Materials Science
Finite-temperature Fe K-edge X-ray absorption simulations reveal local structural dynamics of an iron(II) photosensitizer in solution and the crystalline phase
Patrick Müller, Lorena Fritsch, Matthias Bauer et al. (+1 more)
Interpreting metal K-edge spectra of flexible photosensitizers requires a structural model that separates electronic signatures from thermal motion, solvent disorder, and
crystal-packing effects. We combine Fe K-edge X-ray absorption measurements with second-generation Car–Parrinello ab initio molecular dynamics and all-electron Gaussian and augmented-plane-wave simulations for an iron(II) N-heterocyclic carbene photosensitizer in acetonitrile solution and in the crystalline phase. Ensemble-averaged spectra reproduce the main near-edge features in both environments and preserve the experimentally observed similarity of the first Fe coordination shell upon dissolution. Comparison with radial distributions extracted from extended fine-structure measurements validates the Fe–N and Fe–C coordination shells sampled by the trajectories, while element-resolved pair distributions explain why higher-shell experimental contrast is rapidly lost. The same dynamical ensembles reveal a broad out-of-plane distribution of the terpyridine nitrogen atom and a nearly octahedral distribution of the Fe-centered coordination planes. The results show that finite-temperature X-ray absorption simulations can provide a compact structural-dynamics picture of molecular transition metal photosensitizers by linking local spectra, solvent-phase ligand motion, and medium-range structural disorder within one trajectory-based description.
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All authors Patrick Müller, Lorena Fritsch, Matthias Bauer, Thomas D. Kühne
General Relativity and Quantum Cosmology
Hawking Temperatures of Dynamical Black Holes from the RVB–Residue Method:Vaidya and Kinnersley Geometries
Wen-Xiang Chen
This paper develops a local residue-based extension of the Robson–Villari–Biancalana method for calculating Hawking temperatures of dynamical black holes. Since non-stationary black holes generally do not admit a global timelike Killing vector, their temperature must be understood in a local, near-horizon, and quasi-stationary sense. By analytically continuing the near-horizon radial function into the complex plane, the Hawking temperature can be extracted from the residue of the inverse horizon function at the simple pole corresponding to the local horizon. This residue prescription is first applied to the Vaidya black hole, where it reproduces the standard local trapping-horizon temperature (T=1/(8\pi M(v))). The method is then extended to the arbitrarily accelerating Kinnersley black hole, whose horizon depends on time and angular coordinates. In this case, the RVB–residue method yields a point-dependent local Hawking temperature consistent with the generalized tortoise-coordinate approach. The results show that the RVB–residue method can be naturally generalized from stationary black holes to dynamical and non-spherical black holes, provided that the temperature is interpreted as a local near-horizon quantity rather than a global
equilibrium temperature.
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Space Physics
LEAP: A Rapid Neural Surrogate of Multi-Fluid MHD at Europa
Sachin Alexander Reddy, Abigail R. Azari, Corey J. Cochrane et al. (+6 more)
Characterizing Europa's subsurface ocean is a key objective of the Europa Clipper and JUICE missions in the search for life beyond Earth. Although the ocean's induced
magnetic field provides key constraints on habitability, interpretation is complicated by perturbations arising from Jupiter's
plasma interaction with Europa. Physics-based models (e.g. magnetohydrodynamic, MHD) required to characterize these effects are physically comprehensive, but have a prohibitive computational cost. To address this, we introduce Learning Europa's Atmosphere and
Plasma (LEAP), a
transformer-based surrogate trained on outputs from a state-of-the-art multi-fluid MHD code to predict
magnetic field perturbations along spacecraft trajectories. LEAP evaluates in milliseconds on a laptop, whereas MHD takes 12 hrs on a high-performance computer (~40,000x speed-up). The model has test set errors of -/+ 2.6 nT, and for the Galileo E4 and E14 flybys of Europa it matches the parent MHD model in accuracy. Its enhanced speed enables large-scale parameter surveys and probabilistic estimations of
plasma conditions, establishing a new framework for accelerated
plasma interaction modeling. LEAP can also inform future MHD simulations while learning from them. Beyond Europa, this framework could be expanded to planning future missions or to other high-priority bodies, including Uranus and Neptune.
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All authors Sachin Alexander Reddy, Abigail R. Azari, Corey J. Cochrane, Xianzhe Jia, Tom A. Nordheim, Lukas Mandrake, Steven D. Vance, Camilla Harris, Ioana Ciucǎ
Nuclear Theory
Charm quark production in heavy-ion collisions as a signature of pre-equilibrium
Maurice Coquet, Thomas Faure, Sören Schlichting et al. (+2 more)
The relative abundances and kinematic distributions of
hadrons containing (anti)charm
quarks are key observables for deconfinement, heavy-
quark diffusion and hadronization in heavy-ion collisions. The production of (anti)charm
quarks is commonly associated to the initial hard scatterings in hadronic collisions. Based on previous studies on dilepton production, we evaluate the (anti)charm
quark production from the pre-
equilibrium phase. A non-negligible contribution to the overall charm
quark production is found albeit large theoretical uncertainties are limiting factors. We conclude that precise total charm production measurements combined with progress on charm production calculations from the initial hard scatterings can be used to infer information on the pre-
equilibrium stage.
