<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, May 23, 2016 at 2:57 PM, Anders Sandberg <span dir="ltr"><<a href="mailto:anders@aleph.se" target="_blank">anders@aleph.se</a>></span> wrote:</div><div class="gmail_quote"><br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
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O<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>n 2016-05-23 19:19, John Clark wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><font size="4"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">>> </div>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></div></span></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"> </blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000"><span class=""><div dir="ltr">
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<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">> </div>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></div></blockquote><div><br></div><div><font size="4"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"></div>The present<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>lithium <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">and Helium </div>abundance<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> </div>gives a tight constraint on the amount of normal baryonic matter (matter made from electrons neutrons and protons) that <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">could have </div>existed at the time of nucleosynthesis<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">, and there is not nearly enough of it to account for </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">Dark Matter. So whatever Dark Matter is it can not be normal </div>baryonic matter<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> and it can't be made of Stellar Black Holes that came from burnt out stars either because stars are made </div>baryonic matter<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> and there was never enough </div>baryonic matter<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">. But Dark Matter </div><span style="font-family:arial,helvetica,sans-serif">might be made of Primordial Black Holes that were made of stuff that was never baryonic and formed not one minute after the Big Bang as <div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">Helium and </div>Lithium w<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">ere</div> but less than a thousandth of a second after the Big Bang.</span></font></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><br></div></div><div><font size="4"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">Primordial Black Holes </div><font face="arial, helvetica, sans-serif">could solve another </font><div class="gmail_default" style="display:inline"><font face="arial, helvetica, sans-serif">mystery too. Astronomers have found a 12 billion solar mass supermassive Black Hole that existed just 900 million years after the Big Bang, and they've had a very hard time explaining how a Black Hole could get that big so quickly from the merger of much smaller Stellar Black Holes that were produced from dead stars. But if you had 100 solar mass Black Holes around since day one, and if they were very very common, in fact if 85% of all matter was in that form, then the creation of a 12 billion solar mass Black Hole 900 million years later is much easier to explain. </font></div></font></div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">> </div>I thought the gravitational lensing studies ruled out black hole
halos fairly strongly.</div></blockquote><br><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><font size="4">The number of </font></div><font size="4">gravitational lensing<div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"> events that have been observed has ruled out Dark Matter being made of Black Holes larger than 100 solar masses, but not smaller. And the fact that we don't see a lot of widely spaced binary stars moving in strange orbits rules out Dark Matter made of Black Holes smaller than 10 solar masses but not larger. Nothing has ruled out Dark Matter being in the 10 to 100 solar mass range and LIGO found Black Holes right smack in the middle of that range. </div><br></font></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><font size="4"><br></font></div></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline"><font size="4"> John K Clark</font></div></div><div><br></div><div><br></div><div> </div></div></div></div>