42 research outputs found
Cosmological contribution from population III stars in ultracompact minihalos
In this work, we investigate the effect of Population~III~(Pop.~III) stars in
ultracompact minihalos~(UCMHs) on the cosmic ionization history using the
Planck observation data. Although high-redshift astrophysics is not understood
yet, UCMHs could host the Pop.~III stars like the halos formed in the standard
structure formation scenario. Such Pop.~III stars would emit ionizing photons
during their main sequence and facilitate cosmic reionization in high
redshifts. To study their effects on the global ionization, we model the cosmic
reionization evolution based on the ``tanh"-type reionization model which is
expressed by with additional two parameters characterizing
the initial mass of UCMHs and the number density of UCMHs. We implement the
Monte Carlo Markov Chain analysis with the latest Planck observation data for
our reionization model. As the result, we found that if the UCMH initial mass
is larger than , the number density of UCMHs is
strictly limited. Then we obtained the constraint on the amplitude of the
primordial power spectrum through the constraint on the UCMH number density
like in the scales, , when we assume that the standard ``tanh"-type
reionization occurs by , so that we set .Comment: 12 pages, 7 figure
Translating nano-Hertz gravitational wave background into primordial perturbations taking account of the cosmological QCD phase transition
The evidence of the nano-Hertz stochastic gravitational wave (GW) background
is reported by multiple pulsar timing array collaborations. While a prominent
candidate of the origin is astrophysical from supermassive black hole binaries,
alternative models involving GWs induced by primordial curvature perturbations
can explain the inferred GW spectrum. Serendipitously, the nano-Hertz range
coincides with the Hubble scale during the cosmological quantum chromodynamics
(QCD) phase transition. The influence of the QCD phase transition can modify
the spectrum of induced GWs within the nano-Hertz frequency range,
necessitating careful analysis. We estimate GWs induced by power-law power
spectra of primordial curvature perturbations taking account of the QCD phase
transition. Then we translate the implication of the NANOGrav data into the
constraint on the power spectrum of the primordial curvature perturbation,
which suggests that one may miss the correct interpretation if neglecting the
QCD effect. We also derive fitting formulae for their amplitude and scale
dependence, helping to update the constraint in future experiments.Comment: 7 pages, 5 figure
Primordial black holes and gravitational waves induced by exponential-tailed perturbations
Primordial black holes (PBHs) whose masses are in
have been extensively studied as a
candidate of whole dark matter (DM). One of the probes to test such a PBH-DM
scenario is scalar-induced stochastic gravitational waves (GWs) accompanied
with the enhanced primordial fluctuations to form the PBHs with frequency
peaked in the mHz band being targeted by the LISA mission. In order to utilize
the stochastic GWs for checking the PBH-DM scenario, it needs to exactly relate
the PBH abundance and the amplitude of the GWs spectrum. Recently in Kitajima
et al., the impact of the non-Gaussianity of the enhanced primordial curvature
perturbations on the PBH abundance has been investigated based on the peak
theory, and they found that a specific non-Gaussian feature called the
exponential tail significantly increases the PBH abundance compared with the
Gaussian case. In this work, we investigate the spectrum of the induced
stochastic GWs associated with PBH DM in the exponential-tail case. In order to
take into account the non-Gaussianity properly, we employ the diagrammatic
approach for the calculation of the spectrum. We find that the amplitude of the
stochastic GW spectrum is slightly lower than the one for the Gaussian case,
but it can still be detectable with the LISA sensitivity. We also find that the
non-Gaussian contribution can appear on the high-frequency side through their
complicated momentum configurations. Although this feature emerges under the
LISA sensitivity, it might be possible to obtain information about the
non-Gaussianity from GW observation with a deeper sensitivity such as the
DECIGO mission.Comment: 33 pages, 19 figure
Constraint on the early-formed dark matter halos using the free-free emission in the Planck foreground analysis
We provide a new constraint on the small-scale density fluctuations,
evaluating the diffuse background free-free emission from dark matter halos in
the dark ages. If there exists a large amplitude of the matter density
fluctuations on small scales, the excess enhances the early formation of dark
matter halos. When the virial temperature is sufficiently high, the gas in a
halo is heated up and ionized by thermal collision. The heated ionized gas
emits photons by the free-free process. We would observe the sum of these
photons as the diffuse background free-free emission. Assuming the analytical
dark matter halo model including the gas density and temperature profile, we
calculate the intensity of the diffuse background free-free emission from
early-formed dark matter halos in the microwave frequency range. Comparing with
the recent foreground analysis on cosmic microwave background, we obtain the
constraint on the excess of the density fluctuations on small scales. Our
constraint corresponds to for with assuming the delta-function-type curvature power
spectrum. Therefore, our constraint is the most stringent constraint on the
perturbations below scales.Comment: 12 pages, 6 figure
Identification of Candidate Genes for Mutated Phenotype by Genome Analysis of Ion-beam-induced Rice Mutants
Ion beams are useful mutagens for plant and microbe breeding. They are thought to cause mutations by distinct mechanism from chemical mutagens or gamma rays. To understand the property of induced mutations at a genomic level, we have conducted exome analysis of genomic DNA of rice mutants isolated from a carbon ion-beam-mutagenized population. Five independent rice (cultivar Nipponbare) mutant lines (2 dwarfs and 3 early-heading-date mutants), of which phenotype was confirmed in the M3 generation, were isolated from seed-irradiated popullation (40 Gy of 320-MeV 12C6+ ions). The exome analysis identified a total of 56 mutations. The average number of mutations per line was 11.2 ± 3.3. Among 56 mutations, 6 (1.2 mutations per line on average) were classified as high-impact mutations that cause a frame shift or loss of exons and putativelly generate defective proteins. The identification of a small number of high-impact mutation suggests that it could be easy to detect a causal gene responsible for the mutant phenotype. Indeed, we have found candidate genes likely causing the mutant phenotype in the 4 out of the 5 mutants