8,380 research outputs found
New Gauged N=8, D=4 Supergravities
New gaugings of four dimensional N=8 supergravity are constructed, including
one which has a Minkowski space vacuum that preserves N=2 supersymmetry and in
which the gauge group is broken to . Previous gaugings used the
form of the ungauged action which is invariant under a rigid symmetry
and promoted a 28-dimensional subgroup ( or the
non-semi-simple contraction ) to a local gauge group. Here, a
dual form of the ungauged action is used which is invariant under
instead of and new theories are obtained by gauging 28-dimensional
subgroups of . The gauge groups are non-semi-simple and are different
real forms of the groups, denoted , and the new
theories have a rigid SU(2) symmetry. The five dimensional gauged N=8
supergravities are dimensionally reduced to D=4. The gauge
theories reduce, after a duality transformation, to the
gauging while the gauge theory reduces to the gauge
theory. The new theories are related to the old ones via an analytic
continuation. The non-semi-simple gaugings can be dualised to forms with
different gauge groups.Comment: 33 pages. Reference adde
Flux Compactifications of M-Theory on Twisted Tori
We find the bosonic sector of the gauged supergravities that are obtained
from 11-dimensional supergravity by Scherk-Schwarz dimensional reduction with
flux to any dimension D. We show that, if certain obstructions are absent, the
Scherk-Schwarz ansatz for a finite set of D-dimensional fields can be extended
to a full compactification of M-theory, including an infinite tower of
Kaluza-Klein fields. The internal space is obtained from a group manifold
(which may be non-compact) by a discrete identification. We discuss the
symmetry algebra and the symmetry breaking patterns and illustrate these with
particular examples. We discuss the action of U-duality on these theories in
terms of symmetries of the D-dimensional supergravity, and argue that in
general it will take geometric flux compactifications to M-theory on
non-geometric backgrounds, such as U-folds with U-duality transition functions.Comment: Latex, 47 page
Recommended from our members
Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To assess whether blue-light filtering spectacle lenses impart effects on visual function, provide protection to the macula, or both. We will also examine potential effects on the sleep-wake cycle
Moody's Correlated Binomial Default Distributions for Inhomogeneous Portfolios
This paper generalizes Moody's correlated binomial default distribution for
homogeneous (exchangeable) credit portfolio, which is introduced by Witt, to
the case of inhomogeneous portfolios. As inhomogeneous portfolios, we consider
two cases. In the first case, we treat a portfolio whose assets have uniform
default correlation and non-uniform default probabilities. We obtain the
default probability distribution and study the effect of the inhomogeneity on
it. The second case corresponds to a portfolio with inhomogeneous default
correlation. Assets are categorized in several different sectors and the
inter-sector and intra-sector correlations are not the same. We construct the
joint default probabilities and obtain the default probability distribution. We
show that as the number of assets in each sector decreases, inter-sector
correlation becomes more important than intra-sector correlation. We study the
maximum values of the inter-sector default correlation. Our generalization
method can be applied to any correlated binomial default distribution model
which has explicit relations to the conditional default probabilities or
conditional default correlations, e.g. Credit Risk, implied default
distributions. We also compare some popular CDO pricing models from the
viewpoint of the range of the implied tranche correlation.Comment: 29 pages, 17 figures and 1 tabl
Does sleep education change sleep parameters? Comparing sleep education trials for middle school students in Australia and New Zealand
Background: Adolescents suffer daytime consequences from sleep loss. Sleep education programs have been developed in an attempt to increase sleep knowledge and/or duration. This paper presents data from three trials of the Aus-tralian Centre for Education in Sleep (ACES) program for adolescents.Methods: The ACES program was delivered to 69 Australian adolescents in a pre-post cross-sectional design (mean age 15.2) and 29 New Zealand adolescents in a randomised control trial (mean age 14.8 years). Assessments in sleep parame-ters were undertaken at baseline and post intervention.Results: Where sleep knowledge was evaluated (Australian trials), significant improvements were shown in all trials (All p <0.05). Where sleep duration was assessed (New Zealand trial) significant improvements were found in week and weekend sleep duration [F(1, 27)=4.26, p=0.04). Both, students and teachers found the program feasible, interesting, and educational.Conclusions: ACES sleep education programmes can improve both sleep knowledge and sleep duration in adolescents. Improving the programme so sleep knowledge attained equates to actual sleep behaviour change are areas for future direc-tion. Collectively these findings provide encouraging signs that adolescents can improve their sleep knowledge and behav-iour with sleep education which bodes well for sleep-related health and psycho-social issues
