Papers

Optical frequency combs form phase-locked spectral lines arranged on an equidistant grid fully defined by two degrees of freedom, i.e., the repetition rate and frequency offset. Stabilizing these parameters to a common frequency reference results in a coherent frequency ruler, central for modern precision metrology. However, extending this level of stability to chip-scale microcombs remains an outstanding challenge. Here, we demonstrate a self-stabilizing mechanism based on self-injection locking of a selected comb line via an external feedback loop. This process establishes a second anchor point in addition to the pump, thereby constraining the comb's frequency noise dynamics. We show that, with an appropriate choice between pump frequency noise and feedback strength, collective fluctuations of the repetition rate are strongly suppressed. The result is a microcomb exhibiting ultralow phase noise and dramatically reduced timing jitter. In a 100 GHz silicon nitride soliton microcomb, we achieve an unprecedented combination of high-conversion efficiency, sub-Hertz intrinsic linewidth across the entire C band, and an integrated timing jitter of 1 fs. This approach enables chip-scale microcombs with remarkable noise performance and fs-level pulse stability, surpassing conventional noise limits and opening new avenues for precision metrology at the chip scale.

Cavity light-matter interaction has recently emerged as a new avenue for manipulating material properties without driving fields. Here, we demonstrate that cavity vacuum fluctuations can induce macroscopic polarization (magnetization), even in materials that lack spontaneous polarization (net magnetization) in free space. Starting from the effective photon-free quantum-electrodynamics Hamiltonian, we identify all crystallographic (magnetic) point groups that allow such cavity-induced responses. We derive the form of the corresponding response tensors based on symmetry analysis, whose elements can be obtained by quantum electrodynamical density functional theory (QEDFT) calculations. As representative examples, we show that the cavity-induced polarization in $\alpha$-quartz can be continuously controlled by rotating the cavity. For antiferromagnetic Mn$_3$Sn, we demonstrate that cavity-induced symmetry breaking generates an out-of-plane magnetization, accompanied by an anomalous Hall conductivity component that is forbidden outside the cavity. Our work establishes symmetry as a guiding principle for cavity materials engineering and provides a route for controlling polarization and magnetization through quantum vacuum fluctuations, i.e., cavity materials engineering.

The work presents analytical solutions to the Schrodinger equation for the Killingbeck potential, a Hybrid model combining harmonic, linear and Coulomb terms, and which is also an approximate model of Yukawa-type potentials. The radial Schrodinger equation is solved by means of the series expansion method, thus yielding the exact expressions of both bound-states solutions and eigen-functions for the systems; these systems include quarkonium and confined hydrogen-like atoms in plasma environments. Furthermore, we offer a constructive commentary on the work of Obu et al. (East Eur. J. Phys. 3, 146-157, 2023), with the aim of clarifying a mathematical misstatement used in their analytical treatment of analogous systems.

An endless radio-frequency (RF) phase shifter is designed using ferroelectric capacitors. An endless phase winds continuously and without bound while every control voltage executes a bounded periodic cycle. A new scheme for an endless RF phase shifter is proposed and studied in the framework of an equivalent circuit. Besides the endless property, this phase shifter offers an exceptionally low insertion-loss, high-speed and high-power capability. The device may perform as an exact frequency translator whose offset is locked to the bias repetition frequency. Optimized realizations are given at 400 and 800 MHz with full conductor-loss accounting: 0.19 and 0.28 dB average insertion loss. A phase advance rate of a few microseconds per turn is limited only by the bias electronics, and power capability on the order of 100 kW may be achieved through stacked-wafer construction. An instantaneous bandwidth of approximately 2.5% is loss-limited rather than mechanism-limited. The design surpasses the best endless phase shifter in the literature, the rotary-field ferrite device, in speed, loss, and power, and improves on the serrodyne ferroelectric frequency translator in efficiency and drive electronics requirements.

