Introduction
Cluster algebras were originally introduced to aid the study of specific topics in Lie theory, but have since become much more widespread --- discussion of the applications of cluster algebras will be reserved for the “Applications” section of this paper, and will include more information on their origins. This paper will introduce the concept of “cluster algebras” in a freshman-friendly way. Before we can begin to really understand what this concept is, this paper will first introduce (or at least refresh your memory on) the ideas of graphs, group/ring theory, and “algebra” in a general sense.
For those with a basic knowledge of graph theory and algebra, a cluster algebra can be understood as a commutative subring (under a field of rational functions F) formed from the iterative mutation of an initial “seed” (or set) of elements from F (such that they can be used to generate F). The general idea here is that we start with a set of variables (the “initial seed”), then generate a directed tree which includes all possible states of iterated mutation (where this mutation is with respect to a particular variable within the seed in question), then take the union of all rational expressions, denoted by X, that arise within these new sets (which we call “clusters”) --- the ring generated by these cluster variables, R[X], is what we call the cluster algebra (which is naturally a subring of the field F, since in this context, F inherently includes the initial seed’s variables, meaning the constructed cluster variables are also members of F).
For those with little-to-no background in algebra, this paper will hopefully make the previous paragraph much less daunting, and perhaps even intuitive.
