def1 -- degrees of a basis of T^1

Synopsis

Usage:

D = def1 L
Inputs:
- L, a list, generators of a semigroup
Optional inputs:
- BaseField
- JustDegs
Outputs:
- D, a list, degrees of a basis of T^1(semigroupRing L)

Description

T^1(B) is the tangent space to the versal deformaion of the ring B, and is finite dimensional when B has isolated singularity. If B = S/I is a Cohen presentation, then T^1(B) = coker Hom(Omega_S, B) -> Hom(I/I^2, B). When B is a semigroup ring, then Henry Pinkham proved that an open subset of the space of elements of T1 of negative degree correspond to smoothings of the projective cone of the semigroup ring to Riemann surfaces

i1 : def1{2,3}

o1 = {-6, -4}

o1 : List

Ways to use def1:

def1(List)

For the programmer

The object def1 is a method function with options.