Astrophysics of Galaxies
LightCube: A Parsec-Resolution 3D Model of the Local Far-Ultraviolet Interstellar Radiation Field
Hannah V. Bish, J.E.G. Peek, Catherine Zucker et al. (+5 more)
We present a three-dimensional model of the local interstellar radiation field (ISRF) in the ultraviolet (UV). Using UV flux measurements from the TD1 catalog and
stellar distances from
Gaia and Hipparcos, we construct a catalog of
stars that we expect to dominate the UV flux in the nearby
Galaxy. We use the radiative transfer code DIRTY to model the propagation of
photons from these
stars through a 3D
dust map, including the effects of scattering and absorption. The result is LightCube, a model of the ultraviolet ISRF out to 1.25 kpc from the Sun, with a maximum linear resolution of 1 pc. We model the ISRF in the four TD1 bands (1565 A, 1965 A, 2365 A, and 2740 A), as well as a single value for the full FUV range, and calculate the ISRF at the Sun to be 5.65$\times$10$^{-14}$ erg cm$^{-3}$ from 912 A to 2000 A. The modeled ISRF is quite variable, with more than an order of magnitude variation seen in dense regions, and about half that in lower density regions. By comparing LightCube to an estimate of the 3D distribution of total-to-selective extinction ratio, $R_V$, we find a positive correlation between UV flux and $R_V$ in regions of low UV radiation.
Read the full abstract ▾
All authors Hannah V. Bish, J.E.G. Peek, Catherine Zucker, Karl D. Gordon, Claire E. Murray, Susan E. Clark, Mathieu Willems, Erika Hamden
High Energy Physics (Theory)
Quantum Selection of Classical Histories
Omer Guleryuz
Can a finite
quantum episode populate a classical future that the same prepared state never reaches deterministically? We show that it can, using inflation as a cosmological laboratory. In our supergravity realization, two classical continuations already exist, but the prepared state reaches only one without noise. A stable
entropy direction temporarily becomes light without a tachyonic instability, allowing mode-derived phase-space fluctuations to access the competing continuation. Finite-horizon first passage assigns it a \(0.33\)–\(0.40\) conditional weight across three nearby CMB-normalized realizations, while suppressing the
stochastic source restores its exact deterministic zero. The
entropy sector then becomes heavy again, and the selected histories continue classically. A finite
quantum episode can thus leave a lasting redistribution among classical futures.
Read the full abstract ▾
Quantum Physics
Stochastic transport of a Goldstone mode in a self-organized atomic crystal
Zhanhai Yu, Di Xiang, Xiaotian Zhang et al. (+1 more)
Spontaneous breaking of a continuous
symmetry produces a massless Goldstone mode that can evolve across a degenerate
manifold at zero energy cost. Goldstone modes have been identified primarily through excitation spectra, mode softening or collective oscillations. However, their time-domain transport under intrinsic fluctuations and dissipation has remained largely unexplored. Here we directly track the
stochastic transport of a Goldstone mode in a self-organized atomic
crystal inside an optical ring cavity. The ring cavity maps the order-parameter phase onto the real-space position of the emergent
crystal. Without any external perturbation, fundamental
photon-scattering
recoil drives the collective transport, while cavity dissipation generates friction. We monitor individual trajectories of the atoms and their self-generated optical
lattice by measuring the cavity output phase. We find that the
diffusion constant decreases as $1/N$, indicating that all atoms move collectively as a rigid object rather than independently. By tuning the Langevin driving force and cavity-mediated damping, we show that the normalized
diffusion constant collapses onto a single universal curve. This work extends the study of continuous
symmetry breaking from excitation-frequency measurements to real-time tracking of transport, and opens routes for studying non-
equilibrium collective transport,
phonon dynamics, and defect formation in driven-dissipative
quantum matter.
Read the full abstract ▾
All authors Zhanhai Yu, Di Xiang, Xiaotian Zhang, Hao Zhang
Chemical Physics
Real-Time Emergence of Charge-Transfer-to-Solvent States from Core Excitation
Jiří Suchan, B. Scott Fales, Benjamin G. Levine et al. (+2 more)
Charge-transfer-to-solvent (CTTS) excitations provide a chemically central route to generating hydrated electrons and initiating redox chemistry in solution, yet the earliest stage of CTTS—the formation of the excited state itself—is usually treated as instantaneous. Here we present a time-domain perspective of how CTTS character builds up during core-level photoexcitation of an aqueous metal ion. Using time-dependent configuration interaction, we simulate the coherent
evolution of a dense
manifold of core-excited states and track the ultrafast flow of electronic charge from the initially localized site into solvent-supported final states. We find that the dynamics evolves from a few-state, oscillatory behavior to effectively irreversible delocalization, as the charge disperses among many coupled configurations, providing a microscopic mechanism for the early-time emergence of CTTS character. Our results offer a transparent real-time interpretation of what core-level spectroscopies and core-hole-clock-type measurements can probe in solutions, outlining experimental signatures for probing the build-up of CTTS states on the core-hole-lifetime timescale. Looking ahead, attosecond and sub-femtosecond X-ray pump–probe approaches at X-ray free-electron
lasers provide a realistic route to directly time-resolve the core-excited CTTS wave packets in solution.
