187 research outputs found
Generalized Slow Roll for Large Power Spectrum Features
We develop a variant of the generalized slow roll approach for calculating
the curvature power spectrum that is well-suited for order unity deviations in
power caused by sharp features in the inflaton potential. As an example, we
show that predictions for a step function potential, which has been proposed to
explain order unity glitches in the CMB temperature power spectrum at
multipoles l=20-40, are accurate at the percent level. Our analysis shows that
to good approximation there is a single source function that is responsible for
observable features and that this function is simply related to the local slope
and curvature of the inflaton potential. These properties should make the
generalized slow roll approximation useful for inflation-model independent
studies of features, both large and small, in the observable power spectra.Comment: 13 pages, 21 figures, submitted to Phys. Rev.
Cosmological Information in the Intrinsic Alignments of Luminous Red Galaxies
The intrinsic alignments of galaxies are usually regarded as a contaminant to
weak gravitational lensing observables. The alignment of Luminous Red Galaxies,
detected unambiguously in observations from the Sloan Digital Sky Survey, can
be reproduced by the linear tidal alignment model of Catelan, Kamionkowski &
Blandford (2001) on large scales. In this work, we explore the cosmological
information encoded in the intrinsic alignments of red galaxies. We make
forecasts for the ability of current and future spectroscopic surveys to
constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations
(BAO) in the cross-correlation function of intrinsic alignments and the galaxy
density field. For the Baryon Oscillation Spectroscopic Survey, we find that
the BAO signal in the intrinsic alignments is marginally significant with a
signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of
galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is
completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic
survey following the EUCLID redshift selection function, we find
signal-to-noise ratios of 12 and 15, respectively. Local type primordial
non-Gaussianity, parametrized by fNL = 10, is only marginally significant in
the intrinsic alignments signal with signal-to-noise ratios < 2 for the three
surveys considered.Comment: 20 pages, 13 figures, version accepted to JCA
B-mode CMB Polarization from Patchy Screening during Reionization
B-modes in CMB polarization from patchy reionization arise from two effects:
generation of polarization from scattering of quadrupole moments by
reionization bubbles, and fluctuations in the screening of E-modes from
recombination. The scattering contribution has been studied previously, but the
screening contribution has not yet been calculated. We show that on scales
smaller than the acoustic scale (l>300), the B-mode power from screening is
larger than the B-mode power from scattering. The ratio approaches a constant
~2.5 below the damping scale (l>2000). On degree scales relevant for
gravitational waves (l<100), screening B-modes have a white noise tail and are
subdominant to the scattering effect. These results are robust to uncertainties
in the modeling of patchy reionization.Comment: 4 pages, 1 figure; minor changes matching PRD published versio
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