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Tuesday 14 July

Optics

Structured Optical Fields Reveal Nanoscale Chiral Light-Matter Interactions Governed by Optical Chirality

Atsushi Kamegaya, Shun Hashiyada and Yoshito Y. Tanaka

Optical chirality has been proposed as the local electromagnetic quantity governing chiral light-matter interactions, yet in conventional circularly polarized fields its magnitude is locked to the electric energy density, obscuring its independent role. Here we create a structured optical field in which optical chirality arises spatially in magnitude and sign while the electric energy density remains nearly uniform. A single chiral nanoparticle exhibits a differential response that follows this spatial variation, whereas no modulation is observed for an achiral nanoparticle, providing direct experimental evidence that optical chirality governs nanoscale chiral light-matter interactions. Measurements of wavelength-dependent optical rotation further provide an experimental estimate of the chiral polarizability, predicting a chiral gradient force of approximately 100 fN and a one-dimensional trapping potential exceeding the thermal energy at room temperature under optimized aqueous trapping conditions.
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Optics · Cross-listed from cond-mat.mtrl-sci

Quantized Photocurrents in Gapless Topological Matter

Byunghoon Kim, Tenzin Norden, Mohammad Yahyavi et al. (+17 more)

The quantum Hall effect establishes that topology can fix a material response to integer multiples of fundamental constants when an energy gap isolates the relevant symmetry-protected electronic states. Whether such universal quantization can also emerge in gapless matter, where topological bands coexist with a continuum of metallic excitations, has remained a fundamental question in the field of quantum materials. Chiral topological semimetals provide a unique setting in which to explore this principle; when optical transitions are confined to a single chiral node, the resulting circular photogalvanic effect is predicted to be quantized by the topological charge of the node. In real materials, however, this nonlinear optical phenomenon has remained experimentally elusive, obscured by trivial band transitions, insufficient energy separation between node pairs, and their relative positions with respect to the Fermi level. Here we observe a quantized circular photogalvanic effect in the chiral topological semimetal Rh0.95Ni0.05Si. Band engineering via Ni substitution opens a photon-energy window dominated by interband optical transitions at the {\Gamma}-point multifold node. This allows circularly polarized near- to mid-infrared pulses to drive a helicity-odd terahertz response that manifests three hallmarks of quantization: a sharp onset, a photon-energy-independent plateau governed by the magnitude of the monopole charge, and an abrupt long-wavelength cutoff imposed by Pauli blocking. Our work thus establishes an all-optical analogue of the quantum Hall effect and a new paradigm to realize topological quantization in gapless matter.
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All authors Byunghoon Kim, Tenzin Norden, Mohammad Yahyavi, Kaustuv Manna, Tyler A. Cochran, Zi-Jia Cheng, Xian P. Yang, Yu-Xiao Jiang, Xiangyu Luo, Payman Kazemikhah, Areeq Hasan, Vladimir N. Strocov, Sergey Shilov, Ilya Belopolski, Claudia Felser, Md Shafayat Hossain, Rohit P. Prasankumar, Guoqing Chang, M. Zahid Hasan, Prashant Padmanabhan

Data Analysis and Statistics · Cross-listed from astro-ph.IM

Demystifying image-recovery from radio interferometers: toward a multiscale predictive model

Dan Miao and Guang-Xing Li

Radio interferometers suffer from the missing short-spacing problem, losing large-scale diffuse emission. This missing flux underestimates gas mass and biases key metrics like star formation efficiency. Quantifying this scale-dependent loss currently relies on computationally intensive mock observations, lacking an analytical image-domain framework. We introduce the Constrained Diffusion Decomposition (CDD) method to decompose an input image ($I_{\mathrm{in}}$) into $n$ continuous scale-space components, denoted as $I_l = \mathrm{CDD}_l(I_{\mathrm{in}})$ for $l \in [1, n]$, and apply it to simulated Atacama Large Millimeter/submillimeter Array (ALMA) observations of the Perseus molecular cloud across multiple array configurations. We find that the interferometric spatial filtering response can be mathematically decoupled: the scale-dependent flux recovery fraction follows a one-dimensional error function (erf), defined as $R(l) = \frac{B}{2} \left[ 1 - \mathrm{erf}\left( \frac{l - c_{\mathrm{recover}}}{w} \right) \right]$, where compact structures are effectively recovered, while extended emission decays monotonically as scales approach the maximum recoverable scale. The proposed CDD–erf framework predicts the spatially filtered interferometric image $I_{\mathrm{pred}}$ directly in the image domain, bypassing visibility simulations, mapping the true sky brightness distribution via the equation $I_{\mathrm{pred}} = \sum_{l=1}^{n} [ \mathrm{CDD}_l(I_{\mathrm{in}}) \times R(l)]$. This provides a quantitative bridge between model and interferometric observations.
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Applied Physics

Space-Time Modulated vs 2-Bit Reflect-Arrays: A Comparison of Main Beam Gain and Sidelobe Level Performance

Muhammad Rizwan Akram and Douglas H. Werner

This paper presents a comprehensive analysis of the phase errors introduced by 2-bit reflectarray architectures and investigates their impact on aperture synthesis for beam-steering applications. Building upon this analysis, an amplitude-aware synthesis technique based on space-time modulated (STM) reflect-arrays is proposed to mitigate the main-beam gain degradation commonly associated with STM-based equivalent phase generation while preserving the enhanced phase resolution enabled by temporal coding. A 10{\lambda}by 10{\lambda} reflect-array aperture with {\lambda}/2 inter-element spacing is considered, where the desired aperture phase distribution is synthesized using a library of achievable reflection coefficients generated from all possible combinations of four 2-bit phase states distributed across (L) temporal segments. The proposed approach introduces a phase-tolerance window and selects the reflection state with the highest reflectance within the allowable phase range. By exploiting the inherent amplitude diversity of the STM state space, the proposed approach maximizes aperture efficiency while maintaining the desired beam-steering phase distribution. Numerical results demonstrate that the method substantially reduces the gain penalty typically associated with STM reflect-arrays along with providing significant sidelobe suppression.
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Optics

