Superconductivity
Solid-state reaction synthesis of superconducting refractory-metal germanides for Ge/SiGe quantum devices
Sebastiaan R. Roelofs, Jan Cornelis Wolff, Nick van Loo et al. (+3 more)
Solid-phase reactions offer a route to integrate
superconductors into Ge/SiGe
heterostructures, but forming high-quality superconducting layers near the buried Ge
quantum well remains challenging. We investigate reactions of V, Ta, and Nb with elemental Ge and with the Si$_{0.2}$Ge$_{0.8}$ barrier of Ge/SiGe
heterostructures at processing temperatures of 365-390 $^\circ$C. Cross-sectional electron microscopy and low-temperature electrical transport show that deposition on Ge at 390 $^\circ$C, in which approximately 2 nm metal increments are separated by growth stops for in-situ annealing, produces reactions throughout the deposited films and superconducting transitions at approximately 0.14 K for V-Ge, 2.1 K for Ta-Ge, and 2.8 K for Nb-Ge. The Nb-Ge layer has an out-of-plane critical field of approximately 0.8 T at 2.1 K. In the
heterostructure samples, intermixing is confined to regions approximately 5-12 nm thick near the metal-SiGe interface, leaving a substantial residual metal layer. Microscopy and transport together suggest that this residual film dominates the measured superconducting response. These results establish low-temperature formation of superconducting refractory-metal-Ge layers while identifying the limited interfacial reaction as the principal obstacle to extending this approach toward the buried
quantum well.
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All authors Sebastiaan R. Roelofs, Jan Cornelis Wolff, Nick van Loo, Karina L. Hudson, Giordano Scappucci, Greg P. Mazur
High Energy Physics (Phenomenology)
The decay $\eta_c\to p\bar p\eta$ with meson–baryon final-state interactions
Jing Song, Yu-Shan Ren and Eulogio Oset
We study the decay \(\eta_c\to p\bar{p}\eta\) by combining the SU(3)
flavor structure of the primary production with final-state interactions in the \(p\eta\) and \(\bar{p}\eta\) subsystems, using the
chiral unitary approach. The low-energy \(S_{11}\) dynamics, including the dynamically generated \(N^*(1535)\), is incorporated into the complete coupled-channel amplitude, and a phenomenological \(N^*(1895)\) contribution is included coherently. The \(p\eta\) and \(\bar{p}\eta\) invariant-mass distributions are well described, and the \(p\bar{p}\) distribution is predicted as a kinematic reflection of the \(\eta N\) dynamics. The results support the dynamical interpretation of the \(N^*(1535)\) and suggest possible additional \(S_{11}\) strength near \(1.9\)~GeV.
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High Energy Physics (Theory)
Yan Liu and Hong-Da Lyu
We study how the critical behavior of
holographic superconductors controls the interior geometry of charged black holes. Although the exterior condensate vanishes at criticality, the critical zero mode develops logarithmic oscillations near the Reissner–Nordström Cauchy horizon, rendering the interior critical limit nonuniform. We show that the transmitted critical-mode amplitude, together with local Cauchy-horizon quantities, fixes both the leading Einstein–Rosen collapse $\Delta z_{\rm ER}$ width and the phase $\Theta_J$ in the subsequent Josephson regime. If the condensate obeys $t\equiv1-T/T_c\propto\epsilon^{2r}$, then $\Delta z_{\rm ER}\propto t^{1/r}$ and $\Theta_J\propto t^{-1/r}$. This Josephson phase is transferred to the first Kasner epoch, producing oscillatory Kasner exponents and an accumulation law $t_n\sim n^{-r}$ for successive zeros of the scalar velocity. The critical zero mode fixes the leading collapse and phase coefficients, which are quantitatively confirmed by fully nonlinear solutions in both the ordinary and tricritical cases. At low temperature, the interior instead depends on the infrared completion of the zero-temperature geometry. Thus near-critical scaling is governed by critical-mode transmission, whereas the low-temperature behavior is controlled by the infrared endpoint.
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Mesoscale and Nanoscale Physics
Tara Murphy, Lorenzo Peri, Giovanni A. Oakes et al. (+8 more)
Electron cotunneling in
semiconductor quantum dots is a higher-order tunneling mechanism that connects initial and final charge states through energetically inaccessible virtual intermediate configurations. In
quantum-dot arrays, such processes can produce simultaneous charge motion across multiple tunnel junctions and enable transitions that would otherwise be suppressed by Coulomb blockade. Here, building on an earlier proof-of-principle demonstration, we investigate
radio-frequency (rf)-driven correlated cotunneling and its application to dispersive
quantum-dot readout. Using both theoretical modeling and experimental measurements in two different foundry-fabricated silicon devices, we show that an external rf drive can induce correlated cyclic single-electron transitions, resulting in enhanced charge-polarization of the system. We develop a general theoretical framework for rf electron-cascade readout, which exploits cotunneling events in
quantum-dot systems with three or more dots to produce a relative signal enhancement, and extend its experimental demonstration to a gate-sensed device architecture. Our results establish the operating principles of rf electron-cascade readout and provide a route to increased dispersive readout fidelity in
semiconductor quantum computing architectures.
