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Physics

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Friday 14 August

Atmospheric and Oceanic Physics · Cross-listed from cs.CY

Meteorology-driven Causal Nowcasting of Fugitive Landfill Emissions from Measured Coupling Timescales

Timothy C. Pearce, David J. T. Smith, Alec Dobney et al. (+1 more)

Which meteorological processes control exposure to fugitive gases downwind of a source, and on what timescales, have largely been inferred from dispersion theory and partial field evidence. Here we show that the meteorological drivers of elevated hydrogen sulphide (H$_2$S) exposure at a long-monitored European landfill, and the timescales over which each acts, can be identified directly from monitoring data. Wind direction, wind speed and atmospheric pressure form the causal core, with the share of directed information carried by pressure increasing with aggregation scale. The recovered timescales are consistent with those expected from the underlying atmospheric processes. We use these driver timescales to initialise CAIRN (Causal-Anchored Inference for Receptor Nowcasting), a machine-learning nowcaster with fast and slow memory components. Trained on past exceedances of WHO guideline levels, CAIRN nowcasts them from surface weather measurements and the calendar alone, without hand-engineered features. Combining four such nowcasters produces a site-level, tiered alert that agrees substantially with that generated by a direct sensor network and tracks an independent record of community odour reports. Meteorological variables can therefore serve as an inference-time proxy for exposure relative to WHO guideline levels, and they link atmospheric dynamics to community impact as an episode unfolds.
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All authors Timothy C. Pearce, David J. T. Smith, Alec Dobney, Alessia Freddo

Accelerator Physics

Particle tracking with physics-informed deep learning methods

Matthias Remta, Anja Beck, Shanthalakshmi Kilambi et al. (+2 more)

Simulating the motion of charged particles in electromagnetic fields is essential for designing and optimising particle accelerators. Conventional tools rely on symplectic integration schemes, which provide high accuracy but are computationally expensive. As a consequence, optimisation in moderate to high-dimensional parameter spaces as well as simulations of tens of thousands to millions of particles can be computationally prohibitive. This contribution explores the possibilities of employing modern machine-learning based tools, in particular SympNet and DeepONet, to enable fast particle simulations. A major novelty is the modification of the conventional SympNet architecture to enable learning of parametric Hamiltonian dynamics. The models are trained and tested on a toy setup of a circular accelerator comprising two different types of quadrupole magnets with varying field strengths. All models achieved faster inference than the symplectic integrator, at the expanse of significantly reduced accuracy. The SympNet implementation achieved the lowest mean squared error. Additionally, a DeepONet was employed to predict the evolution of particle densities, derived from the single-particle simulations.
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All authors Matthias Remta, Anja Beck, Shanthalakshmi Kilambi, Thomas Zhang, Francesco Velotti

Materials Science

Dispersive-phonon-driven room-temperature Ni1+-Ni2+ polaron hopping in spin-charge coupled rutile niobate

Gourab Roy, Mohit Kumar, Sayan Ghosh et al. (+4 more)

Understanding how lattice dynamics mediate polaron hopping is essential for designing multifunctional correlated oxides. Here, we demonstrate room-temperature dispersive phonon excitations and elucidate the Ni1+-Ni2+ polaron-hopping mechanism and the presence of rare spin-charge-phonon coupling even in a magnetically short-range-ordered state in rutile niobate, a rare room-temperature magnetodielectric system. We reveal room-temperature dispersive phonon excitations using inelastic neutron scattering (INS), complemented by machine-learning-based phonon calculations, to establish the microscopic origin of the polaron-hopping mechanism. Experimental evidence of dispersive phonon-driven polaron hopping is scarce. INS measurements show significant dispersive phonon excitations at 21, 33, and 47 meV, implying collective lattice dynamics that enable delocalized polaron propagation via coupled charge-spin-phonon interactions. Dispersive phonons couple to charge carriers and promote correlated NiO6 lattice distortions, facilitating delocalized polaron hopping. Low-energy magnetic excitations at 4 and 8 meV indicate the presence of local short-range magnetic correlations or spin-orbit-coupling-induced anisotropy in deformed NiO6 octahedra, which are thoroughly discussed. Machine-learning phonon calculations replicate the experimentally observed phonon excitations and demonstrate lattice instability, which is compatible with dynamic local distortions caused by polaron production. These findings provide microscopic evidence for a coupled charge-spin-phonon mechanism that mediates polaron hopping in rutile oxide systems.
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All authors Gourab Roy, Mohit Kumar, Sayan Ghosh, Ekta Kushwaha, Manh Duc Le, Devashibhai T. Adroja, Tathamay Basu

Geophysics · Cross-listed from stat.ML

Extending Occam's inversion with lasso fusion, overcomplete dictionaries, and isotropic total variation regularisation

Anandaroop Ray

Occam's inversion is a robust algorithm to perform nonlinear geophysical inversion. It provides the smoothest model within observation noise, thereby discouraging geological overinterpretation. While Occam originally penalised l2 model roughness, l1 can be used to provide models that are visually sharp. However, l1 regularised geophysical inversion has diverged from the larger body of statistics and imaging literature. For example, l1 regularisation with a difference operator (i.e., total variation) in multiple dimensions has two distinct forms, only one of which is invariant to edge orientation – a distinction often overlooked in geophysics. In one dimension this reduces to the fused lasso problem in statistics. Within the Occam framework, for l2 data norm and l1 model regularisation, we show that lasso fusion through either synthesis or analysis leads to the same 1D problem. We extend the framework to multiple dimensions and to operators such as wavelet transforms in a dictionary, unravelling the mathematics behind three commonly used solvers for l1 regularised problems. These are coordinate descent, iteratively reweighted least squares (IRLS), and split Bregman. We use them to solve a sequence of problems that are linear (1D regression, 2D deblurring) and nonlinear (1D airborne transient electromagnetics) including a field data example. We recommend coordinate descent for 1D problems, and IRLS over split Bregman for 2D problems, with IRLS requiring up to an order of magnitude fewer least squares solves. We hope this work will further encourage geophysicists to adopt l1 regularised inversion, by presenting its various forms as a familiar Occam's inversion.
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Mesoscale and Nanoscale Physics

Disorder signatures emerging at millikelvin temperatures in Si/SiGe field-effect stacks

Lino Visser, Alberto Mistroni, Yuji Yamamoto et al. (+9 more)

The performance and scalability of electron spin qubits based on gate-defined quantum-dots in undoped Si/SiGe field-effect stacks remain constrained by disorder originating from the gate stack. Its coupling to the quantum well can be reduced by increasing the Si quantum well depth, while electrostatic charge history, for example through interface-trap filling, can further modify the effective disorder landscape. Although such disorder is commonly benchmarked through mobility measurements using magnetotransport and Hall bar devices, dedicated investigations at millikelvin temperatures relevant for quantum-dot operation remain limited. Here, we use temperature-dependent magnetotransport on Hall bar shaped field-effect transistors to investigate how mobility-based disorder signatures depend on quantum-well depth and charge history from \(1.5~\mathrm{K}\) down to the millikelvin regime. We show that magnetotransport characterization at \(1.5~\mathrm{K}\) captures the dominant mobility improvement associated with reduced dielectric-interface coupling, but can underestimate disorder differences that emerge at millikelvin temperatures, particularly in the low-density regime. Our results therefore highlight that millikelvin magnetotransport characterization of Hall bar devices can provide additional insight for optimizing Si/SiGe field-effect stacks, particularly in the context of gate-defined quantum dot spin qubits.
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All authors Lino Visser, Alberto Mistroni, Yuji Yamamoto, Fabian Fidorra, Oksana Fursenko, Steffen Marschmeyer, Marvin H. Zoellner, Giovanni Capellini, Dominique Bougeard, Vincent Mourik, Marco Lisker, Felix Reichmann

Materials Science

Microscopic investigation of spin dynamics in the single-chain magnet Sr4Mn2CoO9

G. Roy, S. Ghosh, M. Kumar et al. (+8 more)

One-dimensional single-chain magnets offer a unique platform for studying the interplay of crystal-field effects, exchange interactions, and lattice dynamics. Here, we investigate spin excitations in Sr4Mn2CoO9 using inelastic neutron scattering (INS) and theoretical modelling. INS reveals two low-energy magnetic excitations at 4 and 7 meV from Mn-Co-Mn spin chains, alongside higher-energy crystal-electric-field (CEF) excitations from two crystallographically inequivalent Co2+ sites. Interestingly, these spin excitations persist at room temperature, demonstrating dynamic magnetic correlations in the absence of long-range order. Furthermore, the crystal-field modelling, based on Stevens operator formalism, reproduces well the CEF spectra, establishing Ising-like Kramers ground-state doublets with strong uniaxial magnetic anisotropy for both Co2+ ions. In addition, the spin wave simulation using SpinW reproduces the spin excitation spectrum and reveals microscopic exchange interactions in two non-interacting Mn-Co-Mn spin chains. Finally, machine-learning lattice-dynamics calculations confirm the phonon spectrum and spin-phonon coupling. By projecting the exchange Hamiltonian onto CEF ground-state doublets, we estimate exchange-induced splittings matching the observed excitations. Thus, our results elucidate low-energy spin dynamics arising from combined crystal-field anisotropy and exchange interactions, with the persistent low-energy excitation providing a microscopic pathway for thermally activated spin relaxation. Furthermore, this work delivers a unified microscopic understanding of the interplay between crystal-field effects, magnetic exchange, and lattice dynamics in Sr4Mn2CoO9, advancing insights into spin dynamics in low-dimensional transition-metal oxides.
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All authors G. Roy, S. Ghosh, M. Kumar, E. Kushwaha, J. Sannigrahi, V. Caignaert, W. Prellier, D. T. Adroja, D. Voneshen, V. Hardy, T. Basu

Instrumentation and Detectors

Variable-Path-Length FTIR of E. coli in Aqueous Media

Jonathan Matsuura, Andrew Huang, Jaehyeon Kim et al. (+3 more)

Transmission infrared spectroscopy has been widely used for chemical analysis of biological samples in aqueous environments. However, its scope of applications has been limited by the path length, which is either too large or fixed, posing challenges for analyzing highly absorbing or heterogeneous samples. In this work, a mid-infrared (mid-IR) optical fiber probe was used for Fourier transform infrared (FTIR) micro-spectroscopy of aqueous Escherichia coli (E. coli) samples, providing continuous tuning of optical path length and sampling of near-surface and bulk regions. The mid-IR absorbance of the protein signal at 1548 cm-1 increased linearly with path length, consistent with the Beer-Lambert law. Path-length dependent spectra were used to calculate the spatially heterogeneous absorption coefficient of E. coli suspensions in aqueous media. The results demonstrate the ability of our fiber-based technique to resolve signals originating from different depths into the biological solution.
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All authors Jonathan Matsuura, Andrew Huang, Jaehyeon Kim, Ching-Ping Chang, Kai Zhang, Yingjie Zhang

Quantum Physics

Exchange-only qubit stabilized by a single-spin qubit

Irina Heinz, Mira Sharma and Joris Kattemölle

Hybrid approaches that combine different spin qubit encodings offer promising advantages. In particular, the additional degrees of freedom available in exchange-only qubits and their extensions enable enhanced spin lifetimes and facilitate error detection through the use of auxiliary spins. We show that integrating Loss-DiVincenzo with exchange-only qubits provides a practical route to realizing these benefits while remaining compatible with spin-shuttling architectures. We further demonstrate how the singlet-only exchange-only qubit can be employed for error detection, and we present a fault-tolerant $\pi$-rotation about each of the three control axes of the (singlet-only) exchange-only qubit. By enabling error detection at the lowest encoding level, our approach effectively converts charge and nuclear noise into erasures, thereby suppressing error propagation and potentially enhancing the performance of quantum error-correction schemes. More broadly, our work establishes a new perspective on the singlet-only exchange-only qubit as a logical encoding, opening the door to fault-tolerant gate constructions and spin-tailored quantum error-correction protocols for semiconductor-based quantum computing.
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Medical Physics

