- #1
Mentz114
- 5,432
- 292
I'm trying to get a metric in the frame of a boosted observer. The spacetime in question has coframe and frame basis vectors
[tex]
\begin{align*}
\vec{\sigma}^0 = \frac{-1}{\sqrt{F}}dt\ \ \ \ & \vec{e}_0 = -\sqrt{F}\partial_t \\
\vec{\sigma}^1 = \sqrt{F}dz\ \ \ \ & \vec{e}_1 = \frac{1}{\sqrt{F}}\partial_z \\
\vec{\sigma}^2 = \sqrt{F}dr\ \ \ \ & \vec{e}_2 = \frac{1}{\sqrt{F}}\partial_r \\
\vec{\sigma}^3 = r\sqrt{F}d\phi\ \ \ \ & \vec{e}_3 = \frac{1}{r\sqrt{F}}\partial_\phi
\end{align*}
[/tex]
Boosting the coordinate frame basis by [itex]\beta[/itex] in the [itex]\phi[/itex] direction gives the new frame basis
[tex]
\begin{align*}
\vec{f}_0 &= -\gamma\sqrt{F}\partial_t + \gamma\beta \frac{1}{r\sqrt{F}}\partial_\phi \\
\vec{f}_1 &= \frac{1}{\sqrt{F}}\partial_z \\
\vec{f}_2 &= \frac{1}{\sqrt{F}}\partial_r \\
\vec{f}_3 &= \gamma\frac{1}{r\sqrt{F}}\partial_\phi + \gamma\beta \sqrt{F}\partial_t
\end{align*}
[/tex]
Now, my problem is reading off the new coframe basis [itex]s[/itex]. My attempt is below, but I'm only 50% confident it's right.
[tex]
\begin{align*}
{\vec{s}}^0 &= (\gamma\sqrt{F})^{-1}dt+(\gamma\beta)^{-1}r\sqrt{F}d\phi \\
{\vec{s}}^1 &= \sqrt{F}dz \\
{\vec{s}}^2 &= \sqrt{F}dr \\
{\vec{s}}^3 &= \gamma^{-1}r\sqrt{F}d\phi + (\gamma\beta)^{-1}\sqrt{F}dt
\end{align*}
[/tex]
The metric that arises from this is sort of plausible. I'd appreciate any pointers, particularly to any errors.
[tex]
\begin{align*}
\vec{\sigma}^0 = \frac{-1}{\sqrt{F}}dt\ \ \ \ & \vec{e}_0 = -\sqrt{F}\partial_t \\
\vec{\sigma}^1 = \sqrt{F}dz\ \ \ \ & \vec{e}_1 = \frac{1}{\sqrt{F}}\partial_z \\
\vec{\sigma}^2 = \sqrt{F}dr\ \ \ \ & \vec{e}_2 = \frac{1}{\sqrt{F}}\partial_r \\
\vec{\sigma}^3 = r\sqrt{F}d\phi\ \ \ \ & \vec{e}_3 = \frac{1}{r\sqrt{F}}\partial_\phi
\end{align*}
[/tex]
Boosting the coordinate frame basis by [itex]\beta[/itex] in the [itex]\phi[/itex] direction gives the new frame basis
[tex]
\begin{align*}
\vec{f}_0 &= -\gamma\sqrt{F}\partial_t + \gamma\beta \frac{1}{r\sqrt{F}}\partial_\phi \\
\vec{f}_1 &= \frac{1}{\sqrt{F}}\partial_z \\
\vec{f}_2 &= \frac{1}{\sqrt{F}}\partial_r \\
\vec{f}_3 &= \gamma\frac{1}{r\sqrt{F}}\partial_\phi + \gamma\beta \sqrt{F}\partial_t
\end{align*}
[/tex]
Now, my problem is reading off the new coframe basis [itex]s[/itex]. My attempt is below, but I'm only 50% confident it's right.
[tex]
\begin{align*}
{\vec{s}}^0 &= (\gamma\sqrt{F})^{-1}dt+(\gamma\beta)^{-1}r\sqrt{F}d\phi \\
{\vec{s}}^1 &= \sqrt{F}dz \\
{\vec{s}}^2 &= \sqrt{F}dr \\
{\vec{s}}^3 &= \gamma^{-1}r\sqrt{F}d\phi + (\gamma\beta)^{-1}\sqrt{F}dt
\end{align*}
[/tex]
The metric that arises from this is sort of plausible. I'd appreciate any pointers, particularly to any errors.