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Understanding Quantum Gravity from Very Early Universe

从早期宇宙了解量子引力

基本信息

批准号：
2308845
负责人：
Anzhong Wang
金额：
$ 15万
依托单位：
Baylor University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2023
资助国家：
美国
起止时间：
2023-05-01 至 2026-04-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2308845&HistoricalAwards=false
关键词：
Understanding Quantum Gravity Very Early

项目摘要

A theory of quantum gravity still remains elusive, despite enormous efforts in the past century. Quantum gravity is needed not only for conceptual reasons but also for the understanding of fundamental issues in physics, such as the big bang and black hole singularities. Various candidates have been proposed, and the research supported by this grant is devoted to loop quantum gravity. When applying it to cosmology - the loop quantum cosmology, a coherent picture of Planck scale physics has emerged: the big bang singularity is replaced by a quantum bounce, purely due to quantum geometric effects. This research investigates systematically this and related issues and shall combine studies in challenging physics problems with advanced mathematical methods, which will provide outstanding opportunities for students and collaborators across several different areas of physics and applied mathematics. The theory, techniques and methods to be developed will be used not only in the aforementioned fields, but also in a wider range of fundamental issues in physics and applied mathematics. Particular attention will be put to recruit and attract students from under-represented groups in STEM fields and engineering.Despite the various successes of Loop Quantum Cosmology (LQC), an important issue is its connection to loop quantum gravity (LQG). The starting point of LQC is first to reduce the Hamiltonian by imposing homogeneity and then to quantize the classically reduced Hamiltonian by using the techniques of LQG. However, in LQG the processes of symmetry reduction and quantization do not commute in general, and it is important to understand how well the physics of the full LQG is captured by LQC. In the past couple of years, modified loop quantum cosmologies have been intensively studied, and the progress made so far is very encouraging, but several fundamental questions still remain, due to the dramatic change of the evolution of the universe in the pre-bounce phase. The research of this award will be devoted to investigating systematically: (i) quantum cosmological perturbations and initial conditions from the full theory of loop quantum gravity; (ii) the evolutions of inhomogeneities, anisotropies and non-Gaussianities; and (iii) resolutions of anomalies found in recent cosmological observations, and observational signals of loop quantum gravity for current and forthcoming observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

尽管在过去的世纪里人们付出了巨大的努力，但量子引力理论仍然难以捉摸。量子引力不仅是概念上的需要，也是理解物理学基本问题的需要，比如大爆炸和黑洞奇点。已经提出了各种候选人，这项资助支持的研究致力于圈量子引力。当把它应用到宇宙学--圈量子宇宙学时，普朗克尺度物理学的一个连贯的图景出现了：大爆炸奇点被量子反弹所取代，纯粹是由于量子几何效应。本研究系统地调查这一问题和相关问题，并应结合联合收割机研究具有挑战性的物理问题与先进的数学方法，这将为学生和合作者在物理学和应用数学的几个不同领域提供出色的机会。要开发的理论，技术和方法不仅将用于上述领域，而且还将用于物理学和应用数学中更广泛的基本问题。尽管圈量子宇宙学（LQC）取得了各种成功，但一个重要的问题是它与圈量子引力（LQG）的联系。LQC的出发点是首先通过施加齐次性来约化哈密顿量，然后利用LQG的技术对经典约化的哈密顿量进行反演算。然而，在LQG中，对称性约化和量子化的过程一般不会交换，重要的是要理解LQC对完整LQG物理的捕获程度。在过去的几年里，修正的圈量子宇宙学得到了深入的研究，迄今为止取得的进展是非常令人鼓舞的，但由于宇宙在前反弹阶段的演化发生了巨大变化，一些基本问题仍然存在。该奖项的研究将致力于系统地研究：（一）圈量子引力完整理论中的量子宇宙学扰动和初始条件;（二）非均匀性、各向异性和非高斯性的演化;以及（iii）最近宇宙学观测中发现的异常的分辨率，该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的学术价值和更广泛的影响审查标准。