Peer Revenue Impact factor: volatile

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics

Watch Physics

Sunday 12 July

General Physics

Three Chiral Families from a Monopole Product over $S^2\times\mathbb{C}P^2$

Edward J. Shaya

We study the chiral zero-mode spectrum of the compact six-manifold $X_6=S^2\times \mathbb{C}P^2$ in a ten-dimensional Kaluza-Klein setting. We review the monopole Dirac index on $S^2$ and the $\mathrm{Spin}^{c}$ index analysis, showing that $\mathbb{C}P^2$ admits a minimal unit-index chiral sector. Dolan and Nash established the $\mathrm{Spin}^c$ index mechanism on complex projective spaces and showed that $\mathbb{C}P^2$ can supply a one-family chiral building block with Standard-Model-like quantum numbers. The step taken here is to place the $\mathbb{C}P^2$ sector on the six-dimensional product $S^2\times\mathbb{C}P^2$ and use an independently quantized monopole sector on $S^2$ to control the multiplicity. Unlike Calabi–Yau model-building constructions, where the family number is tied to vector-bundle and quotient data, this homogeneous product gives the three-family count through the factorized Dirac-index formula: $ N_{\rm fam} = {\rm index} D_{S^2 \times \mathbb{C}P^2}=\bigl({\rm index} D_{S^2,m}\bigr) \,\bigl({\rm index} D_{\mathbb{C}P^2,n}\bigr)=m\,\frac{n^2-1}{8}$. The canonical complex $\mathrm{Spin}^{c}$ structure on $\mathbb{C}P^2$ has $n=3$ and unit index. We show that this index is saturated by exactly one chiral zero mode and no opposite-chirality vectorlike partner. Thus, two flux sectors produce exactly three chiral internal zero modes: $(m,n)=(3,3)$ and $(m,n)=(1,5)$. Saturation is proved for all odd $n\geq 3$. This homogeneous product isolates the family number in an elementary geometric formula. For a 10D Weyl fermion valued in a visible $\mathbf{16}$ of $\mathrm{Spin}(10)_G$, Lorentz branching shows these internal zero modes yield three left-handed 4D $\mathbf{16}_G$ multiplets. The analysis is restricted to the spectral and index-theoretic problem; moduli stabilization and phenomenological dynamics are deferred to a companion paper.
Read the full abstract

Physics Education

The Quantum Learning Pyramid (QLP): A Novel, Holistic, Industry-Ready Curriculum and Pedagogical Methodology for Quantum Computing Education

Arun Govindankutty

Quantum computing education is becoming urgent as industry demand and national initiatives grow rapidly. This paper introduces the Quantum Learning Pyramid (QLP), a unified pedagogical framework for undergraduate and graduate education in quantum information and computing. The QLP follows a four-tier structure that integrates phenomenological understanding, computational thinking, hardware-aware development, and societal context. The curriculum is designed using spiral progression, competency-based pathways, and authentic assessment. Instruction is grounded in active and project-based learning, aligned with ACM/IEEE curriculum guidelines. Core topics include quantum mechanics fundamentals, qubit operations, and key algorithms, while advanced modules address error correction, cryptography, and quantum hardware. Hands-on learning is supported through simulation platforms, cloud-accessible quantum processors, and hybrid laboratory environments. Interdisciplinary case studies and real-system experimentation are embedded throughout. The proposed framework bridges theory and practice and provides a scalable roadmap for developing a quantum-ready workforce and scientifically informed citizens.
Read the full abstract

Materials Science · Cross-listed from math.NA

When is the combined load identifiable from a stress-intensity profile? A coupled forward-inverse study on SIFBench finite-element data

Giansalvo Cirrincione and Filippo Grassia

This work studies the inverse problem of recovering the relative magnitudes of the tension, bending, and bearing loads acting on a crack from its stress-intensity-factor profile along the crack front, using the public SIFBench finite-element data. The central claim is not forensic load recovery on field cases, but a rigorous characterization of when the combined load is identifiable at all, together with an estimator that returns calibrated uncertainty precisely in the regimes where it is not. For a known geometry the forward map from loads to profile is exactly linear, and identifiability reduces to a single geometric question: whether the three elementary load profiles are linearly independent as functions along the front. When they are nearly dependent, many different load combinations produce almost the same profile and the inverse problem is illposed; the analysis shows that the degree of ill-posedness is controlled by an intrinsic stability margin, not by the conditioning number alone. A single crack-front operator serves both as a structured forward surrogate and as the differentiable map required by a simplex-constrained, set-valued inverse estimator. On the SIFBench corner-crack scenario the empirical behaviour matches the theory: the typical geometry is well posed while a sizable minority is genuinely ill-posed, so a point estimate is reliable on the majority and provably uninformative on the rest. Validation is on controlled synthetic noise; no real fracture cases are used or claimed.
Read the full abstract

Quantum Physics

Double Covariance Model for Entangled Quantum States: Gaussian Reduction to Second Order Covariances

