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thin square (Definition)

Let us consider first the concept of a tree that enters in the definition of a thin square. Thus, a simplified notion of thin square is that of ``a continuous map from the unit square of the real plane into a Hausdorff space $X_H$ which factors through a tree'' ([1]).

Definition 0.1   A tree, is defined here as the underlying space $ |K| $ of a finite $ 1 $ -connected $ 1 $ -dimensional simplicial complex $ K $ and boundary $ \partial{I}^{2} $ of $ I^{2} = I \times I $ (that is, a square (interval) defined here as the Cartesian product of the unit interval $I :=[0,1]$ of real numbers).
Definition 0.2   A square map $ u:I^{2} \longrightarrow X $ in a topological space $ X $ is thin if there is a factorisation of $ u $ , $$ u : I^{2} \stackrel{\Phi_{u}}{\longrightarrow} J_{u} \stackrel{p_{u}}{\longrightarrow} X, $$ where $J_{u}$ is a tree and $ \Phi_{u} $ is piecewise linear (PWL) on the boundary $ \partial{I}^{2} $ of $ I^{2} $ .

Bibliography

1
R. Brown, K.A. Hardie, K.H. Kamps and T. Porter., A homotopy double groupoid of a Hausdorff space , Theory and Applications of Categories 10,(2002): 71-93.
2
R. Brown and C.B. Spencer: Double groupoids and crossed modules, Cahiers Top. Géom.Diff., 17 (1976), 343-362.
3
R. Brown and G. H. Mosa: Double algebroids and crossed modules of algebroids, University of Wales-Bangor, Maths Preprint, 1986.
4
K.A. Hardie, K.H. Kamps and R.W. Kieboom., A homotopy 2-groupoid of a Hausdorff Applied Categorical Structures, 8 (2000): 209-234.
5
Al-Agl, F.A., Brown, R. and R. Steiner: 2002, Multiple categories: the equivalence of a globular and cubical approach, Adv. in Math, 170: 711-118.




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See Also: copula

Other names:  AlgebraicallyThinSquares
Also defines:  tree, square
Keywords:  thin square, tree, square interval
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Cross-references: thin, topological space, map, real numbers, unit, Cartesian product, interval, boundary, simplicial complex, finite
There are 60 references to this entry.

This is version 18 of thin square, born on 2008-09-04, modified 2009-02-02.
Object id is 10988, canonical name is ThinSquare.
Accessed 1878 times total.

Classification:
AMS MSC55U40 (Algebraic topology :: Applied homological algebra and category theory :: Topological categories, foundations of homotopy theory)
 55N20 (Algebraic topology :: Homology and cohomology theories :: Generalized homology and cohomology theories)
 55N33 (Algebraic topology :: Homology and cohomology theories :: Intersection homology and cohomology)
 18D05 (Category theory; homological algebra :: Categories with structure :: Double categories, $2$-categories, bicategories and generalizations)

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