- #1
ohwilleke
Gold Member
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The parameterized post-Newtonian formalism is an approximation of general relativity that is easier to calculate with that applies in "weak" gravitational fields where objects are "slow" moving.
My question is: "What is the approximate domain of applicability of the post-Newtonian formalism?"
In other words, how weak is "weak" and how slow is "slow" and whether there are other circumstances where the formalism breaks down.
I could imagine that another way of answering the question would be to identify fact patterns where the post-Newtonian formalism makes sense (e.g. perhaps the precession of Mars), and fact patterns where the post-Newtonian formalism doesn't make sense (e.g. perhaps a binary set of black holes spiraling into each other starting at a fairly "short distance").
I see that there are several previous discussions on the post-Newtonian formalism at PF but none seem to address this particular question.
To be clear: I am not asking about the range of post-Newtonian formalism parameters that are consistent with empirical measurement. I'm simply asking when a simplification of GR often used as a calculation short-cut is valid.
My question is: "What is the approximate domain of applicability of the post-Newtonian formalism?"
In other words, how weak is "weak" and how slow is "slow" and whether there are other circumstances where the formalism breaks down.
I could imagine that another way of answering the question would be to identify fact patterns where the post-Newtonian formalism makes sense (e.g. perhaps the precession of Mars), and fact patterns where the post-Newtonian formalism doesn't make sense (e.g. perhaps a binary set of black holes spiraling into each other starting at a fairly "short distance").
I see that there are several previous discussions on the post-Newtonian formalism at PF but none seem to address this particular question.
To be clear: I am not asking about the range of post-Newtonian formalism parameters that are consistent with empirical measurement. I'm simply asking when a simplification of GR often used as a calculation short-cut is valid.