21,369 reputation
11432
bio website at.yorku.ca/cgi-bin/bbqa
location Netherlands
age 44
visits member for 3 years, 10 months
seen 10 hours ago

Got a PhD in topology in 98, now a cryptographer.


17h
revised $\{p_{n}\}$ is a sequence of real numbers. Prove $\limsup$ $\{p_{n}\} < \infty$ if and only if $\{p_{n}\}$ is bounded above.
edited tags
17h
comment $\{p_{n}\}$ is a sequence of real numbers. Prove $\limsup$ $\{p_{n}\} < \infty$ if and only if $\{p_{n}\}$ is bounded above.
I think it's fine.
17h
revised What is the probability that two five card hands have the same pair?
edited tags
20h
comment Is continuity in topology well-defined?
+1 for using square brackets
20h
revised Show that $(\overline A ∪ B) ∩ (\overline C - A) = (\overline C - A)$.
edited tags
22h
comment Applications of Baire's Threom
"Almost all" continuous functions are nowhere differentiable... This is one of Munkres' applications.
1d
revised Let $(X,d)$ be a metric space, $C$ a compact subset, and $K$ a closed subset. Prove that $K \cap C = \emptyset$ iff $d(K,C) > 0$.
edited body
1d
answered Continuity of function proof
1d
answered attack on RSA (factoring when knowing e and d)
1d
answered Let $(X,d)$ be a metric space, $C$ a compact subset, and $K$ a closed subset. Prove that $K \cap C = \emptyset$ iff $d(K,C) > 0$.
1d
revised Homeomorphism(topological spaces) version of Cantor–Bernstein–Schroeder theorem
added 42 characters in body
1d
comment Homeomorphism(topological spaces) version of Cantor–Bernstein–Schroeder theorem
@NateEldredge Indeed, I will edit it.
1d
answered Does every homogeneous space allow a group structure?
1d
answered Homeomorphism(topological spaces) version of Cantor–Bernstein–Schroeder theorem
1d
answered Inverse limit of countable (or even finite) sets
2d
answered how to do Diffie-Hellman-Merkle Key Exchange
2d
comment The name for the quotient property.
@Vadim At least I haven't seen it used that way. But of course there might very well be papers written on it that I haven't read. You might try MathOverflow as well, people there might know it under some name.
2d
revised The name for the quotient property.
edited body
2d
answered The name for the quotient property.
2d
comment Using induction for $x^n - 1$ is divisible by $x - 1$
You don't assume it's true for $n=1$, you show it. So what do you get for $n=1$?