On the Thermodynamic Limit of the Lipkin Model

The thermodynamic limit of the Lipkin model is investigated. While the limit turns out to be rather elusive, the analysis gives strong indications that the limit yields two analytically dissociated operators, one for the normal and one for the deformed phase. While the Lipkin Hamiltonian is hermitian and has a second order phase transition in finite dimensions (finite particle number), both properties seem to be destroyed in the thermodynamic limit.Comment: 9 pages, 3 figures to appear in JPhys

The Economic Value of Remote Sensing of Earth Resources from Space: An ERTS Overview and the Value of Continuity of Service. Volume 1: Summary

An overview of the ERTS program is given to determine the magnitude of the benefits that can be reasonably expected to flow from an Earth Resources Survey (ERS) Program, and to assess the benefits foregone in the event of a one or two-year gap in ERS services. An independent evaluation of the benefits attributable to ERS-derived information in key application areas is presented. These include two case studies in agriculture-distribution, production and import/export, and one study in water management. The cost-effectiveness of satellites in an ERS system is studied by means of a land cover case study. The annual benefits achieveable from an ERS system are measured by the in-depth case studies to be in the range of $430 to$746 million. Benefits foregone in the event of a one-year gap in ERS service are estimated to be $147 to$220 million and $274 to$420 million for a two-year gap in ERS service

Chirality of wave functions for three coalescing levels

The coalescence of three levels has particular attractive features. Even though it may be difficult to realise such event in the laboratory (three additional real parameters must be adjusted), to take up the challenge seems worthwhile. In the same way as the chiral behaviour of a usual EP can give a direction on a line, the state vectors in the vicinity of an EP3 provide an orientation in the plane. The distinction between left and right handedness depends on the distribution of the widths of the three levels in the vicinity of the point of coalescence.Comment: Manuscript has been discussed in June 2007 with the experimental group under Professor Achim Richter at the TU Darmstadt. It has been presented at the 6th International Workshop on Pseudo Hermitian Hamiltonians, London, 16-18 July 2007. An expanded version is being prepared for publication. 3 Figures, 11 page

Resonance scattering and singularities of the scattering function

Recent studies of transport phenomena with complex potentials are explained by generic square root singularities of spectrum and eigenfunctions of non-Hermitian Hamiltonians. Using a two channel problem we demonstrate that such singularities produce a significant effect upon the pole behaviour of the scattering matrix, and more significantly upon the associated residues. This mechanism explains why by proper choice of the system parameters the resonance cross section is increased drastically in one channel and suppressed in the other channel.Comment: 4 pages, 3 figure

Feasibility Framing: Media Responses to the 2018 Intergovernmental Panel on Climate Change Special Report

With an associated warming of 0.85°C documented between 1880 and 2012, climate change has altered the frequency of extreme weather events, contributed to rising sea level, impacted biodiversity, and has become a growing concern (Allen et al. 53). Created in 1988, the Intergovernmental Panel on Climate Change (IPCC) compiles research on climate change for the use of policymaking. While the IPCC targets policymakers, the public generally learns science through media outlets (Schmidt et al.). On 8 October 2018, the IPCC released a special report titled, “Global Warming at 1.5°C.” Media outlets quickly responded to this report

Economic Opportunities of Space Enterprise in the Next Decades

At this juncture of the United States Space Program a major opportunity exists to give a new impetus to space applications (and space sciences) for the next two decades. It involves a redirection of the U.S. Space Programs from an emphasis of means to one emphasizing scientific and economic application goals of space technology. This opportunity comes about with the successful deployment of the Space Shuttle System in the early 1980s. Four topics are emphasized: 1) The Development of Global Information Systems; 2) Large Space Structures Applications; 3) Space as an Energy Base for Mankind; and 4) Likely Phases of Space Application Development

Instabilities, nonhermiticity and exceptional points in the cranking model

A cranking harmonic oscillator model, widely used for the physics of fast rotating nuclei and Bose-Einstein condensates, is re-investigated in the context of PT-symmetry. The instability points of the model are identified as exceptional points. It is argued that - even though the Hamiltonian appears hermitian at first glance - it actually is not hermitian within the region of instability.Comment: 4 pages, 1 figur

Glutamate and purine catabolites in relation to free radical production during focal ischemia-reperfusion : an in vivo study in cats

The in-vivo interrelation between excitotoxicity and oxidative stress following cerebral ischemia in cats was investigated. To elucidate the role of this mechanism in cerebral ischemia, the study presented herein sought to investigate the spatial and temporal features of the free radical response to elevations of glutamate and purine catabolites in a reproducible model of in vivo focal ischemia/reperfusion. The time course of neurochemical and Reactive Oxygen Species (ROS) were simultaneously conducted in ischemic focus and perifocal region of the brain.peer-reviewe