| 研究課題/領域番号 |
26400252
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| 研究機関 | 首都大学東京 |
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研究代表者 |
Sergei V.Ketov 首都大学東京, 理工学研究科, 准教授 (70347269)
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| 研究期間 (年度) |
2014-04-01 – 2019-03-31
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| キーワード | inflation / modified gravity / supergravity / dark energy / string theory |
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| 研究実績の概要 |
Our main research achievements during the second year of research were related to our theoretical advances in understanding two-field inflation in the phenomenogically viable scenarios of inflation, such as Starobinsky modified gravity and the so-called helical-phase models where inflaton is identified with a phase of a complex scalar field. Starobinsky inflation is a very simple model of R+R^2 gravity, which is consistent with observationhal data, whose inflaton is spin-0 part of space-time metric (so-called scalaron). Scalaron is expected to mix with other scalars (such as Higgs), so that it is important to study stability of Starobinsky inflation against scalaron couplings to other (scalar) particles. Given one extra scalar coupled to scalaron, it leads to two-field inflationary models that are much more complicated than single-field inflationary models. Any two-field inflationary model implies the existence of the so-called primordial iso-curvature perturbations that may be observed in a future. Our findings support robustness of Starobinsky two-field inflation for a certain range of its parameters characterized by low tensor-to-scalar ratio (less than 0.06) and small runnning of scalar index (less than 0.05). We found for the first time several new helical-phase inflationary models in N=1 supergravity by using a more economical (single-superfield) framework versus the previous literature.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Our progress in theoretical studies of two-field Starobinsky inflation was smooth and beyond our expectations. Reheating in those models is not much different from the original Starobinsky model, so that this part of research was successfully finished. As regards helical-phase inflation in supergravity,
we got viable inflationary dynamics consistent with observations, but still have a problem of restoration of supersymmetry after inflation. Despite of our considerable efforts and a lot of calculations, we could not finish our search for meta-stable de-Sitter vacua in type-IIA superstrings compactified on rigid Calabi-Yau spaces. Here our progress was less than expected. However, we now have a lot of new results that just have to be completed and published.
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| 今後の研究の推進方策 |
Based on our research experience in the previous two years, we identified the main problems for the future work. First, we would like to modify our single-superfield helical-phase inflationary models so that they allow supersymmetry breaking after inflation. Then our inflationary models would be compatible with low-energy supersymmetry breaking towards some version of Minimal Supersymmetric Standard Model. Second, we would like to study inflation in the context of GUT-theories coupled to supergravity, i.e. unify cosmological inflation and Grand Unification of fundamental forces in N=1 supergravity. And, third, complete our calculations of scalar potentials and their extrema in the gauged N=2 supergravity originating from type-IIA superstrings compactified on rigid Calabi-Yau spaces. And, of course, we want to publish our new results and present them at international conferences in Japan and overseas.
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