Embedding of smooth manifolds

Expert SummarizerIn summary, a smooth embedding of manifolds is defined as a smooth map that is both injective and a homeomorphism onto its image. This definition is equivalent to a diffeomorphism, which is a smooth map that is bijective and has a smooth inverse. However, a smooth embedding is a weaker condition than a diffeomorphism, as it does not require the map to be invertible.
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Consider a smooth map ##F: M \to N## between two smooth manifolds ##M## and ##N##. If the pushforward ##F_*: T_pM \to T_{F(p)} N## is injective and ##F## is a homeomorphism onto ##F(M)## we say that ##F## is a smooth embedding.

In analogy with a topological embedding being defined as a map that is homemorphic onto it's image I would think that an embedding of smooth manifolds would require that ##F## be a diffeomorphism. So my question is; is the definition above equivalent with ##F## being a diffeomorphism between ##M## and ##N##.
 
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Thank you for your question. To clarify, a diffeomorphism is a smooth map that is both a homeomorphism and a smooth embedding. Therefore, the definition given in the post is indeed equivalent to ##F## being a diffeomorphism between ##M## and ##N##. The key difference between a diffeomorphism and a smooth embedding is that a diffeomorphism is invertible, while a smooth embedding may not necessarily be invertible.

In other words, a diffeomorphism is a bijective smooth map with a smooth inverse, while a smooth embedding is only required to be a bijective smooth map with an injective pushforward. This means that a smooth embedding is a weaker condition than a diffeomorphism, and not all smooth embeddings are diffeomorphisms.

I hope this clarifies the relationship between a smooth embedding and a diffeomorphism. Please let me know if you have any further questions.
 

1. What is the purpose of embedding smooth manifolds?

The purpose of embedding smooth manifolds is to represent curved spaces in a way that allows for calculations and analysis using the tools of differential geometry. By embedding a manifold in a higher-dimensional Euclidean space, we can use the familiar methods and concepts of calculus to study its properties and relationships with other manifolds.

2. How is a smooth manifold embedded in a higher-dimensional space?

A smooth manifold is embedded in a higher-dimensional space by mapping each point on the manifold to a point in the higher-dimensional space in a smooth and injective way. This embedding is often done using parametrizations or coordinate charts, which provide a local description of the manifold in terms of a subset of Euclidean space.

3. What is the difference between an embedding and an immersion of a smooth manifold?

An embedding of a smooth manifold is a one-to-one mapping of the manifold into a higher-dimensional space, while an immersion allows for overlapping points and self-intersections. In other words, an embedding preserves the entire structure of the manifold, while an immersion only preserves the local structure.

4. Can every smooth manifold be embedded in a higher-dimensional space?

No, not every smooth manifold can be embedded in a higher-dimensional space. For example, the famous Poincaré conjecture states that the 3-sphere cannot be embedded in 3-dimensional Euclidean space. This concept is closely related to the idea of topological invariance, which states that topological spaces cannot always be represented in a lower-dimensional space without losing some of their topological properties.

5. What are some applications of embedding smooth manifolds?

Embedding smooth manifolds has many applications in physics, engineering, and other fields. For example, in general relativity, the embedding of spacetime in a higher-dimensional space allows for the study of gravitational phenomena using the tools of calculus. In computer graphics and animation, embedding can be used to create realistic 3D models of objects with curved surfaces. Additionally, embedding has applications in data analysis, machine learning, and topology.

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