Regular homotopy

Regular homotopy

In the mathematical field of topology, a regular homotopy refers to a special kind of homotopy between immersions of one manifold in another. In particular, the homotopy must go through immersions and extend continuously to a homotopy of the tangent bundle.

Similar to homotopy classes, one defines two immersions to be in the same regular homotopy class if there exists a regular homotopy between them.

The Whitney-Graustein theorem classifies the regular homotopy classes of a circle into the plane; two immersions are regularly homotopic if and only if their Gauss maps have the same winding number. Stephen Smale classified the regular homotopy classes of an "k"-sphere immersed in mathbb R^n. A corollary of his work is that there is only one regular homotopy class of a "2"-sphere immersed in mathbb R^3. In particular, this means that sphere eversions exist, i.e. one can turn the 2-sphere "inside-out".

References

*Hassler Whitney, " [http://www.numdam.org/numdam-bin/item?id=CM_1937__4__276_0 On regular closed curves in the plane] ". Compositio Mathematica, 4 (1937), p. 276-284
*Stephen Smale, "A classification of immersions of the two-sphere". Trans. Amer. Math. Soc. 90 1958 281--290.
*Stephen Smale, "The classification of immersions of spheres in Euclidean spaces". Ann. of Math. (2) 69 1959 327--344.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Homotopy — This article is about topology. For chemistry, see Homotopic groups. The two dashed paths shown above are homotopic relative to their endpoints. The animation represents one possible homotopy. In topology, two continuous functions from one… …   Wikipedia

  • Smale's paradox — In differential topology, Smale s paradox states that it is possible to turn a sphere inside out in 3 space with possible self intersections but without creating any crease, a process often called sphere eversion ( eversion means to turn inside… …   Wikipedia

  • Link group — In knot theory, an area of mathematics, the link group of a link is an analog of the knot group of a knot. They were described by John Milnor in his Bachelor s thesis, (Milnor 1954). Contents 1 Definition 2 Examples 3 …   Wikipedia

  • List of mathematics articles (R) — NOTOC R R. A. Fisher Lectureship Rabdology Rabin automaton Rabin signature algorithm Rabinovich Fabrikant equations Rabinowitsch trick Racah polynomials Racah W coefficient Racetrack (game) Racks and quandles Radar chart Rademacher complexity… …   Wikipedia

  • Ambient isotopy — In the mathematical subject of topology, an ambient isotopy, also called an h isotopy, is a kind of continuous distortion of an ambient space , a manifold, taking a submanifold to another submanifold. For example in knot theory, one considers two …   Wikipedia

  • Minimax eversion — In geometry, minimax eversions are a class of sphere eversions, constructed by using half way models. It is a variational method, and consists of special homotopies (they are shortest paths with respect to Willmore energy); contrast with Thurston …   Wikipedia

  • Total curvature — In mathematical study of the differential geometry of curves, the total curvature of a plane curve is the integral of curvature along a curve taken with respect to arclength::int a^b k(s),ds.The total curvature of a closed curve is always an… …   Wikipedia

  • Covering space — A covering map satisfies the local triviality condition. Intuitively, such maps locally project a stack of pancakes above an open region, U, onto U. In mathematics, more specifically algebraic topology, a covering map is a continuous surjective… …   Wikipedia

  • Glossary of topology — This is a glossary of some terms used in the branch of mathematics known as topology. Although there is no absolute distinction between different areas of topology, the focus here is on general topology. The following definitions are also… …   Wikipedia

  • Degree of a continuous mapping — This article is about the term degree as used in algebraic topology. For other uses, see degree (mathematics). A degree two map of a sphere onto itself. In topology, the degree is a numerical invariant that describes a continuous mapping between… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”