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Physics

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Wednesday 26 August

Pattern Formation and Solitons

Numerical Direct Scattering Transform for Dark Solitons

Ilya Mullyadzhanov, Sergey Dremov and Andrey Gelash

We introduce a numerical direct scattering transform scheme for dark solitons of the nonlinear Schrodinger equation, enabling the identification and complete characterization of nonlinear coherent structures in defocusing media with a continuous-wave (CW) background. Our scheme is based on numerically solving the auxiliary Zakharov-Shabat scattering problem with CW boundary conditions and on analytically derived expressions that relate the elements of the transfer matrix to the scattering data for dark solitons and continuous-spectrum waves. To test our approach, we consider two analytically solvable cases of the scattering problem: i) rectangular, and ii) hyperbolic tangent hollows in the CW background, which can contain an arbitrary number of dark solitons, with known scattering data. We revisit the analytical derivations and obtain a complete set of soliton parameters represented by discrete eigenvalues and norming constants. By supplementing the direct scattering transform algorithm with high-precision arithmetic to accurately recover soliton norming constants, we provide a robust method to analyze data from numerical or natural experiments on complex wave fields in optical, hydrodynamical, and other physical systems.
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Plasma Physics

Experimental Characterization of Additively Manufactured Metallic Alloys for Electric Propulsion Applications

J. Chamberlain and A. Shashurin

This work explores the sputtering of additively manufactured (AM) materials for use in gridded ion source applications. The first part of the paper uses 316L stainless steel as an example to demonstrate that additively manufactured material does not exhibit adverse sputtering behavior, such as higher sputter yield, compared with conventionally manufactured material. To this end, three additively manufactured 316L stainless steel samples were exposed to the beam of a KDC-40 electrostatic gridded ion source at three distinct energy levels of 400, 600, and 800 eV on each side of the sample for a duration of one hour. The samples were masked to create a distinct boundary between treated and untreated regions, identifiable using profilometry, and were biased to -18V for testing. Samples were then examined using a Bruker optical profilometer and further processed using the open-source software Gwyddion to evaluate the sputtering yield. The sputter yield varied in the range 0.2-2 atoms/ion for 400-800 eV ions and increased with ion energy. The measured sputtering yield was fairly consistent with predictions from analytical models developed in prior literature, while exhibiting some variations potentially due to added effects of increased temperature and oxide layers. The second part of the paper demonstrates feasibility of using an additively manufactured tungsten-rhenium grids in existing KDC-40 electrostatic gridded ion source.
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Mathematical Physics · Cross-listed from math.NA

A family of second order, linear, unconditionally stable methods for the Cahn-Hilliard-Navier-Stokes equations

Daozhi Han, Nan Jiang, Jonah H. Nissan et al. (+1 more)

We present a family of second-order, linear, unconditionally stable implicit-explicit (IMEX) methods for the Cahn-Hilliard-Navier-Stokes (CHNS) equations modeling matched-density two-phase flows. The proposed semi-discrete scheme combines extrapolation of the nonlinear terms with an auxiliary-variable formulation of the nonlinear free-energy term and a temporal-curvature regularization controlled by a parameter $\epsilon$. We establish a discrete energy estimate showing unconditional long-time stability of the method for $\theta\in(1/2,1]$ and $\epsilon\geq0$. The resulting scheme requires only linear solves at each time step. Numerical experiments demonstrate approximately second-order temporal convergence and examine mass conservation, energy dissipation, numerical robustness, and several representative interfacial-flow problems, including spinodal decomposition, droplet shape relaxation, two-phase lid-driven cavity flow, and Rayleigh-Taylor instability.
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All authors Daozhi Han, Nan Jiang, Jonah H. Nissan, Sayantan Sarkar

Superconductivity

Electrical manipulation of oxygen stoichiometry in multiterminal YBa$_2$Cu$_3$O$_{7-\delta}$ junctions

Daniel Stoffels, Caio C. Quaglio-Gomes, Nicolas Lejeune et al. (+7 more)

Local manipulation of oxygen stoichiometry offers a route to control the electronic properties of complex oxides, yet the selective modification of individual current-carrying branches through oxygen redistribution remains unexplored in multiterminal high-temperature superconducting junctions. In a YBa$_2$Cu$_3$O$_{7-\delta}$ Y-shaped three-terminal device, we demonstrate the possibility to electrically control oxygen vacancy migration on a hand-picked terminal while largely preserving the other two. Oxygen-depleted propagating fronts are directly visualized by the resulting change in optical reflectivity and they are linked to the evolution of the electrical response. The process is highly directional and determined by the polarity of the applied current, allowing for the creation of either a converging or a diverging propagating front from the central node of the Y-shaped device. The associated changes in resistance exhibit relaxation on a timescale of minutes, driven by the vacancy concentration gradient. Effects of oxygen migration are also mapped by Kelvin Probe Force Microscopy and Scanning Laser Microscopy, which probe work-function changes and spatially resolved variations in the superconducting transition, respectively. Notably, the Tc contrast revealed by the latter provides a quantitative handle on the underlying oxygen content, enabling direct visualization of oxygen redistribution. Finite-element modeling and nanoprobe X-ray diffraction qualitatively reproduce the observed vacancy redistribution. These results establish a post-fabrication route to locally tune properties of superconducting multiterminal devices such as nanocryotrons, yTron, and tunable weak links.
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All authors Daniel Stoffels, Caio C. Quaglio-Gomes, Nicolas Lejeune, Emile Fourneau, Pedro Schio, Huidong Li, Lourdes Fabrega, Anna Palau, Maycon Motta, Alejandro V. Silhanek