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All authors Maurice Coquet, Thomas Faure, Sören Schlichting, Mika Spier, Michael Winn
Astrophysics of Galaxies
Integral Field Unit Spectroscopy with One Fiber
Zehao Peng, Biprateep Dey, Chris J. Maddison et al. (+1 more)
Integral field unit (IFU) spectroscopy provides spatially resolved spectra across
galaxies, offering crucial insights into their
evolution. However, its high observational cost limits current IFU
datasets to $\sim 10^4$ objects. We present a multi-modal, probabilistic foundation model that predicts high-resolution spectra with calibrated uncertainties at arbitrary spatial locations within a
galaxy directly from broadband images. Built on a masked autoencoder framework, our architecture injects fiber positional encodings and
redshift aware wavelength encodings, enabling spatially conditioned predictions. Trained on 4.7 million images and single fiber spectroscopic observations from the Dark Energy Spectroscopic Instrument (DESI) survey, our model exploits the natural variance of fiber placements and the morphological self-similarity of
galaxies to achieve IFU-like capabilities without any IFU training data. Predicted emission line flux maps match independent IFU observations from the Mapping Nearby
Galaxies at APO (MaNGA) survey, with performance comparable to a supervised baseline trained directly on IFU data.
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All authors Zehao Peng, Biprateep Dey, Chris J. Maddison, Joshua S. Speagle
Materials Science
Graphlet Histogram Representation Database of Inorganic Crystals
Aaditya Panigrahi, Yanjun Liu, Omri Lesser et al. (+2 more)
Machine learning models for materials property prediction increasingly rely on representations learned end-to-end from large density-functional-theory databases, limiting their applicability when only scarce experimental data are available. Domain-knowledge-driven representations precomputed from
crystal structures alone offer a data-efficient, interpretable alternative, but existing approaches capture at most composition or bonding connectivity and discard local structural geometry. Here, we present Graphlet-MP, a database of graphlet histogram representations for 149,082 inorganic
crystals from the Materials Project (MP). Seventy-nine distributions describe each material over three hierarchical graphlet orders: atomic sites, bonded pairs, and bond-angle triplets, extracted via screened Voronoi tessellation from the crystallographic information file. We provide a complete technical specification of the representation, an Earth Mover's Distance metric for comparing materials in this space, and the full precomputed database. An accompanying open-source codebase enables users to generate graphlet histograms for arbitrary
crystal structures, including experimentally determined ones, and to extend the database to new materials or target properties.
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All authors Aaditya Panigrahi, Yanjun Liu, Omri Lesser, Krishnanand Mallayya, Eun-Ah Kim
High Energy Astrophysical Phenomena
Radio precursors of monster shocks: a mechanism for fast radio bursts from SGR 1935+2154
Andrei M. Beloborodov
Kilohertz perturbations in active magnetars evolve into monster radiative shocks at radii $r\sim 10^8$ cm. The shock generates X-rays and a semi-coherent
radio precursor, which strongly interacts with the magnetospheric
plasma ahead of the shock. We show that this interaction self-regulates the precursor emission and find its self-consistent frequency and luminosity. The precursor frequency falls in the GHz band and its production peaks when the shock expands to $r\approx 10^9$ cm. The resulting GHz burst has a sub-millisecond duration and energy ${\cal E}_{\rm FRB}\approx 10^{34}{\cal E}_{38}^{0.2}$ erg where ${\cal E}$ is the energy of the primary magnetosonic disturbance that launched the shock. As the GHz burst propagates to the light cylinder $R_{\rm LC}\sim 10^{10}$ cm, it faces a threat of being absorbed by the magnetosphere. The burst escapes if the local
plasma density at $R_{\rm LC}$ is $\sim 30$ times lower than typically expected for active magnetars, so distant observers need some luck to see the
radio burst. The shock X-rays follow the
radio waves with a millisecond delay. Shocks from kilohertz disturbances with energies ${\cal E}\sim 10^{38}$ erg generate X-ray and
radio bursts similar to the activity detected in SGR 1935+2154.
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Fluid Dynamics
Effect of a magnetostatic field on laminar premixed hydrogen-air flames
Tristan Lapaire, Sofiane Al Kassar, Antonio Attili et al. (+1 more)
Magnetic fields have shown potential to affect flame characteristics; however, the mechanisms of interaction are not fully understood. This paper investigates the effect of
magnetic fields on premixed hydrogen-air flames that are prone to intrinsic instabilities, with a focus on the role of
magnetic forces on the flame behaviour. The study is conducted using direct numerical simulations. Two flame conditions, both with an equivalence ratio of 0.5, are studied, one with the reactants at atmospheric conditions and the other at high pressure and high temperature. Different configurations of the
magnetic field are investigated, each characterised by a different gradient of the square of the magnitude of the
magnetic field, oriented in the direction opposite to the velocity of the incoming reactants. Results show that the investigated configurations of the
magnetic field can reduce the flame consumption speed, an effect that is substantial in the lower pressure case, while it becomes negligible at high pressure. The effect of the
magnetic forces increases with increasing gradient of the
magnetic field and is mainly due to the reduction of the flame area. Results also show that the effects of
magnetic fields on the reactivity of the flame and on the small
cell structures developed along the flame front are negligible. Analysis of the force contributions demonstrates that the change in the flame area is caused by the rotational component of the
magnetic forces, which alter the vorticity of the flow such that the finger-like structures formed by hydrodynamic instabilities tend to close. These forces are significant at low pressure, while they become negligible compared to the pressure gradient at high pressure. Ultimately, the results of this work indicate that
magnetic forces have the potential to change the flame behaviour, a mechanism that could be used for active control of flames.
