Introduction to Cluster Algebras. Chapters 1-3
  This is a preliminary draft of Chapters 1-3 of our forthcoming textbook "Introduction to Cluster Algebras." This installment contains:   Chapter 1. Total positivity   Chapter 2. Mutations of quivers and matrices   Chapter 3. Clusters and seeds 
Sergey Fomin, Lauren Williams, Andrei Zelevinsky
math.CO math.RA math.RT