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  2. Law of symmetry (crystallography) - Wikipedia

    en.wikipedia.org/wiki/Law_of_symmetry...

    [17] The point group T d (tetrahedral symmetry) is a subgroup of index 2 of point group O h (octahedral symmetry). In his 1815 law of symmetry papers Haüy postulated the idea of rotational symmetry in crystals but he considered only a single (vertical) axis of rotation, which made it difficult to explain the observed crystal forms with ...

  3. Floer homology - Wikipedia

    en.wikipedia.org/wiki/Floer_homology

    The homological mirror symmetry conjecture of Maxim Kontsevich predicts an equality between the Lagrangian Floer homology of Lagrangians in a Calabi–Yau manifold and the Ext groups of coherent sheaves on the mirror Calabi–Yau manifold. In this situation, one should not focus on the Floer homology groups but on the Floer chain groups.

  4. Reflection symmetry - Wikipedia

    en.wikipedia.org/wiki/Reflection_symmetry

    In mathematics, reflection symmetry, line symmetry, mirror symmetry, or mirror-image symmetry is symmetry with respect to a reflection. That is, a figure which does not change upon undergoing a reflection has reflectional symmetry. In 2-dimensional space, there is a line/axis of symmetry, in 3-dimensional space, there is a plane of symmetry

  5. Homological mirror symmetry - Wikipedia

    en.wikipedia.org/wiki/Homological_mirror_symmetry

    Mirror symmetry not only replaces the homological dimensions but also the symplectic structure and complex structure on the mirror pairs. That is the origin of homological mirror symmetry. In 1990-1991, Candelas et al. 1991 had a major impact not only on enumerative algebraic geometry but on the whole mathematics and motivated Kontsevich (1994).

  6. Klein bottle - Wikipedia

    en.wikipedia.org/wiki/Klein_bottle

    The boundary homomorphism is given by ∂D = 2C 1 and ∂C 1 = ∂C 2 = 0, yielding the homology groups of the Klein bottle K to be H 0 (K, Z) = Z, H 1 (K, Z) = Z×(Z/2Z) and H n (K, Z) = 0 for n > 1. There is a 2-1 covering map from the torus to the Klein bottle, because two copies of the fundamental region of the Klein bottle, one being ...

  7. Symmetry (geometry) - Wikipedia

    en.wikipedia.org/wiki/Symmetry_(geometry)

    A drawing of a butterfly with bilateral symmetry, with left and right sides as mirror images of each other.. In geometry, an object has symmetry if there is an operation or transformation (such as translation, scaling, rotation or reflection) that maps the figure/object onto itself (i.e., the object has an invariance under the transform). [1]

  8. Chirality (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Chirality_(mathematics)

    A scalene triangle does not have mirror symmetries, and hence is a chiral polytope in 2 dimensions. In two dimensions, every figure which possesses an axis of symmetry is achiral, and it can be shown that every bounded achiral figure must have an axis of symmetry.

  9. Mirror matter - Wikipedia

    en.wikipedia.org/wiki/Mirror_matter

    Mirror matter could have been diluted to unobservably low densities during the inflation epoch. Sheldon Glashow has shown that if at some high energy scale particles exist which interact strongly with both ordinary and mirror particles, radiative corrections will lead to a mixing between photons and mirror photons. [22]