Mesoscale and Nanoscale Physics
Coexisting Charge Density Wave and Superconducting Order in Quantizing Magnetic Fields
Ron Q. Nguyen, Peiyu Qin, Hai-Tian Wu et al. (+12 more)
Charge density wave (CDW) and superconductivity are both common in strongly interacting electron systems. While CDW order is ubiquitous in both
quantum Hall systems and unconventional
superconductors, superconductivity is generally suppressed by the strong
magnetic fields required for Landau quantization. Here we investigate the intertwined CDW and superconducting phases of rhombohedral hexalayer
graphene (R6G) in a large displacement field, which generates tunable flat band edges, and a strong
magnetic field, which generates a
manifold of nearly degenerate Landau levels. We find a series of integer
quantum Hall effects with
Hall conductance
quantum numbers that deviate from nearby integer filling factors, an observation that can be explained only by CDW order that mixes many Landau levels. We also find a nearby superconducting phase stabilized by perpendicular
magnetic fields and persists deep within the
quantum Hall regime. This intertwinement provides new insight into superconductivity in R6G at zero
magnetic field.
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All authors Ron Q. Nguyen, Peiyu Qin, Hai-Tian Wu, Sparsh Mishra, Tobias Wolf, Joseph Roll, Erin Morissette, Naiyuan J. Zhang, Sarah Alkidim, Kenji Watanabe, Takashi Taniguchi, Aaron W. Hui, Dima E. Feldman, Allan MacDonald, J.I.A. Li
Optics
Surface-exciton enhanced SHG response in few-layer 2H-TMDC
H. Hübschmann, G. Berth, M. Groll et al. (+6 more)
We explore the nonlinear optical properties of few-layer MoS2 by means of polarization and
laser-power-dependent measurements as well as ab initio techniques. While for even layer samples a weak second-harmonic (SH) signal can be attributed to the presence of surface defects or interface effects, our measurements resolve a layer-number dependent signal for odd-layer samples. For the excitation energy of 780 nm, we find that the SH intensity decreases steadily with the layer number. Our simulations demonstrate that this effect cannot be purely attributed to modifications of the band structure, but requires the inclusion of excitonic effects and can be explained by the increasing delocalization of
excitons with increasing sample thickness.
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All authors H. Hübschmann, G. Berth, M. Groll, K. Burgholzer, A. Bonanni, K. D. Jöns, U. Gerstmann, W. G. Schmidt, A. Bocchini
Atmospheric and Oceanic Physics
A Mutual Information-Based Ensemble Kalman Filter
Tadashi Tsuyuki and Shunji Kotsuki
Ensemble Kalman filters (EnKFs) are widely used for data assimilation in geophysical systems. Among various implementations, the local ensemble transform Kalman filter (LETKF) has gained popularity because of its computational efficiency. However, the deterministic EnKF such as the LETKF is known to be less robust than the
stochastic EnKF in strongly nonlinear regimes. We generalize the LETKF such that it contains a
stochastic term and includes the
stochastic EnKF within it. We adaptively optimize the parameter that determines the weight of the
stochastic term based on an identity of mutual information, which is satisfied by the Kalman filter in linear Gaussian systems. As the analysis perturbation equations of EnKFs are decomposed into a system of equations for modes that are uncorrelated with each other, the application of mutual information is easily achieved. The generalized LETKF thus optimized is named the mutual information-based ensemble Kalman filter (MI-EnKF). The MI-EnKF indirectly uses the third- and fourth-order moments of the forecast ensemble through
entropy. To speed up calculations of
entropy, we create a lookup table based on maximum
entropy distributions. We conduct data assimilation experiments using the Lorenz-96 model to confirm the validity of the optimization method of MI-EnKF. When the observation operator is linear, the ML-EnKF shows the same analysis accuracy as the LETKF. When the observation operator is strongly nonlinear, the MI-EnKF is more accurate than both LETKF and
stochastic EnKF regardless of ensemble size. Optimizing just the first mode can lead to significant improvements, but positive impacts of increasing the number of optimized modes are not observed unless the ensemble size is large. The optimized parameter values indicate that the optimal EnKF lies between the deterministic EnKF and the
stochastic EnKF.
