13,325 reputation
4377
bio website wwwmath.uni-muenster.de/…
location Münster
age 39
visits member for 4 years, 9 months
seen Jul 16 at 12:21

I am a mathematician based in Münster, Germany. A fellow MO user once described me as a ''very homotopy-theoretic geometric topologist'' and I largely approve this description.


Jun
28
comment Automorphism group of a fiber bundle surjects onto diffeomorphism group?
If $P$ is a natural fibre bundle, then - by definition - any diffeomorphism is covered by a bundle automorphism.
Jun
14
awarded  Nice Answer
Apr
13
awarded  Nice Answer
Feb
17
revised Homotopy spheres with vanishing and non-vanishing $\alpha$-invariant
added 444 characters in body
Feb
6
awarded  Nice Answer
Feb
4
awarded  Necromancer
Jan
7
answered The periodic values in Bott periodicity
Jan
7
answered How to show the square root function of a positive semidefinite matrix is differentiable?
Jan
5
revised Homotopy spheres with vanishing and non-vanishing $\alpha$-invariant
added 3 characters in body
Dec
13
answered Equation for non-invertible elements in Clifford algebras
Dec
2
comment Local index formula for >ungraded< elliptic operators
Typically, you would replace the operator $P$ by $P \oplus P^{\ast}: E \oplus F \to E \oplus F$. This is graded, and the index (in the graded sense) is the usual index. An ungraded operator has an index in $K^1$, but only if it is self-adjoint.
Nov
26
comment Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
I think I agree. What I did not realize was that $F$ is obtained from $(x/2)/\sinh(x/2)$ by a simple scaling in the argument. In that case, the components of the multiplicative seqeunce of $F$ are obtained from the components of the A-hat-genus by multiplication with constants.
Nov
24
awarded  Favorite Question
Nov
20
awarded  Enlightened
Nov
20
awarded  Nice Answer
Nov
20
comment Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
yes, the formula has a typo in it.
Nov
19
comment Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
@Juan: I could have guessed. I came across the paper, but did not understand what is going on. Can you tell me what the index theoretic significance of the Mayer class is?
Nov
19
answered Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
Nov
19
comment Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
And where does the Mayer class come from? I am just curious.
Nov
19
comment Is true that $\left[\frac{\hat{A}(\mathbb HP^m)} { \hat{M}(\mathbb HP^m) }\right]_{4m} = 0$?
What is the Mayer class? I have never heard about it.