A CM based equalizer for space-time spreading over channels with inter-Symbol interference

Space-time block coding (STBC) and a number of derivative techniques have been developed to maximize the diversity gain of a multi-input multi-output (MIMO) channel. This was later generalized for multi-user DS-CDMA systems through space-time spreading (STS), [3] and [4], which assumed flat fading as well as the availability of full channel state information (CSI) at the receiver. This paper focuses on the development of a blind chip-rate method for the equalization of STS over channels with inter-symbol interference (ISI). Simulation results are presented to demonstrate the convergence and noise resilience of the derived algorithm

Spectral Properties of M87 Using Two-Component Flow

We fit the observational data for M87 using two-component advective disk model. We show that the flat spectrum from the nucleus of M87 is due to synchrotron radiation produced by non-thermal electrons in the CENBOL. The non-thermal distribution is produced due to acceleration of electrons across the shock in a sub-Keplerian flow.Comment: 4 Pages, 1 Figures, Proceeding of the 2nd Kolkata Conference on "Observational Evidence for the Black Holes in the Universe", Published in AIP, 200

Consistent 3D Quantum Gravity on Lens Spaces

We study non-perturbative quantization of 3d gravity with positive cosmological constant (de Sitter space being the prototype vacuum solution, whose Euclideanization of course gives the three sphere) on the background topology of lens space, which is a three spheres modulo a discrete group. Instead of the strategy followed by a recent work \cite{Castro:2011xb}, which compares results in the second and first order formulations of gravity, we concentrate on the later solely. We note, as a striking feature, that the quantization, that relies heavily on the axiomatics of topological quantum field theory (TQFT) can only be consistently carried by augmenting the conventional theory by an additional topological term coupled through a dimensionless parameter. More importantly the introduction of this additional parameter renders the theory finite.Comment: New section and references added. Accepted in Phys. Rev. D for publicatio

Boosts, Schwarzschild Black Holes and Absorption cross-sections in M theory

$D$ dimensional neutral black strings wrapped on a circle are related to $(D-1)$ dimensional charged black holes by boosts. We show that the boost has to be performed in the covering space and the boosted coordinate has to be compactified on a circle with a Lorentz contracted radius. Using this fact we show that the transition between Schwarzschild black holes to black p-branes observed recently in M theory is the well-known black hole- black string transition viewed in a boosted frame. In a similar way the correspondence point where an excited string state goes over to a neutral black hole is mapped exactly to the correspondence point for black p-branes. In terms of the $p$ brane quantities the equation of state for an excited string state becomes identical to that of a 3+1 dimensional massless gas for all $p$. Finally, we show how boosts can be used to relate Hawking radiation rates. Using the known microscopic derivation of absorption by extremal 3-branes and near-extremal 5D holes with three large charges we provide a microscopic derivation of absorption of 0-branes by seven and five dimensional Schwarzschild black holes in a certain regime.Comment: Some references added, minor clarifications (harvmac, 16 pages

Zero-point quantum swing of magnetic couples

Quantum fluctuations are ubiquitous in physics. Ranging from conventional examples like the harmonic oscillator to intricate theories on the origin of the universe, they alter virtually all aspects of matter -- including superconductivity, phase transitions and nanoscale processes. As a rule of thumb, the smaller the object, the larger their impact. This poses a serious challenge to modern nanotechnology, which aims total control via atom-by-atom engineered devices. In magnetic nanostructures, high stability of the magnetic signal is crucial when targeting realistic applications in information technology, e.g. miniaturized bits. Here, we demonstrate that zero-point spin-fluctuations are paramount in determining the fundamental magnetic exchange interactions that dictate the nature and stability of the magnetic state. Hinging on the fluctuation-dissipation theorem, we establish that quantum fluctuations correctly account for the large overestimation of the interactions as obtained from conventional static first-principles frameworks, filling in a crucial gap between theory and experiment [1,2]. Our analysis further reveals that zero-point spin-fluctuations tend to promote the non-collinearity and stability of chiral magnetic textures such as skyrmions -- a counter-intuitive quantum effect that inspires practical guidelines for designing disruptive nanodevices

Bound on Hardy's non-locality from the principle of Information Causality

Recently,the principle of nonviolation of information causality [Nature 461,1101 (2009)], has been proposed as one of the foundational properties of nature. We explore the Hardy's nonlocality theorem for two qubit systems, in the context of generalised probability theory, restricted by the principle of nonviolation of information causality. Applying, a sufficient condition for information causality violation, we derive an upper bound on the maximum success probability of Hardy's nonlocality argument. We find that the bound achieved here is higher than that allowed by quantum mechanics,but still much less than what the nosignaling condition permits. We also study the Cabello type nonlocality argument (a generalization of Hardy's argument) in this context.Comment: Abstract modified, changes made in the conclusion, throughout the paper we clarified that the condition used by us is protocal based and is only a sufficient condition for the violation of information causalit

Do the mildly superluminal VLBI knots exclude ultrarelativistic blazar jets?

We compute the effective values of apparent transverse velocity and flux boosting factors for the VLBI radio knots of blazar jets, by integrating over the angular distributions of these quantities across the widths of jets with finite opening angles but constant velocities. For high bulk Lorentz factors (Gamma > 10) variations across the jet can be quite large if the opening angle, omega, is even a few degrees on sub-parsec scales. The resulting apparent speeds are often much lower than those obtained from the usual analyses that ignore the finite jet opening angles. We can thus reconcile the usually observed subluminal or mildly superluminal speeds with the very high (>~ 20) Gamma factors, required by the inverse Compton origin and rapid variability of TeV fluxes, as well as by intraday radio variability. Thus it is possible to associate the VLBI radio knots directly with shocks in the ultra-relativistic main jet flow, without invoking very rapid jet deceleration on parsec scales, or extremely unlikely viewing angles.Comment: 10 pages, 1 figure, to appear in ApJ Letters, Nov. 10 2004 issu

Nonlocality without inequality for spin-s system

We analyze Hardy's non-locality argument for two spin-s systems and show that earlier solution in this regard was restricted due to imposition of some conditions which have no role in the argument of non-locality. We provide a compact form of non-locality condition for two spin-s systems and extend it to n number of spin-s particles. We also apply more general kind of non-locality argument still without inequality, to higher spin system.Comment: 6 page

The Reciprocal Reshaping of the American Dream and American Religion

Religion has played an important role in the creation and dissemination of the idea now called the American Dream since the discovery of the North American continent. The first iteration of the American Dream manifested in the sixteenth century as a Return to Eden. The next phase was best represented by the Puritan quest for freedom of religion. In the eighteenth century, independence was the object of the American Dream. This was supported by the First Great Awakening. The nineteenth century American Dream can be characterized as opportunity as evidenced by immigration, westward migration, and the growth of commercial enterprise. The twentieth century American Dream began under the banner of achievement. After World War I, the advertising sector shanghaied the American Dream so that the measure of success was the acquisition of wealth and material goods. Religion, through acts of omission and acts of commission enabled the American Dream to become individual, materialistic, and debt-ridden. The twenty-first century war on terror, ascent of China, and economic collapse has called to question the future of the American Dream. There is a dire need for a fundamental recast of the next chapter of the American Dream. By guiding a return to the earlier American Dreams, religion could play a seminal role in this endeavor