RUI: Looking beyond LCDM-- observational consequences of models that ease the Hubble tension

在过去的二十年里，宇宙学测量的精确度越来越高，揭示了挑战标准宇宙学模型的有趣张力。其中最紧迫的问题是科学家们在估计当前宇宙膨胀率（即哈勃常数）的两种不同方法之间存在分歧。一种估计是基于对超新星的直接观测；另一种是基于间接测量，利用对大爆炸余辉的观测。虽然这两种估计的数据过去是一致的，但测量精度的进步现在使哈勃常数的值在统计上有所不同。这种“哈勃张力”可能会向科学家们指出标准宇宙模型中没有包含的新的、意想不到的物理学。拟议的研究将通过细化这种张力可能意味着新的和意想不到的物理过程来推进宇宙学领域，这样做有可能增强我们对宇宙起源和演化的理解。随着宇宙学观测变得更加精确，数据中的张力也出现了。其中最重要的是“哈勃张力”，在测量当前宇宙膨胀率（称为哈勃常数）的几种独立方法之间有4-6西格玛的分歧。这些方法可以根据它们的测量是间接的（涉及宇宙微波背景或重子声学振荡）还是直接的（涉及校准的Ia型超新星或强透镜时间延迟）进行分组。有趣的是，间接方法发现的共同值低于使用直接探针发现的值。很难在标准宇宙模型的背景下解释这种张力，但最近的工作已经将这种张力解释为早期宇宙中额外物质（具有一组特定属性）的证据，非标准中微子相互作用的证据，或者在形成宇宙微波背景的过程中电子与质子重新结合的方式的修改。拟议的研究将探索这些模型的基本观测结果，阐明解决哈勃张力所需的基本动力学，创造新的工具来表征其预测特征，并阐明其新颖和意想不到的动力学。这项研究的结果将通过提供必要的工具来确定哈勃张力是否为我们提供了对标准宇宙学模型的重大修订。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over the past twenty years, greater precision in cosmological measurements have revealed intriguing tensions that challenge the standard cosmological model. The most pressing of these is a disagreement between two distinct ways scientists estimate the current expansion rate of the universe (known as the Hubble constant). One estimate is based on direct measurement that uses observations of supernovae; the other is based on indirect measurement that uses observations of the afterglow of the big bang. Whereas the data from these two estimates used to agree, advances in measurement precision now yield values for the Hubble constant that are statistically different. This ‘Hubble tension’ may be pointing scientists to new and unexpected physics not included in the standard cosmological model. The proposed research will advance the field of cosmology by refining what this tension may signify about new and unanticipated physical processes and in doing so has the potential to enhance our understanding of the origin and evolution of the universe. As cosmological observations have become more precise, tensions in the data have appeared. The most significant of these is the “Hubble tension”, a 4-6 sigma disagreement between several independent methods to measure the current expansion rate of the universe (known as the Hubble constant). These methods can be grouped based on whether their measurements are indirect (involving the cosmic microwave background or baryon acoustic oscillations) or direct (involving calibrated type Ia supernovae or strong lens time delays). Intriguingly, the indirect methods find a common value that is lower than those found using direct probes. It has been difficult to explain this tension in the context of the standard cosmological model, but recent work has interpreted this tension as evidence for either additional material in the early universe (with a particular set of properties), for non-standard neutrino interactions, or for modifications to the way in which the electrons recombined with protons during the process that formed the cosmic microwave background. The proposed research will explore the essential observational consequences of these models, articulate the basic dynamics required to resolve the Hubble tension, create new tools with which to characterize their predicted features, and articulate their novel and unexpected dynamics. The outcome of this research will advance the field of cosmology by providing the necessary tools to establish if the Hubble tension is pointing us towards a significant revision of our standard cosmological modelThis 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.