Dynamics and phenomenology of quantum gravity

量子引力动力学和现象学

• 批准号: RGPIN-2015-05150
• 负责人: Smolin, Lee
• 金额: $ 1.38万
• 依托单位: University of Waterloo
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - 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=614482
• 关键词: Dynamics; phenomenology; quantum; gravity

The aim of this proposal is to make definitive progress on the problem of quantum gravity, which is to bring together the two revolutionary developments initiated early in the 20th century: relativity and quantum theory. In the last 25 years a great deal of progress has been made, and indeed there are several promising directions under development. But so far none are completely satisfactory. In particular, none has made novel predictions which have been confirmed by experiment. In the proposed work we aspire to “make a push for the summit” and complete the remaining steps needed to generate experimental predictions from o quantum theory of gravity. We aim to accomplish this by joining together results and tools from several related approaches. In particular, we seek to link more theoretical approaches with more phenomenological approaches, and so be able to test basic principles by experiment. A basic and experimentally confirmed principle of gravitational theories which we implement in this proposal is background independence. This means that space and time, rather than being fixed stages on which the drama of nature play out, have a dynamical geometry which evolves in relation to matter. We build on recent progress in background independent approaches, especially loop quantum gravity. Recently several milestones have been achieved including explanations for black hole entropy and temperature, confirmations that general relativity is recovered as a semiclassical limit and increasing evidence that spacetime singularities are eliminated. These build confidence, so now is the time to raise the stakes and take on two key challenges: 1) Does the theory make experimental predictions by which it can be tested? 2) If correct, loop quantum gravity frames the language by which the other forces and particles are described. Are there then implications for the question of how gravity is to be unified with the rest of nature? Recent developments provide the basis for fresh attacks on these key questions. We start by joining two theoretical directions together, which are loop quantum gravity with causal set models of quantum spacetime. We plan to derive from these phenomenological models of the influence of quantum geometry on the propagation of photons and elementary particles. These describe effects such as an energy dependence of the speed of light which are consequences of the breaking or deforming of the symmetries of physics. These effects are in fact constrained by recent observations of photons from gamma ray bursts or cosmic rays from active galactic nuclei. We attack unification by building on two recent developments, one concerning the existence of chiral fermions, as required for the standard model, the other a natural extension of the theory that unifies general relativity with Yang-Mills theory. This offers a natural explanation for parity violation in the standard model.

这个提议的目的是在量子引力问题上取得决定性的进展，这是把20世纪初开始的两个革命性的发展：相对论和量子理论结合在一起。在过去25年中，已经取得了很大的进展，而且确实有几个有希望的方向正在发展之中。但到目前为止，没有一个是完全令人满意的。特别是，没有一个人提出过被实验证实的新预测。在拟议的工作中，我们渴望“推动峰会”，并完成从量子引力理论产生实验预测所需的剩余步骤。 我们的目标是通过将几种相关方法的结果和工具结合在一起来实现这一目标。特别是，我们试图将更多的理论方法与更多的现象学方法联系起来，从而能够通过实验来测试基本原理。 我们在这个建议中实现的一个基本的和实验证实的引力理论原则是背景独立性。这意味着空间和时间，而不是自然戏剧上演的固定舞台，具有相对于物质演化的动态几何学。 我们建立在背景独立的方法，特别是圈量子引力的最新进展。最近已经取得了几个里程碑，包括解释黑洞熵和温度，确认广义相对论是恢复作为一个半经典极限和越来越多的证据表明，时空奇点被消除。这些建立了信心，所以现在是时候提高赌注并接受两个关键挑战了：1）理论是否可以进行实验预测，以检验它？2)如果正确的话，圈量子引力就构成了描述其他力和粒子的语言。那么，引力如何与自然界的其他部分统一起来的问题是否有其含义呢？ 最近的事态发展为对这些关键问题的新攻击提供了基础。我们首先将两个理论方向结合在一起，这是圈量子引力与量子时空的因果集模型。我们计划从这些唯象模型中推导出量子几何对光子和基本粒子传播的影响。这些描述的效果，如能量依赖的光速，这是破坏或变形的物理对称性的后果。事实上，这些影响受到最近对伽马射线爆发光子或活动星系核宇宙射线的观测的限制。 我们攻击统一的基础上建立两个最近的发展，一个关于手征费米子的存在，作为标准模型所需的，其他的理论，统一广义相对论与杨米尔斯理论的自然延伸。这为标准模型中的宇称违背提供了一个自然的解释。