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  2. Set theory - Wikipedia

    en.wikipedia.org/wiki/Set_theory

    For example, the set containing only the empty set is a nonempty pure set. In modern set theory, it is common to restrict attention to the von Neumann universe of pure sets, and many systems of axiomatic set theory are designed to axiomatize the pure sets only. There are many technical advantages to this restriction, and little generality is ...

  3. Algebra of sets - Wikipedia

    en.wikipedia.org/wiki/Algebra_of_sets

    It is the algebra of the set-theoretic operations of union, intersection and complementation, and the relations of equality and inclusion. For a basic introduction to sets see the article on sets, for a fuller account see naive set theory, and for a full rigorous axiomatic treatment see axiomatic set theory.

  4. Glossary of set theory - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_set_theory

    The inclusive or operation in a Boolean algebra. (In ring theory it is used for the exclusive or operation) ~. 1. The difference of two sets: x ~ y is the set of elements of x not in y. 2. An equivalence relation. \. The difference of two sets: x \ y is the set of elements of x not in y.

  5. Abstract algebra - Wikipedia

    en.wikipedia.org/wiki/Abstract_algebra

    The permutations of the Rubik's Cube form a group, a fundamental concept within abstract algebra. In mathematics, more specifically algebra, abstract algebra or modern algebra is the study of algebraic structures, which are sets with specific operations acting on their elements. [ 1 ] Algebraic structures include groups, rings, fields, modules ...

  6. Tautology (logic) - Wikipedia

    en.wikipedia.org/wiki/Tautology_(logic)

    This means, in particular, the set of tautologies over a fixed finite or countable alphabet is a decidable set. As an efficient procedure, however, truth tables are constrained by the fact that the number of valuations that must be checked increases as 2 k, where k is the number of variables in the formula. This exponential growth in the ...

  7. Paradoxes of set theory - Wikipedia

    en.wikipedia.org/wiki/Paradoxes_of_set_theory

    Set theory as conceived by Georg Cantor assumes the existence of infinite sets. As this assumption cannot be proved from first principles it has been introduced into axiomatic set theory by the axiom of infinity, which asserts the existence of the set N of natural numbers. Every infinite set which can be enumerated by natural numbers is the ...

  8. Number theory - Wikipedia

    en.wikipedia.org/wiki/Number_theory

    t. e. Number theory (or arithmetic or higher arithmetic in older usage) is a branch of pure mathematics devoted primarily to the study of the integers and arithmetic functions. German mathematician Carl Friedrich Gauss (1777–1855) said, "Mathematics is the queen of the sciences—and number theory is the queen of mathematics." [ 1 ]

  9. Gödel's completeness theorem - Wikipedia

    en.wikipedia.org/wiki/Gödel's_completeness_theorem

    Gödel's completeness theorem is a fundamental theorem in mathematical logic that establishes a correspondence between semantic truth and syntactic provability in first-order logic. The completeness theorem applies to any first-order theory: If T is such a theory, and φ is a sentence (in the same language) and every model of T is a model of φ ...