RUI: Spatial and Temporal Dynamics of Matter in Intense Laser Fields

在过去的几年里，世界各地的许多实验室已经开始开发高功率激光系统来产生电磁辐射脉冲，这些脉冲的能量如此之大，以至于探测和控制物质状态的新途径很快就可以测试出来。伊利诺伊州立大学的研究小组计划用从头算计算机模拟来伴随这些发展，这种模拟可以提供微观的视角，以完全的时间和空间分辨率来观察电子和正电子与光子的相对论性相互作用。对这些基本过程的更好理解可能会为在很短的时间尺度上控制原子、化学甚至生物过程开辟新的途径。该基金的另一项重要任务是为本科生提供获得研究经验的机会。这种教育经历为他们提供了重要的技能，包括团队合作，获得耐力，智力灵活性和解决重大研究问题的经验，以及在会议和出版物中传达结果。通过在数值时空网格上求解相对论量子电动力学的狄拉克-麦克斯韦方程组，得到了计算机模拟结果。这些非摄动的大规模计算非常耗费CPU时间，但由于最近大规模并行计算机专用数值算法的发展进展，这些计算已经成为可能。这些计算是在伊利诺伊州和德克萨斯州的XSEDE超级计算机集群上进行的。当前资助的一个具体目标是首次模拟一般情况下激光场诱导的电子-正电子对产生过程，在这种情况下，两个产生的粒子之间的吸引库仑力被考虑在内。对简化模型系统的初步模拟表明，我们目前对这一过程的理论理解可能需要修正，因为这种（迄今为止被忽视的）粒子间力可能在动力学中起主要作用。

During the last years numerous laboratories worldwide have begun to develop high-powered laser systems to create electromagnetic radiation pulses that are so energetic that new avenues to probe and control the states of matter can be tested soon. The research team at Illinois State University plans to accompany these developments with ab initio computer simulations that can provide microscopic insight into the relativistic interaction of electrons and positrons with photons with full temporal as well as spatial resolution. A better understanding of these fundamental processes might open new ways to control atomic, chemical and even biological processes on very short time scales. An important mission for the grant is also to give undergraduate students the opportunity to gain research experience. This educational experience provides them with important skills including working as a team, gaining the endurance, intellectual flexibility and experience to tackle serious research problems, and communicating results in conferences and publications. The computer simulations are obtained by solving the coupled set of Dirac-Maxwell equations of relativistic quantum electrodynamics on a numerical space-time grid. These non-perturbative large-scale calculations are very CPU time consuming but have become possible due to recent progress in the development of specialized numerical algorithms for massively parallel computers. The calculations are performed in Illinois and also at the XSEDE supercomputer cluster in Texas. A specific goal of the current grant is to simulate for the first time the laser-field induced electron-positron pair-creation process for a general situation for which the attractive Coulomb force between the two created particles is taken into account. Preliminary simulations for simplified model systems suggest that our present theoretical understanding of this process might need to be revised as this (so far neglected) inter-particle force might play a major role for the dynamics.