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11h
comment Is $(\mathbb{R},\tau_B)$ a separable space?
If "adding the limit points to a countable set can not turn it [into an] uncountable set", then how can any uncountable space be separable?
11h
answered Is $(\mathbb{R},\tau_B)$ a separable space?
17h
revised closedness of a sublattice under complements
added 16 characters in body
17h
answered closedness of a sublattice under complements
17h
comment closedness of a sublattice under complements
What if $X=\{\emptyset,\{a\},\{b\},\{a,b\}\}$ and $A=\{\emptyset,\{a\},\{a,b\}\}$? Why isn't that a counterexample?
1d
revised Cardinality problem: if $|A-B|=|B-A|$ then $|A| = |B|$
deleted 27 characters in body
1d
comment Counting of edges coloring in a graph
I think you should recheck those automorphisms.
1d
comment Does the Cartesian product of an infinite family have all the elements we expect?
You might as well focus on the simple special case where $A_i=\{0,1\}$ for each $i\in\mathbb N$. So, does $\mathcal P(\mathbb N)$ really contain every possible subset of $\mathbb N$?
1d
answered Cardinality problem: if $|A-B|=|B-A|$ then $|A| = |B|$
1d
comment Finite projective planes
Is there always an arc or size $n$?
1d
accepted Finite projective planes
Aug
15
comment Finite projective planes
@Casteels Oh, the sets I was asking about are called "arcs"? I didn't know that. Thanks for your comment and the reference. If you post your comment as an answer, I will accept it.
Aug
15
asked Finite projective planes
Aug
11
comment On partitions of closed bounded interval by closed non-empty sets
The closed interval $[a,b]$ (where $a\lt b$) can be partitioned into $2^{\aleph_0}$ nonempty closed sets. On the other hand, it cannot be partitioned into $n$ nonempty closed sets if $2\le n\le\aleph_0$. For $\aleph_0\lt n\lt2^{\aleph_0}$ I guess there are consistency results both ways, but I wouldn't know.
Aug
10
answered Prove that if one of the numbers $(2^n)-1$, $(2^n)+1$ is prime, then the other is composite.
Aug
10
revised nth convolved Fibonacci numbers of order 6 modulo m
corrected spelling and capitalization
Aug
9
answered Fixed point for a continuous function on a compact set?
Aug
3
comment Are $\mathbb{R_k}$ and $\mathbb{R_L}$ really non-comparable topologies?
What are the definitions of $\mathbb{R_L}$ and $\mathbb{R_k}$?
Aug
1
comment Dense subset of $[0,1]$ with Lebesgue measure $\epsilon$
@copper.hat Because $[0,\epsilon]\cup\mathbb Q$ is not a subset of $[0,1]$.
Jul
31
comment Find a subgroup of $S_4$ that is isomorphic to V, the Klein group.
$V_4$? What is the subscript for? I thought the "V" stood for "4"?