منابع مشابه
A family of 4-designs on 38 points
Using the Kramer-Mesner method, 4-(26, 6, λ) designs with PSL(2, 25) as a group of automorphisms and with λ in the set {30, 51, 60, 81, 90, 111} are constructed. The search uses specific partitioning of columns of the orbit incidence matrix, related to so-called “quasi-designs”. Actions of groups PSL(2, 25), PGL(2, 25) and twisted PGL(2, 25) are being compared. It is shown that there exist 4-(2...
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This paper examines some of the properties of point-weight incidence structures, i.e. incidence structures for which every point is assigned a positive integer weight. In particular it examines point-weight designs with a design condition that stipulates that any two “identical” sets of t points must lie on the same number of blocks. We introduce a new class of designs with this property: row-s...
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This survey discusses recent developments in the context of spherical designs and minimal energy point configurations on spheres. The recent solution of the long standing problem of the existence of spherical t-designs on S with O(td) number of points by A. Bondarenko, D. Radchenko, and M. Viazovska attracted new interest to this subject. Secondly, D. P. Hardin and E. B. Saff proved that point ...
متن کاملTwo Results on Special Points
We show that there is a nowhere ccc σ-compact space which has a remote point. We show that it is consistent to have non-compact σ-compact separable space X such that every point of the remainder is a limit of a countable discrete subset of non-isolated points of X. This example shows that one cannot prove in ZFC that every locally compact non-compact space has discrete weak P -points.
متن کاملNonincident points and blocks in designs
In this paper, we study the problem of finding the largest possible set of s points and s blocks in a balanced incomplete block design, such that that none of the s points lie on any of the s blocks. We investigate this problem for two types of BIBDs: projective planes and Steiner triple systems. For a projective plane of order q, we prove that s ≤ 1 + (q + 1)(√q − 1) and we also show that equa...
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ژورنال
عنوان ژورنال: Discrete Mathematics
سال: 1997
ISSN: 0012-365X
DOI: 10.1016/s0012-365x(96)00021-0