Contractible simplicial objects

Michael Barr; John F. Kennison; Robert M. Raphael

Commentationes Mathematicae Universitatis Carolinae (2019)

  • Volume: 60, Issue: 4, page 473-495
  • ISSN: 0010-2628

Abstract

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We raise the question of when a simplicial object in a catetgory is deemed contractible. The literature offers three definitions. One is the existence of an “extra degeneracy”, indexed by - 1 , which does not quite live up to the name. This can be strengthened to a “strong extra degeneracy". Another possibility is that it be homotopic to a constant simplicial object. Despite claims in the literature to the contrary, we show that all three are distinct concepts with strong extra degeneracy implies extra degeneracy implies homotopic to a constant and give explicit examples to show the converses fail.

How to cite

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Barr, Michael, Kennison, John F., and Raphael, Robert M.. "Contractible simplicial objects." Commentationes Mathematicae Universitatis Carolinae 60.4 (2019): 473-495. <http://eudml.org/doc/295068>.

@article{Barr2019,
abstract = {We raise the question of when a simplicial object in a catetgory is deemed contractible. The literature offers three definitions. One is the existence of an “extra degeneracy”, indexed by $-1$, which does not quite live up to the name. This can be strengthened to a “strong extra degeneracy". Another possibility is that it be homotopic to a constant simplicial object. Despite claims in the literature to the contrary, we show that all three are distinct concepts with strong extra degeneracy implies extra degeneracy implies homotopic to a constant and give explicit examples to show the converses fail.},
author = {Barr, Michael, Kennison, John F., Raphael, Robert M.},
journal = {Commentationes Mathematicae Universitatis Carolinae},
keywords = {contractible; homotopic to a constant; reduced homotopy; partial simplicial object},
language = {eng},
number = {4},
pages = {473-495},
publisher = {Charles University in Prague, Faculty of Mathematics and Physics},
title = {Contractible simplicial objects},
url = {http://eudml.org/doc/295068},
volume = {60},
year = {2019},
}

TY - JOUR
AU - Barr, Michael
AU - Kennison, John F.
AU - Raphael, Robert M.
TI - Contractible simplicial objects
JO - Commentationes Mathematicae Universitatis Carolinae
PY - 2019
PB - Charles University in Prague, Faculty of Mathematics and Physics
VL - 60
IS - 4
SP - 473
EP - 495
AB - We raise the question of when a simplicial object in a catetgory is deemed contractible. The literature offers three definitions. One is the existence of an “extra degeneracy”, indexed by $-1$, which does not quite live up to the name. This can be strengthened to a “strong extra degeneracy". Another possibility is that it be homotopic to a constant simplicial object. Despite claims in the literature to the contrary, we show that all three are distinct concepts with strong extra degeneracy implies extra degeneracy implies homotopic to a constant and give explicit examples to show the converses fail.
LA - eng
KW - contractible; homotopic to a constant; reduced homotopy; partial simplicial object
UR - http://eudml.org/doc/295068
ER -

References

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  5. Hamada S., 10.4995/agt.2015.1826, Appl. Gen. Topol. 16 (2015), no. 1, 15–17. MR3338816DOI10.4995/agt.2015.1826
  6. Khalimskiĭ E. D., The topologies of generalized segments, Dokl. Akad. Nauk SSSR 189 (1969), 740–743 (Russian). MR0256359
  7. Linton F. E. J., Applied functorial semantics, II, Sem. on Triples and Categorical Homology Theory, ETH, Zürich, 1966/67, Springer, Berlin, 1969, pages 53–74. MR0249485
  8. Meyer J.-P., 10.1016/0022-4049(84)90005-7, J. Pure Appl. Algebra 33 (1984), no. 2, 163–207. MR0754954DOI10.1016/0022-4049(84)90005-7
  9. Riehl E., Categorical Homotopy Theory, New Mathematical Monographs, 24, Cambridge University Press, Cambridge, 2014. MR3221774

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