Quarks in cosmos and heavy ion collisions

宇宙学和粒子物理学之间存在着基本的联系，它们在所有尺度上都得到了很好的确立。特别是，早期宇宙的物理学、重生、宇宙学的核合成等都是基于我们对粒子物理学的现代理解。这一认识使早期宇宙成为研究基础物理的绝佳实验室，特别是该理论的真空结构。相反，基础物理在高温下的行为知识提供了关于大爆炸后不久发生的事情的信息。更值得注意的是，这些QCD尺度上的现象原则上可以在RHIC(相对论重离子对撞机)、布鲁克海文国家实验室和大型强子对撞机(瑞士日内瓦)的重离子碰撞中进行实验测试，在那里可以实现这种不寻常的环境。该项目的目标是研究QCD作为标准模型的一部分，在不寻常的环境中，当温度T、化学势和所谓的theta参数非零时。这一知识给出了大约140亿年前在温度T=170 MeV的大爆炸后不久发生的事情的可靠信息。理解相应的相图(作为这些外部参数的函数)是QCD中最具挑战性的问题之一。人们普遍认为，在QCD相变过程中，theta参数并没有消失。**我的项目的第一部分致力于使用QCD的简化版本来研究所有这些困难的问题，然而，它保留了强耦合QCD的所有相关元素，如禁闭、拓扑扇区的简并、非平凡的theta依赖以及许多其他重要方面，使我们能够测试强相互作用QCD的一些吸引人的特征，包括长程有序的一些方面。相应的研究还揭示了强耦合QCD与一些拓扑有序凝聚态系统之间的深层联系。**我项目的第二部分是将这些全新的想法应用于重离子碰撞、天体物理学和宇宙学。特别是，由于RHIC和大型强子对撞机正在进行的非常有趣的实验，QCD中局域CP不变性的破坏在过去几年里一直是一个密集研究的主题。解释观察到的不对称性的主要思想是假设有效的CP违反theta参数是作为碰撞的结果而在大范围内诱导的。这导致了大的CP奇域。为什么这些CP奇数域很大？我们认为QCD中的长程有序是造成这种反常行为的原因。由于存在theta参数时夸克和反夸克之间相互作用的差异，可能会发生局部电荷分离。这种现象可以在RHIC和大型强子对撞机上得到测试。RHIC和大型强子对撞机的初步结果支持电荷分离效应本质的观点。最后，我们将同样的想法应用于宇宙学。这些拓扑场的独特特征激发了一种假设，即宇宙中观察到的暗能量实际上可能与这种纯拓扑、非传播的长程场有关。值得注意的是，这种全新的能量在原则上可以通过测量所谓的拓扑卡西米尔效应在实验室中进行研究。

There are fundamental links between cosmology and particle physics, which have been well established at all scales. In particular, the physics of the early Universe, baryogenesis, cosmological nucleosynthesis, etc. is based on our modern understanding of particle physics. This realization has made the early Universe a marvellous laboratory for studying fundamental physics, in particular the vacuum structure of the theory. Conversely, knowledge of the behaviour of fundamental physics at high temperature gives information about what happened shortly after the Big Bang. What is more remarkable is the fact that these phenomena at the QCD scale can be, in principle, experimentally tested in heavy ion collisions at RHIC (relativistic heavy ion collider), Brookhaven National Laboratory, and at the LHC (Geneva, Switzerland) where such unusual environment can be achieved. The goal of the project is the study of QCD as part of the standard model in the unusual environment when temperature T, chemical potential and the so-called theta- parameter are non-zero. This knowledge gives a reliable information about what have happened about 14 billion years ago soon after the Big Bang at the temperature T=170 MeV. The understanding of the corresponding phase diagram (as a function of these external parameters) is one of the most challenging problems in QCD. It is generally accepted that the theta parameter was not vanishing during the QCD phase transition. * *First part of my project is devoted to study all these hard questions using a simplified version of QCD, which however preserves all the relevant elements of strongly coupled QCD such as confinement, degeneracy of topological sectors, nontrivial theta dependence, and many other important aspects which allow us to test some fascinating features of strongly interacting QCD, including some aspects of the long range order. The corresponding studies also reveal a deep relation between strongly coupled QCD and some topologically ordered condensed matter systems. * *The second part of my project is application of these fundamentally new ideas to heavy ion collisions, astrophysics and cosmology. In particular, the violation of local CP invariance in QCD has been a subject of intense studies for the last couple of years as a result of very interesting ongoing experiments at RHIC and the LHC. The main idea to explain the observed asymmetries is to assume that the effective CP violating theta parameter is induced on a large scale as a result of collision. This leads to large CP odd domains. Why are these CP odd domains large? We argue that the long range order in QCD is responsible for such an unusual behaviour. Due to the differences in interactions between quarks and antiquarks in the presence of the theta parameter the local separation of charges may take place. This phenomenon can be tested at RHIC and the LHC. Preliminary results at RHIC and the LHC support the ideas on the nature of the charge separation effect. Finally, we apply the same ideas to cosmology. The unique features of these topological fields have inspired a proposal that the observed dark energy in the universe may in fact be related to such pure topological, non- propagating, long-ranged fields. It is quite remarkable that this fundamentally new type of energy can be, in principle, studied in a laboratory by measuring the so-called topological Casimir Effect.