PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 631 April 2, 2003   by Phillip F. Schewe, Ben Stein, and James
Riordon

THE FIRST-EVER LARGE CHINA-TAIWAN SCIENTIFIC COLLABORATION has carried out
a reactor experiment which puts a new upper limit on the neutrino magnetic
moment.  Consider first the electron; it not only has electrical charge but
also spin, which means that it will act like a tiny
magnet.   Even a neutral atom, because of its internal distribution of
negative and positive charge, can have a nonzero magnetic moment.
Consequently neutral atoms can be controlled, to some extent, by magnetic
fields.  But what about a neutrino?  Neutrinos may well possess a small
amount of mass, But what about magnetism?  Can they effectively have a tiny
bit of charge or internal structure?  A nonzero neutrino magnetic moment
provides the neutrino with a way to interact electromagnetically with the
world; generally the neutrino is thought to interact only via the weak
nuclear force.  Evidence for nonzero magnetic moment would show up in
several ways: in anomalous electron-neutrino scattering, in radiative decays
in which the neutrino casts off a gamma ray, and in various astronomical
settings, such as supernovas.  The TEXONO collaboration, using neutrinos
from the 2.9-GW Kuo-Sheng Nuclear Power Station in Taiwan, looked for a
characteristic anomalous electron energy spectrum arising from
electron-neutrino scattering.  They did not see any such evidence, and from
this they derive the best direct-laboratory upper limit on neutrino magnetic
moment, 1.3 x 10^-10 times the magnetic moment of the electron (a unit also
known as the Bohr magneton).  The team also derives an indirect bound on
neutrino radiative decays.  (Li et al., Physical Review Letters, April 4
2003; contact Henry Wong, Academia Sinica, Taiwan, 886-2-2789-6789,
htwong{at}phys.sinica.edu.tw ) The TEXONO Collaboration is supported by
several research institutions (see the website at
hepmail.phys.sinica.edu.tw/~texono ) and their respective funding agencies
from Taiwan and China. An efficient flow of students and scientists moves in
both directions.

SPACESHIP TRAVEL TO ANOTHER UNIVERSE THROUGH A BLACK HOLE may be highly
improbable, but it cannot be ruled out, according to a new analysis that
explores the idea of "hybrid singularity."  As science fiction fans know,
anyone who wishes to fall into a black hole and re-emerge at some distant
location or even an another universe would have to go through a forbidding
region inside the black hole known as a "space-time singularity."
Traditionally this means negotiating a region of infinite density exerting
destructive, tide-like distortions on any "extended object" such as a
spaceship, molecule, or anything that is not truly point-like.  Physicists
now suspect this picture is incomplete and that a second and potentially
milder type of singularity might exist.  Known as a "Cauchy horizon
singularity," it would impart only finite tidal distortions on extended
objects.
The kinder, gentler singularity should only develop when a regular stream
of matter or energy falls into the hole. Previous analyses have considered
only streams that were brief bursts. But long-duration
"non-compact" streams
of radiation, like the cosmic microwave background, can also fall into the
black hole.  In a more comprehensive analysis that  takes these
"non-compact" sources into account, Lior Burko of the University of Utah
(burko{at}physics.utah.edu) explores how a black hole's interior is affected
by such infalling radiation.   If the non-compact sources are weak, Burko
shows, a hybrid singularity forms:  a strong sector (inevitably destructive)
and a weak sector (finite tidal distortions). Conceivably, a spaceship
entering through the weak sector could travel unscathed to another part of
space-time.   If the perturbations due to non-compact sources are large,
however, Burko shows that the singularity ends up being strong, and
destructive, everywhere in the black hole. Whether black hole singularities
in our universe are strong-only or hybrid in nature depends on incompletely
known cosmological parameters (such as the expansion rate of the universe
and the nature of dark energy).  Several factors may ultimately rule out the
possibility of hyperspace travel. They include: (1) the possibility that
"weak" sectors may still be much too hazardous for travel; (2) overwhelming
effects on the black hole from actual non-compact sources and (3) a working
theory of quantum gravity, which may reveal other factors that rule out
hyperspace  travel.  But for now, Burko says, the  possibilities are open.
(Burko, Physical Review Letters, 28 March 2003)

STRETCHABLE GOLD CONDUCTORS.  New, stretchable gold conductors have been
developed by Princeton University researchers. The conductors may be the
answer to problems that arise when engineers build oddly shaped devices
(such as retina-inspired photosensor arrays, for example), or when making
connections to sensors attached to the skin or other flexible surfaces. The
researchers (Stephanie Lacour, 609-258-3582, slacour{at}princeton.edu) built
their new conductors by depositing layers of gold about 100 nanometers thick
on a substrate of poly-dimethyl siloxane (PDMS), a type of plastic material
commonly used in microelectronics-related research and manufacture. (An
underlying 5-nanometer layer of chromium helped to ensure that the gold
would adhere to the PDMS.) Once they had deposited the gold, the researchers
found that compressive stresses in the metal caused the film to buckle,
forming parallel wrinkles in strips of the material. The wrinkles smooth
out, as expected, when the film is stretched by a few tenths of a percent,
but surprisingly the material remained conducting as the film was stretched
up to twenty-three percent beyond its relaxed length. Simple strips of gold
film, on the other hand, break when stretched as little as one percent. As
it was stretched, cracks developed in the gold layer, but current continued
to flow along the strip. The researchers suspect that a thin conductive
metal layer, perhaps only a single molecule thick, may bridge the cracks and
account for the conductivity of the stretched film, although confirmation of
this hypothesis is still forthcoming. (Lacour et al., Applied Physics
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