6,285 research outputs found
Progress in weakly coupled string phenomenology
The weakly coupled vacuum of heterotic string theory remains
an attractive scenario for particle physics. The particle spectrum and the
issue of dilaton stabilization are reviewed. A specific model for hidden sector
condensation and supersymmetry breaking, that respects known constraints from
string theory, is described, and its phenomenological and cosmological
implications are discussed.Comment: 15 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/48640.p
Life cycle assessment of Swiss organic farming systems
The impacts of organic and integrated farming systems in Switzerland on the environment have been assessed in a comprehensive study by the life cycle assessment method. This paper reports a comparison of the treatments of the DOC experiment. Organic farming showed clear ecological advantages particularly for eco- and human toxicity, resource use and biodiversity. These ecological advantages only partly apply to nutrient losses and are not always found for single products. Per kg of organic product, higher impacts were often found for global warming potential, ozone formation, eutrophication and acidification compared to integrated production. In the same crop rotation with the same amount of organic fertilisers there were no systematic differences in soil quality of organic compared with integrated production. Further improvement of the environmental performance of organic farming should focus on achieving higher yields of good quality – especially in potatoes and cereals - by using inputs more efficiently and minimising nitrogen losses
Long Distance Contribution to
We revisit the calculation of the long distance contribution to . We discuss this process within the framework of chiral
perturbation theory, and also using simple models for the vertex. We argue that it is unlikely that this mode can be used to
extract information on short distance parameters. The process
is also long-distance dominated and we find that .Comment: References added, one typo corrected. Version to appear in Nuclear
Physics
Proton - Lambda correlations in Au-Au Collisions at GeV from the STAR experiment
The space-time evolution of the source of particles formed in the collision
of nuclei can be studied through particle correlations. The STAR experiment is
dedicated to study ultra-relativistic heavy ions collisions and allows to
measure non-identical strange particle correlations. The source size can be
extracted by studying , ,
and correlation functions. Strong interaction potential has
been studied for these systems using an analytical model. Final State
Interaction (FSI) parameters have been determined and has shown a significant
annihilation process present in and systems
not present in and .Comment: contribution to the 20th Winter Workshop on Nuclear Dynamic
Incident-energy and system-size dependence of directed flow
We present STAR's measurements of directed flow for charged hadrons in Au+Au
and Cu+Cu collisions at GeV and 62.4 GeV, as a
function of pseudorapidity, transverse momentum and centrality. We find that
directed flow depends on the incident energy, but not on the system size. We
extend the validity of limiting fragmentation hypothesis to different collision
systems.Comment: Quark Matter 2006 proceedings, 4 pages, 4 figures, submitted to J.
Phys.
New approach to nonlinear electrodynamics: dualities as symmetries of interaction
We elaborate on the duality-symmetric nonlinear electrodynamics in a new
formulation with auxiliary tensor fields. The Maxwell field strength appears
only in bilinear terms of the corresponding generic Lagrangian, while the
self-interaction is presented by a function E depending on the auxiliary
fields. Two types of dualities inherent in the nonlinear electrodynamics models
admit a simple off-shell characterization in terms of this function. In the
standard formulation, the continuous U(1) duality symmetry is nonlinearly
realized on the Maxwell field strength. In the new setting, the same symmetry
acts as linear U(1) transformations of the auxiliary field variables. The
nonlinear U(1) duality condition proves to be equivalent to the linear U(1)
invariance of the self-interaction E. The discrete self-duality (or
self-duality by Legendre transformation) amounts to a weaker reflection
symmetry of E. For a class of duality- symmetric Lagrangians we introduce an
alternative representation with the auxiliary scalar field and find new
explicit examples of such systems.Comment: Latex file, 21 page
Plans for Kaon Physics at BNL
I give an overview of current plans for kaon physics at BNL. The program is
centered on the rare decay modes K+ --> pi+ nu nubar and KL --> pi0 nu nubar.Comment: 10 pages, 8 figures. Uses espcrc2.sty. For the proceedings of HIF04:
High Intensity Frontier Workshop, La Biodola, Isola D'Elba, June 5-8, 200
Application of the operator product expansion to the short distance behavior of nuclear potentials
We investigate the short distance behavior of nucleon-nucleon (NN) potentials
defined through Bethe-Salpeter wave functions, by perturbatively calculating
anomalous dimensions of 6-quark operators in QCD. Thanks to the asymptotic
freedom of QCD, 1-loop computations give certain exact results for the
potentials in the zero distance limit. In particular the functional form of the
S-state central NN potential at short distance is predicted to be a little
weaker than . On the other hand, due to the intriguing character of the
anomalous dimension spectrum, perturbative considerations alone can not
determine whether this potential is repulsive or attractive at short distances.
A crude estimation suggests that the force at short distance is repulsive, as
found numerically in lattice QCD. A similar behavior is found for the tensor
potential.Comment: 40 pages, no figure
Gaugino Condensation with S-Duality and Field-Theoretical Threshold Corrections
We study gaugino condensation in the presence of an intermediate mass scale
in the hidden sector. S-duality is imposed as an approximate symmetry of the
effective supergravity theory. Furthermore, we include in the K\"ahler
potential the renormalization of the gauge coupling and the one-loop threshold
corrections at the intermediate scale. It is shown that confinement is indeed
achieved. Furthermore, a new running behaviour of the dilaton arises which we
attribute to S-duality. We also discuss the effects of the intermediate scale,
and possible phenomenological implications of this model.Comment: 19 pages, LaTeX, 3 postscript figures include
One-loop Regularization of Supergravity II: The Dilaton and the Superfield Formulation
The on-shell regularization of the one-loop divergences of supergravity
theories is generalized to include a dilaton of the type occurring in effective
field theories derived from superstring theory, and the superfield structure of
the one-loop corrections is given. Field theory anomalies and quantum
contributions to soft supersymmetry breaking are discussed. The latter are
sensitive to the precise choice of couplings that generate Pauli-Villars
masses, which in turn reflect the details of the underlying theory above the
scale of the effective cut-off. With a view to the implementation the
Green-Schwarz and other mechanisms for canceling field theory anomalies under a
U(1) gauge transformation and under the T-duality group of modular
transformations, we show that the K\"ahler potential renormalization for the
untwisted sector of orbifold compactification can be made invariant under these
groups.Comment: 46 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/43259.p
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