Strongly Correlated Electrons
Geng-Dong Zhou and Zhi-Da Song
Entanglement entropy (EE) is commonly studied using real-space bipartitions. We show that, in
quantum impurity models, an energy-space bipartition, equivalent to the momentum-space bipartition of the bath, can display universal behavior. Motivated by poor man's scaling, we logarithmically discretize the bath and partition it into high- and low-energy sectors. For models with
Fermi-
liquid fixed points, including the Anderson model and fully screened or underscreened Kondo models, the low-energy EE flows to constants independent of model parameters. These constants are integer multiples of $\ln 2$ plus corrections that depend only on the logarithmic discretization parameter $\Lambda$. We show that scale invariance of the fixed-point wavefunction in energy space maps to effective translation invariance along a one-dimensional chain, allowing the fixed points to be classified by one-dimensional topological band theory. With low-energy
chiral symmetry, each $\ln 2$ contribution originates from a topological edge mode. We also study transitions between distinct
Fermi-
liquid fixed points using the local-singlet–Kondo-singlet transition in a two-orbital Anderson model driven by an inter-orbital
antiferromagnetic coupling. The local-singlet phase has an effectively decoupled
impurity and nearly vanishing EE, whereas the Kondo-singlet phase has finite EE larger than $\ln 2$ per
spin and orbital. When
chiral symmetry holds at low energies, this distinction corresponds to a topological transition of the effective bath chain. At the non-
Fermi-
liquid critical point, the EE develops an unstable plateau. Its $\Lambda$ dependence resembles that of the overscreened two-channel Kondo model, supporting universality within the same non-
Fermi-
liquid universality class.
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Superconductivity
Anomalous Microwave Response in YBCO Resonators beyond the Two-Level-System Model
Kaiwen Zheng, Nathan J. Johnson, Nathan T. Thobaben et al. (+5 more)
We report the microwave response of coplanar-waveguide (CPW) resonators fabricated from $\mathrm{YBa_2Cu_3O_{7-\delta}}$ (YBCO) thin films over temperatures from approximately $70~\mathrm{mK}$ to $40~\mathrm{K}$. The resonators exhibit internal quality factors $Q_\mathrm{i}$ in the range of $4\times10^3$ to $10^4$ at 70 mK, which increase to a maximum of approximately $8\times10^3$ to $1.2\times10^4$ near $6~\mathrm{K}$. At low temperatures, both $Q_\mathrm{i}$ and the fractional shift of the resonance frequency $\Delta f_\mathrm{r}/f_\mathrm{r}$ increases with temperature, qualitatively resembling behavior commonly associated with two-level-system (TLS) defects. However, neither response saturates on the temperature scale set by the resonator frequency, and the loss exhibits no observable microwave-power dependence. We show that low-temperature frequency upturn may be better described by an additional paramagnetic response associated with defect-induced local moments or Andreev bound states, while the low-temperature loss follows an approximately logarithmic temperature dependence whose microscopic origin remains unresolved. These measurements establish the millikelvin performance of patterned YBCO resonators and show that their low-temperature response cannot be understood within the conventional TLS framework alone.
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All authors Kaiwen Zheng, Nathan J. Johnson, Nathan T. Thobaben, Sidharth Duthaluru, Haochen Shen, Denae T. Cherry, David S. Wisbey, Kater W. Murch
High Energy Astrophysical Phenomena
Binary neutron star populations across cosmic time: the impact of binary stellar evolution uncertainties
Mathieu Venet and Irina Dvorkin
We investigate the impact of uncertainties in binary
stellar evolution on the formation efficiency and cosmological merger rate of BNS systems. In particular, we aim to determine whether robust signatures of binary
evolution can be identified across a broad range of
metallicities. We perform a systematic exploration of 72 binary
evolution models using the population synthesis code
COSMIC. We vary four key parameters controlling the onset and efficiency of common-envelope
evolution, the natal kick prescription, and the treatment of kicks during the common envelope phase. For each model, we compute the BNS formation efficiency and cosmological merger rate using several prescriptions for the
cosmic metallicity-
redshift relation. We identify characteristic features in the
metallicity dependence of the BNS formation efficiency that arise from specific evolutionary processes. These include the onset of first-
giant-branch skipping at low
metallicity and a non-monotonic
evolution between $Z=10^{-3}$ and $7.5\times 10^{-3}$. All models also predict a bimodal distribution of BNS progenitor masses associated with two distinct formation channels. The common envelope ejection efficiency and natal kick prescription remain the dominant sources of uncertainty, producing variations of several orders of magnitude in both the BNS formation efficiency and the cosmological merger rate. Finally, we show that different combinations of binary-
evolution parameters can produce similar merger-rate histories, highlighting significant degeneracies among population-synthesis models. Current gravitational-wave observations can rule out only the least efficient formation scenarios. Breaking these degeneracies will require larger samples of BNS mergers expected from future third-generation gravitational-wave observatories, and improved observational constraints on the
evolution of
metallicity across
cosmic time.