Astrophysics of Galaxies

Accretion Disk Sizes and Temperature Profiles in Lensed Quasars: NIR Microlensing Challenges Thin Disk Theory

V. Motta and E. Mediavilla

Microlensing and reverberation mapping measurements of quasar accretion disk sizes and temperature gradients disagree with thin disk theory predictions. Previous microlensing results rely on heterogeneous wavelength coverage -primarily UV broad emission lines (BELs) from small samples -probing the disk only out to a typical radius of $\lesssim$5 light days on average. We use microlensing estimates from an homogeneous sample of near-infrared (NIR) observations of lensed quasars (21 image-pairs from 7 lens systems) to extend disk size measurements out to 14 light days. This analysis leverages narrow emission lines (NELs), which provide a more reliable microlensing-free baseline than BEL cores. We derive Bayesian accretion disk size estimates that reproduce the observed microlensing magnifications, as simulated from magnification maps. NEL-based sizes yield a logarithmic slope of $p=0.68\pm0.23$, consistent with prior estimates corresponding to inner disk regions ($r \lesssim$5 light days). Using a new homogeneous NIR dataset that allows us to reach radial distances of up to 14 light days, we find that accretion disks in these previously unexplored regions are also larger and exhibit steeper temperature gradients than thin disk theory predicts. The increased precision allows us to reject the theoretical logarithmic slope $p=4/3$ at the 98% confidence level. Any hypothesis invoking BLR contamination to explain this discrepancy must account for how such contamination modulates the underlying accretion disk such that the combination of both results in a power law with logarithmic slope $p=0.68\pm0.23$ across a broad wavelength baseline spanning from $\sim$X-Ray to $\sim 5000$Å.
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Mathematical Physics · Cross-listed from math.PR

Rotated semicircle laws for permanental roots of Gaussian random matrices

Renjie Feng and Dong Yao

For matrices drawn from the standard Gaussian orthogonal ensemble (GOE) and Gaussian unitary ensemble (GUE), we prove that the normalized zero counting measure of the permanental characteristic polynomial $Per(zI_N-H_N)$ converges almost surely to the standard Wigner semicircle law on $[-2,2]$, rotated by $\pi/2$ onto the imaginary axis. This proves the conjecture proposed by Fyodorov in \cite{Fyodorov2006}.
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General Relativity and Quantum Cosmology · Cross-listed from math.AP

Dual modes in Kerr spacetimes and the Whiting transform: Mode stability revisited

Oliver Petersen and András Vasy

The purpose of the paper is to place Whiting's classical growing mode stability argument, extended to real frequencies by Shlapentokh-Rothman for the scalar wave equation and by Andersson, Ma, Paganini and Whiting in general, in the framework of classical PDE theory. The key steps are: a description of the dual or adjoint modes, a singular phase space pairing argument which is technically executed via the Fourier transform, followed by a standard unique continuation result. One part of our description of the dual modes connects them directly to the standard mode solutions which are smooth over the event horizon. In the zero spin case, there is a geometric interpretation of this: quasinormal modes (for non-zero real frequencies) which are smooth across the future event horizon can be extended as distributional QNM solutions by 0 through the past event horizon. We also describe the behavior of mode solutions at the bifurcate sphere.
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Fluid Dynamics

A Scalable OpenLB LAMMPS Framework for Fully Resolved Simulations of Hindered Settling of Arbitrary Non-Spherical Particles

Varghese Babu, Adrian Kummerländer, Mathias J. Krause et al. (+2 more)

Hindered settling of non spherical particles remains significantly less understood than spherical particles due to the computational challenges in resolving the complex contact mechanics and hydrodynamic interactions. In this paper, we present a scaleable fluid structure interaction (FSI) framework coupling the open-source LBM software in OpenLB with the Discrete Element Method (DEM) implemented in LAMMPS to simulate arbitrary shaped rigid bodies in a fluid. Particle contacts are captured using a multi-sphere "clump" representation in DEM, while particle geometries are resolved on the fluid grid via voxelization. We validate our model against single and multi-particle benchmarks, and proceed to study the hindered setttling of cubes in systems containing upto 100,000 cubes. Our simulations show distinct differences between the settling of cubes and sphere, as cubes form pronounced coordination shells without face-parallel contact, in contrast to the contact-dominated clustering observed in spheres. Our results find that correlation length in velocity fluctuations scale with system size even for the largest system studied. These findings highlight the role of particle morphology in suspension dynamics and demonstrate a robust framework for simulating large-scale geotechnical and particulate flows.
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All authors Varghese Babu, Adrian Kummerländer, Mathias J. Krause, Santosh Ansumali, Dilip Gersappe

Earth and Planetary Astrophysics

Benchmark Brown Dwarfs as Chemical Laboratories: Linking System Bulk Properties to Atmospheric Retrievals

Viktória Kecskeméthy, Ben Burningham, Fei Wang et al. (+8 more)

