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We answer a question of Abhyankar by constructing an algebraic closure of the field of power series over a field of positive characteristic, using "generalized power series". (The corresponding construction in characteristic 0 dates back to…

Algebraic Geometry · Mathematics 2007-05-23 Kiran S. Kedlaya

In this paper we give a survey of recent methods for the asymptotic and exact enumeration of number fields with given Galois group of the Galois closure. In particular, the case of fields of degree up to 4 is now almost completely solved,…

Number Theory · Mathematics 2015-06-26 Henri Cohen

We introduce a new fundamental group scheme for varieties defined over an algebraically closed field of positive characteristic and we use it to study generalization of some of C. Simpson's results to positive characteristic. We also study…

Algebraic Geometry · Mathematics 2015-03-24 Adrian Langer

Let $k$ be an algebraically closed field of characteristic zero, $F$ be an algebraically closed extension of $k$ of transcendence degree one, and $G$ be the group of automorphisms over $k$ of the field $F$. The purpose of this note is to…

Algebraic Geometry · Mathematics 2009-04-07 M. Rovinsky

We show that the isomorphy type of every finitely generated field $K$ with $\chr(K)\neq2$ is encoded by a \textit{\textbf{single\ha3explicit\ha3axiom}} $\istp K\!$ \textit{\textbf{in\ha3the\ha3language\ha3of\ha3fields}}, i.e., for all…

Algebraic Geometry · Mathematics 2019-01-14 Florian Pop

We prove that the class of separably algebraically closed valued fields equipped with a distinguished Frobenius endomorphism $x \mapsto x^q$ is decidable, uniformly in $q$. The result is a simultaneous generalization of the work of…

Logic · Mathematics 2025-09-17 Yuval Dor , Yatir Halevi

The tilting correspondence is a fundamental property of perfectoid fields. In this note, we show that the tilting construction can also be used to detect perfectoid fields among nonarchimedean fields. In particular, for $K$ a complete…

Number Theory · Mathematics 2023-01-24 Ehsan Shahoseini , Kiran S. Kedlaya

We characterize those valued fields for which the image of the valuation ring under every polynomial in several variables contains an element of maximal value, or zero.

Commutative Algebra · Mathematics 2013-04-02 Salih Azgin , Franz-Viktor Kuhlmann , Florian Pop

We give a survey of Darboux type theorems in multisymplectic geometry. These theorems establish when a closed differential form of a certain type admits a constant-coefficient expression in some local coordinate system. Beyond the classical…

Symplectic Geometry · Mathematics 2025-06-26 Leonid Ryvkin

These notes are an introduction to and an overview of the theory of algebraic surfaces over algebraically closed fields of positive characteristic. After some background in characteristic-p-geometry, we sketch the Kodaira-Enriques…

Algebraic Geometry · Mathematics 2014-12-03 Christian Liedtke

We introduce and study a natural class of fields in which certain first-order definable sets are existentially definable, and characterise this class by a number of equivalent conditions. We show that global fields belong to this class, and…

Logic · Mathematics 2023-06-22 Philip Dittmann , Dion Leijnse

Differential algebraic geometry seeks to extend the results of its algebraic counterpart to objects defined by differential equations. Many notions, such as that of a projective algebraic variety, have close differential analogues but their…

Algebraic Geometry · Mathematics 2015-05-14 William D. Simmons

These notes form part of a joint research project on the logic of fields with many valuations, connected by a product formula. We define such structures and name them {\em globally valued fields} (GVFs). This text aims primarily at a proof…

Logic · Mathematics 2022-12-15 Itaï Ben Yaacov , Ehud Hrushovski

We use a category-theoretic formulation of Aczel's Fullness Axiom from Constructive Set Theory to derive the local cartesian closure of an exact completion. As an application, we prove that such a formulation is valid in the homotopy…

Category Theory · Mathematics 2020-12-18 Jacopo Emmenegger

We derive several existence results concerning cycle types and, more generally, the "mapping behavior" of complete mappings. Our focus is on so-called first-order cyclotomic mappings, which are functions on a finite field $\mathbb{F}_q$…

Number Theory · Mathematics 2021-05-04 Alexander Bors , Qiang Wang

Let $\mathbb{F}$ be an algebraically closed field of characteristic zero. Recently, we proved that isotypic blocks are functorially equivalent over $\mathbb{F}$. In this article we provide an example of functorially equivalent blocks which…

Group Theory · Mathematics 2024-01-18 Deniz Yılmaz

We present an overview of some recent developments in the theory of generalized formal series, grounded in diffeological geometric framework. These constructions aim to offer new tools for understanding infinite-dimensional phenomena in…

History and Overview · Mathematics 2025-08-25 Jean-Pierre Magnot

We show that each local field $\mathbb{F}_q((t))$ of characteristic $p > 0$ is characterised up to isomorphism within the class of all fields of imperfect exponent at most $1$ by (certain small quotients of) its absolute Galois group…

Number Theory · Mathematics 2025-10-15 Philip Dittmann

We provide a complete system of invariants for the formal classification of complex analytic unipotent germs of diffeomorphism at $\cn{n}$ fixing the orbits of a regular vector field. We reduce the formal classification problem to solve a…

Dynamical Systems · Mathematics 2017-02-10 Javier Ribón

An expansion of a definably complete field either defines a discrete subring, or the image of a definable discrete set under a definable map is nowhere dense. As an application we show a definable version of Lebesgue's differentiation…

Logic · Mathematics 2016-01-19 Antongiulio Fornasiero , Philipp Hieronymi