Chemical Physics
Optical absorption spectra from the $GW$-Bethe-Salpeter framework for thousands of atoms
Maximilian Graml, Ritaj Tyagi, Rémi Pasquier et al. (+2 more)
The frequency-dependent absorption and emission of light determine the colors of matter and underpin today's technologies, from solar
cells to light-emitting diodes. Predicting optical properties from first principles remains a computational challenge, especially for large and disordered systems. The $GW$ plus Bethe-Salpeter equation ($GW$-BSE) approach provides predictive accuracy for optical properties, but conventional implementations become costly as system size grows. Here, we present a $GW$-BSE framework combining real-time propagation, atom-centered basis sets, and a locally optimized real-space resolution of the identity. The cost of each propagation step scales quadratically with system size and roughly equals the cost of one self-consistent-field iteration in a density-functional calculation with a semilocal functional. This computational efficiency allows us to calculate the absorption spectrum of a nanographene containing 4616 atoms and opens a path toward routine calculations of optical properties for large disordered systems.
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All authors Maximilian Graml, Ritaj Tyagi, Rémi Pasquier, Štěpán Marek, Jan Wilhelm
Solar and Stellar Astrophysics
Metallicity does not reorder line-to-line sensitivity to granulation in solar-like stars
Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev et al. (+2 more)
Stellar granulation imprints line-dependent wavelength shifts and profile variations that limit the precision of radial velocity (RV) measurements used for
exoplanet detection and characterization. Understanding how the sensitivity of individual spectral lines to granulation depends on stellar parameters is therefore essential for mitigating granulation-induced RV signals. Here, we investigate the effect of
metallicity using MURaM 3D magnetohydrodynamic simulations of stellar granulation including a small-scale dynamo for
metallicities $\mathrm{M/H}=\{-1.0,-0.5,0.0,0.3,0.5\}$. We synthesize spectra of neutral and ionized lines spanning a broad range of lower excitation potentials and transition probabilities using the MPS-ATLAS code, assuming local thermodynamic
equilibrium. We quantify the sensitivity to granulation using the continuum-intensity-weighted standard deviations of the line centre-of-
gravity wavelength and equivalent width, denoted by $\sigma_\lambda$ and $\sigma_W$, respectively. Both metrics increase systematically with
metallicity at disc centre owing to the combined effects of more vigorous convection and
metallicity-dependent changes in the line opacity. We find that the correlation between the solar ($\mathrm{M/H}=0.0$) and non-solar sensitivity metrics remains high from the disk center to the stellar limb. This indicates that the relative ordering of line sensitivities is robust against changes in viewing angle and
metallicity. Consequently, line masks calibrated on the solar spectrum can be reliably applied to radial-velocity measurements of
stars with non-solar
metallicities, provided they have solar effective temperature and surface
gravity.
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All authors Dušan Vukadinović, Sowmya Krishnamurthy, Valeriy Vasilyev, Veronika Witzke, Andrew Collier Cameron
Solar and Stellar Astrophysics
Probing Massive Star Formation with Intrinsic Multiplicity Constraints from TESS Eclipsing Binaries
Jasmine Vrancken, Alex Kemp, Andrew Tkachenko et al. (+2 more)
Massive
stars play a central role in stellar and galactic
evolution as progenitors of
supernovae,
neutron stars, black holes, and gravitational wave sources. Despite their importance, the dominant formation mechanisms of massive binaries remain poorly constrained observationally. We aim to use a large, homogeneous sample of eclipsing binaries to observationally constrain binary formation across a wide range of primary masses and test predictions from various formation scenarios. We combine photometric time series data from TESS with distance measurements from Gaia DR3 and near infrared photometry from 2MASS to analyze an all-sky sample of eclipsing binaries. By accounting for observational and
geometric selection effects, we derive bias corrected estimates of the binary fractions and orbital parameter distributions across different mass bins. We derive bias corrected binary fractions and bias corrected distributions of orbital period and radius-to-separation ratio for systems spanning primary masses from 1.1 Msun to 47 Msun. For primary masses up to 5 Msun, the observed distributions show close agreement with theoretical predictions for systems formed via disk fragmentation followed by migration. At higher masses, we observe an apparent deficit of very short period systems relative to theoretical expectations, although this regime is also expected to be affected by incompleteness. Overall, the observed properties exhibit a gradual transition across the full range of primary masses. Within the orbital period range accessible to our sample, the results do not require a sharp transition in binary properties between F- and O-type
stars. The observed continuity is consistent with disk fragmentation followed by migration acting across a broad range of stellar masses, although the present data do not uniquely require this formation pathway and alternative channels may also contribute.
