Monday, November 10, 2008

Why do matter and anti-matter annihilate?

Trivially, it is because the particles have a "matter charge" that is conserved. Add a particle to its anti-particle and they cancel out the matterness, leaving the more ephemeral aspects to come squirting out, often in the form of simple, energetic force carriers.

Why matterness should be conserved is an open question in physics. Things like momentum are conserved because of symmetries. If all positions in space are equivalent, then the rate of change of position has to be constant in the absence of "action". Thus momentum is conserved.

What the symmetrical thing might be for matterness/antimatterness is not obvious, nor is "action" in this context. The Schrödinger wave equation does not explain any sort of substructure we can sink our hooks into. Surely particles must get their properties for reasons, but clues as to how they do it are few.

Particle models based on topology and shape are attractive because they allow complicated relationships to flower from simple foundations. For example, we can pick two knots that fall apart into a simple loop when cut and spliced to each other. Or a pair of complementary Möbius strips that untwist when spliced together. Alas, deducing fields and forces from tangles seems to be a hard problem.

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