Chemical Physics
Solid-State NMR Dipolar Recoupling in Presence of Large Chemical Shielding Anisotropies by Quaternion-Based Effective Hamiltonian Optimal Control
Enikő Baligács, Nino Wili, José P. Carvalho et al. (+2 more)
Dipolar recoupling is a key element in magic-angle-spinning (MAS) solid-state NMR spectroscopy with reintroduced dipole-dipole coupling interactions providing information about internuclear distances and enabling transfer of polarization between
spins in resolution-enhancing multiple-dimensional experiments. Such methods may be challenged in many important applications by the presence of large anisotropic
nuclear spin interactions such as chemical shielding anisotropy. In this paper, we address this challenge by presenting quaternion-based optimal control. This is founded in single-
spin operations enabling optimization of effective
Hamiltonians with reduced influences from anisotropic shielding. Along with the principles underlying such optimizations, we present numerical and experimental demonstration of 19F to 13C polarization transfer in presence of 19F chemical shielding anisotropy.
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All authors Enikő Baligács, Nino Wili, José P. Carvalho, Anders Bodholt Nielsen, Niels Chr. Nielsen
Biological Physics
Stochastic Yield Catastrophe in Delay-Facilitated Self-Assembly
Richard Swiderski, Severin Angerpointner and Erwin Frey
Self-assembly of supramolecular structures in
cells and synthetic applications often proceeds under unfavorable biochemical conditions and at low copy numbers of final target structures, ranging from tens of bacterial microcompartments to a single bacterial flagellum per
cell. Spatial organization through coupled reaction compartments of different reactivity (delay-facilitated assembly) can recover high yield in such environments at the mean-field level, but its robustness to
stochastic fluctuations at low target numbers is unclear. Using
stochastic simulations of a minimal two-compartment model, we show that delay-facilitated assembly is susceptible to a
stochastic yield catastrophe at low target numbers: even when each compartment in isolation allows for high-yield assembly, slow exchange between them induces a substantial drop in the final yield. We trace the mechanism to a specific assembly stage, where the random order of rate-limiting exchange events of subunits and partially completed structures determines the ratio of productive growth to excess nucleation. Restricting the exchange of larger structures – either by suppressing it entirely or letting exchange rates decrease with size – restores most of the yield without altering the mean-field behavior. The same phenomenology appears for two-dimensional hexagonal subunits and in a cytosol-membrane geometry, where
diffusion-limited exchange naturally implements the required size dependence. Our results show that equal success of assembly strategies at high target numbers does not imply their equal success at low target numbers, and that competing slow events occurring in random order are a common signature of
stochastic yield catastrophes.
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Materials Science
Chemical short-range order controls deformation pathways in a complex concentrated alloy
Angelo F. Andreoli, Gabriela B. Ribeiro, Guilherme C. Stumpf et al. (+12 more)
Chemical short-range order (CSRO) is an intrinsic feature of complex concentrated
alloys (CCAs), yet its influence on deformation mechanisms is controversial because of the inconclusive state of concurrent CSRO quantification during deformation. Here, we provide experimental evidence that CSRO acts as an intrinsic thermodynamic state variable governing stacking-fault energetics and deformation pathways in a Co30Cr40Ni30
alloy. By comparing quenched (CSRO-lean) and aged (CSRO-enriched) conditions with equivalent grain structure and phase constitution, we isolate the influence of atomic-scale chemical ordering on mechanical behavior. Calorimetry confirms reversible CSRO formation, while synchrotron X-ray diffraction and electron microscopy reveal that CSRO suppresses deformation-induced fcc-hcp martensitic transformation at both room and cryogenic temperatures. Despite differences in transformation dynamics, the macroscopic tensile response is still broadly similar. Atomistic simulations show that CSRO increases both stable and unstable stacking-fault energies, raising the energetic barrier for partial-dislocation activity and stabilizing the fcc
lattice against transformation. Together, the experimental and computational results establish CSRO as an added degree of freedom for tuning stacking-fault energetics and controlling deformation pathways in complex concentrated
alloys.
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All authors Angelo F. Andreoli, Gabriela B. Ribeiro, Guilherme C. Stumpf, Maria F. L. Valverde, Gustavo Bertoli, Vinícius P. Bacurau, David D. S. Silva, Pedro H. F. Oliveira, Eric M. Mazzer, Mamta Silwal, Garritt J. Tucker, Rodrigo Freitas, Martin Sahlberg, Daniel Miracle, Francisco G. Coury
Materials Science
Revealing the MoS2 Growth Mechanism in Chemical Vapor Deposition: Real-Time Imaging and Statistical Analysis
Faizal Arifurrahman, Tianshu Zhai, Yuguo Wang et al. (+4 more)
Chemical Vapor Deposition (CVD) is a promising method for scalable synthesis of two-dimensional transitional metal dichalcogenides (TMDs) such as MoS2, but challenges in reproducibility and controllability persist due to an incomplete understanding of their dynamic growth mechanisms. While in-situ characterization methods could provide valuable insights, it remains challenging to track a large ensemble of
crystals to enable quantitative, statistical analysis. Here, we address this gap by developing and applying a semi-automated image processing pipeline to analyze in-situ optical microscopy footage of MoS2 growth. This framework enables the high-throughput reconstruction of complete growth trajectories for over 400 individual
crystals from a single experiment. Our statistical analysis demonstrates that MoS2 crystallization is governed by an edge-attachment-limited mechanism rather than by precursor
diffusion. Furthermore, MoS2
crystals exhibit non-competitive growth, indicating that precursor supply does not limit the growth of neighboring flakes until physical impingement occurs. These findings provide direct, quantitative evidence that advances the fundamental understanding of TMD growth, establishing a powerful methodology for rational optimization of the CVD growth of two-dimensional materials.