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Instrumentation and Methods for Astrophysics
The Atacama Large Aperture Submillimeter Telescope (AtLAST): enabling large-scale sub-mm science beyond 2030
Claudia Cicone, Tony Mroczkowski, Evanthia Hatziminaoglou et al. (+38 more)
AtLAST is designed to be the largest (sub-)mm single-dish astronomical observatory and the first
climate-neutral modern research infrastructure. It offers a unique combination of large aperture (50 m), large field of view (>1 deg), fast scanning speed (up to 3 deg/s), and high surface accuracy (20micron nighttime half wavefront error) that allows >=50% Ruze efficiency up to 1 THz. The design features a rocking chair mount with an active main reflector surface, a high precision closed-loop metrology system, and the space to house six major instruments. Instruments will be periodically updated as spectroscopic focal plane array, detector, coherent amplifier, and
semiconductor technologies used in readout and backend electronics will advance over the next decades. AtLAST will be a multi-purpose facility that will produce transformational results in nearly all fields of Astrophysics, such as Astrochemistry,
Galactic and Extragalactic Astronomy, Cosmology, Planetary science,
Stellar and
Solar Physics, High energy astrophysics, and Time domain astronomy. Its unrivalled throughput of 6170 m^2 deg^2 will enable wide-field unbiased surveys. These will overcome extragalactic confusion noise and enable the detection of normal
galaxy populations out to z=7. AtLAST will reveal and characterise the missing
baryons in the Universe, by mapping the elusive, low surface brightness gas within and around
galaxies across
cosmic time. AtLAST will be the first green off-grid observatory, powered by a bespoke renewable energy system and reusing its braking energy thanks to a cutting-edge energy recovery system. By sharing surplus power and technological know-how with local communities, AtLAST will contribute to energy justice in Chile. AtLAST's new bold
vision of a sustainable pursuit of breakthrough astronomy is an exceptional opportunity to shape the future of scientific research infrastructures. [abridged]
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All authors Claudia Cicone, Tony Mroczkowski, Evanthia Hatziminaoglou, Matthias Reichert, Sabrina Sartori, Amelie Saintonge, Pamela Klaassen, Francisco Montenegro-Montes, Martin Timpe, Aleksej Kiselev, Danilo Koeltzsch, Carlos De Breuck, Pamela Pizarro, Eelco van Kampen, Tinus Stander, Dirk Muders, Yiqing Song, Kotaro Kohno, Sergio Poppi, Yoichi Tamura, Stefan Thoms, Hans Kaercher, Sven Wedemeyer, Alessandro Attoli, Stephen Molyneux, Bruno Silva, Guillermo Valenzuela Venegas, Paola Velasco-Herrejon, Marianne Zeyringer, Yogesh Kumar Yadav, Mark Booth, Carlos Alberto Duran, Lars-Ake Nyman, Serni Ribo, Francisca Kemper, Manuel Groh, Leandro Aggio, Mathias Hudoba de Badyn, Benjamin Magnelli, Mats Kirkaune, Akira Endo
General Relativity and Quantum Cosmology
Emergent cosmology and gravity from quantum time?
Ovidiu Cristinel Stoica
Macroscopic observables allow the recovery of intrinsic dynamics from stationary
quantum states. I show that, by interpreting the squared amplitude as the probability density for each definite value of intrinsic time, a
curvature emerges in the time direction. For example, from the perspective of intrinsic
quantum time, the Friedmann-Lemaître-Robertson-Walker cosmological model emerges from spherically symmetric stationary solutions in four-dimensional Euclidean space, without presupposing
gravity. If there is no unique direction of time,
curvature emerges in all spacetime dimensions, without presupposing
gravity, from the variable amplitude of the stationary wavefunction alone. This opens a new possibility that general relativity or some modification of it emerges from intrinsic time observables.
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Computational Physics
Watts per event: evaluating Sustainability of HEP Event Generators beyond the LHC era
Szabolcs Molnár, Gábor Bíró, Gábor Papp et al. (+1 more)
The development, tuning and operation of Monte Carlo event generators beyond the LHC era require vast amount of resources. In this study we investigate the sustainability of these software with a containerized set of tools (named 77rev/propripy), by benchmarking the HIJING++ heavy-ion Monte Carlo event generator. We analyze the performance of various CPU architectures and show that by choosing the level of multithreading properly, the cost of event generation can be optimized. The presented approach can reduce the energy footprint of high-energy physics event generators and therefore alleviate the ever-increasing, ubiquitous computational challenges.
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All authors Szabolcs Molnár, Gábor Bíró, Gábor Papp, Gergely Gábor Barnaföldi
Computational Physics
dpti: An Automated Thermodynamic Integration Workflow for Phase Diagram Calculations with Machine Learning Interatomic Potentials
Fengbo Yuan, Xin Zhong, Donghao Zheng et al. (+4 more)
Thermodynamic integration (TI) is a widely used approach for computing free energies and phase diagrams. However, TI calculations driven by machine learning interatomic potentials (MLIPs) remain technically challenging because they require careful design of reversible integration paths and many closely related molecular dynamics (MD) tasks for each phase and state point. To address these challenges, we present dpti, an open-source Python package that automates TI workflows for phase diagram calculations with MLIPs. dpti connects reference systems with analytically known free energies to MLIP-described atomic and molecular solids and
liquids through reversible integration paths. Given JSON input files, dpti generates and runs the required MD tasks, computes free energy contributions, estimates errors, and propagates coexistence points into phase boundaries. We demonstrate the usage of dpti with two examples driven by Deep Potential models: a silica phase diagram involving beta-quartz, coesite, and melt, and the ice Ih-
liquid water phase boundary. dpti provides a useful tool for automated phase diagram calculations of materials modeled by MLIPs.
