A Polish space is not always homeomorphic to a computably presented Polish space. In this article, we examine degrees of non-computability of presenting homeomorphic copies of compact Polish spaces. We show that there exists a $\mathbf {0}'$ -computable low $_3$ compact Polish space which is not homeomorphic to a computable one, and that, for any natural number $n\geq 2$, there exists a Polish space $X_n$ such that exactly the high $_{n}$ -degrees are required to present the homeomorphism type of $X_n$. (...) Along the way we investigate the computable aspects of Čech homology groups. We also show that no compact Polish space has a least presentation with respect to Turing reducibility. (shrink)

The appearance and intensive development of a socialist orientation as a distinctive form of noncapitalist development of formerly oppressed countries and peoples are among the outstanding phenomena of our time and require the most serious theoretical and methodological interpretation. The national-democratic revolutions that have taken place in these countries have removed the bases of imperialist and feudal domination, interrupted the rise of capitalism at its earliest level, and embarked on a noncapitalist path of social progress. A gradual process bringing the (...) orientation toward socialism into convergence with a people's democratic development of society began in the course of radical reorganization of precapitalist or early capitalist structures. (shrink)

The Wadge hierarchy was originally defined and studied only in the Baire space. Here we extend the Wadge hierarchy of Borel sets to arbitrary topological spaces by providing a set-theoretic definition of all its levels. We show that our extension behaves well in second countable spaces and especially in quasi-Polish spaces. In particular, all levels are preserved by continuous open surjections between second countable spaces which implies e.g., several Hausdorff–Kuratowski -type theorems in quasi-Polish spaces. In fact, many results hold not (...) only for the Wadge hierarchy of sets but also for its extension to Borel functions from a space to a countable better quasiorder Q. (shrink)

Attempts to extend the classical Hausdorff difference hierarchy to the case of partitions of a space to k > 2 subsets lead to non‐equivalent notions. In a hope to identify the “right” extension we consider the extensions appeared in the literature so far: the limit‐, level‐, Boolean and Wadge hierarchies of k ‐partitions. The advantages and disadvantages of the four hierarchies are discussed. The main technical contribution of this paper is a complete characterization of the Wadge degrees of Δ02‐measurable k (...) ‐partitions of the Baire space. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim). (shrink)

We consider fine hierarchies in recursion theory, descriptive set theory, logic and complexity theory. The main results state that the sets of values of different Boolean terms coincide with the levels of suitable fine hierarchies. This gives new short descriptions of these hierarchies and shows that collections of sets of values of Boolean terms are almost well ordered by inclusion. For the sake of completeness we mention also some earlier results demonstrating the usefulness of fine hierarchies.

The wedge hierarchy was originally defined and studied only in the Baire space (and some other zero-dimensional spaces). Here we extend the Wadge hierarchy of Borel sets to arbitrary topological spaces by providing a set-theoretic definition of all its levels. We show that our extension behaves well in second countable spaces and especially in quasi-Polish spaces. In particular, all levels are preserved by continuous open surjections between second countable spaces which implies e.g. several Hausdorff-Kuratowski-type theorems in quasi-Polish spaces. In fact, (...) many results hold not only for the Wadge hierarchy of sets but also for its extension to Borel functions from a space to a countable better quasiorder Q. (shrink)

We establish some results on the Borel and difference hierarchies in φ-spaces. Such spaces are the topological counterpart of the algebraic directed-complete partial orderings. E.g., we prove analogs of the Hausdorff Theorem relating the difference and Borel hierarchies and of the Lavrentyev Theorem on the non-collapse of the difference hierarchy. Some of our results generalize results of A. Tang for the space Pω. We also sketch some older applications of these hierarchies and present a new application to the question of (...) characterizing the ω-ary Boolean operations generating a given level of the Wadge hierarchy from the open sets. (shrink)

It is well known that any finitary operation is recursive in a suitable total numeration. A. Orlicki showed that there is an ω-operation not recursive in any total numeration. We will show that any ω-operation is recursive in a partial numeration.

We state some general facts on r.e. structures, e.g. we show that the free countable structures in quasivarieties are r.e. and construct acceptable numerations and universal r.e. structures in quasivarieties. The last facts are similar to the existence of acceptable numerations of r.e. sets and creative sets. We state a universality property of the acceptable numerations, classify some index sets and discuss their relation to other decision problems. These results show that the r.e. structures behave in some respects better than (...) the recursive structures. (shrink)

The article reviews the concepts of the multi-author book Society. National Strategy. War: Political and Strategic Lessons of the First World War. This collective research is notable for rich original scientific apparatus and methodological proficiency. Thus, the analysis of participating countries is conducted according to a single template, which includes: the state of pre-war society in all participating countries ; goals of engaging in war and expectations of the powerful and financial elites for the war ; assessment of how did (...) different strata of society find the war; the evolution of the morale of the people during the war; problems that arose during the war ; the evolution of women’s position in society during the war, the development of a broad segment of women-workers, the extension of emancipation as one of the positive results of the war; the outcome of the war for the country. Special attention is drawn to the pacifist nature of the ideology of the reviewed research, demonstration of deprivation and suffering of people in all countries. The book’s authors identify the main causes of the First World War: ambitions and inefficiency of the world’s elites, the lack of a coherent strategy. As the result, the USA, thanks to their strategy, received the maximum dividends with minimal participation. At the same time, it is noted that the context of research on the nature of war should be expanded to take into account the general competition of countries and civilizations. The authors comprehensively analyze the informational and propaganda activities of the participating countries and conclude that England’s activities in this field were the most effective. Based on the methodology of this collective research, the nature of a future world war, its potential participants and their goals can be considered. (shrink)

We prove that for any k≥3 each element of the h-quasiorder of finite k-labeled forests is definable in the ordinary first order language and, respectively, each element of the h-quasiorder of countable k-labeled forests is definable in the language Lω1ω, in both cases provided that the minimal non-smallest elements are allowed as parameters. As corollaries, we characterize the automorphism groups of both structures and show that the structure of finite k-forests is atomic. Similar results hold true for two other relevant (...) structures: the h-quasiorder of finite k-labeled trees and of finite k-labeled trees with a fixed label of the root element. (shrink)

A way to a self-consistent physically acceptable formulation of quantum gravity field theory is found. The simplified model of quantized conformally-flat gravity and a massive scalar field is analyzed.