Soft Condensed Matter
Modelling the onset and evolution of immiscible viscous fingering in porous media
Paulo L. K. Caetano Chang, Kundan Kumar, Arne Skauge et al. (+1 more)
The simulation of viscous fingering in porous media is of direct relevance to displacement processes in petroleum engineering and hydrogeology. Building on recent work proposing a modelling approach for well-defined fingers at very adverse viscosity ratios, we investigate the physical mechanisms behind viscous fingering and the modelling requirements for capturing the finger scales and saturation patterns observed in experiments. We simulate and match a viscous fingering experiment at a viscosity ratio of $\mu_{o}/\mu_{w}{=}2000$, discussing the physical significance of each modelling step. Linear stability analysis is used to characterize the early-stage instability of the displacement. Subsequent numerical simulations show that, for the simulated finger scales to match the experiment, the most unstable wavelength at onset must be several times smaller than the desired finger width—so that, after accounting for shielding and merging in the nonlinear regime, the fingers remain thin. Small-scale channelling effects are also required to disrupt the trailing stable region commonly observed in simulations of viscous fingering in nearly homogeneous media. Finally, we show that including a weakly oil-wet capillary pressure function enables our model to capture the bypassed oil observed in the experiment.
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All authors Paulo L. K. Caetano Chang, Kundan Kumar, Arne Skauge, Kenneth S. Sorbie
High Energy Physics (Phenomenology)
Effective flavor interaction for the charged-lepton mass hierarchy and the Koide relation
Olivier Rousselle
This article proposes a dynamical framework to address the charged-
lepton mass hierarchy and derive the empirical Koide formula. We postulate a $U(3)_F$
flavor symmetry at the high-energy scale, where a heavy dynamical flavon field couples to the electroweak
Higgs sector via an effective operator. As the universe cools, spontaneous
symmetry breaking of the
flavor group occurs following the pattern $U(3)_F \to U(1)^3_F$. Subsequently, the electroweak
symmetry breaking at the
Fermi scale generates the charged-
lepton mass
matrix. The phenomenological values of these masses are determined in the infrared regime, where the effective potential governing the flavon VEV undergoes a dynamical
vacuum alignment.The stable minimum of this potential enforces an algebraic equipartition between the
flavor-singlet and
flavor-octet invariants ($I_{(0)} = I_{(8)}$). This
geometric equilibrium yields the Koide mass ratio ($Q=2/3$), successfully identifying the dynamically generated
eigenvalues with the physical pole masses of the electron,
muon, and tau.
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Statistical Mechanics
Exact expressions of correlation functions between two spins in the boundary row of the two-dimensional rectangular Ising model with periodic-free boundary conditions and finite size
Mei Tao
We present exact expressions of correlation functions between two
spins in the boundary row of the two-dimensional rectangular Ising model with periodic-free boundary conditions and finite size. Some properties of exact expressions obtained are discussed. The fundamental property of the Ising model that the long range order emerge as the temperature decrease is shown clearly; expressions of the correlation functions in the thermodynamic limit varies depending on the order of taking limits of two parameters L and N; the impact of different sizes on correlation functions is illustrated with the aid of diagrams. Expressions of the correlation function discussed in this paper in the thermodynamic limit has been presented by previous researchers, and we prove that expressions obtained in this article is identical in form to expressions provided by previous researchers in the thermodynamic limit.
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General Relativity and Quantum Cosmology · Cross-listed from cs.MS
DSLHyPE-a DSL kernel language for the Exascale Hyperbolic PDE Engine ExaHyPE
Timothy J.R. Stokes, Nick Brown, Thomas A. Flynn et al. (+2 more)
We introduce a bilingual domain-specific
language (DSL) for modelling compute kernels within a generic solver for
hyperbolic partial differential equations (PDEs). Users express PDE terms, i.e.~the underlying physics, in a familiar native
language such as C or C++, while the numerical scheme is specified in a Python-embedded DSL, DSLHyPE. DSLHyPE's compiler lowers the Python description to MLIR and introduces a translation pass that integrates it with native code likewise mapped to MLIR. Our approach keeps the numerical representation and the physics implementation separate for as long as possible, while delegating optimization to the compiler through existing MLIR optimization passes. This separation of concerns benefits researchers developing numerical schemes on top of existing PDE implementations or with applications involving nonlinear systems whose PDE terms must solve PDEs themselves. We demonstrate the feasibility of the approach using a gravitational-wave solver and a matter-
evolution solver on x86 processors and H200 GPUs.
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All authors Timothy J.R. Stokes, Nick Brown, Thomas A. Flynn, Maurice Jamieson, Tobias Weinzierl
Instrumentation and Methods for Astrophysics
The Cross-Survey Decade: A Call to Action
Gioia Rau, Robert Benjamin, Federica Bianco et al. (+24 more)
By 2027, three flagship wide-field surveys will be operating simultaneously from ground and space, observing overlapping sky and representing more than $6 billion in US and European public investment. Together they will produce overlapping petabyte-scale
datasets across thousands of square degrees. This is a different class of challenge: the observations are no longer the bottleneck; realizing their joint scientific return now depends on shared computational infrastructure and coordination. Decades of community studies show that combining these
datasets does more than improve precision. For science ranging from weak
lensing to transient discovery and
Galactic-plane astronomy, joint processing and analysis can unlock capabilities no single survey provides alone. Yet the required infrastructure – joint pixel-level processing, cross-calibration and validation, interoperable data access, and the people to build and sustain it – falls outside any single mission or institution's mandate. We issue a call to action for cross-survey science infrastructure, built around four pillars: (1) joint pixel-level processing and validation; (2) an AI-ready data substrate for scientific foundation models; (3) standardized, interoperable data access across surveys, democratizing participation in astrophysical discovery; and (4) dedicated personnel and career pathways. We outline concrete steps for policymakers, agencies, observatories, universities, the research community, and philanthropy, and argue that the moment to act is now, while foundational technical choices can still be aligned at a fraction of the cost of reconciling them later.
