23.1. Motivation and Introduction The standard Big-Bang model of cosmology provides a successful framework in which to understand the thermal history of our Universe and the growth of cosmic structure, but it is essen...23.1. Motivation and Introduction The standard Big-Bang model of cosmology provides a successful framework in which to understand the thermal history of our Universe and the growth of cosmic structure, but it is essentially incomplete. As described in Sec. 22.2.4 in ＂Big Bang Cosmology＂ review, Big-Bang cosmology requires very specific initial conditions. It postulates a uniform cosmological background, described by a spatially-flat, homogeneous and isotropic Robertson-Walker （RW） metric （Eq. （22.1） in ＂Big Bang Cosmology＂ review）, with scale factor R（t）. Within this setting, it also requires an initial almost scale-invariant distribution of primordial density perturbations as seen, for example, in the cosmic microwave background （CMB） radiation （described in Chap. 28, ＂Cosmic Microwave Background＂ review）, on scales far larger than the causal horizon at the time the CMB photons last scattered.展开更多
文摘23.1. Motivation and Introduction The standard Big-Bang model of cosmology provides a successful framework in which to understand the thermal history of our Universe and the growth of cosmic structure, but it is essentially incomplete. As described in Sec. 22.2.4 in ＂Big Bang Cosmology＂ review, Big-Bang cosmology requires very specific initial conditions. It postulates a uniform cosmological background, described by a spatially-flat, homogeneous and isotropic Robertson-Walker （RW） metric （Eq. （22.1） in ＂Big Bang Cosmology＂ review）, with scale factor R（t）. Within this setting, it also requires an initial almost scale-invariant distribution of primordial density perturbations as seen, for example, in the cosmic microwave background （CMB） radiation （described in Chap. 28, ＂Cosmic Microwave Background＂ review）, on scales far larger than the causal horizon at the time the CMB photons last scattered.
