The known (explicit) examples of Riemann surfaces not definable over their field of moduli are those with that field being a subfield of the reals but which cannot be defined over the reals. In this paper we provide explicit ...

We provide the theoretical foundation for the Lyndon-Hochschild-Serre spectral sequence as a tool to study the group cohomology and with this the group extensions in the category of definable groups. We also present various ...

We study four types of equational definability of factor congruences in varieties with 0 → and 1 →. The paper completes the work of a previous paper on left equational definability of factor congruences.

For a variety with weak existentially definable factor congruences, we characterize whenthe properties "e is a central element" and "e and f are complementary central elements"are definable by (∀ V p = q)-formulas and by ...

Se decriben los grupos definibles en los números p-ádicos con el lenguaje de cuerpo valuado excepto por subgrupos de índice finite y cocientes finitos. Igualmente se describen los grupos definibles en la aritmética de ...

In this article, we formally define and investigate the computational complexity of the definability problem for open first-order formulas (i.e. quantifier free first-order formulas) with equality. Given a logic L, the ...

Una variedad tiene congruencias Factor Definibles (DFC) si los núcleos de las proyecciones canónicas en productos directos son definibles por una formula de primer orden \Phi cuyos parámetros son elementos centrales. Los ...

This study was undertaken to determine the nutritional requirements of Lactobacillus delbrueckii subsp. lactis and to develop a minimal chemically defined medium that supports sustained growth of these microorganisms. The ...

Three important results about the expressivity of a modal logic L are the Characterization Theorem (that identifies a modal logic L as a fragment of a better known logic), the Definability Theorem (that provides conditions ...