The dimensions of elementary particles in quantum physics and string theory

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I noticed that in quantum physics, an elementary particle has no dimensions, and is point like, but in string theory has one dimension. Why is this?
 

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mathman
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I noticed that in quantum physics, an elementary particle has no dimensions, and is point like, but in string theory has one dimension. Why is this?
This may sound silly, but basically it is because the theories are different. String theory is looking at things on a much smaller length scale than quantum theory.
 
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Probably you mean "mass dimension"? In supersymmetric theories, the anticommutator of two susy generators Q is equal to the momentum P, which has mass dimension 1. From here, dimension of Q follows: it is 1/2. Similarly, by imposing that the action has 0 dim, you can find that a scalar field has dimension 1, a spinorial field 3/2, etc.
 
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T=0
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Thnx guys, great help.
 

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