New theory says dark matter actually shapes the universe

• It is known that dark matter interacts weakly with the visible universe, but was this always the case?

• Physicists modeled the theoretical space of inflation, which scientists use to study the period after the Big Bang, to study these interactions.

• During this period, dark matter may have interacted with the rest of the universe more equally than visible matter.

In new peer-reviewed research, a team of Northeastern University researchers say dark matter may have played a much larger role in the birth of the visible universe than we thought. It’s an important claim, as physicists largely view dark matter as an unexplained and relatively stable part of the equation, rather than an active player in shaping our visible universe. While scientists largely agree that dark matter is very, very weakly connected to the visible universe, these researchers raised the question: Is there a place where it could be on equal footing?

It seems intuitive that dark matter (which makes up 95% of the universe today) must have played a role in the Big Bang that launched the universe into existence, but supporting this with evidence is deceptively difficult. In some math and coding courses, you learn the concept of a black box function, where you enter a value and see the result, but you never see the deterministic process that happens in the middle that causes the result to pop up at the end. The Big Bang may be the ultimate black box function, which scientists can only try to reverse engineer using increasingly well-founded hypotheses.

In their paper, Ph.D. Candidates Jinzheng Li and Professor Pran Nath must model the Big Bang and a series of interactions to reverse engineer the effects of dark matter. They tested the idea that dark matter and visible matter are more closely connected than we thought, i.e. there may be more coupling between dark matter and normal matter than expected. In physics, coupling is any type of connection between two particles through one of four fundamental forces: gravity, electromagnetism, weak interaction, or strong interaction. When you add dark matter and dark energy into the mix, there’s also a weak interaction that’s much weaker than that.

Using weak interactions, scientists can consider models other than the Standard Model to try to explain the universe. Just like replacing .0001 so you’re not dividing by zero. If all dark matter is weakly coupled to the visible universe, this would strengthen the idea that the visible universe has an outsized influence in physics. After the influence of dark matter is essentially reduced to zero, we can continue to use the Standard Model without any particularly disturbing outliers in the mathematical harmony.

But what if this isn’t always the case?If it can be said that it is most At a critical moment, dark matter and visible matter come together in a more democratic way, powerful enough that both sides have a more balanced say in what’s going on in our universe?

To figure this out, the team looked at a theoretical space called the inflaton, which scientists use to help understand and model the incredibly rapid expansion, or inflation, of the earliest universe. If we no longer assume that dark matter only participates in weak couplings in the inflaton, a whole new parameter suddenly comes into play. [T]The team wrote that the hidden and visible sectors could be democratically coupled to the inflaton, in which case the hidden and visible sectors would reach thermal equilibrium at the end of reheating or at the end of the inflationary period.

While this idea may conflict with the Standard Model, the researchers explain that’s part of why it should interest scientists. [T]They concluded that the analysis showed the inclusion of hidden sectors that appear in various particle physics models outside the Standard Model, and therefore their inclusion would be relevant for an accurate description of physical phenomena.

In other words, we should consider all possibilities when explaining how the universe came to be.

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