Beyond general relativity

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• 批准号: RGPIN-2020-05569
• 负责人: Seahra, Sanjeev
• 金额: $ 1.75万
• 依托单位: University of New Brunswick
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=758887
• 关键词: Beyond; general; relativity

Our current best theory of gravity is Einstein's general relativity. It provides an excellent description of the motion of bodies in the solar system, the way binary pulsars lose energy via gravitational radiation, and the force of attraction between masses separated by distances as small as a millimetre. But all is not well with the model: Recent observations have shown that the expansion of the universe is accelerating, not decelerating as you might expect from ordinary relativity. Also, it is notoriously difficult to come up with a quantum theory of gravity; that is, a theory that is a harmonious blend of the physics we understand from the subatomic world and Einstein's picture of gravitation as a manifestation of the geometry of the universe. To address these shortcomings, many radical ideas have been proposed, such as the possibility that the universe has extra dimensions, or that our understanding of quantum mechanics is somehow flawed or incomplete. It is impossible to know which of these alternative models is correct without subjecting them to experimental tests. The primary goal of my research is to work out what effects these models have on actual experiments or observations. For example, I study models where our standard picture of quantum mechanics, the theory that governs the subatomic world, gets modified in a profound way. Such modifications alter the behaviour of the universe at very early times, when the seeds of galaxies were created by primordial quantum fluctuations. This affects the relic radiation from the big bang we observe today, and hence provides a means of testing the theory. I am also interested in models that assume that on the smallest scales the structure of spacetime is not continuous, like liquid water, but granular, like sand. This idea is important because everything we see in the universe today formed out of waves in space and time. If we track these waves further and further into the past, they get smaller and smaller until they are eventually tiny enough to "see" the discrete, grainy structure of spacetime. The shape of these waves---and the structures they spawned---in today's universe is directly influenced by their behaviour in the past. So it may be possible to see the echoes of the granular nature of our universe in the positions of celestial bodies today. By deriving the precise effects alternative theories have on observations, I hope to obtain new and novel ways of constraining or ruling out these models, thus bringing us closer to understanding the true nature of gravity in the universe.

我们目前的最佳重力理论是爱因斯坦的一般相对论。它很好地描述了太阳系中身体运动的方式，二进制脉冲星通过重力辐射损失能量的方式，以及质量在距离距离小至毫米的距离之间的吸引力。但是，所有模型都不好：最近的观察结果表明，宇宙的扩展正在加速，而不是您可能从普通相对论中期望的那样减速。而且，众所周知，很难提出一种重力理论。也就是说，一种理论是我们从亚原子世界中理解的物理学的和谐融合，爱因斯坦的引力图片是宇宙几何形状的体现。 为了解决这些缺点，已经提出了许多激进的想法，例如宇宙具有额外的维度，或者我们对量子力学的理解是有缺陷或不完整的。如果不对它们进行实验测试，则不可能知道这些替代模型中的哪个是正确的。我的研究的主要目标是确定这些模型对实际实验或观察的影响。例如，我研究了我们的标准量子力学图片（控制亚原子世界的理论）以深刻的方式修改的模型。这种修饰改变了当时星系的种子是通过原始量子波动创建的，在很早就改变了宇宙的行为。这影响了我们今天观察到的大爆炸的遗物辐射，因此提供了一种测试理论的方法。 我还对假定时空结构在最小的尺度上并不连续的模型感兴趣，例如液态水，而是颗粒状，如沙子。这个想法很重要，因为我们今天在宇宙中看到的一切都是由时空和时间上的波浪形成的。如果我们在过去越来越进一步跟踪这些波浪，它们会变得越来越小，直到它们最终足够微小，可以看到时空的离散，粒状结构。这些波浪的形状以及它们在当今宇宙中产生的结构直接受到过去的行为的影响。因此，有可能看到我们宇宙颗粒状本质在当今天体的位置的回声。通过得出精确的替代理论对观察的替代效果，我希望获得限制或排除这些模型的新的新颖方式，从而使我们更加了解宇宙中重力的真实本质。