Cosmic Inflation

What is Cosmic Inflation?

Cosmic inflation is the theory that the universe underwent a brief period of exponential expansion a small fraction of a second after the Big Bang singularity. This idea was initially introduced in the 1980s as the most natural solution to several problems with the standard Big Bang model, including the Flatness Problem, the Horizon Problem, and the Magnetic Monopole Problem.

Primordial Gravitational Waves

Although inflation has been very successful at explaining our measurements of the universe, there are still some predictions of this theory that have not been experimentally verified. One prediction is that inflation would produce primordial gravitational waves in the early universe with an amplitude proportional to the square of the energy scale at inflation. These gravitational waves would in turn imprint B-modes patterns in the CMB, which we can search for today.

Experiments like BICEP/Keck target B-mode polarization at the degree scale, which is the angular scale at which primordial gravitational waves are predicted to generate the most B-modes in the CMB. These measurements provide insight on possible inflation models, and a detection of inflationary B-modes would be "smoking gun" evidence for inflation.