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  2. Golden ratio - Wikipedia

    en.wikipedia.org/wiki/Golden_ratio

    The golden ratio was called the extreme and mean ratio by Euclid, [2] ... the quotient approximates ... The quasi-one-dimensional Ising ferromagnet ...

  3. Homotopy groups of spheres - Wikipedia

    en.wikipedia.org/wiki/Homotopy_groups_of_spheres

    An ordinary sphere in three-dimensional space—the surface, not the solid ball—is just one example of what a sphere means in topology. Geometry defines a sphere rigidly, as a shape. Here are some alternatives. Implicit surface: x 2 0 + x 2 1 + x 2 2 = 1; This is the set of points in 3-dimensional Euclidean space found

  4. Rayleigh quotient - Wikipedia

    en.wikipedia.org/wiki/Rayleigh_quotient

    In mathematics, the Rayleigh quotient [1] (/ ˈ r eɪ. l i /) for a given complex Hermitian matrix and nonzero vector is defined as: [2] [3] (,) =. For real matrices and vectors, the condition of being Hermitian reduces to that of being symmetric , and the conjugate transpose x ∗ {\displaystyle x^{*}} to the usual transpose x ...

  5. Quotient - Wikipedia

    en.wikipedia.org/wiki/Quotient

    For example, density (mass divided by volume, in units of kg/m 3) is said to be a "quotient", whereas mass fraction (mass divided by mass, in kg/kg or in percent) is a "ratio". [8] Specific quantities are intensive quantities resulting from the quotient of a physical quantity by mass, volume, or other measures of the system "size". [3]

  6. Isoperimetric inequality - Wikipedia

    en.wikipedia.org/wiki/Isoperimetric_inequality

    For a given closed curve, the isoperimetric quotient is defined as the ratio of its area and that of the circle having the same perimeter. This is equal to = and the isoperimetric inequality says that Q ≤ 1. Equivalently, the isoperimetric ratio L 2 /A is at least 4 π for every curve.

  7. Compactness measure - Wikipedia

    en.wikipedia.org/wiki/Compactness_measure

    A common compactness measure is the isoperimetric quotient, the ratio of the area of the shape to the area of a circle (the most compact shape) having the same perimeter. . In the plane, this is equivalent to the Polsby–Popper t

  8. Sweedler's Hopf algebra - Wikipedia

    en.wikipedia.org/wiki/Sweedler's_Hopf_algebra

    Sweedler's 4-dimensional Hopf algebra H 4 is the quotient of this by the relations x 2 = 0, g 2 = 1, gx = –xg. so it has a basis 1, x, g, xg (Montgomery 1993, p.8). Note that Montgomery describes a slight variant of this Hopf algebra using the opposite coproduct, i.e. the coproduct described above composed with the tensor flip on H 4 ⊗H 4.

  9. Surface-area-to-volume ratio - Wikipedia

    en.wikipedia.org/wiki/Surface-area-to-volume_ratio

    Plot of the surface-area:volume ratio (SA:V) for a 3-dimensional ball, showing the ratio decline inversely as the radius of the ball increases. A solid sphere or ball is a three-dimensional object, being the solid figure bounded by a sphere. (In geometry, the term sphere properly refers only to the surface, so a sphere thus lacks volume in this ...