Verifying termination and error-freedom of logic programs with block declarations

We present verification methods for logic programs with delay declarations. The verified properties are termination and freedom from errors related to built-ins. Concerning termination, we present two approaches. The first approach tries to eliminate the well-known problem of speculative output bindings. The second approach is based on identifying the predicates for which the textual position of an atom using this predicate is irrelevant with respect to termination. Three features are distinctive of this work: it allows for predicates to be used in several modes; it shows that block declarations, which are a very simple delay construct, are sufficient to ensure the desired properties; it takes the selection rule into account, assuming it to be as in most Prolog implementations. The methods can be used to verify existing programs and assist in writing new programs

Semantics of Input-Consuming Logic Programs

Input-consuming programs are logic programs with an additional restriction on the selectability (actually, on the resolvability) of atoms. this class of programs arguably allows to model logic programs employing a dynamic selection rule and constructs such as delay declarations: as shown also in [5], a large number of them are actually input-consuming. \ud in this paper we show that - under some syntactic restrictions - the tex2html_wrap_inline117-semantics of a program is correct and fully abstract also for input-consuming programs. this allows us to conclude that for a large class of programs employing delay declarations there exists a model-theoretic semantics which is equivalent to the operational one

Hall Effect of Spin Waves in Frustrated Magnets

We examine a possible spin Hall effect for localized spin systems with no charge degrees of freedom. In this scenario, a longitudinal magnetic field gradient induces a transverse spin current carried by spin wave excitations with an anomalous velocity which is associated with the Berry curvature raised by spin chirality, in analogy with anomalous Hall effects in itinerant electron systems. Our argument is based on a semiclassical equations of motion applicable to general spin systems. Also, a microscopic model of frustrated magnets which exhibits the anamalous spin Hall effect is presented.Comment: 5 pages, title and presentation style are changed, accepted for publication in Phys. Rev. Let

Ergebnisse biologischer Studien an s\ufcdamerikanischen Termiten (Aus dem Italienischen, \ufcbersetzt von Dr. med. P. Speiser)

Volume: 7Start Page: 289End Page: 29

On Boolean functions encodable as a single linear pseudo-Boolean constraint

A linear pseudo-Boolean constraint (LPB) is an expression of the form a/sub 1/ ldr l/sub 1/+ ... + a/sub m/ ldr l/sub m/ >or= d, where each l/sub i/ is a literal (it assumes the value 1 or 0 depending on whether a propositional variable x/sub i/ is true or false) and a/sub 1/,...,a/sub m/, d are natural numbers. An LPB is a generalisation of a propositional clause, on the other hand it is a restriction of integer linear programming. LPBs can be used to represent Boolean functions more compactly than the well-known conjunctive or disjunctive normal forms. In this paper, we address the question: how much more compactly? We compare the expressiveness of a single LPB to that of related formalisms, and give an algorithm for computing an LPB representation of a given formula if this is possible.Anglai