# All Questions

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### A Künneth-Theorem version for relative singular cohomology

I'm not an expert in algebraic topology, but sometimes I need some results from this area, for example tools to determine singular cohomology groups of product spaces. The Künneth-Theorem which I ...
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### Connected sum of two “same” Kleins bottles [migrated]

If I have two surfaces of Klein's bottle, K, given by edge words [a b- a- b-] and [a- b a b] what space do I get when I identify same edges. In other words, i have two same Klein's bottles that are ...
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### Numerical invariants for a graph or its complement that are bounded by some constant

I'm looking for numerical graph invariants that are bounded by a constant either for a graph $G$ or its complement $\bar{G}$. (The complement graph $\bar{G}$ has the same set of vertices as $G$ but ...
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### Equivalence of first order quasilinear PDE to linear PDE [migrated]

Given a system of nonlinear PDE of the special form: $\sum_{i=1}^n A_i(x, \phi) - \frac{\partial \phi_j}{\partial x_i} = B_j(x,\phi)$ $(1)$ with $(j=1,...,m)$ and $x \in R^n,\phi \in R^m$. If we ...
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### Properties of bipartite graphs

For a connected bipartite graph $G$ are the two following properties equivalent: 1)Every minimal cycle in $G$ has length 4, that is every cycle of length strictly greater than 4 can be divided in ...
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### When does the radius of convergence of the product of two $p$-adic power series increase?

Let $p$ be a prime number and denote by $R(f)$ the radius of convergence of a power series $f(x) \in \mathbb{C}_p[[x]]$, where $\mathbb{C}_p$ is the completion of the algebraic closure of ...
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### Obstructed automorphisms of schemes

Let $X$ be a smooth projective scheme over a field $\mathbf{k}$ of characteristic zero such that $\mathrm{H}^0(X, \mathrm{T}X)$ vanishes, and let $f$ be an automorphism of $X$. I would like to have an ...

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