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[Phys-l] A NEW WAY TO LOOK AT GRAVITY.




The great physics theory divide between gravity and the quantum field theory
is the certainly the most pressing problem in fundamental physics. If in
fact the unification scale is at the TEV level, we may finally be able to shine
the light of experiment at the boundary of quantum theory and general
relativity. But there is something very different about gravity. Unlike the other
forces of nature, it is universal. No species of matter evades it effect.
The great drive in physics is for a quantum theory of gravity. But this goal
has proved illusive. This is because the gravity field itself is space time,
the background on which all of physics is written. In order to have a
quantum field theory of gravity, it seems likely that the clear separation between
matter and geometry may be lost. Rather we may need a new model with pre-
geometric degrees of freedom.
However, the commonality of gravity to all matter states suggests that it
may, in fact, not be a fundamental force at all. Rather gravity may be an “
induced force” which emerges from quantum field theory like hydrodynamics emerges
from molecular physics. One such gravity model is Sakharov’s induced gravity
theory. This model incorporates Lorentz’s vision of the possibility of
gravity merely being an effective force induced by residual electromagnetic
forces. Since in this model the action terms would contain both classical and
quantum terms, this model leads to a “semi-classical quantum “gravity theory.
In the sense that space time may be quantized, (seemingly required by the
Holographic principle) it would be the quantization of collective excitations of
the vacuum state. Because gravity is the result of the mutual interaction of
the fundamental quantum fields we could retain space time as mere
background, therefore avoiding the objection to semi classical models raised by Terno.
Sakharov’s starting point is to notice that gravitation consists, not in the
existence of space time curvature, but in the existence of a large “metrical
elasticity” which opposed the curvature of space time, except near
concentrations of matter. The equations of general Relativity arise from the action
principle obtained by adding to the action of the matter fields the Einstein
Hilbert action. The action is then proportional scalar curvature term
multiplied by the inverse of Newton’s constant. Therefore the unification scale, the
mass cutoff value is a property of the collective excitations of the vacuum
states.
Continuing with this line of reasoning, Sakharov was able to show that in
simple models of matter fields, the proportionality constant in the effective
action is given by an infinite sum over masses of the fluctuation quanta (the
virtual ZPE quanta) which are present. So when spacetime is curved, the action
arising from quantum fluctuations is altered and is only partially canceled
by the renormalization constant computed in flat spacetime.
Obviously this has important consequences for quantum theory treatment of
the vacuum especially as it relates to the Higgs field and gravity. This calls
into question the whole program of quantization of these fields from first
principles. Rather, the quantum model of the degrees of freedom utilized in
condensed matter physics seems more appropriate.
Recently, a new paradigm has been introduced into physics which modifies our
understanding of the ZPE fluctuations of the vacuum. This idea first
proposed by Bob Klauber, and subsequently by numerous physicists including Moffat,
Sundrum and Kaplan , and T hooft to name just a few, resurrects the discarded “
unphysical” negative energy states in an attempt to solve the infamous zero
point energy problem, the prediction of an immense vacuum energy density,
which of course we don’t observe.
While the application of these negative energy states to solve the ZPE
problem varies in detail in the various proposals, the basic idea is the same for
all of them. In addition to the matter states normally described in Quantum
Field Theory, which Klauber calls the traditional states and Moffat the positon
particles, we double the number of possible matter states by including the
negative energy quanta which Klauber calls the supplemental states and Moffat
labels as the negaton particles.
This, in my opinion adds ammunition to the idea that the condensed matter
physics paradigm may be usefully applied to vacuum physics. Given that at some
fundamental level the actual nature of spacetime and its manifestation matter
states may be the emergent properties of a model based on pre- geometric
degrees of freedom, we can view the entities of quantum field theory as
collective excitation of this underlying pre geometric structure. Therefore it may be
possible to model the positon and negaton virtual states of the vacuum in a
way which is similar in principle to the electron and hole model used in solid
state physics.
In a vacuum absent any gravitational effect ( zero cc) all the models
utilizing these extra matter states postulate a perfect canceling balance between
the virtual positon ( positive cc contribution) and the negatons ( negative cc
contribution). In other word a space time with zero curvature.
However, in our Universe the observed cc is not zero. This would mean, based
on the model utilizing these negative energy states, that there are more
positon virtual states than negaton states in vacuum with negative space time
curvature. Using the solid state analogy, we can view this as a “depletion” of
negaton virtual states.
But what process can effect this depletion? I think the answer to this
question points to the Davies –Hawking-Unruh effect as a manifestation of a
process that effects this depletion. Non inertial frames “promote” virtual
particles into real particles. The gravity field is by definition an acceleration
field. By the equivalence principle they are the same thing.
So using this proposal we can say that negative curvature depletes negaton
virtual states and positive curvature depletes positon states. The application
of these negative energy states provides a mechanism to alter the action
density arising from quantum fluctuations. Therefore we can describe gravity as
a field induced by the collective action of the quantum states.
Now of course this is just the bare skeleton of an idea that may or may not
make sense, and may or may not be able to be made rigorous enough to be taken
seriously. But I believe it has enough potential to be at least worth a post
here.
Bob Zannelli





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