Kavli Affiliate: Masahiro Kawasaki
| First 5 Authors: Masahiro Kawasaki, Kazuyoshi Miyazaki, Kai Murai, Hiromasa Nakatsuka, Eisuke Sonomoto
| Summary:
Ultra-light axion-like particle (ULAP) with mass $m sim 10^{-22}
~mathrm{eV}$ has recently been attracting attention as a possible solution to
the small-scale crisis. ULAP forms quasi-stable objects called
oscillons/I-balls, which can survive up to a redshift $z sim 10$ and affect
the structure formation on a scale $sim mathcal{O}(0.1)~mathrm{Mpc}$ by
amplifying the density fluctuations. We study the effect of oscillons on 21~cm
anisotropies caused by neutral hydrogen in minihalos. It is found that this
effect can be observed in a wide mass range by future observations such as
Square Kilometer Array~(SKA) if the fraction of ULAP to the total dark matter
density is $mathcal{O}(0.01 text{–} 0.1)$.
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