By implementing a genetic algorithm we search for stable vacua in Type IIB nongeometric flux compactification on an isotropic torus with orientifold 3-planes. We find that the number of stable dS and AdS vacua are of the same order. Moreover we find that in all dS vacua the multi-field slow-roll inflationary conditions are fulfilled. Specifically we observe that inflation is driven by the axio-dilaton and the Kähler moduli. We also comment on the existence of one stable dS vacuum in the presence of exotic orientifolds. 1 cesaredas@fisica.ugto.mx 2 luisreydb@fisica.ugto.mx 3 oloaiza@fisica.ugto.mx 4 msabido@fisica.ugto.mx 1 arXiv:1302.0529v3 [hep-th] 10 Nov 2013Recently, there has been a huge interest in the search for classical de Sitter (dS) vacua within the context of superstring compactification. In the last few years, some constraints have been imposed by estimating the contributions to the effective scalar potential from each of the components that play a role in the compactification process. For instance, there is a no-go theorem, indicating that the existence of dS vacua in compactifications threaded with standard NS-NS and R-R fluxes is incompatible with inflation[1]. Recently, in the context of these standar type IIB compactifications, it has been shown the existence of classical dS vacua in specific and suitable D-brane configurations with orientifold planes [2][3][4]. On the other hand, further studies show that by considering a bigger set of allowed fluxes and more general structures for the internal geometry, it is possible to find some stable dS vacua [5][6][7][8][9][10][11][12][13][14][15][16][17][18] although their compatibility with inflation has not been studied in detail. In this work we present some stable dS vacua consistent with inflation.There are some essential ingredients string compactifications should contain to enhance the chances of finding stable dS vacua: a negative curved internal manifold and a small number of moduli fields [19][20][21].Here, we take the approach consisting in computing the scalar potential from a superpotential with all the above features. Specifically, a compactification on a negatively curved manifold with a superpotential W that depends at tree level on a small set of moduli is achieved by considering a type II string compactification on a six-dimensional isotropic torus in the presence of non-geometric fluxes [22][23][24][25]. (2.12) where J = (j±, k) and M = (m±). The Bianchi identity Q · H 3 = 0 decomposes as A M J · A M J = (A M J ) δ (A M J ) λ η δλ = 0, (2.13) for j = j , diag(η) = {−1, 1, 1, 1} and for the combinations M = (0+), J = {(2, 0+), (1, 3−)} and M = (3−), J = {(1, 2−), (2, 1+)}, while Q · Q = 0 decomposes as,

We construct a noncommutative extension of the Loop Quantum Cosmology effective scheme for the open FLRW model with a free scalar field via a theta deformation. Firstly, a deformation is implemented in the configuration sector, among the holonomy variable and the matter degree of freedom. We show that this type of noncommutativity retain, to some degree, key features of the Loop Quantum Cosmology paradigm for a free field. Secondly, a deformation is implemented in the momentum sector, among the momentum associated to the holonomy variable and the momentum associated to the matter field. We show that the density, as in the case of Loop Quantum Cosmology is also bounded, furthermore, its maximum value is the same.

In this paper, we present an analysis of a chiral cosmological scenario from the perspective of K-essence formalism. In this setup, several scalar fields interact within the kinetic and potential sectors. However, we only consider a flat Friedmann–Robertson–Lamaître–Walker universe coupled minimally to two quintom fields: one quintessence and one phantom. We examine a classical cosmological framework, where analytical solutions are obtained. Indeed, we present an explanation of the “big-bang” singularity by means of a “big-bounce”. Moreover, having a barotropic fluid description and for a particular set of parameters, the phantom line is in fact crossed. Additionally, for the quantum counterpart, the Wheeler–DeWitt equation is analytically solved for various instances, where the factor-ordering problem has been taken into account (measured by the factor Q). Hence, this approach allows us to compute the probability density of the previous two classical subcases. It turns out that its behavior is in effect damped as the scale factor and the scalar fields evolve. It also tends towards the phantom sector when the factor ordering constant Q≪0.

In this paper we present an analysis of a chiral cosmological scenario from the perspective of the K-essence formalism. In this setup, several scalar fields interact within the kinetic and potential sectors. However, we only consider a flat Friedmann-Robertson-Lamaître-Walker (FRLW) universe coupled minimally to two quintom fields: one quintessence and one phantom. We examine a classical cosmological framework, where analytical solutions are obtained. Indeed, we present an explanation of the big-bang singularity by means of a big-bounce. Moreover, having a barotropic fluid description and for a particular set of parameters the phantom line is in fact crossed. On the other hand, for the quantum counterpart, the Wheeler-DeWitt equation is analytically solved for various instances, including the factor ordering problem with a constant Q. Hence, this approach allows us to compute the probability density, which behavior is in effect damped in the two subcases solves classically, observing that the probability density is opens in the direction of the evolution in the phantom field when the factor ordering constant is more negative. In other subcase the universe is quantum forever and the classical universe never takes place.

In this work, first, we study a flat Friedmann–Robertson–Walker Universe with two scalar fields but only one potential term, which can be thought as a simple quintessence plus a K-essence model. Employing the Hamiltonian formalism we are able to obtain the classical and quantum solutions. The second model studied, is also a flat Friedmann–Robertson–Walker Universe with two scalar fields, with the difference that the two potentials are considered as well as the standard kinetic energy and the mixed term (chiral field approach). Regarding this second model, it is shown that setting to zero the coefficient accompanying the mixed momenta term, two possible cases can be studied: a quintom like case ( m + 12 ) and a quintessence like case ( m − 12 ). For both scenarios classical and quantum solutions are presented.