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All authors Faizal Arifurrahman, Tianshu Zhai, Yuguo Wang, Jing Zhang, Andrew L. Hitt, Jun Lou, Ming Tang
Quantum Physics
A Reservoir Computing Approach to Quantum Gate Synthesis
Francesco Caravelli, Roberto Menta and Antonio Sannia
Quantum gate synthesis is essential for implementing
quantum algorithms on real hardware, yet existing methods are often computationally demanding. Here, we introduce a novel approach based on reservoir computing, which we name Group Reservoir Computing, an efficient machine-learning paradigm for learning temporal dynamics whose training reduces to a single linear regression, to reduce the resources required. The method is grounded in the Wei–Norman decomposition, which provides a compact description of the
evolution. We prove that the reconstructed dynamics always remain
unitary by construction and derive formal error bounds that establish the theoretical validity of the strategy. On the standard single-
qubit gate set the trained network produces a control pulse in a single pass, with mean fidelity 0.94 across the eight
benchmark gates; used to warm-start gradient-based optimization, it roughly halves the number of iterations that plain gradient ascent needs to reach a target fidelity, so that the relevant figure of merit is the time to reach that threshold rather than the final accuracy after a fixed budget. Owing to its general formulation, the method applies to any finite-dimensional hardware platform; the route to multiqubit synthesis is discussed in the closing section.
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High Energy Physics (Phenomenology)
Tailored PDFs for new physics searches
Elie Hammou
Parton Distribution Functions (PDFs) at large Bjorken-$x$ are mostly constrained by high-energy measurements, and thus risk to absorb the energy-growing effects of unaccounted new physics (NP) if it were present in the high-energy tails of
hadron-
collider observables used in global PDF fits. If undetected, such contamination biases the resulting PDFs and can potentially hide the absorbed NP signals from subsequent searches. We illustrate this effect in a Standard Model Effective Field Theory (SMEFT) risk-assessment scenario affecting high-mass Drell-Yan production at the High-Luminosity LHC, and compare two strategies to obtain robust PDFs and SMEFT bounds: conservative fits that exclude data above an energy cut, and simultaneous fits of PDFs and Wilson coefficients performed with the SIMUnet tool. Both approaches are shown to successfully recover the injected new physics that is otherwise absorbed and hidden by the PDFs.
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Mesoscale and Nanoscale Physics
Realization and manipulation of spiral charge density waves in a two-dimensional metal
Lili Zhou, Ruizi Zhang, Chen Si et al. (+14 more)
Nearly degenerate charge-density-wave (CDW) states play a central role in the competition among collective phenomena. In real materials, however, these states are often intertwined by disorder, hindering their disentanglement and control. Here we show that strain can lift this near-degeneracy and spatially separate distinct CDW states in NbSe2. Using van der Waals (vdW) interactions, we stabilize a micron-scale strain network that produces spatially inhomogeneous strain fields. Within this landscape, the intrinsic 3 * 3 CDW superlattice of pristine NbSe2 transforms into an isolated unidirectional 4 * 1 order under 1D-confined compression, and into a 2 * 2 order under biaxial tension. The 4 * 1 CDW has a multiband origin and exhibits markedly enhanced thermal stability, persisting up to 70 K. At strain-network nodes, it further develops into
chiral spiral textures, which can be melted by voltage pulses. These results establish strain as a powerful approach to disentangle, stabilize and manipulate competing electronic orders.
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All authors Lili Zhou, Ruizi Zhang, Chen Si, Zhaoteng Dong, Mengya Ren, Keru Guo, Can Zhang, Jizheng Wu, Fudi Zhou, Huixia Yang, Yaxin Zhao, Guoyuan Yang, Xiaolong Xu, Yuanxiao Ma, Xiao Kong, Yu Zhang, Yeliang Wang
Superconductivity
Superconducting proximity effect in a strongly correlated charge-transfer insulator
Mengya Ren, Yaoyao Chen, Fudi Zhou et al. (+9 more)
Proximity-induced superconductivity in strongly correlated
insulators provides a versatile route for engineering
quantum states of matter and artificial systems with tailored functionalities. However, microscopic interplay between superconductivity and correlated insulating states remains poorly understood. Here we use ultralow-temperature scanning tunnelling microscopy (STM) to systemically investigate superconducting proximity effects in a charge-transfer
insulator. Via STM tip manipulation, atomically sharp lateral junctions composed of superconducting monolayer H-NbSe2 and charge-transfer insulating monolayer T-NbSe2 are constructed, enabling direct access to tunable coupling regimes. In the weak-coupling regime, there is a robust proximity-induced superconducting gap in T-NbSe2, with a reduced gap value relative to that of H-NbSe2. Upon entering the strong-coupling regime, T-NbSe2 exhibits a superconducting gap comparable to that of H-NbSe2, accompanied by pronounced particle-hole-symmetric in-gap bound states, consistent with Yu-Shiba-Rusinov-like excitations. These findings establish monolayer H/T-NbSe2 lateral junctions as a model platform for elucidating superconducting proximity effects in strongly correlated charge-transfer
insulators.
