass radius matches the simulated descendant size with a scatter of $\approx 0.12$-$0.15$ dex and no significant systematic dependence on progenitor properties, while a commonly used dissipation correction applied to gas-rich mergers under-predicts the post-merger size by up to $\approx 0.4$ dex in a cosmological context and increases the overall scatter. The per-merger size growth increases monotonically with the
stellar mass ratio of the merging pair, from $\lesssim 0.03$ dex for minor mergers to $\approx 0.10$ dex for equal-mass mergers. From the energy-conservation
estimator, we analytically derive the size growth efficiency per unit accreted
stellar mass, $\eta \equiv \mathrm{d}\log_{10} r_{\star}/\mathrm{d}\log_{10} M_{\star}$, and show that $\eta$ reaches $\approx 2$ only in the idealised limit of collisionless minor mergers with zero orbital energy; as $\eta$ is highly sensitive to the orbital energy at the time of merging, the minor merger channel cannot be established as the driver of the rapid size growth of massive
galaxies without better constraints on this quantity. Beyond the size growth, mergers systematically reduce rotational support and increase triaxiality in proportion to mass ratio, but even the most nearly equal-mass mergers do not always fully destroy the disc, in tension with the complete disc destruction assumed in several semi-analytic models.
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All authors Kai Wang, Carlton Baugh, Sownak Bose, Shaun Cole, Carlos S. Frenk, Cedric Lacey, Shengdong Lu, Peder Norberg, Isabel Santos-Santos, Francesco Shankar, Tom Theuns, Tao Wang
Fluid Dynamics
Drop Spray Electrification
Riko Kazama, Masaya Toda, Hans-Jürgen Butt et al. (+1 more)
Charge separation during the breakup of water drop has been recognized since the early studies of waterfall and spray electrification, yet the role of controlled drop fragmentation at structured
liquid-repellent surfaces remains unclear. Here we show that water drops impacting superhydrophobic meshes generate charged secondary droplets as
liquid penetrates and fragments through the mesh pores. By combining Faraday-cup charge measurements with high-speed imaging, we identify how the charge depends on the Weber number and on the pathway of spray formation. No measurable charge is detected below the penetration threshold. At low Weber numbers,
recoil jet formation gives a high charge per unit spray mass, whereas at intermediate Weber numbers both
recoil jets and impact-induced jets contribute to charging. At higher Weber numbers, pancake bouncing suppresses
recoil jet formation, so charging is dominated by impact induced penetration and the total charge approaches a saturated value. We further show that smaller mesh pores enhance the charge-to-mass ratio and that conductive meshes provide stable charging under repeated impacts by dissipating residual surface charge. These findings provide design principles for superhydrophobic mesh platforms for spray charging and rain-driven energy harvesting.
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All authors Riko Kazama, Masaya Toda, Hans-Jürgen Butt, Rutvik Lathia
Medical Physics
A Unified Analytical Framework for LYSO-SiPM Scintillation Pulse Dynamics
Ao Qiu and Qingguo Xie
Existing scintillation-detector models typically treat scintillation kinetics, optical transport, silicon photomultiplier (SiPM) response, and timing statistics separately, limiting end-to-end prediction of waveform formation and detector performance. We present a unified analytical framework for lutetium-yttrium oxyorthosilicate (LYSO)-SiPM scintillation detectors that links these processes within a single forward model. The framework incorporates finite thermalization, depth-dependent optical transit-time spread, and microcell occupancy dynamics to provide a physics-based description of macroscopic pulse formation. It yields closed-form exponentially modified Gaussian pulses in the linear regime, state-dependent integral solutions in saturation, and recovers the conventional bi-exponential pulse model—ubiquitously used yet hitherto only empirically justified in scintillation pulse fitting and sparse-sampling reconstruction—as a controlled reduction of the full optoelectronic cascade. Experimental validation on 10,000 directly digitized Na-22 pulses shows that the dynamic saturation model captures amplitude-dependent waveform distortion and is favored by the Akaike information criterion (AIC) over a matched bi-exponential baseline in 100/100 high-amplitude pulses and 98/100 medium-amplitude pulses. By coupling the dynamic triggering rate to compound Poisson statistics, the framework also predicts current-variance envelopes and Fisher-information-based timing limits, including an intrinsic coincidence timing resolution lower bound of about 100 ps full width at half maximum (FWHM) for a reference 511-keV LYSO-SiPM configuration. These results deepen the physical understanding of scintillation-detector waveform formation and timing limits by clarifying how scintillation kinetics, optical transport, and SiPM microcell dynamics jointly shape the observed response.
