Physicists
have proposed our universe might be a tiny patch of a much larger cosmos that
is constantly and rapidly inflating and popping off new universes. In our
corner of this multiverse, the mass of the Higgs boson was low enough that this
patch did not collapse like others may have. (Image credit: MARK
GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)
The Higgs
boson, the mysterious particle that loans other particles their mass, could
have kept our universe from collapsing. And its properties might be a sign that
we live in a multiverse of parallel worlds, a wild new theory proposes.
That
theory, in which different regions of the universe have diverse sets of
physical laws, would propose that only worlds in which the Higgs boson is little
would survive.
If true,
the new theory would require the creation of new particles, which in turn would
describe why the strong force — which eventually keeps atoms from collapsing —
seems to follow certain symmetries. And along the way, it could help reveal the
nature of dark matter — the mysterious substance that makes up most matter.
A tale of
two Higgs
In 2012,
the Large Hadron Collider achieved a truly monumental feat; this underground
particle accelerator along the French-Swiss border detected for the first time
the Higgs boson, a particle that had eluded physicists for decades. The Higgs
boson is a cornerstone of the Standard Model; this particle gives other
particles their mass and creates the distinction between the weak nuclear force
and the electromagnetic force.
But with
the good news came some bad. The Higgs had a mass of 125 gigaelectronvolts
(GeV), which was orders of magnitude smaller than what physicists had thought
it should be.
To be
perfectly clear, the framework physicists use to describe the zoo of subatomic
particles, known as the Standard Model, doesn't actually predict the value of
the Higgs mass. For that theory to work, the number has to be derived
experimentally. But back-of-the-envelope calculations made physicists guess
that the Higgs would have an incredibly large mass. So once the champagne was
opened and the Nobel prizes were handed out, the question loomed: Why does the
Higgs have such a low mass?
In
another, and initially unrelated problem, the strong force isn't exactly
behaving as the Standard Model predicts it should. In the mathematics that
physicists use to describe high-energy interactions, there are certain
symmetries. For example, there is the symmetry of charge (change all the
electric charges in an interaction and everything operates the same), the
symmetry of time (run a reaction backward and it's the same), and the symmetry
of parity (flip an interaction around to its mirror-image and it's the same).
In all
experiments performed to date, the strong force appears to obey the combined
symmetry of both charge reversal and parity reversal. But the mathematics of
the strong force do not show that same symmetry. No known natural phenomena
should enforce that symmetry, and yet nature seems to be obeying it. What
gives?
The
world's largest atom smasher, the Large Hadron Collider, forms a 17-mile-long
(27 kilometers) ring under the French-Swiss border.
A matter
of multiverses
A pair of
theorists, Raffaele Tito D'Agnolo of the French Alternative Energies and Atomic
Energy Commission (CEA) and Daniele Teresi of CERN, thought that these two
problems might be related. In a paper published in January to the journal
Physical Review Letters, they outlined their solution to the twin conundrums.
Their
solution: The universe was just born that way.
They
invoked an idea called the multiverse, which is born out of a theory called
inflation. Inflation is the idea that in the earliest days of the Big Bang, our
cosmos underwent a period of extremely enhanced expansion, doubling in size
every billionth of a second.
Physicists
aren't exactly sure what powered inflation or how it worked, but one outgrowth
of the basic idea is that our universe has never stopped inflating. Instead,
what we call "our universe" is just one tiny patch of a much larger
cosmos that is constantly and rapidly inflating and constantly popping off new
universes, like foamy suds in your bathtub.
Different
regions of this "multiverse" will have different values of the Higgs
mass. The researchers found that universes with a large Higgs mass find
themselves catastrophically collapsing before they get a chance to grow. Only
the regions of the multiverse that have low Higgs masses survive and have
stable expansion rates, leading to the development of galaxies, stars, planets
and eventually high-energy particle colliders.
To make a
multiverse with varying Higgs masses, the team had to introduce two more
particles into the mix. These particles would be new additions to the Standard
Model. The interactions of these two new particles set the mass of the Higgs in
different regions of the multiverse.
And those two new particles are also capable of doing other things.
The newly
proposed particles modify the strong force, leading to the charge-parity
symmetry that exists in nature. They would act a lot like an axion, another
hypothetical particle that has been introduced in an attempt to explain the
nature of the strong force.
The new
particles don't have a role limited to the early universe, either. They might
still be inhabiting the present-day cosmos. If one of their masses is small
enough, it could have evaded detection in our accelerator experiments, but
would still be floating around in space.
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