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All authors Mengya Ren, Yaoyao Chen, Fudi Zhou, Can Zhang, Zhaoteng Dong, Lili Zhou, Quanzhen Zhang, Huixia Yang, Xiaolong Xu, Yuanxiao Ma, Yu Zhang, Yeliang Wang
Quantum Physics
Continuous limit of the square well problem in quantum mechanics
Matheus D. Moro, Thiago T. Tsutsui, Antonio S. M. de Castro et al. (+1 more)
The free-particle and square-well potentials are two of the most emblematic problems in
quantum mechanics, illustrating essential concepts such as matter waves, energy quantization, and bound states. It is therefore natural to consider how the free-particle solutions emerge from the square well as the width approaches infinity. In this work, we present a systematic procedure to demonstrate this transition by applying a
Fourier transform to the wave equation.
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All authors Matheus D. Moro, Thiago T. Tsutsui, Antonio S. M. de Castro, Fabiano M. Andrade
Mathematical Physics
A Geometric Derivation of the Einstein Equations from the Causal Action Principle
Felix Finster and Christoph Krpoun
The causal action principle for causal
fermion systems is analyzed for a minimizing measure whose support is assumed to have the structure of a smooth
manifold $\tilde{M}$. The concept of osculating
vacua is introduced. It is shown that the Lagrangian induces on $\tilde{M}$ a Lorentzian metric. Moreover, the Euler-Lagrange equations of the causal action imply that the
Ricci tensor must satisfy the Einstein equations of General Relativity for an energy-momentum tensor given in terms of a power expansion in the regularization length. The gravitational coupling constant is found to be the square of the regularization length. Our methods provide a systematic procedure for deriving corrections to the Einstein equations. The paper includes a self-contained introduction to causal variational principles and the causal action principle. Most
geometric structures (connection, Riemannian metric and
curvature) are introduced and analyzed in the general setting of causal variational principles for an arbitrary dimension of $\tilde{M}$. The Lorentzian setting works only for causal
fermion systems and is worked out only in four spacetime dimensions.
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Mesoscale and Nanoscale Physics
Phonon down-conversion by normal metals for superconducting devices
Guglielmo La Magna and Gianluigi Catelani
Thanks to low dissipation, superconducting devices are promising for a number of applications, such as detectors and implementations of
quantum computation. However, their working can be adversely impacted by quasiparticles, which is why so-called quasiparticle poisoning mechanisms and their mitigation are under intense investigation. Here we focus on one poisoning mechanism, namely pair-breaking
phonons, and its mitigation through down-conversion by a normal-metal film - the process in which scattering of high-energy
phonons by electrons lowers the energy of the former below the pair-breaking threshold. To study the down-conversion, we introduce a model based on kinetic equations, which we solve both analytically (approximately) and numerically in the steady state. We use the solution to the estimate a properly-defined down-conversion efficiency which depends on material parameters (such as the strength of electron-
phonon interaction and the
phonon transmission coefficient at interfaces) and film and substrate thicknesses. Interestingly, we find that the efficiency is nearly optimal above a minimum metal thickness, typically between 50 and 500 nm depending on the metal-substrate combination.
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Medical Physics
Direct probabilistic IMPT treatment planning with setup and range errors for neuro-oncological patients
Jelte R. de Jong, Sebastiaan Breedveld, Steven J. M. Habraken et al. (+4 more)
To show clinical feasibility of a previously proposed probabilistic planning approach that can precisely optimize for clinical goals with patient-specific acceptance probabilities on a neuro-oncological patient group, we compared probabilistic plans with (automated) robust plans for one patient (group A) that could achieve sufficient clinical target coverage and for four patients (group B) where target coverage had to be compromised due to organ-at-risk (OAR) dose constraints. The probabilistic approach is percentile-based and uses the fact that a (dose) percentile can be approximated as a linear combination of its expected value and standard deviation. The optimization has a nested structure: the inner optimization optimizes the beam weights for a given percentile estimate, while an outer loop iteratively updates and improves the accuracy of the percentile estimate. For every outer iteration, the optimization is warm-started from the previous iteration. Percentiles are efficiently calculated by sampling a
polynomial chaos expansion of the dose-influence
matrix. The patient in group A achieved cumulative OAR dose reductions (of OAR-related DVH-metrics) of 19 GyRBE, for identical target coverage. Target coverage improved for all patients in group B (the 10th percentile of $D_{99.8\%}$ increased up to 0.93 GyRBE), at the same time reaching cumulative OAR dose reductions (of OAR-related DVH-metrics) up to 33 GyRBE. Probabilistic plans were optimized in 44h to 141h. For two representative patients, eliminating warm-starting (i.e., the outer loop) from the approach reduced total optimization times to below 10h (which took originally 80h and 141h). Compared to robust optimization methods, the probabilistic approach achieves improved trade-offs between probabilistic target coverage and OAR sparing, potentially leading to better treatments.
