Henno Brandsma

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bio website at.yorku.ca/cgi-bin/bbqa
location Netherlands
age 43
visits member for 2 years, 5 months
seen 8 hours ago
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Got a PhD in topology in 98, now a cryptographer.


260 Answers

newest activity votes
3
Some contradiction in an open problem
3
convert decimal 1024 to hexadecimal
3
Urysohn Metrization Theorem: show that $F$ is continuous.
3
$X$ is dense in $X^*$
3
Definition of a basis for a particular topological space
3
topological property of the log function
3
Simple question regarding factoring quadratics
3
Why does “separable” imply the “countable chain condition”?
3
Fixed Set Property?
3
continuous $f:X\rightarrow X'$, $X,X'$ metric spaces properties
3
A complete Boolean algebra $B$ satisfies the $\kappa$-chain condition if and only if $B$ is $\kappa$-saturated
3
$\mathbb{Q}$ in metric space $(\mathbb{R},d)$ neither open nor closed
3
accumulation points
3
Is there another method to characterize Lindelöf property?
3
Does a dense $G_\delta$ subset of a complete metric space without isolated points contain a perfect set?
3
Is there an easy example of a vector space which can not be endowed with the structure of a Banach space
3
Is there a countable, regular space with no isolated points which is not homeomorphic to the rationals?
3
Connectedness problem and countability of compact subsets of the Sorgenfrey line
3
Several questions around the exponential law
3
to show that $(X\times Y)\setminus(A\times B)$ is connected
3
Understanding relation between Quotient Space and $S^1$
3
show that $X$ is compact
3
Difference between “Show” and “Proof”
3
Rijndael S-Box Permutation Group
3
how to find the unique smallest topology?
3
Show that a subset $A$ of $R$ is open iff it is countable union of open intervals
3
Verifying a Closure Operation
2
How easily to check: $f$ is a closed map?
2
Is this proof on the product of $X$ OK?
2
Prove that $X\times Y$, with the product topology is connected
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