Nonequilibrium Corrections to the Spectra of Massless Neutrinos in the Early Universe

Distortion of the equilibrium spectra of cosmic neutrinos due to interaction with hotter electrons and positrons in the primeval cosmic plasma is considered. The set of integro-differential kinetic equations for neutrinos is accurately numerically solved. The relative corrections to neutrino energy densities are approximately 0.9% for $\nu_e$ and 0.4% for $\nu_\mu$ and $\nu_\tau$. This effect results in $1.4 \cdot 10^{-4}$ increase in the primordial $^4 He$ abundance.Comment: 28 pages including 6 figures. Latex

Cosmological Implications of Neutrinos

The lectures describe several cosmological effects produced by neutrinos. Upper and lower cosmological limits on neutrino mass are derived. The role that neutrinos may play in formation of large scale structure of the universe is described and neutrino mass limits are presented. Effects of neutrinos on cosmological background radiation and on big bang nucleosynthesis are discussed. Limits on the number of neutrino flavors and mass/mixing are given.Comment: 41 page, 7 figures; lectures presented at ITEP Winter School, February, 2002; to be published in the Proceeding

Exercise mediates the association between positive affect and 5-year mortality in patients with ischemic heart disease

Background Positive affect has been associated with better prognosis in patients with ischemic heart disease, but the underlying mechanisms remain unclear. We examined whether positive affect predicted time to first cardiac-related hospitalization and all-cause mortality, and whether exercise mediated this relationship in patients with established ischemic heart disease. Methods and Results The sample comprised 607 patients with ischemic heart disease from Holbæk Hospital, Denmark. In 2005, patients completed the Global Mood Scale (GMS) to assess positive affect and a purpose-designed question on exercise. Data on mortality and hospitalization were collected from Danish national registers for the period 2006–2010. Adjusted Cox and logistic regression were used to analyze the mediation model. Because no significant association between positive affect and cardiac-related hospitalization was found, we constructed no mediation model for hospitalization. Importantly, patients with high positive affect had a significantly reduced risk of all-cause mortality (hazard ratio, 0.58; 95% confidence interval, 0.37–0.92; unadjusted analysis) and were more likely to exercise (odds ratio, 1.99; 95% confidence interval, 1.44–2.76; unadjusted analysis; odds ratio, 1.48; 95% confidence interval, 1.03–2.13; adjusted analysis). When controlling for positive affect and other relevant variables, patients engaged in exercise were less likely to die during follow-up (hazard ratio, 0.50; 95% confidence interval, 0.31–0.80; P=0.004). Importantly, exercise acted as a mediator in the relationship between positive affect and mortality. Conclusions Patients with higher levels of positive affect were more likely to exercise and had a lower risk of dying during 5-year follow-up, with exercise mediating the relationship between positive affect and mortality. Interventions aimed at increasing both positive affect and exercise may have better results with respect to patients’ prognosis and psychological well-being than interventions focusing on 1 of these factors alone

Neutrino oscillations in the early universe: How large lepton asymmetry can be generated?

The lepton asymmetry that could be generated in the early universe through oscillations of active to sterile neutrinos is calculated (almost) analytically for small mixing angles, sin 2\theta < 10^{-2}. It is shown that for a mass squared difference, \delta m^2=-1 eV^2 it may rise at most by 6 orders of magnitude from the initial ``normal'' value of 10^{-10}, since the back-reaction from the refraction index terminates this rise while the asymmetry is still small. Only for very large mass differences, \delta m^2 about 10^9 eV^2, the lepton asymmetry could reach a significant magnitude exceeding 0.1.Comment: 25 pages, LaTeX (5 graphs

Heavy sterile neutrinos: Bounds from big-bang nucleosynthesis and SN 1987A

Cosmological and astrophysical effects of heavy (10 - 200 MeV) sterile Dirac neutrinos, mixed with the active ones, are considered. The bounds on mass and mixing angle from both supernovae and big-bang nucleosynthesis are presented.Comment: 19 pages, 5 figures, 1 table. Some references adde

Cosmological and astrophysical bounds on a heavy sterile neutrino and the KARMEN anomaly

Constraints on the lifetime of the heavy sterile neutrino, that was proposed as a possible interpretation of the KARMEN anomaly, are derived from primordial nucleosynthesis and SN 1987A. Together with the recent experimental bounds on the nu_s lifetime, SN 1987A completely excludes this interpretation. Nucleosynthesis arguments permit a narrow window for the lifetime in the interval 0.1-0.2 sec. If nu_s possesses an anomalous interaction with nucleons, the SN bounds may not apply, while the nucleosynthesis ones would remain valid.Comment: Figure 7 changed. (30 pages, 7 ps-figures, 2 tables. Subm to NPB