Read the full abstract ▾
All authors Jiří Suchan, B. Scott Fales, Benjamin G. Levine, Eva Muchová, Petr Slavíček
Mesoscale and Nanoscale Physics
Scalable, Simple, and Versatile Encapsulation of 2D Materials and Devices
Gabriel Natale, Uma Chirkova, Flávio Henriques Feres et al. (+16 more)
Air-sensitive 2D materials present a fundamental challenge for device integration. Encapsulation is often required to preserve intrinsic properties, yet conventional protection strategies often fail for thicker layers and complicate fabrication. Here, we demonstrate that electron-beam (e-beam) evaporated aluminum
oxide ($\mathrm{AlO}_x$) serves as both an effective encapsulation layer and a platform for direct device fabrication. Unlike transfer-based approaches, this scalable method is compatible with thicker flakes and full device or wafer coverage. It requires no stacking procedures and enables contacts without post-encapsulation etching. Using rare-earth tritellurides ($\mathrm{RTe}_3$, R = La, Er), semimetallic $\mathrm{WTe}_2$, and superconducting $\mathrm{FeTe}_x\mathrm{Se}_{1-x}$, we show that $\mathrm{AlO}_x$ suppresses oxidation and preserves intrinsic optical and electronic properties. We establish substrate-dependent optimization of encapsulation across a range of flake thicknesses, demonstrate that ultrathin $\mathrm{AlO}_x$ preserves $\mathrm{WTe}_2$'s plasmonic response and maintains superconducting performance in $\mathrm{FeTe}_x\mathrm{Se}_{1-x}$. Thus we overcome the longstanding tradeoff between encapsulation and straightforward device fabrication in fragile
quantum materials.
Read the full abstract ▾
All authors Gabriel Natale, Uma Chirkova, Flávio Henriques Feres, Ran Jing, Michael Geiwitz, Wenyao Liu, Emma Low, Josh Leeman, Kyung-Mo Kim, Leslie M. Schoop, Mohamed Shehabeldin, Qiong Ma, Michael A. Susner, Pijush Bhattacharya, Genda Gu, Katherine Lee, James Hone, Mengkun Liu, Kenneth S. Burch
Instrumentation and Methods for Astrophysics
The MICADO first light imager for the ELT: first on-bench performance tests of the SCAO hybrid LQG+Integrator controller
N. Levraud, F. Ferreira, A. Sevin et al. (+6 more)
The Extremely Large Telecope (ELT) is expected to begin scientific operations in 2030, with MICADO as its first-light imager. The Single Conjugate Adaptive Optics (SCAO) system for MICADO is currently being assembled and tested at the Observatoire de Paris. MICADO's baseline AO control strategy uses a hybrid approach: a Linear Quadratic Gaussian (LQG) regulator for low-order modes, optimised to adapt to the disturbance caused by vibrations and ELT windshake, and an integral action controller for higher-oder modes. Despite the non linearity of the Pyramid Wavefront Sensor (PyWFS), the so-called "optical gains", LQG control has proven to be highly effective in simulation. It has been shown that the LQG regulator is resilient to optical gain variations in the loop or to inaccuracies in their estimation. Increasing the number of modes controlled by the LQG regulator would therefore make the controller less sensitive to the optical gains, which are notoriously difficult to estimate during operation. A first hybrid controller, with only tip-tilt controlled with LQG control, has been validated using COMPASS, the end-to-end, GPU-accelerated, AO simulation platform. We will present the first experimental validation of this hybrid controller on the MICADO-SCAO bench. We will also present results obtained by increasing the number of modes controlled with LQG control and the work carried out to go towards an autonomous LQG regulator.
Read the full abstract ▾
All authors N. Levraud, F. Ferreira, A. Sevin, E. Gendron, N. Galland, H.-F. Raynaud, Y. Clénet, R. Davies, C. Kulcsár
Fluid Dynamics
How well can Diffusion Models learn Lagrangian-Tracer Statistics in Non-reciprocal Turbulence?
Pratyush Jha, Biswajit Maji and Rahul Pandit
Recent advances in generative artificial intelligence have led to significant potential applications in conventional fluid flows, including those that are turbulent. Can these methods be carried over to studies of novel types of
turbulence, such as
turbulence induced by non-reciprocity in binary-fluid systems? To answer this question, we analyze the statistics of Lagrangian-tracer particles in non-reciprocal binary-fluid
turbulence, which has been studied recently in the non-reciprocal Cahn-Hilliard-Navier-Stokes (NRCHNS). We obtain our ground-truth data via extensive pseudospectral direct numerical simulations (DNSs) of the two-dimensionsl (2D) NRCHNS model. Our study yields a variety of intriguing results for probability distribution functions (PDFs) for particle accelerations and velocity-component PDFs; the latter turn out to be bimodal, completely unlike their 2D-fluid-
turbulence counterparts. We relate this bimodality to lane-type structures in Eulerian-velocity components. Furthermore, we characterize Lagrangian multiscaling via Lagrangian velocity increments, their structure functions and flatnesses, and multiscaling exponent ratios, for the first time in non-reciprocal hydrodynamics. Finally, we use generative
diffusion models to obtain synthetic Lagrangian trajectories for the NRCHNS system, assess how effectively they can emulate the Lagrangian statistics that we obtain from our DNSs, and highlight open challenges in the application of generative artificial intelligence in non-reciprocal systems.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Mobility Enhancement in Si/SiGe Quantum Well Enabled by a Buried Si Layer Trapping Oxygen Impurities
Felix Reichmann, Alberto Mistroni, Fabian Fidorra et al. (+4 more)
Reducing disorder in undoped Si/SiGe field-effect
heterostructures remains an important materials challenge for scalable
quantum devices, particularly electron
spin qubits. Background
impurities such as oxygen have been identified as mobility-limiting, yet practical
heterostructure-design strategies for suppressing their incorporation remain underexplored, and their influence across different transport regimes is not fully established. Here, we demonstrate a simple route to oxygen reduction and mobility enhancement in Si/SiGe
quantum-well
heterostructures grown by reduced-pressure chemical vapor deposition (RP-CVD) on 200 mm Si(100) substrates through the introduction of a thin, electrically passive buried Si layer within the lower SiGe barrier. Secondary-ion mass spectrometry shows that the buried Si layer reproducibly reduces the oxygen background in the subsequently grown SiGe by approximately a factor of five, without modifying the active
quantum-well region. Density- and temperature-dependent magnetotransport measurements further show that this reduction increases the electron mobility, while leaving the percolation density and density-dependent mobility scaling largely unchanged. Upon cooling to 0.3 K, both high- and low-oxygen devices exhibit similar density-dependent fractional mobility enhancements, indicating that the reduced oxygen background improves momentum relaxation without substantially altering the dominant low-density disorder landscape. These results establish the buried Si layer as a straightforward and process-compatible
heterostructure-design element for reducing oxygen incorporation and improving transport in 200 mm CVD-grown Si/SiGe
quantum-device materials.