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Astrophysics of Galaxies
Cosmic Pairs: A DESI Census of Dual and Offset AGN as Precursors to Massive Black Hole Binaries
Ekaterine Dadiani, Antonella Palmese, Yihao Zhou et al. (+52 more)
We present a systematic census of dual and offset active
galactic nuclei (AGN) using spectroscopic data from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI). After correcting for observational systematics, our final sample contains $>7,000$ dual AGN and 27,000
galaxy pairs containing one AGN over the
redshift range $0 \lesssim z \lesssim 3.6$. This sample expands the known dual AGN sample by $\sim 1-2$ orders of magnitude at $0.2 \lesssim z \lesssim 0.4$, includes $\sim 50$
dwarf dual AGN candidates in a regime where only a handful were previously known, and triples the census at $z>2$. Dual AGN are preferentially found at small separations, consistent with merger-driven triggering of AGN activity. The two members of a pair differ in their
star formation response: the more massive (primary) host changes little with separation, while the less massive (secondary) lies $\sim 0.3$ dex above matched inactive and one-AGN companions at the same projected separation in main-sequence offset. Using ASTRID simulations, we predict that the fraction of DESI dual AGN whose central black holes will merge by $z \sim 0$ increases with
redshift, reaching $\sim 76\%$ by $z \sim 2$, while the fraction producing LISA-detectable mergers peaks at $\sim 37\%$ near $z \sim 0.9$. These results provide the largest uniformly selected spectroscopic sample of kpc-scale dual and offset AGN candidates from a single survey, connecting their host-
galaxy and AGN demographics to the progenitor population of massive black hole mergers detectable by LISA.
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All authors Ekaterine Dadiani, Antonella Palmese, Yihao Zhou, Nianyi Chen, Tiziana Di Matteo, Alejandro Eróstegui, Mar Mezcua, Jessica Nicole Aguilar, Steven Ahlen, Stephen Bailey, Florian Beutler, Davide Bianchi, David Brooks, Todd Claybaugh, Axel de la Macorra, Arjun Dey, Biprateep Dey, Peter Doel, Victoria A. Fawcett, Benjamin Floyd, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Mustapha Ishak, Robert Kehoe, Anthony Kremin, Ofer Lahav, Andrew Lambert, Martin Landriau, Laurent Le Guillou, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Seshadri Nadathur, Enrique Paillas, Will J. Percival, Francisco Prada, Ignasi Pérez-Ràfols, Ragadeepika Pucha, Corentin Ravoux, Graziano Rossi, Rossana Ruggeri, Eusebio Sanchez, Christoph Saulder, David Schlegel, Michael Schubnell, Hee-Jong Seo, Joseph Harry Silber, Małgorzata Siudek, Gregory Tarlé, Benjamin Alan Weaver, DESI Collaboration
Quantum Physics
Area-Information Trade-Offs in Acceleration Radiation from Atoms Falling into Black Holes
Yusef Maleki, Gustavo Valdivia-Mera, Carlos R. Ordonez et al. (+2 more)
We develop a
geometric theory of information processing in the Horizon-brightened acceleration radiation (HBAR) channel, in which the radiative horizon-area change provides an
entropy budget for the information carried by the radiation field. Building on the
quantum-optical description of atom–field interactions near the horizon and the resulting HBAR thermodynamic correspondence, we derive area-cost laws in the near-steady, thermally saturated regime. The accessible classical information and the mutual information generated between the radiation field and its environment are bounded by the associated radiative horizon-area budget. Reliability is incorporated through Fano's inequality, which translates a prescribed decoding error probability into an area requirement. We further derive Fisher-information speed limits that constrain the statistical
evolution of the radiation field and place a lower bound on the duration required for correlation generation. Together, these results establish a bits-per-area principle linking black-hole thermodynamics, information geometry, and
quantum information in the HBAR framework.
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All authors Yusef Maleki, Gustavo Valdivia-Mera, Carlos R. Ordonez, Horacio E. Camblong, Marlan O. Scully
Astrophysics of Galaxies
Exploring the Limits of Spectral Line Stacking in Spectral Line Data and Application Toward the Detection of Bulk $^{13}$C Enrichment of Aromatics in TMC-1
Miya Duffy, Ryan A. Loomis, Martin S. Holdren et al. (+9 more)
The formation history of polycyclic aromatic hydrocarbons (PAHs) in the interstellar medium remains a topic of active debate, with proposed mechanisms ranging from high-temperature
stellar ejecta processes to low-temperature chemistry within molecular clouds. Recently, the identification of small PAHs in the cold, dark cloud TMC-1 has provided some circumstantial evidence of the latter. If these are formed in situ, their isotopic ratios, particularly $^{12}$C/$^{13}$C, should reflect the local, bulk material of the molecular cloud; in contrast, PAHs formed in the circumstellar envelopes of evolved
stars may show enhanced $^{13}$C abundances. The expected
radio signals of these $^{13}$C substituted species will be faint, and thus we conducted a detailed proof-of-concept analysis examining whether spectral line stacking and matched filtering techniques can robustly retrieve signal from multiple singly substituted $^{13}$C isotopologues in aggregate. We find that while retrieved signal decreases in the limit of spectral line confusion, false-positive detections are exceedingly improbable at the adopted 5$\sigma$ matched filter response detection threshold. We then demonstrate the technique on actual observational data of isotopologues of HC$_9$N toward TMC-1. Finally, we show using synthetic data that if laboratory rotational spectra of all singly substituted $^{13}$C isotopologues of cyanonaphthalene and cyanopyrene isomers existed, current observations of TMC-1 would be sensitive enough to discriminate between a local, bulk $^{12}$C/$^{13}$C ratio and one with an enhanced $^{13}$C abundance suggestive of inheritance.
