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Elliptic, parabolic and hyperbolic operators. Laplace, Laplace-Beltrami, Schrödinger, Dirac. Exterior derivative and Lie derivative operators.

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}( …
Ali Taghavi's user avatar
1 vote
1 answer
156 views

The index of certain differential operator on tori

Assume that $J$ is an almost complex structure on torus $\mathbb{T}^2$. Let $X$ be a non vanishing vector field on the torus. Let $g$ be a Riemannian metric with corresponding $LC$ connection …
Ali Taghavi's user avatar
3 votes
1 answer
221 views

An elliptic operator whose corresponding symbol Hamiltonian vector field has an isolated per...

Let $D$ be a differential operator on the space of smooth functions on a manifold $M$. The symbol of $D$ can be considered as a Hamiltonian on the cotangent bundle $T^*M$. We call …
Ali Taghavi's user avatar
1 vote
1 answer
98 views

Conjugacy of $L_X$ operators

Assume that $X$ is a vector field on a $n$ dimensional manifold $M$.Let $0\leq i,j \leq n$. 1.Is there a linear isomorphism $T:\Omega^i(M) \to \Omega^j(M)$ with $L_X T=T L_X$? 2.Is there a linear i …
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. So the codimension of the image …
Ali Taghavi's user avatar
1 vote
0 answers
59 views

Ellipticity of certain differential operator associated to a pair of vector field via curvat...

What is a precise example of the following situation: A compact Riemanian manifold $M$ admits two vector field $X,Y$ such that the the operator $$Z\mapsto R(X,Y)Z$$ Would be an elliptic operator and …
Ali Taghavi's user avatar
0 votes
0 answers
62 views

A uniform upper bound for Fredholm index of Laplace quasi-operators on a compact paralleliza...

Assume that $M$ is a compact parallelizable manifold. Is there an upper bound for the absolute value of Fredholm index of all operators in the form $D=\sum_{i=1}^n \partial^2/\partial{X_i^2} …
Ali Taghavi's user avatar
2 votes
1 answer
206 views

On which subspace $W\subset C^{\infty}[0,1]$ is $(Df)(x)=xf'(x)$ a bounded operator provided...

I have already asked this question on MSE; now I repeat it on MO. https://math.stackexchange.com/questions/4132346/on-which-subspace-w-subset-c-infty0-1-is-df-xfx-a-bounded-operator First we introd …
Ali Taghavi's user avatar
20 votes
1 answer
1k views

Derivation on real analytic manifolds

Let $M$ be a real analytic manifold. By $C^{\omega}(M)$ we mean the algebra of all analytic functions from $M$ to $\mathbb{R}$. Assume that $D$ is a derivation on $C^{\omega}(M)$ . Is there a …
Ali Taghavi's user avatar
5 votes
0 answers
278 views

The Spectrum of certain differential operators

We fix a Hilbert space isomorphism $\phi:H^{1}\to H^{2}$. Here by $H^{s},\;s=1,2,\;$ we mean the sobolev space on $\mathbb{R}^{2}$ or $S^{2}$. We consider the following polynomial vector field on …
Ali Taghavi's user avatar
1 vote
1 answer
123 views

Invariance of the space of harmonic functions under derivation associated to a non-vanishing...

Let $X$ be a non-vanishing real analytic vector field on an open manifold $M$. What kind of obstructions would appear when we search for a Riemannian metric on $M$ such that the space of …
Ali Taghavi's user avatar
5 votes
0 answers
217 views

A differential operator analogy of certain fact in real analysis of smooth functions

Let $E\to M$ be a smooth vector bundle over a smooth manifold $M$. Let $D$ be a differential operator defined on the space $\Gamma(E)$ of smooth sections of $E$. We fix a section $s\in \Gamma(E)$. Ass …
Ali Taghavi's user avatar
5 votes
1 answer
450 views

An alternative representation of the principal symbol of the Laplace operator

Assume that $(M,g)$ is a $n$ dimensional Riemannian manifold. We denote by $\Delta$, the Laplacian associated to this Riemannian structure. Are the following two conditions equivalent? First condition …
Ali Taghavi's user avatar
3 votes
1 answer
363 views

When is the exterior derivation $d$ a Lie algebra morphism?

In this question we search for some conditions under which the exterior derivation $d:\Omega^i(M)\to \Omega^{i+1}(M)$ on a differentiable manifold $M$ is a Lie algebra morphism in a certain sense. We …
Ali Taghavi's user avatar
1 vote
0 answers
308 views

A differential operator associated with a vector field on the torus

Assume that $X$ is a non vanishing vector field on the torus $\mathbb{T}^2$. We define two linear operators $T,S$ on the space of smooth functions on $\mathbb{T}^2$ as follows: $T(f)= …
Ali Taghavi's user avatar

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