\(A_\infty \)-Category Theory

2 Gradings

Definition 1 Parity group
#

The type of parities is \(\mathbb {Z}/2\mathbb {Z}\), implemented as ZMod 2.

Definition 2 Grading
#

A grading on a type \(\beta \) consists of an additive commutative group structure on \(\beta \), together with homomorphisms

\[ \phi : \mathbb {Z} \to \beta , \qquad \sigma : \beta \to \mathbb {Z}/2\mathbb {Z}, \]

such that \(\sigma (\phi (n))\) is the parity class of \(n\) for every integer \(n\).

Definition 3 Integer shift
#

For a grading index \(\beta \), is the image of \(n \in \mathbb {Z}\) under the distinguished map \(\phi : \mathbb {Z} \to \beta \).

Definition 4 Graded \(R\)-module
#

For a commutative ring \(R\), a graded \(R\)-module is a \(\beta \)-indexed family of \(R\)-modules, implemented as a graded object in ModuleCat R.

Definition 5 \(R\)-linear graded quiver
#

An \(R\)-linear graded quiver on an object type \(\mathrm{Obj}\) assigns to each pair of objects \((X,Y)\) a graded \(R\)-module of morphisms from \(X\) to \(Y\).