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Quantum Physics
Quantum error correction with global control
Roberto Menta, Lindsay Bassman Oftelie, Ashkan Abedi et al. (+5 more)
Reaching fault tolerance means scaling
qubit counts by orders of magnitude, a jump that conventional superconducting architectures cannot sustain without solving the so-called `wiring problem'. Global control sidesteps this bottleneck, but implementing
quantum error correction (QEC) on previously proposed global architectures incurs extremely steep overhead costs, due to the need for separate correction procedures for the computational and auxiliary
qubits that comprise the global device. We resolve this by introducing the first globally-controlled architecture with zero
qubit overhead. Every physical
qubit is a computational
qubit, and thus, every
qubit is protected under a single error correcting scheme. We identify a class of cyclic stabilizer codes realizable through global iSWAP and single-
qubit gates, yielding QEC thresholds nearly seven orders of magnitude larger than previous estimates for globally-controlled arrays. We further show these thresholds improve systematically as the global architecture is augmented with a limited amount of local measurement sites, demonstrating a trade-off between wiring simplicity and fault-tolerant performance.
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All authors Roberto Menta, Lindsay Bassman Oftelie, Ashkan Abedi, Francesco Cioni, Marco Polini, Seth Lloyd, Francesco Caravelli, Vittorio Giovannetti
Physics Education
A multi-agent AI classroom based on dual-process reasoning hazards: a pilot with prospective physics teachers
Eugenio Tufino
Responding productively, in real time, to the
reasoning students actually produce is among the most difficult and slowest to acquire of the skills physics teachers develop, and prospective teachers get few opportunities to practise it before entering a classroom. In this pilot study, we describe a simulated class of five AI students, each consistently enacting a distinct
reasoning pattern drawn from the dual-process theory (DPT) "hazards" framework of physics education research, and report on its first use in a university course for prospective physics teachers. Fifteen graduate students worked through an instructional sequence on DPT and questioning strategies. They then diagnosed two parallel sets of written vignettes, in a crossover arrangement, before and after interacting in pairs with the simulated class on a static-friction problem. The data set is completed by individual written hypotheses and reflections, the session logs and a short feedback questionnaire. Diagnostic scores improved significantly from PRE to POST (n = 11 paired, Wilcoxon p = 0.014, r = 0.79; on a 0-18 scale). During the simulation itself, however, participants asked predominantly uniform guiding questions, and the DPT vocabulary they had been taught appeared in only 2 of 71 substantive teacher turns, while seven of thirteen POST sheets used it readily. We read this knowing-doing gap not as a failure but as a snapshot of where each participant stands on the developmental trajectory of responsiveness to student ideas, a trajectory the simulation makes visible with transcript-level granularity. We discuss design, findings and implications for physics teacher preparation.
