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Scale-dependent knowledge

  1. Nov 16, 2005 #1


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    I would like to know your thoughts about the following two fact in physics;

    1) Physics is scale-dependent; at each scale of distences we have different degrees of freedom and different dynamics, we need a different theory.
    2) Physics at a larger scale decoples from the physics at smaller scale. More precisely, a theory at a larger scale remember only finite number of parameters from the theories at smaller scale. For example, if we want to describe atoms, we do not need to know anything about the nucleus except its mass and charge. This decopling is the reason behind our current understanding of the world.If there was no decopling, it would be necessary for us to know quantum field theory to bescribe the motion of rigid body.

    The aim is to explain;
    1) how this decopling takes place,
    2) why information is transmitted from scale to scale through finite number of parameters.

    Try to incorporate in your thoughts as much as you can of the following;
    i) correspondence principle,
    ii) invariance principles,
    iii) renormalization group methods.


    Last edited: Nov 16, 2005
  2. jcsd
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