Dark Energy May Have Caused The Universe To Expand Rapidly After The Big Bang

Physicists proposed a new model that uses dark energy to explain the rapid expansion of the universe right after the Big Bang. They also said gravitational waves from the beginnings of the universe should be detectable using the new model.  ( Sidharth Nikam/Jet Propulsion Laboratory/Cal-Tech )

Researchers say dark energy may have caused the universe's rapid expansion a fraction of a second following the Big Bang.

Dark Inflation Model

Theoretical physicists at the Faculty of Physics of the University of Warsaw have advanced a new model that takes into account the role that dark energy and dark matter may have played during the cosmic inflation, an exponential expansion of space-time believed to have occurred over just a tiny fraction of a second immediately following the Big Bang.

The model proposes that dark energy and dark matter may have driven the rapid expansion of the universe. It also predicts that new technologies currently being developed should be able to track down gravitational waves that appeared right after the universe came into being.

Details are published in the Journal of Cosmology and Particle Physics.

Current Theory Of Cosmic Inflation

Current technologies allow scientists to study as far back as the creation of cosmic microwave background, which happened 380,000 years after the Big Bang.

CMB is the radiation left over from the universe's explosive beginnings. It has been found to be surprisingly consistent, even throughout places in the universe that are too far apart from each other that light would not have been able to travel between them during the 380,000 years the universe had existed.

In 1980, astrophysicist Alan Guth suggested that the universe must have gone through a quick and enormous expansion within 10^-32 of a second. That is the number 0, followed by a decimal point, 32 zeroes, and a 1. Thus, the theory of cosmic inflation was born and has been generally accepted over the years.

Guth said that a hypothetical high-energy quantum field called an inflaton field and corresponding particles called inflatons set off the expansion. The problem with this theory, however, is that scientists do not know the energy levels where inflation occurred.

Moreover, following inflation, which cooled off the early universe, one should be able to see a reheating period to stay consistent with current models. However, scientists do not know when, how, or if this happened.  

"The range of energies at which inflation could have occurred is vast," says Prof. Zygmunt Lalak of UW Physics, "stretching over 70 orders of magnitude.

Dark Energy And Inflation

Physicists believe 69 percent of the known universe is dark energy, while dark matter makes up 26 percent. Only 5 percent is known to comprise ordinary matter.

Both dark energy and dark matter have no known interactions or very weak interactions with ordinary matter. In fact, astronomers are only beginning to observe their presence through the gravitational effect they have on cosmic bodies.  

The UW team thinks that since dark energy makes up a large portion of the universe, it may have had an enormous role during its first moments.

"We started with the assumption that since today dark matter and dark energy comprise up to 95 percent of the universe's structure, then both factors must have also been extremely important immediately after the Big Bang," main author of study Michael Artymowski explains. "This is why we describe the dark sector of the universe as responsible for the inflation process."

The model proposes that inflation works on a scalar field, which means the expanding universe will eventually slow down and stop expanding. At this point, new particles should be formed due to gravitation, some of which may be identified through the Standard Model of Physics and others may not.

Inflatons should still be abundant when inflation ends, but they would have moved to a low-energy state. The team says their model estimates the thermal history of the universe more accurately than previous models.

Gravitational Waves From The Big Bang

Gravitational waves are ripples in space-time created by events releasing massive amounts of energy. They were first observed in the collisions of neutron stars and black holes.

Existing models of inflation show gravitational waves must occur due to the rapid expansion of the universe. Unfortunately, current evidence points to primordial gravitational waves now being too weak to be detected.

However, the researchers think that taking dark energy into account would allow them to register gravitational waves from the Big Bang.

"Gravitational waves lose energy as radiation. However, inflatons must lose it significantly faster," says Artymowski. "If inflation involved the dark sector, the input of gravitational waves increased proportionally."

The team believes that new technologies being developed will allow scientists to spot early gravitational waves rippling over from 13.8 billion years ago.

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