- #1
Taha
- 2
- 0
Homework Statement
Two plane gravitational waves with TT (transverse-traceless) amplitudes, ##A^{\mu\nu}## and ##B^{\mu\nu}##, are said to have orthogonal polarizations if ##(A^{\mu\nu})^*B_{\mu\nu}=0##, where ##(A^{\mu\nu})^*## is the complex conjugate of ##A^{\mu\nu}##. Show that a 45 degree rotation of ##B^{\mu\nu}## makes it proportional to ##A^{\mu\nu}##.
Homework Equations
For waves propagating in the z direction under the TT gauge, ##A^{xx}##, ##A^{xy}##, and ##A^{yy}=-A^{xx}## are the only non-zero components.
The Attempt at a Solution
$$(A^{\mu\nu})^*B_{\mu\nu}=2(A^{xx})^*B_{xx}+2(A^{xy})^*B_{xy}=0$$
$$B_{xy} = -B_{xx}\frac{(A^{xx})^*}{(A^{xy})^*}$$
$$ (B_{\mu\nu})=B_{xx}\begin{pmatrix}
1 & -(A^{xx})^*/(A^{xy})^*\\
-(A^{xx})^*/(A^{xy})^* & -1\\
\end{pmatrix} = \frac{B_{xx}}{(A^{xy})^*}\begin{pmatrix}
(A^{xy})^* & -(A^{xx})^*\\
-(A^{xx})^* & -(A^{xy})^*\\
\end{pmatrix}$$
At this point, I'm not really sure what to do. I don't know what it means to "rotate" a matrix so I assume the correct thing to do is complex rotate each component, but I'm not entirely sure what this entails either. I tried multiplying each component by ##e^{i\pi/4}=(1+i)/\sqrt{2}## but I'm not sure how this helps. Any advice?