Read the full abstract ▾
All authors Felix Reichmann, Alberto Mistroni, Fabian Fidorra, Giovanni Capellini, Yuji Yamamoto, Marco Lisker, Marvin H. Zoellner
Cosmology and Nongalactic Astrophysics
Near universality of nonlinear transverse and radial velocity responses in spherical collapse with arbitrary radial profiles
Valerio Marra
The nonlinear relation between density and expansion is usually formulated for a homogeneous spherical top hat, which has a single local Hubble rate. A smooth spherical profile instead expands differently along ($H_{\parallel}$) and across ($H_{\perp}$) the radial direction-a direct signature of radial inhomogeneity. We show that, for growing-mode pressureless matter with a cosmological constant, the complete shellwise response is nevertheless fixed by one top-hat function. Given the local density contrast $\delta(t,r)$ and the enclosed contrast $\Delta(t,r)$, a transverse response and its derivative determine $H_{\perp}$ and $H_{\parallel}$. The linear and second-order limits are algebraic maps whose only dynamical input is the usual growth rate $f$. An exact equal-age construction supplies the nonlinear response without integrating an
evolution equation. We check that it reconstructs full $\Lambda$LTB profiles to numerical precision. We also provide a derivative-aware, cosmology-independent three-term symbolic fit that requires only $f$, $\delta$, and $\Delta$. Across a representative set of matter-
curvature-
redshift combinations and for a shell located in the compensated transition, the maximum relative errors are $0.3\%$ and $0.7\%$ in the transverse and radial responses, respectively. This compact formulation separates the production of a density profile from its expansion response and makes the effect of radial gradients explicit.
Read the full abstract ▾
Astrophysics of Galaxies
Non-isothermal vertical distribution functions for the Milky Way
Maria Djurić and Ralph Schönrich
The vertical structure of our
Galaxy has commonly been assumed to follow a pseudo-isothermal distribution. However, there is no a priori reason to expect this form to arise from scattering by
giant molecular clouds (GMCs), since GMCs are confined to a narrow layer around the
Galactic midplane and therefore do not randomise
stars uniformly in vertical phase space. We first present a simple statistical argument to derive a new vertical distribution function (DF), in the limiting case of a razor-thin distribution of GMCs, which admits an extra factor of ${J_z}^{-\alpha}$, where $\alpha>0$ and varies for different potentials. In light of this, we revisit the
diffusion coefficients for vertical heating from the mechanics of two-body scattering, in a more realistic, extended distribution of GMCs. The resulting drift and
diffusion coefficients are strongly non-linear in $v_z$, particularly at low relative velocities, where the effective range of weak, local encounters can vanish. We determine stationary solutions, and also numerically solve the orbit-averaged Fokker–Planck equation with time-dependent coefficients. We find, in both cases, a vertical action distribution that deviates from that of the pseudo-isothermal case, and propose a new, family of vertical DFs that generalise the pseudo-isothermal form. We find the two primary
agents of non-isothermality are: (i) a GMC distribution confined near the midplane, and (ii) the fact that the Coulomb logarithm, $\Lambda$ is strongly velocity-dependent at small velocities, and cannot be treated as a constant, contrary to the commonly adopted assumption.
Read the full abstract ▾
Disordered Systems and Neural Networks · Cross-listed from math.PR
Universality and sharp thresholds for ellipsoid fitting
Frederic Koehler and Youngtak Sohn
We establish a sharp phase transition for fitting random vectors by an ellipsoid. The random vectors have independent subgaussian coordinates with mean zero, variance one, and a common fourth moment, and the number of vectors is proportional to the square of the dimension. We identify an explicit satisfiability threshold such that, with high probability, a positive definite ellipsoid passes through every data point below the threshold, whereas no positive semidefinite fit exists above it. We also determine the optimal squared fitting error throughout the unsatisfiable regime. In particular, the threshold depends on the coordinate distributions only through their common fourth moment, revealing a fourth moment universality phenomenon. For standard Gaussian data the threshold is $1/4$, resolving the ellipsoid fitting
conjecture.
