DIMMING SUPERNOVAS WITHOUT COSMIC
ACCELERATION. Several years ago two different studies of
distant supernovas seemed to suggest that the expansion of the
universe was not slowing but actually accelerating (go to
www.aip.org/physnews/update and see Update 361). One
implication of this would be the existence of some kind of anti-
gravity or "dark energy" responsible for counteracting the mutual
gravitational attractiveness thought to be operating among all the
galaxies. But could there be another explanation for the observed
dimness of distant supernovas? Scientists from Los Alamos and
Stanford say yes, there is. John Terning
(terning@particle.lanl.gov, 505-665-0437), Csaba Csaki, and
Nemanja say that the dimness might arise when photons from the
supernovas turn into axions on their way to Earth. Axions are
hypothetical particles which are thought to account for some of the
asymmetries between left-handed and right-handed things in the
universe. The occasional transformation of a photon into an axion
and back again would be analogous to the oscillation of one
neutrino species into another and back again; in the oscillation
process at least one of the species must have some mass. The
axions would probably have a very low mass, something like 10^-
16 eV. Terning says that the axion hypothesis nicely recreates the
observed supernova luminosity actually observed. A direct search
for axions is underway at the CERN Axion Solar Telescope
(CAST), http://axnd02.cern.ch/CAST/). (Csaki et al., Physical
Review Letters, 22 April 2002; text at
www.aip.org/physnews/select; see also http://t8web.lanl.gov/people/terning/axion.html)