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All authors Jasmine Vrancken, Alex Kemp, Andrew Tkachenko, Conny Aerts, Hugues Sana
Quantum Physics
Beyond QAOA: A Review of AI and Quantum Computing for Adaptive Combinatorial Optimization
Hoong Chuin Lau
Near-term
quantum approaches to combinatorial optimization are limited by
qubit counts,
circuit fidelity, sampling cost, and the difficulty of encoding constraints, while machine learning is increasingly used to configure and control
quantum optimization workflows. We call such workflows adaptive: decisions conventionally fixed in advance, from formulation and penalties to shot budgets, backends, and whether to invoke a
quantum processor at all, are made by learned policies that respond to the instance, the progress of the solve, or the hardware. This review examines three paradigms, AI for
quantum optimization,
quantum for AI-driven optimization, and AI-
quantum co-optimization, and organizes the literature by the decision being learned rather than by application. A structured search identified a 119-paper corpus, of which 67 papers form an evidence core coded in detail. The evidence is considerably stronger for AI-assisted
quantum optimization than for the reverse direction: learning already reduces
quantum evaluations, improves initialization, supports decomposition and penalty control, and mitigates noise, whereas evidence that
quantum computation improves learned optimizers remains largely confined to small-scale simulation. Experimental controls are thin: of 52 studies in the three paradigms, 22 include no classical baseline, the
quantum contribution is fully isolated in 10 of 24 where an ablation applies, and the median largest experiment uses 16
qubits. We introduce an M0-M5 evidence hierarchy, from simulation to practical
quantum advantage, and find no broadly convincing result at the highest level. We argue that scaling is increasingly a systems problem: the question is not only whether a problem fits on a
quantum processor, but how classical and
quantum resources should be allocated across the optimization process.
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Instrumentation and Methods for Astrophysics
A Coherent Harmonic Summing Pulsar Search Code
Scott M. Ransom
Pulsars have narrow pulses, so their signals spread over many harmonics in a
Fourier transform. Standard
pulsar searches add the powers of those harmonics and discard their phases, which throws away the pulse shape and some of the signal. Folding the time series at each trial period keeps both, but is expensive even with the Fast Folding
Algorithm (FFA). We describe CoherentSearch.jl, an open-source Julia code that reconstructs the pulse profile at every trial
spin frequency directly from the
Fourier transform. It interpolates the complex amplitudes of typically 60 harmonics, inverse transforms them into a profile, and tests that profile against boxcar templates of many widths. Because the input spectrum is normalized, the noise in every profile is known in closed form, so one threshold gives one false-alarm rate across the whole search. In an injection study of over 860,000 simulated
pulsars at a matched false-alarm rate, the new search recovers 76% of the
pulsars in white noise, against 64% for riptide's FFA in its recommended configuration and 42% for PRESTO's accelsearch, and its threshold does not move under red noise. On one CPU core it is 1.4-2.2 times faster than riptide at matched frequency coverage, it scales to 27 times faster on 48 cores, and modern GPUs run it up to nine times faster than a 20-core workstation.
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High Energy Physics (Phenomenology)
Flavour decomposition of the nucleon tensor multipole moments
U. Özdem
We compute the chiral-odd form factors $H_T$, $E_T$ and $\hT$ of the nucleon in light-cone QCD sum rules, separately for the $u$ and $d$
quarks, and organise them into the tensor monopole, dipole and quadrupole moments $g_T$, $\kappa_T$ and $Q_T$. The quadrupole moment, with no chiral-even counterpart at leading twist, and the isoscalar channel, whose sum rules were derived but never evaluated, are new in this framework. The form factors are read from a Lorentz basis independent only after canonical ordering of the Dirac strings; three of the eight surviving structures give the three form factors separately, and the one usually used for the tensor charge is not among the eight. Two exact results follow analytically. The $d$-
quark contributions to $E_T$ and $\hT$ are equal and opposite in the chiral limit, broken in proportion to the
quark mass and the twist-six amplitude $\mathcal{V}_6$, so the $d$-
quark sector carries a single independent function; and the isoscalar tensor charge receives no leading-twist contribution, its twist-three terms cancelling between the flavours. Neither is visible without resolving the flavours. At $\mu^2=1$~GeV$^2$ the two distribution-amplitude sets give $g_T^{u-d}=1.27(7)$, $1.08(6)$, $\kappa_T^{u-d}=1.35(62)$, $1.58(59)$, $Q_T^{u-d}=-4.40(83)$, $-4.20(73)$ and $g_T^{u+d}=0.39(7)$, $0.38(6)$, $\kappa_T^{u+d}=4.47(62)$, $4.32(59)$, $Q_T^{u+d}=2.41(53)$, $1.56(30)$. The mean-field relation $2\hT^{u-d}=-E_T^{u-d}$, tested without any large-$N_c$ assumption, holds in sign and order of magnitude, with ratio $0.64(16)$ and $0.67(15)$ against the predicted unity. In the impact-parameter plane the moments displace the two flavour distributions in opposite transverse directions by nearly equal amounts, $\langle b_y\rangle=0.37$ and $-0.37$~fm, and elongate both across the polarisation axis, the $d$
quark some five to six times more strongly
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Materials Science
Can end-to-end learning from raw electronic structure explain magnetic anisotropy?
Rafał Topolnicki, Jan Navrátil and Piotr Błoński
Machine-learning models trained directly on electronic spectra can predict
spin–orbit-driven properties, yet models with comparable predictive accuracy may learn different electronic dependencies. We examine this problem using
magnetic anisotropy in atomic-scale magnets and a validation strategy designed to assess the physical relevance of learned spectral relationships. We compare a bidirectional gated recurrent unit and a one-dimensional convolutional neural network, both trained to predict
magnetic anisotropy energy (MAE) from
spin- and orbital-resolved scalar-relativistic densities of states (SR-DOS). Despite comparable in-domain (ID) accuracy, the architectures learn only partly overlapping spectral dependencies. Shapley additive explanations identify spectral features shared between the two architectures that can be associated with plausible
spin–orbit-coupling pathways consistent with second-order perturbation theory (PT2). Adding PT2-derived MAE contributions to the model inputs has little effect on ID performance but can improve transfer beyond the training domain, with gains differing between architectures. Controlled spectral perturbations further demonstrate that similar attribution patterns do not imply the same functional dependence of the predicted MAE on spectral weight. The contrasting responses provide a functional context for architecture-dependent out-of-domain transfer. End-to-end learning can identify candidate electronic signatures of
magnetic anisotropy. Their credible microscopic interpretation, however, rests on convergent evidence from predictive performance, model comparison, physical theory, controlled spectral interventions, and evaluation under distribution shift.