Identifying the critical state of mature seismic gaps is challenging, especially when anthropogenic stress perturbations, such as reservoir impoundment, superimpose on tectonic loading. Here, utilizing a high-resolution dense array catalog from the Qiaojia-Dongchuan seismic gap (hosting the second-largest hydropower station in the world), we reveal a distinct vertical decoupling mechanism. The shallow activities exhibit high b-values (1.0), indicative of fluid-driven reservoir-triggered seismicity. Conversely, deep seismicity (20 km) outlines a 'locked asperity' characterized by low b-values (less than 0.8) and high Coulomb stress accumulation rate. We further identify a complex dipping structure, suggesting compound fault kinematics. Additionally, the calculated stress accumulation suggests this seismic gap is in a critical state with elevated rupture potential. Our findings indicate that shallow induced seismicity can mask the silent accumulation of deep tectonic strain. This decoupling model provides a new framework for assessing seismic risks in reservoir-fault systems globally.

We evaluate the radiative-mode active galactic nucleus (AGN) feedback models of EAGLE, SIMBA, and TNG100 by comparing their predictions for the AGN-host galaxy relationship to new observational constraints. Owing to incomplete knowledge of the underlying physics, these models differ substantially, and it remains unclear whether any of them accurately reflect reality. In a previous study, based on the demographics of narrow line AGN, we constrained $F_{\mathrm{AGN}}$, the intrinsic fraction of galaxies hosting a radiative AGN with Eddington ratio $\lambda > 10^{-3}$, as a function of host stellar mass ($M_*$) and specific star formation rate (sSFR). Observationally, $F_{\mathrm{AGN}}$ declines strongly with $M_*$ for quiescent galaxies, while remaining approximately constant for star-forming systems. In this study, we find that none of the simulations reproduce these trends even qualitatively, indicating a mismatch between the simulated and observed radiative AGN populations. Additionally, since EAGLE does not explicitly distinguish between radio and radiative modes, we compare its predictions for $F_{\mathrm{AGN}}(M_*, \mathrm{sSFR})$ to our novel measurements of the combined radiative and radio mode AGN fractions. For EAGLE's constant coupling efficiency $\epsilon_{\mathrm{f}} = 0.15$, and for the adopted standard bolometric and jet-power conversion factors in the observations, the total AGN feedback energy in EAGLE is broadly consistent with observations, though with Eddington ratios a factor of 10 greater than is observed. More detailed comparisons of EAGLE's assumptions with observations are therefore required before drawing firm conclusions.

We present a recipe for simulating one-dimensional quantum systems for low and high energies with $L$ qubits within the framework of first quantisation. Assuming a minimum grid spacing $\Delta L$ in the finite-difference method, the generalised uncertainty principle (GUP) is derived analytically and shows distinct properties for low- and high-energy quantum systems. In the low-energy regime, the GUP approaches to the standard Heisenberg uncertainty principle (HUP) for $ \Delta L \ll \hbar$. However, for finite $\Delta L \neq 0$, the GUP mathematically provides three different regions dependent on the average momentum and suggests that a wavefunction can exhibit a single-point localisation at the finite momentum uncertainty due to lack of grid resolution. We then derive a new expression for the high-energy momentum and focus on two specific cases relevant to relativistic aspects. First, if the HUP is relaxed and the high-energy momentum is matched to the special-relativistic one, the resulting GUP predicts the existence of a minimum length with non-zero mass for high energy despite the continuous limit $\Delta L = 0$. Second, enforcing consistency with the HUP allows the recovery of a canonical high-energy representation with no minimum length. But this requirement brings incompatibility with the special-relativistic momentum and suggests a modified energy-momentum equation. Therefore, we believe that the proposed momentum formulation provides a novel pathway to investigate quantum gravity phenomena for high energy using quantum simulation tools.

We conduct a non-relativistic study of plasma screening effects on hydrogen-like atomic systems using the Screened Coulomb Potential (SCP i.e. Yukawa potential). The radial Schrödinger equation is first reduced to a bi-confluent Heun (BCH) equation for the Killingbeck potential which is the truncated version of the SCP, and we write the exact BCH eigenfunctions and eigenenergies. We then study the limitations of these BCH solutions and obtain an analytic description valid for weak to moderate screening using the BCH functional form. The corrected eigenfunctions are constructed order by order up to O(k^3); they are expressed in terms of the Laguerre polynomials and reduces exactly to Coulomb eigenfunctions when k=0. Using these Functions, the energy spectrum is computed via two analytic methods: (i) direct evaluation of the full Yukawa Hamiltonian expectation value, and (ii) the Hellmann-Feynman theorem, yielding integral representation. All methods presented here provide explicit analytical formulas for both wavefunctions and eigenenergies valid for different ranges of the screening. These methods establish a powerful analytic framework for studying confined quantum systems. The thermodynamic properties are also derived using the BCH formulation.

