563 research outputs found
Improved convergence analysis of stochastic gradient adaptive filters using the sign algorithm
Journal ArticleAbstract-Convergence analysis of stochastic gradient adaptive filters using the sign algorithm is presented in this paper. The methods of analysis currently available in literature assume that the input signals to the filter are white. This restriction is removed for Gaussian signals in our analysis. Expressions for the second moment of the coefficient vector and the steady-state error power are also derived. Simulation results are presented, and the theoretical and empirical curves show a very good match
production and dimuon enhancement in heavy ion collisions
Dilepton production in heavy ion collisions, in the Intermediate Mass Region
(IMR) has consistently shown an excess over theoretical estimates. An attempt
to understand this discrepancy between the observed dilepton pairs and the
theoretical estimate is made here through the production of the meson
and estimates obtained by NRQCD calculations. We find that production
offers a satisfactory quantitative picture for explaining the discrepancy.Comment: LateX, 6 pages, 2 figures (eps
J/psi Spin Asymmetries in the Colour-Octet Model
We investigate the pattern of asymmetries in the colour-octet model for
inclusive production of charmonium with polarised initial state hadrons and
photons. We find that singly polarised asymmetries vanish. The double polarised
asymmetry for J/psi involves a new combination of long-distance matrix element.
We also investigate the asymmetries for eta_c, chi_c and Upsilon production.
The asymmetries distinguish well between different models of charmonium
production.Comment: LaTeX source, 18 page
NRQCD Analysis of Bottomonium Production at the Tevatron
Recent data from the CDF collaboration on the production of spin-triplet
bottomonium states at the Tevatron p \bar p collider are analyzed within the
NRQCD factorization formalism. The color-singlet matrix elements are determined
from electromagnetic decays and from potential models. The color-octet matrix
elements are determined by fitting the CDF data on the cross sections for
Upsilon(1S), Upsilon(2S), and Upsilon(3S) at large p_T and the fractions of
Upsilon(1S) coming from chi_b(1P) and chi_b(2P). We use the resulting matrix
elements to predict the cross sections at the Tevatron for the spin-singlet
states eta_b(nS) and h_b(nP). We argue that eta_b(1S) should be observable in
Run II through the decay eta_b -> J/psi + J/psi.Comment: 20 pages, 3 figure
Approximations and their consequences for dynamic modelling of signal transduction pathways
Signal transduction is the process by which the cell converts one kind of signal or stimulus into another. This involves a sequence of biochemical reactions, carried out by proteins. The dynamic response of complex cell signalling networks can be modelled and simulated in the framework of chemical kinetics. The mathematical formulation of chemical kinetics results in a system of coupled differential equations. Simplifications can arise through assumptions and approximations. The paper provides a critical discussion of frequently employed approximations in dynamic modelling of signal transduction pathways. We discuss the requirements for conservation laws, steady state approximations, and the neglect of components. We show how these approximations simplify the mathematical treatment of biochemical networks but we also demonstrate differences between the complete system and its approximations with respect to the transient and steady state behavior
Quarkonium Production at High-Energy Colliders
The theoretical description of heavy quarkonium production at high-energy
p-pbar and e-p colliders is reviewed. Predictions based on non-relativistic QCD
factorisation are confronted with recent charmonium and bottomonium data from
the Tevatron and HERA. Potential shortcomings of the present theoretical
analyses are discussed, and the prospects for quarkonium physics at the
upgraded Tevatron and HERA colliders and at the LHC are summarised.Comment: 61 pages, 20 figures. To be published in Progress in Particle and
Nuclear Physics, Vol. 47, issue
Probing Noncommutative Space-Time in the Laboratory Frame
The phenomenological investigation of noncommutative space-time in the
laboratory frame are presented. We formulate the apparent time variation of
noncommutativity parameter in the laboratory frame due to the
earth's rotation. Furthermore, in the noncommutative QED, we discuss how to
probe the electric-like component
by the
process at future linear collider.
We may determine the magnitude and the direction of
by detailed study of the apparent time
variation of total cross section.
In case of us observing no signal, the upper limit on the magnitude of
can be determined independently of its
direction.Comment: 12 pages, 7 figures, typos are corrected, one graph have been added
in figure
2-D Magnetohydrodynamic Simulations of Induced Plasma Dynamics in the Near-Core Region of a Galaxy Cluster
We present results from numerical simulations of the cooling-core cluster
A2199 produced by the two-dimensional (2-D) resistive magnetohydrodynamics
(MHD) code MACH2. In our simulations we explore the effect of anisotropic
thermal conduction on the energy balance of the system. The results from
idealized cases in 2-D axisymmetric geometry underscore the importance of the
initial plasma density in ICM simulations, especially the near-core values
since the radiation cooling rate is proportional to . Heat conduction
is found to be non-effective in preventing catastrophic cooling in this
cluster. In addition we performed 2-D planar MHD simulations starting from
initial conditions deliberately violating both thermal balance and hydrostatic
equilibrium in the ICM, to assess contributions of the convective terms in the
energy balance of the system against anisotropic thermal conduction. We find
that in this case work done by the pressure on the plasma can dominate the
early evolution of the internal energy over anisotropic thermal conduction in
the presence of subsonic flows, thereby reducing the impact of the magnetic
field. Deviations from hydrostatic equilibrium near the cluster core may be
associated with transient activity of a central active galactic nucleus and/or
remnant dynamical activity in the ICM and warrant further study in three
dimensions.Comment: 16 pages, 13 figures, accepted for publication in MNRA
Compton scattering in Noncommutative Space-Time at the NLC
We study the Compton scattering in the noncommutative counter part of QED (NC
QED). Interactions in NC QED have momentum dependent phase factors and the
gauge fields have Yang Mills type couplings, this modifies the cross sections
and are different from the commuting Standard Model. Collider signals of
noncommutative space-time are studied at the Next Linear Collider (NLC)
operating in the mode. Results for different polarised cases are
presented and it is shown that the Compton process can probe the noncommutative
scale in the range of 1 - 2.5 TeV for typical proposed NLC energies.Comment: 12 pages, 5 Postscript figures, version to appear in Phys. Rev.
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