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All authors Gioia Rau, Robert Benjamin, Federica Bianco, Ranga-Ram Chary, Andy Connolly, Cecilia Garraffo, Suvi Gezari, Leanne P. Guy, Željko Ivezić, Stephanie Juneau, Vicky Kalogera, Mansi M. Kasliwal, François Lanusse, Zack Li, Rachel Mandelbaum, Peter Melchior, Stella Offner, Antonella Palmese, Jason Rhodes, Edward Schlafly, Kartik Sheth, Rachel Street, Michael Troxel, Tony Tyson, Beth Willman, Michael Wood-Vasey, Yuanyuan Zhang
Data Analysis and Statistics
Multivariate amplitude analysis of the cascade particle decays based on the Nearest Neighbors fitting
I. V. Yeletskikh and A. O. Vasyukov
The Nearest Neighbors estimation of likelihood is implemented for the multivariate amplitude analysis of the cascades of particle decays. In this approach Monte Carlo simulated events that are used to describe data are assigned weights dependent on the parameters of the theoretical fitting model. Each of such weighted events is considered as contributing to N-dimensional probability density function in it's neighborhood in the parameter space. No analytic p.d.f. or cpu-intensive re-generation of N-dimensional p.d.f. at each fit step are required. The method allows accurate accounting for reconstruction effects, demands modest cpu resources and can be effectively multi-threaded. General setup of the fit as well as toy example of the amplitude analysis of B-
meson decays are demonstrated.
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General Relativity and Quantum Cosmology
Thermodynamics, topology and non-Abelian instability of the five-dimensional Einstein–Yang–Mills black hole with exponential entropy correction
Aram Bahroz Brzo, Peshwaz Abdulkareem Abdoul, Behnam Pourhassan et al. (+1 more)
The five-dimensional Einstein–Yang–Mills black hole obtained from the higher-dimensional Wu–Yang ansatz carries a logarithmic non-Abelian contribution to the metric function, making it an analytically tractable setting for studying how gauge charge reshapes horizon thermodynamics beyond four dimensions. We derive expressions for the mass–radius relation, the Hawking temperature, the
entropy, the Yang–Mills potential and the first law, and record the
curvature invariants, which show that the logarithm sharpens the central singularity rather than smoothing it. A non-perturbative exponential
entropy correction is then added, and the corrected heat capacity and free energies are obtained analytically. The geometry is extremal at $r_h=|Q|$ and the heat capacity diverges at $r_h=\sqrt{3}\,|Q|$, a Davies-type point. The correction moves that point inward, $r_{\rm tr}/|Q|\simeq\sqrt{3}-9\lambda\alpha\eta\,e^{-3\sqrt{3}\lambda}$. Using the generalized off-shell free energy we find a conserved topological charge $W=0$ carried by a stable–unstable defect pair whose inner member alone responds to the correction. We then solve the spherically symmetric
magnetic Yang–Mills perturbation sector, which probes the gauge field itself rather than a test scalar. Two independent numerical schemes agree to better than $1.2\times10^{-7}$ and give a purely imaginary unstable mode whose growth rate falls monotonically from $\Gamma_{0}r_h=0.414753$ at $Q/r_h\to0$ to $0.317520$ at $Q/r_h=0.99$, passing through the Davies scale without any feature. Because the effective potential decays as $-9/(4r_{*}^{2})$, with a coefficient above the critical value $1/4$, the sector supports an infinite
geometric tower of unstable modes accumulating at $\Gamma\to0$ with the charge-independent ratio $\Gamma_{n+1}/\Gamma_{n}\to e^{-\pi/\sqrt{2}}\simeq0.108453$, which we confirm numerically.
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All authors Aram Bahroz Brzo, Peshwaz Abdulkareem Abdoul, Behnam Pourhassan, Izzet Skalli
General Relativity and Quantum Cosmology
Renormalization group improved black holes in non-commutative momentum-dependent spacetime geometry
Gema Ilham Baskara Darman, Ar Rohim and Anto Sulaksono
We investigate black holes (BHs) in momentum-dependent spacetime geometry and assess its
quantum Reissner-Nordström (RN) consistency with the weak
gravity conjecture (WGC).
Quantum corrections are introduced through the non-commutative momentum space
algebra as the quantization process, and spacetime renormalization approach as a map between momentum and spacetime spaces. For the Schwarzschild case, thermodynamic analysis indicates the existence of a hot (non-zero temperature) BH remnant when evaporation stops (the
entropy becomes zero), obeying a complementary third law for black hole thermodynamics. We extend this framework to the RN solution and examine its extremal limit. For large BHs with $M \gg M_P$ ($M_P$ for Planck mass), the
quantum-improved RN geometry exhibits a non-zero Hawking temperature in the extremal case, consistent with the WGC, which stipulates that extremal states should not be exactly stable or cold. The resulting momentum-dependent metric and thermodynamic properties are shown to reproduce the results derived from the Poincaré
algebra (classical model) in the infrared (IR) regime.
