Are Global and Local Coordinate Charts Different in Differentiable Manifolds?

[mikeeey]

Hello every one

Can one say , that
A globle coordinate chart is a cartesian coordinate
And a local coordinate chart is any kind of curvilinear coordinate ?Thanks

 

[Fredrik]

No. A global chart doesn't have to have orthogonal axes, it just has to be defined on the entire manifold rather than on some proper subset of it.

 

[mikeeey]

Then the global coordinate chart would be a rectilinear coordinate ( generalization of cartesian coordinate ) may be affine ( not orthogonal )

 

[mikeeey]

No. A global chart doesn't have to have orthogonal axes, it just has to be defined on the entire manifold rather than on some proper subset of it.

 

[WWGD]

What do you mean by Cartesian coordinates and axes? What are curvilinear coordinates?

 

[mikeeey]

What do you mean by Cartesian coordinates and axes? What are curvilinear coordinates?

Cartesian coordinates (i.e. The position vector is the same every where in the space ) but curvilinear coordinates ( the coordinates can change in angles from point to point in the space ) i.e the axes are curved

 

[WWGD]

Cartesian coordinates (i.e. The position vector is the same every where in the space ) but curvilinear coordinates ( the coordinates can change in angles from point to point in the space ) i.e the axes are curved

Seems you need a map that preserves the inner-product globally, to map Cartesian coordinates to Cartesian coordinates, since orthogonality is/can be defined in terms of the inner -product..

 

[mikeeey]

Seems you need a map that preserves the inner-product globally, to map Cartesian coordinates to Cartesian coordinates, since orthogonality is/can be defined in terms of the inner -product..

The map is linear and the linear operator is the derivative , sometime linear map ( transformation ) is called the jacobian matrix
Hint : dot product does not mean there is an orthogonality ! Generally non orthogonal but specially orthogonal

 

[WWGD]

The map is linear and the linear operator is the derivative , sometime linear map ( transformation ) is called the jacobian matrix
Hint : dot product does not mean there is an orthogonality ! Generally non orthogonal but specially orthogonal

You're right, but I was referring to the inner-product, not the dot product . But the Jacobian is a local linear map describing the (local) change in the function. The local properties of a fuction and of its Jacobian do not always preserve properties globally. I guess the inner-product is a tensor, so we could see the effect of induced map on tensors.

 

[mikeeey]

You're right, but I was referring to the inner-product, not the dot product . But the Jacobian is a local linear map describing the (local) change in the function. The local properties of a fuction and of its Jacobian do not always preserve properties globally. I guess the inner-product is a tensor, so we could see the effect of induced map on tensors.

First inner product is the generalization of dot product ( in tensor algebra mostly u have 4 products of vector spaces 1- tensor product ( outer ) 2- inner product 3- wedge product 4- symmetric product , with these product u can decompose any tensor )
Secondly jacobian matrix is for globle and local coordinates scine its inversible matrix

 

[WWGD]

First inner product is the generalization of dot product ( in tensor algebra mostly u have 4 products of vector spaces 1- tensor product ( outer ) 2- inner product 3- wedge product 4- symmetric product , with these product u can decompose any tensor )
Secondly jacobian matrix is for globle and local coordinates scine its inversible matrix

I am not sure I am understanding you. Which map is linear, the derivative? Yes , of course it is, but unless the original map is itself linear, the Jacobian at one point does not globally describe the map.Jacobian is not always invertible. Take any map between manifolds of different dimension. The Jacobian will be (represented by) an $n \times m$ matrix, which cannot be invertible.. And, as a generalization of the derivative, the Jacobian is a local map describing local change in function, unless map is linear. In what sense is the inner-product a generalization. You mean that in 1D there is an inner -product? Still, it is a covariant 2 -tensor , so we can study the effects of the map using the effects of the induced map between the tangent spaces.

 

[mikeeey]

M

Jacobian is not always invertible. Take any map between manifolds of different dimension. The Jacobian will be (represented by) an $n \times m$ matrix, which cannot be invertible.. And, as a generalization of the derivative, the Jacobian is a local map describing local change in function, unless map is linear. In what sense is the inner-product a generalization. You mean that in 1D there is an inner -product? Still, it is a covariant 2 -tensor , so we can study the effects of the map using the effects of the induced map between the tangent spaces.

my friend if a map is not invertible then the manifold is not homeomorphic ( it must be $n \times n$ so u can use the transition maps ) ( jacobian matrix is used for the same manifold for different charts of the same manifold ) and the inner product is used in higher dimensions ( see wikipedia , inner prod. Is the generalization of dot product )

 

[mikeeey]

B

I am not sure I am understanding you. Which map is linear, the derivative? Yes , of course it is, but unless the original map is itself linear, the Jacobian at one point does not globally describe the map.Jacobian is not always invertible. Take any map between manifolds of different dimension. The Jacobian will be (represented by) an $n \times m$ matrix, which cannot be invertible.. And, as a generalization of the derivative, the Jacobian is a local map describing local change in function, unless map is linear. In what sense is the inner-product a generalization. You mean that in 1D there is an inner -product? Still, it is a covariant 2 -tensor , so we can study the effects of the map using the effects of the induced map between the tangent spaces.

A manifold contains two types of general sapces are the topological space for continuity ... And other properties and a vector space so we can define tanget spaces and fields and covariant derivatives ... And other properties

 

[WWGD]

O.K, maybe I did not understand the maps you are referring to. Yes, chart maps are invertible and actually diffeomorphisms, so, within a chart, what you say is true, between an open set in the manifold and an open subset of $\mathbb R^n$. If your manifold is globally diffeomorphic to some other one, then the Jacobian is an invertible map.

 

[WWGD]

B
A manifold contains two types of general sapces are the topological space for continuity ... And other properties and a vector space so we can define tanget spaces and fields and covariant derivatives ... And other properties

That is all clear, I guess I am not understanding well what you are referring to; let me leave this discussion between you and Fredrik.

 

[mikeeey]

That is all clear, I guess I am not understanding well what you are referring to; let me leave this discussion between you and Fredrik.

Thanks for the conversation , by the way I am an engineer in mechanics this discussion is far a way from mechanics ,but I am interested in general relativity that deals with manifolds .
Thanks

 

[WWGD]

Sure, no problem, it is always good to exchange ideas and test your knowledge; can always sharpen up understanding. Unfortunately, we seemed to be at cross-hairs, talking about different things; hope next exchange will be more productive.