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All authors Miya Duffy, Ryan A. Loomis, Martin S. Holdren, Andrew Lipnicky, D. Archie Stewart, Gabi Wenzel, Ci Xue, Annapoorani Hariharan, Ilsa R. Cooke, Anthony J. Remijan, Michael C. McCarthy, Brett A. McGuire
Strongly Correlated Electrons
Excited state optimization for strongly correlated quantum defects using ensemble variational Monte Carlo
Kevin G. Kleiner and Lucas K. Wagner
Using the recently introduced ensemble variational Monte Carlo (VMC), we study optimized wave functions for strongly correlated point defects, including nitrogen-vacancy and silicon-vacancy centers in diamond and substitutional iron and chromium
impurities in aluminum nitride. We study the effects of fully optimized determinant expansion parameters, orbitals, and Jastrow correlation factors on these systems. We find that orbitals from the hybrid functional PBE0 are much better (have lower objective functional) than semilocal PBE, which results in changes in the excitation energies up to 0.5 eV. Further improvements can be made by directly optimizing the objective functional, resulting in changes in excitation energies up to 0.2 eV. The most important parameter varies from defect to defect, reinforcing the necessity of optimizing all parameters to obtain accurate excited states in strongly correlated defects.
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Materials Science
Evolution of Irradiation-Induced Defect Landscape through Edge Dislocation and Vacancy Loop Interactions in Tungsten
Soumya Mishra and Suchandrima Das
Structural materials in fusion reactors develop irradiation-induced defect populations that govern their mechanical behaviour. While advanced microscopy provides detailed characterisation of such defects, their dynamic
evolution through dislocation-defect interactions during plastic deformation remains unresolved. Here, we address this gap using molecular dynamics simulations to resolve dislocation-defect interaction mechanisms and the resulting
evolution of defect morphology and obstacle strength. Tungsten is the leading candidate
plasma-facing material for fusion reactors, where vacancy loops are common irradiation defects. Using vacancy loops as a prototype defect, we systematically investigate their interactions with edge dislocations by varying loop size, orientation, and dislocation-loop intersection position. Parallel loops exhibit three distinct
evolution pathways: complete annihilation, transformation into weaker remnant defects, or defect transport, depending on the intersection position and loop size. In contrast, inclined closed loops undergo dislocation reactions that produce sessile $\langle010\rangle$ dislocation segments, leading to substantially higher obstacle strengths with little sensitivity to the intersection position. Repeated dislocation interactions further demonstrate that the defect landscape is not static: remnant defects can persist, transform, or lose their ability to impede subsequent dislocations, depending on the preceding interaction mechanism. These results show that the obstacle strength of a vacancy loop is governed not only by its initial size and orientation, but also by its interaction history and the resulting defect structure.
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Materials Science
Machine Learning for Designing Undesignable Metal-Organic Frameworks
Satya Kokonda
Many crucial processes are too complex for computational modeling, requiring experimentation to identify promising materials. Here, a methodology for material design is presented, while photocatalysis is presented as a specific case-study. Metal-Organic Frameworks (MOFs) are a subset of highly promising porous nanomaterials, used in a variety of unmodellable applications. Reinforcement learning generated 60,000 novel MOFs optimized for CO/H20 selectivity. A predictor funnel system was created, iteratively removing low-scoring MOFs to 10,986 potential candidates, improving computational efficiency by 276%. While trained
Crystal Graph Convolutional Neural Network (CGCNN) models predicted features for creating a fitness function incorporating stability, catalytic ability, material cost, sustainability, and adsorption while allowing the inclusion of application specific design criterion. This designed function provides a computational method to model photocatalytic performance- and filtered down to two promising MOFs which each pass a myriad of synthesis criteria, first a Cr-based MOF with photocatalyst score 230% higher than the control. Second, a Zn-based MOF outperforms the best control across all relevant metrics, demonstrating robustness against variable fitness functions. This work designed 20 materials, each 125% better than the control for this application. Furthermore, analysis revealed insightful design patterns, such as the significant influence of metal cluster N262 on catalytic performance, providing a method for future work to narrow the chemical space. By incorporating industrially applicable features such as cost or stability of the material, this work successfully designs industrially promising materials in otherwise unmodellable processes such as drug delivery, while paving a method for multi-objective optimization incorporating 260% more features than prior work.
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High Energy Physics (Phenomenology)
Photon-Tagged Energy Flow in Inclusive Endpoint $B$ Decays
Shuai Zhao
We introduce a $B$-decay tagged energy correlator (BTEC) to resolve the angular structure of energy flow in inclusive $B$ decays in the endpoint region, focusing on the direct-
photon contribution to $\overline B\to X_s\gamma$. At leading power and at the natural collinear angular scale $\tau\sim s\sim Q\Lambda_{\rm QCD}$, we derive a factorization relation involving the standard hard coefficient and $B$-
meson shape function together with a new measured
quark jet function; no new leading-power nonperturbative function is introduced. We calculate the measured jet function at one-loop accuracy and verify that its angular integral reproduces the standard inclusive
quark jet function. For the central Bosch–Lange–Neubert–Paz parameter set, an illustrative
benchmark gives $3 - 16\%$ migration outside the fixed angular cuts $\tau_c=2 - 4~{\rm GeV}^2$. With an independently constrained shape function, the angular cumulatives provide a closure test of leading-power endpoint factorization and are sensitive to direct-$O_7$ power corrections and resolved-
photon effects. The BTEC thereby adds information on the angular structure of the inclusive
recoil jet beyond the ordinary
photon spectrum and may improve signal–background discrimination when their energy-flow profiles differ.
