Non-derivable strongly regular graphs from quasi-symmetric designs
| Autor: | Rajendra M. Pawale, Shubhada M. Nyayate, Mohan S. Shrikhande |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Discrete mathematics
Block graph Strongly regular graph Symmetric graph Voltage graph 0102 computer and information sciences 01 natural sciences Distance-regular graph Theoretical Computer Science law.invention Combinatorics 010201 computation theory & mathematics law Line graph Random regular graph Discrete Mathematics and Combinatorics Regular graph Mathematics |
| Zdroj: | Discrete Mathematics. 339:759-769 |
| ISSN: | 0012-365X |
| Popis: | A quasi-symmetric design (QSD) is a ( v , k , λ ) design with two intersection numbers x , y , where 0 ? x < y < k . The block graph of QSD is a strongly regular graph (SRG). It is known that there are SRGs which are not block graphs of QSDs. We derive necessary conditions on the parameters of a SRG to be feasible as the block graph of a QSD. We apply these conditions to rule out many infinite families of such SRGs.We also show that the pseudo Latin square graph L 5 ( n ) , n ? 5 ; the Negative Latin square graphs N L e ( e 2 + 3 e ) and N L e ( e + 2 ) , with 2 ? e or their complements cannot be the block graph of a QSD. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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