Dark energy from quantum wave function collapse of dark matter

Dynamical wave function collapse models entail the continuous liberation of a specified rate of energy arising from the interaction of a fluctuating scalar field with the matter wave function. We consider the wave function collapse process for the constituents of dark matter in our universe. Beginning from a particular early era of the universe chosen from physical considerations, the rate of the associated energy liberation is integrated to yield the requisite magnitude of dark energy around the era of galaxy formation. Further, the equation of state for the liberated energy approaches $w \to -1$ asymptotically, providing a mechanism to generate the present acceleration of the universe.Comment: 5 pages in Elsevier style to match with version published in Phys. Lett.

Modelling of photonic wire Bragg Gratings

Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

Classical Vs Quantum Probability in Sequential Measurements

We demonstrate in this paper that the probabilities for sequential measurements have features very different from those of single-time measurements. First, they cannot be modelled by a classical stochastic process. Second, they are contextual, namely they depend strongly on the specific measurement scheme through which they are determined. We construct Positive-Operator-Valued measures (POVM) that provide such probabilities. For observables with continuous spectrum, the constructed POVMs depend strongly on the resolution of the measurement device, a conclusion that persists even if we consider a quantum mechanical measurement device or the presence of an environment. We then examine the same issues in alternative interpretations of quantum theory. We first show that multi-time probabilities cannot be naturally defined in terms of a frequency operator. We next prove that local hidden variable theories cannot reproduce the predictions of quantum theory for sequential measurements, even when the degrees of freedom of the measuring apparatus are taken into account. Bohmian mechanics, however, does not fall in this category. We finally examine an alternative proposal that sequential measurements can be modelled by a process that does not satisfy the Kolmogorov axioms of probability. This removes contextuality without introducing non-locality, but implies that the empirical probabilities cannot be always defined (the event frequencies do not converge). We argue that the predictions of this hypothesis are not ruled out by existing experimental results (examining in particular the "which way" experiments); they are, however, distinguishable in principle.Comment: 56 pages, latex; revised and restructured. Version to appear in Found. Phy

Introduction to decoherence theory

This is an introduction to the theory of decoherence with an emphasis on its microscopic origins and on a dynamic description. The text corresponds to a chapter soon to be published in: A. Buchleitner, C. Viviescas, and M. Tiersch (Eds.), Entanglement and Decoherence. Foundations and Modern Trends, Lecture Notes in Physics, Vol 768, Springer, Berlin (2009)Comment: 57 pages, 2 figures; some new material added and typos corrected. This corresponds to the published versio

Tobacco control law enforcement and compliance in odisha, India - implications for tobacco control policy and practice

Contains fulltext : 110004.pdf (publisher's version ) (Open Access)Introduction: Tobacco use is a leading cause of deaths and disabilities in India, killing about 1.2 lakh people in 2010. About 29% of adults use tobacco on a daily basis and an additional 5% use it occasionally. In Odisha, non-smoking forms are more prevalent than smoking forms. The habit has very high opportunity cost as it reduces the capacity to seek better nutrition, medical care and education. In line with the WHO Framework Convention on Tobacco Control (FCTC), the Cigarettes and Other Tobacco Products Act (COTPA) is a powerful Indian national law on tobacco control. The Government of Odisha has shown its commitment towards enforcement and compliance of COTPA provisions. In order to gauge the perceptions and practices related to tobacco control efforts and level of enforcement of COTPA in the State, this cross-sectional study was carried out in seven selected districts. Materials and methods:A semi-structured interview schedule was developed, translated into Odiya and field-tested for data collection. It mainly contained questions related to knowledge on provisions of section 4-7 of COTPA 2003, perception about smoking, chewing tobacco and practices with respect to compliance of selected provisions of the Act. 1414 samples were interviewed. Results: The highest percentage of respondents was from the government departments. 70% of the illiterates consumed tobacco as compared to 34% post graduates. 52.1% of the respondents were aware of Indian tobacco control laws, while 80.8% had knowledge about the provision of the law prohibiting smoking in public places. However, 36.6% of the respondents reported that they had 'very often' ' seen tobacco products being sold 'to a minor', while 31.2% had seen tobacco products being sold 'by a minor'. In addition, 24.8% had 'very often' seen tobacco products being sold within a radius of 100 yards of educational institutions