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Elliptic, parabolic and hyperbolic operators. Laplace, Laplace-Beltrami, Schrödinger, Dirac. Exterior derivative and Lie derivative operators.
8
votes
0
answers
474
views
Measuring the non-commutativity of the codifferential and pullbacks
$\newcommand{\id}{\operatorname{Id}}$
$\newcommand{\TM}{\operatorname{TM}}$
$\newcommand{\Hom}{\operatorname{Hom}}$
$\newcommand{\M}{\mathcal{M}}$
$\newcommand{\R}{\mathbb{R}}$
$\newcommand{\N}{\mathc …
7
votes
3
answers
843
views
"Universal" differential identities
(This is a cross-post from MSE).
Let $f:\mathbb{R}^d \to \mathbb{R}$ be smooth. The mixed derivatives commute: $f_{xy}=f_{yx}$. This identity is "universal" in the sense that it holds for any smooth …
5
votes
1
answer
221
views
Are all the mappings which satisfy this equation scaled isometries?
Let $M,N$ be smooth oriented $d$-dimensional Riemannian manifolds, $\, f:M \to N$ a smooth map. Let $\Omega^1(M,f^*TN)=\Gamma(T^*M \otimes f^*TN)$ be the space of $f^*TN$-valued one-forms.
Let $d$ …
4
votes
2
answers
508
views
Is the kernel of the coderivative infinite-dimensional?
$\newcommand{\al}{\alpha}$
$\newcommand{\euc}{\mathcal{e}}$
$\newcommand{\Cof}{\operatorname{Cof}}$
$\newcommand{\Det}{\operatorname{Det}}$
Let $M,N$ be smooth $n$-dimensional Riemannian manifolds (p …
3
votes
1
answer
175
views
Does the space of harmonic forms change continuously with the metric?
Let $(M,g_0)$ be a closed $n$-dimensional Riemannian manifold. Let $1<k<n$ be fixed, and let $\Delta_{g_0}:\Omega^k(M) \to \Omega^k(M)$ be the $g_0$-Laplacian. Let $H^k_{g_0}=\text{ker} \Delta_{g_0}$. …
2
votes
2
answers
2k
views
Commuting of exterior derivative and contraction (vector-valued forms)
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$\newcommand{\tr}{\operatorname{tr}_{\eta}}$
$\newcommand{\al}{\alpha}$
$\newcommand{\be}{\beta}$
$\newcommand{\til}{\tilde}$
Let $E$ be a smooth vector bundle over a mani …
1
vote
Accepted
Does the space of harmonic forms change continuously with the metric?
I think the answer is positive.
Let $D$ be the subspace of smooth closed $k$-forms on $M$. Equip $D$ with the supremum- $C^1$ norm:
$$
\| \omega \|_{C^1,sup}:=\max\{ \|\omega\|_{sup}, \|T\omega\|_{su …