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All authors Tara Murphy, Lorenzo Peri, Giovanni A. Oakes, Jacob F. Chittock-Wood, Ross C. C. Leon, Fabrizio Berritta, Amber Heskes, David Wise, Anasua Chatterjee, Ferdinand Kuemmeth, M. Fernando Gonzalez-Zalba
Atmospheric and Oceanic Physics
A Net Flux-Weighted Analytical Generalization of the Greenhouse Effect Beyond the Gray Approximation
Carmine Serio
Analytical greenhouse models traditionally rely on the gray approximation, simplifying radiative transfer but treating optical depth as an unconstrained parameter that yields unrealistic surface temperatures. We derive an exact, closed-form solution directly from Schwarzschild's equations for a non-gray atmosphere. While the gray approach is physically inadequate because it over-weights saturated bands that carry negligible net energy transport, we show that the non-gray formulation constrains column optical depth via the surface net radiative flux, naturally accounting for the atmospheric window without ad hoc corrections. The resulting effective optical depth penalizes saturated cores due to the negative spectral covariance between opacity and transmission. This shifts the computed surface
equilibrium to an observationally consistent 288 K, yielding a purely radiative Transient
Climate Response of +2.18 K under doubled \ce{CO2}, fully consistent with Intergovernmental Panel on
Climate Change estimates. The framework eliminates any theoretical basis for greenhouse-effect saturation. While not intended to replace three-dimensional general circulation models, this work reconciles classical radiative transfer with modern
climate estimates, demonstrating that proper flux-weighting aligns analytical theory with anthropogenic warming.
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Quantum Physics
Universal and rigorous asymptotic convergence of standard macroscopic quantum electrodynamics to the modified Langevin noise formalism
A. Ciattoni
The standard Langevin noise formalism (LNF) is a well-established approach for macroscopic
quantum electrodynamics in unbounded lossy media, and accordingly, its application to finite objects requires endowing the surrounding
vacuum with a fictitious absorption that is taken to asymptotically vanish. Existing justifications for such a singular limiting procedure have been mainly restricted to phenomena governed by
vacuum fluctuations and medium-induced interactions (Casimir-Polder forces, thermal radiation,
quantum emitter dynamics, etc.), thereby strictly excluding scenarios that involve the scattering of external
quantum radiation. Conversely, the modified Langevin noise formalism (MLNF) has recently been established as the complete canonical
quantum theory for arbitrary macroscopic systems and electromagnetic processes, entirely bypassing the need for limiting procedures, treating incident
quantum radiation fields as independent degrees of freedom, and exactly reducing to the LNF for unbounded media. In this work, we demonstrate that the LNF limiting procedure is universally valid by showing that it recovers any physical prediction of the MLNF across all regimes, including arbitrary
quantum scattering processes. Specifically, we introduce a suitable mapping associating any MLNF state and observable with a corresponding entity within the LNF augmented by fictitious
vacuum absorption. We then rigorously prove that, as the fictitious absorption tends to zero, every LNF
matrix element constructed via this mapping exactly converges to its MLNF original, so that the limiting procedure establishes the asymptotic convergence of the LNF to the MLNF.
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Astrophysics of Galaxies
Spatio-temporal progression of star formation in the Carina OB1 association
C. Göppl and T. Preibisch
The Carina OB1 association, harboring the famous Carina Nebula near its center, is the most massive, well-studied OB association in our
Galaxy. Containing several massive
star clusters with different ages, it shows a complex spatio-temporal structure. We explore the formation history and kinematic
evolution of the eight most massive clusters in Car OB1. We determine the cluster ages,
stellar populations, the initial massive
star content, and the number of
supernova explosions since the time of each cluster's formation. Using
Gaia DR3 astrometry, we determine the 3D configuration of the association and perform a traceback analysis of the cluster positions over the last 13 Myr. The traceback analysis places the birth location of the oldest (13 Myr) cluster, NGC 3293, in the Carina spiral arm. Approximately four Myr later, a series of 11
supernova explosions started in NGC 3293. We construct a possible scenario in which the expanding bubble driven by these
supernova explosions interacted with the southern part of the original cloud complex and led to the sequential formation of the younger clusters in the central Carina Nebula. Our scenario suggests that the sequence of 16+/-4
supernova explosions in the association during the last 10 Myr played an important role in creating the massive clusters in Car OB1. However, the
supernova feedback does not dominate the large-scale expansion of the association; the general expansion rather seems to reflect the initial kinematics of the original unbound cloud complex.
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Quantum Physics
Error-Transparent Code Switching Between Permutation-Invariant Codes with Transversal Clifford and Icosahedral Gates
Zachary P. Bradshaw
Code switching moves an encoded
qubit between two codes whose transversal gates together are universal, but the switching operation itself is usually not transversal and can spread a single fault into an uncorrectable error. We study switching between two permutation-invariant codes on the same
qubits, one with transversal Clifford gates and one with transversal gates from the non-Clifford binary icosahedral group. Both are compatible with transversal $X$, $Z$, and $F = HS^\dagger$, and the encoders with this property form a small linear space. We show that its codes of distance at least three are cut out by at most two quadratic equations, and that all of them have the same error geometry in the sense that their single-
qubit error states have the same inner products. It follows that a switching
unitary commuting with
qubit permutations and with the shared transversal gates at every instant, and tolerating one single-
qubit fault at an unknown time, exists if and only if the two codes are joined by a continuous path of distance-three codes. Such a switch can be made error transparent, so that a fault at any moment reaches the target code as the same single-
qubit error. For real encoders, the distance-three codes are the solutions of a single quadratic equation, and on thirteen
qubits, they form an explicit circle through two Clifford codes and an icosahedral code. We construct the switching
unitary along this circle as a collective operator, leaving its synthesis into physical control open, and verify that its recovery infidelity per fault is at machine precision, whereas two natural alternatives leave average infidelities of $0.13$ and $0.85$. A survey over odd
qubit numbers up to $29$ lists where such switches exist.
