Applications Of Strongly Regular Graphs I am currently working on a thesis regarding some existence problems on strongly regular graphs. But it is actually my first encounter with them. Though i am done solving my problems, But in order to have a better feel of this concept, i want to lay my hands on applications. I have searched a lot of the articles on SRGs but i haven't gotten anyone dealing with applications. Please can anyone suggest an application, or a paper or material that deals with applications of SRGs or DRGs. Thanks
 A: Not really an application per se, but rather a connection with the notion of strong regularity and the isomorphism problem. What follows is just a shallow description but I can add references/expand if you need something more.
It is well known that if a graph has many different eigenvalues (multiplicity of eigenvalues is bounded) then the isomorphism problem on such a class of graphs is solvable in polynomial time.
As an interesting fact almost all graphs have distinct eigenvalues.
Now a strongly regular graph is characterized as a graph having precisely three distinct eigenvalues so in this sense its far from the property described above. 
As it turns out there is no efficient algorithm for isomorphism of strongly-regular graphs and in particular Babai conjectures that the hardest instance of the isomorphism problem is in fact attained for strongly-regular graphs.
Looking from another perspective the isomorphism problem is equivalent to computing the automorphism group of a graph and specifically this implies that one is able to distinguish different vertices of a graph.
In this sense strongly-regular graphs are hard to attack since almost all vertices look the same - they all have the same number of neighbors and the number of common neighbors of two vertices only depends on their adjacency.
Again, what I am saying is quite informal but I guess it can give you an insight into the notion of SRG's.
