Sep 11, 2023 05:04 PM
https://www.universetoday.com/163112/the...-universe/
EXCERPTS: [...] there is the fact that the cosmic microwave background is almost a perfect blackbody. There are small fluctuations in its temperature, but it is much more uniform than it should be. To account for this, astronomers have proposed a period of tremendous expansion just after the Big Bang, known as early cosmic inflation. We have not observed any direct evidence of it, but the model solves so many cosmological problems that it’s widely accepted. If the model is accurate, then the Universe is on the order of 10^26 times larger than the observable universe.
So given all of this theoretical and observational evidence, how could anyone argue that the Universe is small? It has to do with string theory and the swamplands.
[...] When you separate the promising theoretical lands from the swamp, what you are left with are theories where early cosmic inflation isn’t an option. Most of the inflationary string theory models are in the swampland. This leads one to ask whether you could construct a model cosmology that matches observation without early inflation. Which brings us to this new study.
[...] The authors demonstrate that under just the right conditions, you could construct a higher-dimensional structure within string theory that matches observation and avoids the swampland. Based on their toy models, the Universe may only be a hundred or a thousand times larger than the observed universe. Still big, but downright tiny when compared to the early inflation models.
All of this is pretty speculative, but in a way so is early cosmic inflation... (MORE - missing details)
EXCERPTS: [...] there is the fact that the cosmic microwave background is almost a perfect blackbody. There are small fluctuations in its temperature, but it is much more uniform than it should be. To account for this, astronomers have proposed a period of tremendous expansion just after the Big Bang, known as early cosmic inflation. We have not observed any direct evidence of it, but the model solves so many cosmological problems that it’s widely accepted. If the model is accurate, then the Universe is on the order of 10^26 times larger than the observable universe.
So given all of this theoretical and observational evidence, how could anyone argue that the Universe is small? It has to do with string theory and the swamplands.
[...] When you separate the promising theoretical lands from the swamp, what you are left with are theories where early cosmic inflation isn’t an option. Most of the inflationary string theory models are in the swampland. This leads one to ask whether you could construct a model cosmology that matches observation without early inflation. Which brings us to this new study.
[...] The authors demonstrate that under just the right conditions, you could construct a higher-dimensional structure within string theory that matches observation and avoids the swampland. Based on their toy models, the Universe may only be a hundred or a thousand times larger than the observed universe. Still big, but downright tiny when compared to the early inflation models.
All of this is pretty speculative, but in a way so is early cosmic inflation... (MORE - missing details)