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Relativity, Cosmology, and Time

Theory of Cosmic Inflation and Acceleration

Cosmic Acceleration Astronomical observations over the last 20 years have indicated that the universe has experienced two periods of acceleration (see Figure 10j). The first one was a very rapid expansion soon after the Big Bang. It is usually referred to as inflation. The dark energy accelerated expansion is gentler, and has occurred only recently in the current epoch. The inflation is explained by an as yet un-identified scalar field (inflaton) undergoing a phase transition. While there are three categories of theory for the accelerated expansion: modifications to general relativity perhaps with extra dimensions, a cosmological constant, and a universal evolving scalar field. None of these offers a satisfactory explanation (see a 2015 update on "Vacuum Energy Density").

Figure 10j Cosmic Inflation [view large image]

The followings provide a mathematical description of cosmic inflation and expansion without invoking a detailed mechanism.

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