158 research outputs found

    The hierarchy problem, radion mass, localization of gravity and 4D effective Newtonian potential in string theory on S1/Z2S^{1}/Z_{2}

    Full text link
    We present a systematical study of brane worlds in string theory on S1/Z2S^{1}/Z_{2}. Starting with the toroidal compactification of the NS/NS sector in (D+d) dimensions, we first obtain an effective DD-dimensional action, and then compactify one of the (D1)(D-1) spatial dimensions by introducing two orbifold branes as its boundaries. By combining the Gauss-Codacci and Lanczos equations, we write down explicitly the general gravitational field equations on each of the two branes, while using distribution theory we express the matter field equations on the branes in terms of the discontinuities of the first derivatives of the matter fields. Afterwards, we address three important issues: (i) the hierarchy problem; (ii) the radion mass; and (iii) the localization of gravity, the 4-dimensional Newtonian effective potential and the Yukawa corrections due to the gravitational high-order Kaluza-Klein (KK) modes. With a very conservative estimation, we find that the radion mass is of the order of 102GeV10^{-2} GeV. The gravity is localized on the visible brane, and the spectrum of the gravitational KK modes is discrete and can be of the order of TeV. The corrections to the 4-dimensional Newtonian potential from the higher order of gravitational KK modes are exponentially suppressed and can be safely neglected in current experiments. In an appendix, we also present a systematical and pedagogical study of the Gauss-Codacci equations and Israel's junction conditions across a (D-1)-dimensional hypersurface, which can be either spacelike or timelike.Comment: Considerably extended, Revtex4, 19 pages, 5 figures, published in IJMPA, 25, 1661-1698 (2010

    Accelerating Universes in String Theory via Field Redefinition

    Full text link
    We study cosmological solutions in the effective heterotic string theory with α\alpha'-correction terms in string frame. It is pointed out that the effective theory has an ambiguity via field redefinition and we analyze generalized effective theories due to this ambiguity. We restrict our analysis to the effective theories which give equations of motion of second order in the derivatives, just as "Galileon" field theory. This class of effective actions contains two free coupling constants. We find de Sitter solutions as well as the power-law expanding universes in our four-dimensional Einstein frame. The accelerated expanding universes are always the attractors in the present dynamical system.Comment: 22 pages, 3 figures, some additional formulae adde

    Search for the decay KL03γK_L^0 \rightarrow 3\gamma

    Full text link
    We performed a search for the decay KL03γK_L^0 \rightarrow 3\gamma with the E391a detector at KEK. In the data accumulated in 2005, no event was observed in the signal region. Based on the assumption of KL03γK_L^0 \rightarrow 3\gamma proceeding via parity-violation, we obtained the single event sensitivity to be (3.23±0.14)×108(3.23\pm0.14)\times10^{-8}, and set an upper limit on the branching ratio to be 7.4×1087.4\times10^{-8} at the 90% confidence level. This is a factor of 3.2 improvement compared to the previous results. The results of KL03γK_L^0 \rightarrow 3\gamma proceeding via parity-conservation were also presented in this paper
    corecore