Does positive curvature disprove eternal inflation?

In summary, there is ongoing debate in the scientific community about whether positive curvature in the universe disproves the theory of eternal inflation. Some argue that positive curvature indicates a finite universe, making the idea of eternal inflation impossible. Others suggest that the concept of eternal inflation can still be applied to a positively curved universe. More research and evidence is needed to fully understand the relationship between positive curvature and eternal inflation.
  • #1
windy miller
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According to this paper, eternal inflation would be falsified by positive curvature:
http://arxiv.org/pdf/1203.6876v2.pdf
However the proposer of eternal inflation, Alex Vilenkin, has suggested spontaneous creation of the universe from"nothing". Apparently this doesn't violate the conservation of energy as i a closed universe the positive energy of matter is balanced by the negative energy of gravity. but as I understood it a closed universe has positive curvature which would rule out eternal inflation, wouldn't it? or why wouldn't it ?
 
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  • #2
windy miller said:
According to this paper, eternal inflation would be falsified by positive curvature:
http://arxiv.org/pdf/1203.6876v2.pdf
However the proposer of eternal inflation, Alex Vilenkin, has suggested spontaneous creation of the universe from"nothing". Apparently this doesn't violate the conservation of energy as i a closed universe the positive energy of matter is balanced by the negative energy of gravity. but as I understood it a closed universe has positive curvature which would rule out eternal inflation, wouldn't it? or why wouldn't it ?
Yes, a closed universe has positive curvature.

The "zero energy universe" isn't really something that makes a whole lot of difference. Energy is just not conserved in General Relativity. You can recover energy conservation only in very special circumstances, but there's no reason to believe that those circumstances apply to reality. Sean Carroll has a pretty good blog post on the subject:
http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/
 
  • #3
Thanks for the quick reply, ok let's put energy conservation aside. Vilenkin claims his model of spontaneous creation from nothing needs a closed universe. See here: http://inference-review.com/article/the-beginning-of-the-universe
he also claims the universe undergoes eternal inflation. But the previous paper seems to say this would rule out eternal inflation. So it seems I have misunderstood something along the way.
 
  • #4
Why do you think that a closed universe is incompatible with future-eternal inflation?
 
  • #5
Because as I understand it a closed universe has positive curvature and according to papers like the one I cited above positive curvature would rule out eternal inflation.
 
  • #6
Eternal inflation, as I understand it, results in causally disconnected 'bubble' universes. I fail to grasp how the curvature in any particular 'bubble' universe could have any observable consequences in another causally disconnectes 'bubble' universe.
 
  • #7
windy miller said:
Because as I understand it a closed universe has positive curvature and according to papers like the one I cited above positive curvature would rule out eternal inflation.
But the Guth et al. paper involves an observational constraint on positive curvature; Vilenkin's closed universe could still be viable as long as the observable patch is sufficiently flat (equivalently, the radius of the universe is sufficiently large).
 
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1. What is curvature and how is it related to inflation?

Curvature refers to the amount of bending or warping in a space or surface. Inflation is a theory in physics that proposes that the universe underwent a rapid expansion in the early moments after the Big Bang. The concept of curvature is important in inflation theory because it helps explain how the universe expanded so uniformly and smoothly.

2. How does inflation explain the flatness of the universe?

One of the key predictions of inflation theory is that the universe is flat, meaning that the angles of a triangle add up to 180 degrees and parallel lines never meet. Inflation explains this by proposing that the early universe underwent a period of rapid expansion, smoothing out any curvature and making the universe appear flat on a large scale.

3. Can inflation be tested or observed?

Although there is no direct evidence of inflation, its predictions can be tested through observations of the cosmic microwave background radiation and the distribution of galaxies in the universe. These observations have provided support for inflation theory and its predictions about the flatness and uniformity of the universe.

4. How does inflation impact our understanding of the origin of the universe?

Inflation has greatly influenced our understanding of the origin of the universe. It provides a plausible explanation for the observed flatness and uniformity of the universe, as well as the origin of the large-scale structure of the universe. Inflation theory also helps reconcile some inconsistencies in the Big Bang theory, such as the horizon problem and the flatness problem.

5. Are there any alternative theories to inflation?

There are several alternative theories to inflation, such as the steady-state theory and the ekpyrotic/cyclic model. These theories propose different mechanisms for the expansion of the universe and its observed properties. However, inflation remains the most widely accepted theory due to its ability to explain a wide range of observations and its consistency with general relativity.

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