8 research outputs found
Generating the curvature perturbation at the end of inflation
The dominant contribution to the primordial curvature perturbation may be
generated at the end of inflation. Taking the end of inflation to be sudden,
formulas are presented for the spectrum, spectral tilt and non-gaussianity.
They are evaluated for a minimal extension of the original hybrid inflation
model.Comment: 5 pages. v3: as it will appear in JCA
Observing Brane Inflation
Linking the slow-roll scenario and the Dirac-Born-Infeld scenario of
ultra-relativistic roll (where, thanks to the warp factor, the inflaton moves
slowly even with an ultra-relativistic Lorentz factor), we find that the KKLMMT
D3/anti-D3 brane inflation is robust, that is, enough e-folds of inflation is
quite generic in the parameter space of the model. We show that the
intermediate regime of relativistic roll can be quite interesting
observationally. Introducing appropriate inflationary parameters, we explore
the parameter space and give the constraints and predictions for the
cosmological observables in this scenario. Among other properties, this
scenario allows the saturation of the present observational bound of either the
tensor/scalar ratio r (in the intermediate regime) or the non-Gaussianity f_NL
(in the ultra-relativistic regime), but not both.Comment: 31 pages, 12 figures; typo correcte
Non-gaussianity from the inflationary trispectrum
We present an estimate for the non-linear parameter \tau_NL, which measures
the non-gaussianity imprinted in the trispectrum of the comoving curvature
perturbation, \zeta. Our estimate is valid throughout the inflationary era,
until the slow-roll approximation breaks down, and takes into account the
evolution of perturbations on superhorizon scales. We find that the
non-gaussianity is always small if the field values at the end of inflation are
negligible when compared to their values at horizon crossing. Under the same
assumption, we show that in Nflation-type scenarios, where the potential is a
sum of monomials, the non-gaussianity measured by \tau_NL is independent of the
couplings and initial conditions.Comment: 15 pages, uses iopart.sty. Replaced with version accepted by JCAP;
journal reference adde
Observational Signatures and Non-Gaussianities of General Single Field Inflation
We perform a general study of primordial scalar non-Gaussianities in single
field inflationary models in Einstein gravity. We consider models where the
inflaton Lagrangian is an arbitrary function of the scalar field and its first
derivative, and the sound speed is arbitrary. We find that under reasonable
assumptions, the non-Gaussianity is completely determined by 5 parameters. In
special limits of the parameter space, one finds distinctive ``shapes'' of the
non-Gaussianity. In models with a small sound speed, several of these shapes
would become potentially observable in the near future. Different limits of our
formulae recover various previously known results.Comment: 53 pages, 5 figures; v3, minor revision, JCAP version; v4, numerical
coefficients corrected in Appendix B, discussion on consistency condition
revise
Observational Signatures and Non-Gaussianities of General Single Field Inflation
We perform a general study of primordial scalar non-Gaussianities in single
field inflationary models in Einstein gravity. We consider models where the
inflaton Lagrangian is an arbitrary function of the scalar field and its first
derivative, and the sound speed is arbitrary. We find that under reasonable
assumptions, the non-Gaussianity is completely determined by 5 parameters. In
special limits of the parameter space, one finds distinctive ``shapes'' of the
non-Gaussianity. In models with a small sound speed, several of these shapes
would become potentially observable in the near future. Different limits of our
formulae recover various previously known results.Comment: 53 pages, 5 figures; v3, minor revision, JCAP version; v4, numerical
coefficients corrected in Appendix B, discussion on consistency condition
revise
Non-Gaussianity as a Probe of the Physics of the Primordial Universe and the Astrophysics of the Low Redshift Universe
A new and powerful probe of the origin and evolution of structures in the
Universe has emerged and been actively developed over the last decade. In the
coming decade, non-Gaussianity, i.e., the study of non-Gaussian contributions
to the correlations of cosmological fluctuations, will become an important
probe of both the early and the late Universe. Specifically, it will play a
leading role in furthering our understanding of two fundamental aspects of
cosmology and astrophysics: (i) the physics of the very early universe that
created the primordial seeds for large-scale structures, and (ii) the
subsequent growth of structures via gravitational instability and gas physics
at later times. To date, observations of fluctuations in the Cosmic Microwave
Background (CMB) and the Large-Scale Structure of the Universe (LSS) have
focused largely on the Gaussian contribution as measured by the two-point
correlations (or the power spectrum) of density fluctuations. However, an even
greater amount of information is contained in non-Gaussianity and a large
discovery space therefore still remains to be explored. Many observational
probes can be used to measure non-Gaussianity, including CMB, LSS,
gravitational lensing, Lyman-alpha forest, 21-cm fluctuations, and the
abundance of rare objects such as clusters of galaxies and high-redshift
galaxies. Not only does the study of non-Gaussianity maximize the science
return from a plethora of present and future cosmological experiments and
observations, but it also carries great potential for important discoveries in
the coming decade.Comment: 8 pages, 1 figure. Science White Paper submitted to the Cosmology and
Fundamental Physics (CFP) Science Frontier Panel of the Astro 2010 Decadal
Survey (v2,v3,v4) More co-signers and references adde