bio  website  fernunihagen.de/analysis 

location  Germany  
age  36  
visits  member for  2 years, 1 month 
seen  6 hours ago  
stats  profile views  1,278 
I work on evolution equations, sometimes on their applications too. I am interested in PDEs and functional analysis. I am fond of algebraic graph theory.
1d

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Disruptive innovations in mathematical notations
notation for matrices! which made matrix multiplication possible in the very first place. 
Oct 20 
accepted  eigenvalue estimate of the adjacency matrix 
Oct 13 
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eigenvalue estimate of the adjacency matrix
On the Spectral Radius of (0,1)Matrices, LAA 1985 
Oct 10 
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eigenvalue estimate of the adjacency matrix
thanks a lot! by now i have found a further upper estimate in a paper by brualdi and hoffman, but i am still quite surprised that so little is known about the adjacency matrix  as opposite to the laplacian, in particular. 
Oct 9 
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eigenvalue estimate of the adjacency matrix
$\lambda_\min $ 
Oct 9 
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eigenvalue estimate of the adjacency matrix
plus, $A^T=A$ anyway :) 
Oct 9 
asked  eigenvalue estimate of the adjacency matrix 
Sep 24 
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Examples for Markov generators with pure point spectrum
I don't quite understand what you mean by saying that "the only three generators that can arise are the OrnsteinUhlenbeck, Laguerre and Beta generator". If you consider the Laplacian as a (very) special case of the OrnsteinUhlenbeck operator, then I agree. In any case, $\Delta$ on $L^2(\Omega)$, $\Omega=1$, with Neumann boundary conditions seems to be what you need: It generates a Markov semigroup under very mild regularity assumption on $\partial\Omega$ and its spectrum can be almost arbitrarily complicated, the main constraint being the (dimension dependent) Weyl asyptotic formula. 
Sep 15 
answered  Results true in a dimension and false for higher dimensions 
Sep 13 
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Another kind of the positivity of matrices
a matrix fulfilling your notion of positivity is called "positive definite" in linear algebra  that is, in each linear algebra textbook. you can look for answers there. 
Sep 1 
awarded  Revival 
Aug 29 
awarded  Yearling 
Jul 2 
awarded  Curious 
Jun 27 
revised 
Find multiple nonadjacent paths in a graph
added 121 characters in body 
Jun 27 
answered  Find multiple nonadjacent paths in a graph 
Jun 16 
revised 
Continuity with values in L^2
added 1 character in body 
Jun 10 
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$H^s(\mathbb T)$ is a Banach algebra for $s>1/2$
But 7.57 is an imbedding result for Sobolev spaces on domains of $\mathbb R^n$! How does this implies the claimed property? I have checked a bit in the literature: It seems that Thm. 3.5 in Sobolev spaces on Riemannian manifolds by E. Hebey settles my question. 
Jun 7 
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$H^s(\mathbb T)$ is a Banach algebra for $s>1/2$
Can you provide a reference for your last assertion? Does one have that $W^{s,p}(M)\hookrightarrow L^\infty(M)$ if $sp>{\rm dim } M$? 
Jun 5 
accepted  doublystochastic isomorphisms of graphs 
Jun 3 
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How to model a timediscrete heat equation on a graph?
I see. But then why won't you use a timecontinuous model? Then the solution would be given by the semigroup generated by the Laplacian (with negative sign if you want to converge towards equilibrium). 