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General Relativity and Quantum Cosmology
Quark Stars in $f(T,\mathcal{T}) $ Gravity: Structure, Stability, and Observational Constraints
Takol Tangphati, Ayan Banerjee, Izzet Sakalli et al. (+2 more)
Quark stars-hypothetical compact
stars made entirely of deconfined
quark matter-offer a clean testing ground for
gravity beyond general relativity. We study their structure in $f(T,\mathcal{T})$
gravity, a teleparallel theory in which torsion is coupled directly to the trace of the energy-momentum tensor through a single constant coupling. Using the standard MIT bag description of
quark matter, we solve the modified
stellar structure equations and follow how the mass, radius, compactness, and surface
redshift respond as the coupling is varied across its full admissible range. The maximum mass turns out to depend on the coupling in a non-monotonic way: it rises above the general relativity value, peaks near 2.02
solar masses at a moderate positive coupling, and then falls steeply as the coupling approaches a critical value at which the structure equations become singular. The two-
solar-mass
pulsar constraint is satisfied within a finite window of positive couplings. All configurations on the candidate stable branch satisfy causality and remain below the standard general-relativistic compactness and surface-
redshift benchmarks.
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All authors Takol Tangphati, Ayan Banerjee, Izzet Sakalli, Sayantan Ghosh, Aseel Smerat
Earth and Planetary Astrophysics
High-Resolution Dayside Spectroscopy of the Ultra-Hot Jupiter WASP-178b with GHOST/Gemini South
Caitlin E. Bell, Emily K. Deibert, Adam B. Langeveld et al. (+4 more)
We present high-resolution dayside spectroscopy of the ultra-hot Jupiter WASP-178b obtained with the Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South Observatory. The observations cover pre- and post-eclipse orbital phases, lasting approximately 9 hours in total, and represent the first published high-resolution optical dayside emission spectroscopy of WASP-178b's atmosphere, complementing previous near-infrared dayside spectroscopy. We verify the presence of a thermal inversion in the dayside atmosphere with a high-significance (8.3$\sigma$) detection of neutral iron emission via the Doppler cross-correlation technique, alongside hints of neutral Si and Ca emission. We also carry out model injection/recovery tests for other atmospheric species, which indicate that we do not expect to detect the majority of species searched for in this work, assuming our models are accurate representations of the
planet's atmosphere. Finally, we place our results into context with previous work, showing how our tentative detection of neutral Si complements existing space-based observations and adds a new data point to previous detections of Si in ultra-hot Jupiter atmospheres. Our high-resolution observations provide important context about the dayside of WASP-178b, shedding light on 3D atmospheric processes and the extreme conditions present in ultra-hot Jupiter atmospheres.
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All authors Caitlin E. Bell, Emily K. Deibert, Adam B. Langeveld, Ernst de Mooij, Ray Jayawardhana, Laura Flagg, Jake D. Turner
Optics
Fresnel Drag in the Homogenization Limit with Space-Time-Modulated Wire Media
A. B. Yakovlev, M. G. Silveirinha, A. Pal et al. (+1 more)
Space-time modulations of the electromagnetic response offer new opportunities for wave control. In particular, such systems can emulate moving-medium responses and the associated Fresnel drag in the homogenization limit. Existing approaches require the simultaneous microscopic modulation of both permittivity and permeability, which is difficult to realize in practice. Here, we show that modulating a metallic response overcomes this limitation and enables strong moving-medium-like effects using purely electric modulation. We illustrate this mechanism with a space-time-modulated wire medium, described through Lorentz transformations and quasi-static homogenization. The resulting effective medium is nonreciprocal and bianisotropic and supports a pronounced synthetic Fresnel-drag effect. For a finite-thickness slab, this response leads to nonreciprocal scattering while preserving global energy conservation for propagating waves. Remarkably, the synthetic Fresnel drag also produces velocity-dependent reflection and transmission Goos-Hänchen shifts, providing a direct signature of the effective motion.
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All authors A. B. Yakovlev, M. G. Silveirinha, A. Pal, M. H. Zadeh
High Energy Physics (Theory)
Spectator Axions in String Inflation and Primordial Black Holes
Michele Cicoli, Dario L. Lorenzoni, Evan McDonough et al. (+1 more)
We study the impact of light spectator
axions on the seeding of
primordial black holes (PBHs) during inflation in string theory.
Primordial black holes exhibit unique and novel phenomenology, and may constitute the observed dark matter.
Cosmic inflation provides a mechanism for producing them, but such inflation models typically feature Planckian field excursions, necessitating an ultraviolet completion into
quantum gravity. String theory provides a natural framework for doing so, and indeed Fibre Inflation has been shown to produce PBHs while satisfying constraints from
cosmic microwave background data. In this work we study the dynamics of
axions during Fibre Inflation, and find a diverse and rich set of possibilities, including turns in field space and enhancement of
primordial perturbations. We find that across most of parameter space, notably an
axion with a far sub-Planckian decay constant $f\ll M_{\rm Pl}$, there is a negligible impact on the power spectrum of
curvature perturbations, indicating an overall robustness of the model. On the other hand, an
axion with a larger but still sub-Planckian decay constant, $f\gtrsim {\cal O}(0.1) M_{\rm Pl}$, and an exponentially small prefactor of its non-perturbative potential, can enhance the growth of perturbations, making it easier to achieve the amplification needed to seed PBHs, effectively realizing
axion-assisted PBHs in string theory.
