Collaborative Research: Probing Dark Lights with Big Bang Nucleosynthesis and the Cosmic Microwave Background

该奖项资助了伊利诺伊大学的布莱恩·菲尔兹教授和加州大学戴维斯分校的劳埃德·诺克斯教授的研究活动。大爆炸核合成(BBN)理论描述了在大爆炸的第一秒钟内产生最轻元素--氢、氦和锂的过程。BBN对宇宙轻元素丰度的预测与观测结果大体一致；这种一致性是热大爆炸模型的一大成功。此外，BBN还提供了宇宙中普通物质(“重子”)含量的量度，以及可见和不可见形式(例如中微子和任何其他形式的“暗光”)的相对论粒子(“辐射”)的总含量。在过去的十年里，宇宙微波背景(CMB)已经成为对宇宙重子的一种精确而独立的测量。因此，比较BBN和CMB重子测量提供了对热大爆炸宇宙学的新的基础性检验，并揭示了一个“锂问题”。BBN/CMB的这一连接现在正准备开启一种全新的可能性。最近和即将对CMB进行的首次测量将不仅同时探测宇宙重子，而且还将探测宇宙辐射以及氦丰度本身。这将使强大的新宇宙学测试成为可能：第一次，BBN的预测可以用非常精确的CMB数据完全验证。协议将戏剧性地证明标准宇宙论的一致性，而任何差异都将探索新的物理。菲尔兹和诺克斯教授将评估和解释BBN和CMB的比较，开发工具来高效和准确地比较BBN和CMB的数据。将首次使用马尔科夫链蒙特卡罗方法来评估BBN的不确定性；这将使BBN预测和CMB数据能够直接和一致地结合在一起，并对结果进行统计表征。作为分析的一部分，将生成、测试并公开发布新的开源BBN代码。预计这项工作将产生更广泛的影响。一个公开可用的开源BBN代码将被发布。此外，CMB和早期宇宙粒子天体物理学社区之间，以及更广泛的粒子天体物理、宇宙学和天文学社区之间将建立新的强大联系。研究生，包括正规的研究指导课程，将接受综合这些方法的培训，并以跨学科的方式工作。此外，教授们还介绍了。菲尔兹将继续实施强有力的、持续的外展计划，其中包括学校访问和公开讲座，将这一前沿科学带给更广泛的受众。

This award funds the research activities of Professor Brian Fields at the University of Illinois and Professor Lloyd Knox at the University of California Davis.The theory of big bang nucleosynthesis (BBN) describes the production of the lightest elements--hydrogen, helium, and lithium--in the first seconds of the big bang. BBN predictions for cosmic light-element abundances are in broad agreement with observations; this concordance is a major success of the hot big bang model. Moreover, BBN provides a measure of the ordinary matter ("baryon") content of the universe, as well as total content in relativistic particles ("radiation") in both visible and invisible form (e.g., neutrinos and any other forms of "dark light"). In the past decade, the cosmic microwave background (CMB) has emerged as a precise and independent measure of cosmic baryons. Comparing BBN and CMB baryon measures thus has provided a new fundamental test of the hot big bang cosmology, and reveal a "lithium problem." This BBN/CMB connection is now poised to open qualitatively new possibilities. Recent and upcoming measurements of the CMB for the first time will simultaneously probe not only cosmic baryons, but also cosmic radiation as well as the helium abundance itself. This will enable powerful new tests of cosmology: for the first time, the predictions of BBN can be tested entirely with very precise CMB data. Agreement would dramatically demonstrate the consistency of the standard cosmology, while any difference probes new physics. Professors Fields and Knox will both evaluate and interpret the BBN-CMB comparison, develop tools to efficiently and accurately compare BBN and CMB data. For the first time, a Markov-chain Monte Carlo approach will be used to evaluate BBN uncertainties; this will allow a direct and consistent means of combining BBN predictions and CMB data and statistically characterizing the results. As part of this analysis, a new open-source BBN code will be produced, tested, and publicly released.It is expected that this work will have substantial broader impacts. A publicly available open source BBN code will be released. Moreover, new and strong links will be forged among the CMB and early-universe particle astrophysics communities, and more widely among the particle astrophysics, cosmology, and astronomy communities. Graduate students, both in formal courses in research mentoring, will be trained to synthesize these approaches and to work in an interdisciplinary way. In addition, Profs. Fields will maintain vigorous, sustained outreach programs which include school visits and public lectures bringing this forefront science to a wider audience.