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All authors Fengbo Yuan, Xin Zhong, Donghao Zheng, Jinzhe Zeng, Linfeng Zhang, Han Wang, Yifan Li
Statistical Mechanics
Geometric Characteristics of Subproblems in Ising-Machine-Assisted Large Neighborhood Search
Masashi Yamashita and Shu Tanaka
Large-scale quadratic unconstrained binary optimization (QUBO) formulations of constrained combinatorial optimization problems often exceed the input-size limit of present Ising machines or suffer from degraded solution quality as the number of binary variables increases. Large neighborhood search (LNS) mitigates this difficulty by sequentially optimizing restricted subproblems, but the structural factors that distinguish subproblems beyond the number of binary variables remain insufficiently characterized. In this study, we examine vehicle routing problems and compare a construction based on the vehicle routes of the current solution, denoted by LNS-K, with a construction based on QUBO variables and constraint relations, denoted by LNS-Q, while controlling the number of binary variables in the subproblems. Under the tested conditions, LNS-K obtained shorter total distances than LNS-Q in the matched-size comparisons, and the position variance, a measure of the spatial spread of the selected customers, decreased during the iterations in LNS-K. These observations suggest that subproblem design for sequential optimization with Ising machines should consider not only subproblem size but also semantic and
geometric structures inherited from the current solution.
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Atomic Physics
Investigating Role of Electron Correlation Effects via Triple Excitations for Precise Evaluation of Energies and Hyperfine Structure Constants in $^{23}$Na
Vaibhav Katyal and B.K. Sahoo
Accurate determination of hyperfine structure constants in atomic systems provides important insight into the interplay of electron correlation and relativistic effects in the
nuclear region. Although sodium (Na) is a relatively light atom, previous all-order relativistic many-body calculations of the
magnetic dipole hyperfine constants for the low-lying states of $^{23}$Na show noticeable discrepancies with experiment. To address this, we calculate the ionization potentials and hyperfine structure constants of $^{23}$Na using relativistic coupled-cluster theory with explicit inclusion of triple excitations. We further incorporate corrections from the Breit interaction,
quantum electrodynamics, and the Bohr-Weisskopf (BW) effect. Results from lower-order methods are also presented to assess the importance of different physical contributions across states. Our calculations demonstrate that contributions from the lower-order relativistic and BW effects play almost similar roles with the electron correlation effects, including triple excitations, and are essential for reconciling theoretical predictions with experimental observations. This study can also serve as a useful guide for understanding the role of triples in heavier alkali systems.
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Instrumentation and Methods for Astrophysics
In-Band Scattering and Absorption of Infrared Blocking Foam Filters for Millimeter-wave Cameras
Alex Thomas, Bugao Zou, Shreya Sutariya et al. (+11 more)
Expanded closed-
cell polymer foams are widely used as thermal infrared (IR) blocking filters in millimeter-wave cameras, particularly for
Cosmic Microwave Background observations. Precise knowledge of their millimeter-wave properties is essential for optimizing sensitivity. We present broadband (150 GHz - 2 THz) transmittance spectroscopy of Styroace-II and several Zotefoam filters, fitting their spectra with a radiative transfer model incorporating dielectric absorption and Rayleigh, Mie, and higher-order scattering. For a typical 5~cm thick filter stack at 280~GHz, Styroace-II exhibits ${\sim}10\%$ scattering with absorption estimated as ${\lesssim}5\%$ by effective-medium theory, while Zotefoam HD30 offers superior performance at ${\sim}3\%$ scattering and absorption likewise bounded to ${{\lesssim}0.3\%}$. Each model component is constrained at the ${\sim}0.1\%$ transmittance level for millimeter wavelengths. We observe batch-to-batch scattering variability of up to 2 percentage points in foams with multiple tested batches. Less commonly used Zotefoam formulations (LD15 and LD24) can further reduce in-band scattering to ${<}1\%$ while maintaining negligible in-band absorption and likely comparable IR blocking due to shared polyethylene absorption features and similar
cell sizes. Based on this work, a filter constructed from the best measured LD24 batch has replaced the Styroace-II filter in a Simons Observatory 220/280 GHz Small Aperture
Telescope.
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All authors Alex Thomas, Bugao Zou, Shreya Sutariya, Yuhan Wang, Gabriele Coppi, Samuel Day-Weiss, Nicholas Galitzki, Kathleen Harrington, Erin Healy, Claire Lessler, Aashrita Mangu, Jeffrey McMahon, Michael D. Niemack, Edward J. Wollack
Quantum Physics
Canonical quantization of neurons
Alexander He, Nana Liu and Mark M. Wilde
Canonical quantization provides a systematic procedure for constructing
quantum models from classical
Hamiltonians. Here, we apply this principle to a fundamental computational primitive of machine learning: the
neuron. Specifically, by viewing a
neuron as a composition of an energy function and an activation function, we quantize this model by replacing the energy function with a
quantum Hamiltonian and applying the activation function to it through
matrix functional calculus. This results in an activation observable that can be measured on an input
quantum state. We investigate the use of these quantized
neurons for function approximation, where the objective is to learn an unknown observable from labeled
quantum data. For this purpose, we develop hybrid
quantum-classical
algorithms for training and evaluation, including procedures for measuring the activation observable and estimating gradients of the squared loss error. Our
algorithms for gradient estimation rely on basic primitives like classical random sampling, the Hadamard test, and
Hamiltonian simulation, and those for measuring an activation observable rely on
quantum algorithms known as the power of one qumode and Schroedingerization. Numerical experiments demonstrate that our quantized
neurons exhibit enhanced expressive capabilities relative to corresponding classical
neurons on representative learning tasks. Our work establishes canonical quantization as a principled framework for constructing
quantum machine learning primitives and provides a foundation for developing neural architectures tailored to
quantum data.
