5 research outputs found
Large non-Gaussianities in the Effective Field Theory Approach to Single-Field Inflation: the Bispectrum
The methods of effective field theory are used to study generic theories of
inflation with a single inflaton field and to perform a general analysis of the
associated non-Gaussianities. We investigate the amplitudes and shapes of the
various generic three-point correlators, the bispectra, which may be generated
by different classes of single-field inflationary models. Besides the
well-known results for the DBI-like models and the ghost inflationary theories,
we point out that curvature-related interactions may give rise to large
non-Gaussianities in the form of bispectra characterized by a flat shape which,
quite interestingly, is independently produced by several interaction terms. In
a subsequent work, we will perform a similar general analysis for the
non-Gaussianities generated by the generic four-point correlator, the
trispectrum.Comment: Version matching the one published in JCAP, 2 typos fixed, references
added. 30 pages, 20 figure
An Estimator for statistical anisotropy from the CMB bispectrum
Various data analyses of the Cosmic Microwave Background (CMB) provide
observational hints of statistical isotropy breaking. Some of these features
can be studied within the framework of primordial vector fields in inflationary
theories which generally display some level of statistical anisotropy both in
the power spectrum and in higher-order correlation functions. Motivated by
these observations and the recent theoretical developments in the study of
primordial vector fields, we develop the formalism necessary to extract
statistical anisotropy information from the three-point function of the CMB
temperature anisotropy. We employ a simplified vector field model and
parametrize the bispectrum of curvature fluctuations in such a way that all the
information about statistical anisotropy is encoded in some parameters
lambda_{LM} (which measure the anisotropic to the isotropic bispectrum
amplitudes). For such a template bispectrum, we compute an optimal estimator
for lambda_{LM} and the expected signal-to-noise ratio. We estimate that, for
f_{NL} ~ 30, an experiment like Planck can be sensitive to a ratio of the
anisotropic to the isotropic amplitudes of the bispectrum as small as 10%. Our
results are complementary to the information coming from a power spectrum
analysis and particularly relevant for those models where statistical
anisotropy turns out to be suppressed in the power spectrum but not negligible
in the bispectrum.Comment: 25 pages, LaTeX file. Matches version accepted for publication in
JCAP; some references added; Appendix C added to explain the order of the
Edgeworth expansion employe
Statistical Anisotropy from Anisotropic Inflation
We review an inflationary scenario with the anisotropic expansion rate. An
anisotropic inflationary universe can be realized by a vector field coupled
with an inflaton, which can be regarded as a counter example to the cosmic
no-hair conjecture. We show generality of anisotropic inflation and derive a
universal property. We formulate cosmological perturbation theory in
anisotropic inflation. Using the formalism, we show anisotropic inflation gives
rise to the statistical anisotropy in primordial fluctuations. We also explain
a method to test anisotropic inflation using the cosmic microwave background
radiation (CMB).Comment: 32 pages, 5 figures, invited review for CQG, published versio
Prospects for fundamental physics with LISA
In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the very broad range of topics that might be relevant to LISA,we present here a sample of what we view as particularly promising fundamental physics directions. We organize these directions through a “science-first” approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics
Prospects for fundamental physics with LISA
We provide an updated assessment of the fundamental physics potential of LISA. Given the very broad range of topics that might be relevant to LISA, we present here a sample of what we view as particularly promising directions, based in part on the current research interests of the LISA scientific community in the area of fundamental physics. We organize these directions through a ``science-first'' approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics