I am not sure - a manifold is locally connected and has countable basis?

In summary, the conversation discusses an exercise in a book that states if a manifold M has a sub-manifold N and an open set V, then the intersection of V and N is a countable collection of connected open sets. The speaker is unsure why this exercise only applies to sub-manifolds and wonders if it is an easy consequence of the fact that a manifold is locally connected and has a countable basis. They later clarify their confusion about the definitions of sub-manifolds and submanifolds.
  • #1
mahmoud2011
88
0
I am not sure -- a manifold is locally connected and has countable basis?

There is an Exercise in a book as following :

Given a Manifold M , if N is a sub-manifold , an V is open set then V [itex]\cap[/itex] N is a countable collection of connected open sets .

I am asking why he put this exercise for only the case of sub-manifold , Is n't this an immediate consequence of the fact that a manifold is locally connected and has countable basis ?

I am not sure from what I say ?? I think there can't be exercise as easy as I think , I think I am wrong .


Thanks
 
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  • #2


I am sorry , I was having a confusion in the definitions between what is the n-submanifold property and what is the sub-manifold .

Thanks
 
  • #3


The definition I know has it that S is a

submanifold o fM if S is embedded in M in the same way as R^k is embedded /sits-in

R^{k+j} in the "standard way", i.e., where (x_1,..,x_k)-->(x_1,x_2,...,x_k, 0,0,..,0)

So S is a submanifold of M if there are subspace charts mapping points of S into

points of the form (x_1,...,x_k, 0,0,..,0).
 
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1. What is a manifold?

A manifold is a mathematical object that can be thought of as a generalization of a plane or a curved surface in higher dimensions. It is a topological space that locally resembles Euclidean space.

2. What does it mean for a manifold to be locally connected?

Local connectedness is a topological property of a space that means every point in the space has a neighborhood that is connected. In the context of manifolds, this means that the manifold can be divided into smaller connected pieces that fit together smoothly.

3. What is a countable basis?

A countable basis is a collection of open sets in a topological space that can be used to generate all other open sets in the space. In other words, any open set in the space can be expressed as a union of elements from the countable basis.

4. Why is it important for a manifold to have a countable basis?

A countable basis is important because it allows us to study the properties of a manifold by looking at its local behavior. It also makes it easier to define and work with continuous functions on the manifold.

5. How do we prove that a manifold is locally connected and has a countable basis?

To prove that a manifold is locally connected, we can show that every point has a connected neighborhood. To prove that it has a countable basis, we can construct a countable collection of open sets that cover the manifold and show that any open set can be expressed as a union of elements from this collection.

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