RE: Sean Carroll's everyday equation.
July 23, 2016 at 6:22 am
(This post was last modified: July 23, 2016 at 6:29 am by Alex K.)
The constraint k<Lambda on the path integral is an interesting issue. It says that one should not average over *all* ways the fields and spacetime can bend and change, but only those above a certain length scale, leaving out those below a certain scale (e.g. the planck scale). This is why this number Lambda is called a "cut off". This takes care of the fact that we don't know how quantum gravity works near the planck scale - what is ordinarily summarized too simplistically as "we don't have a theory of quantum gravity". The above Functional therefore only yields a consistent description of nature at energies below the planck energy.
The fool hath said in his heart, There is a God. They are corrupt, they have done abominable works, there is none that doeth good.
Psalm 14, KJV revised edition
