38 research outputs found
The Leptonic Decay Constants of Mesons and the Lattice Resolution
We present a high statistics study of the leptonic decay constant of
heavy pseudoscalar mesons using propagating heavy Wilson quarks within the
quenched approximation, on lattices covering sizes from about 0.7~fm to 2~fm.
Varying between 5.74 and 6.26 we observe a sizeable dependence of
when one uses the quark field normalization that was suggested by
Kronfeld and Mackenzie, compared with the weaker dependence observed for the
standard relativistic norm. The two schemes come into agreement when one
extrapolates to . The extrapolations needed to reach the
continuum quantity introduce large errors and lead to the value
~GeV in the quenched approximation. This suggests that much more
effort will be needed to obtain an accurate lattice prediction for .Comment: 11 pages Latex + 5 tables + 8 postscript figures, unix shell archive,
DESY preprint DESY 93-17
Membrane-Protein Interactions in a Generic Coarse-Grained Model for Lipid Bilayers
We study membrane-protein interactions and membrane-mediated protein-protein
interactions by Monte Carlo simulations of a generic coarse-grained model for
lipid bilayers with cylindrical hydrophobic inclusions. The strength of the
hydrophobic force and the hydrophobic thickness of the proteins are
systematically varied. The results are compared with analytical predictions of
two popular analytical theories: The Landau-de Gennes theory and the elastic
theory. The elastic theory provides an excellent description of the fluctuation
spectra of pure membranes and successfully reproduces the deformation profiles
of membranes around single proteins. However, its prediction for the potential
of mean force between proteins is not compatible with the simulation data for
large distances. The simulations show that the lipid-mediated interactions are
governed by five competing factors: Direct interactions, lipid-induced
depletion interactions, lipid bridging, lipid packing, and a smooth long-range
contribution. The mechanisms leading to "hydrophobic mismatch" interactions are
critically analyzed.Comment: 16 pages, 8 figures, accepted for publication in Biophysical Journa
An assessment of Evans' unified field theory I
Evans developed a classical unified field theory of gravitation and
electromagnetism on the background of a spacetime obeying a Riemann-Cartan
geometry. This geometry can be characterized by an orthonormal coframe theta
and a (metric compatible) Lorentz connection Gamma. These two potentials yield
the field strengths torsion T and curvature R. Evans tried to infuse
electromagnetic properties into this geometrical framework by putting the
coframe theta to be proportional to four extended electromagnetic potentials A;
these are assumed to encompass the conventional Maxwellian potential in a
suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity
was adopted by Evans to describe the gravitational sector of his theory.
Including also the results of an accompanying paper by Obukhov and the author,
we show that Evans' ansatz for electromagnetism is untenable beyond repair both
from a geometrical as well as from a physical point of view. As a consequence,
his unified theory is obsolete.Comment: 39 pages of latex, modified because of referee report, mistakes and
typos removed, partly reformulated, taken care of M.W.Evans' rebutta
Beliefs regarding fundamental value and optimal investing
Investor beliefs, Mispricing, Optimal portfolios, Range reversion, Risk premium, G11,