Pole inflation from non-minimal coupling to gravity

Abstract

Transforming canonical scalars to the Einstein frame can give a multifield generalization of pole inflation (namely, a scalar with a divergent kinetic term) at vanishing field-dependent Planck mass. However, to obtain an attractor, the scalar potential must obey certain non-generic conditions. These are automatically satisfied in Quantum Field Theories with dimension-less couplings. The resulting models of pole inflation have special inflationary predictions determined by the full RG running of couplings. Acceptable predictions for the tensor/scalar ratio arise for perturbative but moderately large couplings, so we explore the possible QFT runnings: to confinement, to an IR fixed point, and to a UV fixed point.

An Alternative Framework for E-Model Inflation in Supergravity

“…It is well-known [1][2][3][4] that the presence of a pole in the kinetic term of the inflaton gives rise to inflationary models collectively named α-attractors [5][6][7][8][9][10][11][12][13]. These models can be classified [9][10][11][12][13][14] into E-Model Inflation (EMI) [7] (or α-Starobinsky model [6]) and T-Model Inflation (TMI) [15], depending on the form of the inflationary potential, V α , expressed in terms of the canonically normalized inflaton φ. Namely, V α can be defined as follows…”

Traversing a kinetic pole during inflation: primordial black holes and gravitational waves

“…A suitable choice is a generic potential made inflationary by an extra non-integrable pole with p ′ > 2, see eq. ( 10) of [5]. Table 1 shows that the p = 1 critical case is less strongly tuned than p > 1.…”

“…Significant changes occur at two critical values: p = 1 and p = 2. A pole with p ≥ 2 is non-integrable: the ϕ region near the pole becomes an infinite range of the canonical ϕ can field, so the potential gets infinitely stretched acquiring a nearly-flat inflationary form [1][2][3][4][5]. 3 This paper focuses instead on an integrable pole with 0 < p < 2, that gives a finite stretching of the potential around the pole, where the potential acquires the form of an exact inflection point…”

“…where the scalar potential V can undergoes an infinite stretch, acquiring the flatness needed to support inflation. Pole inflation models have been motivated invoking string theory, supergravity [1][2][3][4] or a non-minimal scalar coupling f (ϕ)R to gravity [5].…”

Higgs-Dilaton inflation in Einstein-Cartan gravity

“…On the other hand, for an almost vanishing ∆ leading to degenerate roots θ + θ − T 1, the pole structure become approximately cubic. This gives rise to a new attractor solution where the spectral tilt and the tensor-to-scalar ratio approach the values [95,98]…”