著者

Umemura Masayuki Susa Hajime Hasegawa Kenji Suwa Tamon Semelin Benoit

出版者

Oxford University Press

雑誌

Progress of theoretical and experimental physics (ISSN:20503911)

巻号頁・発行日

vol.1, pp.01A306, 2012-10

被引用文献数

8

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Firstly, the formation of first objects driven by dark matter is revisited by high-resolution hydrodynamic simulations. It is revealed that dark matter halos of ∼104 M⊙ can produce first luminous objects with the aid of dark matter cusps. Therefore, the mass of first objects is smaller by roughly two orders of magnitude than in the previous prediction. This implies that the number of Population III stars formed in the early universe could be significantly larger than hitherto thought. Secondly, feedback by photo-ionization and photo-dissociation photons in the first objects is explored with radiation hydrodynamic simulations, and it is demonstrated that multiple stars can form in a 105 M⊙ halo. Thirdly, the fragmentation of an accretion disk around a primordial protostar is explored with photo-dissociation feedback. As a result, it is found that photo-dissociation can reduce the mass accretion rate onto protostars. Also, protostars as small as 0.8 M⊙ may be ejected and evolve while keeping their mass, which might be detected as the “real first stars” in the Galactic halo. Finally, state-of-the-art radiation hydrodynamic simulations are performed to investigate the internal ionization of first galaxies and the escape of ionizing photons. We find that UV feedback by forming massive stars enhances the escape fraction even in a halo as massive as > 6 × 109 M⊙, while it reduces the star formation rate significantly. This may have a momentous impact on cosmic reionization.

著者

Ozawa A. Uesaka T. Wakasugi M.

出版者

Oxford University Press

雑誌

Progress of theoretical and experimental physics (ISSN:20503911)

巻号頁・発行日

vol.2012, no.1, pp.03C009, 2012-12

被引用文献数

55

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We describe the rare-RI (radioactive isotope) ring at the RI Beam Factory (RIBF). The main purpose of the rare-RI ring is to measure the mass of very neutron-rich nuclei, the production rates of which are very small (hence ‘rare RI’) and the lifetimes of which are predicted to be very short. In the rare-RI ring, there are two innovative pieces of apparatus: individual injection, which can realize the injection of 200 A MeV rare RIs one by one, and a cyclotron-like storage ring, which allows high isochronous magnetic fields with large angular and momentum acceptances. With these devices, we will achieve a 10−6 mass resolution, and will be able to access rare RIs, the production rate of which is down to 1 event/day/pnA. Construction of the rare-RI ring started in fiscal year 2012.

著者

Ejiri Shinji Kanaya Kazuyuki Umeda Takashi

出版者

Oxford University Press

雑誌

Progress of theoretical and experimental physics (ISSN:20503911)

巻号頁・発行日

vol.2012, no.1, pp.01A104, 2012-09

被引用文献数

5 5

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The WHOT-QCD Collaboration is pushing forward a series of lattice studies of quantum chromodynamics (QCD) at finite temperatures and densities using improved Wilson quarks. Because Wilson-type quarks require more computational resources than the more widely used staggered-type quarks, various theoretical and computational techniques have to be developed and applied. In this paper, we introduce a fixed-scale approach armed with a T-integration method, a Gaussian method based on cumulant expansion, and a histogram method combined with the reweighting technique. Using these methods, we have carried out the first study of finite-density QCD with Wilson-type quarks and the first calculation of the equation of state with 2+1 flavors of Wilson-type quarks. We present the results of these studies and discuss perspectives towards clarification of the properties of 2+1 flavor QCD at the physical point at finite temperatures and densities.