We present the first atmospheric retrieval analysis of two compositional benchmark mid-L dwarfs – SDSSJ141659.78+500626.4 and GJ 499 C – using the Brewster retrieval framework, where the wide benchmark nature of these systems provides independent constraints on age and bulk composition from their stellar primaries. These targets were observed with JWST using NIRSpec Prism and MIRI LRS, providing low-resolution ($R$ $\sim$ 100) spectra between 0.6–14.0 $\mathrm{\mu}$m with high signal-to-noise ratios (SNR $\sim$100 – 600). For SDSSJ141659.78+500626.4, the retrieved cloud combination of a high-altitude enstatite slab and low-altitude iron deck clouds matches phase-equilibrium predictions based on the primary star's Mg/Si ratio. We retrieve a super-solar C/O = 0.71$^{+0.01}_{-0.01}$ and slightly metal-rich [M/H] = 0.22$^{+0.03}_{-0.03}$. This C/O ratio can only be reconciled with the value inferred for the primary if additional oxygen sequestration beyond the retrieved cloud mass is present, or if there are uncertainties in the adopted opacities or other model deficiencies. The inferred [C/H] and [O/H] are 0.31$\pm$0.03 and 0.19$\pm$0.03, respectively, which are consistent within the relatively large uncertainties of the host star abundances. For GJ 499 C, the retrieved silicon-monoxide and forsterite slab clouds are difficult to explain with simple phase-equilibrium assumptions, yielding Mg/Si $\sim$ 1.9. We estimate C/O = 0.69$^{+0.02}_{-0.02}$ and [M/H] = 0.13$^{+0.04}_{-0.06}$. For both objects, the inferred radii of 0.85$^{+0.01}_{-0.01}$ $R_{\mathrm{Jup}}$ and 1.00$^{+0.02}_{-0.02}$ $R_{\mathrm{Jup}}$ and masses of 73.7$^{+4.9}_{-9.2}$ $M_{\mathrm{Jup}}$ and 68.0$^{+8.5}_{-12.7}$ $M_{\mathrm{Jup}}$ are consistent with evolutionary models and system ages, highlighting the plausibility of our results.
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All authors Viktória Kecskeméthy, Ben Burningham, Fei Wang, Austin J. Rothermich, Jacqueline K. Faherty, Genaro Suárez, Caprice L. Phillips, Melanie Rowland, Channon Visscher, Johanna M. Vos, Daniella C. Bardalez Gagliuffi

Quantum Physics

A heterogeneously integrated coupled-cavity frequency beam splitter

Lucas M. Cohen, Manuel H. Muñoz-Arias, Mohan Sarovar et al. (+6 more)

Frequency encoded photonic qubits promise a scalable path towards high-dimensional quantum information processing, but require efficient components for coherently mixing frequency modes. Coupled cavity modulators provide this functionality by using only a single driving microwave tone to couple hybridized optical supermodes. Here, we demonstrate a heterogeneously integrated thin-film lithium-niobate-on-silicon coupled-cavity modulator that realizes tunable bidirectional frequency mode transformations, including \(50/50\) beam splitting and near complete frequency swapping with \(>20~\mathrm{dB}\) pump extinction at a \(10~\mathrm{GHz}\) supermode splitting. Because the electro-optic film is bonded onto a foundry fabricated silicon photonics platform, the approach is compatible with co-integration of photon pair sources, spectral filters, active tuning elements, and single photon detectors. We also bond thin-film lithium tantalate onto the same coupled-cavity platform, demonstrating material flexibility for scalable integrated frequency bin quantum photonic circuits.
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All authors Lucas M. Cohen, Manuel H. Muñoz-Arias, Mohan Sarovar, Nicholas A. Boynton, Shawn C. Arterburn, Thomas A. Friedmann, Nils T. Otterstrom, Paul S. Davids, Michael Gehl

Quantum Physics

Immittance formulas for exact blackbox quantization and divergence-free effective models in circuit QED

Philippe Gigon, Peter Rabl and Adrian Parra-Rodriguez

Building on the first-order circuit quantization method [arXiv:2304.12252, arXiv:2401.09120], we provide simple formulas to construct exact Hamiltonians for Josephson-junction-based superconducting qudits capacitively, inductively, or galvanically coupled to passive linear environments. These environments may be multiport, multimode, discrete or continuous, reciprocal or nonreciprocal, and are characterized directly by their impedance or admittance matrices. In the weak-coupling regime, we further derive divergence-free dispersive Hamiltonians for mode-resolved environments and transition-resolved weak-coupling master equations for dissipative continua. Mode structure, frequency renormalizations, environment-mediated interactions, decay rates, and directional cross couplings then follow from the same causal immittance response, while spurious Lamb-shift divergences arising from uncontrolled approximations in previous treatments are made explicit and avoided. We apply the theory to a set of illustrative circuits comprising a discrete resonator filter, finite-band metamaterial environments, nonreciprocal waveguide-QED systems, and superconducting giant atoms, for which analytical response matrices can be obtained, although the method is particularly well suited to numerical responses from electromagnetic solvers or experimental characterization. We thereby extend the black-box quantization framework to multiport, dissipative, and nonreciprocal settings, establishing a simple and scalable route toward optimized and automated electromagnetic design of large-scale superconducting quantum hardware.
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Materials Science

Electron spin resonance driven photogalvanic effect in graphene-based structures

C. Bray, I. Yahniuk, L. E. Golub et al. (+13 more)

We report an electron-spin-resonance-driven linear photogalvanic effect (LPGE) in unbiased monolayer graphene and WSe_2/graphene heterostructures. Under linearly polarized 45–75 GHz radiation, the photovoltage exhibits pronounced resonant features in both Faraday and Voigt geometries. Multiple resonances associated with the electron spin resonance in graphene are observed for both out-of-plane and in-plane magnetic-field orientations. Their magnetic-field positions vary linearly with frequency, their amplitudes reverse sign across the charge-neutrality point, and the resonant contribution has the opposite sign to the nonresonant Drude photogalvanic background. We develop a microscopic theory in which radiation-induced momentum alignment followed by skew scattering generates both contributions. Their opposite signs originate from the orthogonal momentum alignments produced by indirect Drude absorption and direct spin-resonant transitions. The theory describes well the main features of the observed resonant photocurrent and provides a microscopic description of ESR-induced LPGE in two-dimensional systems. These results establish the photogalvanic response as a probe of ESR in unbiased micron-scale graphene-based devices.
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All authors C. Bray, I. Yahniuk, L. E. Golub, M. Marocko, C. Consejo, B. Benhamou-Bui, Ziyang Gan, A. George, A. Turchanin, P. Sadovyi, K. Watanabe, T. Taniguchi, J. Eroms, J. Fabian, F. Teppe, S. D. Ganichev

