504 research outputs found
Gravitino/Axino as Decaying Dark Matter and Cosmological Tensions
In supersymmetric axion models, if the gravitino or axino is the lightest
SUSY particle (LSP), the other is often the next-to-LSP (NLSP). We investigate
the cosmology of such a scenario and point out that the lifetime of the NLSP
naturally becomes comparable to the present age of the universe in a viable
parameter region. This is a well-motivated example of the so-called decaying
dark matter model, which is recently considered as an extension of the
CDM model to relax some cosmological tensions.Comment: 16 pages, 2 figures, Journal versio
AMS-02 Antiprotons from Annihilating or Decaying Dark Matter
Recently the AMS-02 experiment reported an excess of cosmic ray antiprotons
over the expected astrophysical background. We interpret the excess as a signal
from annihilating or decaying dark matter and find that the observed spectrum
is well fitted by adding contributions from the annihilation or decay of dark
matter with mass of O(TeV) or larger. Interestingly, Wino dark matter with mass
of around 3 TeV, whose thermal relic abundance is consistent with present dark
matter abundance, can explain the antiproton excess. We also discuss the
implications for the decaying gravitino dark matter with R-parity violation.Comment: 12 pages, 3 figure
B-mode polarization induced by gravitational waves from kinks on infinite cosmic strings
We investigate the effect of the stochastic gravitational wave (GW)
background produced by kinks on infinite cosmic strings, whose spectrum was
derived in our previous work, on the B-mode power spectrum of the cosmic
microwave background (CMB) anisotropy. We find that the B-mode polarization due
to kinks is comparable to that induced by the motion of the string network and
hence the contribution of GWs from kinks is important for estimating the B-mode
power spectrum originating from cosmic strings. If the tension of cosmic
strings \mu is large enough i.e., G\mu >~ 10^{-8}, B-mode polarization induced
by cosmic strings can be detected by future CMB experiments.Comment: 13 pages, 1 figur
Supersymmetric Flaxion
Recently, a new minimal extension of the Standard Model has been proposed,
where a spontaneously broken, flavor-dependent global U(1) symmetry is
introduced. It not only explains the hierarchical flavor structure in the quark
and lepton sector, but also solves the strong CP problem by identifying the
Nambu-Goldstone boson as the QCD axion, which we call flaxion. In this work, we
consider supersymmetric extensions of the flaxion scenario. We study the CP and
flavor violations due to supersymmetric particles, the effects of R-parity
violations, the cosmological gravitino and axino problems, and the cosmological
evolution of the scalar partner of the flaxion, sflaxion. We also propose an
attractor-like inflationary model where the flaxion multiplet contains the
inflaton field, and show that a consistent cosmological scenario can be
obtained, including inflation, leptogenesis, and dark matter.Comment: 30 pages, 2 figures; v2: version published in JHE
Gravitational waves from kinks on infinite cosmic strings
Gravitational waves emitted by kinks on infinite strings are investigated
using detailed estimations of the kink distribution on infinite strings. We
find that gravitational waves from kinks can be detected by future pulsar
timing experiments such as SKA for an appropriate value of the the string
tension, if the typical size of string loops is much smaller than the horizon
at their formation. Moreover, the gravitational wave spectrum depends on the
thermal history of the Universe and hence it can be used as a probe into the
early evolution of the Universe.Comment: 29 pages, 4figure
- …