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Physics

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Friday 24 July

Nuclear Experiment

Light hadron production measurements with Au+Au Collisions from $\sqrt{s_{NN}} = 3.2$–$4.5$ GeV with STAR

Mathias C. Labonté

One of the main physics goals of the Beam Energy Scan program at RHIC is to study the QCD phase diagram, specifically around the phase transition between the quark-gluon plasma and hadronic matter. Beam Energy Scan Phase-I studied Au+Au collisions from center-of-mass energy ($\sqrt{s_{NN}}$) of 7.7 to 62.4 GeV. Beam Energy Scan Phase-II extended these measurements in several important ways, one of which was the addition of a fixed-target program that pushed the collision energy down to 3.0 GeV (or baryon chemical potential, $\mu_B$, up to 720 MeV). Fixed-target collisions at STAR allow for a more extensive scanning of the QCD phase diagram to an important region where the QCD critical point may lie, and to a region dominated by dense baryonic matter. One key measurement in the fixed-target program is the spectrum of the lightest hadrons ($\pi^{\pm}$, $K^{\pm}$, p) as a function of transverse momentum, rapidity, and collision centrality. From the $p_T$ spectra, a blast-wave model is used to study the temperature at kinetic freeze-out and the surface velocity of the expanding matter. These results provide important input to models of heavy ion collisions at these energies, and can help constrain the equation of state of QCD matter. Here, results are shown for four collision energies in the fixed-target range: $\sqrt{s_{NN}} = 3.2$, 3.5, 3.9, and 4.5 GeV.
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Strongly Correlated Electrons

Single crystal growth, structural and magnetic properties of CeZn$_{2-x}$Ga$_{2+x}$

Danila Sokratov, H. Cein Mandujano, Ram Kumar et al. (+9 more)

The tetragonal BaAl$_4$ ($I4/mmm$) parent structure underpins a diverse family of materials exhibiting novel phenomena, including nematic superconductivity, topological semimetallicity, and heavy fermion behavior. The recent growth of ternary R-Zn-Ga compounds, such as the previously reported CeZn$_2$Ga$_2$, has explored some of the members exhibiting rare-earth magnetism within this family. In this paper, we report on the structural and magnetic properties of single crystals of CeZn$_{2-x}$Ga$_{2+x}$, a Ga-rich analogue of CeZn$_2$Ga$_2$. Our CeZn$_{2-x}$Ga$_{2+x}$ samples exhibit magnetic properties distinct from the paramagnetic behavior previously reported for CeZn$_2$Ga$_2$. We observe a magnetic transition around 4 K, pronounced metamagnetic states at low temperatures, and strong magnetic anisotropy. Though there are batch-to-batch variations that suggest a strong sensitivity to local structural imperfections, we consistently see the presence of magnetic transitions and metamagnetic states in our crystals. To investigate the local structural sensitivity hypothesis, we performed Reverse Monte Carlo analysis of collected powder neutron diffraction data, revealing the presence of significant local crystallographic disorder of the magnetic Ce site. Our findings demonstrate that the positional disorder drives competing ferromagnetic and antiferromagnetic correlations that lead to the observed spin glass behavior and complex anisotropic magnetism. This study illustrates that tuning the local crystallographic disorder enables engineering frustrated magnetic states in BaAl$_4$-type and similar intermetallic structures.
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All authors Danila Sokratov, H. Cein Mandujano, Ram Kumar, Jared Z. Dans, Phineas Sobel, Nicholas A. Crombie, Alicia Manjón-Sanz, Danielle R. Yahne, Philip Piccoli, Peter Y. Zavalij, Efrain E. Rodriguez, Johnpierre Paglione

High Energy Physics (Theory)

Mass/electric versus NUT/magnetic charges: duality from scattering amplitudes in $D\geq4$ and for all bosonic spins

Ricardo Monteiro, Lecheng Ren and Daniel Siretanu

We revisit Kerr-NUT metrics and related spin-$s$ fields in $D\geq4$, and study their associated scattering amplitudes. Starting in position space, we highlight the interpretation of mass and (multiple) NUT charges as being associated to distinct solutions of the rotation-deformed radial equation, which is made explicit in Cartesian multi-Kerr-Schild coordinates. This interpretation extends to electromagnetism with magnetic-type charges, and also extends to higher-spin counterparts, in accordance with the classical double or multi copy. We then establish a notion of “electric-magnetic" duality in higher dimensions, relating mass/electric to NUT/magnetic charges, which generalises the $D=4$ case in a novel manner. For $D\geq6$, this involves the choice where the multiple magnetic charges are equal. The duality is revealed in momentum space, by the 3-point scattering amplitudes that generate the solutions. For all spins, these amplitudes are constructed from a spin-raising operator $\mathcal S_\mu$ and take the form $\varepsilon^{\mu_1\cdots\mu_s}{\mathcal S}_{\mu_1}\cdots {\mathcal S}_{\mu_s}$ acting on a scalar seed. The scalar seed of the electric sector is dual to that of the magnetic sector: where the former's rotation dependence resums to a Bessel function $J_{\frac{D-5}{2}}$, the latter resums to a Bessel function $J_{-\frac{D-5}{2}}$. Finally, we explore the notion of self-duality that arises from this picture. Studying the classical $2\!\mapsto\!2$ amplitudes that determine leading-order scattering, we find no evidence of a higher-dimensional analogue of the integrability of $D=4$ self-dual gravity.
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Instrumentation and Methods for Astrophysics