Materials Science

Oxidation-resilient structural modifications in Nickel-functionalized 3D-graphene for hydrogen storage applications

Filippo Fincato, Ylea Vlamidis, Markus Leitgeb et al. (+6 more)

Porous materials represent a versatile solution for several applications. Indeed, the recent development of a new material, named 3D-Graphene, which combines the exceptional characteristics of graphene with a three-dimensional structure, opens perspectives for applications where a high surface-to-volume ratio is beneficial. In this study, we explore the functionalization of 3D-Graphene with nickel (Ni)-nanoparticles as a strategy to enhance hydrogen storage capabilities, and we assess the influence of the NPs on hydrogen uptake and oxidation resilience. The morphology and structural properties of pristine and Ni-functionalized samples were characterized using Scanning Electron Microscopy. Additionally, X-ray Photoelectron Spectroscopy was employed to analyze the surface chemical composition of the functionalized samples. Samples have been hydrogenated supplying molecular or atomic hydrogen, and hydrogen storage performance was assessed through Thermal Desorption Spectroscopy. Afterwards, oxidation effects were systematically studied by exposing the samples to atmospheric oxygen, followed by further hydrogenation experiments. Our results indicate that Ni functionalization influences both hydrogen adsorption and oxidation behavior, with potential implications for improving the stability of the material, especially for hydrogen storage applications.
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All authors Filippo Fincato, Ylea Vlamidis, Markus Leitgeb, Georg Pfusterschmied, Ulrich Schmid, Valentina Zannier, Silvia Rubini, Stefan Heun, Stefano Veronesi

Plasma Physics

First Plasma Commissioning and Operational Highlights from India's First Spherical Tokamak at IPR

Kishore Mishra, Aditya Verma, N. Mansoori et al. (+73 more)

A compact Spherical Tokamak(ST) is commissioned at Institute for Plasma Research (IPR) to explore low aspect ratio tokamak physics and technologies that complement to the existing high aspect ratio tokamaks namely ADITYA-U and SST-1 by enabling studies on non-inductive startup, current drive in over dense plasmas, and shaped plasma physics on a low cost platform. The device, India's first spherical tokamak has completed major mechanical, magnetic, and electrical integration, and the coil system has been successfully tested with series of integrated commissioning. First plasma experiments have been carried out with a modest Ohmic system assisted by a 2.45GHz microwave system, supported by a centralized control and data acquisition system. An initial diagnostic set comprising visible imaging, spectroscopy, magnetics, and radiation monitors required for machine operation has been installed. This paper presents the integrated commissioning experiences and first plasma experiments of the newly installed machine.
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All authors Kishore Mishra, Aditya Verma, N. Mansoori, Saurabh Verma, Y. Paravastu, M. S. Khan, Arvind Kumar, S. G. Thatipamula, Vishal Verma, M Sheetal, Mohit, U. Thaker, Ayush, Jignesh Patel, Praveenlal, Jagabandhu Kumar, F. S. Pathan, S. Ranjithkumar, S. Sam, Prasada Rao P., A. Jaiswal, S. Jha, Neelam Ramaiya, Utsav Rajvanshi, Santosh Pandya, K. Tahaliyani, S. Purohit, Suraj Gupta, Kiran Patel, Suman Aich, D. Kumawat, Deepak Kumar, Saurav Kumar, Rahul Kumar, Vismaysinh Raulji, Pramila, Praveena Kumari, Minsha Shah, Arun Prakash, Narendra Bhupesh, Amit K. Singh, V. Menon, Deepti Sharma, A. Kundu, G. K. Rajan, Prakash Parmar, Ankit Kumar, Vishnu Patel, Imran Mansuri, M Bhandarkar, H. Chudasma, Atish Sharma, Kirit Patel, H Masand, Prem Kumar, Parmesh Kumar, S Kannaujiya, Pramod Parmar, Arvind L. Thakur, C. G. Virani, Ankit Kumar, K. K. Ambulkar, Vilas Chaudhari, C. Danani, Y. S. S. Srinivas, S. Nair, K. Mahajan, R. Rajpal, M. B. Chowdhury, Manoj Kumar, S. K. Pathak, P. K. Sharma, Z. Khan, E. Rajendrakumar, J. Ghosh, Team ST

Strongly Correlated Electrons

Rare-earth oxysulfides RE$_2$O$_2$S as model mixed-anion frustrated magnets

Austin M. Ferrenti, Ksenia Khoroshun, Mohamed Oudah et al. (+3 more)

The study of low-dimensional and anisotropic magnetism is a promising avenue for the discovery of novel quantum phenomena. Mixed-anion materials, defined by the coordination of metal cations by two or more distinct anionic species, provide an intrinsically anisotropic platform for the tuning of structural, magnetic, and electronic properties. In this work, we report the synthesis and characterization of a family of rare-earth oxysulfide (RE$_2$O$_2$S) antiferromagnets (AFM) possessing a triangular-bilayer slab lattice geometry. Long-range AFM order is observed for the majority of compositions, with several (RE = Ce, Pr, Nd, Sm) having been previously unreported. Although assumed to form stoichiometrically, pair distribution function (PDF) analysis provides evidence for significant, synthesis-dependent interslab structural disorder as RE$_2$O$_{2+x}$S$_{1-x}$, resulting in significant variability in the bulk magnetic response of the Nd member. This work highlights the tunability of frustrated magnetic ground states in rare-earth-based mixed-anion materials, and the importance of thorough structural characterization in the discovery of new mixed-anion magnets.
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All authors Austin M. Ferrenti, Ksenia Khoroshun, Mohamed Oudah, Graham King, Jonathan Gaudet, Alannah M. Hallas