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All authors Tristan Lapaire, Sofiane Al Kassar, Antonio Attili, Andrea Giusti
Quantum Physics
Trainability of IQP Quantum Circuit Born Machines Under Gaussian Initialization
Gennaro De Luca, Vinayak Sharma and Aviral Shrivastava
Quantum Circuit Born Machines (QCBMs) offer a natural approach to generative machine learning by leveraging the Born rule. Recent work has provided a method to classically train QCBMs with Instantaneous
Quantum Polynomial (IQP)
circuits via the Maximum Mean Discrepancy (MMD) loss. Despite the assumed intractability of sampling from IQP
circuits classically, their expectation values can be computed classically, enabling training of these IQP QCBMs. However,
quantum machine learning (QML) models have various other challenges, including trainability issues caused by exponential concentration or barren plateaus. While these issues have been explored for parameters sampled from a uniform distribution, little work has been done to rigorously treat the use of arbitrary Gaussian initialization schemes. This work leverages Stein's lemma and Lipschitz concentration bounds for Gaussian random variables to provide an analytical lower bound of the variance of the gradient and a probabilistic concentration bound of the deviation of the gradient from its mean. It discusses strategies to either avoid or encourage exponential concentration, as well as the conditions under which barren plateaus are more likely to occur.
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Materials Science
Pressure-Driven Structural Phase Competition and Functional Response in Layered LiInP2S6
Xiaochi Xie, Pegah Mohammadi and Sobhit Singh
Understanding how hydrostatic pressure modifies interlayer interactions and competing ionic configurations is essential for controlling the emergent functional properties of layered
quantum materials. Here, using first-principles density-functional theory calculations, we investigate the pressure-dependent structural, mechanical, electronic, and optical properties of three competing LiInP2S6 polymorphs: the monoclinic C2/c phase and the trigonal P-31c phase in both in-layer and in-gap configurations. Our results reveal a pressure-induced structural phase transition from the monoclinic ground-state C2/c phase to a trigonal P-31c in-layer phase at ~0.38 GPa, driven by enhanced interlayer coupling and anisotropic
lattice compression. In contrast, the trigonal P-31c in-gap phase remains energetically unfavorable due to its stronger interlayer ionic interactions and reduced compressibility. All phases remain mechanically stable under compression (0-26 GPa) and exhibit enhanced mechanical
rigidity, elastic wave velocities, and Debye temperatures with increasing pressure. Remarkably, the electronic and optical properties within each phase remain highly robust under pressure, with only moderate changes in the band gap and optical absorption edge (UV-Visible range) under pressure; however, substantial modifications emerge across the pressure-induced structural phase transition. These findings establish LiInP2S6 as a pressure sensitive ionic-vdW material in which subtle changes in interlayer interactions govern structural stability and functional properties.
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General Relativity and Quantum Cosmology
Gravitational Wave Energy Emitted in the Head-On Collision of Two Black Holes
Nesibe Derin Sivrioglu and Robert R. Caldwell
What is the spectrum of gravitational radiation produced by the head-on collision of two equal-mass black holes? The emission is dominated by low frequency bremsstrahlung, producing a flat energy spectrum. But where does the spectrum turn over? We propose that the lowest quasinormal mode of the final black hole marks the end of the low-frequency domain. The result is an analytic model of the total emitted energy as a function of the black hole velocity in the center of mass frame. With no free parameters, the model predicts that in the speed-of-light limit, 13.8% of the total initial energy is emitted in gravitational radiation, in good agreement with numerical relativity. This result also enables calculation of the nonlinear contribution to the
memory, a persistent distortion of the spacetime after passage of the gravitational wave burst. Advances in numerical relativity simulations will enable tests of our model for increasingly relativistic speeds, providing insight into this extreme collision.
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Instrumentation and Methods for Astrophysics
The Case for High-Resolution Infrared Spectroscopy with the Habitable Worlds Observatory
Daniel Jaffe, Gregory Mace, Erica Sawczynec et al. (+2 more)
A high-resolution near-IR spectroscopy capability on the Habitable Worlds Observatory (HWO) could strongly and efficiently advance many of the mission's goals. The technical barriers that made such a capability unfeasible on previous missions have largely been eliminated. Many HWO science case development documents require high spectral resolution in the IR and others would benefit significantly from it. High resolution improves the detectability of weak, unresolved features, aids identification of those features and provides additional information about radial velocity and line shape. It will be significantly easier to remove contaminating
stellar features from high-resolution data. Silicon diffractive optics, immersion gratings and grisms, together with the new generation of low-noise, low dark-current avalanche photodiode arrays, make it possible to design a very compact high-resolution spectrograph that can cover the entire 1.1-2.0 micron band in a single exposure that would realize all of these advantages. We outline here the case for such an instrument and the technology development pathway needed to mature it in preparation for the HWO mission.
