Abstract
Our journey through time in the previous chapter has taken us to the very earliest epoch in the history of the universe that cosmologists are still confident to talk about and, more importantly, should also be listened to. This epoch is called inflation.
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Notes
- 1.
We should keep in mind that 10−36 is a rather tiny number, there are 35 zeroes after the decimal point before the 1 appears.
- 2.
Some models of inflation predict an even larger amount of expansion.
- 3.
We should keep in mind, however, that no atoms exist during inflation.
- 4.
The number of scalar fields depends on the particular model of inflation. Different models of inflation have different physical and observational consequences, like the amount of accelerated expansion they provide and the distribution of density fluctuations they generate, see Sect. 9.4.
- 5.
We can perform some “geometry in curved space” in two dimensions quite easily. For the closed geometry we can use for example a grapefruit. If we draw an equator on the fruit and follow the procedure to construct parallel lines we will find that they indeed meet at the poles. It is more difficult to find a saddle these days, and we should avoid drawing on it, the same is true for a pringle.
- 6.
For the analogy to be more precise, if you wish, you could imagine you are two-dimensional living in the surface.
- 7.
Inflation does not violate causality: information exchange takes place in a causal region before inflation. Inflation can’t be used to transmit signals faster than light.
- 8.
Inflation provides what is called a nearly “scale-invariant” spectrum of density fluctuations. This means that the size-distribution of the fluctuations does not depend on or change with scale: the size of the fluctuations is proportional to the horizon size, which is roughly constant during inflation.
- 9.
The density fluctuations responsible for structure formation are on much larger, super-horizon scales at this time, with amplitudes of roughly 10−5 relative to the average density.
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Malik, K.A., Matravers, D.R. (2019). How Did It All Begin?. In: How Cosmologists Explain the Universe to Friends and Family. Astronomers' Universe. Springer, Cham. https://doi.org/10.1007/978-3-030-32734-7_9
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DOI: https://doi.org/10.1007/978-3-030-32734-7_9
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