arXiv subjects

Pengwei Zhao

Publications and source records attributed to Pengwei Zhao.

At least 19 recordsLinked to original sources

arXiv2026

Emergence of the halo in $^{11}$Li from full nuclear many-body dynamics

The two-neutron halo nucleus $^{11}$Li is a paradigmatic quantum many-body system whose large spatial extent and weak binding have long challenged a microscopic description from first principles. Using a neural-network variational Monte Carlo approach, we present an \textit{ab initio} demonstration that the halo structure of $^{11}$Li emerges directly from the underlying nuclear interactions and full many-body dynamics. The calculation employs an essential nuclear Hamiltonian constrained solely by few-body observables and reproduces the binding and separation energies of Li isotopes, as well as the isotopic trend of their matter radii. We identify a correlation between the halo size in $^{11}$Li and the splitting of $P$-wave neutron-alpha scattering phase shifts, establishing the crucial role of neutron-alpha spin-orbit interactions in halo formation. Dineutron correlations are found to arise naturally from the many-body wave function without assuming a preformed core-plus-valence-neutron structure. These results provide a microscopic understanding of halo formation in $^{11}$Li and establish a link between few-body scattering observables and emergent many-body structure.

nucl-th↗

arXiv2026

Efficient emulation of nuclear ground states with neural-network variational Monte Carlo and eigenvector continuation

An efficient emulator for \emph{ab initio} calculations of nuclear ground-state properties is developed by integrating the neural-network variational Monte Carlo framework, FeynmanNet, with the eigenvector continuation. It enables the calculation of observables for different Hamiltonians with minimal computational cost, while delivering ground-state energies with errors below $0.5\%$ compared to the full FeynmanNet results. With this emulator, the ground-state energies and charge radii of ${}^{16}\mathrm{O}$, ${}^{15}\mathrm{O}$, ${}^{14}\mathrm{O}$, ${}^{15}\mathrm{N}$, and ${}^{14}\mathrm{C}$ are computed using a nuclear Hamiltonian derived from the leading-order pionless effective field theory, with a large number of different values of low-energy constants (LECs). Then, we perform a global sensitivity analysis of the ground-state energies, charge radii, separation energies of selected nuclei for the three LECs in the Hamiltonian, to identify how each LEC contributes to the variances of these observables. It shows that the two-body LEC in the $^3S_1$ channel is the most influential LEC governing these nuclear bulk properties. Finally, the correlations among the ground-state energies of $^4$He, $^{12}$C, and $^{16}$O are investigated by varying the LECs in the Hamiltonian. The analysis reveals that the experimental ground-state energies of $^{12}$C and $^{16}$O cannot be reproduced simultaneously by varying the LECs in the leading-order pionless Hamiltonian. This suggests that additional ingredients in the leading-order Hamiltonian are required to improve its description of light nuclei. The present work establishes an efficient framework for global sensitivity analysis and uncertainty quantification in the quantum Monte Carlo calculations for light and medium-mass nuclei.

nucl-th↗

arXiv2026

Effects of Geomagnetic Cutoff Rigidity Variations during Forbush Decreases

Forbush decreases (FDs) are short-term reductions in galactic cosmic ray flux caused by interplanetary disturbances. During some interplanetary coronal mass ejection (ICME) events, neutron monitor (NM) data also contain variations produced by geomagnetic storms. Earlier studies emphasized apparent effects near 10~GV, but storm-time changes in geomagnetic cutoff rigidity can either increase or decrease the ground-level count rate. Using a recently published hourly proton flux reconstructed from NM data for May 2011 through October 2019, the interval covered by the published AMS daily proton fluxes, we show that these localized anomalies can extend to lower rigidities and reach 1~GV in some events. Such effects can bias the rigidity dependence inferred from NM-based hourly proton spectra during disturbed intervals. Because AMS measures proton rigidity directly in space, its daily proton spectrum is not affected by cutoff variations at ground stations and provides a stable reference. We therefore use AMS to constrain corrections for selected events. The correction removes localized anomalies while preserving the broader FD evolution, and for a representative ICME event it brings the corrected daily averages closer to the AMS measurements. Our results show that short-timescale cosmic ray variability during FDs reflects both heliospheric modulation and storm-time changes in geomagnetic shielding.

