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Physics

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Wednesday 24 June

Computational Physics

AeroProp-X: An Open-Source, Self-Verifying Method-of-Characteristics Toolkit for Edge-Capable Rocket Nozzle Design and Aerothermodynamic Analysis

Aryuemaan Kumar Chowdhury

The design of supersonic rocket nozzles by the Method of Characteristics is a mature discipline, yet the software that implements it is frequently either proprietary, heavyweight, or opaque, which limits reproducibility and classroom and field use. This paper presents AeroProp-X, an open-source, dependency-light toolkit that synthesizes shock-free minimum-length nozzle contours and evaluates their ideal aerothermodynamic performance entirely on commodity hardware without graphics acceleration or network access. The central contribution is methodological rather than physical: the planar characteristics solver is made self-verifying by exploiting an exact gas-dynamic invariant, namely that the computed exit wall height ratio must equal the isentropic area ratio at the design Mach number, so that every generated contour reports its own discretization error automatically. We describe the governing theory, the layered software architecture, and the synthesis algorithm, and we validate the implementation against analytic compressible-flow tables and against the expansion ratios of historical flight engines. The solver reproduces tabulated gas-dynamic quantities to table precision and converges to the exact area ratio with relative error below three parts in ten thousand, while remaining small enough to run interactively on an embedded-class processor. We argue that built-in verifiability, dependency minimalism, and explicit scoping of the ideal-flow assumptions together make the tool well suited to education, preliminary design, and reproducible research.
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Physics and Society

OhmicFlow: Forecasting transit passenger flow under extreme weather disruptions via Ohm's law

Tianhao Li, Xintian Liu and Zhan Zhao

As climate change intensifies, extreme weather events (EWEs) increasingly disrupt the supply-demand balance of mass transit systems. Accurate and reliable prediction of origin-destination (OD) passenger flow is essential for timely emergency response, but remains difficult under abnormal conditions. Although existing physics-informed methods can enhance model robustness, they remain insufficient for transit systems under extreme weather disruptions, where passenger flow fluctuations are jointly shaped by the redistribution of latent demand as a direct result of EWEs (i.e., direct effects) and the increase in travel impedance due to EWE-induced supply contraction and congestion effects (i.e., indirect effects). To address these limitations, we first conceptualize the transit network as an electrical circuit, treating latent demand as voltage, travel impedance as resistance and passenger flow as current, and then propose the OhmicFlow framework to jointly predict these variables under disruptions through Ohm's law. Specifically, a future-aware spatiotemporal backbone is used as an ammeter to predict disrupted passenger flow, and its replica is reused as a bypass voltmeter with impedance controlled in the inputs to infer latent demand counterfactually and in parallel. Travel impedance under foreseeable EWE disruptions is further modeled using a thermistor analogy, enabling dynamic estimation by coupling supply contraction with congestion effects. A multi-objective loss is incorporated to fit observed data while enforcing the Ohmic constraint. Empirical experiments based on 10 years of Shenzhen Metro data covering 17 EWEs show that OhmicFlow consistently outperforms various baseline methods, achieving lower prediction errors across various chronological training settings while improving uncertainty calibration, robustness, transferability, and interpretability.
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Instrumentation and Detectors

Gate Voltage Effect on Pulse Detection Efficiency of Perimeter-Gated SPADs

Hunter Guthrie, Md Sakibur Sajal, Zexi Liu et al. (+1 more)

Perimeter-gated single-photon avalanche diodes (pg-SPADs) are known for their dynamic dark noise modulation capabilities. They are reported to trade noise for photon sensitivity under continuous illumination. However, the implications of this trade-off have not heretofore been studied with pulsed optical systems. This work bridges this gap. We demonstrate that pg-SPADs fabricated in a 0.35 $\mu$m standard CMOS process trade-off pulse detection efficiency for a reduction in the the spread of spurious events within a burst window. Consequently, herein, we propose guidelines for the optimal use of pg-SPADs in pulsed LIDAR applications in view of the observed trade-off.
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All authors Hunter Guthrie, Md Sakibur Sajal, Zexi Liu, Marc Dandin

High Energy Physics (Theory)

A Spectral Criterion for Emergent Gravity

Jinku Guo

We give a source-resolved spectral criterion for long-range tensor exchange between conserved matter sources. Exact channel elimination preserves the propagation kernel together with the source and readout maps and the direct response. Common-space estimates control the residue at the displaced critical root of a finite approximation. A positive Källen-Lehmann representation identifies this residue with a zero-invariant-mass atom even at a continuum endpoint. For a complete positive Lorentz-covariant conserved stress tensor we classify the null-shell measure and prove that its TT atomic weight vanishes. A reduced compact spectral realisation instead carries internal tensor vertices into an external two-helicity response. Conservation reduces the leading vertex of localised stationary matter to its total energy. The mixed residue then factorises into the two energies and a common propagation coefficient. Spatial resolvent estimates determine the potential and force with finite-size corrections. Normalisation through the matter vertex leaves one dimensional calibration for the overall Planck scale. The spectral residue fixes the dimensionless exchange strength. The resulting response admits an Einstein-matter effective description under the stated positivity and helicity assumptions together with universal soft coupling and local nonlinear consistency.
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Instrumentation and Detectors

Direct Time-of-Flight Measurement Accuracy Improvement With Perimeter-Gated SPADs

Md Sakibur Sajal, Hunter Guthrie, Zexi Liu et al. (+1 more)

