3,377 reputation
1937
bio website jakitoimgeisterhaus.blogspot.…
location Munich, Germany
age 38
visits member for 3 years, 6 months
seen 19 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.


Jun
9
answered Is there a (foundational) type theory with the features I'm looking for?
Jun
7
comment Is there a (foundational) type theory with the features I'm looking for?
@user18921 I think that yes, it has support for (primitive?) recursively defined sets. To see this, try to start with the constant $0$ and the successor relation $S$, and then recursively define addition, multiplication and exponentiation. Then decide for yourself, whether the support for recursive definitions is good enough. I haven't checked whether $\mu$-recursion is also available, but I guess that it is indeed.
Jun
7
answered Is there a (foundational) type theory with the features I'm looking for?
Jun
3
comment How do I turn a “broken” plot into a smooth curve
@Lee There are some options for making such methods "reproducible, repeatable and programmable". The method with the exponential function already satisfies this property without any further modification. For the method with the cubic polynomial, I added a suggestion how to make it reproducible. I'm not sure why you stress VBA.
Jun
3
revised How do I turn a “broken” plot into a smooth curve
propose a way to make the polynomial method more "reproducible, repeatable and programmable"
Jun
1
answered How do I turn a “broken” plot into a smooth curve
Jun
1
answered Why aren't there any first-order sentences which have the property of being true in all non-standard models of PA and false in the standard one?
Jun
1
comment Can the divergence theorem be restricted to flat surfaces?
Oh man, you really seem to have problems with the English language. Even a flat surface is still not restricted to $\mathbb R^2$. The non-mathematical meaning the word "surface" is the outer face of an object. What you probably mean is called an "area" or a (two dimensional) "domain".
Jun
1
answered Can the divergence theorem be restricted to flat surfaces?
Jun
1
revised Can the divergence theorem be restricted to flat surfaces?
Talking about surfaces in the plane would be boring
May
30
answered Provocations on the existence of mathematical objects
May
25
reviewed Approve Find a matrix $P$ that orthogonally diagonalizes $A$ and determine $P^{-1}AP$
May
24
comment Does every function with $f_x,f_y>0,f_{xx},f_{yy}<0$ with particular condition have to satisfy $f_{xy}/f_{xx} = -x/y$?
No, this should definitively not be posted at mathoverflow. Your condition $f(\lambda x, \lambda y)=\lambda f(x,y)$ forces the derivative in x-direction along the x-axis to be constant, so that you limes conditions cannot be satisfied everywhere. So of course nobody can give a counterexample, because there is no example at all to satisfy these conditions.
May
22
comment Understanding properties and criticisms of a (specific) sequent calculus
To be honest, I don't really see how this "intended reading" is any different from the rules themselves, except for the turnstile. Also, I guess the main part of Peter Smith's criticism referred to the (missing) subformula property of (PC) and (Ctr). This answer doesn't mention (PC) and (Ctr) explicitly, but it seems as if they are unchanged.
May
20
answered Shall remainder always be positive?
May
19
comment Difference between bound and free variable
philosophy.stackexchange.com/questions/7827/…
May
19
comment Difference between bound and free variable
math.andrej.com/2012/12/25/…
May
19
comment Difference between bound and free variable
@MauroALLEGRANZA I tried to incorporate your suggestiongs into my anser. I agree that $P(x)$ has no fixed meaning. There are many reasonable ways to assign meaning to it. It makes most sense to strive for functoriality of truth values for these meanings. The drawback of the definition I gave is that it hides the fact that even $\forall x (P(x)\implies Q(x))$ can take truth values in a Boolean algebra. But I hope that it might be relatively easy to understand for somebody with a "bivalued" classical mindset.
May
19
revised Difference between bound and free variable
tried to incorporate comments by Mauro ALLEGRANZE
May
19
answered Difference between bound and free variable