Thermal non-Gaussianity in Near-Milne universe

Abstract

The thermal non-Gaussianity in Near-Milne universe is investigated in this letter. Through classifying thermal fluctuations into two types, one characterized by a phase transition and the other without phase transition, we show that for fluctuations undergoing a phase transition, the non-Gaussianity depends linearly on $k$, but in non-phase transition case it is proportional to $k^{-3\gamma },\gamma >0$. Moreover, if the phase transition scenario is similar to that in holographic cosmology, we find that the non-Gaussianity $f_{NL}^{equil}$ can reach $\mathcal{O}(1)$ or larger than $\mathcal{O}(1)$ by fine tuning of the equation of state ${\omega }_C$. Especially at the limit of ${\omega }_C\to -5/3$, the non-Gaussianity can be very large. On the other hand, for non-phase transition case, the non-Gaussianity estimator $f_{NL}^{equil}$ is approximately $f_{NL}^{equil}\simeq 5/108$ when the energy is sub-extensive, especially when $\gamma \to 0^{+}$. However, when $\gamma \to 4$, large non-Gaussianity can be obtained.

11 pages, no figure, version to be published in PLB

References in corpus (8)

• String Gas Cosmology and Structure Formation
• Non-perturbative Gravity, Hagedorn Bounce & CMB
• Generating the Curvature Perturbation at the End of Inflation in String Theory
• More on the Spectrum of Perturbations in String Gas Cosmology
• Thermal fluctuations in loop cosmology
• Holography and the scale-invariance of density fluctuations
• Near-Milne realization of scale-invariant fluctuations
• Thermal non-Gaussianity in holographic cosmology

Cited by in corpus (5)

• Cosmological perturbations from statistical thermal fluctuations
• Thermodynamics of String Field Theory Motivated Nonlocal Models
• Quadra-Spectrum and Quint-Spectrum from Inflation and Curvaton Models
• Gravitational-wave background in bouncing models from semi-classical, quantum and string gravity
• Thermal fluctuations in viscous cosmology