Let be an order in an algebraic number field. If is a principal order, then many explicit results on its arithmetic are available. Among others, is half-factorial if and only if the class group of has at most two elements. Much less is known for non-principal orders. Using a new semigroup theoretical approach, we study half-factoriality and further arithmetical properties for non-principal orders in algebraic number fields.
We find a generator of the function field on the modular curve X₁(4) by means of classical theta functions θ₂ and θ₃, and estimate the normalized generator which becomes the Thompson series of type 4C. With these modular functions we investigate some number theoretic properties.
Fix an integer . Rikuna introduced a polynomial defined over a function field whose Galois group is cyclic of order , where satisfies some mild hypotheses. In this paper we define the family of generalized Rikuna polynomials of degree . The are constructed iteratively from the . We compute the Galois groups of the for odd over an arbitrary base field and give applications to arithmetic dynamical systems.
We consider positional numeration system with negative base , as introduced by Ito and Sadahiro. In particular, we focus on arithmetical properties of such systems when is a quadratic Pisot number. We study a class of roots of polynomials , , and show that in this case the set of finite -expansions is closed under addition, although it is not closed under subtraction. A particular example is , the golden ratio. For such , we determine the exact bound on the number of fractional digits...
L’anneau des entiers d’une extension galoisienne de peut ne pas être localement libre sur son ordre associé dans l’algèbre du groupe : c’est le résultat principal de l’étude de la structure galoisienne des extensions sauvagement ramifiées d’un corps local absolument non ramifié, dans le cas où le groupe d’inertie est cyclique.
This is a survey of some consequences of the fact that the fundamental group of the orbifold with singular set the Borromean link and isotropy cyclic of order 4 is a universal kleinian group.