Quarks in cosmos and heavy ion collisions

宇宙中的夸克和重离子碰撞

• 批准号: SAPIN-2014-00026
• 负责人: Zhitnitsky, Ariel
• 金额: $ 6.34万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=669820
• 关键词: Quarks; cosmos; heavy; ion; collisions

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.

宇宙学和粒子物理学之间存在着基本的联系，这些联系在所有尺度上都得到了很好的证实。特别是早期宇宙的物理学、重子发生、宇宙核合成等都是基于我们对粒子物理学的现代理解。 这种认识使早期宇宙成为研究基础物理，特别是真空结构理论的奇妙实验室。相反，对高温下基础物理行为的了解可以提供有关大爆炸后不久发生的事情的信息。 更值得注意的是，原则上，这些 QCD 尺度的现象可以在布鲁克海文国家实验室的 RHIC（相对论性重离子对撞机）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，在这些地方可以实现这种不寻常的环境。该项目的目标是在温度 T、化学势和所谓的 theta 参数非零的异常环境中研究 QCD 作为标准模型的一部分。 这些知识提供了关于大约 140 亿年前大爆炸后不久在 T=170 MeV 温度下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，theta 参数在 QCD 相变期间不会消失。 * *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难题，然而，它保留了强耦合 QCD 的所有相关元素，例如限制、拓扑扇区的简并性、非平凡的 theta 依赖性以及许多其他重要方面，这些方面使我们能够测试强相互作用 QCD 的一些令人着迷的特征，包括长程有序的某些方面。相应的研究还揭示了强耦合QCD与一些拓扑有序凝聚态物质系统之间的深刻关系。 * *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 LHC 正在进行的非常有趣的实验，违反 QCD 中的局部 CP 不变性一直是过去几年中深入研究的主题。解释观察到的不对称性的主要思想是假设有效 CP 违反 theta 参数是由于碰撞而大规模引起的。这导致了大的 CP 奇数域。为什么这些 CP 奇域很大？我们认为 QCD 中的长程有序是造成这种不寻常行为的原因。 由于在存在 theta 参数的情况下夸克和反夸克之间相互作用的差异，可能会发生电荷的局部分离。这种现象可以在 RHIC 和 LHC 上进行测试。 RHIC 和 LHC 的初步结果支持了关于电荷分离效应本质的想法。最后，我们将相同的想法应用于宇宙学。 这些拓扑场的独特特征激发了一种提议，即宇宙中观测到的暗能量实际上可能与这种纯拓扑、非传播、长程场有关。值得注意的是，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研究这种全新类型的能量。