A subset of hydrogen-poor supernovae (SNe) exhibit signatures of interaction with nearby dense circumstellar material (CSM). These SNe may originate from interacting binary systems, in which the SN progenitor experiences intense mass loss when it overflows its Roche lobe close to core collapse. In this work, we explore the appearance of SNe from low-mass stripped star progenitors in binary systems, for a range of initial orbital periods and masses. We model the CSM based on the stripped stars' mass loss history in binary stellar evolution simulations, then numerically explode the progenitors to calculate the SN light curves. Shock cooling emission (SCE) from the CSM dominates the early light curves, followed by SCE from the extended helium envelopes of the stripped stars, which form helium recombination plateaus. The appearance and properties of our model light curves are reflected in a subset of Type Ib/n SNe from the literature. Some of our models tend to evolve rapidly and are quite hot during SCE, so they may naturally explain some fraction of fast blue optical transients (FBOTs). Since the mass loss history of our binary progenitor models can produce dense CSM out to ~10^18 cm, interaction of this CSM with the SN shock could generate bright late-time radio emission in the years after the optical SN. Searching for late time rising radio emission from FBOTs could be used to test which events are explained by the scenario we explore here.

We present FlareEUV, a multimodal deep learning framework for predicting daily extreme ultraviolet (EUV) irradiance at 6.5 nm over three consecutive days during significant solar flares, using multi-instrument observations from NASA's Solar Dynamics Observatory (SDO). We consider 33 significant flares in the period between 2011 and 2014 in Solar Cycle 24. The SDO observations include 13 co-aligned full-disk images, comprising eight AIA EUV/UV and five HMI magnetic/continuum products. FlareEUV learns the relationship between magnetic structure and coronal emission from the raw imaging data using a lightweight attention-based architecture. Our experimental results demonstrate the good performance of FlareEUV in short-term EUV irradiance forecasting during the significant flares and its superiority over baseline methods.

We introduce the method of “intelligent qubits,” which replace live observers in Wigner's friend and Frauchiger–Renner thought experiments, in order to expose the source of the paradoxes: tacit substitution of Boolean hidden variables for non-commuting quantum propositions. The fallacy traces back to London and Bauer's attempt (1939) to legitimize a self-referential interpretation of observers' “introspection,” and thus intertwines the measurement and mind-body problems. We cut the Gordian knot by abandoning reductionism, and describe an alternative which fits, we argue, equally naturally with both physics and anthropology takes on the problems.

Subterranean and mound-building termites excavate, transport, and build within the same granular substrate that later regulates how they sense, move, and deposit material. From antennal-scale contacts through body-scale traffic to meter-scale architecture, this review synthesizes three linked problems: how workers sense local geometry and physical cues during search and excavation; how traffic moves through narrow, evolving conduits; and how excavation and deposition remodel the substrate that guides later behavior. Across these length scales, noisy local interactions couple sensing, transport, and construction through a shared material medium, leading to emergent order at the colony scale. We emphasize what is established experimentally, where evidence remains sparse or limited to a few model systems, and how emerging imaging, tracking, and modeling tools are making these feedbacks quantitatively accessible. We use this synthesis to motivate a quantitative physics-of-life framework for termite colonies that continually rewrite the medium through which they sense, move, and build.

We consider the typical tight - binding model of Dirac semimetal in the presence of both magnetic and electric fields. The electric conductivity reveals dependence on magnetic field. We calculate this dependence in the limit of strong magnetic field, when the given model is described effectively by the one - dimensional SSH model because the dynamics in the plane orthogonal to magnetic field is reduced to that of the lowest Landau level (LLL). Considering the small temperature limit we take into account dissipation due to scattering on impurities. The corresponding dissipation rate is calculated explicitly. The obtained results confirm that the source of the magnetoconductivity in this system is chiral magnetic effect.

