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Complex, contact, Riemannian, pseudo-Riemannian and Finsler geometry, relativity, gauge theory, global analysis.

29 votes
1 answer
3k views

Is there an explicit formula for the hessian of "Determinant"?

Let $f: G= \mbox{GL}(n,\mathbb{R}) \to \mathbb{R}$ be the determinant function. Then $\mbox{Hess} (f)$ is a two linear map on $M_{n}(\mathbb{R})\simeq T_{e}(G)$ where $e$ is the neutral element of $G$ …
Ali Taghavi's user avatar
23 votes
1 answer
1k views

Eigenvalues of Laplace operator

Assume that $(M,g)$ is a Riemannian manifold. Is there any relation between the sequence of eigenvalues of Laplace operator acting on the space of smooth functions and the sequence of eigenvalues of …
Ali Taghavi's user avatar
21 votes
3 answers
2k views

Manifolds with polynomial transition maps

Title edited I thank მამუკა ჯიბლაძე and Corbennick for their suggestion on the title of this question. I changed the title based on the suggestion of Corbennick. What is an example of a m …
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
17 votes
2 answers
1k views

Are there some intrinsic invariants of surfaces other than Gaussian curvature?

The principal curvatures of a surface is denoted by $\kappa_{1}, \kappa_{2}$. Let $P(x,y)$ be a polynomial with real coefficients. Assume that $P(\kappa_{1}, \kappa_{2})$ is an intrinsically inv …
Ali Taghavi's user avatar
17 votes

Finding a 1-form adapted to a smooth flow

If the vector field is geodesible then such $1$ - form exists. A geodesible flow on a manifold $M$ is a one dimensional foliation associated with a non vanishing vector field such that …
Ali Taghavi's user avatar
14 votes
1 answer
2k views

The perturbation of non-Hamiltonian algebraic vector fields

In this question, we are interested in the number of limit cycles which appears in the following perturbational system: \begin{equation}\cases{ x'=y -x^{2}+\epsilon P(x,y) \\ y'=-x+\epsilon Q(x,y) } …
Ali Taghavi's user avatar
13 votes
0 answers
799 views

Hilbert 16th problem and dynamical Lefschetz trace formula

I would like to apply the known version of the conjectural formula (11) page 10 of the paper Number theory and dynamical Lefschetz trace formula. Disclaimer: I do not have a complete unde …
Ali Taghavi's user avatar
13 votes
5 answers
3k views

A geometric proof of the Gauss-Lucas theorem

Motivated by a geometric proof of the Fundamental Theorem of Algebra we ask: Is there a geometric proof for the Gauss-Lucas theorem? Since we are working on a half plane, can one imagine a possible p …
Ali Taghavi's user avatar
12 votes
3 answers
2k views

Limit cycles as closed geodesics (in negatively or positively curved space)

Updated 1/25/2023 I just added a related post below: Jacobi fields, Conjugate points and limit cycle theory EDIT: Here is a related post which concern quadratic vector fields rather than Van de …
Ali Taghavi's user avatar
12 votes
3 answers
851 views

A nontrivial principal bundle which satisfies Leray-Hirsch theorem

What is an example of a nontrivial principal bundle whose fibre space $G$, total space $P$ and base space $M$ are compact connected manifolds (the fiber $G$ is a compact Lie group) such that $$H^*(P,\ …
Ali Taghavi's user avatar
11 votes
1 answer
510 views

A very torsioned closed curve in space

Is there a simple smooth closed curve $\gamma$ in $\mathbb{R}^{3}$ such that for all $x,y\in \gamma$ with $x \neq y $, $l_{x}$ and $l_{y}$ are skew lines, where $l_{x} $ and $l_{y}$ are s …
Ali Taghavi's user avatar
11 votes
Accepted

Are there vector fields which are gradients with respect to one metric but not another?

Consider the vector field $$X=(y-10x)\partial_x-x\partial_y$$ it is not a gradient vector field with respect to the standard Riemannian metric of $\mathbb{R}^2$ but it is a gradient …
Ali Taghavi's user avatar
11 votes
1 answer
439 views

Lie subalgebras of $\chi^{\infty}(M)$ of codimension $n = \dim M$

For a connected $n$-manifold $M$, the Lie algebra of all smooth vector fields is denoted by $\chi^{\infty}(M)$. For a point $p\in M$ we define $L_{p}=\{X\in \chi^{\infty}(M)\mid X(p)=0\}$. Of course …
Ali Taghavi's user avatar
10 votes
3 answers
713 views

Number of disjoint simple closed geodesics

According to Jairo comment on the first version of this question I revise the question as follows; Let $g$ be a real analytic Riemannan metric on $S^{2}$. Is it true to say that: There are at most a …
Ali Taghavi's user avatar

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