3-D Simulations of i-Process Nucleosynthesis in the Early Universe

早期宇宙中 i-Process 核合成的 3-D 模拟

基本信息

批准号：
1440025
负责人：
Paul Woodward
金额：
$ 1.54万
依托单位：
University of Minnesota-Twin Cities
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2014
资助国家：
美国
起止时间：
2014-09-01 至 2015-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1440025&HistoricalAwards=false
关键词：
Simulations Process Nucleosynthesis Early Universe

项目摘要

Astronomical observations are now probing the early stages of the universe, in which galaxiesdeveloped and merged, and the formation of the structures in the universe at the present erawas set in motion. An important part of this story is the chemical evolution of galaxies. Theformation of the elements in the first stars and their subsequent dispersal are powerful tracersof structure formation and evolution in the early universe. This project involves the simulationof processes deep inside stars of the early universe that experience hydrogen ingestionevents caused by mixing of material across the boundaries of convection zones. In 1-D stellarevolution simulations, these give rise to rapid hydrogen burning, with enormous energy releaseand causing nucleosynthesis by neutron capture from neutron fluxes intermediate between theslow (s) and rapid (r) processes. This is the intermediate, or i-process nucleosynthesis thatis targeted in this study. Accurate treatment of the convective boundary mixing that drivesthis i-process requires full 3-D simulation. The rapid hydrogen burning that ensues, togetherwith the very large luminosities involved make 3-D simulation affordable on NSF?s powerfulnew supercomputing platform, Blue Waters, at NCSA.A new and powerful capability will be built in this project to simulate these events by couplingtogether 3-D simulations that cover brief time intervals with 1-D simulations spanning muchlonger times. In some cases that will be addressed, it is possible to simulate the entire eventin 3-D. In others, 3-D simulations performed at intervals as part of a coupled 1-D and 3-Dstellar evolution calculation will serve to recalibrate the coefficients in approximate 1-D modelsfor dynamic mixing processes. Such coupled calculations will use these periodic modelrecalibrations to validate the use of the models as the calculation progresses. When unacceptablylarge revisions of model "constants" are indicated, a recomputation with 3-D recalibrationstaken at shorter time intervals will result. This new process is called autocorrecting modeling.It involves periodic generation of large amounts of 3-D data from simulation codes. This datageneration is followed by a detailed analysis of the data in terms of 1-D models. The resultsof this analysis are then fed back into the 1-D stellar evolution computation. Pioneering thisnew approach is a major challenge of the project; the database of condensed simulation resultsthat will be built in the process will be a significant outcome of the project. This data will bemade available first to collaborators and ultimately to the broad community. It will be possibleto use this data to formulate, validate, and refine simplified models of the convective boundarymixing processes that are a major focus of this study. It will also be possible for others,potentially using quite different simulation software, to use this data to adopt an autocorrectingmodeling approach in studies of related problems. In the first year of this project, a continuationof present work with the well observed case of Sakurai's object is planned along with applicationof the new techniques to simulations of low-mass, low-metallicity AGB stars.

现在，天文观测正在探测宇宙的早期阶段，其中星系开发和合并，以及在当前的Erawas开始运动中宇宙中宇宙中的结构的形成。这个故事的重要部分是星系的化学演化。第一颗恒星中元素及其随后的散布的形式是早期宇宙中结构形成和进化的强大示踪物。该项目涉及早期宇宙中恒星内部的过程模拟，这些过程经历了由于在对流区域的各个边界中混合材料而引起的氢摄入量。在1-D星静脉模拟中，这些模拟引起了快速的氢燃烧，并具有巨大的能量释放，从而导致中子磁通中的中子通量中间引起的核合成，并在theslow（s）和快速（R）过程之间引起中间体。这是本研究中针对的中间或I过程。对流边界混合的准确处理，即动力学I-Process需要完整的3D模拟。随之而来的快速氢燃烧，涉及的非常大的照明性使3D模拟在NCSA的NSF强大NEW SUPERCOUTION平台Blue Waters上负担得起。该项目将在该项目中建立一个新的强大功能，以模拟这些事件，以通过3-D模拟与1-D Simulate couplingTogeTher 3-D模拟进行1-D Simulation simulation simulation simulation跨度范围跨度范围。在某些情况下，将要解决的情况，可以模拟整个Eventin 3-D。在其他情况下，作为耦合1-D和3-DSTELLAR进化计算的一部分进行的3-D模拟将用于重新校准，以在近似1-D模型的动态混合过程中重新校准。此类耦合计算将使用这些定期模型验证来验证模型的使用。当指示模型“常数”的不可接受的修订时，会在较短的时间间隔内用3-D重新启动的重新计算。这个新过程称为自动校正建模。它涉及从模拟代码定期生成大量3-D数据。此数据代理之后是对数据模型的详细分析。然后将该分析的结果反馈到1-D恒星演化计算中。开创此新方法是该项目的主要挑战。凝结模拟结果的数据库将在此过程中构建，这将是项目的重要结果。这些数据将首先向合作者提供，最终向广泛的社区提供。可以使用此数据来制定，验证和完善对流边界混合过程的简化模型，这是本研究的主要重点。其他人也有可能使用完全不同的仿真软件，使用这些数据在相关问题的研究中采用自动校正模型方法。在该项目的第一年中，计划在现有的樱井对象案例中进行现在的工作，并计划将新技术应用于低质量，低金属性AGB星的模拟。