Phased-array radio interferometers with fixed antennas are a highly scalable design which can achieve a large gain. However they are complex systems and challenging to calibrate. Here we examine the response of an International LOFAR Station, the high-band antennas of the Irish LOFAR station. In modelling our measured responses, we account for projection effects, the frequency-dependence of the aperture efficiency and pulsar spectra, as well as sky and instrumental noise contributions. We perform long-track observations of 11 bright pulsars as they move across the sky, apply RFI mitigation and determine the signal-to-noise ratio response as a function of time, elevation and azimuth. We use the DreamBeam software to model the beam response of the station to compare with what is observed. The sensitivity map so obtained was validated using observations of PSR B0329+54 on the Swedish LOFAR station. As expected, the sensitivity is higher near the zenith. However, an asymmetry with respect to the zenith point is detected. Characterising the instrumental response in azimuth reveals a better performance as the targets rise, as compared to when they set. This trend is seen for all pulsars and is consistent with other International Stations. The magnitude of the effect can exceed 20%. We consider variations in the beam model and noise level, both frequency- and time- dependent, to try to account for this. A possible explanation for the hysteresis-like response in elevation could be an imbalanced signal weighting of the polarisation components. This work addresses the importance of accurate beam modelling and noise evaluation for the LOFAR 2.0 system upgrade as well as being relevant to the under-construction SKA-Low facility.

I report a previously undocumented, large-amplitude systematic dependence of the median Gaia $G$-band magnitude of CRF3 sources on ra\_dec\_corr, which reflects the preferred direction of scans, accompanied by a partially correlated trend in the BP/RP flux excess factor. Given the imminent release of Gaia DR4, the purpose of this note is alerting the community to this artifact.

Continuous measurement is commonly associated with decoherence and the loss of symmetry. Here, we show that weak continuous measurements can instead act selectively: depending on the measured observable, they may either preserve or remove a dynamical relation between initially mirrored states. Using tunneling between the $|+1\rangle$ and $|-1\rangle$ states of a spin-1 system, we demonstrate that measurements of $S_x$ and $S_y$ break the symmetry of the tunneling dynamics in the presence of a longitudinal bias, whereas measurement of $S_z$ leaves it intact. We formulate this behavior within the Lindblad framework, support it with numerical simulations, and reproduce the dissipative dynamics in a two-qubit quantum circuit using Trotterized evolution and stochastic collective rotations. Our results establish continuous measurement as a selective tool for controlling dynamical symmetry in open quantum systems.

Hydrogen-isotopologues are commonly used to trace the chemical processing and origin of hydrogen-bearing species throughout the Universe, however, their abundance remains unconstrained for extrasolar planets. Here, we report atmospheric retrieval evidence for the deuterated water molecule HDO in an exoplanet atmosphere, retrieved from James Webb Space Telescope transmission spectra of the hot Jupiter WASP-39 b, resulting in a deuterium-to-hydrogen ratio in water of $4.0^{+1.3}_{-1.1} \times 10^{-3}$. The inferred value is substantially higher than those measured for the Solar System gas giants and overlaps numerically with values reported for some protostellar and inner Solar System environments. This enrichment may reflect either inherited water-rich material accreted beyond the snow line or isotopic processing in the observable atmosphere through transport, photochemistry, and subsequent escape.

Quantum state tomography estimates an unknown density operator from measurement data. Dense reconstruction however, can be impractical for many-qubit systems because the Hilbert-space dimension grows exponentially. This contribution develops a rank-adaptive matrix-free approach to low-rank quantum state tomography based on rank-one atomic coordinates. The density operator is represented as a convex combination of pure-state atoms, which preserves positivity and unit trace while avoiding dense density, measurement, and gradient matrices. The resultant algorithm combines atom updates, simplex-constrained coefficient reweighting, and periodic spectral refactorization using only predicted probability vectors, atom vectors, and descriptor-level measurement actions. These computations decompose across measurement outcomes, and admit a master–worker implementation with the measurements partitioned across workers. A rank penalty adapts the representation size during optimization. Provable feasibility, prediction consistency, monotone descent of the penalized objective, and an exact spectral proximal characterization of the refactorization step are established. Simulations with Pauli measurements show favorable accuracy–runtime–memory tradeoffs relative to competing alternatives.