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General Relativity and Quantum Cosmology
Relational Wigner-Smith Duration in Wheeler-DeWitt Scattering
Daulet Berkimbayev
A closed Friedmann-Lemaitre-Robertson-Walker Wheeler-DeWitt model is formulated as an exact reflection problem. The derivative of its reflection phase defines a relational crossing duration whose first two clock moments follow from a covariant scalar-clock observable. An analytic expression is obtained for this duration, its classical recollapse limit, and the leading
quantum correction. A finite spectral packet also gives an operational, equal-prior minimum error probability for distinguishing the two orientations of recollapse with a
geometric reading. The construction is extended to a bounded finite
quantum detector. Its multichannel reflection
matrix yields probe transitions, spectral-probe correlations, and a
matrix duration. A direct weak-coupling calculation verifies the predicted transition and duration scalings. Scalar-clock conditioning and oriented
geometric sections are shown to be local representations of the same positive-frequency Dirac sector. These results define duration and transition observables entirely through correlations and scattering records of a stationary constrained state, without introducing a background clock.
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General Relativity and Quantum Cosmology
On the Tidal and Frame-Drag Fields in General Relativity
Rahulkumar Solanki
It is known that in
vacuum, two infinitesimally separated timelike observers under free fall notice a relative acceleration due to the
tidal field (or the `electric' part of the Weyl tensor), and if they are carrying inertial guidance gyroscopes, they notice relative precession between these gyroscopes due to the frame-drag field (or the `
magnetic' part of the Weyl tensor). The frame-drag field thus has no Newtonian analog. In this paper, for a family of timelike observers carrying inertial gyroscopes and forming a congruence, we define these fields as constraint equations in the presence of matter using (1+3) covariant splitting of spacetime. Unlike Newtonian
gravity, the relative velocities of the observers around a closed contour formed by their spatial separations (and a temporal vector that closes this contour if the congruence is not hypersurface orthogonal) do not add up to zero due to the frame-drag field and momentum density of the fluid. Moreover, the relative orientations of the gyroscope
spins around the same contour do not generally cancel out due to the
tidal field, the fluid variables (anisotropic pressure and energy density), and the spatial cross-product of relative velocities associated with the separation vectors that form the contour. Additionally, it is shown that even in the absence of the frame-drag field, neighboring observers see relative precession between their gyroscopes when their relative velocity and acceleration are non-parallel due to differential Thomas precession.
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Materials Science
Jessica McDivitt, Dimitar Pashov, Mark van Schilfgaarde et al. (+4 more)
AgCrP2S6 combines a low-
symmetry thiophosphate framework with an
antiferromagnetic Cr sublattice and nonmagnetic Ag sites, providing a setting in which covalency and
magnetic localization compete in the low-energy optical response. We combine single-
crystal x-ray diffraction, Raman spectroscopy,
lattice-dynamical calculations, and self-consistent vertex corrected Feynman diagrammatic many-body approaches to determine the structural, electronic, and excitonic properties of bulk AgCrP2S6. The material remains monoclinic between 100 and 300 K, with additional Ag-site disorder resolved at low temperature, and the optimized structure is dynamically stable. The many-body calculations yield a reduced quasiparticle gap relative to Cr trihalides, but the lowest
excitons remain predominantly local: the calculated low-energy (~1.4 eV) excitation cluster is best described as a weakly bright, strongly anisotropic Frenkel
exciton with dominant onsite d-d character and substantial ligand-assisted d-p admixture.
Symmetry analysis in the C2h setting identifies this state as predominantly Bu and constrains its leading
exciton-
phonon coupling channels to Ag diagonal renormalization and Bg-mediated bright-dark mixing. These results place AgCrP2S6 in a localized excitonic regime in which the stronger p-d hybridization, relative to the more ionic Cr trihalides, narrows the quasiparticle gap, while the
antiferromagnetic exchange and Ag-site dilution disfavor the intersite coherence associated with strongly delocalized low-energy
excitons.
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All authors Jessica McDivitt, Dimitar Pashov, Mark van Schilfgaarde, Justin C. Johnson, Jeffrey L. Blackburn, Anna A. Berseneva, Swagata Acharya
Atomic Physics
Directional Hydrogen Migration in Acetonitrile Dication in Asymmetric Ultrashort Intense Laser Fields
Sato Miyasaka, Yuki Ono, Hiroka Hasegawa et al. (+3 more)
We investigate intramolecular hydrogen migration in acetonitrile dication in phase-controlled $\omega$-$2\omega$ intense
laser fields (800 and 400 nm, 3.3$\times$10$^{14}$ W/cm$^2$) using three-dimensional coincidence ion momentum imaging. The two-body Coulomb explosion pathway, CH$_3$CN$^{2+}$ $\rightarrow$ CH$_3^+$ + CN$^+$, exhibits a clear phase-dependent fragment asymmetry along the
laser polarization direction, showing that the tunnel ionization preferentially prepares the acetonitrile dication with the methyl group pointing toward the smaller amplitude side of the
laser electric fields. The Coulomb explosion pathway occurring after the migration of a single hydrogen atom, CH$_3$CN$^{2+}$ $\rightarrow$ CH$_2^+$ + HCN$^+$, shows a pronounced reduction in the fragment asymmetry. A clear deuteration effect observed for the asymmetry of the hydrogen-migration pathway suggests that the two-color asymmetric
laser field has a significant impact on directionality of intramolecular hydrogen migration in acetonitrile dication.
