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Natural weak factorization systems
 Archivum Mathematicum
"... Dedicated to Jiˇrí Rosick´y at the occasion of his sixtieth birthday Abstract. In order to facilitate a natural choice for morphisms created by the (left or right) lifting property as used in the definition of weak factorization systems, the notion of natural weak factorization system in the categor ..."
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Dedicated to Jiˇrí Rosick´y at the occasion of his sixtieth birthday Abstract. In order to facilitate a natural choice for morphisms created by the (left or right) lifting property as used in the definition of weak factorization systems, the notion of natural weak factorization system in the category K is introduced, as a pair (comonad, monad) overK 2. The link with existing notions in terms of morphism classes is given via the respective Eilenberg– Moore categories. 1.
LeftDetermined Model Categories and Universal Homotopy Theories
"... We say that a model category is leftdetermined if the weak equivalences are generated (in a sense specified below) by the cofibrations. While the model category of simplicial sets is not leftdetermined, we show that its nonoriented variant, the category of symmetric simplicial sets (in the sense ..."
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We say that a model category is leftdetermined if the weak equivalences are generated (in a sense specified below) by the cofibrations. While the model category of simplicial sets is not leftdetermined, we show that its nonoriented variant, the category of symmetric simplicial sets (in the sense of Lawvere and Grandis) carries a natural leftdetermined model category structure. This is used to give another and, as we believe simpler, proof of a recent result of D. Dugger about universal homotopy theories. 1
Metric, Topology and Multicategory  A Common Approach
 J. Pure Appl. Algebra
, 2001
"... For a symmetric monoidalclosed category V and a suitable monad T on the category of sets, we introduce the notion of reflexive and transitive (T , V)algebra and show that various old and new structures are instances of such algebras. Lawvere's presentation of a metric space as a Vcategory is incl ..."
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Cited by 12 (7 self)
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For a symmetric monoidalclosed category V and a suitable monad T on the category of sets, we introduce the notion of reflexive and transitive (T , V)algebra and show that various old and new structures are instances of such algebras. Lawvere's presentation of a metric space as a Vcategory is included in our setting, via the BettiCarboniStreetWalters interpretation of a Vcategory as a monad in the bicategory of Vmatrices, and so are Barr's presentation of topological spaces as lax algebras, Lowen's approach spaces, and Lambek's multicategories, which enjoy renewed interest in the study of ncategories. As a further example, we introduce a new structure called ultracategory which simultaneously generalizes the notions of topological space and of category.
Free Quillen Factorization Systems
, 2002
"... The notion of Quillen factorization system is obtained by strengthening the left and right lifting properties in a Quillen model category to the unique diagonalization property. An equivalent description of this notion is given in terms of a double factorization system which decomposes each arrow u ..."
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The notion of Quillen factorization system is obtained by strengthening the left and right lifting properties in a Quillen model category to the unique diagonalization property. An equivalent description of this notion is given in terms of a double factorization system which decomposes each arrow uniquely into three factors. The free category with Quillen factorization system over a given category is described.
Categorical aspects of polar decomposition
, 2010
"... Polar decomposition unquestionably provides a notion of factorization in the category of Hilbert spaces. But it does not fit existing categorical notions, mainly because its factors are not closed under composition. We observe that the factors are images of functors. This leads us to consider notion ..."
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Polar decomposition unquestionably provides a notion of factorization in the category of Hilbert spaces. But it does not fit existing categorical notions, mainly because its factors are not closed under composition. We observe that the factors are images of functors. This leads us to consider notions of factorization that emphasize reconstruction of the composite
ON THE FUNCTOR ℓ 2
"... and both categories are enriched over algebraic domains. The functor preserves daggers, monoidal structures, enrichment, and various (co)limits, but has no adjoints. Up to unitaries, its direct image consists precisely of the partial isometries, but its essential image consists of all continuous lin ..."
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and both categories are enriched over algebraic domains. The functor preserves daggers, monoidal structures, enrichment, and various (co)limits, but has no adjoints. Up to unitaries, its direct image consists precisely of the partial isometries, but its essential image consists of all continuous linear maps between Hilbert spaces. 1.
BY
"... All Rights ReservedTo L, who let me go.Table of Contents Acknowledgments....................................... Abstract............................................ Preface............................................. vi ..."
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All Rights ReservedTo L, who let me go.Table of Contents Acknowledgments....................................... Abstract............................................ Preface............................................. vi
Higher Dimensional Categories: Model Categories and Weak Factorisation Systems
, 2007
"... Loosely speaking, “homotopy theory ” is a perspective which treats objects as equivalent if they have the same “shape ” which, for a category theorist, occurs when there exists a certain class W of morphisms that one would like to invert, but which are not in fact isomorphisms. Model categories prov ..."
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Loosely speaking, “homotopy theory ” is a perspective which treats objects as equivalent if they have the same “shape ” which, for a category theorist, occurs when there exists a certain class W of morphisms that one would like to invert, but which are not in fact isomorphisms. Model categories provide a setting in which one can do “abstract homotopy
FACTORIZATION SYSTEMS
"... Abstract. These notes were written to accompany a talk given in the Algebraic Topology and Category Theory Proseminar in Fall 2008 at the University of Chicago. We first introduce orthogonal factorization systems, give a few examples, and prove some basic theorems. Next, we turn to weak factorizatio ..."
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Abstract. These notes were written to accompany a talk given in the Algebraic Topology and Category Theory Proseminar in Fall 2008 at the University of Chicago. We first introduce orthogonal factorization systems, give a few examples, and prove some basic theorems. Next, we turn to weak factorization systems, which play an important role in the theory of model categories, a connection which we make explicit. We discuss what it means for a weak factorization system to be functorial and observe that functoriality does not guarantee the existence of natural lifts. This leads us, naturally one might say, to the definition of a natural weak factorization system, which is where we conclude these notes. The reader is assumed to have some familiarity with category theory — functors, limits and colimits, naturality, monads and comonads, comonoids, 2categories, and some basic categorical terminology; [9] is a good reference for any concepts that may be unfamiliar.