First order phase transitions beyond the Standard Model

LIGO/Virgo合作对引力波的直接探测表明，一扇关于宇宙的新窗口现在已经打开，有可能彻底改变我们对其历史的认识。同样，在大型强子对撞机（LHC）上发现希格斯粒子也引发了对基本粒子质量起源的全面理解。这些最基本的物理学链在早期宇宙中大约10皮秒时联系在一起，当时发生了电弱相变，希格斯场“打开”。这个过程可能是一个剧烈的过程，产生的引力波可以被灵敏度在毫赫兹波段的天基引力波探测器探测到。欧洲航天局最近批准了一项这样的使命，激光干涉仪空间天线（丽莎），将于2034年发射。丽莎有可能直接探测宇宙在大约10皮秒的年龄时的状况，同时探测质量产生的物理学。早期宇宙一级相变的特征如下。能量标度由临界温度Tc设定，低于该温度，希格斯相的气泡可以自发地成核和生长。单位体积的气泡成核速率可以用转变速率参数B来计算，即激活势垒的变化速率。第三个参数a大致上是希格斯场的势能与热能的比值，后者控制着流体的剪切应力，而流体剪切应力是引力波的来源。效率取决于最后一个参数，即相边界膨胀的速度vw。人们强烈希望确定引力波功率谱作为这些参数的函数（Hn，a，B，vw），该项目旨在通过改进参数的计算将该程序与基础物理学联系起来（H_n，a，B，vw），从而使功率谱的计算精度达到20%，壁面速度vw是最不确定的参数，对于低值高达因子2。这个项目开发和应用新的方法来提高vw计算的精度到所需的5%水平。格子蒙特卡罗技术具有很好的潜力，因为它们适当地处理了W和Z场的IR模式，这是显著不确定性的来源。该项目将探索使用全息方法来强相互作用场理论，以计算从对偶5维引力理论的解决方案的热激活率。

The direct detection of gravitational waves by the LIGO/Virgo collaboration shows that a new window on theUniverse is now open, with the potential to revolutionise our knowledge of its history. Equally, the discoveryof the Higgs particle at the Large Hadron Collider (LHC) has triggered a hunt for a complete understanding ofthe origin of elementary particle masses. These most fundamental strands of physics are linked in the earlyUniverse at around 10 picoseconds, when the electroweak phase transition took place, and the Higgs field"turned on". This process could have been a violent one, generating gravitational waves detectable by spacebasedgravitational wave detectors with sensitivity in the millihertz band. The European Space Agency hasrecently approved just such a mission, Laser Interferometer Space Antenna (LISA), which will launch by2034. LISA has the potential to directly probe of the conditions of the Universe at an age of about 10picoseconds, and at the same time the physics of mass generation. .An early Universe first-order phase transition is characterised as follows. The energy scale is set by thecritical temperature Tc, below which bubbles of the Higgs phase can spontaneously nucleate and grow. Thebubble nucleation rate per unit volume is calculable in terms of the transition rate parameter b, the rate of thechange of the activation barrier. The third parameter a is roughly the potential energy in the Higgs fieldrelative to the thermal energy, which controls the fluid shear stresses, the source for the gravitational waves.The efficiency depends on the final parameter, the speed with which the phase boundary expands vw.There is a strong drive towards the determination of the gravitational wave power spectrum as a function ofthe parameters (Hn,a,b,vw), This project aims to link this programme back to fundamental physics byimproving the computation of the parameters (Hn,a,b,vw) from the masses and coupling constants ofunderlying particle physics models, so that the power spectrum can be computed with 20% accuracy.The wall speed vw is the parameter with the most uncertainty, up to a factor two for low values. This projectwill develop and apply new methods to improve the accuracy of the vw calculation to the required 5% level.Lattice Monte Carlo techniques have good potential, as they treat properly the IR modes of the W and Zfields which are the source of significant uncertainty. The project will explore the use the holographicapproach to strongly-interacting field theories to compute the thermal activation rate from a solution to thedual 5-dimensional gravitational theory.