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  2. Rank of a group - Wikipedia

    en.wikipedia.org/wiki/Rank_of_a_group

    The rank of a symmetry group is closely related to the complexity of the object (a molecule, a crystal structure) being under the action of the group. If G is a crystallographic point group, then rank(G) is up to 3. [9] If G is a wallpaper group, then rank(G) = 2 to 4. The only wallpaper-group type of rank 4 is p2mm. [10]

  3. Grushko theorem - Wikipedia

    en.wikipedia.org/wiki/Grushko_theorem

    In the mathematical subject of group theory, the Grushko theorem or the Grushko–Neumann theorem is a theorem stating that the rank (that is, the smallest cardinality of a generating set) of a free product of two groups is equal to the sum of the ranks of the two free factors.

  4. Free group - Wikipedia

    en.wikipedia.org/wiki/Free_group

    A free group of finite rank n > 1 has an exponential growth rate of order 2n − 1. A few other related results are: The Nielsen–Schreier theorem: Every subgroup of a free group is free. Furthermore, if the free group F has rank n and the subgroup H has index e in F, then H is free of rank 1 + e(n–1). A free group of rank k clearly has ...

  5. Social rank theory - Wikipedia

    en.wikipedia.org/wiki/Social_rank_theory

    Social rank theory provides an evolutionary paradigm that locates affiliative and ranking structures at the core of many psychological disorders. In this context, displays of submission signal to dominant individuals that subordinate group members are not a threat to their rank within the social hierarchy. This helps to achieve social cohesion.

  6. Hanna Neumann conjecture - Wikipedia

    en.wikipedia.org/wiki/Hanna_Neumann_conjecture

    rank(L) − 1 ≤ (rank(H) − 1)(rank(K) − 1). Here for a group G the quantity rank(G) is the rank of G, that is, the smallest size of a generating set for G. Every subgroup of a free group is known to be free itself and the rank of a free group is equal to the size of any free basis of that free group.

  7. Group theory - Wikipedia

    en.wikipedia.org/wiki/Group_theory

    Group theory has three main historical sources: number theory, the theory of algebraic equations, and geometry.The number-theoretic strand was begun by Leonhard Euler, and developed by Gauss's work on modular arithmetic and additive and multiplicative groups related to quadratic fields.

  8. Dominance hierarchy - Wikipedia

    en.wikipedia.org/wiki/Dominance_hierarchy

    A high-ranking male mandrill advertises his status with bright facial coloration. [1]In the zoological field of ethology, a dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system.

  9. Glossary of group theory - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_group_theory

    The group consists of the finite strings (words) that can be composed by elements from A, together with other elements that are necessary to form a group. Multiplication of strings is defined by concatenation, for instance (abb) • (bca) = abbbca. Every group (G, •) is basically a factor group of a free group generated by G.