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Materials Science
A General Algorithm for Minimal Uncoupled Stress–Strain Calculations of Elastic Constant
S. I. Simak and Utkarsh Singh
We have developed a general
algorithm for constructing the minimum number of strain configurations required to extract second-order elastic constants from first-principles stress-strain calculations without algebraic coupling between the constants targeted for extraction. The method operates on the sparsity structure of the
symmetry-reduced elastic stiffness
matrix, represented by an auxiliary binary
matrix, and generates admissible strain patterns algorithmically rather than prescribing separate strain sets for individual
crystal symmetries. Each independent elastic constant is obtained from a single stress component, while additional stress relations generated by the same deformation provide internal consistency checks. Because the six-dimensional strain space contains only 2^6-1=63 non-empty strain patterns, the minimality of the resulting sets can be verified exactly for every elastic-
symmetry type considered. The construction reproduces established high-efficiency strain sets in cases where they are minimal and yields improved sets for
symmetry classes in which previously tabulated schemes require additional configurations. Because the formulation is based on stress-strain derivatives, it can also be readily extended to finite temperatures using consistently sampled ensemble-averaged thermodynamic stresses. Explicit strain sets are derived for all elastic-
symmetry types spanning the 230 crystallographic space groups, and their accuracy and computational efficiency are benchmarked against established approaches.
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Materials Science
Interlayer ferromagnetic order revealed through pressure-enhanced interlayer exchange coupling in Fe$_3$GaTe$_2$
Riku Iimori and Takashi Kimura
Van der Waals ferromagnets possess finite interlayer
magnetic coupling despite their layered
crystal structures, and this coupling plays an important role in determining their
magnetic properties. In this study, we performed magnetization measurements on high-quality Fe$_3$GaTe$_2$ single
crystals while selectively tuning the interlayer coupling using hydrostatic pressure. We identified two characteristic temperatures, $T_{\rm inf1}$ and $T_{\rm inf2}$, below the Curie temperature with opposite pressure dependences: $T_{\rm inf1}$ is associated with thermally activated domain-wall depinning, whereas $T_{\rm inf2}$ reflects the formation of interlayer ferromagnetic order. Both temperatures exhibit pronounced pressure dependences, in sharp contrast to the nearly pressure-independent Curie temperature associated with intralayer ferromagnetic order. First-principles calculations revealed a substantial pressure-induced enhancement of the interlayer exchange interaction and reasonably reproduced $T_{\rm inf2}$ and its pressure dependence. These results demonstrate that the emergence of interlayer
magnetic ordering can be predicted from the microscopic interlayer exchange coupling, establishing a predictive framework for understanding and designing interlayer coupling phenomena in layered
magnetic materials.
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Biological Physics
Three-dimensional imaging of isolated membrane-protein complexes in vacuo with an X-ray laser
Kartik Ayyer, Tej Varma Yenupuri, Johan Bielecki et al. (+51 more)
The prospect of imaging single biomolecules, viruses and
cells with intense, ultrashort X-ray pulses has driven the development of X-ray free-electron
lasers (XFELs). However, the weak scattering from small particles is easily swamped by background from residual gas, which has so far limited applications to strongly scattering targets such as viruses,
cell organelles and
cells. Here we report a three-dimensional (3D) reconstruction of an isolated 1-MDa membrane-
protein complex, photosystem I (PS I), from single-particle diffraction data. PS I trimers were aerosolised by charge-reduction electrospray ionisation and injected into the European XFEL beam, with partial helium gas exchange reducing background scattering by 80%. From 32 788 diffraction patterns of single trimers in random orientations, we reconstructed the 3D electron density to a resolution of 3.8 nm, limited by the detector geometry. The disc-shaped density, about 22 nm across and 10 nm thick, matches the size of a PS I trimer in a detergent micelle and is consistent with the compaction predicted by molecular dynamics simulations of the complex in vacuo and observed in native mass spectrometry. These results show that membrane-
protein complexes can be imaged in vacuo with X-ray
lasers, an important step towards ultrafast diffractive imaging of single macromolecules.
