12,650 research outputs found

    Dispelling the Anthropic Principle from the Dimensionality Arguments

    Get PDF
    It is shown that in d=11 supergravity, under a very reasonable ansatz, the nearly flat spacetime in which we are living must be 4-dimensional without appealing to the Anthropic Principle. Can we dispel the Anthropic Principle completely from cosmology?Comment: 7 pages, Essa

    B ->\eta_c K(\eta_c^\prime K) decays in QCD factorization

    Full text link
    We study the exclusive decays of BB meson into pseudoscalar charmonium states ηc\eta_c and ηc\eta_c^\prime within the QCD factorization approach and find that the nonfactorizable corrections to naive factorization are infrared safe at leading-twist order. The spectator interactions arising from the kaon twist-3 effects are formally power-suppressed but chirally and logarithmically enhanced. The theoretical decay rates are too small to accommodate the experimental data. On the other hand, we compare the theoretical calculations for J/ψ,ψJ/\psi, \psi^\prime, and ηc,ηc\eta_c, \eta_c^\prime, and find that the predicted relative decay rates of these four states are approximately compatible with experimental data.Comment: 8 pages, LaTex, 1 figure, one footnote and two references adde

    The BXsl+lB\to X_sl^+l^- and BXsγB\to X_s \gamma decays with the fourth generation

    Full text link
    If the fourth generation fermions exist, the new quarks could influence the branching ratios of the decays of BXsγB\to X_s \gamma and BXsl+lB\to X_sl^+l^-. We obtain two solutions of the fourth generation CKM factor VtsVtbV^{*}_{t^{'}s}V_{t^{'}b} from the decay of BXsγB\to X_s \gamma. We use these two solutions to calculate the new contributions of the fourth generation quark to Wilson coefficients of the decay of BXsl+lB\to X_sl^+l^-. The branching ratio and the forward-backward asymmetry of the decay of BXsl+lB\to X_sl^+l^- in the two cases are calculated. Our results are quite different from that of SM in one case, almost same in another case. If Nature chooses the formmer, the BB meson decays could provide a possible test of the forth generation existence.Comment: 10 pages, 5 figure

    Enhancing Autonomy in VTOL Aircraft Based on Symbolic Computation Algorithms

    Get PDF
    Research into the autonomy of small Unmanned Aerial Vehicles (UAVs), and especially on Vertical Take Off and Landing (VTOL) systems has intensified significantly in recent years. This paper develops a generic model of a VTOL UAV in symbolic form. The novelty of this work stems from the designed Model Predictive Control (MPC) algorithm based on this symbolic model. The MPC algorithm is compared with a state-of-the-art Linear Quadratic Regulator algorithm in attitude rate acquisition and its more accurate performance and robustness to noise is demonstrated. Results for the controllers designed for each of the aircraft’s angular rates are presented in response to input disturbances

    Electronic Structure of KFe2_2Se2_2 from First Principles Calculations

    Full text link
    Electronic structure and magnetic properties for iron-selenide KFe2_2Se2_2 are studied by first-principles calculations. The ground state is stripe-like antiferromagnetic with calculated 2.26 μB\mu_B magnetic moment on Fe atoms; and the J1J_1, J2J_2 coupling strengths are calculated to be 0.038 eV and 0.029 eV. The states around EFE_F are dominated by the Fe-3d orbitals which hybridize noticeably to the Se-4p orbitals. While the band structure of KFe2_2Se2_2 is similar to a heavily electron-doped BaFe2_2As2_2 or FeSe system, the Fermi surface of KFe2_2Se2_2 is much closer to \fs11 system since the electron sheets around MM is symmetric with respect to xx-yy exchange. These features, as well as the absence of Fermi surface nesting, suggest that the parental KFe2_2Se2_2 could be regarded as an electron over-doped 11 system with possible local moment magnetism.Comment: accepted by Chinese Physics Letter, to appear as Chinese Physics Letter, Vol 28, page 057402 (2011

