[Paleopsych] The perfect liquid
Euterpel66 at aol.com
Euterpel66 at aol.com
Fri Apr 22 17:55:58 UTC 2005
RHIC Scientists Serve Up Perfect Liquid
These images contrast the degree of interaction and collective motion, or
"flow," among quarks in the predicted gaseous quark-gluon plasma state (Figure
A, see mpeg _animation_ (http://www.bnl.gov/video/files/anigas_v3.mpg) ) vs.
the liquid state that has been observed in gold-gold collisions at RHIC
(Figure B, see mpeg _animation_ (http://www.bnl.gov/video/files/aniliquid_v3.mpg)
). The green "force lines" and collective motion (visible on the animated
version only) show the much higher degree of interaction and flow among the
quarks in what is now being described as a nearly "perfect" liquid. See _larger_
image.Tampa FL (SPX) Apr 19, 2005
The four detector groups conducting research at the Relativistic Heavy Ion
Collider (RHIC) - a giant atom "smasher" located at the U.S. Department of
Energy's Brookhaven National Laboratory - say they've created a new state of
hot, dense matter out of the quarks and gluons that are the basic particles of
atomic nuclei, but it is a state quite different and even more remarkable than
had been predicted.
In peer-reviewed papers summarizing the first three years of RHIC findings,
the scientists say that instead of behaving like a gas of free quarks and
gluons, as was expected, the matter created in RHIC's heavy ion collisions
appears to be more like a liquid.
"Once again, the physics research sponsored by the Department of Energy is
producing historic results," said Secretary of Energy Samuel Bodman, a trained
"The DOE is the principal federal funder of basic research in the physical
sciences, including nuclear and high-energy physics. With today's announcement
we see that investment paying off."
"The truly stunning finding at RHIC that the new state of matter created in
the collisions of gold ions is more like a liquid than a gas gives us a
profound insight into the earliest moments of the universe," said Dr. Raymond L.
Orbach, Director of the DOE Office of Science.
Also of great interest to many following progress at RHIC is the emerging
connection between the collider's results and calculations using the methods of
string theory, an approach that attempts to explain fundamental properties of
the universe using 10 dimensions instead of the usual three spatial
dimensions plus time.
"The possibility of a connection between string theory and RHIC collisions is
unexpected and exhilarating," Dr. Orbach said.
"String theory seeks to unify the two great intellectual achievements of
twentieth-century physics, general relativity and quantum mechanics, and it may
well have a profound impact on the physics of the twenty-first century."
The papers, which the four RHIC collaborations (BRAHMS, PHENIX, PHOBOS, and
STAR) have been working on for nearly a year, will be published simultaneously
by the journal Nuclear Physics A, and will also be compiled in a special
Brookhaven report, the Lab announced at the April 2005 meeting of the American
Physical Society in Tampa, Florida.
These summaries indicate that some of the observations at RHIC fit with the
theoretical predictions for a quark-gluon _plasma_
(http://www.spacedaily.com/news/physics-05s.html#) (QGP), the type of matter postulated to have existed
just microseconds after the Big Bang.
Indeed, many theorists have concluded that RHIC has already demonstrated the
creation of quark-gluon plasma.
However, all four collaborations note that there are discrepancies between
the experimental data and early theoretical predictions based on simple models
of quark-gluon plasma formation.
"We know that we've reached the temperature [up to 150,000 times hotter than
the center of the sun] and energy density [energy per unit volume] predicted
to be necessary for forming such a plasma," said Sam Aronson, Brookhaven's
Associate Laboratory Director for High Energy and Nuclear Physics.
But analysis of RHIC data from the start of operations in June 2000 through
the 2003 physics run reveals that the matter formed in RHIC's head-on
collisions of gold ions is more like a liquid than a gas.
That evidence comes from measurements of unexpected patterns in the
trajectories taken by the thousands of particles produced in individual collisions.
These measurements indicate that the primordial particles produced in the
collisions tend to move collectively in response to variations of pressure
across the volume formed by the colliding nuclei.
Scientists refer to this phenomenon as "flow," since it is analogous to the
properties of fluid motion.
However, unlike ordinary liquids, in which individual molecules move about
randomly, the hot matter formed at RHIC seems to move in a pattern that
exhibits a high degree of coordination among the particles - somewhat like a school
of fish that responds as one entity while moving through a changing
"This is fluid motion that is nearly 'perfect,'" Aronson said, meaning it can
be explained by equations of hydrodynamics.
These equations were developed to describe theoretically "perfect" fluids -
those with extremely low viscosity and the ability to reach thermal
equilibrium very rapidly due to the high degree of interaction among the particles.
While RHIC scientists don't have a direct measure of viscosity, they can
infer from the flow pattern that, qualitatively, the viscosity is very low,
approaching the quantum mechanical limit.
Together, these facts present a compelling case: "In fact, the degree of
collective interaction, rapid thermalization, and extremely low viscosity of the
matter being formed at RHIC make this the most nearly perfect liquid ever
observed," Aronson said.
In results reported earlier, other measurements at RHIC have shown "jets" of
high-energy quarks and gluons being dramatically slowed down as they traverse
the hot fireball produced in the collisions.
This "jet quenching" demonstrates that the energy density in this new form of
matter is extraordinarily high - much higher than can be explained by a
medium consisting of ordinary nuclear matter.
"The current findings don't rule out the possibility that this new state of
matter is in fact a form of the quark-gluon plasma, just different from what
had been theorized," Aronson said.
Many scientists believe this to be the case, and detailed measurements are
now under way at RHIC to resolve this question.
Theoretical physicists, whose standard calculations cannot incorporate the
strong coupling observed between the quarks and gluons at RHIC, are also
revisiting some of their early models and predictions.
To try to address these issues, they are running massive numerical
simulations on some of the world's most powerful _computers_
Others are attempting to incorporate quantitative measures of viscosity into
the equations of motion for fluid moving at nearly the speed of light.
One subset of calculations uses the methods of string theory to predict the
viscosity of the liquid being created at RHIC and to explain some of the other
Such studies will provide a more quantitative understanding of how "nearly
perfect" the liquid is.
The unexpected findings also introduce a wide range of opportunity for new
scientific discovery regarding the properties of matter at extremes of
temperature and density previously inaccessible in a laboratory.
"The finding of a nearly perfect liquid in a laboratory experiment recreating
the conditions believed to have existed a few microseconds after the birth
of the universe is truly astonishing," said Praveen Chaudhari, Director of
"The four RHIC collaborations are now collecting and analyzing very large new
data sets from the fourth and fifth years of operation, and I expect more
exciting and intriguing revelations in the near future."
Believe those who are seeking the truth. Doubt those who find it.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the paleopsych