Killing vectors of minkowski space

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Discussion Overview

The discussion revolves around the identification and understanding of Killing vectors in Minkowski space, focusing on how these vectors relate to isometries such as rotations, boosts, and translations. Participants explore the mathematical representation and implications of these vectors within the context of general relativity and differential geometry.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about deriving the number of isometries (3 rotational, 3 boosts, 3 spatial translations, and 1 time translation) from the general form of Killing vectors in Minkowski space.
  • Another participant suggests that the four translations arise from the term \( t^a \) and notes that if \( \omega \) is traceless, it has 3 symmetric degrees of freedom (boosts) and 3 anti-symmetric degrees of freedom (rotations).
  • A participant seeks clarification on how to show that there are 6 components of \( \omega \), questioning the distinction between boosts and rotations.
  • There are references to external threads that may provide additional insights into the topic.
  • One participant asserts that any vector in Minkowski space can be considered a Killing vector, suggesting that this leads to the conservation of energy and momentum in this space.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the decomposition of Killing vectors into isometries, with some confusion remaining about the mathematical representation and implications. No consensus is reached on the clarity of these concepts.

Contextual Notes

Participants mention difficulties with notation and representation, particularly with the term \( \partial / \partial x^a \) and its relation to translations. There is also uncertainty about the interpretation of the components of \( \omega \) and their classification.

WannabeNewton
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How does one know from the general form of the killing vectors in minkowski space:
X[tex]^{a}[/tex] = [tex]\omega[/tex]_a_b(x[tex]^{a}[/tex]) + t[tex]^{a}[/tex]

that there are 3 rotational isometries, 3 boosts, 3 spatial translations, and 1 time translation from that general form? It has me very confused >.<
 
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I can't read your notation so I could be wrong. The four translations are obviously from ta and if [itex]\omega[/itex] is traceless then it has 3 symmetric degrees of freedom ( boosts) and 3 anti-symmetric df (rotation) .
 
Mentz114 said:
I can't read your notation so I could be wrong. The four translations are obviously from ta and if [itex]\omega[/itex] is traceless then it has 3 symmetric degrees of freedom ( boosts) and 3 anti-symmetric df (rotation) .

Omega is a rank two anti symmetric tensor sorry I couldn't get latex to work properly. I understand the part with the translation but how can you show that there are 6 components of omega with 3 being boosts and the other 3 being rotations? Also a lot of my books represent the translations in terms of [tex]\partial[/tex] / [tex]\partial[/tex]x[tex]^{a}[/tex] - are they simply representing translations as displacements or is there a way in which you can extract the differentials from t[tex]^{a}[/tex]?
 
WannabeNewton said:
Omega is a rank two anti symmetric tensor ...
In that case I'm baffled. I'll have to read George Jones' thread again because I didn't see how spatial rotations and boosts are accommodated.
 
George Jones said:

Thanks I think I get it now. If minkowski space killing vectors are this confusing to me I can't imagine schwarzschild or robertson metrics. Sucks for me considering how important these isometries seem to be.
 
Any vector in Minkowski space is a Killing vector, because any directional derivative of the metric with respect to displacement is zero. You can think of it as degenerate eigen vectors. Any complete set spanning the space works as well as any other.

As a consequence, the energy and momentum in Minkowski space are absolutely conserved.
 

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