Direct time of flight (dToF) measurements are susceptible to errors because of system-level and circuit-level timing jitters. In addition, device-level uncertainty stemming from the dark noise of single-photon avalanche diode (SPAD) contributes to the aggregated error. We demonstrate that perimeter gating can help reduce the device-level detection inaccuracy for SPAD devices by reducing the dark noise probability. Specifically, in this work, we developed a general framework to accurately estimate the dToF jitters stemming from different source levels and analyzed a counter-based time to digital converter (TDC) circuit that are commonly used in such systems. We have also measured dToFs using a perimeter-gated SPAD (pg-SPAD) detector fabricated in a 0.35 $\mu$m standard CMOS process. Experimental results show that pg-SPADs can improve measurement accuracy in both free-running and time-gated operations.
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All authors Md Sakibur Sajal, Hunter Guthrie, Zexi Liu, Marc Dandin

Accelerator Physics

Comments on the paper "Eliminating beam-induced depolarizing effects in the hydrogen jet target for high-precision proton beam polarimetry at the Electron-Ion Collider"

Andrei Poblaguev

A critical review of the methodology used in F. Rathmann et al., Phys. Rev. Accel. Beams 29, 021001 (2026), to evaluate beam-induced depolarization of the Atomic Polarized Hydrogen Gas Jet (HJET) target at the Electron–Ion Collider (EIC) is presented. It is shown that several key assumptions underlying that analysis – including the introduction of a photon emission threshold, the application of Fermi's Golden Rule to coherent hyperfine transitions, the interpretation of power broadening as a physical linewidth increase, and the treatment of spatial magnetic fields – are either incorrect or internally inconsistent. As a consequence, the predicted large depolarization effects are demonstrated to be artifacts of the adopted methodology rather than genuine physical phenomena. A consistent quantum-mechanical treatment based on the time-dependent Schrödinger equation shows that beam-induced depolarization probabilities at the EIC are negligibly small.
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Chemical Physics

Large CISS Polarization from the Hierarchy Between Transport and Geometrical Spin Currents

Zeev Vager

Large spin polarization observed in chiral-induced spin selectivity (CISS) remains difficult to explain quantitatively. Experimental polarizations measured in chiral molecular systems are often substantially larger than expected from weak microscopic spin-orbit interaction in organic materials. We revisit the geometrical spin current introduced previously for electrons constrained to curved paths and propose a scale argument relevant to transport through double-stranded DNA (dsDNA). Estimation of the intrinsic geometrical spin-current scale using representative dsDNA parameters yields current magnitudes substantially larger than measured transport currents in many CISS experiments. We suggest that this hierarchy allows transport to be interpreted as weak leakage from underlying curved spin-current states. Within this picture, large CISS polarization emerges as transport selection of pre-existing spin-current branches.
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High Energy Physics (Theory)

Quantum Black Hole Chemistry from Double Holography

Naman Kumar

Extended black hole thermodynamics highlights a sharp tension in the usual holographic dictionary: at fixed boundary conformal frame, changing the AdS radius changes both the central charge and the spatial volume of the CFT, so that the color and volume sectors of the first law becomes degenerate. We show that this degeneracy is naturally removed for quantum black holes in Karch–Randall double holography. The mechanism is intrinsically semiclassical. Replacing the holographic regulator surface by a physical brane induces gravity coupled to a cutoff CFT, so classical bulk black holes become lower-dimensional quantum black holes whose geometry includes the cutoff-matter stress tensor to all orders in backreaction. This backreacting matter sector supplies a color variable distinct from the defect volume. We demonstrate the mechanism explicitly for the quantum BTZ black hole. Thus quantum backreaction resolves the same color-volume degeneracy addressed by the recent Weyl-factor proposal, but without introducing a non-standard boundary Weyl factor. Instead, the missing thermodynamic direction is supplied by the physical cutoff-matter sector of the doubly holographic quantum black hole.
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Statistical Mechanics

Comment on "Fundamental limit of phonon Tesla valve for heat rectification from first principles"

Samuel Huberman and Aleksei Sokolov

Thermal rectification is a two-terminal property: the same device must carry different heat-current magnitudes when two reservoir temperatures are interchanged. In this Comment on Ref.~\cite{WuHu2026}, we ask whether the reported ratio $\gamma=R_{\mathrm{f}}/R_{\mathrm{b}}$ can represent such a two-terminal rectification ratio within the fixed-background linearized phonon Boltzmann transport equation (BTE) used in that work. We show that, for a passive two-terminal reservoir problem, any fixed linearized BTE whose scattering operator preserves a uniform equilibrium temperature shift, and whose boundary-value problem is well posed, gives equal forward and reverse resistance magnitudes. A direction-dependent response can still occur under a prescribed gradient-weighted source–sink protocol, but such a response should be distinguished from two-terminal thermal rectification.
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Quantum Physics

Quantum typicality survives non-Abelian gauge constraints: exact analytical prediction confirmed in $SU(2)$ lattice gauge theory

Zhi-Wei Wang and Samuel L. Braunstein

Arguments for emergent spacetime require that quantum typicality, the generic absence of inter-subsystem correlations, persists on the physical Hilbert space of a gauge theory, where non-Abelian constraints could in principle inject geometry-supporting entanglement. Using $SU(2)$ lattice gauge theory on two-dimensional tori ($d_{\mathrm{phys}}$ up to $4{,}193$), we show that it does: the typical mutual information between strictly disjoint links matches an exact parameter-free analytical prediction combining a microcanonical baseline with Haar-random fluctuations. The Kogut-Susskind Hamiltonian generates correlations from states of definite geometry (such as the electric vacuum), while generic states show only regression to the mean, establishing that the arrow of correlation growth requires a non-generic initial condition.
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General Physics

