The shear dynamo problem for small magnetic Reynolds numbers

We study large-scale dynamo action due to turbulence in the presence of a linear shear flow, in the low conductivity limit. Our treatment is nonperturbative in the shear strength and makes systematic use of both the shearing coordinate transformation and the Galilean invariance of the linear shear flow. The velocity fluctuations are assumed to have low magnetic Reynolds number (Rm) but could have arbitrary fluid Reynolds number. The magnetic fluctuations are determined to lowest order in Rm by explicit calculation of the resistive Green's function for the linear shear flow. The mean electromotive force is calculated and an integro-differential equation is derived for the time evolution of the mean magnetic field. In this equation, velocity fluctuations contribute to two different kinds of terms, the C and D terms, in which first and second spatial derivatives of the mean magnetic field, respectively, appear inside the spacetime integrals. The contribution of the D terms is such that the time evolution of the cross-shear components of the mean field do not depend on any other components excepting themselves. Therefore, to lowest order in Rm but to all orders in the shear strength, the D terms cannot give rise to a shear-current assisted dynamo effect. Casting the integro-differential equation in Fourier space, we show that the normal modes of the theory are a set of shearing waves, labelled by their sheared wavevectors. The integral kernels are expressed in terms of the velocity spectrum tensor, which is the fundamental quantity that needs to be specified to complete the integro-differential equation description of the time evolution of the mean magnetic field.Comment: Near-final version; Accepted for publication in the Journal of Fluid Mechanics; References added; 22 pages, 2 figure

Telecommunications infrastructure and economic growth: Evidence from developing countries.

Often, it has been observed that telecommunication infrastructure development and economic growth proceed together. While this relationship has been studied in the context of developed (OECD) countries, in this study, we investigate this simultaneous relationship between telecommunications and the economic growth, using data for developing countries. Using 3SLS, we estimate a system of equations that endogenize economic growth and telecom penetration (respectively production function and demand for telecom services), along with supply of telecom investment and growth in telecom penetration. We estimate this system of equations separately for main telephone lines and cell phones. We find that while traditional economic factors explain demand for main line phones, they do not explain demand for cell phones. We also find significant impacts of cellular services on national output, when we control for the effects of capital and labour. The impact of telecom penetration on total output is, however, significantly lower for developing countries than that reported for OECD countries, dispelling the convergence hypothesis.Telecommunication ; Infrastructure ; Economic growth ; Reverse causality ; Developing countries

Constraining the Randall-Sundrum Model Using Diphoton Production at Hadron Colliders

Virtual effects of gravitons in the production of diphotons at the upgraded Tevatron and at the LHC are analysed with the idea of probing the parameter space of the Randall-Sundrum (RS) model. It is shown that this process yields stringent constraints on the parameter space of the RS model. We show that data on diphoton production from Tevatron Run II will be sensitive to a masses of the first graviton resonance in the range of 700-1150 GeV, while at LHC the mass range probed will be in the region of 3.5 -- 5.5 TeV.Comment: 8 pages, Latex file + 1 ps figur

Profitability Study of MPAA Rated Movies

Concerned with the limited number of family oriented films currently produced each year and an increase in the number of films containing sex and violence, The Dove Foundation is interested in determining which films, by MPAA rating, produce the greatest profits as well as the highest rates of return on investment (ROI)

Charmonium Production at the LHC

The analyses of large transverse momentum charmonium production at the Tevatron have shown that fragmentation of gluons is an important production mechanism. We study large-$p_T$ charmonium production in $pp$ collisions at the LHC, and find that due to the copious gluon production at this energy, the gluon fragmentation contribution completely overwhelms the fusion contribution and the charm quark fragmentation contribution. Our analysis shows that for $J/\psi$ production at the LHC, there is a significant event rate even for $p_T \sim$~100~GeV. The measurement of the cross-section at such large values of $p_T$ will provide a very important test of the fragmentation mechanism.Comment: 9 pages including 2 postscript figure