12,513 research outputs found
Cosmological Constraints on Dissipative Models of Inflation
(Abridged) We study dissipative inflation in the regime where the dissipative
term takes a specific form, \Gamma=\Gamma(\phi), analyzing two models in the
weak and strong dissipative regimes with a SUSY breaking potential. After
developing intuition about the predictions from these models through analytic
approximations, we compute the predicted cosmological observables through full
numerical evolution of the equations of motion, relating the mass scale and
scale of dissipation to the characteristic amplitude and shape of the
primordial power spectrum. We then use Markov Chain Monte Carlo techniques to
constrain a subset of the models with cosmological data from the cosmic
microwave background (WMAP three-year data) and large scale structure (SDSS
Luminous Red Galaxy power spectrum). We find that the posterior distributions
of the dissipative parameters are highly non-Gaussian and their allowed ranges
agree well with the expectations obtained using analytic approximations. In the
weak regime, only the mass scale is tightly constrained; conversely, in the
strong regime, only the dissipative coefficient is tightly constrained. A lower
limit is seen on the inflation scale: a sub-Planckian inflaton is disfavoured
by the data. In both weak and strong regimes, we reconstruct the limits on the
primordial power spectrum and show that these models prefer a {\it red}
spectrum, with no significant running of the index. We calculate the reheat
temperature and show that the gravitino problem can be overcome with large
dissipation, which in turn leads to large levels of non-Gaussianity: if
dissipative inflation is to evade the gravitino problem, the predicted level of
non-Gaussianity might be seen by the Planck satellite.Comment: 14 pages, 9 figures, Accepted by JCAP without text changes,
References adde
Universality of Electron Mobility in LaAlO/SrTiO and bulk SrTiO
Metallic LaAlO/SrTiO (LAO/STO) interfaces attract enormous attention,
but the relationship between the electron mobility and the sheet electron
density, , is poorly understood. Here we derive a simple expression for
the three-dimensional electron density near the interface, , as a
function of and find that the mobility for LAO/STO-based interfaces
depends on in the same way as it does for bulk doped STO. It is known
that undoped bulk STO is strongly compensated with background donors and acceptors. In intentionally doped
bulk STO with a concentration of electrons background impurities
determine the electron scattering. Thus, when it is natural to see
in LAO/STO the same mobility as in the bulk. On the other hand, in the bulk
samples with the mobility collapses because scattering happens on
intentionally introduced donors. For LAO/STO the polar catastrophe
which provides electrons is not supposed to provide equal number of random
donors and thus the mobility should be larger. The fact that the mobility is
still the same implies that for the LAO/STO the polar catastrophe model should
be revisited.Comment: 4 pages and 1 figur
Electronic structure and light-induced conductivity in a transparent refractory oxide
Combined first-principles and experimental investigations reveal the
underlying mechanism responsible for a drastic change of the conductivity (by
10 orders of magnitude) following hydrogen annealing and UV-irradiation in a
transparent oxide, 12CaO.7Al2O3, found by Hayashi et al. The charge transport
associated with photo-excitation of an electron from H, occurs by electron
hopping. We identify the atoms participating in the hops, determine the exact
paths for the carrier migration, estimate the temperature behavior of the
hopping transport and predict a way to enhance the conductivity by specific
doping.Comment: 4 pages including 4 figure
A lattice NRQCD computation of the bag parameters for = 2 operators
We present an update of our NRQCD calculation of at =5.9 with
increased statistics. We also discuss a calculation of , which is relevant
to the width difference in the mixing.Comment: LATTICE99 (Heavy Quarks), 3 pages, 2 figures, espcrc2.st
eHealth interventions for the prevention of depression and anxiety in the general population: a systematic review and meta-analysis.
BACKGROUND: Anxiety and depression are associated with a range of adverse outcomes and represent a large global burden to individuals and health care systems. Prevention programs are an important way to avert a proportion of the burden associated with such conditions both at a clinical and subclinical level. eHealth interventions provide an opportunity to offer accessible, acceptable, easily disseminated globally low-cost interventions on a wide scale. However, the efficacy of these programs remains unclear. The aim of this study is to review and evaluate the effects of eHealth prevention interventions for anxiety and depression. METHOD: A systematic search was conducted on four relevant databases to identify randomized controlled trials of eHealth interventions aimed at the prevention of anxiety and depression in the general population published between 2000 and January 2016. The quality of studies was assessed and a meta-analysis was performed using pooled effect size estimates obtained from a random effects model. RESULTS: Ten trials were included in the systematic review and meta-analysis. All studies were of sufficient quality and utilized cognitive behavioural techniques. At post-treatment, the overall mean difference between the intervention and control groups was 0.25 (95% confidence internal: 0.09, 0.41; p = 0.003) for depression outcome studies and 0.31 (95% CI: 0.10, 0.52; p = 0.004) for anxiety outcome studies, indicating a small but positive effect of the eHealth interventions. The effect sizes for universal and indicated/selective interventions were similar (0.29 and 0.25 respectively). However, there was inadequate evidence to suggest that such interventions have an effect on long-term disorder incidence rates. CONCLUSIONS: Evidence suggests that eHealth prevention interventions for anxiety and depression are associated with small but positive effects on symptom reduction. However, there is inadequate evidence on the medium to long-term effect of such interventions, and importantly, on the reduction of incidence of disorders. Further work to explore the impact of eHealth psychological interventions on long-term incidence rates
Flavor-Changing Processes in Extended Technicolor
We analyze constraints on a class of extended technicolor (ETC) models from
neutral flavor-changing processes induced by (dimension-six) four-fermion
operators. The ETC gauge group is taken to commute with the standard-model
gauge group. The models in the class are distinguished by how the left- and
right-handed components of the quarks and charged leptons transform
under the ETC group. We consider and other pseudoscalar
meson mixings, and conclude that they are adequately suppressed if the and
components of the relevant quarks are assigned to the same (fundamental or
conjugate-fundamental) representation of the ETC group. Models in which the
and components of the down-type quarks are assigned to relatively conjugate
representations, while they can lead to realistic CKM mixing and intra-family
mass splittings, do not adequately suppress these mixing processes. We identify
an approximate global symmetry that elucidates these behavioral differences and
can be used to analyze other possible representation assignments.
Flavor-changing decays, involving quarks and/or leptons, are adequately
suppressed for any ETC-representation assignment of the and components
of the quarks, as well as the leptons. We draw lessons for future ETC model
building.Comment: 25 page
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