MRI-guided cardiac radiotherapy using a 1.5 T MR-linac: surveying emerging patterns of care

O. Akdag, S. Mandija, J. Pomp et al. (+11 more)

Background: Cardiac tumours are rare and treated by surgical resections, which are complex, invasive and carry procedural risks. MRI-guided radiotherapy (MRgRT) noninvasively facilitates conformal dose deliveries using soft-tissue imaging and adaptive radiotherapy techniques. Aim: To assess the application of MRgRT for cardiac tumours, we conducted a patterns-of-care analysis with users of the 1.5T MR-linac. Materials & methods: A survey was distributed to users of the 1.5T MR-linac that treated patients with cardiac tumours. The survey included 30 questions concerning the patient cohort, imaging, treatment planning/simulation, radiotherapy treatment and treatment outcome. Results: Users from six international institutes completed the survey reporting twelve cardiac MRgRT treatments between 2021-2024. The median age[range] of the patients was 59[16-81] years with 50% of the cases concerning the treatment of primary tumours. The prescribed dose ranged between 30-60 Gy, with 30 Gy being prescribed the most (59%). In 75% of the cases, the treatment plans were delivered in five fractions with 6-8 Gy per fraction. Daily images were acquired with T1- and T2-weighted MRI and respiratory motion monitoring was performed in 92% of the cases using cine imaging. A single case was treated with intrafraction motion management using a novel vendor-provided gating solution on the MR-linac. Treatment outcomes were reported for 50% of the cases. All, but one case, attained local control using MRgRT without serious adverse events (grade$\geq$3). Conclusion: This study provides real-world insights into the feasibility and early outcomes to aid the development of cardiac MRgRT treatment recommendations and protocol harmonization.
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All authors O. Akdag, S. Mandija, J. Pomp, M.P.W. Intven, X. Chen, J. Yang, S. Oh, M. Trombetta, H. Tan, J. De Leon, M. Jameson, E. Efe, C. Önal, M.F. Fast

Quantum Physics

Foundation Neural Effective Hamiltonian for Strongly Correlated Quantum Materials

Lixing Zhang, Hongjie Jiang and Di Luo

Simulating strongly correlated quantum materials often involves not a single Hamiltonian, but a family of Hamiltonians whose ground states evolve across experimentally tunable couplings. Foundation neural quantum states (FNQS) offer a promising route to amortizing many-body calculations across such families, but can lose accuracy near phase transitions and still incur non-negligible sampling costs that grow with the number of target couplings. We introduce the Foundation Neural Effective Hamiltonian (FNEH), which projects a Hamiltonian family onto a compact subspace spanned by FNQS sampled at selected couplings. By variationally combining FNQS across parameter space, FNEH systematically improves their ground-state approximation and can recover phase boundaries that the foundation model misidentifies. Once the required operator matrix elements are sampled, FNEH enables sweeps over couplings, observables, and phase boundaries at a cost governed by the small effective-Hamiltonian dimension, without repeated neural-network sampling at every target coupling. We demonstrate FNEH in strongly correlated moiré materials, where it accurately resolves competing phases, enables high-resolution multidimensional phase scans, and substantially reduces the computational cost of exploring many target Hamiltonians. The results open a new avenue for studying strongly correlated quantum materials with foundation models.
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Quantum Physics

Synthesizing In-Bulk Topological Corner States via Giant Atoms

Zhao-Min Gao and Xin Wang

Corner states in higher-order topological insulators are typically confined to geometric corners, limiting their flexibility for scalable quantum information processing. We propose a scheme to synthesize topological corner states at arbitrary positions within the bulk of a two-dimensional Su-Schrieffer-Heeger (SSH) lattice by coupling it to giant atoms. By engineering an L-shaped multi-point coupling that satisfies the vacancy-like dressed state (VDS) condition, where the photonic wavefunction vanishes at the coupling sites to form an artificial bulk boundary, we derive the conditions for synthesizing a zero-energy corner state at any target position. We demonstrate that the engineered corner state exhibits high fidelity and spatial localization, remaining robust against realistic disorder. Extending to multi-atom networks, we realize a versatile quantum switch via a giant superatom, enabling multi-channel control over 0D corner states and 1D edge states through the dual-resonance condition. Furthermore, we demonstrate the coherent interactions between two giant atoms mediated by VDS-engineered corner states. Governed by a sublattice selection rule, the coupling activates exclusively in intersecting configurations and decays exponentially with distance. Our work establishes a highly reconfigurable platform for embedding topological boundary modes within the bulk, offering a robust pathway for scalable topological quantum networks.
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General Relativity and Quantum Cosmology

Asymptotic flatness beyond General Relativity

David Maibach

The asymptotic symmetry group of asymptotically flat spacetimes gives rise to balance flux equations that constrain, fully non-perturbatively, the asymptotic strain measured by gravitational-wave detectors. Such constraints are sharp tools for identifying features such as the memory effect. As detector sensitivities improve, it becomes imperative to place the most promising beyond-GR candidates on the same footing. Whether the asymptotically flat framework applies to such theories at all is far from obvious and requires careful analysis of the additional degrees of freedom reaching future null infinity. In this work, we address this question. We integrate the Bondi-Sachs hierarchy in the presence of an arbitrary stress-energy tensor and extract the falloff conditions its components must satisfy for the standard metric decay to close. We then feed the most general scalar-vector-tensor (SVT) theory with second-order equations of motion through this framework. Recasting the field equations in the effective Einstein form $G_{\mu\nu}=T^{\rm eff}_{\mu\nu}/G_4(\Phi,X)$ and evaluating every operator in the SVT Lagrangian against the falloff table, we condense the outcome into a constraint table for the coupling functionals and their derivatives at the asymptotic vacuum, sharpened by the additional equations of motion and vacuum stability. Remarkably few conditions survive. The scalar potential must vanish to cubic order at the asymptotic vacuum, the asymptotic Newton constant must be finite and positive, the scalar and vector modes must be canonically normalized, and the conformally coupled sector carries a frame subtlety. Every other coupling functional is protected by the theory's structure. The constraint table thus provides a diagnostic for screening beyond-GR models against asymptotic flatness and establishes the BMS group as the asymptotic symmetry group across the entire SVT class.
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Nuclear Theory

