Real observers solving imaginary problems

Abstract

The sphere partition function is one of the simplest euclidean gravity computations. It is usually interpreted as count of states. However, the one loop gravity correction contains a dimension dependent phase factor, $i^{D+2}$, which seems confusing for such an interpretation. We show that, after including an observer, this phase gets mostly cancelled for the quantity that should correspond to a count of states. However, an overall minus sign remains.

17 pages, 3 figures. V2: Some conclusions changed, there is now an uncancelled minus sign. V3: reference added