Why does walking to the center of a merry-go-round feel so hard? Coriolis stabilization and the metabolic cost of staying on track

Mario J. Pinheiro

We revisit Feynman's classic carousel problem (Feynman Lectures, Vol.~1, Sec.~19.4), in which a student walks radially inward on a platform driven at constant angular velocity $\omega_0$ by an external motor. Working consistently in the frame co-rotating with the platform, we show that the student's kinetic energy in that frame is exactly constant: the mechanical work done by the real radial friction force is exactly cancelled by the work done against the centrifugal inertial force. The Coriolis inertial force, and the equal-and-opposite tangential friction force required to cancel it and keep the student on a straight radial path, do zero mechanical work, because both are perpendicular to the radial velocity. Yet generating that tangential force costs metabolic energy – precisely the effect Feynman flagged with “one has to lean over and push sidewise.” The mechanical model adopted here (a point mass with kinematically imposed trajectory) is deliberately silent about internal physiology; the metabolic cost discussion of Sec.~\ref{sec:cost} is a separate phenomenological layer, explicitly flagged as such, not derived from the mechanics. We give an order-of-magnitude metabolic estimate, an entropy-production argument connecting the exercise to the second law, a feedback (PD-controller) reformulation of the same physics, and a playground experiment students can run with a phone and a heart-rate strap. Throughout, we are explicit about reference frames and about the limits of each model.
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2606.27400 · 24 Jun · 5 pages, 2 figures. v2: Substantially revised following correspondence with K.T. McDonald (Princeton). Reference frame errors corrected; kinetic energy in rotating frame shown to be constant; lab-frame energy budget closed explicitly. Terminology updated from "fictitious" to "inertial forces". McDonald's independent note on the rolling-wheel mechanics cited as a companion reference

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Solar and Stellar Astrophysics

Nautilus: Fast Time-Resolved Spectroscopy of GKM Stellar Flares and Their Implications for Planetary Habitability

Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti et al. (+10 more)

Low-mass GKM dwarfs are prime targets for finding habitable-zone Earth-sized planets, but their frequent flares, especially on M~dwarfs, can strongly affect planetary atmospheres through enhanced UV/XUV radiation and stellar proton events, which can drive complex photochemistry and accelerate atmospheric escape. Current atmospheric and habitability models of planets around low-mass stars often rely on simplified flare inputs, such as fixed-temperature blackbodies or approximate optical-to-UV/XUV conversions. However, recent observations show that M~dwarfs' flare temperatures and spectral shapes can vary significantly with flare energy, phase, and stellar type, and that optical-based flare observations may underestimate the flare energy in the UV. Time-resolved spectroscopic flare observations of G- and K-dwarfs also remain rare compared to those of M dwarfs. Here, we propose that the Nautilus Space Observatory concept can provide a unique opportunity to obtain fast-cadence, precisely flux-calibrated, moderate-resolution NUV-to-NIR spectroscopy of flares across a large sample of GKM dwarfs. These observations will measure the time-dependent flare energy budget from the near-UV/blue continuum to the optical and near-infrared continuum, while resolving key chromospheric lines that trace the underlying flare physics. We aim to construct a statistical library of empirical flare spectral templates organized by flare and stellar properties, including flare energy, flare phase, and host-star spectral type. This library will provide a practical bridge between observed stellar flare properties and the radiation inputs required for planetary atmospheric evolution and habitability simulations.
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All authors Chia-Lung Lin, Adina D. Feinstein, Jeff Valenti, Mark S. Giampapa, Dániel Apai, Julien de Wit, Valeriy Vasilyev, Alexander Shapiro, Prajwal Niraula, Benjamin V. Rackham, Noah Tuchow, Ana Glidden, Nadiia Kostogryz

Optics

A unified framework for sensitivity comparison across stimulated Raman, stimulated Raman photothermal, and mid-infrared photothermal microscopy

Keiichiro Toda and Takuro Ideguchi

Label-free vibrational microscopy based on Raman scattering and mid-infrared (MIR) absorption has advanced biological imaging through the development of diverse high-sensitivity modalities. However, rigorous sensitivity comparisons across these techniques remain lacking. Here, we establish a unified theoretical framework for quantitatively comparing the shot-noise-limited sensitivities of stimulated Raman scattering (SRS), MIR photothermal (MIP), and stimulated Raman photothermal (SRP) microscopy. The framework is built on two quantities: an effective absorption coefficient, which places SRS on the same footing as linear absorption, and a photothermal (PT) factor, which isolates the contribution specific to PT readout. Using experimentally realistic parameters, we show that MIR absorption coefficients for representative polar vibrational modes are typically about two orders of magnitude larger than the effective absorption coefficients of SRS, even for strong off-resonant Raman bands. In MIP, however, this intrinsic advantage is partly offset by a small PT factor, limiting the net sensitivity gain over SRS to several-fold and, at most, about one order of magnitude. In SRP, by contrast, burst-pulse thermal accumulation substantially increases the PT factor. Under ideal shot-noise-limited conditions with matched per-pulse excitation-energy conditions in water, SRP is predicted to provide sensitivities several-fold higher than those of SRS and to approach those of MIP. This framework provides a common basis for sensitivity assessment across vibrational imaging modalities and clarifies how absorption strength, photothermal accumulation, and readout conditions determine the practical advantages of each modality.
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High Energy Physics (Phenomenology)