SuperFIRE: Concept evolution of a seeing-limited broadband spectrograph for the GMT

Gustav M. Pettersson, Gábor Fűrész, Nathan P. Lourie et al. (+4 more)

We are developing the SuperFIRE concept, which builds on the heritage of the FIRE spectrograph at Magellan, as a broadband (about 340 nm to 2.5 um) intermediate resolution (R=10,000) single-shot natural seeing spectrograph for the Giant Magellan Telescope (GMT) with support from the Kavli Foundation. This single-object spectrograph is envisioned as a first-light instrument that can operate in natural seeing and grow in long-term capability as the telescope and adaptive optics systems mature. Here we discuss how the science cases and design have evolved since the concept was initially conceived and presented at SPIE in Edinburgh ten years ago. The primary drivers for the design changes are fast follow-up of faint transients and multi-messenger events, and complementarity to JWST observations in the infrared. By leveraging fast low-noise detectors and modern fabrication techniques we expect high throughput and low scatter that delivers sky limited performance in a few minutes of integration time for fast response and deep integrations. SuperFIRE will operate as a practical point-and-shoot follow-up spectrograph thanks to a versatile standard configuration that needs minimal observing or planning overheads and is insensitive to atmospheric conditions.
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All authors Gustav M. Pettersson, Gábor Fűrész, Nathan P. Lourie, F. Elio Angile, Jill Juneau, Gerardo Berlanga Molina, Robert A. Simcoe

Quantum Gases

Emergent integrable dynamics in a non-integrable Rydberg-atom chain

Gianluca Morettini, Luca Capizzi, Leonardo Mazza et al. (+1 more)

We show that integrable and non-integrable dynamics can coexist in the same Rydberg-atom chain, depending on the initial state in which the system is prepared. In the setting we consider, Rydberg atoms mainly experience an effective dipolar interaction and, within the nearest-neighbor approximation, their dynamics can be mapped onto an effective integrable Fermi gas with ballistic transport. The inclusion of longer-range couplings, however, is essential for the theory to be predictive; those terms break the conservation laws associated with integrability, enabling, in particular, the emergence of genuine diffusive transport. We study the dynamics generated by a bipartition protocol and reveal a sharp qualitative change in behavior as the particle density is varied, suggesting the possibility of accessing weaker and stronger integrability breaking dynamics in the same Hamiltonian depending on the relevance of local interactions. We propose a theoretical mechanism that accounts for the differences. Our findings provide clear and concrete evidence that integrability breaking is not solely a property of the Hamiltonian and of the magnitude of the couplings that break integrability, but also of the state in which the system is prepared.
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All authors Gianluca Morettini, Luca Capizzi, Leonardo Mazza, Maurizio Fagotti

Chemical Physics

CP2K: An electronic structure and molecular dynamics software package - Dynamics, Transport, and Spectroscopic Response

Jan Wilhelm, Anna-Sophia Hehn, Hossam Elgabarty et al. (+39 more)

One of the distinguishing aspects of CP2K is its seamless integration of diverse structural and transition-state optimization techniques with advanced sampling approaches including Monte Carlo, molecular dynamics, and metadynamics, enabling the efficient exploration of complex potential- and free-energy landscapes, including rare events. These capabilities are combined with a broad hierarchy of energy and force evaluation methods, ranging from classical and machine-learned interaction potentials and mixed quantum-classical multiscale and semiempirical schemes, to highly accurate quantum-mechanical electronic-structure approaches. At the heart of the latter lies the Gaussian and plane-wave framework, along with its augmented all-electron generalization, which have been described in detail in our previous code review [T. D. Kühne et al., J. Chem. Phys. 152, 194103 (2020)]. Building on this foundation, the present work revisits the methods within CP2K that turn electronic structure into dynamics, transport, and spectroscopic response. Particular emphasis is placed on the coupling between static response calculations and nuclear motion: spectra may be evaluated at optimized structures, averaged over thermally sampled configurations, obtained from time-correlation functions along ab-initio or path integral molecular trajectories, or followed in real time together with electronic and nuclear dynamics. The same modular structure also enables equilibrium and biased transport simulations, from Kubo-type linear response to open-boundary approaches under external potentials, highlighting CP2K's unique capability to unify quantum chemistry with quantum and statistical mechanics within a versatile, holistic simulation environment.
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All authors Jan Wilhelm, Anna-Sophia Hehn, Hossam Elgabarty, Beliz Sertcan Gökmen, Maximilian Graml, Stepan Marek, Ritaj Tyagi, Frederick Stein, Johann V. Potoschnig, Augustin Bussy, Christian S. Ahart, Zehua Chen, Linnea Andersson, Zdenek Futera, Filip Ivanovic, Margherita Buraschi, Christoph Schran, Remi Pasquier, Leonard Prokisch, Bibek Samal, Jelena Schmitz, Shridhar Sanjay Shanbhag, Harald Forbert, Ole Schütt, Franz Pöschl, Sebastian Ehlert, Stefano Battaglia, Michele Nottoli, Benjamin Stamm, Vamsee Voora, Rustam Z. Khaliullin, Sergey K. Chulkov, Matt B. Watkins, Clotilde S. Cucinotta, Jochen Blumberger, Chao Zhang, Yang Yang, Dominik Marx, Matthias Krack, Jürg Hutter, Marcella Iannuzzi, Thomas D. Kühne

