Instrumentation and Detectors
neBEM: A GPU-accelerated Electrostatic Field Solver
Shubhabrata Dutta, Purba Bhattacharya, Tanay Dey et al. (+2 more)
Accurate electric field estimation is critical for the design and optimization of Micro Pattern Gaseous Detectors (MPGDs). The nearly exact Boundary Element Method (neBEM) offers high precision field computation but is limited by long CPU runtime arising from its complex analytical formulations. This work presents a comprehensive optimization of the neBEM solver, focusing on a hybrid hardware acceleration strategy using OpenMP for multi-core CPUs and GPU acceleration using NVIDIA's CUDA. A key contribution is the new implementation of a dynamic space charge calculation, which has also been designed to be accelerated by CUDA. This primary acceleration is complemented by enhanced algorithmic optimizations to reduce the complexity of the problem. The proposed implementation achieves substantial speedups while preserving inherent accuracy of the solver. Simulations on staggered thick Gas Electron Multiplier geometries demonstrate agreement with other commercially available field solvers, verifying the fidelity of accelerated neBEM. Benchmarking tests show a significant speedup, enabling rapid yet precise simulations for complex MPGD configurations. These improvements make GPU-accelerated neBEM a practical tool for large-scale detector simulation.
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All authors Shubhabrata Dutta, Purba Bhattacharya, Tanay Dey, Nayana Majumdar, Supratik Mukhopadhyay
Mesoscale and Nanoscale Physics
Gate-Controlled Spin Qubits in Confined Altermagnets
Hamed Vakili
We propose gate-defined
spin qubits in electrostatically confined altermagnetic
quantum dots. Elliptical confinement of the $d$-wave altermagnetic structure produces a low-energy doublet with opposite
spin polarization. For the range of parameters used here, the
qubit states energy gap lies in the microwave range while the leakage gap remains in the meV range. Even without
spin-orbit coupling, time-dependent simulations show that a phase-controlled quadrupolar gate drive about a fixed bias point implements $X_{\pi/2}$ and $X_\pi$ rotations by resonantly modulating the confinement anisotropy. We extend the study to two-
qubits using a double
quantum dot. We show that the double
quantum dot spectrum can be cleanly projected onto isolated
quantum dot product states with a nonzero nonlocal Pauli block in the effective logical two-
qubit Hamiltonian. Resonant central-barrier modulation then drives the logical two-
qubit component close to a maximally entangled state. These calculations show anisotropic altermagnetic
quantum dots as a route to locally gate-controlled
spin qubits without requiring
spin-orbit coupling.
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Optics
A Novel Arm-Length Stabilization Scheme for Gravitational-Wave Detectors with AlGaAs/GaAs Coated Mirrors
Jian Liu, Juntao Pan, Carl Blair et al. (+7 more)
The arm length stabilisation system is employed in gravitational-wave detectors to reduce the velocity of the mirrors such that the arm cavities can be brought onto resonance in a controlled manner required to attain the detector operating point. For future upgrades of current gravitational wave detectors such as A#, which will incorporate AlGaAs/GaAs coatings, the current frequency-doubled arm length stabilisation system is unsuitable due to excessive absorption of the frequency-doubled 532nm beam by the AlGaAs/GaAs coating. We propose a novel multi-wavelength arm length stabilisation scheme that uses both frequency-doubled and frequency-tripled beams. The 1596nm auxiliary locking beam is outside the absorption bands of AlGaAs/GaAs coating. It is frequencytripled to 532nm and phase-locked with the 1064nm science
laser through its second harmonic at 532 nm. In a tabletop setup, we experimentally demonstrated the stable cavity detuning and robust cavity locking transition by controlling the 1596nm
laser and 1064nm
laser phase locked loop. This demonstration confirmed that the proposed novel arm length stabilisation scheme is compatible with future upgrades or third-generation gravitational wave detectors that use AlGaAs/GaAs-coated test masses.
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All authors Jian Liu, Juntao Pan, Carl Blair, Chiara Di Fronzo, Li Ju, Chunnong Zhao, Sheon S. Y. Chua, Bram J. J. Slagmolen, Nutsinee Kijbunchoo, David Ottaway
Cosmology and Nongalactic Astrophysics
CHEX-MATE: AMALGAM weak-lensing analysis of 41 Planck Sunyaev-Zel'dovich-selected galaxy clusters
Keiichi Umetsu, Raphael Gavazzi, Mauro Sereno et al. (+20 more)
We present a weak-
lensing shear analysis of 41 Planck SZ-selected
galaxy clusters at $0.11\le z\le 0.55$ from the CHEX-MATE sample, using wide-field Subaru/Suprime-Cam and CFHT/MegaPrime imaging from the AMALGAM project. We detect the azimuthally averaged weak-
lensing signal around the X-ray peak of each cluster, achieving a median S/N of 6.5 per cluster. The $45^\circ$-rotated component has a median S/N of -0.1 and ranges from -1.8 to +1.8, consistent with zero. We model the excess surface mass density profile of each cluster with an NFW profile to infer weak-
lensing mass and concentration constraints. The total systematic uncertainty in the weak-
lensing mass calibration is assessed to be $8\%$. Using a hierarchical
Bayesian framework, we then derive weak-
lensing-calibrated scaling relations for the
halo concentration, $c_{200}$, as a function of $M_{200}$ and
redshift, and for the Planck SZ mass proxy, $M_{SZ}$, as a function of $M_{500}$ and
redshift, while accounting for sample selection effects, weak-
lensing modelling biases, and residual calibration uncertainty. At $M_{200}=10^{15}M_\odot$ and $z=0.25$, we find $c_{200}=3.53\pm0.71$ with an intrinsic scatter of $0.22\pm0.04$ dex. The inferred normalisation and scatter are consistent with recent $\Lambda$CDM predictions for massive
haloes, with no significant mass or
redshift dependence over the probed range. For the Planck mass proxy, our baseline regression yields $M_{SZ}/M_{500}=0.83\pm0.09$ at $M_{500}=7\times10^{14}M_\odot$ and $z=0.25$, with an intrinsic scatter of $0.10\pm0.02$ dex. A restricted model with fixed unit mass slope and no
redshift evolution gives $1-b=0.72\pm0.11$. We also provide weak-
lensing-calibrated posterior estimates of $M_{500}$ for the sample based on the baseline $M_{SZ}$–$M_{500}$–$z$ relation. These results provide an initial weak-
lensing mass calibration for CHEX-MATE multi-probe cluster studies.
