The Maryland model is a critical theoretical model in quantum chaos.This model describes the motion of a spin-1/2particle on a one-dimensional lattice under the periodical disturbance of the external delta-function-li...The Maryland model is a critical theoretical model in quantum chaos.This model describes the motion of a spin-1/2particle on a one-dimensional lattice under the periodical disturbance of the external delta-function-like magnetic field.In this work,we propose the linearly delayed quantum relativistic Maryland model(LDQRMM)as a novel generalization of the original Maryland model and systematically study its physical properties.We derive the resonance and antiresonance conditions for the angular momentum spread.The“characteristic sum”is introduced in this paper as a new measure to quantify the sensitivity between the angular momentum spread and the model parameters.In addition,different topological patterns emerge in the LDQRMM.It predicts some additions to the Anderson localization in the corresponding tight-binding systems.Our theoretical results could be verified experimentally by studying cold atoms in optical lattices disturbed by a linearly delayed magnetic field.展开更多
The non-Hermitian PT-symmetric system can live in either unbroken or broken PT-symmetric phase. The separation point of the unbroken and broken PT-symmetric phases is called the PT-phase-transition point.Conventionall...The non-Hermitian PT-symmetric system can live in either unbroken or broken PT-symmetric phase. The separation point of the unbroken and broken PT-symmetric phases is called the PT-phase-transition point.Conventionally, given an arbitrary non-Hermitian PT-symmetric Hamiltonian, one has to solve the corresponding Schrodinger equation explicitly in order to determine which phase it is actually in. Here, we propose to use artificial neural network(ANN) to determine the PT-phase-transition points for non-Hermitian PT-symmetric systems with short-range potentials. The numerical results given by ANN agree well with the literature, which shows the reliability of our new method.展开更多
Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been obse...Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been observed using α-decay spectroscopy [Z. Y. Zhang et al., Phys. Rev. Lett. 122, 192503(2019);L. Ma et al., Phys. Rev.Lett. 125, 032502(2020);Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502(2021)]. In spite of these achievements,some neutron-deficient key nuclei in this mass region are still unknown in experiments. Machine learning algorithms have been applied successfully in different branches of modern physics. It is interesting to explore their applicability in α-decay studies. In this work, we propose a new model to predict the α-decay energies and half-lives within the framework based on a machine learning algorithm called the Gaussian process. We first calculate the α-decay properties of the new actinide nucleus 214 U. The theoretical results show good agreement with the latest experimental data, which demonstrates the reliability of our model. We further use the model to predict the α-decay properties of some unknown neutron-deficient actinide isotopes and compare the results with traditional models. The results may be useful for future synthesis and identification of these unknown isotopes.展开更多
Superstrong static electric fields could deform Coulomb barriers between α clusters and daughter nuclei,and bring up the possibility of speeding up α decays. We adopt a simplified model for the spherical α emitter^...Superstrong static electric fields could deform Coulomb barriers between α clusters and daughter nuclei,and bring up the possibility of speeding up α decays. We adopt a simplified model for the spherical α emitter^(212)Po and study its responses to superstrong static electric fields. We find that superstrong electric fields with field strengths|E|～0.1 MV/fm could turn the angular distribution of α emissions from isotropic to strongly anisotropic, and speed upα decays by more than one order of magnitude. We also study the influences of superstrong electric fields along the Po isotope chains, and discuss the implications of our studies on α decays in superstrong monochromatic laser fields. The study here might be helpful for future theoretical studies of α decay in realistic superstrong laser fields.展开更多