An Ultraviolet Finite Theory of Scalars

Francesco Calisto and Clifford Cheung

We construct a theory of scalars that is free of short-distance infinities to all orders in perturbation theory. Loop divergences are neutralized by momentum-dependent interactions that are ghost free and polynomially bounded. The finite counterparts of the usual one-loop scalar self-energy and beta function are straightforwardly computed. In a variant of this model, the one-loop mass renormalization is zero due to an inversion that swaps the ultraviolet and the infrared.
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High Energy Astrophysical Phenomena

Nuclear Isomers and Their Impact on Gamma-Ray Emission in Binary Neutron Star Mergers

M. C. Babiuc Hamilton, A. P. Gross and O. T. Odney

The multi-messenger observations of GW170817 have provided strong evidence that binary neutron star mergers are a site of heavy-element production through the rapid neutron capture process. The decay of unstable $r$-process nuclei produces a significant number of $\gamma$-rays, which not only power the associated kilonova, but may also be observable in current and future $\gamma$-ray observatories, providing a direct probe of the nuclei synthesized. Current models of the emitted $\gamma$-rays link a nuclear reaction network with individual decay spectra. Typically, only the population of the ground state of the nuclei is tracked in the reaction network, and rapid de-excitation of the daughter nuclei is assumed when calculating the decay spectra. This may not be accurate in nuclei where there are longer-lived, high-energy nuclear isomers. In this work, we relax these assumptions, modeling the dynamic behavior of nuclear isomers for a select list of nuclei. These isomers are included as independent states in the network, with temperature-dependent effective transition rates between ground and isomeric states and $\beta$-feeding probabilities calculated using the nuclear level structure. We estimate the $\gamma$-ray flux from isomeric transitions, finding that the 743.3 keV line of Nb-97m and the 555.6 keV line of Y-91m may be detectable in $\gamma$-ray observatories such as COSI, AMEGO, and LOX at galactic distances. These results, calculated for a small fraction of nuclei with isomers, highlight the need for the robust inclusion of nuclear isomers in nuclear reaction networks, as well as careful modeling of the resultant $\gamma$-ray spectroscopy to characterize observational signals.
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Astrophysics of Galaxies

Columba: isolated dwarf galaxy populations in diverse cosmological environments simulated with a cold interstellar medium

Jemima M. Briggs, Azadeh Fattahi, Robert A. Crain et al. (+7 more)

We introduce a suite of LambdaCDM cosmological, hydrodynamical simulations that track the evolution of a large population of dwarf galaxies. The suite comprises zoom-in simulations of 25 spherical, under-dense regions of r=5cMpc, selected to span $\approx1.5$ dex in mean enclosed density, covering voids to filamentary structures, whilst excluding haloes of Milky Way-mass or larger. The simulations achieve a mass resolution of $\sim 10^5$ solar masses with a galaxy formation model including cold, dense interstellar gas and whose subgrid stellar feedback efficiency reproduces the z=0 galaxy stellar mass function. We investigate the impact of the cosmic environment on dwarf galaxy formation and evolution. We find that the 5 cMpc environment influences the normalisation of the halo and galaxy mass functions, but does not significantly affect the stellar mass - halo mass (SMHM) relation and halo occupation fraction for galaxies with $M_{\star}=10^6-10^9$ solar masses. Instead, host halo concentration, estimated from DM-only counterparts, is more important: both the fraction of haloes hosting a resolved galaxy and the scatter about the SMHM relation correlate positively with concentration. Owing to halo assembly bias, concentration also influences galaxy formation times, such that at fixed halo mass more concentrated haloes host galaxies that are both older and more massive. The offset from the mean SMHM relation also anti-correlates with $t_{90}$, the time at which 90 percent of a galaxy's stellar mass has assembled. These correlations between halo properties and galaxy star formation histories present testable predictions for forthcoming observational surveys.
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All authors Jemima M. Briggs, Azadeh Fattahi, Robert A. Crain, Yannick M. Bahe, Sylvia Ploeckinger, Matthieu Schaller, Alejandro Benítez-Llambay, Evgenii Chaikin, Alexander J. Richings, Joop Schaye

Mesoscale and Nanoscale Physics

Quantum Hall effect in three-dimensional lattice induced by Wannier-Stark-Landau localization

D.-H.-Minh Nguyen

We study the quantum Hall effect in a cubic lattice subjected to parallel electric and magnetic fields aligned along a crystal axis. The dual fields confine electrons in three dimensions with their classical orbits residing on the surface of a finite-size cylinder. In the quantum limit, the spectrum yields a three-dimensional generalization of the Hofstadter butterfly, featuring equidistant resonances near the spectral center and discrete levels near the boundaries. When the Fermi energy lies within these spectral gaps, the Hall conductance in the plane normal to the fields is quantized while other components of the conductance tensor vanish. Under open boundary conditions, this quantum Hall state exhibits topological chiral hinge modes protected by bulk Chern numbers. Our results offer a novel platform for studying the quantum Hall effect in both solid-state heterostructures and synthetic lattices.
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Chemical Physics

Vacuum Moisture Swing Direct Air Capture: A Low-Thermal, Water-Managed Pathway for Scalable CO2 Removal

Stephano Sinyangwe, Sierra Binney, Gray Becker et al. (+2 more)

