Timeline for What is an algorithm for generating a set of null (spacetime) vectors that add to zero? [closed]
Current License: CC BY-SA 3.0
12 events
| when toggle format | what | by | license | comment | |
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| Feb 15, 2018 at 8:51 | history | closed |
user6976 Johannes Hahn David Handelman Max Alekseyev Ben McKay |
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| Feb 14, 2018 at 22:42 | answer | added | Ning Bao | timeline score: 1 | |
| Feb 14, 2018 at 22:32 | comment | added | Ning Bao | Thank you! I think that @AndreasBlass's modifcation to AlexM's solution solves my problem. | |
| Feb 14, 2018 at 22:22 | comment | added | Todd Trimble | For the sake of convenience to @AndreasBlass and others, AlexM's comment read: "Let $s=(0,0,0,0)$. Generate $x,y,z$ and then compute $t=\sqrt{x^2+y^2+z^2}$; let $s=s+(t,x,y,z)$. Do this $n−1$ times. Let the $n$-th vector be $−s$." | |
| Feb 14, 2018 at 22:11 | comment | added | Ning Bao | Is the idea to randomly generate the first n-2 vectors, find a vector that will cancel those, and then decompose that vector into a sum of 2 null vectors? | |
| Feb 14, 2018 at 22:10 | comment | added | Ning Bao | What is the process that you referred to by AlexM? Can you recreate it? | |
| Feb 14, 2018 at 22:08 | comment | added | Andreas Blass | @AlexM Please un-delete your comment, because I refer to it in a corrected version. | |
| Feb 14, 2018 at 22:07 | comment | added | Andreas Blass | Unless I'm making a silly mistake, every time-like or space-like vector can be expressed as a sum of two null vectors (in infinitely many ways --- there seems to be a free paramater ranging over a 2-dimensional sphere). So use @AlexM's process for $n-2$ steps and then write the final $-s$ as the sum of two null vectors. | |
| Feb 14, 2018 at 21:56 | comment | added | Andreas Blass | @AlexM. The last vector in your algorithm, the $-s$ that cancels the sum of the previous vectors, won't generally satisfy $-t^2+x^2+y^2+z^2=0$. | |
| Feb 14, 2018 at 20:59 | review | Close votes | |||
| Feb 15, 2018 at 8:51 | |||||
| Feb 14, 2018 at 20:14 | review | First posts | |||
| Feb 14, 2018 at 20:44 | |||||
| Feb 14, 2018 at 20:14 | history | asked | Ning Bao | CC BY-SA 3.0 |