Andrei Khrennikov

We propose a novel approach to the problem of interconnecting the probabilistic formalisms of classical and quantum physics, focusing on its most challenging aspect: the classical probabilistic generation of entangled states. We show that the statistics encoded in the density operators of composite quantum systems correspond to fourth-order classical statistics. Specifically, to generate a density operator, one must consider the covariance of a random covariance operator. We term this framework the Double Covariance Model (DCM). This double covariance possesses a non-trivial internal structure that arises from the interplay between two distinct time scales, combining temporal and statistical covariances. In this article, we exploit a well-known property of Gaussian processes: the second-order moment determines the moments of higher orders, specifically the fourth-order moment. This Gaussian reduction simplifies the DCM by reducing it to second-order statistics. Utilizing (circular) Gaussian processes simplifies and generalizes the DCM construction for entangled states, rendering it mathematically rigorous. Furthermore, it clarifies the classical probabilistic meaning of concurrence, a foundational quantitative measure of entanglement.
Read the full abstract

Solar and Stellar Astrophysics

Closed-form representations of extended astrophysical thermonuclear functions

Subrat Parida

Reaction rate determination is an essential problem in the theories of cosmological and stellar nucleosynthesis. I investigate the closed-form analytic evaluation of thermonuclear reaction rates, which are necessary for both cosmic and celestial nucleosynthesis. An alternate velocity distribution to the Maxwell-Boltzmann distribution can be considered in nuclear fusion processes occurring in the interior of stars when there is a diversion from hydrostatic equilibrium. The extension of non-resonant reaction rate integrals in standard, cut-off, depletion, and screening instances is examined in this study, utilising the MacDonald distribution. This study is primarily on the use of generalized special functions that represent the extended non-resonant thermonuclear functions in mathematical physics. Moreover, an attempt is made to analyse the reaction probability integrals corresponding to the several forms of the slowly varying cross-section factor S(E).
Read the full abstract

Adaptation and Self-Organizing Systems

Self-Healing Coordination in Cognitive Swarm Agents with Bloch-Type Perceptual Memory

Jyotiranjan Beuria

Reactive flocking models usually map current local observations directly to motion, leaving limited room for internal perceptual state to shape recovery after disruption. Building on a non-Markovian collective-motion model based on self-regulated perceptual dynamics, we ask whether the Bloch-type slow-fast architecture can support self-healing coordination in cognitive swarm agents. Each agent carries a bounded Bloch-type perceptual register coupled to a slow regulatory state. The slow state is not treated as a standalone memory store; here, perceptual memory is used operationally to denote history-dependent cue resolution within the closed slow-fast loop. The Bloch update is a positivity-preserving effective dynamics for internal perceptual alternatives, not a microscopic quantum claim. We evaluate the architecture in a non-periodic, obstacle-rich drone migration task with finite speed, bounded turning, collision avoidance, altitude regulation, and a fixed migratory drive. Multi-seed ablations compare the full slow-fast architecture with memoryless and partial-feedback baselines using recovery time, largest-cluster restoration, polar order, local coherence, collision risk, and path efficiency. Results show that the main functional impact is on self-healing: after obstacle-induced fragmentation, the closed slow-fast loop accelerates restoration of spatial connectedness, whereas an uncoupled slow trace behaves like a memoryless controller.
Read the full abstract

Quantum Physics

The quantum coherence as a phase property of the wave function

Ivan Georgiev Koprinkov

The quantum coherence as a phase property of the most fundamental quantum mechanical entity, the wave function, is explained for the first time. Phase-sensitive nonadiabatic dressed states, arising from the interaction of a quantum system and a coherent external electromagnetic field, are used in these considerations. Two types of phase correlations in the multilevel phase-sensitive nonadiabatic dressed states are found: a rapidly changing phase correlation between the real and the virtual components and a stationary phase correlation between different virtual components of these states.
Read the full abstract

Physics Education

Student Perspectives on Traditional Pedagogy Used in Graduate Physics Coursework

Kevin Coldren, Nkodia Ngondala, Audrey Claar et al. (+2 more)

Graduate programs in STEM disciplines are central to preparing future researchers and professors. Program requirements for students often include taking several graduate-level courses. Anecdotal evidence suggests that graduate coursework in physics in particular features outdated and ineffective pedagogical methods, with high emphasis on mathematical rigor in place of conceptual learning or connections made with authentic research. Prior physics education research indicates that students can leave graduate courses with shortcomings in conceptual understanding of covered topics. This pilot study is designed to document student perspectives on their graduate coursework in a single U.S. R1 physics Ph.D. program. A total of 14 semi-structured interviews were conducted with students enrolled in the program, and thematic analysis was conducted on five of these interviews for this paper. The resulting themes are discussed, including the prevalence of traditional passive lecture pedagogy and students placing high value on course content relevant to research.
Read the full abstract

All authors Kevin Coldren, Nkodia Ngondala, Audrey Claar, Mike Verostek, Diana Sachmpazidi

Pattern Formation and Solitons

Exact vector Akhmediev breathers dominated by a linearly stable frequency

Wen-Rong Sun, Chong Liu, Lei Wang et al. (+1 more)

In the scalar nonlinear Schrodinger equation, an Akhmediev breather (AB) is dominated by a frequency that lies inside the modulation instability gain band. This exactly correspondence between instability and breathers is challenged in vector systems such as the Manakov system, where the gain spectrum splits into disconnected lobes separated by stable gaps. We analytically and numerically construct an AB that is generated by unstable modes but is spectrally dominated by a stable harmonic at its peak. Numerical simulations starting from a simple continuous wave background perturbed only by the unstable harmonics confirm that the stable component emerges spontaneously and becomes dominant without any initial seed. We identify the precise parameter window in which this phenomenon occurs and show that this passive amplification of the linearly stable component is driven by four-wave mixing, which accounts for 96% of the nonlinear forcing. Given the universality of the Manakov system across nonlinear physics, from nonlinear optics to ultracold quantum gases, these results open an experimentally accessible new perspective on breather dynamics, one in which linearly stable frequencies can dominate.
Read the full abstract