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All authors Keiichi Umetsu, Raphael Gavazzi, Mauro Sereno, Nobuhiro Okabe, Emmanuel Bertin, Gianluca Castignani, Stefano Ettori, Fabio Gastaldello, Carlo Giocoli, Scott T. Kay, Junhan Kim, Maggie Lieu, Lorenzo Lovisari, Ben J. Maughan, Mario Nonino, Lorenzo Pizzuti, Etienne Pointecouteau, Gabriel W. Pratt, Mario Radovich, Elena Rasia, Mariachiara Rossetti, Harshda Saxena, Jack Sayers
Earth and Planetary Astrophysics
Bayesian analysis of Gaia epoch astrometry and radial velocities with kima
Thomas A. Baycroft, João P. Faria and Jean-Baptiste Delisle
Context. The next data release from the
Gaia space
telescope is expected to result in tens of thousands of newly detected
exoplanets, as well as detection and 3D orbital constraints on binary
stars and even black holes. Many of these will warrant in-depth analyses of the astrometric data, as well as radial velocity follow-up. This will require dedicated tools to exploit this wealth of data. Aims. We provide open-source software to analyse epoch astrometric data from
Gaia, both alone and simultaneously with radial velocities. Methods. We add two models to the open-source orbit-fitting codebase kima, and test these on both real an simulated data. This code uses diffusive nested sampling to explore the parameter space, calculate evidences for model comparison, and perform parameter estimation. Results. We show that the results obtained are consistent with published/expected values, validating the use of kima for analysis of
Gaia data. We explore various attributes of kima's
Gaia model including using it to potentially distinguish true orbits from scan-angle dependent signals.
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Cosmology and Nongalactic Astrophysics
Minimal Extensions of the $\alpha$-Starobinsky Model: Reconciling ACT DR6 and Reheating Constraints
Nehla Shobcha, Norma Sidik Risdianto and Romy Hanang Setya Budhi
The latest combined data from the Atacama Cosmology
Telescope (ACT) DR6, Planck, and DESI yields a scalar spectral index $n_s = 0.9743 \pm 0.0034$, which lies approximately $2\sigma$ above the prediction of the standard $\alpha$-Starobinsky inflation model. To address this tension, we propose two minimal extensions that preserve the model's plateau structure and attractor properties: a multiplicative exponential modification and an additive
polynomial deformation, both governed by a single small perturbative parameter $\delta>0$. We analytically derive the slow-roll parameters and inflationary observables up to second order in $\delta$ and integrate them with reheating dynamics via the consistency equation. It is shown that the $\delta$ term effectively shifts $n_s$ into the $1\sigma$ confidence region of the joint P-ACT-LB-BK18
dataset without violating the tensor-to-scalar ratio bound ($r < 0.038$). The viable parameter space at $1\sigma$ requires $\alpha \lesssim 35$ with $\delta \sim \mathcal{O}(10^{-2})$ for the exponential model, while the additive model requires $\delta \sim \mathcal{O}(10^{-3})$ for $p=1$ and $\delta \sim \mathcal{O}(10^{-4})$ for $p=2$. For the e-folding range $N_k \in [50, 65]$, the relevant reheating equation of state is $0<\omega_{\mathrm{re}}\le1$. All viable scenarios yield a reheating temperature $T_{\mathrm{re}} \sim 10^9$ GeV, which is safely above the Big Bang Nucleosynthesis (BBN) bound and below the gravitino overproduction limit.
