检索结果-内蒙古大学图书馆

Merging ab initio theory and few-body approach for (d, p) reactions

JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS 2020年第6期47卷

作者： Rotureau, J. Potel, G. Li, W. Nunes, F. M. Michigan State Univ NSCL FRIB Lab E Lansing MI 48824 USA

A framework for A(d, p)B reactions is introduced by merging the microscopic approach to computing the properties of the nucleon-target systems and the three-body n + p + A reaction formalism, thus providing a consistent link between the reaction cross sections and the underlying microscopic structure. In this first step toward a full microscopic description, we focus on the inclusion of the neutron-target microscopic properties. The properties of the neutron-target subsystem are encapsulated in the Green's function which is computed with the coupled Cluster theory using a chiral nucleon-nucleon and three-nucleon interactions. Subsequently, this many-body information is introduced in the few-body Green's Function Transfer approach to (d, p) reactions. Our benchmarks on stable targets Ca-40,Ca-48 show an excellent agreement with the data. We then proceed to make specific predictions for (d, p) on neutron rich Ca-52,Ca-54 isotopes. These predictions are directly relevant to testing the new magic numbers N = 32, 34 and are expected to be feasible in the first campaign of the projected frib facility.

关键词： structure reaction ab-initio rare isotope

来源：评论

学校读者我要写书评

暂无评论

Nudged elastic band approach to nuclear fission pathways

引用

Physical Review C 2022年第5期105卷 054302-054302页

作者： Eric Flynn Daniel Lay Sylvester Agbemava Pablo Giuliani Kyle Godbey Witold Nazarewicz Jhilam Sadhukhan Department of Physics and Astronomy and FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA FRIB/NSCL Laboratory Michigan State University East Lansing Michigan 48824 USA Department of Statistics and Probability Michigan State University East Lansing Michigan 48824 USA Physics Group Variable Energy Cyclotron Centre Kolkata 700064 India Homi Bhabha National Institute Mumbai 400094 India

Background: The nuclear fission process is a dramatic example of the large-amplitude collective motion in which the nucleus undergoes a series of shape changes before splitting into distinct fragments. This motion can be represented by a pathway in the many-dimensional space of collective coordinates. Within a stationary framework rooted in a static collective Schrödinger equation, the collective action along the fission pathway determines the spontaneous fission half-lives as well as mass and charge distributions of fission fragments.

关键词： Collective models Fission Isomer decays Lifetimes & widths Nuclear decay Nuclear density functional theory Nuclear many-body theory A ≥ 220

来源：评论

学校读者我要写书评

暂无评论

Reduced Basis Method for Few-body Bound State Emulation

arXiv

引用

arXiv 2024年

作者： Cheng, R.Y. Niu, Y.B. Ma, Y.G. He, W.B. Wang, S.M. Godbey, K. Institute of Modern Physics Fudan University Shanghai200433 China Shanghai Research Center for Theoretical Nuclear Physics NSFC and Fudan University Shanghai200438 China FRIB NSCL Laboratory Michigan State University East LansingMI United States

Recent advances in both theoretical and computational methods have enabled large-scale, precision calculations of the properties of atomic nuclei. With the growing complexity of modern nuclear theory, however, also comes the need for novel methods to perform systematic studies and quantify the uncertainties of models when confronted with experimental data. This study presents an application of such an approach, the reduced basis method, to substantially lower computational costs by constructing a significantly smaller Hamiltonian subspace informed by previous solutions. Our method shows comparable efficiency and accuracy to other dimensionality reduction techniques on an artificial three-body bound system while providing a richer representation of physical information in its projection and training subspace. This methodological advancement can be applied in other contexts and has the potential to greatly improve our ability to systematically explore theoretical models and thus enhance our understanding of the fundamental properties of nuclear systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

来源：评论

学校读者我要写书评

暂无评论

Nuclear Shell Model and Level Density 6th

Nuclear Shell Model and Level Density

引用

6th International Workshop on Compound-Nuclear Reactions and Related Topics, CNR 2018

作者： Zelevinsky, Vladimir Karampagia, Sofia Department of Physics and Astronomy and NSCL/FRIB Michigan State University East LansingMI United States Department of Physics Grand Valley State University AllendaleMI United States

ISBN: (纸本)9783030580810

We discuss the shell-model description of the nuclear level density and underlying physics. The reliable results can be derived avoiding the full diagonalization of the huge Hamiltonian matrices. Taking into account all available interactions (not only the most collective ones) is necessary to explain the smooth energy behavior of the level density. In particular, the popular "constant temperature model" gives a good description of the results but turns out to be unrelated to the suggested pairing phase transition reflecting the fast chaotization of many-body dynamics. © 2021, This is a U.S. government work and not under copyright protection in the U.S.;foreign copyright protection may apply.