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All authors Sato Miyasaka, Yuki Ono, Hiroka Hasegawa, Runa Kuroda, Akitaka Matsuda, Akiyoshi Hishikawa
Astrophysics of Galaxies
Osvan M. Portilla-Narvaez, Javier Zaragoza-Cardiel, Gisela N. Ortiz-León et al. (+6 more)
Some interactions between
galaxies produce
tidal tails primarily composed of material from their disks. Within these tails, concentrations of gas and
stars can form, resembling
dwarf galaxies. These
tidal objects often begin to form
stars and become dynamically independent of their parent
galaxies, leading to their classification as
Tidal Dwarf Galaxies (TDGs). By definition, TDGs should consist solely of baryonic material, with a negligible dark matter fraction. In this study, we analyze the dynamics of two TDGs in the Arp 72 system using high-resolution H{\alpha} observations obtained with the MEGARA multi-spectrograph at the GTC (Gran Telescopio Canarias) and neutral hydrogen (HI) data from the GMRT (
Giant Metrewave
Radio Telescope). The HI data were also used to determine the gas mass. We derived the rotation curves and velocity dispersion from the kinematic data, which allowed us to estimate the dynamical mass of the systems. The TDGs were modeled through 3D fitting as rotating disks with additional pressure support, assuming a mass distribution following an exponential law. The gas mass was combined with the
stellar mass to determine the total baryonic mass. Under specific dynamical considerations, we established the relationship between the dynamical mass and the baryonic mass. Additionally, we used the pressure-support corrected circular velocity to compare the behavior of TDGs in the context of the baryonic Tully-Fisher relation (BTFR) with the literature, showing how detached TDGs fall off the relation. The two studied objects are consistent with the expected properties of a TDG.
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All authors Osvan M. Portilla-Narvaez, Javier Zaragoza-Cardiel, Gisela N. Ortiz-León, Y. D. Mayya, Beverly J. Smith, Chandreyee Sengupta, Mark L. Giroux, S. Comerón, Luz I. Alvarez-Cruz
Mesoscale and Nanoscale Physics
Isolating the natural edges of bilayer graphene in gate-defined mesoscopic devices
Francesco Blanda, Grazia Raciti, Thilo Glatzel et al. (+8 more)
We introduce a graphite-gated architecture for
bilayer graphene devices in which the active device is completely isolated from the natural
graphene edges. Using a single patterned graphite-gate layer, we realize a fully electrostatically defined
Hall-bar. Longitudinal and
Hall measurements reveal mesoscopic transport features, including
Hall-effect quenching and magnetoresistance peaks associated with boundary scattering. The dependence of the mesoscopic features on the carrierdensity shows that the effective channel width increases with the
Fermi level and the electrostatic confinement at the gate-defined boundaries, and indicates that the carriers scatter at the electrostatic boundary. Raman spectroscopy and Kelvin probe force microscopy suggest that this boundary is disordered due to the used fabrication methods. Comparably, the
quantum mobility in a fieldeffect transistor fabricated with the same architecture is not limited by boundary scattering and the visibility of
quantum oscillations down to 4 mT suggests a record value of 2.5 x 10^6 cm2/Vs.
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All authors Francesco Blanda, Grazia Raciti, Thilo Glatzel, Aurin Strathmann, Fabrizio Volante, Kenji Watanabe, Takashi Taniguchi, Ilaria Zardo, Thomas Ihn, Klaus Ensslin, Andrea Hofmann
Space Physics
Evolution of lunar wake potentials: structure, energy conversion, and their imprints on velocity distributions
Xin An, Vassilis Angelopoulos, Jasper S. Halekas et al. (+4 more)
We study the
evolution of electric potentials in the lunar wake. The wake potential exhibits two distinct spatial scales. The macroscopic scale arises from
solar wind expansion into the
vacuum, with a potential length-scale growing with distance from the Moon; the microscopic scales arises from ion acoustic shocks near the wake center, with transition layers spanning tens of local Debye lengths. This two-scale potential mediates energy conversion between ions and electrons during wake refilling. The macroscale potential retards electrons and accelerates ions to supersonic velocities, converting electron thermal energy to ion kinetic energy. The microscale potential then decelerates ions to subsonic velocities and heats both species, converting ion kinetic energy back to thermal energy. Together, the two-scale potential imprints distinct signatures on velocity distributions, including ion beams and electron flat-top distributions, consistent with ARTEMIS observations.
