Abstract
According to the multiverse worldview, the constants of nature vary from one part of the universe to another. In some regions the constants allow for the existence of life, and that is where observers will evolve and those constants will be measured.
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Notes
- 1.
If the vacuum landscape is indeed as rich as string theory suggests, it will include vacua with practically any values of the constants. So the USO will have no problem finding regions where X varies while the other constants are nearly fixed.
- 2.
This is a bit of an oversimplification. Some properties of galaxies may in fact change due to variation of life-neutral constants. For example, if the density fluctuations get larger, galaxies form earlier and have a higher density of matter. As a result, close encounters between stars, which can disrupt planetary orbits and extinguish life, become more common.
- 3.
The referee of the Astrophysical Journal objected to publishing papers based on anthropic reasoning, so in order for Martel Shapiro and Weinberg to get their 1998 paper accepted, they had to convince the editor, that if \(\rho_{v}\) was ever measured to be below a certain value, this would show that anthropic reasoning could not explain it. Of course, the value of \(\rho_{v}\) turned out to be just in the sweet spot for an anthropic explanation to make perfect sense.
- 4.
See question 4 to convince yourself that it is sufficient to use volume fractions, instead of actual volumes, to calculate probabilities.
- 5.
The distribution for the cosmological constant in Fig. 21.2 was calculated using the scale factor measure. In fact, analysis shows that this distribution is not very sensitive to the choice of measure, so the prediction for the cosmological constant is rather robust and is not expected to change much when the measure problem is finally resolved.
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Perlov, D., Vilenkin, A. (2017). The Principle of Mediocrity. In: Cosmology for the Curious. Springer, Cham. https://doi.org/10.1007/978-3-319-57040-2_21
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