182,453 reputation
18247496
bio website boolesrings.org/asafk
location Israel
age 29
visits member for 4 years, 6 months
seen 3 hours ago

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

Set theorist to-be.


Please do not make any "congratulatory" posts when I cross some reputation threshold.


1h
awarded  notation
5h
comment Real solutions of $x^n + y^n = (x+y)^n$
I'll get back to this discussion when you rethink about the associativity of $-$, or lack thereof. In the meantime, goodnight.
5h
comment Real solutions of $x^n + y^n = (x+y)^n$
Uhm, no, $(-x)+(-y)=(-1)+(-1)=-2$.
5h
revised $\mathbb{Z}_{(2)}$ has one maximal ideal
added 35 characters in body
6h
comment intersection of infinite collection of finite sets?
@Alfred: Since when cardinals are real numbers?
6h
comment Real solutions of $x^n + y^n = (x+y)^n$
$x=y=-1$ and $n=1$, then $-2$ is definitely not positive. If $n=3$ then you get terms of different signs as well.
7h
revised What does it mean for a function to be $\Omega(1)$?
edited tags
7h
comment Why is the well ordering principle counter-intuitive?
@David: I don't think that the proof is hard, although I wouldn't characterize it as particularly easy. I would also think that an easier way of doing so would be to first prove that there a well-ordering which does not embed into the set (as Hartogs original theorem that predates the von Neumann ordinals), and then prove that every well-ordered set is isomorphic to a unique ordinal.
8h
revised Union and Intersection
edited tags
9h
answered Is $\text{Hom}(\prod_p \Bbb Z/p\Bbb Z, \Bbb Q) = 0$ possible without choice?
11h
comment Is $\text{Hom}(\prod_p \Bbb Z/p\Bbb Z, \Bbb Q) = 0$ possible without choice?
@OohAah: Ah!!! Of course.
12h
comment Problem with the definition of tree in descriptive set theory
No, a branch is a function which is the union over a maximal chain from $T$.
12h
awarded  Nice Answer
12h
comment Problem with the definition of tree in descriptive set theory
Once again, why $x$ is a function into the tree? It's a function into $A$.
12h
comment Problem with the definition of tree in descriptive set theory
Why $x\colon\Bbb N\to A^\Bbb N$?
12h
revised Problem with the definition of tree in descriptive set theory
added 343 characters in body
12h
comment Problem with the definition of tree in descriptive set theory
Yes. An the branch is a function whose finite initial segments are in the tree.
12h
answered Problem with the definition of tree in descriptive set theory
13h
comment Is there a notation for being “a finite subset of”?
The symbol $\infty$ should never be used to denote a cardinal or an ordinal. It can, however, be used to denote something "not finite", and therefore $|A|<\infty$ is a perfectly valid way to denote finiteness.
15h
comment Is there a notation for being “a finite subset of”?
@Lehs: Formulas are clear when the notation is truly simplifying; the language is clear when there are not too many conjunctions, implications and negations.