Tensor non-Gaussianities from non-minimal coupling to the inflaton

TY - JOUR

T1 - Tensor non-Gaussianities from non-minimal coupling to the inflaton

AU - Dimastrogiovanni, Emanuela

AU - Fasiello, Matteo

AU - Tasinato, Gianmassimo

AU - Wands, David

N1 - 21 pages, 7 figures

PY - 2019/2/8

Y1 - 2019/2/8

N2 - Tensor non-Gaussianity represents an important future probe of the physics of inflation. Inspired by recent works, we elaborate further on the possibility of significant primordial tensor non-Gaussianities sourced by extra fields during inflation. Unitarity constraints limit the impact of extra (spinning) particle content by means of a lower bound on the corresponding mass spectrum. For spin-2 particles, this takes the form of the well-known Higuchi bound. Massive (mgsim H) particles will typically decay during inflation unless they are non-minimally coupled to the inflaton sector: the inflating field "lifts" the dynamics of the extra field(s), effectively getting around the limits imposed by unitarity. There exist several models that realize such a mechanism, but we focus here on the set-up of [1] where, through an EFT approach, one is able to capture the essential features common to an entire class of theories. In the presence of an extra massive spin-2 particle, the interactions in the tensor sector mimic very closely those in the scalar sector of quasi-single-field inflationary models. We calculate the tensor bispectrum in different configurations and extract its dependence on the extra tensor sound speed. We show in detail how one may obtain significant tensor non-Gaussianities whose shape-function interpolates between local and equilateral, depending on the mass of the extra field. We also estimate the LISA response functions to a tensor bispectrum supporting the intermediate-type shapes we find.

AB - Tensor non-Gaussianity represents an important future probe of the physics of inflation. Inspired by recent works, we elaborate further on the possibility of significant primordial tensor non-Gaussianities sourced by extra fields during inflation. Unitarity constraints limit the impact of extra (spinning) particle content by means of a lower bound on the corresponding mass spectrum. For spin-2 particles, this takes the form of the well-known Higuchi bound. Massive (mgsim H) particles will typically decay during inflation unless they are non-minimally coupled to the inflaton sector: the inflating field "lifts" the dynamics of the extra field(s), effectively getting around the limits imposed by unitarity. There exist several models that realize such a mechanism, but we focus here on the set-up of [1] where, through an EFT approach, one is able to capture the essential features common to an entire class of theories. In the presence of an extra massive spin-2 particle, the interactions in the tensor sector mimic very closely those in the scalar sector of quasi-single-field inflationary models. We calculate the tensor bispectrum in different configurations and extract its dependence on the extra tensor sound speed. We show in detail how one may obtain significant tensor non-Gaussianities whose shape-function interpolates between local and equilateral, depending on the mass of the extra field. We also estimate the LISA response functions to a tensor bispectrum supporting the intermediate-type shapes we find.

KW - astro-ph.CO

KW - gr-qc

KW - hep-ph

KW - hep-th

KW - RCUK

KW - STFC

KW - ST/N000668/1

KW - ST/P00055X/1

UR - https://arxiv.org/abs/1810.08866

U2 - 10.1088/1475-7516/2019/02/008

DO - 10.1088/1475-7516/2019/02/008

M3 - Article

VL - 2019

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

SN - 1475-7516

IS - 02

M1 - 008

ER -