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This tag is used if a reference is needed in a paper or textbook on a specific result.

15 votes
0 answers
715 views

Is this "Homology" useful to study?

In the usual singular homology of a topological space $X$, one consider the free abelian group generated by all continuous maps from the standard simplex $\Delta^{n}$ to $X$. Now we can r …
Ali Taghavi's user avatar
8 votes
1 answer
619 views

Why is this group called "The Holomorph of a group"

Many years ago I found in google the notation "Holomorph of group". It is the semi direct product of $G$ with $Aut(G)$. Why is the term "Holomorph" used here, while it is usually used for complex anal …
Ali Taghavi's user avatar
7 votes
2 answers
2k views

The integral of torsion

I found the following * exercise (exercise *9) in page 407 of the book of do Carmo "Differential geometry of curves and surfaces". This problem is a classical theorem which is referenced in the book …
Ali Taghavi's user avatar
6 votes

Ways to prove the fundamental theorem of algebra

There is an alternative proof for FTA using "Fredholm operators on Hilbert spaces": Assume that $P(z)=z^n+a_{n-1}z^{n-1}+\ldots+a_1 z+a_0$ has no root in $\mathbb{C}$. Then for every $\epsilon$ the …
6 votes
2 answers
429 views

Metrics on the space of $C^{*}$ algebras

I think that there is a metric on the huge space of all $C^{*}$ algebras. What is the explicit definition of this metric?may you introduce me a reference? Moreover is the restriction of this metr …
Ali Taghavi's user avatar
6 votes
2 answers
853 views

A dynamical system defined by the Riemann zeta function

Let $\zeta$ be the classical Riemann zeta function. We define a differential equation on $\mathbb{R}^{2} \setminus \{1\}$ by $\dot Z= \zeta(Z)$. From a foliation point of view this vector …
Ali Taghavi's user avatar
5 votes
1 answer
326 views

"Determinant" rather than "trace" in the alternative formula "Lefschetz number"

For a self map $f$ on a topological space $X$ we replace "trace" with "determinant" in the alternative Lefschetz formula $$\Lambda(f)=\sum(-1)^i trace(f^*)|H^i(X,\mathbb{Q})$$ So we have $$\Lam …
Ali Taghavi's user avatar
5 votes
2 answers
366 views

The unit tangent bundle of 2- or 4-manifolds as a principal $S^{1}$- or $S^{3}$-bundle

What type of obstructions have been studied so that the unit tangent bundle of a Riemannian 2-(4-)manifold have a structure of a principal $S^{1}$-($S^{3}$-)bundle?
Ali Taghavi's user avatar
5 votes
1 answer
562 views

Geometric invariants of a Riemannian manifold encoded in certain moment map

Let $(M,g)$ be a Riemannian manifold with isometric group $G=Iso(M,G)$. The metric gives an isomorphism between tangent and cotangent bundle of $M$. So $g$ induce a natural symplectic structure on $ …
Ali Taghavi's user avatar
5 votes
2 answers
1k views

Unreasonable application of mathematics to the other areas [closed]

What are some papers or talks on the philosophy of mathematics which contains some statements about the unnecessary and unreasonable application of mathematics in other areas of science? I found …
Ali Taghavi's user avatar
4 votes
1 answer
339 views

On differential equation $Z'=Z^2-Z$ on a $C^*$ algebra

Let $A$ be a Banach or a $C^*$ algebra. We consider the differential equation $$(*)\;\;\;\;Z'=Z^2-Z$$ on $A$. Obviously the singularities of this systems are just the idempotents of the …
Ali Taghavi's user avatar
4 votes
0 answers
241 views

Non-commutative analogue of a certain fact in differential geometry

In the literature, is there a non-commutative analogue of the fact that every Riemannian manifold whose isometry group has sharp dimension must be a constant curvature manifold?
Ali Taghavi's user avatar
3 votes
0 answers
255 views

Graded structures for simple $C^{*}$ algebras without nontrivial idempotent

Edit(A confession): I just realized that the question is trivial: Since one can easily prove that the convex hull of the spectrum of every nontrivial homogeneous element of a $\mathbb{Z}_{n}$-graded …
Ali Taghavi's user avatar
2 votes
1 answer
187 views

Unitization via "End points compactification"

We know that every compactification of locally compact Hausdorff spaces correspond to a unitization of $C^{*}$ algebras. For example the one point compactification corresponds to the minimal uni …
Ali Taghavi's user avatar
2 votes

Generalization of winding number to higher dimensions

In your question you mentioned the word "Fredholm index". So I would like to say that in the circle case there are two different interpretations of Fredholm index of certain lin …
Ali Taghavi's user avatar

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