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

“大爆炸”理论为宇宙从最早的已知时期到随后的大规模演化提供了一个完善的宇宙学模型。该模型追溯了宇宙的膨胀，从一个非常高的密度和温度状态的初始条件开始，这几乎是但不是完全光滑的，它为广泛的已知现象提供了一个全面的解释，包括轻元素的丰度，宇宙微波背景辐射，以及大尺度结构的分布。虽然已确立的“大爆炸”理论没有解释初始条件的问题，但目前的证据表明，整个可观测宇宙是在亚核体积的剧烈指数“膨胀”中产生的，持续时间约为万亿分之一秒的万亿分之一秒。在这个短暂的暴胀期之后，宇宙继续膨胀，但速度变慢了。虽然基本的“暴胀范式”被大多数科学家所接受，但导致暴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），其振幅可以衡量暴胀的能量尺度。CGB在宇宙微波背景（CMB）的极化中留下了微弱的特征，探测这种极化特征可以说是当今宇宙学中最重要的目标。这个奖项将解决人类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察来实现的。社区推动的Astro2010年十年调查将对CGB的搜索描述为“最令人兴奋的探索”，强调“中期投资需要用于探测CMB （b模）极化的系统”。2005年，NASA/DOE/NSF CMB研究工作组将该课题确定为该领域的最高优先级，并确定了引力波与密度波动之比的目标灵敏度为r ~ 0.01。这样的测量有望对慢滚膨胀模型进行决定性的测试，该模型通常预测引力波信号在r~0.01或更高，产生以度角尺度达到峰值的CMB b模式波动。正在进行的BICEP系列实验致力于实现这一科学目标。这项实验于2006年开始在南极进行，并一直在不懈地绘制一个800平方度的天空区域，这个区域位于银河系前景较低的地方，被称为“南洞”。该奖项将通过BICEP阵列计划支持CMB“第三阶段”科学观测和分析，该计划将测量五个频段的极化天空。在保守地考虑了银河系尘埃、银河系同步辐射和CMB透镜前景之后，根据已经取得的成绩推断，预计它对暴胀引力波振幅的最终灵敏度将达到“sigma r”0.005。这项测量将为大多数慢滚动膨胀模型提供一个明确的测试，并将实现或超过工作组在2005年为灵敏度设定的目标。该项目将继续为本科生、研究生和博士后（包括那些来自代表性不足群体的人）提供优秀的培训，这些实验室在这方面有特殊的记录。宇宙学和南极洲的研究都吸引了公众的想象力，使这一组合成为激发科学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.