Riemann curvature space

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Definition

Given data

A real vector space V with an inner product g (making it into the usual Euclidean space).

Definition part

The Riemann curvature space over V, denoted RC(V), is the space of multilinear forms on V in 4 variables, satisfying the following identities:

  1. R(X,Y,Z,T)=R(Y,X,Z,T) (viz R is antisymmetric in the first two variables)
  2. R(X,Y,Z,T)=R(X,Y,T,Z) (viz R is antisymmetric in the last two variables)
  3. R(X,Y,Z,T)+R(Y,Z,X,T)+R(Z,X,Y,T)=0 (The first Bianchi identity)
  4. R(X,Y,Z,T)=R(Z,T,X,Y) (this follows from the above three)

Note that RC(V) sits naturally as a subspace inside the space Sym2(Alt2(V)) (follows from the facts (1), (2) and (4).