- #1
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We can write the Minkowski metric as
[tex]ds^2 = -c^2dt^2 + d\mathbf{x}^2[/tex]
or if we wanted different units for the metric
[tex]ds^2 = -dt^2 + \frac{d\mathbf{x}^2}{c^2}[/tex]
If we make c a function of time we have
[tex]ds^2 = -dt^2 + \frac{d\mathbf{x}^2}{c(t)^2}[/tex]
Which looks exactly like the FRW metric where c(t) = 1/a(t). So two questions: is my logic here correct? and if so, is it possible to tell the difference, in a purely gravitational way, between an FRW universe and a Minkowski universe with variable speed of light?
[tex]ds^2 = -c^2dt^2 + d\mathbf{x}^2[/tex]
or if we wanted different units for the metric
[tex]ds^2 = -dt^2 + \frac{d\mathbf{x}^2}{c^2}[/tex]
If we make c a function of time we have
[tex]ds^2 = -dt^2 + \frac{d\mathbf{x}^2}{c(t)^2}[/tex]
Which looks exactly like the FRW metric where c(t) = 1/a(t). So two questions: is my logic here correct? and if so, is it possible to tell the difference, in a purely gravitational way, between an FRW universe and a Minkowski universe with variable speed of light?