All authors Wen-Rong Sun, Chong Liu, Lei Wang, Fabio Baronio

Quantum Physics

$p$-Form Gauge Dynamics and Digital Quantum Simulation – Flux and Cosmological Constant Neutralization

Soo-Jong Rey

I develop a Hamiltonian framework for ${\mathbb Z}_k$ $p$-form gauge fields on arbitrary oriented cell complexes in arbitrary dimensions. Gauge qudits are defined by $p$-cells, charged boundary qudits by $(p-1)$-cells, Gauss-law generators by boundary map $\partial_p$, and magnetic checks by $\partial_{p+1}$. The same cellular structure produces local dressed Wilson operators, and at $k=2$ a Calderbank-Shor-Steane check complex relevant to quantum error correction. I then specialize to $p=2, k=2$, where the magnetic 3-cell term is absent and the one-form Gauss-law can be solved exactly. The physical Hilbert space is parameterized by plaquette electric-flux variables, while the link configuration is reconstructed as the dynamical boundary of the evolving flux domains. The reduced Hamiltonian is an Ising-type plaquette model, where its local transverse-field term is the physical image of the boundary-dressed Wilson operator $\sigma_p^z\prod_{\ell\in\partial p}\tau_\ell^z$. A tube-cap quench compares two initial flux fillings with the same initial boundary loops. Exact diagonalization on $4\times4$, $6\times4$, and $5\times5$ tori finds that the cap loses $20$-$37\%$ of its occupied-flux area, while the tube remains nearly pinned. A finite-size scaling locates a dynamical crossover of tension-to-density ratio near $(m/\varepsilon_E)_c\simeq1.89$. The unreduced plaquette-plus-link encoding provides local Gauss-law checks and a direct digital implementation, while the reduced plaquette-only Hamiltonian supplies the exact benchmark. The result places the specific top-form discharge and the cosmological constant neutralization calculation inside a general higher-form Hamiltonian and coding framework.
Read the full abstract

Quantum Physics

Randomized Quantum Optimal Control

Leeseok Kim, Francisco Riberi, Kevin Baca et al. (+1 more)

Quantum optimal control (QOC) aims to find control functions that optimally steer a quantum system toward a target operation. We introduce a randomized QOC framework where optimization is carried over an ensemble of control functions and their probabilities, instead of a single set of functions. Using this framework, we prove that randomized QOC can reach a target accuracy faster than any deterministic protocol under the same resource constraints. We also develop general symmetry-based constructions that convert a given control into an ensemble of controls that can systematically reduce the error. We benchmark these constructions for CNOT implementation and find that the resulting randomized protocol quadratically suppresses the error of the optimized deterministic solution. In addition, we introduce randomized GRAPE, which generalizes GRAPE to directly optimize control ensembles and their associated probabilities. Finally, as a related application, we discuss randomized boundary-pulse constructions {that enhance} robustness against coherent noise.
Read the full abstract

All authors Leeseok Kim, Francisco Riberi, Kevin Baca, Milad Marvian

Superconductivity

A minimal model for the Weyl nodes and Fermi arcs of PtBi$_2$

Tobias Cristófoli, Manuel Alonso Lemos, Jorge I. Facio et al. (+1 more)

Weyl semimetals host topologically protected Fermi arcs on their surfaces, originating from the Chern number of the bulk Weyl nodes. In trigonal PtBi$_2$, superconducting signatures have been associated with the Fermi arcs. Theoretical descriptions of this surface superconductivity have so far relied on effective models that are not directly tied to the microscopic electronic structure of the material. In this work we develop a minimal description of the low-energy bands guided by density functional theory calculations and fully constrained by the relevant crystalline and time-reversal symmetries. The model captures the evolution of the Weyl nodes with spin-orbit coupling, including node annihilations, and is able to describe the spin-momentum locking of the surface Fermi arcs. It reproduces the orbital content and the band topology of PtBi$_2$ and provides a starting point for further studies.
Read the full abstract

All authors Tobias Cristófoli, Manuel Alonso Lemos, Jorge I. Facio, Pablo S. Cornaglia

Solar and Stellar Astrophysics

Investigating the electron temperature of [Ar IV] in planetary nebulae using the DESIRED database

