Dynamically induced Planck scale and inflation in the Palatini formulation

Abstract

We present * two scale invariant models of inflation in which the addition of quadratic in curvature terms in the usual Einstein-Hilbert action, in the context of Palatini formulation of gravity, manages to reduce the value of the tensor-to-scalar ratio. In both models the Planck scale is dynamically generated via the vacuum expectation value of the scalar fields.

Scalaron–Higgs inflation reloaded: Higgs-dependent scalaron mass and primordial black hole dark matter

“…The unification of these two models results in the two-field scalaron-Higgs model [15][16][17][18] (in the Palatini formalulation of the model [19][20][21][22][23] the scalaron is not a dynamical degree of freedom). Various aspects of this model have been studied, including the dependence of the inflationary dynamics on the initial conditions [18,24,25], the properties of its RG improvement [18,[26][27][28][29][30][31][32], the stabilization of the SM vacuum [18,33], the (p)reheating scenario [34][35][36][37], and a multifield amplification mechanism that leads to features in the inflationary power spectrum [18].…”

Minima of classically scale-invariant potentials

“…Similarly, the framework has also been invoked within neutrino phenomenology [15,[17][18][19][20][21][22] and within dark energy model building [23,24]. Another topic that certainly draws from this fascinating principle is the cosmological inflation [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], since the flat potentials used to describe the expansion epoch easily allow quantum corrections to determine the properties of the theory. The possible presence of radiatively generated minima in scalar potentials has also been investigated in other branches of cosmology, for example in connection with phase transitions and gravitational wave production [42][43][44][45][46], or within models of dark matter [9,14,15,19,[47][48][49][50][51][52][53][54].…”

Quintessential inflation in Palatini f(R) gravity

“…However, Palatini gravity does affect our scenario. Firstly, it "flattens" the inflaton scalar potential [28][29][30][31][32] so that the desired inflationary plateau can be attained even with an originally steep scalar potential. Secondly, the theory is expected to introduce modifications to the kination period, after primordial inflation, and also in the late Universe, when the inflaton field becomes quintessence.…”