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All authors Kartik Ayyer, Tej Varma Yenupuri, Johan Bielecki, Lutz A. Eichacker, J. Domingo Meza-Aguilar, Louise J. Persson, Lena Worbs, Patrick Adams, Roberto Alvarez, Adil Ansari, Alfredo Bellisario, Rebecca Boll, Carl Caleman, Sebastian Cardoch, Andrea Castoldi, Joe P. J. Chen, Cyril Danilevski, Merle Dechering, Simon Dold, Armando D. Estillore, Alberto De Fanis, Lukas V. Haas, Patrick Konold, David Lomitze, Abhishek Mall, Dimitra Manatou, Iñaki de Diego Martinez, Parichita Mazumder, Andrew J. Morgan, Anna Munke, Yevheniy Ovcharenko, Matteo Porro, Safi Rafie-Zinedine, Amit K. Samanta, Christina Schmidt, Arezu Sehati, Jonas A. Sellberg, Björn Senfftleben, Carolin Seuring, Zhou Shen, Nicusor Timneanu, Sergey Usenko, Daniel Westphal, August Wollter, Tamme Wollweber, Paul Lourdu Xavier, Henry N. Chapman, Janos Hajdu, Richard A. Kirian, Jochen Küpper, Erik G. Marklund, Petra Fromme, Michael Meyer, Filipe R. N. C. Maia
Chemical Physics
Predictable Accuracy of Martini 3 Absolute Protein-Ligand Binding Free Energies across 15 Targets
Luis J. Walter and Tristan Bereau
Alchemical free-energy calculations predict
protein-ligand binding affinities with close-to-experimental accuracy, but their cost restricts them to small sets of ligands. Coarse-grained (CG) models such as Martini 3 retain a rigorous statistical-mechanical treatment at a fraction of this cost, yet their accuracy for
protein-ligand binding has not been assessed systematically. Here, we compute absolute binding free energies for 172 ligands across 15
protein targets with a Martini 3 double-decoupling protocol and compare them against atomistic FEP+ and OpenFE references. Martini underbinds for every target, by 2.7 to 8.7 kcal/mol. This offset is systematic: it comprises a uniform contribution that grows with the number of charged pocket residues. A linear model in this number, which requires only the
protein structure, reduces the mean absolute error from 5.7 to 1.2 kcal/mol in leave-one-out cross-validation, close to the 1.0 kcal/mol obtained with exact per-target offsets. The ranking of ligands within a target varies more widely (median Spearman $\rho$ of 0.32, from $-$0.41 to 0.89) and is rationalized by the structure-activity relationship of each series: Martini ranks ligands well when their affinity is driven by hydrophobicity, $\pi$-stacking, or size, and poorly when it is driven by hydrogen bonding or charge. Both trends follow from Martini's calibration against bulk partitioning, which captures neither the dielectric environment of a binding pocket nor the directionality of hydrogen bonds. While MMGBSA retains the atomistic detail needed to rank congeneric ligands, Martini yields physically meaningful free energies, and its coarse-graining maps many atomistically distinct molecules onto one representation, making it a complementary tool for rapidly spanning chemical space.
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Superconductivity
Electric and Heat Transport in One-Dimensional SNS Junctions with Energy-Dependent Transmission
Kai Tsutsumi and Shun Uchino
We investigate the phase-independent dc components of the electric and heat currents through a one-dimensional
superconductor-normal-metal-
superconductor (SNS) junction subject to chemical-potential and temperature differences between two superconducting reservoirs. Using a scattering approach based on the Bogoliubov-de Gennes equations, we incorporate multiple Andreev reflections while retaining the energy dependence of transmission through the normal region. We compare energy-independent,
quantum-dot-type, and
quantum-point-contact transmission profiles. At low bias, both currents exhibit nonlinear features associated with the superconducting gap and multiple Andreev reflections. Their responses to a temperature difference depend remarkably on the transmission profile. At a small finite bias, the electric current depends weakly on the temperature difference for the energy-independent and
quantum-dot-type profiles, whereas the
quantum-point-contact profile produces a pronounced nonlinear response. The heat current depends nonlinearly on the temperature difference for all three profiles over the parameter range investigated. These results highlight the role of the transmission profile in nonlinear electric and heat transport through SNS junctions and provide a microscopic reference for related transport studies in mesoscopic fermionic superfluid junctions.
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General Relativity and Quantum Cosmology
Nonreciprocal black holes with primary hair in beyond Horndeski gravity: Exact solutions and stability
Sebastian Bahamonde, Theodoros Nakas and Simon Iteanu
We develop a novel systematic method for constructing exact, static, and asymptotically flat black-hole solutions in shift-symmetric and $Z_2$-symmetric beyond Horndeski theories. In contrast to previous studies, our approach does not rely on the restrictive reciprocal condition $g_{tt}g_{rr}=-1$, allowing for more general geometries characterized by two independent metric functions. The resulting solution space contains two qualitatively distinct types of hair originating from different branches of the theory. One branch is characterized by khronometric hair, while the other by genuine scalar hair. In both, the scalar profile defines a nontrivial preferred foliation, but the shift-
symmetry Noether current and the associated propagating degree of freedom are trivial for the former and nonvanishing for the latter. Focusing mainly on the second branch, we derive several distinct families of exact black-hole solutions. In general, these solutions are singular and exhibit primary scalar hair associated with an independent scalar charge. Nevertheless, we demonstrate that they can be regularized to yield regular black-hole or solitonic configurations, for which the scalar hair becomes secondary. We further investigate the stability properties of these solutions under linear perturbations by analyzing the axial sector and the monopole $(\ell=0)$ mode of the even-parity sector. For representative solutions with scalar hair, the perturbative analysis provides evidence for linear stability under the modes considered.
