U.S.-Japan Cooperative Research: Phase Transitions in Dense Astrophysical Plasmas

该奖项为罗切斯特大学物理与天文学系Hugh M Van Horn教授和日本东京大学物理系Setsuo Ichimaru教授为期两年的致密天体物理等离子体合作研究项目提供支持。在密集的天体物理对象中，如中子星、白矮星、低质量恒星（褐矮星）、太阳内部和巨行星，电离的原子核和电子的集合构成密集的等离子体，它们表现出各种各样的相变。近年来，由于凝聚态理论的进步和计算机模拟能力的进步，对致密天体物理等离子体中的相变过程进行详细分析已经成为可能。这项建议的目的是对其中一些相变过程进行理论和计算机模拟研究。要研究的过程包括：(1)中子星可能有玻璃壳而不是结晶壳的可能性，以及由此产生的后果；(2)在极冷白矮星中作为能量来源的二元碳/氧和铁/碳混合物中存在相分离的可能性；(3)铁/氢相分离，这可能对低质量恒星和“褐矮星”的演化产生有趣的影响；(4)巨行星和褐矮星中的氢/氦相分离，这可能是这些天体中重要的能量来源。参与这次合作的两个小组可以很好地互补。日本科学家在与此次合作相关的致密等离子体物理和凝聚态物理领域有着悠久的重要贡献，并且对天体物理应用也有浓厚的兴趣。这个美国小组对天体物理学也有类似的兴趣，同时对高密度物质的相关特性也有浓厚的兴趣。如果成功，该项目将对致密等离子体物理、凝聚态物理和天体物理学之间的交叉学科的研究问题做出重大贡献。

This award provides support for a two year cooperative research project on dense astrophysical plasmas, between Professor Hugh M Van Horn, Department of Physics and Astronomy, University of Rochester, and Professor Setsuo Ichimaru, Department of Physics, University of Tokyo, Japan. In dense astrophysical objects, such as neutron stars, white dwarfs, low mass stars (brown dwarfs), the solar interior, and giant planets, collections of ionized nuclei and electrons constitute dense plasmas, which exhibit various kinds of phase changes. In recent years, due to advancements in condensed-matter theories coupled with progress in computer-simulation capabilities, it has become possible to carry out detailed analyses of those phase-transition processes in dense astrophysical plasmas. The aim of this proposal is to undertake theoretical and computer-simulation studies on a number of those phase transition processes. The processes to be studied include: (1) the possibility that neutron stars may have glassy rather than crystalline crusts, and what the consequences are of that; (2) the possibilities of phase separation in binary carbon/oxygen and iron/carbon mixtures, which have been suggested as energy sources in very cool white dwarfs; (3) iron/hydrogen phase separation, which may have interesting consequences for the evolution of low mass stars and "brown dwarfs"; and (4) hydrogen/helium phase separation in giant planets and brown dwarfs, which may prove a significant energy source in these bodies. The two groups involved in this collaboration complement each other well. The Japanese scientists have a long history of important contributions in areas of dense plasma physics and condensed matter physics relevant to this collaboration, and also have a strong interest in astrophysical applications. The US group has a similar interest in astrophysics, together with a strong interest in the relevant properties of matter at high densities. If successful this project will make a significant contribution to research problems at the interface between the disciplines of dense plasma physics, condensed matter physics and astrophysics.