Chinese Scholar Yang Jian liang Putting Wrongs to Rights in Astrophysics

heyuhua said:
the equation (1) is just the harmonic condition which is often used, can be see in any a textbook , don't you know? and again, in the short discussion we only deal with the static gravitational field of spherical symmetry and how a free particle moves in the static gravitational field of spherical symmetry, obviously don't come down to universal question, why must you talk about universe here?
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the more detailed derivation in the addree
http://prep.istic.ac.cn/preprint/inte.html?action=getFile&id=2c928282510e4d7301630bd90e712128
 
NotEinstein said:
Only if you ignore the gravitational contribution of the earth, which might be a fine approximation in some situations.


Have you even read Yang's articles yourself? We're not talking about a static gravitational field. Yang's explicitly sets the velocity of the perfect fluid to zero. In other words, we're talking about a static perfect fluid. And yes, that leads to a static gravitational field, but it also means that there can be no moving particles, because there can be no movement.
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the static gravitational field's sour is regarded as perfect fluid, or say that its energy-stress tenor equals the one of perfect fluid, thus the metrics of the static gravitational field can be solved in use of field equation with the energy-stress tenor as gravitational source, there is no difficult to understand
 
heyuhua said:
the static gravitational field's sour is regarded as perfect fluid, or say that its energy-stress tenor equals the one of perfect fluid, thus the metrics of the static gravitational field can be solved in use of field equation with the energy-stress tenor as gravitational source, there is no difficult to understand
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You keep missing the point: Yang takes the perfect fluid to be static as well. All subsequent discussion about moving particles thus become nonsense, because in Yang's universe there can be no motion.
 
NotEinstein said:
That document still contains the minus-sign difference in the partially contracted Ricci tensor, and it still doesn't contain an explanation for it. Look, it's clear you have no idea what you're doing; is there any chance of getting in direct contact with Yang?
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the minus-sign difference is entirely correct and it comes from the defination of Ricci tensor, you may see any textbook and no exception about this
 
heyuhua said:
the minus-sign difference is entirely correct and it comes from the defination of Ricci tensor, you may see any textbook and no exception about this
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I've already pointed out it's in direct conflict with both Wikipedia and Carroll, so your claim that it's in all textbooks is false. Why do you continue to lie about this?
 
NotEinstein said:
You keep missing the point: Yang takes the perfect fluid to be static as well. All subsequent discussion about moving particles thus become nonsense, because in Yang's universe there can be no motion.
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this implies that you don't know, at all, what general relativity is to do, isn't the sun's gravitational field the static gravitational field? isn't the earth moving in the gravitational field? if object cann't move in static field it has no value to study the static gravitational field, now you need learn basic conceptions of general relativity
 
NotEinstein said:
I've already pointed out it's in direct conflict with both Wikipedia and Carroll, so your claim that it's in all textbooks is false. Why do you continue to lie about this?
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whether the defination of Ricci tensor is different in different textbook? at least I don't see
 
heyuhua said:
this implies that you don't know, at all, what general relativity is to do, isn't the sun's gravitational field the static gravitational field?
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Not really; the sun is moving too, due to the planets. Look up the term "barycenter". But under the approximation that the gravity of the planets can be ignored, then yes, the sun's gravitational field is static.

heyuhua said:
isn't the earth moving in the gravitational field?
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Yes, and that's where the difference is. In Yang's universe, nothing can move per construction. You keep missing this point. Re-read Yang's articles where it discusses the values of $$U^\mu$$.

heyuhua said:
if object cann't move in static field
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I never claimed that.

heyuhua said:
it has no value to study the static gravitational field, now you need learn basic conceptions of general relativity
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Erm, it's you that is completely misunderstanding Yang's work due to your misconceptions about what is static. Perhaps you should re-read Yang's work more carefully?

heyuhua said:
whether the defination of Ricci tensor is different in different textbook? at least I don't see
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If that's the case, then Yang is thus proven wrong. This difference in minus-sign trickles down into the EFE, so that fully explains where Yang's sign-swap is coming from: it's a simple mathematical mistake. A mistake Yang's been propagating for almost ten years. What a waste of time...:O
 
NotEinstein said:
Only if you ignore the gravitational contribution of the earth, which might be a fine approximation in some situations.


Have you even read Yang's articles yourself? We're not talking about a static gravitational field. Yang's explicitly sets the velocity of the perfect fluid to zero. In other words, we're talking about a static perfect fluid. And yes, that leads to a static gravitational field, but it also means that there can be no moving particles, because there can be no movement.
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yes, the earth doesn't indeed contribute to the sun's gravitational field, in which the earth runs, like a charge moving in electric field of the other charge, the moving charge doesn't contribute to the electric field, we often discuss the equation a charge moves in the electric field formed by another change , so is gravitation
 
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heyuhua said:
yes, the earth doesn't indeed contribute to the sun's gravitational field, in which the earth runs, like a charge moving in electric field of the other charge, the moving charge doesn't contribute to the electric field, we often discuss the equation a charge moves in the electric field formed by another change , so is gravitation
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Perhaps "contribute" wasn't the right word. "Affect"? "Change"? Again, look up barycenters; the gravitation of earth does affect the position of the sun, and thus it affects the gravitational field of the sun.
 
NotEinstein said:
Perhaps "contribute" wasn't the right word. "Affect"? "Change"? Again, look up barycenters; the gravitation of earth does affect the position of the sun, and thus it affects the gravitational field of the sun.
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indeed the earth has a contribution to the gravitational field of the sun-earth system, but the earth's contribution to the gravitational field often is neglected, the earth moves in the gravitational field is similar to that a test charge moves in the electric field of other charges
 
a charge can moves in the static electric field formed by other change, why cann't an object move in the static gravitational field?
 
heyuhua said:
indeed the earth has a contribution to the gravitational field of the sun-earth system, but the earth's contribution to the gravitational field often is neglected,
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Can the contribution of Jupiter also be neglected?

heyuhua said:
the earth moves in the gravitational field is similar to that a test charge moves in the electric field of other charges
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Sure, but when you do this approximation, you are effectively setting the mass of earth to zero. Yang's article clearly doesn't do that, as the moving particle is explicitly given a mass $$m$$ that's non-zero, but without any other restrictions. (It by the way also uses the relativistic mass, which is another mistake.)
 
heyuhua said:
a charge can moves in the static electric field formed by other change, why cann't an object move in the static gravitational field?
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No, the question should be: if all charges are static (= stationary), can you have a moving charge?
 
NotEinstein said:
No, the question should be: if all charges are static (= stationary), can you have a moving charge?
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how do you deal with the motion of a charge in a static electric field? do you think the charge cann't have electricity? similarly, why cann't the particle moving in static gravitational field have mass? the subject we are talking here is indeed too low level, your confusions is simply similar to a student, your foundation of physics is too poor , I don't expect you have such confusions that shouldn't take on at all. I suggest you learn a bit of electrostatics, know the method to deal with the motion of a charge in static electric field
 
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