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Band-power reconstruction of the primordial fluctuation spectrum by the maximum likelihood reconstruction method
Ryo Nagata, Jun'ichi Yokoyama
The primordial curvature fluctuation spectrum is reconstructed by the maximum likelihood reconstruction method using the five-year Wilkinson Microwave Anisotropy Probe data of the…
Gravitational wave background as a probe of the primordial black hole abundance
Ryo Saito, Jun'ichi Yokoyama
Formation of significant number of primordial black holes (PBHs) is realized if and only if primordial density fluctuations have a large amplitude, which means that tensor perturba…
Constraints on the time variation of the fine structure constant by the 5-year WMAP data
Masahiro Nakashima, Ryo Nagata, Jun'ichi Yokoyama
The constraints on the time variation of the fine structure constant at recombination epoch relative to its present value, $Δα/α\equiv (α_{\mathrm{rec}} - α_{\mathrm{now}})/α_{\mat…
Reconstruction of the primordial fluctuation spectrum from the five-year WMAP data by the cosmic inversion method with band-power decorrelation analysis
Ryo Nagata, Jun'ichi Yokoyama
The primordial curvature fluctuation spectrum is reconstructed by the cosmic inversion method using the five-year WMAP data of the cosmic microwave background temperature anisotrop…
Single-field inflation, anomalous enhancement of superhorizon fluctuations, and non-Gaussianity in primordial black hole formation
Ryo Saito, Jun'ichi Yokoyama, Ryo Nagata
We show a text-book potential for single-field inflation, namely, the Coleman-Weinberg model can induce double inflation and formation of primordial black holes (PBHs), because flu…
Probing reheating temperature of the universe with gravitational wave background
Kazunori Nakayama, Shun Saito, Yudai Suwa +1
Thermal history of the universe after big-bang nucleosynthesis (BBN) is well understood both theoretically and observationally, and recent cosmological observations also begin to r…
Constraints on scalar-tensor models of dark energy from observational and local gravity tests
Shinji Tsujikawa, Kotub Uddin, Shuntaro Mizuno +2
We construct a family of viable scalar-tensor models of dark energy (DE) which possess a phase of late-time acceleration preceded by a standard matter era, while at the same time s…
Generation of Large-Scale Magnetic Fields in Single-Field Inflation
Jerome Martin, Jun'ichi Yokoyama
We consider the generation of large-scale magnetic fields in slow-roll inflation. The inflaton field is described in a supergravity framework where the conformal invariance of the…
Formation of intermediate-mass black holes as primordial black holes in the inflationary cosmology with running spectral index
Toshihiro Kawaguchi, Masahiro Kawasaki, Tsutomu Takayama +2
Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology if the primordial perturbation spectrum has a large and n…
Scale dependence of the primordial spectrum from combining the three-year WMAP, Galaxy Clustering, Supernovae, and Lyman-alpha forests
Bo Feng, Jun-Qing Xia, Jun'ichi Yokoyama
We probe the scale dependence of the primordial spectrum in the light of the three-year WMAP (WMAP3) alone and WMAP3 in combination with the other cosmological observations such as…
Weighing neutrinos in the presence of a running primordial spectral index
Bo Feng, Jun-Qing Xia, Jun'ichi Yokoyama +2
The three-year WMAP(WMAP3), combined with other cosmological observations from galaxy clustering and Type Ia Supernova (SNIa), prefers a non-vanishing running of the primordial spe…
Constraining Cosmological Parameters by the Cosmic Inversion Method
Noriyuki Kogo, Misao Sasaki, Jun'ichi Yokoyama
We investigate the question of how tightly we can constrain the cosmological parameters by using the ``cosmic inversion'' method in which we directly reconstruct the power spectrum…
Reconstructing the Primordial Spectrum with CMB Temperature and Polarization
Noriyuki Kogo, Misao Sasaki, Jun'ichi Yokoyama
We develop a new method to reconstruct the power spectrum of primordial curvature perturbations, , by using both the temperature and polarization spectra of the cosmic microw…
Reconstructing the Primordial Spectrum from WMAP Data by the Cosmic Inversion Method
Noriyuki Kogo, Makoto Matsumiya, Misao Sasaki +1
We reconstruct the primordial spectrum of the curvature perturbation, , from the observational data of the Wilkinson Microwave Anisotropy Probe (WMAP) by the cosmic inversion…
Probing the star formation epoch with Wilkinson Microwave Anisotropy Probe (WMAP) data and high-redshift QSOs
Jun'ichi Yokoyama
Using the values of the cosmological parameters obtained from Wilkinson Microwave Anisotropy Probe (WMAP) and the cosmological chemical clock observed by high-redshift quasars, it…
Cosmic Inversion II --An iterative method for reproducing the primordial spectrum from the CMB data--
Makoto Matsumiya, Misao Sasaki, Jun'ichi Yokoyama
Pursuing the original idea proposed in our previous paper (Paper I), we improve the method to determine the shape of the initial curvature perturbation spectrum from the CMB…
Cosmic Inversion: Reconstructing primordial spectrum from CMB anisotropy
Makoto Matsumiya, Misao Sasaki, Jun'ichi Yokoyama
We investigate the possibility of reconstructing the initial spectrum of density fluctuations from the cosmic microwave background (CMB) anisotropy. As a first step toward this pro…
Cosmological perturbations from multi-field inflation in generalized Einstein theories
Alexei A. Starobinsky, Shinji Tsujikawa, Jun'ichi Yokoyama
We study cosmological perturbations generated from quantum fluctuations in multi-field inflationary scenarios in generalized Einstein theories, taking both adiabatic and isocurvatu…
Inflation and the dwarf galaxy problem
Jun'ichi Yokoyama
Cosmological N-body simulations with scale-invariant initial perturbations show too many virialized objects of dwarf-galaxy masses in a typical galactic halo in contradiction to ob…
What happens when the inflaton stops during inflation
Osamu Seto, Jun'ichi Yokoyama, Hideo Kodama
The spectrum of adiabatic density perturbation generated during inflation is studied in the case the time derivative of an inflation-driving scalar field (inflaton) vanishes at som…
Primordial Black Holes and Primordial Nucleosynthesis I: Effects of Hadron Injection from Low Mass Holes
K. Kohri, Jun'ichi Yokoyama
We investigate the influence of hadron injection from evaporating primordial black holes (PBHs) in the early stage of the primordial nucleosynthesis era (t = 10^{-3} - 10^4 sec). T…
Sample Variance of the Higher-Order Cumulants of Cosmic Density and Velocity Fields
Naoki Seto, Jun'ichi Yokoyama
If primordial fluctuation is Gaussian distributed, higher-order cumulants of the cosmic fields reflect nonlinear mode coupling and provide useful information of gravitational insta…
Sample variance of the cosmic velocity field
Naoki Seto, Jun'ichi Yokoyama
Since the cosmic peculiar velocity field depends on small wave-number modes strongly, we cannot probe its universal properties unless we observe a sufficiently large region. We cal…
Chaotic new inflation and formation of primordial black holes
Jun'ichi Yokoyama
It is shown that in a number of scalar potentials with an unstable local maximum at the origin chaotic inflation is followed by new inflation if model parameters are appropriately…