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All authors Michele Cicoli, Dario L. Lorenzoni, Evan McDonough, Francisco G. Pedro
Quantum Physics
Geometry-Induced Domain-Wall Pinning and $\mathbb{Z}_2$ Asymmetry in Nominally One-Dimensional Rydberg Arrays
Elijah Pelofske, Frank Barrows and Cristiano Nisoli
We perform experiments on QuEra's neutral-Rydberg-atom Aquila
quantum computer, using quasi-adiabatic
evolution on 1-dimensional models. We use hardware fine-tuning to balance the measurement statistics close to zero net magnetization, in two different
geometric outlines: one closed triangular model with 33 atoms, and one 47-atom square with an engineered atom vacancy. The nature of this processor restricts the geometry of the atoms that can be programmed to a 2D plane. We report effects not predicted by the pure 1D Ising model, such as pinning of domain walls and $\mathbb{Z}_2$
symmetry breaking due to the interplay between van der Waals interactions and the Rydberg blockade. In particular, atoms around the atom vacancy and at the vertices of the 1-dimensional square-outline model strongly prefer the Rydberg state, leading to the effective model having a
ferromagnetic bond across the vacancy.
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Instrumentation and Methods for Astrophysics
Laboratory characterization of iLocater
Marcelo Tala Pinto, Marshall C. Johnson, Julia Brady et al. (+18 more)
iLocater is a diffraction-limited, fiber-fed spectrograph designed for the Large Binocular
Telescope (LBT), which targets high-precision radial velocity measurements in the near-infrared. Prior to deployment, comprehensive laboratory characterization was essential to validate instrument performance and inform
alignment strategies. This paper presents results from four key areas of lab characterization: (1) adjustment and optimization of detector orientation to optimize spectrum
alignment with the detector pixel grid across the focal plane; (2) the design and installation of a LED illumination source to enable high-fidelity flat-fields; (3) a model-based focusing methodology using OpticStudio image simulations to optimize the optical
alignment of the spectrograph; and (4) assessment of instrument mechanical and optical stability under laboratory conditions. Together, these efforts established baseline performance metrics and demonstrated instrument readiness for delivery and on-sky commissioning.
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All authors Marcelo Tala Pinto, Marshall C. Johnson, Julia Brady, Xavier Lesley-Saldaña, Jonathan Crass, Allie Renshaw, Michael Engelman, Brian Sands, Daniel Pappalardo, Christian Schwab, Julian Stürmer, Dane Zielinski-Nicolson, Stanimir Letchev, Matheus J. Castro, Thomas Legero, Ondrej Kitzler, Jacob Pember, Richard Pogge, Justin R. Crepp, Andrew Bechter, Eric Bechter
Strongly Correlated Electrons
Flat-band formation and chiral superconductivity in driven topological insulators
Suman Jyoti De, Leo Goutte, Kartiek Agarwal et al. (+1 more)
We demonstrate that circularly polarized light can be used to Floquet-engineer nearly flat or Mexican-hat like electronic bands on the surface of three-dimensional topological
insulators (3D TIs), which under suitable conditions, can support topological superconductivity via purely repulsive Coulomb interactions. The driving acts not merely by gapping out the Dirac cone on the surface of the 3D TI, but can be used to diminish, and even flip in sign, the intrinsic
curvature of the surface state dispersion away from the Dirac point. Using parameters for canonical 3D TIs, we find that the flat band limit is attained for reasonable electric fields and the bands realized by changing the strength of the driving field have a similar energetic and spatial profile to those obtained in rhombohedral
graphene under varying displacement field, where the case for superconductivity with purely repulsive interactions has recently been made. We find that, with the aid of appropriately placed screening metallic gate, one can obtain $T_c \sim 7 $K in this setup while avoiding Wigner crystallization for low electron densities in the range of $10^{11}-10^{12}/\text{cm}^2$.
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All authors Suman Jyoti De, Leo Goutte, Kartiek Agarwal, T. Pereg-Barnea
Earth and Planetary Astrophysics
A Systematic Trend in the Observed vs. Predicted Radii of Transiting Brown Dwarfs
Thomas G. Beatty
Transiting brown
dwarfs provide a direct empirical test of substellar evolutionary models, and with more than 50 now known we can carry out this test at the population level. We compared the observed masses and radii of 31 field-age, weakly irradiated transiting brown
dwarfs to the Sonora Diamondback, Sonora Bobcat, and ATMO 2020 grids, and a subset of 23 of them to the irradiated models of Mukherjee et al. (2026). In every comparison we find a radius-dependent trend, with fits of $R_{\rm pred}$ versus $R_{\rm obs}$ yielding slopes of $0.3{-}0.4$, shallower than the one-to-one relation at $3.7{-}8\sigma$. The mean inflation is $5{-}14\%$ depending on the grid, reaching $\sim20\%$ among the largest objects. We also measure an intrinsic dispersion of $8{-}12\%$, two to three times the measurement uncertainty. While the mean inflation offset varies by a factor of three among grids, this dispersion does not, indicating that it is a property of the population and not the models. We find no correlation with mass,
equilibrium temperature, orbital separation,
tidal heating rate, or age, and only a marginal ($1.7\sigma$) trend with host-
star metallicity. Most notable is the absence of any trend with irradiation, which argues against hot Jupiter-like
stellar heating as the primary cause. We instead suggest that brown
dwarfs span a wider range of atmospheric boundary conditions than current grids represent. The brown
dwarf radius inflation is comparable to that in fully convective M
dwarfs, and it is likely the transiting counterpart to the luminosity discrepancies seen in dynamical-mass
benchmarks. If the trend extends below the deuterium-burning limit, it would bias directly imaged
planet mass estimates, overestimating luminosity-age masses by several to ten percent and requiring spectroscopic-
gravity masses to be revised upward by $\sim20{-}45\%$.