Direct Air Capture remains highly energy intensive, with most systems relying on high-temperature regeneration of amines or metal oxides. Here we present the first comprehensive evaluation of a low-temperature DAC process based on a moisture-swing mechanism that reversibly captures and releases CO2 using commercial ion exchange resins. The proposed vacuum moisture swing, VMS, process replaces thermal regeneration with a low-temperature water vapor stripping step driven by vacuum evaporation. A cyclic model, informed by experimentally measured water and CO2 sorption kinetics, was optimized across air relative humidity of 20 to 80 percent and kinetic regimes of 0.5 to 2.0x baseline. Optimized VMS operation at 20 percent relative humidity achieves CO2 productivities of 0.2 to 0.6 kg CO2 per kg sorbent per day, comparable to or exceeding high-temperature amine systems without external heat input. Electrical energy required for gas and vapor flow and CO2 compression to 0.1 MPa ranges from 1 to 15 MJ per kg CO2, driven primarily by vapor flow in the stripping step. At a representative productivity of 0.5 kg CO2 per kg sorbent per day, energy demand is about 2.5 MJ per kg CO2, surpassing typical productivity, energy tradeoffs, but with water losses of 1.4 to 3.5 kg water per kg CO2 due to evaporation, similar to liquid-based systems. Water loss scales with productivity and decreases under higher humidity and faster kinetics. The VMS process manages water through vacuum-driven evaporation and condensation, enabling the use of non-fresh or saline water sources. This work establishes a low-temperature DAC pathway that integrates realistic CO2 and water transport with built-in water management.
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All authors Stephano Sinyangwe, Sierra Binney, Gray Becker, Peter Schulze, Jennifer L. Wade

General Relativity and Quantum Cosmology

Massive boson stars: Waveform-based branch diagnosis with neural reconstruction

Bo-Xuan Ge

We investigate whether the dynamical merger branch of massive boson-star collisions can be inferred from the gravitational waveform without supplying the intrinsic source parameters. Using an existing equal-mass, head-on numerical-relativity catalogue, we construct branch-conditioned reduced-basis surrogates for the real $(2,0)$ and $(4,0)$ modes and perform parameter-blind waveform inference. On a frozen test set of 60 held-out samples, the correct branch is recovered for all samples using either mode, showing that the branch information is not confined to the dominant $(2,0)$ channel. The inference also recovers $|\phi_c|$ with a mean relative error of $4.30\%$ and selects the correct $\lambda$ from $\{10,50,100,300\}$ in $68.3\%$ of the test samples. These results demonstrate waveform-based branch and source-parameter inference within the present noiseless numerical-relativity catalogue.
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Cosmology and Nongalactic Astrophysics

Overview of 21cm Experiments at high redshift with SKAO

EoR/CD Science Working Group, Gianni Bernardi, Daniela Breitman et al. (+81 more)

We provide an overview of the eight SKAO Science Book chapters that motivate the Epoch of Reionisation and Cosmic Dawn experiments with SKA-Low. We describe the individual SKA-Low experiments and expected sensitivity - power spectrum, tomography, 21-cm forest, cross-correlations, building on the broad observational plan laid out in the 2015 SKA Science Book. Finally, we outline features of the telescope that will be critical for the success of EoR/CD science, e.g., beam apodization, substations, and multi-beaming.
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All authors EoR/CD Science Working Group, Gianni Bernardi, Daniela Breitman, Abhirup Datta, Anastasia Fialkov, Leon V.E. Koopmans, Adrian Liu, Yi Mao, Garrelt Mellema, Florent Mertens, Andrei Mesinger, Jonathan Pritchard, Aurel Schneider, Cathryn M. Trott, Yidong Xu, Anshuman Acharya, Satadru Bag, Rennan Barkana, Nichole Barry, Oliver Basquette, Michele Bianco, Stefanie A. Brackenhoff, Carlo Burigana, Isabella P. Carucci, Emilio Ceccotti, Arnab Chakraborty, Samir Choudhuri, Tirthankar Roy Choudhury, Benedetta Ciardi, Hector Afonso G. Cruz, Saswata Dasgupta, Kanan K. Datta, Pratika Dayal, Eloy de Lera Acedo, Khandakar Md Asif Elahi, Ivelin Georgiev, Sukhdeep Singh Gill, Sambit K. Giri, Adelie Gorce, Quan Guo, Caroline Heneka, Ian Hothi, Anne Hutter, Piyanat Kittiwisit, Bohua Li, Yashrajsinh Mahida, Barun Maity, Suman Majumdar, Avery Meiksin, Romain Meriot, Arnab Mishra, Shikhar Mittal, Rajesh Mondal, Lauro Moscardini, Julian Munoz, Satyapan Munshi, Pravin Kumar Natwariya, Leon Noble, Oscar Sage David O'Hara, Pierre Ocvirk, Samit Kumar Pal, Yannic Pietschke, Steven G. Piyanat, Rashmi Sagar, Rasha M. Samir, Mario G. Santos, Benoit Semelin, Rahul Shah, Yali Shao, Abinash Kumar Shaw, Hayato Shimabukuro, Peter H. Sims, Tomas Soltinsky, Guochao Sun, Anshuman Tripathi, Tiziana Trombetti, Ceren Ulusoy, Maio Umberto, Jochen Weller, Sarod Yatawatta, Shintaro Yoshiura, Bin Yue, Saleem Zaroubi, Qian Zheng

Soft Condensed Matter

Frustrated shapes of solid domains in fluid membrane vesicles: From rolls and folds to crumples and wrinkles

