Hi all, I have a bit of a variation of a question I asked some time ago. Webb et al. continue to publish results which suggest that the fine structure constant may vary over space and time. I realize the results are controversial - what I'm wondering: If the fine structure constant were shown to vary, would this imply a difference in the vacuum energy density at different points in spacetime? (since, e.g., the value of c could change) I guess I'm wondering if you would use a different Feynman diagram for e.g. an electron moving through the vacuum at one point in spacetime (where alpha has one value) as compared with another point (where alpha has a different value)? Or does the vacuum energy density have to remain constant across spacetime? Apologies if this question isn't very clear - still learning :). Thanks all!