A programming-language extension for distributed real-time systems

In this paper we propose a method for extending programming languages that enables the specification of timing properties of systems. The way time is treated is not language specific and the extension can therefore be included in many existing programming languages. The presented method includes a view on the system development process. An essential feature is that it enables the construction of (hard) real-time programs that may be proven correct independently of the properties of the machines that are used for their execution. It therefore provides a similar abstraction from the execution platform as is normal for non-real-time languages. The aim of this paper is to illustrate the method and demonstrate its applicability to actual real-time problems. To this end we define a simple programming language that includes the timing extension. We present a formal semantics for a characteristic part of the language constructs and apply formal methods to prove the correctness of a small example program. We consider in detail a larger example, namely the mine-pump problem known from the literature. We construct a real-time program for this problem and describe various ways to map the program to an implementation for different platforms

Detailed analysis of quantum phase transitions within the u(2)u(2) algebra

We analyze in detail the quantum phase transitions that arise in models based on the $u(2)$ algebraic description for bosonic systems with two types of scalar bosons. First we discuss the quantum phase transition that occurs in hamiltonians that admix the two dynamical symmetry chains $u(2)\supset u(1)$ and $u(2)\supset so(2)$ by diagonalizing the problem exactly in the $u(1)$ basis. Then we apply the coherent state formalism to determine the energy functional. Finally we show that a quantum phase transition of a different nature, but displaying similar characteristics, may arise also within a single chain just by including higher order terms in the hamiltonian.Comment: 5 figure

Mean-field analysis of interacting boson models with random interactions

We investigate the origin of the regular features observed in numerical studies of the interacting boson model with random interactions, in particular the dominance of L=0 ground states and the occurrence of vibrational and rotational band structures. It is shown that all of these properties can be interpreted and explained in terms of a Hartree-Bose mean-field analysis, in which different regions of the parameter space are associated with geometric shapes. The same conclusions hold for the vibron model.Comment: 8 pages, 4 figures, 2 tables. Physical Review C, in pres

Regular spectra in the vibron model with random interactions

The phenomenom of emerging regular spectral features from random interactions is addressed in the context of the vibron model. A mean-field analysis links different regions of the parameter space with definite geometric shapes. The results that are, to a large extent, obtained in closed analytic form, provide a clear and transparent interpretation of the high degree of order that has been observed in numerical studies.Comment: 19 pages, 8 figures, 2 tables. Physical Review C, in pres

The object-oriented real-time systems (OORTS) workshop : meeting summary

The workshop was held in San Antonio Texas in conjunction with the 7th IEEE Symposium on Parallel and Distributed Processing (SPDP) on October 27th, 1995. It was organized in cooperation with the Software Engineering Laboratory at NJIT with support from the U.S. Naval Surface Warfare Center and the faculty of Mathematics and Computing Science of the Eindhoven University of Technology

The object-oriented real-time systems (OORTS) workshop : meeting summary

The workshop was held in San Antonio Texas in conjunction with the "7th IEEE Symposium on Parallel and Distributed Processing" (SPDP) on October 27th, 1995. It was organized in cooperation with the Software Engineering Laboratory at NJIT with support from the U.S. Naval Surface Warfare Center and the faculty of Mathematics and Computing Science of the Eindhoven University of Technology