J. García-Rojas, E. Reyes-Rodríguez, J. E. Méndez-Delgado et al. (+9 more)

(Abridged) We investigate the behaviour of the electron temperature derived from [Ar IV] lines, Te([Ar IV]), in a sample of PNe to characterize the thermal structure of high-excitation gas and compare it with the predictions of standard photoionisation models. Using the DEep Spectra of ionised REgions Data Base Extended (DESIRED-E), we selected a sample of 57 PNe for which Te([Ar IV]), Te([O III]), and ne([Ar IV]) could be determined simultaneously and homogeneously. We performed a detailed comparison between these observational diagnostics and a suite of over 160000 photoionisation models from the Mexican Million Models Database (3MdB). We find that the observed Te([Ar IV]) values are systematically higher than those predicted by pure photoionisation models for a given Te([O III]), i.e. approximately 31 percent of the PNe sample exhibits a Te([Ar IV]) more than 2sigma higher than photoionization model predictions. This discrepancy persists regardless of the specific set of auroral lines used for the diagnostic or the choice of atomic data (transition probabilities and collision strengths) adopted in the calculations. Other high-ionisation Te diagnostics, compiled from the DESIRED database or from the literature, however, do not show such behaviour, though the statistics for these are much more limited. The fact that models succeed for the highest-ionisation species but fail specifically for [Ar IV] suggests that the discrepancy is not due to a global inner-nebula heating mechanism. Instead, it points toward a localized physical effect or a limitation in the current understanding of the ionisation stratification and atomic physics specific to the Argon ion stages. This "[Ar IV] anomaly" must be resolved to ensure the reliability of abundance determinations in high-excitation nebulae.
Read the full abstract

All authors J. García-Rojas, E. Reyes-Rodríguez, J. E. Méndez-Delgado, C. Morisset, D. Jones, C. Esteban, F. F. Rosales-Ortega, V. Gómez-Llanos, M. Orte-García, L. E. Martínez-Rivero, Y. Hong, X. Fang

History and Philosophy of Physics

The Emergence of Astroparticle Physics: From Cosmic-Ray Physics to a new Scientific Field

Luisa Bonolis

Astroparticle physics emerged during the late twentieth century as a new interdisciplinary field at the intersection of particle physics, astrophysics, and cosmology. This article examines the historical mechanisms through which it took shape as a distinct scientific field, focusing on the progressive interaction of previously separate experimental cultures, research traditions, and scientific communities. It argues that astroparticle physics emerged not through the simple convergence of established disciplines, but through the gradual reorganization of high-energy research around scientific problems that transcended traditional disciplinary boundaries. Three broad historical trajectories shaped this process: the transformation of postwar cosmic-ray physics; the emergence of a high-energy Universe through relativistic astrophysics and new astronomical windows; and the growing interaction between particle physics and cosmology. Their progressive interaction transformed naturally occurring particles into astrophysical messengers and the Universe itself into a laboratory for investigating fundamental physics beyond the reach of terrestrial accelerators. At the same time, new experimental practices, international collaborations, scientific forums, and institutional structures progressively gave organizational form to this emerging research landscape. More broadly, the emergence of astroparticle physics illustrates how new interdisciplinary fields develop through the co-evolution of scientific questions, experimental cultures, research communities, and institutions.
Read the full abstract

Materials Science

A Cluster-Based Model of the Spectrum of Erbium-Doped GdVO$_4$

Zachary H. Roberts, Masaya Hiraishi, Luke S. Trainor et al. (+1 more)

Experimental observations of rare-earth ions doped into an antiferromagnetic crystal show an enriched optical spectrum. In this paper we present a cluster-based model to describe erbium ions doped into a gadolinium vanadate (Er:GdVO$_4$) host crystal, wherein the erbium ion couples directly to its four nearest neighbour gadolinium ions, which in turn couple to the mean field of the rest of the crystal. Compared to previous models in the literature, the parameters used to fit this model are fewer in number, with clearer physical origins. Agreement with the experimentally observed optical spectrum of Er:GdVO$_4$ suggests that our model succeeds in capturing the most important interactions of the system, suggesting that it may be useful for predicting microwave-to-optical transduction in future experiments.
Read the full abstract

All authors Zachary H. Roberts, Masaya Hiraishi, Luke S. Trainor, Jevon J. Longdell

High Energy Physics (Theory)

Krylov Complexity from Loschmidt Amplitude

Debarghya Chakraborty

Krylov complexity is a powerful diagnostic of quantum dynamics, with clear connections to other measures of quantum chaos and operator growth. One such measure is the Loschmidt amplitude, defined as the overlap of initially identical states evolved under two slightly different Hamiltonians. Its decay in certain systems is controlled by the classical Lyapunov exponent. Using the algebraic properties of the Krylov complexity operator, we express Krylov complexity as the derivative of a Loschmidt amplitude whose perturbation is parameterized by an angular variable $\phi$. This formulation allows us to define a spectral propagator that encodes the entire complexity distribution, which we characterize for specific types of systems. We study the two-dimensional quantum geometry spanned by time and $\phi$ where the original and deformed trajectories reside, demonstrating that Krylov complexity is upper-bounded by its volume. We also express the time derivative of Krylov complexity in terms of a distinct Loschmidt amplitude. Depending on the growth of the Lanczos coefficients, the perturbation term in this amplitude can be truncated. We propose that the strength of this perturbation provides a classification scheme for Krylov complexity dynamics and relate it to the $\phi$-derivative of the spectral propagator. Using this analytical framework, we derive general relations between the time-dependence of the survival amplitude and Krylov space measures.
Read the full abstract

