[Paleopsych] The perfect liquid

Euterpel66 at aol.com Euterpel66 at aol.com
Fri Apr 22 17:55:58 UTC 2005

_ (http://www.spacedaily.com/cosmology.html) 
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  
chemical engineer.  
"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_ 
(http://www.spacedaily.com/news/physics-05s.html#) .  
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 
 surprising findings.  
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  
Brookhaven Lab.  
"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."  

Lorraine  Rice

Believe those who are seeking the truth. Doubt those who find it.  
---Andre Gide  

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