Pulsation evolution and hydrodynamics of rapidly rotating stars

随着高性能数字计算机的出现，我们对恒星结构和演化的认识大大增加了。到目前为止，我们已经了解了恒星的基本生命周期大约40年了，但我们无法与越来越精确的观测相匹配，这表明我们并不是什么都了解。例如，传统的模型既不能预测某些元素表面丰度的增强，这些元素必须在恒星深处产生并运输到表面，也不能预测所有观测到的比太阳大得多的恒星的振荡周期的正确值。传统模型中未包括的自转已被确定为造成这些差异的可能原因。这不仅可能是由于旋转力引起的恒星结构的改变，而且还可能是由于旋转引起的不稳定性引起的短期和中期时间尺度的运动。由这些不稳定性产生的运动在整个恒星中传输物质和角动量。本研究中提出的多维计算可以充分再现给定角动量分布的恒星结构。随着进一步的发展，预计这些旋转不稳定性所产生的组成和角动量分布的演变也可以被跟踪。这可以让我们缩小恒星角动量分布的可能性。这种物质和角动量的重新分配在恒星生命的早期就开始了。恒星演化的后期阶段将受此影响，这可能是理解这些后期阶段观测和模型之间的一些差异的关键。所使用的计算方法在许多其他研究领域都有应用：气候研究、湍流研究和国防相关工作。

Our knowledge of the structure and evolution of stars has increased greatly with the advent of high powered digital computers. We have understood the basic life cycle for stars for about four decades now, but our failure to match increasingly refined observations demonstrates that we do not understand everything. For example, the traditional models predict neither the enhancement of the surface abundances of some elements which must be created deep inside the star and transported to the surface nor the correct values for all the observed oscillation periods of stars appreciably more massive than the sun.Rotation, not included in the traditional models,  has been identified as the possible reason for these discrepancies. This may come not only through the alteration of the stellar structure produced by the rotational force, but also through short and intermediate time scale motion produced by instabilities that rotation can cause. The motion produced by these instabilities transports material and angular momentum throughout the star.  The multi-dimensional calculations proposed in this research can be expected to reproduce the stellar structure adequately for a given angular momentum distribution. With some further development, it is expected that the evolution of the composition and angular momentum distributions produced through these rotational instabilities can be followed as well. This should allow us to narrow the possible angular momentum distribution possibilities that stars have. This redistribution of material and angular momentum begins early in the star's life. Later stages of stellar evolution will be affected by this and this may be the key to understanding some discrepancies between observation and models in these later phases as well.The computational methods utilized have application in many other areas of research: climate studies, turbulence research, and defense related work.