Observational constraints on inflationary potentials within the quantum collapse framework

Abstract

The physical mechanism responsible for the emergence of primordial cosmic seeds from a perfect isotropic and homogeneous Universe has not been fully addressed in standard cosmic inflation. To handle this shortcoming, D. Sudarsky et al have developed a proposal: the self-induced collapse hypothesis. In this scheme, the objective collapse of the inflaton's wave function generates the inhomogeneity and anisotropy at all scales. In this paper we analyze the viability of a set of inflationary potentials in both the context of the collapse proposal and within the standard inflationary framework. For this, we perform a statistical analysis using recent CMB and BAO data to obtain the prediction for the scalar spectral index ns in the context of a particular collapse model: the Wigner scheme. The predicted ns and the tensor-to-scalar ratio r in terms of the slow roll parameters is different between the collapse scheme and the standard inflationary model. For each potential considered we compare the prediction of ns and r with the limits established by observational data in both pictures. The result of our analysis shows in most cases a difference in the inflationary potentials allowed by the observational limits in both frameworks. In particular, in the standard approach the more concave a potential is, the more is favored by the data. On the other hand, in the Wigner scheme, the data favors equally all type of concave potentials, including those at the border between convex and concave families. I. INTRODUCTIONAccording to most recent data reported by the Planck mission [1-3], the early Universe is consistent with the description provided by cosmic inflation, which assumes an accelerated expansion of the primordial Universe [4][5][6][7]. In the simplest scenario, the matter driving the inflationary stage is characterized by a single scalar field, called the inflaton, with canonical kinetic term minimally coupled to gravity [8]. Moreover, the standard paradigm considers that the inflationary expansion amplifies the quantum fluctuations of the scalar field and converts them into classical perturbations which leave their imprint as temperature and polarization anisotropies in the Cosmic Microwave Background (CMB) [9][10][11][12][13][14]. The observational data from CMB anisotropies constrain the parameters associated to the spectra of primordial fluctuations. Those parameters characterize the amplitude and shape of the scalar/tensor spectra. In particular, Planck 2015 data [2] yield the values ln(10 10 As) = 3.094 ± 0.034 and n s = 0.9645 ± 0.0049 at 68% confidence level corresponding to the scalar amplitude A s and spectral index n s respectively. 1 On the other hand, a measurement of the tensor amplitude A t and spectral index n t requires the B-mode polarization of the CMB, which has not been detected. In fact, it is not known if the tensor spectrum is consistent with a perfect scale invariant spectrum or exhibits some degree of tilt. Regarding the tensor spectrum amplitude, current data can only establish an upper bound...

Collapse models and cosmology

“…Recently, the collapse models have started to be considered in Cosmology [16][17][18][19][20][21][22][23][24], in particular in the context of cosmic inflation, with two essential motivations: to avoid conceptual problems related to the absence of an observer in the very early universe; and to use the high-accuracy cosmological data constraining inflation as a probe of the free parameters characterizing collapse models [24]. The goal of this paper is to briefly review these recent works.…”