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Quantum Physics
Parameter-Dependent Noise Resilience in the Quantum Approximate Optimization Algorithm
Jorja Kirk and Ashley Montanaro
The
Quantum Approximate Optimization
Algorithm (QAOA) is a variational
quantum algorithm used for solving combinatorial optimization problems, which is thought to be a promising application of near-term
quantum hardware. However, high rates of noise in these devices can obscure meaningful results. Therefore, it is crucial to understand and suppress the effects of noise on the
algorithm's output. Here, we find that the stability of the
algorithm in the presence of noise is dependent on its variational parameters. Using a Pauli noise model, we derive an upper bound on the total variation distance between the noisy and noiseless
circuit output as a function of these parameters. Results from noisy simulations support this bound and give insight into the best methods to use for parameter generation in the presence of noise. We also introduce new methods of optimization using error penalties and truncated search based on this bound to manufacture error resilience. We extend this analysis to the
quantum adiabatic
algorithm (QAA) by taking the continuous limit of the QAOA.
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Materials Science
Predicting plasmonic pole representations of complex dielectric spectra using convolutional neural networks
Dario A. Leon
Extracting spectral properties such as energy position, broadening, and spectral weight from dielectric spectra is critical for interpreting collective electronic excitations in many-body physics. Conventional approaches typically rely on nonlinear fitting procedures that can be computationally demanding and highly sensitive to initialization and fitting choices. In this work, we develop a convolutional neural-network framework for the direct inversion of dielectric spectra into their underlying plasmonic pole structures using a multipole-Padé representation. Rather than training on a constrained database of spectra associated with a specific set of materials, the network is trained entirely on synthetic spectra generated from the analytical multipole-Padé expression with randomized parameters. This enables the network to learn the general mapping between the spectra and their features in an unbiased way, without requiring large, material-specific
datasets derived from real materials. We demonstrate that the synthetically trained network generalizes to complex first-principles and experimental dielectric spectra, extracting the underlying pole parameters with high accuracy in a single forward pass. This approach provides an efficient and robust alternative to conventional nonlinear fitting, enabling high-throughput, automated analysis of dielectric spectra across diverse materials and applications.
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Materials Science
Mode-selective electron-phonon coupling drives charge density waves in the kagome metals YRu$_3$Si$_2$ and LaRu$_3$Si$_2$
Wenqian Tu, Run Lv, Dingfu Shao et al. (+2 more)
YRu$_3$Si$_2$ and LaRu$_3$Si$_2$ host the highest charge density wave (CDW) transition temperatures ever reported in kagome metals, $T_{\mathrm{CDW}}\approx 800$ and 400~K, with propagation vectors $Q_{\mathrm{CDW}}\approx(1/2,0,0)$ and $(1/4,0,0)$, respectively. The microscopic mechanism behind these record values has remained unresolved. Here, we combine anharmonic
phonon renormalization extracted from molecular dynamics driven by a machine-learned force field with mode-resolved electron-
phonon coupling (EPC) analysis to identify this mechanism. The CDW is driven by mode-selective EPC: the Ru out-of-plane
phonon modes couple the Ru-$d_{xz}/d_{yz}$ and Si-$p_x/p_y$ orbitals, and the
phonon linewidth peaks sharply at $Q_{\mathrm{CDW}}$, while the featureless electronic susceptibility rules out Fermi-surface nesting.
Phonon anharmonicity melts the CDW, and the anharmonic
phonon spectra reproduce both $Q_{\mathrm{CDW}}$ and $T_{\mathrm{CDW}}$ in good agreement with experiments. Molecular dynamics simulations also visualize the CDW melting in real space. Chemical bonding analysis further shows that the smaller Y$^{3+}$ radius strengthens the Ru-Ru bonds, enhancing
lattice rigidity and accounting for the factor-of-two higher $T_{\mathrm{CDW}}$ of YRu$_3$Si$_2$. Our results establish a unified microscopic picture of CDW formation and melting in kagome metals YRu$_3$Si$_2$ and LaRu$_3$Si$_2$.
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All authors Wenqian Tu, Run Lv, Dingfu Shao, Yuping Sun, Wenjian Lu
Mathematical Physics · Cross-listed from math.PR
On the asymptotic behavior of the number variance of random points on the unit torus
Christoph Aistleitner, Siegfried Hörmann and Maryna Manskova
The study of the distribution of real sequences in the unit
torus has a long and rich history. There are many notions which describe the “pseudo-random” behavior of a given deterministic sequence (often of arithmetic origin), such as equidistribution (which describes the distribution on a “global scale”) or the pair correlation (which is a “local-scale” statistics). Another popular and important statistics, which can be applied to all ranges from global via intermediate to local, is the number variance $V_N(s)$, which describes the mean-square fluctuation of the number of elements of an initial segment of the sequence in an interval of length $s$, when moving this interval around the
torus. In the terminology of
quantum chaology, where such statistics are used to describe the distribution of the energy levels of a system, pseudo-random behavior is called Poissonian behavior. Since the number variance is an important indicator to qualify pseudo-random behavior, it is quite surprising that the literature does not seem to contain a precise description of the distribution and of the almost sure asymptotic behavior of the number variance in the truly random case (i.i.d.\ random points), even in the comparatively simple setup of uniformly distributed points on the unit
torus. In the present paper we calculate the distribution of the number variance with high precision throughout a wide range of the parameter $s$, and determine the precise threshold (in terms of $s$) where the “Poissonian” asymptotics $V_N(s) \sim N s$ breaks for a typical realization of a random sequence. Key technical input comes from the Komlós–Major–Tusnády
theorem and the Karhunen-Loève decomposition.