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Fluid Dynamics
Efficient Time-Domain Simulation of USV Motions in Short-Crested Irregular Waves Using an IRF-Based Framework
Fei Duan, Zihao Wang, Yaohua Zhou et al. (+1 more)
Traditional time-domain prediction of vessel motions in irregular waves usually relies on superposing responses from many regular-wave components, which is computationally expensive for long-duration simulation and real-time applications. This issue is particularly relevant to unmanned surface vehicles (USVs), for which efficient and realistic motion prediction is needed for seakeeping assessment, simulation-based testing, and control-system development. This study applies an impulse response function (IRF)-based time-domain framework to predict vessel motions in short-crested irregular waves. Froude-Krylov, diffraction, and radiation loads are obtained from frequency-domain analysis and transformed into the time domain. Instantaneous responses are then evaluated directly through convolution-based force reconstruction, reducing the need for repeated regular-wave simulations. Weak nonlinear restoring effects are included by instantaneous wetted-surface pressure integration, and directional wave spectra are used to represent realistic sea states. The framework is validated against model-test measurements of an offshore supply vessel in long-crested beam irregular waves and full-scale measurements of a USV operating in real sea conditions. Predicted significant amplitudes, mean zero-crossing periods, standard deviations, and motion time histories agree well with measurements. The effect of directional-spectrum discretization is also examined. Results show that motion amplitudes are moderately sensitive to directional resolution, whereas motion periods are relatively insensitive. A 30 deg directional interval provides a practical balance between prediction accuracy and computational cost. The proposed framework offers an efficient tool for high-fidelity time-domain prediction of USV motions in realistic directional irregular seas.
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All authors Fei Duan, Zihao Wang, Yaohua Zhou, Qing Xiao
Fluid Dynamics
Dynamics of diffusive-convective staircases in the ocean
Mary-Louise Timmermans and Jeffrey R. Carpenter
Diffusive-convective (DC) staircases in the ocean are observed across a wide range of settings, but their formation, structure, and persistence are not fully understood. Theories for DC staircases are reviewed to identify mechanisms governing their development and
evolution. Staircase
evolution through layer merging and possibly interface splitting, including the relationship to background
turbulence, is assessed. Oceanographic examples illustrate the variety of settings in which DC staircases are found, and how they can persist under weak
turbulence but are disrupted when
turbulence becomes sufficiently strong. Key open questions are identified, highlighting the challenge of linking small-scale processes to the large-scale coherence and persistence of DC staircases in the ocean.
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Strongly Correlated Electrons
Fluctuation exchange study on the electron-hole asymmetry of the superconductivity across 1/3 filling in the trilayer Hubbard model
Yushi Yamada, Masataka Kakoi, Masayuki Ochi et al. (+1 more)
We study within the fluctuation exchange approximation the trilayer Hubbard model where three layers of the Hubbard model are coupled by large interlayer hoppings so that the overlap of the bonding, nonbonding, and antibonding bands is relatively small. We pay special
attention to the band fillings close to 1/3, for which the bonding and nonbonding bands as a whole are close to half filling. For relatively small values of the onsite $U$, superconductivity roughly exhibits electron-hole symmetric behavior, as expected for a nearly half-filled two-band system. By contrast, an asymmetry appears when $U$ becomes large, where superconductivity is more favored in the hole-doped regime, i.e., in the regime where electrons are removed from 1/3 filling. We attribute this asymmetry to the asymmetric renormalization of the bonding, nonbonding, and antibonding bands when $U$ is large.
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All authors Yushi Yamada, Masataka Kakoi, Masayuki Ochi, Kazuhiko Kuroki
Strongly Correlated Electrons
Density-wave order enhances the phonon thermal Hall effect in a trilayer nickelate
Qiaochao Xiang, Enkang Zhang, Xiaokang Li et al. (+6 more)
Ruddlesden–Popper nickelates have emerged as a promising platform for high-temperature superconductivity, yet the role of
lattice degrees of freedom in their correlated normal state remains largely unexplored. Here, we report the observation of a finite
phonon thermal
Hall effect in the trilayer nickelate La$_4$Ni$_3$O$_{10}$ at ambient pressure. Remarkably, the thermal
Hall response is strongly enhanced below the density-wave transition at $T^*\approx140$ K, exhibiting two distinct plateaus in the thermal
Hall resistivity. The characteristic energy scale extracted from the thermal
Hall response ($\sim4.1$ meV) closely matches the
magnon–
phonon crossing span energy ($\sim3.2$ meV), pointing to
magnon–
phonon hybridization as the primary mechanism enhancing the thermal
Hall effect. These results provide new insight into the interplay between
lattice and
spin excitations in nickelates, with implications for understanding both their superconductivity and the multiple possible origins of insulating thermal
Hall signals.
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All authors Qiaochao Xiang, Enkang Zhang, Xiaokang Li, Xiaodong Guo, Mengfei Zhu, Jun Zhao, Guang-Ming Zhang, Liang Li, Zengwei Zhu
Instrumentation and Methods for Astrophysics
Improving Radio Source Count Estimation Using Kernel Density Estimation
Luozhenhan Liu, Zunli Yuan, Wenjie Wang et al. (+1 more)
Radio source counts provide a fundamental census of
cosmic radio emission, yet their estimation is usually based on coarse histograms that suffer from bin-choice bias, boundary effects, and survey incompleteness. We apply and rigorously evaluate kernel density estimation (KDE) as a anonparametric alternative to the conventional binned method for estimating differential
radio source counts. Using simulated flux-limited samples derived from an input luminosity function model, we compare the performance of standard KDE, adaptive KDE, and traditional binning methods. Our results show that KDE-based approaches yield more accurate and stable estimates, particularly in the high-flux regime where data are sparse and conventional methods struggle. We also apply the adaptive KDE method to real observational data from the LOFAR Two-Metre Sky Survey Deep Fields. Our analysis robustly confirms the pronounced “drop and bump" feature at sub-mJy flux densities, but also reveals that a secondary, modest bump seen in the binned data at ~ $\sim 10$ mJy is likely a binning artifact. We also demonstrate the flexibility of KDE in addressing observational incompleteness through weighted estimation, which applies weights continuously at the level of individual sources rather than averaging them in discrete bins. These strengths make KDE a powerful tool for source-count analyses in current and future
radio surveys and, more broadly, in analogous studies at other wavelengths. All computations in this study are implemented with AstroKDE, a Python package we have developed for astronomical applications.