Read the full abstract ▾
Quantum Physics
On supporting affine functionals for Entanglement of Formation
A.S.Holevo and M.E.Shirokov
In several articles, the authors assume that the convex roof structure of the EoF and finite-dimensionality of subsystems $A$ and $B$ guarantee the existence of the (global) supporting affine functional for the EoF at any state of the system $AB$. This means that for any state $\rho$ of $AB$ there is a Hermitian operator $\Lambda_\rho$ on $\mathcal{H}_{AB}=\mathcal{H}_A\otimes\mathcal{H}_B$ such that $E_F(\rho)=\mathrm{Tr}\Lambda_\rho\rho$ and $E_F(\sigma)\geq\mathrm{Tr}\Lambda_\rho\sigma$ for any state $\sigma$ of $AB$. We present an explicit example showing that, when $\rho$ is degenerate, this is not true even in the simplest case when $A$ and $B$ are
qubit systems. The construction is based on the fact that the existence of a supporting affine functional for the EoF at a state $\rho$ is equivalent to the Lipschitz lower semicontinuity of the EoF at this state $\rho$. We use Wootters' formula and the help of Claude Fable 5 to find a state $\rho$ of the system $AB$ for which the latter property does not hold. We also describe conditions for the existence the local and global supporting affine functionals for the EoF at a given state of both finite and infinite-dimensional bipartite
quantum systems. These conditions allow us to find Lipschitz lower semicontinuity bounds for the EoF at a given finite rank state $\rho$ (i.e. inequalities of the form $\,E_F(\rho)-E_F(\sigma)\leq C_\rho\|\rho-\sigma\|_1$) with and without restrictions on the support of the state $\sigma$.
Read the full abstract ▾
Materials Science
Temperature dependence of the charge density from first principles: application to the (222) forbidden reflection in silicon
Jean Paul Nery, Raveena Gupta, Olle Hellman et al. (+2 more)
Forbidden reflections (FRs) in X-ray diffraction have inherently weak intensity and have long been studied, in particular in
semiconductors like silicon. They serve as sensitive probes of
symmetry breaking, local strain,
impurities, and weak charge redistribution. Despite extensive experimental work, the theory of their temperature dependence has typically relied on simplified models. While atomic Debye-Waller factors work well on allowed reflections, their applicability to the valence charge between atoms, which determines the intensity of FRs such as Si (222), is questionable, and previous agreement between theory and experiment relied on ad-hoc Debye-Waller corrections. We compute the temperature-dependent valence charge density $\rho(\mathbf{r},T)$ of silicon from first principles, using two methods: (i) perturbation theory, and (ii) averaging over thermally distorted supercells in a non-perturbative approach. The perturbative expression for the charge density is far more demanding than that for electronic energies, since it depends on the wavefunctions themselves and requires an explicit sum over unoccupied bands. We use an acoustic sum rule to express the second derivatives of the potential in terms of first derivatives, making the expression tractable within existing frameworks. The (222) FR then follows directly from the
Fourier transform of $\rho(\mathbf{r},T)$, with no ad-hoc factors. Both methods give similar results, in reasonable agreement with experiment, with thermal expansion noticeably affecting the temperature dependence. The charge density answers a question the measured intensities could not settle: how the valence charge actually redistributes with temperature. Relative to the rigid model, we find more charge in the bonds and less in the core regions, a redistribution that shows up in the intensity as a somewhat weaker temperature dependence of the (222) FR.
Read the full abstract ▾
All authors Jean Paul Nery, Raveena Gupta, Olle Hellman, Philip B. Allen, Matthieu J. Verstraete
Astrophysics of Galaxies
$N$-body simulations of the open cluster population in the Milky Way and the impact of GMC encounters
Timmi G. Jørgensen and Ross P. Church
We investigate the population of open clusters in the
Solar Neighbourhood and model the effect of encounters with
giant molecular clouds (GMCs) over the last 1 Gyr. We combine a
Galactic model with $N$-body simulations of 20692 unique clusters in the mass range $[50-24000]$ $\mathrm{M}_{\odot}$. Each cluster is simulated twice: with and without
tidal forces from the GMCs. We find that an initial cluster mass function truncated at $\sim 9000$ $\mathrm{M}_{\odot}$ best reproduces the observed mass function
evolution. For the age function, the observations show a decline in clusters for ages older than $\sim 1$ Myr, whereas our simulated clusters show a decline after $\sim 50$ Myr. The observed early disruption suggests that some clusters form supervirial, whereas our simulated clusters are created in virial
equilibrium. Low-mass ($<600 \, \mathrm{M}_{\odot}$) clusters are most sensitive to GMC encounters, which accelerate their disruption in the first $\sim 200$ Myr. After $\sim 500$ Myr, the impact of GMCs becomes irrelevant since the clusters will have been destroyed regardless of whether they experience GMC encounters or not. The survival of intermediate-mass ($600-6000\, \mathrm{M}_{\odot}$) clusters is significantly reduced by GMCs at ages up to 1 Gyr. High-mass ($>6000 \, \mathrm{M}_{\odot}$) clusters survive to 1 Gyr with minimal disruption with or without GMCs. We find that clusters that have had strong GMC encounters within the last $20$ Myr should have
tidal tails that are randomly orientated with respect to the
Galactic centre.
Read the full abstract ▾
Quantum Physics
Randomness can be certified in energy-constrained semi-device-independent scenarios
Shashank Kumar Ranu, Lewis Wooltorton, Alastair A. Abbott et al. (+1 more)
The prepare-and-measure framework based on energy constraints offers a practical middle ground between fully device-dependent and device-independent
quantum cryptography. The only assumption on an otherwise uncharacterized prepare-and-measure device is that the energy of the prepared states is bounded. Existing security analyses of this framework assume that the preparation and measurement devices share at most classical correlations, and under this assumption certified lower bounds on the extractable randomness have been established. Recent work has shown that an adversary who pre-distributes
entanglement between the devices can mount attacks that are strictly more powerful than those available when the devices share only classical correlations, reducing the extractable randomness below the previously certified rates. This leaves open the fundamental question of whether randomness can be certified at all in this scenario. We address this open question by constructing semidefinite programming relaxations of the guessing probability by adapting the Navascués-Pironio-Acín hierarchy to the energy-constrained setting where shared
entanglement between the devices is permitted. Our relaxations yield certified lower bounds on the extractable randomness without enforcing any restrictions on the dimensions of the
quantum state shared between the preparation and measurement devices. We show that these certified lower bounds are strictly positive for a range of energy values, thereby answering the open question affirmatively: certified randomness generation is theoretically possible in the energy-constrained SDI framework even in the presence of a fully
quantum adversary.