High Energy Physics (Theory)

Tensor Catalyzed Decoherence of Primordial Scalar Fluctuations

C.P. Burgess, D. Dineen, R. Holman et al. (+1 more)

We provide the first complete calculation of the leading contribution to the decoherence of primordial fluctuations in the scalar part of the metric fluctuations within simplest, single-clock, inflationary models, assuming decoherence comes from gravitational interactions with an environment made up of the other, unmeasured, short-wavelength scalar and tensor modes. We include the contributions from all of the contributing interactions at leading order in powers of $(H/M_p)^2$ and of the slow-roll parameter $\epsilon_1$. Unlike all extant calculations in the literature we find a result that is not slow-roll suppressed (and so is the same order of magnitude as tensor-mode decoherence). The difference arises because the dominant decoherence comes from interactions that involve both the tensor and scalar environments simultaneously (and so are missed when they are examined separately). We verify that the leading contributions to decoherence are UV finite (as they must be). We confirm that the interactions driving decoherence become time-local and Gaussian in the deep super-Hubble inflationary regime and show how this can be used to reliably compute the evolution of the purity in the late-time regime relevant for observations (where naive perturbation theory is known to break down). The same derivation shows explicitly why the effects that undermine perturbation theory for decoherence do not also undermine the basic inflationary prediction for the amplitude of primordial fluctuations (in agreement with general arguments).2
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All authors C.P. Burgess, D. Dineen, R. Holman, Greg Kaplanek

Earth and Planetary Astrophysics

Tracing outer planetary systems through white dwarf pollution in wide binaries

Carolina Lizana-Vidal, Claudia Aguilera-Gómez, Laura K. Rogers et al. (+5 more)

White dwarf (WD) atmospheric metal pollution provides strong evidence for the presence of remnant planetary material and it can be used as an indirect tracer of outer planetary systems. We analyze whether the presence of a wide stellar companion affects the occurrence of outer planetary systems by comparing the incidence of calcium (Ca) pollution in hydrogen-atmosphere WDs in wide binaries and in apparently single stars. We construct two sample pairs: a large homogeneous SDSS low-resolution spectroscopic set and a smaller high-resolution sample. For each WD, we measure Ca abundances or upper limits and compute detectability-corrected cumulative pollution fractions that account for variations in effective temperature, signal-to-noise ratio, and spectral resolution. In the SDSS-based samples, we find pollution fractions <1%, defined as the fraction of WDs with detected Ca, for both single WDs and WDs in wide binaries. After correcting for detectability, the cumulative abundance distributions of the two populations are statistically consistent. The same conclusion is obtained for the higher-resolution samples, despite their different raw detection fractions. Our results indicate no statistically significant difference in the occurrence rate of remnant outer planetary systems between single stars and stars with wide (~200 au) companions, within the current uncertainties. These uncertainties are significant because the samples contain only a small number of polluted WDs. The corrected detectability cumulative fraction approach used here provides a framework for comparing samples with different detection sensitivities and can be extended to larger spectroscopic datasets. Such samples will be required to determine whether wide stellar companions affect the survival and delivery of planetary material and to search for more subtle trends, for example, as a function of companion separation.
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All authors Carolina Lizana-Vidal, Claudia Aguilera-Gómez, Laura K. Rogers, Amy Bonsor, María Ignacia Muñoz-Arriagada, Patrick Dufour, Constanza Bravo-Parra, Ema Salugova

General Relativity and Quantum Cosmology

Universal relations applied to proto-neutron star generated gravitational waves from three-dimensional core collapse supernova simulations

