How can I solve for Equation 2.16 in Srednicki?

  • Context: Graduate 
  • Thread starter Thread starter LAHLH
  • Start date Start date
  • Tags Tags
    Srednicki
Click For Summary

Discussion Overview

The discussion revolves around solving for Equation 2.16 in Srednicki's work, specifically starting from Equation 2.14. Participants are exploring the mathematical manipulations involved in deriving the equation, including the use of transformations and the implications of certain assumptions.

Discussion Character

  • Mathematical reasoning
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant presents a derivation starting from Equation 2.14 and expresses uncertainty about how to proceed after reaching a certain point in the manipulation.
  • The same participant questions whether they can equate terms involving the transformation matrix \(\Lambda\) and the matrix \(M^{\mu\nu}\) directly, indicating a need for further clarification on the treatment of these terms.
  • Another participant expresses confusion regarding the role of the metric in the generator commutation relation, suggesting a potential misunderstanding or misalignment in the derivation process.
  • A third participant provides a link to a previous discussion that may contain relevant information, indicating that they believe it could assist in clarifying the current issue.

Areas of Agreement / Disagreement

Participants do not appear to reach consensus on the correct approach to take from the current point in the derivation. There are expressions of confusion and differing perspectives on the role of certain mathematical elements.

Contextual Notes

Participants have not fully resolved the implications of their assumptions regarding the transformation matrix and its relationship to the matrix \(M^{\mu\nu}\). The discussion reflects ongoing uncertainty about the mathematical steps required to progress towards Equation 2.16.

LAHLH
Messages
405
Reaction score
2
Hi,

I'm having a little troubling reaching this equation. I'm starting with 2.14 which is:

U(\Lambda)^{-1} M^{\mu\nu} U(\Lambda)=\Lambda^\mu{}_{\rho}\Lambda^\nu{}_{\sigma} M^{\rho\sigma}

Now letting \Lambda=1+\delta\omega and using U(1+\delta\omega)=I+\frac{i}{2\hbar} \delta\omega_{\mu\nu}M^{\mu\nu}, I get:

U(1+\delta\omega )^{-1} M^{\mu\nu} U(1+\delta\omega)=\Lambda^\mu{}_{\rho}\Lambda^\nu{}_{\sigma} M^{\rho\sigma}

=> (I-\frac{i}{2\hbar} \delta\omega_{\alpha\beta}M^{\alpha\beta}) M^{\mu\nu}( I+\frac{i}{2\hbar} \delta\omega_{\xi\chi}M^{\xi\chi})=\Lambda^\mu{}_{\rho}\Lambda^\nu{}_{\sigma} M^{\rho\sigma}

=> M^{\mu\nu}+\frac{i}{2\hbar} \delta\omega_{\xi\chi}M^{\mu\nu}M^{\xi\chi}-\frac{i}{2\hbar} \delta\omega_{\alpha\beta}M^{\alpha\beta}M^{\mu\nu}=\Lambda^\mu{}_{\rho}\Lambda^\nu{}_{\sigma} M^{\rho\sigma}

I'm not really sure where to go from here, I guess I can't simply say \Lambda^\mu{}_{\rho}\Lambda^\nu{}_{\sigma} M^{\rho\sigma}=M^{\mu\nu} and cancel this from each side?
Not sure how else I could get some that had \delta\omega in every term otherwise, so I can equate the antisymmetric parts of there coefficients as Srednicki suggests.

Thanks for any help
 
Physics news on Phys.org
I have no idea how the metric has found its way into the generator commutation relation, v confused
 
Ah thanks so much, I did do a search for Srednicki but didn't see that thread, thanks again.
 

Similar threads

  • · Replies 0 ·
Replies
0
Views
1K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 24 ·
Replies
24
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 3 ·
Replies
3
Views
942
  • · Replies 2 ·
Replies
2
Views
1K