Geunwoong Jeon, Anthony N. A. Prempeh, Maria M. Santore et al. (+1 more)

Fluid-solid composite vesicles, comprising 2D solid domains integrated into a topologically-closed fluid bilayer membrane, exhibit complex morphologies arising from the geometric frustration between spherical closure of the membrane and 2D solid elasticity. This scenario is distinct from the better studied case of multi-fluid domain vesicles. Here, we study the elastic energies and shape equilibria of a closed vesicle membrane containing a single, flexible circular solid domain using discrete finite-element (Surface Evolver) simulations, determining the key physical and mechanical parameters to govern shape selection. While we find that the 2D solid (shear) elasticity has minimal impact on the highly-under inflated morphologies, the geometrically non-linear resistance of the solid to Gaussian curvature substantially impacts the shape and elastic patterns form for inflated vesicles, by an amount that it grows with ratio of vesicle size to the elastic thickness of solid. For sufficiently large (thin) vesicles we characterize a generic sequence of ground state patterns of solid shape with increasing inflation: from cylindrical rolls and isometric folds to spatially complex patterns of crumples and wrinkles and ultimately to smooth caps. This sequence of non-isometric patterns at high-inflation is shown to be governed by the same far-from-threshold mechanics used to describe similar shape transitions in microscopic sheets on curved liquid interfaces, establishing that inflated shapes are governed by two basic mechanical scales of membrane tension. We find our predictions for highly-anisotropic shape equilibria of fluid-solid composite vesicles closely match experimentally observed shapes of giant unilamellar vesicles of phase-separated DPPC and DOPC.
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All authors Geunwoong Jeon, Anthony N. A. Prempeh, Maria M. Santore, Gregory M. Grason

General Relativity and Quantum Cosmology

Stueckelberg Gauge Invariant Formulation of MOG

John W. Moffat

We develop a Stueckelberg gauge-invariant formulation of modified gravity (MOG). The massive vector field is made gauge-invariant by introducing a compensating scalar field, without requiring a Higgs field, spontaneous symmetry breaking, or a vacuum expectation value to fix the effective Newtonian gravitational coupling. This separates the gauge-invariant origin of the vector mass from the cosmological evolution of the gravitational coupling. The formulation preserves the finite-range vector interaction of MOG, while allowing the effective gravitational coupling to be treated as an independent scalar or scale-dependent quantity. This distinction is important for cosmological tests, since early-universe constraints and late-time large-scale gravitational phenomena need not be tied to a symmetry-breaking vacuum. The Stueckelberg formulation provides a gauge-invariant framework for comparing MOG with nucleosynthesis, cosmic microwave background, large-scale structure, lensing, and distance data.
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Solar and Stellar Astrophysics

A Spitzer Space Telescope Exploration Science Program to Search for Y Dwarf Variability

Michael C. Cushing, Jesica L. Trucks, Kevin K. Hardegree-Ullman et al. (+10 more)

We present the results of a Spitzer Space Telescope Exploration Science Program to search for and characterize variability in Y dwarfs. We observed 14 Y dwarfs over a 24 hr period at [3.6] and [4.5] and then repeated the observations a few months later. We add two Y dwarfs, WD 0806-661B and WISE J085510.83-071442.5, that were also observed with Spitzer so that our sample includes all Y dwarfs observed for variability with Spitzer. We infer variability fractions of 59%+-15% and 64%+10%-13% for [3.6], and [4.5], in the first epoch, and 35%+17% -11% and 75%+8% -15% in the second epoch. We also find that Y dwarf Spitzer light curves are generally stable over timescales of months, but in some cases can show clear changes in amplitude. Combining our results with a similar Spitzer survey of L and T dwarfs by Metchev et al. (2015), we find the mid-infrared variability fraction of L, T, and Y dwarfs weakly supports the hypothesis that brown dwarf variability is caused by variations in the horizontal and/or vertical structure of condensate clouds.
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All authors Michael C. Cushing, Jesica L. Trucks, Kevin K. Hardegree-Ullman, Adam J. Burgasser, Sean J. Carey, Jonathan J. Fortney, Christopher R. Gelino, John E. Gizis, J. Davy Kirkpatrick, Sandy Leggett, Gregory N. Mace, Mark S. Marley, Caroline V. Morley

Instrumentation and Methods for Astrophysics

In situ cryogenic characterization of proton damage in thick p-channel skipper CCDs

Brandon M. Roach, Brenda Cervantes Vergara, Alex Drlica-Wagner et al. (+14 more)

Skipper charge-coupled devices (CCDs) are an offshoot of standard silicon pixel detectors and are capable of performing repeated non-destructive charge measurements, enabling deeply sub-electron readout noise. This capability has opened the door to single-photon counting from the near-infrared ($\sim$1.1\,$\mu$m) to the soft X-ray (several keV), making these devices strong candidates for future astronomical instruments operating in the photon-starved limit. Furthermore, the p-channel architecture used to fabricate Skipper CCDs on n-type silicon has been demonstrated to have an increased hardness to the intense radiation environment of space. Building upon previous irradiation campaigns on room-temperature sensors, here we describe the first radiation-hardness tests of p-channel skipper CCDs at their cryogenic operating temperatures. We assess the performance of the floating-gate output stage and global CCD parameters (charge transfer inefficiency, dark current, hot pixels, and charge traps). We find that these devices maintain excellent performance after displacement damage doses equivalent to ${\sim}$10 years at the Earth/Sun L2 Lagrange point, demonstrating for the first time that these sensors remain radiation-hard in realistic deep-space thermal and radiation environments.
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All authors Brandon M. Roach, Brenda Cervantes Vergara, Alex Drlica-Wagner, Phoenix Alpine, Ana Martina Botti, Claudio Chavez, Julian Cuevas-Zepeda, Juan Estrada, Guillermo Fernandez Moroni, Nora Hoch, Stephen E. Holland, Blas Irigoyen Gimenez, Agustin Lapi, Santiago Perez, Nathan Saffold, Javier Tiffenberg, Yikai Wu