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All authors Jelte R. de Jong, Sebastiaan Breedveld, Steven J. M. Habraken, Mischa S. Hoogeman, Jenneke I. de Jong, Danny Lathouwers, Zoltán Perkó
Astrophysics of Galaxies
Mapping Dust Attenuation at Kiloparsec Scales. IV. A Dust-model Interpretation of Attenuation Curves in Nearby Galaxies
Ruonan Guo, Cheng Li, Tao Jing et al. (+3 more)
In this fourth paper on kiloparsec-scale
dust attenuation, we ask whether the empirical trends found in Papers I–III can be translated into effective
dust properties. Using attenuation curves for 2487 high-continuum-S/N spaxels in 91 SwiM v4.2
galaxies, we construct a grid of uniform-screen
dust models composed of astronomical silicate and graphite grains with MRN-like size distributions. We fit the normalized attenuation-curve shape to constrain model parameters and then use the attenuation amplitude to estimate the model-dependent
dust mass surface density. The inferred
dust masses, compositions, and small-grain fractions are therefore effective quantities defined within the adopted attenuation model. The fitted models reproduce the main attenuation-curve variations and provide a direct bridge to Papers I–III: within this model, the relative 2175Å\ bump sequence maps mainly onto the effective fraction of small graphitic/carbonaceous grains, while the NUV-slope sequence maps onto the effective small-silicate grain fraction and total silicate mass fraction. Non-SF regions have higher
dust mass surface densities but lower
dust-to-
stellar mass ratios than SF regions, separating absolute
dust content from
dust content per unit
stellar mass. Regions with larger specific H$\alpha$ surface brightness have larger
dust-to-
stellar mass ratios but lower inferred small-grain fractions, especially lower small-silicate fractions. In non-SF regions this quantity is interpreted as ionized-gas emission per unit
stellar mass rather than as a direct sSFR. These model-dependent trends support a picture in which local
dust processing changes the relative abundance of small grains and thereby shapes the attenuation-curve variations found across the series.
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All authors Ruonan Guo, Cheng Li, Tao Jing, Shuang Zhou, Niu Li, Zhuo Cheng
Solar and Stellar Astrophysics
Cradle of Life: From the Formation of Stars to Habitable Worlds with the SKAO
Eleonora Bianchi, Joseph R. Callingham and the Cradle of Life working group
This chapter provides an overview of the different science cases covered by the "Cradle of Life" working group, which aims to leverage the capabilities of the Square Kilometre Array Observatory (SKAO) to trace the physical and chemical pathways toward
stars and
planets formation, how such
stars impact their
planets, and whether life could exist in such conditions. At its highest frequencies, the SKAO will probe the earliest stages of the raw material fuelling
planet formation, while enabling deep, unprecedented searches for prebiotic molecules both in high-mass and
solar-type protostars. Concurrently, the lowest frequencies will be deployed to detect and characterize exoplanetary
magnetic fields via their auroral
radio emission, and the type of space weather a
planet experiences from its host
star. Across the entire frequency range, the SKA
telescopes will conduct systematic searches of technosignatures. Together, these high-impact research areas establish a comprehensive roadmap for the SKAO to uncover the origins of life in the universe.
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Fluid Dynamics
Evaluation of State-of-the-Art Deep Learning Architectures for Aerodynamical Predictions
Jan Scherz, Derrick Hines and Philipp Bekemeyer
Surrogate models are used to substitute classical numerical solvers in engineering applications where the computational cost of the latter becomes infeasible. For instance, in aerodynamics such models offer cost-effective alternatives to computational fluid dynamics in problems such as shape optimization and load analysis, which oftentimes require high-fidelity simulations for a multitude of different parameter combinations. A specific class of deep learning-based surrogate models termed operator learning models directly approximates the solution operators to the partial differential equations underlying the physical phenomenon, thereby learning to replicate solutions to entire families of problems. However, while nowadays numerous architectures of this type get published, corresponding
benchmark studies remain scarce. In this article, we advance the study of AI-based surrogate methods by thoroughly benchmarking four state-of-the-art operator learning models on their aptitude for applications in aerospace engineering. In two experiments, we assess the models' capabilities of predicting the surface pressure distribution on two-dimensional airfoil shapes of varying complexity and on an industrial-scale three-dimensional aircraft configuration. Thereby, we evaluate the models' abilities to fulfill frequent requirements in aerodynamics such as capturing discontinuities (shocks) in the solutions, scalability towards excessive amounts of mesh points and handling of data scarcity. Accompanied by a careful analysis, our findings drive forward the field of AI-based surrogate modeling by providing detailed insights into the strengths and weaknesses of the individual architectures, thus allowing to identify priorities for future developments. In particular the Bi-Stride Multi-Scale Graph Neural Network and Transolver(++) are highlighted as promising surrogate models for aerodynamical applications.