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Mathematical Physics · Cross-listed from math.PR
Phase transition in the antiferromagnetic Ising model with external field
Jianping Jiang and Sike Lang
Consider the nearest-neighbor
antiferromagnetic Ising model on $\mathbb{Z}^d$, $d\ge2$, at inverse temperature $\beta$ and in a uniform external field $h$. Let $\beta_c(d)$ be the critical inverse temperature of the zero-field Ising model. We prove that for every $\beta>\beta_c(d)$, the Gibbs state is not unique whenever $|h|$ is sufficiently small. This extends a previous result of Dobrushin (1968) from sufficiently large $\beta$ to every $\beta>\beta_c(d)$.
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Strongly Correlated Electrons
Unveiling High-Energy Ultrafast Responses Driven by Fermi-Level Gap Opening in Charge-Density Waves
Qiong Wu, Tianchen Hu, Junhan Huang et al. (+8 more)
Ultrafast pump-probe spectroscopy is indispensable for investigating interactions, collective excitations, and nonequilibrium dynamics in
superconductors and correlated electron systems. However, how a small gap opening near
Fermi surface affects the spectral changes in the high-energy interband transition region remains elusive. To address this issue, we perform systematic studies of carrier relaxation dynamics in the prototype charge-density-wave (CDW) material EuAl4. We find that the CDW gap shrinks substantially under optical pumping. This band renormalization strongly modulates interband transitions associated with the gap edge, inducing a pronounced transient reflectivity change at the corresponding probe energies. These results establish a direct link between low-energy order-parameter dynamics and high-energy spectral responses, providing a general framework for interpreting transient signals in gapped
quantum materials.
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All authors Qiong Wu, Tianchen Hu, Junhan Huang, Yongjie Liu, Fei Sun, Shuxiang Xu, Li Yue, Zijian Lin, Xinyu Zhou, Tao Dong, Nan-Lin Wang
Superconductivity
Paramagnon softening upon doping in oxychloride cuprate superconductors
Chafic Fawaz, Léo Gaspard, Laura Chaix et al. (+15 more)
Understanding how
magnetic excitations and exchange interactions evolve with doping is crucial for deciphering the physics that shapes the phase diagram of high-temperature cuprate
superconductors. Here, we clearly determine the behavior of the paramagnon dispersion in the oxychloride cuprate Na$_{x}$Ca$_{2-x}$CuO$_2$Cl$_2$ up to the highest doping level. We find that the paramagnon bandwidth, defined by the energy at the $X$ zone boundary $(0.5,0,0)$, remains unchanged within experimental uncertainty, even though it exhibits significant broadening. In contrast, along the nodal direction $\Gamma-M$ (i.e., from $(0,0,0)$ to $(0.5,0.5,0)$), the paramagnon energy shows a marked softening with doping, with a shift of up to $\Delta E\sim150$ meV at the midpoint of the zone for the highest doping, which is about half of its initial value in the
antiferromagnetic phase. Calculations of the dynamical
spin structure factor for a one-band Hubbard model, including hopping terms up to the third-nearest neighbor ($t^{\prime\prime}$), explain this behavior and accurately reproduce the observed wave vector dependence and directional variation in the Brillouin zone.
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All authors Chafic Fawaz, Léo Gaspard, Laura Chaix, Luca Laveder, Benjamin Bacq-Labreuil, Victor Porée, Flora Yakhou-Harris, Kurt Kummer, Nicholas B. Brookes, Alessandro Nicolaou, Hajime Yamamoto, Yuichi Okazaki, Ikuya Yamada, Masaki Azuma, David Santos-Cottin, Marie-Aude Méasson, Benjamin Lenz, Matteo d'Astuto
Quantum Physics
On the Completeness of Quantum Mechanics: Sources, Records and Probabilities
Mustafa Bakr
Can
quantum mechanics be complete without being fundamental? Under stated source, detector, and statistical conditions, we reconstruct the
quantum representation and Born probabilities and prove complete algebraic closure of the admitted
quantum predictions without requiring a collapse postulate. We further show that many familiar
quantum paradoxes arise from conflating coherent processes with retained records or probabilities with realized outcomes. We also ask whether mathematics as a whole, or the source architecture itself, emerges from a deeper structure.
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Quantum Physics
The diffusive spectral gap of the qubit eSWAP chain
Yanying Liang and Haoran Zhu
We prove that the second-moment
Hamiltonian of the open
qubit eSWAP chain has a diffusive spectral gap, resolving a
conjecture of Li, Zheng, Liu, Jiang, and Liu. We also characterise the ground space on every connected interaction graph with at least five vertices and prove a uniform lower bound for the unnormalised complete-graph gap. We apply these results to sequential and brickwork
circuits and prove that the periodic chain also has a diffusive spectral gap.
