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Putting the 'bang' in the Big Bang: Physicists simulate critical 'reheating' period that kickstarted the Big Bang in the universe's first fractions of a second

As the Big Bang theory goes, somewhere around 13.8 billion years ago the universe exploded into being, as an infinitely small, compact fireball of matter that cooled as it expanded, triggering reactions that cooked up the first stars and galaxies, and all the forms of matter that we see (and are) today.

Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. During this period, matter -- a cold, homogeneous goop -- inflated exponentially quickly before processes of the Big Bang took over to more slowly expand and diversify the infant universe.

Recent observations have independently supported theories for both the Big Bang and cosmic inflation. But the two processes are so radically different from each other that scientists have struggled to conceive of how one followed the other.

Now physicists at MIT, Kenyon College, and elsewhere have simulated in detail an intermediary phase of the early universe that may have bridged cosmic inflation with the Big Bang. This phase, known as "reheating," occurred at the end of cosmic inflation and involved processes that wrestled inflation's cold, uniform matter into the ultrahot, complex soup that was in place at the start of the Big Bang.

"The postinflation reheating period sets up the conditions for the Big Bang, and in some sense puts the 'bang' in the Big Bang," says David Kaiser, the Germeshausen Professor of the History of Science and professor of physics at MIT. "It's this bridge period where all hell breaks loose and matter behaves in anything but a simple way."

Journal Reference:
Rachel Nguyen, Jorinde van de Vis, Evangelos I. Sfakianakis, John T. Giblin, David I. Kaiser. Nonlinear Dynamics of Preheating after Multifield Inflation with Nonminimal Couplings. Physical Review Letters, 2019; 123 (17) DOI: 10.1103/PhysRevLett.123.171301

Original Submission