Microscopic Approaches to Collective Motion in Nuclei

在原子核中发生的丰富多样的结构和过程中，那些被称为“集体运动”的结构和过程之所以被称为集体运动，是因为原子核中的所有或大部分核子（质子和中子）都参与并一起运动。例子包括巨大的共振，整个原子核像果冻一样摆动或振动，两个原子核之间的碰撞，它们要么粘在一起，要么穿过对方，这取决于两个原子核相互发射的方式等细节。我们最近发展了模拟原子核集体运动的能力，只需要对问题的布局或原子核中单个核子之间的相互作用做很少的假设。我们计算的第一个结果显示了对集体运动的新预测，例如与另一个原子核碰撞引起的质子和中子自旋方向的对齐，并提供了对完全变形的原子核的巨大共振的第一次计算，这种共振进入了完整的微观细节。尽管取得了这些成功，但我们开发的方法在计算某些数量时天生就能做得很好，但在计算其他数量时天生就不能做得很好。我们想改进这种方法，以便更好地考虑到已知会发生的效应，即核子有配对的倾向，同时也使我们能够预测一整套性质，比如碰撞过程中质量碎片的分布。这些结果将从单个核子之间的相互作用和我们对原子核中不同结构以及潜在核力的理解的角度，提高我们对核过程的理解。

Among the rich variety of structures and processes that occur in atomic nuclei, those that fall under the term 'collective motion' are so-called because all or most of the nucleons (protons and neutrons) in the nucleus take part and move together. Examples include giant resonances in which the whole nucleus wobbles or vibrates like a jelly, and collisions between two nuclei in which they might either stick together or pass through each other, depending on details such as the way in which the two nuclei are fired at one another. We have recently developed the ability to simulate collective motion in nuclei using very few assumptions about the layout of the problem or the interaction between the individual nucleons in the nucleus. The first results of our calculations have shown new predictions of collective motion, such as the alignment of the direction of spin of the protons and neutrons induced by the collision with another nucleus, and have provided the first calculations of the giant resonance of a completely deformed nucleus which go into full microscopic detail. Despite these successes, the methods we have developed are inherently able to do well at calculating some quantities, but inherently unable to do well at calculating others. We want to improve the method to allow the effect, which is known to occur, that nucleons have a tendancy to pair up to be better taken into account, and also to allow us predict a whole class of properties, such as the distribution of mass fragments during collisions. The results will improve our understanding of nuclear processes from the point of view of the interaction between the individual nucleons and our understanding of different structures that occur in nuclei, and the underlying nuclear force.