Thermal leptogenesis in a model with mass varying neutrinos

In this paper we consider the possibility of neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling between the right-handed neutrinos and the dark energy scalar field, the Quintessence. In our model, the right-handed neutrino masses change as the Quintessence scalar evolves. We then examine in detail the parameter space of this model allowed by the observed baryon number asymmetry. Our results show that it is possible to lower the reheating temperature in this scenario in comparison with the case that the neutrino masses are unchanged, which helps solve the gravitino problem. Furthermore, a degenerate neutrino mass patten with $m_i$ larger than the upper limit given in the minimal leptogenesis scenario is permitted.Comment: 18 pages, 7 figures, version to appear in PR

Cold Plus Hot Dark Matter Cosmology in the Light of Solar and Atmospheric Neutrino Oscillations

We explore the implications of possible neutrino oscillations, as indicated by the solar and atmospheric neutrino experiments, for the cold plus hot dark matter scenario of large scale structure formation. We find that there are essentially three distinct schemes that can accommodate the oscillation data and which also allow for dark matter neutrinos. These include (i) three nearly degenerate (in mass) neutrinos, (ii) non-degenerate masses with $\nu_\tau$ in the eV range, and (iii) nearly degenerate $\nu_\mu-\nu_\tau$ pair (in the eV range), with the additional possibility that the electron neutrino is cosmologically significant. The last two schemes invoke a `sterile' neutrino which is light (< or ~ eV). We discuss the implications of these schemes for $\bar{\nu}_\mu - \bar{\nu}_e$ and $\nu_\mu - \nu_\tau$ oscillation, and find that scheme (ii) in particular, predicts them to be in the observable range. As far as structure formation is concerned, we compare the one neutrino flavor case with a variety of other possibilities, including two and three degenerate neutrino flavors. We show, both analytically and numerically, the effects of these neutrino mass scenarios on the amplitude of cosmological density fluctuations. With a Hubble constant of 50 km s$^{-1}$ Mpc$^{-1}$, a spectral index of unity, and $\Omega_{baryon} = 0.05$, the two and three flavor scenarios fit the observational data marginally better than the single flavor scheme. However, taking account of the uncertainties in these parameters, we show that it is premature to pick a clear winner.Comment: 1 LaTEX file plus 1 uuencoded Z-compressed tar file with 3 postscript figure

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries