Does Borel Cantelli lemma apply to infinite universes?

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SUMMARY

The Borel-Cantelli lemma states that if a sequence of events \(E_n\) is independent and the sum of their probabilities diverges to infinity, then the probability of infinitely many of these events occurring is 1. This discussion clarifies that while infinitely many occurrences of \(E_n\) can happen, it does not imply that all occurrences must happen. The example provided illustrates that in an infinite universe scenario, both the occurrence and non-occurrence of an event can have a probability of 1, highlighting the complexity of infinite probabilities.

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calios
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guys I am bit confused with the statement borel cantelli lemma 2 :
"If the events En are independent and the sum of the probabilities of the En diverges to infinity, then the probability that infinitely many of them occur is 1"

this state if probability of A occur > 0 .
and if the probabilities of A diverges to infinity, then the probability that infinitely many of A occur is 1

the problem is
if probability of opposite A, event[not A] > 0
and if the probabilities of "not A" diverges to infinity
then the probability that infinetely many of [not A] occur is 1.
in other way the probability of A doest occur is 1 too? :confused:

this correct? :confused:
or i made a mistake ? thank you
 
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Borel-Cantelli says that the probability that infinitely many of the En occur is 1. It doesn't say that all the En must occur.

Likewise, it might be that infinitely many of the Enc occur. It's not said that they must all occur.

For example, the sequence 0,1,0,1,0,1,... becomes infinitely many times 0 and is infinitely times in the complement of 0.
 
micromass said:
Borel-Cantelli says that the probability that infinitely many of the En occur is 1. It doesn't say that all the En must occur.

Likewise, it might be that infinitely many of the Enc occur. It's not said that they must all occur.

For example, the sequence 0,1,0,1,0,1,... becomes infinitely many times 0 and is infinitely times in the complement of 0.

oke u mean..
ley say we have infinite many universe,
and probability Earth occur is 1/6, the probability Earth does not occur is 5/6
so the probability of infinite many Earth occur is 1. and the probability of infinite many Earth does not occur is 1 too.
in infinite universe both are happened right?
 
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