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General Relativity and Quantum Cosmology
Gauge versus (hidden) physical symmetries of FLRW cosmologies
Andrea Calcinari, Adrià Delhom, Federico Greco et al. (+2 more)
In generally covariant theories,
evolution in coordinate time is a gauge transformation, so that a
symmetry made manifest in a gauge-fixed description need not be a
symmetry of the physical dynamics. At the same time, deparametrisation removes gauge redundancies but may hide physical
symmetries, in particular those that depend on the chosen physical clock. We investigate the relation between gauge and hidden physical
symmetries in flat FLRW geometry coupled to an arbitrary number $n$ of free massless scalar fields. We show that conformal Killing vectors of the minisuperspace metric generate conserved charges that are Dirac observables and hence gauge-invariant. Their Poisson
algebra realises the maximal conformal
algebra $\mathfrak{conf}(n,1)\simeq\mathfrak{so}(n+1,2)$, extending previous single-field results to arbitrary $n$. We then revisit the Eisenhart–Duval lift in a family of gauges and show that the resulting
symmetry algebra is gauge dependent. Only in the harmonic gauge does the
algebra enlarge to the Schrödinger
algebra, which is thus not a physical
symmetry. Finally, we show that deparametrisation maps the lifted charges to gauge-invariant Dirac observables, which always realise a subalgebra of $\mathfrak{conf}(n,1)$, recovering it in full in the harmonic gauge. Our results provide a systematic framework for disentangling gauge from physical
symmetries in minisuperspace models, recovering charges to which reduced phase-space descriptions are structurally blind, and extending naturally to models with potentials.
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All authors Andrea Calcinari, Adrià Delhom, Federico Greco, Daniele Oriti, Néstor Rivero
Optics
Physics-Informed Neural Networks for 2D Plane Wave Scattering in Arbitrary Dielectric Structures
Zheng-Yu Huang, Yu Tian, Jing-Wen Zhang et al. (+1 more)
In this paper, we introduce a meshless physics-informed neural network based computational framework for solving two-dimensional electromagnetic wave scattering in inhomogeneous media. The framework embeds frequency-domain Maxwell equations and radiation boundary conditions directly into the neural network loss function, enabling accurate prediction of scattered fields for both transverse
magnetic (TM) and transverse electric (TE) polarizations across various dielectric configurations. Application of the method to single-cylinder, concentric multilayer cylindrical shells, three arbitrarily arranged cylinders, and composite irregular structures demonstrates that for the TM polarization, all relative $L^{2}$ errors mostly remain at particularly low levels of $\le0.1$. For the TE polarization, sharp variations of the dielectric properties of scatterers lead to singularities in the governing equations, which result in decreased accuracy of the method. This challenge is overcome by introducing at dielectric boundaries a
hyperbolic-tangent smoothing function. This procedure significantly improves the accuracy of the method, with the corresponding results closely matching the predictions of the finite-difference time-domain method. This framework exhibits stable convergence behavior across all of the investigated configurations, thus confirming its robustness and scalability to complex electromagnetic scattering problems.
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All authors Zheng-Yu Huang, Yu Tian, Jing-Wen Zhang, Nicolae C. Panoiu
Optics
New techniques for high-resolution imaging and high-precision wavefront sensing via masked-aperture interferometry
Nithyanandan Thyagarajan, Bojan Nikolic, Chris Carilli et al. (+2 more)
Achieving high-angular-resolution imaging on subarcsecond scales is fundamentally limited by wavefront aberrations imparted by the propagation medium and by optical elements along the light path. Accurate recovery of source structure at these fine angular scales therefore relies on precise, real-time sensing and correction of wavefront aberrations. Drawing inspiration from
radio interferometry, we have developed different approaches using masked apertures that directly measure both the amplitude and phase of the distortions to the electromagnetic wavefront while simultaneously reconstructing the underlying source structure. First is
radio interferometry style self-calibration which can recover the complex electric field aberrations across the aperture with subarcsecond phase accuracy, equivalent to nanometer-level precision in optical pathlength, and simultaneously reconstruct the source structure with milliarcsecond (sub-micron) accuracy. Second is closure invariant-based source reconstruction which allows to bypass self-calibration and errors therein entirely while achieving comparable fidelity in the recovered source structure. These methods have been validated on the ALBA synchrotron beamline. Together, these methods provide a reliable framework for nanometre-scale high-precision wavefront sensing and subarcsecond-scale high angular resolution imaging, enabling new possibilities for masked-aperture interferometry. Potential applications span laboratory and synchrotron facilities to astronomy, including beam diagnostics in the Large
Hadron Collider and masked-aperture interferometry on space
telescopes such as the James Webb Space
Telescope.
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All authors Nithyanandan Thyagarajan, Bojan Nikolic, Chris Carilli, Laura Torino, Ubaldo Iriso
High Energy Physics (Experiment)
First Experimental Bounds on Transverse Plasmon Solar Axions with ANAIS-112
S. J. Hollick, M. Giannotti, J. Ruz et al. (+16 more)
Solar axion-like particles (ALPs) can be resonantly produced through the conversion of transverse plasmons in the
magnetic field of the
solar interior, introducing a production mechanism complementary to the conventional Primakoff process. In this Letter, we report the first experimental search for
solar ALPs produced through this mechanism. Using an exposure of 625.75 kg$\times$yr from ANAIS-112, we search for the annual modulation of the flux induced by the variation of the Earth–Sun distance, assuming detection through inverse Primakoff conversion in the detector. Modulation amplitudes fitted in 1 keV bins between 1–20 keV are consistent with the absence of modulation, yielding the first constraints on the
axion–
photon coupling that include the resonant transverse-plasmon flux, $g_{a\gamma} < 1.32\times 10^{-9} \mathrm{GeV}^{-1}$ (90% C.L.) at $m_a \simeq 150$ eV. This previously unexplored production channel extends the sensitivity of ANAIS-112 in the mass range 35–280 eV, where, for the expected
solar magnetic-field models, the transverse-plasmon flux exceeds the Primakoff flux by up to two orders of magnitude.
