1,750 research outputs found
Inflation and flat directions in modular invariant superstring effective theories
The potential during inflation must be very flat in, at least, the direction
of the inflaton. In renormalizable global supersymmetry, flat directions are
ubiquitous, but they are not preserved in a generic supergravity theory. It is
known that at least some of them are preserved in no-scale supergravity, and
simple generalizations of it. We here study a more realistic generalization,
based on string-derived supergravity, using the linear supermultiplet formalism
for the dilaton. We consider a general class of hybrid inflation models, where
a Fayet-Illiopoulos term drives some fields to large values. The potential
is dominated by the term, but flatness is preserved in some directions.
This allows inflation, with the dilaton stabilized in its domain of attraction,
and some moduli stabilized at their vacuum values. Another modulus may be the
inflaton.Comment: 19 pages, REVTEX, further typos, refs fixe
On Black Hole Detection with the OWL/Airwatch Telescope
In scenarios with large extra dimensions and TeV scale gravity ultrahigh
energy neutrinos produce black holes in their interactions with the nucleons.
We show that ICECUBE and OWL may observe large number of black hole events and
provide valuable information about the fundamental Planck scale and the number
of extra dimensions. OWL is especially well suited to observe black hole events
produced by neutrinos from the interactions of cosmic rays with the 3 K
background radiation. Depending on the parameters of the scenario of large
extra dimensions and on the flux model, as many as 28 events per year are
expected for a Planck scale of 3 TeV.Comment: 8 pages, including 7 color figures, three figure captions corrected,
minor changes for clarification, one reference adde
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
One-Loop Pauli-Villars Regularization of Supergravity I: Canonical Gauge Kinetic Energy
It is shown that the one-loop coefficients of on-shell operators of standard
supergravity with canonical gauge kinetic energy can be regulated by the
introduction of Pauli-Villars chiral and abelian gauge multiplets, subject to a
condition on the matter representations of the gauge group. Aspects of the
anomaly structure of these theories under global nonlinear symmetries and an
anomalous gauge symmetry are discussed.Comment: 46 pages, full postscript also available from
http://phyweb.lbl.gov/theorygroup/papers/preprints.html/41981.ps . Misprints
and errors in equations present in the original version have been correcte
Impact of a Randomized Campus/Community Trial to Prevent High-Risk Drinking Among College Students
High-risk drinking by college students continues to pose a significant threat to public health. Despite increasing evidence of the contribution of community-level and campus-level environmental factors to high risk drinking, there have been few rigorous tests of interventions that focus on changing these interlinked environments. The Study to Prevent Alcohol Related Consequences (SPARC) assessed the efficacy of a comprehensive intervention using a community organizing approach to implement environmental strategies in and around college campuses. The goal of SPARC was to reduce high-risk drinking and alcohol-related consequences among college students
Supersymmetry and Superstring Phenomenology
We briefly cover the early history of supersymmetry, describe the relation of
SUSY quantum field theories to superstring theories and explain why they are
considered a likely tool to describe the phenomenology of high energy particle
theory beyond the Standard Model.Comment: 18 pages. To be published in ``Supersymmetry on the Eve of the LHC'',
a special volume of the European Physical Journal C (EPJC) dedicated to the
memory of Julius Wes
Regulatory Response to Carbon Starvation in Caulobacter crescentus
Bacteria adapt to shifts from rapid to slow growth, and have developed strategies for long-term survival during prolonged starvation and stress conditions. We report the regulatory response of C. crescentus to carbon starvation, based on combined high-throughput proteome and transcriptome analyses. Our results identify cell cycle changes in gene expression in response to carbon starvation that involve the prominent role of the FixK FNR/CAP family transcription factor and the CtrA cell cycle regulator. Notably, the SigT ECF sigma factor mediates the carbon starvation-induced degradation of CtrA, while activating a core set of general starvation-stress genes that respond to carbon starvation, osmotic stress, and exposure to heavy metals. Comparison of the response of swarmer cells and stalked cells to carbon starvation revealed four groups of genes that exhibit different expression profiles. Also, cell pole morphogenesis and initiation of chromosome replication normally occurring at the swarmer-to-stalked cell transition are uncoupled in carbon-starved cells
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