Probing Fundamental Theories with Early Universe Observations

我从事理论宇宙学和引力理论的工作，使用早期宇宙和黑洞的模型来测试潜在的新物理。我提出的研究重点是宇宙膨胀如何结束和重新升温，以及如何在宇宙微波背景辐射和宇宙大尺度结构中探测到这一过程的可观测痕迹。*膨胀的想法巧妙地解决了宇宙学中的几个长期存在的问题，并已被宇宙微波背景(CMB)各向异性的观测所壮观地证实。虽然宇宙在膨胀，但它的内容却是冷的。但最终，通胀必须结束，推动通胀的磁场必须衰落，将能量储存到高能粒子中。这种再加热“煮沸”真空，开启了我们所知的热大爆炸历史。虽然膨胀创造了宇宙中的所有能量，但再加热可能创造了所有的熵。人们对这些能量尺度下的基本物理知之甚少，在可预见的未来，宇宙学观测可能是我们唯一的信息来源。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，而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观测刚刚达到了从简单膨胀引起的高斯波动中分离其他影响所需的精度。*我方法的准确性使我们能够证明，预热通常会在膨胀产生的原始非高斯曲率波动的基础上产生原始非高斯曲率波动，这表现在大型宇宙结构中，并表现为偏振和温度CMB各向异性。非高斯性通常是间歇性的，是由场的相空间中的非线性演化形成的焦散线驱动的。在最简单的预热四次模型中，它表现为间歇性冷点，类似于在CMB天空中观察到的冷点。我的直接目标是开发分析工具，在CMB地图中搜索这种类型的非高斯性，并探索普朗克数据可以对预热施加的限制，以及与人们对通胀预期的原始波动的统计各向同性和高斯性的其他一般性偏差。为了实现这些目标，我加入了普朗克协作，目前我正在为该协作进行各向同性、统计分析和通胀方面的工作。从长远来看，我计划研究重新加热后的热化过程，并调查大规模结构形成如何跟踪重新加热产生的原始波动。*我的研究计划为HQP培训提供了大量机会，包括非常理想的计算方法技能和行业需求的并行计算，以及获得使用普朗克最新温度和极化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.