I tagged this for del.icio.us, but on reflection, it deserves better than to be buried in a links dump. It’s so rare that the New York Times notices physics that doesn’t cost billions of dollars, that Kenneth Chang’s article on glass deserves its own post.
Peter G. Wolynes, a professor of chemistry at the University of California, San Diego, thinks he essentially solved the glass problem two decades ago based on ideas of what glass would look like if cooled infinitely slowly. “I think we have a very good constructive theory of that these days,” Dr. Wolynes said. “Many people tell me this is very contentious. I disagree violently with them.”
Others, like Juan P. Garrahan, professor of physics at the University of Nottingham in England, and David Chandler, professor of chemistry at the University of California, Berkeley, have taken a different approach and are as certain that they are on the right track.
“It surprises most people that we still don’t understand this,” said David R. Reichman, a professor of chemistry at Columbia, who takes yet another approach to the glass problem. “We don’t understand why glass should be a solid and how it forms.”
It’s not my area, but the article at least appears to give a good overview of the problem, and the range of possible solutions. The guy in the office next to mine studies glass transitions, so maybe I’ll ask him what he thinks of the science.
And, hey, it’s non-collider physics in the Mainstream Media. Woo-hoo!
Doesn’t most of the collider science reporting in the mainstream media deal with 1/ it’s size, and 2/ that MOST scientist think it WON’T end creation?
just saying,
-michael
The greatest insight in the paper that triggered the New York Times piece is that glass is “frustrated.” It is trying to crystallize, but it keeps being stuck with icosahedral assemblies of molecules, and icosahedra don’t close-pack in 3-D Euclidean space.
Some quasicrystals in 3-D have icosahedral symmetry, just as Penose tiles can have 5-fold symmetry in 2-D. This can be seen as projection from 4-D or 5-D crystals into 3-D where they cannot be crystals.
It hinges on the oddities of Low Dimensional Topology.
There are an infinite number of regular polygons in 2-D (equilateral triangle, square, pentagon, hexagon, …).
There are exactly 5 convex regular 3-D polyhedra (tetrahedron, octahedron, cube, dodecahedron, icosahedron).
There are exactly 6 convex regular 4-D polytopes. 5-cell (pentachoron) (4-simplex), 8-cell (Tesseract) (4-cube), 16-cell (4-orthoplex, 4-cross-polytope), the beautiful 24-cell (hyperdiamond) which has no analogues in lower or higher domensions, 120-cell (hyperdodecahedron), and 600-cell (hypericosahedron).
For n>4 there are only the three regular n-dimensional polytopes, the simplex with n+1 vertices, the hypercube with 2^n vertices, and the hyperoctahedron = cross polytope = orthoplex with 2n vertices.
Again, things get more complicated if we allow nonconvex shapes (i.e. star polyhedra, star polytopes, which in any case don’t exist for more than 4 dimensions) and hyperbolic spaces where we can pack more stuff into a uniformly curvy cosmos.
Glassy mysteries are because we have 3 spatial dimensions. How odd that we happen to live in such a world. Is it a “coincidence?” Is there a Low Dimensional Topology Anthropic Argument?
The chemist will be wrong with a workable heuristic. The physicist will be correct with a hellacious theory. The chemist plus combinatorial experiment will make stuff in the here and now. The physicist plus supercomputer time will abundantly publish.
What you want as product in the next business quarter? Elegance is financed by net retained earnings (or social activism: waste not, get not).
On reflection? Clearly, this amorphous topic will become somewhat of a polarizing issue.
(Igor! Quick! We need more optics puns!
Nooooo!)
The greatest insight in the paper that triggered the New York Times piece is that glass is “frustrated.” It is trying to crystallize, but it keeps being stuck with icosahedral assemblies of molecules, and icosahedra don’t close-pack in 3-D Euclidean space.
Well, that is one view: frustration due to competing geometric constraints on small and large scales. But it is a very mathematical way of looking at the problem that isn’t necessarily applicable to real molecules, particularly anisotropic or flexible ones. A more physical way of looking at glass, which is more relevant to the work discussed in the article, is in terms of dynamical frustration: the system’s rearrangements are slow because particles are densely packed and/or not moving fast enough to bounce off each other productively.