Large Parallel Cosmic String Simulation

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“宇宙弦将基础物理学的基本理论与最大尺度上的宇宙观测联系起来。宇宙弦是无限细的，甚至是宇宙学长度的基本物体。它们可能来自场论中的对称破缺，也可能是弦论的基本弦或一维“D膜”。它们可以在宇宙微波背景、宇宙射线、超高能中微子或重力波中产生观测信号。如果宇宙弦被探测到，它们将提供一个了解基础物理和能量的窗口，这是任何加速器都无法企及的。要解释宇宙弦的观测结果，或者从非观测中确定宇宙弦性质的极限，需要对宇宙弦网络有定量的了解。特别是，由于大多数宇宙弦的特征都来自弦环，因此了解弦环的密度、大小和形状是至关重要的，因为弦环的影响可能会被检测到。由于宇宙弦过程的高度非线性性质，要准确理解弦网络，就需要进行数值模拟。本项目将开发新的并行模拟代码，使用适合并行计算的算法，在生成初始条件和分析模拟数据方面比以前的代码更加灵活。并行计算将提供比以前模拟的大几百倍，也许一千倍的模拟量，并且模拟时间间隔增加到10倍。这将允许更多的时间来消除初始条件伪影，并使弦网络呈现其最终的缩放形式，从中可以提取重要的网络参数。该项目将通过研究生本科生的参与以及通过代表性不足的学生参与研究的机会产生更广泛的影响。其结果将通过在期刊上发表广泛传播，并在万维网上向公众提供。它将通过进一步将对宇宙的研究与对自然基本规律的研究联系起来来造福社会。

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Cosmic strings connect fundamental theories of basic physics with observation of the universe on the largest scales. Cosmic strings are infinitesimally thin or even fundamental objects of cosmological length. They can arise from symmetry breaking in field theory or they can be the fundamental strings of string theory or 1-dimensional "D-branes". They can produce observational signatures in the cosmic microwave background, in cosmic rays, in ultra-high-energy neutrinos, or in gravity waves. If cosmic strings are detected, they will provide a window onto fundamental physics and energies beyond the reach of any accelerator. To interpret a cosmic string observation or to set limits on cosmic string properties from non-observation requires a quantitative understanding of the cosmic string network. In particular, since most cosmic string signatures arise from string loops, it is vital to know the density, sizes, and shapes of the loops whose effects might be detected. Because of the highly nonlinear nature of cosmic string processes, accurate understanding of the string network requires numerical simulation.This project will develop a new parallel simulation code, using algorithms adapted to parallel computing, and with more flexibility in generating initial conditions and analyzing the simulation data than previous codes. Parallel computing will provide for a simulation volume hundreds, perhaps a thousand times larger than has been simulated before, and an increase in the simulated time interval of up to factor of 10. This will allow much more time for initial condition artifacts to be damped out and for the string network to assume its final scaling form, from which the important network parameters can be extracted.The project will have a broader impact through the involvement of graduate undergraduate students and through opportunities for students from under-represented groups to participate in research. Its results will be broadly disseminated through publication in journals and made available to the public on the World Wide Web. It will benefit society by further connecting studies of the universe with studies of the fundamental laws of nature.