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| In [[abstract algebra]], a branch of pure [[mathematics]], an '''MV-algebra''' is an [[algebraic structure]] with a [[binary operation]] <math>\oplus</math>, a [[unary operation]] <math>\neg</math>, and the constant <math>0</math>, satisfying certain axioms. MV-algebras are the [[Algebraic semantics (mathematical logic)|algebraic semantics]] of [[Łukasiewicz logic]]; the letters MV refer to ''many-valued'' logic of Łukasiewicz. MV-algebras coincide with the class of bounded commutative [[BCK algebra]]s.
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| ==Definitions==
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| An '''MV-algebra''' is an [[algebraic structure]] <math>\langle A, \oplus, \lnot, 0\rangle,</math> consisting of
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| * a [[empty set|non-empty]] [[Set (mathematics)|set]] <math>A,</math>
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| * a [[binary operation]] <math>\oplus</math> on <math>A,</math>
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| * a [[unary operation]] <math>\lnot</math> on <math>A,</math> and
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| * a constant <math>0</math> denoting a fixed [[element (mathematics)|element]] of <math>A,</math>
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| which satisfies the following [[identity (mathematics)|identities]]:
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| * <math> (x \oplus y) \oplus z = x \oplus (y \oplus z),</math>
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| * <math> x \oplus 0 = x,</math>
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| * <math> x \oplus y = y \oplus x,</math>
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| * <math> \lnot \lnot x = x,</math>
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| * <math> x \oplus \lnot 0 = \lnot 0,</math> and
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| * <math> \lnot ( \lnot x \oplus y)\oplus y = \lnot ( \lnot y \oplus x) \oplus x.</math>
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| By virtue of the first three axioms, <math>\langle A, \oplus, 0 \rangle</math> is a commutative [[monoid]]. Being defined by identities, MV-algebras form a [[variety (universal algebra)|variety]] of algebras. The variety of MV-algebras is a subvariety of the variety of [[BL (logic)|BL]]-algebras and contains all [[Boolean algebra (structure)|Boolean algebra]]s.
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| An MV-algebra can equivalently be defined (Hájek 1998) as a prelinear commutative bounded integral [[residuated lattice]] <math>\langle L, \wedge, \vee, \otimes, \rightarrow, 0, 1 \rangle </math> satisfying the additional identity <math>x \vee y = (x \rightarrow y) \rightarrow y.</math>
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| ==Examples of MV-algebras==
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| A simple numerical example is <math>A=[0,1],</math> with operations <math>x \oplus y = \min(x+y,1)</math> and <math>\lnot x=1-x.</math> In mathematical fuzzy logic, this MV-algebra is called the ''standard MV-algebra'', as it forms the standard real-valued semantics of [[Łukasiewicz logic]].
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| The ''trivial'' MV-algebra has the only element 0 and the operations defined in the only possible way, <math>0\oplus0=0</math> and <math>\lnot0=0.</math>
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| The ''two-element'' MV-algebra is actually the [[two-element Boolean algebra]] <math>\{0,1\},</math> with <math>\oplus</math> coinciding with Boolean disjunction and <math>\lnot</math> with Boolean negation. In fact adding the axiom <math>x \oplus x = x</math> to the axioms defining an MV-algebra results in an axiomantization of Boolean algebras.
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| If instead the axiom added is <math>x \oplus x \oplus x = x \oplus x</math>, then the axioms define the MV<sub>3</sub> algebra corresponding to the three-valued Łukasiewicz logic Ł<sub>3</sub>{{Citation needed|reason=Axiomatizations of Ln need Grigolia's axioms|date=February 2013}}. Other finite linearly ordered MV-algebras are obtained by restricting the universe and operations of the standard MV-algebra to the set of <math>n</math> equidistant real numbers between 0 and 1 (both included), that is, the set <math>\{0,1/(n-1),2/(n-1),\dots,1\},</math> which is closed under the operations <math>\oplus</math> and <math>\lnot</math> of the standard MV-algebra; these algebras are usually denoted MV<sub>n</sub>.
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| Another important example is ''Chang's MV-algebra'', consisting just of infinitesimals (with the [[order type]] ω) and their co-infinitesimals.
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| Chang also constructed an MV-algebra from an arbitrary [[Linearly ordered group|totally ordered abelian group]] ''G'' by fixing a positive element ''u'' and defining the segment [0, ''u''] as { ''x'' ∈ ''G'' | 0 ≤ ''x'' ≤ ''u'' }, which becomes an MV-algebra with ''x'' ⊕ ''y'' = min(''u'', ''x''+''y'') and ¬''x'' = ''u''−''x''. Furthermore, Chang showed that every linearly ordered MV-algebra is isomorphic to an MV-algebra constructed from a group in this way.
