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Thursday, April 26, 2012

fine structure constant

what would be different in cosmology if the fine structure constant would not be 1/137 but 1/138?

bonus points: why do we know that it has has stayed constant in the course of cosmic history?

As to the bonus points, I'll answer with a counter question: Why are you so certain that the fine structure constant is actually constant? The question is still controversial.

Generally, there are different techniques which might help us to answer that question. I especially like:

- ... the Oklo natural nuclear fission reactor, although the time-scale might be too small.

-- ... measuring the CMB imprint of the 21cm hyperfine transition in neutral hydrogen (see Khatri et al. 2007)

There is a nice summary of various techniques and results on wikipedia: http://en.wikipedia.org/wiki/Fine-structure_constant#Is_the_fine_structure_constant_actually_constant.3F

Stellar evolution would be different. The change would be enough to effect the production of carbon: http://adsabs.harvard.edu/abs/2010A%26A...514A..62E

The alteration of the fine structure constant would alter hydrogene energy levels. Thereby it would alter the recombination epoch.

The equation used to estimate this for a given ionization fraction is the Saha equation. I haven't yet put numbers in to see how much impact such a small alteration can have. But the binding energy appears in an exponent.

As to the bonus points, I'll answer with a counter question: Why are you so certain that the fine structure constant is actually constant? The question is still controversial.

ReplyDeleteGenerally, there are different techniques which might help us to answer that question. I especially like:

- ... the Oklo natural nuclear fission reactor, although the time-scale might be too small.

-- ... measuring the CMB imprint of the 21cm hyperfine transition in neutral hydrogen (see Khatri et al. 2007)

There is a nice summary of various techniques and results on wikipedia: http://en.wikipedia.org/wiki/Fine-structure_constant#Is_the_fine_structure_constant_actually_constant.3F

Stellar evolution would be different. The change would be enough to effect the production of carbon: http://adsabs.harvard.edu/abs/2010A%26A...514A..62E

ReplyDeleteThe alteration of the fine structure constant would alter hydrogene energy levels. Thereby it would alter the recombination epoch.

ReplyDeleteThe equation used to estimate this for a given ionization fraction is the Saha equation. I haven't yet put numbers in to see how much impact such a small alteration can have. But the binding energy appears in an exponent.