3,228 reputation
1833
bio website jakitoimgeisterhaus.blogspot.…
location Munich, Germany
age 38
visits member for 3 years, 2 months
seen 5 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.


Aug
20
comment A question about convolution of two distributions
@ShanLinHuang Yes, this is the intention of the condition. By the way, did you notice that I didn't really indicate how to show $u*v \in \mathcal{S}'(\mathbb R)$?
Aug
20
asked Is the set of all definable subsets of the natural numbers recursively enumerable?
Aug
19
revised Riemann hypothesis and diophantine equation
All references and diophantine equations for this I have seen so far are of the sort "RH <=> no solution"
Aug
19
suggested suggested edit on Riemann hypothesis and diophantine equation
Aug
15
comment A question about convolution of two distributions
I added a translation into english. I just found the mentioned lecture notes online: math.unice.fr/~frou/ACdistributions.html The cited theorem is from section II.4. However, it won't evoke the same emotions and memories for somebody who hasn't met André Cérezo...
Aug
15
revised A question about convolution of two distributions
added the translation of the cited theorem
Aug
15
answered A question about convolution of two distributions
Aug
11
awarded  Fanatic
Aug
3
comment Continuity equation on manifolds
The following (non-English) presentation gives answers to this question on the last two slides.
Aug
2
comment Determining sparse frequency distribution via discrete Fourier transform
I assumed that it is known that the signal has period $2\pi$. I further assumed that it is known that uniform sampling with a spacing smaller than $\frac{\pi}{400}$ is sufficient.
Aug
2
revised Determining sparse frequency distribution via discrete Fourier transform
updated to v2 of cited paper and included updated information in the answer
Aug
2
answered Determining sparse frequency distribution via discrete Fourier transform
Jul
15
answered How can I intuit the role of the central limit theorem in breaking the curse of dimensionality for Monte Carlo integration
Jul
12
answered Fourier transform eigenvalues
Jul
11
answered viscosity solution vs. weak solution
Jul
11
comment viscosity solution vs. weak solution
For nonlinear PDEs like a Hamilton-Jacobi equation or a hyperbolic systems of conservation laws, a weak solution need not be unique. For a Hamilton-Jacobi equation, the viscosity solution is a special weak solution which turns out to exist and be unique. For hyperbolic systems of conservation laws, a similar concept is the entropy solution, which can be shown to exist and be unique in a number of "sufficiently well understood" situations.
Jul
11
comment How can I intuit the role of the central limit theorem in breaking the curse of dimensionality for Monte Carlo integration
This answer cites a very readable survey article about sparse grids and the course of dimensionality. Regarding your questions, "including a variety of length scales" goes in the right direction, but there are many other intuitive explanations. You could work with space filling curves, investigate enumeration schemes for $\mathbb Z^n$ or look at multivariate polynomials of a fixed degree. What would you prefer for an answer?
Jul
11
revised Why Monte Carlo integration is not affected by curse of dimensionality?
added 57 characters in body
Jul
9
accepted Weak categoricity in first order logic
Jul
9
comment Weak categoricity in first order logic
Thanks for your answer. I have some questions/remarks: I don't understand what you mean with your first sentence. I don't understand the example with the additive group of integers. I don't understand the notion of "primal model", and couldn't find it via googling. Is it correct that if the minimal model exists and is unique, then it is also a prime model? Does infinitary logic requires a sufficiently strong set theory (like required for second order logic)?