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Adaptation and Self-Organizing Systems
Steering the dynamics by controlling the temporal interaction network
Melvyn Tyloo
Many real-world coupled dynamical systems have their interaction structure and strength that evolve or adapt over time. Here, we investigate how one can control the state of a system by tuning its temporal interaction network. We present a framework based on nonlinear optimal control, where one has control over the time-dependent coupling
matrix of a dynamical system. We show how to obtain the gradient of the Lagrangian functional of a generic optimal control problem using the adjoint method, where the control variables are multiplicative inputs. We illustrate the theory with the precision cost that aims at steering the nodal states to prescribed target trajectories. We first focus on a linear time-variant system for which further expressions of the gradient can be obtained. Second, we uncover the temporal interaction that pushes a nonlinear neural units model towards target trajectories. For both systems, we numerically solve the optimal control problem, imposing various constraint on the structure of the controlled edges. The workflow presented here can be leveraged to steer the dynamics of systems with artificial or engineered interaction that is tunable.
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Soft Condensed Matter
Inhomogeneous thinning of dielectric membranes under uniaxial tension and electric fields
Xiang Yu and Yibin Fu
Dielectric elastomers exhibit rich electromechanical instabilities arising from the coupling between mechanical deformations and electric fields. A widely used approach for analyzing instabilities in dielectric elastomers is the Hessian stability criterion proposed by Zhao and Suo (2007), which identifies the onset of instability of a homogeneous deformation but does not determine how the deformation develops beyond the instability threshold. To address this problem, we investigate dielectric membranes subjected to uniaxial tension and an electric field. Starting from a three-dimensional nonlinear electroelastic formulation, we derive asymptotically consistent reduced models, including a membrane model and a plate model, using the variational-asymptotic method. A linear bifurcation analysis first shows that the Hessian stability criterion is equivalent to a zero-wavenumber bifurcation condition, thereby establishing a direct connection between energy-based stability analysis and bifurcation theory. A subsequent weakly nonlinear analysis demonstrates that the zero-wavenumber bifurcation gives rise to localized necking, manifested as inhomogeneous thinning of the membrane. The weakly nonlinear predictions are further validated by numerical simulations. Furthermore, for the plane-stress configuration considered here, the membrane model accurately captures both the onset of instability and the associated localization behavior, while bending effects remain small. These results identify the deformation associated with the Hessian instability and provide a framework for understanding electromechanical instabilities in dielectric membranes.
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Plasma Physics
Quasi mono-energetic, relativistic electron acceleration in a femtosecond, high intensity laser excited solid magnet
Trishul Dhalia, Anandam Choudhary, C. Aparajit et al. (+6 more)
The interaction of ultraintense
lasers with magnetized overdense
plasmas reveals a fundamentally new regime of
laser-driven particle acceleration. Particle-in-
cell simulations demonstrate the generation of directional, quasi-monoenergetic electrons in the MeV energy range superimposed on a broad thermal electron background with the estimated acceleration gradient of 3.6 MeV/{\mu}m, which is the highest till date. In contrast to conventional
laser-
plasma accelerators, which rely on underdense
plasmas and are therefore constrained to relatively low
plasma densities and limited beam charge, the present scheme operates in
plasmas with densities orders of magnitude higher, opening new possibilities for the generation of high-flux energetic electron beams. A central result of this work is the demonstration of the excitation of electron Bernstein waves during relativistic
laser interaction with magnetized overdense
plasmas. The subsequent Landau damping of these electrostatic warm-
plasma modes selectively transfers energy to resonant electrons, leading to the emergence of quasi-monoenergetic spectral peaks at energies that can be tuned through the applied
magnetic field. To support the simulation results, we experimentally demonstrate the directional emission of energetic electrons from a simple permanent-magnet target irradiated by an ultraintense
laser pulse, highlighting the practical feasibility of controlled electron-beam generation in dense
plasma environments. These findings establish electron Bernstein waves as an efficient mediator of
laser energy coupling in overdense
plasmas and introduce a new paradigm for controlled particle acceleration and energy deposition in high-energy-density
plasma systems.
