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

	Galactic DM is prohibited from high velocity because it has to
stay bound to the galaxy.  If axions are a part of Galactic DM, then they
should have fairly low velocities.  That they have low mass (.3-.6eV, I
think) doesn't matter if you have a //lot// of them, or they are merely
one kind of DM particle in a zoo of them.  Also, axions with high velocity
ought to be rare, because in order to get to a high speed localy, a
primordial axion would need to interact with some particle.  Gravity isn't
likely to do that, and electromagnetic interactions cause decay.
Therefore I doubt that there is a local population of axions with a large
average velocity.  
	Which leads me to a pipedream i had last night.  Given that there
is a lot of DM out there, thinned out though it may be, a starship could
use it as a fuel and/or reaction mass, at least at high speed when the
flux is higher.  Anyone know of any exotic particles that decay
covienienly, preferably liberating lots of juice as they do so?

On Thu, 18 Feb 1999, AJ & AJ Crowl wrote:

> 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.
> Adam
> PS
> 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
> 'still
> >> 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
> into
> >> >photons in the presence of a strong magnetic field.  Of course, if they
> >> >exist in large quantity in interstellar space, the magnetic field from
> any
> >> >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
> out
> >> 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
> decay
> >> you'll be fending off a whole lot more radiation from interstellar gas
> >> interacting with your scoop fields - synchrotron radiation would get
> pretty
> >> bad ar close to c.
> >>
> >> Adam
> >>
> >>
> >>
> >
> >