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| I have corrected the metric given in terms of the Brinkmann coordinates to include only the vacuum metrics. In the form previously given, we would allow either nongravitational radiation, or gravitational radiation, or both. In other words, we would have a null dust solution, not a vacuum |
I have corrected the metric given in terms of the Brinkmann coordinates to include only the vacuum metrics. In the form previously given, we would allow either nongravitational radiation, or gravitational radiation, or both. In other words, we would have a null dust solution, not a vacuum solution! The term "gravitational wave" implies (at least to my mind) a vacuum pp-wave, in which there is no nongravitational massless radiation (in particular, no electromagnetic radiation) accompanying the gravitational radiation. | ||
| It is unfortunately true that "*-metric" is a standard term in the literature, but a metric tensor is a tensor field on a spacetime, not the spacetime itself. Since it is so easy to use less confusing terminology, why not do so? I would prefer to replace "pp-wave metrics" with "pp-waves" or "pp-wave spacetimes", but haven't done that, principally because I don't (yet) know how. | It is unfortunately true that "*-metric" is a standard term in the literature, but a metric tensor is a tensor field on a spacetime, not the spacetime itself. Since it is so easy to use less confusing terminology, why not do so? I would prefer to replace "pp-wave metrics" with "pp-waves" or "pp-wave spacetimes", but haven't done that, principally because I don't (yet) know how. | ||
Revision as of 03:19, 24 May 2005
I have corrected the metric given in terms of the Brinkmann coordinates to include only the vacuum metrics. In the form previously given, we would allow either nongravitational radiation, or gravitational radiation, or both. In other words, we would have a null dust solution, not a vacuum solution! The term "gravitational wave" implies (at least to my mind) a vacuum pp-wave, in which there is no nongravitational massless radiation (in particular, no electromagnetic radiation) accompanying the gravitational radiation.
It is unfortunately true that "*-metric" is a standard term in the literature, but a metric tensor is a tensor field on a spacetime, not the spacetime itself. Since it is so easy to use less confusing terminology, why not do so? I would prefer to replace "pp-wave metrics" with "pp-waves" or "pp-wave spacetimes", but haven't done that, principally because I don't (yet) know how.