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All authors Trishul Dhalia, Anandam Choudhary, C. Aparajit, Amit D. Lad, Ankit Dulat, Yash M. Ved, Rohit Juneja, Amita Das, G Ravindra Kumar
Fluid Dynamics
Nanosecond DBD-Induced Shock and Thermal Perturbations on Blunt Bodies in Hypersonic Flow
Nadav Friedman, Kostiantyn Kuzmenko, Oshri Ifergan et al. (+1 more)
Nanosecond-pulsed dielectric barrier discharge (DBD)
plasma actuators were investigated on a generic blunt body in a Mach 6 Ludwieg tube to characterize the pressure and thermal perturbations relevant to hypersonic boundary-layer transition control. Complementary quiescent experiments were also conducted over ambient pressures representative of those predicted in the model nose region to isolate the influence of local thermodynamic conditions on actuator operation. Pulse-energy measurements and schlieren imaging showed that decreasing pressure reduced the deposited electrical energy per pulse, weakened the actuator-generated shock, and increased the spatial extent of the residual heated region owing to energy deposition over a larger
plasma volume. Under Mach 6 Ludwieg-tube conditions, the actuator-generated shock interacted with and reflected from the detached bow shock, temporarily increasing the bow-shock stand-off distance by approximately 11%, while the residual heated region was advected downstream along the body. The schlieren images further permitted the
evolution of the thermal disturbance to be distinguished from that of the actuator-generated shock. The results demonstrate two distinct perturbation mechanisms – a short-duration compression wave and a longer-lived thermal disturbance – whose relative importance is governed by the local thermodynamic conditions and which may independently promote hypersonic boundary-layer transition.
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All authors Nadav Friedman, Kostiantyn Kuzmenko, Oshri Ifergan, David Greenblatt
Quantum Physics
Quantum Hashing via Constrained Rydberg Many-Body Dynamics
Han-Chao Chen, Xin Liu, Zheng-Yuan Zhang et al. (+2 more)
In this Letter, we show that constrained many-body dynamics in Rydberg atom arrays naturally gives rise to a
quantum hashing mechanism. By encoding ternary strings into deterministic trajectories in the state space, the classical information space is mapped onto a
quantum state ensemble in the
Hilbert space with an induced
geometric structure. Statistical analysis reveals that this ensemble exhibits high probability near-orthogonality, random-like distribution, and broad
geometric coverage. These
geometric features naturally give rise to the essential cryptographic properties of
quantum hashing, including low collision probability, one-wayness, tamper sensitivity, and
privacy preservation. Our results demonstrate that the cryptographic functionality of
quantum hashing need not rely on deliberately engineered
algorithms, but can instead emerge naturally from constrained many-body dynamics, identifying
quantum dynamics itself as a physical resource for cryptographic information processing.
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All authors Han-Chao Chen, Xin Liu, Zheng-Yuan Zhang, Dong-Sheng Ding, Bao-Sen Shi
Geophysics
Joint Velocity Slope Diffusion Prior for Structurally Constrained Velocity Model Building
Francesco Brandolin and Tariq Alkhalifah
High-resolution velocity models are crucial for reservoir characterization and subsurface delineation. However, the band limited nature of our surface recorded data limits resolution. Utilizing well measurements to enhance the resolution of our subsurface models is an important objective. To this end, we present a
diffusion-guided framework for structurally preconditioned velocity-model reconstruction from sparse well-log information. The proposed approach combines plane-wave PDE regularization, structurally preconditioned inversion, and measurement-guided
diffusion posterior sampling within a unified formulation. Local structural slopes estimated through plane-wave destruction are used both to propagate well information along geological dip directions and to guide the
diffusion sampling process through a joint velocity–slope generative prior. Numerical experiments on the Volve synthetic model and the Viking Graben field
dataset demonstrate that the proposed framework improves structural continuity, lateral consistency, and geological realism compared with conventional structurally preconditioned inversion approaches while maintaining computationally practical inference through DDIM sampling.
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High Energy Physics (Theory)
The causal set reduction formula
Stav Zalel
We derive a reduction formula for
matrix elements on a causal set background. We derive an infinite tower of relations between correlators, akin to the Schwinger-Dyson equations of the continuum. Combining these two results we are able to express
matrix elements in three different forms: as a path integral and as two distinct sums of correlators. We sketch the form that our method - which circumvents explicit use of differential equation of motion operators - takes in flat continuum spacetime where it provides an alternative expression for the standard LSZ result.
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Quantum Physics
Extending the Bloch sphere model to an N-qubit system
Francisco Piñero, Cristian Franco, Hernán I. de la Cruz et al. (+5 more)
The Bloch sphere is an elegant tool for representing single-
qubit states. However, a widely accepted generalization for multi-
qubit systems with
entanglement remains absent. We propose a novel
geometric model extending the Bloch sphere representation to arbitrary $N$-
qubit systems using $2^N-1$ spheres. We demonstrate that any pure 2-
qubit state is uniquely described by three spheres: two for individual
qubits and a third encapsulating bipartite
entanglement. Generalizing this, we establish an $N$-
qubit parameterization through the hierarchical application of controlled rotation gates along the $Z$ and $Y$ axes. We formally prove a strict bijection between the standard state vector representation and our model's angular parameters. This framework provides an intuitive visualization of multiple
entanglement, offering potential computational advantages for
quantum simulators and new analytical perspectives on
quantum gates.
