Solving thermal QCD using string theory techniques

使用弦理论技术求解热 QCD

• 批准号: SAPIN-2014-00025
• 负责人: Dasgupta, Keshav
• 金额: $ 3.57万
• 依托单位: McGill University
• 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=648685
• 关键词: Solving; thermal; QCD; using; string

My research directions at McGill in the last few years have been along strongly coupled gauge theories, an example being Quantum Chromodynamics (QCD). In particular I have attempted to have some analytical control over these theories. Clearly standard perturbative techniques, like Feynman diagrams, are not useful to analyze these theories because of strong interactions. In the limit where the number of "colors" N is made large, a new development in the field of string theory has shown that there could be a dual gravitational description of these theories wherein all the non-perturbative physics can be analyzed simply using classical supergravity techniques! In the past few years we have been able to develop a model purely using supergravity techniques that mimic large N thermal QCD both at low and high energies. We have been using this model to compute many observable physics of thermal QCD, namely shear viscosity, entropy, QGP phase, confinement and deconfinement dynamics, quarkonium melting etc. These developments are timely no doubt and for the next few years I want to devote my time to develop the picture further and extend this to the color superconductivity phase. The physics of large N thermal QCD and color superconductivity have amazing similarities, and the gravitational description that we have developed here could probably be used to study this further. Additionally, the model that we have developed behave well at high energies too. This is one advantage that I believe is missing in many of the other models proposed in the literature. The high energy behavior of standard QCD is simple: it is an almost free theory. In the large color limit i.e in the large N limit, the high energy behavior is conformal or alternatively, scale-invariant. This is exactly how our model behaves at high energies. In the gravitational dual, the high energy behavior is captured by the regions at large radius and the low energy behavior is captured by the regions at small radius. However the full gravitational dual solution is still not been constructed, and one of my long term aim would be to complete this picture. The exercise is technically challenging, but I believe that with efforts and with the help of my graduate students, we should be able to complete the dual description. Once the dual description is laid out, it will be very interesting to work out analytically the various properties of QCD which were impossible to solve using previous techniques. My second proposal is to work on certain aspects of cosmology that has recently generated some interest. For sometime it was thought that string theory would easily generate de-Sitter type vacua provided certain no-go conditions were violated. A candidate solution was also proposed that took into account various non-perturbative effects that gave us a way at least to study de-Sitter solutions in string theory, although no explicit solutions were constructed. However, recently, certain issues were raised regarding this approach. One of my aim for next year or so would be to resolve this issue. This is a technically challenging exercise as explicit supergravity solutions in string theory that give rise to accelerating universe is very hard to construct. If successful, this would probably be the first non-trivial example of a time-dependent supergravity solution. My third proposal would be to elaborate on the recently proposed gauge/gravity duality in heterotic string theory wherein we gave the gravity dual for a gauge theory whose field theory description was completely mysterious. My aim would be to learn about this theory using our proposed dual. Finally, my fourth proposal would be to extend the newly found conformal Seiberg-Witten type gauge theories using techniques of string theory.

在过去的几年中，我在麦吉尔的研究指示一直沿着强烈的量规理论依赖，一个例子是量子染色体动力学（QCD）。特别是我试图对这些理论进行一些分析控制。显然，像Feynman图一样，标准的扰动技术对于分析这些理论而没有有用。在“颜色” n数量大的限制中，弦理论领域的一个新发展表明，可以对这些理论有双重引力描述，其中所有非扰动物理都可以简单地使用经典的超级重力技术进行分析！在过去的几年中，我们能够使用纯粹使用超级强大n热QCD在低能和高能量下模仿大N热QCD的模型。我们一直在使用该模型来计算许多可观察到的热QCD物理学，即剪切粘度，熵，QGP相，限制和反登录动力学，Quarkonium熔化等。这些发展无疑是及时的，在接下来的几年中，我想花费时间来进一步发展图片，并将其扩展到彩色超级尺寸。大N热QCD和颜色超导性的物理学具有惊人的相似性，我们在这里开发的引力描述可能可用于进一步研究。此外，我们开发的模型在高能方面也表现得很好。这是我认为在文献中提出的许多其他模型中缺少的优点。标准QCD的高能量行为很简单：这几乎是自由理论。在较大的颜色极限（即在大N极限中），高能量行为是保形的或替代的，比例不变。这正是我们的模型在高能量下的行为方式。在重力双重的情况下，高能量行为是由较大半径处的区域捕获的，低能行为是由小半径的区域捕获的。但是，仍未构建完整的引力双重解决方案，我的长期目标之一就是完成这张照片。这项运动在技术上具有挑战性，但我相信，在努力和研究生的帮助下，我们应该能够完成双重描述。一旦列出了双重描述，可以通过分析QCD的各种属性来使用以前的技术来解决QCD的各种属性，这将是非常有趣的。我的第二个建议是研究宇宙学的某些方面，这些方面最近引起了人们的兴趣。有时候，有人认为弦理论会很容易产生de-sitter类型的真空吸尘器，只要违反了某些不做条件即可。还提出了一种候选解决方案，该解决方案考虑了各种非扰动效应，这至少使我们在弦理论中研究了脱水液解决方案，尽管没有构建明确的解决方案。但是，最近，关于这种方法提出了某些问题。我明年左右的目标之一是解决此问题。这是一项在技术上具有挑战性的练习，因为弦理论中的显式超级解决方案很难构建加速宇宙。如果成功的话，这可能是时间依赖性超级重力解决方案的第一个非平凡示例。我的第三个提议是详细介绍杂音弦理论中最近提出的量规/重力二元性，其中我们为仪表理论提供了重力二重性，该理论的现场理论描述完全是神秘的。我的目的是使用我们提出的双重二元了解这一理论。最后，我的第四个建议是使用字符串理论技术扩展新发现的Seiberg-witten类型规格。