Cosmological solutions to the Lithium problem:
Big-bang nucleosynthesis with photon cooling,
X-particle decay and a primordial magnetic field
Phys. Rev. D 90, 023001
Constraint on the X particle parameters and the PMF strength and energy density.
The 7Li abundance calculated in BBN with the baryon-to-photon ratio
fixed from fits to the CMB power spectrum is inconsistent with the observed
lithium abundances on the surface of metal-poor halo stars. Previous cosmological
solutions proposed to resolve this 7Li problem include photon cooling
(possibly via the Bose-Einstein condensation of a scalar particle) or the decay of
a long-lived X-particle (possibly the next-to-lightest supersymmetric particle).
In this paper, We reanalyze these solutions, both separately and in concert. We also
introduce the possibility of a primordial magnetic field (PMF) into these models.
We constrain the X-particles and the PMF parameters by the observed light element
abundances using a likelihood analysis to show that the inclusion of all three
possibilities leads to an optimum solution to the lithium problem. We deduce
allowed ranges for the X-particle parameters and energy density in the PMF that
can solve 7Li problem.
Please visit here
(details in Japanese) for more detail.
Accepted for publication as
a Regular Article in Physical Review D.
CMB with the background primordial magnetic field
The contribution of the PMF and the standard cosmological parameters on the CMB.
We investigate the effects of the background PMF on the CMB. The sound speed of
the tightly coupled photon-baryon fluid is increased by the background PMF.
The increased sound speed causes the odd peaks of the CMB temperature fluctuations
to be suppressed, and the CMB peak positions to be shifted to larger scale.
The background PMF causes the stronger decaying potential, and increases
the amplitude of the CMB. These two effects of the background PMF on a smaller
scale cancel out, and the overall effects of the background PMF are suppression
of the CMB around the first peak and shifting peaks to large scale.
We also discuss obtaining information about the PMF generation mechanisms,
and examine the non-linear evolution of the PMF by the constraint on the maximum
scale for the PMF distributions. Finally, we discuss degeneracies between
the PMF parameters and the standard cosmological parameters.
Please visit here (details in Japanese) for more detail.
Accepted for publication as a Regular Article in Physical Review D.