So my argument goes like this:
say we have an object that is nearly at the density required for a black hole. Then we Lorentz boost into a new frame, the object is Lorentz contracted and therefore the density increases above the black hole limit.
As a mere change of frame can't have physical effects it surely can't create a black hole and therefore a moving black hole needs a larger density.
Is this correct and if it is how does this come out of General Relativity?
