Abstract
Brane Supersymmetry Breaking is a peculiar string-scale mechanism that can unpair Bose and Fermi excitations in orientifold models. It results from the simul- taneous presence, in the vacuum, of collections of D-branes and orientifolds that are not mutually BPS, and is closely tied to the scale of string excitations. It also leaves behind, for a mixing of dilaton and internal breathing mode, an exponential potential that is just too steep for a scalar to emerge from the initial singularity while descending it .A s a result, in this class of models the scalar can generically bounce off the exponential wall, and this dynamics brings along, in the power spectrum, an infrared depression typically followed by a pre-inflationary peak. We elaborate on a possible link between this type of bounce and the low-� end of the CMB angular power spectrum. For the first 32 multi- poles, one can reach a 50% reduction in χ 2 with respect to the standard ΛCDM setting.
Highlights
Despite the intricacies of their vacuum configurations and a number of vexing open questions, StringTheory [1] and its low–energy Supergravity [2] provide a profound and concrete candidate framework for High–Energy Physics beyond the Standard Model
For a mixing of dilaton and internal breathing mode, an exponential potential that is just too steep for a scalar to emerge from the initial singularity while descending it. In this class of models the scalar can generically bounce off the exponential wall, and this dynamics brings along, in the power spectrum, an infrared depression typically followed by a pre–inflationary peak
The four–dimensional models of Particle Physics inspired by String Theory are relatively under control in the presence of several supercharges, but the breaking of Supersymmetry is fraught with technical and conceptual complications
Summary
Despite the intricacies of their vacuum configurations and a number of vexing open questions, String. For γ ≥ 1 only the climbing solution exists, and remarkably the low–energy Supergravity (1) for the ten–dimensional Sugimoto model in [4] corresponds precisely to the critical value γ = 1 This property continues to hold for compactifications, insofar as the other scalar Φs is somehow stabilized by corrections that are implicitly present in eq (2) and, as we have already cautioned, up to higher–derivative string terms [9]. If γ < √1 , even in the presence of other mild corrections V (φ), a class of which we shall soon consider in a bottom–up approach, the bounce is followed by the onset of an inflationary phase This setting is clearly not fully realistic, since for one matter it does not address the exit problem, but our aim is more modestly to elaborate on the behavior of a climbing scalar near the turning point, under the (strong) assumption that its effects be accessible to us via the low– CMB. We shall present some new results on improved power spectra and corresponding CMB fits, some of which were described in preliminary form by one of us during the Summer of 2014 [24]
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