Soft Condensed Matter

Assembly pathways of anisotropic lipid membrane-deforming colloids

Ali Azadbakht, Thomas Weikl and Daniela J. Kraft

Membrane-deformation mediated interactions play an important role in the spatial organization of proteins on the cell membrane. Although interactions between isotropic membrane deformations have been extensively investigated, the role of anisotropic deformations remains largely unexplored despite their prevalence in biological systems. Here, we experimentally investigate the assembly of anisotropic colloidal objects that deform a lipid membrane while being confined underneath it, without direct attachment. Combining experiments and numerical calculations, we analyze how a wide range of shapes, including ellipsoids, dumbbells, cubes, scalene triangles, tetrahedra, and bent rods, interact with each other through the membrane deformations they induce. We find that membrane-deforming objects initially attract through regions of highest curvature and subsequently reorient into close packed arrangements with an approximately spherical circumference. This is achieved through the alignment of flat faces - if possible in register - and locally optimized geometric packing, with regions of high curvature imposing energy barriers that influence the assembly pathway. Our work reveals general principles how anisotropic membrane deformations govern the assembly pathways and final particle arrangements, providing new insights into the behavior of membrane-deforming proteins and other inclusions.
Read the full abstract

Applied Physics

Multiple Band-Gaps through the Coupling of Unit Cells from the Same Metamaterial: the Dual Cell method

Plastiras Demetriou

This study investigates how the coupling of two unit cells belonging to the same mechanical metamaterial into a dual unit cell configuration, can produce a new metamaterial with enhanced wave attenuation capabilities. For two metamaterials, two different unit cell coupling configurations are examined in 2D (side by side and chessboard), with particular emphasis on maintaining a plane crystallographic group of high symmetry, in order to simplify band structure calculations given the complexity of the geometry. It is shown that for specific configurations and choices of unit cell, multiple directional and/or omnidirectional band-gaps can appear, some of which can exhibit enhanced attenuation. The way in which these band-gaps emerge is described through applying the same procedure on 1D spring mass chains. Results support the idea that any band-gap metamaterial could have a much more efficient version which can be constructed purely from its own unit cells.
Read the full abstract

Materials Science

High-Mobility Ge-Doped $\beta$-Ga$_2$O$_3$ Growth on Sapphire by Low-Pressure Chemical Vapor Deposition

Ahmed Ibreljic, Saleh Ahmed Khan, Sourav Sarker et al. (+5 more)

In this work, high-quality Ge-doped (-201) $\beta$-Ga$_2$O$_3$ thin films were heteroepitaxially grown on c-plane sapphire substrates with offcut angles of 0 deg, 2 deg, 6 deg, and 8 deg using low-pressure chemical vapor deposition (LPCVD). Increasing sapphire offcut promoted step-flow growth, resulting in improved terrace alignment, reduced surface roughness, and enhanced crystalline quality. Phase-pure monoclinic $\beta$-Ga$_2$O$_3$ with strong (-201) preferential orientation was confirmed by X-ray diffraction and Raman spectroscopy, while X-ray photoelectron spectroscopy revealed near-stoichiometric composition with an O/Ga ratio of 1.48. Electrical transport properties exhibited a strong dependence on substrate offcut angle, with room-temperature Hall mobility increasing from 15 to 117 cm$^2$/V s as the offcut angle increased from 0 deg to 6 deg, across carrier concentrations spanning $1.43 \times 10^{17}$ to $2.75 \times 10^{18}$ cm$^{-3}$. The 6 deg offcut sample achieved a room-temperature mobility of 117 cm$^2$/V s at a carrier concentration of $1.43 \times 10^{17}$ cm$^{-3}$ and a peak low-temperature mobility of 337 cm$^2$/V s at 128 K with a carrier concentration of $8.96 \times 10^{16}$ cm$^{-3}$, representing the highest reported room-temperature and low-temperature mobilities for Ge-doped $\beta$-Ga$_2$O$_3$ films grown on sapphire substrates. Carrier concentration and mobility data were analyzed using charge-neutrality and Boltzmann transport models incorporating donor activation together with polar optical phonon, ionized impurity, neutral impurity, acoustic deformation potential, and dislocation scattering mechanisms. The fitting revealed shallow donor activation energies of 12.5-19 meV, a deeper donor level at 80 meV, low acceptor compensation ($< 5 \times 10^{15}$ cm$^{-3}$), and threading dislocation densities on the order of $10^9$ cm$^{-2}$.
Read the full abstract

All authors Ahmed Ibreljic, Saleh Ahmed Khan, Sourav Sarker, Ibrahim Isah, Stephen Margiotta, Michael Davenport, Stephen Lam, Anhar Bhuiyan

Materials Science

High-Quality Ge-Doped (010) $\beta$-Ga$_2$O$_3$ Homoepitaxial Films Grown by Low-pressure CVD: Structural, Electrical, and Schottky Diode Characteristics

Ahmed Ibreljic, Saleh Ahmed Khan, Sourav Sarker et al. (+3 more)

