标题： 关于“由剪切和广义黏性加速的宇宙膨胀” 显示英文标题

标题： Comment on "Accelerating cosmological expansion from shear and bulk viscosity"

摘要： 在最近的一封信[Phys. Rev. Lett. 114 091301 (2105)]中，即使没有整体粘度的贡献，当前宇宙加速的原因也被确定为具有缺陷的相对论流体的剪切粘度。本文的主要观点是，如果存在的话，剪切粘度只能在充分小于哈勃半径内的足够小尺度上导致膨胀加速。 显示英文摘要

摘要： In a recent Letter [Phys. Rev. Lett. 114 091301 (2105)] the cause of the acceleration of the present Universe has been identified with the shear viscosity of an imperfect relativistic fluid even in the absence of any bulk viscous contribution. The gist of this comment is that the shear viscosity, if anything, can only lead to an accelerated expansion over sufficiently small scales well inside the Hubble radius.