    On Gravitational anomaly and Hawking radiation near weakly isolated horizon

    Full text link
    Based on the idea of the work by Wilczek and his collaborators, we consider the gravitational anomaly near weekly isolated horizon. We find that there exists a universal choice of tortoise coordinate for any weakly isolated horizon. Under this coordinate, the leading behavior of a quite arbitrary scalar field near horizon is a 2-dimensional chiral scalar field. This means we can extend the idea of Wilczek and his collaborators to more general cases and show the relation between gravitational anomaly and Hawking radiation is a universal property of black hole horizon.Comment: 14 page

    A High-Density SNP and SSR Consensus Map Reveals Segregation Distortion Regions in Wheat

    Get PDF
    Citation: Li, C. L., Bai, G. H., Chao, S. M., & Wang, Z. H. (2015). A High-Density SNP and SSR Consensus Map Reveals Segregation Distortion Regions in Wheat. Biomed Research International, 10. doi:10.1155/2015/830618Segregation distortion is a widespread phenomenon in plant and animal genomes and significantly affects linkage map construction and identification of quantitative trait loci (QTLs). To study segregation distortion in wheat, a high-density consensus map was constructed using single nucleotide polymorphism (SNP) and simple sequence repeat (SSR) markers by merging two genetic maps developed from two recombinant-inbred line (RIL) populations, Ning7840 x Clark and Heyne x Lakin. Chromosome regions with obvious segregation distortion were identified in the map. A total of 3541 SNPs and 145 SSRs were mapped, and the map covered 3258.7 cM in genetic distance with an average interval of 0.88 cM. The number of markers that showed distorted segregation was 490 (18.5%) in the Ning7840 x Clark population and 225 (10.4%) in the Heyne x Lakin population. Most of the distorted markers (630) were mapped in the consensus map, which accounted for 17.1% of mapped markers. The majority of the distorted markers clustered in the segregation distortion regions (SDRs) on chromosomes 1B, 2A, 2B, 3A, 3B, 4B, 5A, 5B, 5D, 6B, 7A, and 7D. All of the markers in a given SDR skewed toward one of the parents, suggesting that gametophytic competition during zygote formation was most likely one of the causes for segregation distortion in the populations

    Multiparty simultaneous quantum identity authentication based on entanglement swapping

    Get PDF
    We present a multiparty simultaneous quantum identity authentication protocol based on entanglement swapping. In our protocol, the multi-user can be authenticated by a trusted third party simultaneously

    Decays of J/ψJ/\psi and ψ\psi^\prime into vector and pseudoscalar meson and the pseudoscalar glueball-qqˉq\bar{q} mixing

    Get PDF
    We introduce a parametrization scheme for J/ψ(ψ)VPJ/\psi(\psi^\prime)\to VP where the effects of SU(3) flavor symmetry breaking and doubly OZI-rule violation (DOZI) can be parametrized by certain parameters with explicit physical interpretations. This scheme can be used to clarify the glueball-qqˉq\bar{q} mixing within the pseudoscalar mesons. We also include the contributions from the electromagnetic (EM) decays of J/ψJ/\psi and ψ\psi^\prime via J/ψ(ψ)γVPJ/\psi(\psi^\prime)\to \gamma^*\to VP. Via study of the isospin violated channels, such as J/ψ(ψ)ρηJ/\psi(\psi^\prime)\to \rho\eta, ρη\rho\eta^\prime, ωπ0\omega\pi^0 and ϕπ0\phi\pi^0, reasonable constraints on the EM decay contributions are obtained. With the up-to-date experimental data for J/ψ(ψ)VPJ/\psi(\psi^\prime)\to VP, J/ψ(ψ)γPJ/\psi(\psi^\prime)\to \gamma P and PγγP\to \gamma\gamma, etc, we arrive at a consistent description of the mentioned processes with a minimal set of parameters. As a consequence, we find that there exists an overall suppression of the ψ3g\psi^\prime\to 3g form factors, which sheds some light on the long-standing "ρπ\rho\pi puzzle". By determining the glueball components inside the pseudoscalar η\eta and η\eta^\prime in three different glueball-qqˉq\bar{q} mixing schemes, we deduce that the lowest pseudoscalar glueball, if exists, has rather small qqˉq\bar{q} component, and it makes the η(1405)\eta(1405) a preferable candidate for 0+0^{-+} glueball.Comment: Revised version to appear on J. Phys. G; An error in the code was corrected. There's slight change to the numerical results, while the conclusion is intac
    corecore