35,547 research outputs found

    The inflation-output nexus:empirical evidence from India, Brazil and South Africa

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    In this paper we study the relationship between output and inflation for India, Brazil, and South Africa using the EGARCH model. For India and South Africa, we find evidence for: (1) the Cukierman and Meltzer hypothesis that inflation volatility raises inflation; (2) the Friedman hypothesis that inflation raises inflation volatility; and (3) the Black hypothesis that output volatility raises output growth, and that output volatility reduces inflation. For Brazil, we do not find any evidence of a systematic relationship between inflation and output growth.Output, inflation, EGARCH model, volatility

    Global dynamics of radiatively inefficient accretion flows: advection versus convection

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    We obtain global solutions of radiatively inefficiently accretion flows around black holes. Whether and where convection develops in a flow are self-consistently determined with the mixing-length theory. The solutions can be divided into three types according to the strength of normal viscosity. Type I solution corresponds to large viscosity parameter \alpha \ga 0.1, which is purely advection-dominated and with no convection, and has been extensively studied in the literature. Type II solution is for moderate α0.01\alpha \sim 0.01, which has a three-zone structure. The inner zone is advection-dominated, the middle zone is convection-dominated and ranges from a few tens to a few thousands of gravitational radii, and the outer zone is convectively stable and matches outward a Keplerian disc. The net energy flux throughout the flow is inward as in type I solution. Type III solution which is for small \alpha \la 0.001 consists of two zones as Abramowicz et al. suggested previously: an inner advection-dominated zone and an outer convection-dominated zone, separated at a radius of a few tens of gravitational radii. This type of solution has an outward net energy flux. In both type II and III solutions the radial density profile is between the 1/2 law of self-similar convection-dominated accretion flow model and the 3/2 law of self-similar advection-dominated accretion flow model, and the efficiency of energy release is found to be extremely low. Our results are in good agreement with those of recent numerical simulations.Comment: 13 pages, 2 figures, accepted for publication in MNRA

    Has the structural break slowed down growth rates of stock markets?

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    In this paper, we use the common structural break test suggested by Bai et al. (1998) to test for a common structural break in the stock prices of the US, the UK, and Japan. On the basis of the structural break, we divide each country‟s stock price series into sub-samples and investigate whether or not the structural break had slowed down the growth of stock markets. Our main findings are that when stock markets are modeled in a trivariate sense the common structural break turns out to be 1990:02, with the confidence interval including several episodes, such as the asset price bubble when housing prices and stock prices in Japan reached a peak in 1988/1989, the early 1990s recession in the UK, the business cycle peak of July 1990, the August 1990 Iraqi invasion of Kuwait and the March 1991 business cycle trough. Annual average growth rates suggest that the structural break has slowed down the growth rate of the US, UK and Japanese stock markets.Common Structural Break Test, Stock Markets

    Effect of Canard on the Characteristics of a 65° Delta Wing-A Preliminary Analysis of Experimental Data.

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    The experimental data available on a 65° swept-back, cropped delta wing with a canard has been analysed to study the effects of canard. Two sets of results are available : the first set is with a wing having sharp leading edges and the second set with a wing having rounded' leading edges. The tests were carried out at Mach numbers of 0.4 and 0.85 (Reynolds - number of 9.106 based on wing root chore) for the first set and at 0.5, 0.7, 0.85 and 1.2 (Reynolds number of 4.5.10^6 based on wing root chord) for the second set. The main effect of the canard is to delay leading edge separation in the forward part of the rounded leading edge wing. In the case of the sharp leading edge wing, although earlier measurements have shown that the canard is able to suppress leading edge separation, there is no direct evidence of this in the present measurements. However, the results do show a significant weakening of the wing vortex in the presence of the canard

    Black Holes in Astrophysics

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    This article reviews the current status of black hole astrophysics, focusing on topics of interest to a physics audience. Astronomers have discovered dozens of compact objects with masses greater than 3 solar masses, the likely maximum mass of a neutron star. These objects are identified as black hole candidates. Some of the candidates have masses of 5 to 20 solar masses and are found in X-ray binaries, while the rest have masses from a million to a billion solar masses and are found in galactic nuclei. A variety of methods are being tried to estimate the spin parameters of the candidate black holes. There is strong circumstantial evidence that many of the objects have event horizons. Recent MHD simulations of magnetized plasma accreting on rotating black holes seem to hint that relativistic jets may be produced by a magnetic analog of the Penrose process.Comment: To appear in a forthcoming Special Focus Issue on "Spacetime 100 Years Later" published by the New Journal of Physics (http://www.iop.org/EJ/njp) The article, finalized in October, 2004, consists of 21 pages of text, 3 figures and 6 movies (found at http://www.cfa.harvard.edu/~narayan/NJP
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