astro-ph.SR↗

arXiv2026

PRBench: End-to-end Paper Reproduction in Physics Research

AI agents powered by large language models exhibit strong reasoning and problem-solving capabilities, enabling them to assist scientific research tasks such as formula derivation and code generation. However, whether these agents can reliably perform end-to-end reproduction from real scientific papers remains an open question. We introduce PRBench, a benchmark of 30 expert-curated tasks spanning 11 subfields of physics. Each task requires an agent to comprehend the methodology of a published paper, implement the corresponding algorithms from scratch, and produce quantitative results matching the original publication. Agents are provided only with the task instruction and paper content, and operate in a sandboxed execution environment. All tasks are contributed by domain experts from over 20 research groups at the School of Physics, Peking University, each grounded in a real published paper and validated through end-to-end reproduction with verified ground-truth results and detailed scoring rubrics. Using an agentified assessment pipeline, we evaluate a set of coding agents on PRBench and analyze their capabilities across key dimensions of scientific reasoning and execution. The best-performing agent, OpenAI Codex powered by GPT-5.3-Codex, achieves a mean overall score of 34%. All agents exhibit a zero end-to-end callback success rate, with particularly poor performance in data accuracy and code correctness. We further identify systematic failure modes, including errors in formula implementation, inability to debug numerical simulations, and fabrication of output data. Overall, PRBench provides a rigorous benchmark for evaluating progress toward autonomous scientific research.

cs.CL↗

arXiv2026

Temporal Berry Phase and the Emergence of Bose-Glass-Analog Phase in a Clean U(1) Superfluid

The (2+1)-dimensional U(1) sigma model with temporal Berry phase term captures zero-temperature phase-fluctuation-driven superfluid (SF) transitions in two spatial dimensions. From renormalization group (RG) analysis of its dual representation -- vortex loop gas model --, we clarify that the Berry phase leads to space-time anisotropic interference in vortex-loop proliferation, resulting in a quasi-disordered phase with short-ranged spatial yet persistent temporal phase coherence. The phase shares physical properties of the Bose glass phase known from disordered boson systems, suggesting a unified topological origin for the emergence of the glassy phase in phase-fluctuation-driven superfluid transitions.

cond-mat.supr-con↗

arXiv2026

Magnetopological mechanics in Maxwell lattice frustrated Mott insulators

Topological boundary modes, a hallmark of quantum topological phases, remarkably occur in classical mechanical systems through an interesting correspondence with the quantum case. Here, we explore the Maxwell lattice frustrated Mott insulators and argue that the combination of the intrinsic spin-lattice coupling and the spin exchanges could induce the topological mechanics with topological boundary floppy modes in the phonon spectra. This mechanism and phenomena are dubbed magnetic topological mechanics, or, magnetopological mechanics in short. Focusing on a two-dimensional kagom\'e lattice spin model, we illustrate how strong spin-lattice coupling drives a spontaneous lattice distortion, resulting in the topological Maxwell lattice with the topological polarization and non-trivial phonon spectra. Moreover, the magnetic field, that directly changes the spin state, indirectly influences the lattice structure via the spin-lattice coupling, thereby providing a method to control the Maxwell lattice and the boundary modes. We expect this work to inspire interests in the Maxwell lattice Mott insulating materials and the coupling between lattices and electronic orders.

cond-mat.str-el↗

arXiv2026

Pairing correlations, orientations and quantum fluctuations in one- and two-nucleon transfer reactions at sub-barrier energies

This work investigates one- and two-neutron transfer in the $^{96}\text{Zr} + {}^{40}\text{Ca}$ reaction at sub-barrier energies using a microscopic framework based on time-dependent covariant density functional theory (TD-CDFT). Pairing correlations are incorporated via the time-dependent BCS approximation, which is shown to significantly enhance pair transfer, as evidenced by an increased two-neutron transfer probability. The oblate deformation of $^{96}$Zr causes the transfer probabilities to vary by orders of magnitude with orientation; a direct comparison with experiment is enabled by averaging results over thirteen systematically chosen orientations. While the orientation-averaged one-neutron transfer probabilities agree well with data, the two-neutron channel is suppressed below the Coulomb barrier. This suppression is attributed to missing quantum fluctuations in the semiclassical TD-CDFT approach. To test this, we employ the generalized time-dependent generator coordinate method (TDGCM), which confirms that quantum fluctuations are essential for an accurate description of sub-barrier two-neutron transfer dynamics.

