3,228 reputation
1833
bio website jakitoimgeisterhaus.blogspot.…
location Munich, Germany
age 38
visits member for 3 years, 2 months
seen 4 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
awarded  Custodian
Jun
9
reviewed Close Frogs on lotus trees
Jun
9
comment Is there a (foundational) type theory with the features I'm looking for?
@MaliceVidrine I wouldn't necessary agree to your statements about NF(U), but you are right that I will need at least "Inf" in addition to TST, and that "Choice" won't really hurt. I don't know how to parse "Small Ordinals", but I guess it's something harmless similar to "Choice". I think the reason why Holmes and I discuss TST is that it is a baseline, which already has a quite significant consistency strength, but can be directly traced back to a philosophical position with corresponding explicit ontological commitments.
Jun
9
revised Is there a (foundational) type theory with the features I'm looking for?
Add a reference to the place where Randall Holmes discusses TST, and to ARD Mathias' papers
Jun
9
answered Type theory as foundations
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 suggested edit on 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?