Mathematical Physics · Cross-listed from cs.LG

Beyond Feedforward Networks: Reentry Neural Systems as the Fundamental Basis of Subjecthood and Intrinsic Safety of Next-Generation AGI

A. S. Ushakov and Yu. N. Berdinsk

We propose a complete architectural blueprint for safe artificial general intelligence based on a closed reentry loop (D <-> I cycle). In contrast to feedforward networks, which are directed acyclic graphs (C=0, S=0) incapable of self-reference, the proposed architecture contains a structural cycle (C >= 1) with self-sustaining amplification (rho > 1), mathematically guaranteeing the emergence of a self-model, instrumental self-preservation, and unprogrammed goal-directed behaviour. The agent's goals are encoded as a non-textual D-vector in the architecture itself, making them immune to reinterpretation and prompt injection. We present the S-measure – a polynomial-time [O(N^3)] computable alternative to Tononi's NP-hard Phi – with machine-verified Lean 4 proof that S>0 implies positive integrated information. The work provides full Python/NumPy implementations (Tarjan-based cycle complexity, Delta-S barrier), industrial horizontal scaling via Apache Kafka and Docker Compose, a taxonomy of six epochs of AI evolution, a zoo of future reentry architectures (RAS, diffusion attractors, fractal loops), gauge-invariant networks for safe swarms, fault-tolerance and recovery protocols, and eight falsifiable predictions. All formal proofs are machine-verified in Lean 4. This architecture is deployable today and represents a topologically protected, safe-by-design approach to AGI.
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Physics Education

Data-Driven by Design: Building a Reflective Physics Graduate Program

Kevin Coldren and Diana Sachmpazidi

Well-documented research on physics graduate education has demonstrated long-standing issues that hinder equitable student access and participation. Addressing these challenges can be particularly difficult because they are often rooted in entrenched disciplinary and departmental cultures that tend to be rigid and resistant to change. In this work, we aim to cultivate a data-driven culture of cyclic self-reflection and action to proactively identify and address issues that affect student well-being and success in both a new physics and a long-standing astrophysics graduate program within a single institution. Drawing primarily on qualitative data (open-ended survey responses and focus-group interview data) from 15 students in both programs, we collaborated with the program leadership to identify actionable steps for improvement. In this paper, we present findings on student experiences across the two programs and discuss implications for research and practice. More broadly, this work provides a framework for graduate programs seeking to build a data-driven culture that improves student experiences.
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High Energy Astrophysical Phenomena

A Census of Variable and Transient Radio Sources Within High-Energy Neutrino Fields

Florian Rösch, Matthias Kadler, Roger P. Deane et al. (+3 more)

The origin of high-energy cosmic neutrinos detected by the IceCube observatory is a hotly debated topic in astroparticle physics. Neutrinos can be produced via interactions of high-energy protons with photons. There are multiple candidate source classes which can accelerate cosmic particles to the energies required to emit high-energy cosmic neutrinos and which have in common that they lead to variable/transient radio emissions. However, so far only a few active galactic nuclei (AGNs) could be associated with high confidence with IceCube neutrinos. The bulk of the diffuse neutrino flux might be emitted from a rather faint and numerous source population. The sub-mJy low-frequency radio sky may harbor these neutrino emitters that have gone unnoticed in previous searches. SKA-Mid continuum observations of high-energy neutrino fields will yield the most complete census of coincident transient and variable radio sources that might be associated with the neutrino emission. In previous MeerKAT observations of the IceCube gold alert IC240929A at 815 MHz, we detect about 550 faint radio sources inside the 90% uncertainty region of this neutrino field with flux densities between $169\,\mathrm{\mu Jy}$ and $140\,\mathrm{mJy}$. In its AA4 configuration, SKA-Mid will achieve about four times the sensitivity of MeerKAT, allowing for the detection of even fainter radio sources within such neutrino fields. By adding wide-field VLBI analysis of the fields under consideration, all neutrino-candidate radio sources can be tested for high brightness-temperature compact emission (indicative of an AGN classification) and milliarcsecond-scale resolved structures.
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All authors Florian Rösch, Matthias Kadler, Roger P. Deane, Philip G. Edwards, Karl Mannheim, Jack F. Radcliffe

Quantum Gases

Non-ergodic dynamical phase transition via a zero-mode exceptional point in a non-Markov atomic Josephson junction

Koichiro Furutani

Open quantum systems typically lose their initial memory due to the environmental decoherence resulting in thermalization. We demonstrate a striking breakdown of this paradigm in a head-to-tail Bose-Josephson junction, which is described by an intrinsically momentum-coupled Caldeira-Leggett model. Through exact non-Markov Langevin simulations, we discover a novel type of non-ergodic dynamical phase transitions into a running state, which has no counterpart in Markov limit. Crucially, we reveal that this transition is fundamentally governed by a zero-mode exceptional point emerging from the non-Markov friction. This topological origin is characterized by the winding of the response function. Finally, numerical quantum simulations of an equivalent driven XXZ spin chain confirm that this exceptional-point-induced signature robustly survives as a dynamical crossover against strong quantum fluctuations and the dynamical backreaction of the environment. This macroscopic robustness offers a promising platform for long-lived quantum memories in dissipative environments.
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Chemical Physics

