Implementing a Shared Dataspace Language on a Message-Based Multiprocessor

The term shared dataspace refers to the general class of models and languages in which the principal means of communication is a common, content-addressable data structure called a dataspace. This paper reports on progress we have made toward the development of prototype implementation of a shared dataspace language, Swarm, on a hypercube multiprocessor. The paper includes an informal overview of the Swarm language, describes the design organization of a transaction processing system which forms the kernels of a Swam implementation, and explains the algorithms implementing a subset of Swarm embedded in the language C

Energy Density-Flux Correlations in an Unusual Quantum State and in the Vacuum

In this paper we consider the question of the degree to which negative and positive energy are intertwined. We examine in more detail a previously studied quantum state of the massless minimally coupled scalar field, which we call a ``Helfer state''. This is a state in which the energy density can be made arbitrarily negative over an arbitrarily large region of space, but only at one instant in time. In the Helfer state, the negative energy density is accompanied by rapidly time-varying energy fluxes. It is the latter feature which allows the quantum inequalities, bounds which restrict the magnitude and duration of negative energy, to hold for this class of states. An observer who initially passes through the negative energy region will quickly encounter fluxes of positive energy which subsequently enter the region. We examine in detail the correlation between the energy density and flux in the Helfer state in terms of their expectation values. We then study the correlation function between energy density and flux in the Minkowski vacuum state, for a massless minimally coupled scalar field in both two and four dimensions. In this latter analysis we examine correlation functions rather than expectation values. Remarkably, we see qualitatively similar behavior to that in the Helfer state. More specifically, an initial negative energy vacuum fluctuation in some region of space is correlated with a subsequent flux fluctuation of positive energy into the region. We speculate that the mechanism which ensures that the quantum inequalities hold in the Helfer state, as well as in other quantum states associated with negative energy, is, at least in some sense, already ``encoded'' in the fluctuations of the vacuum.Comment: 21 pages, 7 figures; published version with typos corrected and one added referenc

Mass scaling and non-adiabatic effects in photoassociation spectroscopy of ultracold strontium atoms

We report photoassociation spectroscopy of ultracold $^{86}$Sr atoms near the intercombination line and provide theoretical models to describe the obtained bound state energies. We show that using only the molecular states correlating with the $^1S_0$$+$$^3P_1$ asymptote is insufficient to provide a mass scaled theoretical model that would reproduce the bound state energies for all isotopes investigated to date: $^{84}$Sr, $^{86}$Sr and $^{88}$Sr. We attribute that to the recently discovered avoided crossing between the $^1S_0$$+$$^3P_1$ $0_u^+$ ($^3\Pi_u$) and $^1S_0$$+$$^1D_2$ $0_u^+$ ($^1\Sigma^+_u$) potential curves at short range and we build a mass scaled interaction model that quantitatively reproduces the available $0_u^+$ and $1_u$ bound state energies for the three stable bosonic isotopes. We also provide isotope-specific two-channel models that incorporate the rotational (Coriolis) mixing between the $0_u^+$ and $1_u$ curves which, while not mass scaled, are capable of quantitatively describing the vibrational splittings observed in experiment. We find that the use of state-of-the-art ab initio potential curves significantly improves the quantitative description of the Coriolis mixing between the two -8 GHz bound states in $^{88}$Sr over the previously used model potentials. We show that one of the recently reported energy levels in $^{84}$Sr does not follow the long range bound state series and theorize on the possible causes. Finally, we give the Coriolis mixing angles and linear Zeeman coefficients for all of the photoassociation lines. The long range van der Waals coefficients $C_6(0_u^+)=3868(50)$~a.u. and $C_6(1_u)=4085(50)$~a.u. are reported.Comment: 14 pages, 7 tables, 5 figures. Submitted to Phys. Rev.

The investment location decisions in the steel industry

The global dimension of the economy in general and of the steel industry in particular makes the decision regarding the location of new production facilities a challenge for managers. This paper tries to provide tools that make the decision taking process easier. Is assumed that certain tax levy rates are important to this process and they are compared and analyzed. Finally, based on this analysis this paper tries to prioritize some countries in terms of their economic attractiveness in order to identify the most suitable country for placing a steel factory

The investment location decisions in the steel industry

The global dimension of the economy in general and of the steel industry in particular makes the decision regarding the location of new production facilities a challenge for managers. This paper tries to provide tools that make the decision taking process easier. Is assumed that certain tax levy rates are important to this process and they are compared and analyzed. Finally, based on this analysis this paper tries to prioritize some countries in terms of their economic attractiveness in order to identify the most suitable country for placing a steel factory

Dynamical mechanism of atrial fibrillation: a topological approach

While spiral wave breakup has been implicated in the emergence of atrial fibrillation, its role in maintaining this complex type of cardiac arrhythmia is less clear. We used the Karma model of cardiac excitation to investigate the dynamical mechanisms that sustain atrial fibrillation once it has been established. The results of our numerical study show that spatiotemporally chaotic dynamics in this regime can be described as a dynamical equilibrium between topologically distinct types of transitions that increase or decrease the number of wavelets, in general agreement with the multiple wavelets hypothesis. Surprisingly, we found that the process of continuous excitation waves breaking up into discontinuous pieces plays no role whatsoever in maintaining spatiotemporal complexity. Instead this complexity is maintained as a dynamical balance between wave coalescence -- a unique, previously unidentified, topological process that increases the number of wavelets -- and wave collapse -- a different topological process that decreases their number.Comment: 15 pages, 14 figure

Averaged Energy Inequalities for the Non-Minimally Coupled Classical Scalar Field

The stress energy tensor for the classical non-minimally coupled scalar field is known not to satisfy the point-wise energy conditions of general relativity. In this paper we show, however, that local averages of the classical stress energy tensor satisfy certain inequalities. We give bounds for averages along causal geodesics and show, e.g., that in Ricci-flat background spacetimes, ANEC and AWEC are satisfied. Furthermore we use our result to show that in the classical situation we have an analogue to the phenomenon of quantum interest. These results lay the foundations for analogous energy inequalities for the quantised non-minimally coupled fields, which will be discussed elsewhere.Comment: 8 pages, RevTeX4. Minor typos corrected; version to appear in Phys Rev