arXiv subjects

Yinu Zhang

Publications and source records attributed to Yinu Zhang.

13 recordsLinked to original sources

arXiv2026

Dynamical selection of fragment shell effects in spontaneous fission of $^{240}$Pu, $^{232}$Th, and $^{264}$Fm

Understanding how fragment shell effects influence spontaneous fission mass yields remains a central challenge in nuclear fission theory. This work investigates the role of shell effects in the spontaneous fission of $^{240}$Pu, $^{232}$Th, and $^{264}$Fm by combining microscopic collective dynamics with fragment-level shell analysis. A two-step framework is employed: first, the tunneling from the inner to outer turning points is described using the Wentzel-Kramers-Brillouin approximation along the least-action path on a potential energy surface calculated from constrained Hartree-Fock-Bogoliubov theory. Second, the dissipative descent from the outer turning points to scission is simulated via Langevin dynamics in a large collective space of quadrupole and octupole deformations. Fragment shell effects are quantified using smoothed level density indicators for representative even-even fragment pairs extracted from Langevin scission configurations. The analysis reveals that enhanced yields arise from a coherent overlap among dynamically populated scission configurations, low-energy regions on the fragment potential energy surfaces, and low neutron and/or proton level densities near the Fermi surface. Proton shell effects provide persistent microscopic selectivity in both light and heavy fragments across asymmetric channels, while neutron shell effects offer additional stabilization. Deformed shell effects at finite quadrupole and octupole deformations play a crucial role in stabilizing asymmetric fission channels. This work demonstrates that fission fragment yields reflect shell-favored configurations that are made accessible by the potential energy surface topology and populated by stochastic dynamics, with the largest yields corresponding to configurations where shell gaps provide maximal binding.

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arXiv2026

New perspective on cold fusion reactions: A microscopic description

A microscopic framework that combines the Hartree-Fock-Bogoliubov (HFB) approach with the fusion by diffusion (FBD) model is proposed to investigate the synthesis mechanism of superheavy nuclei (SHN). For the reaction $^{48}\text{Ca}+^{208}\text{Pb}$, the calculated evaporation-residue cross section (ERCS) reproduces the experimental data reasonably well. The method enables self-consistent extraction of the fusion injection point and inner barrier from HFB potential-energy surfaces (PES), thereby incorporating nuclear structure effects while eliminating phenomenological tuning at the fusion stage. For cold-fusion reactions, the PES features a hyperasymmetric valley driven by shell effects. This $^{208}$Pb anchored valley connects the entrance channel to compound nucleus formation and provides an exit channel for cluster decay. We further investigate the cold-fusion reactions $^{54}\text{Cr}+^{208}\text{Pb}$ and $^{58}\text{Fe}+^{208}\text{Pb}$, obtaining a near-exponential decrease of $P_{\text{CN}}$ with compound-nucleus charge $Z$, consistent with established systematics. This approach demonstrates a self-consistent framework that can reduce uncertainties in the fusion stage of SHN production.

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arXiv2026

From $\alpha$ decay to cluster decay: an extreme case of transfer learning

When training data are limited, data-driven models are especially vulnerable to optimization-related fluctuations from random initialization and to sampling-induced bias from insufficient training data. We address both challenges with transfer learning (TL): deep neural networks (DNNs) are first pretrained on $\alpha$ decay half-lives and then fine-tuned on a small cluster decay dataset. The pretraining stage provides a physically informed initialization that stabilizes optimization, while transferred global decay systematics regularize the fit and reduce sensitivity to training set composition. Despite extreme data sparsity, the resulting models accurately predict cluster decay half-lives for parent nuclei from $^{221}$Fr to $^{242}$Cm. We further quantify how initialization and sample selection affect predictive accuracy and robustness, demonstrating that TL enables stable and reliable learning in the small-sample regime.

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arXiv2025

Axially Deformed Proton-Neutron Relativistic Quasiparticle Finite Amplitude Method for Charge-Exchange Transitions

The quasiparticle finite amplitude method (QFAM) is extended to describe charge-exchange transitions based on the relativistic Hartree-Bogoliubov model, adopting the point-coupling energy density functional DD-PC1 and a finite-range separable pairing force. After validation through comparison with relativistic quasiparticle random-phase approximation (QRPA) results in spherical nuclei, the deformation effects on isobaric analog resonances (IAR) and Gamow-Teller (GT) transitions in Zn isotopes are investigated. The GT strength exhibits significant fragmentation in deformed nuclei. The analysis of summed strengths and centroid energies in GT resonance region between the $K=0$ and $K=1$ components reveals that prolate configurations exhibit stronger $K=1$ strength and lower $K=1$ centroid energy, while oblate shapes show an opposite behavior, with stronger $K=0$ strength and lower $K=0$ energy. The effects of isoscalar pairing on GT strength distributions for different shape configurations are also examined.

