291 research outputs found
EVM and Achievable Data Rate Analysis of Clipped OFDM Signals in Visible Light Communication
Orthogonal frequency division multiplexing (OFDM) has been considered for
visible light communication (VLC) thanks to its ability to boost data rates as
well as its robustness against frequency-selective fading channels. A major
disadvantage of OFDM is the large dynamic range of its time-domain waveforms,
making OFDM vulnerable to nonlinearity of light emitting diodes (LEDs). DC
biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM
(ACO-OFDM) are two popular OFDM techniques developed for the VLC. In this
paper, we will analyze the performance of the DCO-OFDM and ACO-OFDM signals in
terms of error vector magnitude (EVM), signal-to-distortion ratio (SDR), and
achievable data rates under both average optical power and dynamic optical
power constraints. EVM is a commonly used metric to characterize distortions.
We will describe an approach to numerically calculate the EVM for DCO-OFDM and
ACO-OFDM. We will derive the optimum biasing ratio in the sense of minimizing
EVM for DCO-OFDM. Additionally, we will formulate the EVM minimization problem
as a convex linear optimization problem and obtain an EVM lower bound against
which to compare the DCO-OFDM and ACO-OFDM techniques. We will prove that the
ACO-OFDM can achieve the lower bound. Average optical power and dynamic optical
power are two main constraints in VLC. We will derive the achievable data rates
under these two constraints for both additive white Gaussian noise (AWGN)
channel and frequency-selective channel. We will compare the performance of
DCO-OFDM and ACO-OFDM under different power constraint scenarios
Supersymmetric Relations Among Electromagnetic Dipole Operators
Supersymmetric contributions to all leptonic electromagnetic dipole operators
have essentially identical diagramatic structure. With approximate slepton
universality this allows the muon anomalous magnetic moment to be related to
the electron electric dipole moment in terms of supersymmetric phases, and to
radiative flavor changing lepton decays in terms of small violations of slepton
universality. If the current discrepancy between the measured and Standard
Model values of the muon anomalous magnetic moment is due to supersymmetry, the
current bound on the electron electric dipole moment then implies that the
phase of the electric dipole operator is less than . Likewise
the current bound on decay implies that the fractional
selectron-smuon mixing in the left-left mass squared matrix, \delta m_{\smuon
\selectron}^2 / m_{\slepton}^2, is less than . These relations and
constraints are fairly insensitive to details of the superpartner spectrum for
moderate to large .Comment: Latex, 38 pages, 2 figure
Two-loop Barr-Zee type Contributions to in the MSSM
We consider the contribution of a two-loop Barr-Zee type diagram to
in the minimal supersymmetric standard model (MSSM). At relatively
large , we show that the contribution of light third generation
scalar fermions and neutral CP-even Higgs, , can easily explain the
very recent BNL experimental data. In our analysis prefers negative
and positive . It is more sensitive to the chirality flipping
h^0(H^0)\wt{f}_R^*\wt{f}_L rather than chirality conserving couplings.Comment: 10 pages, 5 figures, references adde
Nearly Bi-Maximal Neutrino Mixing, Muon g-2 Anomaly and Lepton-Flavor-Violating Processes
We interpret the newly observed muon g-2 anomaly in the framework of a
leptonic Higgs doublet model with nearly degenerate neutrino masses and nearly
bi-maximal neutrino mixing. Useful constraints are obtained on the rates of
lepton-flavor-violating rare decays ,
and as well as the - conversion ratio .
We find that , and
depend crucially on possible non-zero but samll values of the
neutrino mixing matrix element , and they are also sensitive to the
Dirac-type CP-violating phase. In particular, we show that , and are approximately in the ratio if is much larger than , and in the
ratio if is much lower than , where and are the corresponding mass-squared
differences of atmospheric and solar neutrino oscillations.Comment: LaTex 6 pages (2 PS figures). Phys. Rev. D (in printing
Lepton Dipole Moments and Rare Decays in the CP-violating MSSM with Nonuniversal Soft-Supersymmetry Breaking
We investigate the muon anomalous magnetic dipole moment (MDM), the muon
electric dipole moment (EDM) and the lepton-flavour-violating decays of the
lepton, and , in the CP-violating
Minimal Supersymmetric Standard Model (MSSM) with nonuniversal
soft-supersymmetry breaking. We evaluate numerically the muon EDM and the
branching ratios and , after taking
into account the experimental constraints from the electron EDM and muon MDM.
Upon imposition of the experimental limits on our theoretical predictions for
the aforementioned branching ratios and the muon MDM, we obtain an upper bound
of about on the muon EDM which lies well within the
explorable reach of the proposed experiment at BNL.Comment: Latex, 26 pages, 8 figures, accepted for publication in Phys. Rev.
