1,721,178 research outputs found

    On two-intersection sets with respect to hyperplanes in projective spaces

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    In \cite{BLLA} a construction of a class of two-intersection sets with respect to hyperplanes in PG(r1,qt)PG(r-1,q^t), rtrt even, is given, with the same parameters as the union of (qt/21)/(q1)(q^{t/2}-1)/(q-1) disjoint Baer subgeometries if tt is even and the union of (qt1)/(q1)(q^t-1)/(q-1) elements of an (r/21)(r/2-1)-spread in PG(r1,qt)PG(r-1,q^t) if tt is odd. In this paper we prove that although they have the same parameters, they are different. This was previously proved in \cite{BABLLA} in the special case where r=3r=3 and t=4t=4

    Scattered spaces with respect to a spread in PG(n,q)

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    A scattered subspace of PG(n1,q)PG(n-1,q) with respect to a (t1)(t-1)-spread SS is a subspace intersecting every spread element in at most a point. Upper and lower bounds for the dimension of a maximum scattered space are given. In the case of a normal spread new classes of two intersection sets with respect to hyperplanes in a projective space are obtained using scattered spaces

    On the classification of semifield flocks

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    It is shown that the only semifield flocks of the quadratic cone of PG(3,qn)PG(3,q^n) with q4n28n+2q \geq 4n^2-8n+2 are the linear flocks and the Kantor-Knuth semifield flocks. This follows from the main theorem which states that there are no subplanes of order qq contained in the set of internal points of a conic in PG(2,qn)PG(2,q^n) for those qq exceeding the bound

    The Kakeya problem: a gap in the spectrum and classification of the smallest examples

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    The authors present a new example of a small Kakeya set in the affine plane AG(2,q) and they give the classification of the smallest Kakeya sets with at most 1/2q(q+2)+q/4 points, in case q even

    Linear (q+1)(q+1)-fold blocking sets in {\rm PG}(2,q\sp4).

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    A (q+1)(q+1)-fold blocking set of size (q+1)(q4+q2+1)(q+1)(q^4 + q^2 + 1) in PG(2,q4)PG(2,q^4) is constructed, which is not the union of q+1q+1 disjoint Baer subplanes

    The finite field Kakeya problem

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    A Besicovitch set in AG(n; q) is a set of points containing a line in every direction. The Kakeya problem is to determine the minimal size of such a set. We solve the Kakeya problem in the plane, and substantially improve the known bounds for n > 4
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