Constraining holographic inflation with WMAP

In a class of recently proposed models, the early universe is strongly coupled and described holographically by a three-dimensional, weakly coupled, super-renormalizable quantum field theory. This scenario leads to a power spectrum of scalar perturbations that differs from the usual empirical LCDM form and the predictions of generic models of single field, slow roll inflation. This spectrum is characterized by two parameters: an amplitude, and a parameter g related to the coupling constant of the dual theory. We estimate these parameters, using WMAP and other astrophysical data. We compute Bayesian evidence for both the holographic model and standard LCDM and find that their difference is not significant, although LCDM provides a somewhat better fit to the data. However, it appears that Planck will permit a definitive test of this holographic scenario.Comment: 24 pages, 9 figs, published versio

Gating of high-mobility InAs metamorphic heterostructures

We investigate the performance of gate-defined devices fabricated on high mobility InAs metamorphic heterostructures. We find that heterostructures capped with In$_{0.75}$Ga$_{0.25}$As often show signs of parallel conduction due to proximity of their surface Fermi level to the conduction band minimum. Here, we introduce a technique that can be used to estimate the density of this surface charge that involves cool-downs from room temperature under gate bias. We have been able to remove the parallel conduction under high positive bias, but achieving full depletion has proven difficult. We find that by using In$_{0.75}$Al$_{0.25}$As as the barrier without an In$_{0.75}$Ga$_{0.25}$As capping, a drastic reduction in parallel conduction can be achieved. Our studies show that this does not change the transport properties of the quantum well significantly. We achieved full depletion in InAlAs capped heterostructures with non-hysteretic gating response suitable for fabrication of gate-defined mesoscopic devices

Holographic predictions for cosmological 3-point functions

We present the holographic predictions for cosmological 3-point correlators, involving both scalar and tensor modes, for a universe which started in a non-geometric holographic phase. Holographic formulae relate the cosmological 3-point functions to stress tensor correlation functions of a holographically dual three-dimensional non-gravitational QFT. We compute these correlators at 1-loop order for a theory containing massless scalars, fermions and gauge fields, and present an extensive analysis of the constraints due to Ward identities showing that they uniquely determine the correlators up to a few constants. We define shapes for all cosmological bispectra and compare the holographic shapes to the slow-roll ones, finding that some are distinguishable while others, perhaps surprisingly, are not.Comment: 51pp; 4 fig

LUNASKA experiments using the Australia Telescope Compact Array to search for ultra-high energy neutrinos and develop technology for the lunar Cherenkov technique

We describe the design, performance, sensitivity and results of our recent experiments using the Australia Telescope Compact Array (ATCA) for lunar Cherenkov observations with a very wide (600 MHz) bandwidth and nanosecond timing, including a limit on an isotropic neutrino flux. We also make a first estimate of the effects of small-scale surface roughness on the effective experimental aperture, finding that contrary to expectations, such roughness will act to increase the detectability of near-surface events over the neutrino energy-range at which our experiment is most sensitive (though distortions to the time-domain pulse profile may make identification more difficult). The aim of our "Lunar UHE Neutrino Astrophysics using the Square Kilometer Array" (LUNASKA) project is to develop the lunar Cherenkov technique of using terrestrial radio telescope arrays for ultra-high energy (UHE) cosmic ray (CR) and neutrino detection, and in particular to prepare for using the Square Kilometer Array (SKA) and its path-finders such as the Australian SKA Pathfinder (ASKAP) and the Low Frequency Array (LOFAR) for lunar Cherenkov experiments.Comment: 27 pages, 18 figures, 4 tables

Antenatal care of women who use opioids:A qualitative study of practitioners’ perceptions of strengths and challenges of current service provision in Scotland

