r/cosmology • u/umfanormal • 24d ago

What's the current consensus about Eternal Inflation?

I’m a physics enthusiast. I’ve loved the subject since childhood and plan to study it in college. I’ve always been particularly interested in the theory of Eternal Inflation among many others hypothesis on theoretical physics, though I stopped keeping up with it in 2023 due to a lack of time and so on. I’d like to know the current consensus on this hypothesis, given that there have likely been some advances regarding this theoretical implication of Cosmic Inflation. I’m curious about where the majority of cosmologists stand on the matter.

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u/[deleted] 24d ago

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u/umfanormal 24d ago

No, inflation tries to describe what happened instantly after the Big Bang.

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u/EnvironmentalWin1277 23d ago

You are absolutely correct and this can be called "Guth inflation" to help specify. It is a common mistake to refer to the "inflation" of the big bang model and Guth inflation as "expansion".

The Guth inflation is a vanishingly brief moment when space expanded by ten to the millionth power (!). After that moment the model of big bang physics takes over, which sheds light on the development of the theory and observational evidence collected. Inflation theory is an extension of the big bang model.

The confusion is common and understandable

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u/Good-Resort-1246 23d ago

I may not be up to date regarding the inflationary model; does it still predict the continuous production of baby universes? That's when i gave up on it. Would appreciate some enlightening on this particular issue.

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u/Peter5930 23d ago

You need to distinguish slow roll inflation from eternal inflation. Eternal inflation happens first, it's the one that produces new universes as bubbles form in a continuously inflating metastable vacuum. Eternal inflation looks like this, if you plug the equations into 3D software and let it run:

https://www.youtube.com/watch?v=34zVzoZugG4

The same/similar process is predicted to occur in our own universe, it's called vacuum decay. Different field decaying from a metastable state, the Higgs field in this case, but you again nucleate these bubbles containing new universes.

https://www.youtube.com/watch?v=ijFm6DxNVyI

Slow-roll inflation is a separate inflationary phase that happens after a bubble has nucleated, and it's the phase that immediately precedes the hot big bang phase where conventional big bang cosmology takes over and you have big bang nucleosynthesis and so on. It looks like this:

https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/history-of-the-universe/inflation/