69,794 research outputs found

    How bio-friendly is the universe

    Full text link
    The oft-repeated claim that life is written into the laws of nature are examined and criticized. Arguments are given in favour of life spreading between near-neighbour planets in rocky impact ejecta (transpermia), but against panspermia, leading to the conclusion that if life is indeed found to be widespread in the universe, some form of life principle or biological determinism must be at work in the process of biogenesis. Criteria for what would constitute a credible life principle are elucidated. I argue that the key property of life is its information content, and speculate that the emergence of the requisite information-processing machinery might require quantum information theory for a satisfactory explanation. Some clues about how decoherence might be evaded are discussed. The implications of some of these ideas for fine tuning are discussed.Comment: 11 page conference report, no figure

    Quantum fluctuations and life

    Full text link
    There have been many claims that quantum mechanics plays a key role in the origin and/or operation of biological organisms, beyond merely providing the basis for the shapes and sizes of biological molecules and their chemical affinities. These range from the suggestion by Schrodinger that quantum fluctuations produce mutations, to the conjecture by Hameroff and Penrose that quantum coherence in microtubules is linked to consciousness. I review some of these claims in this paper, and discuss the serious problem of decoherence. I advance some further conjectures about quantum information processing in bio-systems. Some possible experiments are suggested.Comment: 10 pages, no figures, conference pape

    Calibrating the parameters: changing hearts and minds about open access monographs

    Get PDF
    The advent of open access (OA) publishing presents welcome new opportunities for reducing the barriers of cost and time to the dissemination of research work in UK universities. However, it does present some challenges to the traditional model of monograph publication in the humanities and social sciences. In common with many other academic institutions, the University of Sussex is developing policies that will permit it to embrace OA publication. This paper describes how, in doing this, Sussex is addressing the challenges associated with OA to ensure that the careers of doctoral students, academics and researchers are not affected adversely by the change in the publishing landscape for monographs both in the UK and internationall

    New methods for B meson decay constants and form factors from lattice NRQCD

    Get PDF
    We determine the normalisation of scalar and pseudoscalar current operators made from non-relativistic bb quarks and Highly Improved Staggered light quarks in lattice Quantum Chromodynamics (QCD) through O(αs)\mathcal{O}(\alpha_s) and ΛQCD/mb\Lambda_{\text{QCD}}/m_b. We use matrix elements of these operators to extract BB meson decay constants and form factors, then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the BB meson decay constants and form factors. We provide a new value for the BB and BsB_s meson decay constants from lattice QCD calculations on ensembles that include uu, dd, ss and cc quarks in the sea and those which have the u/du/d quark mass going down to its physical value. Our results are fB=0.196(6)f_B=0.196(6) GeV, fBs=0.236(7)f_{B_s}=0.236(7) GeV and fBs/fB=1.207(7)f_{B_s}/f_B =1.207(7), agreeing well with earlier results using the temporal axial current. By combining with these previous results, we provide updated values of fB=0.190(4)f_B=0.190(4) GeV, fBs=0.229(5)f_{B_s}=0.229(5) GeV and fBs/fB=1.206(5)f_{B_s}/f_B = 1.206(5).Comment: 14 pages, 10 figure

    Quarkonium spin structure in lattice NRQCD

    Get PDF
    Numerical simulations of the quarkonium spin splittings are done in the framework of lattice nonrelativistic quantum chromodynamics (NRQCD). At leading order in the velocity expansion the spin splittings are of O(MQv4)O(M_Q v^4), where MQM_Q is the renormalized quark mass and v2v^2 is the mean squared quark velocity. A systematic analysis is done of all next-to-leading order corrections. This includes the addition of O(MQv6)O(M_Q v^6) relativistic interactions, and the removal of O(a2MQv4)O(a^2 M_Q v^4) discretization errors in the leading-order interactions. Simulations are done for both S- and P-wave mesons, with a variety of heavy quark actions and over a wide range of lattice spacings. Two prescriptions for the tadpole improvement of the action are also studied in detail: one using the measured value of the average plaquette, the other using the mean link measured in Landau gauge. Next-to-leading order interactions result in a very large reduction in the charmonium splittings, down by about 60% from their values at leading order. There are further indications that the velocity expansion may be poorly convergent for charmonium. Prelimary results show a small correction to the hyperfine splitting in the Upsilon system.Comment: 16 pages, REVTEX v3.1, 5 postscript figures include
    • …
    corecore