On the Axiomatizability of Certain Classes of Modules.
On the planarity of the equilateral, isogonal pentagon.
On the structure and classification of SOMAs: Generalizations of mutually orthogonal Latin squares.
Order with successors is not interprétable in RCF
Using the monotonicity theorem of L. van den Dries for RCF-definable real functions, and a further result of that author about RCF-definable equivalence relations on ℝ, we show that the theory of order with successors is not interpretable in the theory RCF. This confirms a conjecture by J. Mycielski, P. Pudlák and A. Stern.
Orthogonality as single primitive notion for metric planes.
Point-reflections in metric plane.
Radical parallelism on projective lines and non-linear models of affine spaces.
Representations of Reals in Reverse Mathematics
Working in the framework of reverse mathematics, we consider representations of reals as rapidly converging Cauchy sequences, decimal expansions, and two sorts of Dedekind cuts. Converting single reals from one representation to another can always be carried out in RCA₀. However, the conversion process is not always uniform. Converting infinite sequences of reals in some representations to other representations requires the use of WKL₀ or ACA₀.
Současný stav ve výzkumu základů matematiky
Sul problema dell'autoriferimento
We formulate, within the frame-theory for the foundations of Mathematics outlined in [2], a list of axioms which state that almost all "interesting" collections and almost all "interesting" operations are elements of the universe. The resulting theory would thus have the important foundational feature of being completely self-contained. Unfortunately, the whole list is inconsistent, and we are led to formulate the following problem, which we call the problem of self-reference: "Find out...
The best possible unification for any collection of physical theories.
The lattice of bi-numerations of arithmetic. I.
The lattice of bi-numerations of arithmetic. II.
The process of induction as a non-classical logic's double negation: evidence from classical scientific theories.
The strength of Turing determinacy within second order arithmetic
We investigate the reverse mathematical strength of Turing determinacy up to Σ₅⁰, which is itself not provable in second order arithmetic.
The theory of Archimedean real closed fields in logics with Ramsey quantifiers
Trames, classifications, définitions
L'article part d'une analogie entre trames et partitions, définitions conceptuelles et optiques. On montre que les divisions d'un espace de concepts ressemblent souvent à celles de l'espace réel. On étudie alors quelques exemples de pavage d'un espace conceptuel (Aristote) et on compare les processus dichotomiques platoniciens (générateurs de définitions) aux filtres d'une algèbre booléenne. Par la suite, on généralise ces modèles, considérant des structures floues et des «ensembles approximatifs»...
Ueber den allgemeinen Functionsbegriff und dessen Darstellung durch eine willkürliche Curve
Una lógica modal para la geometría esférica de incidencia.
Habitualmente, las geometrías de incidencia están basadas en estructuras bisurtidas formadas por puntos y rectas, y conectadas por una relación entre ambas clases. En lo que sigue, introducimos una estructura monosurtida, que llamamos Marco Esférico de Incidencia, la cual resulta adecuada, para construir una base semántica que permita su consideración en el lenguaje modal. Construiremos así un sistema axiomático para dicho lenguaje, que estaría determinado por la estructura creada, es decir probaremos...
Una proposta di teorie base dei Fondamenti della Matematica
Vengono proposte alcune teorie base dei Fondamenti della Matematica che assumono come concetti primitivi i concetti di numero naturale, collezione, qualità, operazione e relazione; le operazioni e le relazioni considerate possono essere più o meno complesse: il numero naturale che indica il grado di complessità è detto arietà. Nelle teorie considerate è raggiunto un alto grado di autoreferenza.