What are valid Preferred Frames?

[Varon]

Supposed, for sake of discussions. There are preferred frames.

Could a field (field in the context of higgs field, or other fields) be a preferred frame? What is a valid preferred frame where it is instantaneously to say communication between 100 billion light years distance and not violating causality (because in SR, anything superluminal without preferred frame can have frames where things go backward in time)?

 

[atyy]

A preferred frame is usually something which reveals an underlying symmetry of all solutions, or of the particular solution being studied.

In Newtonian physics, the preferred frames are Galilean inertial frames. All Galilean inertial frames are equally preferred, so within that class of frames, there are no preferred frames.

In special relativity, the preferred frames are Lorentz inertial frames. All Lorentz inertial frames are equally preferred, so within that class of frames, there are no preferred frames. (These preferred frames are due to the metric field, not the Higgs field.)

In general relativity, there are no preferred frames covering all of spacetime for all solutions. In all solutions, there are local preferred frames which the local Lorentz inertial frames. In some solutions, such as the FRW solution, there is a global coordinate system in which the spatial slices are isotropic and homogeneous, and this coordinate system is in that particular sense "preferred".

In all cases, whether a "preferred" or "non-preferred" frame is used (keep in mind that we have defined several different meanings of those words), the theory predicts the same result for any experiment.

 

[Varon]

A preferred frame is usually something which reveals an underlying symmetry of all solutions, or of the particular solution being studied.

In Newtonian physics, the preferred frames are Galilean inertial frames. All Galilean inertial frames are equally preferred, so within that class of frames, there are no preferred frames.

In special relativity, the preferred frames are Lorentz inertial frames. All Lorentz inertial frames are equally preferred, so within that class of frames, there are no preferred frames. (These preferred frames are due to the metric field, not the Higgs field.)

In general relativity, there are no preferred frames covering all of spacetime for all solutions. In all solutions, there are local preferred frames which the local Lorentz inertial frames. In some solutions, such as the FRW solution, there is a global coordinate system in which the spatial slices are isotropic and homogeneous, and this coordinate system is in that particular sense "preferred".

In all cases, whether a "preferred" or "non-preferred" frame is used (keep in mind that we have defined several different meanings of those words), the theory predicts the same result for any experiment.

I'm talking in the context of superluminal signalling. If one can transmit signal faster than light.. it can go backward in time in certain frames of reference. But not so if you have a preferred frame where you transmit the signal. No causality problem would result. Hence, could this hypthetical preferred frame for instantaneous signalling across the universe be a field (field in the sense of higgs field or other field)? What are valid preferred frames in this sense?