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## Main Question or Discussion Point

I have two questions regarding Kerr black holes, which I am hoping some of you might be able to shed some light on for me.

1. What is the physical significance / meaning of the

2. With regards to the hypothetical closed time-like curves beyond the Cauchy horizon, how would a test particle need to free-fall in order to describe such a geodesic ? Would it have to fall through the Cauchy horizon in a specific manner to "enter" a CTC, or does it always happen when you cross this boundary ?

I am aware of the instability issue in the Kerr geometry; the above questions are meant only to help me better understand the geometric structure of this metric.

1. What is the physical significance / meaning of the

**ergosurface, the one beyond the inner horizon ? If considered as a boundary surface, what would it separate from what ?***inner*2. With regards to the hypothetical closed time-like curves beyond the Cauchy horizon, how would a test particle need to free-fall in order to describe such a geodesic ? Would it have to fall through the Cauchy horizon in a specific manner to "enter" a CTC, or does it always happen when you cross this boundary ?

I am aware of the instability issue in the Kerr geometry; the above questions are meant only to help me better understand the geometric structure of this metric.