Given a smooth vector bundle $E$ with *non-compact* base, let
$\Gamma(E)$ be the space of $C^\infty$ sections equipped with *compact-open* $C^\infty$-topology.

I have heard that $\Gamma(E)$ is not locally-contractible. Why not?

Is $\Gamma(E)$ contractible? Visibly any section can be joined to the zero section by "straight line", doesn't this prove that $\Gamma(E)$ is contractible?

Is it true that every convex subset of $\Gamma(E)$ is contractible? The argument of 2 seems to apply, but then it seems plausible that each section has an arbitrary small convex neighborhood, contradicting 1.

CLARIFICATION: One source of "rumor 1" is the book "The Convenient Setting of Global Analysis" freely available
here. On page
429 one reads: "Unfortunately, for non-compact $M$, the space $C^\infty(M, N)$ is not locally contractible in the compact-open $C^\infty$-topology". Another source is the discussion in Hirsch's book in the beginning of Chapter 2, which says "It can be shown that
$C^\infty(M, N)$ has very nice features, e.g. it has a complete metric, and a countable base; if $M$ is *compact*, it is locally contractible and $C^r(M, \mathbb R^n)$ is a Banach space for $2\le r<\infty$".

Thus I assumeed that in general, if $M$ is non-compact, then the space $\Gamma(E)$ is not (or maybe just need not be?) locally contractible. Also I am uncertain whether $C^\infty(M, \mathbb R^n)$ or $\Gamma(E)$ is a topological vector space, is it really? There seems to be a sequence of semi-norms giving these spaces a structure of Frechet spaces, but then they must be locally convex, hence locally contractible. Obviously, I am missing something.

In response to comments I ask a more specific question.

**Question.** Let $T_{r,s}(M)$ denote the space of $C^\infty$-smooth $(r,s)$-tensors on a connected non-compact $C^\infty$ manifold $M$. For $k$ with $2\le k\le \infty$, give $T_{r,s}(M)$ the weak $C^k$-topology as in Hirsch's book (roughly for $k$ finite we require that given $\epsilon>0$ and compact subset $K$ all derivatives up to $k$ are $\epsilon$-close over $K$, and for $k=\infty$ we take the union of all $C^k$-topologies for all finite $k$ under the inclusions $C^\infty\to C^k$). Now I ask

*Is $T_{r,s}(M)$ a Fréchet space with respect to the weak $C^k$-topology?*

In particular, I want to conclude that $T_{r,s}(M)$ is locally contractible, and any convex subset of $T_{r,s}(M)$ is contractible; I think Fréchet spaces must have this property.

introductionto a chapter and so should be taken as such. You should read the whole chapter to discover the meaning behind those words. I don't have the source for the second quote to hand, but there's still a mistake there: C^\infty(M,R^n) is not a Banach space. Generally, "compact-open" is a bit misused and so one should always ask "what exactly do you mean?". In particular, the KM book has quite an extensive discussion on the different topologies and I recommend that you read that and then ask a more focussed question. $\endgroup$ – Loop Space May 14 '10 at 11:43