459,150 research outputs found
Coherent states, displaced number states and Laguerre polynomial states for su(1,1) Lie algebra
The ladder operator formalism of a general quantum state for su(1,1) Lie
algebra is obtained. The state bears the generally deformed oscillator
algebraic structure. It is found that the Perelomov's coherent state is a
su(1,1) nonlinear coherent state. The expansion and the exponential form of the
nonlinear coherent state are given. We obtain the matrix elements of the
su(1,1) displacement operator in terms of the hypergeometric functions and the
expansions of the displaced number states and Laguerre polynomial states are
followed. Finally some interesting su(1,1) optical systems are discussed.Comment: 16 pages, no figures, accepted by Int. J. Mod. Phy.
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Robust H∞ control for discrete-time fuzzy systems with infinite-distributed delays
Copyright [2009] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This paper is concerned with the robust H∞ control problem for a class of discrete-time Takagi-Sugeno (T-S) fuzzy systems with time delays and uncertain parameters. The time delay is assumed to be infinitely distributed in the discrete-time domain, and the uncertain parameters are norm-bounded. By using the linear matrix inequality (LMI) technique, sufficient conditions are derived for ensuring the exponential stability as well as the H infin performance for the closed-loop fuzzy control system. It is also shown that the controller gain can be characterized in terms of the solution to a set of LMIs, which can be easily solved by using standard software packages. A simulation example is exploited in order to illustrate the effectiveness of the proposed design procedures
A synchronous binary array divider
An asynchronous binary divider formed of an array of identical logic cells is described. Each cell includes a single bit binary subtractor and a selection gate. The array is connected to divisor, dividend, quotient and remainder registers. Divisor and dividend numbers are read into the divisor and dividend registers, respectively. The array of identical logic cells performs the division in parallel asynchronously and places the results of the division in the quotient and remainder registers for subsequent readout
Array multiplier
Digital array multiplier consisting of any number of identical digital adder cells in a repetitive planar configuration functions as a modular multiplier for use in computer applications of airborne vehicles. The modular multiplier utilizes large scale integration and metal oxide semiconductors
Magnetic spin excitations in diluted ferromagnetic systems: the case of
We propose a theory which allow to calculate the magnetic excitation spectrum
in diluted ferromagnetic systems. The approach is rather general and based on
the Self-Consistent local Random Phase Approximation in which disorder
(dilution) and thermal fluctuations are properly treated. To illustrate its
reliability and accuracy we calculate the magnetic excitation in the diluted
III-V magnetic semiconductor . It is shown that dilution has
a drastic effect on the excitation spectrum, indeed well defined magnon
excitations exist only in a small region of the Brillouin zone centered around
the point. We also calculate the spin stiffness in optimally annealed
sample as a function of concentration. A comparison to available
measurements is done. We find a very good agreement for both the Curie
temperature and the spin stiffness measured in well annealed samples and
provide a plausible explanation for the very small values measured in as grown
samples.Comment: The manuscript has been modified, 4 figures are included. Accepted
for publication in Eur. Phys. Let
sigma and f_0(980) substructures from gamma-gamma to pi-pi, J/psi, phi radiative and D_s semi-leptonic decays
Using an improved "analytic K-matrix model", we reconsider the extraction of
the sigma/f_0(600) and f_0(980) gamma-gamma widths from gamma-gamma to pi-pi
scatterings data of Crystal Ball and Belle. Our main results are summarized in
Tables 3 and 4. The averaged sigma "direct width" to gamma-gamma is 0.16(3) keV
which confirms a previous result of [1] and which does neither favour a large
four-quark (diquark-antidiquark) nor a molecule nor a pure \bar qq component.
The "direct width" of the f_0(980) of 0.28(2) keV is much larger than the
four-quark expectation but can be compatible with a \bar ss or gluonium
component. We also found that the rescattering part of the amplitude is
relatively large indicating an important contribution of the meson loops in the
determination of the gamma-gamma total widths. This is mainly due to the large
couplings of the sigma and f_0(980) to pi-pi and/or \bar KK, which can also be
due to a light scalar gluonium with large OZI violating couplings but not
necessary to a four-quark or molecule state. Our average results for the total
(direct+rescattering) gamma-gamma widths: Gamma_sigma^{tot}= 3.08(82) keV,
Gamma_{f_0}^{tot}= 0.16(1) keV} are comparable with the ones from dispersion
relations and PDG values. Using the parameters from QCD spectral sum rules, we
complete our analysis by showing that the production rates of unmixed scalar
gluonia sigma_B(1) and G (1.5-1.6) agree with the data from J/\psi, phi
radiative and D_s semi-leptonic decays.Comment: 11 pages, 6 figures (1 more figure added in Fig 6), 4 tables :
version appeared on-line in doi:10.1016/j.physletb.2010.12.00
Oxygen Isotope Effect on the Spin State Transition in (PrSm)CaCoO
Oxygen isotope substitution is performed in the perovskite cobalt oxide
(PrSm)CaCoO which shows a sharp spin
state transition from the intermediate spin (IS) state to the low spin (LS)
state at a certain temperature. The transition temperature of the spin state
up-shifts with the substitution of by O from the resistivity
and magnetic susceptibility measurements. The up-shift value is 6.8 K and an
oxygen isotope exponent () is about -0.8. The large oxygen isotope
effect indicates strong electron-phonon coupling in this material. The
substitution of O by O leads to a decrease in the frequency of
phonon and an increase in the effective mass of electron (), so that
the bandwidth W is decreased and the energy difference between the different
spin states is increased. This is the reason why the is shifted to high
temperature with oxygen isotopic exchange.Comment: 4 pages, 3 figure
Gravitino dark matter from gluino late decay in split supersymmetry
In split-supersymmetry (split-SUSY), gluino is a metastable particle and thus
can freeze out in the early universe. The late decay of such a long-life gluino
into the lightest supersymmetric particle (LSP) may provide much of the cosmic
dark matter content. In this work, assuming the LSP is gravitino produced from
the late decay of the metastable gluino, we examine the WMAP dark matter
constraints on the gluino mass. We find that to provide the full abundance of
dark matter, the gluino must be heavier than about 14 TeV and thus not
accessible at the CERN Large Hadron Collider (LHC).Comment: discussions added (version in PRD
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