Superconductivity

Symmetry Origins of the Field-Free Superconducting Diode Effect in the Kagome Superconductor CsV$_3$Sb$_5$

Xin-Jie Liu, Shengbiao Sun, Ke-Fan Song et al. (+14 more)

Field-free superconducting diode effects require both inversion-symmetry breaking and an internal time-reversal-symmetry (TRS) breaking field, making them sensitive probes of hidden order in superconductors. In centrosymmetric kagome AV$_3$Sb$_5$, the inversion symmetry generally should generally preclude the observation of the superconducting diode effect. Furthermore, though TRS breaking has been reported in the superconducting regime of CsV$_3$Sb$_5$, whether it is generated by superconductivity or inherited from charge-density-wave (CDW) order remains unresolved. Here we show that pristine CsV$_3$Sb$_5$ devices exhibit no intrinsic field-free superconducting diode effect, whereas surface oxidation or asymmetric etching activates a large nonreciprocal supercurrent. Moreover, the response is stochastic, with sweep-dependent polarity and magnitude, indicating metastable TRS-breaking domain configurations. Small out-of-plane magnetic fields stabilize the superconducting diode response, consistent with field selection of such domains. Finally, when long-range CDW order is suppressed by Ti doping, the SDE disappears. Our results establish the symmetry requirements for the field-free SDE in CsV$_3$Sb$_5$, reveal its stochastic domain-controlled character, and link superconducting-state TRS breaking to CDW-related order.
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All authors Xin-Jie Liu, Shengbiao Sun, Ke-Fan Song, Jia-Peng Peng, Xilin Feng, Lang Xiao, Tong Liu, Qilin Han, Ya-Qing Bie, Ning Kang, Xiaosong Wu, Yanfei Wu, Shouguo Wang, Kam Tuen Law, Shuo Wang, Dapeng Yu, Ben-Chuan Lin

General Relativity and Quantum Cosmology

Atmospheric Newtonian noise in torsion-balance measurements of the gravitational constant $G$

Jyotirmaya Mohanta and Yutaka Shikano

Measurements of Newton's gravitational constant remain limited by environmental and apparatus-dependent systematics whose treatment is often less explicit than that of instrumental noise. Among these, atmospheric density fluctuations generate unshieldable gravity gradients that couple directly to torsion-balance observables as atmospheric Newtonian noise. Here, we develop a GUM-consistent framework for propagating this contribution through the torque estimator into the uncertainty budget of torsion-balance measurements. We derive closed-form spatial transfer functions for two benchmark geometries: a two-mass dumbbell, which provides an upper-coupling reference, and a perfectly symmetric cross, which serves as an idealized rejection limit and exposes the trade-off between suppressing low-order environmental coupling and preserving signal response. We also separate stationary correlated inputs from non-stationary baseline drift, using the Ornstein–Uhlenbeck process only as a benchmark for the former. Atmospheric pressure benchmarks indicate that the resulting background contribution is below present reference uncertainty levels, but can become relevant as systematic floors approach the part-per-million regime. This framework provides a practical route for incorporating site-specific environmental gravity gradients into future torsion-balance uncertainty budgets.
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Quantum Physics

The Gain-Engineered Transmon

Ian Yang, Francesco Adinolfi, Alessandro Bruno et al. (+3 more)

The interaction between a qubit and its environment can be engineered such that one error channel dominates over all others, resulting in noise bias. This property enables error correction codes to focus on the dominant error type, thereby significantly reducing the number of physical systems required for fault-tolerant quantum computation. However, engineering noise bias typically introduces complexity at the physical system level, which decreases its usefulness by limiting scalability. Here, we introduce and experimentally realize a noise-biased qubit in a standard transmon-readout resonator circuit, one of the most common superconducting architectures, by only adding a single microwave tone. We encode the qubit in the transmon $|\mathrm{g}\rangle$- and $|\mathrm{f}\rangle$-states, and engineer a frequency-selective gain channel that counteracts single-photon loss errors between the computational states. We demonstrate an order-of-magnitude enhancement in relaxation time compared to the $|\mathrm{g}\rangle-|\mathrm{e}\rangle$ encoding, conceding only a factor-of-two decrease in the echo-coherence time. Furthermore, we show that this qubit is compatible with fast, high-fidelity operations. Our results open a path towards using this system as a simple building-block for hardware-efficient quantum error detection and correction schemes.
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All authors Ian Yang, Francesco Adinolfi, Alessandro Bruno, Venus Hasanuzzaman Kamrul, Daniel Z. Haxell, Alexander Grimm

High Energy Physics (Theory)

Notes on Gepner Construction

Kanade Nishikawa and Taizan Watari

In this note, we describe the Gepner construction purely as orbifold (rather than a beta-prescription or orbifold-like process). This is done by distinguishing orbifolding by a chiral symmetry from that by a left-right diagonal symmetry, and also by exploiting an extra degree of freedom available in orbifolds of Type 0 SCFTs. We also describe by using the Arf theory how the extra freedom in Type 0 SCFT orbifolds in general (not just in the Gepner construction) should be implemented in higher genus amplitudes. This note also determines when a combinatorial data set of a Gepner construction has a mirror Gepner construction, and also provides two thinking frameworks to determine the SCFT vertex operators of the Gepner model SCFTs with phase ambiguity and branch cuts under control.
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Materials Science

