You're ok, OnlyMe, and I know you mean well. However, you have just conflated universal expansion hypothesis/interpretations with GR theory of gravitation as it affects local matter moving through space and NOT with space as origin's statement re 'expanding space' implied without any explanation as to how that supposedly expanding space can carry galaxies with it.
GR is all about natural geodesics through space, not about space itself expanding in big bang hypothesis manner.
I would appreciate it if you kept your assumptions/conflations out of my exchange with origin, in the context wherein I just want his explanation/mechanism for his claim that 'expanding space' supposedly makes distant galaxies move with space in addition to their normal proper motion through space.
If neither he nor anyone else can do that, then his claim must fall under the category of inferred speculations and not fact. I've no objections to that. OK? Thanks.
So...
...origin, my last post/question to you remains to be answered in the context you claimed about expanding space and galaxy motion above that of proper motion. Thanks.
The expansion of space and especially the acceleration of the expansion of space is, at least temporarily associated with Dark Energy. (Temporarily only because Dark Energy is an unknown place holder.) If you read up on Dark Energy, you will find that it is often associated with or described mathematically as a function of the cosmological constant.
Now, check out the history of the cosmological constant and you will find that Einstein introduced it, initially with the intent of preventing a run away expansion of spacetime or the universe, within the context of GR. Depending on the value of the cosmological constant the universe expands and then collapses back on itself, remains exactly the same (IE in a steady state), expands forever or even expands forever in an accelerating way.
So..., the expansion of space and the accelerating expansion of space are specifically the domain of GR.
But, that was not my point. What you missed is that what I was referring to is that the relationship between space and matter is specifically the domain of general relativity and NO ONE can tell you exactly what the mechanism of that interaction is. The geometry and dynamics is at least partially described, we learn more all the time. But the mechanics remains a mystery.
You phrased a challenge that specifically asked for information that NO ONE can provide.
If you had asked for an explaintion of the logic, reason and theory, behind how the expansion and accelerating expansion could explain superluminal recession WITHOUT superluminal velocities, the situation would have been more reasonable.
On the other hand that would not have served the same ends that seem apparent in your initial question and this last response.