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Chemical Physics
Non-Perturbative Vibrational Excitation by Arbitrary Electric Fields from Classical Phase-Space Dynamics
Sameernandan Upadhyayula and Jiří J. L. Vaníček
We present a non-perturbative framework for the
quantum treatment of vibrational excitation in molecular systems driven by electric fields with arbitrary time dependence. For harmonic potentials with linear dipole coupling, the field-induced dynamics is exactly described by a displaced coherent state, whose
evolution is completely determined by a complex phase-space coordinate. Closed-form expressions for this coordinate reveal a clear distinction between resonant and non-resonant regimes. The resulting vibrational populations follow a Poisson distribution determined by a dimensionless time-dependent phase-space displacement, for both resonant and non-resonant driving. Resonant driving results in an enhanced phase-space displacement, whereas finite detuning between the driving and vibrational frequencies leads to an exponential suppression of the phase-space displacement and vibrational excitation. While the approach reduces to the standard time-dependent perturbation theory in the weak-field limit, it remains valid in the strong-field regime, where perturbative treatments fail. Our results provide a transparent phase-space picture of vibrational control and enable non-perturbative state preparation in ultrafast spectroscopy.
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Materials Science
Robust skyrmion nucleation and transport via composition gradient in rare earth-transition metal ferrimagnets
Pietro Diona, Luca Maranzana and Sergey Artyukhin
Magnetic skyrmions are typically nucleated via localized excitation methods, such as
laser heating,
spin-orbit torques, or engineered defects, and their controlled transport is often limited by the skyrmion Hall effect. Here, we demonstrate that spatial gradients in rare-earth–transition-metal
alloys, achievable through patterned
laser writing, enable both deterministic nucleation and controlled transport. The strategy leverages engineered compositional gradient to cross the magnetization compensation point, defining regions with opposite magnetization. An out-of-plane
magnetic field selectively reverses the magnetization, generating a skyrmion. Crucially, the same compositional design enables a channel tuned to the
spin angular momentum compensation point, where skyrmions are driven by
spin-orbit torques at high velocity with vanishing skyrmion Hall effect. Local composition variations act as pinning sites, enabling threshold-controlled trapping and release.
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Mathematical Physics
Wrinkling of a bilayered cylinder under tension
Chiara Lonati, Sairam Pamulaparthi Venkata, Kevin Moerman et al. (+3 more)
We study near-surface tension instabilities in bilayered cylinders composed of an incompressible core coated with a thin compressible film. In theory, circumferential wrinkles with axial wavefronts may appear on the outer surface when the cylinder is stretched. We analyze these instabilities through modelling, numerics, finite element simulations, and controlled experiments. We show that the wrinkle amplitude and wavelength depend on the Poisson ratio of the coating and the ratio of the film and substrate shear moduli. We find that the lower the film's Poisson ratio, the earlier the wrinkles emerge under tension. This observation motivates us to use auxetic films (with negative Poisson ratios) with bespoke microstructures in the finite element simulations and the experiments. For the latter, we fabricated 3D-printed soft cylinders with stiff auxetic outer layers and subjected them to axial loading. Although simulations predicted clear wrinkle formation, experimental observation proved more elusive due to the small amplitude of the wrinkles.
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All authors Chiara Lonati, Sairam Pamulaparthi Venkata, Kevin Moerman, Olga Petrenko, Michel Destrade, Valentina Balbi
Soft Condensed Matter
Autonomous thermodynamic cycles via robotic mobility and sensing
Sofia Kuperman, Ezra Ben-Abu, Yaron Veksler et al. (+3 more)
Thermodynamic cycles are the foundation of energy conversion across natural and engineered systems, transforming heat into useful work. However, these cycles traditionally operate between fixed thermal reservoirs, restricting them to specific locations and temperature differences. Here, we introduce autonomous thermodynamic cycles enabled by robotic mobility and sensing, allowing
robots to perform thermodynamic cycles by accessing spatially varying temperature fields. We experimentally realize this concept using multistable gas-filled capsules that circulate within the system across a thermal gradient. Our model reveals that rapid transitions in the capsules' energy states allow the system to operate as a mobile heat engine that harvests and stores energy. By linking the capsule-scale internal energy dynamics to the
robot's large-scale navigation strategy, we optimize locomotion paths that balance motion cost and energy harvesting. These findings demonstrate that thermodynamic cycles can emerge when autonomous systems navigate their environments, offering an artificial analog of organisms that forage for energy across spatial resources.