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All authors Xin An, Vassilis Angelopoulos, Jasper S. Halekas, Terry Z. Liu, Shaosui Xu, Andrew R. Poppe, Ferdinand Plaschke
Mesoscale and Nanoscale Physics
Optical Voltage Profiling of 2D Semiconductors via Proximal Exciton Sensing
Ha-Leem Kim, Hyungbin Lim, Yuanyi Yang et al. (+6 more)
High contact resistances in atomically thin
semiconductors often mask intrinsic electrical transport properties, particularly at low carrier densities where exotic correlated states emerge. We introduce optical voltage profiling, a noninvasive wide-field technique that replaces local voltage probes with a proximal monolayer MoSe$_2$
exciton sensor. Isolated by thin hexagonal boron nitride, this sensor converts the target's local electrostatic potential into spatially resolved modulations of
exciton reflectance. Through pixel-wise in situ calibration, these signals yield quantitative two-dimensional voltage maps of an actively biased
semiconductor device. Using this method, we demonstrate the carrier-density-driven metal-
insulator transition in
bilayer MoSe$_2$ and obtain channel resistances below 1 k$\Omega$ despite M$\Omega$-scale two-terminal resistances in the metallic region. The optically derived resistance exhibits a metal-
insulator crossover near the resistance
quantum $h/e^2$, and the voltage maps and reconstructed local conductivity reveal pronounced spatial heterogeneity in both insulating and metallic regimes. Beyond resolving channel resistance under high contact-resistance conditions, the technique provides spatially resolved access to microscopic transport heterogeneity in functional van der Waals devices.
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All authors Ha-Leem Kim, Hyungbin Lim, Yuanyi Yang, Ruishi Qi, Ruichen Xia, Can Uzundal, Takashi Taniguchi, Kenji Watanabe, Feng Wang
Materials Science
Magnetic interactions and origin of high Curie temperatures in high Mn content (MnSb2Te4)x(Sb2Te3)1-x quantum materials
Candice R. Forrester, Christophe Testelin, Kaushini Wickramasinghe et al. (+3 more)
Understanding the
magnetic interactions that promote high TC in topological
quantum materials is essential to effectively design materials whose
magnetic configuration persists at high temperatures and are thus practical to integrate into commercial spintronic devices. Here we provide evidence of the origin of the high TC observed in mixed Mn1+ySb2-yTe4 septuple layers and Sb2-yMnyTe3 quintuple layer structures. Analysis of the quintuple layer/septuple layer structures explored their
magnetic behavior through different models of Mn-incorporation in the
crystal, evidenced as Mn
spin S = 5/2, and provided an explanation for the low magnetization per Mn atom observed, signature of competing
ferromagnetic and
antiferromagnetic interactions between Mn2+ ions. Our studies provide insight to better understand and control the Mn incorporation in our samples to optimize their properties.
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All authors Candice R. Forrester, Christophe Testelin, Kaushini Wickramasinghe, David Hrabovsky, Lia Krusin-Elbaum, Maria C. Tamargo
Plasma Physics
Plasma dynamics near the magnetic X-point of the two-wire model: Theory and Simulation
Bin Ahn
The two-wire model (TWM) is a
magnetic configuration generated by two parallel current-carrying wires, and it contains an X-point at its center and a separatrix. Since the TWM
magnetic field is described by a closed-form analytic expression and contains no guide field, it offers a tractable setting for studying how a true
magnetic null shapes
plasma dynamics. This work investigates two complementary regimes: collisionless charged particle dynamics and collisional low temperature
plasma transport. In the collisionless regime, a Lagrangian analysis identifies two particle motion invariants: the total kinetic energy and the base field line value, which is derived from the conserved axial canonical momentum. Collisionless test particle simulations show that the
magnetic moment undergoes shifts when the particle traverses the large gradient region near the null. These shifts enable particles to migrate, the phenomenon in which a particle gyrating about one branch of a base field line jumps to the corresponding branch on the other side of the X-point. A threshold energy for migration is derived, and an empirical expression for the migration confinement time is formulated. In the collisional regime, reduced drift-
diffusion models for low temperature
plasmas are developed in a conformal field-aligned coordinate system, and they predict density plateau formation near the separatrix in the strongly magnetized regime. Self-consistent particle-in-
cell simulations are performed to verify the predicted density plateau. The two complementary studies establish a fundamental understanding of
plasma dynamics near a true
magnetic null for both the collisionless and collisional regimes.
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Earth and Planetary Astrophysics
The Inbound Gas and Dust Evolution of Interstellar Comet 3I/ATLAS from Optical Spectroscopy and Multi-band Photometry
Toni Santana-Ros, Alexey Sergeyev, Oleksandra Ivanova et al. (+9 more)
Interstellar objects (ISOs) provide direct constraints on the composition and
evolution of extrasolar planetary systems. As the third confirmed ISO, comet 3I/ATLAS offers a rare opportunity to study pristine material from another
star system. We present a systematic multi-band monitoring campaign conducted from 2025 July to September. To minimize systematic uncertainties, we utilized a homogeneous
dataset of SDSS $g', r', i', z_s$ and Johnson-Cousins $BVR$ imaging obtained with MuSCAT3/4 on the 2.0-m Faulkes
Telescopes and the 1.5-m Maidanak
telescope. We employed a novel multi-aperture technique providing a robust, distance-independent characterization of the coma, alongside optical spectroscopy from SALT and the Nordic Optical
Telescope. 3I/ATLAS exhibited a stable reddish color with no significant secular variation during its inbound journey. Spectroscopic analysis reveals carbon-chain depletion, with CN as the only prominent molecular emission. Coma morphology, analyzed via azimuthal averaging and rotational gradient filters, shows a persistent sunward jet at a position angle of $\sim$280$^{\circ}$, indicating sustained and localized outgassing from a high-latitude active region. Light-scattering modeling demonstrates that the observed colors and polarization are consistent with dense aggregates of organic matter and silicate minerals, while water ice sublimation remained insufficient to alter the optical properties. The stability of the coma structures and the homogeneous nature of our
dataset indicate that 3I/ATLAS underwent a steady activation phase, preserving a volatile-rich but carbon-chain-poor composition. This characterization points to an object formed in a distinct protoplanetary environment and provides a definitive record of its pre-perihelion
evolution.
