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Re: starship-design: A few thoughts on drag & exoitc stuff(was 'still doing stardrives')

Hi Group,

Nels I think you're confusing two different types of DM. Axions are very
light particles - fractions of an electron volt - so they can't be WIMPs
[Weakly Interacting Massive Particles.] They're kind of like neutrinos for
SUSY and would make great "hot" DM. Neutralinos are massive - 60 GeV at the
lightest - and so make great WIMPs. Every baryon should have a corresponding
neutralino, so they'd very neatly explain DM's proportion to "light matter"
~ 100/1. Axions wouldn't sink into the Sun, since they flit around at near c
constantly, but neutralinos would. However I personally think that
helioseismological data rules out any kind of solar core cooling explanation
of the solar neutrino problem. Neutrino oscillations are the most likely
option since the deficit seems to selectively hit certain parts of the
neutrino spectrum.


Heavy DM also explains why DM seems to congregate more at the cluster
level - it'd take longer to clump at galactic densities than "light matter",
so most of it would still be infalling.

----- Original Message -----
From: N. Lindberg <nlindber@u.washington.edu>
To: starship design <starship-design@lists.uoregon.edu>
Sent: Thursday, February 18, 1999 6:11 AM
Subject: Re: starship-design: A few thoughts on drag & exoitc stuff(was
'still doing stardrives')

>  I read an abstract recently of an experimental setup to measure axion
>decay in a strong magnetic field. Preliminary results indicate that
>_something_ is going on.  Also there was some kind of result at the Gran
>Sasso facility in Italy having to do with dark matter (WIMPs as I recall).
>Look it up if you're interested.  Another thing that I forgot to mention,
>if axions are a big part of DM, then they would tend to sink to the center
>of the sun locally.  Their presence could help to explain the 'solar
>neutrino problem' that so vexes the standard model.
> Nels
>On Wed, 17 Feb 1999, AJ & AJ Crowl wrote:
>> Hi Group,
>> ----- Original Message -----
>> From: N. Lindberg <nlindber@u.washington.edu>
>> To: L. Clayton Parker <lparker@cacaphony.net>
>> Cc: <KellySt@aol.com>; <jthunderbird@nternet.com>;
>> <starship-design@lists.uoregon.edu>
>> Sent: Wednesday, February 10, 1999 3:55 AM
>> Subject: starship-design: A few thoughts on drag & exoitc stuff(was
>> doing stardrives')
>> > One of the candidates for the 'dark matter' that accounts for 90%
>> >of our universe and our galaxy is a low-rest mass particle called the
>> >axion.  This is one of those wierd things that are predicted by SUSY and
>> >superstring theories.  It has the interesting property that it decays
>> >photons in the presence of a strong magnetic field.  Of course, if they
>> >exist in large quantity in interstellar space, the magnetic field from
>> >Bussard scoop would cause their decay.  At low speeds (relative to the
>> >galactic DM halo) the microwaves produced wouldn't be a big deal, but at
>> >high speed they could produce enourmous effects.  I have no idea whether
>> >this would produce drag, thrust, or a force normal to the path.
>> > Best Regards,
>> > Nels Lindberg
>> >
>> Interesting thought. Reminds me of Haisch and co's work on inertia as the
>> ZPF's reaction to an accelerating charge. Perhaps Dark Matter will turn
>> to be neutralinos instead, since some researchers think they've actually
>> found a few. I think if you're moving fast enough to worry about axion
>> you'll be fending off a whole lot more radiation from interstellar gas
>> interacting with your scoop fields - synchrotron radiation would get
>> bad ar close to c.
>> Adam