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  2. Arithmetic genus - Wikipedia

    en.wikipedia.org/wiki/Arithmetic_genus

    When n=1, the formula becomes =,. According to the Hodge theorem , h 0 , 1 = h 1 , 0 {\displaystyle h^{0,1}=h^{1,0}} . Consequently h 0 , 1 = h 1 ( X ) / 2 = g {\displaystyle h^{0,1}=h^{1}(X)/2=g} , where g is the usual (topological) meaning of genus of a surface, so the definitions are compatible.

  3. Point groups in three dimensions - Wikipedia

    en.wikipedia.org/wiki/Point_groups_in_three...

    When comparing the symmetry type of two objects, the origin is chosen for each separately, i.e., they need not have the same center. Moreover, two objects are considered to be of the same symmetry type if their symmetry groups are conjugate subgroups of O(3) (two subgroups H 1, H 2 of a group G are conjugate, if there exists g ∈ G such that H 1 = g −1 H 2 g).

  4. Stein manifold - Wikipedia

    en.wikipedia.org/wiki/Stein_manifold

    Let X be a connected, non-compact Riemann surface.A deep theorem of Heinrich Behnke and Stein (1948) asserts that X is a Stein manifold.. Another result, attributed to Hans Grauert and Helmut Röhrl (1956), states moreover that every holomorphic vector bundle on X is trivial.

  5. Dynkin diagram - Wikipedia

    en.wikipedia.org/wiki/Dynkin_diagram

    The right map is simply an inclusion – undirected Dynkin diagrams are special cases of Coxeter diagrams, and Weyl groups are special cases of finite Coxeter groups – and is not onto, as not every Coxeter diagram is an undirected Dynkin diagram (the missed diagrams being H 3, H 4 and I 2 (p) for p = 5 p ≥ 7), and correspondingly not every ...

  6. Angle of incidence (optics) - Wikipedia

    en.wikipedia.org/wiki/Angle_of_incidence_(optics)

    Focusing X-rays with glancing reflection. When dealing with a beam that is nearly parallel to a surface, it is sometimes more useful to refer to the angle between the beam and the surface tangent, rather than that between the beam and the surface normal. The 90-degree complement to the angle of incidence is called the grazing angle or glancing ...

  7. Smith chart - Wikipedia

    en.wikipedia.org/wiki/Smith_chart

    A point with a reflection coefficient magnitude 0.63 and angle 60° represented in polar form as , is shown as point P 1 on the Smith chart. To plot this, one may use the circumferential (reflection coefficient) angle scale to find the ∠ 60 ∘ {\displaystyle \angle 60^{\circ }\,} graduation and a ruler to draw a line passing through this and ...

  8. Coxeter group - Wikipedia

    en.wikipedia.org/wiki/Coxeter_group

    In two dimensions, the dihedral groups, which are the symmetry groups of regular polygons, form the series I 2 (p), for p ≥ 3. In three dimensions, the symmetry group of the regular dodecahedron and its dual, the regular icosahedron , is H 3 , known as the full icosahedral group .

  9. Forbidden graph characterization - Wikipedia

    en.wikipedia.org/wiki/Forbidden_graph...

    Outerplanar graphs: K 4 and K 2,3: Graph minor Diestel (2000), [1] p. 107: Outer 1-planar graphs: Six forbidden minors Graph minor Auer et al. (2013) [2] Graphs of fixed genus: A finite obstruction set Graph minor Diestel (2000), [1] p. 275: Apex graphs: A finite obstruction set Graph minor [3] Linklessly embeddable graphs: The Petersen family ...