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All authors Daniel Jaffe, Gregory Mace, Erica Sawczynec, Ueejeong Jeong, Caroline Morley
Superconductivity
Microscopic Investigation of the Superconducting State in CuCo$_{2}$S$_{4}$: Evidence for an Intermediate-Coupling Fully Gapped Superconductor
K. Panda, A. Bhattacharyya, Liang-Wen Ji et al. (+4 more)
The thiospinel compound CuCo$_2$S$_4$ provides an attractive platform for exploring superconductivity in transition-metal chalcogenide spinels. Here, we report the first microscopic investigation of the superconducting state in CuCo$_2$S$_4$ using
muon spin rotation and relaxation ($\mu$SR) measurements, complemented by magnetization and heat-capacity experiments. The temperature dependence of the superconducting depolarization rate obtained from transverse-field $\mu$SR measurements indicates a fully gapped superconducting order parameter. The extracted gap ratio $2\Delta(0)/(k_{\mathrm{B}}T_\mathrm{SC}) = 3.95(2)$ exceeds the BCS weak-coupling value of 3.53, placing CuCo$_2$S$_4$ in the intermediate electron-
phonon coupling regime. Zero-field $\mu$SR measurements were performed to probe possible time-reversal
symmetry breaking (TRSB) in the superconducting state. Within the experimental resolution, no additional spontaneous internal
magnetic fields are observed below $T_c$. However, due to the presence of a
ferromagnetic impurity phase and the associated fast-relaxing signal component, the sensitivity of the present measurements to weak spontaneous fields is reduced. Consequently, while no evidence for TRSB is detected, its existence cannot be definitively ruled out. Overall, our combined thermodynamic and $\mu$SR results demonstrate that CuCo$_2$S$_4$ exhibits a fully gapped superconducting state with intermediate coupling strength, consistent with conventional $s$-wave superconductivity in this cobalt-based thiospinel system.
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All authors K. Panda, A. Bhattacharyya, Liang-Wen Ji, Jing Li, R. Stewart, D. T. Adroja, Guang-Han Cao
Astrophysics of Galaxies
Aether-SHELLQs: JWST integral-field spectroscopy of candidate obscured quasars at z ~ 6
Yoshiki Matsuoka, Roberto Decarli, Emanuele Paolo Farina et al. (+12 more)
We present James Webb Space
Telescope (JWST) NIRSpec integral field unit (IFU) observations of six
galaxies at $z \sim 6$, obtained as part of the Aether project (General Observers program 5645). The targets were originally identified by the Subaru High-$z$ Exploration of Low-Luminosity
Quasars (SHELLQs) survey, as candidate obscured
quasars with luminous ($\gtrsim10^{43}$ erg s$^{-1}$) but narrow ($\lesssim500$ km s$^{-1}$) Ly$\alpha$ emission. Two objects exhibit a broad component in their Balmer lines (FWHM $>3000$ km s$^{-1}$), indicating the presence of active
galactic nuclei (AGNs), while the remaining four show similar profiles in permitted and forbidden lines. Combining these data with similar SHELLQs objects reported previously, we find that the presence of broad lines is strongly correlated with Ly$\alpha$ luminosity ($L_{\rm Ly\alpha}$); the inferred AGN fraction is $>$77 % and $<$15 % above and below $L_{\rm Ly\alpha} =10^{44}$ erg s$^{-1}$, respectively.
Dust-extinction corrections inferred from the Balmer decrement would imply unrealistically high Ly$\alpha$ luminosities, suggesting that the line-emitting gas consists of multiple zones. The IFU data reveal diverse spatial structures. The AGN hosts are compact, whereas the other
galaxies show extended ionized gas on scales up to 10 kpc and
star formation rates of 60 - 600 $M_\odot$ yr$^{-1}$. One of the extended objects exhibits a signature of rotation, while most of the others show little ordered kinematics, with velocity widths (FWHM) up to 200 - 300 km s$^{-1}$. These objects populate the intermediate luminosity regime between classical luminous
quasars and the low-luminosity AGNs discovered by JWST, including Little Red Dots, potentially linking the two populations.
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All authors Yoshiki Matsuoka, Roberto Decarli, Emanuele Paolo Farina, Anniek J. Gloudemans, Eduardo Bañados, Fabrizio Arrigoni Battaia, Anna-Christina Eilers, Chiara Mazzucchelli, Michael A. Strauss, Hyewon Suh, Maxime Trebitsch, Fabian Walter, Feige Wang, Kentaro Aoki, Junya Arita
Atomic Physics
Profiling a Rydberg-Atom Electric Field Sensor for Off-Resonant Detection of Sub-100 MHz RF Signals
Michael A. Viray, Abby Halasi-Kun, Baran N. Kayim et al. (+3 more)
We present a Rydberg-Atom electric field sensor optimized to detect signals at sub-100 MHz carrier frequencies. The sensing setup employs a sapphire vapor
cell that allows for detection of signals below 100~MHz – typical vapor
cells made of glass or quartz demonstrate strong screening of
radio frequency (RF) signals in this frequency regime. Applied signals are detected by observing AC Stark shifts in the atomic vapor energy levels. As a test case for the commercial utility of this receiver, we perform our tests at several carrier frequencies in the Industrial, Scientific, and Medical (ISM) band. At each carrier frequency, we report sensitivity, minimum detectable field, and detectable electric-field dynamic range. We also present a routine for optimizing off-resonant signal detection by tuning experimental parameters such as Rydberg coupler
laser detuning and RF local oscillator strength. This Python-based optimization routine, which can be used at any off-resonant carrier frequency, is shared on Github for others to use in their own investigations.