Read the full abstract ▾
All authors Shashank Kumar Ranu, Lewis Wooltorton, Alastair A. Abbott, Omar Fawzi
Fluid Dynamics
Dynamical slowdown, bottlenecks, and multiscaling in Voigt-regularised turbulence
Anikat Kankaria, Bikram Pal, Edriss S. Titi et al. (+1 more)
We investigate bottleneck formation in
turbulence using the Voigt-regularised SABRA model and DNS of the corresponding Voigt-Navier-Stokes (NSV) equations. The Voigt regularisation introduces a scale-dependent slowdown of nonlinear interactions without enhancing dissipation, providing a natural setting to study the interplay between nonlinear transfer and thermalised behaviour. We find three distinct spectral regimes: an inertial range at $k<k_I$, an intermediate
equilibrium-like range associated with partial thermalisation for $k_I<k<k_{II}$, and a high-$k$ thermal regime for $k>k_{II}$, where the Voigt contribution dominates the conserved invariant. The crossover to the high-$k$ regime occurs at $k_{II}\sim 1/\alpha$, while $k_I$ marks the onset of thermalised behaviour. Equal and multi-time statistics reveal a progressive suppression of intermittency and a tendency towards Gaussianity at small scales, together with a transition from dynamic multiscaling in the turbulent regime to simple scaling in the
equilibrium ranges. The shell model resolves these three regimes over a broad range of scales, while DNS of the corresponding NSV equations reproduces the same qualitative trends, including bottleneck formation, delayed cascade completion, reduced intermittency, and a tendency towards Gaussianity at small scales. We find that bottleneck formation might be associated with scale-dependent dynamical slowdown and incipient thermalisation, rather than being purely dissipative in origin. We provide strong evidence that, in the regime where the regularization parameter $\alpha$ is much smaller than the dissipation length scale, the Voigt model reproduces the same inertial-range turbulent regime and
turbulence statistics as the Navier-Stokes (NS) equations. This provides evidence that the Voigt model constitutes an excellent practical approximation to the NS equations for small $\alpha$.
Read the full abstract ▾
All authors Anikat Kankaria, Bikram Pal, Edriss S. Titi, Samriddhi Sankar Ray
Earth and Planetary Astrophysics
Dust torques for realistic dust size distributions
V. Roatti, G. Picogna and F. Marzari
Previous studies have shown that a population of
dust particles with a fixed Stokes number can exert a substantial torque on a low-mass
planet embedded in a protoplanetary disk, modifying its migration rate. We aim to characterize the
dust torque on a low-mass
planet for a realistic distribution of
dust grain sizes. We performed 2D hydrodynamical simulations of
planet-disk interactions using the PLUTO code, with the addition of Lagrangian superparticles representing
dust dynamics. We apply an energy-based criterion to exclude the particles that are gravitationally bound to the
planet, to prevent circumplanetary flow to contaminate the torque measurements. We find that the
dust torque is dominated by the largest grains in the size distribution and is highly sensitive to the maximum grain size. For typical disk conditions, the torque becomes positive for marginally coupled particles ($\mathrm{St} \gtrsim 10^{-2}$) and can exceed the gas torque in the presence of cm-sized pebbles, leading to outward migration of low-mass
planets. Unlike previous studies, the turbulent
dust diffusion has a negligible influence on the torque over the explored range of $\alpha = 10^{-4}$ to $3\times 10^{-3}$. The dominant contribution arises from within the planetary Hill sphere, highlighting the need for high spatial resolution and accurate integration of particle trajectories. We derive a scaling law for the
dust torque as a function of the maximum grain size and the planetary mass, suitable for implementation in population synthesis models.
Read the full abstract ▾
Soft Condensed Matter
Nonparametric multiscale modeling of boundary lubrication: hexadecane in highly pressurized gold asperity contacts
Hannes Holey, Michael Moseler, Peter Gumbsch et al. (+1 more)
Boundary lubrication is governed by molecular processes at the sliding interface that are inaccessible to classical continuum descriptions. While molecular dynamics (MD) simulations can resolve these processes in atomistic detail, incorporating their output into engineering-scale models through semi-empirical constitutive laws becomes increasingly difficult as confinement approaches the molecular scale. Here, we apply a nonparametric multiscale framework based on Gaussian process (GP) regression to model boundary lubrication of hexadecane confined between gold surfaces under pressures up to 1 GPa and gap heights down to 1.4 nm. The GP surrogates are trained on nonequilibrium MD simulations of the confined fluid and directly provide stress predictions to a continuum thin-film solver, circumventing the need for fixed-form constitutive laws. The framework naturally captures molecular phenomena such as density layering, viscosity changes, and the strongly nonlinear wall slip that dominates the frictional response at high pressures and small gap heights. Our results reproduce the atomistic
benchmark data of Codrignani et al., demonstrating that nonparametric surrogate models offer a flexible and physically transparent route toward predictive continuum modeling of boundary lubrication.