nucl-th↗

arXiv2025

Non-local orbital-free density functional theory incorporating nuclear shell effects

Incorporating nuclear shell effects within the framework of orbital-free density functional theory (DFT) has remained a longstanding challenge in nuclear physics. While the Hohenberg-Kohn theorem formally guarantees the existence of an orbital-free density functional that is capable of describing all many-body effects, including shell effects, practical attempts since the 1970s have consistently failed to capture such effects. This persistent difficulty has even led to the misconception that the orbital-free DFT is inherently unable to describe nuclear shell effects. Here we develop a {\it non-local} orbital-free DFT approach for atomic nuclei and demonstrate that nuclear shell effects can be successfully incorporated into the orbital-free DFT through the construction of a non-local kinetic energy density functional. In particular, we show that the non-local orbital-free functional yields a nucleon localization function that, as an established indicator of shell effects, exhibits consistent behavior with the exact Kohn-Sham solution.

nucl-th↗

arXiv2025

Simulational and theoretical studies of the Anderson transition in the chiral symmetry classes with weak topology

Combining lattice model simulations with a field theory study of effective theories, we investigate the nature of the Anderson transition in chiral symmetry classes with one-dimensional (1D) weak topology. In the simulation study, we extend previous transfer matrix analyses to the chiral symplectic class, and study numerical Lyapunov exponents via a finite-size scaling (FSS) analysis that assumes spatially isotropic scaling. The analysis shows that, as in the other two chiral symmetry classes, the weak topology induces an intermediate quasi-localized (QL) phase between metal and Anderson insulator phases. In this QL phase, the localization length of wave functions diverges exclusively along the direction of the 1D weak topology. In the field theory study, we revisit and extend our previous two-dimensional (2D) renormalization group (RG) analysis to all three chiral classes, now newly incorporating a one-loop renormalization of the weak topological term in the analysis. The revised analysis reveals that a quasi-localized strong-coupling fixed point previously reported in the chiral unitary class is unstable under this new inclusion; instead, the strong-coupling phase is entirely governed by a stable fixed point with conventional localized character. Nevertheless, in the chiral unitary and chiral symplectic classes, the RG analysis still yields the hallmark of the 1D weak topology through the spatially anisotropic scaling of the Anderson transition criticality. These theoretical findings suggest that the quasi-localized phase observed numerically in 2D models may be an artifact of the spatially isotropic scaling assumption in the FSS analysis. A conclusive numerical identification of this phase therefore requires a finite-size scaling approach that accommodates generic (anisotropic) spatial scaling.

cond-mat.dis-nn↗

arXiv2025

Zemach radii and nuclear structure effects in hyperfine splitting of Lithium

Nuclear structure effects are essential for describing hyperfine splittings from high-precision atomic spectroscopy measurements. These effects are often parametrized by the effective or elastic Zemach radii, with their difference poorly understood. We solve the longstanding discrepancy between the effective and elastic Zemach radii in ${}^6$Li and ${}^7$Li by performing \emph{ab initio} nuclear structure calculations that take into account nuclear polarizability effects. Our results demonstrate that nuclear polarizability effects, negligible in ${}^7$Li, dominate in ${}^6$Li and explain the observed significant deviation between the effective and elastic Zemach radii. Furthermore, we show that the ratios between the nuclear polarizability contributions in different nuclei are universal in the limit of closure and SU(4) symmetry of nuclear forces. In particular, the nuclear polarizability contribution in an odd-odd nucleus is enhanced by a factor of $\mu_p/(\mu_p+\mu_n)\simeq 3$, with $\mu_{n,p}$ denoting the nucleon magnetic moments, compared to its odd-$A$ isotopes. The same mechanism also explains the Zemach radius deviations observed in ${}^2$H and ${}^3$He. These findings establish nuclear polarizability as the dominant source of isotope-dependent nuclear corrections to hyperfine splitting in light atoms.

