222 research outputs found
Quantization of Fayet-Iliopoulos Parameters in Supergravity
In this short note we discuss quantization of the Fayet-Iliopoulos parameter
in supergravity theories. We argue that in supergravity, the Fayet-Iliopoulos
parameter determines a lift of the group action to a line bundle, and such
lifts are quantized. Just as D-terms in rigid N=1 supersymmetry are interpreted
in terms of moment maps and symplectic reductions, we argue that in
supergravity the quantization of the Fayet-Iliopoulos parameter has a natural
understanding in terms of linearizations in geometric invariant theory (GIT)
quotients, the algebro-geometric version of symplectic quotients.Comment: 21 pages, utarticle class; v2: typos and tex issue fixe
Christian Mysticism in Theory and Practice: Nathan Söderblom And Sadhu Sundar Singh
Naturally, contributions from places other than this one will be encouraged, indeed, sought. There could be no other way to promote a more wide understanding of Religion in Australia, than this. Religious Traditions journal in other words, though meant in part to be the product of a need felt among Australian "religionists", must, by dint of that very fact, take its place besides other international Journals in the field
Yucca Mountain Climate Technical Support Representative
The principal investigator (PI), Saxon Sharpe, for Task ORD-FY04-012, DOE Cooperative Agreement DE-FC28-04RW12232, will serve as Yucca Mountain Climate Technical Support Representative for the Department of Energy (DOE) in a series of activities related to past, present, and future climate for the Yucca Mountain Project (YMP) climate program.
As stated in the Viability Assessment of a Repository at Yucca Mountain: “Climate and its changes over time directly affect system performance at Yucca Mountain.” Currently, information from climate studies is used in models that support the Total System Performance Assessment and Licensing Application. It is a model component of all key attributes in the repository safety strategy (limited water contacting waste package, long waste package lifetime, low rate of release of radionuclides from breached waste packages, and radionuclide concentration reduction during transport from the waste packages). Elements of the climate program are also directly related to the Nuclear Regulatory Commission’s (NRC) Key Technical Issue of Unsaturated and Saturated Zone Flow Under Isothermal Conditions and, in addition, address other NRC Key Technical Issues
Technical Memo: Incorporating Mixture Toxicity into Bayesian Networks to calculate risk to pesticides in the Upper San Francisco Estuary.
This memo presents the methods we have developed to calculate risk of mixtures of pesticides for the Upper San Francisco Estuary (USFE). We used curve fitting to estimate the exposure-response curves for each individual chemical and then the mixture. For the mixture the models were normalized for specific ECx values. In that way the curve fitting was optimized for effects that are similar to most threshold values. A Bayesian network was then built that incorporated four different pesticides and a specific mode of action. The input distributions of the pesticides were measured amounts from each of the six risk regions. Sensitivity analysis identified the components of the Bayesian network most important in determining the toxicity. We did demonstrate that curve fitting using additive models for mixtures can be used to estimate fish toxicity in this proof-of-concept model. Bifenthrin and the specific risk region were the two variables that were most important to the risk calculation. These techniques appear applicable to estimating risk due to the variety of chemicals and other stressors in the USFE and to the multiple endpoints under managemen
Lrp4 Modulates Extracellular Integration of Cell Signaling Pathways in Development
The extent to which cell signaling is integrated outside the cell is not currently appreciated. We show that a member of the low-density receptor-related protein family, Lrp4 modulates and integrates Bmp and canonical Wnt signalling during tooth morphogenesis by binding the secreted Bmp antagonist protein Wise. Mouse mutants of Lrp4 and Wise exhibit identical tooth phenotypes that include supernumerary incisors and molars, and fused molars. We propose that the Lrp4/Wise interaction acts as an extracellular integrator of epithelial-mesenchymal cell signaling. Wise, secreted from mesenchyme cells binds to BMP's and also to Lrp4 that is expressed on epithelial cells. This binding then results in the modulation of Wnt activity in the epithelial cells. Thus in this context Wise acts as an extracellular signaling molecule linking two signaling pathways. We further show that a downstream mediator of this integration is the Shh signaling pathway
Rigidly Supersymmetric Gauge Theories on Curved Superspace
In this note we construct rigidly supersymmetric gauged sigma models and
gauge theories on certain Einstein four-manifolds, and discuss constraints on
these theories. In work elsewhere, it was recently shown that on some
nontrivial Einstein four-manifolds such as AdS, N=1 rigidly supersymmetric
sigma models are constrained to have target spaces with exact K\"ahler forms.
Similarly, in gauged sigma models and gauge theories, we find that
supersymmetry imposes constraints on Fayet-Iliopoulos parameters, which have
the effect of enforcing that K\"ahler forms on quotient spaces be exact. We
also discuss general aspects of universality classes of gauged sigma models, as
encoded by stacks, and also discuss affine bundle structures implicit in these
constructions.Comment: 23 pages; references added; more discussion added; v4: typos fixe
The Taming of Closed Time-like Curves
We consider a orbifold, where acts by time and space
reversal, also known as the embedding space of the elliptic de Sitter space.
The background has two potentially dangerous problems: time-nonorientability
and the existence of closed time-like curves. We first show that closed causal
curves disappear after a proper definition of the time function. We then
consider the one-loop vacuum expectation value of the stress tensor. A naive
QFT analysis yields a divergent result. We then analyze the stress tensor in
bosonic string theory, and find the same result as if the target space would be
just the Minkowski space , suggesting a zero result for the
superstring. This leads us to propose a proper reformulation of QFT, and
recalculate the stress tensor. We find almost the same result as in Minkowski
space, except for a potential divergence at the initial time slice of the
orbifold, analogous to a spacelike Big Bang singularity. Finally, we argue that
it is possible to define local S-matrices, even if the spacetime is globally
time-nonorientable.Comment: 37 pages, LaTeX2e, uses amssymb, amsmath and epsf macros, 8 eps and 3
ps figures; (v2): Two additional comments + one reference added; (v3):
corrections in discussion of CTCs + some clarification
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