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All authors Luozhenhan Liu, Zunli Yuan, Wenjie Wang, Chuanqi Li
Solar and Stellar Astrophysics
Kepler Image-Subtracted Light Curves and Variable Star Catalog of NGC 6819
Melinda Soares-Furtado, Rianna Kuenzi, Rachel Lee McClure et al. (+11 more)
Variable
stars in open clusters are valuable probes of
stellar evolution. They provide precise measurements of
stellar properties, constrain cluster ages and distances, and trace the angular momentum
evolution of
stellar populations. To advance these studies, we applied image subtraction and systematic reduction techniques to the NGC 6819 Kepler superstamp time-series data (Quarters 1-16), using the
Gaia DR3 catalog to identify the positions of individual sources. We produce 81,498 high-precision light curves for 11,055 sources in the crowded field harboring the 2.5 Gyr open cluster NGC 6819. Our detrended light curves achieve a best root-mean-square precision of 33 ppm (6.5-hour bins) for
stars with Kepler magnitudes 12 - 12.5 mag, falling to 79 ppm at 14 - 14.5 mag. Using
Gaia DR3 proper motions, and parallaxes, we distinguished likely cluster members from field
stars. We identified and classified 87 periodic variables that are potential members of NGC 6819, including 26 newly-discovered variables. We make our light curves and variable classifications publicly available to enable further studies of
stellar variability and angular momentum
evolution in this intermediate-aged open cluster.
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All authors Melinda Soares-Furtado, Rianna Kuenzi, Rachel Lee McClure, Nicholas T. Marston, Evan Linck, Robert D. Mathieu, Andrew Vanderburg, Joel D. Hartman, Kyle Cudworth, Robert Gagliano, Thomas Jacobs, Martti H. Kristiansen, Mark Omohundro, Hans Martin Schwengeler
Cosmology and Nongalactic Astrophysics
Constant-Roll Inflation: Analytical Formulae for Power Spectrum and Implications for Induced Gravitational Waves
Hayato Motohashi, Shi Pi, Yuichiro Tada et al. (+1 more)
Constant-roll inflation provides a simple and analytically tractable framework for describing transient departures from slow roll, including non-attractor phases that can enhance the
primordial curvature perturbation on small scales. In this work, we investigate the
curvature power spectrum generated in a slow-roll–constant-roll–slow-roll scenario, focusing on the positions and amplitudes of the two characteristic peaks associated with the two transitions. We show that, in the parameter range where both peaks are well separated and sufficiently pronounced, the underlying constant-roll parameters can be reconstructed from the peak positions and amplitudes without performing a brute-force parameter scan. In addition, we construct a smoothed analytic approximation to the power spectrum, designed for efficient estimates of scalar-induced gravitational waves and related phenomenological applications.
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All authors Hayato Motohashi, Shi Pi, Yuichiro Tada, Jianing Wang
High Energy Physics (Phenomenology)
Neutrinoless double $\beta$ decay and leptogenesis in seesaw model
Kazuo Fujikawa
The
fermion $\nu_{R}+C\overline{\nu_{R}}^{T}$ in the Type I seesaw model, which is commonly identified with a Majorana
fermion, is not a Majorana
fermion and thus no neutrinoless double $\beta$ decay (in the case of $\nu_{L}-C\overline{\nu_{L}}^{T}$) due to the
theorem on the absence of a Majorana-Weyl
fermion in the representation of the d=4 Lorentz group. The leptogenesis is realized naturally together with the neutrinoless double $\beta$ decay by first defining C symmetric Majorana
fermions in the seesaw model using an analogue of the Bogoliubov transformation.
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Superconductivity
Multiple phases in K2Cr3As3: a playground for manipulating topological superconductivity
Seigo Ogawa, Tomoki Miyoshi, Saki Uchida et al. (+4 more)
Spin-triplet topological
superconductors are rare but of fundamental interest as they can host Majorana bound states that can be used in fault-tolerant
quantum computing. Recent efforts have been devoted to searching for
spin-triplet states in U-based compounds, but these materials have a low transition temperature (Tc) and coexisting competing orders, which creates significant experimental challenges and often leads to contradictory conclusions. The Cr-based candidate K2Cr3As3 offers a promising alternative: it has a much higher Tc of 6.2 K and no
magnetic order. Here we report a hallmark signature of
spin-triplet superconductivity arising from the internal
spin degrees of freedom via
nuclear magnetic resonance measurements, and demonstrate the high tunability of the topological phases. We discovered three distinct superconducting phases and revealed the
evolution of the paired-
spins direction (d(k)-vector). At low
magnetic fields, K2Cr3As3 evolves from a helical (Phase A) to a
chiral state (Phase B) with a rotation of the d(k)-vector from in-plane to out-of-plane direction upon cooling, although both phases have point nodes in the gap. A linenodal gap is realized in the high-field Phase C, where the d(k)-vector lies in the basal plane. These findings establish K2Cr3As3 as a model
spin-triplet
superconductor and a promising platform for manipulating topological phases.
