- #1

latentcorpse

- 1,444

- 0

anyway i. using a orthonormal basis method to get the curvature tensors and hence the einstein eqns

i have [itex]w^0=Le^adt, w^1=Le^a d \theta, w= \left( \begin{array}{c} w^2 \\ w^3 \end{array} \right)=L \left( \begin{array}{cc} M_{22} & M_{23} \\ M_{32} & M_{33} \end{array} \right)[/itex]

the structure eqn is [itex]dw^{\mu}=w^\mu_\nu \wedge w^\nu[/itex] and is rewritten in terms of the one-form matrices [itex]\Omega_0=\left( \begin{array}{c} w^2_0 \\ w^3_0 \end{array} \right), \Omega_1 \left( \begin{array}{c} w^2_1 \\ w^3_1 \end{array} \right), \Omega=w^2_3 \epsilon[/itex] where [itex]\epsilon= \left( \begin{array}{cc} 0 & 1 \\ -1 & 0 \end{array} \right)[/itex]

the structure eqns become

[itex]dw^0=w^0_1 \wedge w^1 + \hat{\Omega_0} \wedge w[/itex] (1)

[itex]dw^1=w^0_1 \wedge w^0 - \hat{\Omega_1} \wdge w[/itex] (2)

[itex]dw=\Omega_0 \wedge w^0 + \Omega_1 \wedge w^1 + \Omega \wedge w[/itex]

where the antisymmetry [itex]w_{\mu \nu}=-w_{\nu \mu}[/itex] has been used.

the antisymmetric derivatives are copmuted to be

[itex]dw^0=L^{-1} a' e^{-a} w^1 \wedge w^0[/itex]

[itex]dw^1=L^{-1} \dot{a} e^{-a} w^0 \wedge w^1[/itex]

[itex]dw=L^{-1} e^{-a} (Pw^0+uw^1) \wedge w[/itex]

where [itex]P=\dot{M}M^{-1},U=M'M^{-1}[/itex]

i should mention that L is a constant and a is a function of [itex]\theta,t[/itex]

so I'm having a few problems with what should be straightforward differential geometry:

(i) in (1) and (2) why is there a hat on the Omega matrices? what does this signify? some sort of antisymmetric version of Omega?

(ii) in (2), if you plug the numbers into the structure eqns, the first term should just be [itex]w^1_0 \wedge w^1[/itex] but they somehow rearrange to [itex]w^0_1 \wedge w^1[/itex]. How does this work?

(iii) finally, and probably most importantly, how do they get [itex]dw^0,dw^1[/itex] and [itex]dw[/itex]?