It is now widely accepted that the universe emerged about 13.8 billion years ago in a phenomenon we now call the Big Bang. Our current model of the universe’s formation tells us that it underwent a brief period of exponential expansion trillionths of trillionths of a second after the Big Bang — a phenomenon called “cosmic inflation.” During this period, space-time burgeoned from being smaller than a proton to a fabric that stretched across light-years.
Here’s where we run into a problem. Although inflation does explain the origin of large-scale structures in the cosmos and why the universe appears isotropic, we do not have any proof that this inflation took place, and a potential discovery of primordial gravitational waves — something that was hailed as a “smoking gun” of cosmic inflation — was later debunked.
This is why physicists are constantly on the lookout for something that can back up the cosmic inflation hypothesis — say, the detection of an inflaton, the as-of-yet-hypothetical particle that scientists believe drove inflation, and its associated field.
Scientists also assume that in a fraction of a second after the Big Bang, when the universe was roughly the size of a football, these inflatons would have undergone intense fluctuations, and would have formed clumps that would have caused them to oscillate in localized regions of space. Physicists call these standing waves oscillons and believe they would have emitted gravitational waves that were so strong that they can, in theory, be detected even today.
Now, a team of researchers from the University of Basel in Switzerland has taken a major step toward the discovery of these gravitational waves by calculating the precise shape of oscillons’ signals emitted less than a second after the Big Bang.
The signal of the oscillon, which appears as a pronounced peak in a background of a broad spectrum of gravitational waves, was calculated using numerical simulations.
“We would not have thought before our calculations that oscillons could produce such a strong signal at a specific frequency,” Stefan Antusch, a professor of theoretical physics at the university, said in a statement. “Although the oscillons have long since ceased to exist, the gravitational waves they emitted are omnipresent — and we can use them to look further into the past than ever before.”
Now that the shape of the oscillon’s signal has been predicted, the next step would be to try and actually discover the gravitational waves they emitted using powerful detectors such as LIGO, which, in 2015, made the first-ever detection of gravitational waves.
If such signals are discovered, it would provide an incontrovertible proof of cosmic inflation, solving, among other things, the horizon problem, which deals with the fact that the universe has a uniform temperature even though heat-carrying particles would not have had enough time to reach all the corners of the cosmos.
The research was published in the latest edition of the journal Physical Review Letters.
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