nucl-th↗

arXiv2025

Theory of the Anderson transition in three-dimensional chiral symmetry classes: Connection to type-II superconductors

Phase transitions governed by topological defects constitute a cornerstone of modern physics. Two-dimensional (2D) Anderson transitions in chiral symmetry classes are driven by the proliferation of vortex-antivortex pairs -- a mechanism analogous to the Berezinskii-Kosterlitz-Thouless (BKT) transition in the 2D XY model. In this work, we extend this paradigm to three-dimensional (3D) chiral symmetry classes, where vortex loops emerge as the key topological defects governing the Anderson transition. By deriving the dual representation of the 3D nonlinear sigma model for the chiral unitary class, we develop a mean-field theory of its Anderson transition and elucidate the role of 1D weak band topology in the Anderson transition. Strikingly, our dual representation of the 3D NLSM in the chiral symmetry class uncovers its connection to the magnetostatics of 3D type-II superconductors. The metal-to-quasilocalized and quasilocalized-to-insulating transitions in 3D chiral symmetry class share a unified theoretical framework with the normal-to-mixed and mixed-to-superconducting transitions in 3D type-II superconductors under an external magnetic field, respectively.

cond-mat.dis-nn↗

arXiv2025

Classical symmetry enriched topological orders and distinct monopole charges for dipole-octupole spin ices

Distinct symmetry enriched topological orders often do not have classical distinctions. Motivated by the recent progress on the pyrochlore spin ice materials based on the dipole-octupole doublets, we argue that the dipolar spin liquid and the octupolar spin liquid can be distinguished through the magnetic charges of the magnetic monopoles in the classical spin ice regime. It is observed and predicted that the long-range dipole-dipole interaction renders the magnetic monopole of the dipolar spin ice a finite magnetic charge via the dumbbell picture even in the classical regime. For the octupolar spin ice, however, a zero magnetic charge is expected from this mechanism in the classical regime. We expect this smoking-gun observation to resolve the debate on the nature of Ce$_2$Sn$_2$O$_7$, and more broadly, this work may inspire further experiments and thoughts on the Ce-pyrochlore spin liquids, Nd-pyrochlore antiferromagnets, Er-based spinels, and the distinct properties of the emergent quasiparticles in various symmetry enriched topological phases.

cond-mat.str-el↗

arXiv2025

Topological effect on order-disorder transitions in U(1) sigma models

U(1) non-linear sigma model (NLSM) with a one-dimensional (1D) Berry phase is studied by a renormalization group theory. Order-disorder transition in U(1) NLSMs in $D \!\ (\ge 2)$-dimensional space ($d+1$-dimensional spacetime; $d\ge 1$) is instigated by the proliferation of vortex excitations, where the 1D Berry phase term confers finite phase factors upon those vortex excitations that have finite projection in a subspace complementary to a topological direction with the 1D Berry phase. A destructive interference effect caused by the phase factors may help to develop an intermediate quasi-disorder phase between ordered and disorder phases, which has a divergent order-parameter correlation length along the topological direction, and a finite correlation length along the other directions. In order to explore such a possibility in $D=3$, we develop a perturbative renormalization group theory of a 3D model of vortex loops, in which loop segments interact via a $1/r$ Coulomb interaction. We derive renormalization group (RG) equations among vortex-loop fugacity, Berry phase term, and the Coulomb potential. Approximate analyses of the RG equations show that near an order-disorder transition point, vortex loops are anomalously elongated along the topological direction. Utilizing a duality mapping to a lattice model of a type-II superconductor under a magnetic field, we also argue that a global phase diagram of the 3D U(1) sigma model with 1D Berry phase must have the quasi-disorder phase between ordered and disorder phases.

cond-mat.str-el↗

arXiv2025

Chiral symmetry and peripheral neutron-$\alpha$ scattering

We propose and demonstrate that peripheral neutron-$\alpha$ scattering at low energies can serve as a sensitive and clean probe of the long-range three-nucleon forces. To this aim, we perform {\it ab initio} quantum Monte Carlo calculations using two- and three-nucleon interactions derived in chiral effective field theory up to third expansion order. We show that the longest-range three-nucleon force stemming from the two-pion exchange plays a crucial role in the proper description of the neutron-$\alpha$ $D$-wave phase shifts. Our Letter reveals the predictive power of chiral symmetry in the few-body sector and opens a new direction for probing and constraining three-nucleon forces.