Enhancement of alpha-decay by positive hexadecapole deformation

Kai Ren, Minghui Hu, Pengfei Ma et al. (+2 more)

Whether hexadecapole deformation ($\beta_4$) influences $\alpha$ decay remains controversial: machine-learning analyses suggest a strong link to cluster preformation, while empirical formulas find only marginal effects. We show that this discrepancy originates in the treatment of shell effects—without an explicit shell correction, residuals near magic numbers are absorbed into the deformation coefficients, obscuring the genuine $\beta_4$ dependence. Adding the inverse Casten factor $C_{pn}$, which encodes valence proton–neutron correlations relative to the nearest closed shells, and the parent-nucleus deformation $\beta_4^{(p)}$ to the Royer formula reduces the root-mean-square deviation from 0.309 to 0.184 for 192 even–even nuclei. The fitted negative $\beta_4^{(p)}$ coefficient shows that positive hexadecapole deformation systematically shortens half-lives, consistent with enhanced $\alpha$-cluster preformation at locally convex surface regions. For the $Z=94$ isotopic chain (Pu), where pronounced $\beta_4^{(p)}>0$ occurs, the original Royer formula overestimates half-lives by up to $\sim\!0.5$~dex, providing a clear, testable signature of this surface-preformation effect. The same correction also improves the UDL and yields predictions for 1060 even–even nuclei.
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All authors Kai Ren, Minghui Hu, Pengfei Ma, Junlong Tian, Cheng Li

Quantum Physics

Local geometry for Schmidt number witnesses

Young-Hoon Kiem and Seung-Hyeok Kye

Suppose that $F_E$ is the face of the convex set of all $m\otimes n$ bi-partite states which consists of states with ranges contained in a subspace $E$. By the result in [Phys. Rev. A 112 (2025), 032426], there exist Schmidt number $\ell$ witnesses outside of the face $F_{E^\perp}$ if and only if $\ell\le\mu$, where $\mu$ is the minimum of Schmidt ranks of nonzero vectors in $E$. In this paper, we show that every neighborhood of the projection state located at the center of $F_{E^\perp}$ contains Schmidt number $\ell$ witnesses if and only if $\ell\ge\mu$. In order to understand the local shape of the convex sets of $k$-blockpositive matrices around this projection state, we introduce principal supporting hyperplanes, and show that they correspond to vectors in $E$ with Schmidt rank $\le k$. Using techniques from algebraic geometry, we show that the inclusions between these convex sets are detected by principal supporting hyperplanes through the projection state for generic subspaces $E$, while for non-generic subspaces they may not be detected by any supporting hyperplane.
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High Energy Physics (Phenomenology)

Probing the Single Production of First-Generation Singlet Vector-like Leptons at Future $e^+e^-$ Colliders

Yao-Bei Liu and Stefano Moretti

We study the single production of first-generation weak-isosinglet vector-like leptons (VLLs) at future $e^+e^-$ colliders through $e^+e^-\to e^\pm E^\mp$, with the subsequent decays $E^\pm\to W^\pm\nu_e$, $e^\pm Z$, and $e^\pm h$. For the heavy VLL masses considered, the hadronic decays of the $W$ and $Z$ bosons are reconstructed as fat-jets, while the Higgs boson is reconstructed from two resolved $b$-tagged jets at $\sqrt{s}=1~{\rm TeV}$ and as a fat-jet at $\sqrt{s}=1.5~{\rm TeV}$. Using detector-level Monte Carlo simulations for the 1~TeV ILC and 1.5~TeV CLIC, we perform a baseline cut-based analysis in which the well-defined two-body production kinematics are exploited through a mass-hypothesis-dependent selection on the associated-electron energy. At fixed nominal center-of-mass energy, this observable is in one-to-one correspondence with the VLL recoil mass and therefore provides a common mass-sensitive discriminator for all three decay channels. We derive the $2\sigma$ exclusion and $5\sigma$ discovery reaches on the VLL–electron mixing angle $\sin\theta_L$ as functions of the integrated luminosity. For the benchmark points studied, sizeable sensitivity is retained at $m_E=900~{\rm GeV}$ at the ILC and $m_E=1400~{\rm GeV}$ at CLIC, while the accessible values of $\sin\theta_L$ extend below the reference electroweak precision bound used in this study. These results demonstrate the complementary potential of direct searches for first-generation singlet VLLs at future lepton colliders.
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High Energy Physics (Theory)

Dirac, Majorana, and Weyl Spinors in Arbitrary Dimension and Signature

Jan Hajer

Fermionic field types in arbitrary signature are often inferred from complex Spin representations alone, which obscures distinctions associated with real structures, disconnected spacetime reflections, and action-level bilinear constraints. We give a convention-explicit classification that treats the full real Clifford algebra and its even subalgebra separately, thereby distinguishing pinors from spinors and Pin-equivariant Majorana-type structures from structures that are only Spin-equivariant. Adjoint, complex-conjugation, and transposition intertwiners are combined with elementary and collective reflection lifts into a unified sign calculus. The resulting local Clifford classification is organised into thirty-two periodicity sectors determined by the Bott class and the total dimension modulo eight, without including theory-dependent gauge, anomaly, or global constraints. For each sector, we identify the available Dirac, Weyl, Majorana, symplectic Majorana, Majorana-Weyl, and symplectic Majorana-Weyl fields. The existence of an invariant pairing is distinguished from intertwiner compatibility, Grassmann and chiral selection rules, covariant index contraction, and Hermiticity of local bilinear operators.
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Solar and Stellar Astrophysics

Magnetoacoustic Portals in Quiet-Sun Fluxtubes Revealed by Chromospheric Spectropolarimetry with SUNRISE III/SCIP

