9 research outputs found
Cosmic microwave background constraints on dark energy dynamics: analysis beyond the power spectrum
We consider the distribution of the non-Gaussian signal induced by weak
lensing on the primary total intensity cosmic microwave background (CMB)
anisotropies. Our study focuses on the three point statistics exploiting an
harmonic analysis based on the CMB bispectrum. By considering the three
multipoles as independent variables, we reveal a complex structure of peaks and
valleys determined by the re-projection of the primordial acoustic oscillations
through the lensing mechanism. We study the dependence of this system on the
expansion rate at the epoch in which the weak lensing power injection is
relevant, probing the dark energy equation of state at redshift corresponding
to the equivalence with matter or higher (). We evaluate the impact
of the bispectrum observable on the CMB capability of constraining the dark
energy dynamics. We perform a maximum likelihood analysis by varying the dark
energy abundance, the present equation of state and . We show
that the projection degeneracy affecting a pure power spectrum analysis in
total intensity is broken if the bispectrum is taken into account. For a
Planck-like experiment, assuming nominal performance, no foregrounds or
systematics, and fixing all the parameters except , and the
dark energy abundance, a percent and ten percent precision measure of and
is achievable from CMB data only. These results indicate that the
detection of the weak lensing signal by the forthcoming CMB probes may be
relevant to gain insight into the dark energy dynamics at the onset of cosmic
acceleration.Comment: 14 pages, 9 figures. Matching version accepted by Physical Review D.
High resolution figures available upon request to the author
Constraining the dark energy dynamics with the cosmic microwave background bispectrum
We consider the influence of the dark energy dynamics at the onset of cosmic
acceleration on the Cosmic Microwave Background (CMB) bispectrum, through the
weak lensing effect induced by structure formation. We study the line of sight
behavior of the contribution to the bispectrum signal at a given angular
multipole : we show that it is non-zero in a narrow interval centered at a
redshift satisfying the relation , where the
wavenumber corresponds to the scale entering the non-linear phase, and is
the cosmological comoving distance. The relevant redshift interval is in the
range 0.1\lsim z\lsim 2 for multipoles 1000\gsim\ell\gsim 100; the signal
amplitude, reflecting the perturbation dynamics, is a function of the
cosmological expansion rate at those epochs, probing the dark energy equation
of state redshift dependence independently on its present value. We provide a
worked example by considering tracking inverse power law and SUGRA Quintessence
scenarios, having sensibly different redshift dynamics and respecting all the
present observational constraints. For scenarios having the same present
equation of state, we find that the effect described above induces a projection
feature which makes the bispectra shifted by several tens of multipoles, about
10 times more than the corresponding effect on the ordinary CMB angular power
spectrum.Comment: 15 pages, 7 figures, matching version accepted by Physical Review D,
one figure improve