R. Daniel Murphy, Anthony Mezzacappa, Colter J. Richardson et al. (+3 more)

Using asteroseismology techniques, several relations have been developed that relate the quasi-normal, non-radial oscillation mode frequencies of the proto-neutron star (PNS) to the high frequency component of core collapse supernova (CCSN) generated gravitational waves predicted from simulation. These relations are universal in the sense that they are parameterized entirely by PNS properties, e.g., mean density or surface gravity, and are independent of both progenitor properties, e.g., zero age man sequence (ZAMS) mass or metallicity, and the physics included in CCSN simulations, e.g., nuclear equation of state (EOS). In this work, we apply several externally developed universal relations to PNS evolution data–specifically the mass, M, and radius, R,–generated from both two- and three-dimensional CCSN simulations and compare the resulting PNS oscillation frequencies predicted by the universal relations to the peak gravitational wave frequencies computed directly from the simulation-produced spectrogram. Additionally, we use the gravitational wave spectrogram peak frequencies as input to the universal relations and compare the predicted PNS properties from each relation to the true PNS properties as determined by the simulations. In this way, we show what these universal relations would predict for the PNS properties and their evolution from a real CCSN gravitational wave detection in the best case scenario, i.e., no detector noise. Our results indicate that caution must be exercised when using these universal relations, particularly when interpreting their predictions for PNS evolution from a gravitational wave detection, and that, given the extent to which we do see agreement between asteroseismological predictions and simulation outcomes, further development of universal relations would be beneficial.
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All authors R. Daniel Murphy, Anthony Mezzacappa, Colter J. Richardson, Pedro Marronetti, Eric J. Lentz, Ryan E. Landfield

Optics

Combined Cavity Alignment and Mode-Mismatch Sensing using RF-QPD Sensors

Mitchell Schiworski and Stefan Ballmer

In this article we describe a scheme for sensing both the mode mismatch and alignment of a cavity which does not require custom sensors and uses only Quadrant Photo-Detectors (QPDs). The technique is simple relying upon cylindrical lenses and thoughtful Gouy phase telescope design, and is trivial to implement alongside a Pound-Drever-Hall (PDH) locking scheme. The Gouy phase telescope design utilizes all three of the QPDs to sense each degree of freedom which also increases sensitivity and provides redundancy. The technique we show also works without RF modulation, which is useful for providing other general diagnostic information in complex optical experiments. An analytical overview of the technique as well as generic design equations for the Gouy phase telescope is provided. Finally, a detailed optical simulation is presented to verify the technique.
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Soft Condensed Matter

From Local Structure to Thermodynamics and Transport of Water with Machine Learning Force Fields

Andreas Kretschmer, Florian Altmann, Nader Nour et al. (+2 more)

We evaluate machine learning force fields derived from different density functional theory exchange correlation functionals using the full six-dimensional pair correlation function of liquid water, three-body structural descriptors, excess entropy, and transport properties. The predicted microscopic structure and dynamics depend strongly on the underlying functional: neglecting dispersion produces pronounced overstructuring, overly negative excess entropy, and suppressed diffusion. Translational and orientational entropy contributions are tightly coupled and together exhibit a clear relationship with the reduced selfdiffusion coefficient. Among the tested models, RPBE-D3 provides the most consistent agreement with experiment across structural, thermodynamic, and transport properties. The classical SPC/E model serves as an additional reference and displays notable similarities to RPBE-D3, consistent with the comparable Born effective and partial charges of the two models.
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All authors Andreas Kretschmer, Florian Altmann, Nader Nour, Alper T. Celebi, Markus Valtiner

Soft Condensed Matter

Bimodal colloids highlight the structural mirror of rigidity percolation and yielding

Robert A. Campbell, Ziye Zhuang, Ali Mohraz et al. (+1 more)

In metastable particulate gels, it is tempting to believe that the dynamic similarities between the fluid-to-solid non-linear phase transition of rigidity percolation and the solid-to-fluid transition that occurs during yielding represent mirror images of the same continuous process. Even though these behaviors are clearly dynamically similar, their multi-scale nature makes it difficult to determine if they could also follow a unified structural pathway. We know from model monodisperse colloidal gels that both yielding and the elastic modulus seem to be heavily influenced by a small subset of topologically distinct singly-connected bridges linking mesoscale features. Here we use particle simulations to examine the participation of different classes of particle-level bonds and their contributions to the bulk mechanical response. We find that rigidity is disproportionately supported by singly connected intercluster bridges, whereas yielding localizes at bonds with high edge-betweenness centrality (EBC); strikingly, these independently identified populations substantially overlap and perform comparable mechanical roles. Bimodality exposes this correspondence by concentrating large-particle contacts in both populations, thereby providing a compositional label for the common backbone. Thus, rigidity and yielding are opposing mechanical manifestations of the same mesoscale structure: the intercluster bottlenecks that establish rigidity are also the sites at which rigidity is preferentially lost.
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All authors Robert A. Campbell, Ziye Zhuang, Ali Mohraz, Safa Jamali

Optics

Clarifying the energy storage capabilities of virtual critical coupling under realistic excitation constraints

Valentin Mazières, Théo Delage, Jérôme Sokoloff et al. (+1 more)