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Atomic Physics
A cryogenic apparatus with a rotatable substrate for matrix isolation spectroscopy of BaF in neon crystals down to 3.2 K
Alessandro Lippi, Diego Bisero, Caterina Braggio et al. (+7 more)
We present a new experimental apparatus for
matrix isolation spectroscopy capable of growing cryogenic
crystal matrices doped with barium monofluoride (BaF), a candidate for measurements of the electron electric dipole moment (eEDM). \\ In this work, BaF molecules are produced in a cryogenic buffer-gas source and used to dope a neon
matrix grown on a substrate, cooled by a cryocooler, reaching temperatures as low as 3.2 K. A rotatable flange allows for multiple substrate orientations, optimizing spectroscopic investigations and
matrix crystal growth. \\ Fluorescence emission analysis of BaF in neon
crystal show emission when exciting the $A\,^2\Pi_{1/2}$, $A\,^2\Pi_{3/2}$ and $B\,^2\Sigma^+$ states, along with the presence of fluorescence from barium atoms in the
crystal. A first estimation of the column density of BaF in the
crystal is given on the order of $5 \times 10^{-13} \, \text{cm}^{-2}$. \\ We also demonstrated the production of BaF using parahydrogen as the buffer gas of the cryogenic source, a first step toward BaF molecules embedded in a para-hydrogen
matrix. \\ Finally, we also observed fast fluorescence decay, attributed to optical bleaching effects, whose amplitude arise at lower temperatures or higher
laser intensities, introducing a systematic effect to be studied in future experiments.
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All authors Alessandro Lippi, Diego Bisero, Caterina Braggio, Giovanni Carugno, Roberto Calabrese, Federico Chiossi, Marco Guarise, Madiha M. Makhdoom, Giuseppe Messineo, Jacopo Pazzini
Cosmology and Nongalactic Astrophysics
Limits on the size of electron density fluctuations in the early universe and implications for the Hubble tension
Gabriel P. Lynch, Jens Chluba, Richard Battye et al. (+1 more)
Little is known about the early universe on scales smaller than those resolved by the
cosmic microwave background (CMB), where electron density fluctuations on kiloparsec to megaparsec scales are expected in many extensions of LCDM. These fluctuations nonetheless leave two imprints on the CMB. They accelerate recombination, the effect behind previous constraints and proposals to raise the inferred Hubble constant, $H_0$. Through correlations along the line of sight, they also reduce the effective Thomson scattering rate, enhancing
diffusion damping by an amount that grows with their coherence length. We implement both effects in a modified Boltzmann code, classito, and use CMB data from Planck, ACT DR6, and SPT-3G D1 to place the first limits on such fluctuations that include this modified
photon transport. We find no evidence for them: the variance of the electron density contrast is below $0.21$ ($95\%$ CL), falling to $0.033$ for a coherence length of $2\,{\rm Mpc}$, and we present these limits in terms of the electron power spectrum at $1\,{\rm Mpc}^{-1}\lesssim k\lesssim10^2\,{\rm Mpc}^{-1}$. We also reassess small-scale electron density fluctuations as a resolution of the Hubble tension. In Planck data the transport effect is partially degenerate with accelerated recombination, widening the range of $H_0$ allowed: combined with a distance-ladder prior, Planck gives $H_0 = 71.1\pm0.7\,{\rm km\,s^{-1}\,Mpc^{-1}}$ and an improved fit relative to LCDM. ACT and SPT-3G break this degeneracy, chiefly through the temperature–$E$-mode correlation in the damping tail, and with the same prior they give only $H_0 = 69.3\pm0.5\,{\rm km\,s^{-1}\,Mpc^{-1}}$ and no preference over LCDM. With our treatment and publicly available code, models that generate small-scale electron density fluctuations can be directly confronted with CMB data through the variance and coherence length that they predict.
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All authors Gabriel P. Lynch, Jens Chluba, Richard Battye, Geoffrey Vasil
Soft Condensed Matter
Metastability and nucleation of bubbles in active chiral systems
Raphael Maire, Alessandro Petrini, Umberto Marini Bettolo Marconi et al. (+1 more)
Bubbles frequently emerge in dense
chiral active fluids, yet it remains unclear whether they result from an instability of the homogeneous state or from rare nucleation events within a metastable phase. Here we develop a nucleation theory for
chiral bubble formation by reducing the hydrodynamic equations to a single collective coordinate, the bubble radius. This reduction yields an effective nonlinear potential that captures the radial dynamics and predicts distinct stable, metastable, and unstable regimes of the homogeneous state. In the metastable regime, the theory identifies a critical bubble radius and an associated effective mechanical-work barrier, while its large-radius behavior determines whether bubble growth saturates at a finite size or becomes unbounded. We further analyze the stability of circular bubbles against noncircular perturbations, finding growing modes that can lead to elongation and breakup. The theoretical predictions are tested against event-driven molecular-dynamics simulations of
chiral hard disks, which reproduce the predicted trends in the critical radius, nucleation barrier, and selected bubble size. Our results establish a unified framework for stability and nucleation in
chiral active fluids and suggest routes to control bubble formation in experiments with spinning colloids and
chiral spinners.