Takayoshi Oba, Yukio Katsukawa, Masahito Kubo et al. (+36 more)

Acoustic waves propagate into the chromosphere, contributing to energy transport and their dynamics. Their upward propagation is restricted to frequencies above the acoustic cutoff frequency. The magnetic field configuration plays a key role in determining whether acoustic waves can propagate upward because the cutoff frequency is reduced in regions where the field is inclined with respect to gravity, forming so-called magnetoacoustic portals. Previous studies linked magnetic fields and oscillations in quiet regions, but these analyses were based on photospheric magnetic field information, leaving chromospheric structure unconstrained. This study investigates the coupling between acoustic waves and magnetic topology using photospheric and, for the first time, chromospheric spectropolarimetry in a quiet region, obtained with the Sunrise Chromospheric Infrared SpectroPolarimeter (SCIP) aboard the Sunrise iii balloon-borne solar observatory launched in 2024. The SCIP sit-and-stare observations sampled magnetic features in which the line-of-sight field strength exhibits multiple sharp spatial peaks in the photosphere while becoming broader and weaker at two heights in the chromosphere, indicating expanding fluxtubes. The chromospheric velocity field in these fluxtubes exhibits strong 5-minute oscillations, while the surrounding regions show weak 3-minute oscillations. In these fluxtubes, sawtooth temporal velocity variations are associated with intensity enhancements, suggesting steepened shocks. Fluxtubes with low-frequency oscillations are identified not only in network regions but also in weak internetwork regions. These results provide observational evidence that fluxtubes expanding into the chromosphere act as magnetoacoustic portals, in both network and internetwork regions, allowing low-frequency waves to propagate upward and driving chromospheric dynamics via shocks.
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All authors Takayoshi Oba, Yukio Katsukawa, Masahito Kubo, Yusuke Kawabata, Takuma Matsumoto, Ryohtaroh T. Ishikawa, Yoshihiro Naito, Toshifumi Shimizu, Hirohisa Hara, Fumihiro Uraguchi, Toshihiro Tsuzuki, Kazuya Shinoda, Tomonori Tamura, Yoshinori Suematsu, Jose Carlos del Toro Iniesta, David Orozco Suárez, Maria Balaguer Jiménez, Azaymi L. Siu-Tapia, Carlos Quintero Noda, Sami K. Solanki, Andreas Lagg, Achim Gandorfer, Pietro Bernasconi, Thomas Berkefeld, Tino L. Riethmüller, Alberto Álvarez-Herrero, H. N. Smitha, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Hanna Strecker, Dušan Vukadinović

Materials Science

Probing intrinsic magnetic phases in low-dimensional nearly twin-free NiPS$_3$ single crystals

Yeochan An, Heejun Yang, Sung Jin Park et al. (+6 more)

We report the intrinsic thermal and magnetic properties of the low-dimensional van der Waals (vdW) antiferromagnet NiPS$_3$ and explore its emergent magnetic phases by controlling crystallographic twinning. Using nearly twin-free crystals, we resolve intrinsic properties that are typically obscured by multidomain effects in bulk samples. Magnetization results reveal a highly anisotropic, sharp spin-flop transition, confirming the high domain purity of our crystals. Furthermore, high-precision thermodynamic and transport data reveal a broad fluctuation regime around the Néel temperature ($T_{\mathrm{N}}$ = 157.5 K), with a heat capacity anomaly and a concurrent suppression of thermal conductivity. Field-dependent thermal transport shows a small but distinct contribution from spin-lattice coupling, as evidenced by the dip at the spin-flop transition. We develop a theoretical model to explain these properties reported in this paper, with good agreement between experiment and theory. Our work establishes a definitive baseline for bulk properties of NiPS$_3$ and demonstrates the feasibility of resolving intrinsic anisotropies by addressing crystallographic twinning in vdW magnets.
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All authors Yeochan An, Heejun Yang, Sung Jin Park, Giung Park, Woonghee Cho, Pyeongjae Park, Seokhwan Yun, Yoshimitsu Kohama, Je-Geun Park

High Energy Physics (Phenomenology)

Exploring the chiral magnetic effect in Au+Au collisions at $\sqrt{s_{NN}}=7.7-200$ GeV through Chiral Anomaly Transport

Zilin Yuan, Anping Huang, Guo-Liang Ma et al. (+2 more)

High-energy heavy-ion collisions have the potential to create local domains of chirality-imbalanced quarks, reflecting the topological characteristics of quantum chromodynamics. This phenomenon can potentially induce local $\mathcal{P}$ and $\mathcal{CP}$ violations in the quark-gluon plasma. The Chiral Magnetic Effect (CME) predicts an electric charge separation along the intense magnetic field generated during these collisions, which is typically investigated through charge-dependent azimuthal correlations ($\Delta\gamma$). In this work, we investigate the CME in Au+Au collisions at $\sqrt{s_{NN}} = 7.7 - 200$ GeV using a multiphase transport (AMPT) model equipped with a Chiral Anomaly Transport (CAT) module. we employ two independent methods: direct subtraction of the correlator $\langle N_{part}\Delta\gamma\rangle$ between simulations with zero and finite chiral chemical potential $\mu_5$, and the event-shape-selection (ESS) approach. Our results reveal a significant CME signal within the energy range of 11.5-27 GeV and the centrality range of $20-50\%$, where the AMPT model aligns well with STAR experimental data. Furthermore, the CME fractions extracted by both methods are consistent within uncertainties across these energies. However, the CME signal disappears at both 7.7 and 200 GeV. These findings underscore that the observability of the CME critically depends on both the dynamic evolution of the magnetic field and the chemical freeze-out time of the partonic phase, which vary significantly with collision energy.
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All authors Zilin Yuan, Anping Huang, Guo-Liang Ma, Mei Huang, Guannan Xie

Chemical Physics

Poly(1,4-anthraquinone) as an Organic Cathode Material: Simulation of Observable Bonding Properties to Li, Na, Mg, and Ca

Laura Femmer, Lukas Köbbing, Juliane Heitkämper et al. (+9 more)

