Abstract
Working in the Large Volume Scenario (LVS) of IIB Calabi-Yau flux compactifications, we construct inflationary models from recently computed higher derivative (α′)3-corrections. Inflation is driven by a Kähler modulus whose potential arises from the aforementioned corrections, while we use the inclusion of string loop effects just to ensure the existence of a graceful exit when necessary. The effective inflaton potential takes a Starobinsky-type form V=V0(1−e−νϕ)2, where we obtain one set-up with ν=−1/√3 and one with ν=2/√3 corresponding to inflation occurring for increasing or decreasing ϕ respectively. The inflationary observables are thus in perfect agreement with PLANCK, while the two scenarios remain observationally distinguishable via slightly varying predictions for the tensor-to-scalar ratio r. Both set-ups yield r≃ (2… 7) × 10−3. They hence realise inflation with moderately large fields (Δϕ∼ 6 MPl) without saturating the Lyth bound. Control over higher corrections relies in part on tuning underlying microscopic parameters, and in part on intrinsic suppressions. The intrinsic part of control arises as a leftover from an approximate effective shift symmetry at parametrically large volume.
Highlights
Working in the Large Volume Scenario (LVS) of IIB Calabi-Yau flux compactifications, we construct inflationary models from recently computed higher derivative (α )3corrections
In this paper we report on an improved construction of Starobinsky-type plateau potentials in type IIB string compactifications based on the original setup of fibre inflation in [20]
For the simple toy K3-fibred geometries we are looking at, we find that the structure of the four-derivative √α -correctio√n [25] generating the plateau region of the potential leads to values for ν = 2/ 3, ν = 1/ 3 differing between inflation rolling to the left, and to the right, respectively
Summary
We will begin by briefly reviewing the framework of LVS. Our starting point is the large volume limit of the low-energy 4D N = 1 - effective action of type IIB Calabi-Yau-orientifold compactifications with background fluxes [26, 27] including the leading order (α )3-corrections to the bulk fields [26] and string-loop corrections [28, 29]. The background fluxes admit supersymmetric minima for the dilaton as well as complex structure moduli at tree level After replacing these fields with their respective minima in the effective Lagrangian, the theory is subject to the following Kahler and superpotential. The non-perturbative corrections from wrapped D-branes induce a term in the superpotential. The Kahler potential includes string-loop corrections which are induced from the exchange of closed strings carrying KaluzaKlein momentum as well as from the exchange of winding strings. Their general form was inferred in [29] to be δK(KgsK). The string-loop correction δV(gs) is interesting for those compactification-geometries for which V LVS has a flat direction or no minimum at large volume exists. A particular case, in which V LVS has an exact flat direction was studied in [20, 24]
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