TY - JOUR

T1 - Suppressing the impact of a high tensor-to-scalar ratio on the temperature anisotropies

AU - Contaldi, Carlo R.

AU - Peloso, Marco

AU - Sorbo, Lorenzo

PY - 2014/7/1

Y1 - 2014/7/1

N2 - The BICEP2 collaboration has reported a strong B mode signal in the CMB polarization, which is well fit by a tensor-to-scalar ratio of r 0.2. This is greater than the upper limit r < 0.11 obtained from the temperature anisotropies under the assumption of a constant scalar spectral index n s. This discrepancy can be reduced once the statistical error and the contamination from polarized dust are accounted for. If however a large value for r will be confirmed, it will need to be reconciled with the temperature anisotropies data. The most advocated explanation involves a variation of n s with scales (denoted as running) that has a magnitude significantly greater than the generic slow roll predictions. We instead study the possibility that the large scale temperature anisotropies are not enhanced because of a suppression of the scalar power at large scales. Such a situation can be achieved for instance by a sudden change of the speed of the inflaton (by about 14%), and we show that it fits the temperature anisotropies and polarization data considerably better than a constant running (its χ2 improves by ∼ 7.5 over that of the constant running, at the cost of one more parameter). We also consider the possibility that the large scale temperature fluctuations are suppressed by an anti-correlation between tensor and scalar modes. Unfortunately, while such effect does affect the temperature fluctuations at large scales, it does not affect the temperature power spectrum and cannot, therefore, help in reconciling a large value of r with the limits from temperature fluctuations.

AB - The BICEP2 collaboration has reported a strong B mode signal in the CMB polarization, which is well fit by a tensor-to-scalar ratio of r 0.2. This is greater than the upper limit r < 0.11 obtained from the temperature anisotropies under the assumption of a constant scalar spectral index n s. This discrepancy can be reduced once the statistical error and the contamination from polarized dust are accounted for. If however a large value for r will be confirmed, it will need to be reconciled with the temperature anisotropies data. The most advocated explanation involves a variation of n s with scales (denoted as running) that has a magnitude significantly greater than the generic slow roll predictions. We instead study the possibility that the large scale temperature anisotropies are not enhanced because of a suppression of the scalar power at large scales. Such a situation can be achieved for instance by a sudden change of the speed of the inflaton (by about 14%), and we show that it fits the temperature anisotropies and polarization data considerably better than a constant running (its χ2 improves by ∼ 7.5 over that of the constant running, at the cost of one more parameter). We also consider the possibility that the large scale temperature fluctuations are suppressed by an anti-correlation between tensor and scalar modes. Unfortunately, while such effect does affect the temperature fluctuations at large scales, it does not affect the temperature power spectrum and cannot, therefore, help in reconciling a large value of r with the limits from temperature fluctuations.

KW - CMBR theory

KW - ination

UR - http://www.scopus.com/inward/record.url?scp=84904009266&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84904009266&partnerID=8YFLogxK

U2 - 10.1088/1475-7516/2014/07/014

DO - 10.1088/1475-7516/2014/07/014

M3 - Article

AN - SCOPUS:84904009266

SN - 1475-7516

VL - 2014

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 7

M1 - 014

ER -