Scale dependence of local $f_{NL}$ (2009)
Byrnes, Christian T., Nurmi, Sami, Tasinato, Gianmassimo, Wands, David
We consider possible scale-dependence of the non-linearity parameter $f_{NL}$ in local and quasi-local models of non-Gaussian primordial density perturbations. In the simplest model where the...
Non-Gaussianity beyond slow roll in multi-field inflation (2009)
Byrnes, Christian T., Tasinato, Gianmassimo
We study the non-Gaussianity generated during multiple-field inflation. We provide an exact expression for the bispectrum parameter f_NL which is valid beyond the slow-roll regime, valid for certain...
Large non-Gaussianity from two-component hybrid inflation (2008)
Byrnes, Christian T., Choi, Ki-Young, Hall, Lisa M. H.
We study the generation of non-Gaussianity in models of hybrid inflation with two inflaton fields, (2-brid inflation). We analyse the region in the parameter and the initial condition space where a...
We analyse models of inflation in which isocurvature perturbations present during inflation are converted into the primordial curvature perturbation during instant preheating. This can be due to an...
Conditions for large non-Gaussianity in two-field slow-roll inflation (2008)
Byrnes, Christian T., Choi, Ki-Young, Hall, Lisa M. H.
We study the level of primordial non-Gaussianity in slow-roll two-field inflation. Using an analytic formula for the nonlinear parameter f_nl in the case of a sum or product separable potential, we...
Conditions for large non-Gaussianity in two-field slow-roll inflation (2008)
Byrnes, Christian T., Choi, Ki-Young, Hall, Lisa M.H.
16 pages, 6 figures, 1 table.-- PACS number: 98.80.Cq.
Diagrammatic approach to non-Gaussianity from inflation (2007)
Byrnes, Christian T., Koyama, Kazuya, Sasaki, Misao, Wands, David
We present Feynman type diagrams for calculating the n-point function of the primordial curvature perturbation in terms of scalar field perturbations during inflation. The diagrams can be used to...
Primordial trispectrum from inflation (2006)
Byrnes, Christian T., Sasaki, Misao, Wands, David
We use the delta N-formalism to describe the leading order contributions to the primordial power spectrum, bispectrum and trispectrum in multiple-field models of inflation at leading order in a...
Curvature and isocurvature perturbations from two-field inflation in a slow-roll expansion (2006)
Byrnes, Christian T., Wands, David
We calculate the power spectra of primordial curvature and isocurvature perturbations from a general two field inflation model at next-to-leading order correction in a slow-roll expansion. In...
Scale-invariant Perturbations from Chaotic Inflation (2005)
Byrnes, Christian T., Wands, David
Vacuum fluctuations in the inflaton field driving chaotic inflation with a quadratic potential give a red spectrum of primordial density perturbations, n=0.97. However angular fluctuations in an...