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All authors Raphael Maire, Alessandro Petrini, Umberto Marini Bettolo Marconi, Lorenzo Caprini
Materials Science
Computing at the Edge Enabled by Indoor Photovoltaics and Ferroelectrics
Robert L. Z. Hoye, Markus Hellenbrand, Nuno Estrócio et al. (+17 more)
The exponential, pervasive rise of artificial intelligence (AI), hosted in large data centres, will test the limits of the underpinning infrastructure, including electricity and water supplies, which are becoming increasingly precious resources. Rather than performing all AI computations in centralized servers, for many functionalities, these can be performed locally across a network of billions of small, autonomous nodes, saving substantial energy costs associated with communication. This alternative paradigm is known as edge computing, or distributed intelligence (DI), but has been held back by the lack of availability of reliable local energy supplies matching the energy requirements of the computational infrastructure. Opportunities to address this challenge are emerging with rapid advances in high-performance indoor photovoltaics (IPVs) for local energy harvesting, as well as reductions in computational cost through neuromorphic or in-
memory computing devices. In this perspective, we discuss the requirements of IPVs for DI, the extent to which emerging materials fulfil these requirements, and how current gaps could be addressed. We make the case that (anti)ferroelectric materials can surpass bottlenecks for both electrostatic energy storage and low-power in-
memory neuromorphic computing. The core theme of this perspective is that co-creation between energy harvesting, storage and computing is essential for making DI a reliable and more sustainable alternative to centralized AI.
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All authors Robert L. Z. Hoye, Markus Hellenbrand, Nuno Estrócio, Austin M. Kay, Alice Scardina, Alessandro Mezzetti, Ignasi Fina, Jorge Íñiguez-González, Luís S. Marques, Francesco Matteucci, Quanxi Jia, Judith L. MacManus-Driscoll, Bert Offrein, Florencio Sánchez, Beatriz Noheda, George Koutsourakis, Marina Freitag, Gregory Burwell, Giulia Grancini, Jose P. B. Silva
Computational Physics
A Contrast-Source Inversion Scheme Based on Stochastic Optimization and Plug-and-Play Regularization
Lingqi Gao and Hakan Bagci
An electromagnetic inversion scheme that integrates
stochastic optimization (STO) and plug-and-play (PNP) regularization into contrast-source inversion (CSI), termed STO-PNP-CSI, is developed. Standard CSI solves for the contrast source vector of every transmitter at each iteration, which is expensive in a multi-transmitter configuration. STO instead solves for only one randomly selected contrast source vector per iteration, which reduces the per-iteration cost and can help the inversion escape poor local minima and saddle points. The resulting loss of information, however, increases the ill-posedness of the inversion. To counter this, the Swin-Conv-UNet (SCUNet) denoiser is plugged into the CSI scheme as an implicit regularizer, supplying a learned prior that is stronger than conventional hand-crafted ones and stabilizes the reconstruction. The proposed STO-PNP-CSI is applied to both synthetic and experimental data. The results show that it yields accurate reconstructions at substantially lower computational cost than CSI, including under strong nonlinearity and measurement noise.
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Quantum Physics
Training Variational Quantum Algorithms Is NP-Hard, Even Locally
Dax Enshan Koh, Triscia Mundo, Iosif Sakos et al. (+1 more)
Variational
quantum algorithms (VQAs) generally rely on classical optimization to train parameterized
quantum circuits. This training seeks to minimize an objective function, and its efficiency is central to the practical success of these
algorithms. However, globally minimizing such training objectives over the
circuit parameters is known to be $\mathsf{NP}$-hard, limiting the prospect of general guarantees for efficient training. In this Letter, we prove that even the weaker task of finding a local minimum of such VQA training objectives is strongly $\mathsf{NP}$-hard, including when the objective admits efficient classical evaluation. Moreover, we show that this hardness persists even for the task of finding a parameter vector within $\ell_p$-distance strictly less than $\pi/2$ of some local minimizer, for every $p\geq 1$. Our central technical result is that approximating a local minimizer of a Hermitian trigonometric
polynomial is strongly $\mathsf{NP}$-hard. By explicitly constructing
quantum circuits whose training objectives reproduce these hard instances, we obtain a
polynomial-time reduction to VQA training. Our results establish a fundamental computational barrier to variational
quantum training: even reaching the vicinity of a local minimum remains hard in the worst case.
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All authors Dax Enshan Koh, Triscia Mundo, Iosif Sakos, Antonios Varvitsiotis
High Energy Astrophysical Phenomena
Fast Bayesian Updating of the Neutron-Star Equation of State with Neural Posterior and Evidence Estimation
Prashant Thakur
We present two complementary neural routes for microscopic
neutron-
star EOS inference: truncated sequential neural posterior estimation with mixture importance sampling (TSNPE+MIS), which targets one observation, and amortized neural posterior estimation with importance sampling (A-NET+IS), which is reused across
nuclear inputs and NICER sources. Both are corrected against the original prior and full likelihood, with the effective sample size as a diagnostic. We test nucleonic and hyperonic relativistic mean-field models with
nuclear data, NICER, GW170817, and pQCD. For the fiducial analyses, both agree with UltraNest in the parameter posteriors and 90% mass-radius and
tidal-deformability bands. TSNPE+MIS band-edge differences are only 0.024-0.033 km and 1.02-1.03%, while A-NET+IS differences are 0.019-0.050 km and 0.86-1.13%. TSNPE+MIS reduces the computing time by factors of 1.6-2.3; after training, A-NET+IS is 15-240 times faster per configuration. The frozen A-NET also analyzes three NICER sources absent from training, including the newly reported high-mass, compact PSR J1614-2230 posterior. For this source, the inferred $R_{1.4}$ agrees with UltraNest within 0.010 km for nucleonic matter and 0.009 km for hyperonic matter. We also introduce a Green-function Evidence Network (EN), a regression-based variant of Evidence Networks and, to our knowledge, the first Evidence Network applied to
neutron-
star EOS inference. After a one-time cost, its network queries return absolute evidences in about 0.03 s for new
nuclear data and 3.5 s for a new NICER source; all 16 differences from UltraNest are below $1\sigma$, and independent importance-sampling evidences agree within the quoted EN uncertainties. Under the adopted likelihood, both evidence calculations favor nucleonic matter by Bayes factors of about 22:1-27:1.
