Non-Affine Connections: Why & What?

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In summary, an affine connection on a smooth manifold, also known as a covariant derivative, is a choice of connection that makes the manifold look infinitesimally like Euclidean space, not just smoothly but as an affine space. This terminology is due to Cartan and is based on the identification of tangent spaces in Euclidean space by translation. The term "affine" refers to the idea that the connection connects neighboring tangent spaces in a way that resembles affine spaces. It is possible to have a "non-affine connection" that does not have this property of connecting neighboring tangent spaces in an affine manner.
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Geometry_dude
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"Everyone" knows what an affine connection on a smooth manifold is a.k.a. covariant derivative. My questions are:
i) Why are those connections called affine?
ii) Is there a mathematical object that 'connects neighboring tangent spaces', that could be termed a 'non-affine connection'?
 
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I quote wikipedia: "The terminology [affine connection] is due to Cartan and has its origins in the identification of tangent spaces in Euclidean space Rn by translation: the idea is that a choice of affine connection makes a manifold look infinitesimally like Euclidean space not just smoothly, but as an affine space."

http://en.wikipedia.org/wiki/Affine_connection
 

1. What are non-affine connections?

Non-affine connections are mathematical constructs used in differential geometry to describe the curvature of surfaces. They are a generalization of the concept of an affine connection, which is used in the study of Euclidean spaces.

2. Why are non-affine connections important?

Non-affine connections are important because they allow for a more accurate description of the geometry of curved surfaces, such as those found in general relativity. They also play a crucial role in the study of submanifolds, which are lower-dimensional objects embedded in higher-dimensional spaces.

3. How do non-affine connections differ from affine connections?

The main difference between non-affine connections and affine connections is that the latter assumes a constant metric, while the former allows for a varying metric. This means that non-affine connections can better describe the curvature of non-Euclidean spaces.

4. What are some applications of non-affine connections?

Non-affine connections have many applications in fields such as physics, engineering, and computer graphics. They are used to model the behavior of elastic materials, to study the dynamics of particles in curved spaces, and to generate realistic animations of deformable objects.

5. How are non-affine connections related to Riemannian geometry?

Non-affine connections are a generalization of the affine connection used in Riemannian geometry. They are used to define the Riemann curvature tensor, which is a measure of how much a surface is curved. Non-affine connections also play a key role in the theory of geodesics, which are the shortest paths on curved surfaces.

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