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Topic Name: Physicists see similarities in stream of granular particles, exotic plasma at birth of universe
Category: Advanced Materials
Research persons: Sidney Nagel, Heinrich Jaeger, Xiang Cheng, German Varas
Location: University of Chicago, United States
Details
Streams of granular particles bouncing off a target in a simple tabletop experiment produce liquid-like behavior also witnessed in a massive research apparatus that simulates the birth of the universe. A team led by the
University of Chicago's Sidney Nagel and Heinrich Jaeger report this surprising finding in the Oct. 27-Nov. 2 issue of Physical Review Letters.
"Nature plays the tricks that it knows how to play over and over again," said Nagel, the Stein Freiler Distinguished Service Professor in Physics at Chicago. Nagel and Jaeger co-authored the paper, along with Xiang Cheng, a graduate student in physics at Chicago; German Varas, a graduate student in physics at the
University of Chile; and Daniel Citron, a Chicago undergraduate in physics.
Scientists have attained a good understanding of equilibrium phenomena, which
are governed primarily by temperature or pressure. But what about phenomena that
have been pushed far beyond their equilibrium states, like a jet of sand"
What about quark-gluon plasma, the mixture of subatomic particles that existed
for perhaps a few millionths of a second after the big bang"
"We really don't know what the right concepts are to describe
this," Nagel said. "We love the physics of granular material because
it allows us entrée into this question in relatively simple experiments."
In designing their tabletop experiment, the Chicago team addressed a
fundamental question about equilibrium: Under what conditions does a collection
of molecules, sand grains or other particles behave like a liquid"
Macroscopic and subatomic particles sometimes behave in similar ways. The
particles in the Chicago experiment are large enough to allow scientists to
track under precisely controlled conditions, an option not available on the
subatomic scale.
A paper published in 1883 that described the water-bell phenomenon inspired
the granular-stream experiment. The paper reports how a stream of water hitting
a narrow, flat, circular target becomes transformed into the thin, hollow shape
of a bell. Would a stream of granular materials do likewise"
Cheng, the Chicago graduate student, performed an experiment to find out. He
blasted globs of glass and copper beads through a tube into a flat target.
"The answer is you can in fact see those bells," said Jaeger, a
Professor in Physics. "Specifically, we find that the rapid collisions of
densely packed particles produce the liquid state that we can then observe
afterward, when everything flies apart and produces these beautiful envelope
structures."
Scientists have seen similar structures in the quark-gluon plasma experiments
conducted at Brookhaven National Laboratory with the Relativistic Heavy Ion
Collider. The $500 million RHIC smashes gold atoms into each other at nearly the
speed of light. The tabletop Chicago experiment launches jets of granular
materials into a flat target at no more than 12 miles an hour.
"There couldn't be anything farther apart than our experiments and those
at RHIC," Nagel said. For that very reason, the Chicago team conducted
their test under a variety of conditions to ensure that interactions between the
granular particles and the air did not affect the experimental result. "The
key ingredient is the high density of rapid collisions," Jaeger said.
The similarity between the granular-jet and RHIC experiments are surprising
because scientists would expect quantum physics to dominate the results of the
latter. Quantum physics typically rules the atomic and subatomic world.
Classical physics, meanwhile, applies to the much larger objects of everyday
life.
Nevertheless, the RHIC scientists have interpreted their results in a
classical way. "They say it's like a liquid. That's a classical concept.
Then they ascribe to this liquid such things as viscosity. Well, that's a
classical concept," Nagel said. "Some of these phenomena that appear
at this very microscopic, quantum scale echo phenomena that occur on the
classical scale.
"That's the amazing thing about physics. The laws you have at one level
really are the same as at other levels, or at least influence what happens at
other levels. Certain principles are just invariant. Conservation of energy and
momentum-you can't get away from these things on any scale."
Note for Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when grains collide). The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations. Thus, the lower size limit for grains in granular material is about 1 µm. On the upper size limit, the physics of granular materials may be applied to ice floes where the individual grains are icebergs.
Examples of granular materials would include nuts, coal, sand, rice, coffee, corn flakes, fertilizer, and ball bearings. Powders are a special class of granular material due to their small particle size, which makes them more cohesive and more easily suspended in a gas. Granular materials are commercially important in applications as diverse as pharmaceutical industry, agriculture, and energy production. Research into granular materials is thus directly applicable and goes back at least to Charles-Augustin de Coulomb, whose law of friction was originally stated for granular materials.
According to material scientist Patrick Richard, "Granular materials are ubiquitous in nature and are the second-most manipulated material in industry (the first one is water)".
Note for Relativistic Heavy Ion Collider
The Relativistic Heavy Ion Collider (RHIC) is a heavy-ion collider located at and operated by Brookhaven National Laboratory (BNL) in Upton, New
York. By using RHIC to collide ions traveling at relativistic speeds, physicists study the primordial form of matter that existed in the universe shortly after the Big
Bang, and also the structure of protons.
At present, RHIC is the most powerful heavy-ion collider in the world. It is also distinctive in its capability to collide spin-polarized protons.
RHIC is an intersecting storage ring (ISR) particle accelerator. Two independent rings (arbitrarily denoted as "blue" and "yellow" rings, see also the photograph) allow a virtually free choice of colliding projectiles. The RHIC double storage ring is itself hexagonally shaped and 3834 m long in circumference, with curved edges in which stored particles are deflected by 1,740 superconducting niobium titanium magnets. The six interaction points are at the middle of the six relatively straight sections, where the two rings cross, allowing the particles to collide. The interaction points are enumerated by clock positions, with the injection point at 6 o'clock.
About Researchers:
Sidney R. Nagel, Ph.D.
Member, UChicago Argonne, LLC Board of Governors for Argonne National Laboratory
Stein-Freiler Distinguished Service Professor, Department of Physics, James Franck Institute, The University of Chicago
Sidney Nagel specializes in the physics of solids, liquids and granular materials. Much of his work has drawn attention to phenomena scientists have regarded as outside the realm of traditional physics, including the physics of granular materials such as sand and coffee stains, which appear to be simple but in fact involve deep scientific issues.
His work has included developing ways to protect transplanted cells used to fight diabetes and other diseases.
Heinrich Jaeger
Professor in Physics and the James Franck Institute, Director of the Materials Research Science and Engineering Center
Areas of Expertise:
Physics
Technology: Granular materials, nanotechnology, Superconductivity
Art: Science and art
Media Contact:
Steve Koppes
(773) 702-8366
s-koppes@uchicago.edu
Background:
Jaeger specializes in the study of nanoscale physics. At this scale, metallic, superconducting and semiconducting structures display properties that differ fundamentally from behavior on larger scales. Another interest of Jaeger's is the flow of granular materials, including dry sand and powders. These materials perplex physicists because they exhibit flow behavior far different from ordinary solids, liquids and gases. Yet understanding the peculiar behavior of granular materials is vital for predicting and controlling them under a variety of industrial, civil engineering and scientific conditions. With colleagues in the arts, Jaeger launched the "S3 Project: the Sights and Sounds of Science" in 2003, to explore and encourage the relationship between science and art.
Xiang Cheng
Ph.D. Candidate, Department of Physics, The University of Chicago.
Address:
The James Franck Institute
The University of Chicago
929 E 57th Street
Chicago, Illinois 60637, USA
Office: CIS-E038
Phone: (773) 702-7204 and (773) 702-6075
Email: xcheng@uchicago.edu
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