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All authors S. J. Hollick, M. Giannotti, J. Ruz, J. K. Vogel, R. M. Alkaddah, J. Amaré, J. Apilluelo, S. Bharat, S. Cebrián, D. Cintas, I. Coarasa, E. García, M. Martínez, Y. Ortigoza, A. Ortiz de Solórzano, T. Pardo, J. Puimedón, M. L. Sarsa, C. Seoane
High Energy Physics (Theory)
NLSM amplitudes from a quartic two-derivative theory
Qu Cao, Zhenqi Han and Fan Zhu
We revisit the well-known nonlinear sigma model (NLSM), an effective field theory describing the scattering of $\mathrm{SU}(N)$ Goldstone
bosons and characterized by an infinite tower of two-derivative interactions. We introduce a local scalar Lagrangian involving two scalar fields $\psi^\pm$ carrying opposite "polarities", whose interacting part consists of a single
polynomial quartic two-derivative operator, and prove that it reproduces planar NLSM amplitudes at all loop orders. This quartic two-derivative formulation reveals a previously hidden simplicity of the NLSM: its Feynman rules involve only a single quartic interaction vertex, making the Adler zero and the leading double-soft factor manifest at all loop orders on generalized cuts and significantly improving the efficiency of high-multiplicity computations. We also suggest a possible analogous description of the NLSM +$ \phi^3 $ theory in terms of a finite tower of local interactions.
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General Relativity and Quantum Cosmology
Inflation in unimodular loop quantum cosmology
Steffen Gielen and Rita B. Neves
We study inflation in the setting of unimodular loop
quantum cosmology, where time
evolution is defined in unimodular time rather than with respect to a free, massless scalar field as is standard in loop
quantum cosmology. The unimodular setting leads to a natural Schrödinger time
evolution in a time coordinate with clear
geometric meaning, defined independently of any particular matter content; an inflaton can be included but is not needed as a clock. We review the unimodular version of loop
quantum cosmology and comment on possible connections to full (unimodular) loop
quantum gravity. Then, focusing on semiclassical effective equations, we derive analytical solutions in simple cases such as a constant potential, emphasising the use of a unimodular time coordinate. We also discuss numerical solutions for phenomenologically interesting cases such as a quadratic potential and Starobinsky inflation, comparing different possible choices of initial conditions. In particular, we show that choosing an $\alpha$-attractor potential allows for models of a bounce either dominated by kinetic or potential energy, which are compatible with observations while potentially including observable imprints of the
quantum-
gravity regime.
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General Relativity and Quantum Cosmology
Nonlinear Dynamics near the Threshold of Gravitational Collapse
Jaime Redondo-Yuste and Josu C. Aurrekoetxea
Perturbation theory is an essential tool to model and interpret gravitational dynamics, for example, binary black hole mergers. Therefore it is also crucial to precisely understand its regimes of validity. The collapse of a scalar field under its own self-
gravity provides a clean laboratory to study these questions. By varying the field's initial amplitude we can transition smoothly between a perturbative regime, where the field scatters in an approximately flat spacetime; and a nonperturbative regime, where a black hole forms in finite time. In this work, we use numerical relativity simulations of this set-up to investigate the accuracy of a perturbative expansion around flat spacetime, including next-to-next-to-leading order effects. Our simulations show deviations from these perturbative predictions before black hole formation, once the maximum luminosity of the process is sufficiently large, $L_{peak} \sim 10^{-2} L_{Planck}$. We characterize these nonlinear effects including a
redshift of the driving frequency and a power-law spectral amplitude, which we show is consistent with approximate discrete self-similarity. These results provide a step forward towards understanding the limits of perturbative expansions in more realistic strong-
gravity phenomena such as non-spherical collapse and high-velocity black hole mergers.
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Quantum Physics
Restrictions on non-Clifford fault tolerance and ruling out beyond-SQL quantum metrology
Constantin Cedillo Vayson de Pradenne, Ishaan Kannan, Harald Putterman et al. (+1 more)
Quantum metrology promises a quadratic speedup over the standard
quantum limit (SQL), but signal-aligned noise is expected to preclude this advantage in realistic settings. A potential route around known no-go results is to encode the sensors in a
quantum code where the physical signal acts transversally as a logical gate. Understanding restrictions on transversal non-Clifford gates is therefore central to both
quantum metrology and fault-tolerant
quantum computation. Here, we prove such restrictions and apply them to transversal sensing. For any stabilizer code of distance $d\ge 3$ supporting a transversal logical action in level $D$ of the Clifford hierarchy, every stabilizer generating set must contain a check of weight at least $2^D$. Moreover, any $r$-level concatenated realization satisfies $r\leq \lfloor \log_2 n/D\rfloor$, forcing $r=1$ and ruling out concatenation when applied to beyond-SQL metrology. We then show that transversal single-
qubit rotations by a small angle $\theta$ can only induce a nontrivial logical action on an $n$-
qubit code if its checks include irreducible stabilizers of weight $\Omega(1/(n|\theta|^2))$. Here, many single-
qubit errors commute with every stabilizer or logical Pauli below this weight and are only detected by a high-weight check, so their syndromes cannot be fault-tolerantly reconstructed from low-weight normalizer measurements. Since beyond-SQL transversal sensing requires $|\theta| = o(n^{-1/2})$, the weight of checks required for syndrome extraction diverges with $n$. Finally, we prove a broader metrological no-go
theorem that avoids the assumptions of the
quantum Cramér-Rao bound: constant-strength signal-aligned noise rules out any asymptotic advantage over the SQL in AC or DC sensing, even with biased
estimators, nonstabilizer or approximate encodings,
quantum memory, intermediate measurements, or adaptive control.
