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| Natura: | Preprint |
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2024
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| Accesso online: | https://arxiv.org/abs/2403.00519 |
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| _version_ | 1866917601575174144 |
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| author | De Beule, Jan Mannaert, Jonathan Storme, Leo |
| author_facet | De Beule, Jan Mannaert, Jonathan Storme, Leo |
| contents | This paper focuses on non-existence results for Cameron-Liebler $k$-sets. A Cameron-Liebler $k$-set is a collection of $k$-spaces in $\mathrm{PG}(n,q)$ or $\mathrm{AG}(n,q)$ admitting a certain parameter $x$, which is dependent on the size of this collection. One of the main research questions remains the (non-)existence of Cameron-Liebler $k$-sets with parameter $x$. This paper improves two non-existence results. First we show that the parameter of a non-trivial Cameron-Liebler $k$-set in $\mathrm{PG}(n,q)$ should be larger than $q^{n-\frac{5k}{2}-1}$, which is an improvement of an earlier known lower bound. Secondly, we prove a modular equality on the parameter $x$ of Cameron-Liebler $k$-sets in $\mathrm{PG}(n,q)$ with $x<\frac{q^{n-k}-1}{q^{k+1}-1}$, $n\geq 2k+1$, $n-k+1\geq 7$ and $n-k$ even. In the affine case we show a similar result for $n-k+1\geq 3$ and $n-k$ even. This is a generalization of earlier known modular equalities in the projective and affine case. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_00519 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | On two non-existence results for Cameron-Liebler $k$-sets in $\mathrm{PG}(n,q)$ De Beule, Jan Mannaert, Jonathan Storme, Leo Combinatorics This paper focuses on non-existence results for Cameron-Liebler $k$-sets. A Cameron-Liebler $k$-set is a collection of $k$-spaces in $\mathrm{PG}(n,q)$ or $\mathrm{AG}(n,q)$ admitting a certain parameter $x$, which is dependent on the size of this collection. One of the main research questions remains the (non-)existence of Cameron-Liebler $k$-sets with parameter $x$. This paper improves two non-existence results. First we show that the parameter of a non-trivial Cameron-Liebler $k$-set in $\mathrm{PG}(n,q)$ should be larger than $q^{n-\frac{5k}{2}-1}$, which is an improvement of an earlier known lower bound. Secondly, we prove a modular equality on the parameter $x$ of Cameron-Liebler $k$-sets in $\mathrm{PG}(n,q)$ with $x<\frac{q^{n-k}-1}{q^{k+1}-1}$, $n\geq 2k+1$, $n-k+1\geq 7$ and $n-k$ even. In the affine case we show a similar result for $n-k+1\geq 3$ and $n-k$ even. This is a generalization of earlier known modular equalities in the projective and affine case. |
| title | On two non-existence results for Cameron-Liebler $k$-sets in $\mathrm{PG}(n,q)$ |
| topic | Combinatorics |
| url | https://arxiv.org/abs/2403.00519 |