Observational signals from phase transitions in the early Universe

其目的是计算宇宙早期相变的观测信号，并评估探测的前景。一个特别的焦点将是来自一阶电微弱相变的引力波，这些引力波可以在未来的天基探测器上探测到，例如酶联免疫吸附试验。最近的研究表明，声波产生是引力波的主要来源，功率谱可能比迄今所认为的大几个数量级。对于这种功率谱的形状，以及它与相变的热力学参数(如潜热)之间的关系，以及它与标准模型以外的理论的基本参数之间的关系，人们仍然知之甚少。湍流的作用根本没有被数值研究过。来自这些理论研究的信息对ELISA设计工作至关重要，该工作旨在为科学目标，包括相变等宇宙源优化其配置。该项目将(A)利用刚刚完成的PRACE Tier-0项目的数据，寻找引力波功率谱的分析模型；(B)开发当前用于模拟早期宇宙相变的代码，以便能够准确地模拟湍流；(C)对相变产生的湍流进行数值模拟；(D)将结果纳入一阶相变的引力波功率谱的完整模型中；(E)利用酶联免疫吸附试验数据调查模型选择的前景；(F)利用从其他早期宇宙过程中获得的信号，例如充气后再加热或宇宙弦，利用所获得的知识和数值技能。该项目将与赫尔辛基大学物理系合作开展。计算将使用当地、国家和国际超级计算设施，采用解析和数值技术相结合的方法。

The aim is to calculate observational signals from phase transitions the very early universe, and to assess the prospects for detection. A particular focus will be the gravitational waves from a first order electroweak phase transition, which are detectable at future space-based detectors such as eLISA. Recent work has shown that acoustic production is the main source of gravitational waves, and the power spectrum can be orders of magnitude greater than hitherto suspected. There is still little understanding of the shape of this power spectrum, and how it is related to the thermodynamic parameters of the phase transition such as the latent heat, which are in turn related to the fundamental parameters of theories beyond the Standard Model. The role of turbulence has not been studied numerically at all. Information from these theoretical studies are vital for eLISA design work, which seeks to optimise its configuration for science targets, including for cosmological sources such as phase transitions.The project will (a) seek analytical models of the gravitational wave power spectrum, using data from a PRACE Tier-0 project which has just finished; (b) develop current code for simulating early universe phase transitions so that turbulent flows can be accurately modelled; (c) perform numerical simulations of turbulent flows generated by phase transitions; (d) incorporate the results into a complete model of the gravitational wave power spectrum from a first order phase transition; (e) investigate the prospects for model selection with eLISA data and (f) use knowledge and numerical skills gained for signals from other early universe processes such as reheating after inflation or cosmic strings. The project will be carried out in a collaboration with the Department of Physics at the University of Helsinki. Calculations will be done with a mixture of analytic and numerical techniques, using local, national and international supercomputing facilities.