The Big Bang Theory says that the physical universe – space, time, matter and energy – expanded from a very tiny, hot and dense point into an ever-expanding space – known as inflation. But what if there were two periods of inflation, with a second, shorter one taking place when the universe was just seconds old?

A new theory from physicists at the U.S. Department of Energy’s Brookhaven National Laboratory, Fermi National Accelerator Laboratory, and Stony Brook University suggests a shorter secondary inflationary period that could account for the amount of dark matter estimated to exist throughout the cosmos.

“In general, a fundamental theory of nature can explain certain phenomena but it may not always end up giving you the right amount of dark matter,” said Hooman Davoudiasl, group leader at Brookhaven National Laboratory and an author of the paper. “If you come up with too little dark matter you can suggest another source but having too much is a problem,” he added.

Dark matter is the dominant form of substance in the universe, which leads physicists to devise theories and experiments to explore its properties and understand how it originated. Measuring the amount of dark matter in the universe is no easy task. It is dark after all, so it doesn’t interact in any significant way with ordinary matter.

Some theories that elegantly explain perplexing oddities in physics — for example, the inordinate weakness of gravity compared to other fundamental interactions such as the electromagnetic, strong nuclear, and weak nuclear forces — cannot be fully accepted because they predict more dark matter than empirical observations can support.

This new theory solves that problem. Davoudiasl and his colleagues add a step to the commonly accepted events at the inception of space and time.

In their study, the researchers say there was a second period of inflation between the fraction of a second when the universe exploded to the cooling period that has continued to this day.

In standard cosmology, the exponential expansion of the universe called cosmic inflation began perhaps as early as 10-35 seconds after the beginning of time. This explosive expansion of the entirety of space lasted mere fractions of a fraction of a second, eventually leading to a hot universe, followed by a cooling period that has continued until the present day. Then, when the universe was just seconds to minutes old — that is, cool enough — the formation of the lighter elements began. Between those milestones, there may have been other inflationary interludes, said Davoudiasl.

This secondary inflation would not have been as “grand or as violent” as the first, Davoudiasl said, but it could help explain the dilution of dark matter.

Davoudiasl and his colleagues suggest that this inflationary period was powered by interactions in a “hidden sector” of physics. This milder period of inflation, characterised by a rapid increase in volume, would dilute primordial particle abundances, potentially leaving the universe with the density of dark matter we observe today.

Hooman Davoudiasl, who led the group, said: “It’s definitely not the standard cosmology, but you have to accept that the universe may not be governed by things in the standard way that we thought. But we didn’t need to construct something complicated. We show how a simple model can achieve this short amount of inflation in the early universe and account for the amount of dark matter we believe is out there.”

Proving the theory is another thing entirely, Davoudiasl said there may be a way to look for at least the very feeblest of interactions between the hidden sector and ordinary matter.

“If this secondary inflationary period happened, it could be characterized by energies within the reach of experiments at accelerators such as the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider,” he said. Only time will tell if signs of a hidden sector show up in collisions within these colliders, or in other experimental facilities.

The researchers will publish their theory online on January 18 in Physical Review Letters.