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All authors Toni Santana-Ros, Alexey Sergeyev, Oleksandra Ivanova, Sofiia Mykhailova, Johannes Markkanen, Igor Luk'yanyk, Tomasz Kwiatkowski, Dagmara Oszkiewicz, Antti Penttilä, Nicolas Erasmus, Kamoliddin Ergashev, Yurij Krugly
Materials Science
Interface-Controlled Spin-Orbit Torques in Rare-Earth Synthetic Ferrimagnets Probed by Sagnac Magneto-Optics and Harmonic Hall Measurements
Akilan K, Koral Aykin, Jose-Luis Ampuero et al. (+6 more)
Spin-orbit torque (SOT) provides an efficient route for manipulating magnetization in spintronic devices, and its accurate quantification is essential. Here, we investigate Co/Gd-based synthetic ferrimagnets using complementary magnetotransport and magneto-optical techniques. We use a Sagnac magneto-optical interferometry method to directly quantify current-induced magnetization tilting and extract the damping-like SOT effective field. The Sagnac measurements show good agreement with harmonic
Hall analysis across different Co/Gd and Gd/Pt/Co
heterostructures, providing a quantitative determination of the damping-like SOT effective field that does not rely on electrical transport signatures. By varying the Gd thickness and multilayer stacking order, we demonstrate that the damping-like torque is strongly influenced by
spin transport and angular momentum conversion at rare-earth and heavy-metal interfaces. The observation of a finite torque in Gd/Pt/Co/Pt structures, where conventional Pt
spin Hall contributions are expected to compensate, highlights the active role of the Gd layer in SOT generation. Furthermore, interface engineering enables perpendicular
magnetic anisotropy in Gd/Pt/Co/Al
heterostructures with a 2-nm-thick Co layer, allowing current-induced SOT switching at current densities of 8-10 MA/cm$^2$. These results establish rare-earth-based synthetic ferrimagnets as a versatile platform for engineering
spin-orbit phenomena and optimizing low-power spintronic devices.
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All authors Akilan K, Koral Aykin, Jose-Luis Ampuero, Laurent Badie, Stephane Mangin, Sébastien Petit-Watelot, Michel Hehn, Andrew D. Kent, J.-Carlos Rojas-Sánchez
Quantum Physics
Variational Quantum Algorithms for Hyperelasticity: Incorporating Nonlinear Constitutive Behavior
Uditnarayan Kouskiya and Caglar Oskay
This paper extends a recently proposed Variational
Quantum Algorithm framework for nonlinear elasticity to a broader class of constitutive nonlinearities involving rational powers of the stretch. One-dimensional incompressible Ogden and Mooney-Rivlin models are employed as representative examples to demonstrate the proposed methodology. Nonlinear constitutive terms are transformed into forms compatible with the available
quantum algorithmic primitives through the introduction of auxiliary variables and penalty constraints, yielding approximate solutions via a Variational
Quantum Algorithm. An iterative correction strategy based on a sequence of Variational
Quantum Algorithms is then introduced to improve solution accuracy. A Numerical example demonstrates the proposed approach.
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Instrumentation and Methods for Astrophysics
The Atacama Cosmology Telescope: Passband Measurements with an Analysis of Systematic Errors
Thomas Alford, Rahul Datta, Erminia Calabrese et al. (+14 more)
We present measurements of the spectral response of the four Advanced ACTPol (AdvACT) multichroic detector arrays, which observed in frequency bands centered near 30, 40, 90, 150, and 220 GHz. The passbands were measured with a
Fourier transform spectrometer (FTS) combined with coupling optics that direct and match the output of the FTS to the AdvACT receiver. We perform optical simulations of the FTS and coupling optics in order to model frequency-dependent systematic effects in this system. We use these simulations to apply corrections to the measurements and evaluate the remaining systematic uncertainty. We combine these systematic estimates with statistical errors to determine the measured passbands and their uncertainties from our FTS measurement, which are typically 0.75 to 1.5% per detector array. We present the passband characteristics for all measurements made by ACT in a common framework. Additionally, we discuss the performance achieved as well as ways to improve passband measurements in the future.
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All authors Thomas Alford, Rahul Datta, Erminia Calabrese, Steve K. Choi, Shannon M. Duff, Adriaan J. Duivenvoorden, Joseph Golec, Matthew Hasselfeld, J. Colin Hill, Johannes Hubmayr, Jeffrey McMahon, Michael D. Niemack, Lyman A. Page, Alex Thomas, Cristian Vargas, Yuhan Wang, Edward J. Wollack
Quantum Physics
Adolfo G. Grushin
The
quantum geometric tensor has been shown to bound the gap, optical absorption, and dielectric susceptibilities of materials. Here we derive new
quantum-
geometric bounds on the magnitude and sign of the Casimir force between two-dimensional plates in the long-distance limit. These bounds limit the previously attributed benefit of increasing the plate's Chern number to maximize repulsion, and give a
quantum geometric origin to the stronger attractive force of metallic plates, regardless of their Chern number. These bounds allow us to infer that flat Chern bands that saturate
geometric bounds, including Landau levels and moiré flat bands, enlarge the window where Casimir repulsion exists and bring the repulsive crossover to smaller, more experimentally relevant distances. We derive estimates for material platforms such as twisted MoTe$_2$. Our work shows that
quantum-
geometric bounds constrain repulsive Casimir forces beyond previously known
theorems, and suggests new optimization strategies to observe repulsion.