CP Violation in Kaon System in Supersymmetric SU(5) Model with Seesaw-Induced Neutrino Masses
CP violations in the kaon system are studied in supersymmetric SU(5) model
with right-handed neutrinos. We pay a special attention to the renormalization
group effect on the off-diagonal elements of the squark mass matrices. In
particular, if the Yukawa couplings and mixings in the neutrino sector are
sizable, off-diagonal elements of the right-handed down-type squark mass matrix
are generated, which affect CP and flavor violations in decay processes of the
kaon. We calculate supersymmetric contributions to epsilon (as well as Delta
m_K), Br(K_L -> pi^0 nu \bar{nu}), and epsilon'/epsilon in this framework. We
will see that the supersymmetric contribution to the epsilon parameter can be
as large as (and in some case, larger than) the experimentally measured value.
We also discuss its implication to future tests of the unitarity triangle of
the Kobayashi-Maskawa matrix.Comment: 30 pages, 5 figue
Moderate and heavy metabolic stress interval training improve arterial stiffness and heart rate dynamics in humans
Traditional continuous aerobic exercise training attenuates age-related increases of arterial stiffness, however, training studies have not determined whether metabolic stress impacts these favourable effects. Twenty untrained healthy participants (n = 11 heavy metabolic stress interval training, n = 9 moderate metabolic stress interval training) completed 6 weeks of moderate or heavy intensity interval training matched for total work and exercise duration. Carotid artery stiffness, blood pressure contour analysis, and linear and non-linear heart rate variability were assessed before and following training. Overall, carotid arterial stiffness was reduced (p 0.05). This study demonstrates the effectiveness of interval training at improving arterial stiffness and autonomic function, however, the metabolic stress was not a mediator of this effect. In addition, these changes were also independent of improvements in aerobic capacity, which were only induced by training that involved a high metabolic stress
Supersymmetric Dark Matter and Yukawa Unification
An analysis of supersymmetric dark matter under the Yukawa unification
constraint is given. The analysis utilizes the recently discovered region of
the parameter space of models with gaugino mass nonuniversalities where large
negative supersymmetric corrections to the b quark mass appear to allow
unification for a positive sign consistent with the and constraints. In the present analysis we use the
revised theoretical determination of ()
in computing the difference which takes account of
a reevaluation of the light by light contribution which has a positive sign.
The analysis shows that the region of the parameter space with
nonuniversalities of the gaugino masses which allows for unification of Yukawa
couplings also contains regions which allow satisfaction of the relic density
constraint. Specifically we find that the lightest neutralino mass consistent
with the relic density constraint, unification for SU(5) and
unification for SO(10) in addition to other constraints lies in the region
below 80 GeV. An analysis of the maximum and the minimum neutralino-proton
scalar cross section for the allowed parameter space including the effect of a
new determination of the pion-nucleon sigma term is also given. It is found
that the full parameter space for this class of models can be explored in the
next generation of proposed dark matter detectors.Comment: 28 pages,nLatex including 5 fig
Muon anomalous magnetic dipole moment in supersymmetric theories
We study the muon anomalous magnetic dipole moment in supersymmetric
theories. The impact of the recent Brookhaven E821 experimental measurement on
both model-independent and model-dependent supersymmetric parameter spaces is
discussed in detail. We find that values of tan\beta as low as 3 can be
obtained while remaining within the E821 one-sigma bound. This requires a light
smuon; however, we show that, somewhat surprisingly, no model-independent bound
can be placed on the mass of the lightest chargino for any tan\beta greater
than or equal to 3. We also show that the maximum contributions to the
anomalous magnetic moment are insensitive to CP-violating phases. We provide
analyses of the supersymmetric contribution to the muon anomalous magnetic
moment in dilaton-dominated supergravity models and gauge-mediated
supersymmetry-breaking models. Finally, we discuss how other phenomena, such as
, relic abundance of the lightest superpartner, and the Higgs
mass may be correlated with the anomalous magnetic moment, but do not
significantly impact the viability of a supersymmetric explanation, or the mass
limits obtainable on smuons and charginos.Comment: 28 page
B -> X_s gamma in Supersymmetry with Explicit CP Violation
We discuss B -> X_s gamma decay in both constrained and unconstrained
supersymmetric models with explicit CP violation within the minimal flavor
violation scheme by including tan(beta) -enhanced large contributions beyond
the leading order. In this analysis, we take into account the relevant
cosmological and collider bounds, as well as electric dipole moment
constraints. In the unconstrained model, there are portions of the parameter
space yielding a large CP asymmetry at leading order (LO). In these regions, we
find that the CP phases satisfy certain sum rules, e.g., the sum of the phases
of the \mu parameter and the stop trilinear coupling centralize around \pi with
a width determined by the experimental bounds. In addition, at large values of
tan(beta), the sign of the CP asymmetry tracks the sign of the gluino mass, and
the CP asymmetry is significantly larger than the LO prediction. In the
constrained minimal supersymmetric standard model based on minimal
supergravity, we find that the decay rate is sensitive to the phase of the
universal trilinear coupling. This sensitivity decreases at large values of the
universal gauino mass. We also show that for a given set of the mass
parameters, there exists a threshold value of the phase of the universal
trilinear coupling which grows with tan(beta) and beyond which the experimental
bounds are satisfied. In both supersymmetric scenarios, the allowed ranges of
the CP phases are wide enough to have phenomenological consequences.Comment: 25 pages, 11 figures. Added references, made minor changes in the
text; journal versio
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