3 research outputs found
Higher Curvature Corrections to Primordial Fluctuations in Slow-roll Inflation
We study higher curvature corrections to the scalar spectral index, the
tensor spectral index, the tensor-to-scalar ratio, and the polarization of
gravitational waves. We find that the higher curvature corrections can not be
negligible in the dynamics of the scalar field, although they are energetically
negligible. Indeed, it turns out that the tensor-to-scalar ratio could be
enhanced and the tensor spectral index could be blue due to the Gauss-Bonnet
term. We estimate the degree of circular polarization of gravitational waves
generated during the slow-roll inflation. We argue that the circular
polarization can be observable with the help both of the Gauss-Bonnet and
parity violating terms. We also present several examples to reveal
observational implications of higher curvature corrections for chaotic
inflationary models.Comment: 12 pages, 4 figure
Probing polarization states of primordial gravitational waves with CMB anisotropies
We discuss the polarization signature of primordial gravitational waves
imprinted in cosmic microwave background (CMB) anisotropies. The high-energy
physics motivated by superstring theory or M-theory generically yield parity
violating terms, which may produce a circularly polarized gravitational wave
background (GWB) during inflation. In contrast to the standard prediction of
inflation with un-polarized GWB, circularly polarized GWB generates
non-vanishing TB and EB-mode power spectra of CMB anisotropies. We evaluate the
TB and EB-mode power spectra taking into account the secondary effects and
investigate the dependence of cosmological parameters. We then discuss current
constraints on the circularly polarized GWB from large angular scales (l < 16)
of the three year WMAP data. Prospects for future CMB experiments are also
investigated based on a Monte Carlo analysis of parameter estimation, showing
that the circular polarization degree, varepsilon, which is the asymmetry of
the tensor power spectra between right- and left-handed modes normalized by the
total amplitude, can be measured down to |varepsilon| 0.35(r/0.05)^{-0.6}.Comment: 28 pages, 9 figures, Accepted for publication in JCA