- #1
Cerenkov
- 274
- 53
Hello.
I've recently been reading this paper... https://arxiv.org/pdf/gr-qc/0001099.pdf ...in the hope that I can begin to understand some the role of the energy conditions in General Relativity. But I'm not making much progress and so I've turned to this paper... https://arxiv.org/pdf/1405.0403.pdf
This section makes some sense to me.
The interpretation of the geometric form of the SEC is similar to that of the NEC. According to equation (2.5.1), the geometric form of the SEC requires that timelike geodesic congruences tend to be convergent in sufficiently small neighborhoods of every spacetime point. This implies that congruences of null geodesics at that point are also convergent. Similarly, according to equation (2.5.2), the interpretation of the physical form is that observers following timelike geodesics will see that “gravity” tends locally to be “attractive” in its action on stuff following both timelike and null geodesics.
I understand the above to (very loosely) mean the following.
1. In GR, gravity is always attractive.
2. The SEC requires that gravity should always act in an, 'attractive' manner.
3. The SEC is violated in situations where space-time is being affected by the opposite of gravity's attraction, i.e., when repulsion occurs.
Please understand that these are very tentative ideas and I probably haven't worded this post anywhere near accurately enough to do justice to the matters in question. Therefore, any help given with the accuracy, meaning and understanding of this issue would be greatly appreciated. I'm here to learn and will gladly accept correction and guidance - because I need these things to learn and progress.
Thank you.
Cerenkov.
I've recently been reading this paper... https://arxiv.org/pdf/gr-qc/0001099.pdf ...in the hope that I can begin to understand some the role of the energy conditions in General Relativity. But I'm not making much progress and so I've turned to this paper... https://arxiv.org/pdf/1405.0403.pdf
This section makes some sense to me.
The interpretation of the geometric form of the SEC is similar to that of the NEC. According to equation (2.5.1), the geometric form of the SEC requires that timelike geodesic congruences tend to be convergent in sufficiently small neighborhoods of every spacetime point. This implies that congruences of null geodesics at that point are also convergent. Similarly, according to equation (2.5.2), the interpretation of the physical form is that observers following timelike geodesics will see that “gravity” tends locally to be “attractive” in its action on stuff following both timelike and null geodesics.
I understand the above to (very loosely) mean the following.
1. In GR, gravity is always attractive.
2. The SEC requires that gravity should always act in an, 'attractive' manner.
3. The SEC is violated in situations where space-time is being affected by the opposite of gravity's attraction, i.e., when repulsion occurs.
Please understand that these are very tentative ideas and I probably haven't worded this post anywhere near accurately enough to do justice to the matters in question. Therefore, any help given with the accuracy, meaning and understanding of this issue would be greatly appreciated. I'm here to learn and will gladly accept correction and guidance - because I need these things to learn and progress.
Thank you.
Cerenkov.