Non-Gaussianity from Quantum Fluctuations during Inflation Kin-Wang Ng Institute of Physics

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Non-Gaussianity from Quantum Fluctuations during
InflationKin-Wang Ng Institute of Physics
Institute of Astronomy and Astrophysics
Academia Sinica, Taiwan, ROC
2nd KIAS Workshop on Cosmology and Structure
Formation KIAS, Seoul, Korea Sep 20-21, 2006
CH Wu, KW Ng, WL Lee, DS Lee, YY Charng,
astro-ph/0604292
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Introduction

• WMAP 3-year data and other CMB expts
• Challenges to standard slow-roll inflation?!
• low CMB quadrupole , running spectral index,
  nongaussianity, south-north asymmetry, axis of
  evil (in Parks talk),..
• Inflaton coupled to other quantum fields
• natural, reheating,..
• still single-field inflation (see
  multi-field inflation in Stewards talk)
• Quantum environment behaves like colored
• quantum noise kicks inflaton (Brownian
  motion)
• Noise-induced (passive) inflaton fluctuations
• in addition to active de Sitter quantum
  fluctuations

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WMAP 3-year TT, TE, EE, CMB power spectra
low quadrupole
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Cosmological Parameters
ns0.961 _at_ k0.05Mpc-1
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WMAP3 Data on Running Spectral Idex
r tenor/scalar ns scalar spectral
index dns/dlnk running index
ns 0.05 0.961
k0.002Mpc-1
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PR(k) (d?/?)2
dn/dlnk ltlt n-1
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WMAP3 and inflation models
These models predict that
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?2Fd?/?
WMAP3 Data on Non-Gaussianity
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A Challenge to Standard Slow-roll inflation!?

• Chaotic inflation classical fluctuations
  driven by a white noise (Starobinsky) or by a
  colored noise (Liguori, Matarrese et al.) coming
  from high-k inflaton
• Driven by a colored noise from interacting
  quantum environment (Wu et al)
• Others

• Slow-roll conditions violated after horizon
  crossing (Leach et al)
• General slow-roll condition (Steward)
• n-1dn/dlnk
• Multi-field (Vernizzi, Tent, Rigopoulos,
  Yokoyama et al)
• etc

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Our Inflaton-Scalar Interacting Model
Single-field inflationltsgt 0
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Trace out sigma field to obtain
Colored, dependent on history
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Dominant passive fluctuations and low CMB
quadrupole
assuming no active de Sitter quantum fluctuations
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Low CMB quadrupole and onset of inflation
at large k
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Conclusions

• Hints from WMAP3 data on beyond standard
  slow-roll inflation
• We propose a new dynamical source for density
  perturbation Colored Quantum Noise
• - give a low CMB quadrupole
• - probing the first few efoldings of
  inflation !?
• Working on running spectral index and
  non-Gaussianity, both are natural with colored
  noise

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