Virtual critical coupling (VCC) has emerged as a promising approach for achieving reflectionless excitation of resonant systems through tailored incident waveforms. However, the energy storage enhancement often attributed to VCC is generally assessed without considering practical constraints imposed by the excitation source. In this work, we revisit the energy storage capabilities of VCC under a realistic maximum-amplitude constraint. Using temporal coupled-mode theory, we derive analytical expressions for the stored energy of continuous wave (CW), ideal VCC (IVCC), and constrained VCC (CVCC) excitations. While the conventional IVCC excitation leads to higher stored energy than CW excitation due to its exponentially increasing incident amplitude, we show that this enhancement originates from the larger incident energy delivered by the unconstrained waveform. When the maximum excitation amplitude is fixed, the proposed CVCC excitation stores less energy than CW excitation throughout the excitation duration, while preserving the high energy transfer efficiency and reflectionless excitation enabled by VCC. The analytical expressions are used to analyze both an ideal lossless resonator and an experimentally lossy microwave cavity previously used for plasma ignition by VCC. The results clarify that VCC should primarily be regarded as a method for improving energy transfer efficiency and controlling transient excitation, rather than as an intrinsic mechanism for increasing the absolute stored energy under realistic source limitations.
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All authors Valentin Mazières, Théo Delage, Jérôme Sokoloff, Olivier Pascal

Applied Physics

A Single-Tuning-Element Loaded Pixelated Tunable Band-Pass Filters with Low Loss via Inverse Synthesis on Massive-Scale Dataset

Woojun Lee, Pouya Faeghi and Jeffrey S. Walling

This paper presents a novel three-phase inverse-design flow for synthesizing tunable pixelated band-pass filters. The workflow consists of: 1) acquisition of a massive dataset ~300000 5-port S-parameter samples using the group's custom electromagnetic solvers accelerated by method-of-moments pre-computation; 2) identification of an initial seed through brute-force search with dataset augmentation by dynamically reassigning the input, output, and tuning ports and randomly applying open or short terminations to the remaining ports; and 3) fine-tuning of the selected seed using a direct-binary-search algorithm. Two design targets are considered: 4G mid-/high-band tunable band-pass filters and 5G n79/UNIII-band tunable band-pass filters. One designed filter achieves a 28% tuning range, with passband peaks reconfigured from 4.64 to 6.16 GHz and insertion loss from 1.3 to 1.8 dB in simulation. All inversely designed filters use only a single varactor, representing the first reported demonstration of continuously reconfigurable inverse design in the microwave regime.
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Cosmology and Nongalactic Astrophysics

Stability in Axion Inflation with Strong Backreaction from a Massive Vector Boson

Michael J. Baker, Joaquim Iguaz Juan and Lorenzo Sorbo

We study a modification of the model of axion inflation coupled to a $U(1)$ gauge field where the vector field is massive. In the conventional scenario with a massless gauge field, the onset of the regime where the gauge field strongly backreacts on the inflaton displays an instability whose nonlinear evolution and endpoint remain poorly understood. We argue that, if the gauge field is massive enough, the transition to the strong backreaction regime instead occurs smoothly, avoiding this instability. This observation suggests that axion inflation with massive gauge fields admits a controllable strong backreaction regime, so that a phenomenologically viable realization of inflation might be possible in this class of models.
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Nuclear Theory

What we talk about when we talk about nuclear structure

S. Ragnar Stroberg

I provide and introductory overview of the field of nuclear structure, with a focus on physical concepts. I describe some basic nuclear structure observables, followed by a qualitative description of nuclear forces. I then outline some nuclear structure models which are most widely used to interpret the experimental data in terms of interacting protons and neutrons.
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Mathematical Physics · Cross-listed from math.AP

Dispersive Estimates for Dirac Operators with General Domain Walls: One and Two Dimensions

M. Burak Erdogan, Joseph Kraisler and Amir Sagiv

We establish dispersive decay estimates for two-dimensional Dirac equations with bounded and unbounded domain walls, together with estimates for the analogous one-dimensional problem. These are paradigmatic models of bulk-edge correspondence in topological insulators, yet their dispersive dynamics have not been previously studied. We show that topologically equivalent models may exhibit qualitatively different dynamics. Our new approach allows us to analyze models which are beyond the usual framework of localized perturbations of constant-coefficient Dirac operators.
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General Relativity and Quantum Cosmology

Casimir traversable wormholes in Gauss-Bonnet gravity

Mohammad Reza Mehdizadeh and Amir Hadi Ziaie

In this work, we study Casimir wormhole solutions and investigate satisfaction of energy conditions in the framework of Einstein-Gauss-Bonnet (EGB) gravity. We firstly find traversable wormhole solutions supported by a general form for the Casimir energy density. Applying a specific redshift function, we choose suitable parameters that respect the energy conditions in the vicinity of the throat due to the presence of higher order curvature terms. Then, we check the energy conditions considering non-constant redshift function and for suitable choice of model parameters, we find that these conditions are satisfied at infinity as well as in the vicinity of the throat. The stability of the Casimir traversable wormhole solutions are investigated using the Tolman-Oppenheimer-Volkoff (TOV) equation. Finally, we study trajectory of null as well as timelike particles in the wormhole spacetime.
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Physics and Society