关键词： Quantum theory

来源：评论

学校读者我要写书评

暂无评论

Analysis of Ayscough’s Telescope Adapted to Use at Sea

arXiv

引用

arXiv 2022年

作者： Nesterenko, Igor FRIB NSCL Michigan State University East LansingMI48824 United States Budker Institute of Nuclear Physics Novosibirsk630090 Russia

An unambiguous accordance between an objective lens for Ayscough′s telescope ′Adapted to Use at Sea′ and another compound lens which was described by William Eastland in well-known Quere during the trial in October of 1765 was revealed. Preliminary analysis of small fragments of Quere from Eastland′, Stedman′ and Champneys′ testimonies was carried. © 2022, CC BY-SA.

关键词： Telescopes

来源：评论

学校读者我要写书评

暂无评论

Coupled-Cluster Computations of Optical Potential for Medium-Mass Nuclei

引用

FRONTIERS IN PHYSICS 2020年 8卷

作者： Rotureau, Jimmy Michigan State Univ NSCL FRIB Lab E Lansing MI 48824 USA

Recent progress in the numerical solution of the nuclear many-body problem and in the development of nuclear Hamiltonians rooted in Quantum Chromodynamics, has opened the door to first-principle computations of nuclear reactions. In this article, we discuss the current status ofab initiocalculations of nucleon-nucleus optical potentials for medium-mass systems, with a focus on results obtained with the coupled-cluster method.

关键词： nuclear reactions nuclear structure optical potential ab-initiomethod Green's function chiral effective field theory

来源：评论

学校读者我要写书评

暂无评论

Effective Description of (formula presented) and the Search for a Narrow (formula presented) Resonance 22nd

Effective Description of (formula presented) and the Search ...

引用

22nd International Conference on Few-Body Problems in Physics, FB22 2018

作者： Fossez, K. Rotureau, J. Nazarewicz, W. Michel, N. Ploszajczak, M. NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States Department of Physics and Astronomy and NSCL/FRIB Laboratory Michigan State University East LansingMI48824 United States CEA/DSM - CNRS/IN2P3 BP 55027 Caen Cedex14076 France

ISBN: (纸本)9783030323561

Open quantum systems that are at or beyond the limit of particle-emission stability exhibit generic features stemming from their coupling to an environment of positive energy states and decay channels. In nuclear physics, the exotic helium isotopes (formula presented) and the four-neutron system (formula presented) represent two prototypical cases of open quantum systems whose structures are highly impacted by the environment. In the first part, a practical approach inspired by halo effective field theory for the description of (formula presented) within tens of keV uncertainties is presented and the parity inversion in (formula presented), as well as the possible two-neutron decay of (formula presented) are discussed. The second part discusses the last ab initio results on the four-neutron system obtained using chiral forces and including continuum couplings. © Springer Nature Switzerland AG 2020.

关键词： Neutrons

来源：评论

学校读者我要写书评

暂无评论

Bayes goes fast: Uncertainty quantification for a covariant energy density functional emulated by the reduced basis method

引用

FRONTIERS IN PHYSICS 2023年 10卷

作者： Giuliani, Pablo Godbey, Kyle Bonilla, Edgard Viens, Frederi Piekarewicz, Jorge Michigan State Univ NSCL Lab FRIB E Lansing MI 48824 USA Michigan State Univ Dept Stat & Probabil E Lansing MI 48824 USA Stanford Univ Dept Phys Stanford CA 94305 USA Rice Univ Dept Stat Houston TX 77251 USA Florida State Univ Dept Phys Tallahassee FL 32306 USA

A covariant energy density functional is calibrated using a principled Bayesian statistical framework informed by experimental binding energies and charge radii of several magic and semi-magic nuclei. The Bayesian sampling required for the calibration is enabled by the emulation of the high-fidelity model through the implementation of a reduced basis method (RBM)-a set of dimensionality reduction techniques that can speed up demanding calculations involving partial differential equations by several orders of magnitude. The RBM emulator we build-using only 100 evaluations of the high-fidelity model-is able to accurately reproduce the model calculations in tens of milliseconds on a personal computer, an increase in speed of nearly a factor of 3,300 when compared to the original solver. Besides the analysis of the posterior distribution of parameters, we present model calculations for masses and radii with properly estimated uncertainties. We also analyze the model correlation between the slope of the symmetry energy L and the neutron skin of Ca-48 and Pb-208. The straightforward implementation and outstanding performance of the RBM makes it an ideal tool for assisting the nuclear theory community in providing reliable estimates with properly quantified uncertainties of physical observables. Such uncertainty quantification tools will become essential given the expected abundance of data from the recently inaugurated and future experimental and observational facilities.

