Radion inflation in higher-dimensional gravity theory

Abstract

We study a radion model for inflation and density perturbation identifying the scalar field arising from the five-dimensional gravity on M 4 × S 1 with the inflaton. The inflaton potential arising from 5D graviton and matter one-loop effects is shown to possess the desirable slow-roll property. This radion model contains only a small number of parameters and there is an ample parameter region which reproduces (without fine-tuning) all precision astrophysical data.

Inflation from radion gauge-Higgs potential at Planck scale

“…From (3.10), a and x are determined as a ≃ 2.2 × 10 −6 m 5 and x ≃ 788. 6 As an illustration, the V (x, θ) is depicted in Fig. 3, for a specific value of L and m. The inflaton mass M ϕ is given by…”

“…and its magnitude is estimated as 5 If one considers the running of spectral index that corresponds to third and higher derivatives of the potential with respect to the inflaton, the higher-order terms (k > 2) are necessary to evaluate it correctly [12]. 6 We drop the infinite part of a and show only the finite part. We need a fine tuning to determine a, and this is a sort of fine-tuning problem known as the cosmological constant problem.…”

“…The scalar potential can be induced radiatively and stabilized by local symmetries. Typical ones are the extranatural inflation model [4,5] and the radion inflation model [6]. In the former model, a scalar field called "gauge-Higgs" appears from the extra-dimensional component(s) of the gauge field.…”

Implications for the hierarchy problem, inflation and geodesic motion from fiber fabric of spacetime

“…( 23), only the first two terms in the potential V (T ) have the significant contribution as seen in Eq. (24). Whereas, the higher order terms of the potential in terms of the canonically normalized field T would be highly suppressed by the further powers of 1/M * and hence they are well-approximately ignored.…”

“…This still remains an open question and an active field of research. There have been the investigations which explore the possibility of the radion field as a natural candidate for the inflaton [20][21][22][23][24]. Here, the potential of the radion field is effectively generated by coupling to the matter fields or quantum effects and breaks explicitly the higher dimensional general covariance.…”