Final Answers
© 2000-2023 Gérard P. Michon, Ph.D.

Manifolds

Manifolds are a bit like pornography:
hard to define, but you know one when you see one.

Shmuel Weinberger (1963-)
Michon
border
border
border

Related articles on this site:

Related Links (Outside this Site)

Category Theory Stanford Encyclopedia of Philosophy (1996, 2014).
CT: An abstact setting for analogy and comparison R. Brown & T.Porter.
Categorification by John C. Baez (1998).
Categories, Quantization, and Much More by John Baez (April 2006).
The n-Category Café by John Baez, David Corfield, Alexander Hoffnung et al.
The n-categorical point of view lives on at nLab.

Wikipedia : Manifold | History of manifolds and varieties | Orbifold

Videos : The Mystery of 3-Manifolds (2010) Bill Thurston (1946-2012)
What is a Manifold? (Paris, 2010) by Misha Gromov (1943-).

Vector Bundles, Gauge theory (1:33:28) K Raviteja (2015年08月27日).

What is a Manifold? by Bijan Haney (2016) 1: Point-Set Topology. 2: Topological Concepts. 3: Separation. 4: Countability & Continuity. 5: Compactness & Connectedness. 6: Metrizable Manifolds. 7: Differentiable Manifolds. 8: Diffeomorphisms. 9: Tangent Space. 10: Basis Vectors. 11: Cotangent Space. 12: Fiber Bundles. 14: Tangent Bundle. 15: Quotient Spaces. 16: Moebius Strip. 17: Metric Spaces. 18: Homotopy.

border
border

Topological and Smooth Manifolds


(2014年12月23日) Manifold (French: variété) and homotopy type.
Topological, Piecewise-linear or Smooth Manifolds.

A topological manifold of dimension n is a metrizable space (a second-countable Hausdorff space) locally homeomorphic to Rn (or an open ball thereof).

Parametrization, chart, atlas.

Embedding theorem : Every manifold of dimension n can be embedded in R2n+1

[画像: Come back later, we're still working on this one... ]

Topological manifold | Differentiable manifold

Whitney embedding theorem | Hassler Whitney (1907-1989)

Topological manifold (18:03) and smooth manifold (27:09) by Harish Seshadri (2017年08月29日).

"Differential Topology" (AMS Lectures at Cornell, Aug. 30 - Sept. 2, 1965) by John W. Milnor (1931-)
1 : Definitions. Mappings. 2 : Poincaré conjecture. Tangent bundles. 3 : Grassmann manifold.

Differentiable Manifolds (1:43:11) by Frederic P. Schuller (#7, 2016年03月12日).


(2020年10月03日) Direct sum of two manifolds
The dimension of the sum is the sum of the dimensions.

[画像: Come back later, we're still working on this one... ]

Diffeomorphism | Smoothness classes


(2020年10月03日) Connected sum of two manifolds (fiber sum).
Cut off two identical submanifolds and glue the matching boundaries.

One important special case is the connected sum of manifolds of identical dimensions, off a given pair of points. This is done by cutting off a small enough manifold homeomorphic to a ball around both points and gluing together the two boundaries so created.

[画像: Come back later, we're still working on this one... ]

Connected sums | Disc theorem (1960) | Richard S. Palais (1931-)


(2020年09月15日) Diffeomorphism

[画像: Come back later, we're still working on this one... ]

Diffeomorphism | Smoothness classes


(2020年10月05日) Tangent verctors and tangent bundle thereof.

A smooth curve g in a smooth manifold M is, by definition, a C¥ function from R (or any interval thereof) to M.

What's traditionally called the tangent vector to g at point g at point p = g at point g(0) is best defined as the linear form (formally called the directional derivative operator along g at point p) which maps any form of f of C¥(M) to the scalar ( f o g)'(0).

[画像: Come back later, we're still working on this one... ]

Two curves which have the same tangent vector at a given point are said to be tangent to each other.

Diffeomorphism | Smoothness classes

Differential structures (1:44:14) by Frederic P. Schuller (Lec 09, 2015年09月21日).


(2020年09月27日) Pushforward: Total derivative of a smooth map.
The dual operation is a pullback.

[画像: Come back later, we're still working on this one... ]

Pushforward | Pullback | Differential forms | Partial derivatives

Manifolds, Derivations & Push-Forwards (59:50) by James Cook (2015年11月09日).


(2020年10月03日) Toppological Manifolds and Bundles.

Loosely speaking, a topological manifold is a topological space which is locally homeomorphic to a d-dmensional Euclideam space.

Formally, a paracompact Hausdorff space M is a d-dimensional (topolological) manifold when every point x of M possesses an open neighborhood homeomorphic to a subset of Rd.

[画像: Come back later, we're still working on this one... ]

Differential forms | Partial derivatives

Topological manifolds and manifold bundles (1:49:17) by Frederic Schuller (Lec 06, 2015年09月21日).


(2020年09月15日) Immersion of one differentiable manifold into another:
Differentiable map whose derivative is everywhere injective.

[画像: Come back later, we're still working on this one... ]

Immersion


(2020年09月15日) Embedding of one differentiable manifold into another:
An embedding is an injective immersion (i.e., no "self-intersections").

[画像: Come back later, we're still working on this one... ]

Nash Embedding Theorem :

A compact m-dimensional Riemannian manifold can be smoothly embedded isometrically in a Euclidean space of (3m+11)m/2 dimensions.

Embedding

Difference between immersion and embedding. (StackExchange, 2011年09月28日).

Nash Embedding Theorem (13:41) by Edward T. Crane (Numberphile, 2015年05月31日)
Embedding a Torus (12:57) by James Grime (Numberphile, 2015年05月31日)

border
border
visits since December 24, 2014
(c) Copyright 2000-2023, Gerard P. Michon, Ph.D.

AltStyle によって変換されたページ (->オリジナル) /