Peak-Decomposition-Free Inverse Metrology of Hyperspectral Moiré Photoluminescence

Katsunori Wakabayashi

Hyperspectral photoluminescence (PL) of moiré transition-metal dichalcogenide heterobilayers encodes spatially varying exciton landscapes, but extracting that information is hampered by the ambiguity of multi-peak spectral decomposition. Here we develop a peak-decomposition-free inverse framework for quantitative optical metrology of effective disorder coordinates. From the raw cube $I(x,y,E)$ we construct physically motivated descriptor maps – centroid energy, dominant emission energy, spectral width, low/high spectral-weight ratio, and dominant–centroid offset. Their spatial autocorrelation hierarchy and covariance structure form a robust descriptor fingerprint of multi-scale disorder-sensitive spectral statistics. By matching these descriptor summary statistics to a minimal smooth-plus-trap generative model through a grid-Bayesian inverse, we infer effective disorder coordinates $\Thetaeff=\{\Ws,\xis,\Wt,\nt\}$ with explicit uncertainties. Using synthetic PL cubes generated from controlled multi-scale landscapes, we recover the well-identified smooth-disorder coordinates and constrain the trap sector up to a strength–density degeneracy. We report this degeneracy explicitly as an intrinsic identifiability limit rather than a deficiency of the method, and map four canonical disorder regimes onto a disorder-coordinate diagram. The descriptor statistics are stable against shot noise and pixel pitch, and behave predictably under optical-resolution and energy-window changes. The same pipeline ingests experimental cubes without modification, making it directly applicable to two-dimensional and moiré materials. Our results establish descriptor-based hyperspectral PL as a practical, minimal-assumption route to optical disorder diagnostics and provide the validated core of a reusable analysis workflow (HyperPL-Diag) for moiré exciton systems.
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Optics

Selective avoidance of multiple line-of-sight obstacles at 130~m using locally bending space-time wave packets

Layton A. Hall, Murat Yessenov, Isabelle Lebron et al. (+1 more)

Self-accelerating optical beams follow curved trajectories rather than propagating rectilinearly, which raises the prospect for avoiding line-of-sight (LoS) obstacles blocking the beam path. However, if a conventional laser beam is intercepted by an obstacle en route to an intended LoS target, then replacing this beam with a bending beam is not adequate: the obstacle is avoided but the target cannot be concomitantly reached. Rather, a laser beam that locally bends around the obstacle – before continuing along its rectilinear path – is needed. Here we show that engineering the spatiotemporal spectrum of a pulsed beam yields a space-time wave packet whose propagation dynamics can be tuned at will to locally bend around one or multiple obstacles, thereby avoiding them, to selectively reach a designated target. We carry out our experiments over distances extending to 130~m from the source, carried out in an open-air environment. In one scenario, the beam is incident on a target placed between two LoS obstacles, one preceding it and one following it – both of which are avoided. In a second scenario, the locally bending beam avoids one and then two LoS obstacles preceding the intended target. These results may contribute to applications requiring selective incidence on targets in remote sensing, stand-off detection, directed energy, for optical and radio-frequency communications in presence of LoS obstacles, and for selectively delivered radiation therapies.
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All authors Layton A. Hall, Murat Yessenov, Isabelle Lebron, Ayman F. Abouraddy

Plasma Physics

Full-Path Nonlinear Modeling of Microwave Power Transmission Through Ionospheric Plasma for Space Solar Power Station

Pengan Guo, Lei Chang, Yuhan Chen et al. (+5 more)

Space Solar Power Station (SSPS) concepts rely on gigawatt-class microwave beams to carry orbital solar energy through the ionosphere, where the beam and the plasma form a coupled nonlinear system: the field heats electrons, the heating alters the collision frequency and plasma density, and the modified medium in turn reshapes the field. To our knowledge, this work is the first study to quantify this two-way interaction between microwave power transmission and the ionospheric plasma environment through full-path nonlinear modeling. The 340 km path from 400 km to 60 km altitude is reconstructed by 34 cascaded two-dimensional axisymmetric finite-element full-wave segments with complex-field transfer, using International Reference Ionosphere (IRI) electron-density and NRLMSISE-00 neutral-atmosphere inputs. A Shallow Neural Network (SNN) surrogate replaces the implicit electron energy balance with an explicit closure that maps altitude and local field magnitude to electron temperature and effective collision frequency, enabling stable nonlinear iteration. For 1 GW beams at 2.45 GHz and 5.8 GHz, the volume-integrated Ohmic deposition is 29.4 kW and 5.11 kW, respectively – fractional losses of order $10^{-5}$ – and the ratio between the two bands follows the $\omega^{-2}$ scaling of collisional absorption. The deposition concentrates near 95 km altitude, where the product of electron density and collision frequency peaks, whereas the electron-temperature perturbation (up to 3815 K) maximizes in the F region, where cooling is weakest; ponderomotive density depletion remains below 0.02%. The ionosphere is therefore effectively transparent to the SSPS power budget but not to the beam phase: localized heating and refractive perturbation accumulate phase-front distortion relevant to phased-array beam control, rectenna phase compensation, and environmental assessment.
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All authors Pengan Guo, Lei Chang, Yuhan Chen, Ya Gao, Longshuai Ye, Jikai Sun, Huaiqing Zhang, Jian Li

