Anzahl theorems for disjoint subspaces generating a non-degenerate subspace II: quadratic forms
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| Format: | Preprint |
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2024
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| _version_ | 1866914952025997312 |
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| author | De Boeck, Maarten Van de Voorde, Geertrui |
| author_facet | De Boeck, Maarten Van de Voorde, Geertrui |
| contents | In this paper, we solve a classical counting problem for non-degenerate quadratic forms defined on a vector space in odd characteristic; given a subspace $π$, we determine the number of non-singular subspaces that are trivially intersecting with $π$ and span a non-singular subspace with $π$. Lower bounds for the quantity of such pairs where $π$ is non-singular were first studied in `Glasby, Niemeyer, Praeger (Finite Fields Appl., 2022)', which was later improved for even-dimensional subspaces in `Glasby, Ihringer, Mattheus (Des. Codes Cryptogr., 2023)' and generalised in `Glasby, Niemeyer, Praeger (Linear Algebra Appl., 2022)'. The explicit formulae, which allow us to give the exact proportion and improve the known lower bounds were derived in the symplectic and Hermitian case in `De Boeck and Van de Voorde (Linear Algebra Appl. 2024)'. This paper deals with the more complicated quadratic case. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2409_12312 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Anzahl theorems for disjoint subspaces generating a non-degenerate subspace II: quadratic forms De Boeck, Maarten Van de Voorde, Geertrui Combinatorics 51A50, 51E20 In this paper, we solve a classical counting problem for non-degenerate quadratic forms defined on a vector space in odd characteristic; given a subspace $π$, we determine the number of non-singular subspaces that are trivially intersecting with $π$ and span a non-singular subspace with $π$. Lower bounds for the quantity of such pairs where $π$ is non-singular were first studied in `Glasby, Niemeyer, Praeger (Finite Fields Appl., 2022)', which was later improved for even-dimensional subspaces in `Glasby, Ihringer, Mattheus (Des. Codes Cryptogr., 2023)' and generalised in `Glasby, Niemeyer, Praeger (Linear Algebra Appl., 2022)'. The explicit formulae, which allow us to give the exact proportion and improve the known lower bounds were derived in the symplectic and Hermitian case in `De Boeck and Van de Voorde (Linear Algebra Appl. 2024)'. This paper deals with the more complicated quadratic case. |
| title | Anzahl theorems for disjoint subspaces generating a non-degenerate subspace II: quadratic forms |
| topic | Combinatorics 51A50, 51E20 |
| url | https://arxiv.org/abs/2409.12312 |