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visits member for 2 years, 7 months
seen May 15 '13 at 22:45

Jul
2
awarded  Curious
Jun
25
awarded  Revival
Mar
22
comment Maximal ideals of the rings of Baire- One Functions
Isn't $Ba_1(X)$ a commutative C*-algebra (in which case it is certainly a PM-ring)?
Mar
21
awarded  Yearling
Jul
20
comment Characterizing Posets by Functions Into Natural Numbers
@Nik. What I had in mind amounts to taking finite subsets of the set of prime numbers whereas you are allowing arbitary subsets. (Actually in $Z$ shouldn't you be including the zero ideal as a prime ideal, so that $P$ isn't an unordered set?) Your approach seems to jettison the topology that is available if $P$ is a poset of prime ideals. But I suppose that not every poset is a poset of prime ideals of a ring?
Jul
19
comment Characterizing Posets by Functions Into Natural Numbers
Presumably in the case when $P$ is the poset of prime ideals of a ring, $P^∗$ is isomorphic to the lattice of semiprime ideals?
Jul
18
accepted countably complete filters
Jun
30
comment countably complete filters
Thanks. I will have to think about this. Presumably the definition of a Lindelof element is not quite right?
May
22
answered About subspaces of $F$-spaces
May
16
comment iterating ultrapowers of C*-algebras: the Calkin algebra
Many thanks. Fascinating!
May
16
accepted iterating ultrapowers of C*-algebras: the Calkin algebra
May
11
comment F-spaces and points whose complements are C*-embedded
Thanks. A more complicated problem than I realised! Is it known what the situation is for Shelah's model with no P-points?
May
11
accepted F-spaces and points whose complements are C*-embedded
May
10
asked F-spaces and points whose complements are C*-embedded
May
9
revised iterating ultrapowers of C*-algebras: the Calkin algebra
corrected tags
May
9
asked iterating ultrapowers of C*-algebras: the Calkin algebra
May
9
accepted iterating ultrapowers of C*-algebras
May
2
comment iterating ultrapowers of C*-algebras
I now understand from Nik's answer that the natural containment is strict at each stage, so in this sense the process never stabilizes. On the other hand, as far as constructing new C*-algebras is concerned, the process 'stabilizes' as soon at the ultrapower is isomorphic as a C*-algebra to its predecessor. So I am very interested in this question of whether $A^1$ and $A^2$ are C*-isomorphic (under CH).
May
2
comment closed meagre sets
Thanks for this: it gives an easy way of visualizing a meagre subset of $C$.
May
2
comment iterating ultrapowers of C*-algebras
@ Joel. Yes, I was just thinking of external isomorphism. So in my question, I am interested in whether $A^1$ and $A^2$ are isomorphic as C*-algebras.