Bianchi spaces and their 3-dimensional isometries as S-expansions of 2-dimensional isometries

In this paper we show that some 3-dimensional isometry algebras, specifically those of type I, II, III and V (according Bianchi's classification), can be obtained as expansions of the isometries in 2 dimensions. It is shown that in general more than one semigroup will lead to the same result. It is impossible to obtain the algebras of type IV, VI-IX as an expansion from the isometry algebras in 2 dimensions. This means that the first set of algebras has properties that can be obtained from isometries in 2 dimensions while the second set has properties that are in some sense intrinsic in 3 dimensions. All the results are checked with computer programs. This procedure can be generalized to higher dimensions, which could be useful for diverse physical applications.Comment: 23 pages, one of the authors is new, title corrected, finite semigroup programming is added, the semigroup construction procedure is checked by computer programs, references to semigroup programming are added, last section is extended, appendix added, discussion of all the types of Bianchi spaces is include

A Unification Free Introduction to Logic Programming

In this paper, we give a new presentation of the fundamental results of the theory of Logic Programming, which differs from classical introductions in at least two ways: the use of predicate algebras to deal with model theoretical aspects and the parameterization of the resolution algorithm with respect to the specific unification algorithm implemented

Semantics for a Quantum Programming Language by Operator Algebras

This paper presents a novel semantics for a quantum programming language by operator algebras, which are known to give a formulation for quantum theory that is alternative to the one by Hilbert spaces. We show that the opposite category of the category of W*-algebras and normal completely positive subunital maps is an elementary quantum flow chart category in the sense of Selinger. As a consequence, it gives a denotational semantics for Selinger's first-order functional quantum programming language QPL. The use of operator algebras allows us to accommodate infinite structures and to handle classical and quantum computations in a unified way.Comment: In Proceedings QPL 2014, arXiv:1412.810

Abstract State Machines 1988-1998: Commented ASM Bibliography

An annotated bibliography of papers which deal with or use Abstract State Machines (ASMs), as of January 1998.Comment: Also maintained as a BibTeX file at http://www.eecs.umich.edu/gasm

Facilitating modular property-preserving extensions of programming languages

We will explore an approach to modular programming language descriptions and extensions in a denotational style. Based on a language core, language features are added stepwise on the core. Language features can be described separated from each other in a self-contained, orthogonal way. We present an extension semantics framework consisting of mechanisms to adapt semantics of a basic language to new structural requirements in an extended language preserving the behaviour of programs of the basic language. Common templates of extension are provided. These can be collected in extension libraries accessible to and extendible by language designers. Mechanisms to extend these libraries are provided. A notation for describing language features embedding these semantics extensions is presented

A Note on Logic Programming Fixed-Point Semantics

In this paper, we present an account of classical Logic Programming fixed-point semantics in terms of two standard categorical constructions in which the least Herbrand model is characterized by properties of universality. In particular, we show that, given a program $P$, the category of models of $P$ is reflective in the category of interpretations for $P$. In addition, we show that the immediate consequence operator gives rise to an endofunctor ${T}_P$ on the category of Herbrand interpretations for $P$ such that category of algebras for ${T}_P$ is the category of Herbrand models of $P$. As consequences, we have that the least Herbrand model of $P$ is the least fixed-point of ${T}_P$ and is the reflection of the empty Herbrand interpretation