Addendum: Symmetries of the energy-momentum tensor

In recent papers [1-3], we have discussed matter symmetries of non-static spherically symmetric spacetimes, static plane symmetric spacetimes and cylindrically symmetric static spacetimes. These have been classified for both cases when the energy-momentum tensor is non-degenerate and also when it is degenerate. Here we add up some consequences and the missing references about the Ricci tensor.Comment: 7 pages, no figure, LaTe

Classification of Static Plane Symmetric Spacetimes according to their Matter Collineations

In this paper we classify static plane symmetric spacetimes according to their matter collineations. These have been studied for both cases when the energy-momentum tensor is non-degenerate and also when it is degenerate. It turns out that the non-degenerate case yields either {\it four}, {\it five}, {\it six}, {\it seven} or {\it ten} independent matter collineations in which {\it four} are isometries and the rest are proper. There exists three interesting cases where the energy-momentum tensor is degenerate but the group of matter collineations is finite-dimensional. The matter collineations in these cases are either {\it four}, {\it six} or {\it tenComment: 15 pages, LaTex, no figure

Spherical Thin-Shell Wormholes and Modified Chaplygin Gas

The purpose of this paper is to construct spherical thin-shell wormhole solutions through cut and paste technique and investigate the stability of these solutions in the vicinity of modified Chaplygin gas. The Darmois-Israel formalism is used to formulate the stresses of the surface concentrating the exotic matter. We explore the stability of the wormhole solutions by using the standard potential method. We conclude that there exist more stable as well as unstable solutions than the previous study with generalized Chaplygin gas \cite{15}.Comment: 18 pages, 6 figure

Identifying reverse 3PL performance critical success factors

The reverse and third party logistics operational process is now well known and established to be a vital component of modern day supply chain and product / service-based organizations (Marasco, 2007). Apart from being a vital component of such enterprises, many researchers and practitioners have also been noting the importance of this approach and its impact on customer service, satisfaction, profitability and other key performance indicators (Autry et al., 2001). However, studies relating to reverse 3PL performance are still limited. This research attempts to examine the factors that influence the reverse logistics performance within 3PL, within a specific case study organization in Thailand, which aims to add to work carried out relating to such operations in this part of the world such as by Bhatnagar et al. (1999). This research uses a combination of a qualitative case study along with a quantitative approach (Fuzzy Cognitive Mapping) to model and analyse the constructs which underpin the dynamics involved within a 3PL scenario. As such, both the combined approaches are based upon the development and testing of a hypothesis via empirical primary and computational data. Hence, using extant literature, and combined qualitative and quantitative research approaches, the paper identifies significant and pertinent critical success factors for reverse 3PL performance (centred around the indogenous/exogenous relationship between information systems, resource commitment and organizational structure). The paper also explores the deep inter-relationships involved within 3PL operations using the Fuzzy Cognitive Mapping technique, contributing to the existing literature on reverse 3PL and performant supply chains, and identifying critical success factors and underlying determinants of reverse 3PL of use to those industry and investigating the area from an academic perspective