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All authors Sofia Kuperman, Ezra Ben-Abu, Yaron Veksler, Anna Zigelman, Sefi Givli, Amir D. Gat
High Energy Physics (Theory)
Extremal black hole mimickers: geometry, stability, and long-delay signal trains
Sergey N. Solodukhin
We present a spacetime that serves as a horizonless mimicker of extremal black holes. Unlike previously studied mimickers of black holes with non-degenerate horizons, whose geometries are of the wormhole type and consist of two asymptotically flat regions connected by a very long throat, the mimicker of an extremal black hole possesses a single asymptotically flat region at one end and an infinitely long throat at the other. In the throat region, the spacetime approaches the direct-product geometry $M_{1,1} \times S^2$, where $M_{1,1}$ is two-dimensional Minkowski spacetime and $S^2$ is the two-sphere. We investigate scalar-field dynamics and the fate of the Aretakis instability. Although Aretakis-like modes arise in a local analysis of the throat, they do not lead to a physical instability of the mimicker. A scalar perturbation initially localized in the throat gives rise, at late times, to a sequence of signals with a characteristic separation $t_{\rm delay}\sim 1/\lambda$, where $\lambda\ll 1$ is a deformation parameter. This timescale is parametrically larger than the echo time $t_{\rm echo}\sim \ln(1/\lambda)$ characteristic of non-extremal black-hole mimickers. We refer to this sequence as a long-delay signal train. Geometrically, the periodicity of the long-delay signals is associated with periodic geodesics on $S^2$. We then extend the construction to extremal Kerr. In this case, the throat region approaches a generalized product geometry involving $M_{1,1}$ and a two-dimensional surface $\Sigma_2$. The corresponding signals are expected to form a quasi-periodic signal train, reflecting the quasi-periodic geodesic motion on $\Sigma_2$. We also comment on the generalization to wormhole mimickers of non-extremal black holes and on the implications of these results for unitarity in the context of the AdS/CFT correspondence.
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Quantum Physics
Error-Corrected Memory and Logic on a Heavy-Hex Superconducting-Qubit Processor
Campbell K. McLauchlan, Georgia M. Nixon, Julien M. Drouet et al. (+7 more)
Large
quantum computations require high-fidelity error-corrected
memory and fault-tolerant logical operations. To achieve these with superconducting
circuits,
quantum processors will need many components operating with low error rates. In practice, fabrication of monolithic superconducting devices produces unavoidable heterogeneity in component performance, which the
quantum computer must accommodate. We implement strategies to operate a large dynamic compass code on an array of 156 superconducting
qubits arranged on a heavy-hexagonal
lattice, making use of the entire monolithic
quantum processor and redesigning our measurement schedule to exclude underperforming components. We demonstrate improvements of up to $35\%$ in logical error probabilities for a
memory experiment by using a noise-informed decoder combined with strategies to exclude the worst-performing
qubits and couplers, along with post-selecting on shots with a low probability of leakage errors. In addition to these
memory results, we also observe performance gains of up to $56\%$ when these strategies are applied to measurement-based logic, demonstrated by stability experiments. We furthermore demonstrate high-fidelity fault-tolerant logic through
lattice surgery. Through pre-selection filtering techniques, we can obtain Bell fidelities above $77\%$, and further logical gap post-selection using exclusive decoding increases these fidelities to above $97\%$. Our experiments demonstrate that high performance can be maintained in key elements of fault-tolerant
quantum memory and logic when working on monolithic superconducting
quantum processors with underperforming components, by using a suite of noise-informed
quantum error correction strategies.
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All authors Campbell K. McLauchlan, Georgia M. Nixon, Julien M. Drouet, Xanda C. Kolesnikow, Seok-Hyung Lee, James Raftery, Karthik Siva, Stephen D. Bartlett, Benjamin J. Brown, Robin Harper
Materials Science
Epitaxial growth of WO3 on r-plane sapphire by hot-filament metal-oxide deposition using CO2 as a precursor
Laurent Souqui, Lewis J. Adams, Andreas Tsampanakis et al. (+2 more)
The deposition of epitaxial films of WO3 by hot-filament metal-oxide deposition using CO2 as a precursor was demonstrated. The films were obtained at a low growth rate of 0.25 nm/min. The optical properties of the film were assessed by variable-angle spectroscopic ellipsometry, indicating transparency across the visible spectrum and high absorption above 3 eV.
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All authors Laurent Souqui, Lewis J. Adams, Andreas Tsampanakis, David Rehnlund Maibach, Per Eklund
General Relativity and Quantum Cosmology
Beyond the Dolgov-Kawasaki instability: Covariant scalaron stability, entropy transport, and inner horizons in f(R) gravity
Francisco S. N. Lobo and Francisco Tello-Ortiz
The Dolgov-Kawasaki instability tests the local scalaron response in metric $f(R)$
gravity, but does not determine strong-field horizon dynamics. We separate these questions using $F=f_R$ and the Legendre potential $\mathcal U(F)=FR-f$. The scalaron restoring coefficient is $m_{\rm sc}^2=(F-Rf_{RR})/(3f_{RR})$, whereas exact spherical Wald-area transport identities cancel the scalaron Hessian. Their Einstein-frame interpretation distinguishes longitudinal kinetic focusing from potential-dependent cross-focusing. We prove that, at fixed constant-
curvature background with tracefree matter, transport depends only on $(f,f_R)$, while the scalaron mass depends on the independently adjustable $f_{RR}$. Reissner-Nordström in $f(R)=R+\alpha R^2$ gives an exact discriminator: identical background transport coexists with opposite scalaron mass signs. A charged solution with varying $F$ and a cosmological check test the identities beyond this constant-$F$ sector. For a nonzero massive scalaron tail transmitted to a nondegenerate Cauchy horizon, a conditional fixed-background estimate gives a nonintegrable contribution to generalized
entropy focusing. This estimate does not establish nonlinear mass inflation or a particular extendibility class. The results provide a layered framework for coupling regularity, background transport, scalaron stability, and nonlinear inner-horizon
evolution.
