Quantification over propositional formulas in probability logic: decidability issues

A language for reasoning about probability is generalized by adding quantifiers over propositional formulas to the language. Then relevant decidability issues are considered. In particular, the results presented demonstrate that a rather weak fragment of the new language has an undecidable validity problem. On the other hand, it is stated that a restricted version of the validity problem is decidable for ∀∃-sentences.     

The logical consequence relation of propositional tense logic

This work concerns the model theory of propositional tense logic with the Kripke relational semantics. It is shown (i) that there is a formula y whose logical consequences form a complete II set, and (ii) that for 0 ≦ m < ω+ ω there are formulas γ_m such that all models of γ_m are isomorphic and have cardinality x_m, where x₀ = χ₀, x_m+1 = 2^xm, and x_ω = lim{x_m < | m ω}. Familiarity with the relational semantics for modal and tense logic ([1] or [3], for example) will be presumed. A knowledge of recursion theory would be helpful, although some background material will be provided.     

A topological characterization of consistency of logic theories in propositional logic

The main purpose of this note is to characterize consistency of logic theories in propositional logic by means of topological concept. Based on the concepts of truth degree of formulas and similarity degree between formulas the concept of logic metric space has been proposed by the first author. It is proved in this note that a closed logic theory Γ is consistent if and only if it contains no interior point in the logic metric space. Moreover the relationship between logic closedness and topological closedness of a logic theory Γ is discussed. Finally, the concept of full divergency is also characterized by means of the topological concept of density. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A note on decidability of variables in intuitionistic propositional logic

An answer to the following question is presented: given a proof in classical propositional logic, for what small set of propositional variables p does it suffice to add all the formulae to Γ in order to intuitionistically prove A? This answer is an improvement of Ishihara's result for some cases.     

逻辑系统L_3中公式的随机真度及近似推理

利用赋值集的随机化方法,在三值Lukasiewicz命题逻辑系统中引入公式的随机真度,证明了随机真度的MP规则、HS规则及交推理规则;同时引入公式间的随机相似度和伪距离,建立了随机逻辑度量空间,推导出随机相似度的若干性质,证明了随机逻辑度量空间中逻辑运算的连续性;并在随机逻辑度量空间中提出了三种不同类型的近似推理模式,证明了三种近似推理模式的等价性.     

The logic of risky knowledge,reprised

Much of our everyday knowledge is risky. This not only includes personal judgments, but the results of measurement, data obtained from references or by report, the results of statistical testing, etc. There are two (often opposed) views in artificial intelligence on how to handle risky empirical knowledge. One view, characterized often by modal or nonmonotonic logics, is that the structure of such knowledge should be captured by the formal logical properties of a set of sentences, if we can just get the logic right. The other view takes probability to be central to the characterization of risky knowledge, but often does not allow for the tentative or corrigible acceptance of a set of sentences. We examine a view, based on ?-acceptability, that combines both probability and modality. A statement is ?-accepted if the probability of its denial is at most ?, where ? is taken to be a fixed small parameter as is customary in the practice of statistical testing. We show that given a body of evidence Γ_δ and a threshold ?, the set of ?-accepted statements Γ_? gives rise to the logical structure of the classical modal system EMN, the smallest classical modal system E supplemented by the axiom schemas M: □_?(?∧ψ) → (□_??∧□_?ψ) and N: □_??.     

The distribution of prime divisors in finitely generated domains

In this paper we show that each divisor class of a finitely generated k-algebra R (k a field) contains a prime divisor if k is Hilbertian or if dim R≥ 2. On the way we also obtain partial results for domains finitely generated over an one-dimensional noetherian domain. Received: 27 June 1998     

The transcendental rank of the formulas of an S1-categorical theory

In this paper we investigate the transcendental rank introduced by Morley. We introduce the concept of a fibering and prove a series of lemmas about fibering, on the basis of which we prove the main theorems: on an estimate for the rank of a formula (Theorem 3); on the summation of ranks (Theorem 2); and a reproof of Baldwin's theorem on the finiteness of the rank of S₁-categorical theories (Theorem 1).     

The Skolemization of prenex formulas in intermediate logics

The skolem class of a logic consists of the formulas for which the derivability of the formula is equivalent to the derivability of its Skolemization. In contrast to classical logic, the skolem classes of many intermediate logics do not contain all formulas. In this paper it is proven for certain classes of propositional formulas that any instance of them by (independent) predicate sentences in prenex normal form belongs to the skolem class of any intermediate logic complete with respect to a class of well-founded trees. In particular, all prenex sentences belong to the skolem class of these logics, and this result extends to the constant domain versions of these logics.     

The generation of formulas held in common knowledge

Common knowledge of a finite set of formulas implies a special relationship between syntactic and semantic common knowledge. If S, a set of formulas held in common knowledge, is implied by the common knowledge of some finite subset of S, and A is a non-redundant semantic model where exactly S is held in common knowledge, then the following are equivalent: (a) S is maximal among the sets of formulas that can be held in common knowledge, (b) A is finite, and (c) the set S determines A uniquely; otherwise there are uncountably many such A. Even if the knowledge of the agents are defined by their knowledge of formulas, 1) there is a continuum of distinct semantic models where only the tautologies are held in common knowledge and, 2) not assuming that S is finitely generated (a) does not imply (c), (c) does not imply (a), and (a) and (c) together do not imply (b). Received November 1999/Revised version January 2000     

The possibility of integral formulas in R n

We consider the integral We solve the problem of determination of necessary and sufficient conditions in order that (u) be independent of the values of u(x) inside a bounded domain . These conditions are written in the form of a set of differential equations for the functions f(x,u,¯p,T^ij) on the set m{x; u+¯p+ T^ij<}. For such functions (u) is represented in the form of a boundary integral.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 52, pp. 35–51, 1975.