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Solar and Stellar Astrophysics
SPHERE/ZIMPOL observations of the symbiotic system R Aquarii. II. Dynamics of the dust in the Mira wind and the Halpha gas in the jet
H.M. Schmid, E. Lagadec, J. Milli et al. (+17 more)
R Aqr is a resolved symbiotic Mira binary and a prototype target for the study of complex hydrodynamic processes including
dust-driven mass loss, mass transfer,
accretion, and jet
outflows and the formation of strongly asymmetric structures. We investigate for R Aqr the central Halpha emission from the ionized gas and the polarization from scattering
dust based on SPHERE/ZIMPOL maps with a resolution of about 25 mas (5 AU). Data for four epochs were taken, including the
dust eclipse around 2021, to follow structural changes. The central Halpha gas traces the orbital motion of the hot component. The polarization from scattering
dust shows interaction effects near the binary (<60 AU), including a flattened distribution in the orbital plane, corotating
dust, and a reduction of the scattering signal during the
dust eclipse. The polarization shows at >60 AU a steady
outflow with about a dozen
dust clouds, a few of which have a comet-like core and tail features. The
dust velocity is about 20 km/s, and this is faster than for the CO gas measured with ALMA. Several prominent Halpha clouds also show scattering polarization because they are just partly ionized
dust clouds from the Mira wind. We also found small faster-moving transient Halpha clouds, pointing to
outflow instabilities and shocks. The observed angular shift of Halpha during the
dust eclipse, can be explained by strong illumination changes from the hot component. At larger separation, the H$\alpha$ clouds move faster (>100 km/s), in agreement with previous studies. This acceleration is probably a result of gas heating by photoionization and shocks, and the produced overpressure gives rise to the two well-known jet-like features expanding in polar directions. The presented R Aqr data are very useful to clarify the complex hydrodynamics taking place in AGB binaries.
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All authors H.M. Schmid, E. Lagadec, J. Milli, C. Tschudi, J. Ma, N. Engler, J.L. Beuzit, A. Boccaletti, G. Chauvin, R. Claudi, S. Desidera, K. Dohlen, M. Feldt, R. Gratton, Th. Henning, M. Kasper, M. Langlois, F. Ménard, D. Mouillet, A. Vigan
High Energy Physics (Phenomenology)
Boosted top tagging via lepton-in-jet topology for vector-like quark searches in FCC-hh
Sanchari Bhattacharyya, Biplob Bhattacherjee, Kirana K. K. et al. (+1 more)
In this paper, we present a machine-learning-based framework for identifying leptonically decaying, highly boosted top
quarks, $t\to b\ell\nu$, at the Future Circular
Collider:
hadron-
hadron mode (FCC-hh) operating at a center-of-mass energy of $\sqrt{s}=100$~TeV. At these energies, the large Lorentz boost causes the top-
quark decay products to become highly collimated, with the
lepton embedded within the resulting top-
quark jet. In this regime, it is not a priori clear whether constituent-based jet taggers, which rely on information from individual jet constituents, retain the high discrimination power achieved at LHC energies. To answer this question, we employ two complementary approaches: a variable-based tagger trained with a deep neural network (DNN) using physics-motivated observables and a constituent-based Particle
Transformer (ParT) acting on the jet constituents. Both approaches are optimised for the characteristic non-isolated
lepton signature of boosted leptonic top decays and achieve comparable performance in discriminating leptonic top jets from hadronic top jets and heavy-
flavor $b$- and $c$-jet backgrounds. We then incorporate the tagging framework into an event-level search for single production of a vector-like $B^\prime$
quark decaying through $B^\prime\to tW$, and use it to evaluate sensitivity to $B^\prime$ in the range of $3$ to $10$~TeV. For the reference $B^\prime$
benchmark, the proposed search strategy achieves a $5\sigma$ discovery reach of approximately $7$~TeV under the width requirement $\Gamma_{B^\prime}/m_{B^\prime}<25\%$, in both the statistics-only and $10\%$ background systematic uncertainty scenarios. Relaxing the width requirement to $\Gamma_{B^\prime}/m_{B^\prime}\lesssim 50\%$ extends the discovery reach to approximately $10$~TeV.
