Cosmological and Astrophysical Signatures of Axions

该奖项资助莱斯大学安德鲁·朗教授的研究活动。40多年前，人们提出了一种假设的基本粒子，即轴子，用来解释中子的一个令人困惑的特性。在接下来的几十年里，人们一直在进行实验活动，试图在实验室中探测轴子和类轴子粒子。通过他的工作，朗教授的目标是对轴子的几个宇宙学和天体物理学特征做出可靠的预测。这些理论预测将激发未来的观测，促进数据的解释，目标是使发现轴子成为可能。这些努力通过促进基础科学的进步来促进国家利益，因为轴子的发现将对我们对自然规律和宇宙组成的理解产生深远的影响。除了其核心科学目标之外，该项目还将产生更广泛的重大影响。至少有一名研究生研究员将协助龙教授的研究，从而为早期职业物理学家提供必要的培训机会。此外，龙教授还将在当地高中进行讲座，并邀请学生参观大学校园，以鼓励下一代科学家。从技术上讲，这个研究项目分为三个目标。首先，龙教授的研究小组将研究轴子弦如何在宇宙微波背景辐射的极化上留下微妙的印记。他们将结合分析和数值方法计算适当的两点相关函数，并通过将这些预测与现有数据和下一代调查的预测灵敏度进行比较，他们将评估这些宇宙学测量对探测轴子弦的有效性。其次，他们将研究当轴子星穿越中子星的强磁场环境时产生的电磁辐射。他们将用数值晶格模拟来模拟这个系统，计算结果的辐射谱，直接从模拟中得到，也使用偶极子近似，并评估用无线电观测来探测这种辐射的前景。作为第三个也是最后一个目标，PI小组将研究包括我们自己的太阳在内的恒星发出的轴子粒子。通过关注以前未被研究过的轴子粒子和普通物质之间的相互作用，该小组将计算这些恒星产生的轴子通量，评估这种辐射对恒星温度的影响，并评估最近与恒星轴子发射有关的异常的含义。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。

This award funds the research activities of Professor Andrew Long at Rice University. Over 40 years ago a hypothetical elementary particle known as the axion was proposed to explain a perplexing property of the neutron. For the following decades experimental campaigns have been underway to try to detect axions and axion-like particles in the laboratory. Through his work Professor Long aims to make robust predictions for several cosmological and astrophysical signatures of axions. These theoretical predictions will motivate future observations and facilitate the interpretation of data, with the goal of making possible the discovery of the axion. These efforts advance the national interest by promoting the progress of fundamental science, since the discovery of an axion would have deep and far-reaching implications for our understanding of the laws of nature and the composition of the Universe. In addition to its central science objectives, this project will have substantial broader impacts. At least one graduate student researcher will assist Professor Long’s research, thereby providing an opportunity for essential training of early-career physicists. In addition, Professor Long will deliver lectures at local high schools and invite students to visit the campus of his university in order to encourage the next generation of scientists. More technically, this research program is divided into three objectives. First, Professor Long's research group will study how axion strings may leave a subtle imprint on the polarization of the cosmic microwave background radiation. They will calculate the appropriate two-point correlation function using a combination of analytical and numerical methods, and by comparing these predictions with the existing data and the projected sensitivities of next-generation surveys, they will evaluate the efficacy of these cosmological measurements to probe axion strings. Second, they will study the electromagnetic radiation produced when an axion star transits the strong magnetic field environment of a neutron star. They will model this system with a numerical lattice simulation, calculate the resultant radiation spectrum, both directly from the simulation as well as using a dipole approximation, and assess the prospects for detecting this radiation with radio observations. As the third and final objective, the PI’s group will study the emission of axion particles from stars including our own Sun. By focusing on a previously-unstudied interaction between the axion particles and ordinary matter, the group will calculate the flux of axions produced by these stars, evaluate the effect that this radiation has on the temperature of the star, and assess the implications for recent anomalies related to stellar axion emission.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.