Searcharxiv⌕ Search

arXiv subjects

Gabriel Villa-Salvador

Publications and source records attributed to Gabriel Villa-Salvador.

15 recordsLinked to original sources
arXiv2024

Extended genus fields of abelian extensions of rational function fields

In this paper we obtain the extended genus field of a finite abelian extension of a global rational function field. We first study the case of a cyclic extension of prime power degree. Next, we use that the extended genus fields of a composite of two cyclotomic extensions of a global rational function field is equal to the composite of their respective extended genus fields, to obtain our main result. This result is that the extended genus field of a general finite abelian extension of a global rational function field, is given explicitly in terms of the field and of the extended genus field of its "cyclotomic projection".

math.NT↗
arXiv2022

Genus Field and Extended Genus Field of an Elementary Abelian Extension of Global Fields

In the present work we give the construction of the genus field and the extended genus field of an elementary abelian $l$-extension of a field of rational functions, where $l$ is a prime number. In the Kummer case, if $K$ is contained in a cyclotomic funtion field, the construction is given using Leopoldt's ideas by means of Dirichlet characters. Following the definition of Anglès and Jaulent of extended Hilbert class field, we obtain the extended genus field of an elementary abelian $l$-extension of a field of rational functions.

math.NT↗
arXiv2022

Class fields, Dirichlet characters and extended genus fields of global function fields

We obtain the extended genus field of an abelian extension of a rational function field. We follow the definition of Anglès and Jaulent, which uses class field theory. First we show that the natural definition of extended genus field of a cyclotomic function field obtained by means of Dirichlet characters is the same as the one given by Anglès and Jaulent. Next we study the extended genus field of a finite abelian extension of a rational function field along the lines of the study of genus fields of abelian extensions of rational function fields and compare this approach with the one given by Anglès and Jaulent.

math.NT↗
arXiv2022

Function field genus theory for non-Kummer extensions

In this paper we first obtain the genus field of a finite abelian non-Kummer $l$--extension of a global rational function field. Then, using that the genus field of a composite of two abelian extensions of a global rational function field with relatively prime degrees is equal to the composite of their respective genus fields and our previous results, we deduce the general expression of the genus field of a finite abelian extension of a global rational function field.

math.NT↗
arXiv2021

Genus fields of Kummer extensions of rational function fields

In this paper we obtain the genus field of a general Kummer extension of a global rational function field. We study first the case of a general Kummer extension of degree a power of a prime. Then we prove that the genus field of a composite of two abelian extensions of a global rational function field with relatively prime degrees is equal to the composite of their respective genus fields. Our main result, the genus of a general Kummer extension of a global rational function field, is a direct consequence of this fact.

math.NT↗
arXiv2020

Genus fields of Kummer $\ell^n$-cyclic extensions

We give a construction of the genus field for Kummer $\ell^n$-cyclic extensions of rational congruence function fields, where $\ell$ is a prime number. First, we compute the genus field of a field contained in a cyclotomic function field, and then for the general case. This generalizes the result obtained by Peng for a Kummer $\ell$-cyclic extension. Finally, we study the extension $(K_1K_2)_{\frak{ge}}/(K_1)_{\frak{ge}}(K_2)_{\frak{ge}}$, for $K_1$, $K_2$ abelian extensions of $k$.

math.NT↗
arXiv2019

Genus fields of global fields

In this paper we obtain the extended genus field of a global field. First we define the extended genus field of a global function field and we obtain, via class field theory, the description of the extended genus field of an arbitrary global function field. In the last part of the paper we use the techniques for function fields to describe the extended genus field of an arbitrary number field.

math.NT↗
arXiv2017

Genus fields of finite abelian extensions

In this paper we find the genus field of finite abelian extensions of the global rational function field. We introduce the term conductor of constants for these extensions and determine it in terms of other invariants. We study the particular case of finite abelian $p$--extensions and give an explicit description of their genus field.

math.NT↗
arXiv2016

Abelian $p$-extensions and additive polynomials

In this work we present some arithmetic properties of families of abelian $p$--extensions of global function fields, among which are their generators and their type of ramification and decomposition.

math.NT↗
arXiv2016

Cogalois theory and Drinfeld modules

In this paper we generalize the results of \cite{sanchez} to rank one Drinfeld modules with class number one. We show that, in the present form, there does not exist a cogalois theory for Drinfeld modules of rank or class number larger than one. We also consider the torsion of the Carlitz module for the extension ${\mathbb{F}}_{q}(T)(Λ_{P^{n}}) /{\mathbb{F}}_{q}(T)(Λ_{P})$.

math.NT↗
arXiv2015

Genus Fields of Congruence Function Fields

Let $k$ be a rational congruence function field and consider an arbitrary finite separable extension $K/k$. If for each prime in $k$ ramified in $K$ we have that at least one ramification index is not divided by the characteristic of $K$, we find the genus field $\g K$, except for constants, of the extension $K/k$. In general, we describe the genus field of a global function field.

math.NT↗
arXiv2014

Congruence Function Fields with Class Number One

We prove that there exists, up to isomorphism, exactly one function field over the finite field of two elements of class number one and genus four. This result, together with the ones of MacRae, Madan, Leitzel, Queen and Stirpe, establishes that there exist eight non-isomorphic congruence function fields of genus larger than zero and class number one.

math.NT↗
arXiv2014

Genus fields of abelian extensions of congruence rational function fields

In the published version of this paper [Finite Fields and Their Applications {\bf 20} (2013) 40--54], there is an error in the proof of Theorem 4.2 of the paper. Here we correct the error and give the right statments for Theorems 4.2, 4.5 and 5.2 We give a construction of genus fields for congruence function fields. First we consider the cyclotomic function field case following the ideas of Leopoldt and then the general case. As applications we give explicitly the genus fields of Kummer, Artin--Schreier and cyclic $p$--extensions. Kummer extensions were obtained previously by G. Peng and Artin--Schreier extensions were obtained by S. Hu and Y. Li.

math.NT↗
arXiv2013

A combinatorial proof of the Kronecker--Weber Theorem in positive characteristic

In this paper we present a combinatorial proof of the Kronecker--Weber Theorem for global fields of positive characteristic. The main tools are the use of Witt vectors and their arithmetic developed by H. L. Schmid. The key result is to obtain, using counting arguments, how many $p$--cyclic extensions exist of fixed degree and bounded conductor where only one prime ramifies are there. We then compare this number with the number of subextensions of cyclotomic function fields of the same type and verify that these two numbers are the same.

math.NT↗