Abstract
I point out a simple but usually overlooked fact about the cosmological constant problem: to solve the cosmological constant problem it is sufficient to find a symmetry or mechanism that sets the cosmological constant to zero or to a tiny value at some time in the past, provided that general relativity is the relevant theory of gravity, and the energy-momentum tensor (excluding the part of the form of a cosmological constant) is conserved. The relevant symmetry or mechanism need not be applicable today. Any additional cosmological constant term induced by a phase transition in the energy-momentum tensor in this case is compensated by a shift in the cosmological constant term of gravitational origin.
Highlights
Einstein’s field equations are 8π GRμν − 2 gμν R − gμν Λ = c4 Tμν (1)where Rμν, gμν, Λ, G, c, and Tμν are the Ricci tensor, the metric tensor, the cosmological constant, Newton’s gravitational constant, the speed of light, and the energy–momentum tensor, respectively, and R = gμνRμν
It may have set the cosmological constant to zero or to a tiny value in the past and this is sufficient for the solution of the cosmological constant problem (CCP) that symmetry or mechanism may not be surviving today
If the cosmological constant problem is set to some value by some mechanism or some symmetry at some initial time it will remain so provided that general relativity is the relevant theory of gravity
Summary
If the cosmological constant problem is set to some value (e.g., to zero or to a tiny value) by some mechanism or some symmetry at some initial time it will remain so provided that general relativity is the relevant theory of gravity.
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