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All authors Seigo Ogawa, Tomoki Miyoshi, Saki Uchida, Kazuaki Matano, Shinji Kawasaki, Yoshihiko Inada, Guo-qing Zheng
Materials Science
Low-temperature magnetic-field-driven thermal oscillator based on metal-superconductor joint
Poonam Rani and Yoshikazu Mizuguchi
Thermal control is one of the important technologies for fundamental science and thermal management. Among them, thermal oscillators have been in demands in the field of materials science and device application. In general, flexible frequency, amplitude, and waveform are needed for useful thermal oscillator, and the stability of the average temperature is also highly required. However, thermal oscillators based on an AC-current-driven heater require complicated control of input power to achieve the above-mentioned flexibility and stability of the outputs. Here, we demonstrate that magnetically-driven thermal oscillators fabricated using a metal-
superconductor (Cu-Pb) joint achieve those requirements easily by tuning the applied
magnetic field (H). A DC-current-driven heater is attached on the metal (Cu) side, and the
superconductor (Pb) edge is attached to thermal bath. We use a sharp and huge change in thermal conductivity at the superconducting transition of the Pb wire to generate thermal oscillation at the Cu-wire side. A sine-shaped thermal oscillation with an amplitude of 180 mK and a frequency of 0.17 Hz is observed with highly stable average temperature. Furthermore, a larger amplitude is achieved in a square-shaped oscillation with a larger H amplitude. Our thermal oscillator with temperature stability, large amplitude, and relatively high frequency will work as a flexible AC heat source at cryogenic temperatures.
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Materials Science
Reversible non-equilibrium phase transformation in amorphous germanium
Yang Huang, Marek Mihalkovič and Michael Widom
First principles molecular dynamics simulations of germanium reveal a reversible
liquid-glass transition below the
equilibrium melting point with a wide hysteresis loop. Direct calculation of the
liquid and amorphous state free energies, enabled by absolute
entropy calculations, verify that the transition is first order in character between two metastable phases. These results lend credence to models of explosive recrystallization from amorphous Ge thin films, through a metastable
liquid state and finally reaching the low temperature crystalline structure.
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Physics and Society
Regimes of Influence under Trust-Distrust Gating
Razieh Masoumi, Ahana Biswas and Yu-Ru Lin
In many social communities, individuals can simultaneously trust and distrust the same source, a feature standard opinion-dynamics models often ignore. We formalize this ambivalence with Gated Network Credence, in which each directed relationship encodes distinct trust and distrust assessments. These jointly determine "net trust" – the willingness to rely on a source – and "uncertainty" – the conflict between trust and distrust within the same relationship.
Agents update beliefs only when net trust exceeds a threshold and uncertainty falls below another, yielding an effective influence graph whose
topology drives long-run belief states. Sweeping both thresholds uncovers four regimes – Accommodating, Evaluative, Friction-averse, and Guarded – that differ in openness to trust and conflict. Under the modeled family of trust-distrust coupling and prestige-biased trust allocation, the model exhibits a hub-periphery reversal: in the Evaluative regime, high-degree
agents contribute more strongly to the limiting belief, whereas in the Friction-averse regime, stringent uncertainty filtering can disproportionately remove hub-directed influence channels and reduce their contribution to the collective
equilibrium. This conditional pattern recurs across synthetic network
topologies and two empirical network evaluations. Our results show that belief dynamics depend not only on network structure but also on how relational ambivalence between trust and distrust gates interpersonal influence.
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Statistical Mechanics
Two-Dimensional Phase Transitions in Classical Systems: 60 Years after the Hohenberg-Mermin-Wagner Theorem
Ruijian Zhu and Yanting Wang
In 1966, Hohenberg, Mermin and Wagner proved that long-wavelength fluctuations destabilize the long-range order of continuous
symmetry in two-dimensional (2D) systems. Later in the 1970s, Berezinskii, Kosterlitz and Thouless developed the BKT theory describing an unconventional phase transition between quasi-long-range and short-range order in 2D systems driven by the binding-unbinding of topological defects, which has become a fundamental topic in statistical mechanics, condensed matter physics, and soft matter physics. One of the most important applications of the BKT theory is the melting of 2D
crystals, whose mechanisms are not yet fully understood. Recently, this topic has been extended to the area of active matter, where the non-
equilibrium nature leads to novel phenomena that deviate from the Hohenberg-Mermin-Wagner
theorem. In this review, we first focus on the recent theoretical and computational progress in the 2D melting problem in passive systems, and then summarize the inspiring results obtained from non-
equilibrium systems. The review closes with comments on several promising directions for predicting 2D melting scenarios and for understanding the non-
equilibrium nature in 2D active matter systems.