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All authors Michael A. Viray, Abby Halasi-Kun, Baran N. Kayim, Brian C. Sawyer, Robert Wyllie, David S. La Mantia
Quantum Physics
Towards the implementation of a quantum classifier
Lorenzo Confalonieri
In this work, we investigate the use of a
quantum circuit as a binary classification model in the context of
quantum machine learning. We call this model, binary
quantum classifier. First, we describe fundamental concepts of
quantum computing and introduce the computational tool used: Qibo, an open-source framework for efficient
quantum simulations and
quantum hardware control. Then, we describe how to design a binary
quantum classifier for the classification of images and small arrays of variables by showing how to input data in the
circuit, defining a
quantum circuit model Ansatz with trainable parameters and a loss function, and implementing multiple minimizers. We test our
quantum classifier with two data sets. The first one is the MNIST data set which is composed of handwritten digits (reduced to only handwritten zeros and handwritten ones for binary classification). We study the behavior of different minimizers by increasing the number of layers of the Ansatz. The second data set represents two different high energy collisions that can occur at
colliders such as LHC (CERN). Due to in-time
proton-
proton interactions known as pile-up, we distinguish two different data sets: "without pile-up" and "with pile-up". These collisions can be represented by images of size 32x32 or by six high-level variables that we call features. By increasing the size of the training data set and the number of layers of the Ansatz, we search for the best minimizer. Splitting the data set in training set and test set, we compute: ROC curve, AUC score, confusion
matrices and test set accuracy. For "with pile-up" images, we compare the results obtained with the
quantum classifier with a small convolutional neural network. We conclude that is possible to build a binary
quantum classifier with a
quantum circuit and we highlight its performances and limitations in comparison with classical technologies.
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Soft Condensed Matter
Beyond the Markovian limit: Exact solutions for active motion in a power-law viscoelastic bath
Mintu Karmakar, Jure Dobnikar and Ignacio Pagonabarraga
Active particles from bacteria to synthetic microswimmers often navigate viscoelastic media with complex relaxation dynamics. The classical active Brownian model that assumes instantaneous friction is clearly not applicable to describe such motility, while the non-Markovian processes combined with viscoelasticity are relatively unexplored. Here, we develop an analytical theory for an active particle in a power-law viscoelastic medium by solving coupled non-Markovian generalized Langevin equations for translational and rotational degrees of freedom. The viscoelastic
memory results in novel phenomena such as fractional short-time transport, enhanced long-time persistence, and de-correlation of the instantaneous force and the swimmer orientation. We demonstrate that the
memory kernel controls the anomalous scaling exponents, while the activity determines the crossover between sub-diffusive, ballistic and diffusive regimes. Our work provides a framework for theoretical description of biological and synthetic micro swimmers in complex biological and polymeric environments.
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Materials Science
Synthesis and Characterization of Atomically-Sharp Superconductor-Dielectric Interface
Nathan Sitaraman, Zhaslan Baraissov, Alexis Grassl et al. (+4 more)
Modification of
superconductor-dielectric interfaces is known to strongly impact coherence times of superconducting
quantum devices. This relationship is thought to arise from differences in the concentration of "two-level system" defects in the disordered dielectrics and
superconductor-dielectric interfaces; these defects couple to electromagnetic modes in the device and cause dissipation. Zirconium
oxide barrier layers on niobium have emerged as a promising pathway to low-loss interfaces in recent years, evidently due to the crystalline nature of these layers in comparison to the amorphous niobium native
oxide. We explain the unique ability of zirconium
oxide to form a crystalline layer, to maintain a sharp interface with metallic niobium, and to prevent niobium
oxide re-growth in terms of the chemical properties of ZrO$_2$ and the Nb-Zr-O ternary system. We demonstrate a new method to grow air-stable zirconium
oxide layers on niobium with a higher level of crystallinity and a sharper
oxide-metal interface than previously shown, and provide the first comprehensive microscopic analysis of ZrO$_2$ capping layer properties. These developments pave the way toward vital performance advances in superconducting
quantum devices.
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All authors Nathan Sitaraman, Zhaslan Baraissov, Alexis Grassl, Hongbin Yang, Daniel Tong, David Muller, Matthias Liepe
Mathematical Physics
Exceptional Points as Manifestations of Analyticity Breakdown in the 't Hooft Model
Kejun Liu
We use the exactly-solvable t Hooft model of 1+1D large-N_c QCD as a rigorous laboratory for the breakdown of analyticity of a causal response function, the
meson two-point function. A PT-symmetric deformation i gamma(x-1/2) of the light-cone
meson operator, the analogue of an imaginary chemical potential, drives the lowest two
mesons to an exceptional point (EP) at gamma_c. Recasting the resolvent as a Jacobi continued fraction yields gamma_c in closed form: 2 pi g^2 N_c at the two-pole level, converging to 7.966 g^2 N_c by depth five – an analytic, not numerical, threshold. The square-root exponent nu=1/2 is fixed by the 2x2 Jordan form and confirmed by finite-size scaling to N=1999. The breakdown has an unambiguous time-domain signature: the propagator norm is bounded for gamma < gamma_c, grows linearly at gamma_c (the Jordan secular law), and exponentially beyond – observable, since the deformed operator is a non-Hermitian Wannier-Stark ladder, in photonic and topolectrical analogues. The threshold is locked to confinement, gamma_c propto g^2 N_c, and recurs as a uniform EP cascade; a second, non-reciprocal deformation yields an exactly-exponential non-Hermitian skin effect. This is the first analytically-controlled instance of exceptional-point analyticity breakdown in a confining gauge theory.