The Woods-Saxon-Gaussian （WSG） potential is proposed as a new phenomenological potential to sys- tematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of tile alpha-cluster s...The Woods-Saxon-Gaussian （WSG） potential is proposed as a new phenomenological potential to sys- tematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of tile alpha-cluster structures in various alpha ＋ closed shell nuclei. It modifies the original Woods Saxon （WS） potential with a shifted Gaussian factor centered at the nuclear surface. The free parameters in the WSG potential are determined by reproducing the correct level scheme of ^212Po=^208Pb＋α. It is found that the resulting WSG potential matches the NI3Y double-folding potential at tile surface region and makes corrections to the inner part of the cluster-core l）otential. It was also determined that the WSG potential, with nearly identical parameters to that of ^212Po （except for a rescale（l radius）, could also be used to describe alpha-cluster structures in ^20Ne=^16O＋α and ^44Ti = ^40Ca＋α. In all lhrec cases, the calculated values of the level schemes, electromagnetic transitions, and alpha-decay half-lives agree with the experimental data. which indicates that the WSG potential could indeed capture many important features of the alpha-cluster structures in alpha ＋ closed shell nuclei. This study is a useful complement to the existing cluster-core potentials ill literature. The Gaussian form factor centered at the nuclear surface might also help to improve our understailding of the alpha-cluster formation, which occurs in the same general region.展开更多
We investigate low-lying bound states of the neutron-rich nucleus ^15B by assuming it is a three-body system made of an inert core 13 B and two valence neutrons. The three-body wave functions are obtained using the Fa...We investigate low-lying bound states of the neutron-rich nucleus ^15B by assuming it is a three-body system made of an inert core 13 B and two valence neutrons. The three-body wave functions are obtained using the Faddeev formalism. Special attention is paid to the excited state at 3.48（6） MeV observed in the 13 C（14 C,12 N）15 B reaction, whose properties are less clear theoretically. In our three-body model, besides the ground state 3/21, a second 3/22^-state is discovered at around 3.61 MeV, which might be identified with the excited state observed at3.48（6） MeV. We study this 3/22^-state in detail. It turns out to be a two-neutron halo state with a large matter radius rm≈4.770 fm. ＆nbsp展开更多
基金Project supported by the Science and Technology Development Fund(FDCT)of Macao,China(Grant Nos.0014/2022/A1 and 0042/2018/A2)the National Natural Science Foundation of China(Grant Nos.11761161001,12035011,and 11975167)
文摘The Maryland model is a critical theoretical model in quantum chaos.This model describes the motion of a spin-1/2particle on a one-dimensional lattice under the periodical disturbance of the external delta-function-like magnetic field.In this work,we propose the linearly delayed quantum relativistic Maryland model(LDQRMM)as a novel generalization of the original Maryland model and systematically study its physical properties.We derive the resonance and antiresonance conditions for the angular momentum spread.The“characteristic sum”is introduced in this paper as a new measure to quantify the sensitivity between the angular momentum spread and the model parameters.In addition,different topological patterns emerge in the LDQRMM.It predicts some additions to the Anderson localization in the corresponding tight-binding systems.Our theoretical results could be verified experimentally by studying cold atoms in optical lattices disturbed by a linearly delayed magnetic field.
基金Supported by the National Natural Science Foundation of China (Grant Nos.11535004,11975167,11761161001,11375086,11565010,11881240623 and 11961141003)the National Key R&D Program of China (Grant Nos.2018YFA0404403 and 2016YFE0129300)+1 种基金the Science and Technology Development Fund of Macao (Grant No.008/2017/AFJ)the Fundamental Research Funds for the Central Universities (Grant Nos.22120210138 and 22120200101)。
文摘The non-Hermitian PT-symmetric system can live in either unbroken or broken PT-symmetric phase. The separation point of the unbroken and broken PT-symmetric phases is called the PT-phase-transition point.Conventionally, given an arbitrary non-Hermitian PT-symmetric Hamiltonian, one has to solve the corresponding Schrodinger equation explicitly in order to determine which phase it is actually in. Here, we propose to use artificial neural network(ANN) to determine the PT-phase-transition points for non-Hermitian PT-symmetric systems with short-range potentials. The numerical results given by ANN agree well with the literature, which shows the reliability of our new method.