Read the full abstract ▾
All authors Hannes Holey, Michael Moseler, Peter Gumbsch, Lars Pastewka
Quantum Physics
Quantum Chaos and Quantum Optimal Transport
Jordan Cotler and Felipe Hernández
Chaos in classical systems can be characterized by Lyapunov exponents that measure the exponential divergence of nearby trajectories, but directly extending this framework to
quantum mechanics has been a persistent challenge. The wavelike nature of
quantum states and the non-commutative geometry of
quantum phase space obstruct a straightforward generalization of classical chaos theory. Here we develop a rigorous approach to
quantum chaos by leveraging
quantum optimal transport theory, which provides the missing
geometric foundation for measuring distances between extended
quantum distributions. We define
quantum Lyapunov exponents that naturally avoid divergences encountered when naïvely generalizing classical exponents, and show that in the semiclassical limit they recover the classical global expansion rate, and hence the usual maximal Lyapunov exponent when they coincide. Our framework provides a tight connection between the divergence of classical trajectories and semiclassical phase space
evolution, and additionally clarifies the role of out-of-time-order correlators as diagnostics of
quantum chaos. These results establish
quantum optimal transport as a unifying mathematical foundation for
quantum chaos theory, providing new tools to characterize dynamical behavior across the full range of
quantum dynamics from simple few-body models to complex many-body systems.
Read the full abstract ▾
Superconductivity
High-Temperature Superconductivity of the Fe-Se-H compound
S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov et al. (+4 more)
Using an EPR spectrometer, the dependences of microwave power absorption on
magnetic field up to 6000 Oe were measured at temperatures of 3.6-25 K and 295 K in a powdered compound Fe-Se-H, obtained by thermal
diffusion of hydrogen into a FeSe single
crystal with a critical temperature of 8 K. The shape of the dependences and the analysis of the measurement results confirm the superconductivity of the Fe-Se-H compound at normal pressure, both at temperatures of 3.6-25 K and at 295 K, i.e., at room temperature.
Read the full abstract ▾
All authors S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov, V.P. Timofeev, V.P. Koverya, I.S. Bondarenko, A.V. Krevsun
Solar and Stellar Astrophysics
Panchromatic Spectra of Nearby Low-mass and Sun-like Stars with Directly Imageable Habitable Zones
Sarah Peacock, Breanna A. Binder, Edward W. Schwieterman et al. (+4 more)
Characterizing the high-energy radiation environments of
stars plays a critical role in determining which systems'
planets are capable of retaining atmospheres and sustaining habitable conditions. X-ray through ultraviolet (UV) radiation drives atmospheric photochemistry, heating, and escape, making accurate characterization of
stellar high-energy emission essential for both interpreting future
exoplanet observations and identifying the most promising targets for life detection. We construct panchromatic spectral energy distributions (SEDs) spanning the X-ray through
radio for 12 nearby low-mass and Sun-like
stars with directly imageable habitable zones that are prioritized targets for the Habitable Worlds Observatory (HWO) and Extremely Large
Telescopes (ELTs). These SEDs are generated using forward
stellar atmosphere models guided and constrained by available archival X-ray and UV observations. We find that many
stars in this sample exhibit elevated high-energy radiation environments relative to the modern Sun, with habitable zone X-ray and extreme UV (XUV) fluxes frequently exceeding
solar values by 1-2 orders of magnitude. The elevated emission likely reflects a combination of sample selection effects, differences in
stellar age and rotation, and intrinsic
magnetic variability, with multi-epoch observations demonstrating that variability alone can significantly alter inferred radiation environments. These results highlight high-energy radiation as an important discriminator in identifying the most promising habitable
planet hosts and demonstrate the need for expanded X-ray and UV observations to complete the
stellar characterization necessary for HWO target prioritization.
Read the full abstract ▾
All authors Sarah Peacock, Breanna A. Binder, Edward W. Schwieterman, Margaret C. Turnbull, Stephen R. Kane, Katherine Garcia-Sage, Alison Farrish
Quantum Physics
Tsirelson's nonclassicality witness under dissipative dynamics
Nguyen Vu Khoi Huynh, Nicky Nel Narido Labayna, Martine Schut et al. (+1 more)
A dynamics-based test, originally proposed by Tsirelson for the harmonic oscillator, provides a method for certifying quantumness under the assumption of a known
Hamiltonian. These tests, however, are typically proposed for isolated systems, an assumption that breaks down in experimental implementation. In this paper, we extend the protocol to the harmonic oscillator coupled to standard models of dissipation: thermal relaxation, pure dephasing, and the Caldeira–Leggett model. Using the Moyal-Wigner formalism of
quantum mechanics in phase space, we show that the introduction of dissipation requires a dissipation-dependent shift of the classical bound, and provide the threshold under which the nonclassicality witness retains its validity.