Plasma Physics

Nonlinear Tearing Modes in Current-Vortex Sheets

D. Urbanski, F. L. Waelbroeck and A. Tenerani

The linear and nonlinear development of instabilities and Alfvén resonances in a plane current-vortex sheet is presented here for sheared equilibrium profiles $\boldsymbol{B_{y0}} = \tanh(z)\boldsymbol{\hat{y}}$ and $\boldsymbol{V_{y0}} = M_0\tanh(z/r)\boldsymbol{\hat{y}}$. We extend Rutherford's nonlinear model for constant-psi magnetic islands to account for a sheared equilibrium flow and determine the flow's impact on the magnetic island's nonlinear evolution for $M_0<1$. In this regime, the flow introduces two nonlinear contributions: a polarization current term and a modification of the saturation term derived by Militello and Porcelli (2004). We find that the polarization current generated by the equilibrium flow consistently reduces the nonlinear growth rate of the tearing mode. The flow-induced modification of the saturation term, however, depends on the magnetic-to-velocity shear width ratio, $r$. For $r=1$, the saturation term is unchanged from the case without flow. For $r>1$, it increases in magnitude with $M_0$, strengthening its stabilizing effect and further reducing the island growth rate. In contrast, for $r<1$, the saturation term decreases in magnitude with increasing $M_0$ and can become positive, leading to a transition from a stabilizing to a destabilizing contribution. Nevertheless, throughout the parameter range considered, the combined effect of the polarization current and modified saturation term is to slow the growth of the magnetic island. Finally, we find that, in the presence of Alfvén resonances, the magnetic island's growth in the nonlinear regime is no longer adequately characterized by constant-psi, and the dynamics of such islands are not captured by the model.
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Plasma Physics

A Collocated Boris Integrator in Flux Coordinates: Balancing Accuracy, Conservation, Cost and Robustness

Mingyuan Li and Chang Liu

When the guiding-center description fails and the full gyromotion must be resolved for energetic particles in complex configurations like stellarators, charged-particle integrators must be formulated directly in the curvilinear flux coordinates. The Boris algorithm, which adopts a staggered scheme in Cartesian coordinates, is phase-space-volume-preserving and second-order accurate; but a direct port to flux coordinates degrades the position update to first order, because the evolving basis vectors of the curvilinear frame make the starting-point metric deviate from the ideal midpoint metric. We construct a collocated, midpoint-predicted Boris algorithm in flux coordinates, restoring second-order accuracy at the cost of one additional field evaluation per step. In reactor-scale stellarator magnetic fields, the scheme recovers second-order convergence in every coordinate component, retains near-machine-precision energy conservation and a bounded magnetic moment, and demonstrates greater orbit robustness than Staggered Boris and RK4 at coarse time steps.
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Monday 13 July

General Physics

Observational Viability of $\phi^{2}$-Superpotential Inflation with GUP-Induced Corrections

Narges Rashidi and Maryam Roushan

We study a $\phi^{2}$-superpotential inflationary model within a GUP-inspired quantum-gravity framework. Using horizon thermodynamics, we review the GUP-corrected Friedmann equations obtained by combining the temperature–surface-gravity relation with a modified entropy–area law. Reformulating the dynamics via a superpotential $W(\phi)$ with $\phi=\phi(a)$, we obtain the corresponding slow-roll parameters and derive GUP-modified expressions for the scalar spectral index and the tensor-to-scalar ratio, leading to a deformation of the standard inflationary consistency relation. Adopting the quadratic ansatz $W(\phi)=\tfrac{1}{2}m^{2}\phi^{2}$, we evaluate the observables $(n_{s},r)$ and compare them with the Planck 2018 TT, TE, EE + lowE + lensing + BK18 + BAO, DESI + CMB + DESY5, and Planck2018 + ACT + lensing + BK18 + BAO (from DESI) datasets. The analysis shows that, for moderately negative values of the effective GUP parameter $\beta$ and sub-unity values of the phenomenological superpotential parameter $C$, the model predictions can fall within the $68\%$ and $95\%$ confidence regions of current observations. These results indicate that GUP-inspired corrections can shift the $(n_{s},r)$ predictions of a quadratic superpotential toward the observationally favored region.
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General Physics

A Spectral Phase Admissibility Certificate for Complex Linear Maps

Snigdha Chandan Khilar

The paper imports the Kontsevich Segal Witten criterion from quantum gravity into machine learning to evaluate complex linear maps Standard techniques analyze magnitude or positive definiteness whereas this method exclusively limits the collective phase of a spectrum The researchers create three distinct differentiable certificates comprising a determinant sector a subset product envelope and the full criterion The subset envelope prevents all exterior power eigenvalues from touching the negative real axis This constraint precisely matches the accept or reject choices of an exponential minor enumeration while reducing processing expenses drastically The team provides a differentiable enforcement application via a Schur parameterization The document also identifies crucial boundaries regarding where this system works The constraint cannot balance deep linear propagation since restricting the phase budget damages eigenvector conditioning Furthermore the technique remains completely blind to magnitude based targets like normalizing flow likelihoods Thus researchers must restrict this tool specifically to models that process the argument of a spectral product
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General Physics

Examining the Linear and Quadratic Dark Energy Parameterizations with DESI DR2 via AIC and BIC Selection

Laiphangbam Khumaba Mangang, Yumnam Prakash Singh and N. Chandrachani Devi

We examine whether or not the current observational preference for a dynamical dark energy(DE), as reported by DESI, is an artifact of the chosen functional form of dark energy equation of state (EoS) parameter $w(z)$ by considering a higher-order quadratic extension in EoS. We explore three distinct parameterizations of the DE models: the two-parameter (linear) Chevallier-Polarski-Linder (CPL) and Wang models, alongside a three-parameter parabolic (quadratic) formulation. Using a joint dataset of CMB measurements from Planck and ACT DR6, baryon acoustic oscillations of DESI DR2, and Type Ia supernovae from Pantheon+ and DES-SN5YR, we constrain the model parameters and observe a maximum frequentist preference of up to $\sim 4\sigma$ for these dynamical models. Specifically, the joint CMB + DESI + DES-SN5YR combination yields a substantial improvement in fit over $\Lambda\text{CDM}$, with $\Delta\chi^2_{\text{min}}$ values of $-20.5$, $-19.4$, and $-21.7$ for CPL, Wang, and Parabolic models, respectively. In addition, the Akaike Information Criterion (AIC) provides weak to no evidence for $\Lambda$CDM, consistently favoring the dynamical DE models instead. On the other hand, the Bayesian Information Criterion (BIC) imposes a heavy penalty on all the three models, reflecting its high sensitivity to dataset size and model complexity. We find at best a mild support for CPL and Wang models but the Parabolic model is strongly disfavored ($\Delta \text{BIC} \sim +6.4$ to $+15.6$). Furthermore, due to its expanded parameter space, the Parabolic model exhibits a significant reduction in the Figure of Merit (FoM) compared to the two-parameter counterparts, demonstrating that the current cosmological datasets do not yet justify an introduction of the higher-order DE models. So, as a result, the two-parameter descriptions of $w(z)$ remain the optimal choice for testing the dynamical DE signatures.
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General Physics

Vacuum Spin-Torsion Energy Density and Two-Modulus Stability on $S^2\times\mathbb{C}P^2$

Edward J. Shaya

In Einstein–Cartan–Kaluza–Klein compactification on $S^2\times\mathbb{C}P^2$, elimination of the non-propagating torsion generates a quartic spin-current contact interaction whose vacuum expectation value is nonzero even at zero fermion occupation. We reduce the ten-dimensional $\Gamma_{ABC}$ structure to the zero-mode sector and find that the reduction is channel-resolved: each of the three internal Cartan-plane bilinears contribute with the opposite sign to the external (axial) channel, so that the full trace is $R_{ch} = T_{\rm vac}/T_{\rm axial} = 1 + 3\,(-1) = -2$. The vacuum term is therefore twice the axial estimate and opposite in sign, and, combined with the elimination constant $c_{10} = -\kappa_{10}/32$, verified by explicit Clifford computation, it is attractive and proportional to $N_{\rm fam}^2$. We obtain the separated-point correlator, which in the continuum scales as $N_{\rm fam}^2 d_R/(V_6\,r^6)$, and, conditional on the physical quantum-boundary prescription, evaluate it at the minimum supported separation. The finite-density piece of the same correlator has the same sign and grows with chemical potential. Binding deepens after nucleation; the single-particle Hartree self-contraction vanishes for chiral zero modes. Using the derived $1/(a_1^2a_2^4)$ vacuum term with the Einstein-frame curvature and quantized-flux contributions, we analyze a coupled two-modulus toy potential. At fiducial couplings, the $(m,n)=(3,3)$ sector has a finite-radius stationary point with positive Hessian in both radion directions, while the four-family $(4,3)$ minimum lies beyond the adopted quantum-curvature boundary. The three-family sector $(1,5)$ is also locally stable but is less bound. 3-family dominance of the thermal nucleation weight further imposes the condition $\kappa_4 \lesssim 7.5\,(16/B)\,\ell_P^2$. These results serve as inputs to our higher-level synthesis.
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Instrumentation and Detectors

Demonstration of 255-kV high-voltage generation with a Cavallo multiplier system

S. M. Clayton, T. M. Ito, A. Jacobs et al. (+11 more)

Many cryogenic precision measurements require large electric fields in environments where conventional high-voltage feedthroughs are impractical. To address this, we developed a Cavallo electrostatic multiplier designed for in situ high-voltage generation under such conditions. Here, we report a room-temperature demonstration of this device. Using a mechanically translated transfer electrode and a custom rotary field mill for noncontact voltage measurement, the system reached output voltages up to approximately $255~\mathrm{kV}$ from a $25~\mathrm{kV}$ DC-biased input voltage in approximately $600~\mathrm{Torr}$ of SF$_6$. The charging curves are quantitatively described by a capacitance-based model once realistic electrode misalignment is included. Voltage-hold measurements show picoampere-scale leakage currents on long time scales, whereas operation near the maximum voltage is limited by transient discharge processes associated with electrode surface condition and local field enhancement, rather than by the intrinsic dielectric strength of the gas. These results demonstrate the Cavallo multiplier as a viable low-current, in situ high-voltage source and indicate that electrode surface preparation, alignment tolerances, and insulation performance are the principal requirements for reliable operation in future cryogenic implementations.
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All authors S. M. Clayton, T. M. Ito, A. Jacobs, A-T. Le, M. F. Makela, C. M. O'Shaughnessy, N. S. Phan, E. Renner, T. A. Sandborn, T. J. Schaub, I. L. Smythe, J. Surbrook, M. A. Blatnik, B. W. Filippone

Instrumentation and Detectors

Operando Measurements of Pressure-Based PDMS Deformations in Electrochemical Microfluidic Devices

F. Lavanchy, Y. Sasaki, T. Minami et al. (+1 more)

Polymer based microfluidics, using polydimethylsiloxane (PDMS), are highly adaptable platforms for electrochemical studies commonly used for numerous applications. Deformations of these PDMS devices due to the flow pressure drop in microchannels have been widely documented in literature but cannot be prevented in all applications even though it is critical to measure quantitative data. In this work, we show that in electrochemical microfluidic devices used in energy conversion systems, the velocity profiles and channel deformations can be quantitatively measured based on spectro-electrochemistry and numerical simulations of Hagen-Poiseuille flows. PDMS deformations are found amplified in the case of large channel aspect ratios (i.e. close to 100), with deformation $\Delta$ h / h 0 > 100 % at 50 kPa, and start to be non-negligible > 10 % for channel internal pressure above 5 kPa. Finally, by considering these channel deformations in the Beer-Lambert law, we show that accurate absorbance and concentration measurements can be obtained using visible spectroscopy regardless the channel internal pressure.
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All authors F. Lavanchy, Y. Sasaki, T. Minami, S. Chevalier

Biological Physics

Influence of Oscillating Magnetic Fields on the Electric Dipole Moment of Radical Pairs in Cryptochrome Based Magnetoreception

Ali Soltanmanesh, Mahboobe Sehati, Sareh Rostami et al. (+2 more)

Radical pairs induced by light-driven reduction of cryptochrome protein constitute a spin dependent mechanism that is accompanied by an electric dipole moment and is found to be sensitive to external magnetic fields. In this research, to investigate for the further proof of such model, the simultaneous effect of the Earth's static magnetic field and the time-dependent magnetic field noise on the electric dipole moment of the radical pair has been studied within the quantum mechanical framework. The effect of the external magnetic field discussed in different angles regarding the Earth magnetic field within various frequencies and magnitudes. The sensitivity of the system behavior to the external magnetic field frequencies and magnitudes, vastly differs among the changes in the magnetic field angle to the Earth's static field. Furthermore, the sensitivity studied under the effect of the environmental noise. The relative spatial orientation of the two magnetic field components plays an important role in the time evolution of the electric dipole moment. Also, deeper discussions on specific relative orientations of the external magnetic fields, such as 24 degree, shows that the quantum model of radical pairs which is based on dipole moment, is in agreement with the results of the birds behavorial studies. These findings provide new insights into the sensitivity of the radical pair model to the combination of magnetic fields and may contribute to a comprehensive understanding of the phenomenon of magnetoreception and the advancement of bioinspired magnetic sensors.
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All authors Ali Soltanmanesh, Mahboobe Sehati, Sareh Rostami, Abolfazl Bahrampour, Alireza Bahrampour

Medical Physics

AQP4 Regulates Gap-Dominated Glymphatic Clearance through Dynamic Gliovascular Coupling

Tanran Zhang, Huaxiong Huang, Robert Eisenberg et al. (+1 more)

Aquaporin-4 (AQP4) is enriched at perivascular astrocytic endfeet, and impaired AQP4 function or localization is associated with reduced glymphatic transport. However, mechanical models suggest that pressure-driven exchange across the gliovascular interface occurs predominantly through inter-endfoot gaps rather than directly through the AQP4-rich membrane. How AQP4 regulates clearance in such a gap-dominated system remains unclear. We develop a reduced arterial PVS-ECS-venous PVS model coupling vascular deformation, AQP4-mediated endfoot water exchange, dynamic inter-endfoot gap regulation, and tracer transport. Cardiac-like oscillations generate strong bidirectional exchange but weak net clearance, whereas asymmetric vasodilation enhances directional transport by suppressing recovery-phase backflow. Dynamic gap regulation provides additional hydraulic rectification. Although gap-mediated flux is much larger than direct AQP4-mediated flux, PVS-facing AQP4 substantially affects clearance by altering the pressure–volume balance and hence the driving force for the dominant gap pathway. Reducing PVS-facing AQP4 permeability, or redistributing AQP4 away from the PVS-facing membrane at fixed total conductance, reduces cumulative venous output by about 40%. Aging-like changes in vascular motion, PVS mechanical coupling, and perivascular AQP4 enrichment further compound this impairment. These results suggest that AQP4 regulates gap-dominated glymphatic clearance through dynamic hydraulic coupling at the gliovascular interface.
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All authors Tanran Zhang, Huaxiong Huang, Robert Eisenberg, Shixin Xu

Atmospheric and Oceanic Physics · Cross-listed from stat.ML

Disentangling Forced and Internal Climate Variability in Single Realizations using Dynamic Mode Decomposition with Control

Nathan Mankovich, Andrei Gavrilov and Gustau Camps-Valls

We show that a single climate realization can be decomposed into forced and internal components by treating external forcing as a dynamical driver within a linear stochastic system, an idea grounded in pullback attractor theory. In doing so, we address a central methodological challenge in climate science with direct implications for climate projection and the detection and attribution of the forced response, disentangling the forced climate response from internal variability in a single observed record. Statistical methods range from approaches trained on large ensembles to techniques operating on single realizations. The latter often rely on linear frameworks such as linear inverse models (LIMs) and linear regression. LIMs ignore forcing predictors, whereas linear regression omits climate system dynamics. Here we introduce PullbackDMDc, a method grounded in non-autonomous dynamical systems theory and dynamic mode decomposition with control (DMDc), incorporating pullback attractor estimation to decompose a single climate realization into spatial modes and their associated forced and internal components, yielding a physically interpretable picture of the underlying dynamics. We illustrate the utility of PullbackDMDc for Earth System Model (ESM) evaluation by applying it to near-surface air temperature and sea-level pressure from reanalysis and four ESM large ensembles. PullbackDMDc estimates the forced response with skill matching or exceeding established baselines and identifies optimal forcing predictors against model-based ground truth. Its internal variability components reveal that ESMs qualitatively capture interannual and decadal modes while exhibiting systematic differences relative to each other and to observations. Skillful forced response estimation and a novel decomposition position PullbackDMDc as a practical tool for single-realization climate analysis and ESM evaluation.
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Plasma Physics

