Sneutrino Tribrid Inflation, Metastable Cosmic Strings and Gravitational Waves

Abstract

We present a successful realization of sneutrino tribrid inflation model based on a gauged U (1) B−L extension of Minimal Supersymmetric Standard Model (MSSM). A single interaction term involving the B −L Higgs field and the right-handed neutrinos serves multiple purposes. These include the generation of heavy Majorana masses for the right-handed neutrinos to provide an explanation for the tiny neutrino masses via the seesaw mechanism, a realistic scenario for reheating and non-thermal leptogenesis with a reheat temperature as low as 10 6 GeV, and a successful realization of inflation with right-handed sneutrino as the inflaton. The matter parity which helps avoid rapid proton decay survives as a Z 2 subgroup of a U (1) R-symmetry. Depending on the choice of model parameters yields the following predicted range of the tensor to scalar ratio, 3 × 10 −11 r 7 × 10 −4 (6 × 10 −7 r 0.01), and the running of the scalar spectral index, −0.00022 dn s /d ln k −0.0026 (−0.00014 dn s /d ln k 0.005), along with the B −L breaking scale, 3×10 14 M/GeV 5×10 15 (6×10 15 M/GeV 2 × 10 16 ), calculated at the central value of the scalar spectral index, n s = 0.966, reported by Planck 2018. The possibility of realizing metastable cosmic strings in a grand unified theory setup is briefly discussed. The metastable cosmic string network admits string tension values in the range 10 −8 Gµ s 10 −6 , and predicts a stochastic gravitational wave background lying within the 2-σ bounds of the recent NANOGrav 12.5-yr data.

PBH-infused seesaw origin of matter and unique gravitational waves

“…For a sufficiently high U (1) symmetry breaking scale (Λ CS 10 9 GeV), the resulting GW background is detectable at ongoing and near future GW experiments. This makes CS generated GW an outstanding probe of super-high scale BSM physics [18,[35][36][37][38][39][40][41][42][43][44][45][46] which can not be probed directly at terrestrial experiments. The key parameter related to CS is their normalised tension Gµ ∼ GΛ 2 CS with G being Newton's constant.…”

Probing Leptogenesis and Pre-BBN Universe with Gravitational Waves Spectral Shapes

“…where r = α/ΓGµ and Ω r ≃ 9 × 10 −5 . Such strong GWs as a consequence of a very high scale symmetry breaking thus serves as an outstanding probe of particle physics models [73][74][75][76][77][78]. Possibly the most important recent development is the finding of a stochastic common spectrum process across 45 pulsars by NANOGrav PTA [79], which if interpreted as GWs, corresponds to a strong amplitude and is better fitted with cosmic strings [28,80,81] than the single value power spectral density as predicted by supermassive black hole models.…”

Constraining the Cosmic Strings Gravitational Wave Spectra in No Scale Inflation with Viable Gravitino Dark matter and Non Thermal Leptogenesis

“…Once the string is cut, the monopoles at the two ends are quickly pulled together due to string tension, forcing them to annihilate. If the string network is sufficiently long-lived, it can generate a stochastic gravitational wave background (SGWB) in the range of ongoing and future gravitational wave (GW) experiments [29,30].…”