I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), struck me as incredible:-

"there are about seven protons for every neutron at the beginning of
nucleogenesis....... This fraction is in favour of protons initially
primarily because because lower mass of the proton favors their
production."

Why my astonishment?

1) The masses of protons and neutrons are almost identical.
2) Two ups and one down seems as likely a bundle to me as two downs
and one up when my quark soup starts to cool enough.
3) Proton and electron masses are vastly different but we still end up
with them in equal numbers, regardless.

Could I be correct in concluding, therefore, that the above given
reason for this ratio of 7 to 1 is merely a conjured up excuse for
introducing yet a further cosmological fudge factor into the
concordance model?

Or is there some rational reason why we would genuinely expect twice
as many ups as downs in our quark soup?

If there is no rational reason, and ups and downs had actually been
poured in in equal measure (by a more unbiased chef), what difference,
if any, would that then make to the subsequent nucleosynthesis brewing
time, and the resultant ratio of protons (hydrogen nuclei) to alpha
particles (helium nuclei), eventually?

Chalky wrote:

I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), struck me as incredible:-

"there are about seven protons for every neutron at the beginning of
nucleogenesis....... This fraction is in favour of protons initially
primarily because because lower mass of the proton favors their
production."

Why my astonishment?

1) The masses of protons and neutrons are almost identical.
2) Two ups and one down seems as likely a bundle to me as two downs
and one up when my quark soup starts to cool enough.
3) Proton and electron masses are vastly different but we still end up
with them in equal numbers, regardless.

Could I be correct in concluding, therefore, that the above given
reason for this ratio of 7 to 1 is merely a conjured up excuse for
introducing yet a further cosmological fudge factor into the
concordance model?

Or is there some rational reason why we would genuinely expect twice
as many ups as downs in our quark soup?

If there is no rational reason, and ups and downs had actually been
poured in in equal measure (by a more unbiased chef), what difference,
if any, would that then make to the subsequent nucleosynthesis brewing
time, and the resultant ratio of protons (hydrogen nuclei) to alpha
particles (helium nuclei), eventually?

Protons are stable in free space. Neutrons decay with a mean-life of
885.7 seconds or a half-life of 613.9 sec. Roughly equal production
rates sustained over about an hour award you your net skew.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

On Jun 7, 11:36*pm, Uncle Al wrote:
Chalky wrote:

I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), *struck me as incredible:-

"there are about seven protons for every neutron at the beginning of
nucleogenesis....... This fraction is in favour of protons initially
primarily because because lower mass of the proton favors their
production."

Why my astonishment?

1) The masses of protons and neutrons are almost identical.
2) Two ups and one down seems as likely a bundle to me as two downs
and one up when my quark soup starts to cool enough.
3) Proton and electron masses are vastly different but we still end up
with them in equal numbers, regardless.

Could I be correct in concluding, therefore, that the above given
reason for this ratio of 7 to 1 is merely a conjured up excuse for
introducing yet a further cosmological fudge factor into the
concordance model?

Or is there some rational reason why we would genuinely expect twice
as many ups as downs in our quark soup?

If there is no rational reason, and ups and downs had actually been
poured in in equal measure (by a more unbiased chef), what difference,
if any, would that then make to the subsequent nucleosynthesis brewing
time, and the resultant ratio of protons (hydrogen nuclei) to alpha
particles (helium nuclei), eventually?

Protons are stable in free space. *Neutrons decay with a mean-life of
885.7 seconds or a half-life of 613.9 sec. *Roughly equal production
rates sustained over about an hour award you your net skew.

Agreed, entirely. But that is not the point. The bulk of that neutron
decay would necessarily occur AFTER the period of primordial
nucleosynthesis. Consequently the question is,

A) does such an increase in initial neutrons (and corresponding
decrease in protons) alter the dynamism sufficiently _during_ the
period of primordial nucleosynthesis , to alter the predicted of
helium fraction, or

B) Did Gamov factor all this in during his original calculation, and
Wiki ha just got its summary a bit wrong.

On a related point, how robust was Gamov's analysis anyway? I mean to
say, I have never seen anyone say, oops, we need to resurrect the
cosmological constant, plus alter dark matter proportions, then, oops
we now need to check if this alters primordial nucleosynthesis
predictions too.

On Jun 7, 10:19 am, Chalky wrote:
I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), struck me as incredible:-

"there are about seven protons for every neutron at the beginning of
nucleogenesis....... This fraction is in favour of protons initially
primarily because because lower mass of the proton favors their
production."

Why my astonishment?

1) The masses of protons and neutrons are almost identical.

On closer examination of the soup, the following statement needs
revision:

2) Two ups and one down seems as likely a bundle to me as two downs
and one up when my quark soup starts to cool enough.

Actually, I find two downs and one up is the preferred option because
they are electrically neutral. Under charge conservation, every
instance of two ups and one down, must have the associated generation
of one free electron at the big bang.

Diner at the Big Bang Restaurant... "Waiter, what is this strange bug
in my soup"
Waiter........"With all due respect Sir, those aren't strange bugs in
your soup, they are an in house speciality of the Chef...Fishy quarks"

On Jun 7, 11:36 pm, Uncle Al wrote:

Protons are stable in free space. Neutrons decay with a mean-life of
885.7 seconds or a half-life of 613.9 sec. Roughly equal production
rates sustained over about an hour award you your net skew.

I have just checked the ref again, and quote from just before my
earlier quotation:

"Combining thermodynamics and the changes brought about by cosmic
expansion, one can calculate the fraction of protons and neutrons
based on the temperature at this point. The answer is that there are
about seven protons for every neutron at the beginning of
nucleogenesis, a ratio that would remain stable even after
nucleogenesis is over."

