What is Manifold: Definition and 327 Discussions

In mathematics, a manifold is a topological space that locally resembles Euclidean space near each point. More precisely, an n-dimensional manifold, or n-manifold for short, is a topological space with the property that each point has a neighborhood that is homeomorphic to an open subset of n-dimensional Euclidean space.
One-dimensional manifolds include lines and circles, but not figure eights. Two-dimensional manifolds are also called surfaces. Examples include the plane, the sphere, and the torus, and also the Klein bottle and real projective plane.
The concept of a manifold is central to many parts of geometry and modern mathematical physics because it allows complicated structures to be described in terms of well-understood topological properties of simpler spaces. Manifolds naturally arise as solution sets of systems of equations and as graphs of functions. The concept has applications in computer-graphics and augmented-reality given the need to associate pictures (texture) to coordinates (e.g. CT scans).
Manifolds can be equipped with additional structure. One important class of manifolds are differentiable manifolds; their differentiable structure allows calculus to be done. A Riemannian metric on a manifold allows distances and angles to be measured. Symplectic manifolds serve as the phase spaces in the Hamiltonian formalism of classical mechanics, while four-dimensional Lorentzian manifolds model spacetime in general relativity.
The study of manifolds requires working knowledge of calculus and topology.

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  1. F

    Are second derivative symmetric in a Riemannian manifold?

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  2. atyy

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  3. M

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  4. M

    Why the figure of eight is not a manifold?

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  5. F

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  6. U

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  7. TrickyDicky

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  8. M

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  10. T

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  11. W

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  13. S

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  14. M

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  15. wolram

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  16. P

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  17. Markus Hanke

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  18. Chris L T521

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  19. M

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  21. S

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  22. K

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  31. A

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  32. S

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  33. W

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  34. ShayanJ

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  35. M

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  36. R

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  37. B

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  38. V

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  40. L

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  42. M

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  43. S

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  44. C

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  45. O

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  46. H

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  47. P

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  48. C

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  49. S

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  50. P

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