基金National Key R&D Program of China(2018YFA0404403,2016YFE0129300)National Natural Science Foundation of China(11535004,11761161001,11375086,11120101005,11175085,11235001,11565010,and11881240623)+1 种基金Science and Technology Development Fund of Macao(008/2017/AFJ)China Postdoctoral Science Foundation(2018M640470)~~
基金Supported by the National Natural Science Foundation of China(12035011,11975167,11761161001,11565010,11961141003,11905103,11947211)the National Key R&D Program of China(2018YFA04044032016YFE0129300)+2 种基金the Science and Technology Development Fund of Macao(008/2017/AFJ)the Fundamental Research Funds for the Central Universities(22120210138)the China Postdoctoral Science Foundation(2019M660095,2020T130478)。
文摘Neutron-deficient actinide nuclei provide a valuable window to probe heavy nuclear systems with large proton-neutron ratios. In recent years, several new neutron-deficient Uranium and Neptunium isotopes have been observed using α-decay spectroscopy [Z. Y. Zhang et al., Phys. Rev. Lett. 122, 192503(2019);L. Ma et al., Phys. Rev.Lett. 125, 032502(2020);Z. Y. Zhang et al., Phys. Rev. Lett. 126, 152502(2021)]. In spite of these achievements,some neutron-deficient key nuclei in this mass region are still unknown in experiments. Machine learning algorithms have been applied successfully in different branches of modern physics. It is interesting to explore their applicability in α-decay studies. In this work, we propose a new model to predict the α-decay energies and half-lives within the framework based on a machine learning algorithm called the Gaussian process. We first calculate the α-decay properties of the new actinide nucleus 214 U. The theoretical results show good agreement with the latest experimental data, which demonstrates the reliability of our model. We further use the model to predict the α-decay properties of some unknown neutron-deficient actinide isotopes and compare the results with traditional models. The results may be useful for future synthesis and identification of these unknown isotopes.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11535004,11761161001,11375086,11120101005,11175085 and 11235001the National Key R&D Program of China under Grant No.2018YFA0404403+1 种基金the National Major State Basic Research and Development of China,under Grant No.2016YFE0129300the Science and Technology Development Fund of Macao under Grant No.008/2017/AFJ
文摘Superstrong static electric fields could deform Coulomb barriers between α clusters and daughter nuclei,and bring up the possibility of speeding up α decays. We adopt a simplified model for the spherical α emitter^(212)Po and study its responses to superstrong static electric fields. We find that superstrong electric fields with field strengths|E|～0.1 MV/fm could turn the angular distribution of α emissions from isotropic to strongly anisotropic, and speed upα decays by more than one order of magnitude. We also study the influences of superstrong electric fields along the Po isotope chains, and discuss the implications of our studies on α decays in superstrong monochromatic laser fields. The study here might be helpful for future theoretical studies of α decay in realistic superstrong laser fields.
基金Supported by the National Natural Science Foundation of China(11535004,11761161001,11375086,11120101005,11175085,11235001)the National Key R&D Program of China(2018YFA0404403,2016YFE0129300)the Science and Technology Development Fund of Macao(008/2017/AFJ)
文摘The Woods-Saxon-Gaussian （WSG） potential is proposed as a new phenomenological potential to sys- tematically describe the level scheme, electromagnetic transitions, and alpha-decay half-lives of tile alpha-cluster structures in various alpha ＋ closed shell nuclei. It modifies the original Woods Saxon （WS） potential with a shifted Gaussian factor centered at the nuclear surface. The free parameters in the WSG potential are determined by reproducing the correct level scheme of ^212Po=^208Pb＋α. It is found that the resulting WSG potential matches the NI3Y double-folding potential at tile surface region and makes corrections to the inner part of the cluster-core l）otential. It was also determined that the WSG potential, with nearly identical parameters to that of ^212Po （except for a rescale（l radius）, could also be used to describe alpha-cluster structures in ^20Ne=^16O＋α and ^44Ti = ^40Ca＋α. In all lhrec cases, the calculated values of the level schemes, electromagnetic transitions, and alpha-decay half-lives agree with the experimental data. which indicates that the WSG potential could indeed capture many important features of the alpha-cluster structures in alpha ＋ closed shell nuclei. This study is a useful complement to the existing cluster-core potentials ill literature. The Gaussian form factor centered at the nuclear surface might also help to improve our understailding of the alpha-cluster formation, which occurs in the same general region.
基金Supported by National Natural Science Foundation of China(Grant No.11535004,11761161001,11375086,11120101005,11175085and 11235001)the National Major State Basic Research and Development of China,Grant No.2016YFE0129300the Science and Technology Development Fund of Macao under Grant No.068/2011/A
文摘We investigate low-lying bound states of the neutron-rich nucleus ^15B by assuming it is a three-body system made of an inert core 13 B and two valence neutrons. The three-body wave functions are obtained using the Faddeev formalism. Special attention is paid to the excited state at 3.48（6） MeV observed in the 13 C（14 C,12 N）15 B reaction, whose properties are less clear theoretically. In our three-body model, besides the ground state 3/21, a second 3/22^-state is discovered at around 3.61 MeV, which might be identified with the excited state observed at3.48（6） MeV. We study this 3/22^-state in detail. It turns out to be a two-neutron halo state with a large matter radius rm≈4.770 fm. ＆nbsp