We introduce an adaptive simulated annealing algorithm to search for moderately-sized quantum error-correcting codes with high encoding rates and large distances. Our search targets two classes of stabilizer codes: (1) CSS codes, and (2) a subclass of CSS codes that we call “self-dual with equivalent logicals” (SWEL) codes, the latter of which which admit transversal implementations of logical Hadamard and phase gates that can be leveraged to construct fault-tolerant gate sets. The search is guided by an energy function that acts as a surrogate for the logical error rate in a code-capacity noise model, combining code distance with a count of minimum-weight logical operators to resolve the discrete plateaux that impede naïve distance optimization. For block lengths of up to $50$ physical qubits, our search finds state-of-the-art CSS and SWEL codes whose distances frequently meet or exceed the variants of the quantum Gilbert-Varshamov bound. In addition to providing favorable seed codes for fault-tolerant architectures based on code concatenation, the codes found in this work are promising candidates for high-rate code demonstrations on near-term quantum computing hardware.

We trap submicroscopic silica spheres coated with randomly distributed titanium dioxide nanoparticles in optical tweezers with Laguerre-Gaussian modes and observe orbital dynamics that differ from those of achiral silica spheres. We show that the disordered nanoparticle coating generates an effective chiral geometry, giving rise to enhanced enantioselective chiral optical forces and a measurable modification of the orbital period. A theoretical model based on the Mie-Debye formalism, including optical aberrations, not only quantitatively explains the experimental results but also allows to characterize the Pasteur parameter quantifying the chiroptical response of individual composite particles. These findings constitute direct experimental evidence of chiral optical forces exerted by structured light beams on individual chiral particles and identify disorder-enabled, all-dielectric particles as a versatile material platform to tailor chiral optical forces at the nanoscale.

Photogenerated polarons are fundamental to the photophysics of transition metal oxide semiconductors. It is therefore imperative to understand the mechanisms by which polarons form upon photoexcitation of transition metal oxides to realize their potential in photoapplications. Hematite ({\alpha}-Fe2O3) is known to form photoexcited small polarons, which limit its performance as a photoelectrocatalyst for water oxidation. Here, we report a systematic comparison of the electronic, optical and vibrational properties of hematite to those other metal oxides in the corundum crystal family that elucidates the impact of d-orbital radius on carrier-phonon coupling. Three corundum metal oxides are analyzed: {\alpha}-Al2O3 (no d-electrons), {\alpha}-Fe2O3 (3d), and {\alpha}-Rh2O3 (4d) with a combined approach of resonance Raman spectroscopy, thermal difference optical spectroscopy, and computational modeling of electronic and vibrational states. We find that the Raman spectrum of {\alpha}-Al2O3 does not change as the Raman excitation is varied across the visible region, as there is no optical absorption. In contrast, both {\alpha}-Fe2O3 and {\alpha}-Rh2O3 exhibit strong coupling of phonons to optical transitions at the onset of absorption, which is evidence of excitation into a polaronic state. Closely comparing the optical polaronic properties of {\alpha}-Fe2O3 and {\alpha}-Rh2O3, we establish that increased lattice covalency in {\alpha}-Rh2O3 arising from the increased radial extension of the 4d orbitals influences which phonon modes mediate photogenerated polaron formation.

This work develops a cavitation-consistent acoustic perturbation framework for predicting sound generation and propagation in cavitating flows. Unlike conventional acoustic perturbation equations for single-phase or weakly compressible flows, the proposed formulation embeds cavitation physics directly into the acoustic equations. The cavitation acoustic perturbation equations (CAPE) incorporate vapor mass transfer, mixture compressibility, and pressure-rate effects within a unified formulation, allowing cavitation-induced noise sources to be resolved in the computational domain. The numerical framework is verified using one-dimensional wave-propagation problems. The solutions become insensitive to further mesh and time-step refinement, the perfectly matched layer suppresses boundary reflections, and the predicted attenuation over a range of source frequencies follows Stokes' sound attenuation law. The framework is then applied to cavitating flow past a circular cylinder and a NACA hydrofoil. The non-cavitating benchmark shows dipole-like radiation associated with unsteady loading, whereas cavitating cases exhibit monopole-like or geometry-modulated radiation caused by volumetric phase change. Source-term analyses identify tonal frequencies associated with vortex shedding, cavity shedding, and collapse-induced excitation. The phase-change terms provide a direct volumetric contribution to the monopole-like source, while localized collapse events appear through amplification of the pressure-rate source. The proposed framework extends acoustic perturbation methods to cavitating multiphase flows and provides an efficient tool for hydroacoustic prediction, source localization, and mechanism analysis in marine and hydraulic applications.

