Saturday, April 17, 2010

Physics Quote Of The Day

This from Introduction to Effective Field Theory by C.P. Burges,
Renormalization is a practice which used to be widely regarded as distasteful, and so was largely done in the privacy of one’s own home. That has all changed. As used in effective field theories renormalizing is not only respectable, it is often the smart thing to do...
For those who don't know what renormalization is, a good lay explanation probably is: when you calculate quantities like the mass or charge of a particle in quantum field theories they turn out to be infinite.  However, once you realize these quantities can change with energy scale, they become finite functions of energy scale.  This process of converting physical quantities to functions of energy scale is called renormalization.

 The values of these functions at different energy scales have been confirmed in particle accelerators.  Sometimes you here physicists say these "quantities" run.  This is just a fancy way of saying they change for different energy scales.  For some quantities, like those related to the graviton, this processes doesn't work, which is why you hear people say gravity isn't renormalizable.

Now, why is this funny?  Because not too long ago, this process was very difficult and seemed very fishy that it worked. (Now we know better.)  It was embarrassing, to many physicists, in the same way some other things may be embarrassing if they are not done privacy in your own home.

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