Collaborative Research: Imaging the Beginning of Time from the South Pole: The next Stage of the BICEP Program

大爆炸理论为宇宙从其已知的最早时期到随后的大规模演化提供了一个完善的宇宙学模型。该模型从非常高密度和温度状态的初始条件开始追踪宇宙的膨胀，这种状态几乎但不是完全平滑的，它对一系列目前已知的现象提供了全面的解释，包括轻元素的丰度、宇宙微波背景辐射和大尺度结构的分布。虽然已建立的“大爆炸”理论留下了解释初始条件的悬而未决的问题，但目前的证据与整个可观测宇宙是在持续约万亿分之一秒的亚核体积戏剧性、指数级的“膨胀”中产生的。在这一短暂的通货膨胀期之后，宇宙继续膨胀，但速度较慢。虽然基本的“膨胀范式”被大多数科学家接受，但导致膨胀的详细粒子物理机制仍不为人所知。据信，这种剧烈的时空膨胀会产生原始引力波，现在正在膨胀的宇宙中传播，从而形成宇宙引力波背景(CGB)，其幅度测量膨胀的能量尺度。CGB在宇宙微波背景(CMB)的偏振信号上留下了一个微弱的印记，而探测这个偏振信号可以说是当今宇宙学最重要的目标。该奖项将回答人类有史以来提出的最古老的问题之一--“宇宙是如何开始的？”它是通过在地球上最有趣的地方之一--南极洲的南极站--进行的观测而获得的。由社区推动的2010年天体十年调查将寻找CGB描述为“最激动人心的探索”，强调“需要对旨在探测CMB(B模式)极化的系统进行中期投资”。2005年，NASA/DOE/NSF CMB研究任务组将这一主题确定为该领域的最高优先事项，并确定了引力波与密度涨落之比的目标灵敏度为r~0.01。这样的测量承诺了对慢滚膨胀模型的明确测试，这些模型通常预测引力波信号在r~0.01或更高，产生CMB B模波动，在度角尺度上达到峰值。正在进行的BICEP系列实验致力于实现这一科学目标。该实验于2006年开始在南极运行，并一直在银河系前景中被称为南洞的低空区域无情地绘制出800平方度的天空区域。该奖项将通过BICEP阵列计划支持CMB“第三阶段”科学的科学观测和分析，该计划将在五个频段测量极化天空。据预测，在保守地考虑了银河系尘埃、银河系同步辐射和CMB透镜前景后，它对膨胀引力波的幅度将达到0.005的最终敏感性。这一衡量标准将对大多数慢速通胀模型进行最终检验，并将实现或超过工作组在2005年设定的敏感性目标。该项目将继续在这方面有出色记录的实验室为本科生、研究生和博士后研究员(包括来自任职人数不足的群体)提供出色的培训。宇宙学和南极洲的研究都吸引了公众的想象力，使这种结合成为激发人们对科学感兴趣的非常有效的工具。

The theory of the "Big Bang" provides a well-established cosmological model for the Universe from its earliest known periods through its subsequent large-scale evolution. The model traces the expansion of the Universe, starting from initial conditions of a very high density and temperature state which is almost but not perfectly smooth, and it offers a comprehensive explanation for a broad range of now-known phenomena, including the abundance of light elements, the cosmic microwave background radiation, and the distribution of large scale structures. While the established "Big Bang" theory leaves open the question of explaining the initial conditions, current evidence is consistent with the entire observable Universe being spawned in a dramatic, exponential "inflation" of a sub-nuclear volume that lasted about one trillionth of a trillionth of a trillionth of a second. Following this short inflationary period, the Universe continues to expand, but at a less rapid rate. While the basic "inflationary paradigm" is accepted by most scientists, the detailed particle physics mechanism responsible for inflation is still not known. It is believed that this violent space-time expansion would have produced primordial gravitational waves now propagating through the expanding universe, thus forming a cosmic gravitational-wave background (CGB) the amplitude of which measures the energy scale of inflation. The CGB imprints a faint signature in the polarization of the Cosmic Microwave Background (CMB), and detecting this polarization signature is arguably the most important goal in cosmology today. This award will address one of the oldest questions ever posed by mankind, "How did the Universe begin?", and it does so via observations made at one of the most intriguing places on Earth, South Pole Station in Antarctica. The community-driven Astro2010 Decadal Survey described the search for the CGB as "the most exciting quest of all", emphasizing that "mid-term investment is needed for systems aimed at detecting the (B-mode) polarization of the CMB". In 2005, the NASA/DOE/NSF Task Force on CMB Research identified this topic as the highest priority for the field and established a target sensitivity for the ratio of gravitational waves to density fluctuations of r ~ 0.01. Such measurements promise a definitive test of slow-roll models of inflation, which generally predict a gravitational-wave signal around r~0.01 or above, producing CMB B-modes fluctuations that peak on degree angular scales. The ongoing BICEP series of experiments is dedicated to this science goal. The experiment began operating at South Pole in 2006 and has been relentlessly mapping an 800 square degree region of the sky in a region of low in Galactic foregrounds known as the Southern Hole. This award will support science observations and analysis for the CMB "Stage 3" science with the BICEP Array program that will measure the polarized sky in five frequency bands. It is projected to reach an ultimate sensitivity to the amplitude of inflationary gravitational waves of "sigma r" 0.005, extrapolating from achieved performance and after conservatively accounting for the Galactic dust, Galactic synchrotron radiation, and CMB lensing foregrounds. This measurement will offer a definitive test of most slow-roll models of Inflation, and will realize or exceed the goals set by the Task Force in 2005 for sensitivity. The project will continue to provide excellent training for undergraduate and graduate students and postdoctoral fellows (including those from underrepresented groups) in laboratories that have exceptional track records in this regard. Cosmology and research in Antarctica both capture the public imagination, making this combination a remarkably effective vehicle for stimulating interest in science.