Uncertainty in Measurements of Distance

Ng and van Dam have argued that quantum theory and general relativity give a lower bound of L^{1/3} L_P^{2/3} on the uncertainty of any distance, where L is the distance to be measured and L_P is the Planck length. Their idea is roughly that to minimize the position uncertainty of a freely falling measuring device one must increase its mass, but if its mass becomes too large it will collapse to form a black hole. Here we show that one can go below the Ng-van Dam bound by attaching the measuring device to a massive elastic rod. Relativistic limitations on the rod's rigidity, together with the constraint that its length exceeds its Schwarzschild radius, imply that zero-point fluctuations of the rod give an uncertainty greater than or equal to L_P.Comment: 5 pages LaTe

Simulating quantum effects of cosmological expansion using a static ion trap

We propose a new experimental testbed that uses ions in the collective ground state of a static trap for studying the analog of quantum-field effects in cosmological spacetimes, including the Gibbons-Hawking effect for a single detector in de Sitter spacetime, as well as the possibility of modeling inflationary structure formation and the entanglement signature of de Sitter spacetime. To date, proposals for using trapped ions in analog gravity experiments have simulated the effect of gravity on the field modes by directly manipulating the ions' motion. In contrast, by associating laboratory time with conformal time in the simulated universe, we can encode the full effect of curvature in the modulation of the laser used to couple the ions' vibrational motion and electronic states. This model simplifies the experimental requirements for modeling the analog of an expanding universe using trapped ions and enlarges the validity of the ion-trap analogy to a wide range of interesting cases.Comment: (v2) revisions based on referee comments, figure added for clarity; (v1) 17 pages, no figure

UNION DENSITY EFFECTS IN THE SUPERMARKET INDUSTRY

Higher union density (the percentage of employees in an area who belong to unions) is known to raise the wages of union members. We find that in the supermarket industry, higher density locally also leads to higher wages for non-union members. Despite this, workers who are not in unions lose ground relative to union members. For a 10% increase in local union densities in the supermarket industry it is estimated that the wages of union employees in that labor market will increase by 5.3% and by 1.2% for nonunion. Hence, the union wage premium will increase in regions with higher union densities. At the time of the last national examination of the retail industry in 1977, union influence in the retail food industry was near its peak. Subsequently union membership and influence have declined. In 1993 a reported 25.7% of supermarket employees listed themselves as union members, a decline from 29.4% in 1984 (NBER, 1995). After conducting an extensive review of wage estimation literature, we focus on the structure of wages in the supermarket industry between 1984 and 1993. The effect of union penetration in local markets on nonunion wages or the "spill-over" effect, is an important focus of this study. While it is widely accepted that the higher the union percentage in local labor markets the higher the wages for those in the union, the corresponding effect has not been closely examined for the nonunion sector. To investigate this phenomenon we first replicate as closely as possible the results of a previous supermarket wage study (Belman and Voos, 1993). Following a baseline comparison of this initial estimation, we enlarge the data set to include individuals in rural areas and from additional years. By using a more sophisticated estimation technique we find that increasing union densities positively affect union and nonunion wages. The significant results for the nonunion sector is of particular importance, as this is the first confirmation of this effect to the best of our knowledge.Agribusiness, Labor and Human Capital, Marketing,

Entanglement between the future and past in the quantum vacuum

We note that massless fields within the future and past light cone may be quantized as independent systems. We show that the vacuum is an entangled state of these systems, exactly mirroring the known entanglement between the spacelike separated Rindler wedges. We describe a detector which exhibits a thermal response to the vacuum when switched on at t=0. The feasibility of experimentally detecting this effect is discussed.Comment: 4 pages, 1 figur

PERTS: A Prototyping Environment for Real-Time Systems

PERTS is a prototyping environment for real-time systems. It is being built incrementally and will contain basic building blocks of operating systems for time-critical applications, tools, and performance models for the analysis, evaluation and measurement of real-time systems and a simulation/emulation environment. It is designed to support the use and evaluation of new design approaches, experimentations with alternative system building blocks, and the analysis and performance profiling of prototype real-time systems

Customers as decision-makers: strategic environmental assessment in the private sector

Despite its diversification and global spread, strategic environmental assessment (SEA) remains limited mainly to activities characterised by well-defined planning processes, typically within the public sector. This article explores the possible application of SEA within certain private-sector contexts where higher-level strategy-making itself is inherently weaker and development is often piecemeal and reactive. The possible adaptation of SEA to the preparation of a strategic document by a particular industrial concern in the UK is examined: this draws attention to the multi-actor nature of development processes within the industry. This leads to the suggestion that SEA in this setting should be thought of as a form of environmental advocacy oriented towards industrial customers, who are understood as sharing a decision-making role in infrastructure development.</p