Systematics of multi-field effects at the end of warped brane inflation

Article
Report number	arXiv:0807.1927 ; MAD-TH-08-10 ; CERN-PH-TH-2008-146 ; CERN-PH-TH-2008-146 ; MAD-TH-08-10
Title	Systematics of multi-field effects at the end of warped brane inflation
Author(s)	Chen, Heng-Yu (Wisconsin U., Madison) ; Gong, Jinn-Ouk (Wisconsin U., Madison) ; Shiu, Gary (Wisconsin U., Madison ; CERN)
Publication	2008
Imprint	15 Jul 2008
Number of pages	42
In:	JHEP 09 (2008) 011
DOI	10.1088/1126-6708/2008/09/011
Subject category	Particle Physics - Theory
Abstract	We investigate in the context of brane inflation the possibility of additional light scalar fields generating significant power spectrum and non-Gaussianities at the end of inflation affecting the CMB scale observations. We consider the specific mechanism outlined by Lyth and describe the necessary criteria for it to be potentially important in a warped throat. We also discuss different mechanisms for uplifting the vacuum energy which can lead to different dominant contributions of the inflaton potential near the end of inflation. We then apply such criteria to one of the most detailed brane inflation models to date, and show that inflation can persist towards the tip of the throat, however for the specific stable inflationary trajectory, the light residual isometry direction becomes degenerate. We also estimate the effects for other inflationary trajectories with non-degenerate residual isometries.
Copyright/License	Open Access

$(Left) the inflaton potential (\ref{MathbbVphi}) and (right) the slow-roll parameter $\varepsilon$ (\ref{epsilonSR2}). {We normalize $\mpl = 1$ and for simplicity we set $A_0 = 1$.} The point $r/\epsilon^{2/3} = 1$ denotes the tip from which there is no further radial displacement. As shown in the right panel, thepotential is very flat near the tip.$ $(Left) the inflaton potential (\ref{MathbbVphi}) and (right) the slow-roll parameter $\varepsilon$ (\ref{epsilonSR2}). {We normalize $\mpl = 1$ and for simplicity we set $A_0 = 1$.} The point $r/\epsilon^{2/3} = 1$ denotes the tip from which there is no further radial displacement. As shown in the right panel, thepotential is very flat near the tip.$ $(Upper left) the inflaton potential (\ref{delicatepotential}) and the resulting slow-roll parameters, (upper right) $\varepsilon$ and (lower left) $\eta$. We show both cases where the Coulombic piece proportional to $r^{-4}$ is present (solid line) and absent (dotted line). As can be seen, without the Coulombic term inflation proceeds deep inside the throat, i.e. very small $r$ region, but (\ref{delicatepotential}) is no more valid there. In the lower right panel, we show $-\dot{H}/H^2$ which is {\em exactly} equivalent to the acceleration of the scale factor: $-\dot{H}/H^2 < 1$ means acceleration. Clearly, the criteria $|\eta| = 1$ {\em does not} guarantee that inflation ends at the corresponding point, especially when the Coulombic term is negligible which is the scenario we discussed in the maintext.$ Show more plots

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