7,229 research outputs found
On curves with one place at infinity
Let be a plane curve. We give a procedure based on Abhyankar's
approximate roots to detect if it has a single place at infinity, and if so
construct its associated -sequence, and consequently its value
semigroup. Also for fixed genus (equivalently Frobenius number) we construct
all -sequences generating numerical semigroups with this given genus.
For a -sequence we present a procedure to construct all curves having
this associated sequence.
We also study the embeddings of such curves in the plane. In particular, we
prove that polynomial curves might not have a unique embedding.Comment: 14 pages, 2 figure
Isolated factorizations and their applications in simplicial affine semigroups
We introduce the concept of isolated factorizations of an element of a
commutative monoid and study its properties. We give several bounds for the
number of isolated factorizations of simplicial affine semigroups and numerical
semigroups. We also generalize -rectangular numerical semigroups to the
context of simplicial affine semigroups and study their isolated
factorizations. As a consequence of our results, we characterize those complete
intersection simplicial affine semigroups with only one Betti minimal element
in several ways. Moreover, we define Betti sorted and Betti divisible
simplicial affine semigroups and characterize them in terms of gluings and
their minimal presentations. Finally, we determine all the Betti divisible
numerical semigroups, which turn out to be those numerical semigroups that are
free for any arrangement of their minimal generators
Cyclotomic numerical semigroups
Given a numerical semigroup , we let be its semigroup polynomial. We study cyclotomic numerical semigroups;
these are numerical semigroups such that has all its roots
in the unit disc. We conjecture that is a cyclotomic numerical semigroup if
and only if is a complete intersection numerical semigroup and present some
evidence for it. Aside from the notion of cyclotomic numerical semigroup we
introduce the notion of cyclotomic exponents and polynomially related numerical
semigroups. We derive some properties and give some applications of these new
concepts.Comment: 17 pages, accepted for publication in SIAM J. Discrete Mat
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