6 ms·
As I remember it (from 40+ years ago, and well before dark energy was discussed), lambda naturally arises as a constant of integration in GR rather than being "
by tengwar2 2y ago
As I remember it (from 40+ years ago, and well before dark energy was discussed), lambda naturally arises as a constant of integration in GR rather than being "invented" as in the usual story. Assuming this to be true, I'd suggest that any model should either allow for a non-zero lambda, or give a reason for it to be zero. I.e. even if an alternative for dark energy is found, we still have to deal with lambda.
- antognini 2y agoYes, given the equations of GR, there's no particular reason to assume that the cosmological constant should be zero. (Though one of the major problems in theoretical physics is that back-of-the-envelope estimates as to what it "should" be give numbers that are ~120 orders of magnitude larger than its observed value. So if dark energy is a cosmological constant, it's not really understood why it is non-zero, but extremely small.)
- SoftTalker 2y agoIsn't that why they came up with "dark matter" i.e. invisible, undetectable mass.
- antognini 2y agoNo, dark matter is quite different. There are a number of different lines of evidence for dark matter. One of these is sort of similar to dark energy, in that it is needed to explain the slower-than-expected expansion of the universe at early times. But the most compelling line of evidence for dark matter (IMO) is baryon acoustic oscillations in the CMB.
- floxy 2y agoI thought that lambda was directly in the differential equation form? Rμν − (1/2)*gμν*R + Λ*gμν = (8*π*G / c^4) * Tμν