In this work, Ge-doped $\beta$-Ga$_2$O$_3$ homoepitaxial films were grown on native (010) $\beta$-Ga$_2$O$_3$ substrates using low-pressure chemical vapor deposition (LPCVD). Controlled $n$-type doping was achieved with room-temperature carrier concentrations ranging from $7.4\times10^{17}$ to $2.57\times10^{18}\ \mathrm{cm}^{-3}$ and corresponding electron mobilities of 105-62 cm$^2$/V$\cdot$s. The films exhibited smooth surface morphology with RMS roughness values of 2.94-3.97 nm, while X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy confirmed phase-pure $\beta$-Ga$_2$O$_3$ with excellent crystalline quality and near-stoichiometric composition. Temperature-dependent Hall measurements on the film with a room-temperature carrier concentration of $7.4\times10^{17}\ \mathrm{cm}^{-3}$ and mobility of 105 cm$^2$/V$\cdot$s yielded a peak electron mobility of 234 cm$^2$/V$\cdot$s at 116 K, while charge-neutrality and transport modeling revealed a dominant shallow donor level with an activation energy of 14 meV, confirming efficient electrical activation of Ge donors. Vertical Ni/$\beta$-Ga$_2$O$_3$ Schottky barrier diodes fabricated using the Ge-doped drift layer exhibited good rectifying behavior with a turn-on voltage of 0.74 V, an ideality factor of 1.32, a Schottky barrier height of 1.02 eV, and a specific on-resistance of 2.49 m$\Omega\cdot$cm$^2$. Capacitance-voltage measurements yielded a net donor concentration of $7.7\times10^{17}\ \mathrm{cm}^{-3}$ and a Schottky barrier height of 1.13 eV, in good agreement with Hall and current-voltage measurements. These results demonstrate that LPCVD enables controllable Ge doping while maintaining high structural and electronic quality, establishing LPCVD-grown Ge-doped $\beta$-Ga$_2$O$_3$ as a promising platform for future high-voltage power electronic devices.
Read the full abstract

All authors Ahmed Ibreljic, Saleh Ahmed Khan, Sourav Sarker, Stephen Margiotta, Stephen Lam, Anhar Bhuiyan

High Energy Physics (Theory)

The Euler-Heisenberg action for a $U(1)\times U(1)$ dyon quantum electrodynamics

D.O.R. Azevedo, T.S. Dias and E.D. Pereira

The one-loop effective Lagrangian of quantum electrodynamics for dyons (dQED) with a $U(1) \times U(1)$ gauge symmetry is derived using the Schwinger proper-time method. We identify the analog of the Schwinger pair-production limit and compute the corresponding nonlinear equations of motion. The electromagnetic response of the model is analyzed by linearizing the equations of motion around a purely magnetic background. From the resulting plane-wave solutions, we obtain the effective permittivity and permeability tensors, along with the associated dispersion relations and refractive indices for parallel and perpendicular polarization modes. The refractive indices involve hybrid superpositions of both gauge sectors, as illustrated in the symmetric case $q_{(1)} = q_{(2)}$. In this background, the model exhibits vacuum birefringence, indicating that the quantum vacuum behaves as an anisotropic medium. All results consistently reduce to the standard Euler-Heisenberg predictions of QED when the magnetic charge vanishes.
Read the full abstract

High Energy Physics (Phenomenology)

Multipole structure of the $N \to \Delta$ Transition Generalized Parton Distributions

June-Young Kim and Hyun-Chul Kim

We establish the multipole structure of the $N \to \Delta$ transition at the level of the generalized parton distributions (GPDs). We decompose the four transition GPDs into one monopole, two dipole, and one quadrupole components in the transverse plane by a multipole expansion of the covariant transition matrix element in terms of the three-dimensional spin-transition tensors and the transverse momentum transfer. These multipole components are in one-to-one correspondence with the light-front helicity amplitudes. In the zero-skewness limit, the multipole GPDs define impact-parameter transition densities, which generalize the transverse transition charge densities to the $x$-dependent level. These transition densities arise from non-diagonal matrix elements between two distinct hadronic states and must therefore be distinguished from the diagonal densities of the nucleon and the $\Delta$. The multipole transition densities visualize the monopole, dipole, and quadrupole structures of the partonic $N \to \Delta$ transition in the transverse plane.
Read the full abstract

Quantum Physics

Driven Quantum Stars as Controlled Primitives for Real-Time Spin Dynamics

Michael Chertkov

Quantum advantage in real-time spin dynamics should be assessed against the strongest relevant classical substitutes, not merely against the qubit nature of the microscopic system. We develop a physics-based diagnostic for this boundary by reducing a qubit spin model to a spin-Landau–Lifshitz (LL) classical sector and organizing the residual quantum sector as controlled corrections. The control parameter is graph coordination: we study a spin star with \(d\) leaves and \(O(1/d)\) hub–leaf couplings. In its homogeneous form the star benchmarks the transition from LL-substitutable dynamics to genuinely quantum, discrete-sector interference; in its fully driven form, with time-dependent fields and bilinear couplings, it is the basic message-passing primitive for tree and loopy spin structures. For coherent-state return amplitudes we prove exact leaf elimination and derive a continuous-time \(1/d\) hierarchy. L0 is a driven one-spin weak-mean-field theory, while G1 is a Gaussian nonlocal-in-time influence correction coupling leaf two-time kernels to the hub weak two-point function. On bounded finite-time windows away from zeros of the boundary amplitudes, the hierarchy gives \(\log\mathcal A-\log\mathcal A_{\rm L0}=O(1/d)\) and \(\log\mathcal A-\log\mathcal A_{\rm L0}-\Delta_{\rm G1}=O(1/d^2)\); numerical tests on fully driven anisotropic ensembles give slopes \(-1.05\) and \(-2.03\). Static, inhomogeneous, aligned, and fully driven stars provide validation rungs, and comparison with a temporal matrix-product influence-matrix baseline delineates complementary regimes. Unlike rank compression on a Trotter grid, the hierarchy is ordered by a physical parameter, formulated in continuous time, and each truncation level is itself a physical theory, with the LL sector as the high-coordination limit.
Read the full abstract