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All authors Sanchari Bhattacharyya, Biplob Bhattacherjee, Kirana K. K., Swagata Mukherjee
Instrumentation and Detectors
A Cryogenic Geophone with stable response from Room Temperature to millikelvin
Stefano Pirro, Marco Ricci and Simone Cioccolini
With the development of pulse-tube cryocoolers, the availability and use of low-temperature environments have increased exponentially in recent years. However, replacing
liquid helium with a mechanical cooling device has, since its introduction, highlighted the need to attenuate the mechanical vibrations generated by the cryocooler itself. In the case of dilution refrigerators, which are capable of reaching temperatures on the order of few mK, the issue of mechanical vibrations reaching the experimental setup is, in many situations, extremely critical. This has led to the development of several customized experimental approaches aimed at attenuating vibrations. However, the inertial measurement of vibrations at cryogenic and, in particular, ultracryogenic temperatures has relied on customized sensors, since no commercially available, calibrated instruments exist for measurements at these temperatures. Nevertheless, many research groups employ commercial geophones that are recalibrated at low temperatures. This approach, however, is not free from systematic errors and presents significant challenges in quantitatively assessing the absolute response. In this work, we describe the development of cryogenic geophones exhibiting an almost temperature-independent response, from room temperature down to approximately 10 mK.
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Quantum Physics
The magic cost of fermionic randomness
Chenfeng Cao, Yifan Tang and Jens Eisert
Sampling-based
quantum advantage raises a basic resource question: how much non-Gaussianity is needed to reproduce the random-
matrix statistics often associated with
quantum chaos? Passive fermionic linear optics preserves Gaussian structure, and even Haar-random mode mixing fails to anticoncentrate for Slater inputs. We show that overcoming this obstruction requires an extensive input resource. For any pure half-filled input state, the one-body defect $\nu$, defined as the summed occupation variance of the natural orbitals, must scale linearly with system size. For products of bounded-size blocks on $4N$ modes, this condition is also sufficient, with normalized collision moment asymptotic to $2N/\nu$, compared with the Porter-Thomas value 2. For four-mode products, the full Porter-Thomas moment hierarchy is recovered precisely when the defect density tends to its maximum. Assuming average-case hardness, approximate classical sampling remains hard near maximal density, with an error tolerance that increases with the density. Two-copy number fluctuations measure $\nu$ directly, and the same quantity lower-bounds the combined cost of non-Gaussian resource modes and parity-preserving local gates in deterministic exact preparation. Fermionic randomness therefore carries an extensive magic cost, with a quantitative link between sampling statistics, preparation resources, and an experimentally accessible witness.
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Astrophysics of Galaxies
Large-Scale Stellar Bars and Nuclear Activity in Narrow-Line Seyfert 1 Galaxies
Po-Chieh Yu
We present a statistical comparison between barred and unbarred narrow-line Seyfert 1
galaxies (NLS1s) to investigate the role of large-scale
stellar bars in fueling AGN with low-mass black holes. From a parent sample of 492 NLS1s selected from SDSS and Pan-STARRS1 (PS1), we construct a PS1-resolved matched sample of 101 barred and 101 unbarred NLS1s, matched in
redshift, inclination, and image quality. Unbarred NLS1s are modestly but consistently brighter than barred NLS1s in several optical AGN luminosity indicators, including $\lambda L_{\lambda}(5100~A)$, broad H$\alpha$, broad H$\beta$, narrow H$\alpha$, narrow H$\beta$, and [O III]~$\lambda 5007$, with typical offsets of $\sim 0.1$–$0.25$ dex; the broad H$\alpha$ and narrow-line offsets are statistically significant, while the continuum and broad H$\beta$ offsets are marginal. Monte Carlo resampling and a
Bayesian model support the same direction of offset. In contrast, the main narrow-line diagnostics, including [O III]/H$\beta$, O3N2, and the [S II]-based electron density, are statistically consistent between the subsamples, although barred NLS1s show a higher N2 ratio. Within the barred subsample, the bar strength parameter $e_{\max}$ shows a mild anti-correlation with the optical continuum and broad Balmer-line luminosities. These results indicate that large-scale
stellar bars are not associated with enhanced instantaneous optical AGN luminosity. Instead, barred systems may experience more regulated or time-variable inner gas delivery, building circumnuclear gas reservoirs without necessarily increasing
accretion power observed at the epoch traced by optical AGN emission.
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Mesoscale and Nanoscale Physics
Sven Bjarke Gudnason and Muneto Nitta
We perform an exhaustive study of the parameter space of the
chiral magnetic model with a Dzyaloshinskii-Moriya interaction, an in-plane anisotropy term and an out-of-plane Zeeman
magnetic field. We map out the phase diagram for the model and find a
chiral soliton lattice hosted on a
chiral soliton lattice as the ground state in a particular corner of the phase diagram. There is a smooth crossover, as opposed to a phase transition, to the skyrmion
crystal lattice phase. Finally, we also discover excited composite
soliton states such as an anti-skyrmion coexisting with a bimeron or an anti-bimeron.
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Nuclear Theory
Sensitivity of fission barrier heights to nuclear matter properties
X. Zhang, K. Hagino and J. M. Yao
We systematically investigate the correlations between
nuclear fission properties and the surface energy coefficient $a_{\rm surf}$ extracted from semi-infinite
nuclear matter. To this end, we employ the covariant density functional theory based on a point-coupling energy density functional (EDF). Taking $^{240}$Pu and $^{236}$U as representative examples, we employ Gaussian-process emulators to construct the joint posterior distributions of $a_{\rm surf}$ and selected fission observables, constrained by the ground state properties of the two
nuclei. The results reveal a strong correlation between $a_{\rm surf}$ and the fission barrier heights. A sensitivity analysis further shows that the height of the outer fission barrier is governed predominantly by the isoscalar-vector derivative coupling constant $\delta_V$ in the point-coupling EDF, whereas that of the inner barrier is by the combined effects of $\delta_V$ and several mutually correlated coupling constants.
