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On 2016-05-24 01:33, John Clark wrote:<br>
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cite="mid:CAJPayv1r4FYa11PmH7d6TDrPBvGCw755ANSAZF=TskD_SZr+Zg@mail.gmail.com"
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<div class="gmail_extra">On Mon, May 23, 2016 at 2:57 PM, Anders
Sandberg <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:anders@aleph.se" target="_blank">anders@aleph.se</a>></span>
wrote:
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n 2016-05-23 19:19, John Clark wrote:<br>
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We know from the percentage of the elements
Hydrogen, Deuterium, Helium and Lithium how
much regular matter was around one minute after
the Big Bang when nucleosynthesis cooked up
these elements, and there is no room for Dark
Matter.</font></blockquote>
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Huh? Can you unfold how the nucleosynthesis data doesn't
fit dark matter? Last time I checked the literature
(fall last year) there was a fairly decent parameter
window of the nuclei/DM parameter space, where lithium
abundance was used as a sensitive constraint on the
properties of DM. <br>
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The present
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lithium
<div class="gmail_default"
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Helium </div>
abundance
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gives a tight constraint on the amount of normal
baryonic matter (matter made from electrons neutrons and
protons) that
<div class="gmail_default"
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have </div>
existed at the time of nucleosynthesis
<div class="gmail_default"
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and there is not nearly enough of it to account for </div>
<div class="gmail_default"
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Matter. So whatever Dark Matter is it can not be
normal </div>
baryonic matter
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and it can't be made of Stellar Black Holes</div>
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<br>
So how does this rule out WIMPs? In fact, if I understand the models
right, WIMPs are much better at explaining halo shapes than MACHOs.
While it might be annoying to posit some new weakly interacting
particle, there is ample precedent for them existing (neutrinos) and
they sometimes show up because of other theories (axinos and Susy).
It seems a bit premature to immediately latch on to black holes.<br>
<br>
Although it does indeed nicely explain that early black hole. Of
course, we should be able to figure out a frequency distribution of
early too large holes from this theory and check it. <br>
<br>
<pre class="moz-signature" cols="72">--
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University</pre>
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