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Instrumentation and Methods for Astrophysics
Exploring the Orbital Stability of Large, Lightweight Mirrors around Exoplanets
Shauna M. Sallmen Eric J. Korpela
Extraterrestrial civilizations might place large, lightweight mirrors into orbit around an
exoplanet, either to alter its
climate or to provide illumination to the
planet's dark side. We previously analyzed the detectability of a fleet of 1km x 1km, 1000 kg mirrors (Korpela, Sallmen, & Leystra Greene 2015). Because these mirrors are large and lightweight, their orbits are significantly affected by the
star's radiation pressure (RP). We created a simulation package based on the REBOUND N-body simulator, incorporating RP that directs starlight towards the
planet's center. RP can always affect mirror orbits, or only during orbital night. We have simulated mirrors in initially circular orbits around
exoplanets at various locations in the habitable zones of eight types of main-sequence
stars. Initial mirror orbit sizes range from 2 to 10
planet radii, and we included 4 different initial mirror orbit orientations. For each simulation, we have the mirror's survival time, trajectory, distance from the
planet center at each time, and velocity relative to the
planet at each time. We present an analysis of trends in mirror orbit stability, and relate these to the ratios of RP and gravitational accelerations, as well as the ratio of
planet orbit period to mirror orbit period.
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Materials Science
Predicting Defect States: A Quick Screening Protocol for Substitutional Point Defect Engineering
Hyosik Kang and Lukas Muechler
Point defects in crystalline materials play a central role in determining electronic, optical, and
magnetic properties. However, systematic exploration of defect configurations remains computationally expensive because large supercell calculations are required to approximate isolated defects under periodic boundary conditions. We present a unit-
cell-based tight-binding protocol that enables rapid pre-screening of substitutional defects. The protocol extracts Wannier tight-binding
Hamiltonians from small, fully relaxed unit
cells of the host and defect-like systems, replicates the host
Hamiltonian to construct a supercell model, and introduces the defect by modifying only the on-site energies at the substitution site while leaving the hopping parameters unchanged. We validate the protocol across three diverse systems: isostructural substitutional defects in transition-metal dichalcogenides (M$_\mathrm{Mo}$ MoS$_2$, M = Ce, Zr, Nb, Tc, and Ru),
symmetry-breaking carbon substitutions in hexagonal boron nitride (C$_\mathrm{B}$C$_\mathrm{N}$ h-BN), and nitrogen-vacancy (NV$^-$) centers in diamond. These case studies span two-dimensional and three-dimensional hosts, simple substitutions, and substitution-vacancy complexes. In all cases, the protocol successfully captures the number of in-gap states, their degeneracies, and their shallow or deep character relative to host band edges, despite some quantitative deviations in absolute energy positions. We further identify limitations for vacancies of highly electronegative atoms and for charge-state or
spin-polarization effects, both of which involve self-consistent charge redistribution not captured by the protocol.
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Optics
Effective Training Principles of Physical Reservoirs
Sobhi Saeed, Mehmet Müftüoglu, Glitta R. Cheeran et al. (+3 more)
Reservoir computers benefit from the inherent complexity of optical phenomena, which provide rich, often nonlinear dynamics. However, training directly on the reservoir's output renders the system prone to overfitting and computationally inefficient during the training phase. In this work, we investigate strategies to mitigate overfitting and reduce computational overhead through output
pruning and regularization. We compare loss-minimizing search methods (Equal Search and Branch and Bound) against an output-oriented statistical filtering approach (Variance Filter) and random
pruning, highlighting advantages and disadvantages of each approach and the overall importance of informed reservoir output sampling, particularly for a shrinking latent space. We further demonstrate that enforcing readout selection across the full output spectrum improves performance, especially for non-iterative methods. Additionally, we examine L1 and L2 regularization techniques (LASSO and ridge regression), both of which significantly enhance performance on highly nonlinear tasks such as the Spiral
Benchmark. While our methods are of general use, results are obtained from and discussed exemplarily for a nonlinear fiber-optical extreme learning machine. Overall, this study provides a deep analysis of the reservoirs' hidden-layer filtering mechanisms and the output-layer training, enabling optimized performance in physical reservoir computing systems.
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All authors Sobhi Saeed, Mehmet Müftüoglu, Glitta R. Cheeran, Juliane Heim, Bennet Fischer, Mario Chemnitz
Nuclear Theory
Determining universal spectra from probability distributions
Charles Kacir, Joseph Moscoso, Amy Nicholson et al. (+2 more)
The probability distribution of a two-particle correlation function computed over background auxiliary field configurations, used to generate the interactions, has been shown to inform about the spectra of universal $n$-body clusters [1]. Here, we utilize two approaches, a numerical
lattice computation and an analytic expansion in the limit of large numbers of identical species, in an attempt to refine the initial predictions. Exploratory calculations in these directions are presented, and future investigations laid out.
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All authors Charles Kacir, Joseph Moscoso, Amy Nicholson, Thomas R. Richardson, Cade Rodgers
High Energy Physics (Phenomenology)
Doubly-strange hidden-charm pentaquarks from the Fermi statistics of the light-quark cloud
Halil Mutuk
We extend the baryo-charmonium picture of pentaquarks – a color-octet $c\bar c$ core bonded to a color-octet light-
quark cloud – to the doubly-strange sector $c\bar c ssq$. The mass splittings are set entirely by the light cloud, so the only new inputs are the strange-strange couplings $J^{ss}$, fixed by a second application of the chromomagnetic scaling, and an additive strange-mass increment taken from the observed $P_c\!\to\!P_{cs}$ shift. We obtain two negative-parity triplets, one produced with a kaon and one with an antiproton, the lowest kaon-associated $\tfrac12^-$ state near $4.60$~GeV and the antiproton-associated triplet some $120$~MeV below. The robust, distinctive prediction is that the upper two kaon-associated states form a near-degenerate doublet, in sharp contrast to the well-separated triplets of the lighter sectors – a sparse, fixed-spacing pattern that sets the scheme apart from the molecular and diquark alternatives. The internal splittings follow without adjustment from the measured $P_c$ and $P_{cs}$ spectra; the absolute scale relies on the additive strange-mass ansatz, the main assumption of the extrapolation. The predicted masses agree with recent molecular coupled-channel and QCD sum-rule results.
