Scalar Perturbations in Scalar Field Quantum Cosmology

In this paper it is shown how to obtain the simplest equations for the Mukhanov-Sasaki variables describing quantum linear scalar perturbations in the case of scalar fields without potential term. This was done through the implementation of canonical transformations at the classical level, and unitary transformations at the quantum level, without ever using any classical background equation, and it completes the simplification initiated in investigations by Langlois \cite{langlois}, and Pinho and Pinto-Neto \cite{emanuel2} for this case. These equations were then used to calculate the spectrum index $n_s$ of quantum scalar perturbations of a non-singular inflationary quantum background model, which starts at infinity past from flat space-time with Planckian size spacelike hypersurfaces, and inflates due to a quantum cosmological effect, until it makes an analytical graceful exit from this inflationary epoch to a decelerated classical stiff matter expansion phase. The result is $n_s=3$, incompatible with observations.Comment: 10 pages, 2 figures, accepted version to Physical Review D 7

Evaluation of a computer-generated perspective tunnel display for flight path following

The display was evaluated by monitoring pilot performance in a fixed base simulator with the vehicle dynamics of a CH-47 tandem rotor helicopter. Superposition of the predicted future vehicle position on the tunnel image was also investigated to determine whether, and to what extent, it contributes to better system performance (the best predicted future vehicle position was sought). Three types of simulator experiments were conducted: following a desired trajectory in the presence of disturbances; entering the trajectory from a random position, outside the trajectory; detecting and correcting failures in automatic flight. The tunnel display with superimposed predictor/director symbols was shown to be a very successful combination, which outperformed the other two displays in all three experiments. A prediction time of 4 to 7 sec. was found to optimize trajectory tracking for the given vehicle dynamics and flight condition. Pilot acceptance of the tunnel plus predictor/director display was found to be favorable and the time the pilot needed for familiarization with the display was found to be relatively short

Do subleading corrections to Bekenstein-Hawking entropy hold the key to quantum gravity?

Black-holes are considered to be theoretical laboratories for testing models of quantum gravity. It is usually believed that any candidate for quantum gravity must explain the microscopic origin of the Bekenstein-Hawking ($S_{_{\rm BH}}$) entropy. In this letter, we argue (i) the requirement for a candidate approach to go beyond $S_{_{\rm BH}}$ and provide generic subleading corrections, and (ii) the importance to {\it disentangle} and identify the degrees of freedom leading to $S_{_{\rm BH}}$ and its subleading corrections. Using the approach of entanglement of modes across the horizon, we show that the microscopic degrees of freedom that lead to $S_{_{\rm BH}}$ and subleading corrections are different. We further show, using microcanonical and canonical ensemble approaches, that the quantum entanglement predicts generic power-law corrections to $S_{_{\rm BH}}$ and that the corrections can be identified with the kinematical properties of the event-horizon.Comment: 6 pages, Final version, To appear in MPL

Announcement Effects on Bank Stock Prices: Citicorp\u27s Increase in Loan Loss Reserves For Third World Debt

Citicorp\u27s announcement of a sizeable increase to its loan loss reserve account was a landmark public admission of possible loan default by Third World debtor nations. This paper analyzes the impact of the announcement on Citicorp, the banking industry, and the stock market. The results provide evidence of a positive response to Citicorp\u27s action. There is additional evidence that the size of the market response is related to an individual bank\u27s degree of international loan exposure

The Significance of Porfolio Lenders to Real Estate Brokers

For the reasons observed in the sample of mortgage loans examined, the real estate brokerage industry will continue to depend heavily on portfolio lending to finance residential housing transactions. This paper examines a sample of residential mortgages to determine the breadth of lending by home type and customer credit qualification. The findings show that portfolio lending is required to satisfy homebuyers with heterogenous mortgage loan needs. Comparative analysis of credit decisions provides evidence of sound lending.

A trigonometric interpolation approach to mixed-type boundary problems associated with permeameter shape factors

[1] Hydraulic conductivity is a fundamental hydrogeological parameter, whose in situ measurement at a local scale is principally performed through injection tests from screened probes or using impermeable packers in screened wells. The shape factor F [L] is a proportionality constant required to estimate conductivity from observed flow rate to injection head ratios, and it depends on the geometric properties of the flow field. Existing approaches for determination of F are either based on geometric or mathematical simplifications and are limited to particular assumptions about the flow domain's external boundaries. The present work presents a general semianalytical solution to steady state axisymmetric flow problems, where external boundaries may be nearby and of arbitrary combinations of impermeable and constant head type. The inner boundary along the probe or well may consist of an arbitrary number of impermeable and constant head intervals resulting in a mixed-type boundary value problem, for which a novel and direct solution method based on trigonometric interpolation is presented. The approach is applied to generate practical nondimensional charts of F for different field and laboratory situations. Results show that F is affected by less than 5% if a minimum distance of 10 probe or well diameters is kept between the injection screen and a nearby boundary. Similarly, minimum packer lengths of two well diameters are required to avoid increasing F by more than 10%. Furthermore, F is determined for laboratory barrel experiments giving guidelines for achieving equal shape factors as in field situations without nearby boundaries. F for the theoretical case of infinitely short packers is shown to be infinitely large