Gravitational DePhaser: A Temporal Gravitational Lensing Model for Creative Audio Processing

Carlos Darío Badilla Cerdas

Classical delay, chorus, and reverb effects model multiple pro- pagation paths using discrete delays or statistical distributions. This work proposes a model inspired by gravitational lensing, where an audio signal is treated as a wave packet traversing a temporally distorted potential rather than physical spacetime. The distortion generates multiple effective propa- gation paths with different delays, phases, and gains, producing controlled constructive and destructive interference.
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Instrumentation and Detectors

Commissioning and first results from the Cold Radon Emanation Facility

Emily Perry, Chamkaur Ghag, Maurits Van der Grinten et al. (+4 more)

Radon emanation from detector materials is a critical background for next-generation rare event searches, in particular those using noble liquid targets. While highly sensitive screening facilities mitigate this risk prior to detector construction, room-temperature assays often fail to predict cold emanation rates due to temperature-dependent diffusion suppression. The Cold Radon Emanation Facility at Rutherford Appleton Laboratory addresses this by performing high-sensitivity assays at detector operating temperatures. It includes a 2.7 L small-sample chamber, a 200 L chamber for large as-built components operated with a radon concentration line, a cryogenic infrastructure enabling measurements of emanation as a function of temperature, and an electrostatic radon detector, which achieves a minimum detectable activity of ~0.05 mBq at 90% CL. Commissioning results and initial comparative assays are reported, including a preliminary indication of a factor of ~2 suppression of $^{222}$Rn emanation in a titanium sample at cryogenic temperatures. This result, obtained as part of commissioning measurements, illustrates the potential impact of temperature-dependent effects and underscores the importance of in-situ cold assays for future noble liquid detector components.
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All authors Emily Perry, Chamkaur Ghag, Maurits Van der Grinten, Ruben Saakyan, Andrew Stevens, Mark Tucker, Umit Utku

Optics

AI-interpreted Optical Scattering for Robust and Focal Depth-Aware Imaging

Eunji Ko, Patrick Ross, Corey Hart et al. (+1 more)

Optical scattering has conventionally been regarded as an impediment in imaging research due to the degradation of image quality during reconstruction. Nevertheless, this study explores two cases in which optical scattering may serve a beneficial role in image reconstruction tasks. We compared the No Scattering MNIST dataset with three Scattering MNIST datasets, each generated under distinct scattering conditions. To assess the information content of the resulting speckle patterns, we employed a Variational Autoencoder (VAE) approach which achieves accuracy comparable to state-of-the-art deep learning approaches, but has an interpretable latent space. We find that scattering can enhance data robustness against spatial pixel loss by effectively distributing information. We also demonstrate that scattering can enable distinctions of focal depth information. We anticipate that these findings will contribute to more efficient imaging techniques, particularly in the presence of obstacles and three-dimensional signals.
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All authors Eunji Ko, Patrick Ross, Corey Hart, Wolfgang Losert

Quantum Physics

Universal scaling framework for parameterized quantum evolutions at criticality

Jan T. Schneider, Cristian Tabares, Alejandro González-Tudela et al. (+1 more)

Variational ansätze are a cornerstone of quantum many-body physics, providing compact approximations to complex ground states using finite resources. Recent quantum-technology advances have introduced a new class based on layered parameterized evolutions. Assessing whether they can represent critical ground states is challenging: correlations span all length scales, while finite circuit depth limits how far they extend. Building on finite-resource scaling from tensor networks, we assign each ansatz an emergent correlation length $\xi_D$, the longest range over which it faithfully captures critical correlations. Its growth with refinement parameter $D$, $\xi_D \propto D^\kappa$, defines an exponent $\kappa$ measuring how efficiently an architecture converts resources into long-distance correlations. Applying this framework to the critical transverse-field Ising model, with $D$ the circuit depth of parameterized evolutions, we compare ansätze with nearest-neighbor and long-range generators, and layers where generators act separately or combined. All ansätze are compatible with algebraic growth, but fitted exponents range from $\kappa\simeq1$ to $\kappa\simeq3$. Exponential interactions give the largest exponents, while power-law interactions stay close to nearest-neighbor behavior, showing long-range support alone gives no scaling advantage. Combined-generator layers generally outperform separable ones, so layer organization matters alongside interaction range. Finally, a quasiparticle analysis shows finite depth leaves an unresolved window of width $\xi_D^{-1}$ around the low-energy modes responsible for long-distance correlations. The emergent correlation length thus acts as an infrared resolution scale, providing a benchmark for critical-state preparation and a guide for designing resource-efficient variational architectures.
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All authors Jan T. Schneider, Cristian Tabares, Alejandro González-Tudela, Luca Tagliacozzo

