Probing Fundamental Theories with Early Universe Observations

我研究理论宇宙学和引力理论，使用早期宇宙和黑洞的模型来测试潜在的新物理学。我建议的研究重点是如何通货膨胀结束和宇宙的再加热发生，以及如何在宇宙微波背景辐射和宇宙的大尺度结构中检测到这一过程的可观察痕迹。暴胀的想法巧妙地解决了宇宙学中几个长期存在的问题，并且已经被宇宙微波背景（CMB）各向异性的观测所证实。当宇宙膨胀时，它的内容是冷的。但最终，暴胀必须结束，驱动暴胀的场必须衰变，将能量储存到高能粒子中。这种再加热使真空沸腾，开始了我们所知的热大爆炸历史。当暴胀创造了宇宙中所有的能量时，再加热可能创造了所有的熵。我们对这些能量尺度下的基本物理学知之甚少，宇宙学观测可能是我们在可预见的未来唯一的信息来源。虽然没有光子从这个时代直接到达我们，因为宇宙充满了热等离子体，并且在重组之前是不透明的，但早期宇宙的膨胀历史以原始曲率波动的形式印在天空上，CMB观测刚刚达到所需的精度，以从简单的膨胀导致的高斯波动中解开其他影响。我的方法的准确性使我们能够表明，预热一般会在暴胀产生的曲率波动之上产生原始的非高斯曲率波动，表现在大的宇宙结构以及偏振和温度CMB各向异性中。这种非高斯性往往是间歇性的，并且是由场相空间中非线性演化过程中形成的焦散线驱动的。在最简单的四次预热模型中，它表现为间歇性的冷点，类似于在CMB天空中观察到的冷点。我的近期目标是开发分析工具，在CMB图中搜索这种类型的非高斯性，并探索普朗克数据对预热的约束，以及其他与暴胀所期望的统计各向同性和高斯性的原始波动的一般偏差。为了实现这些目标，我加入了普朗克合作组织，目前我正在为该合作组织研究各向同性和统计分析以及膨胀。从长远来看，我计划研究再加热后热化是如何进行的，并研究大尺度结构的形成如何追踪再加热的原始波动。我的研究计划为HQP培训提供了许多机会，包括行业需求的计算方法和并行计算方面的非常理想的技能，以及使用普朗克最新温度和偏振CMB数据所需的技能。

I work on theoretical cosmology and theories of gravity, using models of the early Universe and black holes to test for potential new physics. My proposed research focuses on how inflation ended and reheating of the universe happened, and how to detect observable traces of this process in the cosmic microwave background radiation and the large scale structure of the universe.***The idea of inflation neatly solves several long-standing issues in cosmology, and has been spectacularly confirmed by observations of the Cosmic Microwave Background (CMB) anisotropies. While the Universe is inflating, its contents are cold. But eventually, inflation has to end and the field driving the inflation must decay, depositing energy into high-energy particles. This reheating "boils" the vacuum and starts the hot big bang history as we know it. While inflation creates all the energy in the universe, reheating likely creates all the entropy. Very little is known about the fundamental physics at these energy scales, and cosmological observations could be our only source of information for the foreseeable future. While no photons reach us directly from this epoch as the universe is filled with hot plasma and is opaque until recombination, the expansion history of the early universe is imprinted on the sky in the form of primordial curvature fluctuations, and CMB observations just reached precision required to disentangle other effects from Gaussian fluctuations due to simple inflation.***The accuracy of my methods enabled us to show that preheating generically creates primordial non-Gaussian curvature fluctuations on top of the ones produced by inflation, manifested in large cosmic structures and as polarization and temperature CMB anisotropies. The non-Gaussianity is often intermittent, and is driven by caustics forming in the nonlinear evolution in the field phase space. In the simplest quartic model of preheating, it is manifested as intermittent cold spots, similar to the one observed on the CMB sky. My immediate goal is to develop analysis tools that search for this type of non-Gaussianity in the CMB maps, and explore constraints Planck data can place on preheating, as well as other generic deviations from the statistical isotropy and Gaussianity of primordial fluctuations one expects from inflation. I joined Planck collaboration to achieve these goals, and I am currently working on isotropy and statistics analysis and inflation for the collaboration. In the long-term, I plan to study how thermalization proceeds after reheating, and investigate how large scale structure formation traces primordial fluctuations from reheating.***My research program provides numerous opportunities for HQP training, including highly desirable skills in computational methods and parallel computing in demand by industry, and access to the skills needed to work with the most recent temperature and polarization CMB data from Planck.