Consistent Initial States with Constant Circuit Depth for Quantum Computational Chemistry

Lily Barta and Jakob S. Kottmann

Variational quantum eigensolvers have been extensively studied, yet there are still no methods that offer black-box applicability with consistent performance. Separable pair approximations promise to be candidates for such methods: they compile to shallow constant-depth quantum circuits with linear gate count and parameter dependence and circumvent most bottlenecks of variational quantum algorithms through their classical simulability. At the same time, they seamlessly integrate into prominent more general circuit designs and subspace strategies. So far, their capability as a consistent method has only been indicated and demonstrations have been restricted to manually designed model systems. In this work, we extensively evaluate the consistency of SPA states for hydrogen chains, alkanes, and small molecules within an orbital-optimized VQE framework. Our benchmarks demonstrate consistent approximations with classical complexity comparable to Hartree-Fock. While SPA can serve as a useful low-cost standalone approximation, its restriction to the seniority-zero subspace makes it best suited as a scalable, chemically consistent initial state for more expressive correlation treatments when high quantitative accuracy is required. Our open-source implementation within the tequila framework allows convenient use of the algorithms as a standalone method or as a subpart of more extensive procedures.
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Instrumentation and Detectors

Calibration and Performance of Germanium High Voltage Detectors for SuperCDMS SNOLAB

M.F. Albakry, I. Alkhatib, D. Alonso-González et al. (+141 more)

As SuperCDMS SNOLAB is getting ready to search for low mass dark matter particles, using cryogenic Ge and Si detectors, a set of six of the new SuperCDMS High Voltage (HV) detectors (four Ge and two Si) were tested in the Cryogenic Underground TEst facility (CUTE) at SNOLAB. This provided the first opportunity to gain experience with this new detector type and assess their performance thoroughly under low background conditions. Here we describe the SuperCDMS HV detector concept and discuss some of the newly developed analysis methods and approaches. Focusing on the Ge detectors, we investigate the detector performance under voltage bias (up to 90 V), exercise the low energy (keV to sub-keV range) calibration based on the electron capture peaks generated by the decay of $^{71}$Ge, assess the detector resolution, and demonstrate the unexpected (and encouraging) ability of these detectors to also measure high energy interactions in the hundreds of keV range with good resolution (better than 3% at 356 keV).
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All authors M.F. Albakry, I. Alkhatib, D. Alonso-González, J. Anczarski, T. Aralis, T. Aramaki, A. Ashtari Esfahani, I. Ataee Langroudy, R. Bhattacharyya, A.J. Biffl, P.L. Brink, M. Buchanan, R. Bunker, B. Cabrera, R. Calkins, R.A. Cameron, P. Camus, C. Cartaro, D.G. Cerdeño, Y.-Y. Chang, M. Chaudhuri, J.-H. Chen, R. Chen, J. Cooley, J. Corbett, P. Cushman, R. Cyna, S. Das, K. Dering, S. Dharani, M.L. di Vacri, M.D. Diamond, M. Elwan, S. Fallows, E. Figueroa-Feliciano, S.L. Franzen, G. Gerbier, R. Germond, A. Gevorgian, M. Ghaith, G. Godden, S.R. Golwala, G. Gonzalez, J. Hall, C.A.S. Harms, C. Hays, B.A. Hines, Z. Hong, L. Hsu, M.E. Huber, V. Iyer, M. Jha, V.K.S. Kashyap, M.H. Kelsey, K.T. Kennard, Z. Kromer, A. Kubik, N.A. Kurinsky, J. Leyva, J. Liu, Y. Liu, E. Lopez Asamar, P. Lukens, R. López Noé, R. Mahapatra, J.S. Mammo, A. Mayer, P.C. McNamara, É. Michaud, E. Michielin, K. Mickelson, N. Mirabolfathi, M. Mirzakhani, B. Mohanty, D. Mondal, D. Monteiro, S. Nagorny, J. Nelson, H. Neog, H. Nguyen, J.L. Orrell, M.D. Osborne, S.M. Oser, P. Pakarha, L. Pandey, S. Pandey, R. Partridge, P.K. Patel, D.S. Pedreros, W. Peng, M.A. Penner, W.L. Perry, R. Podviianiuk, M. Potts, S.S. Poudel, A. Pradeep, M. Pyle, W. Rau, A. Rehberg, R. Ren, T. Reynolds, M. Rios, A. Roberts, A.E. Robinson, L. Rosado Del Rio, J.L. Ryan, T. Saab, D. Sadek, B. Sadoulet, S. Salehi, J. Sander, A. Sattari, R.W. Schnee, S. Scorza, B. Serfass, R.S. Shenoy, A. Simchony, P. Sinervo, Z.J. Smith, R. Soni, K. Stifter, M. Stukel, H. Sun, E. Tanner, N. Tenpas, D. Toback, R. Underwood, A.N. Villano, J. Viol, O. Wen, Z. Williams, M.J. Wilson, J. Winchell, J. Xiong, S. Yellin, B.A. Young, B. Zatschler, S. Zatschler, A. Zaytsev, E. Zhang, J. Zheng, L. Zheng, A. Zuniga, M.J. Zurowski