Gravity Saved the Universe After the Big Bang

The anisotropies of the cosmic microwave background (CMB) as observed by the satellite Planck. This snapshot of the oldest light in our universe was imprinted when the universe was just 380,000 years old / D. Ducros, ESA and the Planck Collaboration
Janet Fang 18 Nov 2014, 23:32

During the accelerated expansion of the early universe, the production of the Higgs boson—the elementary particle responsible for giving mass to all particles—should have led to instability, followed by collapse. At least that’s what some recent studies suggest. 

But the universe didn’t collapse immediately after the Big Bang, and now researchers think they know why. The answer isn’t some new physics that we have yet to understand: It’s quite simply, gravity. The spacetime curvature (gravity, in effect) provided the stability needed for the universe to survive early expansion, according to a new study published in Physical Review Letters this week.

An international team led by Matti Henrikki Herranen from the University of Copenhagen studied the interaction between the Higgs particle and gravity, and how it varies with energy. Even a small interaction, they found, would be enough to stabilize the universe against decay. 

“The Standard Model of particle physics, which scientists use to explain elementary particles and their interactions, has so far not provided an answer to why the universe did not collapse following the Big Bang,” study co-author Arttu Rajantie of Imperial College London says in a news release. “Our research investigates the last unknown parameter in the Standard Model—the interaction between the Higgs particle and gravity.”

He adds: “This parameter cannot be measured in particle accelerator experiments, but it has a big effect on the Higgs instability during inflation. Even a relatively small value is enough to explain the survival of the universe without any new physics!” Here’s a timeline of the universe: 

Next, the team wants to look at this interaction in more detail using cosmological observations from current and future European Space Agency measurements of cosmic microwave background radiation (above) and gravitational waves. The cosmic microwave background is a snapshot of the oldest light in the universe, back when it was just 380,000 years old. The observations could help explain the effect that their interaction would have had on the development of the early universe. “If we are able to do that,” Rajantie says, “we will have supplied the last unknown number in the Standard Model of particle physics.” 

Images: D. Ducros, ESA and the Planck Collaboration (top), NASA/WMAP Science Team via Phys.org (middle)

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