Poly(1,4-anthraquinone) (P14AQ) has emerged as a promising cathode material, offering high capacity and good cycling stability, yet the atomic-scale mechanisms governing metal-ion binding and electrochemical behavior remain poorly understood. To address this, we investigate the binding mechanisms of Li, Na, Mg, and Ca to P14AQ using quantum mechanical methods, particularly DFT and DFTB. A key challenge lies in the material's structural complexity: multiple conformers of P14AQ are energetically similar but kinetically isolated due to significant energy barriers. To account for this, we develop an automated method to generate all unique P14AQ conformers for a periodic polymer chain without rotational duplicates through an orientation labeling scheme. For each conformer, we systematically place a metal atom adjacent to every oxygen site, enabling a complete exploration of binding configurations. We observe two structural motifs: a single metal-oxygen bond and coordination to two opposite oxygen atoms. While Li and Na exhibit continuous energy distributions, Mg and Ca show an energy gap between the two motifs, with a strong preference for the two-oxygen binding configuration. Galvanostatic measurements support these findings by showing lower gravimetric capacities for Ca and Mg than for Li and Na. For Na, the different numbers of metal-oxygen bonds are reflected in the two voltage plateaus observed experimentally. Overall, the combined computational and experimental results explain the higher capacity of monovalent ions in P14AQ: divalent ions cannot bind efficiently to a single oxygen site due to unfavorable energetics, and the conformational distribution of the polymer chain prevents optimal coordination.
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All authors Laura Femmer, Lukas Köbbing, Juliane Heitkämper, Sibylle Riedel, Devran Cay, Florin Adler, Birgit Esser, Alexander J. C. Kuehne, Zhirong Zhao-Karger, Piotr de Silva, Juan Maria García-Lastra, Birger Horstmann

Cosmology and Nongalactic Astrophysics

Cosmographic Reconstruction of the Quintessence Potential in Scalar-Tensor Gravity

G. Antonopoulos and L. Perivolaropoulos

We generalise the cosmographic reconstruction programme of Chakraborty, Dunsby & Scherrer to scalar-tensor gravity. Working in the Jordan frame with a general non-minimal coupling $F(\Phi)$, we derive exact closed-form expressions for the potential slope $\lambda_U$, the coupling slope $\lambda_F$, and their curvature parameters $\Gamma_U$ and $\Gamma_F$ in terms of the cosmographic parameters $(q,j,s)$, the Planck-mass running $\alpha_M = d\ln F/d\ln a$ and its derivatives. We express $\alpha_M$ and its derivatives in terms of a set of coefficients $g_n$ describing the time variation of the gravitational constant $G\propto F^{-1}$, casting all four quantities in fully observable form. We then evaluate the reconstruction against current data, including DESI~DR2 baryon acoustic oscillation measurements and Lunar Laser Ranging constraints on $\dot G/G$, propagating the cosmographic uncertainties through to the reconstructed potential. All expressions reduce analytically to those of Chakraborty, Dunsby & Scherrer in the minimally-coupled limit, which we verify symbolically. We find that the potential slope $\lambda_U$ is recovered at the few-tenths level while the curvature $\Gamma_U$ is essentially unconstrained. We further show that the positivity of the scalar kinetic term is equivalent to $w_{\rm eff,0}\ge-1$, so that the region of cosmographic parameter space closed to minimally-coupled quintessence is exactly the phantom region, and that the non-minimal coupling reopens it through a single coefficient $g_2$ of the gravitational tower. Because Lunar Laser Ranging forces $|g_1|\lesssim2\times10^{-4}$ while the reconstruction is sensitive to $g_2\sim O(0.1)$, the framework presupposes that $\alpha_M$ is passing through zero at the present epoch, as expected on the Damour–Nordtvedt least-coupling attractor.
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Quantum Physics

The Organization of Environmental Coupling Shapes What Quantum Reservoirs Remember

Markus Baumann, Itamar Fink, Johannes Wittmann et al. (+2 more)

For an open quantum reservoir, how the system forgets is part of how it computes. Quantum reservoir computing processes input streams with fixed quantum dynamics and trains only a linear readout. Dissipation can make old inputs fade, but prior studies commonly fix the environmental process and tune only its strength. Here we show numerically that the coupling pattern, meaning whether transitions connect to separate or shared environmental channels, changes which parts of the input history remain accessible. Paired simulations of finite spin reservoirs keep the Hamiltonian, inputs, measurements, and readout fixed. The tested patterns produce distinct task profiles, with no universal winner. Shared relaxation preserves more recent input history than independent local loss, and the retained memory changes when the qubits contribute with different relative phases to the shared decay channel. This ordering recurs across system sizes, Hamiltonians, input protocols, and targeted controls. Environmental coupling is therefore more than a damping parameter: it is a design layer that shapes not only how quickly information fades, but which input history remains available for computation.
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All authors Markus Baumann, Itamar Fink, Johannes Wittmann, Claudia Linnhoff-Popien, Jonas Stein

Strongly Correlated Electrons

Topological phases and quantum criticality from $SU(2)$ Chern-Simons-matter theories

Yunchao Hao, Yingcheng Li, Kangle Li et al. (+1 more)

Motivated by recent numerical studies where various $SU(2)$ Chern-Simons-matter theories emerge, we analytically study topological phases and quantum criticality in two-dimensional systems described by such theories. First, we classify $SU(2)_k$ topological orders in all lattice spin systems with a $p4\times SO(3)$ symmetry, where $k$ is an arbitrary nonzero integer. We find that for each odd $k$, the topological order can emerge in systems with an arbitrary Lieb-Schultz-Mattis (LSM) anomaly, and the symmetry cannot permute anyons. If the system has a nontrivial (respectively, trivial) LSM anomaly, then there is exactly one (respectively, nine) symmetry-enriched topological (SET) phases. On the other hand, $SU(2)_k$ topological order with any even $k$ can only emerge in systems with a trivial LSM anomaly. If $k\notin\{6, 10, 14, \cdots\}$, the symmetry cannot permute anyons, and there are 16 SET phases. If $k\in\{6, 10, 14, \cdots\}$, there are 4 different ways how the symmetry can permute anyons, and there are 64 SET phases. Next, we analyze the $SU(2)_k$ Chern-Simons theories coupled to $N_f$ flavors of gapless matter fields that can be either bosonic or fermionic. For both types of theories, we consider a joint large-$N_f$ and large-$k$ limit with $N_f/k$ fixed, and compute the scaling dimensions of the bilinear operators of the bosons or fermions to the order of $1/N_f$. These results sharpen our understanding of these emergent exotic topological phases and quantum criticality, and provide useful guidance to explore them further.
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All authors Yunchao Hao, Yingcheng Li, Kangle Li, Liujun Zou

