# All Questions

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### proof non diagonalizable matrix is not an inner product [on hold]

Given $A \in M_n(\Bbb C)$ and $<x,y>_A = x^TA\overline y$ I need to proof that if A is non diagonalizable then $<.,.>_A$ is not an inner product. I thought about: Let A be non ...
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### reference needed for some well know results on cohomology of the orbit spaces

The following results are well known If the group $\mathbb Z_2$ acts freely on a mod $2$ cohomology $n$-sphere $X$, then the orbit space $X/\mathbb Z_2$ is a cohomology real projective $n$-space. ...
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### How to get transition matrix of markov process? [migrated]

I am monitoring a Markov process with ~21 states. I know all the states, initial state and what states transitions can/cannot be, so that zero elements of transition matrix are known. I know the ...
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### Maximal $k$-chordal subgraph

Recall that a graph is called $k$-chordal if any cycle $C$ of length $> k$ contains a chord, i.e. an edge joining to non-consecutive vertices in $C$. Let $f(n, k)$ be the minimal number of edges ...
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### Vector bundle for prescribed Stiefel-Whitney classes

I hope this is not trivial. Let $B$ be a nice topological space (paracompact, CW-complex or whatever you think is nice) For $i=1,\ldots,n$ let $x_i \in H^i(B,\mathbb{Z}_2)$ be certain cohomology ...
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### Looking for a canonical (matroid polytope) subdivision of the hypersimplex

A matroid polytope is the convex hull of the indicator vectors of the bases of a matroid, and a matroid polytope subdivision (MPS) is a polyhedral subdivision of a matroid polytope whose cells are ...
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### Link for “A spine for Teichmüller space”, preprint by Thurston

Can someone please give any link or mention any source where I can find the following preprint. W.Thurston, A spine for Teichmüller space, preprint, three pages, 1986.
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### partition of an integer n into atmost k =O(log n) parts

Suppose you have a partition p of n into atmost k parts, say $$\{i_1, i_2, ..., i_j, ..., i_{k-1}\}$$ For example $\{1, 4\}$ is a partition of 10 into 3 parts (in this notation i am specifying the ...
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### Concentration of sum of powers of normals

Let $Z_1,Z_2,\ldots,Z_n$ be i.i.d. copies of a random variable $Z$ distributed as $\frac{1}{\sqrt{2}}X+i\frac{1}{\sqrt{2}}Y$ with $X$ and $Y$ independent standard Normal random variables ...
The following question is mainly inspired by this previous one Which manifolds admit a diffeomorphism of order $n$? and some answers given there. For $d\geq 2$, let $\mathbb{B}^d$ denote the closed ...