
A linear space \(S\) is called \(d\)-homogeneous, if whenever the linear structures induced on two subsets \(S_1\) and \(S_2\) of cardinality at most \(d\) are isomorphic, there is at least one automorphism \(S\) mapping \(S_1\) onto \(S_2\); if every isomorphism from \(S_1\) to \(S_2\) can be extended to an automorphism of \(S\), we shall say that \(S\) is \(d\)-ultrahomogeneous. \(S\) is called homogeneous (resp. ultrahomogeneous) if it is \(d\)-homogeneous (resp. ultrahomogeneous) for all positive integers \(d\). In this paper it is obtained a complete classification of all homogeneous (resp. ultrahomogeneous) linear spaces \(S\), without making any finiteness assumption on the number of points of \(S\). Theorem. Any 6-homogeneous linear space is homogeneous. Any homogeneous linear space is one of the following: (1) a linear space reduced to a single point (and no line) or to a single line; (2) a linear spaces all of whose lines have exactly two points; (3) the Desarguesian affine plane \(AG(2,3)\); (3) one of the Desarguesian projective planes \(PG(2,2)\), \(PG(2,3)\) or \(PG(2,4)\). Any homogeneous linear space is ultrahomogeneous, except \(AG(2,3)\) and \(PG(2,4)\). Note also that \(PG(2,5)\) is not homogeneous, but it is \(5\)-homogeneous.
Mathématiques, homogeneous linear spaces, automorphisms, Computational Theory and Mathematics, linear space, Discrete Mathematics and Combinatorics, Finite partial geometries (general), nets, partial spreads, Theoretical Computer Science
Mathématiques, homogeneous linear spaces, automorphisms, Computational Theory and Mathematics, linear space, Discrete Mathematics and Combinatorics, Finite partial geometries (general), nets, partial spreads, Theoretical Computer Science
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 7 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Average | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Average |