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Quantum Physics
From Solid-State Spin Defects to Fluorescent Proteins: A Perspective on Quantum Optical Sensing Platforms for Biomedical Applications
Jyotiprakash Parhi, Ayan Majumder and Kasturi Saha
Quantum optical sensing has evolved from isolated solid state
spin defect platforms to increasingly bio-integrated systems designed for biomedical applications. This review presents a perspective on this transition, spanning nitrogen vacancy centers in diamond to emerging fluorescent
protein based
spin qubits. Advances in diamond fabrication have enabled photonic cavities, nanomechanical resonators, and microstructured devices that enhance
spin photon interactions and room temperature sensitivity. Exploration of
spin defects in alternative materials further expands the sensing landscape. Parallel progress toward biological compatibility includes chip based architectures for in vitro and in vivo studies, microfluidic integration, and minimally invasive nanodiamond probes capable of intracellular nanothermometry and nanorheometry. Improvements in surface functionalization have enhanced coherence and sensing reliability in complex environments. Collectively, these advances highlight the progress and remaining challenges toward application oriented
quantum sensing for the life sciences.
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Materials Science
The role of density in shaping electron trapping in amorphous silicon nitride
Jonathon Cottom and Emilia Olsson
The electronic properties of amorphous silicon nitride vary with processing, which often changes stoichiometry and density together. Separating their contributions is essential to connect film structure with electron trapping. Across 499 stoichiometric configurations spanning 2.86-3.19g cm$^{-3}$, porosity controls the trapping mixture. Lower density increases accessible void fraction from 8.4 to 12.6%, expands internal surface and more than triples the supply of free three-coordinate Si precursors. Capture at pre-existing Si dangling bonds (K centres) rises from 9 to 29%, while induced-K and polaronic trapping decline. A neutral precursor fingerprint predicts the trapping mixture in held-out configurations and reproduces its density dependence. Local compensation controls K-centre activation, electronic competition selects capture, and bond strain predicts polaronic relaxation or induced-K formation. Routes involve distinct network volumes but retain their characteristic depths and relaxation energies across the density range. At fixed stoichiometry, density controls the trapping mixture through porosity and precursor availability.
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Earth and Planetary Astrophysics
Gravitational Microlensing
Aikaterini Vandorou and Stela Ishitani Silva
Gravitational microlensing is a unique
planet-detection method that does not rely on detecting light from the host
star or
planet. Instead,
planets are discovered when their gravitational field perturbs the light coming from a distant source. The mechanics of this method offer several advantages. It has the ability to detect wide-orbit
planets of various masses around host
stars of different types, at and beyond the system's snow line. Thus, microlensing complements the other detecting techniques that are more sensitive to close-orbit or high-mass
planets. In this Chapter, we review the microlensing method and discuss how the physical properties, such as mass and distance, can be extracted from the microlensing light curve or from additional high-angular resolution observations. Microlensing is essential for the broader context of
exoplanet demographics, as it can place constraints on
planets, in wide orbits, beyond the snow line. Studying this parameter space can help us unravel the details of
planet formation and how our own Solar System formed. Lastly, we provide an example of how to model a light curve and obtain accurate physical parameters for the host and
planet.
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High Energy Physics (Theory)
Dielectric constant of holographic insulator from quantum geometry
Debabrata Ghorai, Taewon Yuk and Sang-Jin Sin
We study dielectric properties of holographic
insulators from the
quantum geometry of the ground state. We realize the insulating state by the pseudoscalar interaction of holographic
fermions and calculate the fermionic Green function to extract the effective
hamiltonian. We then derive the
quantum metric and Berry
curvature to compute the transports and finally get the dielectric constant from the imaginary part of conductivity.
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Materials Science
Probing $L_z$ Orbital Angular Momentum via Wavefunction-Interference-Induced Charge Order
Jonas Erhardt, Sven Schemmelmann, Fabian Schöttke et al. (+9 more)
Orbital angular momentum (OAM) characterization is central to understanding
quantum materials such as valley Hall and Rashba systems and, through its connection to Berry
curvature, provides key insight into band
topology. Conventional OAM detection via photoemission dichroism, however, is susceptible to interference artifacts and is largely restricted to occupied states. Here, we demonstrate a real-space approach to map the $L_z$ OAM character using scanning tunneling microscopy in triangular atomic monolayers. Unlike photoemission, this method exploits interference effects arising from the $L_z$ orbital phase and the Bloch phase associated with neighboring atoms. This shifts the local density of states (LDOS) maxima to distinct Wyckoff positions between atoms, encoding $L_z$ information into characteristic real-space LDOS patterns. We exemplify this approach in 2D
quantum materials with contrasting $L_z$ sequences, namely Tl/Si(111) and In/SiC(0001) monolayers, identifying $L_z$-dependent LDOS accumulation associated with distinct topological phases in both systems. Our results establish $L_z$-dependent charge localization as a proxy to atomic obstruction for energetically isolated states in triangular
lattices, including transition-metal dichalcogenides.
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All authors Jonas Erhardt, Sven Schemmelmann, Fabian Schöttke, Cedric Schmitt, Lukas Gehrig, Bing Liu, Domenico Di Sante, Giorgio Sangiovanni, Jörg Schäfer, Peter Krüger, Markus Donath, Ralph Claessen