Zero point fields interpreted as interference between different worlds in a many worlds interpretation of quantum mechanics.
Olle Nilsson, January 2008.
In some aspects zero point fields (zpf) yield very real physical manifestations, e.g. in the Casimir effect and as a source of noise in semi classical laser theory. This supports the notion that zpf are real measurable physical phenomena.
On the other hand they seem to give no contribution to gravitation corresponding to their estimated energy summed over all modes within wave lengths above the Plank length, i.e. in the range where we think the known physical laws are valid. This casts serious doubts about the physical reality of zero point energy.
So far no satisfactory way to resolve the apparent discrepancy between the two conclusions seems to have been suggested.
Another riddle of quantum mechanics arises when trying to interpret the collapse of the wave function due to an observation without requiring instant action at a distance (The Einstein-Podolsky-Rosen paradox).
The many worlds interpretation (MWI) of quantum mechanics first introduced by Everett eliminates this problem at the price of accepting the existence of an enormous number of different equally real parallel words.
However, the MWI also seems to open up for a more generally consistent interpretation of zpf.
Since zpf are fundamentally related to the uncertainty relation they should also be related to the merging and splitting of different worlds in MWI. In fact, as far as we know, merging and splitting are the only allowed mutual interactions between the different worlds. If, indeed, zpf are essentially a manifestation of these interactions, or rather interferences, it is not surprising that they have no significant gravitational effects.
As an illustration let us study a simple beam splitter that can be modelled as a matched lossless 4-port.
A beam entering at port 1 or 4 is leaving at ports 2 and 3, the power divided equally between the two ports.
Consider next an interferometer formed by cascading two such beam splitters so that the output 2 of the first beam splitter is connected (by e.g. a single mode fibre optic cable) to the input 1 of the second while the output 3 is connected to the input 4.
A photon entering port 1 of the first beam splitter will then exit the second beam splitter either at output 2 or 3 of the second beam splitter. By adjusting the optical path length difference of the interferometer one can steer the photon to either one of outputs 2 and 3.
In a classical case where there is a large number of mutually coherent photons travelling in both arms this is perfectly natural.
The riddle is that it works even if there is only one photon entering port 1 in each experiment. Since one has never detected a fraction of a photon one should expect the photon to travel in only one of the arms and that multiple repetition of the experiment would yield equal number of outputs from port 2 and 3 on the average.
How can a difference in path length influence a single photon travelling only through one arm?
According to the standard interpretation of quantum mechanics this question cannot be answered within the framework of human perception and intuition and we should not bother
as long as quantum mechanics consistently yields perfect agreement with the most refined experiments.
According to MWI, however, the simple and logical answer is that as the photon hits the first beam splitter the world splits in two equally real worlds. One where the photon travels in one of the arms and one where it travels in the other. If the quantum mechanical phase difference between the two photons at one of the outputs, e.g. port 2 of the second beam splitter is zero the two worlds will merge into one new world in which one photon leaves from port 2 and none from port 3. If the phase difference is p instead the photon leaves from port 3.
Therefore it seems justified to think of the two worlds as interacting with each other in the merging process. It can be observed that the sum of the zpf energy leaving ports 2 and 3 equals the photon energy, hf, in each of the worlds. A similar reasoning applies for a splitting process.
This supports the idea that zpf expresses the interaction between alternative worlds. If so the energy of the zpf in a particular world, A, does not belong to that world but is shared among other worlds interacting with A.
If the zpf energy of “our” world thus belongs to alternative worlds interacting with ours we should not expect any related gravitational effects to be measurable in our world since energy according to what we know has to be strictly conserved in each world separately, except for temporary fluctuations imposed by the uncertainty relation between time and energy.
If one indeed adopts the view that zpf is due to interaction between a multitude of parallel
worlds one is logically more or less forced to adopt also a much broader view. Namely that all quantum manifestations (and therefore many classical as well) are due to such interactions.
As a matter of fact Feynman’s path integral formulation of quantum mechanics seems to support this view if one world is associated with each path.
A serious flaw with these suggestions is that if they are true it seems that they can neither be proved nor disproved using present experimental knowledge. Maybe future astronomical observations can change this.