Castello, Sveva Ilic, Stephane Kunz, Martin

The present epoch of accelerated cosmic expansion is supposed to be driven by an unknown constituent called dark energy, which in the standard model takes the form of a cosmological constant, characterized by a constant equation of state with w = -1. An interesting perspective over the role and nature of dark energy can be achieved by drawing a par...

Antoniadis, Ignatios Guillen, Anthony Tamvakis, Kyriakos
Published in
Journal of High Energy Physics

We study the ultraviolet behaviour of Higgs inflation models above the apparent unitarity violation scale arising from the large non minimal coupling to gravity, by computing on-shell 4-point scattering amplitudes in the presence of a large inflaton background, away from the electroweak vacuum. We find that all tree-level amplitudes are well behave...

Garcia, Marcos A. G. Mambrini, Yann Olive, Keith A. Verner, Sarunas

We consider models for inflation with a stable inflaton. Reheating is achieved through scattering processes such as $\phi \phi \to h h$, where $h$ is the Standard Model Higgs boson. We consider the reheating process in detail and show that for a relatively large coupling (needed for the late annihilations of the inflaton during freeze-out), reheati...

Amadei, Lautaro Perez, Alejandro

We propose a model of inflation driven by the relaxation of an initially Planckian cosmological constant due to diffusion. The model can solve the horizon and flatness problem, and generate a (approximately) scale invariant spectrum of (adiabatic) primordial perturbations with the correct amplitudes and blue tilt without an inflaton. The inhomogene...

Pattison, Chris Vennin, Vincent Wands, David Assadullahi, Hooshyar

We consider the effect of quantum diffusion on the dynamics of the inflaton during a period of ultra-slow-roll inflation. We extend the stochastic-$\delta\mathcal{N}$ formalism to the ultra-slow-roll regime and show how this system can be solved analytically in both the classical-drift and quantum-diffusion dominated limits. By deriving the charact...

Dudas, Emilian Garcia, Marcos A.G. Mambrini, Yann Olive, Keith A. Peloso, Marco Verner, Sarunas

It has been argued that supergravity models of inflation with vanishing sound speeds, $c_s$, lead to an unbounded growth in the production rate of gravitinos. We consider several models of inflation to delineate the conditions for which $c_s = 0$. In models with unconstrained superfields, we argue that the mixing of the goldstino and inflatino in a...

Antoniadis, Ignatios Nanopoulos, Dimitri V. Rizos, John

We study the cosmology of a string derived supersymmetric flipped $SU(5)$ model in the context of free-fermionic heterotic constructions that allow full calculability of the effective supergravity in perturbation theory around the fermionic vacuum where all string moduli have fixed values. The model has 3 generations of chiral families and a Higgs ...

Antoniadis, Ignatios Chatrabhuti, Auttakit

We discuss the possibility that inflation is driven by supersymmetry breaking with the superpartner of the goldstino (sgoldstino) playing the role of the inflaton. Imposing an R-symmetry allows to satisfy easily the slow-roll conditions, avoiding the so-called η-problem, and leads to an interesting class of small field inflation models, characteriz...

Brax, Philippe Kaneta, Kunio Mambrini, Yann Pierre, Mathias

We generalize dark matter production to a two-metric framework whereby the physical metric, which couples to the Standard Model (SM), is conformally and/or disformally related to the metric governing the gravitational dynamics. We show that this setup is naturally present in many Ultra Violet (UV) constructions, from K\"ahler moduli fields to tenso...

Paik, Biplab Khlopov, M.Yu. Kalam, Mehedi Ray, Saibal

Quantum-effective gravity must lead to a regularized cosmology and thereby by itself source and regulate the high energy inflaton fields required for an appropriate inflationary beginning of the Universe. Pursuing this premise, we involve in the generic code of extended theories of gravity in conceiving semi-classical imprinting of quantum effects ...