3,258 reputation
1834
bio website jakitoimgeisterhaus.blogspot.…
location Munich, Germany
age 38
visits member for 3 years, 4 months
seen 3 hours ago

My past research interests included differential algebraic equations, nonlinear analysis and relations between symmetries and structural properties.

I recently investigated hierarchical structures, starting from group cohomology, continuing with semi-group theory and ending with lattices and universal algebra.


Oct
16
reviewed Approve suggested edit on coordinate geometry high level problems
Oct
7
reviewed Close Prove e is a loop iff it is in no spanning trees of G
Oct
7
reviewed Approve suggested edit on infinitely many solutions to $\displaystyle x^n + y^n = z^{n+1}$
Oct
7
comment Are higher order logics substantially stronger than second order
In a certain sense, this answer is only true if the other axioms ensure that there are infinitely many objects/elements in the universe. And if the other axioms already ensure that we have the consistency strength of bounded Zermelo set theory or ZFC set theory, then just adding higher order variables and impredicative comprehension axioms (without using higher order variables in some of the other axioms) won't increase consistency strength any further.
Oct
6
revised Are higher order logics substantially stronger than second order
Oh, I forgot that I wanted to say something about the last word property
Oct
6
answered Are higher order logics substantially stronger than second order
Oct
5
revised Is multiplication in mixed radix numeral systems complicated?
edited tags
Oct
4
asked Is multiplication in mixed radix numeral systems complicated?
Sep
30
awarded  Explainer
Sep
28
comment Why are real numbers useful?
Nice answer, but when you say "And the wanted this line to be with no gaps, to be a continuum," what do you mean by "no gaps"? The rational numbers have no gaps either, in a certain sense. In another sense, the real numbers have gaps too, for example if you look at them as a subset of the surreal numbers. I think instead of the unclear "no gaps", what they really wanted was "completeness" (not necessarily limited to the order) and the Archimedean property: $\forall x\in {\mathbb R} \quad \exists n\in {\mathbb N} \quad x < n$.
Aug
18
answered How much maths can we do in NF(U)?
Aug
17
revised Why learn to solve differential equations when computers can do it?
fixed links
Aug
16
answered Why learn to solve differential equations when computers can do it?
Aug
15
revised Which natural number predicates can be defined in Robinson arithmetic?
edited body
Aug
15
answered Can Goodstein's theorem be expressed as an axiom or axiom scheme in PA?
Aug
15
answered Which natural number predicates can be defined in Robinson arithmetic?
Jul
22
comment Why are box topology and product topology different on infinite products of topological spaces?
@MathsLover The set theoretical topological spaces where defined by Felix Hausdorff in his book "Grundzüge der Mengenlehre", which appeared in 1914. In 1912, Jan Brouwer had started intuitionism, but Felix Hausdorff's work is not really based on it. The linked publication page of Dirk van Dalen is a good source for the connections between formal intuitionistic logic and topological spaces. If the links in that page don't work in your browser, copy the desired "link address" and replace "papers.html" in the current addresss by "articles/..." from the copied "link address".
Jul
20
answered Why are box topology and product topology different on infinite products of topological spaces?
Jul
18
comment Can a biased physical random source be post-processed to control the bias?
@Did Thanks, now I see where I made a mistake in the description of the method. Should be fixed now. This also answers part of my initial confusion, i.e. why I asked this sort of questions in the first place.
Jul
18
revised Can a biased physical random source be post-processed to control the bias?
OK, now I see my mistake in the description of the method