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Chemical Physics
Coupled-cluster molecular properties across the main group that extrapolate beyond training size
Wenhao He, Xu Chen, Noah Song et al. (+10 more)
Coupled-cluster theory defines the accuracy standard for molecular electronic-structure properties but scales too steeply for routine application, whereas density-functional theory is affordable yet systematically biased. We resolve this trade-off with a single equivariant network, HARP (
Hamiltonian Read-out for Properties), that predicts an effective one-electron
Hamiltonian from one inexpensive B3LYP/def2-SVP calculation and derives a broad suite of properties from it (energy, optical gap, dipole, quadrupole, polarizability, Mulliken atomic charges, and Mayer bond orders) at coupled-cluster accuracy across nine main-group elements, including the under-served phosphorus, sulfur, and chlorine chemistries. The model is trained on a new in-house
dataset of multi-property labels computed at the CCSD(T) level for all nine elements. On a held-out test set, it reduces the error of every property by a factor of 3.8 to 270 relative to semi-local, hybrid, and double-hybrid DFT (referenced to composite CCSD(T)/cc-pVTZ), while adding only ~0.1 s wall time per molecule, delivering coupled-cluster-quality predictions at the cost of a single DFT calculation. Critically, deriving every property from a predicted
Hamiltonian rather than pooling per-atom features builds the correct size-scaling into the model architecture: on pi-conjugated oligothiophenes it matches finite-field CCSD polarizability to ~1% and the EOM-CCSD optical gap to ~3% at the largest sizes where those references remain affordable (44 and 37 atoms, where a single CCSD field point already costs ~500x the model's entire inference) and extrapolates the corrected trends to 58-atom chains, a regime where pooling-based architectures fail by construction. Accurate extrapolation is therefore set by the model's inductive bias rather than by the training data.
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All authors Wenhao He, Xu Chen, Noah Song, Haowei Xu, Tim S. Hindges, Bohan Li, Zihan Lin, Yu Yao, Avetik R. Harutyunyan, Fang Liu, Yao Wang, Hao Tang, Ju Li
High Energy Physics (Theory)
A Rotor-Dressed Semiton State in a Monopole–Fermion Model
Yuta Hamada
In four-
flavor massless QED with a
magnetic monopole, a single incident
fermion is scattered into a state carrying a half-integral current vector in each
flavor channel, called the semiton. Recently, the semiton has been interpreted as a twisted-sector
fermion, but its microscopic
Hilbert-space representation has not been fully developed. In this Letter, using a bosonized
fermion–rotor model, we construct the semiton state explicitly. This is achieved by first identifying the correct
vacuum of the system, and then constructing a
unitary operator that shifts the rotor and creates a particle-hole cloud in each
flavor channel. The semiton state is obtained by applying this operator to an ordinary
fermion state. The resulting state has a localized
fermion flavor density in the core region and a half-integral semiton front at the wavepacket. We also show that the state carries the correct $U(1)_M$ charge expectation values and energy-density profile. Our result provides a concrete
Hilbert-space realization of the varying-Fock-space interpretation of monopole–
fermion scattering, advocated in previous works by the author and collaborators.
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High Energy Astrophysical Phenomena
Modeling the Gravitational Wave Signal from the X-ray Pulsar Her X-1
I. D. Markozov, G. K. Pimenov and A. A. Mushtukov
The paper is devoted to modeling the gravitational waves from the X-ray
pulsar Her X-1. The
neutron star is considered as a freely precessing ellipsoid. The gravitational wave signal is calculated in the quadrupole approximation. The $h_{\times}$ and $h_{+}$ polarization profiles are constructed for the precession parameters of the
neutron star in Her X-1 measured in up-to-date works. The possibility of signal detection with the DECIGO
telescope is assessed. The formulas for the semi-analytical modeling of the gravitational wave signal from precessing
neutron stars by the method of perturbations in the small
neutron star ellipticity parameter are deduced.
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High Energy Astrophysical Phenomena
High-Redshift Type Ia Supernovae Exhibit Enhanced Calcium Abundances
Xingzhuo Chen, Ulisses Braga-Neto and Lifan Wang
Type Ia
supernovae (SNe Ia) are major contributors to
cosmic chemical enrichment, and their elemental abundances provide a probe of progenitor properties and explosion physics across
cosmic time. We employ an artificial intelligence-assisted inversion technique to analyze spectra of high-
redshift SNe Ia from the
Supernova Legacy Survey and of gravitationally lensed SNe Ia observed by the James Webb Space
Telescope, extending the sample to
redshift 2.05. We find a positive correlation between SN Ia calcium abundance and
redshift. The
redshift-dependent variation in calcium abundance exceeds that predicted by SN Ia nucleosynthesis simulations with varying progenitor
metallicities, suggesting that high-
redshift SNe Ia may undergo different explosion mechanisms from nearby SNe Ia.
