A previously unknown phase transition in the early universe

Newswise – consider bringing a pot of water to a boil: When the temperature reaches the boiling point, bubbles form in the water, burst and vaporize as the water boils. This continues until there is no more phase change of water from liquid to vapor.

This is roughly the idea of ​​what happened in the very early universe, right after the Big Bang, 13.7 billion years ago.

The idea comes from particle physicist Martin S. Sloth of the Center for Cosmology and Physics of Particle Physics at the University of Southern Denmark and Florian Niedermann of the Nordic Institute for Theoretical Physics (Nordetta) in Stockholm. Niederman is a former postdoctoral researcher in the Sloth Research Group. In this new scientific article, they provide a stronger foundation for their idea.

Many bubbles collide with each other
– One has to imagine that bubbles originated in different places in the early universe. They grew bigger and started bumping into each other. In the end, there was a complex case of bubbles colliding, which released energy and eventually evaporated, says Martin S. Sloth.

The background to their theory of phase changes in a bubble universe is a very interesting problem in calculating the so-called Hubble constant. A value for how fast the universe is expanding. Sloth and Niedermann think the bubble universe is at play here.

The Hubble constant can be calculated very reliably, for example, by analyzing cosmic background radiation or by measuring how fast a galaxy or exploding star is moving away from us. According to Sloth and Niedermann, both methods are not only reliable, but also scientifically recognized. The problem is that neither method leads to the same Hubble constant. Physicists call this problem the “Hubble tension”.

Is there something wrong with our picture of the early universe?
– In science, you should be able to reach the same conclusion using different methods, so here we have a problem. Florian Niedermann said: Why can’t we get the same result when we are so confident in both methods?

Sloth and Niedermann think they’ve found a way to get the same Hubble constant, regardless of the method used. The path begins with a phase transition and a bubble universe – thus the early, bloated universe is associated with the “Hubble tension”.

– If we assume that these methods are reliable – and we believe they are – then the methods may not be the problem. Perhaps we need to look at the starting point, the basis, to which we are applying the methods. Perhaps this basis is wrong.

Unknown dark energy
The basis of these methods is the so-called Standard Model, which assumes that there was a lot of radiation and matter, both normal and dark, in the early universe, and that these were the dominant forms of energy. Radiation and normal matter have been compressed into a dark, hot, and dense plasma; The state of the universe in the first 380,000 years after the Big Bang.

When you base your calculations on the Standard Model, you come to different results for how fast the universe is expanding – and thus different Hubble constants.

But maybe a new form of dark energy was at play in the early universe? Lazy and Nederman think so.

If you introduce the idea that a new form of dark energy in the early universe suddenly began to emerge and undergo a phase transition, the calculations agree. In their model, Sloth and Niedermann arrive at the same Hubble constant when both measurement methods are used. They call this idea Early New Dark Energy – NEDE.

Change from one phase to another – like water to steam
Sloth and Niedermann believe that this new dark energy underwent a phase transition when the universe expanded, shortly before it changed from a hot, dense state of plasma to the universe we know today.

– This means that dark energy in the early universe underwent a phase transition, just as water can change phase between solidification, liquid and vapor. Niederman said the energy bubbles in the process eventually collided with other bubbles and released energy along the way.

– It can last anything from an insanely short time – maybe just the time it takes for two particles to collide – to 300,000 years. We don’t know, but it’s something we’re working to find out, Sloth added.

Do we need new physics?
Therefore, the phase transition model relies on the fact that the universe does not behave as the standard model tells us. It might seem scientifically crazy to suggest that something is wrong with our basic understanding of the universe; That you can only suggest that there are hitherto unknown forces or particles to solve the Hubble tension.

But if we trust observations and calculations, we must accept that our current model of the universe cannot explain the data, and then we must improve the model. Sloth: Not by ditching it and its success so far, but by breaking it down and making it more detailed so you can explain the new and better data, adding:

The phase transition in dark energy appears to be the missing component in the current Standard Model to explain various measurements of the expansion rate of the universe.

Sidebar: How Fast Is the Universe Expanding?

The Hubble constant is a value of how fast the universe is expanding.

In the model of Martin S. Sloth and Florian Niedermann, the Hubble constant is 72. Approx. After all, large distances count, so we must allow for uncertainties of a few decimal places.

What does 72 mean? It means 72 km per second per megaparsec. Megaparsecs are a measure of the distance between two galaxies, for example, and one megaparsec is 30,000,000,000,000,000,000 km. For every megaparsec between us and, say, a galaxy, the galaxy is moving away from us at a speed of 72 km per second.

When you measure the distance to galaxies by supernovae, you get roughly the Hubble constant. 73 (km / s) / Megabrsk. But when measured against the first particles of light (the cosmic background radiation), the Hubble constant is 67.4 (km/s)/Megapresq.

When Sloth and Niedermann changed the basis of these calculations by introducing the presence of a new, early transition dark energy – as described in the article – both types of calculations arrived at the Hubble constant of about 72.

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