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Quantum Physics
A Lie-algebraic approach to non-Markovian quantum dynamics
Haijin Ding, Stephen S.-T. Yau and Zhiwen Zhang
In this paper, we study the non-Markovian
quantum dynamics in
quantum computations from the perspective of a Lie algebraic approach based on numerical analysis. By vectorizing the density
matrix of
quantum states, the non-Markovian evolutions can be represented with high-dimensional linear time-varying equations, where the time-varying parameters arise from the non-Markovian interactions between the
quantum system and environment. We study the Magnus expansion of such linear time-varying
quantum dynamics and clarify how the truncation errors for the first- and second-order Magnus expansions are influenced by the non-Markovian properties. Besides, when the
quantum states are measured for filtering, the dynamics can be modeled as time-varying
stochastic differential equations due to the existence of measurement noise. The Magnus expansions based on
quantum stochastic filtering are different when the
quantum measurement noises are modeled in an {Itô or Stratonovich approach, rendering different truncation errors. Based on this, numerical simulations further demonstrate the efficiency of Magnus expansions in simulating non-Markovian
quantum dynamics without or with stochasticity, and how the truncation errors are influenced by the Lie
algebras in the Liouville space.
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Materials Science
Ultrafast altermagnetophononics
Chenyu Wang, Yaxian Wang and Sheng Meng
Altermagnets feature
symmetry-dictated nontrivial
spin splitting in electronic structure promising for next-generation spintronics, yet their ultrafast dynamical manipulation remains largely unexplored. Here, we establish altermagnetophononics as an efficient route for
magnetic control via selective
symmetry breaking induced by coherent
phonons. Using the prototypical altermagnet $\alpha$-MnTe as an example, we demonstrate that the targeted excitation of B$_{1g}$ mode selectively lifts the
symmetry constraints protecting altermagnetism (AM), driving ultrafast transition into a transient compensated ferrimagnetic (cFiM) phase characterized by a global
spin splitting without net magnetization. Further, we show that the proposed mechanism is broadly applicable by demonstrating a multi-mode
symmetry breaking pathway, and by realizing a ferrimagnetic order with reversible
magnetic moment in metallic CrSb. These findings elucidate the potential to obtain desirable nonequilibrium properties in altermagnets via coherent phononic control over their
spin splittings.
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Instrumentation and Methods for Astrophysics
Fabrication of focusing optics for TA-MOONS: Micro-MOONS
Ceiwynn Longworth, Megan Delamer, Suvrath Mahadevan et al. (+3 more)
Understanding
star and
planet formation requires optical to near-infrared spectroscopic observations of a large number of young
stellar objects. The TIFR-ARIES Multi-Object Optical to Near-infrared Spectrometer's (TA-MOONS) primary objective is to preform a large spectroscopic survey of young
stellar objects across wavelengths of 360 nm to 2.5 microns, with the multiplexed capability of observing up to eight sources simultaneously. Multiplexity is achieved by moving pickup mirrors on robotic arms. One component of this robotic arm system is Micro-MOONS, a micro-optic array, nanofabricated to enable accurate calibration, validation, and positioning of
stellar images onto the pickup mirrors. The micro-mirrors of the Micro-MOONS system are spherically concave, fabricated via two-
photon polymerization(2PP) in the NanoScribe GT2 system, and are printed on
plasma-cleaned silicon substrates using IP-S photoresist, followed by gold coating. 2PP allows for fine, detailed shapes on a sub-micron scale that are otherwise difficult and costly to obtain. The optimization of Micro-MOONS focuses on achieving uniformity, minimizing surface roughness, and preserving the desired radius of
curvature to avoid beam obstruction near the pickup mirrors. This work demonstrates the feasibility of integrating advanced custom-printed micro-optics into multi-object spectroscopic instruments, enabling improved calibration and efficiency in large-scale
stellar surveys.
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All authors Ceiwynn Longworth, Megan Delamer, Suvrath Mahadevan, Joe P. Ninan, Kathleen Gehoski, Krushna Jadhav
High Energy Physics (Theory)
Carroll-Field-Jackiw term in nonlocal Lorentz-violating QED
J. R. Nascimento, A. Yu. Petrov, P. J. Porfirio et al. (+1 more)
We investigate the radiative generation of the Carroll–Field–Jackiw (CFJ) term in nonlocal Lorentz- and CPT-violating extensions of
quantum electrodynamics. Nonlocality is introduced in the fermionic sector through entire form factors depending on the Dirac operator. Using the Fréchet and derivative expansions of the one-loop fermionic determinant, we derive the induced CFJ contribution and analyze its ultraviolet behavior after Wick rotation. For one class of form factors, the loop integrals are absolutely convergent at finite nonlocality scale $\Lambda$, without requiring an additional UV regulator. For another class of form factors, the CFJ coefficient is defined through an Abel regularization prescription. In both cases, the CFJ structure is preserved and its coefficient is continuously modulated by the ratio between the
fermion mass and the nonlocality scale. Thus, nonlocality removes the routing-, surface-term-, and UV-evanescent ambiguities of the finite-$\Lambda$ loop amplitude, although UV convergence alone does not imply complete prescription independence of the finite functional determinant.
