On 10/24/2020 3:56 PM, Lawrence Crowell wrote:
On Saturday, October 24, 2020 at 5:22:32 PM UTC-5 Brent wrote: On 10/24/2020 3:02 PM, Lawrence Crowell wrote:On Saturday, October 24, 2020 at 3:16:31 PM UTC-5 Brent wrote: On 10/24/2020 5:29 AM, Jason Resch wrote:It's using the Planck scale as the upper bound.So what? That's assuming the Planck scale means something, but it's already rejected as 'unatural'. You can't have it both ways. Brent The Planck length is the scale at which the Compton wavelength of a particle is equal to the circumference of a black hole. It is not hard to calculate. This is then the smallest scale at which information can be accessed. It is the smallest region where a qubit can be isolated. With the accelerated expansion of the universe there are vacuum modes passing across the cosmic horizon. However, at the same time transPlanckian modes are stretched across this scale. It is also nature's way of providing a natural renormalization cut-off scale.But the context was calculation of the vacuum energy density. Absent even a theory of quantum gravity I see no reason to take seriously the idea that the vacuum energy density consists of the ground state energy of the various quantum fields, much less that there is some "fine tuned" cancelation of the fermion and boson components. BrentIt is something to take seriously. We can consider it important in an interacting field theoretic sense, where disconnected virtual fields are removed by normal ordering. However, gravitation does rear its head and even the vacuum disconnected from other QFTs has gravitational content.
I'm not saying we shouldn't consider the vacuum energy density of the fields, but that the idea that there is an ensemble of universes densities so that we find ourselves in the one where they almost, but not quite, cancel out seems like no better than the Walter Cronkite explanation, "And that's the way it is." For an ensemble theory to have any weight there would need to be theory that provided some probability distribution for the various fields.
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