Nuclear Experiment

Precision masses of neutron-rich platinum and gold nuclei reveal enhanced $N=126$ shell strength below doubly-magic $^{208}$Pb

David Freire-Fernández, Rui-Jiu Chen, Usama Ahmed et al. (+63 more)

The heaviest stable nuclei in the universe owe their existence to quantum shell structure, the grouping of protons and neutrons into discrete energy levels separated by gaps. The largest known neutron shell gap in stable nuclei, at $N=126$, stabilizes doubly-magic $^{208}$Pb and is responsible for the characteristic abundance peak of heavy elements near gold and platinum produced by the rapid neutron-capture process (r-process). Whether this shell gap persists as protons are removed from lead is a question central to both nuclear structure and the modeling of heavy-element synthesis, yet it has remained unanswered due to the extraordinary difficulty of producing the relevant neutron-rich nuclei. Direct experimental knowledge in this region was essentially absent. Here we report the first precision mass measurements of $^{203,204}$Pt and $^{204,205,206}$Au, performed at GSI using a novel combination of Schottky and isochronous mass spectrometry in a heavy-ion storage ring. The $N=126$ isotones $^{204}$Pt and $^{205}$Au are more strongly bound than the extrapolated trend of the previously known mass surface by 403 and 464~keV, respectively, revealing an unexpectedly enhanced $N=126$ shell strength below doubly-magic $^{208}$Pb. Furthermore, the proton-neutron interaction strength exhibits a hitherto unobserved bifurcation at $N=126$ as protons are removed from $^{208}$Pb. Our results redefine the nuclear mass surface in the neutron-rich heavy-element region and provide direct experimental benchmarks for theoretical models whose extrapolations toward more exotic nuclei are essential for r-process nucleosynthesis calculations.
Read the full abstract

All authors David Freire-Fernández, Rui-Jiu Chen, Usama Ahmed, Helena M. Albers, Jelena Bardak, Carsten Brandau, Jeroen P. Bormans, R. Burcu Cakirli, Rikel Chakma, Maeve Cockshutt, Iris Dillmann, Dmytro Dmytriiev, Siddharth Doshi, Carlo Forconi, Oliver Forstner, Wenwen Ge, Jan Glorius, Magdalena Gòrska, Chris J. Griffin, Alexandre Gumberidze, Regina Hess, Pierre-Michel Hillenbrand, Nicolas J. Hubbard, Calum Jones, Beatriz Jurado, Kanika, Filip G. Kondev, Gregor Kosir, Wolfram Korten, Christophor Kozhuharov, Johan Emil Larsson, Guy Leckenby, Hongfu Li, Menglan Liu, Sergey Litvinov, Yuri A. Litvinov, Zhong Liu, Bernd Lorentz, Hannes Mayr, Esther B. Menz, Tetsuaki Moriguchi, Clemens M. Nickel, Zachary Nunns, Fatma Cagla Ozturk, Nikolaos Petridis, Zsolt Podolyak, Shahab Sanjari, Ragandeep Singh Sidhu, Markus Steck, Thomas Stöhlker, Jelena Vesic, Meng Wang, Qian Wang, Philip M. Walker, Helmut Weick, Michael Weinert, Kathrin Wimmer, Boguslaw Włoch, Xing Xu, Takayuki Yamaguchi, Xinliang Yan, Yue Yu, Cenxi Yuan, Min Zhang, Yuhu Zhang, Xu Zhou

General Relativity and Quantum Cosmology

Post-Newtonian N-Body Dynamics in Extended Theories of Gravity

Antonio Tedesco

We derive the complete first post-Newtonian (1PN) Lagrangian and corresponding equations of motion for the relativistic $N$-body system in Scalar-Tensor-Fourth-Order Gravity (STFOG), including the Non-Commutative Spectral Geometry (NCSG) sector as a special case. In the regime $\Phi \sim \Psi$ ($\gamma \sim 1$), the linearized fourth-order field equations are solved in the Standard Post-Newtonian gauge, and the variational Lagrangian is built directly from the point-particle action. The resulting dynamics is governed by three Yukawa functions $\zeta$, $\mathcal{W}$ and $\Xi$, which encode the scalar, gravitomagnetic and three-body sectors and depend on the effective masses $(m_R,m_Y,m_\phi)$ of the additional propagating modes. In this context, we show that the nonlinear metric component ${}^{(4)}\!g_{00}$ plays no role at 1PN level. The 1PN orbital motion of the above extended theories is thus obtained in closed form, and the Einstein–Infeld–Hoffmann equations are recovered in the corresponding general-relativistic limit. The formalism provides a common framework for relativistic celestial mechanics and applies to Solar System, binary pulsars such as PSR J0737-3039, Galactic-center stellar orbits and triple systems.
Read the full abstract

Earth and Planetary Astrophysics

Stellar Observation Scheduling Optimization for Distributed Space Interferometry Missions

