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- Naoshi Sugiyama
- 1995

Through analytic techniques verified by numerical calculations, we establish general relations between the matter and cosmic microwave background (CMB) power spectra and their dependence on cosmological parameters on small scales. Fluctuations in the CMB, baryons, cold dark matter (CDM), and neutrinos receive a boost at horizon crossing. Baryon drag on the… (More)

- Naoshi Sugiyama
- 1995

Working toward a model independent understanding of cosmic microwave background (CMB) anisotropies and their significance, we undertake a comprehensive and self-contained study of scalar perturbation theory. Initial conditions, evolution, thermal history, matter content, background dynamics, and geometry all play a role in determining the anisotropy. By… (More)

We use cosmological simulations to study the origin of primordial star-forming clouds in a ΛCDM universe, by following the formation of dark matter halos and the cooling of gas within them. To model the physics of chemically pristine gas, we employ a non-equilibrium treatment of the chemistry of 9 + 2 , H −) and include cooling by molecular hydrogen. By… (More)

- Seiji Kawamura, Masaki Ando, +131 authors Taizoh Yoshino
- 2008

We classify the future of the universe for general cosmological models including matter and dark energy. If the equation of state of dark energy is less then −1, the age of the universe becomes finite. We compute the rest of the age of the universe for such universe models. The behaviour of the future growth of matter density perturbation is also studied.… (More)

We consider Bayesian constraints on standard isocurvature baryon models from the slope and normalization of the anisotropy power spectrum detected by the COBE DMR experiment in their 2 year maps. In conjunction with either the amplitude of matter fluctuations 8 or its slope, all open models are ruled out at greater than 95% confidence, whereas… (More)

- Kiyotomo Ichiki, Keitaro Takahashi, Hiroshi Ohno, Hidekazu Hanayama, Naoshi Sugiyama
- Science
- 2006

The origin of the substantial magnetic fields that are found in galaxies and on even larger scales, such as in clusters of galaxies, is yet unclear. If the second-order couplings between photons and electrons are considered, then cosmological density fluctuations, which explain the large-scale structure of the universe, can also produce magnetic fields on… (More)

- K. Kohri, Naoshi Sugiyama
- 2008

The late-time entropy production by the massive particle decay induces the various cosmological effects in the early epoch and modify the standard scenario. We investigate the thermalization process of the neutrinos after the entropy production by solving the Boltzmann equations numerically. We find that if the large entropy are produced at t ∼ 1 sec, the… (More)

- Wayne Hu, Naoshi Sugiyama
- 2008

We introduce a simple yet powerful analytic method which obtains the structure of cosmic microwave background anisotropies to better than 5-10% in temperature uctuations on all scales. It is applicable to any model in which the potential uctuations at recombination are both linear and known. Moreover, it recovers and explains the presence of the \Doppler… (More)

As the data on cosmic microwave background anisotropies improve and potential cosmological applications are realized, it will be increasingly important for theoretical calculations to be as accurate as possible. All modern calculations for innationary-inspired uctuations involve the numerical solution of coupled Boltz-mann equations. There are many… (More)