Bayesian Optimization for Self-Driving Materials Laboratories: From Algorithms to Physics-Informed Workflows

Yuki K. Wakabayashi and Takuma Otsuka

Self-driving laboratories (SDLs) are transforming materials research by closing the loop among synthesis, characterization, data analysis and experimental decision making. Bayesian optimization (BO) is a decision engine for these loops because it can select experiments from scarce and noisy data while balancing exploitation and exploration. Yet real materials campaigns often depart from the standard black-box setting, involving failed or missing experiments, noise and drift, mixed variables, constraints, multiple objectives, variable cost and fidelity, transfer from historical data, batch or asynchronous operation, and prior physics knowledge. This review presents BO for materials SDLs through the lens of these practical challenges. We summarize Gaussian-process-based BO and the formulation of materials goals as quantitative objectives, then discuss major choices in surrogate modelling and acquisition. Particular emphasis is placed on physics-informed Bayesian optimization (PIBO), in which domain knowledge enters through representations, priors, kernels, acquisition functions, and constraints. We survey achievements enabled by BO and related active-learning approaches across semiconductors, catalysis, chemical reactions, batteries, alloys, functional materials and quantum materials, highlighting advances beyond parameter optimization, including new materials and synthesis routes, improved functional performance, and reusable scientific knowledge. We conclude by outlining open problems for BO-driven materials SDLs, including nonstationarity, multimodal observations, adaptive problem formulation, and scientific reasoning by humans, large language models and research agents. Addressing these challenges may advance SDLs beyond efficient optimization toward interpretable and knowledge-generating experimentation.
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Quantum Physics

From Round-Trip State Echo to Error Recovery: Snapshot-Resolved Quantum-Hardware Diagnostics

Isaac Barouch Essayag and Aryeh Lev Zabokritskiy

We examine which conclusions from quantum-hardware benchmarks persist when the same programs are run again. On eight fixed routes of IQM Emerald, round-trip state echo (RTSE), a diagnostic of state return after a round trip, gave mean scores near $0.84$ that differed by only $0.00125$ between two executions. Individual route estimates nevertheless changed by up to $0.06$ in both directions. The mean difference between RTSE and measurement-free teleportation along the same routes shrank from $0.046$ to $0.014$ and was no longer statistically resolved on repetition; none of the four prespecified communication targets met its replication rule. Recovery with an existing four-qubit single-deletion code also changed on repetition: after discarding one encoded qubit in the circuit model, the IQM mean fell from $0.738$ to $0.624$ and failed the replication test against the two-thirds operational reference. In a separate IonQ experiment, recovery means of $0.91$ and $0.92$ passed tests against that reference and against a deliberately incorrect decoder in both executions. These results concern the tested workloads and executions. They show why a nearly unchanged aggregate benchmark score needs to be interpreted alongside individual routes, direct task comparisons, and repeated executions.
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Adaptation and Self-Organizing Systems · Cross-listed from q-bio.PE

What sets the critical genome length for sympatric speciation? A closed form and asymptotic theory

Dan Braha, Marcus A. M. de Aguiar and Vitor M. Marquioni

In the Derrida–Higgs model of sympatric speciation, a sexually reproducing population with finite binary genomes can mate only when the genetic overlap between two individuals exceeds a threshold $q_{\min}$. Depending on the genome length $L$, the population either remains genetically connected or fragments into reproductively isolated species. A central problem is therefore to predict the critical genome length $L_c$ at which fragmentation begins. At finite $L$, fluctuations broaden the overlap distribution and allow genetically distant regions of the population to remain connected. A previously proposed transient variance criterion captures this effect, but its evaluation requires numerical iteration of coupled moment equations. Here we first correct the unrestricted moment equations by removing a previously implicit assumption and then derive an explicit closed form expression for $L_c$. The resulting formula shows that the critical genome length is determined, at the time the mean overlap reaches $q_{\min}$, by the competition between deterministic separation from the unrestricted equilibrium and the transient genealogical variance of the overlap distribution. This expression permits a systematic asymptotic analysis. When the deterministic contribution dominates, $L_c$ becomes essentially independent of the population size $M$ and scales as $\mu^{-2}$. When the transient genealogical variance dominates, $L_c$ grows as $M^{3/2}$ or as $\sqrt{M}/\mu$, depending on how $M$ and the mutation rate $\mu$ jointly vary. Simulations support all predicted behaviors. Our results identify transient genealogical variance as the principal mechanism linking finite genome fluctuations to the onset of reproductive fragmentation and provide a practical analytical prediction for the critical genome length.
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Earth and Planetary Astrophysics

JWST color sequence of transiting exoplanets and directly imaged substellar objects

Guangwei Fu, Joshua D. Lothringer, Sagnick Mukherjee et al. (+4 more)

