arXiv subjects

M. Meo

Publications and source records attributed to M. Meo.

3 recordsLinked to original sources

arXiv2026

More on Pre-Inflationary Non Gaussianities

I generalize the three-point amplitude of curvature perturbations in the climbing scenario inspired by ten-dimensional non-supersymmetric strings to a broader class of exponential potentials, under some assumptions on the smoothing effects of String Theory that favor a bounce Cosmology. The extension can encompass the SO(16)xSO(16) model, together with other scenarios related to supersymmetry breaking in String Theory. The e-fold ranges compatible with Planck data move toward lower values of N for milder potentials and toward larger values for steeper ones. I also compute the three-point amplitudes involving graviton modes in the same bounce scenario, showing in detail their lack of peculiar contributions from the turning point.

hep-th↗

arXiv2025

Primordial Non-Gaussianity from a String-Inspired Cosmology

The interplay between string theory and early-universe cosmology offers promising avenues to explore high-energy regimes where the standard single-field slow-roll model may no longer provide an accurate description. One intriguing scenario emerges from certain non-supersymmetric string models, where supersymmetry breaking induces a non-trivial vacuum energy, or more precisely an exponential potential for scalar fields, and primarily for the dilaton. This setup gives rise to the so-called "climbing scalar" phenomenon, whereby the scalar is forced to emerge from the initial singularity while climbing up the potential, if sufficiently steep. This phase precedes a turning point, and the subsequent descent can support inflation. The resulting pre-inflationary dynamics can leave imprints in cosmological observables. To begin with, it induces a low-frequency cut in the primordial power spectrum that resonates with the lack of power present in the first few CMB multipoles. The main theme of this work is to clarify its possible effect on non-Gaussianities.

hep-th↗

arXiv2025

On Pre-Inflationary non Gaussianities

We explore the three-point amplitude of curvature perturbations in scenarios suggested by high-scale supersymmetry breaking in String Theory, where the inflaton is forced to climb a steep exponential potential. We can do it at the price of some simplifications, and more importantly with some assumptions on the softening effects of String Theory. These suggest a scenario proposed long ago by Gasperini and Veneziano, where the initial singularity is replaced by a bounce, and the resulting analysis rests on a scale $\Delta$ that leaves some signs in the angular power spectrum of the CMB. The amplitude comprises two types of contribution: the first oscillates around the original result of Maldacena and gives no further prospects to detect a non-Gaussian signal, but the second, which is subtly tied to the turning point at the end of the climbing phase, within the window 62<N<66 for the inflationary e-folds could be compatible with Planck constraints and potentially observable. The amplitudes involving the tensor modes contain only the first type of contribution.

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