The authors seem pretty adamant that one needs ~7 protons per neutron
_at the start_ of nucleogenesis, for the arithmetic in the Alpher---
Bethe---Gamow paper to work

Chalky wrote:

On Jun 7, 11:36 pm, Uncle Al wrote:

Protons are stable in free space. Neutrons decay with a mean-life of
885.7 seconds or a half-life of 613.9 sec. Roughly equal production
rates sustained over about an hour award you your net skew.

I have just checked the ref again, and quote from just before my
earlier quotation:

"Combining thermodynamics and the changes brought about by cosmic
expansion, one can calculate the fraction of protons and neutrons
based on the temperature at this point. The answer is that there are
about seven protons for every neutron at the beginning of
nucleogenesis, a ratio that would remain stable even after
nucleogenesis is over."

The authors seem pretty adamant that one needs ~7 protons per neutron
_at the start_ of nucleogenesis, for the arithmetic in the Alpher---
Bethe---Gamow paper to work

What is the density at inception? Is reverse beta-decay by squeezing
Fermi exclusion going to collapse a fraction of hydrogen plasma to
neutrons?
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2

Chalky wrote:
I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), struck me as incredible:-
[[...]]

For a slightly more detailed account, see
http://www.astro.ucla.edu/~wright/BBNS.html
http://astro.berkeley.edu/~mwhite/da...bndetails.html

For a detailed review, see
Gary Steigman
"Primordial Nucleosynthesis in the Precision Cosmology Era"
Annual Review of Nuclear and Particle Science 57, 463-491 (2007)
http://adsabs.harvard.edu/abs/2007ARNPS..57..463S

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

On 9 June, 22:49, Chalky wrote:
On Jun 7, 10:19 am, Chalky wrote:

I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), struck me as incredible:-

"there are about seven protons for every neutron at the beginning of
nucleogenesis....... This fraction is in favour of protons initially
primarily because because lower mass of the proton favors their
production."

Why my astonishment?

1) The masses of protons and neutrons are almost identical.

On closer examination of the soup, the following statement needs
revision:

2) Two ups and one down seems as likely a bundle to me as two downs
and one up when my quark soup starts to cool enough.

Actually, I find two downs and one up is the preferred option because
they are electrically neutral. Under charge conservation, every
instance of two ups and one down, must have the associated generation
of one free electron at the big bang.

Generating free electrons? Seem to be charge consevation bounds why
this does not happen.

Diner at the Big Bang Restaurant... "Waiter, what is this strange bug
in my soup"
Waiter........"With all due respect Sir, those aren't strange bugs in
your soup, they are an in house speciality of the Chef...Fishy quarks"

On Jun 10, 8:32Â*am, Uncle Al wrote:
Chalky wrote:

On Jun 7, 11:36 pm, Uncle Al wrote:

Protons are stable in free space. Â*Neutrons decay with a mean-life of
885.7 seconds or a half-life of 613.9 sec. Â*Roughly equal production
rates sustained over about an hour award you your net skew.

I have just checked the ref again, and quote from just before my
earlier quotation:

"Combining thermodynamics and the changes brought about by cosmic
expansion, one can calculate the fraction of protons and neutrons
based on the temperature at this point. The answer is that there are
about seven protons for every neutron at the beginning of
nucleogenesis, a ratio that would remain stable even after
nucleogenesis is over."

The authors seem pretty adamant that one needs ~7 protons per neutron
_at the start_ of nucleogenesis, for the arithmetic in the Alpher---
Bethe---Gamow paper to work

What is the density at inception? Â*

Dunno but it should be pretty simple to work out approximately. (Mean
density now multiplied by the cube of 13.7 billion years / 3 minutes)

Is reverse beta-decay by squeezing
Fermi exclusion going to collapse a fraction of hydrogen plasma to
neutrons?

Quite possibly, if we are starting out with pure hydrogen plasma (or
its quark soup equivalent)

In this case we are talking about up quark + electron goes to down
quark.

On the other hand, if we start with pure neutron quark soup, the
opposite is far more likely.

down quark goes to up quark + electron.

I don't know if this reaction rate would be the same in quark soup,
but. if it is, your first response suggests you should be able to work
out how many neutrons are needed to make 7 protons and 7 electrons in
3 minutes, a lot faster than me.

Don't worry 'bout no 'left over' neutrons........Baldrick has a

On Jun 10, 8:15*pm, "Jonathan Thornburg [remove -animal to reply]"
wrote:
Chalky wrote:
I have just been boning up on primordial nucleosynthesis, and the
following statement in Wiki (admittedly not always the most reliable
source), *struck me as incredible:-

[[...]]

For a slightly more detailed account, see
*http://www.astro.ucla.edu/~wright/BBNS.html

Phew! That's all right then. So the ratio of protons to neutrons (or,
more precisely, up quarks to down quarks) _is_ ~50/50 initially, as I
was originally expecting.

*http://astro.berkeley.edu/~mwhite/da...bndetails.html

Oh dear. "(After 3 minutes) approximately 25 percent by mass of the
matter in the universe is now in the form of helium nuclei: the rest
consists of protons."

So when is all the non baryonic dark matter supposed to arrive, and
from where?

For a detailed review, see
* Gary Steigman
* "Primordial Nucleosynthesis in the Precision Cosmology Era"
* Annual Review of Nuclear and Particle Science 57, 463-491 (2007)
*http://adsabs.harvard.edu/abs/2007ARNPS..57..463S

Yep, that seems to confirm ratio of protons to neutrons (hence ups to
downs) does tend to unity as T tends to 0.

Thanks for the refs Jonathan, they have been most helpful [and I
haven't even finished reading the last one yet]