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arXiv2025

Concentrated valence nucleons transfer in heavy-ion collisions: implications for questing the stable superheavy elements

The multinucleon transfer process is regarded as a promising pathway for producing the stable superheavy elements. However, the underlying mechanism, especially the possible transfer channels for sailing to the ``island of stability'' are poorly known. In this work, the time-dependent Hartree-Fock theory is used to investigate the collision dynamics of $^{136}$Xe, $^{198}$Pt, $^{238}$U + $^{238}$U reactions. A novel reaction channel of the concentrated valence nucleons (CVN) transferring is found in the collisions heading on the tips of $^{238}$U. These nucleons are transferred with relatively short relaxation time and break the symmetry of nucleon exchange in the early reaction stage. In consequence, the mass equilibrium with relaxation time is deviated from the systematic behavior based on the macroscopic-microscopic potential energy surface. The CVN transfer channel shows promising prospect for producing neutron-rich superheavy nuclei. In this case, we also investigated the angular distributions of products from the CVN transfer channel in the reaction $^{238}$U + $^{238}$U with Tip-Side configuration, and the optimal detection angles are predicted.

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arXiv2024

Bayesian uncertainty quantification for synthesizing superheavy elements

To improve the theoretical prediction power for synthesizing superheavy elements beyond Og, a Bayesian uncertainty quantification method is employed to evaluate the uncertainty of the calculated evaporation residue cross sections (ERCS) for the first time. The key parameters of the dinuclear system (DNS) model, such as the diffusion parameter $\textit{a}$, the damping factor $E_\mathrm{d}$, and the level-density parameter ratio $a_\mathrm{f}/a_\mathrm{n}$ are systematically constrained by the Bayesian analysis of recent ERCS data. One intriguing behavior is shown that the optimal incident energies (OIE) corresponding to the largest ERCS weakly depend on the fission process. We also find that these parameters are strongly correlated and the uncertainty propagation considering the parameters independently is not reasonable. The 2$σ$ confidence level of posterior distributions for $a = 0.586_{-0.002}^{+0.002}$ fm, $E_\mathrm{d} = 25.65_{-3.41}^{+3.43}$ MeV, and $a_\mathrm{f}/a_\mathrm{n} = 1.081_{-0.021}^{+0.021}$ are obtained. Furthermore, the confidence levels of the ERCS and OIE for synthesizing Z = 119 via the reactions($^{54}\mathrm{Cr}+^{243}\mathrm{Am}$), (${}^{50}\mathrm{Ti}+{}^{249}\mathrm{Bk}$), and (${}^{51}\mathrm{V}+{}^{248}\mathrm{Cm}$) are predicted. This work sets the stage for future analyses to explore the OIE and reaction systems for the synthesis of superheavy elements.

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arXiv2023

Role of the isospin diffusion on cluster transfer in $^{12,14}$C + $^{209}$Bi reactions

Heavy-ion collisions at near-barrier energies provide a crucial pathway for investigating nucleon correlations and clustering structures. Recent experimental results showed that the valence neutrons in light projectiles obviously enhance the $α$ transfer. This finding is extremely puzzled and fascinating, because it violates the ground-state $Q$ value systematics unexpectedly. In this work, the time-dependent Hartree-Fock approach is utilized to investigate the cluster transfer. By comparing the reactions $^{12,14}$C + $^{209}$Bi, we discover that above puzzling behavior is because of the strong correlation between isospin diffusion and clustering. Our calculations clearly show that the equilibrium of neutron-to-proton ratio strongly inhibits the clustering. This work opens a prospect for investigating the clustering in open quantum system.

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arXiv2023

Many-body theory for quasiparticle states in superfluid fermionic systems

We present a formalism for the fermionic quasiparticle propagator in a superfluid fermionic system. Starting from a general many-body hamiltonian confined by the two-body instantaneous interaction, the equation of motion for the fermionic propagator is obtained in the Dyson form. Before making any approximation, the interaction kernel is found to be decomposed into the static and dynamical (time-dependent) contributions, while the latter translates to the energy-dependent and the former maps to the energy-independent terms in the energy domain. The three-fermion correlation function being the heart of the dynamical part of the kernel is factorized into the two-fermion and one-fermion ones. With the relaxed particle number constraint, the normal propagator is coupled to the abnormal one via both the static and dynamical kernels, that is formalized by introducing the generalized quasiparticle propagator of the Gor'kov type. The dynamical kernel in the factorized form is associated with the quasiparticle-vibration coupling (QVC) with the vibrations unifying both the normal and pairing phonons. The QVC vertices are related to the variations of the Hamiltonian of the Bogoliubov quasiparticles, which can be obtained by the finite amplitude method.