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All authors Francisco Piñero, Cristian Franco, Hernán I. de la Cruz, Fernando L. Pelayo, Vicente Pascual, Mauro Mezzini, Jose Javier Paulet, Fernando Cuartero
Strongly Correlated Electrons
Optical switching of antiferromagnetic domains by nonreciprocal heat current
Takeshi Hayashida, Shunsuke Izumikawa, Kenta Kimura et al. (+2 more)
What distinguishes front from back? In physics, such directionality emerges only when an underlying
symmetry is broken. Antiferromagnets that inherently break both space-inversion and time-reversal
symmetries provide a striking example, exhibiting nonreciprocal optical responses that depend on the direction of light propagation. Beyond distinguishing
antiferromagnetic domains, we show that this nonreciprocity can deterministically create them. Using mid-infrared light, we demonstrate deterministic switching of
antiferromagnetic domains in the magnetoelectric antiferromagnet LiFePO4, where illumination from opposite sides selectively stabilizes opposite domain states. Remarkably, the switching persists over a broad wavelength range rather than being confined to a narrow transition-specific spectral region, overcoming the spectral and material constraints of resonance-based optical switching schemes. The broadband switching originates from the material's intrinsic nonreciprocity through optically generated heat currents. Our results establish nonreciprocity as a general principle for deterministically controlling
symmetry-broken phases with light.
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All authors Takeshi Hayashida, Shunsuke Izumikawa, Kenta Kimura, Carl S. Davies, Andrei Kirilyuk
Fluid Dynamics
A Multipurpose Thermal Convection Setup to Study Turbulent Super Structures
Hiufai Yik, Constantin Schettler, Eberhard Bodenschatz et al. (+2 more)
A thermal convection apparatus has been designed to study turbulent super structures at high Rayleigh numbers and Prandtl numbers of the order of unity. This apparatus consists of a rectangular
cell with a length of $3.50\,\mathrm{m}$, width of $0.35\,\mathrm{m}$, and variable height, which is fixed at $0.70\,\mathrm{m}$ for the present study. This
cell is installed inside a $5.6\,\mathrm{m}$ long pressure vessel facility, known as Göttingen Uboot, which can be filled with compressed gasses (air, helium, nitrogen, or sulfur hexafluoride) at pressures up to $19\,\mathrm{bar}$, enabling Rayleigh numbers up to $ Ra \leq 5\times 10^{12}$ and Prandtl numbers of approximately $0.7 \leq Pr \leq 0.9$. The convection
cell is bounded vertically by top and bottom plates consisting of a three-layer composite structure in which a thin Lexan plate is sandwiched between highly conductive aluminum plates. This allows for spatially resolved heat flux measurements. Each plate is subdivided into four longitudinal segments that can be independently temperature-controlled to enable homogeneous temperatures and the imposition of horizontal temperature gradients at both the top and bottom boundaries. While the bottom plate is electrically heated, the top plate's temperature is regulated using temperature-controlled circulating pressurized water. The apparatus is well suited for precise heat flux measurements, with the results obtained being in good agreement with those previously reported in the literature.
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All authors Hiufai Yik, Constantin Schettler, Eberhard Bodenschatz, Umesh Madanan, Stephan Weiss
Mathematical Physics
Long-range interactions and Anderson localisation for one-dimensional high-contrast resonator chain
Habib Ammari, Silvo Barandun, Jiayu Qiu et al. (+1 more)
Spectral and transport properties of high-contrast resonator systems can be described in the subwavelength regime in terms of the so-called capacitance operator. In this paper, we consider an infinitely periodic chain of high-contrast resonators in three dimensions. The first result is a precise estimate of the off-diagonal decay rate of the capacitance operator $C$. Importantly, we demonstrate that the decay rate is long-range and critical: as $|n-m|\to\infty$, \begin{equation*} C(n,m)\sim \frac{1}{|n-m|\log^2|n-m|}, \end{equation*} which is $\ell^1$ summable but slower than quadratic. This borderline decay of the off-diagonal entries makes the present proof of Anderson localisation with arbitrary disorder, which is observed numerically in this paper, out of reach; we hope that this physical example of classical wave systems with critical long-range interactions provides new insight in the field of Anderson localisation. As the second main result, based on the off-diagonal decay estimate, we prove a strong convergence of the finite capacitance operator, which corresponds to a truncated chain, to the capacitance operator as the size of the truncated chain grows to infinity. Using this strong convergence, we improve the results of [Ammari et al., SIAM J. Math. Anal., 2023 and Bull. London Math Soc., 2025] by presenting a rigorous estimate of the convergence rate of the spectrum.
