3 research outputs found
Measurement of the space-time interval between two events using the retarded and advanced times of each event with respect to a time-like world-line
Several recent studies have been devoted to investigating the limitations
that ordinary quantum mechanics and/or quantum gravity might impose on the
measurability of space-time observables. These analyses are often confined to
the simplified context of two-dimensional flat space-time and rely on a simple
procedure for the measurement of space-like distances based on the exchange of
light signals. We present a generalization of this measurement procedure
applicable to all three types of space-time intervals between two events in
space-times of any number of dimensions. We also present some preliminary
observations on an alternative measurement procedure that can be applied taking
into account the gravitational field of the measuring apparatus, and briefly
discuss quantum limitations of measurability in this context.Comment: 17 page
A Conformally Invariant Holographic Two-Point Function on the Berger Sphere
We apply our previous work on Green's functions for the four-dimensional
quaternionic Taub-NUT manifold to obtain a scalar two-point function on the
homogeneously squashed three-sphere (otherwise known as the Berger sphere),
which lies at its conformal infinity. Using basic notions from conformal
geometry and the theory of boundary value problems, in particular the
Dirichlet-to-Robin operator, we establish that our two-point correlation
function is conformally invariant and corresponds to a boundary operator of
conformal dimension one. It is plausible that the methods we use could have
more general applications in an AdS/CFT context.Comment: 1+49 pages, no figures. v2: Several typos correcte