There are several ways to solve the problem created by the violation of the Bell inequalities.
The first one, quite popular here but rejected as nonsense by the mainstream, is to question Bell's theorem itself. The second one is to find various loopholes in the experiments which show violations of the Bell inequalities. I will ignore these two possibilities below.
The strongest, most important one in mainstream physics is to preserve Einstein causality (misnamed "locality" as if a theory with maximal speed of information transfer of 1000 c would be "nonlocal") at all costs. The costs are quite big, you have to give up realism, even in such a weak form as EPR realism, you have to weaken the notion of causality too, given that you have to reject the common cause principle. And one can reasonably ask if what remains after this - "signal causality" - is even worth to be named "causality".
But, last, and in the opinion of the mainstream also least, there is another solution - the acceptance of a "hidden" preferred frame.
My impression is that there is a very strong prejudice against this solution, even on the emotional level. I think most of us (me too) have been impressed in childhood by the popular argumentation following Einstein in favor of special relativity, against those "common sense" ideas like absolute simultaneity. And this was a positive impression - else we would have done something completely different, but not physics. So, all the elements we need for strong emotional prejudices are present: Started in childhood, strong impression, emotional importance even for the choice of profession, what else is missed here? All I can do here is to ask the reader to think about this - maybe his response is not that much rational but influenced by such emotional things?
Whatever, I think in a group discussing the foundations of physics there should be some part discussing this particular possibility: That there is a "hidden" preferred frame, and this hidden frame defines a classical notion causality (with common cause principle), some absolute contemporaneity (so that there will be a notion of realism restricted to what exists "now").
The point is that many scientist will have objections against such a preferred frame which can be easily answered - but only if there is a place to discuss them. So I think it would be useful to have some thread to discuss such all the imaginable objections against the preferred frame solution.
In this starting post I will mention two popular objections against a preferred frame: First, that it would be problematic to extend it into the domain of general relativity. This argument was correct for a quite long time, but today a generalization of the Lorentz ether interpretation to gravity is known:
Schmelzer, I. (2012). A Generalization of the Lorentz Ether to Gravity with General-Relativistic Limit. Advances in Applied Clifford Algebras 22(1), 203-242, resp. arxiv:gr-qc/0205035.
It is a different theory of gravity, but very close to the field-theoretic variant of GR. One simply introduces a gauge-breaking term into the Lagrangian which enforces the harmonic gauge. So, in the limit when this term goes to zero we obtain the Einstein equations in harmonic coordinates on a fixed background.
The second is the positivistic one that the preferred frame is not visible. But is the "hidden" preferred frame really hidden? We easily see a simple preferred frame in the global structure of our universe - the CMBR frame. And we have good reasons to believe that it becomes visible below Planck scale: GR is quantized only in its field variant on a flat background, and only as an effective field theory:
Donoghue, J.F. (1994). General relativity as an effective field theory: The leading quantum corrections. Phys Rev D 50(6), 3874-3888
Donoghue, J.F. (1996). The Quantum Theory of General Relativity at Low Energies, Helv.Phys.Acta 69, 269-275, arXiv:gr-qc/9607039
So one can expect that the theory below Planck scale may violate full relativistic symmetry (the SEP) so that the background becomes visible at least in principle for observations below Planck length.
Last but not least, if something which really exists remains unobservable this is not sufficient to reject its existence. But it creates a problem of explanation: Those who propose that the unobservable thing exists have to explain why it is unobservable. Only as long as there is no such explanation, the unobservability is a reasonable argument against its existence.
But an explanation of the Einstein Equivalence Principle (EEP) exists. The EEP has been derived for the generalized Lorentz ether in my paper mentioned above. Moreover, the derivation is quite simple:
Assume we have a completely non-relativistic theory on a Newtonian background. We assume a Lagrange formalism and translational invariance in space and time. Then we look at the Euler-Lagrange equations for the preferred background coordinates. This gives Noether conservation laws for energy and momentum. Assume that the stress-energy-momentum tensor is symmetric. (Lorentz symmetry of the background allows to prove this but is not necessary.) Then, define the "gravitational field" by this stress-energy-momentum tensor on the background:
Make a change of variables so that the gravitational field components become independent variables, and name all other fields beyond the preferred coordinates and the gravitational field "matter fields". Then the Noether conservation law becomes the harmonic coordinate condition.
So now the equation for the preferred coordinates depends only on the "gravitational field", not on any other "matter fields". Then, the action equals reaction principle tells us that the equations for the matter fields should not depend on the preferred coordinates. Thus, the EEP is proven.
What are other objections against the hypothesis of a "hidden" preferred frame?
There are several ways to solve the problem created by the violation of the Bell inequalities.
