scholarly journals Computer algebra investigation of known primitive triangle-free strongly regular graphs

10.29007/bdgp ◽  
2018 ◽  
Author(s):  
Matan Ziv-Av ◽  
Mikhail Klin

With the aid of computer algebra systems COCO and GAP withits packages we are investigating all seven known primitivetriangle-free strongly regular graphs on 5, 10, 16, 50, 56,77 and 100 vertices. These graphs are rank 3 graphs, havinga rich automorphism group. The embeddings of each graphfrom this family to other ones are described, theautomorphic equitable partitions are classified, allequitable partitions in the graphs on up to 50 vertices areenumerated. Basing on the reported computer aided resultsand using techniques of coherent configurations, a few newmodels of these graphs are suggested, which are relying onknowledge of just a small part of symmetries of a graph inconsideration.

10.37236/5067 ◽  
2016 ◽  
Vol 23 (2) ◽  
Author(s):  
Anurag Bishnoi ◽  
Bart De Bruyn

We construct and study a new near octagon of order $(2,10)$ which has its full automorphism group isomorphic to the group $G_2(4):2$ and which contains $416$ copies of the Hall-Janko near octagon as full subgeometries. Using this near octagon and its substructures we give geometric constructions of the $G_2(4)$-graph and the Suzuki graph, both of which are strongly regular graphs contained in the Suzuki tower. As a subgeometry of this octagon we have discovered another new near octagon, whose order is $(2,4)$.


2011 ◽  
Vol 2011 ◽  
pp. 1-12
Author(s):  
Dean Crnković ◽  
Vedrana Mikulić Crnković

We describe a construction of primitive 2-designs and strongly regular graphs from the simple groups , and . The designs and the graphs are constructed by defining incidence structures on conjugacy classes of maximal subgroups of , and . In addition, from the group , we construct 2-designs with parameters and having the full automorphism group isomorphic to .


2015 ◽  
Vol 92 (1) ◽  
pp. 482-486
Author(s):  
A. A. Makhnev ◽  
D. V. Paduchikh

2010 ◽  
Vol 17 (03) ◽  
pp. 389-414 ◽  
Author(s):  
Faryad Ali ◽  
Jamshid Moori

The Fischer group [Formula: see text] is the largest 3-transposition sporadic group of order 2510411418381323442585600 = 222.316.52.73.11.13.17.23.29. It is generated by a conjugacy class of 306936 transpositions. Wilson [15] completely determined all the maximal 3-local subgroups of Fi24. In the present paper, we determine the Fischer-Clifford matrices and hence compute the character table of the non-split extension 37· (O7(3):2), which is a maximal 3-local subgroup of the automorphism group Fi24 of index 125168046080 using the technique of Fischer-Clifford matrices. Most of the calculations are carried out using the computer algebra systems GAP and MAGMA.


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