Why doesn't a real Infinite Redshift Limit occur at R+ for Kerr BHs?

Thread starter JTorn
Start date Nov 12, 2019
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Black hole Infinite Kerr Limit Redshift

Nov 12, 2019

JTorn

Homework Statement: The exercise says the following:

" Considering a body radially infalling towards a Kerr black hole, show that ˙t becomes infinite at the horizon r = r+ but not at the static limit r = R+. Although the r = R+ surface is usually called “infinite redshift surface” (because gtt = 0 there), argue that this is not where the actual infinite redshift takes place (as seen from infinity). What prevents a source of light from being infinitely redshifted at R"

Relevant Equations: We got the formulae for EH raidus (r+) and the radius for Ergosphere (R+).

As I have studied before, I found that Infinite Red Shift occurs where g_tt = 0 but this exercise says that on Kerr's Black Hole it doesn't really work like that.

Right now I'm blocked because I didn't find anything on the internet about it so I don't know how to show this phenomenon. Any help would be great.

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Nov 15, 2019

JTorn

Guess that none knows the answer.

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