Wednesday, June 08, 2005

Asymptotic Freedom: From Paradox to Paradigm

by Frank Wilczek. Lecture on receipt of the 2004 Nobel Prize in Physics.
Preprint at the physics archive.

QCD Lava Lamp (spontaneous quantum fluctuations in the gluon fields)
These pictures make it clear and tangible that the quantum vacuum is a dynamic medium, whose properties and responses largely determine the behavior of matter. ... The masses of hadrons, then, are uniquely associated to tones emitted by the dynamic medium of space when it disturbed in various ways ... We thereby discover, in the reality of masses, an algorithmic, precise Music of the Void. It is a modern embodiment of the ancients’ elusive, mystical “Music of the Spheres”.

Asymptotic freedom was developed as a response to two paradoxes: the weirdness of quarks, and in particular their failure to radiate copiously when struck; and the coexistence of special relativity and quantum theory, despite the apparent singularity of quantum field theory. It resolved these paradoxes, and catalyzed the development of several modern paradigms: the hard reality of quarks and gluons, the origin of mass from energy, the simplicity of the early universe, and the power of symmetry as a guide to physical law.

A beautiful (and often very readable) account of one of the most recent (well, 1972) major advances in theoretical physics.
In theoretical physics, paradoxes are good. That’s paradoxical, since a paradox appears to be a contradiction, and contradictions imply serious error. But Nature cannot realize contradictions. When our physical theories lead to paradox we must find a way out. Paradoxes focus our attention, and we think harder.

"Paradox 1: Quarks are Born Free, but Everywhere They are in
Powerful interactions ought to be associated with powerful radiation. When the most powerful interaction in nature, the strong interaction, did not obey this rule, it posed a sharp paradox.

"Paradox 2: Special Relativity and Quantum Mechanics Both Work"
The second paradox is more conceptual. Quantum mechanics and special relativity are two great theories of twentieth-century physics. Both are very successful. But these two theories are based on entirely different ideas, which are not easy to reconcile. In particular, special relativity puts space and time on the same footing, but quantum mechanics treats them very differently. This leads to a creative tension, whose resolution has led to three previous Nobel Prizes (and ours is another).

So we had the paradox, that combining quantum mechanics and special relativity seemed to lead inevitably to quantum field theory; but quantum field theory, despite sub-stantial pragmatic success, self-destructed logically due to catastrophic screening.

A picture of particle tracks emerging from the collision of two gold ions at high energy. The resulting fireball and its subsequent expansion recreate, on a small scale and briefly, physical conditions that last occurred during the Big Bang

Video, etc of the Nobel Lecture.

See also An Emptier Emptiness a previous post about another Wilczek article.

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