• openAccess   Duality and syzygies for semimodules over numerical semigroups 

      Moyano-Fernández, Julio José; Uliczka, Jan Springer Verlag (2015-02)
      Let Γ=⟨α,β⟩ be a numerical semigroup. In this article we consider the dual Δ∗ of a Γ-semimodule Δ; in particular we deduce a formula that expresses the minimal set of generators of Δ∗ in terms of the generators of Δ. As ...
    • openAccess   Hilbert regularity of Z-graded modules over polynomial rings 

      Bruns, Winfried; Moyano-Fernández, Julio José; Uliczka, Jan Rocky Mountain Mathematics Consortium (2017-06)
      Let M be a finitely generated Z-graded module over the standard graded polynomial ring R=K[X1,…,Xd] with K a field, and let HM(t)=QM(t)/(1−t)d be the Hilbert series of~M. We introduce the Hilbert regularity of~M as the ...
    • openAccess   Hilbert series of modules over positively graded polynomial rings 

      Katthan, Lukas; Moyano-Fernández, Julio José; Uliczka, Jan Elsevier (2016-08)
      In this note, we give examples of formal power series satisfying certain conditions that cannot be realized as Hilbert series of finitely generated modules. This answers to the negative a question raised in a recent article ...
    • openAccess   Lattice paths with given number of turns and semimodules over numerical semigroups 

      Moyano-Fernández, Julio José; Uliczka, Jan Springer US (2014-06)
      Let Γ =< α, ß> be a numerical semigroup. In this article we consider several relations between the so-called Γ -semimodules and lattice paths from (0, α) to (ß,0): we investigate isomorphism classes of Γ -semimodules as ...
    • openAccess   Which series are Hilbert series of graded modules over standard multigraded polynomial rings? 

      Katthän, Lukas; Moyano-Fernández, Julio José; Uliczka, Jan Wiley (2020)
      Consider a polynomial ring 𝑅� with the ℤ𝑛�-grading where the degree of each variableis a standard basis vector. In other words, 𝑅� is the homogeneous coordinate ring ofa product of 𝑛� projective spaces. In this setting, ...