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Instrumentation and Detectors
Radiation damage studies of silicon photomultipliers for the CMS MIP Timing Detector
Y. Musienko, A. Heering, A. Karneyeu et al. (+1 more)
Recently developed 15 um, 20 um, 25 um and 30 um
cell size Hamamatsu Silicon Photomultipliers (SiPMs) were irradiated with reactor
neutrons at JSI (Ljubljana) up to 2*10^14 n/cm^2 (1 MeV equivalent). The parameters of new and irradiated SiPMs were studied using pulsed light illumination. The effects of the
neutron radiation on breakdown voltage, signal amplitude, dark current and noise for these devices are shown and discussed.
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All authors Y. Musienko, A. Heering, A. Karneyeu, M. Wayne
High Energy Astrophysical Phenomena
Internal constitution of the outer crust of non-accreted neutron stars and magnetars
Juliette Servais and Nicolas Chamel
Context. Determining the internal constitution of the outer crust of magnetars is important for interpreting several of their astrophysical manifestations. In particular, the crustal composition is a key input for simulations of r-process nucleosynthesis in
giant flare ejecta. However, traditional methods are computationally expensive, limiting their use in large-scale studies. Although faster iterative approaches exist, they are restricted to unmagnetized matter and strongly quantizing
magnetic fields, leaving the intermediate field strengths characteristic of observed magnetars without an efficient treatment. Aims. We developed the program magcrust to extend these existing iterative approaches, enabling the rapid computation of the outer-crust composition of cold, non-accreted magnetars over the full range of the
magnetic-field strengths inferred for these objects. Methods. Transitions between adjacent crustal layers are computed by solving approximate
equilibrium conditions at the interface.
Nuclear abundances and layer depths are estimated from approximate solutions of Einstein's equations of general relativity. Results. The performance and accuracy of the program were assessed against detailed numerical calculations. Relative deviations from exact transition properties remain within a few percent, and crustal compositions are well reproduced across 17
nuclear mass tables and 1300
magnetic-field strengths from 1E13 to 1E16 G. Computation times are reduced by factors of 1E3-1E7 compared to traditional approaches. Conclusions. This program provides a robust and efficient tool for determining the stratification of magnetars' outer crust over the full range of astrophysically relevant
magnetic-field strengths. Its computational speed makes it well suited to systematic calculations, including sensitivity analyses, uncertainty quantification, and ensemble studies.
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Astrophysics of Galaxies
The emergence of the faint nature of Low Surface Brightness Galaxies in the IllustrisTNG simulation
Luis Enrique Pérez-Montaño, Bernardo Cervantes Sodi, Vicente Rodriguez-Gomez et al. (+2 more)
We employ a simulated sample of
galaxies drawn from the IllustrisTNG suite to study the emergence of the diffuse and extended nature of $\sim12,000$ low surface brightness
galaxies (LSBGs) within a wide
stellar mass range (${M}_{*}=10^{9}-10^{12} \rm{M}_{\odot}$). We employ merger trees to follow the
evolution of their physical properties such as
stellar surface density, specific angular momentum and
halo spin parameter, finding that the central low density nature of LSBGs is mainly a consequence of an increase in their angular momentum and (inner)
halo spin parameter. We also find that
star formation histories of LSBGs are quite similar to their high surface brightness (HSBGs) counterparts, with significant differences not in the time, but in the spatial distribution in which new
stars are forming. We conclude that the mechanisms that favor the emergence of the low surface brightness nature are strongly related with variations in the
spin parameter of host
halos and their angular momentum, deviating the
stellar distribution of
galaxies from their inner regions to their outskirts, leading to a decrease in their central surface brightness. Once the LSBG nature is established,
galaxies are less likely to experience strong variations in their central surface densities and morphology.
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All authors Luis Enrique Pérez-Montaño, Bernardo Cervantes Sodi, Vicente Rodriguez-Gomez, Doris Stoppacher, Tian-Wen Cao
Astrophysics of Galaxies
The Importance of Galaxy-Wide Star Formation in Driving Winds at z~1
Weichen Wang, Susan A. Kassin, S. M. Faber et al. (+11 more)
In this work, we study winds for a representative sample of 86
star-forming
galaxies (SFGs) at z~1 with $M_\star = 10^{9.0}-10^{11.5} M_\odot$, by measuring the Mg II line profiles in deep Keck spectra. A total of 50 (58%) are found to have winds. Unlike local starburst
galaxies, the wind detection rate does not exhibit a threshold in
star-formation rate (SFR) density $\Sigma_\mathrm{SFR}$ at 0.1 Msun/yr/kpc$^2$, but shows a gradual decline around this value. We find correlations between wind velocity $v_\mathrm{wind}$ and SFR, $\Sigma_\mathrm{SFR}$, and
stellar mass, as per previous studies. Intriguingly, the z~1 SFGs appear to follow the same $v_\mathrm{wind}$-SFR relation as local starbursts. A combined fit gives: log $v_\mathrm{wind}$ = 0.16 log SFR + 2.4 (3-sigma significance). This unified relation spans over 4 dex in SFR and agrees with Illustris-TNG. No unified relation is found between $v_\mathrm{wind}$ and
stellar mass, sSFR, or $\Sigma_\mathrm{SFR}$. This suggests winds might be most closely associated with SFR. We examine whether winds in z~1 SFGs are driven by their most compact
star-forming regions. To do so, we consider whether the relation between $v_\mathrm{wind}$ and the $\Sigma_\mathrm{SFR}$ measured from only these regions is stronger than that for the
galaxy-wide $\Sigma_\mathrm{SFR}$. We do not find a stronger correlation, suggesting that winds are most related to $\Sigma_\mathrm{SFR}$ of the entire
galaxy. Collectively, these findings suggest a picture in which
galaxy-wide
star formation plays an important role in driving winds at z~1. Wind bubbles from all
star-forming regions could combine momentum and help lift their entrained gas out of the
galaxy.
