Bracket ring
In
generic d-by-n matrix
(xij).
The bracket ring may be regarded as the ring of polynomials on the image of a Grassmannian under the Plücker embedding.[1]
For given d ≤ n we define as formal variables the brackets [λ1 λ2 ... λd] with the λ taken from {1,...,n}, subject to [λ1 λ2 ... λd] = − [λ2 λ1 ... λd] and similarly for other
transpositions. The set
Λ(n,d) of size generates a polynomial ring K[Λ(n,d)] over a field K. There is a homomorphism Φ(n,d) from K[Λ(n,d)] to the polynomial ring K[xi,j] in nd indeterminates given by mapping
[λ1 λ2 ... λd] to the determinant of the d by d matrix consisting of the columns of the xi,j indexed by the λ. The bracket ring B(n,d) is the image of Φ. The kernel I(n,d) of Φ encodes the relations or syzygies that exist between the minors of a generic n by d matrix. The projective variety defined by the ideal I is the (n−d)d dimensional Grassmann variety whose points correspond to d-dimensional subspaces of an n-dimensional space.[2]
To compute with brackets it is necessary to determine when an expression lies in the ideal I(n,d). This is achieved by a straightening law due to Young (1928).[3]
See also
References
- Zbl 0944.52006
- ^ Sturmfels (2008) pp.78–79
- ^ Sturmfels (2008) p.80
- Dieudonné, Jean A.; Carrell, James B. (1970), "Invariant theory, old and new", Zbl 0196.05802
- Dieudonné, Jean A.; Carrell, James B. (1971), Invariant Theory, Old and New, Boston, MA: Zbl 0258.14011
- Zbl 1154.13003
- Zbl 0727.13005, archived from the originalon 1997-11-15