A TETRAD-based Approach for Theory Development in Information Systems Research

Theory development and theory testing are two primary processes in social science research. Statistical methods and tools are used in various stages of these processes. Information systems researchers have employed many statistical methods and tools for theory testing. However, very few statistical approaches are known to help researchers with theory development. In this paper, we introduce TETRAD as a powerful approach to aid researchers in developing and discovering new theoretical relationships. We illustrate the TETRAD approach by re-analyzing data from two articles published in premier information systems journals. The results from the previous examples demonstrate that TETRAD is a useful tool for uncovering potential theoretical relationships, especially when prior knowledge of underlying theory bases is lacking. We demonstrate that TETRAD is an effective and powerful statistical tool that can assist researchers in the iterative process of theory development

State — Region — Branch — Enterprise: System Sustainability Framework of the Russian Economy

This paper investigates sustainability factors of the Russian economy as a multi-level, multi-entity and multi-aspect socio-economic system from the system perspective. The economic system sustainability concept is formulated as an ability to maintain preconditions for the development by supporting and effective using of economic system structure. The leading role of the community of economic entities at different levels (including the state as the entity of international relations, regions as the entities of Federation, enterprises as the business entities) in the economic sustainability is demonstrated. The necessity of the economic entity network “extension” by strengthening the sustainability of economic sectors is emphasized. The research into the internal basic system structure of an economic entity and external structure of its immediate surroundings in socio-economic, administrative-and-managerial and market environments using the results of the new economic systems theory contributes the evidence of the similarity of these structures to the conclusion. It is shown that each of the systems includes (together with an entity itself) four systems of different types (object, environment, process and project). The entity’s system environment has the same structure in administrative-and-managerial interlevel interactions. This makes it possible to combine the problem of the entity’s sustainability and the issue of the balanced system structures forming the economic entities’ internal and external environments. The method of calculating the index of such balanced systems is given. Recommendations on the selection of economic policy measures aimed at ensuring system sustainability of the Russian economy in the period of crisis are provided. It is shown that such a policy should be carried out in accordance with the principles of economic entity protection; balanced system of the economic entities’ internal and external environment; economic entities’ corporate solidarity regardless of their level in the management hierarchy.This article is supported by the Russian Science Foundation grant, project No. 14-18-02294

The Lazarus project: A pragmatic approach to binary black hole evolutions

We present a detailed description of techniques developed to combine 3D numerical simulations and, subsequently, a single black hole close-limit approximation. This method has made it possible to compute the first complete waveforms covering the post-orbital dynamics of a binary black hole system with the numerical simulation covering the essential non-linear interaction before the close limit becomes applicable for the late time dynamics. To determine when close-limit perturbation theory is applicable we apply a combination of invariant a priori estimates and a posteriori consistency checks of the robustness of our results against exchange of linear and non-linear treatments near the interface. Once the numerically modeled binary system reaches a regime that can be treated as perturbations of the Kerr spacetime, we must approximately relate the numerical coordinates to the perturbative background coordinates. We also perform a rotation of a numerically defined tetrad to asymptotically reproduce the tetrad required in the perturbative treatment. We can then produce numerical Cauchy data for the close-limit evolution in the form of the Weyl scalar $\psi_4$ and its time derivative $\partial_t\psi_4$ with both objects being first order coordinate and tetrad invariant. The Teukolsky equation in Boyer-Lindquist coordinates is adopted to further continue the evolution. To illustrate the application of these techniques we evolve a single Kerr hole and compute the spurious radiation as a measure of the error of the whole procedure. We also briefly discuss the extension of the project to make use of improved full numerical evolutions and outline the approach to a full understanding of astrophysical black hole binary systems which we can now pursue.Comment: New typos found in the version appeared in PRD. (Mostly found and collected by Bernard Kelly

Twisting Null Geodesic Congruences, Scri, H-Space and Spin-Angular Momentum

The purpose of this work is to return, with a new observation and rather unconventional point of view, to the study of asymptotically flat solutions of Einstein equations. The essential observation is that from a given asymptotically flat space-time with a given Bondi shear, one can find (by integrating a partial differential equation) a class of asymptotically shear-free (but, in general, twistiing) null geodesic congruences. The class is uniquely given up to the arbitrary choice of a complex analytic world-line in a four-parameter complex space. Surprisingly this parameter space turns out to be the H-space that is associated with the real physical space-time under consideration. The main development in this work is the demonstration of how this complex world-line can be made both unique and also given a physical meaning. More specifically by forcing or requiring a certain term in the asymptotic Weyl tensor to vanish, the world-line is uniquely determined and becomes (by several arguments) identified as the `complex center-of-mass'. Roughly, its imaginary part becomes identified with the intrinsic spin-angular momentum while the real part yields the orbital angular momentum.Comment: 26 pages, authors were relisted alphabeticall