121,076 reputation
7112231
bio website von-eitzen.de/math/tntrep.xml
location Bonn, Germany
age 48
visits member for 2 years, 2 months
seen 2 hours ago

I did study math and had a knack for it, but I am sooo out of that business now ...


Jan
23
comment Need a translation: Mathspeak to english
en.wikipedia.org/wiki/Map_%28mathematics%29
Jan
23
answered Bounds on cardinality of sum-sets.
Jan
23
comment Statement that is provable in $ZFC+CH$ yet unprovable in $ZFC+\lnot CH$
+1 I think among all answers this is the one best fitting "outside set theory" (it doesn't mention anything about cardinality explcitly) and still looks awfully elementary.
Jan
23
answered Preventing underflow, log sum exp trick
Jan
23
comment polynomial ring over a domain is also a domain + every non-constant polynomial over a certain field has root?
To add to @TobiasKildetoft's and i707107's comments: Consider the algebraic closure $\overline{\mathbb C(T)}$.
Jan
22
comment Proof that there is no Universal Set
@DanulG The meaning of $U$ is specified by the introductory "if all $x$ in $U$, then ..."
Jan
22
answered Why elements in a non-archimedian local field $F$ are of the form $\pi^n u$?
Jan
22
revised Prove: If $\gcd(a,b,c)=1$ then there exists $z$ such that $\gcd(az+b,c) = 1$
added 12 characters in body
Jan
22
answered Ordered abelian groups
Jan
22
answered Prove: If $\gcd(a,b,c)=1$ then there exists $z$ such that $\gcd(az+b,c) = 1$
Jan
22
comment an example of supremum using relation other than <. like using divides etc??
For an arbitrary partial order, we can hardly say more than: use the definition. The infimum with respect to "divides" is (of course) the gcd
Jan
21
awarded  Good Answer
Jan
21
answered Why do these two solids of revolution have different volumes?
Jan
21
answered A question about uniformly continuous
Jan
21
answered How to prove these equalities for $a,b,c \in \mathbb{C}$
Jan
21
answered Do line-by-line statements imply an $\iff$, an $\implies$, or are they ambiguous?
Jan
21
answered Consider $3$ positive real numbers $a,b,c$.Show that there cannot exist two distinct positive integers $m$ and $n$ such that both…
Jan
21
comment What does this mean in (what I think) is a function?
Yes $\mu(12)=0.7$ and also $\mu(42)=0.7$ whereas $\mu(1729)=0$.
Jan
21
answered Solve $ax^t = by^t$ for $ t$
Jan
21
comment A question about limit and sequence
You are taking the minimum of a set oof positive numbers. But the set is infinte, hence the minimum (or rather infimum) might accidentally be zero. This can be repaired by allowing only $0\le p\le 2q$, say