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Astrophysics of Galaxies
Radial gradients revealed by mutliscale outflows from down-the-barrel spectroscopy toward a quasar at redshift 3.4
Weimin Yi, Paola Rodriguez Hidalgo, Chen Chen et al. (+9 more)
Active
galactic nucleus(AGN) feedback is a key ingredient in
galaxy formation models and simulations. From an observational point of view, however, the channels of AGN feedback coupling to the interstellar medium (ISM) and circumgalactic medium (CGM) and hence the impact on
galaxy evolution, are largely uncertain and remain fiercely debated, due primarily to the huge gap from
nuclear to CGM scales. Here we present multi-epoch, down-the-barrel spectroscopy toward a luminous
quasar at $z=3.409$ over two decades, which reveals multiscale
outflows expanding from
nuclear to CGM scales along with characteristic radial gradients. Most strikingly, the trends of trough depth across three different-scale, freely expanding
outflows are opposite between N V and C IV, regardless of the spectral normalization and short-term variability, leading to a tenable gradient of N/C and signaling a critical transition from ejective feedback on small scales to regulative feedback on large scales. Our observations of this
quasar offer valuable diagnostics to explore the realistic wind-ISM/CGM coupling, one of the most challenging tasks in state-of-the-art simulations of feedback.
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All authors Weimin Yi, Paola Rodriguez Hidalgo, Chen Chen, P. B. Hall, Zhicheng He, R. P. Easton, D. P. Schneider, W. N. Brandt, Xue-Bing Wu, Kai-Xing Lu, Chuanjun Wang, Yuanjie Feng
Cosmology and Nongalactic Astrophysics
Universal Fitting Formulae for the Peak Concentration of Dark Matter Halos
Dao-zhou Wang, Weipeng Lin and Tian-Cheng Luan
The prediction of the structural properties of dark matter
halos is crucial for studies in modern cosmology and
galaxy formation. Utilizing a comprehensive suite of N-body simulations spanning diverse cosmologies and box sizes, we derive a universal
halo concentration prescription aligned with the excursion set theory framework. The
halo peak-height parameter is revised to incorporate the linear growth factor at the
halo formation epoch, enhancing its physical relevance to assembly history tracking. For fixed
halo mass, we fit the distributions of the
halo concentration and revised peak height to lognormal functions to extract their peak values. We find that these peaks follow a universal, tight relation invariant to
redshift, box size, initial power spectrum, and cosmology, exhibiting remarkably small scatter. In particular, the relation flattens systematically with increasing revised peak height, approaching an asymptotic value of ~2.54, consistent with previous reports of a concentration floor. The fitting formula consistently describes both the mass-concentration and peak height-concentration relations, easily quantifying how these relations depend on
redshift and cosmological parameters. This universal framework enables robust prediction of the most probable (peak)
halo concentration using our fitting formula or theoretical/semianalytical mass assembly histories. A software package for calculating peak concentrations is publicly available online.
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General Relativity and Quantum Cosmology
Nanohertz gravitational waves from domain walls nucleated during inflation
Zhi-Yong Huang and Tie-Jun Gao
We investigate scalar-induced gravitational waves (SIGWs) produced by domain walls (DWs) nucleated via
quantum tunneling during inflation with an extended nucleation time. In contrast to the small-period nucleation framework, in which DWs form over a narrow interval and possess nearly identical radii, we show that an extended nucleation period leads to a distribution of DW radii characterized by $\gamma\equiv\overline{R^{10}}/(\overline{R^5})^2>1$, which enhances the resulting
curvature perturbations. We construct a two-field inflation model with an inflaton $\phi$ and a spectator field $\chi$ coupled through the potential $V(\phi,\chi)$, where the DW tension $\sigma(t)$ evolves smoothly as the inflaton rolls past a critical value. The characteristic width of this transition determines the cutoff scale $k_{\text{cut}}$ of the
curvature power spectrum, enabling the SIGW peak to be placed in the nanohertz frequency band with detectable amplitude. For three representative parameter sets, we compute the SIGW spectra and find that the peak frequency ranges from $\sim10^{-8}$\,Hz to $\sim10^{-1}$\,Hz, with the nanohertz-peaked spectrum matching the NANOGrav and EPTA signals for suitable parameter choices. By selecting different parameters, our model can produce signals detectable by different gravitational-wave detectors.
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High Energy Astrophysical Phenomena
Radio eclipse of the slowest spinning Galactic-field spider pulsar PSR J1932+2121 and its X-ray emission prospect
Ze-Xin Du, Yun-Wei Yu, Zong-Lin Yang et al. (+5 more)
PSR J1932$+$2121 is a newly discovered spider
pulsar with a pronounced
radio eclipse identified by the Five-hundred-meter Aperture Spherical
radio Telescope (FAST); it provides an ideal laboratory for studying the eclipse mechanism and high-energy emission from its intrabinary shock (IBS). By modeling the orbital-phase-dependent dispersion measure variations and flux profiles during the eclipse region with the wind interaction and IBS geometry, we constrain the system to a nearly edge-on inclination ($i_{\mathrm{o}} \simeq 88.55^{\circ}$) and a weak
stellar wind from a low-mass main-sequence companion. Our analysis of the eclipse mechanism suggests that synchrotron absorption by nonthermal electrons can reproduce the observed flux variations with reasonable parameters for the eclipsing medium. We further predict the synchrotron emission from the IBS in PSR J1932$+$2121, showing that its X-ray flux, particularly near the inferior conjunction of the companion
star, could be detectable with XMM/EPIC, EP/FXT, or eXTP/SFA and should exhibit double-peaked orbital modulation by Doppler boosting. These results provide a theoretical framework for understanding this system and for guiding future multiwavelength probes of spider
pulsars.
