On Fri, 15 Mar 2002, Rose wrote:
> So, if the particles are likely to have a mass as big as 100 a.m.u, are
> they likely to decay into smaller particles or is it difficult to say at
> this stage?  Also, if they do have such a high mass, are they likely to
> account for all the 'missing matter' in the universe?

That's the idea.  It may be that there are several different
species of particles constituting the missing mass.  But our
best guess, and the simplest explanation, is that there is
one dominant species of dark matter and it is made of WIMPs.

> One other thing, sorry if this is a stupid question, but if the particles
> don't have electromagnetic interactions, just how do they interact with the
> nuclei of atoms?   

Good question.  So, in particle theory there are particles
and fields.  Every particle with mass interacts gravitationally,
through the graviton, which is a "quantum" or "package" of energy
of the gravitational field.  Everything with charge interacts
with the electromagnetic field through photons which are
the force carriers of the electromegnetic field (light is a
photon, incidentally).  Every quark (which make up protons and
neutrons) interacts through gluons, which are the "quanta"
(packets) of the strong field. The weak field is another field, a bit more
hard to visualize than gravity and it is in fact related to
the electromagnetic field.  Certain particles (neutrinos, WIMPs?)
interact through the weak field and its "quanta" are called the
"W and Z bosons".  The point is just as things without
charge can interact gravitationally, things without charge can
also interact weakly through weak interactions.  It's non-intuitive,
I know, but sometimes you have to look at things mathematically
to see the underlying symmetry.

Scott Armel-Funkhouser,
Berkeley Cosmology Group