用环境相关的速度统计来区分筛选机制
Distinguishing screening mechanisms with environment-dependent velocity statistics
摘要：
引力的替代理论通常会调用一种依赖于环境的筛选机制，以允许在现象学上有趣的偏离广义相对论（GR）在更大的尺度上表现出来，而在小尺度上则减少到GR。从屏蔽到非屏蔽行为的转变的观察将是超越GR物理学的令人信服的证据。我们表明，成对的奇特的速度统计，特别是相对径向速度色散，$σ_\parallel$，可以用来观察这种转变时，他们被分仓的一些措施晕环境。我们建立了这一点，通过测量径向速度之间的分散对晕在N体模拟三个$f(R)$重力和四个电子模型。我们开发了一个估计只涉及视线速度，以表明这个量是可观察的，并在晕质量，环境密度和孤立晕的结果。周围的密度被认为是最相关的环境措施，它是不同的孤立，以及相关的理论预期的Escherichon模型。通过在环境密度中对$σ_\parallel$进行分仓，我们发现了一个强烈的环境依赖的签名，该签名的速度显示出从GR到非GR行为的明显过渡。对于$f(R)$，未观察到这种转变，因为相关尺度在未筛选状态下很深。在即将到来的特殊速度调查的相对径向速度分散的观测，如果适当的环境，因此，提供了一个有价值的方式来检测修改重力的筛选签名。
英文摘要：
Alternative theories of gravity typically invoke an environment-dependent screening mechanism to allow phenomenologically interesting deviations from general relativity (GR) to manifest on larger scales, while reducing to GR on small scales. The observation of the transition from screened to unscreened behavior would be compelling evidence for beyond-GR physics. We show that pairwise peculiar velocity statistics, in particular the relative radial velocity dispersion, $σ_\parallel$ , can be used to observe this transition when they are binned by some measure of halo environment. We established this by measuring the radial velocity dispersion between pairs of halos in N-body simulations for three $f(R)$ gravity and four symmetron models. We developed an estimator involving only line-of-sight velocities to show that this quantity is observable, and binned the results in halo mass, ambient density, and the isolatedness of halos. Ambient density is found to be the most relevant measure of environment; it is distinct from isolatedness, and correlates well with theoretical expectations for the symmetron model. By binning $σ_\parallel$ in ambient density, we find a strong environment-dependent signature for the symmetron models, with the velocities showing a clear transition from GR to non-GR behavior. No such transition is observed for $f(R)$, as the relevant scales are deep in the unscreened regime. Observations of the relative radial velocity dispersion in forthcoming peculiar velocity surveys, if binned appropriately by environment, therefore offer a valuable way of detecting the screening signature of modified gravity.
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