Read the full abstract ▾
All authors Nguyen Vu Khoi Huynh, Nicky Nel Narido Labayna, Martine Schut, Valerio Scarani
Optics
Ultra-Low-Loss Silicon Nitride on Sapphire for Broad-Transparency Nonlinear and Quantum Photonics
Abdur-Raheem Al-Hallak, Shuai Liu, Kailu Zhou et al. (+9 more)
The field of photonic integrated
circuits (PIC) has flourished in the past two decades, fueling numerous cutting-edge applications across sensing, networking, data interconnect, and
quantum information processing. As a guiding material for PIC, Si$_3$N$_4$ has seen extensive use for its ultra-low loss, broad transparency, and diversity in implementation across both thin and thick films. Although the standard, traditional silicon dioxide (SiO$_2$) on silicon (Si) substrates that underpin the majority of Si$_3$N$_4$ photonics face drawbacks in the form of long-wavelength transparency limited by SiO$_2$, high-stress deposition for anomalous dispersion thick-film Si$_3$N$_4$, and leakage loss to the Si layer for low-confinement thin-film Si$_3$N$_4$. Featuring increased long-wavelength transparency into the mid-infrared, low-stress deposition of Si$_3$N$_4$, and a low index, this work investigates sapphire substrates as alternate hosts for Si$_3$N$_4$ photonics with greater spectral coverage and reduced fabrication complexity. This work presents a robust method of fabricating ultra-low loss photonic integrated
circuits on a 500-nm-thick Si$_3$N$_4$-on-sapphire platform, exhibiting record-low losses below $0.1 \rm \;dB/cm$. Implemented using this process are high-Q microrings with intrinsic quality factors in excess of $4.5\times10^6$ and coupled-ring photonic molecules to support nonlinear gain. Leveraging the achievable low loss and high-Q, this work further reports the first demonstration of Kerr-comb and
soliton generation on the Si$_3$N$_4$-on-sapphire platform. These advances in loss, quality factor, and
soliton generation on this versatile, broad-transparency platform pave the way for future work in spectroscopy and
quantum-enhanced sensing across previously prohibited spectral regions for Si$_3$N$_4$ photonics with reduced fabrication complexity.
Read the full abstract ▾
All authors Abdur-Raheem Al-Hallak, Shuai Liu, Kailu Zhou, Jiangnan Liu, Shawn Chen, James Hu, Ruhi Yusuf, Christopher Rodriguez, Maya Sarram, Yiming Lang, Zetian Mi, Zheshen Zhang
Quantum Physics
Evaluating Quantum Kernel Methods for Track-Based Classification in High-Energy Physics
Emmanuel Billias and Nikos Chrisochoides
We present a systematic design for large-scale
quantum kernel classification, demonstrated through a
quantum support vector classifier (QSVC) for particle-track classification using centroid-based CLAS12 drift-chamber features. Each event is encoded into a six-
qubit state via a fully entangled ZZFeatureMap, whose fidelities define a
quantum kernel within a standard SVM framework. By decoupling state preparation from kernel construction and distributing evaluation across a multi-node MPI-based HPC allocation, the approach scales to 1.0x10^5 training and 4.0x10^5 test events with an exactly constructed kernel
matrix, to our knowledge more than an order of magnitude larger than prior high-energy-physics
quantum-kernel studies. Benchmarked against linear,
polynomial, RBF, and sigmoid SVM kernels and extremely randomized trees (ERT), the ideal QSVC achieves the highest recall (99.99%) among all models. Under a calibrated hardware noise model (FakeMumbaiV2, 500 training / 2,000 test events), AUC falls from 0.9985 to 0.9671 and peak significance improvement falls from 17.5 to ~3.5, yet recall remains at 99.51% – indicating this signal-retention advantage is attenuated but not eliminated by
circuit-level decoherence.
Geometric analysis of the
quantum embedding shows near-orthogonal inter-class states with coherent intra-class neighborhoods under ideal simulation; under noise this structure compresses toward the maximally mixed state while preserving its relative ordering. These results demonstrate a scalable, reproducible workflow for
quantum kernel experimentation at HEP-relevant scale, quantifying the practical cost of realistic hardware noise on
quantum-enhanced classification.
Read the full abstract ▾
Quantum Physics
The Geometry of Dissipative Complexity: A Levi-Type Decomposition Theorem for Markovian Quantum Dynamics via Lie Wedges and Invariant Cones
Yibin Wang and Dhara Thakkar
Lie
algebras describe how control
Hamiltonians combine in closed
quantum systems. In open Markovian systems, however, dissipation introduces irreversible directions that the Lie
algebra alone does not retain. A dynamical Lie wedge preserves this information as a convex cone of locally admissible generators. The classical Levi decomposition separates a finite-dimensional Lie
algebra into semisimple and solvable parts. In this work, we prove a corresponding decomposition and reconstruction
theorem for dynamical Lie wedges. The
theorem decomposes the wedge into semisimple and solvable data, records how these components are coupled, and provides a converse reconstruction of the wedge. The framework yields four structural types of the generated
algebra. We further prove that the total dissipation strength of every admissible generator depends only on its coordinate in the solvable radical. In particular, if the generated Lie
algebra is semisimple, every admissible generator is
Hamiltonian. Together, these results extend Lie-algebraic structural methods to irreversible Markovian control and clarify how dissipation is encoded in the generator geometry.
Read the full abstract ▾
Materials Science
Coupled anisotropic weak topological states and Floquet mixed-parity altermagnetism in two-dimensional Su-Schrieffer-Heeger models
Kunyuan Feng, Xibin Liu, Chenchen Liu et al. (+5 more)
Su-Schrieffer-Heeger (SSH) topological systems and altermagnetic (AM) states are two important research areas in condensed matter physics. Realizing the coupled states between the SSH
lattices and AM phanse in a single syetem remains challenging. However, the Floquet engineering change it. Our work constructs five two-dimensional-(2D-) SSH models to describe the coupled phases of SSH weak topological state and AM order by tight-binding (TB) method. The
evolution of band structures,
spin-splitting, and topological phase transitions under the circularly polarized light (CPL) and relative atomic displacement (RAD) in 2D SSH
lattices were systematically investigated. The results reveal that the inequality of hopping parameters (t1 and t2) serves as the fundamental origin of SSH topological states and AM order. For the 2D nonmagnetic state, anisotropic weak topological states with Zak phase governed edge states are realized by unit
cell selection, similar to the conventional 1D SSH model. The collinear
antiferromagnetic state preserves the
spin-degenerate band structure and intrinsic weak topological properties. Furthermore, the Floquet engineering introduces the AM phase of odd-parity p-wave while the RAD introduces the AM phase of even-parity d-wave. By combining the two effects, the mixed-parity (non-odd/non-even parity) AM phase could be realized, achieving the simultaneous control of the light field of
spin-splitting and topological edge states. The physical mechanisms of Floquet engineering and RAD for the 2D rectangular SSH
lattice are also from the inequality of t1 and t2, which can be not only fully understand by the TB methods, but also in good agreement with the first-principle calculations of 2D carbon-based materials. This work establishes an effective theoretical platform for coupling anisotropic SSH weak topological states and AM orders with multi-parities in 2D systems.
