Baer Subplanes, Ovals and Unitals
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چکیده
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Some geometric aspects of finite abelian group
Let Π be a finite projective plane admitting a large abelian collineation group. It is well known that this situation may be studied by algebraic means (via a representation by suitable types of difference sets), namely using group rings and algebraic number theory and leading to rather strong nonexistence results. What is less well-known is the fact that the abelian group (and sometimes its gr...
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If z has order q* and n is of the form n =m+q, then either k= m(q*+q+ l), or k= (m+q)(q*-q+ 1). Obviously, in case m=O, K is a maximal arc. Moreover, if m = 1 and q is a prime power, then K is either a Baer subplane or a unital [lo]. Furthermore, m pairwise disjoint Baer subplanes of n always yield a set of type (m, m + q) and size m(q* + q + 1). In case rc is Desarguesian, such a set does exis...
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In PG(2, q), q a prime power, we study the set T of Baer subplanes that contain a fixed triangle PQR. To construct a linear rank 2–geometry over T , we determine the dihedral groups, their orders and possible extensions that are generated by the involutions of two Baer subplanes of T . If q+1 is an odd prime, the (q+1)2 Baer subplanes through the triangle PQR are the points of an affine plane A...
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First we define relations between the v = (s2+s+1}(s+l) flags (point-line incident pairs) of a finite projective plane of order s. Two flags a =(p,i) and b =(p' ,l'), where p and p' are two points and l and l' are two lines of the projective plane, are defined to be first associates if either p = p' or l = l'; second associates if p # p', l # l' but either p is incident also with l' or p' is in...
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of order n on V . It follows that R induces a projective collineation φ on the (n−1)dimensional projective space PG(n−1, q). We call φ and any projective collineation conjugate to φ a Frobenius collineation. In the present paper we shall study the case n = 3, that is, the Frobenius collineations of the projective plane PG(2, q). Let P = PG(2, q). Then every Singer cycle σ (see Section 3) of P d...
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