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All authors Habib Ammari, Silvo Barandun, Jiayu Qiu, Alexander Uhlmann
Mesoscale and Nanoscale Physics
Functionalization of $g$-wave altermagnets: spin-splitter effect enabled by surfaces
Sopheak Sorn
We investigate surfaces of a $g$-wave altermagnet(AM) and show that they provide a platform for realizing $d$-wave altermagnetism and the associated
spin-splitter functionality. Using the Kubo formalism applied to a minimal slab model, we evaluate the
spin-splitter effect(SSE) by computing the
spin conductivity corresponding to a transverse
spin current induced by a longitudinal electric field. We find a finite SSE, absent in the bulk, that emerges from surface-induced $d$-wave altermagnetism. Strikingly, the sign pattern of the $d$-wave altermagnetism on both surfaces of the slab geometry is identical to each other, leading to additive contributions to SSE from the two surfaces, with a
spin-splitter angle reaching up to 15 degrees. In addition, this response is intrinsically linked to an accompanying surface-induced weak ferromagnetism, which potentially enables control of altermagnetic domains via an external
magnetic field and provides a route to optimize the SSE functionality. These results can be understood in terms of a bulk-boundary correspondence between surface states and bulk altermagnetic order parameters, where the
magnetic multipolar character of the latter plays a central role. Our findings strongly suggest thin-film engineering as a viable strategy to functionalize non-$d$-wave AMs.
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Mesoscale and Nanoscale Physics
Lindblad theory of linear response susceptibility and dispersive readout in minimal Kitaev junctions
Tobias Kuhn, Raffael L. Klees, Ramón Aguado et al. (+1 more)
The field of hybrid
superconductor-
semiconductor quantum dots is advancing toward the development of functional devices that leverage the advantages of both types of materials. However, the inherent complexity of these devices demands a comprehensive theoretical framework for a complete understanding of their responses to external probes, readout and the dissipation arising from environmental coupling. We present a Lindblad-based linear response formalism that captures the multi-level nature of these devices, their probe-readout flexibility, and the non-
unitary effects of finite-frequency response, including the so-called Sisyphus and Hermes dynamical susceptibilities. These arise from fluctuations in the rates and jump operators, and are hence absent in standard Kubo linear response treatments. We exemplify the framework using
quantum dot-based Kitaev chain setups which are promising candidates for topologically protected Majorana-based parity
qubits. Our results shed light onto the validity of the standard
curvature-based approximation for fermionic parity and
qubit readout, show that Hermes terms compensate decoherence in dispersive readout and implement important corrections beyond thermalized states.
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All authors Tobias Kuhn, Raffael L. Klees, Ramón Aguado, Mónica Benito
Fluid Dynamics
Estimating Hydrodynamic Coefficients for Floating Offshore Structures from Movement Data Using Physics-Informed Neural Networks
Anders Schou, Jens Visbech and Allan Peter Engsig-Karup
We present a method for estimating the hydrodynamic coefficients in the Cummins equations using time-series data from a moving body, such as a floating offshore structure. The proposed data-driven method is based on incorporating the Cummins equations governing the dynamics of a structural body interacting with water waves into a physics-informed neural network (PINN), along with available motion data. The proposed method first estimates the structure's state in terms of translational and rotational degrees of freedom, and then solves the inverse problem to determine the hydrodynamic forces acting on the body, expressed in terms of added mass, damping coefficients, and/or hydrostatic restoring. The Cummins equations are formulated as a first-order system, and both state and parameter estimation are performed using PINNs. The method is verified on the free decay of a sphere and a box. The results demonstrate that it is possible to estimate the state and hydrodynamic coefficients accurately, although accuracy depends on the volume and quality of the movement data.
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Atomic Physics
Super-molasses returns: All optical near-resonance laser cooling and trapping of neutral atoms from background vapor
Matt Himsworth, Chester Camm, Max Carey et al. (+12 more)
Laser cooled and trapped atoms have been the workhorse of atomic physics for the past four decades. The predominant method has been the highly versatile Magneto-Optical Trap. We describe an alternative
laser trap involving a simple geometry of collimated
laser beams that provides both a velocity and position dependent restoring force such that a dense cloud of cold atoms is formed. This technique produces similar atom number ($>10^6$) and density ($10^{10}$\,atoms/cm$^{3}$) to the Magneto-Optical Trap, albeit with no
magnetic field. The beam geometry is compatible with conventional sub-Doppler cooling techniques, allowing the trapped cloud to be cooled to $< 10~\mu$K. We demonstrate the validity and robustness of the trap by capturing $^{87}$Rb atoms directly from the background vapor and provide a theoretical discussion of the underlying principles. This trap has many unique properties that make it highly suitable for
quantum sensing, timing, and computing applications as well as a new tool in fundamental science and metrology.
