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Properties of Incidence Geometries and Coset Geometries

Let us recall definitions of the properties described in this section.

An incidence geometry Gamma is flag--transitive if for every two flags x, y of the same type of Gamma, there exists an element g of Aut(Gamma) such that g(x) = y. We also say that Aut(Gamma) acts flag--transitively in this case.

Moreover, it is a flag--transitive geometry if it contains at least one chamber.

A coset geometry Gamma(G; (G_i)_(i in I)) is flag--transitive if for every two flags x, y of the same type of Gamma, there exists an element g of G such that g(x) = y. It is then a flag--transitive geometry since the set { (G_i)_(i in I) } is a chamber of Gamma.

IsFTGeometry(D) : IncGeom -> BoolElt
Given an incidence geometry D, return true iff the automorphism group of D acts flag--transitively on D and D has at least one chamber.
IsFTGeometry(C) : CosetGeom -> BoolElt
Given a coset geometry C, return true iff the group of C acts flag--transitively on C.
IsFirm(D) : IncGeom -> BoolElt
Given a flag--transitive incidence geometry D, return true iff every flag of D is contained in at least two chambers.
IsFirm(C) : CosetGeom -> BoolElt
Given a flag--transitive coset geometry C, return true iff every flag of C is contained in at least two chambers.
IsThin(D) : IncGeom -> BoolElt
Given a flag--transitive incidence geometry D, return true iff every flag of D is contained in exactly two chambers.
IsThin(C) : CosetGeom -> BoolElt
Given a flag--transitive coset geometry C, return true iff every flag of C is contained in exactly chambers.
IsThick(D) : IncGeom -> BoolElt
Given a flag--transitive incidence geometry D, return true iff every flag of D is contained in exactly three chambers.
IsThick(C) : CosetGeom -> BoolElt
Given a flag--transitive coset geometry C, return true iff every flag of C is contained in exactly three chambers.
IsResiduallyConnected(D) : IncGeom -> BoolElt
IsRC(D) : IncGeom -> BoolElt
Given a flag--transitive incidence geometry D, return true iff every residue of rank at least two of D has a connected incidence graph.
IsResiduallyConnected(C) : CosetGeom -> BoolElt
IsRC(C) : CosetGeom -> BoolElt
Given a flag--transitive coset geometry C, return true iff every residue of rank at least two of C has a connected incidence graph.
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