nucl-th↗

arXiv2024

Z$_2$ topological orders in kagom\'e dipolar systems: Feedback from Rydberg quantum simulator

The mutual feedback between quantum condensed matter and cold atom physics has been quite fruitful throughout history and continues to inspire ongoing research. Motivated by the recent activities on the quantum simulation of topological orders among the ultracold Rydberg atom arrays, we consider the possibility of searching for topological orders among the dipolar quantum magnets and polar molecules with a kagom\'{e} lattice geometry. Together with other quantum interactions such as the transverse field, the dipolar interaction endows the kagom\'e system with a similar structure as the Balents-Fisher-Girvin model and thus fosters the emergence of the $\mathbb{Z}_2$ topological orders. We construct a $\mathbb{Z}_2$ lattice gauge theory to access the topological ordered phase and describe the spinon and vison excitations for the $\mathbb{Z}_2$ topological orders. We explain the spectroscopic consequences for various quantum phases as well as the experimental detection. We further discuss the rare-earth kagom\'{e} magnets, ultracold polar molecules, and cluster Mott insulators for the physical realization.

cond-mat.str-el↗

arXiv2024

Multipolar ferroelectricity in the Mott regime

Ferroelectricity has been one major focus in modern fundamental research and technological application. We consider the physical origin of improper ferroelectricity in Mott insulating materials. Beyond the well-known Katsura-Nagaosa-Balatsky's inverse Dzyaloshinskii-Moriya mechanism for the noncollinearly ordered magnets, we point out the induction of the electric polarizations in the multipolar ordered Mott insulators. Using the multiflavor representation for the multipolar magnetic moments, we can show the crossover or transition from the pure inverse Dzyaloshinskii-Moriya mechanism to the pure multipolar origin for the ferroelectricity, and also incorporate the intermediate regime with the mixture of both origins. We expect our results to inspire a reexamination of ferroelectricity in the multipolar-ordered magnets.

cond-mat.str-el↗

arXiv2024

Measurements of Cosmic Proton Flux through Neutron Monitors Using Deep Networks and Imputation Techniques in the AMS-02 Era

Accurate measurements of cosmic proton flux are essential for studying the modulation processes of cosmic rays during the solar activity cycle. A proton flux measurement method, based on ground-based neutron monitor (NM) data and deep learning techniques, is presented. After the necessary pre-processing of ground-based NM data using a convolutional neural network (CNN) model, we model the relationship between NM observations and proton flux measured by the Alpha Magnetic Spectrometer (AMS). The daily cosmic proton flux, ranging from 1 GV to 100 GV, is obtained for the period from 2011 to 2024, showing strong agreement with the observed values. In addition, daily proton flux is computed for periods when AMS measurements were unavailable due to operational reasons. For the first time, hourly proton flux as a function of rigidity are calculated for the study of the short-time solar activities.

astro-ph.SR↗

arXiv2024

Exact-exchange relativistic density functional theory in three-dimensional coordinate space

The exact-exchange relativistic density functional theory (Ex-RDFT) of atomic nuclei has been solved in three-dimensional lattice space for the first time. The exchange energy is treated within the framework of the orbital-dependent relativistic Kohn-Sham density functional theory, wherein the local Lorentz scalar and vector potentials are derived using the relativistic optimized effective potential method. The solutions of binding energies, charge radii, and density distributions are benchmarked against the traditional relativistic Hartree-Fock approach for spherical and axially deformed nuclei. Furthermore, the triaxial neutron-rich $^{104-120}\text{Ru}$ isotopes are investigated with the exchange correlations, which is beyond the current capacity of the traditional relativistic Hartree-Fock approach. The results notably indicate the $\gamma$-softness of these neutron-rich nuclei, which is consistent with experimental observations. This novel approach establishes a foundation for the study of nuclei without imposing any symmetry restrictions employing relativistic density functional with exchange correlations.

nucl-th↗