Mathematical Logic Quarterly最新文献

Dear Readers,

We wish all of you a happy and successful year 2023.

The issue you are looking at presents our journal in a new layout, the new standardised journal design used by our publisher Wiley-VCH Verlag. Apart from the major changes on the title page of articles, most of the features of the layout of the journal Mathematical Logic Quarterly (MLQ) were retained.

But the appearance of the papers is not the only major change at MLQ. After having served for a dozen years as one of the Managing Editors of MLQ, Benedikt Löwe has decided to step down at the end of 2022. In 2011, the journal underwent some significant changes as it started to be published under the auspices of the Deutsche Vereinigung für Mathematische Logik und für Grundlagenforschung der Exakten Wissenschaften (DVMLG). Benedikt served as vice president (until 2012) and later as president of the DVMLG (2012–2022) and directed this transition forcefully.

In addition to being one of the Managing Editors, Benedikt served as the liaison between the DVMLG, the Editorial Office, the publisher, and the typesetters; he worked closely with our past Editorial Assistants, Peter van Ormondt and Hugo Nobrega, as well as our current Editorial Manager, Thomas Piecha. Benedikt's clear and pronounced ideas about scientific publishing have always been appreciated and certainly significantly formed MLQ's current character. We shall try to keep his clear views on scientific publishing in mind. Thank you, Benedikt, for 12 years of inspiring and productive collaboration.

We are happy that Manuel Bodirsky from the Technische Universität Dresden will replace Benedikt both as Managing Editor and as representative of the DVMLG's Board in the Editorial Office of MLQ. Manuel is well known to us and our authors as he has been a member of the Editorial Board of MLQ since 2017. His main fields of research are Constraint Satisfaction Problems and Universal Algebra. Welcome to the Editorial Office, Manuel!

Since our last editorial was published in Volume 66 (2020), a number of members of the Editorial Board were re-appointed upon nomination by the Board of the DVMLG for another term of office for three years: Steve Awodey, Zoé Chatzidakis, Victoria Gitman, Andrew Marks, and Alexandra Silva for an additional term from 1 January 2021 to 31 December 2023; Nick Bezhanishvili, Su Gao, Maria Emilia Maietti, and Anush Tserunyan for an additional term from 1 January 2022 to 31 December 2024; and John Baldwin, Artem Chernikov, Rod Downey, Ilijas Farah, Ekaterina Fokina, Stefan Geschke, Hajime Ishihara, Franziska Jahnke, and Dima Sinapova for an additional term from 1 January 2023 to 31 December 2025. After nine years of service in the Editorial Board, Jan Krajíček left the board at the end of 2022. Thanks to Jan for his commitment to make MLQ a successful project.

As new members of the Editorial Board, the following researchers were appointed for a first term from 1 January 202

In this paper we start the analysis of the class $�D_{{\aleph }_2}$, the class of cofinal types of directed sets of cofinality at most ℵ₂. We compare elements of $�D_{{\aleph }_2}$ using the notion of Tukey reducibility. We isolate some simple cofinal types in $�D_{{\aleph }_2}$, and then proceed to find some of these types which have an immediate successor in the Tukey ordering of $�D_{{\aleph }_2}$.

We adapt a continuous logic axiomatization of tracial von Neumann algebras due to Farah, Hart and Sherman in order to prove a metatheorem for this class of structures in the style of proof mining, a research programme that aims to obtain the hidden computational content of ordinary mathematical proofs using tools from proof theory.

We define a family of non-principal ultrafilters on $�N$ which are, in a sense, very far from P-points. We prove the existence of such ultrafilters under reasonable conditions. In subsequent articles, we intend to prove that such ultrafilters may exist while no P-point exists. Though our primary motivations came from forcing and independence results, the family of ultrafilters introduced here should be interesting from combinatorial point of view too.

We investigate the cofinality of the strong measure zero ideal for κ inaccessible and show that it is independent of the size of 2^κ.

We exhibit a theory where definable types lack the amalgamation property.

We investigate two variants of splitting tree forcing, their ideals and regularity properties. We prove connections with other well-known notions, such as Lebesgue measurablility, Baire- and Doughnut-property and the Marczewski field. Moreover, we prove that any absolute amoeba forcing for splitting trees necessarily adds a dominating real, providing more support to Hein's and Spinas' conjecture that $��add�\left(�I_{\mathrm{SP}}�\right)�\le �b�$.