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All authors Constantin Cedillo Vayson de Pradenne, Ishaan Kannan, Harald Putterman, Jordan Cotler
Quantum Physics
Quantum vs Classical Erasure: Equal Bounds but Unequal Costs
Jan Neuser, Jake Xuereb, Pharnam Bakhshinezhad et al. (+1 more)
Irreversibility has a fundamental thermodynamic cost, erasing information inevitably generates heat. This connection is quantified by the Landauer bound, which gives the minimum dissipation needed to erase a single bit of information. While this bound applies in both classical and
quantum settings, it is saturated only in idealised limits of infinite resources. Here, we provide a unified first principles description of finite-resource erasure in both classical and
quantum systems. We begin by proving the communal folklore that in the idealised regime the erasure cost of a bit encoded in a
quantum or classical system is the same. Despite this, we show that their practical implementation differs substantially: achieving comparable erasure quality in
quantum systems requires more control, larger accessible energy gaps and longer operation times. Classical protocols can achieve the erasure of a comparable
quantum protocol under far weaker constraints which we expose in trade-off relations. Our results explain why practical erasure schemes fall short of Landauer's bound and show that classical systems enjoy several fundamental thermodynamic advantages.
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All authors Jan Neuser, Jake Xuereb, Pharnam Bakhshinezhad, Marcus Huber
Statistical Mechanics
From pink to brown: Interaction-driven noise color shift in the Aubry-André Model
S. A. Montes-Camacho and E. J. Torres-Herrera
We revisit the metal-
insulator transition in a one-dimensional
lattice subjected to an on-site quasiperiodic potential, modeled using
spin-1/2 particles with tunable nearest-neighbor interactions. To characterize the transition, we examine the power-spectrum, defined as the squared modulus of the
Fourier transform of consecutive level spacings. In the absence of interactions, the power-spectrum fails to capture clear signatures of the transition, consistently exhibiting brown-noise-like behavior across regimes. In contrast, the interacting case reveals a marked change: the metallic phase displays spectral fluctuations consistent with pink noise, while the insulating phase is characterized by brown noise. These results are supported by analyses of the level spacing distribution and the level number variance. Additionally, we demonstrate that both statistics and the structure of energy eigenstates provide reliable indicators of the transition, in both interacting and non-interacting scenarios.
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Quantum Physics
Quantum State Discrimination With Stabilizer Circuits
Benjamin Stratton, Santiago Zamora and Rafael Chaves
The task of
quantum state discrimination provides an operational characterization of distinguishability and plays a central role in
quantum information science. Since the achievable success probability in
quantum state discrimination depends both on the states being discriminated and on the allowed measurements, it is natural to study discrimination under physically motivated measurement constraints. Here, we investigate minimum-error
quantum state discrimination under measurements implementable by both fixed and adaptive stabilizer
circuits. Given arbitrary stabilizer-state ancillas, we show that fixed stabilizer
circuits provide no additional discrimination power, whereas adaptive
circuits do. Then, focusing on single-
qubit systems, we derive analytical expressions for the success probability across both
circuit classes when supplied with arbitrary (non-stabilizer) ancillas, showing that the performance gap between fixed and adaptive
circuits persists. We further consider discrimination with non-stabilizerness incorporated directly into the measurement operators. Here, the optimization is formulated as a semidefinite program, and analytical bounds interpolating between the stabilizer and Helstrom limits for
qubits are derived. Finally, we illustrate applications in
quantum random access codes and bounds on
unitary synthesis fidelity with a finite number of magic states.
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Cosmology and Nongalactic Astrophysics
Gravitational Waves as a Source of Large-Scale White Noise: New Constraints
Gabriela Barenboim and Albert Stebbins
A
stochastic gravitational wave (GW) background sources a shear in the flow of
cosmic fluid which, through non-linear mode coupling, generates large-scale white noise (LSWN) in the kurvature density field. Building on the LSWN framework of our previous work, we derive the amplitude of this GW-induced LSWN and translate the observational non-detection of LSWN into bounds on the production
redshift and density of
gravity waves. In particular, a minimal constraint on
gravity waves with $z=0$ density parameter $\Omega_\mathrm{GW0}^*$ in frequency band $f_*$ generated at
redshift $z_*$ must satisfy ${z_*}^2\,\Omega_\mathrm{GW0}^*<5\times10^7\,(f_*/\mathrm{nHz})^{3/2}$. This, for example, precludes the
gravity waves recently detected by
pulsar timing arrays \cite{NANOGrav:2023hvm} from being present before $z_*\sim10^8$, long after the
quark hadron phase transition. While orders of magnitude stronger than other constraints on
gravity waves, this is a minimal LSWN constraint as realistic modeling of early universe
gravity wave production, including the granularity of the
gravity-wave sources and the LSWN produced by the associated acoustic waves would probably tighten this constraint by orders of magnitude.
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