Pattern Formation and Solitons · Cross-listed from math.AP

Ground States and Periodic–to–Localized Convergence in Two–Dimensional Saturable Discrete Nonlinear Schrödinger Equations

Vassilios M Rothos

We study a two–dimensional discrete nonlinear Schrödinger equation with saturable nonlinearity on the lattice $\mathbb Z^2$. Using a variational approach based on the Nehari manifold, we establish the existence of nontrivial periodic ground states on finite lattices and establish the existence of exponentially localized ground states in $\ell^2(\mathbb Z^2)$. A principal result is the rigorous passage from periodic to localized states: we show that, up to lattice translations, periodic ground states converge strongly in $\ell^2(\mathbb Z^2)$ to a localized ground state as the lattice periods tend to infinity. The analysis combines variational methods, spectral properties of the discrete Laplacian, and concentration–compactness techniques adapted to the two–dimensional discrete setting. We further derive qualitative properties of the resulting solutions, including positivity and exponential localization, and establish a conditional orbital stability result within the Grillakis–Shatah–Strauss framework. Numerical computations illustrate the theoretical results and confirm the predicted convergence and localization behavior.
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Cosmology and Nongalactic Astrophysics

Constraining Primordial Power Asymmetry from Galaxy Clustering and Peculiar Velocity Information

Keita Minato, Atsushi Taruya, Teppei Okumura et al. (+1 more)

Primordial power asymmetry would probe departures from statistical isotropy, offering a clue to the physics of the primordial Universe. We investigate how such asymmetries can be tested with galaxy surveys and quantify how peculiar-velocity information can improve these tests. We develop a unified bipolar spherical harmonic (BipoSH) analysis of the auto- and cross-power spectra of galaxy density and line-of-sight peculiar velocity, and perform Fisher forecasts combining a Euclid-like spectroscopic galaxy survey with peculiar velocities reconstructed from Simons Observatory-like CMB maps through the kinetic Sunyaev-Zel'dovich effect. For dipolar asymmetry, we consider both scale-independent and scale-dependent modulations proportional to $k^{-0.5}$. Galaxy clustering provides most of the constraining power in both cases, while peculiar velocities add only modest information. For quadrupolar asymmetry, we account for the recently identified anisotropic galaxy-bias response and marginalize over its amplitude. We find that galaxy clustering alone suffers from a degeneracy between the primordial quadrupolar modulation and anisotropic galaxy bias. This degeneracy can be substantially broken by adding peculiar-velocity information: the density-velocity cross-spectrum provides complementary information to the galaxy auto-spectrum, while the velocity auto-spectrum constrains the primordial modulation independently of anisotropic galaxy bias. The velocity information becomes increasingly effective for more negative scale dependence, yielding constraints tighter than those from BOSS for scale dependences proportional to $k^{-1}$ and $k^{-2}$. Our results demonstrate that peculiar-velocity information provides a complementary avenue for testing primordial power asymmetry with large-scale structure, particularly for quadrupolar asymmetry in the presence of anisotropic galaxy bias.
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All authors Keita Minato, Atsushi Taruya, Teppei Okumura, Maresuke Shiraishi

Quantum Physics

Classical Limits of Spectral Filtering in Quantum Generative Models

Marco Roth

Spectral filtering has been proposed as a route to regularization in quantum generative models: the quantum Fourier transform exposes the amplitude spectrum of a quantum circuit Born machine, and a diagonal filter suppresses the high frequencies associated with finite-sample noise, an operation whose classical counterpart seemingly requires manipulating an exponentially long amplitude vector. We examine whether this coherent operation produces anything that classical post-processing of samples from the unfiltered model cannot match. Measuring the filter against convolution with a symmetric probability kernel at matched sampling cost, which accounts for the post-selection overhead of attenuation, we derive necessary and sufficient conditions for the gap between the two to vanish. Magnitude (attenuating) filters obey a dichotomy: at a fixed affordability threshold, the filtered output is either a constant-size Fourier object with an efficient classical sampler, or the passband must widen until no fixed frequency is attenuated and the filter no longer smooths. In neither case does the filter create a quantum-classical separation. Whatever separation survives is inherited from the spectral phase of the input state. Numerical experiments on trained circuit Born machines confirm the classification and show that the deciding phases are invisible to the Born-rule training loss and set by the initialization. Within the diagonal family, pure phase filters remain the only spectral operations exempt from these constraints.
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Superconductivity

Simplified Silicon Nitride Nanomembrane Circuits for van der Waals Integration

Tommaso Confalone, Vasilisa Gerega, Flavia Lo Sardo et al. (+8 more)

Two-dimensional (2D) materials and van der Waals (vdW) heterostructures provide an exceptional platform for engineering quantum devices, yet realizing their potential requires electrical integration without compromising the pristine properties of atomically thin crystals through conventional nanofabrication. Transferable circuitry addresses this challenge by decoupling circuit fabrication from device assembly, enabling electrical contacting without directly processing the active material. Here, we introduce SiN$_x$ nanomembrane (NMB) circuits realized through a simplified top-down strategy that reduces fabrication complexity, processing steps and specialized tools required by our previous bottom-up approach. As a stringent benchmark of material preservation, we electrically integrate a four-unit-cell-thick, optimally doped Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ (Bi2201) flake and observe a superconducting transition at T$_c^{inf}$~32K, close to the T$_c^{onset}$~34K measured by susceptibility in the parent crystals. The preservation of superconductivity demonstrates electrical integration of fragile layered materials without direct exposure to conventional cleanroom procedures, providing a versatile platform for integrating increasingly complicated vdW heterostructures, moiré materials, and hybrid quantum architectures.
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All authors Tommaso Confalone, Vasilisa Gerega, Flavia Lo Sardo, Shreya Kumbhakar, Davide Massarotti, Francesco Tafuri, Shigeyuki Ishida, Hiroshi Eisaki, Kornelius Nielsch, Golam Haider, Nicola Poccia

