# Difference between revisions of "ApCoCoA-1:BB.LiftAS"

## BB.LiftAS

Compute the border basis scheme ideal generators obtained from lifting of AS neighbors.

### Syntax

BB.LiftAS(OO:LIST):LIST


### Description

Computes the generators of the border basis scheme ideal <formula>I(\mathbb{B}_\mathcal{O})</formula> that result from the lifting of across-the-street neighbors. The input is a list of terms OO (2nd element of type POLY). The output is a list of poly in the ring <formula>BBS=K[c_{ij}]</formula>.

• @param OO A list of terms representing an order ideal.

• @return A list of generators of the border basis scheme ideal I(B_O) that results from the lifting of across-the-street neighbors in the border of OO. The polynomials will belong to the ring BBS=K[c_{ij}].

#### Example

Use QQ[x,y], DegRevLex;
BB.LiftAS([Poly(1), x, y, xy]);

[BBS :: c[1,2]c[2,3] - c[1,1]c[3,4] + c[1,4]c[4,3] - c[1,3]c[4,4],
BBS :: c[2,2]c[2,3] - c[2,1]c[3,4] + c[2,4]c[4,3] - c[2,3]c[4,4] + c[1,3],
BBS :: c[2,3]c[3,2] - c[3,1]c[3,4] + c[3,4]c[4,3] - c[3,3]c[4,4] - c[1,4],
BBS :: c[3,4]c[4,1] - c[2,3]c[4,2] + c[2,4] - c[3,3]]
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