In the paper, https://www.math.uni-bielefeld.de/~grigor/quivers.pdf
I have two questions regarding the definitions on Page $5$.
- What is $\sum c$ in Equation $3.1$ ? Is this just a new edge connecting the starting vertex of edge $a$ to end vertex of edge $b$ in path $[ab]$?
- What does $N$ stand for in Equations $3.2$, and later in $3.3$? Is this a chain-complex operator?