18 research outputs found
Precise Calculation of the Relic Density of Kaluza-Klein Dark Matter in Universal Extra Dimensions
We revisit the calculation of the relic density of the lightest Kaluza-Klein
particle (LKP) in the model of Universal Extra Dimensions. The Kaluza-Klein
(KK) particle spectrum at level one is rather degenerate, and various
coannihilation processes may be relevant. We extend the calculation of
hep-ph/0206071 to include coannihilation processes with all level one KK
particles. In our computation we consider a most general KK particle spectrum,
without any simplifying assumptions. In particular, we do not assume a
completely degenerate KK spectrum and instead retain the dependence on each
individual KK mass. As an application of our results, we calculate the
Kaluza-Klein relic density in the Minimal UED model, turning on coannihilations
with all level one KK particles. We then go beyond the minimal model and
discuss the size of the coannihilation effects separately for each class of
level 1 KK particles. Our results provide the basis for consistent relic
density computations in arbitrarily general models with Universal Extra
Dimenions.Comment: 44 pages, 19 figures, typeset in JHEP styl
Multiband model for tunneling in MgB2 junctions
A theoretical model for quasiparticle and Josephson tunneling in multiband
superconductors is developed and applied to MgB2-based junctions. The gap
functions in different bands in MgB2 are obtained from an extended Eliashberg
formalism, using the results of band structure calculations. The temperature
and angle dependencies of MgB2 tunneling spectra and the Josephson critical
current are calculated. The conditions for observing one or two gaps are given.
We argue that the model may help to settle the current debate concerning
two-band superconductivity in MgB2.Comment: minor corrections, published in Phys. Rev. B 65, 180517(R) (2002