Quantum Physics

Full-wave nonlinear microscopy reveals guided channel for ultrafast polariton transport

Qingyi Zhou, Piper Fowler-Wright, Zongfu Yu et al. (+2 more)

We show how finite-difference time-domain (FDTD) simulations can be extended to model ultrafast nonlinear microscopy, enabling the prediction of spatially-resolved pump–probe signals in arbitrary electromagnetic environments. Focusing on polariton transport in strongly coupled light–matter systems, we develop a perturbative framework to study the ultrafast propagation of hybrid light–matter excitations in nanophotonic structures. We first apply the framework to a standard distributed Bragg reflector (DBR) cavity, reproducing established results for polariton transport from a multimode Tavis–Cummings model. We then consider the full modal landscape of the same cavity, including guided modes below the light line that are typically neglected in single-mode-family descriptions. Exploiting these modes, we design compact mode converters that transfer radiative cavity polaritons into photon-like guided polaritons and back, utilizing the guided modes for low-loss propagation. Despite molecular dephasing, this enables transport of molecular excitation over a millimeter, an order of magnitude beyond current transport experiments. We further compute the pump–probe differential transmission signal, providing an experimental signature of the mechanism. Our results show that the modal landscape of a photonic cavity can be engineered to bypass limitations commonly assumed to be intrinsic to the transport of molecular polaritons.
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All authors Qingyi Zhou, Piper Fowler-Wright, Zongfu Yu, Joel Yuen-Zhou, Michael Reitz

General Relativity and Quantum Cosmology

Vaidya-Type Solutions of Quasitopological Gravity Interacting with Nonlinear Electrodynamics

Valeri P. Frolov, Chul-Moon Yoo and Andrei Zelnikov

We construct Vaidya-type solutions of quasitopological gravity coupled to nonlinear electrodynamics in arbitrary spacetime dimensions. Starting from the corresponding static spherically symmetric charged solutions, we obtain their dynamical counterparts by promoting the integration constants, in particular the mass and electric charge, to arbitrary functions of the advanced or retarded null coordinate. We show that the resulting field equations are satisfied provided suitable charge-carrying null currents and null fluid fluxes are included. The formalism applies to a broad class of nonlinear electromagnetic theories and provides a simple and systematic method for generating exact radiating charged solutions in quasitopological gravity.
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Quantum Physics

Spin-induced multipartite steady-state entanglement of motional modes in hexagonal boron nitride membranes

Nahid Yazdi, Vahid Salari and Roohollah Ghobadi

In this paper, we focus on a scheme in which three high-quality-factor mechanical modes of a hexagonal boron nitride (hBN) membrane monolayer are coupled to a common optically addressable spin defect present in the membrane via magnetic field interaction. We show that this coupling induces an effective phonon-phonon interaction in the dispersive regime and under appropriate magnetic field and microwave modulation. We derive the Langevin-Heisenberg equations of motion for vibrational modes to analyze optimal parameter regimes for reaching a physically stable system. We also investigate the effect of coupling strength on purity and entanglement. Our results demonstrate that bipartite and genuinely tripartite steady-state entanglement between different vibrational modes of hBN may be achieved in a broad spectrum of experimental parameters. This study has the potential to enable scalability to be implemented for the generation of two-dimensional continuous-variable cluster states for universal quantum computation.
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Quantum Physics

Machine Learning of Quantum Entanglement from Noisy Measurements

Artur Czerwinski, Maciej Wiśniewski and Paweł Moszczyński

In this work, we investigate the application of Machine Learning (ML) algorithms to the identification and quantitative characterization of quantum entanglement in polarization-entangled photon pairs. The analysis is based on simulated symmetric, informationally complete, positive operator-valued measure (SIC-POVM) measurement data, where each two-qubit state is represented by a 16-dimensional measurement vector corresponding to experimentally accessible coincidence counts. The generated SIC-POVM measurement data include Poissonian shot noise. Several supervised ML algorithms, including Logistic Regression, k-Nearest Neighbors, Decision Trees, Support Vector Machines, and Random Forests, are applied to the classification of separable and entangled states directly from raw measurement data, without explicit density matrix reconstruction or the use of conventional separability criteria. The study additionally explores clustering methods and nonlinear regression techniques for estimating continuous entanglement measures. The obtained results demonstrate that ML methods can achieve very high classification accuracy, even under extremely limited training conditions. These findings indicate that ML may provide an efficient alternative to conventional quantum-state analysis under simulated Poissonian noise conditions.
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Quantum Physics

Bias-preserving cat-cat CNOT gate via vacuum-conditional beam-splitter

Yufeng Ye, Connor T. Hann, Kyungjoo Noh et al. (+4 more)

