On the cosmology of type IIA compactifications on SU(3)-structure manifolds

Abstract

We study cosmological properties of type IIA compactifications on orientifolds of SU(3)-structure manifolds with non-vanishing geometric flux. These compactifications give rise to effective 4D N = 1 supergravity theories that do not fall under some recentlyproven no-go theorems against de Sitter vacua and slow-roll inflation. Focusing on a wellunderstood class of models based on coset spaces, however, we can use a refined no-go theorem that rules out de Sitter vacua and slow-roll inflation in all but one case. The refined no-go theorem uses the dilaton and a specific linear combination of the Kähler moduli, which is different from the overall volume modulus. It puts a lower bound on the first slow-roll parameter: ǫ ≥ 2. The only case not ruled out is the manifold SU(2)×SU(2), for which we indeed find critical points with ǫ numerically zero. However, all the points we could find have a tachyon corresponding to an eta-parameter η −2.4.

Universal dS vacua in STU-models

“…One is therefore motivated to try to do without such non-perturbative effects and generate dS solutions perturbatively. This has turned out to be remarkably complicated in simple string motivated examples, and various no-go results have been obtained in the context of geometric compactifications of type II theories [4][5][6].…”

“…As it was discussed before, the eigenvalues of m 2 I J are organised by pairs. For λ T = 4 they take the values 6) and the cosmological constant is then simply…”

R2 inflation from scale invariant supergravity and anomaly free superstrings with fluxes

“…[25,26] and for recent reviews on this subject [27][28][29][30]). For orientifolds with fluxes and branes even some no-go theorems against stable de Sitter vacua were formulated [31] and ways to bypass these arguments were subsequently discussed in [32,33,[33][34][35][36][37][38][39]. In our paper we will show how the scale symmetry of the R 2 supergravity effective actions including matter as well as the non-scale invariant gaugings from quantum effects can be naturally derived from string compactifications with fluxes.…”

Warped Ricci-flat reductions

“…Note that q = 2 is not a legitimate choice and if one demands integer dimensions, we are hence led to only the following choices for (p, q): (5, 6), (6,4) and (8,3). Besides these choices, one can also formally consider large D, q → ∞ limit where one encounters a four-dimensional vacuum (p = 4).…”

“…Nonetheless, it has proven to be notoriously difficult to construct four-dimensional de Sitter solutions in a string theory setting which are classically and quantum mechanically stable and do not have a moduli problem [3,4]. A leading framework [5] and its uplifting procedure to produce dS vacua has recently been called into question [6], leading to a renewed interest in alternatives [7].…”