Automated Outlier-Robust Bayesian Profile Fitting for Magnetically Confined Plasmas with Modified Tanh Profiles and Good-and-Bad Gaussian Mixture Likelihoods

Jaewook Kim, Jekil Lee, Laurent Jung et al. (+2 more)

We present an outlier-robust Bayesian approach for automated kinetic profile fitting in magnetically confined plasmas with the modified tanh (mtanh) parametrisation and demonstrate its implementation on KSTAR. The method addresses two systematic obstacles: anomalous diagnostic channels can bias least-squares fits, and multimodality of the mtanh cost surface can trap deterministic optimisers in secondary minima. The deployed workflow uses a good-and-bad Gaussian mixture likelihood based on the Box–Tiao formulation as the default outlier-robust likelihood for fitted diagnostic channels, with posterior outlier probabilities retained as channel-level quality indicators. The posterior is sampled with an affine-invariant ensemble MCMC sampler initialised near the result of deterministic maximum a posteriori (MAP)-seeking optimisation, reducing sensitivity to secondary minima on the multimodal mtanh surface. A batch automation layer retrieves diagnostic data from MDSplus and fits arbitrary time slices in parallel for the quantities \(n_e\), \(T_e\), \(T_i\), and \(v_T\) for which the relevant diagnostics are available. Results are written in formats suitable for MDSplus upload and downstream analysis. Representative KSTAR H-mode cases show that the mixture likelihood downweights contaminated measurements while preserving plausible pedestal profiles. The workflow provides a practical basis for future large-scale kinetic profile production for kinetic-EFIT, TRANSP, FASTRAN, and data-driven analysis workflows.
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All authors Jaewook Kim, Jekil Lee, Laurent Jung, Sang-hee Hahn, Sehyun Kwak

History and Philosophy of Physics · Cross-listed from cs.GL

The Reconstructions of Konrad Zuse's Z3 Computer

Raul Rojas

This paper reviews the various reconstructions of Konrad Zuse's Z3 computer, built in 1941. The first is the reconstruction made by Zuse himself in the 1960s, which is now housed at the Deutsches Museum in Munich. Second is the 2001 reconstruction, made in Berlin, and which has a didactic purpose. Third is the Z3r, a Z3 reconstruction built by Horst Zuse in honor of his father's 100th birthday. Fourth is the reconstruction by Christoph Traber in Switzerland. All of these machines strive to preserve the cultural heritage that the Z3 represents.
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Popular Physics

Retaining Earth's Habitability Beyond the Life of the Sun

Gabriel Harry

The Earth is rare and large-scale interstellar travel may be unfeasible - instead of migrating to other solar systems, future civilisations on Earth may have to remain. However, left unchecked, the Earth's current habitability will end in one billion years. This paper investigates and conceptualises a set of megaengineering concepts required to safeguard against seven long-term threats to Earth's habitability: solar luminosity, solar engulfment, the end of tectonics, water loss, obliquity and rotation, object collision, and extra-system threats. Implementing and maintaining the set of safeguards would allow the Earth to remain habitable for 9.1 million billion years. This could be raised by an order of magnitude via lifting and moving solar photospheric mass. Compared with alternatives, advantages of the safeguards such as greater feasibility, lower requisite rate of energy production, and utilisation of economically viable space mining infrastructure may present remaining on Earth as a more attractive long-term survival strategy.
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Fluid Dynamics · Cross-listed from math.NA

A Log-Gaussian Scale-Space Limiter for Hybrid Continuum–Ballistic Gas Dynamics

Bjørn Wu

We propose a log-Gaussian scale-space limiter for hybrid continuum–ballistic gas dynamics. The method defines complementary continuum and ballistic weights as Gaussian cumulative probabilities in logarithmic Knudsen-number space and blends Navier–Stokes–Fourier and half-range Maxwellian kinetic fluxes. The method is formulated as a lightweight hybrid closure intended for future implementation in finite-volume, discrete Boltzmann, or gas-kinetic solvers. Reduced one-dimensional closure/profile comparisons against DVM/BGK Fourier and Couette data show that log-Gaussian weighting of NSF and jump/slip-corrected branches improves the tested macroscopic profiles relative to NSF. The same six DVM/BGK profiles are used both as reference profiles and to calibrate K0 and sigma; therefore, the approximately 40 percent reduction in combined mean profile error is an in-sample calibration result for the reduced profile model rather than independent validation or numerical validation of the proposed finite-volume face flux. Additional diagnostics assess non-equilibrium moments, internal parameter robustness, and shock-layer activation.
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Atomic Physics

Defect assignment of the clock site in $^{229}\text{Th:CaF}_2$

Daniel A. Rehn, Harry W. T. Morgan, Harris E. Mason et al. (+6 more)