High Energy Physics (Phenomenology)

Systematic study of fully heavy-flavored tetraquarks $Q_1Q_2\bar{Q}_1\bar{Q}_2\,(Q_{1;2} \in \left\{b;c\right\})$: Mass spectra, threshold analysis, and confrontation with LHC data

André Aimé Atangana Likéné, Alexis Franck Rothen, Dieudonné Nga Ongodo et al. (+2 more)

Experimental searches for fully heavy tetraquark states are actively pursued at the LHC. The LHCb, CMS, and ATLAS collaborations have investigated fully charmed $cc\bar{c}\bar{c}$, mixed $bc\bar{b}\bar{c}$, and fully bottom $bb\bar{b}\bar{b}$ tetraquarks. In particular, narrow structures such as $X(6200)$, $X(6900)$, and $X(7300)$ observed in the di-$J/\psi$ mass spectrum have stimulated considerable theoretical interest. We employ a nonrelativistic diquark-antidiquark model to investigate the mass spectra of ground ($1S$) and excited ($1P$, $2S$, $1D$, $2P$, $3S$, and $4S$) fully heavy tetraquark states. The tetraquarks are modeled as color-singlet bound states of axial-vector diquarks and antidiquarks in the $\mathbf{\bar{3}}$ and $\mathbf{3}$ color representations. The Schrödinger equation is solved numerically using a modified Cornell potential and the three-point central difference method, while spin-dependent interactions are treated nonperturbatively. We investigate a broad range of $J^{PC}$ quantum numbers for $S$-, $P$-, and $D$-wave states. The predicted masses are compared with recent LHC observations and other theoretical calculations, and the stability of the states against strong fall-apart decays is examined. Our results support the interpretation of several observed structures as different excitations of fully charmed tetraquarks and provide useful predictions for their experimental identification.
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All authors André Aimé Atangana Likéné, Alexis Franck Rothen, Dieudonné Nga Ongodo, Germain Hubert Ben-Bolie, Tobias Golling

Materials Science

Electrostatic Phenomenology Benchmarks for Machine-Learned Interatomic Potentials in Electrochemistry: Beyond the Energy-Force Metric

Barbara Sumić, Ria Vasdev, Sudheesh Kumar Ethirajan et al. (+8 more)

Accurate treatment of long-range interactions in machine learning interatomic potentials (MLIPs) is essential for electrochemical simulations. However, aggregate energy and force errors alone are insufficient to establish an MLIP's physical accuracy since they do not detect qualitative inconsistencies in the model such as the prediction of image-charge attraction, dielectric screening, or charge transfer. We introduce a benchmark suite EPhEct (Electrostatic Phenomena for Electrochemistry) of focused test cases designed to evaluate MLIPs on electrochemically relevant physical phenomena. The tests probe for image-charge attraction at a metal electrode, the splitting between longitudinal and transverse optical phonons as a probe of ionic and electronic screening, the dipole moment of interfacial water, and Fermi-level pinning during ion discharge. These tests establish a qualitative diagnostic routine complementary to aggregate energy-force metrics.
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All authors Barbara Sumić, Ria Vasdev, Sudheesh Kumar Ethirajan, Jing Yang, Clotilde S. Cucinotta, Richard G. Hennig, Karsten Reuter, Stefan Ringe, Mira Todorova, Christoph Freysoldt, Jörg Neugebauer

Plasma Physics

Physics of Circular Polarized Ion-Scale Waves in Hybrid Simulations of Alfvénic Fluctuations

Hai Yang Harry Qian, Trevor A. Bowen, Carlos A. Gonzalez et al. (+5 more)

Ion cyclotron waves (ICW) and fast magnetosonic/whistler waves (FMW) are fundamental electromagnetic modes at ion kinetic scales, yet their generation mechanisms and roles in plasma evolution remain poorly understood. We analyze a 2.5D hybrid simulation of broadband Alfvénic fluctuations, where the proton velocity distribution is modeled as a sum of two bi-Maxwellian components: a thermal core and a drifting beam. Using wavelet-based wave identification, bi-Maxwellian VDF fitting, and the PLUME linear dispersion solver, we find that ICW behave as linear modes. Growth is intermittent, occurring when core temperature anisotropy builds up, and is driven mainly by the core (the beam contributes negligibly). Poynting flux analysis shows that ICW are predominantly forward-propagating, with a net energy flux ratio of $+1$ across all frequencies, consistent with the initial condition. FMW present a stark contrast: PLUME solutions often yield very small (near-zero) linear growth/damping rates. The species decomposition breaks down when $|\gamma/\omega_r| \gtrsim 0.368$, indicating that linear theory predicts these waves to be strongly damped and not describable by linear eigenmodes. Nevertheless, FMW are clearly observed in the wavelet helicity spectrogram, indicating that they are generated by nonlinear processes (e.g., parametric decay or phase steepening) and persist despite linear damping. The net energy flux ratio for FMW is close to $+1$ at low frequencies but decreases at higher frequencies, yet never reaches zero (net energy flow remains forward). These results demonstrate that ICW are linear, core-driven waves that transfer energy to the plasma, while FMW are heavily damped, nonlinearly generated waves.
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All authors Hai Yang Harry Qian, Trevor A. Bowen, Carlos A. Gonzalez, Nikos Sioulas, Alfred Mallet, Kristopher G. Klein, Daniel Verscharen, Stuart D. Bale