Multiple inflation

TL;DR

The paper investigates how symmetry breaking in the visible sector, triggered during primordial inflation in $N=1$ supergravity, can generate multiple short inflationary bursts that leave distinctive imprints in the scalar density perturbation, notably notches and variations in the spectral index $n_{\cal R}$. It develops the SUGRA potential, explores slow-roll constraints, and shows how intermediate-scale phase transitions can modify the inflaton mass through gravity, potentially yielding notches in the primordial spectrum and altered CMB signatures. It also introduces a low-scale, late-time thermal inflation to dilute relics like moduli and gravitinos, addressing cosmological problems associated with supersymmetric theories. Observationally, the framework connects to LSS and CMB data, predicting a notch around $k \sim 0.1\,h\,\mathrm{Mpc}^{-1}$ and suppressed secondary Doppler peaks, with future PLANCK measurements capable of testing these claims.

Abstract

Attempts at building an unified description of the strong, weak and electromagnetic interactions usually involve several stages of spontaneous symmetry breaking. We consider the effects of such symmetry breaking during an era of primordial inflation in supergravity models. In cases that these occur along flat directions at intermediate scales there will be a succession of short bursts of inflation which leave a distinctive signature in the spectrum of the generated scalar density perturbation. Thus measurements of the spectral index can directly probe the structure of unified theories at very high energy scales. An observed feature in the power spectrum of galaxy clustering from the APM survey may well be associated with such structure. If so, this implies a characteristic suppression of the secondary Doppler peaks in the angular power spectrum of temperature fluctuations in the cosmic microwave background.

Figures (2)

• Figure 1: The spectral index of the primordial density perturbation implied by the APM data, assuming a critical CDM universe with $\Omega_{\rm N}=0.05$, $h=0.5$, and using two suggested procedures to extract the linear spectrum. A scale-invariant spectrum, the usually assumed generic prediction of inflation, is shown for comparison. The "notch" seen at $k\sim0.1h$ Mpc$^{-1}$ is in accordance with the spectral feature expected due to an intermediate scale symmetry breaking phase transition.
• Figure 2: The power spectrum of CMB anisotropy implied by the APM data, assuming a critical CDM universe with $\Omega_{\rm N}=0.05$, $h=0.5$, and using two suggested procedures to extract the linear spectrum. The upper and lower envelopes correspond to the quoted $\pm1\sigma$ errors in the APM data averaged over 4 zones. The expectation for a COBE-normalized standard CDM model (with $n_{\cal R}=1$) is shown for comparison, along with an unbiased compendium of observational data.