Searching for the Stochastic Gravitational-Wave Background with Advanced LIGO

利用先进的 LIGO 寻找随机引力波背景

• 批准号: 1505870
• 负责人: Vuk Mandic
• 金额: $ 36万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505870&HistoricalAwards=false
• 关键词: Searching; Stochastic; Gravitational; Wave; Background

Among the key predictions of Einstein's General Theory of Relativity is the existence of gravitational waves (GW): ripples moving at the speed of light in the geometry of space-time caused by the fast motion of large masses. Although well tested in terms of their indirect effects, the direct detection of gravitational waves incident on Earth poses an outstanding challenge. The scientific rewards from achieving this ability would be enormous - ranging from probing the extreme dynamics of exploding stars to gleaning information about the state of the Universe almost at the moment of the Big Bang itself. The effort to enable this new window on the Universe has occupied several decades of experimental and technological developments that have pushed the boundaries across diverse fields in the physical sciences. The year 2015 will mark a highly-anticipated watershed moment for the goal of direct detection of gravitational waves, as the second generation of gravitational-wave detectors is commissioned at the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO). The sensitivity of the new aLIGO detectors will be ramped up to become about ten times better than that of the first-generation detectors, opening up a spatial volume for observing GW sources that will be 1000 times larger than before. The aLIGO data will be used to search for a variety of astrophysical and cosmological gravitational wave sources. This specific award will support research that searches the aLIGO data to look for the background signals that arise from gravitational-wave signals from many independent sources. The first observation data from aLIGO is expected in 2015, with the sensitivity and duty-cycle of the detectors steadily increasing over the following three years. This project focuses on the searches for the stochastic gravitational wave background (SGWB), which arises from an incoherent superposition of gravitational-wave signals generated by many independent sources. The SGWB could be of cosmological origin: for example, in inflationary models the SGWB is generated just moments after the Big Bang, implying that the SGWB may contain unique information about the first moments in the evolution of the universe and about the physics of energy scales not accessible in laboratories. Similarly, the SGWB could be of astrophysical origin: for example, summing up contributions from all magnetars or from coalescences of all binary neutron stars and/or black holes in the universe leads to a stochastic gravitational-wave "foreground" that contains information about these most violent objects and events in the universe. The SGWB searches with aLIGO data will be conducted using cross-correlation techniques that were developed and successfully used in the SGWB searches with initial LIGO data. The searches for isotropic SGWB are expected to result in a measurement about 1000x more sensitive than the current best upper limits. Similarly, the searches for anisotropic SGWB will result in about 100x more sensitive measurement than the current best upper limits. Such substantial advances will result in a series of interesting cosmological and astrophysical implications, including detection or new constraints on parity violation in the early universe, evolution of the universe during the first minute after the Big Bang, equation of state in neutron stars, rate of compact binary coalescences and its evolution with redshift.

爱因斯坦广义相对论的关键预测之一是引力波（GW）的存在：由大质量的快速运动引起的时空几何中以光速移动的涟漪。尽管在间接影响方面经过了充分的测试，但直接探测地球上入射的引力波仍面临着巨大的挑战。实现这种能力所带来的科学回报将是巨大的——从探索爆炸恒星的极端动力学到收集几乎在大爆炸本身时刻的宇宙状态信息。为了实现这一观察宇宙的新窗口，我们花费了数十年的实验和技术发展，突破了物理科学不同领域的界限。 2015 年将成为直接探测引力波目标的一个备受期待的分水岭，因为第二代引力波探测器将在先进激光干涉仪引力波天文台 (aLIGO) 投入使用。 新型aLIGO探测器的灵敏度将比第一代探测器提高约10倍，为观测引力波源开辟了比以前大1000倍的空间体积。 aLIGO 数据将用于搜索各种天体物理和宇宙学引力波源。 该奖项将支持搜索 aLIGO 数据的研究，以寻找来自许多独立来源的引力波信号产生的背景信号。 aLIGO 预计将于 2015 年提供第一份观测数据，探测器的灵敏度和占空比将在接下来的三年内稳步提高。 该项目的重点是寻找随机引力波背景（SGWB），它是由许多独立源产生的引力波信号的不相干叠加产生的。 SGWB 可能具有宇宙学起源：例如，在暴胀模型中，SGWB 是在大爆炸后不久生成的，这意味着 SGWB 可能包含有关宇宙演化最初时刻和能量尺度物理的独特信息在实验室中无法访问。类似地，SGWB 可能具有天体物理学起源：例如，将宇宙中所有磁星或所有双中子星和/或黑洞的聚结的贡献相加，得到一个随机引力波“前景”，其中包含有关这些的信息。宇宙中最暴力的物体和事件。 使用 aLIGO 数据进行 SGWB 搜索将使用互相关技术进行，该技术是在使用初始 LIGO 数据进行 SGWB 搜索时开发并成功使用的。对各向同性 SGWB 的搜索预计将产生比当前最佳上限灵敏约 1000 倍的测量结果。同样，对各向异性 SGWB 的搜索将导致比当前最佳上限高约 100 倍的测量灵敏度。这些重大进展将带来一系列有趣的宇宙学和天体物理学意义，包括早期宇宙宇称不守恒的探测或新限制、大爆炸后第一分钟的宇宙演化、中子星的状态方程、致密二元合并及其红移演化。