13,405 reputation
4479
bio website wwwmath.uni-muenster.de/…
location Münster
age 39
visits member for 4 years, 10 months
seen 15 hours ago

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.


Aug
20
awarded  Nice Answer
Aug
15
awarded  Good Answer
Aug
14
awarded  Nice Answer
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?