Predicting the onset of interfacial instabilities is central to understanding turbulent mixing in natural and engineered stratified shear flows. Here, we study the onset of travelling Holmboe waves in confined exchange flows along a slope. Earlier stratified inclined duct experiments have mapped this transition, and stability analyses based on measured or prescribed profiles have explained their emergence. However, a predictive criterion linking forcing, geometry, base flow, and wave onset was still lacking. We closed this gap with a long-duct, sharp-interface asymptotic theory for the three-dimensional laminar exchange flow, including the effects of sidewall friction. The resulting analytical solution naturally identifies a confinement-adjusted Froude number, $Fr^*$, which unifies the effects of forcing and confinement into a single measure of the effective laminar exchange flow. Using this solution to parameterise sidewall drag in a practical width-averaged model, we perform linear stability analyses and numerical simulations at high Schmidt number. Together, linear stability analysis, direct numerical simulations, and existing experiments across a range of duct widths show that wave onset is accurately predicted by an approximately constant critical value of $Fr^*$. Deviations arise only in very narrow ducts, where sidewalls influence instability not only by modifying the laminar exchange flow but also by directly damping perturbations and delaying wave onset. These findings provide a predictive criterion for wave onset, reconcile long-standing discrepancies among experimental configurations, and establish lateral confinement as a fundamental control on the transition from laminar exchange to wave-driven mixing in stratified shear flows.

Quantum error correction can be enhanced by post-selecting out runs that are likely to produce a logical failure, but the most accurate measures for that require costly decoder-level information. We introduce a practical, decoder-agnostic post-selection method that learns directly from syndrome data. The method trains a supervised classifier to distinguish between syndromes from low- and high-noise regimes, and then uses the classifier's output as an abort score for new runs, without requiring logical-error labels, correction operators, or code-specific likelihood calculations. We validate the approach in three complementary settings: circuit-level simulations of the Gross bivariate-bicycle code, code-capacity simulations of the surface code, and experimental logical magic-state distillation data from the QuEra neutral-atom processor. In the Gross and surface codes, learned syndrome post-selection reduces the conditional logical error rate at a fixed acceptance rate, with performance comparable to syndrome-weight filtering. For the surface code, the learned classifier reveals a post-selection transition distinct from the conventional decoding threshold. In the experimental data, the machine-learning score outperforms syndrome-weight post-selection and, when combined with logical-gap filtering, improves the output fidelity beyond using the logical gap alone. These results show that syndrome-only learning provides a scalable and hardware-compatible route to improving the reliability of quantum error correction.

A soft thin elastic disk spinning in a viscous fluid experiences centrifugal tension generated by rotation together with viscous shear generated by the surrounding flow. While the former stabilizes the flat state, the latter can destabilize it. We combine the linearized Föppl-von Kármán equations for a rotating elastic disk with the shear stresses arising from the classical von Kármán swirling flow to derive an elastohydrodynamic stability problem. Linear stability analysis identifies the onset of buckling in terms of two dimensionless control parameters measuring centrifugal stiffening and fluid-induced shear. Above threshold the disk buckles into azimuthally periodic saddle-like modes whose wavenumber increases with increasing rotational tension. The buckled configuration also supports retrograde traveling waves that rotate more slowly than the material frame. These results identify a simple mechanism whereby fluid shear destabilizes rotating elastic structures.

Photoemission is an escape problem, yet first-principles calculations usually trap the electron in a periodic box. We present a parameter-free ab initio framework that removes this artificial boundary by constructing open scattering states for semi-infinite crystal-vacuum interfaces from Wannier Hamiltonians and Green-function embedding. The method gives continuum-normalized time-reversed LEED final states with microscopic quasiparticle attenuation. For Ag(111), it predicts absolute quantum efficiency, vectorial photoemission, and mean transverse energy on the experimental scale.