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arXiv2022

Microscopic response theory for strongly-coupled superfluid fermionic systems

A consistent microscopic theory for the response of strongly-coupled superfluid fermionic systems is formulated. After defining the response as a two-point two-fermion correlation function in the basis of the Bogolyubov's quasiparticles, the equation of motion (EOM) method is applied using the most general fermionic Hamiltonian with a bare two-body interaction, also transformed to the quasiparticle space. As a superfluid extension of the case of the normal phase, the resulting EOM is of the Bethe-Salpeter-Dyson form with the static and dynamical interaction kernels, where the former determines the short-range correlations and the latter is responsible for the long-range ones. Both kernels as well as the entire EOM have the double dimension as compared to that of the normal phase. Non-perturbative approximations via the cluster decomposition of the dynamical kernel are discussed, with the major focus on a continuous derivation of the quasiparticle-phonon coupling variant of the latter kernel, where the phonons (vibrations) are composite correlated two-quasiparticle states unifying both the normal and pairing modes. The developed theory is adopted for nuclear structure applications, such as the nuclear response in various channels. In particular, the finite-amplitude method generalized beyond the quasiparticle random phase approximation, taking into account the quasiparticle-vibration coupling, is formulated for prospective calculations in non-spherical nuclei.

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arXiv2022

Simulating excited states of the Lipkin model on a quantum computer

We simulate the excited states of the Lipkin model using the recently proposed Quantum Equation of Motion (qEOM) method. The qEOM generalizes the EOM on classical computers and gives access to collective excitations based on quasi-boson operators $\hat{O}^\dagger_n(α)$ of increasing configuration complexity $α$. We show, in particular, that the accuracy strongly depends on the fermion to qubit encoding. Standard encoding leads to large errors, but the use of symmetries and the Gray code reduces the quantum resources and improves significantly the results on current noisy quantum devices. With this encoding scheme, we use IBM quantum machines to compute the energy spectrum for a system of $N=2, 3$ and $4$ particles and compare the accuracy against the exact solution. We found that the results of the approach with $α= 2$, an analog of the second random phase approximation (SRPA), are, in principle, more accurate than with $α= 1$, which corresponds to the random phase approximation (RPA), but the SRPA is more amenable to noise for large coupling strengths. Thus, the proposed scheme shows potential for achieving higher spectroscopic accuracy by implementations with higher configuration complexity, if a proper error mitigation method is applied.

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arXiv2022

Many-body approach to superfluid nuclei in axial geometry

Starting from a general many-body fermionic Hamiltonian, we derive the equations of motion (EOM) for nucleonic propagators in a superfluid system. The resulting EOM is of the Dyson type formulated in the basis of Bogoliubov's quasiparticles. As the leading contributions to the dynamical kernel of this EOM in strongly-coupled regimes contain phonon degrees of freedom in various channels, an efficient method of calculating phonon's characteristics is required to successfully model these kernels. The traditional quasiparticle random phase approximation (QRPA) solvers are typically used for this purpose in nuclear structure calculations, however, they become very prohibitive in non-spherical geometries. In this work, by linking the notion of the quasiparticle-phonon vertex to the variation of the Bogoliubov's Hamiltonian, we show that the recently developed finite-amplitude method (FAM) can be efficiently employed to compute the vertices within the FAM-QRPA. To illustrate the validity of the method, calculations based on the relativistic density-dependent point-coupling Lagrangian are performed for the single-nucleon states in heavy and medium-mass nuclei with axial deformations. The cases of $^{38}$Si and $^{250}$Cf are presented and discussed.

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arXiv2020

Temperature evolution of the nuclear shell structure and the dynamical nucleon effective mass

We study the fermionic Matsubara Green functions in medium-mass nuclei at finite temperature. The single-fermion Dyson equation with the dynamical kernel of the particle-vibration-coupling (PVC) origin is formulated and solved in the basis of Dirac spinors, which minimize the grand canonical potential with the meson-nucleon covariant energy density functional. The PVC correlations beyond mean field are taken into account in the leading approximation for the energy-dependent self-energy, and the full solution of the finite-temperature Dyson equation is obtained for the fermionic propagators. Within this approach, we investigate the fragmentation of the single-particle states and its evolution with temperature for the nuclear systems $^{56,68}$Ni and $^{56}$Fe relevant for the core-collapse supernova. The energy-dependent, or dynamical, nucleon effective mass is extracted from the PVC self-energy at various temperatures.

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arXiv2015

Study of weakly-bound odd-A nuclei with quasiparticle blocking

The coordinate-space Hartree-Fock-Bogoliubov (HFB) approach with quasiparticle blocking has been applied to study the odd-A weakly bound nuclei $^{17,19}$B and $^{37}$Mg, in which halo structures have been reported in experiments. The Skyrme nuclear forces SLy4 and UNEDF1 have been adopted in our calculations. The results with and without blocking have been compared to demonstrate the emergence of deformed halo structures due to blocking effects. In our calculations, $^{19}$B and $^{37}$Mg have remarkable features of deformed halos.

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