Non-Gaussianity as a signature of thermal initial condition of inflation

作者：Das Suratna^*; Mohanty Subhendra

来源：Physical Review D - Particles, Fields, Gravitation and Cosmology, 2009, 80(12): 123537.

DOI：10.1103/PhysRevD.80.123537

We study non-Gaussianities in the primordial perturbations in single field inflation where there is a radiation era prior to inflation. Inflation takes place when the energy density of radiation drops below the value of the potential of a coherent scalar field. We compute the thermal average of the two-point, three-point, and four-point correlation functions of inflaton fluctuations. The three-point function is proportional to the slow-roll parameters, and there is an amplification in f(NL) by a factor of 65 to 90 due to the contribution of the thermal bath. We conclude that the bispectrum is in the range of detectability with the 21-cm anisotropy measurements. The four-point function on the other hand appears in this case due to the thermal averaging and the fact that thermal averaging of the four-point correlation is not the same as the square of the thermal averaging of the two-point function. Because of this fact, tau(NL) is not proportional to the slow-roll parameters and can be as large as -42. The non-Gaussianities in the four-point correlation of the order 10 can also be detected by 21-cm background observations. We conclude that a signature of thermal inflatons is a large trispectrum non-Gaussianity compared to the bispectrum non-Gaussianity.

• 出版日期2009-12