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All authors J. R. Nascimento, A. Yu. Petrov, P. J. Porfirio, Ramires N. da Silva
Cosmology and Nongalactic Astrophysics
Evaporating cosmologically coupled black holes
Marco Calzà, Davide Pedrotti, Massimiliano Rinaldi et al. (+1 more)
Cosmologically coupled black holes (CCBHs), whose masses evolve in response to the cosmological expansion, have recently attracted significant theoretical and observational interest. Existing studies have treated CCBHs as purely classical objects, neglecting the effect of Hawking radiation (HR), which competes with the cosmological coupling (CC) mechanism. We take a first step towards studying evaporating CCBHs, adopting a quasi-adiabatic approximation in which the HR rate is evaluated at the instantaneous CCBH mass, and modeling the CC mechanism through the phenomenological scaling of the mass with the scale factor, $M \propto a^k$. We show that, depending on the coupling strength $k$, even late-time CC activation can significantly delay Hawking evaporation, or lead to asymptotic CC-dominated mass growth, with important implications. We set limits on the abundance of
primordial CCBHs from $\gamma$-ray observations, finding limits which are weaker than their uncoupled counterparts, as CCBHs are kept farther from the endpoint of evaporation for a longer time. Unlike standard
primordial black holes, the CCBH formation and present-day masses no longer approximately coincide, even for formation masses $M_{\text{form}} \gtrsim 10^{15}\,{\text{g}}$. Therefore, the same population of
primordial CCBHs may be subject to evaporation limits through its past emission history, as well as to other limits (such as microlensing) through its present-day mass.
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All authors Marco Calzà, Davide Pedrotti, Massimiliano Rinaldi, Sunny Vagnozzi
Fluid Dynamics
Condition for $1/f$ noise to occur along with an example for a diffusion equation
H. Mouri
While $1/f$ noise is ubiquitous and has been found in various systems, its physics remains uncertain. From an analytical study of an ordinary
diffusion equation, we find an additional example of the $1/f$ noise. The formula for this example, together with existing knowledge about scaling in fluid
turbulence, implies a necessary and sufficient condition for the occurrence of any stationary $1/f$ noise. That is, the noise needs to be characterized by two constant frequencies of $f_{\rm low} \ll f_{\rm high}$. For a frequency range from $f = f_{\rm low}$ to $f_{\rm high}$, it is further needed that, except for the mean amplitude of the noise, there is no other constant parameter. Then, at $f_{\rm low} \ll f \ll f_{\rm high}$, the noise scales asymptotically as $1/f$. Being statistical and simple, our condition applies to any system and hence explains the ubiquity of the $1/f$ noise. It is also applicable to some systems with noise of $\alpha \ne 1.0$ for $1/f^{\alpha}$, via intermittency analogous to that of the
turbulence.
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Materials Science
Electron Beam Radiolysis-Assisted Growth of Rutile TiO2 Thin Films
Silu Guo, Nitin Sathish Kumar, Sreejith Nair et al. (+3 more)
A new approach for growing crystalline thin films is developed that takes advantage of electron beam radiolysis being a constructive force to rearrange atoms into a crystalline structure. It is demonstrated that by irradiating the surface of a TiO2 film by an electron beam supplied by a reflection high energy electron diffraction (RHEED) gun inside the MBE chamber during growth, a crystalline film can be grown at much lower substrate temperatures, where deposited films typically appear amorphous. Here, rutile TiO2 films were grown using hybrid molecular beam epitaxy (MBE) allowing atomic level control of growth as well as an observation of radiolysis-driven crystallization. Analysis was carried out using a combination of SEM and atomic-resolution STEM imaging. It is also shown that by tuning the temperature of the substrate and the dose of the electron beam, the degree of crystallinity of the film can be controlled.
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All authors Silu Guo, Nitin Sathish Kumar, Sreejith Nair, Supriya Ghosh, Bharat Jalan, K. Andre Mkhoyan
Materials Science
Temperature-driven sodium-ion dynamical-to-static crossover in the zig-zag ordered phase of Na$_{0.5}$CoO$_2$
Shangfei Wu, Hengxin Tan, Dong Wu et al. (+7 more)
We employ polarization-resolved Raman spectroscopy combined with first-principles calculations to study the sodium-ion
lattice dynamics in a sodium zig-zag ordered cobaltate compound Na$_{0.5}$CoO$_2$. We detect two sodium
phonon modes for the first time, and their mode frequencies are consistent with first-principles
phonon calculations based on an orthorhombic unit
cell. We find that they appear below around $T^*\sim300\pm50$K with large linewidth broadening, much lower than the sodium zig-zag ordering temperature $T_\text{S}\sim460$K, and then narrow at lower temperatures. We interpret the sodium-
phonon anomalies occurring at $T^*$ as a dynamical-to-static crossover involving mainly the motion of sodium ions. Our results suggest that the gradual freezing of the sodium ions and the well-defined static sodium-zigzag order below $T^*$ set the stage for the emergent electronic and
magnetic orders in the CoO$_2$ layer of Na$_{0.5}$CoO$_2$.
