Timeline for Perturbation theory in general relativity using xAct
Current License: CC BY-SA 3.0
15 events
| when toggle format | what | by | license | comment | |
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| Mar 17, 2015 at 10:41 | vote | accept | user1997744 | ||
| Dec 13, 2014 at 15:09 | comment | added | Alexey Bobrick | @user1997744: Cheers! | |
| Dec 13, 2014 at 14:13 | comment | added | user1997744 | I had to travel to Cambridge on business for several days, and I have just returned from the airport. I will be working on it the next few days; I'll let you know. | |
| Dec 13, 2014 at 10:14 | comment | added | Alexey Bobrick | @user1997744: Out of curiosity, was the edit eventually any use? | |
| Dec 9, 2014 at 17:21 | history | edited | Alexey Bobrick | CC BY-SA 3.0 |
Expansion
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| Dec 9, 2014 at 14:30 | comment | added | user1997744 | Yes, that's no problem. I will only be working at linear order, i.e. $g_{\mu\nu} \to g_{\mu\nu} + \epsilon \, h_{\mu\nu} + \mathcal{O}(\epsilon^2)$ | |
| Dec 9, 2014 at 14:23 | comment | added | Alexey Bobrick | @user1997744: Oh, that is indeed quite an honour, thanks! So, speaking of perturbations: xCoba allows you to make expressions, like the original one you've shown, and to evaluate them in terms of h. What it doesn't do, however, is ensuring that all the terms are of the of the same perturbation order. That is probably done by xPert, which I haven't worked with. That might not be a problem, though, if you intend to be in the lowest order, but you should be aware of the fact. | |
| Dec 9, 2014 at 14:00 | comment | added | user1997744 | FYI: If you can show me an example of how to evaluate the perturbations explicitly (with the summation, differentiation, etc) I will certainly include you in the acknowledgements of my paper. | |
| Dec 9, 2014 at 13:54 | comment | added | user1997744 | Well, now you know why I absolutely need xAct; doing it by hand is prohibitively tedious. (Though, I was brave and computed the curvature tensors by hand using differential forms.) | |
| Dec 9, 2014 at 13:24 | comment | added | Alexey Bobrick | @user1997744: Interesting to know, thanks! I used to think that people most commonly do low energy string theory for holography, but in somewhat smaller number of dimensions. | |
| Dec 9, 2014 at 13:11 | comment | added | user1997744 | I'm doing perturbation theory in low energy effective string theory, and I need $D=26$ on grounds of consistency to ensure the central charge $c=0$ such that the trace anomaly vanishes. | |
| Dec 9, 2014 at 13:09 | comment | added | Alexey Bobrick | @user1997744: Yes, it is exactly in xCoba documentation. I will check if I have relevant example for the above metric (still don't have xAct). May I ask, what is the application, which requires working in 26 curved dimensions? | |
| Dec 7, 2014 at 22:30 | comment | added | user1997744 | Thanks, I've used my metric with your code, and it's computed all the curvature tensors (after some time, though I am working in 26 dimensions). Do you know how I can 'plug' it into the perturbation equations, and execute the summation over the indices? | |
| Dec 6, 2014 at 20:47 | history | edited | chris | CC BY-SA 3.0 |
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| Dec 6, 2014 at 17:30 | history | answered | Alexey Bobrick | CC BY-SA 3.0 |