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Quantum Physics
JAQSI: Just Another Quantum Simulator
Melvin Strobl, Maja Franz, Lukas Scheller et al. (+3 more)
Classical simulation supports the development and validation of
quantum algorithms through full-state inspection, controlled noise models and backpropagation, albeit for small
quantum systems. Existing frameworks offer gate-level execution, differentiable pulse-level dynamics or optimised hardware execution. Just another
quantum simulator (JAQSI) combines gate- and pulse-level simulation in one differentiable
circuit model built upon JAX.
Circuits are represented as pure functions of numerical inputs which support vectorised batches and JIT compilation. Within a single
circuit,
matrix-defined operations, gates synthesised from
Hamiltonian time
evolution and noise channels can be composed freely. For a fast simulation, gate and channel fusion reduces passes over the state, while adjoint differentiation computes expectation-value gradients with a constant number of statevectors. At pulse level, JAQSI reduces
evolution under single-term
Hamiltonians to a scalar pulse-area integral and reuses cached execution plans and compiled solvers. In a
benchmark we compare JAQSI with PennyLane, Qiskit, Qibo, Qulacs, QuTiP and dynamiqs. At gate level, we observe performance either on par or an order of magnitude faster across statevector, density, noise and gradient simulation than the compared simulators up to 12
qubits. Beyond 18
qubits, JAQSI is on par with PennyLane Lightning in both statevector and gradient simulation. In the statevector and noisy density-
matrix pulse
benchmarks, it is at least 5 times faster than the other simulators, even with its closed-form solve disabled. Disabling the latter increases its runtime by at most a factor of 1.5. We provide JAQSI as open-source software on GitHub and PyPI.
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All authors Melvin Strobl, Maja Franz, Lukas Scheller, Eileen Kuehn, Wolfgang Mauerer, Achim Streit
Instrumentation and Methods for Astrophysics
Opportunity Lost in Searching for Technosignatures
Steve Prabu, David DeBoer, Andrew Siemion et al. (+6 more)
The sensitivity of
radio technosignature searches has improved dramatically over the last five decades; however, as the RFI environment from which these searches are conducted has become increasingly polluted, our advancements in
telescope sensitivity have not necessarily been complemented by less ambiguous technosignature searches. In this work, we investigate the resulting loss of opportunity to conduct unambiguous technosignature searches from Earth. We introduce three new concepts, opportunity lost, volume lost, and self-censorship, to quantify the impact of orbiting RFI sources on Earth-based technosignature searches. Using publicly available orbital data between 2008 and 2025, we find an approximately two-fold increase in the spatial occupancy of satellites within representative
telescope beams, with the exact magnitude of the loss strongly dependent on
telescope pointing. We further demonstrate that the cumulative effect of faint emission from multiple satellites increase the effective system temperature and consequently reduce the volume over which a technosignature of a given intrinsic power can be detected. Using approximately 10,000 archival observations from the Murchison Widefield Array spanning 2014–2024, we find suggestive evidence for increasing RFI occupancy across most of the frequencies observed by the MWA. While other opportunities for terrestrial technosignature searches exist, we argue for the protection and utilisation of uniquely
radio-quiet environments such as the lunar farside, which offers an opportunity to regain the ability to perform unambiguous technosignature searches that is being progressively lost on Earth.
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All authors Steve Prabu, David DeBoer, Andrew Siemion, Andre R. Offringa, Natasha Hurley-Walker, Charlie K. Ashe, Sofia. Z. Sheikh, Steve Croft, Greg Sleap
Quantum Physics
The quantum-classical bipartite universe and the logical emergence of $\hbar$ from classical temporality
Vincenzo Chilla
We present a foundational reinterpretation of
quantum dynamics based on the standard von Neumann formalism, positing a structural logical bipartition between a classical observational environment and a
quantum observed system. Against universalist frameworks, we argue that theoretical consistency requires distinct propositional logics: Boolean logic governs the environment, while non-Boolean logic applies to the observed system. Within this framework, an ideal classical clock is represented as an open system whose energy spectrum is uniformly discretized. The dynamics follow from the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation under the constraint that the
Hamiltonian remains observable. Although the clock's temporal
evolution is driven by dissipative coupling to the measurement apparatus, it admits a deterministic solution corresponding to information-preserving cyclic dynamics. This deterministic regime may emerge as a logical attractor, stabilized by the Boolean structure inherent to the measurement interaction. Ultimately, $\hbar$ is derived as a fundamental scaling parameter from the classical clock's action operator, revealing that the
quantum of action reflects the discrete logical structure underlying classical temporality. Furthermore, this framework establishes an exact mapping with 't Hooft's cellular automaton formalism, offering an alternative ontological interpretation that not require hidden variables and superdeterministic assumptions. The resulting distinction between
quantum dynamics (as potential recontextualization) and classical dynamics (as temporal actualization) provides a novel logical approach to the measurement problem.
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