Re: Axion? Huh?

[Daniel Schroeder <DSCHROEDER@CC.WEBER.EDU>]

> > Can someone tell me what an axion is, as it applies to particle physics?
> > Thanks in advance.
>
> It is a figment intended as a component of the hot dark matter "theory".
> The latter gives "theory" a bad name.
>
> Leigh

Although it may play an important role in cosmology (if it exists),
the axion was most definitely not invented by or for cosmologists.
It was invented by particle physicists, for reasons coming entirely
from within particle physics.  It's part of a proposed solution to
the so-called "strong CP problem"--the fact that the strong interactions
don't violate CP symmetry even though they could in principle.  Usually
when something doesn't happen, it's because a symmetry prevents it
from happening.  Symmetries in particle physics often imply the
existence of new particles.  That's a rough outline of the reasoning,
if I'm remembering correctly.  For more detail, look in any advanced
treatise on particle physics (such as Cheng and Li) or grand unified
theories (such as Ross).

Dan