Read the full abstract ▾
All authors Kunyuan Feng, Xibin Liu, Chenchen Liu, Siyuan Liu, Lixiu Guan, Xiaobiao Liu, François M. Peeters, Linyang Li
Mathematical Physics · Cross-listed from math.SP
Arbitrarily Fast Quantum Dispersion in Long-Range Crystals
Gaétan Leclerc, Mostafa Sabri and Tuomas Sahlsten
We construct the first examples of one-dimensional long-range
crystals exhibiting arbitrarily fast
polynomial dispersive bounds. The Floquet functions of our
Hamiltonians are highly oscillatory Weierstrass functions, whose rough autosimilar structure drives the fast dispersion. The proof develops a new
Fourier decay theory for $C^\alpha$ images of the Lebesgue measure, based on a Dolgopyat-inspired transfer operator method, and yields a van der Corput lemma for Weierstrass functions. As a consequence, the local time of classical Weierstrass functions of sufficiently large lacunarity exists and is $C^k$, answering a question raised by Geman and Horowitz in 1980.
Read the full abstract ▾
Quantum Gases
The heavy Fermi polaron I: the Lithium-Cesium experiment
Michael Rautenberg, Tobias Krom, Eleonora Lippi et al. (+2 more)
We present details of an experimental platform for studying
Fermi polarons in a
quantum-gas mixture. The system consists of about a thousand bosonic $^{133}$Cs
impurities immersed in a deeply degenerate
Fermi gas ($T/T_F \sim 0.2$) of approximately $2\times 10^5$ $^6$Li atoms in a single hyperfine state, with interspecies interactions tunable via a Feshbach resonance. Using optical Raman spectroscopy without relative momentum transfer, we perform injection spectroscopy and thereby create the
Fermi polaron. Owing to the large mass imbalance between the two species, the setup provides access to previously unexplored regimes of
Fermi polarons.
Read the full abstract ▾
All authors Michael Rautenberg, Tobias Krom, Eleonora Lippi, Lauriane Chomaz, Matthias Weidemüller
High Energy Physics (Phenomenology)
Tomas Brauner and Ramkumar Radhakrishnan
It has been known that in sufficiently strong uniform
magnetic fields, the ground state of
quantum chromodynamics (QCD) supports a spatially modulated condensate of neutral pions, dubbed
chiral soliton lattice (CSL). In this paper, we investigate whether a similar ordered ground state might exist when the external
magnetic field is nonuniform, as appropriate for potential phenomenological applications, including heavy-ion collisions and
neutron stars. To that end, we use the low-energy effective field theory of QCD, restricted to the neutral pions as the sole low-energy degrees of freedom in strong
magnetic fields. In the limit of vanishing pion mass, we achieve a complete characterization of
magnetic fields supporting a CSL-like ground state. Moreover, for a simple but infinite family of
magnetic fields, we find the corresponding CSL state analytically. Going away from the massless limit requires full numerical minimization of the energy functional. Here we provide some sample numerical results, focusing on the qualitative differences as compared to the situations with a uniform
magnetic field or a vanishing pion mass. The main conclusion remains unchanged: while bending the
magnetic field typically reduces the energy gain due to the neutral pion condensation, a CSL-type ground state is still possible. As a byproduct of our work, we map the location of the CSL phase in the phase diagram of QCD in a uniform
magnetic field and finite volume.
Read the full abstract ▾
Applied Physics
Hyperuniformity as a unifying organizational principle across diatom architectures
Eric Ballestero, Chiara Gazzola, Raj Kumar Pal et al. (+2 more)
Diatom frustules have long fascinated scientists for the extraordinary beauty, diversity, and functionality of their intricate silica architectures. Yet, the spatial organization of these structures has so far been primarily described in terms of morphology,
symmetry, and crystallographic order, leaving common statistical properties across distinct diatom architectures largely unexplored. By analyzing diatom frustules through the lens of hyperuniformity for the first time, we reveal a striking commonality across their remarkable diversity: all analyzed genera exhibit signatures of suppressed long-wavelength density fluctuations. Specifically, we find that these architectures range from strongly ordered Class I to disordered Class III hyperuniform systems. We show that local order, spatial correlations, and long-range fluctuation suppression can vary partially independently, giving rise to a continuous spectrum of multiscale architectures. Our multiscale approach reveals that hyperuniformity can be reliably characterized in finite biological structures, beyond what conventional asymptotic diagnostics can resolve. Together, these results prove that hyperuniformity provides a unifying statistical framework for describing diatom diversity beyond conventional classifications of structural order.
Read the full abstract ▾
All authors Eric Ballestero, Chiara Gazzola, Raj Kumar Pal, Vicent Romero-Garc{\i}a, Marco Miniaci