Belkis Cabrera Palmer
In a static spacetime, the Killing time can be used
to measure the time required for signals or objects
to propagate between
two of its orbits. By further restricting to spherically
symmetric cases, one obtains a natural association
between these
orbits and timelike lines in Minkowski space. We prove
a simple theorem to the effect that in any spacetime
satisfying the weak
energy condition the above signaling time is, in this
sense, no faster than that for a corresponding
signal in Minkowski
space. The theorem uses a normalization of Killing
time appropriate to an observer at infinity. We then
begin an investigation
of certain related but more local questions by s
tudying particular families of spacetimes in detail.
Here we are also
interested in restrictions imposed by the dominant
energy condition. Our examples suggest that signaling
in spacetimes
satisfying this stronger energy condition may be
significantly slower than the fastest spacetimes
satisfying only the weak
energy condition.
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