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Superconductivity
Engineering kekule superconductivity from layer-selective interactions in rhombohedral graphene
Hung Dinh Nguyen and Yafis Barlas
At weak coupling, finite-momentum superconductivity is typically associated with broken time-reversal or inversion
symmetry of the
Fermi surface. Here, we show that
lattice-scale pair-density-wave order in rhombohedral multilayer
graphene can arise from layer/orbital-dependent pairing interactions, band chirality, and Dirac-point-centered
Fermi surface
topology while preserving both
symmetries. Using mean-field theory and comparing finite momentum sectors $Q = \pm 2 K_{D}$ with the $ Q = 0$ superconducting state, we find that layer-dependent interactions of opposite signs ($V_{1A}=-V_{JB}=-|V|$) favor an intra-valley Kekulè state with center-of-mass momentum ($ Q=\pm 2 K_D$). In the presence of a time-reversal and inversion
symmetry-preserving Kane-Mele mass ($\lambda$), this state appears only above a critical carrier density ($n^{crit}_{K}(\lambda,J)$). The two superconducting condensates exhibit opposite chirality, $J(-J)$ for $K_D(-K_D) $ valleys, thereby preserving time-reversal and inversion
symmetry. We map the phase diagram and analyze the dependence of $T_c$ on the chirality index $J$ and $\lambda$. We also evaluate the superfluid stiffness in the Kekulè superconducting state, thereby determining the Berezinskii-Kosterlitz-Thouless (BKT) transition temperature. Our results show that orbital-dependent interactions in the presence of band chirality favor finite-momentum pairing in time-reversal and inversion symmetric Dirac materials.
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Mathematical Physics
The Decoherence Exponent: Stable Phase Noise and Constraints on Objective State Reduction
Milen V. Velev and Ivo D. Dinov
Let $L_u$ be a symmetric Levy process representing an unobserved phase lift, coupling to a
quantum system via charge $Q$. Averaging $e^{iL_uQ}$ gives a completely positive dephasing
semigroup. If the characteristic exponent lacks an intrinsic charge scale, the Levy-Khintchine
theorem forces $\eta(\xi)=D | \xi |^{\alpha}$ ($0<\alpha\le2$), so coherences decay at $\Gamma_{ab}=D | q_a-q_b |^{\alpha}$. For integer charge differences, the process descends to the wrapped variable $\Theta_u=L_u\bmod 2\pi$; for real charges, the lift is the relevant phase. Schoenberg's
theorem ensures complete positivity for any finite real spectrum when $0<\alpha\le2$, while $\alpha>2$ yields an analytic obstruction. This boundary is exact, verified numerically here. A Gaussian integrated phase gives quadratic charge dependence, though colored Gaussian noise need not yield a Markov
semigroup. Two idealized non-Gaussian mechanisms are analyzed: inverse-power Poisson shot noise ($\alpha=d/p$) and Bochner subordination of Brownian phase by an $\alpha/2$-stable clock. For a bounded reduction walk, we prove Born probabilities for every symmetric bounded proposal law. Simulations of truncated stable laws ($\alpha=0.5,1,1.5,2$) confirm this law-independence. In continuous time, $\alpha$-stable drivers fail to reduce: the exact-flow (Marcus) equation oscillates, and the naive Ito jump equation fails to preserve state. For Gaussian white noise, the Itô model collapses to Born probabilities, whereas the exact-flow (Stratonovich) model does not collapse without a threshold and yields non-Born exit probabilities. The quadratic case recovers Milburn's small-step limit, not his exact Poisson dynamics. Finally, a bi-temporal geometry is examined as a possible compact phase source, but closed timelike curves, nonunitary
evolution, and an unstable mode tower prevent a consistent field-theoretic realization.
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Cosmology and Nongalactic Astrophysics
PowerFull: fast and accurate computation of the relativistic angular galaxy power spectrum including local primordial non-Gaussianity
Gregory Lukens and Donghui Jeong
Current and forthcoming wide-field
galaxy surveys, such as SPHEREx and Euclid, provide a unique opportunity to probe the ultra-large scales of structure formation, where
primordial non-Gaussianity, often parameterized by $f_\text{NL}$, is expected to leave its most detectable imprint. At the same time, these surveys inevitably enter regimes where relativistic and wide-angle effects become significant, requiring careful modeling to extract unbiased cosmological information. We address these challenges by applying the total-angular-momentum (TAM) formalism to describe
redshift-space clustering beyond the flat-sky approximation. The standard
Fourier-mode description, which characterizes distortions by the angle between a mode and a line of sight, becomes ill-defined over wide fields, whereas the TAM basis naturally separates radial and angular contributions and incorporates the relevant relativistic effects. Within this framework, we provide a new parameterization of wide-angle predictions that can be compared directly with survey data. We then introduce PowerFull, a modification of the Julia-based 2-FAST package, which enables efficient computation of the full relativistic angular power spectrum. Finally, using Fisher information
matrix-based analyses, we show that a survey like SPHEREx reaches $\sigma(f_\text{NL}) \sim 1$, but that neglecting the relativistic and wide-angle contributions shifts the recovered $f_\text{NL}$ by an amount of order its own uncertainty: at this precision the inferred value is biased unless the clustering is modeled consistently.
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