Talk:Proper forcing axiom

Notation question

$[\lambda ]^{\omega }$ Am I correct that this is the power set of $\lambda$ restricted to subsets that are countable (of size $\omega$ ).? Thanks! Zero sharp 05:27, 25 October 2007 (UTC)[reply]

Basically. Sometimes it's taken to mean the set of all strictly increasing functions from ω to λ, but it comes to the same thing. I'm a little surprised to see the notation in this context; I would have expected more

P_{\omega _{1}}(\lambda )

, which means exactly "countable (including finite) subsets of λ". --Trovatore 23:51, 25 October 2007 (UTC)[reply]

Whoops, my bad; it doesn't come to the same thing. Of course not every countable subset of λ is the range of an increasing function from ω. I think this should be examined to see which version is actually meant here. I sort of suspect the version with

P_{\omega _{1}}(\lambda )

is more standard. --Trovatore 23:58, 25 October 2007 (UTC)[reply]

History and Formulation

There should be a history section, explaining that Proper Forcing was developed by Saharon Shelah. Set theorist (talk) 04:30, 17 June 2010 (UTC)[reply]

Yes, there should. Do you work in proper forcing? Maybe you could add it. I know just a little about it. If you're new to WP, just write what you can (hopefully giving references); someone else can clean it up into WP style. --Trovatore (talk) 04:36, 17 June 2010 (UTC)[reply]