The performance of solid-state $^{229}\text{Th}$ nuclear clocks depends sensitively on the microscopic environment of the thorium nucleus in the host crystal. Here we reassess the dominant quadrupole-split thorium site in $^{229}\text{Th:CaF}_2$, which has been assigned to a thorium dimer in recent spectroscopic work. Thermodynamic estimates, density functional theory calculations, and electric-field-gradient comparisons instead favor an isolated $\text{Th}^{4+}$ substitution on a $\text{Ca}^{2+}$ site charge-compensated by two nearby fluorine interstitials in a relaxed $90^\circ$ motif. The same calculation identifies a higher-energy mixed-shell interstitial motif as a plausible minor site. The clock-active quadrupole-split site is therefore controlled by local fluoride compensation rather than unavoidable thorium aggregation. This defect assignment also has implications for achievable linewidths and provides a microscopic basis for reducing broadening in solid-state nuclear clocks.
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All authors Daniel A. Rehn, Harry W. T. Morgan, Harris E. Mason, H. B. Tran Tan, Ricky Elwell, Igor M. Savukov, Michael J. Martin, Andrei Derevianko, Eric R. Hudson

Plasma Physics

Exact Solution of the Direct and Inverse Dynamo Problem in the Expanding Plasma Ball

Yurii V. Dumin

It was found that the differential equation of dynamo effect (i.e., generation of the electric fields and currents) in a uniformly-expanding plasma ball with strongly anisotropic conductivity possesses the unique mathematical property: namely, the spectrum of its eigenvalues is universal and independent of physical parameters of the medium. As a result, it becomes possible to introduce a special set of eigenfunctions - which we called the generalized spherical functions - that can be used to solve the dynamo problem in exactly the same way as ordinary spherical functions are used to solve the Laplace equation. The corresponding exact solutions should be especially valuable for treating the inverse dynamo-problem, i.e., determination of the plasma parameters from the experimentally measured electric fields and currents.
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Medical Physics

Roadmap Towards Quantum Entanglement Positron Emission Tomography (QE-PET)

Paweł Moskal, Shiva Abbaszadeh, Harmanjeet Singh Bilkhu et al. (+19 more)

Annihilation photons are quantum entangled in their polarization, a property that is not accessible in state-of-the-art clinical Positron Emission Tomography (PET). This roadmap describes the current status of research in the emerging field of quantum entanglement applications involving these photons for medical diagnosis. It outlines the underlying physics phenomena and the development of detector systems that can serve as a foundation for future Quantum Entanglement PET (QE-PET) scanners. These scanners will be capable of utilizing the entanglement between annihilation photons by measuring their Compton scattering on electrons. This roadmap comprises up-to-date experimental results on the study of quantum entanglement and the decoherence of annihilation photons, alongside the current theoretical understanding of these phenomena. The methods and detector technologies described herein are being developed (i) in order to enhance standard PET imaging by suppressing random coincidences in the reconstruction of annihilation site density distributions, (ii) in order to establish the degree of quantum entanglement as a diagnostic biomarker for tissue pathology and oxygenation, and (iii) in order to elaborate a method for pH imaging. Whether entanglement-based imaging and pH mapping can be successfully translated into clinical practice remains an open question and a subject of exciting ongoing research. This roadmap serves as an invitation to the scientific community to join this burgeoning field.
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All authors Paweł Moskal, Shiva Abbaszadeh, Harmanjeet Singh Bilkhu, Peter Caradonna, Pragya Das, Praveen Gurunath Bharathi, Ana Marija Kožuljević, Zdenka Kuncic, Deepak Kumar, Mihael Makek, Marek Nowakowski, Siddharth Parashari, Kaustav Prasad, Gregory R. Romanchek, Sushil Sharma, Kenji Shimazoe, Ewa Stępień, Sodai Takyu, Miwako Takahashi, Mizuki Uenomachi, Ritesh Verma, Taiga Yamaya

Atmospheric and Oceanic Physics

Modeling the response of the marine carbon cycle to extreme CO$_2$ injection events

Punit Gandhi, Rowan Lockwood, Corinne Myers et al. (+4 more)

We explore how the response of a conceptual model of the marine carbon cycle depends on the way in which carbon is injected from the atmosphere. We find that, for single-injection pulses, the threshold amount required for a large response of the excitable system depends on pulse duration but not on its specific form. We do, however, see differences in the number of large transient responses in carbon and, correspondingly, the duration of the response for different pulse shapes. These differences are magnified as the system is pushed towards increased excitability and can be understood in terms of the geometry of an increasingly winding heteroclinic orbit. Inspired by Large Igneous Provinces (LIPs), we also consider random sequences of injection pulses. We find a wide range of possible responses for a given overall amount injected and duration, depending on the mean characteristics of the individual pulses. We also identify a resonance-like "Goldilocks" zone, in which intermediate pulse durations or arrival frequencies produce the largest number of repeated transients, and we test the framework with illustrative scenarios motivated by the Siberian Traps and Columbia River Basalt Group.
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All authors Punit Gandhi, Rowan Lockwood, Corinne Myers, Parimita Roy, Ivan Sudakow, James Witts, Hao Helen Zhang

Atomic Physics

Wichmann-Kroll Correction to the Interelectronic Interaction in He- and Li-Like Ions

