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 December 15th, 2016, 12:20 PM #21 Senior Member     Joined: Sep 2015 From: CA Posts: 918 Thanks: 495 scanning all these they all seem to stem from the same basic unease of infinite sets having zero measure. I really like the argument in the xkcd comment. If you pick a random natural number, the next one you pick is almost surely greater than the one you picked. This right here precludes the idea of a uniform distribution on the naturals. The probability of picking any natural number we can represent given the matter available in the universe or less is 0 as there are infinitely many numbers greater than this.
December 15th, 2016, 04:18 PM   #22
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 Originally Posted by Maschke ...I'll offer some perspectives I found regarding putting uniform probability distributions on the naturals.
It looks like I have my homework cut out for me.

 February 23rd, 2017, 07:34 PM #23 Newbie   Joined: Nov 2015 From: hyderabad Posts: 27 Thanks: 0 Arbitrary Set Can anyone explain me what is an Arbitrary set ? and what is an Arbitrary union and Intersection ? if possible with definitions Thank you
February 23rd, 2017, 08:09 PM   #24
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 Originally Posted by Lalitha183 Can anyone explain me what is an Arbitrary set ? and what is an Arbitrary union and Intersection ? if possible with definitions Thank you
In what context?

In general an arbitrary set is an arbitrary set. Any old set at all. Like an arbitrary restaurant, it's just any restaurant that's open when you happen to be hungry. Any old restaurant, any old set.

Arbitrary unions and intersections are just unions and intersections without restriction. For example if I have a collection of sets, in some applications we want to consider only finite intersections, or perhaps countable intersections. Without any restrictions we can consider arbitrary intersections. Intersections of a perhaps uncountable collection of sets.

I hope this vague answer is helpful but if you can say more about why you're asking I can give a more specific answer in the appropriate context.

 February 23rd, 2017, 11:49 PM #25 Newbie   Joined: Nov 2015 From: hyderabad Posts: 27 Thanks: 0 Arbitrary Set Thank you Maschke. I have started reading topology. Here I come across Arbitrary sets more often. Do you mean an orbitrary set is a collection of sets of which cardinality cannot be expressed in a natural number ? Can an arbitrary set be infinite and finite ?
February 24th, 2017, 08:50 AM   #26
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 Originally Posted by Lalitha183 Thank you Maschke. I have started reading topology. Here I come across Arbitrary sets more often. Do you mean an orbitrary set is a collection of sets of which cardinality cannot be expressed in a natural number ? Can an arbitrary set be infinite and finite ?
An arbitrary set could be finite OR infinite, yes. It couldn't be infinite AND finite, that would be a logical contradiction. A particular set is not necessarily a collection of sets unless they say so; although technically in set theory all sets are collections of sets. Perhaps if you give a specific context ...

February 24th, 2017, 08:52 AM   #27
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 Originally Posted by Maschke An arbitrary set could be finite OR infinite, yes. It couldn't be infinite AND finite, that would be a logical contradiction. A particular set is not necessarily a collection of sets unless they say so; although technically in set theory all sets are collections of sets. Perhaps if you give a specific context ...

okay. Thanks for the information 😊

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