Spinless photon dark matter from two universal extra dimensions

We explore the properties of dark matter in theories with two universal extra dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle, representing a six-dimensional photon polarized along the extra dimensions. Annihilation of this 'spinless photon' proceeds predominantly through Higgs boson exchange, and is largely independent of other Kaluza-Klein particles. The measured relic abundance sets an upper limit on the spinless photon mass of 500 GeV, which decreases to almost 200 GeV if the Higgs boson is light. The phenomenology of this dark matter candidate is strikingly different from Kaluza-Klein dark matter in theories with one universal extra dimension. Elastic scattering of the spinless photon with quarks is helicity suppressed, making its direct detection challenging, although possible at upcoming experiments. The prospects for indirect detection with gamma rays and antimatter are similar to those of neutralinos. The rates predicted at neutrino telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for direct detection. Some clarifying remarks include

Supersymmetry for Fermion Masses

It is proposed that supersymmetry (SUSY) maybe used to understand fermion mass hierarchies. A family symmetry Z_{3L} is introduced, which is the cyclic symmetry among the three generation SU(2) doublets. SUSY breaks at a high energy scale ~ 10^{11} GeV. The electroweak energy scale ~ 100 GeV is unnaturally small. No additional global symmetry, like the R-parity, is imposed. The Yukawa couplings and R-parity violating couplings all take their natural values which are about (10^0-10^{-2}). Under the family symmetry, only the third generation charged fermions get their masses. This family symmetry is broken in the soft SUSY breaking terms which result in a hierarchical pattern of the fermion masses. It turns out that for the charged leptons, the tau mass is from the Higgs vacuum expectation value (VEV) and the sneutrino VEVs, the muon mass is due to the sneutrino VEVs, and the electron gains its mass due to both Z_{3L} and SUSY breaking. The large neutrino mixing are produced with neutralinos playing the partial role of right-handed neutrinos. |V_{e3}| which is for nu_e-nu_{tau} mixing is expected to be about 0.1. For the quarks, the third generation masses are from the Higgs VEVs, the second generation masses are from quantum corrections, and the down quark mass due to the sneutrino VEVs. It explains m_c/m_s, m_s/m_e, m_d > m_u and so on. Other aspects of the model are discussed.Comment: 25 pages, 3 figures, revtex4; neutrino oscillation and many discussions added, smallness of the electron mass due to supersymmetry pointed out; v3: numerical errors correcte

Decreased MCM2-6 in Drosophila S2 cells does not generate significant DNA damage or cause a marked increase in sensitivity to replication interference.

A reduction in the level of some MCM proteins in human cancer cells (MCM5 in U20S cells or MCM3 in Hela cells) causes a rapid increase in the level of DNA damage under normal conditions of cell proliferation and a loss of viability when the cells are subjected to replication interference. Here we show that Drosophila S2 cells do not appear to show the same degree of sensitivity to MCM2-6 reduction. Under normal cell growth conditions a reduction of >95% in the levels of MCM3, 5, and 6 causes no significant short term alteration in the parameters of DNA replication or increase in DNA damage. MCM depleted cells challenged with HU do show a decrease in the density of replication forks compared to cells with normal levels of MCM proteins, but this produces no consistent change in the levels of DNA damage observed. In contrast a comparable reduction of MCM7 levels has marked effects on viability, replication parameters and DNA damage in the absence of HU treatment

East Asia and the global/transatlantic/Western crisis

This paper introduces the special collection on East Asia and the Global Crisis. After justifying why a focus on East Asia is appropriate, it draws out the main themes that run through the individual contributions. These are the extent to which the region is decoupling from the global economy (or the West), the increasing legitimacy of statist alternatives to neoliberal development strategies, and the impact of crises on the definition of ―region‖ and the functioning of regional institutions and governance mechanisms

Neutrino Mass from R-parity Violation in Split Supersymmetry

We investigate how the observed neutrino data can be accommodated by R-parity violation in Split Supersymmetry. The atmospheric neutrino mass and mixing are explained by the bilinear parameters $\xi_i$ inducing the neutrino-neutralino mixing as in the usual low-energy supersymmetry. Among various one-loop corrections, only the quark-squark exchanging diagrams involving the order-one trilinear couplings $\lambda'_{i23,i32}$ can generate the solar neutrino mass and mixing if the scalar mass $m_S$ is not larger than $10^9$ GeV. This scheme requires an unpleasant hierarchical structure of the couplings, e.g., $\lambda_{i23,i32}\sim 1$, $\lambda'_{i33} \lesssim 10^{-4}$ and $\xi_i \lesssim 10^{-6}$. On the other hand, the model has a distinct collider signature of the lightest neutralino which can decay only to the final states, $l_i W^{(*)}$ and $\nu Z^{(*)}$, arising from the bilinear mixing. Thus, the measurement of the ratio; $\Gamma(e W^{(*)}) : \Gamma(\mu W^{(*)}) : \Gamma(\tau W^{(*)})$ would provide a clean probe of the small reactor and large atmospheric neutrino mixing angles as far as the neutralino mass is larger than 62 GeV.Comment: 10 pages, 3 figures, version submitted to JHE

Inflation on the Brane with Vanishing Gravity

Many existing models of brane inflation suffer from a steep irreducible gravitational potential between the branes that causes inflation to end too early. Inspired by the fact that point masses in 2+1 D exert no gravitational force, we propose a novel unwarped and non-supersymmetric setup for inflation, consisting of 3-branes in two extra dimensions compactified on a sphere. The size of the sphere is stabilized by a combination of a bulk cosmological constant and a magnetic flux. Computing the 4D effective potential between probe branes in this background, we find a non-zero contribution only from exchange of level-1 KK modes of the graviton and radion. Identifying antipodal points on the 2-sphere projects out these modes, eliminating entirely the troublesome gravitational contribution to the inflationary potential.Comment: 19 pages, 11 figures, JHEP forma

Diagonalization of the neutralino mass matrix and boson-neutralino interaction

We analyze a connection between neutralino mass sign, parity and structure of the neutralino-boson interaction. Correct calculation of spin-dependent and spin-independent contributions to neutralino-nuclear scattering should consider this connection. A convenient diagonalization procedure, based on the exponetial parametrization of unitary matrix, is suggested.Comment: 21 pages, RevTex

How large could the R-parity violating couplings be?

We investigate in detail the predictions coming from the d=4 operators for proton decay. We find the most general constraints for the R-parity violating couplings coming from proton decay, taking into account all fermion mixing and in different supersymmetric scenarios.Comment: 8 pages, several corrections, to appear in J.Phys.G (2005

Precision Electroweak Observables in the Minimal Moose Little Higgs Model

Little Higgs theories, in which the Higgs particle is realized as the pseudo-Goldstone boson of an approximate global chiral symmetry have generated much interest as possible alternatives to weak scale supersymmetry. In this paper we analyze precision electroweak observables in the Minimal Moose model and find that in order to be consistent with current experimental bounds, the gauge structure of this theory needs to be modified. We then look for viable regions of parameter space in the modified theory by calculating the various contributions to the S and T parameters.Comment: v2: 17 pages, 9 figures. Typeset in JHEP style. Added a references and two figures showing parameter space for each of two reference points. Corrected typo