Browsing Research and Publications - Department of Physics & Astronomy by Subject "Particle-theory and field-theory models of the early Universe (including cosmic pancakes, cosmic strings, chaotic phenomena, inflationary universe, etc.)"

Browsing Research and Publications - Department of Physics & Astronomy by Subject "Particle-theory and field-theory models of the early Universe (including cosmic pancakes, cosmic strings, chaotic phenomena, inflationary universe, etc.)"

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  • Okada, Nobuchika (2005-01-19)
    We investigate the thermal production of gravitinos in the context of the brane world cosmology. Since the expansion law is modified from the one in the standard cosmology, the Boltzmann equation for the gravitino production ...
  • Okada, Nobuchika (2009-05-27)
    In Gauss-Bonnet braneworld cosmology, the Friedmann equation of our four-dimensional Universe on 3-brane is modified in a high energy regime (Gauss-Bonnet regime), while the standard expansion law is reproduced in low ...
  • Okada, Nobuchika (2011-12-22)
    The standard model Higgs boson with large nonminimal coupling to the gravitational curvature can drive cosmological inflation. We study this type of inflationary scenario in the context of supersymmetric grand unification ...
  • Okada, Nobuchika (2013-03-12)
    We investigate a scenario of cosmological inflation realized along a flat direction of the minimal seesaw model embedded in supergravity with a noncanonical R-parity violating Kähler potential. It is shown that with ...
  • Okada, Nobuchika (2013-12-03)
    We study the collider signature of pseudo-Dirac heavy neutrinos in the inverse seesaw scenario, where the heavy neutrinos with mass at the electroweak scale can have sizable mixings with the Standard Model neutrinos, while ...
  • Okada, Nobuchika (2012-07-25)
    The Standard Model Higgs boson with the nonminimal coupling to the gravitational curvature can drive cosmological inflation. We study this type of inflationary scenario in the context of supergravity. We first point out ...
  • Okada, Nobuchika (2012-09-21)
    We propose a scenario with a fermion dark matter, where the dark matter particle used to be the Dirac fermion, but it takes the form of the Majorana fermion at a late time. The relic number density of the dark matter is ...
  • Okada, Nobuchika (2009-10-09)
    We propose a simple extension of the minimal universal extra dimension model by introducing a small curvature. The model is formulated as a small anti–de Sitter curvature limit of the five-dimensional standard model (SM) ...
  • Okada, Nobuchika (2011-05-19)
    We investigate the resonant leptogenesis scenario in the minimal B−L extended standard model with the B−L symmetry breaking at the TeV scale. Through detailed analysis of the Boltzmann equations, we show how much the ...
  • Okada, Nobuchika (2012-09-07)
    We propose a cosmological inflationary scenario based on the supergravity-embedded Standard Model supplemented by the right-handed neutrinos. We show that with an appropriate Kähler potential the L−Hᵤ direction gives rise ...
  • Okada, Nobuchika (2010-08-04)
    We reconsider nonminimal λϕ⁴ chaotic inflation which includes the gravitational coupling term ξRϕ², where ϕ denotes a gauge singlet inflaton field and R is the Ricci scalar. For ξ ≫ 1, we require, following recent discussions, ...
  • Okada, Nobuchika (2006-03-10)
    The thermal leptogenesis in brane world cosmology is studied. In brane world cosmology, the expansion law is modified from the four-dimensional standard cosmological one at high temperature regime in the early universe. ...
  • Okada, Nobuchika (2011-08-31)
    We present a successful inflation model based on λϕ⁴ potential in which a standard model (SM) singlet inflaton ϕ, with mass of around a TeV or less, also plays the role of a weakly interacting scalar dark matter particle ...

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