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The Laplacian matrix is the representation of a graph in matrix form.

2 votes
1 answer
153 views

Realization of symbol of Laplace operator via certain integral

Is there an elliptic operator $D$ on $C^{\infty}(S^2)$ whose principal symbol is not identical to thats of Laplacian but it satisfies $\int_{S^2} fDf =\int_{S^2} f\Delta (f)$ for all $f\in C^{\infty}(S …
Ali Taghavi's user avatar
2 votes
0 answers
92 views

Obstructions for existence of a Riemannian metric such that a given function is harmonic

Let $f:\mathbb{R}^{n}\to \mathbb{R}$ be a smooth function. What type of obstructions exist for existence of a Riemannian metric $g$ on $\mathbb{R}^{n}$ such that $f$ is a harmonic functi …
Ali Taghavi's user avatar
2 votes
0 answers
608 views

Is Laplacian a surjective operator?

For a closed manifold the laplacian is almost surjective operator since the index of $\Delta$ is zero and there is no a non constant harmonic function. …
Ali Taghavi's user avatar
5 votes
1 answer
450 views

An alternative representation of the principal symbol of the Laplace operator

We denote by $\Delta$, the Laplacian associated to this Riemannian structure. Are the following two conditions equivalent? …
Ali Taghavi's user avatar
6 votes
2 answers
613 views

On equation $\Delta \circ \partial/\partial X=\partial/\partial X \circ \Delta$ on a Riemann...

Assume that $M$ is a compact Riemannian manifold whose Laplacian is denoted by $\Delta$. Assume that the Euler characteristic of $M$ is zero. …
Ali Taghavi's user avatar
8 votes
1 answer
364 views

Can a harmonic vector field possess a limit cycle?

If this correspondence is denoted by $i$ then the Laplacian of a vector field $X$ is defined as $\Delta X=i^{-1} \Delta (i(X))$. … Where the latter Laplacian is the natural Laplacian on the space of differential forms. …
Ali Taghavi's user avatar
18 votes
3 answers
2k views

Can the Laplace operator on $n-$ manifolds be represented as a sum of $n$ second order deriv...

EDIT: According to some comments on this post I revise the title to remove the misunderestanding. Assume that $M$ is a Riemannian manifold of dimension $n$. The natural Laplace operator associated t …
Ali Taghavi's user avatar
4 votes
1 answer
373 views

Differential inequalities under which a flat function must be identically zero

Let $f:\mathbb{R}\to \mathbb{R}$ be a smooth function which is flat at $0\in \mathbb{R}$. That is $f^{(k)}(0)=0,\; k=0,1,2,\ldots $. Assume that $|f''(x)|\leq M|f(x)|\quad \forall x\in \mathbb{R}$ …
Ali Taghavi's user avatar