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Quantum Physics · Cross-listed from cs.LG
Learning to Rank Tensor Network Contraction Plans for GPU-Accelerated Quantum Circuit Simulation
Alfred M. Pastor, Maribel Castillo and Jose M. Badia
Classical simulation remains essential for developing and validating
quantum algorithms, but its cost grows rapidly with
circuit size. Tensor-network contraction can reduce this cost by exploiting
circuit structure, although its efficiency depends strongly on the chosen contraction plan. On GPUs, plans with similar theoretical complexity may perform very differently because execution also depends on parallelism, reduction structure,
memory traffic, and contraction geometry. We present a learning-to-rank framework for selecting efficient contraction plans before executing them. Each plan is represented by structural features derived directly from its sequence of pairwise contractions, and gradient-boosted rankers are trained from GPU measurements using listwise and pairwise objectives. We evaluate the resulting models on diverse
circuit families, using separate in-distribution and
circuit-family-shift test sets, and compare them with random and MinFill-based baselines. The learned rankers generally identify better plans, with the listwise model providing the strongest overall decision quality. We also study backend shift by comparing empirical plan orderings on two GPU architectures and evaluating the source-trained models on the second device without retraining. The rankings remain substantially, though not perfectly, stable across GPUs, and the models retain useful decision quality. These results support Learning to Rank as a practical way to reduce contraction-plan search, while showing that performance remains partly backend dependent.
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General Relativity and Quantum Cosmology
Asymmetric Quantum Oppenheimer-Snyder Collapse
Michał Bobula and Tomasz Pawłowski
We study black hole formation resulting from the collapse of a homogeneous and isotropic
dust ball within a framework built upon loop
quantum cosmology. Using loop dynamics formulated for Lemaitre-Tolman-Bondi spacetimes—which reduce to the asymmetric loop
quantum cosmological bounce scenario—we analyze the
dust ball undergoing power-law contraction followed by a de Sitter-like expansion. We discover an emergence of a physical shock at the
dust ball surface, characterized by a continuous induced metric and a discontinuous extrinsic
curvature arising from a dynamical mismatch between the expanding interior and the contracting exterior
vacuum shells. Furthermore, we explicitly derive two variants of Schwarzschild-like line elements for the
vacuum sector, and we demonstrate that the resulting spacetime is geodesically complete featuring a rich causal structure. This establishes, for the first time, fully dynamical regular black hole formation within a framework consistent with loop
quantum cosmology.
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Solar and Stellar Astrophysics
Photometric Distances for Metal-poor Giants and a Search for Hypervelocity Stars with LAMOST DR13 and Gaia DR3
Shuai Xu, Haibo Yuan, Bowen Huang et al. (+2 more)
Hypervelocity
stars (HVSs) are
stars with velocities high enough to escape the Milky Way, but their identification depends sensitively on distance estimates, particularly for distant
giants. In this work, we search for metal-poor HVS candidates by combining LAMOST DR13 spectroscopy with
Gaia DR3 astrometry. We calibrate a
metallicity-dependent color–absolute-magnitude relation for normal metal-poor
giants using a high-quality reference sample, and apply it to derive photometric distances for 41{,}331
stars. The relation reproduces the reference absolute magnitudes with a scatter of 0.24\,mag, corresponding to an intrinsic distance uncertainty of $\sim$9.7%. Combining these distances with
Gaia proper motions and LAMOST radial velocities, we identify 13 initially unbound candidates under the
Galactic potential from \citet{McMillan2017}. Spectral inspection indicates that several are chromospherically active binaries or other non-standard systems for which a
giant-
star calibration is unreliable; removing these contaminants leaves nine metal-poor HVS candidates. Backward orbit integrations suggest that one candidate is most consistent with a disk origin, while three have trajectories suggestive of an association with the Sagittarius stream.
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All authors Shuai Xu, Haibo Yuan, Bowen Huang, Xiao Kai, Wuming Yang
High Energy Physics (Phenomenology)
Machine Learning is Good for Physics - and Vice Versa
Michael Krämer and Tilman Plehn
Scientific AI is rapidly transforming fundamental physics research and challenging defining aspects of the fundamental physics methodology. We discuss opportunities and dangers of this transformation and find exciting benefits from a close interaction between AI and fundamental physics, provided that we remain aware of the scientific methodologies of the respective fields. For fundamental physics, we discuss two such aspects: statistical validation and a generalizing theory description, both with the goal of discovering new physics in vast
datasets.
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