I saw that the norm of four acceleration is equal to the magnitude of proper frame's acceleration.(adsbygoogle = window.adsbygoogle || []).push({});

So, if the observer moves in x direction, following equation about norm of it's 4 acceleration is like that

-(d^2 t / dτ^2) + (d^2 x / dτ^2) = d^2 x / dt^2

In comoving frame(proper frame), proper time is equals to t, so the first term in the left side vanishes, and the remain term is equal to the right side.

I tried to proof this relationship generally... but it's very hard for me.

Now I confused whether the general proof exists, or not...

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# The norm of four-acceleration

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