# Anti-matter black hole and time

I have recently read some hard science-fiction story based on an assumption that if time stops (from external observer's perspective) on the event horizon of black hole, then in an anti-matter black hole's horizon the time would pass infinitely fast (same perspective)

I thought it was impossible, but I'm not sure anymore.

What would be the effect of approaching the event horizon of an anti-matter black hole?

Is it possible that an infinity of time passes in a finite time (from our point of view) ?

Fun follow-up: if so, can a result of infinite computation be returned to our timeline?

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More on "anti-matter black holes": physics.stackexchange.com/q/25982/2451 and physics.stackexchange.com/q/5615/2451 – Qmechanic Oct 12 '12 at 23:11

A black hole may result from a gravitational collapse of either matter or antimatter, but the black hole itself is a geometrical object — a feature of the shape of space-time, not a material object. The behaviour of space-time at or near to a black hole is the same however it originates, so long as the bulk is electrically neutral; and a charged black behaves the same regardless of whether its charge is due to having absorbed e.g. more protons or more positrons.

Therefore, there is no real distinction between a "matter" black hole and an "antimatter" black hole; in particular, a black hole which happened to form due to the gravitational collapse of a large amount of antimatter would be indistinguishable from a black hole arising from a collapse of matter (or indeed from a sufficiently dense combination of matter and antimatter, arising from a dense nugget of matter and a dense nugget of antimatter brought together that only achieve the "critical density" as they approach each other).

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"The behaviour of space-time at or near to a black hole is the same however it originates." This is false. For example, a black hole with electrical charge differs from an electrically neutral black hole. – Ben Crowell Oct 13 '12 at 1:22
Thanks for clearing this for me Niel. @BenCrowell Could You elaborate (or better - give a link)? – naugtur Oct 13 '12 at 8:33
@BenCrowell: right, a bit too hastily written. Edited. – Niel de Beaudrap Oct 13 '12 at 9:39
– Ben Crowell Oct 14 '12 at 18:54

## protected by Qmechanic♦Apr 8 '13 at 8:40

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