Time Dependent Quark Masses and Big Bang Nucleosynthesis Revisited

We reinvestigate the constraints from primordial nucleosynthesis on a possible time-dependent quark mass. The limits on such quark-mass variations are particularly sensitive to the adopted observational abundance constraints. Hence, in the present study we have considered updated light-element abundances and uncertainties deduced from observations. We also consider new nuclear reaction rates and an independent analysis of the influence of such quark-mass variations on the resonance properties of the important 3He(d,p)4He reaction. We find that the updated abundance and resonance constraints imply a narrower range on the possible quark-mass variations in the early universe. We also find that, contrary to previous investigations, the optimum concordance region reduces to a (95% C.L.) value of -0.005 < delta m_q/m_q < 0.007 consistent with no variation in the averaged quark mass.Comment: 9 pages, 2 figures, analytic formulae of D and 4He abundances as well as standard BBN prediction added, discussion on the 6Li production added, minor errors fixed, accepted for publication in PR

Axion Production from Landau Quantization in the Strong Magnetic Field of Magnetars

We utilize an exact quantum calculation to explore axion emission from electrons and protons in the presence of the strong magnetic field of magnetars. The axion is emitted via transitions between the Landau levels generated by the strong magnetic field. The luminosity of axions emitted by protons is shown to be much larger than that of electrons and becomes stronger with increasing matter density. Cooling by axion emission is shown to be much larger than neutrino cooling by the Urca processes. Consequently, axion emission in the crust may significantly contribute to the cooling of magnetars. In the high-density core, however, it may cause heating of the magnetar.Comment: 14 pages, 3 figure

Neutron stars in a perturbative f(R)f(R) gravity model with strong magnetic fields

We investigate the effect of a strong magnetic field on the structure of neutron stars in a model with perturbative $f(R)$ gravity. The effect of an interior strong magnetic field of about $10^{17 \sim 18}$ G on the equation of state is derived in the context of a quantum hadrodynamics (QHD) model. We solve the modified spherically symmetric hydrostatic equilibrium equations derived for a gravity model with $f(R)=R+\alpha R^2$. Effects of both the finite magnetic field and the modified gravity are detailed for various values of the magnetic field and the perturbation parameter $\alpha$ along with a discussion of their physical implications. We show that there exists a parameter space of the modified gravity and the magnetic field strength, in which even a soft equation of state can accommodate a large ($> 2$ M$_\odot$) maximum neutron star mass through the modified mass-radius relation

Neutrino induced reactions related to the ν\nu-process nucleosynthesis of 92{}^{92}Nb and 98{}^{98}Tc

It has recently been proposed that ${}^{92}_{41}$Nb and ${}^{98}_{43}$Tc may have been formed in the $\nu$-process. We investigate the neutrino induced reactions related to the $\nu$-process origin of the two odd-odd nuclei. The main neutrino reactions for ${}^{92}_{41}$Nb are the charged-current (CC) $^{92}$Zr($\nu_e,e^{-}$)$^{92}$Nb and the neutral-current (NC) $^{93}$Nb(${\nu} ({\bar \nu}), {\nu}^{'} ({\bar \nu})^{'}$ n)$^{92}$Nb reactions. The main reactions for ${}^{98}_{43}$Tc, are the CC reaction $^{98}$Mo($\nu_e,e^-$)$^{98}$Tc and the NC reaction $^{99}$Ru(${\nu} ({\bar \nu}), {\nu}^{'} ({\bar \nu})^{'}$ p)$^{98}$Tc. Our calculations are carried out using the quasi-particle random phase approximation. Numerical results are presented for the energy and temperature dependent cross sections. Since charge exchange reactions by neutrons may also lead to the formation of ${}^{92}_{41}$Nb and ${}^{98}_{43}$Tc, we discuss the feasibility of the $^{92}$Mo(n,p)$^{92}$Nb and $^{98}$Ru(n,p)$^{98}$Tc reactions to produce these nuclei.Comment: 21 pages, 8 figure

Neutrino self-interaction and MSW effects on the supernova neutrino-process

We calculate the abundances of $^{7}$Li, $^{11}$B, $^{92}$Nb, $^{98}$Tc, $^{138}$La, and $^{180}$Ta produced by neutrino $(\nu)$ induced reactions in a core-collapse supernova explosion. We consider the modification by $\nu$ self-interaction ($\nu$-SI) near the neutrinosphere and the Mikheyev-Smirnov-Wolfenstein effect in outer layers for time-dependent neutrino energy spectra. Abundances of $^{7}$Li and heavy isotopes $^{92}$Nb, $^{98}$Tc and $^{138}$La are reduced by a factor of 1.5-2.0 by the $\nu$-SI. In contrast, $^{11}$B is relatively insensitive to the $\nu$-SI. We find that the abundance ratio of heavy to light nucleus, $^{138}$La/$^{11}$B, is sensitive to the neutrino mass hierarchy, and the normal mass hierarchy is more likely to be consistent with the solar abundances