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Topic: Adjoint functor theorem order theory


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In the News (Wed 23 Dec 09)

  
  Adjoint functors - Wikipedia, the free encyclopedia
Adjoint functors are studied in a branch of mathematics known as category theory.
This functor is left adjoint to the functor that associates to a given ring its underlying multiplicative monoid.
Similarly, the group ring construction yields a functor from groups to rings, left adjoint to the functor that assigns to a given ring its group of units.
en.wikipedia.org /wiki/Adjoint_functors   (3467 words)

  
 Galois connection - Wikipedia, the free encyclopedia
In mathematics, especially in order theory, a Galois connection is a particular correspondence between two partially ordered sets ("posets").
The adjoint functor theorem for order theory states that the converse implication is also valid in certain cases: especially, any mapping between complete lattices that preserves all suprema is the lower adjoint of a Galois connection.
A Galois connection is then nothing but a pair of adjoint functors between two categories that arise from partially ordered sets.
en.wikipedia.org /wiki/Galois_connection   (2130 words)

  
 Encyclopedia: Category theory   (Site not responding. Last check: 2007-10-18)
Such a process is called a functor, and it associates to every object of one category an object of another category, and to every morphism in the first category a morphism in the second.
Adjoint functors: A functor can be left (or right) adjoint to another functor that maps in the opposite direction.
In category theory, an abstract branch of mathematics, the dual of a category C is the category formed by reversing all the morphisms of C. That is, we take Cop to be the category with objects that are those of C, but with the morphisms from X to Y in...
www.nationmaster.com /encyclopedia/category-theory   (4301 words)

  
 Galois connection -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-18)
For an order theoretic example, let U be some (A group of things of the same kind that belong together and are so used) set, and let A and B be the (additional info and facts about power set) power set of U, ordered by inclusion.
The adjoint functor theorem for order theory states that the converse implication is also valid in certain cases: especially, any mapping between (additional info and facts about complete lattice) complete lattices that preserves all suprema is the lower adjoint of a Galois connection.
Every partially ordered set can be viewed as a (A general concept that marks divisions or coordinations in a conceptual scheme) category in a natural way: there is a unique morphism from x to y (additional info and facts about iff) iff x ≤ y.
www.absoluteastronomy.com /encyclopedia/g/ga/galois_connection.htm   (2166 words)

  
 Category theory - Open Encyclopedia   (Site not responding. Last check: 2007-10-18)
Then it becomes possible to relate different categories by functors, generalizations of functions which associate to every object of one category an object of another category and to every morphism in the first category a morphism in the second.
The subsequent development of the theory was powered first by the computational needs of homological algebra; and then by the axiomatic needs of algebraic geometry, the field most resistant to the Russell-Whitehead view of united foundations.
Categorical logic is now a well-defined field based on type theory for intuitionistic logics, with application to the theory of functional programming and domain theory, all in a setting of a cartesian closed category as non-syntactic description of a lambda calculus.
open-encyclopedia.com /Category_theory   (2374 words)

  
 Category theory   (Site not responding. Last check: 2007-10-18)
Dual vectorspace: an example of a contravariant functor from the category of all real vector spaces to the category of all real vector spaces is given by assigning to every vector space its dual space and to every linear map its dual or transpose.
Algebra of continuous functions: a contravariant functor from the category of topological spaces (with continuous maps as morphisms) to the category of real associative algebras is given by assigning to every topological space X the algebra C(X) of all real-valued continuous functions on that space.
Functors like these are called representable, and a major goal in many settings is to determine whether a given functor is representable.
www.sciencedaily.com /encyclopedia/category_theory   (3261 words)

  
 [No title]
This leads to an alternative characterization of algebraic theories via the fre* *e T -algebra functor: the category of simplicial theories is equivalent to the category of those trip* *les on the category of pointed simplicial sets which are degreewise evaluable and commute with filt* *ered colimits.
The loop functor commutes with the forgetful functor, i.e., the underlying simplici* *al set of X is the simplicial set of pointed maps of S1 into the underlying simplicial set of X. *and are a Quillen adjoint functor pair.
We denote by DB the Gamma-ring arising from the theory of augmented commutative* * B-algebras.
hopf.math.purdue.edu /Schwede/stable.txt   (17227 words)

