167,686 reputation
16223455
bio website boolesrings.org/asafk
location Israel
age 29
visits member for 4 years, 2 months
seen 7 mins ago

Ph.D. student in the Hebrew University of Jerusalem.

Set theorist to-be.


6m
revised Rigorous proof that surjectivity implies injectivity for finite sets
deleted 35 characters in body
7m
comment Rigorous proof that surjectivity implies injectivity for finite sets
Oh, that's correct. But that's quite easy to fix, hang on.
28m
comment Rigorous proof that surjectivity implies injectivity for finite sets
That's very nice!
30m
comment Rigorous proof that surjectivity implies injectivity for finite sets
I don't see the typo.
34m
revised Set Theory (Cardinality)
edited tags
35m
answered Rigorous proof that surjectivity implies injectivity for finite sets
45m
reviewed Leave Closed Is local compactness preserved by continuous closed onto functions?
57m
answered Find a topological space X and a compact subset A in X such that closure of A is not compact.
58m
reviewed Approve suggested edit on Find a topological space X and a compact subset A in X such that closure of A is not compact.
2h
revised What does “the support of $f$ lies in $V$ mean?”
edited tags
2h
revised Proving logic statements
edited tags
5h
revised Why non-real means only the square root of negative?
edited tags
5h
revised Give an example of two uncountable sets A and B such that A ∩ B is
edited tags
6h
comment Consistency strength of 0-1 valued Borel measures
I'm not entire sure if that's what you mean, but a real-valued measurable cardinal seems to be a relevant notion here. It's really a measurable cardinal in disguise. But if the continuum is real-valued measurable then there is a measure extending the Lebesgue measure which measures every subset. I suppose that by extending the co-null filter you can obtain a $0$-$1$ measure.
7h
revised Could someone explain aleph numbers?
added 26 characters in body; edited tags
8h
revised Prove that for a subset $A$ of $\mathbb{R}$, if $|A| = \omega$ then $|\mathbb{R} - A| = 2^\omega$
edited tags
8h
comment Prove that for a subset $A$ of $\mathbb{R}$, if $|A| = \omega$ then $|\mathbb{R} - A| = 2^\omega$
In the duplicate question you have a simple proof; in the answers a bit more hands on, in some sense.
9h
revised Work out percentages and commisions
edited tags
9h
comment Could someone explain aleph numbers?
@Joe: I'm not big on believing in things.
9h
comment Could someone explain aleph numbers?
@Julian: Different models of set theory might have different cardinals. What one model of set theory think is $\aleph_1$ might just be a countable ordinal in a larger model.