Background: The increasing rise of women using opioids during pregnancy across the world has warranted concern over the access and quality of antenatal care received by this group. Scotland has particularly high levels of opioid use, and correspondingly, pregnancies involving women who use opioids. The purpose of this study was to investigate the different models of antenatal care for women using opioids during pregnancy in three Scottish Health Board Areas, and to explore multi-disciplinary practitioners’ perceptions of the strengths and challenges of working with women who use opioids through these specialist services.Methods: Thirteen semi-structured interviews were conducted with health and social care workers who had experience of providing antenatal and postnatal care to women who use drugs across three Scottish Health Board Areas: NHS Greater Glasgow and Clyde, NHS Lothian, and NHS Tayside. Framework Analysis was used to analyse interview data. The five stages of framework analysis were undertaken: familiarisation, identifying the thematic framework, indexing, charting, and mapping and interpretation.Results: Each area had a specialist antenatal pathway for women who used substances. Pathways varied, with some consisting of specialist midwives, and others comprising a multidisciplinary team (e.g. midwife, mental health nurse, social workers, and an obstetrician). Referral criteria for the specialist service differed between health board areas. These specialised pathways presented several key strengths: continuity of care with one midwife and a strong patient-practitioner relationship; increased number of appointments, support and scans; and highly specialised healthcare professionals with experience of working with substance use. In spite of this, there were a number of limitations to these pathways: a lack of additional psychological support for the mother; some staff not having the skills to engage with the complexity of patients who use substances; and problems with patient engagement.Conclusions: Across the three areas, there appears to be high-quality multi-disciplinary antenatal services for women who use opioids during pregnancy. However, referral criteria vary and some services appear more comprehensive than others. Further research is needed into the perceptions of women who use opioids on facilitators and barriers to antenatal care, and provision in rural regions of Scotland

Antenatal care of women who use opioids:A qualitative study of practitioners’ perceptions of strengths and challenges of current service provision in Scotland

Background: The increasing rise of women using opioids during pregnancy across the world has warranted concern over the access and quality of antenatal care received by this group. Scotland has particularly high levels of opioid use, and correspondingly, pregnancies involving women who use opioids. The purpose of this study was to investigate the different models of antenatal care for women using opioids during pregnancy in three Scottish Health Board Areas, and to explore multi-disciplinary practitioners’ perceptions of the strengths and challenges of working with women who use opioids through these specialist services.Methods: Thirteen semi-structured interviews were conducted with health and social care workers who had experience of providing antenatal and postnatal care to women who use drugs across three Scottish Health Board Areas: NHS Greater Glasgow and Clyde, NHS Lothian, and NHS Tayside. Framework Analysis was used to analyse interview data. The five stages of framework analysis were undertaken: familiarisation, identifying the thematic framework, indexing, charting, and mapping and interpretation.Results: Each area had a specialist antenatal pathway for women who used substances. Pathways varied, with some consisting of specialist midwives, and others comprising a multidisciplinary team (e.g. midwife, mental health nurse, social workers, and an obstetrician). Referral criteria for the specialist service differed between health board areas. These specialised pathways presented several key strengths: continuity of care with one midwife and a strong patient-practitioner relationship; increased number of appointments, support and scans; and highly specialised healthcare professionals with experience of working with substance use. In spite of this, there were a number of limitations to these pathways: a lack of additional psychological support for the mother; some staff not having the skills to engage with the complexity of patients who use substances; and problems with patient engagement.Conclusions: Across the three areas, there appears to be high-quality multi-disciplinary antenatal services for women who use opioids during pregnancy. However, referral criteria vary and some services appear more comprehensive than others. Further research is needed into the perceptions of women who use opioids on facilitators and barriers to antenatal care, and provision in rural regions of Scotland

The Holographic Universe

We present a holographic description of four-dimensional single-scalar inflationary universes in terms of a three-dimensional quantum field theory. The holographic description correctly reproduces standard inflationary predictions in their regime of applicability. In the opposite case, wherein gravity is strongly coupled at early times, we propose a holographic description in terms of perturbative QFT and present models capable of satisfying the current observational constraints while exhibiting a phenomenology distinct from standard inflation. This provides a qualitatively new method for generating a nearly scale-invariant spectrum of primordial cosmological perturbations.Comment: 20 pages, 5 figs; extended version of arXiv:0907.5542 including background material and detailed derivations. To appear in Proceedings of 1st Mediterranean Conference on Classical and Quantum Gravit

Scale-invariance in expanding and contracting universes from two-field models

We study cosmological perturbations produced by the most general two-derivative actions involving two scalar fields, coupled to Einstein gravity, with an arbitrary field space metric, that admit scaling solutions. For contracting universes, we show that scale-invariant adiabatic perturbations can be produced continuously as modes leave the horizon for any equation of state parameter $w \ge 0$. The corresponding background solutions are unstable, which we argue is a universal feature of contracting models that yield scale-invariant spectra. For expanding universes, we find that nearly scale-invariant adiabatic perturbation spectra can only be produced for $w \approx -1$, and that the corresponding scaling solutions are attractors. The presence of a nontrivial metric on field space is a crucial ingredient in our results.Comment: 23 pages, oversight in perturbations calculation corrected, conclusions for expanding models modifie