Color-magnitude diagrams (CMDs) have been foundational across astrophysics, from galaxies and stars to brown dwarfs, and JWST now extends them to transiting exoplanets and self-luminous substellar objects at overlapping temperatures. We compile JWST dayside emission spectra for 13 transiting giant planets, 57 self-luminous objects, and the irradiated brown dwarf ZTF J0038+2030 B, spanning ~350-2600 K and log g = 2.5-5.5, plus ~2150 SPHEREx ultracool dwarfs, converted to synthetic photometry in 2MASS J/Ks and five NIRCam medium bands isolating H2O, CH4, CO2, and CO. Low gravity and inflated radii make transiting planets resemble young substellar objects, with shallower features and redder colors from high-altitude clouds that raise the photosphere. Transiting planets follow the L-dwarf sequence on the J versus J-K CMD, with WASP-80 b (T_eq~800 K) showing no T-dwarf-like blueward turn, suggesting a delayed or suppressed L/T transition in irradiated, low-gravity atmospheres. Methane onset is delayed from substellar to transiting-planet atmospheres, and cloudy radiative-convective models indicate that lower gravity and cloud back-warming shift atmospheres toward CO-dominated chemistry, suppressing photospheric CH4. The irradiated but old, high-gravity brown dwarf ZTF J0038+2030 B (T_day = 1049 K, log g = 5.4) shows a deep, field-T-dwarf-like dayside methane band, implicating gravity rather than irradiation as the dominant control. CO2-to-CO diagnostics place transiting and directly imaged planetary-mass companions at stronger relative CO2 absorption than field brown dwarfs, consistent with metallicity enhancement from planetesimal accretion. These CMD sequences provide a unified, model-testable map for self-luminous and irradiated atmospheres.
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All authors Guangwei Fu, Joshua D. Lothringer, Sagnick Mukherjee, David K. Sing, Elena Manjavacas, Kevin B. Stevenson, William Balmer

Mathematical Physics

Plasticity as Directional Stationarity: Yielding, Flow, and Hardening from One Functional

Huilong Ren

Traditional plasticity theory is commonly organized through an elastic law, a yield condition, a flow rule, hardening relations, and loading–unloading conditions. This paper formulates these relations through directional stationarity of one scalar functional evaluated over one-sided admissible plastic paths. The first variation determines stress, internal-variable forces, and activity resistance. Restriction to an admissible plastic tangent defines a reduced directional force for each mechanism; its sign and one-sided stationarity give the elastic inequality, complementarity, loading–unloading conditions, and active consistency. Associated response corresponds to alignment between the admissible tangent and the normal to the resulting yield boundary, whereas a nonparallel tangent represents non-associated flow. A self-similarity analysis identifies positively homogeneous stress gauges as a broad associated family and separates the roles of yield-surface shape, isotropic expansion, and kinematic translation. The storage and resistance terms cover isotropic, kinematic, coupled, and gradient hardening, while multiple activity variables describe independently activated mechanisms. A viscous potential extends the construction to rate-dependent evolution. Four closed-form solutions illustrate multi-activity regions, kinematic-hardening fields, pressure-sensitive limit states, and the distinct displacement fields associated with normal and non-normal flow. Time-discrete constitutive integration and dimensional checks are collected in the appendices.
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High Energy Astrophysical Phenomena

Particle acceleration in Alfvénic turbulence with a strong guide field

Daniel Humphrey, Stanislav Boldyrev and Vadim Roytershteyn

Magnetically dominated Alfvénic turbulence creates an effective environment for particle acceleration. However, when a strong mean field is present, traditional mechanisms like mirror and curvature acceleration become inefficient at explaining non-thermal particle energy distributions. Based on numerical and phenomenological study, we propose that in such turbulence, particles are accelerated in charge-starved current sheets, corresponding to current velocities approaching the speed of light. The distributions of the electric currents, plasma density, fluctuations of electric charge, as well as the energy distributions of accelerated particles, approximately follow log-normal statistics. Non-thermal particle distributions thus arise from particle acceleration in these charge-starved current sheets rather than from conventional Fermi-type particle acceleration by turbulent eddies.
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High Energy Physics (Phenomenology)

Color Coherence and the Soft Structure of QCD Jets in Vacuum and the QGP

Paul Caucal and Yacine Mehtar-Tani

We formulate a theoretical framework for the evolution of QCD jets in vacuum and in the quark–gluon plasma through the resummation of large energy logarithms. Exploiting the strong hierarchy between the hard scale of the jet and the energy scale associated with jet energy loss, we show that jet observables near threshold can be formulated in terms of Wilson-line correlators obeying Banfi-Marchesini-Smye (BMS) evolution. In this description, soft radiation resolves the internal color structure of the jet, leading to a hierarchy of non-linear evolution equations that govern the evolution of color coherence and the emergence of decoherent energy loss. For jets propagating through a QCD medium, we demonstrate that medium-induced interactions modify the boundary conditions of the evolution while leaving its ultraviolet structure unchanged. This separation of scales provides a unified description of vacuum-like radiation, medium-induced energy loss, and color coherence. In the large-$N_c$ limit, the resulting evolution is closely related to the Balitsky-Kovchegov equation of high-energy QCD, allowing concepts from saturation physics to be applied to jet quenching. In particular, the medium coherence angle plays a role analogous to the saturation scale and acquires the same asymptotic scaling behavior under evolution. Our framework establishes a perturbative foundation for the study of color coherence effects in jet quenching and provides a unified picture of soft jet evolution in vacuum and in dense QCD matter.
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High Energy Physics (Phenomenology)

Jet Quenching Meets Gluon Saturation

Paul Caucal, Kevin Eisenberg and Yacine Mehtar-Tani

We present a theoretical framework for jet fragmentation in heavy-ion collisions based on the resummation of large energy logarithms. Exploiting the hierarchy of scales characteristic of jet quenching, we show that the jet function obeys the Banfi-Marchesini-Smye evolution equation, with medium-induced energy loss and color decoherence encoded in the initial condition. This structure reveals a close correspondence with saturation physics. In particular, the coherence angle emerges as the analog of the saturation scale and exhibits the same asymptotic scaling behavior under nonlinear evolution. As a proof of principle, we compute the jet nuclear modification factor to quantify the interplay between vacuum radiation and medium-induced color decoherence. Our framework provides a unified perturbative description of vacuum-like parton showers, medium-induced radiation, and color-coherence effects, paving the way for precision studies of jet quenching at RHIC and the LHC.
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Astrophysics of Galaxies

