SETI public: Fw: Physics News Update 664

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Sent: Tuesday, December 02, 2003 11:24 AM
To: ljk4_at_MSN.COM
Subject: Physics News Update 664

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 664 December 2, 2003 by Phillip F. Schewe, Ben Stein, and
James Riordon

THE TOP PHYSICS STORIES OF 2003. The first three on our list
concern the sharpening of our understanding of the big bang era,
evidence for new quark groupings, and progress in manipulating
quantum gases. At the largest size scale, new observations from
the Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital
Survey and other telescopes have reduced the uncertainties in the
values of such cosmic parameters as the Hubble constant, the age of
the universe, and the fractions of total energy vested in the form
of dark and luminous matter
(www.aip.org/enews/physnews/2003/split/624-1.html;
www.aip.org/enews/physnews/2003/split/659-1.html ). Going to the
opposite extreme, at the level of elementary matter, new data
indicate that quarks needn't appear only in clumps of three
(baryons) or two (mesons). Work at SLAC (US) and KEK (Japan) hint
that quarks might also exist in "tetraquark" states
(http://www.aip.org/enews/physnews/2003/split/643-1.html), while
experiments in Japan, the US, Russia, and elsewhere provide evidence
for a "pentaquark" state
(http://www.aip.org/enews/physnews/2003/split/644-1.html ). The
third top story concerns the creation of the first ever Bose
Einstein condensate (BEC) consisting of paired-fermion-atom
molecules. This work is potentially important because mastering the
interactions between fermion atoms in the BEC state might provide
insights into the nature of superconductivity and superfluids
(http://www.aip.org/enews/physnews/2003/split/663-1.html ). Other
notable physics stories from the past year include the controversy
over the use gravitational lensing of distant radio waves by Jupiter
to measure the speed of gravity
(http://www.aip.org/enews/physnews/2003/split/620-1.html ); advances
in the use of attosecond laser pulses in studying chemical reactions
(http://www.aip.org/enews/physnews/2003/split/625-1.html ); the use
of microfluidics---essentially the science of fluids on a chip---in
processing bio-particles such as blood cells and DNA molecules
(http://www.aip.org/enews/physnews/2003/split/627-1.html ); evidence
for the focusing of light in left-handed materials, materials with a
negative index of refraction, and vindication of earlier research in
this area (http://www.aip.org/enews/physnews/2003/split/628-1.html
); first fusion reactions in Sandia's Z machine
(http://www.aip.org/enews/physnews/2003/split/632-1.html ); LIGO's
first scientific publications report no gravity wave events but do
succeed in establishing new upper limits on various wave production
processes (http://www.aip.org/enews/physnews/2003/split/632-2.html
); building a laser based on a single atom at rest
(http://www.aip.org/enews/physnews/2003/split/654-1.html );
amphoteric refraction, both positive and negative refraction, in a
single material
(http://www.aip.org/enews/physnews/2003/split/657-3.html ); and new
work with photonic crystals, including the effects of shock waves
(http://www.aip.org/enews/physnews/2003/split/634-1.html) and energy
shifting (http://www.aip.org/enews/physnews/2003/split/646-1.html).

RELATIVISTIC CHAOS. A new study shows that general relativity, a
theory in which observers in different reference frames measure time
differently, is not incompatible with chaos theory, in which events
unfold in absolute time. Chaos is an ordinary word with lots of
meanings. In physics, however, the meaning is more precise: a
system---a weather system, say---is chaotic if a very slight change
in initial conditions sends the system off into a very different
history. How different? The degree to which a system is chaotic
can be encapsulated in a parameter called the Lyapunov exponent:
when it is positive the system is chaotic and to some extent
unpredictable; for a negative value, the system becomes
nonchaotic---a small perturbation will not radically change its
history. What has worried physicists for many years was the fear
that a shift in a frame of reference might so alter the time
parameter as to change the Lyapunov exponent from null or negative
to positive or vice versa. In other words, the change of frame
would seem to make a chaotic system nonchaotic or vice versa. Now,
the work of Adilson Motter of the Max Planck Institute for Complex
Systems in Dresden, Germany lays this matter to rest. He shows
(motter_at_mpipks-dresden.mpg.de,
http://www.mpipks-dresden.mpg.de/~motter ) that over a wide range of
conditions, a change of time parameter does not alter the Lyapunov
exponent enough to change chaos in a system. Motter believes that
this is good news since the equations of general relativity are
nonlinear, as are those of chaotic systems, and many common
situations described by general relativity, such as the motion of
massive bodies near black holes or a nonuniform expansion of the
universe at the time of the big bang ("mixmaster universe model,"see
http://www.aip.org/enews/physnews/1993/split/pnu158-3.htm ) are
expected to be highly chaotic. (Physical Review Letters, 5 December
2003)

***********
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• Previous message: LARRY KLAES: "SETI public: Binary pulsars boost hope for gravity wave hunters"

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