The essence and the importance of aerobic fitness

Today, students are victims of stress associated with learning and unhealthy lifestyles. In addition, in our time Internet technology and other types of hanging out dominate, which do not involve mobility. Therefore, the importance of physical activity for students cannot be ignored. Now aerobic-fitness is widespread among young people. But not everyone can determine exactly what is hidden by the term

Impact of massive tau-neutrinos on primordial nucleosynthesis. Exact calculations

The influence of a massive Majorana tau-neutrino on primordial nucleosynthesis is rigorously calculated. The system of three integro-differential kinetic equations is solved numerically for the tau-neutrino mass in the interval from 0 to 20 MeV. It is found that the usual assumption of kinetic equilibrium is strongly violated and non-equilibrium corrections considerably amplify the effect. Even a very weak restriction from nucleosynthesis, allowing for one extra massless neutrino species, permits to conclude that m_\nu_\tau < 1 MeV. For a stricter bound, e.g. for dN < 0.3, the limit is m_\nu_\tau < 0.35 MeV.Comment: 30 pages, 9 figures, 2 tables, revised figures, minor change

Study of Thermodynamic Quantities in Generalized Gravity Theories

In this work, we have studied the thermodynamic quantities like temperature of the universe, heat capacity and squared speed of sound in generalized gravity theories like Brans-Dicke, Ho$\check{\text r}$ava-Lifshitz and $f(R)$ gravities. We have considered the universe filled with dark matter and dark energy. Also we have considered the equation of state parameters for open, closed and flat models. We have observed that in all cases the equation of state behaves like quintessence. The temperature and heat capacity of the universe are found to decrease with the expansion of the universe in all cases. In Brans-Dicke and $f(R)$ gravity theories the squared speed of sound is found to exhibit increasing behavior for open, closed and flat models and in Ho$\check{\text r}$ava-Lifshitz gravity theory it is found to exhibit decreasing behavior for open and closed models with the evolution of the universe. However, for flat universe, the squared speed of sound remains constant in Ho$\check{\text r}$ava-Lifshitz gravity.Comment: 15 pages, 12 figure