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

Muon Anomalous g−2g -2 and Gauged Lμ−LτL_\mu - L_\tau Models

In this paper we study $Z'$ contribution to $g -2$ of the muon anomalous magnetic dipole moment in gauged $U(1)_{L_\mu - L_\tau}$ models. Here $L_i$ are the lepton numbers. We find that there are three classes of models which can produce a large value of $g-2$ to account for possible discrepancy between the experimental data and the Standard Model prediction. The three classes are: a) Models with an exact $U(1)_{L_\mu - L_\tau}$. In these models, $Z'$ is massless. The new gauge interaction coupling $e a/\cos\theta_W$ is constrained to be $0.8\times 10^{-3} < |a| < 2.24\times 10^{-3}$. b) Models with broken $U(1)_{L_\mu - L_\tau}$ and the breaking scale is not related to electroweak symmetry breaking scale. The $Z'$ gauge boson is massive. The allowed range of the coupling and the $Z'$ mass are constrained, but $Z'$ mass can be large; And c) The $U(1)_{L_\mu-L_\tau}$ is broken and the breaking scale is related to the electroweak scale. In this case the $Z'$ mass is constrained to be $\sim 1.2$ GeV. We find that there are interesting experimental signatures in $\mu^+\mu^-\to \mu^+\mu^-, \tau^+\tau^-$ in these models.Comment: 13 pages, 9 figure

Deconstructing Gaugino Mediation

We present a model of supersymmetry breaking which produces gaugino masses and negligible scalar masses at a high scale. The model is inspired by ``deconstructing'' or ``latticizing'' models in extra dimensions where supersymmetry breaking and visible matter are spatially separated. We find a simple four-dimensional model which only requires two lattice sites (or gauge groups) to reproduce the phenomenology.Comment: LaTeX, 9 pages, acknowledgements adde

Implications of the Muon Anomalous Magnetic Moment for Supersymmetry

We re-examine the bounds on supersymmetric particle masses in light of the E821 data on the muon anomalous magnetic moment. We confirm, extend and supersede previous bounds. In particular we find (at one sigma) no lower limit on tan(beta) or upper limit on the chargino mass implied by the data at present, but at least 4 sparticles must be lighter than 700 to 820 GeV and at least one sparticle must be lighter than 345 to 440 GeV. However, the E821 central value bounds tan(beta) > 4.7 and the lighter chargino mass by 690 GeV. For tan(beta) < 10, the data indicates a high probability for direct discovery of SUSY at Run II or III of the Tevatron.Comment: 20 pages LaTeX, 14 figures; references adde

Bottom-Tau Unification in SUSY SU(5) GUT and Constraints from b to s gamma and Muon g-2

An analysis is made on bottom-tau Yukawa unification in supersymmetric (SUSY) SU(5) grand unified theory (GUT) in the framework of minimal supergravity, in which the parameter space is restricted by some experimental constraints including Br(b to s gamma) and muon g-2. The bottom-tau unification can be accommodated to the measured branching ratio Br(b to s gamma) if superparticle masses are relatively heavy and higgsino mass parameter \mu is negative. On the other hand, if we take the latest muon g-2 data to require positive SUSY contributions, then wrong-sign threshold corrections at SUSY scale upset the Yukawa unification with more than 20 percent discrepancy. It has to be compensated by superheavy threshold corrections around the GUT scale, which constrains models of flavor in SUSY GUT. A pattern of the superparticle masses preferred by the three requirements is also commented.Comment: 21pages, 6figure

Two-loop Barr-Zee type Contributions to (g−2)μ(g-2)_\mu in the MSSM

We consider the contribution of a two-loop Barr-Zee type diagram to $(g-2)_\mu$ in the minimal supersymmetric standard model (MSSM). At relatively large $\tan\beta$, we show that the contribution of light third generation scalar fermions and neutral CP-even Higgs, $h^0(H^0)$, can easily explain the very recent BNL experimental data. In our analysis $(g-2)_\mu$ prefers negative $A_{f}$ and positive $\mu$. 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

Novel mechanism of steroid action in skin through glucocorticoid receptor monomers

Glucocorticoids (GCs), important regulators of epidermal growth, differentiation, and homeostasis, are used extensively in the treatment of skin diseases. Using keratin gene expression as a paradigm of epidermal physiology and pathology we have developed a model system to study the molecular mechanism of GCs action in skin. Here we describe a novel mechanism of suppression of transcription by the glucocorticoid receptor (GR) that represents an example of customizing a device for transcriptional regulation to target a specific group of genes within the target tissue, in our case, epidermis. We have shown that GCs repress the expression of the basal-cell-specific keratins K5 and K14 and disease-associated keratins K6, K16, and K17 but not the differentiation-specific keratins K3 and K10 or the simple epithelium-specific keratins K8, K18, and K19. We have identified the negative recognition elements (nGREs) in all five regulated keratin gene promoters. Detailed footprinting revealed that the function of nGREs is to instruct the GR to bind as four monomers. Furthermore, using cotransfection and antisense technology we have found that, unlike SRC-1 and GRIP-1, which are not involved in the GR complex: that suppresses keratin genes, histone acetyltransferase and CBP are. In addition, we have found that GR, independently from GREs, blocks the induction of keratin gene expression by AP1. We conclude that GR suppresses keratin gene expression through two independent mechanisms: directly, through interactions of keratin nGREs with four GR monomers, as well as indirectly, by blocking the AP1 induction of keratin gene expression

Anomaly-Mediated Supersymmetry Breaking with Axion

We construct hadronic axion models in the framework of the anomaly-mediated supersymmetry breaking scenario. If the Peccei-Quinn symmetry breaking is related to the supersymmetry breaking, mass spectrum of the minimal anomaly-mediated scenario is modified, which may solve the negative slepton mass problem in the minimal anomaly-mediated model. We find several classes of phenomenologically viable models of axion within the framework of the anomaly mediation and, in particular, we point out a new mechanism of stabilizing the axion potential. In this class of models, the Peccei-Quinn scale is related to the messenger scale. We also study phenomenological aspects of this class of models. We will see that, in some case, the lightest particle among the superpartners of the standard-model particles is stau while the lightest superparticle becomes the axino, the superpartner of the axion. With such a unique mass spectrum, conventional studies of the collider physics and cosmology for supersymmetric models should be altered.Comment: 20 pages, 5 figures, added footnotes and references for section

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 $2 \times 10^{-3}$. Likewise the current bound on $\mu \to e \gamma$ 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 $10^{-4}$. These relations and constraints are fairly insensitive to details of the superpartner spectrum for moderate to large $\tan \beta$.Comment: Latex, 38 pages, 2 figure