Rigid N=2 superconformal hypermultiplets
We discuss superconformally invariant systems of hypermultiplets coupled to
gauge fields associated with target-space isometries.Comment: Invited talk given at the International Seminar "Supersymmetries and
Quantum Symmetries", July 1997, Dubna. Latex, 9 p
Millimeter polarisation of the protoplanetary nebula OH 231.8+4.2: A follow-up study with CARMA
In order to investigate the characteristics and influence of the magnetic
field in evolved stars, we performed a follow-up investigation of our previous
submillimeter analysis of the proto-planetary nebula (PPN) OH 231.8+4.2 (Sabin
et al. 2014), this time at 1.3mm with the CARMA facility in polarisation mode
for the purpose of a multi-scale analysis. OH 231.8+4.2 was observed at ~2.5"
resolution and we detected polarised emission above the 3-sigma threshold (with
a mean polarisation fraction of 3.5 %). The polarisation map indicates an
overall organised magnetic field within the nebula. The main finding in this
paper is the presence of a structure mostly compatible with an ordered toroidal
component that is aligned with the PPN's dark lane. We also present some
alternative magnetic field configuration to explain the structure observed.
These data complete our previous SMA submillimeter data for a better
investigation and understanding of the magnetic field structure in OH
231.8+4.2.Comment: 7 pages, 5 figures, 2 tables. Accepted for publication in MNRA
N=2 supergravity models with stable de Sitter vacua
In the present talk I shall review the construction of N=2 supergravity
models exhibiting stable de Sitter vacua. These solutions represent the first
instance of stable backgrounds with positive cosmological constant in the
framework of extended supergravities (N >=2). After briefly reviewing the role
of de Sitter space--times in inflationary cosmology, I shall describe the main
ingredients which were necessary for the construction of gauged N=2
supergravity models admitting stable solutions of this kind.Comment: Prepared for Workshop on the Quantum Structure of Spacetime and the
Geometric Nature of Fundamental Interactions, Leuven, Belgium, September
13-19 200
U-dual fluxes and Generalized Geometry
We perform a systematic analysis of generic string flux compactifications,
making use of Exceptional Generalized Geometry (EGG) as an organizing
principle. In particular, we establish the precise map between fluxes, gaugings
of maximal 4d supergravity and EGG, identifying the complete set of gaugings
that admit an uplift to 10d heterotic or type IIB supegravity backgrounds. Our
results reveal a rich structure, involving new deformations of 10d supergravity
backgrounds, such as the RR counterparts of the -deformation. These new
deformations are expected to provide the natural extension of the
-deformation to full-fledged F-theory backgrounds. Our analysis also
provides some clues on the 10d origin of some of the particularly less
understood gaugings of 4d supergravity. Finally, we derive the explicit
expression for the effective superpotential in arbitrary N = 1 heterotic or
type IIB orientifold compactifications, for all the allowed fluxes.Comment: 58 pages, 6 table
Toroidal Orientifolds in IIA with General NS-NS Fluxes
Type IIA toroidal orientifolds offer a promising toolkit for model builders,
especially when one includes not only the usual fluxes from NS-NS and R-R field
strengths, but also fluxes that are T-dual to the NS-NS three-form flux. These
new ingredients are known as metric fluxes and non-geometric fluxes, and can
help stabilize moduli or can lead to other new features. In this paper we study
two approaches to these constructions, by effective field theory or by toroidal
fibers twisted over a toroidal base. Each approach leads us to important
observations, in particular the presence of D-terms in the four-dimensional
effective potential in some cases, and a more subtle treatment of the
quantization of the general NS-NS fluxes. Though our methods are general, we
illustrate each approach on the example of an orientifold of T^6/Z_4.Comment: 59 pages, references adde
- âŠ