Collaborative Research: Using the Lyman Alpha Forest to Probe the Structure of the Universe

在过去的几年里，天文学家已经证明，遥远星系中的超新星（SN）比预期的要暗淡。最明显的解释是，它们比我们想象的要远。如果这是真的，这意味着宇宙的膨胀正在加速。理论物理学把这种膨胀的变化归因于所谓的“真空能”。这一发现既带来了重大的新机遇，也带来了一长串令人不安的基本新问题。到目前为止，引力一直是物理学中最难理解的部分，部分原因是它被描述为一个单一的数字：牛顿引力常数G，用来测量它的强度。如果宇宙在加速，那么肯定有第二个数字，这应该有助于我们理解引力物理学。通过这种方式，天文观测正在重新定义我们对基础物理学和整个宇宙的理解。该项目的目标是对宇宙中70%的能量密度是某种形式的神秘真空能量的说法进行独立检验。天文观测是通过实验探索真空能的唯一途径，因为真空能的效应只有在极远的距离上才有意义。特别是，这个项目将通过使用角尺寸作为距离测量来提供对超新星结果的独立检查。星系之间气体的聚集量将沿着视线和横跨天空的角度进行测量。这两种测量之间的关系给出了宇宙的距离，从而给出了宇宙的加速度。这种方法对宇宙长期状态的变化不敏感。这个项目是紧急的，因为真空能仍然是一个未经证实的结果，虽然非常可信，但意义重大，因为我们将有足够的灵敏度，果断地排除超新星所暗示的真空能的数量，如果没有真空能存在的话。除了提供对SN减速宇宙测量的独立检查外，该项目还将改进早期星系间气体聚集的测量。这种团块被认为是由宇宙年轻时的原始量子涨落引起的。这些波动是在不同的时期以不同的方式测量的。然而，目前项目中使用的方法将提供唯一的测量早期星系尺度上物质聚集量的方法。这些新的数据和模拟将与理论预测进行比较，以检验最近的研究，这些研究表明，我们目前关于宇宙中小尺度结构增长的想法是不充分的。本项目由美国国家科学基金会星系外天文学和宇宙学项目（AST/EXC）资助

AST 0098731Tytler In the last few years, astronomers have shown that supernovae (SN), in distant galaxies are fainter than expected. The obvious explanation is that they are farther away than we had thought. If true, this implies that the expansion of the universe is speeding up. This change in expansion is attributed to a so called "vacuum energy" by theoretical physics. This discovery presents both major new opportunities, and a long list of troubling basic new questions. Up to now Gravity has been the hardest part of physics to understand, in part because it has been described by a single number: the Newtonian gravitational constant G which measures its strength. If the universe is speeding up there must be a second number, which should help us understand gravitational physics. In this way, astronomical observations are redefining our understanding of fundamental physics and the universe as a whole. The goals of this project are to provide an independent check of the claim that 70% of the energy density of the universe is some form of mysterious vacuum energy. Astronomical observations are the only way to explore the vacuum energy experimentally, because the effects are significant only over exceedingly large distances. In particular, this project will provide an independent check of the results from supernovae by using angular size as a distance measure. The amount of clumping of the gas between the galaxies will be measured both along the line of sight, and in angle across the sky. The relationship between the two measures gives the distance and hence the acceleration of the universe. The method is insensitive to changes in the state of the universe over long times. The project is urgent, because the vacuum energy remains an unconfirmed, though very plausible, result, and highly significant, because we will have the sensitivity to decisively rule out the amount of vacuum energy suggested by the supernovae, if none were present. In addition to providing an independent check on the SN decelerating universe measurement, this project will also give improved measurements of the clumping of gas between galaxies at early times. This clumping is believed to have arisen from primordial quantum fluctuations when the universe was young.. These fluctuations have been measured at different epochs, and in different ways. However, the methods used in the present project will give the only measurement of the amount of clumping of matter on galaxy sized scales at early times. These new data and simulations will be compared with theoretical predictions, to act as a check on recent investigations which suggest that our present ideas about the growth of small scale structure in the universe are inadequate. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***