Superconducting quantum circuit design is reliant on accurately mapping design parameters to a quantum Hamiltonian. Designers typically rely on computationally intensive finite-element electromagnetic simulations. However, effective circuit-level models can in principle capture much of the relevant physics for these systems, reducing the need for finite-element simulations. A barrier to implementing these simpler models has been the prevalence of distributed elements such as coplanar waveguides resonators in device designs. Techniques for modeling these distributed elements have been developed, but may be difficult to scale, reduce intuition, and give inaccurate results under strong coupling. In this work we describe a simple effective circuit-level model that faithfully reproduces the scattering parameters, and subsequently can predict certain Hamiltonian parameters, for a coupled, distributed element within a broader two-port network even up to strong coupling. Our approach does not explicitly require an electromagnetic simulation. Our model, along with other common lumped models used in black box quantization, is publicly available to researchers via an open-source code package, $\texttt{simpleLOMs}$.

Superoscillations, band-limited signals that locally oscillate faster than their highest Fourier component, have recently enabled superspectroscopy and super-sensing. Previous experiments [Phys. Rev. Lett. 131, 153803 (2023), https://doi.org/10.1103/PhysRevLett.131.153803 and APL Photonics 10, 086107 (2025), https://doi.org/10.1063/5.0271556] relied on combining four quasi-sinusoidal harmonics to generate temporal superoscillations. Here, we show that just two harmonics are sufficient to produce superoscillations of comparable quality, as quantified by the local frequency. By reanalyzing prior experimental data with two harmonics (0.5 and 0.6 THz) and performing new experiments with 0.9 and 1 THz harmonics, we demonstrate a twofold enhancement in local frequency relative to the highest frequency component – matching the enhancement previously achieved with four harmonics. We provide a simple analytical explanation for the bichromatic superoscillations based on near-complete destructive interference, and identify an optimal frequency separation of approximately 10% that balances the superoscillatory frequency enhancement against signal amplitude. This simplification substantially lowers the experimental barrier to implementing superoscillation-based technology.

We investigate the repetitive Penrose process in the spacetime of a Rastall rotating black hole surrounded by a quintessence dark energy field. After reviewing the fundamental properties of the black hole geometry, we formulate the repetitive Penrose process by deriving the conservation equations governing particle splitting within the ergoregion, along with the corresponding iterative evolution equations. The physical conditions required for terminating the energy extraction iterations are established, and the minimum spin thresholds of the decay particles are analyzed to identify the critical stopping criterion. Our analysis reveals that the termination of the repetitive Penrose process is consistently governed by Particle~$0$, which possesses the highest minimum spin threshold among all decay products. Numerical results further demonstrate that the dimensionless Rastall structure parameter $\hat{N}_s$ and the Rastall coupling parameter $\alpha$ significantly influence the evolution of the energy extraction process. At the same decay radii increasing initial values of both parameters boosts the energy utilization efficiency and energy return on investment. Specifically, smaller values of $\hat{N}_s$ enhances the energy utilization efficiency at lower decay radii, shifts the maximum extracted energy toward lower decay radii, and accelerates the depletion of the remaining extractable energy reservoir. This indicates that the repetitive Penrose process is highly favored at lower decay radii. Smaller initial values of $\hat{N}_s$ yield a larger maximum energy return on investment. Similarly, increasing $\alpha$ enhances the energy utilization efficiency, alters the location of the peak extracted energy, and reduces the total extractable energy. But the effects of $\alpha$ on these energetics are very small as compared to $\hat{N}_s$.

Recent JWST and ALMA observations have revealed stellar bars and spirals in gas-rich galactic disks at redshifts as high as $z \simeq 4$. The simplest theoretical paradigm we have for understanding such non-axisymmetric features is the linear theory of swing amplification (SA) in the 2D shearing sheet. However, while the SA mechanism in a gaseous shearing sheet was first studied in 1965, and that in a collisionless stellar sheet in 1966, the coupled star-gas linear SA equations have never been solved explicitly. Here we write down these equations and use them to study the evolution of non-axisymmetric swinging waves in stable disks. We find that waves are often amplified temporarily by factors of $10-100$ or more, and that the maximum non-axisymmetric amplification factor is tightly correlated with the system's distance from the axisymmetric stability boundary in the $(1/Q_\mathrm{s}, 1/Q_\mathrm{g})$ plane. The true star-gas behavior differs significantly from the `two-fluid' idealizations used in the past, because phase mixing of the collisionless stellar component acts as a sink of perturbation energy. Closely analogous results hold for finite-thickness disks except for the shifting of the stability boundary. We provide a python code that calculates the SA factors and maximally-amplified wavelength given the background disk parameters.