关键词： bayesian reduced basis method (RBM) relativistic mean field (RMF) theory nuclear physics density functional theory

来源：评论

学校读者我要写书评

暂无评论

ADG: automated generation and evaluation of many-body diagrams III. Bogoliubov in-medium similarity renormalization group formalism

引用

EUROPEAN PHYSICAL JOURNAL A 2022年第1期58卷 1-18页

作者： Tichai, A. Arthuis, P. Hergert, H. Duguet, T. Tech Univ Darmstadt Dept Phys D-64289 Darmstadt Germany GSI Helmholtzzentrum Schwerionenforsch GmbH ExtreMe Matter Inst EMMI D-64291 Darmstadt Germany Max Planck Inst Kernphys Saupfercheckweg 1 D-69117 Heidelberg Germany Michigan State Univ NSCL FRIB Lab E Lansing MI 48824 USA Michigan State Univ Dept Phys & Astron E Lansing MI 48824 USA Univ Paris Saclay CEA IRFU F-91191 Gif Sur Yvette France Katholieke Univ Leuven Inst Kern & Stralingsfys B-3001 Leuven Belgium

The goal of the present paper is twofold. First, a novel expansion many-body method applicable to superfluid open-shell nuclei, the so-called Bogoliubov in-medium similarity renormalization group (BIMSRG) theory, is formulated. This generalization of standard single-reference IMSRG theory for closed-shell systems parallels the recent extensions of coupled cluster, self-consistent Green's function or many-body perturbation theory. Within the realm of IMSRG theories, BIMSRG provides an interesting alternative to the already existing multi-reference IMSRG (MR-IMSRG) method applicable to open-shell nuclei. The algebraic equations for low-order approximations, i.e., BIMSRG(1) and BIMSRG(2), can be derived manually without much difficulty. However, such a methodology becomes already impractical and error prone for the derivation of the BIMSRG(3) equations, which are eventually needed to reach high accuracy. Based on a diagrammatic formulation of BIMSRG theory, the second objective of the present paper is thus to describe the third version (v3.0) of the ADG code that automatically (1) generates all valid BIMSRG(n) diagrams and (2) evaluates their algebraic expressions in a matter of seconds. This is achieved in such a way that equations can easily be retrieved for both the flow equation and the Magnus expansion formulations of BIMSRG. Expanding on this work, the first future objective is to numerically implement BIMSRG(2) (eventually BIMSRG(3)) equations and perform ab initio calculations of mid-mass open-shell nuclei.

关键词： Perturbation techniques

来源：评论

学校读者我要写书评

暂无评论

The nscl cyclotron gas stopper - Preparing to go 'online'

引用

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 2020年 463卷 293-296页

作者： Schwarz, S. Bollen, G. Lund, K. Magsig, C. Morrissey, D. J. Ottarson, J. Sumithrarachchi, C. Villari, A. C. C. NSCL E Lansing MI 48824 USA Michigan State Univ Dept Phys & Astron E Lansing MI 48824 USA FRIB E Lansing MI USA Michigan State Univ Dept Chem E Lansing MI 48824 USA

The nscl has successfully used linear gas stopping cells for more than a decade to slow down near-relativistic projectile fragments to energies of tens of keV;first for experiments at low energy and later for reacceleration to Coulomb-barrier energies. In order to stop and rapidly extract light and medium-mass fast ions, which are difficult to efficiently thermalize in linear gas cells, a gas-filled, reverse cyclotron has been constructed. The device uses a cyclotron-type magnet and helium gas in a liquid-nitrogen (LN) cooled stopping chamber to confine and slow down the injected beam. The stopped ions are transported to the center of the magnet by an RF-carpet system, extracted axially through the bore with an ion conveyor and accelerated to < 60 keV energy for delivery to the users. For magnet commissioning and low-energy ion tests, the cyclotron gas stopper was constructed in a location that did not allow connection to the nscl high-energy beamlines. However, all other components have been installed for the device. Efficient ion transport has been demonstrated with ions from a movable alkali source with the magnet energized. An experimental vault is being prepared to allow the connection of the cyclotron gas stopper to the nscl beamline. The design for a dedicated momentum-compression beam line, similar to the ones feeding the existing linear gas cells (1,2), is complete and the components are under construction. Offline tests have ended and moving the cyclotron stopper to its destination has begun.

关键词： Gas stopping Radioactive beams Cyclotron

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：