Measuring primordial gravitational waves from CMB B−modes in cosmologies with generalized expansion histories

Journal Article · Fri Feb 01 00:00:00 EST 2013 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2013/02/024· OSTI ID:22282912

Antolini, Claudia; Martinelli, Matteo; Fantaye, Yabebal; Baccigalupi, Carlo ^[1]

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1. SISSA, Via Bonomea 265, Trieste, I-34136 (Italy)

We evaluate our capability to constrain the abundance of primordial tensor perturbations (primordial gravitational waves, PGWs) in cosmologies with generalized expansion histories in the epoch of cosmic acceleration. Forthcoming satellite and sub-orbital experiments probing polarization in the Cosmic Microwave Background (CMB) are expected to measure the B−mode power in CMB polarization, coming from PGWs on the degree scale, as well as gravitational lensing on arcminute scales; the latter is the main competitor for the measurement of PGWs, and is directly affected by the underlying expansion history, determined by the presence of a Dark Energy (DE) component. In particular, we consider early DE possible scenarios, in which the expansion history is substantially modified at the epoch in which the CMB lensing is most relevant. We show that the introduction of a parametrized DE may induce a variation as large as 30% in the ratio of the power of lensing and PGWs on the degree scale. We find that adopting the nominal specifications of upcoming satellite measurements, the constraining power on PGWs is weakened by the inclusion of the extra degrees of freedom, resulting in a reduction of about 10% of the upper limits on r in fiducial models with no GWs, as well as a comparable increase in the error bars in models with non-zero tensor power. Moreover, we find that the inclusion of sub-orbital CMB experiments, capable of mapping the B−mode power up to the angular scales which are affected by lensing, has the effect of restoring the forecasted performances with a fixed cosmological expansion history corresponding to a cosmological constant. Finally, we show how the combination of CMB data with Type Ia SuperNovae (SNe), Baryonic Acoustic Oscillations (BAO) and Hubble constant allows to constrain simultaneously the primordial tensor power and the DE quantities in the parametrization we consider, consisting of present abundance and first redshift derivative of the energy density. We compare this study with results obtained using the forecasted lensing potential measurement precision from CMB satellite observations, finding consistent results.

• OSTI ID: 22282912
• Journal Information: Journal of Cosmology and Astroparticle Physics, Vol. 2013, Issue 02; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
BARYONS
COMPARATIVE EVALUATIONS
COSMOLOGICAL CONSTANT
COSMOLOGY
DEGREES OF FREEDOM
ENERGY DENSITY
EXPANSION
GRAVITATIONAL LENSES
GRAVITATIONAL WAVES
NONLUMINOUS MATTER
OSCILLATIONS
PERTURBATION THEORY
POLARIZATION
RED SHIFT
RELICT RADIATION
SUPERNOVAE
TENSORS