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All authors Shangfei Wu, Hengxin Tan, Dong Wu, Mingshu Tan, Xinyu Zhou, Tianchen Hu, Tao Dong, Feng Jin, Qingming Zhang, Nanlin Wang
Quantum Physics
Quantum Topological Data Encoding
Adam Wesołowski, Dimitrios Thanos, Daniel Leykam et al. (+1 more)
Many
datasets encountered across a wide range of domains possess rich
geometric and topological structure that is difficult to capture using conventional vector-based representations.
Quantum machine learning offers the possibility of processing high-dimensional data in
Hilbert spaces, but its practical success depends critically on how classical data is encoded into
quantum states. We introduce
quantum topological data encoding (QTDE), a general framework for encoding topological information into
quantum states via
topology-driven
quantum evolution. Our method generalises an existing
topology-driven
quantum encoding framework to higher-dimensional data. We test the proposed method on clique-complexes classification tasks, and provide preliminary evidence that
topology-driven
quantum representations can capture discriminative information beyond that available through direct comparisons of classical topological descriptors. The proposed
quantum representations consistently outperform a baseline based on direct comparisons of the combinatorial
Laplacians describing the underlying topological structure. We indicate several areas of application where the framework can be used to provide a more efficient and reliable data representation.
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All authors Adam Wesołowski, Dimitrios Thanos, Daniel Leykam, Lirandë Pira
Materials Science
First-principles Study of Structural and Electronic Properties of Mn-doped Cu2NiXY4 (X=Sn, Ge, Si; Y=S, Se) Chalcogenide Semiconductors
Iskandar Raufzoda, Dilshod Nematov and Amondullo Burhonzoda
In this work, the effect of partial substitution of Mn by Ni on the structural and electronic properties of kesterite systems Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) was studied using density functional theory (DFT). The mBJ+U method was used to characterize the bandgap more accurately. To the best of our knowledge, a systematic comparative study of Mn substitution in the entire Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) family has not been previously performed. Due to crystallographic constraints of the kesterite unit
cell, the substitution of a single Ni atom with Mn corresponds to 50%. This configuration was chosen to study the effect of Mn substitution on the structural and electronic properties of Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) compounds, whereas the study of lower concentrations requires the use of a supercell and is the subject of further research. The calculation results show that the partial substitution of Ni with Mn preserves the tetragonal structure of kesterite and significantly alters the electronic structure. In all the compounds studied, the bandgap decreases from 1.028-3.397 to 1.007-3.333 eV. For example, in the Cu2NiSnS4 system, the bandgap width decreases from 1.59 eV to 1.49 eV. The narrowing of the bandgap results from hybridization between the Mn-3d, Cu-3d, and S/Se-p orbitals near the band edges, leading to a redistribution of electronic states around the
Fermi level. The results demonstrate that Mn substitution is an effective strategy for controlling the electronic properties of Cu2NiXY4 kesterites, offering great promise for use in optoelectronic devices where adjustable bandgaps are required.
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Optics
Maximum non reciprocity in metasurfaces of gyrotropic rods
Ioannis Katsantonis, Constantinos Valagiannopoulos and Anna C. Tasolamprou
Efficiently breaking time-reversal
symmetry at the subwavelength scale remains a cornerstone challenge for advanced electromagnetic wave manipulation. This work presents a rigorous analytical framework, based on cylindrical wave expansion, to investigate and optimize the nonreciprocal scattering of transverse electric waves by magnetically biased plasmonic rods. An intuitive metric is introduced to quantify the breaking of time-reversal
symmetry via the asymmetric lifting of degeneracy between azimuthal modes of opposite angular momentum, hosted by the gyrotropic particles. Leveraging this metric, a comprehensive mapping of the multiparametric space of operational frequency, cyclotron frequency, and cylinder optical size isolates regimes of maximum nonreciprocity. A detailed multipolar decomposition reveals that this extreme behavior stems from the phase-matched asymmetric excitation and interference of localized electric and
magnetic dipole modes. Moving from individual, isolated meta-atoms to collective photonic systems, the optimized cylinders are arranged into a periodic grating. Under oblique incidence, the combination of
geometric asymmetry and
magnetic mode splitting, forces the metasurface to transmit light in a totally different way when excited by opposite sides. The reported findings and design principles offer a versatile blueprint for the development of dynamically tunable flat-optics isolators, directional transceivers, and advanced wavefront routers.
