| Project/Area Number |
15540265
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Nagoya University |
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Principal Investigator |
NAMBU Yasusada Nagoya University, Graduate School of Science, Assoc.Prof., 大学院・理学研究科, 助教授 (40212112)
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| Project Period (FY) |
2003 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 2005: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2004: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2003: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | inflation / inhomogeneous universe / back reaction / 長波長ゆらぎ / 繰り込み群 / 宇宙論的摂動 / gradient expansion / 再加熱 |
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| Research Abstract |
As a preparation to incorporate the quantum effect into spacetime structure, we investigated the gradient expansion approach which is a method to realize a model of inhomogeneous universes. This approach constructs the perturbative solution of the Einstein equation using expansion about the order of the spatial derivative. We succeeded to re-construct the lowest order solution of the gradient expansion by applying the renormalization group method to the cosmological perturbation about a Friedmann-Robertson-Walker universe. As a direct application of this result, we found that only non-adiabatic mode of fluctuation can back react a Friedmann-Robertson-Walker universe and modify its expansion law.
Then using the lowest order gradient expansion, we investigated the dynamics of preheating stage after inflation numerically. In this stage, the metric fluctuation is amplified by the parametric resonance caused by the coherent oscillation of the inflaton field. For a model with two scalar fields, we obtained the evolution of the power spectrum of fluctuations. As the considering model is essentially chaotic system, the spatial correlation of the fields is lost as the system evolves and the spatial pattern evolves to that of the White noise. We found that the evolution of the power spectrum of metric perturbation depends on the initial power index of fluctuation and non-linear effect strongly affects the small scale structure while the large scale structure of which wave length is larger that the horizon scale is not affected by the back reaction effect caused by the parametric resonance.
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