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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612385
• 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有着根本的联系，这在所有尺度上都已经得到了很好的建立。特别是，早期宇宙的物理学，重子生成，宇宙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学，特别是真空结构理论的奇妙实验室。相反，高温下基础物理学行为的知识提供了大爆炸后不久发生的事情的信息。更值得注意的是，这些QCD尺度的现象原则上可以在布鲁克海文国家实验室的RHIC（相对论重离子对撞机）和LHC（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，在温度T，化学势和所谓的θ参数不为零的异常环境中。这一知识提供了关于大约140亿年前在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。一般认为，θ参数在QCD相变过程中并不为零。 我的项目的第一部分是致力于研究所有这些困难的问题，使用一个简化版本的QCD，但保留了强耦合QCD的所有相关元素，如禁闭，拓扑部门的简并性，非平凡的θ依赖性，以及许多其他重要方面，使我们能够测试强相互作用QCD的一些迷人的功能，包括长程有序的一些方面。相应的研究也揭示了强耦合QCD与某些拓扑有序凝聚态系统之间的深刻联系。 我的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，QCD中局部CP不变性的破坏一直是过去几年深入研究的主题。解释所观察到的不对称性的主要思想是假设有效CP违反θ参数是由于碰撞在大尺度上引起的。这导致大的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θ参数时夸克和反夸克之间相互作用的差异，电荷的局域分离可能发生。这种现象可以在RHIC和LHC上得到验证。RHIC和LHC的初步结果支持电荷分离效应的性质。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提议，即在宇宙中观察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，这种全新的能量在理论上可以在实验室中通过测量所谓的拓扑卡西米尔效应来研究。