Ethan Foss, Antonio Rizza and Simone D'Amico

Growing interest in space interferometry for detecting bio-signatures of exoplanets has led to the development of several low-cost mission concepts involving Earth-orbiting formation flying techniques to perform nulling interferometry of incoming light from exoplanetary systems. Pursuing these developments, this work proposes a multi-objective dynamic programming scheme to optimize the balance between fuel expenditure and scientific outcomes of low-cost formation flying space interferometry missions by leveraging several insights from mission design. This scheme accounts for nominal concept of operations constraints, fuel expenditure, and observability conditions to produce a globally optimal Pareto front policy for exoplanetary system observation, and represents one of the first applications of multi-objective optimization to distributed space telescope astronomy.
Read the full abstract

Chemical Physics

Transferable Implicit Solvent Machine Learning Potential for Drugs and Proteins Approaching Ab Initio Accuracy

Jan Eckwert and Julija Zavadlav

Machine learning interatomic potentials (MLPs) have revolutionized atomistic modeling, offering the potential to replace traditional methods like Density Functional Theory (DFT). However, inference time of MLPs is orders of magnitude slower than that of classical force fields, hindering real-world applications for biomolecular systems that require timescales of microseconds and beyond. Implicit solvent MLPs can address this issue, but are faced with data challenges associated with coarse-grained modeling. Consequently, previous approaches relied on empirical force field data, thereby inherently limiting the MLP's accuracy. Here, we introduce the Transferable Water Implicit Network (TWIN), an implicit water MLP parametrized entirely by an Equivariant Graph Neural Network and trained solely on ab initio and experimental labels. We demonstrate TWIN's transferability across drug-like molecules, peptides, and proteins, achieving excellent results on ab initio and experimental crystallographic and NMR benchmarks, consistently outperforming previous machine-learning-based implicit solvent or coarse-grained models. Furthermore, TWIN closely matches DFT-based explicit solvent MLPs while providing a two-order-of-magnitude faster timestep evaluation, paving the way for efficient ab initio-level modeling of biomolecular systems in aqueous environments.
Read the full abstract

Applied Physics · Cross-listed from eess.SY

Model-Free Detection and Accommodation of Sensor Faults for a PEM Electrolyzer

Meziane Ait Ziane, Michel Zasadzinski, Cédric Join et al. (+1 more)

We investigate the detection and accommodation of sensor faults for a proton exchange membrane electrolyzer coupled to a DC/DC converter powered by renewable energy sources. The proposed method for detecting and accommodating the sensor fault is model-free and is based on the concept of ultra-local model that is becoming classic in control engineering. The existing literature on active control tolerant to sensor fault dedicated to this question shows that no previous work has addressed this topic. Our approach mitigates the effect of sensor fault on closed-loop behavior and guarantees the stability and performance of the overall system. Numerical simulations under variations in renewable energy sources validate our approach.
Read the full abstract

All authors Meziane Ait Ziane, Michel Zasadzinski, Cédric Join, Michel Fliess

Optics

Vernier-assisted mode-selective PT symmetry in optoelectronic oscillators

Gazi M. Hasan, Abhijit Banerjee and Trevor J. Hall

Mode-selective PT-symmetry is the manifestation of Vernier-assisted cross-injection between oscillators with unequal delays. PT-symmetry has been proposed as a mechanism for achieving low-noise single-mode operation in optoelectronic oscillators, but existing formulations are typically based on matched delay loops and frequency-independent coupling, leading to symmetry transitions that are global in frequency and therefore not intrinsically mode selective. A more general formulation of PT-symmetric time-delay oscillators is developed in which the coupling operator is allowed to be dispersive. This permits frequency-selective PT-symmetry transitions and removes the requirement for matched delay loops. Two mathematically equivalent but physically distinct realisations are derived. The first corresponds to coupled gain-loss loops connected by a dispersive coupler, while the second corresponds to a pair of equal-gain oscillators coupled through symmetric cross-injection with unequal delays. Numerical simulations confirm the predicted behaviour and demonstrate strong sidemode suppression while preserving the low phase-noise characteristics of large-delay oscillators. The results establish a direct connection between PT-symmetry, cross-injection architectures, and Vernier oscillator design.
Read the full abstract

Strongly Correlated Electrons

Pinwheel-shaped bound triplet pairs in the magnetization plateaus of SrCu$_2$(BO$_3$)$_2$

Igor Vinograd, Philippe Corboz, Steffen Krämer et al. (+5 more)

The sequence of magnetization plateaus at 1/8, 2/15, 1/6, 1/4, 1/3, 2/5, and 1/2 of the saturation observed in SrCu$_2$(BO$_3$)$_2$ remained a puzzle until tensor-networks-based numerical simulations suggested that the low-magnetization plateaus are stabilized as Wigner crystals of spin-2 bound states, and not as one of the standard configurations (semiclassical up-down, or crystals of triplets). We report on $^{63,65}$Cu nuclear magnetic resonance spectra up to 41.9 T: Based on constraints deduced from the 1/3 plateau, we show that the spectra in the 1/8 and 2/15 plateaus indeed agree with the prediction for the spin-2 bound states, while being incompatible with a crystal of triplets. This adds the formation of Wigner crystals of bound states as an alternative fundamental paradigm in the theory of magnetization plateaus.
Read the full abstract

All authors Igor Vinograd, Philippe Corboz, Steffen Krämer, Yanan Li, Frédéric Mila, Hiroshi Kageyama, Masashi Takigawa, Mladen Horvatić