Abstract
E. Corominas introduced recently this notion for posets:P is projective if every mapf fromP 2 toP which is order preserving and idempotent (i.e.f(x, x)=x for allx ε P) is a projection. We consider extensions of this notion to other structures, as well as to maps withn variables. We prove thatn-projectivity forn≥2 is equivalent to 2-projectivity, with a single exception: the structure has the same morphisms as the collection of congruences associated with a vector space over ℤ/2, of dimension at least two. Focusing on relational structures, Arrow's Theorem is introduced as an example. We consider particular types of relational structures: posets, graphs and metric spaces, and discuss for these the specific examples of crowns, cycles and circles.
Similar content being viewed by others
References
Abels, H.,The projection property for buildings, preliminary version, Dec. 1991.
Arrow, K.,Social Choice and Individual Value, J. Wiley, New York, 1963.
Brown, K. S.,Buildings, Springer-Verlag, New York, 1989.
Corominas, E.,Sur les ensembles ordonnés projectifs et la propriété du point fixe. C. R. Acad. Sci. Paris t. 311 Sér. I (1990), 199–204.
Davey, B. A.,Monotone clones and congruence modularity. Order,6 (1990), 389–400.
Davey, B. A., McKenzie, R., Nation, J. B. andPálfy, P. P.,Braids and isotone clones. Algebra Universalis,32 (1994), 153–176.
Delhommé, C.,Propriétés de projection. Ph.D. Thesis. Université Claude-Bernard (Lyon 1) 1995, 148 pp.
Demetrovics, J. andRónyai, L.,Algebraic properties of crowns and fences. Order,6 (1989), 91–100.
Graham, R. L., Rotschild, B. andSpencer, J. H.,Ramsey Theory. John Wiley and Sons, New York, 1980.
Gumm, H. P.,Is there a Mal'cev theory for single algebras? Algebra Universalis,8 (1978), 320–329.
Hobby, D. andMcKenzie, R.,The structure of finite algebras. Contemporary Math.,76 (1988), 203.
Kaarli, K.,Affine complete abelian groups. Math. Nachr.,107 (1982), 235–239.
Langer, H. andPöschel, R.,Relational systems with trivial endomorphisms and polymorphisms, J. Pure Appl. Algebra,32 (1984), 129–142.
Larose, B.,Finite Projective Ordered Sets. Order,8 (1991), 33–44.
Mal'cev, A. I.,Iterative algebras and Post's varieties (Russian). Algebra i Logika,5 (1966), 5–24. English translation in Mal'cev A. I.,The metamathematics of algebraic systems, pp. 396–415, North-Holland, 1971.
McKenzie, R. N., McNulty, G. F. andTaylor, W. T.,Algebras, lattices varieties I. Wadsworth and Brooks/Cole, 1987.
Penot, J. P.,Une vue simplifiée de la théorie de la complexité. Gazette des math.,34 (1986), 62–77.
Pierce, R. S.,Introduction to the Theory of Abstract Algebras. Holt, Rinehart and Winston, New York, 1968.
Post, E.,The Two-valued Iterative Systems of Mathematical Logic. Annals of Math. Studies 5, Princeton University Press, 1941.
Quackenbush, R. W., Personal communication.
Rosenberg, I. G.,Minimal clones I. Lectures in Universal Algebra (L. Szabó and A. Szendrei, eds.), Colloq. Math. Soc. J. Bolyai 43, North-Holland (1986), 405–427.
Strietz, H.,Über Erzeugendenmengen endlicher Partitionenverbände, Studia Sci. Math.,12 (1977), 1–17.
Swierczkowski, S.,Algebras which are independently generated by every n elements. Fund. Math.,49 (1960), 93–104.
Szendrei, A.,Clones in universal algebra, Les Presses, U. de Montréal, Vol. 99, 1986, 166 pp.
Werner, H.,A Mal'cev condition for admissible relations. Algebra Universalis,3/2 (1973), 263.
Zádori, L.,Generation of finite partition lattices. Lectures in Universal Algebra. Colloquia Math. Soc. János Bolyai, Vol. 43, Szeged, 1983, pp. 573–586.
Author information
Authors and Affiliations
Additional information
Author supported by the French group PRC Math-Info, and NSERC of Canada.
Author supported by NSERC Grant OGP 5407 and FCAR Québec grant Eq 0537.
Author supported by NSERC Grant 69-3039.
Rights and permissions
About this article
Cite this article
Pouzet, M., Rosenberg, I.G. & Stone, M.G. A projection property. Algebra Universalis 36, 159–184 (1996). https://doi.org/10.1007/BF01234102
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01234102