0.0.1 Definitions of double, and higher dimensional algebroids, superalgebroids and generalized superalgebras.

Double algebroids

Definition 0.1. A double R–algebroid consists of a double category D, as detailed in ref.[2], such that each category structure has the additional structure of an R–algebroid. More precisely, a double R–algebroid D involves four related R–algebroids:

(0.1)

that satisfy the following rules:

• δ₂ⁱ∂ ₂^j = δ ₁^j∂ ₁ⁱ for i,j ∈{0, 1}

• (0.2)

  for i = 0, 1, β ∈ D and both sides are defined.

• (0.3)

  for all β ∈ D, r,s ∈ R and both sides are defined.

• (0.4)

  for i≠j, whenever both sides are defined.

The definition of a double algebroid specified above was introduced by Brown and Mosa [1]. Two functors can be then constructed, one from the category of double algebroids to the category of crossed modules of algebroids, whereas the reverse functor is the unique adjoint (up to natural equivalence). The construction of such functors requires the following definition.

0.1 Category of double algebroids

A morphism f : D →ℰ of double algebroids is then defined as a morphism of truncated cubical sets which commutes with all the algebroid structures. Thus, one can construct a category DA of double algebroids and their morphisms. The main construction in this subsection is that of two functors η,η′ from this category DA to the category CM of crossed modules of algebroids.

Let D be a double algebroid. One can associate to D a crossed module μ : M→D₁. Here M(x,y) will consist of elements m of D with boundary of the form: 0 1

(0.5)

that is M(x,y) = {m ∈ D : ∂₁¹m = 0 _xy,∂₂⁰m = 1 _x,∂₂¹m = 1 _y}.

0.2 Cubic and Higher dimensional algebroids

One can extend the above notion of double algebroid to cubic and higher dimensional algebroids.

The concepts of 2-algebroid, 3-algebroid,..., n–algebroid and superalgebroid are however quite distinct from those of double, cubic,..., n–tuple algebroid, and have technically less complicated definitions.

References