Cat qubits can exhibit strong noise bias due to their exponentially enhanced bit-flip times and only polynomially reduced phase-flip times with increasing photon number, which makes them attractive candidates for hardware-efficient quantum error correction. However, it is difficult to maintain this strong noise bias in logical operations such as CNOT gates between cats. Here, we propose a coherent CNOT gate scheme between two dissipative cats that preserves the exponential noise bias. The proposed gate relies only on unitary operations, which avoids the non-idealities associated with many existing gate schemes that rely on engineered dissipations. Assuming good component lifetimes and precise nonlinearity engineering, the proposed gate can enable logical memory in the megaquop regime (logical error rates < 10^-6) with a distance-7 repetition code consisting of 13 cat qubits.
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All authors Yufeng Ye, Connor T. Hann, Kyungjoo Noh, Harald Putterman, Ron Belyansky, Arne L. Grimsmo, Oskar Painter

Biological Physics · Cross-listed from cs.HC

Validation of a Real-Time Manual Wheelchair Simulator through Biomechanical and Perceptual Measures: A Comparison with Overground Propulsion

Ateayeh Bayat and Félix Chénier

Purpose: Manual wheelchair simulators can provide a safe and controlled environment for propulsion training, biofeedback, and biomechanical assessment. However, their ecological validity must be established to ensure that simulator-based outcomes reflect overground propulsion. This study aimed to evaluate the ecological validity of a real-time manual wheelchair simulator by comparing biomechanical and perceptual outcomes during matched overground and simulator tasks. Materials and Methods: Thirteen participants (10 able-bodied individuals, 3 experienced manual wheelchair users), performed propulsion tasks overground and on the simulator. Task segments included straight-line propulsion, acceleration, turning, ascending, and descending. Biomechanical outcomes were collected using instrumented wheels and compared between environments using temporal, kinetic, and waveform-based measures. Perceived realism and user experience were assessed using task-specific realism ratings, a post-test questionnaire, and semi-structured interviews. Results: Temporal variables showed relatively small differences between overground and simulator propulsion, whereas kinetic variables showed larger discrepancies, consistent with previous simulator comparisons. Waveform patterns for force, moment, and power demonstrated high similarity between environments. Participants generally reported positive perceptions of realism, safety, and satisfaction, and highlighted the value of practicing wheelchair skills in a controlled environment. Conclusion: The simulator demonstrated partial ecological validity, particularly for temporal and waveform-based propulsion outcomes. Its ability to accommodate the user's own wheelchair configuration may help preserve ergonomics and enhance realism, supporting its potential use as an assistive technology tool for manual wheelchair propulsion training.
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Quantum Physics

ViBra: Configuration Interaction for Anharmonic Vibrational Spectroscopy and Quantum-Sampled Configuration Spaces

Raphael F. Ligorio, Marco Antonio Barroca, Alan Duriez et al. (+1 more)

Quantum-centric workflows are a promising route to improving the accuracy of property predictions in computational chemistry and materials science. By integrating quantum sampling algorithms with classical solvers, electronic structure calculations have recently demonstrated their potential even on noisy intermediate-scale quantum devices. In principle, the method of Vibrational Configuration Interaction (VCI) is suitable for integration with quantum sampling algorithms as well. However, demonstrations of computational workflows for quantum-centric, vibrational property predictions are still lacking. Here, we introduce a methodology for performing anharmonic vibrational structure calculations that can be deployed in a hybrid, quantum-classical mode. Starting from a quartic force field, the approach combines a Vibrational Self-Consistent Field (VSCF) with VCI in either Full, Selected (S-VCI), or Symmetry-Adapted (SA-VCI) mode. In S-VCI, an Epstein-Nesbet perturbative screening significantly reduces the configuration space while retaining high predictive accuracy. A state-list input enables the integration of externally generated vibrational configurations as a seed space. As a proof-of-concept, we demonstrate a hybrid, quantum-classical computational workflow, in which a quantum sampling algorithm provides the seed. Our vibrational wave function analysis package ViBra, equipped with a graphical interface, is available at https://github.com/raphafe96/ViBra.
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All authors Raphael F. Ligorio, Marco Antonio Barroca, Alan Duriez, Mathias B. Steiner

Mesoscale and Nanoscale Physics

Radiative spin caloritronics in nonreciprocal many-body systems

Philippe Ben-Abdallah

We predict the spin thermal Hall effect in nonreciprocal magneto-optical many-body systems, in which a longitudinal radiative heat current generates a transverse accumulation of the spin angular momentum carried by thermal photons. We show that this effect and the inverse spin thermal Hall effect constitute an Onsager-Casimir reciprocal pair, thereby establishing heat and photon spin as coupled transport channels in nonreciprocal photonic systems. The second law of thermodynamics imposes fundamental bounds on the spin-heat coupling, leading to a thermal-spin figure of merit that quantifies the efficiency of radiative spin-heat conversion. Our results establish a complete thermodynamic framework for photon spin caloritronics and lay the conceptual foundations for spin-controlled thermal radiation and nonreciprocal photonic thermal devices.
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