Cosmic Inflation


Cosmic inflation is the exponential expansion of space in the early universe. It occurred at about 1036 seconds after the Big Bang and ended at about 1033 seconds. The inflationary hypothesis was introduced in the early 1980s in an attempt to solve several problems in cosmology. Why is the cosmic microwave background (CMB), the cinder of the Big Bang, the same in all directions? Why is the distribution of matter (galaxies) so uniform at large, cosmic scales? Why is the universe so flat?

If the universe has indeed undergone a brief period of exponential expansion soon after the Big Bang, then all the parts and particles of the universe we see today would be descended from the same origin and have the same temperature. Being extremely tiny at the time of inflation, the quantum effects are important. The quantum fluctuations during inflation provided the seeds for the formation of structures at later time. Also due to the extremely rapid expansion, any possible curvature of space-time would have been stretched to become flat. So far all observations have been consistent with the inflation hypothesis. The most recent BICEP2 discovery (2014) of the imprint of gravitational waves induced during inflation, if confirmed, would be an additional crucial support of the notion.

On the theoretical side, though tremendously successful, the inflation concept does not fit into the standard model of particle physics. Its connection with fundamental physics such as string theory or quantum gravity is yet to be developed. LeCosPA physicists have been active in the investigations of inflation. The efforts have been concentrating in the phenomenology of inflation through analysis of data from the Planck satellite mission, the apparent anomaly of the large-angle correlations in the CMB perturbation amplitudes, the construction of alternative models of inflation, the issue of the evolution of entanglement entropy during inflation, etc.