REBELS-25: multi-phase morphology and kinematics at z = 7.31

Lucie E. Rowland, Hiddo S. B. Algera, Jacqueline Hodge et al. (+23 more)

We present a spatially resolved, multi-wavelength study of the massive, star-forming galaxy REBELS-25 at a redshift of $z=7.31$. We combine new high-resolution ALMA [O III]88$\mu$m observations with resolution-matched [C II], dust continuum, and JWST/NIRSpec IFU spectroscopy, providing a $\lesssim1$ kpc view of the morphology, interstellar medium (ISM) conditions, and multi-tracer gas kinematics of one of the most mature galaxies known in the reionisation era. We find differing morphologies from the rest-frame UV to far-infrared (FIR) emission, with the UV and optical emission appearing clumpy and irregular, whereas the FIR emission is well-described by near-exponential disc profiles, with [C II] being the most extended. Comparing the resolved UV and FIR emission, we find that obscured star formation contributes $\sim55$-$98$% of the total star formation rate across the galaxy, demonstrating that dust obscuration strongly shapes the observed UV and optical morphology. Resolved ionisation-line diagnostics show no significant variation across the source at $\sim1$ kpc resolution, consistent with broadly similar ISM conditions among the identified regions. Kinematic modelling reveals that both the warm ionised gas, traced by [O III]88$\mu$m, and the colder neutral gas, traced by [C II], share the same large-scale rotating structure and are dynamically cold, with ratios of ordered-to-random motion, $V/\sigma$, of $\sim11$ and 4.5, respectively, although we find evidence for non-circular motions that are not well-described by a simple rotating disc. Overall, these results further support a picture in which REBELS-25 hosts a dusty, chemically enriched, and dynamically cold ISM already in place at $z=7.31$.
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All authors Lucie E. Rowland, Hiddo S. B. Algera, Jacqueline Hodge, Mauro Stefanon, Rychard Bouwens, Manuel Aravena, Lucy Astles, Karin Cescon, Elisabete da Cunha, Ilse de Looze, Andrea Ferrara, Rebecca Fisher, Yoshinobu Fudamoto, Thomas Herard-Demanche, Hanae Inami, Mahsa Kohandel, Lena Komarova, Andrés Laza Ramos, Themiya Nanayakkara, Katherine Ormerod, Andrea Pallottini, Siân Phillips, Sander Schouws, Piyush Sharda, Renske Smit, Paul van der Werf

Materials Science

Watching a GaN Transistor Switch: Real-Time Nanoscale Strain and Heat Dynamics

C. Corley-Wiciak, N. T. Sammler, B. Butej et al. (+16 more)

Digital and energy technologies depend on microelectromechanical and power electronic components whose performance is critically impacted by rapid, cyclic deformations. Real-time information on their operation has remained inaccessible due to the need for nanosecond and nanometer resolution in fully integrated devices. We break this limitation by imaging the complete switching cycle of an industrial GaN high electron mobility transistor through stroboscopic dark field X ray microscopy at a fourth-generation synchrotron, resolving electromechanical and thermal micro strain fields across the entire device and correlating them with time dependent voltage characteristics. Coupled simulations benchmarked against the measurements reproduce electric field evolution and transient thermal hotspots. This combined approach provides direct insight into device physics and informs design strategies for next generation energy and information processing technologies.
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All authors C. Corley-Wiciak, N. T. Sammler, B. Butej, M. Petersmann, A.A. Corley-Wiciak, L. Neumann, Juan M. Carrillo-Larrea, P. Schmiedeke, M. Strätgen, P. A. Douissard, S. J. Leake, P. Boesecke, M. Sievers, P. Imrich, M. Nelhiebel, M. Glavanovics, D. Pogany, M. Reisinger, T.U. Schulli

High Energy Astrophysical Phenomena

Winds Against Alignment: AGN Feedback and the Spin Evolution of Massive Black Hole Binaries

Francesco Bollati, Marta Volonteri, Alessandro Lupi et al. (+2 more)

The interaction between massive black hole (MBH) binaries and circumbinary discs (CBDs) affects the spin orientations of merging binaries - a key observable for the future LISA mission. While gas accretion is known to align BH spins with the orbital angular momentum via the Bardeen-Petterson effect, the impact of AGN feedback on this process has remained largely unexplored. We present hydrodynamical simulations of an equal-mass MBH binary embedded in a CBD, using the GIZMO code with a subgrid model that self-consistently evolves BH mass, spin, and anisotropic AGN feedback. We explore different BH spin magnitudes and orientations to identify the configurations producing the strongest feedback effect on the disc structure and binary evolution. AGN winds substantially modify the CBD and minidisc structure, enlarging the central cavity and, after 20-25 binary orbits, destroying the minidiscs in all feedback simulations. Feedback-driven cavity excavation suppresses the gravitational torques driving orbital evolution, causing the binary to stall. AGN feedback dramatically affects MBH accretion, reducing the Eddington ratio by one to two orders of magnitude before ultimately suppressing it entirely. This strongly inhibits Bardeen-Petterson spin alignment, delaying it well beyond the feedback-free timescale. Extending one simulation to 70 binary orbits reveals a feedback-regulated duty cycle of alternating active and quiescent phases, with the binary spending most of its time in low-density, quiescent conditions that further suppress alignment. These results indicate that AGN feedback is an important, previously overlooked channel for preserving spin misalignment in MBH binaries prior to coalescence, with direct implications for interpreting LISA gravitational-wave observations.
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All authors Francesco Bollati, Marta Volonteri, Alessandro Lupi, Massimo Dotti, Francesco Haardt