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| D. Mundici extended the above construction to abelian [[lattice-ordered group]]s. If ''G'' is such a group with strong (order) unit ''u'', then the "unit interval" { ''x'' ∈ ''G'' | 0 ≤ ''x'' ≤ ''u'' } can be equipped with ¬''x'' = ''u''−''x'', ''x'' ⊕ ''y'' = ''u''∧<sub>G</sub> (x+y), ''x'' ⊗ ''y'' = 0∨<sub>G</sub>(''x''+''y''−''u''). This construction establishes a [[categorical equivalence]] between lattice-ordered abelian groups with strong unit and MV-algebras.
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| ==Relation to Łukasiewicz logic==
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| [[C. C. Chang]] devised MV-algebras to study [[many-valued logic]]s, introduced by [[Jan Łukasiewicz]] in 1920. In particular, MV-algebras form the [[algebraic semantics (mathematical logic)|algebraic semantics]] of [[Łukasiewicz logic]], as described below.
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| Given an MV-algebra ''A'', an ''A''-[[Valuation (logic)|valuation]] is a [[homomorphism]] from the algebra of [[propositional formula]]s (in the language consisting of <math>\oplus,\lnot,</math> and 0) into ''A''. Formulas mapped to 1 (or <math>\lnot</math>0) for all ''A''-valuations are called ''A''-[[tautology (logic)|tautologies]]. If the standard MV-algebra over [0,1] is employed, the set of all [0,1]-tautologies determines so-called infinite-valued [[Łukasiewicz logic]].
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| Chang's (1958, 1959) completeness theorem states that any MV-algebra equation holding in the standard MV-algebra over the interval [0,1] will hold in every MV-algebra. Algebraically, this means that the standard MV-algebra generates the variety of all MV-algebras. Equivalently, Chang's completeness theorem says that MV-algebras characterize infinite-valued [[Łukasiewicz logic]], defined as the set of [0,1]-tautologies.
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| The way the [0,1] MV-algebra characterizes all possible MV-algebras parallels the well-known fact that identities holding in the [[two-element Boolean algebra]] hold in all possible Boolean algebras. Moreover, MV-algebras characterize infinite-valued [[Łukasiewicz logic]] in a manner analogous to the way that [[Boolean algebras]] characterize classical [[two-element Boolean algebra|bivalent logic]] (see [[Lindenbaum-Tarski algebra]]).
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| ==Relation to functional analysis==
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| {{expand section|date=November 2012}}
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| MV-algebras were related by D. Mundici to [[approximately finite dimensional C*-algebra]]s by establishing a bijective correspondence between all isomorphism classes of AF C*-algebras with lattice-ordered dimension group and all isomorphism classes of countable MV algebras. Some instances of this correspondence include:
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| {| class="wikitable"
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| |-
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| ! Countable MV algebra !! AF C*-algebra
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| |-
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| | {0, 1} || ℂ
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| |-
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| | {0, 1/''n'', ..., 1 } || M<sub>n</sub>(ℂ), i.e. ''n''×''n'' complex matrices
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| |-
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| | finite || finite-dimensional
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| |-
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| | boolean || commutative
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| |}
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| ==In software==
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| There are multiple frameworks implementing fuzzy logic (type II),
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| and most of them implement what has been called a multi-adjoint logic.
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| This is no more than the implementation of a '''MV-algebra'''.
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| More information available at [[Multi-adjoint logic programming]].
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| ==References==
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| *Chang, C. C. (1958) "Algebraic analysis of many-valued logics," ''Transactions of the American Mathematical Society'' '''88''': 476–490.
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| *------ (1959) "A new proof of the completeness of the Lukasiewicz axioms," ''Transactions of the American Mathematical Society'' '''88''': 74–80.
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| * Cignoli, R. L. O., D'Ottaviano, I. M. L., Mundici, D. (2000) ''Algebraic Foundations of Many-valued Reasoning''. Kluwer.
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| * Di Nola A., Lettieri A. (1993) "Equational characterization of all varieties of MV-algebras," ''Journal of Algebra'' '''221''': 123–131.
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| * Hájek, Petr (1998) ''Metamathematics of Fuzzy Logic''. Kluwer.
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| * Mundici, D.: Interpretation of AF C*-algebras in Łukasiewicz sentential calculus. J. Funct. Anal. 65, 15–63 (1986) {{doi|10.1016/0022-1236(86)90015-7}}
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| ==Further reading ==
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| * {{cite book|author=D. Mundici|title=Advanced Łukasiewicz calculus and MV-algebras|year=2011|publisher=Springer|isbn=978-94-007-0839-6}}
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| ==External links==
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| * [[Stanford Encyclopedia of Philosophy]]: "[http://plato.stanford.edu/entries/logic-manyvalued/ Many-valued logic]" -- by [[Siegfried Gottwald]].
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| [[Category:Algebraic logic]]
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| [[Category:Algebraic structures]]
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| [[Category:Fuzzy logic]]
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| [[Category:Many-valued logic]]
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The individual who wrote the post is known as Jayson Hirano and he completely digs that title. Doing ballet is something she would never give up. Distributing manufacturing is where my primary earnings comes from and it's some thing I truly appreciate. Mississippi is where her house is but her husband wants them to move.
Feel free to surf to my page - telephone psychic (www.sirudang.com)