New Theory Explains Why Our Universe is Three-Dimensional

According to a new theory proposed by University of Edinburgh Professor Arjun Berera and colleagues, shortly after the Universe came into existence it was filled with ‘knots’ formed from flexible strands of energy called flux tubes that link elementary particles together.

This is a graphic depicting formation of flux tube knots in the early Universe. Image credit: Keith Wood, Vanderbilt University.

This is a graphic depicting formation of flux tube knots in the early Universe. Image credit: Keith Wood, Vanderbilt University.

“Although the question of why our Universe has exactly three (large) spatial dimensions is one of the most profound puzzles in cosmology, it is actually only occasionally addressed in the scientific literature,” Professor Berera and co-authors said.

In order to find an answer to this question, they took a common element from the Standard Model of particle physics and mixed it with a little basic knot theory to produce a novel scenario that not only can explain the predominance of three dimensions, but also provides a natural power source for the inflationary growth spurt that most cosmologists believe the Universe went through microseconds after it burst into existence.

“The common element that we borrowed is the ‘flux tube’ comprised of quarks, the elementary particles that make up protons and neutrons, held together by another type of elementary particle called a gluon that ‘glues’ quarks together,” they explained.

“Gluons link positive quarks to matching negative antiquarks with flexible strands of energy called flux tubes.”

“As the linked particles are pulled apart, the flux tube gets longer until it reaches a point where it breaks. When it does, it releases enough energy to form a second quark-antiquark pair that splits up and binds with the original particles, producing two pairs of bound particles.”

“We’ve taken the well-known phenomenon of the flux tube and kicked it up to a higher energy level,” said Vanderbilt University Professor Thomas Kephart.

According to current theories, when the Universe was created it was initially filled with a superheated primordial soup called quark-gluon plasma. This consisted of a mixture of quarks and gluons.

The physicists realized that a higher energy version of the quark-gluon plasma would have been an ideal environment for flux tube formation in the very early Universe. The large numbers of pairs of quarks and antiquarks being spontaneously created and annihilated would create myriads of flux tubes.

Normally, the flux tube that links a quark and antiquark disappears when the two particles come into contact and self-annihilate, but there are exceptions.

If a tube takes the form of a knot, for example, then it becomes stable and can outlive the particles that created it. If one of particles traces the path of an overhand knot, for instance, then its flux tube will form a trefoil knot.

As a result, the knotted tube will continue to exist, even after the particles that it links annihilate each other.

Stable flux tubes are also created when two or more flux tubes become interlinked. The simplest example is the Hopf link, which consists of two interlinked circles.

In this fashion, the entire Universe could have filled up with a tight network of flux tubes.

Then, when the researchers calculated how much energy such a network might contain, they were surprised to discover that it was enough to power an early period of cosmic inflation.

Since the idea of cosmic inflation was introduced in the early 1980s, cosmologists have generally accepted the proposition that the early Universe went through a period when it expanded from the size of a proton to the size of a grapefruit in less than a trillionth of a second.

This period of hyper-expansion solves two important problems in cosmology. It can explain observations that space is both flatter and smoother than astrophysicists think it should be. Despite these advantages, acceptance of the theory has been hindered because an appropriate energy source has not been identified.

“Not only does our flux tube network provide the energy needed to drive inflation, it also explains why it stopped so abruptly,” Professor Kephart said.

“As the Universe began expanding, the flux-tube network began decaying and eventually broke apart, eliminating the energy source that was powering the expansion.”

When the network broke down, it filled the Universe with a gas of subatomic particles and radiation, allowing the evolution of the Universe to continue along the lines that have previously been determined.

The most distinctive characteristic of the new theory is that it provides a natural explanation for a three-dimensional world.

The next step for the authors is to develop their theory until it makes some predictions about the nature of the Universe that can be tested.

Details of the research will be published in the European Physical Journal C, but have been published on arXiv.org ahead of time.

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Arjun Berera et al. 2017. Knotty inflation and the dimensionality of spacetime. European Physical Journal C, in press; arXiv: 1508.01458

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