Thermal non-Gaussianity in holographic cosmology

Abstract

Recently it has been shown that the thermal holographic fluctuations can give rise to an almost scale invariant spectrum of metric perturbations since in this scenario the energy is proportional to the area of the boundary rather than the volume. Here we calculate the non-Gaussianity of the spectrum of cosmological fluctuations in holographic phase, which can imprint on the radiation dominated universe by an abrupt transition. We find that if the matter is phantom-like, the nonGaussianity f equil N L can reach O(1) or even be larger than O(1). Especially in the limit ω → −5/3, the non-Gaussianity is very large and negative. Furthermore, since the energy is proportional to the area, the thermal holographic non-Gaussianity depends linearly on k if we neglect the variation in T during the transition (fixed temperature).

Thermal non-Gaussianity in Near-Milne universe

“…In this letter, we intend to explore the thermal non-Gaussianity in Near-Milne universe. We find that thermal fluctuations in Near-Milne universe can result in a large non-Gaussianity, similar to the case in holographic cosmology [10]. Treating thermal fluctuations as the origin of primordial fluctuations in cosmology was advocated by Peebles [13].…”

“…More discussions can be found in Ref. [10]. However, we must point out that the mechanism of phase transition plays an important role in this scenario.…”

“…The non-Gaussianity of the Cosmic Microwave Background (CMB) has been playing a crucial role in the investigation of the very early universe, since it has become a distinct feature among all kinds of inflation models and their alternatives. For instance, for single field slow roll inflation, the non-Gaussianity is too small to be detected in near future [1,2], however, for models beyond single field slow roll inflation, the non-Gaussianity large enough to be observable can be predicted [3][4][5][6][7][8][9][10][11]. Recently, WMAP 5-year data indicates that at 95% confidence level, the primordial non-Gaussianity parameters for the local and equilateral models are in the region −9 < f local NL < 111 and −151 < f equil NL < 253, respectively [12].…”

“…In this letter, we intend to investigate the thermal non-Gaussianity in this context, following the strategy developed in Ref. [25], which has also been used to investigate the non-Gaussianity in string gas cosmology [26] and holographic cosmology [10].…”

Non-Gaussian distribution and clustering of hot and cold pixels in the five-yearWMAPsky

“…Non‐Gaussianity of the cosmic microwave background (CMB) is progressively becoming a crucial probe of the inflationary dynamics, since models beyond single‐field slow‐roll inflation predict large distinct non‐Gaussianities above the current limit of measurement (Lyth, Ungarelli & Wands 2003; Lyth & Riotto 2006; Bartolo et al 2004; Dvali, Gruzinov & Zaldarriaga 2004; Chen 2005; Seery & Lidsey 2005; Chen & Szapudi 2006; Seery & Hidalgo 2006; Ling & Wu 2009; Senatore, Tassev & Zaldarriaga 2008; Senatore, Smith & Zaldarriaga 2009; Chen et al 2009). Moreover, up to date a number of plausible alternative early universe models also predict skewed primordial fluctuations, and are in principle distinguishable from other scenarios through the shape dependence of high‐order correlation functions (Alishahiha, Silverstein & Tong 2004; Arkani‐Hamed et al 2004; Creminelli & Senatore 2007; Brandenberger 2008; Buchbinder, Khoury & Ovrut 2008; Lehners & Steinhardt 2008; McAllister & Silverstein 2008).…”