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All authors Ze-Xin Du, Yun-Wei Yu, Zong-Lin Yang, Aming Chen, Peng-Fei Wang, Jin-Lin Han, De-Jiang Zhou, Xiao-Peng You
Plasma Physics
Evolution of Transversely Asymmetric Electron Beams in Hollow Plasma Channels
Siqin Ding, Jianfei Hua, Fei Li et al. (+2 more)
Plasma wakefield acceleration in hollow
plasma channels has emerged as a promising approach for positron acceleration, since an electron beam can drive wakes with a transversely uniform accelerating field and no intrinsic defocusing force for positrons. Recently, it was proposed that a transversely asymmetric electron beam can excite quadrupole-dominated wakefield in a hollow channel, enabling the formation of accelerating and focusing fields suitable for positrons. However, the self-consistent
evolution and stability of such asymmetric drivers, which are crucial for sustaining a usable wake over long distances, remain insufficiently understood. In this work, we investigate the
evolution modes of wakefield driven by asymmetric electron beams in hollow
plasma channels using fully three-dimensional particle-in-
cell simulations. We identify two distinct unstable scenarios: a reversal of quadrupole field polarity and continuous penetration of the driver into the
plasma wall. By analyzing the transverse dynamics of the driver and the restoring forces provided by the channel ions, we establish simple physical criteria that ensure stable propagation. These results clarify the fundamental constraints governing asymmetric-driver
evolution, provide practical guidance for realizing long-lived, quasisteady wakes in hollow
plasma channels, and indicate that the scheme can preserve mm$\cdot$mrad-level normalized positron emittance.
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All authors Siqin Ding, Jianfei Hua, Fei Li, Shiyu Zhou, Wei Lu
Cosmology and Nongalactic Astrophysics
Probing Baryonic Feedback Effect with CSST Weak Lensing and Future FRB Measurements
Shuai Feng, Yan Gong, Qi Xiong et al. (+4 more)
We explore the joint probe on the baryonic feedback effect using the weak
lensing measurement from the upcoming Chinese Space-station Survey
Telescope (CSST) photometric survey and the dispersion measure (DM) statistics of the fast
radio bursts (FRBs) from next-generation
radio telescopes, i.e., the Square Kilometre Array (SKA) and the Deep Synoptic Array (DSA-2000). By employing the baryonic
halo model, we compute the matter, electron, and matter–electron power spectra, and generate mock data considering realistic noise and systematic effects based on the designs of the
telescopes. These mock data are then analyzed using the Markov Chain Monte Carlo (MCMC) method to investigate the parameter constraints. We find that CSST weak
lensing alone can constrain the baryonic feedback parameter $\log_{10} T_{\text{AGN}}$ to an accuracy of $3.1\%$, with the sum of
neutrino mass bound $\sum m_{\nu} < 0.53\,\mathrm{eV}$. When performing the $3\times2 \,\mathrm{pt}(e,\mathrm{m})$ analysis, the inclusion of FRB DM measurements can significantly improve the precision of $\log_{10} T_{\text{AGN}}$ to $0.4\%$, and will lead to a better constraint on $\sum m_{\nu}$ with an upper limit $< 0.47\,\mathrm{eV}$ by effectively breaking the degeneracy. Our results demonstrate that the joint observation of future FRB DM and weak
lensing surveys is a powerful tool for probing the baryonic feedback effect, which is helpful in obtaining robust constraints on the
neutrino mass and other important cosmological parameters.
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All authors Shuai Feng, Yan Gong, Qi Xiong, Xiaohui Liu, Hengjie Lin, Dingao Hu, Xuelei Chen
High Energy Physics (Phenomenology)
From the Great Wave of Translation to the Force between Quarks
Chris Quigg
The chance observation of a novel traveling wave in a canal led over time to the formulation of a nonlinear wave equation – the Korteweg–de Vries equation – that describes strikingly robust disturbances now called
solitons. The figure of an isolated
soliton corresponds to a reflectionless potential that supports a single bound state in the one-dimensional Schrödinger equation. An appropriate combination of individual
solitons yields a symmetric reflectionless potential that supports multiple bound states. Thus, the KdV equation opens the path to solving the inverse scattering problem for a collection of bound states. Applied to the quarkonium spectra, this formalism allows the construction of reflectionless approximations to the confining potentials that account for the force between
quarks, and to tests of the
flavor-independence of the interquark interaction.