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All authors Weichen Wang, Susan A. Kassin, S. M. Faber, David C. Koo, Timothy M. Heckman, Xinfeng Xu, Hassen M. Yesuf, Alexander de la Vega, Emily C. Cunningham, Puragra Guhathakurta, Yicheng Guo, Camilla Pacifici, John Pharo, Ying Qin
Quantum Physics
A Cryogenic Hybrid Photonic/CMOS Controller Architecture for Scalable Superconducting Qubit Control
Bowen Liu and Zhaoran Rena Huang
Scaling superconducting
quantum computers toward thousands of control channels remains a difficult hardware problem. This requires reducing room-temperature-to-cryogenic interconnects and 4 K power while retaining channel-specific programmability. We develop a hybrid photonic/CMOS control architecture in which optical fibers distribute shared Gaussian and derivative pulse templates, while local cryogenic CMOS
circuits provide event-rate amplitude programming, pulse blocking, hold-duration control, photodetection, and microwave upconversion. The architecture supports template-based XY/DRAG control and smooth-edged flat-top envelopes for two-
qubit control through separate local signal paths. Compared with full-waveform Cryo-CMOS, it moves high-speed sampled-waveform generation out of each cryogenic channel. Compared with per-channel photonic waveform delivery, it retains a programmable endpoint after optical distribution for applying updated channel coefficients and control states. We evaluate the architecture using post-layout
circuit simulations, optical and interconnect models, and system-level power scaling under a common 4 K output boundary. The modeled downlink power is below 1 mW per
qubit-control channel at the thousand-channel scale, substantially below the normalized full-waveform Cryo-CMOS result and in the same range as the strict 50-ohm direct-detection WDM reference. Simulated I- and Q-path outputs are propagated through a five-level transmon model, while the simulated sample-and-hold output is evaluated in a coupled-transmon model. The tested single-
qubit cases remain below the 10^-3 worst-state error reference, and the representative two-
qubit result remains near the same scale after model-level calibration. These results support low-power photonic delivery with limited in-fridge programmability for template-compatible superconducting-
qubit control.
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Instrumentation and Methods for Astrophysics
Exploring Exoplanets with Interferometry
Sascha P. Quanz, Bertrand Mennesson, Charles Beichman et al. (+27 more)
(Extract from the Executive Summary) Humanity stands at the threshold of answering one of its most profound questions: Does life exist beyond Earth? Ongoing and upcoming space missions, together with powerful ground-based instruments, have prepared the way for a transformational next step - the detailed characterization of Earth analogs orbiting Sun-like and other
stars and the search for atmospheric biosignatures that may indicate life. Within this context, the European Space Agency's Voyage 2050 process has identified the direct detection of thermal emission from temperate terrestrial
exoplanets in the mid-infrared (mid-IR) as a top scientific priority. The Large Interferometer For
Exoplanets (LIFE) - a space-based, mid-IR nulling interferometer - is designed to meet this goal. LIFE will be capable of detecting
climate-relevant gases such as CO$_2$ and H$_2$O, identifying classical biosignatures like O$_3$ and CH$_4$, and probing additional, non-classical biosignatures. It will also provide key data for determining planetary radius, albedo, and temperature, which are essential for assessing habitability. In parallel, the U.S. National Academy has recommended a complementary mission now called the Habitable Worlds Observatory (HWO) - a ~6-meter space
telescope equipped with advanced coronagraphs to suppress starlight by a factor of ~10$^{10}$ across the visible and possibly into the near-infrared and near-ultraviolet. Together, LIFE and HWO offer synergistic capabilities, enabling a comprehensive and robust assessment of the prevalence of life-bearing
exoplanets in our
galactic neighbourhood - a first in human history. By uniting an international and interdisciplinary community of scientists and engineers, LIFE offers a credible pathway toward the direct detection and characterization of potentially habitable - and even inhabited - worlds.
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All authors Sascha P. Quanz, Bertrand Mennesson, Charles Beichman, Jonah T. Hansen, Felix A. Dannert, Andrea Fortier, Michael Ireland, Nicholas Beltsten, Eleonora Alei, Leonid Pogorelyuk, William O. Balmer, Denis Defrère, Gautam Vasisht, Malcolm Fridlund, Romain Laugier, Tiffany Kataria, Eugene Serabyn, Steve Ertel, Hélène Rousseau, Kevin Wagner, Rhonda Morgan, Gerard T. van Belle, Gail H. Schaefer, Jean-Philippe Berger, Taro Matsuo, Ewan Douglas, John D. Monnier, Adrian M. Glauser, Dimitri Mawet, Michael R. Meyer