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Quantum Physics
Post-Critical Meson Dynamics of Kibble-Zurek Excitations in a 5,564-Qubit Quantum Annealer
Francis A. Bayocboc Jr., Jacek Dziarmaga, Marek M. Rams et al. (+1 more)
Quantum phase transitions provide a controlled route for generating many-body excitations, but the dynamics after the critical point can be as important as the initial defect creation. Recent progress in
quantum annealing has made it possible to access coherent nonequilibrium dynamics in programmable Ising systems with thousands of superconducting
qubits. Here we use this capability to study a longitudinally biased
quantum Ising chain, where Kibble–Zurek defect creation is followed by nonintegrable post-critical dynamics. The longitudinal bias confines kink–antikink excitations into mesonic bound states, so that the final
spin configurations encode both the production of defects near the critical point and the subsequent
evolution of the confined excitations. Using energy-scale rescaling and zero-noise extrapolation, we find that the defect density follows the expected biased Kibble–Zurek/Landau–Zener crossover and agrees with
matrix-product-state simulations with uniform bias. In contrast, magnetization, spatial profiles, and minority-domain statistics reveal that mesonic
evolution is interrupted by localization of the post-critical domain pattern.
Matrix-product-state simulations with disorder reproduce this separation between robust defect creation and localized post-critical dynamics. Our results show that large-scale
quantum annealers can probe the fate of critical excitations beyond defect counting.
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All authors Francis A. Bayocboc Jr., Jacek Dziarmaga, Marek M. Rams, Jaka Vodeb
Solar and Stellar Astrophysics
The SKA as a Probe of Heliospheric Turbulence and Radio-wave Propagation Effects
Nicolina Chrysaphi, Eduard P. Kontar, Hamish A. S. Reid et al. (+3 more)
Density
turbulence in the heliosphere can impact traversing
radio photons originating from anywhere in the universe, leading to distortions of both the spectroscopic and imaging properties of the
radio sources. Extra-
solar radio sources exhibit scintillation and angular broadening, while monochromatic signals from spacecraft are spectrally broadened. It was recently demonstrated that such impacts, referred to as
radio-wave propagation effects, are particularly significant in observations of
solar radio bursts excited through the
plasma emission mechanism. A comparison of detailed observations with simulations is required in order to quantify the
radio-wave propagation effects and disentangle the true
radio-source properties from the observed ones, enabling the diagnosis of the heliospheric environment. Consequently, theoretical advancements and our ability to quantify the heliospheric
turbulence depend on the quality and quantity of available observations. SKA pathfinders, like LOFAR, have been key to the significant progress recently achieved, but have also highlighted areas where the available observing capabilities are lacking. The SKA's unrivalled sensitivity will be crucial in identifying and distinguishing fine and faint
radio structures, where our ability to model them defines whether we can accurately describe the heliospheric
turbulence and deduce the fundamental properties of the
radio sources. The SKA will be an indispensable tool in observing
solar radio emissions from the Sun to beyond 1 au, complemented by ground-based interferometers that can reach frequencies down to the ionospheric cut-off at 10 MHz and space-based
radio instruments which cover frequencies down to a few kHz.
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All authors Nicolina Chrysaphi, Eduard P. Kontar, Hamish A. S. Reid, Sophie Musset, Shilpi Bhunia, Kamen Kozarev
Computational Physics
A Showcase of Using the Partial-Structure R1 to Assemble Small-Molecule Crystal Structures
Xiaodong Zhang
Using a few concrete examples this paper has demonstrated a few observations on using the partial-structure R1 (pR1) to assemble small-molecule
crystal structures. (1) Assembling can start with orienting and/or placing large fragments or small fragments containing heavy atom(s). (2) It is handy to attach a fragment to a partial model as only the orientation needs to be optimized. (3) In a structure containing heavy atoms it is impossible to directly calculate the orientations of a light-atom-only fragment. Instead, it is necessary to use residual reflection intensities in which the contribution of the partial model containing all heavy atoms is deducted away. These observations indicate that pR1 is a useful tool for solving some small-molecule
crystal structures.
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Instrumentation and Detectors
Neural-network-based material identification in photon-counting computed tomography using region-of-interest spectral features
A. Miadzvetski, V. Rozhkov, R. Sotenskii et al. (+2 more)
This work investigates the feasibility of neural-network-based material identification based on
photon-counting computed
tomography (PCCT) data. The input data were spectral vectors extracted from regions of interest (ROIs) in reconstructed tomographic slices of a phantom containing La-, Nd-, and Gd-based samples, as well as air, water, bone, and polymethyl methacrylate (PMMA). The original tomographic slices were acquired at 12 detector threshold settings (THL = 45, 55, 65, 75, 85, 95, 105, 115, 125, 135, 145, 165). For model training, the spectra were interpolated onto a uniform grid from THL 45 to THL 165 with a step of one THL unit. Large ROIs, small ROIs, and their combined
dataset were considered. To avoid an overestimated performance caused by correlated ROIs extracted from the same tomographic slice, the data were split into training, validation, and test subsets at the slice level.
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All authors A. Miadzvetski, V. Rozhkov, R. Sotenskii, D. Shashurin, G. Chelkov