The first one, quite popular here but rejected as nonsense by the mainstream, is to question Bell's theorem itself. The second one is to find various loopholes in the experiments which show violations of the Bell inequalities. I will ignore these two possibilities below.
The strongest, most important one in mainstream physics is to preserve Einstein causality (misnamed "locality" as if a theory with maximal speed of information transfer of 1000 c would be "nonlocal") at all costs. The costs are quite big, you have to give up realism, even in such a weak form as EPR realism, you have to weaken the notion of causality too, given that you have to reject the common cause principle. And one can reasonably ask if what remains after this - "signal causality" - is even worth to be named "causality".
But, last, and in the opinion of the mainstream also least, there is another solution - the acceptance of a "hidden" preferred frame.
My impression is that there is a very strong prejudice against this solution, even on the emotional level. I think most of us (me too) have been impressed in childhood by the popular argumentation following Einstein in favor of special relativity, against those "common sense" ideas like absolute simultaneity. And this was a positive impression - else we would have done something completely different, but not physics. So, all the elements we need for strong emotional prejudices are present: Started in childhood, strong impression, emotional importance even for the choice of profession, what else is missed here? All I can do here is to ask the reader to think about this - maybe his response is not that much rational but influenced by such emotional things?
Whatever, I think in a group discussing the foundations of physics there should be some part discussing this particular possibility: That there is a "hidden" preferred frame, and this hidden frame defines a classical notion causality (with common cause principle), some absolute contemporaneity (so that there will be a notion of realism restricted to what exists "now").
The point is that many scientist will have objections against such a preferred frame which can be easily answered - but only if there is a place to discuss them. So I think it would be useful to have some thread to discuss such all the imaginable objections against the preferred frame solution.
In this starting post I will mention two popular objections against a preferred frame: First, that it would be problematic to extend it into the domain of general relativity. This argument was correct for a quite long time, but today a generalization of the Lorentz ether interpretation to gravity is known:
Schmelzer, I. (2012). A Generalization of the Lorentz Ether to Gravity with General-Relativistic Limit. Advances in Applied Clifford Algebras 22(1), 203-242, resp. arxiv:gr-qc/0205035.
It is a different theory of gravity, but very close to the field-theoretic variant of GR. One simply introduces a gauge-breaking term into the Lagrangian which enforces the harmonic gauge. So, in the limit when this term goes to zero we obtain the Einstein equations in harmonic coordinates on a fixed background.
The second is the positivistic one that the preferred frame is not visible. But is the "hidden" preferred frame really hidden? We easily see a simple preferred frame in the global structure of our universe - the CMBR frame. And we have good reasons to believe that it becomes visible below Planck scale: GR is quantized only in its field variant on a flat background, and only as an effective field theory:
Donoghue, J.F. (1994). General relativity as an effective field theory: The leading quantum corrections. Phys Rev D 50(6), 3874-3888
Donoghue, J.F. (1996). The Quantum Theory of General Relativity at Low Energies, Helv.Phys.Acta 69, 269-275, arXiv:gr-qc/9607039
So one can expect that the theory below Planck scale may violate full relativistic symmetry (the SEP) so that the background becomes visible at least in principle for observations below Planck length.
Last but not least, if something which really exists remains unobservable this is not sufficient to reject its existence. But it creates a problem of explanation: Those who propose that the unobservable thing exists have to explain why it is unobservable. Only as long as there is no such explanation, the unobservability is a reasonable argument against its existence.
But an explanation of the Einstein Equivalence Principle (EEP) exists. The EEP has been derived for the generalized Lorentz ether in my paper mentioned above. Moreover, the derivation is quite simple:
Assume we have a completely non-relativistic theory on a Newtonian background. We assume a Lagrange formalism and translational invariance in space and time. Then we look at the Euler-Lagrange equations for the preferred background coordinates. This gives Noether conservation laws for energy and momentum. Assume that the stress-energy-momentum tensor is symmetric. (Lorentz symmetry of the background allows to prove this but is not necessary.) Then, define the "gravitational field" by this stress-energy-momentum tensor on the background:
[tex]g^{ab}\sqrt{|g|} = T^{ab}.[/tex]
Make a change of variables so that the gravitational field components become independent variables, and name all other fields beyond the preferred coordinates and the gravitational field "matter fields". Then the Noether conservation law becomes the harmonic coordinate condition.
So now the equation for the preferred coordinates depends only on the "gravitational field", not on any other "matter fields". Then, the action equals reaction principle tells us that the equations for the matter fields should not depend on the preferred coordinates. Thus, the EEP is proven.
What are other objections against the hypothesis of a "hidden" preferred frame?
