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  2. Inclusion–exclusion principle - Wikipedia

    en.wikipedia.org/wiki/Inclusionexclusion...

    Inclusionexclusion principle. In combinatorics, a branch of mathematics, the inclusionexclusion principle is a counting technique which generalizes the familiar method of obtaining the number of elements in the union of two finite sets; symbolically expressed as. where A and B are two finite sets and | S | indicates the cardinality of a ...

  3. Combinatorial principles - Wikipedia

    en.wikipedia.org/wiki/Combinatorial_principles

    Combinatorial principles. In proving results in combinatorics several useful combinatorial rules or combinatorial principles are commonly recognized and used. The rule of sum, rule of product, and inclusionexclusion principle are often used for enumerative purposes. Bijective proofs are utilized to demonstrate that two sets have the same ...

  4. Möbius inversion formula - Wikipedia

    en.wikipedia.org/wiki/Möbius_inversion_formula

    He noted the relation between such topics as inclusion-exclusion, classical number theoretic Möbius inversion, coloring problems and flows in networks. Since then, under the strong influence of Rota, the theory of Möbius inversion and related topics has become an active area of combinatorics.

  5. Derangement - Wikipedia

    en.wikipedia.org/wiki/Derangement

    In combinatorial mathematics, a derangement is a permutation of the elements of a set in which no element appears in its original position. In other words, a derangement is a permutation that has no fixed points. The number of derangements of a set of size n is known as the subfactorial of n or the n- th derangement number or n- th de Montmort ...

  6. Euler characteristic - Wikipedia

    en.wikipedia.org/wiki/Euler_characteristic

    if X is a stratified space all of whose strata are even-dimensional, the inclusionexclusion principle holds if M and N are unions of strata. This applies in particular if M and N are subvarieties of a complex algebraic variety. [7] In general, the inclusionexclusion principle is false.

  7. Pauli exclusion principle - Wikipedia

    en.wikipedia.org/wiki/Pauli_exclusion_principle

    In quantum mechanics, the Pauli exclusion principle states that two or more identical particles with half-integer spins (i.e. fermions) cannot simultaneously occupy the same quantum state within a system that obeys the laws of quantum mechanics. This principle was formulated by Austrian physicist Wolfgang Pauli in 1925 for electrons, and later ...

  8. Addition principle - Wikipedia

    en.wikipedia.org/wiki/Addition_principle

    A series of Venn diagrams illustrating the principle of inclusion-exclusion.. The inclusionexclusion principle (also known as the sieve principle [7]) can be thought of as a generalization of the rule of sum in that it too enumerates the number of elements in the union of some sets (but does not require the sets to be disjoint).

  9. Set (mathematics) - Wikipedia

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

    The inclusion-exclusion principle for two finite sets states that the size of their union is the sum of the sizes of the sets minus the size of their intersection. The inclusionexclusion principle is a technique for counting the elements in a union of two finite sets in terms of the sizes of the two sets and their intersection.