修正重力的观测检验
Observational Tests of Modified Gravity
摘要：
修正的引力理论比传统的暗能量模型对大尺度结构有更丰富的观测结果，因为即使在线性区域，不同的观测量也不是由单一的增长因子描述的。我们检查的度量的潜力，密度和速度场的扰动之间的关系，并讨论使用引力透镜，星系团丰度，星系团/动力学和ISW效应测量它们的策略。我们展示了如何通过结合这些探测器来测试广泛的一类引力理论。解释观测结果的一个可靠方法是约束两个关键函数：两个度量势的比值，以及泊松方程中引力“常数”与牛顿常数的比值。我们还讨论了携带重力签名的准线性效应，例如通过诱导的三点相关性。暗能量的聚集可以模仿修改后的引力理论的特征，从而混淆了对这些理论的不同特征的搜索。它可以产生压力扰动和各向异性应力，甚至在广义相对论中也打破了两个度规势之间的相等性。有了这两个额外的自由度，一个聚集的暗能量模型能在所有的观测测试中模仿修改后的引力模型吗？我们用具体的例子表明，对度量势和密度扰动的观测约束原则上可以区分引力修正和暗能量模型。我们将我们的结果与其他最近的研究进行了比较，这些研究的假设略有不同（并且结论明显矛盾）。
英文摘要：
Modified gravity theories have richer observational consequences for large-scale structure than conventional dark energy models, in that different observables are not described by a single growth factor even in the linear regime. We examine the relationships between perturbations in the metric potentials, density and velocity fields, and discuss strategies for measuring them using gravitational lensing, galaxy cluster abundances, galaxy clustering/dynamics and the ISW effect. We show how a broad class of gravity theories can be tested by combining these probes. A robust way to interpret observations is by constraining two key functions: the ratio of the two metric potentials, and the ratio of the Gravitational ``constant'' in the Poisson equation to Newton's constant. We also discuss quasilinear effects that carry signatures of gravity, such as through induced three-point correlations. Clustering of dark energy can mimic features of modified gravity theories and thus confuse the search for distinct signatures of such theories. It can produce pressure perturbations and anisotropic stresses, which breaks the equality between the two metric potentials even in general relativity. With these two extra degrees of freedom, can a clustered dark energy model mimic modified gravity models in all observational tests? We show with specific examples that observational constraints on both the metric potentials and density perturbations can in principle distinguish modifications of gravity from dark energy models. We compare our result with other recent studies that have slightly different assumptions (and apparently contradictory conclusions).
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