J. Sommerfeldt, V. A. Yerokhin, Z. Harman et al. (+1 more)

We present a theoretical study of the higher-order QED contribution to the interelectronic interaction in He- and Li-like ions, where a virtual electron-positron loop is inserted into the photon line of the one-photon exchange diagram. Our approach is based on the Dirac-Coulomb Green's function and accounts for the interaction of the virtual $e^+e^-$ pair with the electric field of the nucleus to all orders in $\alpha Z$, with $\alpha$ being the fine-structure constant and $Z$ the atomic charge number. We show that the numerical convergence of the involved integrals can be significantly improved by explicitly subtracting the non-gauge-invariant spurious contributions from the integrands. We present improved numerical values for this contribution to the Lamb shift over a wide range of nuclear charge numbers $Z$. Our calculations agree well with previous results by Artemyev and co-workers [Phys. Rev. A 56, 3529 (1997); Phys. Rev. A 60, 45 (1999)] for He-like ions, but we find a discrepancy in the Li-like case. Moreover, we calculate the finite nuclear size correction to this diagram, which can reduce its size by more than 5% for heavy ions. The improved QED calculations not only decrease the uncertainty of theoretical predictions for the interelectronic interaction in few-electron ions but the methods could also be used in the future to improve calculations of closely related one-electron two-loop QED diagrams.
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All authors J. Sommerfeldt, V. A. Yerokhin, Z. Harman, C. H. Keitel

Optics

Long baseline optical interferometric imaging with active phase stabilization

Joshua J. Collier, Leuca Patmore, John S. Wallis et al. (+3 more)

Astronomical observations allow us to better our understanding of the universe. As we observe smaller and more distance features, we run into the diffraction limit of our observation system. This limit is a function of the wavelength observed and the size of the primary aperture used. We can synthesize a larger primary aperture by implementing interferometry. Long baseline optical interferometry would lead to significant improvements in astronomical imaging resolution. Building optical interferometers with free space baselines becomes significantly more difficult as the baseline increases. A promising alternative is to use optical fiber to connect telescopes. Fiber-based interferometers are much more susceptible to phase noise than their free-space counterparts due to inhomogeneities in the fiber medium. This leads to significant degradation of interferometric signals used for astronomical measurements. We implement phase stabilization techniques used in quantum communications to stabilize an optical interferometer with a 170km pseudo-baseline. We use a quantum optimal measurement technique with this interferometer to resolve the extent of a source four times smaller than the diffraction limit of the system within 1.5% error. These results bring the potential for a full-scale on-sky long baseline interferometer significantly closer. A 350km baseline optical interferometer at 1550nm would allow us to resolve sub microarcsecond features in the universe.
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All authors Joshua J. Collier, Leuca Patmore, John S. Wallis, Elrina Hartman, Benjamin P. Dix-Matthews, David R. Gozzard

Fluid Dynamics · Cross-listed from math.AP

Homothetic Self-Similar Solutions to the Incompressible Navier-Stokes Equations

Tim Binz and Matei P. Coiculescu

We investigate homothetic forward self-similar solutions of the incompressible Navier-Stokes equations: the solutions $\overline{U}$ for which both $\overline{U}$ and $\beta \overline{U}$ are self-similar profiles for some nontrivial $\beta$. Homothetic solutions are, in addition, the only solutions for which a singular limit argument can be used to prove non-uniqueness of Leray-Hopf solutions along the lines of the Jia-Šverák program. In three dimensions, and for sufficiently regular initial data, we prove a Liouville theorem that rules out the existence of non-trivial homothetic solutions. In two dimensions, our Liouville theorem reproves a result of Luo and Shvydkoy that the only decaying homothetic solution with continuous angular data is the Oseen vortex. In addition, we prove that the Euler equations linearized around the Oseen vortex are stable in some subspaces of $L^2(\mathbb{R}^2)$, for example in the space of $2$-fold rotationally symmetric functions. On the other hand, we also discover a homothetic solution for which an unstable approximate eigenvalue of the linearized Euler equations exists.
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2607.12159 · 13 Jul · 31 pages. This new version includes an announcement of sharp rigidity theorems for homothetic solutions and rigidity theorems for (-1)-homogeneous Euler solutions up to the Onsager threshold, which we prove in subsequent work. Due to this new work, we eliminated the old Section 2. We also performed additional revisions to maximize clarity and correctness of our exposition

Abstract PDF $THRM ×2$VRTX ×2$EIGN ×1$HOPF ×1

Physics and Society · Cross-listed from cs.SI

Stop using Media Bias/Fact Check in research

Alejandro Javier Ruiz Iglesias, Julia Witte Zimmerman, Ashley M.A. Fehr et al. (+2 more)

Media Bias/Fact Check (MBFC) purports to quantify the bias, credibility, and factuality of reporting for roughly 10,000 media sources, and the resulting data is commonly used in misinformation research. In the present study, we show that MBFC's methodology does not meet basic standards of rigor for academic research. Despite its widespread prevalence, studies using MBFC rarely examine it carefully, often describing it in ways that contradict its “About” page, or treating it as authoritative despite MBFC's disclaimer that it is “not a tested scientific method... [but] a simple guide to the idea of a source's bias.” We identified no papers that adequately describe MBFC as the opinions of a single person or critically engage with its methodology in order to justify proceeding with its use. We argue that MBFC's data is not neutral or accurate, but a computationally legible account of hegemony, a specious dataset for uncritical research that mistakes the familiarity of the concepts it quantifies with accuracy. Our study concludes with a call for academic researchers to stop using MBFC. MBFC's data quantifies the results of political processes, including campaigns to discredit the press, and presents them as simple facts about the world, thus reproducing the crisis misinformation scholarship exists to address.
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All authors Alejandro Javier Ruiz Iglesias, Julia Witte Zimmerman, Ashley M.A. Fehr, Peter Sheridan Dodds, Christopher M. Danforth