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All authors Matt Himsworth, Chester Camm, Max Carey, Jack Saywell, Jonathan Woods, Vilius Atkočius, Florence Concepcion, Konstantinos Karakostas, Hannah Brady, Doruk Tan Atila, Ellie Heywood, Alex Jantzen, Andrei Dragomir, Christopher Morley, James Bateman
Cosmology and Nongalactic Astrophysics
Spectroscopic redshifts of selected flat-spectrum radio sources I
Dmitry Blinov, Alberto Floris, Andreas Zezas et al. (+5 more)
We present the first results of a spectroscopic campaign carried out as part of the Search for Milli-Lenses (SMILE) program, which aims to constrain the prevalence of gravitational lens systems on milli-arcsecond angular scales (milli-lenses) using high-resolution Very Long Baseline Interferometry (VLBI) imaging. The SMILE parent sample contains ~ 5000
radio-loud active
galaxies, selected as a flux-limited, complete subsample of CLASS (The
Cosmic Lens All-Sky Survey) sources. We compiled
redshift information for the full sample from multiple literature and catalog sources and found that 491 sources have no available
redshift estimate, either spectroscopic or photometric. A further 948 sources have only photometric
redshifts, many of which show substantial discrepancies between catalogs. Reliable
redshifts are essential for VLBI
radio-source studies because they convert angular measurements into physical linear scales, enable estimates of intrinsic luminosities and jet kinematics, and allow robust cosmological and population studies. To address this key limitation for
lensing and population studies, we initiated a dedicated spectroscopic campaign to secure reliable
redshifts for as many targets as possible. This paper focuses on the brightest sources in the SMILE sample. We report newly determined spectroscopic
redshifts for 6 targets out of 15 observed with the Skinakas 1.3 m
telescope.
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All authors Dmitry Blinov, Alberto Floris, Andreas Zezas, Carolina Casadio, Elias Kyritsis, Valentina Missaglia, Vangelis Pantoulas, Avinash Kumar
Instrumentation and Methods for Astrophysics
CausticFlow: An Efficient Machine Learning Framework Combining Neural Differential Equations and Normalizing Flows for Binary Microlensing Parameter Inference
Haibin Ren and Wei Zhu
We introduce CausticFlow, a machine learning framework that combines neural controlled differential equations with normalizing flows to infer binary microlensing parameters. This architecture naturally handles irregularly sampled time series and data gaps while flexibly capturing strongly correlated and
multimodal posterior distributions. Trained on simulated KMTNet-like light curves, CausticFlow generates posterior samples in a fraction of a second, with maximum-a-posteriori estimates achieving typical precisions of $\sim17\%$ for the mass ratio $q$ and $\sim3\%$ for the projected separation $s$. When used as a proposal distribution for downstream local optimization, the framework improves these precisions to $<5\%$ and $<1\%$, respectively, and recovers model $\chi^2$ for $\sim80\%$ of simulated events. We test the generalizability of the framework on 10 real binary
lensing events characterized by higher-order effects, varied cadences, and real-world noise. Despite these mismatches between simulation and reality, CausticFlow successfully recovers the model parameters, light-curve morphology, and
lensing geometry for 7 of the 10 events after simple local refinement, achieving precision levels comparable to those found for simulated data in 10 CPU minutes per event. These results demonstrate that CausticFlow acts as a fast and robust proposal engine that provides informative starting points for downstream local optimization, bridging the gap between the rapid influx of data and the need for systematic modeling in large-scale microlensing surveys such as Roman, CSST, and ET.
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Quantum Physics
Contraction and Expansion Values of Quantum Channels
Ruben Ibarrondo and Mikel Sanz
The contraction coefficient of the trace distance is a central tool in
quantum information, quantifying how strongly a
quantum channel degrades the distinguishability of states. However, being an extremal ratio, it captures only the most optimistic behaviour of the channel and is often trivial, even for very noisy channels. Moreover, a single scalar is poorly suited to describe how contraction accumulates under channel composition. In this work we introduce the contraction and expansion values, two monotone sequences that refine the contraction and expansion coefficients in the same way singular values refine the operator norm. They arise from a min–max variational principle over subspaces of traceless Hermitian operators, admit an operational interpretation in terms of two state-discrimination games, and are shown to coincide with the Gel'fand or Bernstein numbers of the channel restricted to traceless operators. This identification places the sequences within Pietsch's theory of $s$-numbers and yields, in particular, bounds under channel composition that the contraction coefficient alone cannot provide. We establish their main structural properties and compute or estimate them for single-
qubit channels, $d$-dimensional amplitude damping channels, and direct-sum channels.
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Strongly Correlated Electrons
Chirped Floquet linear drives activate forbidden charge-to-spin conversions in Rashba two-dimensional electron gases
Mohsen Yarmohammadi
In Rashba two-dimensional electron gases (2DEGs), charge-to-
spin conversion via the Edelstein effect is conventionally limited to the transverse plane. Accessing longitudinal or out-of-plane pathways typically requires static
magnetic fields or interface engineering, which cause stray fields and lack tunability. While dynamic circular or elliptical Floquet drives can also unlock these forbidden pathways, a simple Floquet linear drive cannot. Here, we propose an alternative approach: a chirped Floquet linear drive. The chirp induces in-plane Floquet-Zeeman fields and an odd-parity momentum drift, which simultaneously break rotational and time-reversal
symmetries. This mechanism activates the forbidden Edelstein charge-to-
spin conversions in Rashba 2DEGs. Experimentally accessible via programmable spatial light modulators or optical delay lines, this tunable chirped linear drive offers a broadly applicable route to
spin-orbit torque switching and high-efficiency spintronics.
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