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Nearness relations in linear spaces

Martin Kalina (2004)

Kybernetika

In this paper, we consider nearness-based convergence in a linear space, where the coordinatewise given nearness relations are aggregated using weighted pseudo-arithmetic and geometric means and using continuous t-norms.

Negaciones en la teoría de conjuntos difusos.

Francesc Esteva (1981)

Stochastica

All the negations of PL(X) satisfying the extension principle and the generalized extension principle are fully described through the negation of L. Necessary and sufficient conditions are given for n to be an ortho or u-complementation and for n to satisfy the DeMorgan laws.

Negative universality results for graphs

S.-D. Friedman, K. Thompson (2010)

Fundamenta Mathematicae

It is shown that in many forcing models there is no universal graph at the successors of regular cardinals. The proof, which is similar to the well-known proof for Cohen forcing, is extended to show that it is consistent to have no universal graph at the successor of a singular cardinal, and in particular at ω + 1 . Previously, little was known about universality at the successors of singulars. Analogous results show it is consistent not just that there is no single graph which embeds the rest, but that...

Několik poznámek k mohutnosti množin

Dalibor Martišek (2022)

Učitel matematiky

Text je stručným přehledem nejdůležitějších vlastností nekonečných množin, mimo jiné vyvrací omyl publikovaný v článku Kuřina & Vondrová: Nekonečno, jak to vlastně je,  UM 2003. "Zip Petera Zamarovského" není bijekcí mezi (0;1)x(0;1) a (0;1), ale pouze injekcí, tudíž ekvivalenci množiny všech bodů čtverce a úsečky nedokazuje. V článku je naznačen jiný důkaz.

New kinds of hybrid filters of EQ-algebras

Akbar Paad (2024)

Mathematica Bohemica

The main goal of this paper is to introduce hybrid positive implicative and hybrid implicative (pre)filters of EQ-algebras. In the following, some characterizations of this hybrid (pre)filters are investigated and it is proved that the quotient algebras induced by hybrid positive implicative filters in residuated EQ-algebras are idempotent and residuated EQ-algebra. Moreover, the relationship between hybrid implicative prefilters and hybrid positive implicative prefilters are discussed and it is...

Non-Glimm–Effros equivalence relations at second projective level

Vladimir Kanovei (1997)

Fundamenta Mathematicae

A model is presented in which the Σ 2 1 equivalence relation xCy iff L[x]=L[y] of equiconstructibility of reals does not admit a reasonable form of the Glimm-Effros theorem. The model is a kind of iterated Sacks generic extension of the constructible model, but with an “ill“founded “length” of the iteration. In another model of this type, we get an example of a Π 2 1 non-Glimm-Effros equivalence relation on reals. As a more elementary application of the technique of “ill“founded Sacks iterations, we obtain...

Nonmeasurable algebraic sums of sets of reals

Marcin Kysiak (2005)

Colloquium Mathematicae

We present a theorem which generalizes some known theorems on the existence of nonmeasurable (in various senses) sets of the form X+Y. Some additional related questions concerning measure, category and the algebra of Borel sets are also studied.

Nonnormality points of βX∖X

William Fleissner, Lynne Yengulalp (2011)

Fundamenta Mathematicae

Let X be a crowded metric space of weight κ that is either κ ω -like or locally compact. Let y ∈ βX∖X and assume GCH. Then a space of nonuniform ultrafilters embeds as a closed subspace of (βX∖X)∖y with y as the unique limit point. If, in addition, y is a regular z-ultrafilter, then the space of nonuniform ultrafilters is not normal, and hence (βX∖X)∖y is not normal.

Nonparametric recursive aggregation process

Elena Tsiporkova, Veselka Boeva (2004)

Kybernetika

In this work we introduce a nonparametric recursive aggregation process called Multilayer Aggregation (MLA). The name refers to the fact that at each step the results from the previous one are aggregated and thus, before the final result is derived, the initial values are subjected to several layers of aggregation. Most of the conventional aggregation operators, as for instance weighted mean, combine numerical values according to a vector of weights (parameters). Alternatively, the MLA operators...

Non-perfect rings and a theorem of Eklof and Shelah

Jan Trlifaj (1991)

Commentationes Mathematicae Universitatis Carolinae

We prove a stronger form, A + , of a consistency result, A , due to Eklof and Shelah. A + concerns extension properties of modules over non-left perfect rings. We also show (in ZFC) that A does not hold for left perfect rings.

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