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Hello; We know that the space of riemannian metrics on a compact manifold is an open cone in the space of symmetric 2-tensors. Is it reasonable to think that metrics with positive sectional curvatur …

Once again stackexchange is not responding to one of my questions (so far no comments, no answers, two up-votes). Hence this "crossposting": Is there a simple (or not simple?) algorithm that will ch …

(I tried asking that on math.stackexchange.com, but did not get a satisfying answer. I am trying here as well, in case someone here will have more insight. The question was eventually abandoned there. …

I have the following minimum problem: $$\tag{1} \min_{u\in W^{1,1}(0,B)} \int_0^B (\sqrt{1+|u^\prime (t)|^2} -a)\ u^{k-1} (t) t^{h-1}\ \text{d} t $$ (where $B>0$, $0 < a < 1$, $h,k\in \mathbb{N}$ a …

Today I came across the integral $\int_a^\infty e^{-bx} I_n(x) dx$ where $I_n$ is the modified Bessel function of the first kind. There is a solution for $a=0$, provided in Gradshteyn and Ryzhik, bu …

Informally, I am wondering if a Boolean algebra $\mathcal{B}$ contains infinitely many disjoint copies of a Boolean algebra $\mathcal{A}$ whenever it contains arbitrarily many disjoint copies of $\mat …

Given is a locally finite countable connected poset which satisfies further the following properties: Let $C$ be any maximal chain ( i.e. inextendible chain) and $A$ be any antichain. Then $A$ is …

Consider the "infinite chessboard" on the plane. Think of it as the lattice $X_1:=\mathbb{Z}^2$, and also finer chessboards $X_n$ corresponding to $\frac{1}{n}\cdot \mathbb{Z}^2$, $n\geq 1$. Given two …

I was looking at the formula to compute the schubert class of a grassmanian in terms of a more elementary schubert cycles via giambelli's formula, and on the other hand Porteous formula tells us how t …

Let $X$ be a scheme. What technical hypotheses must be imposed on $X$ to assure that a point $p \in X$ is closed if and only if the 1-point set $\{p\}$ is constructible?

Possible Duplicate: Is there an integration free proof (or heuristic) that once differentiable implies twice differentiable for complex functions? Is there a way to show that holomorphic func …

Hello, What is a fast way to test whether a partial function can be extended to a chirotope of rank 3 ? That is: I have a domain $E = \{1,...,n\}$ and a partial function $f: E^3 \to \{-1, 0, 1\}$ …

The theorem of uniqueness of solutions of first order, quasilinear, symmetric hyperbolic systems is naturally formulated in terms of so-called lens-shaped domains. Roughly, a domain is lens-shaped if …

Let D be an ample R-divisor, is the round down [mD] very ample for any sufficiently divisible number m? I think it's true. But I do not know how to arrange an argument.

Given a class function $f: G \to \mathbb Q$, where $G$ is a finite abelian group, is there an easy way to decide whether $f$ is an element of the rational representation ring $R_{\mathbb Q}(G)$, i.e. …