We explore the possibility of using a gigaparsec-scale local void to reconcile the Hubble tension. Such a gigaparsec-scale void can be produced by multi-stream inflation where different parts of the observable universe follow different inflationary trajectories. These trajectories become different parts of the observable universe after inflation, when these scales return to the horizon. If these trajectories have different e-folding numbers, these parts of the universe have different energy densities, possibly creating a local large void. The impacts of such a void for cosmological observations are studied, especially those involving supernovae, Baryon Acoustic Oscillations (BAO) and the kinetic Sunyaev-Zel’dovich (kSZ) effect. We show that with the presence of the void, supernovae observations may be more consistent with the CMB. We also estimate the impacts of a local large void on BAO observations. In addition, we show that a local large void and hence its capabilities to ease the Hubble tension is limited by the kSZ effect. As a benchmark model, a 1.7 Gpc scale void with boundary width 0.7 Gpc and density contrast −0.14 may ease the Hubble tension, evading the kSZ limit.

中文翻译：

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千兆帕尺度的局部空洞和哈勃张力

我们探索了使用千兆帕斯卡尺度的局部空隙来调和哈勃望远镜张力的可能性。这种千兆帕斯卡级的空隙可以通过多流膨胀产生，在这种多流膨胀中，可观测宇宙的不同部分遵循不同的膨胀轨迹。当这些标度返回到地平线时，这些轨迹在通货膨胀后成为可观察宇宙的不同部分。如果这些轨迹具有不同的电子折叠数，则宇宙的这些部分具有不同的能量密度，可能会产生局部大的空隙。研究了这样一个空隙对宇宙学观察的影响，特别是涉及超新星，重子声振荡（BAO）和动力学Sunyaev-Zel'dovich（kSZ）效应的影响。我们表明，由于存在空隙，超新星观测可能与CMB更加一致。我们还估计了局部大孔隙对BAO观测的影响。此外，我们表明，局部较大的空隙及其缓解哈勃张力的能力受到kSZ效应的限制。作为基准模型，边界宽度为0.7 Gpc且密度对比度为-0.14的1.7 Gpc标度空隙可以缓解哈勃张力，从而避免了kSZ限制。