The Cosmological Constant and Lorentz Invariance of the Vacuum State

Understand

One hope to solve the cosmological constant problem is to identify a symmetry principle, based on which the cosmological constant can be reduced either to zero, or to a tiny value.

• Here, we note that requiring that the vacuum state is Lorentz invariant significantly reduces the theoretical value of the vacuum energy density.
• Hence, this also reduces the discrepancy between the observed value of the cosmological constant and its theoretical expectation, down from 123 orders of magnitude to 56 orders of magnitude.
• We find that, at one loop level, massless particles do not yield any contribution to the cosmological constant.