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Quantum Physics
An Analysis of Speculative Window Decoders for Quantum Error Correction
Jocelyn Li and Margaret Martonosi
Fault-tolerant
quantum computing is essential for realizing the substantial computational speedups that
quantum computing can bring, but it requires real-time error decoding with high performance. Speculative window decoding improves performance by reducing the time spent waiting for dependencies from prior decoding windows. However, speculative decoders have only been evaluated under the regime of superconducting
qubits with fast gate speeds, surface codes, and matching decoders. Since different
quantum technologies can have slower gate speeds, we evaluate the performance of speculative decoding under slow gate speeds. We also examine its sensitivity to speculation accuracy, decoder latency, processor count, and workload parallelism, which can vary across different
quantum error correction codes, decoders, and hardware platforms. This work presents design principles for identifying when speculative decoding yields the greatest performance improvements. It also reveals the conditions under which non-speculative decoders outperform speculative decoders.
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Applied Physics · Cross-listed from cs.LG
Rapid FinFET Modelling Using an Autoencoder
Amit Sarkar Suman Sau and Swagata Mandal
This work presents a machine learning framework that leverages an autoencoder (AE) for the efficient modeling of FinFET. We first calibrated a BSIM-CMG model to generate a
dataset of current-voltage (ID-VG) characteristics. This data was used to train an autoencoder that compresses full I-V curves into a low-dimensional latent space, which intrinsically encodes key device physics. A key innovation is the explicit incorporation of parameter such as drain to source voltage (VDS) as an input feature, enhancing the model ability to capture bias dependent variation. The trained model successfully reconstructs full I-V curves and directly extracts critical device metrics including threshold voltage (VTH), subthreshold slope (SS), and peak transconductance (gm). This approach demonstrates that data driven compact models, built from actual characterization data, can achieve high accuracy with minimal training data, providing a powerful tool for rapid device characterization, modelling and
circuit level simulation.
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Chemical Physics
Giant and Continuous Ionic Current Oscillation Induced by Dynamic Surface Charge Regulation in Cylindrical Mesopores
Hongwen Zhang, Yujie Zhao, Zekun Gong et al. (+4 more)
Nanofluidic ionic oscillators based on the dynamic regulation of surface charges hold great promise for neuromorphic computing, biosensing, and ionic
circuits. Here, by dynamically adjusting the local charge inversion on pore walls, we present a simple and effective strategy to achieve periodic current oscillations by harnessing the transient adsorption and desorption of Ca2+ ions in cylindrical mesopores under concentration gradients. Based on the combined precision current measurements and multiphysics simulations, we demonstrate that local overadsorption of Ca2+ ions may induce asymmetric bipolar charge distributions along the pore axis, which periodically reverses the direction of electroosmotic flow and modulates the local ion concentration inside the pore, generating highly regular current oscillations. Notably, both the oscillation frequency and the open-state probability of the pore vary nearly linearly with the applied voltage. Moreover, under dynamic voltage scanning, the system exhibits typical memristive hysteresis, and the switching between the open and closed states is highly reproducible. This work not only reveals the dynamic, heterogeneous surface charge regulation by divalent ions, but also provides a simple, material agnostic method for constructing ionic oscillators and memristors based on dynamic adsorption/desorption of multivalent ions.
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All authors Hongwen Zhang, Yujie Zhao, Zekun Gong, Chih-Yuan Lin, Tianyi Sui, Zuzanna Siwy, Yinghua Qiu
General Relativity and Quantum Cosmology
Nonrotating and rotating black holes with secondary disformal hair in a ghost-free metric-affine parity-violating scalar-torsion theory
E. Brito, G. Macedo, J. R. Nascimento et al. (+2 more)
In this paper, we formulate a ghost-free metric-affine scalar-torsion model in which a pseudoscalar field is coupled to the Nieh–Yan density and derivatively coupled to the Einstein-Palatini tensor. The theory is projectively invariant and, in the shift-symmetric sector, depends on the scalar field only through its gradient. After fixing the projective gauge, the independent connection is solved exactly: its symmetric part is the Levi-Civita connection associated with the metric $h_{\mu\nu}$, disformally related to the metric $g_{\mu\nu}$, while its antisymmetric part is a purely axial torsion sourced by $v_\mu=\partial_\mu\vartheta$. We identify a degenerate ghost-free branch, $\alpha=6\beta^2\kappa^2$, for which
Ricci-flat geometries in the $h$-metric frame solve the metric equations and the Noether current vanishes identically. For example, we consider Schwarzschild and Kerr geometries in the $h$-metric frame, which generate disformal deformations on these geometries from the perspective of the $g$-metric frame. For the Schwarzschild black hole in the $h$-metric frame, we construct static and Babichev–Charmousis-like time-dependent scalar profiles, and discuss horizon regularity in Eddington–Finkelstein coordinates. For the Kerr black hole in the $h$-metric frame, we show that regularity on the rotation axis rules out a nontrivial globally real static fixed-norm scalar profile. For the stationary time-dependent branch, axis regularity and asymptotic reality fix $Y_0=-q^2$ and eliminate the angular dependence, yielding a nontrivial future-regular profile in ingoing Kerr coordinates. The Kerr solution with the nontrivial scalar field is stealth only in the $h$-metric frame. In the $g$-metric frame, it produces disformal corrections stemming from the nontrivial scalar field profile and it represents secondary disformal scalar hair rather than primary Noether-charge hair.
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All authors E. Brito, G. Macedo, J. R. Nascimento, A. Yu. Petrov, P. J. Porfírio