761 research outputs found
Diversity Enhancement of MIMO System with GA Optimized Linear Precoding of Orthogonal Space-Time Block Codes
The MIMO (Multiple-Input Multiple-Output) systems in the field of digital communications make it possible to improve data transmission according to two main parameters which are often antagonistic: the information rate and the transmission reliability estimated in average binary error probability (BEP) term. With such systems, CSI (Channel State Information) on transmission is a key point for reducing the BEP thanks to different power allocation strategies. Thus, a linear precoder on transmission associated with a linear decoder on reception can optimize a particular criterion thanks to this information. This paper proposes a MIMO system with precoded orthogonal space-time block codes (OSTBC) optimized by Genetic Algorithm with ZF and MMSE equalization. The performance evaluation is achieved by BER vs. SNR graphs
Universal Programmable Quantum Circuit Schemes to Emulate an Operator
Unlike fixed designs, programmable circuit designs support an infinite number
of operators. The functionality of a programmable circuit can be altered by
simply changing the angle values of the rotation gates in the circuit. Here, we
present a new quantum circuit design technique resulting in two general
programmable circuit schemes. The circuit schemes can be used to simulate any
given operator by setting the angle values in the circuit. This provides a
fixed circuit design whose angles are determined from the elements of the given
matrix-which can be non-unitary-in an efficient way. We also give both the
classical and quantum complexity analysis for these circuits and show that the
circuits require a few classical computations. They have almost the same
quantum complexities as non-general circuits. Since the presented circuit
designs are independent from the matrix decomposition techniques and the global
optimization processes used to find quantum circuits for a given operator, high
accuracy simulations can be done for the unitary propagators of molecular
Hamiltonians on quantum computers. As an example, we show how to build the
circuit design for the hydrogen molecule.Comment: combined with former arXiv:1207.174
Infrared studies of X-ray sources
A detailed study of the infrared radiation from galactic X-ray sources indicates that the galactic bulge sources and X-ray binary sources have different infrared emission characteristics. The galactic bulge sources seem to show a power law dependence between the X-ray flux and the infrared flux emitted by the X-ray source. The results presented suggests that the infrared radiation in the galactic bulge sources is dominated by free-free radiation and, in the case of eclipsing binary sources, the black-body emission from the early-type companion star contributes significantly to the infrared radiation
Proof of all-order finiteness for planar beta-deformed Yang-Mills
We study a marginal deformation of N=4 Yang-Mills, with a real deformation
parameter beta. This beta-deformed model has only N=1 supersymmetry and a
U(1)xU(1) flavor symmetry. The introduction of a new superspace star-product
allows us to formulate the theory in N=4 light-cone superspace, despite the
fact that it has only N=1 supersymmetry. We show that this deformed theory is
conformally invariant, in the planar approximation, by proving that its Green
functions are ultra-violet finite to all orders in perturbation theory.Comment: 27 pages, several figures; v3: minor correction
Contour deformation trick in hybrid NLIE
The hybrid NLIE of AdS_5 x S^5 is applied to a wider class of states. We find
that the Konishi state of the orbifold AdS_5 x (S^5/Z_S) satisfies A_1 NLIE
with the source terms which are derived from contour deformation trick. For
general states, we construct a deformed contour with which the contour
deformation trick yields the correct source terms.Comment: 39 pages, 6 figures, v2: discussion on analyticity constraints
replaced by consistent deformed contou
Study of cosmic ray diurnal variation on a day-to-day basis
From a careful examination of the diurnal variation of cosmic ray intensity at high energies and the interplanetary field characteristics, the average characteristics of diurnal variation were recently explained by us in terms of a balance between outward convection and field aligned diffusion, the latter arising out of a positive radial density gradient. In this paper, we extend this new concept to explain the large variability observed in the diurnal variation on a day-to-day basis and further demonstrate that the measurement of diurnal anisotropy characteristic of cosmic ray particles on a day-to-day basis can be used directly to infer the nature and scale sizes of interplanetary field parameters. Comparing with the magnetic field vector, we show that this simple concept holds good on more than 80% of days. On the rest 20% of days which have a predominant morning maxima, the diurnal anisotropy characteristics seem to indicate the presence of a significant component of transverse diffusion current in addition to the normal convection and diffusion flow. Such days are found to be present in the form of trains of consecutive days and are found to be associated with abrupt changes in the interplanetary field direction having scale sizes >4 hr. The value of K⊥/K|| which is normally about ≤0.05 is found to be ≈1.0 on non-field aligned days
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