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[Phys-l] Quantum Foam I don't Think So



We have discussions on the prediction of a Quantum foam at the Planck
Scale. Wheeler made this prediction an orthodoxy in the physics community. But
the more I study this problem the more I think this prediction is bogus.
First Quantum fluctuations need some measurement process. So asserting any
given region of space time is seething with fluctuations absent any such
process seems simply wrong.


It seems quite clear that were space time a frothy sea of wormholes and
virtual black holes it would be impossible to recover the space time we
observe at the macro scale. It takes some kind of miracle to accomplish this. Of
all the efforts to quantize gravity only two make proposals which seem not
to need such a miracle. These are string theory and causal dynamical
triangulation. String theory accomplishes this because any measure below the
string scale is operationally meaningless due to T duality. Also String theory
seems to be asserting that space time and gravity are emergent properties
of nature, Einstein's equations become perturbative in String theory. Causal
dynamical triangulation accomplishes a recovery of space time by
introducing a micro arrow of time thus creating a "disciplined" causal structure
for space time at any scale. There is no Quantum foam in CDT. Bruce might
find this interesting.

Also the model of gravity I have posted about several times which is a
version of Induced Gravity which models the gravity field as a shift in the
action density of the ZPE in the presence of mass energy also would seem to
avoid any prediction of Quantum foam. This doesn't violate the first point I
made above about the need for a measurement process because in this model
gravity is modeled as a measurement process of the vacuum Quantum states.
Absent such a measurement the vacuum state is unitary. This does imply
however that the gravity field has a temperature and that gravity field violate
the weak energy condition. Some papers I have read suggest this is not a
problem but this is uncertain.

In any case, in this model gravity has a "saturation" value related to
the SUSY breaking scale. This means even given a measurement process at very
low distance scales, the fluctuations can never produce Quantum foam.


Bob Zannelli