[Fwd: Re: WIMPS:wasPhotons in other dimensions]

[Hugh Logan <HloganPHY@CFL.RR.COM>]

This message was apparently inadvertently sent to myself.

-------- Original Message --------
Subject: Re: WIMPS:wasPhotons in other dimensions
Date: Thu, 22 Apr 2004 00:21:26 -0400
From: Hugh Logan <HloganPHY@cfl.rr.com>
Reply-To: HloganPHY@cfl.rr.com
To: HloganPHY@cfl.rr.com
References: <0HW800L4RPUO92@mailgate1.nau.edu>
<a06001209bca5f451d7eb@[144.17.10.100]> <4080F129.5000006@cfl.rr.com>

In a recent message, I quoted an article from Phys. Rev. Focus. Despite
 the level of Phys.Rev. Letters, this appears to be a popular article
 written for a less advanced audience:

> > Incidentally, the name "Kaluza-Klein particle" is now used as the name
> > of a possible candidate for at least one kind of WIMP
> > (Weakly-Interacting Massive Particles) that could make up cold dark
> > matter. There is a short article from Physical Review Focus, "Detecting
> > Dark Dimensions," at http://focus.aps.org/story/v10/st21 with a link to
> > the abstract of Kaluza-Klein Dark Matter
> > Hsin-Chia Cheng, Jonathan L. Feng, and Konstantin T. Matchev
> > Phys. Rev. Lett. 89, 211301 (issue of 18 November 2002). According to
> > the Phys. Rev. Focus article:
> >
> > "Kaluza-Klein particles are named for the two theorists who first
> > proposed that extra dimensions could be "curled up" to a size too small
> > for us to notice them. In the simplest case, these particles would be
> > much like those of the standard model, but would move through four
> > spatial dimensions instead of three. Their momentum along the fourth
> > dimension would appear as additional mass in three dimensions, so we
> > would observe heavy photons or heavy electrons, for example. The smaller
> > the extra dimension, the greater the mass."

I feel uncomfortable about referring to "heavy photons," if by that they
 mean photons with rest mass greater than zero. I can't imagine anything
that we could observe as a photon with a non-zero rest mass. I think
such a "photon" would have a speed v<c, something like George Gamow's
_Mr. Tompkins in Wonderland_. As I recall, Mr. Tompkins fell asleep at a
physics lecture and dreamed about a world in which c was like an
everyday speed in our world. This would be even more bizarre -- with a
wide range of photon masses and speeds. It is my impression that
professional physicists regard mass as a scalar invariant nowadays
rather than "relativistic mass," m=E/c^2. Perhaps the author means more
energetic photons, but I am not sure. I suspect that the Phys. Rev.
Letters article to which the author refers would be more precise.

Perhaps the author meant the superpartner of the photon, a photino.
Since the photon (spin 1) is a boson, its superpartner would be a
fermion. Superpartners of bosons (with integer spin), are fermions (with
odd half-integer spin) and vice-versa. Superpartners of bosons have the
suffix "ino" as illustrated for a photon. Superpartners of fermions have
the prefix "s." The superpartner of a quark with spin 1/2 would be a
squark. It is my understanding that a particle and its superpartner are
separate entities, just as an electron and its antiparticle, the
positron, are. Just as conservation of charge requires equal and
opposite charges to be produced in pair production, a conservation law
in supersymmetry requires that if a particle is produced, its
superpartner must also be produced. However, it is my impression that
the quoted passage from Phys. Rev. Focus refers to one and the same
particle, described from the frame including the extra dimension and
also as observed in our uncompactified space-time, perhaps in an
experiment where it is forced to interact.

Some have compared the requirement that the conservation law regarding
the production of superpartners, none of which have been observed, with
the situation just after Dirac predicted the existence of antimatter.
The discovery of the positron came quickly thereafter. Will it be the
same for superpartners of ordinary particles, at least those that can be
observed at lower energies?

The most likely to be observed WIMP (weakly interacting massive
particle) is regarded to be a neutralino. This is a superposition of
three "ino's," the photino, Higgsino, and Z-ino mixed into arbitrary
combinations called the neutralinos (1). The slide (#52)on detection of
WIMPs in Dr. Jonathan Bagger's presentation (2) referred to in my
earlier posting shows a neutralino being detected in an underground
laboratory. Other ways in which one might find evidence of Kaluza-Klein
dark matter are reported in
http://www.spacedaily.com/news/cosmology-03o.html . K.T.Matchev, one of
the Phys. Rev. Letter article authors, is quoted in this article.

A tutorial, "Superstrings!" by J. Pierre at
http://www.sukidog.com/jpierre/strings/extradim.htm gives an explanation
of how the momentum states of a decompactifying extra dimension can give
rise to a continuum of masses in the non-compactified world, presumably
the 3+1 dimensions of space-time. It is stated,"In particular, a
massless state in the higher dimensional theory will show up in the
lower dimensional theory as a tower of equally spaced massive states." I
presume they are talking about one and the same particle as mentioned
above. I would like to see more specific examples.

Those of us who are not string theorists will, unfortunately, have to
rely on explanations intended for non-specialists. My original posting
was a search for photons that had at least some coordinates in the
hidden dimensions of string theory. According to the reference I
referred to, the hidden dimensions were dark. If so, the hidden
dimensions of string theory would be ruled out. John disagreed with
this, saying, "Flatland is not dark." There was another opinion,
questioning whether the leaking of the electromagnetic field into the
hidden dimensions would cause problems with Gauss's law. I am not even
sure that the hidden dimensions are "flat," since superstring theory,
extended to M-theory, is supposed to reduce to 11-dimensional
supergravity in the low energy limit. But this is going beyond what I
understand.

Still another point to ponder. Although Kaluza-Klein particles have a
compactified dimension, and supersymmetry pertains to them, it is not
clear that they are exactly explained by string theory. I believe
supersymmetry pertained to point particles before it was used in string
theory. The tutorial referred to above seems to make a contrast between
Kaluza-Klein compactified dimensions and those of string theory.

(1)"The Nature of the Dark Matter,
"http://web.mit.edu/~redingtn/www/netadv/specr/012/012.html . At the
bottom of this page, click on "Search for Wimp Dark Matter
(Neutralinos)" and the first sub-section, "Motivation for Supersymmetry."

(2) http://www.physics.fsu.edu/DiracSymposium/Talks/Bagger.pdf  .