  
 Limit-preserving function (order theory)   (Site not responding. Last check: 2007-10-18)
Each of these requirements appears naturally and frequently in many areas of order theory and there are various important relationships among these concepts and other notions such as monotonicity.
In many specialized areas of order theory, one restricts to classes of partially ordered sets that are complete with respect to certain limit constructions.
For example, in lattice theory, one is interested in orders where all finite non-empty sets have both a least upper bound and a greatest lower bound.
www.worldhistory.com /wiki/L/Limit-preserving-function-(order-theory).htm   (1239 words)

  
 Commutative Rings - Irving Kaplansky
The idea of an adjoint functor was formulated by Daniel Kan in 1958.Like many of the concepts in category theory, it was suggested by the needs of homological algebra, which was at the time devoted to computations.
Adjoint functors are one method; the notion of universal properties provide another, essentially equivalent but arguably more concrete approach.Universal properties are also based on category theory.
Then G is right adjoint to F, which expresses the universal property of kernels, and the co-unit of this adjunction yields the natural embedding of a homomorphisms kernel into the homomorphisms domain.A suitable variation of this example also shows that the kernel functors for vector spaces and for modules are right adjoints.
www.vikramasila.org /396489_irving-kaplansky_1114291889commutativeringswherecanibuychristianbookonline.html   (3392 words)

  
 The world's top adjoint functors websites
In accordance with the thinking of Saunders MacLane, any idea such as adjoint functors that occurs widely enough in mathematics should be studied for its own sake.
Let G : D → Ab be the functor which assigns to each homomorphism its kernel and let F : Ab → D be the morphism which maps the group A to the homomorphism A → 0.
Similarly, the group ring construction yields a functor from groupss to rings, left adjoint to the functor that assigns to a given ring its group of units.
dirs.org /wiki-article-tab.cfm/adjoint_functors   (3142 words)

  
 PlanetMath: representable functor
A vast number of important objects in mathematics are defined as representing functors.
Cross-references: decide, natural transformations, theorem, primary, schemes, property, ring, adjoint, Yoneda Lemma, isomorphic, category of sets, category, between, contravariant functor
This is version 7 of representable functor, born on 2001-12-12, modified 2005-09-16.
planetmath.org /encyclopedia/RepresentableFunctor.html   (217 words)

  
 Category Theory
Suffice it to say that adjoint functors pervade mathematics and this pervasiveness is certainly one of the most mysterious fact that category theory reveals about mathematics and probably thinking in general.
In order to give a general definition of the latter, they defined the notion of functor, borrowing the terminology from Carnap, and in order to give a general definition of functor, they defined the notion of category, borrowing this time from Kant and Aristotle.
By the early seventies, the concept of adjoint functors was considered to be the central concept of category theory.
plato.stanford.edu /entries/category-theory   (7029 words)

  
 [No title]
ON AN ADJOINT FUNCTOR TO THE THOM FUNCTOR Yuli B. Rudyak March 1999 Abstract.
We construct a right adjoint functor to the Thom functor, i.e., * *to the functor which assigns the Thom space T to a vector bundle.
However, in order to do t* *he next step, a lifting to the geometrical level, one must prove that the thomific* *ation commutes with the functor Tot, and this problem looks quite complicated, cf.
hopf.math.purdue.edu /Rudyak/ThomAdjoint.txt   (881 words)

  
 Category Theory (Reading Course)
The first is a functor from the category Ens of sets to itself.
Category theory is a kind of network algebra which provides a general framework for describing mathematical objects and their interrelations.
We will develop a few basic notions from category theory, including functors (arrows between categories) and natural transformations (arrows between functors), leading up to the adjoint functor theorem.
www.georgetown.edu /faculty/kainen/category.html   (1030 words)

  
 week190
At the conference, she gave a nice talk about what it means when a quantum theory formulated in terms of C*-algebras has many inequivalent Hilbert space representations.
This is the same as being a totally ordered 0-element set or being a totally ordered 1-element set or being a totally ordered 2-element set or...
Next, suppose H is the structure "being a totally ordered set with 1 or 2 elements".
math.ucr.edu /home/baez/week190.html   (3419 words)

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