Nongaussianity of the curvature perturbation from preheating We
Non-gaussianity of the curvature perturbation from preheating - We propose “Modulated Preheating” mechanism - Kazunori Kohri (郡 和範) Physics Department, Lancaster University Based on Kohri, Lyth, Vlenzuela-Toledo, ar. Xiv: 0904. 0793 [hep-ph]
Abstract • We consider ½ m 2φ2 preheating models • In expanding universe, narrow resonance does not work. Then massless χ quanta are not so sufficiently produced. • In “Modulated Preheating” in broad resonance, a light field σ contributes to curvature perturbation and produces sizable amount of f. NL
Model of preheating • Motivated by particle physics (Chaotic Inflation, Aterm Inflation, Inflection point Inflation. ), we may adopt ½ m 2φ2 for inflaton potential Reduction of ρφ and resonant production ofρχ • See Andrei Frolov’s talk in massless preheating models. See Bond, Frolov, Huang, Kofman, ar. Xiv: 0903. 3407
How large/small is 2 g? • For no radiative corrections to the potential But see Barnaby, Huang, Kofman, Pogosyan, ar. Xiv: 0902. 0615 • Massless fluctuation of χ during inflation
Narrow parametric resonance does occur in expanding universe? • Narrow resonance • Conditions for efficient resonance Big difference from Enqvist, Jokinen, Mazumdar, Vaihkonen (05)
We may need another mechanism • Large fluctuation …
Modulated Reheating Dvali, Gruzinov, Zaldarriaga(04) Kofman (04) Zaldarriaga (04) • If decay rate Γ=1/tdec depends on another field σ
Calculation in modulated reheating
Modulated Preheating See Podolsky, Felder, Kofman, Peloso (05) • Coupling constant g can depend on another Ackerman et al (05) field Broad resonance • Then perturbation produced by σ is important
Mathew Equation Mode expansion Equation of Motion
Instability band Kofman, Linde, Starobinsky(97)
Evolution Kofman, Linde, Starobinsky(97)
End of preheating Kofman, Linde, Starobinsky(97)
Is χ nonrelativistic or relativistic? • χ’ Momentum at the resonance • Mass of χ • After Relativistic particle for
Preheating Npreheat Kofman, Linde, Starobinsky(97) Nend
2 -8 g =10
2 -9 g =10
Analytical estimate of • During preheating φand χare massive st 1 stage
Analytical estimate of nd 2 • After preheating φ is massive, χ is almost massless stage
Spectrum and non-linear parameter
Non-gaussianity
Conclusion • In expanding universe, narrow resonance (g 2<10 -10) does not work, and production of massless χ quanta is insufficient, and then Pζχ and f. NL are very small • In “Modulated Preheating” in broad resonance, massless σ quanta contribute to curvature perturbation and f. NL • Our resuts should be checked by numerical simulation (by using Andrei’s DEFROST or something)
- Slides: 23