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  2. Möbius strip - Wikipedia

    en.wikipedia.org/wiki/Möbius_strip

    In mathematics, a Möbius strip, Möbius band, or Möbius loop [a] is a surface that can be formed by attaching the ends of a strip of paper together with a half-twist. As a mathematical object, it was discovered by Johann Benedict Listing and August Ferdinand Möbius in 1858, but it had already appeared in Roman mosaics from the third century CE .

  3. Non-orientable wormhole - Wikipedia

    en.wikipedia.org/wiki/Non-orientable_wormhole

    The alternative way of connecting the surfaces makes the "connection map" appear the same at both mouths. This configuration reverses the "handedness" or "chirality" of any objects passing through. If a spaceship pilot writes the word "IOTA" on the inside of their forward window, then, as the ship's nose passes through the wormhole and the ship's window intersects the surface, an observer at ...

  4. Orientability - Wikipedia

    en.wikipedia.org/wiki/Orientability

    A torus is an orientable surface The Möbius strip is a non-orientable surface. Note how the disk flips with every loop. The Roman surface is non-orientable.. In mathematics, orientability is a property of some topological spaces such as real vector spaces, Euclidean spaces, surfaces, and more generally manifolds that allows a consistent definition of "clockwise" and "anticlockwise". [1]

  5. Simplicial homology - Wikipedia

    en.wikipedia.org/wiki/Simplicial_homology

    A key concept in defining simplicial homology is the notion of an orientation of a simplex. By definition, an orientation of a k-simplex is given by an ordering of the vertices, written as (v 0,...,v k), with the rule that two orderings define the same orientation if and only if they differ by an even permutation.

  6. Mapping class group - Wikipedia

    en.wikipedia.org/wiki/Mapping_class_group

    Notice that there is an induced action of the mapping class group on the homology (and cohomology) of the space X. This is because (co)homology is functorial and Homeo 0 acts trivially (because all elements are isotopic, hence homotopic to the identity, which acts trivially, and action on (co)homology is invariant under homotopy).

  7. Vector bundle - Wikipedia

    en.wikipedia.org/wiki/Vector_bundle

    The Möbius strip can be constructed by a non-trivial gluing of two trivial bundles on open subsets U and V of the circle S 1. When glued trivially (with g UV =1) one obtains the trivial bundle, but with the non-trivial gluing of g UV =1 on one overlap and g UV =-1 on the second overlap, one obtains the non-trivial bundle E, the Möbius strip

  8. Here's how a US trade war between Mexico, Canada, and ... - AOL

    www.aol.com/heres-us-trade-war-between-181918916...

    Uncertainty will loom over markets even if Trump doesn't follow through with his trade proposals, and the impact could drag on S&P 500 earnings, analysts say.

  9. Homotopy category - Wikipedia

    en.wikipedia.org/wiki/Homotopy_category

    The category of topological spaces Top has topological spaces as objects and as morphisms the continuous maps between them. The older definition of the homotopy category hTop, called the naive homotopy category [1] for clarity in this article, has the same objects, and a morphism is a homotopy class of continuous maps.