Title:  Reaction graphs of combinatorial configurations

The concept of a reaction graph has its origin in mathematical chemistry. A molecular graph represents a constitutional formula of a chemical compound. A reaction graph is used to describe a special kind of a chemical reaction, called rearrangement, which transforms a given compound into an isomorphic compound. A reaction graph is the graph whose vertices are all possible isomorphic states of the compound and whose edges correspond to rearrangements. Instead of chemical compounds, we may consider reaction graphs of various combinatorial configurations where instead of rearrangements we consider certain well-defined small changes. These graphs are usually highly symmetric, and are quite often strongly regular. We present several examples of such reaction graphs.