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How does the cotangent-space definition change for a general manifold M over a field F?

For a smooth manifold MM over a field FF, the cotangent space at pp is defined as Hom⁡(TpM,F)\operatorname{Hom}(T_pM, F). The earlier Rn\mathbb{R}^n example is recovered by taking M=RnM = \mathbb{R}^n and F=RF = \mathbb{R}.

Conditions

  • MM is a smooth manifold.
  • FF is the field over which the manifold is considered.

Reasoning, step by step

  1. Replace the ambient space Rn\mathbb{R}^n with a general smooth manifold MM.
  2. Replace the field R\mathbb{R} with a general field FF.
  3. Define the cotangent space Tp∗MT_p^*M as Hom⁡(TpM,F)\operatorname{Hom}(T_pM, F).

Example

The video displays the generalization Tp∗M=Hom⁡(TpM,F)T_p^*M = \operatorname{Hom}(T_pM, F) and the narrator explains that Rn\mathbb{R}^n is the manifold MM and R\mathbb{R} is the field FF in the earlier example.

Common misconceptions

  • Thinking the generalization only applies to Rn\mathbb{R}^n.
  • Confusing the manifold MM with the field FF.

Watch the explanation

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.