[math-fun] MIT prof, "quark soup", nuclear physics
Last night I attended a very entertaining talk by MIT Prof. Krishna Rajagopal entitled "quark soup" about the discovery that when nuclear particles are heated up to 2 trillion degrees K, they form a _liquid_ of quarks. Apparently, physicists previously thought that the quarks formed a gas, but this was shown to be incorrect. In the course of this talk, Krishna described a "string-like" theory in which only one additional space dimension was added, and in this space dimension there was a bizarre, but almost classical "gravity" generated by a "black hole" (really a "black sheet", since the field is uniform, not radial) which pulled on all objects, but since force of this "gravity" was orthogonal to the usual 3 dimensions, it had only indirect effects. In particular, a quark & an anti-quark could be thought of as tied together with a string which had enough mass that this "gravity" pulled on the string in an analogy to the catenary curve formed by a massy string in 3D with gravity. The force between the two quarks was that resulting from the projection into 3D of these force vectors -- presumably proportional cos(alpha), where alpha is the angle that the "string" made with usual 3D space. This model explains the usual quark-like behavior where the strength of the interaction gets _stronger_ with (usua l 3D) distance, instead of weaker. If you read the popular science literature, then the "man in the street" version of physics spends an inordinate amount of time worrying about "these extra dimensions" & attaches a mystical significance to them. However, how would such an extra "string-like" dimension be all that much different from the extra dimension used in 3D graphics "homogeneous coordinates", where the projection back into 3D is by dividing out the last coordinate ? After all, most "men in the street" ("street people?" :-) wouldn't attach much mystical significance to homogeneous coordinates, would they? --- I asked Krisha afterward if this "gravitational black sheet" obeyed the usual relativistic laws, including having an event horizon in which time slowed to essentially a stop, and he said yes. Apparently, this "black sheet" also supports Hawking radiation! This is all totally cool, and still 18 orders of magnitude larger than the Planck length, so traditional infinitesimal calculus still "works". I guess this really is a new century in physics.
On 7/8/09, Henry Baker <hbaker1@pipeline.com> wrote:
... If you read the popular science literature, then the "man in the street" version of physics spends an inordinate amount of time worrying about "these extra dimensions" & attaches a mystical significance to them.
However, how would such an extra "string-like" dimension be all that much different from the extra dimension used in 3D graphics "homogeneous coordinates", where the projection back into 3D is by dividing out the last coordinate ? After all, most "men in the street" ("street people?" :-) wouldn't attach much mystical significance to homogeneous coordinates, would they?
That's a nice analogy. Unfortunately, its implications are not reassuring. I taught Computer Graphics for a number of years, and my experience was that a large proportion of my class never came to terms with representing a point in 3-space using 4 components. Their reluctance is on the face of it incomprehensible. After all, in Data Representation courses they regularly meet distinct data structure implementations of the same abstract data type --- what's different about coordinate geometry? Another teacher recently suggested that the problem lies with the familiarity and intuitive appeal of the "real" (Cartesian) representation, acting to prevent the student from modelling the data in any other way. There's a larger-scale analogy of this phenomenon in the heliocentricity controversy which embroiled Galileo and Copernicus --- where again, a naturalistic preoccupation with "existence" of an object (the aether, in effect) obscured the fundamental matter of a spatial relationship (indeed, a geometric symmetry as considered by Klein). [It was highly diverting to read, some years ago, that the Vatican had apologised for this incident, and now agreed that the Earth does rotate around the Sun after all. Perhaps in another 250 years or so, they'll have got around to digesting Einstein! And as for the uncertainty principle, well, one does not like to contemplate the consequences ... ] Fred Lunnon
participants (2)
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Fred lunnon -
Henry Baker